TW201836564A - Sheet for absorbent article and absorbent article - Google Patents

Abstract

The present invention provides a sheet for an absorbent article having a better balance between the liquid absorption speed, the liquid return preventing property, and the liquid holding prevention. The sheet for an absorbent article is a nonwoven fabric which comprises a first fiber layer and a second fiber layer located on one main surface of the first fiber layer, wherein the first fiber layer comprises a synthetic fiber containing a water repellent fiber treatment agent (hereinafter referred to as "water repellent fiber"), and a fiber having a water repellency lower than that of the water repellent fiber (hereinafter, "first fiber"); the second fiber layer comprises a fiber having a water repellency lower than that of the water repellent fiber (hereinafter referred to as "second fiber"); the fiber diameter of the water repellent fiber is 23.5 [mu]m or more and 42 [mu]m or less, the fiber diameter of the first fiber is smaller than the fiber diameter of the water repellent fiber, and the ratio (mass%) of the second fibers contained in the second fiber layer is larger than the ratio (mass%) of the water-repellent fibers contained in the first fiber layer.

Description

 Sheet for absorbent articles and absorbent articles  

The present invention relates to a sheet for an absorbent article and an absorbent article.

A sheet constituting an absorbent article such as a sanitary napkin, a disposable diaper, or an incontinence pad, that is, a nonwoven fabric having various constitutions has been proposed as a sheet for an absorbent article. For example, Patent Document 1 proposes an absorbent article in which an intermediate layer is provided between an inner sheet and a liquid permeable surface sheet, wherein at least a portion of the surface sheet is formed by a liquid permeable nonwoven fabric in which a hydrophilic fiber and a water repellent fiber are mixed. . Patent Document 2 proposes an absorbent article having an absorbent body between a water-permeable top sheet and a water-impermeable back sheet, wherein the second sheet disposed between the top sheet and the absorbent body uses the following sheet: The first non-woven layer on the top sheet side and the second non-woven layer disposed on the absorber side, the first non-woven layer is composed of a second non-woven layer which is more hydrophobic and has a higher density, and the second non-woven layer is made of hydrophilic And the density is relatively thin.

 [Previous Technical Literature]    [Patent Literature]  

Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-73759.

Patent Document 2: Japanese Laid-Open Patent Publication No. Hei-4-24026.

The absorbent article generally has a surface sheet, a back sheet, and an absorbent body disposed between the top sheet and the back sheet, and further has other members as needed. The sheet for an absorbent article may be required to have both a high liquid absorption speed, a high liquid repellent property, and a high liquid retention resistance depending on the use form.

In order to rapidly transfer excreted body fluid such as menstrual blood or urine (hereinafter simply referred to as "liquid") to the absorbent body, a high liquid absorption speed is required. "Liquid reflux" means that the liquid that has passed through the surface sheet re-exuds to the surface of the surface sheet, and the amount of liquid that oozes out to the surface due to the reflux of the liquid, that is, the more the liquid return flow, the more uncomfortable the user is. Therefore, "preventing high liquid reflux" means that the liquid return flow is small. "Preservation" means that the sheet itself remains liquid. If the sheet retains a large amount of liquid on the surface or inside, the retained liquid may easily leak out of the surface of the surface sheet due to pressurization or the like, which causes the liquid to flow back. Therefore, "preventing high liquid retention" means that the sheet has a low ability to retain liquid.

An object of the present invention is to provide a sheet for an absorbent article which has an excellent balance of a liquid absorption rate, a liquid repellent property, and a liquid retention prevention property.

The present invention provides a sheet for an absorbent article comprising a first fibrous layer and a second fibrous layer located on one main surface of the first fibrous layer, wherein the first fibrous layer contains water repellency. a synthetic fiber of a fiber treating agent (hereinafter referred to as "water-repellent fiber") and a fiber having a water-repellent degree lower than the water-repellent fiber (hereinafter referred to as "first fiber"), and the second fiber layer includes: The water-repellent fiber is less than the fiber of the water-repellent fiber (hereinafter referred to as "second fiber"), and the fiber diameter of the water-repellent fiber is 23.5 μm or more and 42 μm or less, and the fiber diameter of the first fiber is smaller than that of the water-repellent fiber The ratio (% by mass) of the second fibers contained in the second fiber layer is larger than the ratio (% by mass) of the water-repellent fibers contained in the first fiber layer.

According to the present invention, a sheet for an absorbent article can be obtained which has an excellent balance of a liquid absorption rate, a liquid repellent property, and a liquid retention prevention property. Therefore, when the sheet for an absorbent article is used, for example, as an intermediate sheet disposed between the surface sheet and the absorbent body, the liquid can be more quickly moved to the absorbent body, and the liquid during use can be less reflowed.

Fig. 1 is an electron micrograph of the surface of the nonwoven fabric obtained in Example 4.

Fig. 2 is an electron micrograph of the surface of the nonwoven fabric obtained in Example 7.

Fig. 3 is a schematic view showing the method of measuring the contact angle.

(The completion of this embodiment)

When the sheet for absorbent articles is used as an intermediate sheet (ADL (Absorption Distribution Layer) or a second sheet) disposed between the surface sheet and the absorbent body, it is required to have a liquid absorption speed and prevent it. A sheet for an absorbent article having a more excellent balance between liquid reflowability and liquid retention resistance (hereinafter collectively referred to as "liquid absorption performance"). Further, the intermediate sheet is also expected to have a property of allowing the liquid to be absorbed into the absorbent body with efficiency. For example, when the liquid has a low viscosity such as urine (e.g., viscosity 0.6 mPa ‧ s to 0.9 mPa ‧ s) and the amount of primary excretion is large, the intermediate sheet is required to diffuse the liquid passing through the surface sheet. When the liquid has a high viscosity such as menstrual blood (for example, a viscosity of 7 mPa ‧ to 9 mPa ‧ s) and has a color, the intermediate sheet is required to suppress liquid diffusion in order to make the coloring field observed by the user after absorption in the absorbent body The liquid is quickly transferred to the properties of the absorber. The menstrual blood-absorbing article is required to have concealability (non-observability) of the absorbed liquid, and the smaller the menstrual blood diffusion which can be confirmed visually, the higher the concealability.

The inventors of the present invention reviewed the constitution of the intermediate sheet satisfying the requirements. The inventors of the present invention thought that a sheet satisfying such requirements can be obtained by combining fibers having different degrees of water discharge. However, it has been found that the desired liquid absorbing performance cannot be achieved by merely mixing the fiber systems, and in particular, when the liquid is repeatedly absorbed, the liquid absorbing performance is easily lowered.

Therefore, the inventors of the present invention have reviewed the following structure: the nonwoven fabric has a two-layer structure, one fiber layer (first fiber layer) contains a plurality of fibers having a high degree of water repellency, and the other fiber layer (second fiber layer) contains More water with a lower degree of water. As a result, it is understood that the non-woven fabric having such a two-layer structure can reduce the liquid return flow, can diffuse the liquid when the viscosity of the liquid is low, and can suppress the diffusion of the liquid when the viscosity of the liquid is high, and rapidly transfer the liquid to the absorber. The fiber diameter of the fibers constituting the second fiber layer is made smaller, whereby the diffusion of the fibers can be further promoted when the liquid viscosity is low, and the liquid reflow property is also prevented from being improved.

Moreover, the inventors of the present invention reviewed the configuration of the first fiber layer in order to further improve the liquid absorption performance. As a result, it was found that an interfiber gap between the water-repellent fibers and the water-repellent fibers/first fibers can be formed between the water-repellent fibers and the first fibers, whereby the balance of the liquid-absorbent properties can be further improved.

‧ The first fiber layer is configured to include a synthetic fiber (water-repellent fiber) containing a water-repellent fiber treating agent and a fiber (first fiber) having a water-repellent degree lower than that of the water-repellent fiber.

‧The fiber diameter of the water-repellent fiber is within a specific range.

‧ The fiber diameter of the first fiber is made smaller than the fiber diameter of the water-repellent fiber.

The sheet for absorbent articles of the present embodiment and an absorbent article using the same will be described below.

The sheet for an absorbent article according to the present embodiment is a nonwoven fabric in which a first fiber layer and a second fiber layer located on one main surface of the first fiber layer are contained, and the first fiber layer contains a water-repellent fiber and a first fiber. The water-repellent fiber is a synthetic fiber containing a water-repellent fiber treatment agent, wherein the first fiber system has a water-repellent degree lower than that of the water-removing fiber, and the second fiber layer contains a second fiber, and the second fiber system has a low water-discharging degree. In the fiber of the water-repellent fiber, the fiber diameter of the water-repellent fiber is 23.5 μm or more and 42 μm or less, the fiber diameter of the first fiber is smaller than the fiber diameter of the water-repellent fiber, and the ratio (% by mass) of the second fiber contained in the second fiber layer is larger than The ratio (% by mass) of the water-repellent fibers contained in the first fiber layer.

(water-repellent fiber)

The water-repellent fiber contained in the first fiber layer is a synthetic fiber containing a water-repellent fiber treating agent, and a synthetic fiber in which a water-repellent fiber treating agent is adhered to the surface as described later or a synthetic fiber in which a water-repellent fiber treating agent is dispersed in the fiber. The synthetic fiber itself has a certain degree of water repellency, so that the degree of water repellency can be further improved by further containing the water repellency fiber treating agent.

The degree of water repellency of the water-repellent fibers can be known, for example, by the contact angle. Here, the contact angle refers to the angle at which the free surface of the water contacts the fiber, and the angle between the water surface and the surface of the fiber (the angle inside the water taken). In the present embodiment, the contact angle of the water repellent fiber may be, for example, 100° or more and 135° or less, preferably 100° or more and 130° or less, more preferably 100 or more and 125 or less. The higher the contact angle, the higher the water level. If the contact angle of the water-repellent fiber is too small, the liquid repellent property of the non-woven fabric is lowered.

The contact angle was measured by the following method.

The measurement unit of the zoom lens (manufactured by Keyence Co., Ltd., model: VH-Z100R) equipped with a zoom lens (manufactured by Keyence Co., Ltd.) was fixed in a state of being reversed in the horizontal direction. The nonwoven fabric containing the fibers of the contact angle measurement target was cut so that the longitudinal direction (MD direction) × the horizontal direction (CD direction) became 50 mm × 10 mm, and a measurement sample was produced. In a state where the measurement of the measurement sample is faced upward, the CD direction of the nonwoven fabric is made perpendicular to the lens surface of the zoom lens (that is, the observation direction is parallel to the CD direction), and the measurement sample is placed on the test stand and fixed by tape. Both ends. Further, the observation direction (the direction in which the object is observed by the zoom lens) is not particularly limited as long as it is selected such that the fiber extends in a direction orthogonal to the observation direction. Depending on the type of the non-woven fabric, the direction in which the CD direction of the non-woven fabric becomes, for example, an angle of 45° can be regarded as the observation direction.

Next, water droplets of ion-exchanged water (water temperature of about 20 ° C) were sprayed on the measurement sample using a sprayer so that the size of the mist was as fixed as possible and fine. Within 5 seconds after the spraying, using a zoom lens, the water droplets attached to the surface of the fiber were observed 50 to 1000 times in view of the fiber diameter of the fiber, and an image was taken. Repeat the spraying and image capture to obtain 20 images with clear water droplets. A horizontal image of the fibers is selected from the resulting images. The reason for this is that the contact angle changes if the fiber is tilted. When the number of selected images is 10 or more, use these images to obtain the contact angle. When the number of images in which the fiber is horizontal is less than 10, 20 images are further obtained, and the images in which the fibers are selected are horizontally repeated, until the total number of images in which the fibers are horizontal is 10 or more.

As shown in Fig. 3, the contact angle is the line of water droplets at the contact surface of the water droplets with the air and the fibers, and the angle between the tangential line and the fibers. The contact angle is measured by image analysis processing (for example, "2D image analysis software "MicroMeasure" available from Scalar Co., Ltd.) or a protractor. The contact angle in each selected image is measured and the average value (arithmetic mean value) of these is determined, and the contact angle of the target fiber is measured.

The contact angle can also be measured by a method of taking out the constituent fibers of the measurement target from the measurement surface and then spraying the water droplets on the constituent fibers without using a non-woven fabric.

The following points should be noted when measuring the contact angle.

(1) The contact angle of the water droplets attached to the fibers was measured. The contact angle of water droplets drooping down to the fibers and water droplets wound around two or more fibers was not measured.

(2) When the fiber is subjected to fine crimping such as a spiral shape, the measurement is performed after the crimping is less or the fiber is stretched and released.

(3) If the measurement position is changed or the measurement sample is changed as described above, 10 or more images of the fibers are selected to be horizontal, and the measurement values are averaged to obtain the measurement result of the contact angle. When the degree of hydrophilization of the fiber is high, when the contact angle is measured, the water droplet can be moved on the fiber (that is, the shape of the water droplet can be changed). In this case, consider the movement status and obtain the "contact angle".

When the number of the water droplets moved is less than 40% of the total number of measurement points (when the total of the measurement points of the water droplets are taken, and the total of the water droplets during the shooting and the total of the non-moving conditions) is reached, The image in which the fiber is horizontal is selected to be 10 or more, and the measured value is averaged as the contact angle.

When the number of the water droplets moved is 40% or more of the total number of measurement times until the measurement point of the contact angle reaches 20 o'clock, the contact angle is set to 20 or less.

The synthetic fiber containing the water-repellent fiber treating agent is composed of a thermoplastic resin. The thermoplastic resin is not particularly limited and may be composed of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutyl succinate. Polyester resin such as diester and copolymer; polypropylene, polyethylene (including high density polyethylene, low density polyethylene, linear low density polyethylene, etc.), polybutene-1, and propylene Polypropylene resin such as propylene copolymer (including propylene/ethylene copolymer, propylene/butene-1/ethylene copolymer), and ethylene/vinyl acetate copolymer; nylon 6, nylon 12 and nylon 66 Polyurethane-based resins; acrylic resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefin, and the elastomers thereof are arbitrarily selected.

The synthetic fiber may be a single fiber formed from one or a plurality of thermoplastic resins selected as described above. If a single fiber is used, it is less likely to cause fibrillation and fine powder caused by interfacial peeling between components which are common when using a conjugate fiber. More specifically, the synthetic fiber may be a single fiber composed of one or more resins selected from the group consisting of the polyolefin resin, the polyester resin, the polyamide resin, and the acrylic resin. In particular, the polypropylene single fiber itself has high water repellency, so it can be preferably used, and the polyethylene terephthalate single fiber (compared to polypropylene) has a higher Young's modulus and a non-woven fabric. Therefore, it can be preferably used.

Alternatively, the synthetic fiber may be a composite fiber composed of two or more components (also referred to as "sections"). Generally, two or more components are composed of a thermoplastic resin having mutually different melting points. In the synthetic fiber, each component may be composed of one type of thermoplastic resin or a mixture of two or more kinds of thermoplastic resins. The composite fiber may be, for example, a core-sheath type composite fiber, an island-in-sea type composite fiber, a split type composite fiber, or a side-by-side type composite fiber. The core-sheath type composite fiber may be an eccentric core-sheath type composite fiber in which the core component center and the sheath component center are not coincident in the fiber profile, or a concentric core-sheath type composite fiber in which the core component center and the sheath component center are coincident in the fiber section.

When the synthetic fiber is a conjugate fiber, two or more components may be disposed such that a thermoplastic resin having the lowest melting point constitutes a part of the fiber surface. In this case, in the step of producing the non-woven fabric, if the component of the thermoplastic resin having the lowest melting point (hereinafter referred to as "low-melting component") is heated or melted, the low-melting component becomes a component, and the fibers can be bonded to each other or Followed by other components. The thermoplastic resin composition constituting the composite fiber is, for example, a polyolefin system such as polyethylene/polyethylene terephthalate, polypropylene/polyethylene terephthalate, or propylene copolymer/polyethylene terephthalate. A combination of a resin and a polyester resin; a combination of two types of polyolefin-based thermoplastic resins such as polyethylene/polypropylene, propylene copolymer/polypropylene; and a combination of two types of polyester resins having different melting points.

In addition, the thermoplastic resin exemplified as the constituent component of the single fiber or the composite fiber may contain other components as long as it contains 50% by mass or more of the specifically disclosed thermoplastic resin. The thermoplastic resin specifically disclosed may be contained in an amount of 80% by mass or more, or may be contained in an amount of 90% by mass or more, or the constituent component may be substantially formed of a thermoplastic resin specifically disclosed. Here, in general, it is considered that a thermoplastic resin contains various additives and the like, and the term "substantially" is used. For example, in the combination of polyethylene/polyethylene terephthalate, the "polyethylene" may contain other thermoplastic resins, additives, and the like as long as it contains 50% by mass or more of polyethylene. This is also the same in the following examples.

When the thermoplastic resin having the lowest melting point of the synthetic fiber constitutes the core-sheath type composite fiber of the sheath portion, the core/sheath combination may be, for example, polyethylene terephthalate/polyethylene, polyethylene terephthalate/polypropylene. , polyethylene terephthalate / propylene copolymer, polytrimethylene terephthalate / polyethylene, polybutylene terephthalate / polyethylene, polyethylene terephthalate / copolyester (for example, polyethylene terephthalate copolymerized with isophthalic acid). The sheath-type composite fiber in which the sheath is polyethylene (for example, high-density polyethylene, low-density polyethylene, or linear low-density polyethylene) or copolyester is carried out at a temperature higher than the melting point of the thermoplastic resin constituting the sheath. The heat treatment melts or softens the sheath and has the property of causing the fibers to follow each other.

When the synthetic fiber is a core-sheath type composite fiber, the composite ratio (mass ratio, core/sheath) of the core to the sheath may be, for example, 80/20 to 20/80, and particularly 60/40 to 40/60.

The water-repellent fiber preferably has a function as a component which does not have a component (i.e., a component) which causes the fibers to follow each other. More specifically, the water-repellent fiber preferably has a function that its constituent component does not have a function of melting or softening as a bonding component by, for example, thermal action. Whether or not the component constituting the water-repellent fiber has a function as a binder component differs depending on the type of the thermoplastic resin constituting the water-repellent fiber and the nonwoven fabric production conditions. When the component constituting the water-repellent fiber does not have a function as a bonding component, the number of subsequent dots in the nonwoven fabric can be reduced, and the touch of the nonwoven fabric can be made better. That is, the next point causes a hard touch and a tingling sensation, so the less the point is, the softer the touch of the non-woven fabric is. Further, since the water-repellent fiber has a large fiber diameter as will be described later, when the component constituting the water-repellent fiber has a function as a contact component, a large area or a large volume is formed, and the touch of the nonwoven fabric is lowered.

For example, when the component of the first fiber has a function as a bonding component, and the melting point of the bonding component is 100° C. or higher and 140° C. or lower, the components constituting the water-repellent fiber, particularly the melting point of the component constituting the surface of the water-repellent fiber, for example, It may be 145 ° C or more and 270 ° C or less, preferably 147 ° C or more and 250 ° C or less, more preferably 150 ° C or more and 220 ° C or less. In the specification including the following description, the specific disclosed value of the melting point of the thermoplastic resin means the melting point after spinning unless otherwise specified. Using a differential scanning calorimeter (manufactured by Seiko Instruments Co., Ltd.) and a fiber amount (sample amount) of 5.0 mg, the fiber was melted from room temperature to 300 ° C at a temperature increase rate of 10 ° C/min, and the obtained heat of fusion curve was obtained. The melting point after silk.

The form of the water-repellent fiber treatment agent is not particularly limited. For example, the water-repellent fiber treating agent may be attached to the surface of the synthetic fiber or dispersed in the fiber. The water-repellent fiber treating agent is sprayed onto the surface of the synthetic fiber by spraying or the like, or applied to the surface of the synthetic fiber by any method, whereby it can be attached to the surface of the synthetic fiber. It is also possible to melt-spin the thermoplastic resin having the water-repellent fiber treating agent, whereby the water-repellent fiber treating agent can be dispersed in the fiber.

The type of the water-repellent fiber treating agent is not particularly limited. The water-repellent fiber treating agent can be known. The water-repellent fiber treating agent is, for example, a fiber containing an alkali metal salt, an alkaline earth metal salt, an ammonium salt, or an amine salt of an alkyl phosphate having an alkyl group having an average carbon number of 14 or more, preferably 16 to 22 carbon atoms. a treatment agent; a fiber treatment agent containing a carboxyl modified polyethylene wax having a molecular weight of 1000 to 10000 and an acid value of 5 to 50; and a water-soluble fluorine containing a perfluoroalkyl carboxylate or a perfluoroalkyltrimethylammonium salt; It is a surfactant, an oil-soluble fluorine-based surfactant such as a perfluoroalkyl group-containing oligomer or a perfluoroalkyl ethylene oxide adduct, and a water-repellent oil obtained by polymerizing a fluorine-containing vinyl monomer. Fluorine-containing fiber treatment agent for processing agent; containing polydimethyl methoxyoxane, methyl hydroquinone, amino group modification, epoxy modification, carboxyl modification, quaternary ammonium salt modification, higher alkane a poly-oxygenated fiber treating agent of various modified polyfluorene or a polyfluorene-based surfactant bonded with a polyfluorene and a hydrophilic group; and a known hydrophobic a chemical agent such as an alkyl ketene dimer having a hydrocarbon group of 8 to 40 carbon atoms, a substituted succinic anhydride or a substituted glutaric acid It illustrated the substituted cyclic dicarboxylic acid anhydride of the fiber-treating agent.

The content of the water-repellent fiber treating agent may be 0.1% by mass or more and 2.0% by mass or less based on 100% by mass of the fiber mass (the fiber mass of the fiber treating agent is removed). The content of the water-repellent fiber treating agent is preferably 0.15% by mass or more and 1.0% by mass or less, more preferably 0.2% by mass or more and 0.6% by mass or less.

The water-repellent fiber has a fiber diameter of 23.5 μm or more and 42 μm or less. When the fiber diameter of the water-repellent fiber is within this range, a large interfiber gap can be formed in the first fiber layer. It is difficult for the liquid to remain in the interfiber spaces, especially in the large voids formed by the water repellency fibers and other fibers, and the large voids formed between the water repellency fibers. Therefore, by using the water-repellent fiber of the fiber diameter of the above specific range, it is easy to improve the liquid retention prevention property of the nonwoven fabric. The fiber diameter of the water-repellent fiber is preferably 26.5 μm or more and 37.6 μm or less, more preferably 28.0 μm or more and 33.6 μm or less. Further, the fiber diameter of the water-repellent fiber may be 30.8 μm or more and 41.3 μm or less.

The fiber diameter of the fiber can be obtained by observing the side of the fiber using a scanning electron microscope (SEM, magnification: 50 to 500 times), measuring the fiber diameter of any of the 100 fibers, and calculating the average value thereof. When the fiber does not have a circular cross section, that is, when it has a profiled cross section, the fiber cross section is observed by a scanning electron microscope (magnification: 50 to 500 times), and the fiber length is the longest one of the straight lines connected at any two points on the outer circumference of the fiber. The fiber diameter of other fibers is also determined in the same manner as the fiber diameter described herein.

The fiber length of the water-repellent fiber is not particularly limited, and may be appropriately selected in accordance with the production method of the non-woven fabric. For example, when a carding web is produced to make a non-woven fabric, the water-repellent fibers may be short fibers. When the water-repellent fiber is a short fiber, the fiber length may be, for example, 20 mm or more and 80 mm or less, preferably 28 mm or more and 75 mm or less, more preferably 30 mm or more and 65 mm or less.

(1st fiber)

The first fiber system is less water-repellent than the fiber of the water-repellent fiber. The degree of water withdrawal can be known, for example, from the contact angle. When the degree of water discharge is determined by the contact angle, the contact angle of the first fiber is smaller than the contact angle of the water-repellent fiber. The contact angle of the first fibers may be, for example, 30° or more and 75° or less, preferably 35° or more and 70° or less, more preferably 40 or more and 65 or less. Further, the contact angle of the first fibers may be 35° or more smaller than the contact angle of the water repellent fibers, preferably 40° or more, and more preferably 45° or less. When the difference in contact angle between the water-repellent fiber and the first fiber is small, it is difficult to obtain the effect achieved by using the two types of fibers (the balance of the liquid absorption performance is improved).

The first fiber may be, for example, a synthetic fiber containing a hydrophilic fiber treating agent. When the first fiber is a synthetic fiber, it does not exhibit excessive hydrophilicity. Therefore, it is difficult to maintain a liquid in the nonwoven fabric, and it is easy to improve the liquid retention resistance. The thermoplastic resin constituting the synthetic fiber is as previously described for the water-repellent fiber. Further, the synthetic fiber containing the hydrophilic fiber treating agent may be a single fiber or a composite fiber, and such examples are as previously described for the water-repellent fiber.

When the synthetic fiber constituting the first fiber is a conjugate fiber, the component having the lowest melting point of the conjugate fiber (low-melting component) constitutes at least a part of the surface of the fiber, and the melting point of the low-melting component is lower than the melting point of at least the component constituting the surface of the water-repellent fiber. When such a conjugate fiber is used, the component constituting the water repellency fiber does not have a function as a bonding component, and the first fiber layer can be contained by melting or softening the low melting component of the first fiber, for example, by heating. The constituent fibers are followed by each other. When the low-melting component of the first fiber has a function as a component, the fiber diameter is less than the fiber diameter of the water-repellent fiber, and the area and volume of the next point can be reduced. Therefore, when the constituent component of the coarse water-repellent fiber is used as the bonding component, when the low-melting component of the first fiber is used as the bonding component, the touch of the non-woven fabric is hard to be hardened, and the tingling feeling is less likely to occur, so that the non-woven fabric can be made. The touch is better.

For example, the melting point of the low-melting component of the first fiber may be lower than the melting point of at least the component constituting the surface of the water-repellent fiber by 5 ° C or higher, preferably lower than 7 ° C, more preferably lower than 10 ° C, and even more preferably lower than 20 ° C. the above. When the difference in melting point is small, when the low-melting component is heated to have a function as a bonding component, for example, the component of the water-repellent fiber may be melted or softened to have a function as a bonding component. Further, the melting point of the low melting point component of the first fiber may be, for example, 100 ° C or more and 150 ° C or less, preferably 100 ° C or more and 145 ° C or less, more preferably 100 ° C or more and 140 ° C or less.

The low melting point component of the first fiber may be, for example, polyethylene, and more specifically, high density polyethylene, low density polyethylene, or linear low density polyethylene. Polyethylene has a lower melting point and exhibits adhesion by heating at a lower temperature. Therefore, when the low melting point component of the first fiber is polyethylene, at least a component constituting the surface of the water repellency fiber can be selected from a plurality of thermoplastic resins. In the first fiber, the resin which can be combined with the polyethylene is not particularly limited as long as it has a melting point higher than that of polyethylene, and examples thereof include polypropylene, polyethylene terephthalate, and polybutylene terephthalate. And polytrimethylene terephthalate and the like. Polyethylene, as a fiber constituting at least a part of the surface of the fiber, specifically, a core-sheath type composite fiber in which polyethylene is a sheath component, an island-in-sea type composite fiber in which polyethylene is a sea portion, and a split type composite fiber in which polyethylene is a component. And a side-by-side type composite fiber containing polyethylene as a component.

In the composite fiber in which the low-melting component forms part of the surface of the fiber, the composite ratio (mass ratio, low-melting component/other component) of the low-melting component to the other component is 80/20 to 65/35, preferably 60/40 to 50/ 50. If the proportion of the low melting component is small, the fibers are less likely to follow each other.

When the first fiber is a synthetic fiber containing a hydrophilic fiber treating agent, the form of the hydrophilic fiber treating agent is not particularly limited. The hydrophilic fiber treating agent may be attached to the surface of the synthetic fiber or dispersed in the fiber. The hydrophilic fiber treating agent can be sprayed onto the surface of the synthetic fiber by spraying or the like, or applied to the surface of the synthetic fiber by any method, whereby it can be attached to the surface of the synthetic fiber. The thermoplastic resin kneaded with the hydrophilic fiber treating agent may be melt-spun, whereby the hydrophilic fiber treating agent is dispersed in the fiber.

The type of the hydrophilic fiber treating agent is not particularly limited. Hydrophilic fiber treatment agents are well known. The hydrophilic fiber treatment agent may, for example, be a fiber treatment agent containing a surfactant. An anionic, cationic, amphoteric and nonionic surfactant can be used as the surfactant.

Examples of the anionic surfactant include sodium alkyl phosphate, sodium alkyl phosphate, sodium dialkyl phosphate, sodium sulfosuccinate, sodium alkyl benzenesulfonate, and sulfonic acid. Sodium ester salt, sodium salt of sodium sulphate, and the like. In the anionic surfactant, any alkyl group is preferably a carbon number of 6 to 22. Further, in the anionic surfactant, another alkali metal salt such as a potassium salt or an alkaline earth metal salt (for example, a magnesium salt) may be used instead of the sodium salt.

The cationic surfactant may, for example, be an alkyl (or alkenyl)trimethylammonium halide, a dialkyl (or alkenyl)dimethylammonium halide or an alkyl (or alkenyl)pyridinium halide. The cationic surfactant is preferably one having an alkyl group or an alkenyl group having 6 to 18 carbon atoms. The halogen in the above halide compound may, for example, be chlorine or bromine.

Examples of the amphoteric ionic surfactant include a betaine-type amphoteric surfactant such as an alkyl dimethyl betaine, an amino acid amphoteric surfactant, and an aminosulfonic acid amphoteric surfactant.

Examples of the nonionic surfactant include polyhydric alcohol fatty acid esters such as glycerin fatty acid esters, polyglycerin fatty acid esters, and sorbitan fatty acid esters, alkylene oxide adducts of the aforementioned polyhydric alcohol fatty acid esters, and polycondensation. Oxygen alkyl modified polyoxyl, amine modified polyoxyl and the like.

When the content of the hydrophilic fiber treatment agent is 100% by mass based on the fiber mass (fiber mass other than the fiber treatment agent), it is 0.1% by mass or more and 2.0% by mass or less. The content of the hydrophilic fiber treating agent is preferably 0.15% by mass or more and 1.0% by mass or less, more preferably 0.2% by mass or more and 0.6% by mass or less.

Alternatively, the first fiber may be a natural fiber such as cotton, silk, wool, hemp, and pulp, and a sputum and a plurality obtained by the method of manufacturing the fused fiber, when the degree of water repellency is lower than the degree of water repellency of the water absorbing fiber. Cellulose fiber, copper ammonium hydride obtained by a copper ammonia method, cellulose fiber obtained by a solvent spinning method (LENZING LYOCELL (registered trademark), TENCEL (registered trademark), etc.), and a cellulose fiber obtained by a melt spinning method, and One or a plurality of fibers selected from hydrophilic fibers such as semi-synthetic fibers such as acetate fibers. These fibers may contain a hydrophilic fiber treating agent or may contain a water-repellent fiber treating agent as long as the degree of water repellency is lower than the degree of water repellency of the water-repellent fiber.

The fiber diameter of the first fiber is smaller than the fiber diameter of the water-repellent fiber. In the first fiber layer, a fiber having a lower degree of water repellency is present as a fine fiber, whereby the liquid can be more strongly sucked into the first fiber layer, and the liquid absorption speed can be increased. The fiber diameter of the first fiber may be, for example, 9.5 μm or more and 29.6 μm or less, preferably 11.1 μm or more and 26 μm or less, and more preferably 12.1 μm or more and 23.5 μm or less.

The fiber length of the first fiber is not particularly limited, and may be appropriately selected depending on the production method of the nonwoven fabric or the like. For example, when a carding web is produced to produce a non-woven fabric, the first fiber may be a short fiber. When the first fiber is a short fiber, the fiber length is, for example, 20 mm or more and 80 mm or less, preferably 28 mm or more and 75 mm or less, and more preferably 30 mm or more and 65 mm or less.

(2nd fiber)

The second fiber layer contained in the second fiber layer is less water-repellent than the fiber of the water-repellent fiber. This means that the second fiber is the same as the first fiber. Therefore, the contact angle of the second fiber is the same as the contact angle of the first fiber, and is, for example, 30° or more and 75° or less, preferably 35° or more and 70° or less, and more preferably 40° or more and 65° or less. Further, the contact angle of the second fiber may be 35° or more smaller than the contact angle of the water-repellent fiber, preferably 40° or more, and more preferably 45° or less. Since the second fiber has a low degree of water repellency, if it is contained in the second fiber layer, the liquid sucked into the first fiber layer can be strongly sucked into the second fiber layer, and the liquid can be quickly discharged from the first fiber layer. . When the difference between the contact angle of the water-repellent fiber and the contact angle of the second fiber is small, it is difficult to suck the liquid into the second fiber layer.

The second fiber may be, for example, a synthetic fiber containing a hydrophilic fiber treating agent. When the second fiber is a synthetic fiber, it does not exhibit excessive hydrophilicity, so that the liquid is not easily retained in the nonwoven fabric, and it is easy to improve the liquid retention resistance. The thermoplastic resin constituting the synthetic fiber is as previously described for the water-repellent fiber. Further, the synthetic fiber containing the hydrophilic fiber treating agent may be a single fiber or a composite fiber, and such examples are as previously described for the water-repellent fiber.

When the fiber constituting the second fiber is a conjugate fiber, the component having the lowest melting point (low-melting component) constitutes at least a part of the surface of the fiber, and the melting point of the low-melting component may be lower than the melting point of at least the component constituting the surface of the water-repellent fiber. When such a conjugate fiber is used to form a nonwoven fabric by laminating two fiber webs as described later, the component constituting the water repellency fiber does not have a function as a binder component, and the low melting component of the second fiber can be heated or melted, for example. Thereby, the low melting point component of the second fiber can function as a component of the constituent fibers of the second fiber layer. As described above, when the constituent component of the water-repellent fiber in the first fiber layer does not have a function as a bonding component, it is impossible to form a point where the area or volume is large, and the subsequent point can be reduced, so that the touch of the non-woven fabric is softer. .

The low-melting component constitutes at least a part of the surface of the fiber, and the melting point of the low-melting component is lower than the specific constitution of the composite fiber of the constituent of at least the surface of the water-repellent fiber, as described in the first fiber. Therefore, a detailed description thereof is omitted here.

When the second fiber is a synthetic fiber containing a hydrophilic fiber treating agent, the form of the hydrophilic fiber treating agent is not particularly limited. Examples of the form of the hydrophilic fiber treating agent are as described for the first fiber. Therefore, a detailed description thereof is omitted here.

The type of the hydrophilic fiber treating agent is also not particularly limited. Examples of the hydrophilic fiber treating agent and the content of the hydrophilic treating agent are as described in relation to the first fiber. Therefore, a detailed description thereof is omitted here.

Alternatively, the second fiber may be a fiber other than the synthetic fiber as long as the degree of water repellency is lower than the degree of water repellency of the water repellency fiber. Examples of fibers other than synthetic fibers are as described for the first fibers. Therefore, a detailed description thereof is omitted here.

The fiber diameter of the second fiber is not particularly limited. The fiber diameter of the second fiber may be larger or smaller than the fiber diameter of the water-repellent fiber. Or the fiber diameter of the second fiber may be the same as the fiber diameter of the water-repellent fiber. Further, the fiber diameter of the second fiber may be larger or smaller than the fiber diameter of the first fiber. Alternatively, the fiber diameter of the second fiber may be the same as the fiber diameter of the first fiber.

When the fiber diameter of the second fiber is smaller than the fiber diameter of the water-repellent fiber and is the same as or smaller than the fiber diameter of the first fiber, the liquid recirculating property can be further improved. Further, when the fiber diameter of the second fiber having a small degree of water repellency is small, the fine voids formed by the second fibers have a function as a capillary, and therefore the liquid having a low viscosity is easily diffused in the second fiber layer. When the fiber diameter of the second fiber is small, the liquid having a high viscosity is less likely to diffuse in the second fiber layer. However, this state can improve the concealability of the colored viscous liquid such as menstrual blood in the absorbent article. The fiber diameter of the second fiber may be, for example, 9.5 μm or more and 29.6 μm or less, preferably 11.1 μm or more and 26 μm or less, and more preferably 12.1 μm or more and 23.5 μm or less. When the non-woven fabric of the present embodiment is used for an absorbent article such as a liquid having a high viscosity of menstrual blood, the fiber diameter of the second fiber is preferably 21.0 μm or less. When the fiber diameter of the second fiber is too large, the interfiber space becomes large, the area in which the liquid contacts the fiber is lowered, and the viscosity of the liquid is high, which affects the liquid, and the liquid is not easily transferred to the absorber, and the liquid is easily left in the nonwoven fabric. There is a tendency to reduce concealment.

The fiber length of the second fiber is not particularly limited. The second fiber may be a short fiber like the first fiber. When the second fiber is a short fiber, the specific fiber length is as described for the first fiber. Therefore, a detailed description thereof is omitted here.

(Composition of sheets for absorbent articles (non-woven fabric))

The sheet for an absorbent article according to the present embodiment is a nonwoven fabric, and the second fiber layer containing the second fiber is placed on the main surface of one of the first fiber layers including the water-repellent fiber and the first fiber, and the second fiber layer is contained. The ratio (% by mass) of the second fiber is larger than the ratio (% by mass) of the water-repellent fiber contained in the first fiber layer. When the first fibrous layer of the nonwoven fabric is first brought into contact with the liquid to bring the liquid into contact with the nonwoven fabric, the liquid is first sucked into the fiber having a large gap and containing the water-repellent fiber and the water-repellent degree (the first fiber). The first fiber layer is then strongly inhaled into the second fiber layer. At this time, when the liquid viscosity is low, the second fiber layer is sucked while diffusing the liquid, and when the liquid viscosity is high, the second fiber layer can be sucked without diffusing the liquid. That is, the liquid contacting the nonwoven fabric has a two-stage suction force, and the liquid passes through the first fiber layer through the surface of the first fiber layer, passes through the second fiber layer, and further moves to other members located under the second fiber layer.

First, the first fiber layer and the second fiber layer will be described first.

[1st fiber layer]

The first fibrous layer contains a water repellent fiber and a first fiber. The ratio of the water-repellent fibers in the first fiber layer may be, for example, 5% by mass or more and 50% by mass or less, preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 45% by mass or less. If the ratio of the water-repellent fibers is too small, the effect obtained by containing the water-repellent fibers (especially the retention of liquid retention) cannot be obtained, and if it is too large, the first fiber layer as a whole will bounce off the liquid, and the liquid is difficult to pass in the thickness direction of the nonwoven fabric. .

The ratio of the first fibers in the first fiber layer may be, for example, 50% by mass or more and 95% by mass or less, preferably 50% by mass or more and 90% by mass or less, and more preferably 55% by mass or more and 80% by mass or less. When the ratio of the first fibers is too small, the effect of obtaining the first fibers (especially the effect of sucking the liquid and increasing the liquid absorption speed) cannot be obtained. If the ratio is too large, the ratio of the water-repellent fibers becomes low, and the water-repellent property cannot be obtained. The effect that fiber can achieve.

The first fibrous layer may contain two or more types of water-repellent fibers. For example, the first fibrous layer may contain two or more types of water-repellent fibers having different degrees of water repellency and/or different fiber diameters. When the water repellency (for example, the contact angle) of the two types of water-repellent fibers is different, the first fiber may be selected in such a manner that the water-repellent fiber having a lower water level than the water-removing degree is selected. When two or more types of water-repellent fibers having different fiber diameters are used, the fiber diameter of each of the water-repellent fibers can be selected within the above specific range. Further, the first fiber layer may contain two or more types of first fibers having different degrees of water repellency and/or fiber diameter. The first fiber layer may be composed of two or more layers in which the types and/or mixing ratios of the fibers are different from each other.

The first fibrous layer may contain water-repellent fibers and other fibers than the first fibers. The other fibers are, for example, fibers having the same degree of water repellency as the water repellency fibers but having a fiber diameter not within the above specific range, and fibers having a water repellency lower than that of the water repellency fibers and having a fiber diameter larger than that of the water repellency fibers. When the other fibers are contained, the proportion of the other fibers in the first fiber layer may be, for example, 30% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less.

[2nd fiber layer]

The second fiber layer contains the second fiber. The second fiber system is contained in the second fiber layer in a ratio (%) larger than the ratio (% by mass) of the water-repellent fibers in the first fiber layer. Thereby, the second fiber layer is easily sucked into the liquid, and when the liquid viscosity is low, the liquid is easily diffused in the second fiber layer. The ratio of the second fibers may be, for example, 50% by mass or more, preferably 80% by mass or more, and more preferably 95% by mass or more. Alternatively, the second fiber layer may be composed only of the second fiber. The second fiber layer may contain two or more types of second fibers having a water-repellent degree and/or a different fiber diameter. The second fiber layer may be composed of two or more layers each containing a fiber having a different degree of water repellency and/or a different fiber diameter.

The second fiber may be a fiber composed of the same fiber as the first fiber or a combination of the same thermoplastic resin. For example, in the nonwoven fabric, when the fibers are followed by the first fibers and the second fibers are followed, if the first fibers and the second fibers are fibers of the same fiber or a combination of the same thermoplastic resin, the components are common. When the following components are common to the two fiber layers, the degree of adhesion can be made the same in the first fiber layer and the second fiber layer, and a more homogeneous nonwoven fabric can be obtained.

When the second fiber layer contains fibers other than the second fibers, the other fibers may be water-repellent fibers having a description of the first fiber layer. When the second fiber layer contains the water-repellent fiber, the ratio of the water-repellent fiber may be, for example, 15% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less. When the second fibrous layer contains water-repellent fibers, the water-repellent fibers may be the same as or different from those contained in the first fibrous layer. Further, the degree of water repellency of the other fibers contained in the second fiber layer is greater than the degree of water repellency of the second fibers, and the fiber diameter may be smaller or larger than the fiber diameter of the water repellency fibers contained in the first fiber layer.

[Laminating form of non-woven fabric]

The nonwoven fabric of the present embodiment is a laminated nonwoven fabric in which the second fiber layer is laminated on the main surface of the first fiber layer. The nonwoven fabric of the present embodiment may have a two-layer structure composed of only the first fiber layer and the second fiber layer. Alternatively, the nonwoven fabric of the present embodiment may be a laminated non-woven fabric having three or more layers, and is a second fiber layer of the main surface layer of one side of the first fiber layer, and a fiber of another layer or more of the main surface area of the second fiber layer. Floor. The other fiber layer may be, for example, a fiber layer composed of only the first fiber, a fiber layer composed only of the second fiber, or a first or second fiber different from the first and second fiber layers. And the fiber layer of the fiber whose water level is lower than that of the water-repellent fiber.

[Integration of fibers in non-woven fabrics]

Next, the aspect in which the fibers in the non-woven fabric of the present embodiment are integrated with each other will be described.

The aspect in which the fibers are integrated with each other is not particularly limited. The fibers may be mixed and integrated with each other by a hybrid treatment or a needle sticking method using a high-pressure fluid stream, or may be integrated by the fibers adhering to each other. At least one component of at least one type of fiber constituting the nonwoven fabric can function as a bonding component, whereby the fibers can be bonded to each other or can be realized by using a binder (adhesive).

For example, the fibers can be followed by the components constituting the first fibers and the components constituting the second fibers. In this case, the component constituting the first fiber and the component constituting the second fiber are heated and melted or softened. Alternatively, the composition of the first fiber and the component constituting the second fiber may be carried out by irradiation with an electron beam or the like or by ultrasonic fusion. The fibers are joined to each other by using the first fibers and the second fibers, whereby the fibers can be integrated with each other in a simple manner.

In the first embodiment, it is preferable to use a fiber having a part of the fiber surface (a low melting point component) containing two or more components and having the lowest melting point, and the fibers constituting the first fiber layer are followed by a low melting point component. Similarly, it is preferable that the second fiber system uses a fiber containing a part of the fiber component and having the lowest melting point component (low melting point component) as a part of the fiber surface, and the fibers constituting the second fiber layer are followed by a low melting point component. For example, it can be carried out by heating or melting a low melting point component.

When the low melting point components of the first and second fibers have a function as a bonding component by heating, when the melting point of the low melting point components of the first and second fibers is lower than the melting point of the component constituting at least the surface of the water repelling fiber, The water-repellent fibers do not have a function as a component of the fibers. That is, the water-repellent fibers are not melted or softened by heating, but remain in the form of fibers in the first fiber layer. When the water-repellent fiber does not melt or soften and does not have a function as a bonding component, the number of subsequent dots in the nonwoven fabric can be reduced, and since the area or volume is not formed, the touch of the nonwoven fabric can be made good.

The first fibrous layer and the second fibrous layer may be integrated as a whole or partially joined and integrated. As will be described later, the first fiber web forming the first fiber layer and the second fiber web forming the second fiber layer are superposed to form a laminated fiber web, and the laminated fiber web is subjected to a hybrid treatment (for example, by a mixed treatment of a high-pressure fluid stream) Or the subsequent processing (for example, heat treatment), whereby the entire first fiber layer and the second fiber layer can be integrated. For example, partial bonding of the first fiber layer and the second fiber layer can be achieved by an adhesive, sewing, mixing, or heat pressing. Alternatively, in the nonwoven fabric of the present embodiment, the second fiber layer is located on the main surface of one of the first fiber layers, and the first fiber layer and the second fiber layer may be joined only without being joined.

[Unit weight, etc.]

The unit weight of the nonwoven fabric of the present embodiment is not particularly limited, and may be appropriately selected depending on the use or the like. The unit weight of the nonwoven fabric of the present embodiment may be, for example, 10 g/m ² or more and 80 g/m ² , preferably 12 g/m ² to 70 g/m ² , and more preferably 18 g/m ² to 60 g/m ² . If the unit weight of the non-woven fabric is too small, cracking, wrinkles, or breakage of the nonwoven fabric is likely to occur, and if it is too large, the liquid retention property (maintaining more liquid) or the air permeability can be lowered.

The unit weight of the first nonwoven fabric layer and the second fiber layer can be appropriately selected so that the unit weight of the entire nonwoven fabric can be determined. For example, when the nonwoven fabric is a two-layer structure composed of one first fiber layer and one second fiber layer, the unit weight of the two fiber layers may be such that the ratio of the first fiber layer to the second fiber layer is 80:20. 20:80, preferably 70:30~30:70. When the ratio of the unit weight of the first fiber layer is too small, the liquid suction force of the first fiber layer is lowered, or the second fiber layer retains a large amount of liquid, and the liquid recirculation resistance is lowered. Further, if the ratio of the unit weight of the second fiber layer is too small, the ability of the second fiber layer to take in liquid from the first fiber layer is lowered.

When the nonwoven fabric of the present embodiment is composed of a nonwoven fabric having a two-layer structure, specifically, the unit weight of the first fiber layer may be, for example, 10 g/m ² to 40 g/m ² , preferably 15 g/m ² to 35 g/m. ² , more preferably 20g/m ² ~ 30g/m ² , and the unit weight of the second fiber layer may be, for example, 10g/m ² to 40g/m ² , preferably 15g/m ² to 35g/m ² , more preferably It is from 20 g/m ² to 30 g/m ² .

The specific volume of the nonwoven fabric of the present embodiment is not particularly limited, and may be appropriately selected depending on the use and the like. The specific volume of the nonwoven fabric of the present embodiment may be, for example, 8 cm ³ /g to 80 cm ³ /g, preferably 10 cm ³ /g to 75 cm ³ /g, more preferably 20 cm ³ /g to 65 cm ³ /g. The specific volume can be obtained from the unit weight and the thickness of the non-woven fabric. Here, the thickness of the non-woven fabric is measured in a state where a load of 2.94 cN is applied per 1 cm ² . The larger the specific volume of the non-woven fabric, the higher the air permeability and the cushioning property of the nonwoven fabric. However, if it is too large, the liquid retention property is lowered and the liquid reflow prevention property is lowered.

(manufacturing method of non-woven fabric)

The nonwoven fabric of the present embodiment can be produced, for example, by a production method including the following steps.

Mixing the water-repellent fiber with the first fiber to form the first fiber web; preparing the second fiber web containing the second fiber; superposing the first fiber web and the second fiber web to form the laminated fiber web; and integrating the fiber into the laminated fiber web Processing.

The first fiber web and the second fiber web can be produced by a known method. The form of each fiber web may be, for example, a card web such as a parallel net, an interlaced net, a semi-random net, or a random net. The form of the first web and the second web may be different.

The first fiber web and the second fiber web are superposed to form a laminated fiber web. The process of integrating the fibers with each other is carried out on the laminated fiber web. The treatment for integrating the fibers with each other may be, for example, a hybrid treatment using a high-pressure fluid, or a treatment in which fibers are integrated by mixing, such as a pinning treatment, or a heat treatment or an adhesive treatment.

As described above, the nonwoven fabric of the present embodiment can be followed by the components constituting the first fibers and the components constituting the second fibers. In order to obtain such a non-woven fabric, the laminated fiber web is preferably subjected to heat treatment. By heat treatment, the components constituting the first fiber (for example, the low melting point component of the conjugate fiber) and the component constituting the second fiber (for example, the low melting point component of the conjugate fiber) are melted or softened by heating during heat treatment, and may be laminated. The fibers of the fiber web are each other. The heat treatment may be, for example, hot air processing by hot air blowing, hot roll processing (hot stamping), or heat treatment using infrared rays. The hot air processing is a device in which a hot air of a specific temperature is sprayed onto a laminated fiber web, and can be carried out, for example, using a hot air through heat treatment machine or a hot air spray type heat treatment machine. When the nonwoven fabric of the present embodiment is required to have bulkiness, it is preferably manufactured by performing hot air processing. The specific volume reduction can be comparatively suppressed by the hot air processing.

The heat treatment temperature (for example, the temperature of the hot air) may be a softening or melting temperature of the highest melting point component among the components constituting the first fiber and the components constituting the second fiber. For example, the heat treatment temperature is a temperature above the melting point of the component. Further, the heat treatment temperature is preferably a temperature at which at least the components constituting the surface of the water-repellent fiber are not melted or softened. This is because the components constituting at least the surface of the water-repellent fiber do not have a function as an adhesive component. For example, when both the first fiber and the second fiber contain polyethylene as a component and polyethylene is used as a component, the heat treatment temperature may be 130 to 150 °C.

[use]

The sheet for absorbent articles of the present embodiment can be used as a member constituting an absorbent article. For example, the sheet for absorbent articles of the present embodiment can be used as a surface sheet (also referred to as a top sheet) constituting an absorbent article, an intermediate sheet, and a sheet coated with an absorbent core (also referred to as an SAP sheet, cable). A member such as a pericardium sheet, a back sheet, or the like. The sheet for absorbent articles according to the present embodiment can rapidly transfer excreted body fluid such as urine or menstrual blood absorbed by the surface sheet to the absorbent body, and is preferably used for the intermediate sheet by preventing the liquid from flowing back from the absorbent body. The absorbent article includes, for example, a disposable diaper (including a baby, a care), a sanitary napkin, a postpartum care pad, and an incontinence pad, but the absorbent article is not limited thereto, and the absorbent of the embodiment. The sheet for articles can be used to absorb any articles used for body fluids excreted by the human body.

In the sheet for an absorbent article of the present embodiment, in particular, when a surface sheet or an intermediate sheet is used, it is preferable to use a sheet for an absorbent article such that the first fiber layer is disposed close to the skin side of the user. The surface sheet or intermediate sheet must rapidly transfer the excreted body fluid (liquid) to the absorbent body. In order to satisfy such a demand, it is preferable to arrange the first fibrous layer which is provided with the water-repellent fiber to improve the retention of liquid retention on the skin side.

(absorbent article)

As another embodiment of the present invention, an absorbent article will be described. The absorbent article according to the embodiment has a surface sheet, a back sheet, an absorbent body disposed between the top sheet and the back sheet, and an absorbent article disposed between the top sheet and the absorbent sheet. The intermediate sheet is a sheet for an absorbent article according to the embodiment described above.

The surface sheet is a liquid-permeable non-woven fabric or an apertured film, and has a function of capturing excreted body fluid and rapidly moving the captured excreted body fluid toward the absorber side. In the present embodiment, when the sheet for an absorbent article of the prior embodiment is used as an intermediate sheet, the surface sheet may be a fiber having a fiber diameter smaller than that of the water-repellent fiber contained in the intermediate sheet (conveniently referred to as "Small diameter fiber" is not woven. By combining with such a surface sheet, the combination of the surface sheet and the intermediate sheet has a fiber diameter gradient, so that the liquid can be easily transferred from the surface sheet to the intermediate sheet.

The small-diameter fiber system has, for example, a fiber diameter of 5.0 μm or more smaller than the fiber diameter of the water-repellent fiber, preferably a fiber diameter of 7.0 μm or less, and more preferably a fiber diameter of 10.0 μm or less. The fiber diameter difference between the small-diameter fiber and the water-repellent fiber can be, for example, 20.0 μm or less, preferably 17.0 μm or less, and more preferably 15.0 μm or less. The small diameter fiber may contain two or more types of fiber diameters.

In addition to the small-diameter fibers, the surface sheet may further contain fibers having a fiber diameter smaller than the fiber diameter of the first fibers contained in the intermediate sheet (conveniently referred to as "fine-diameter fibers"). When the surface sheet further contains fine-diameter fibers, the liquid can be easily transferred from the surface sheet to the intermediate sheet, and the surface sheet can be made to have a good touch. The fine fiber type has, for example, a fiber diameter smaller than the fiber diameter of the first fiber by 0.5 μm or more, preferably a fiber diameter of 2.0 μm or less, and more preferably a fiber diameter of 4.0 μm or less. The fiber diameter difference between the small-diameter fiber and the first fiber may be, for example, 12.0 μm or less, preferably 9.0 μm or less, and more preferably 6.0 μm or less. The fine fiber may contain two or more types of fiber diameters.

The non-woven fabric constituting the surface sheet may contain, for example, 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more. The non-woven fabric constituting the surface sheet may contain, for example, 100% by mass or less, preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less. The nonwoven fabric constituting the surface sheet may contain, for example, 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more. The nonwoven fabric constituting the surface sheet may contain, for example, 90% by mass or less, preferably 80% by mass or less, and more preferably 70% by mass or less. The non-woven fabric constituting the surface sheet may contain fibers having a fiber diameter larger than that of the small-diameter fibers, and the ratio thereof may be, for example, 20% by mass or less.

When the surface sheet contains two or more kinds of small-diameter fibers having different fiber diameters or contains small-diameter fibers and fine-diameter fibers, the mixing ratio thereof is not particularly limited. For example, the ratio of each fiber can be selected in such a manner that the larger the fiber diameter is, the larger the content thereof is. Or all of the fibers can be mixed in the same ratio. For example, when the surface sheet contains small-diameter fibers and fine-diameter fibers, the mixing ratio is in mass ratio (small-diameter fiber) from the viewpoint of ensuring good transferability of the liquid to the intermediate sheet and good touch of the surface sheet. The fine fiber is, for example, 20:80 to 80:20, preferably 30:70 to 70:30.

Small-diameter fibers and fine-diameter fibers are less water-repellent than water-repellent fibers. An example of such a fiber is as described in relation to the first fiber contained in the intermediate sheet.

When the fiber contained in the surface sheet is a synthetic fiber containing a hydrophilic fiber treating agent, a fiber containing a hydrophilic fiber treating agent having different water resistance can be mixed. By mixing fibers containing a water-resistant hydrophilic fiber treating agent, liquid retention or liquid reflux in the surface sheet can be reduced, and a decrease in the liquid absorption speed when the liquid is repeatedly absorbed can be suppressed.

The surface sheet contains two or more kinds of fibers having different fiber diameters, and when the fibers are synthetic fibers containing a hydrophilic fiber treating agent, the fiber diameter is compared with the hydrophilic fiber treating agent contained in the fiber having a smaller fiber diameter. The hydrophilic fiber treatment agent contained in the larger fiber may be one which exhibits higher water resistance. A fiber having a small fiber diameter is a fiber having a large specific surface area, and therefore has a tendency to contain more fiber treating agent than a fiber having a larger fiber diameter. Therefore, the variation in the amount of the fiber treating agent contained in the fiber having a smaller fiber diameter is increased. Further, since the hydrophilic fiber treating agent having a low water resistance is liable to fall off, if the water resistance of the hydrophilic fiber treating agent between the two fibers is such that the difference is small, the hydrophilic fiber treating agent is preferably made smaller by the fiber diameter. The fibers are detached. Therefore, if such a difference is made between the water resistance of the hydrophilic fiber treating agent between the two fibers, the amount of the hydrophilic fiber treating agent that passes through the surface sheet can be adjusted, and the surface sheet after the liquid passing can be improved. Water repellency. Thereby, liquid retention or liquid reflux in the surface sheet can be further reduced.

As described above, in order to rapidly transfer the excreted body fluid absorbed by the surface sheet to the absorbent body and absorb the excreted body fluid in the absorbent body, the intermediate sheet is placed between the surface sheet and the absorbent body. When the excretion body fluid is a low viscosity (for example, urine), the intermediate sheet is preferably transferred to the absorber while diffusing and excreting the body fluid. In particular, when the exhaled body fluid is urine, the amount of excretion per one time is large, so that the colloid blocking phenomenon of the absorber can be prevented by diffusing the intermediate sheet. When the excretion body fluid is colored like a menstrual blood and the viscosity is high, in order to improve the concealability of the absorbent article, the intermediate sheet is preferably transferred to the absorber without diffusing the excrement liquid. In the present embodiment, the intermediate sheet may be a sheet for an absorbent article according to the embodiment described above. The back sheet may be a sheet composed of a liquid-impermeable material. The back sheet may or may not be breathable.

The absorber may be, for example, a non-woven fabric composed of one or a plurality of members selected from a polymer absorbent (also referred to as SAP, generally a powder), a pulverized pulp, a fiber assembly, and a film. The film-selected core cladding sheet is covered. Alternatively, the absorber may be formed of a core which is not covered by the core cladding sheet and which is only composed of an absorbent core.

As described above, the absorbent article includes, for example, a disposable diaper, a sanitary napkin, a postpartum care pad, and an incontinence pad, but the absorbent article of the present embodiment is not limited thereto.

 (Example)  

The present embodiment will be described below by way of examples.

The fiber system used in this example was prepared as follows.

The water-repellent fiber 1 is a single fiber composed of a polypropylene having a fiber diameter of 31.2 μm and a fiber length of 51 mm (melting point: 158° C.), and the water-repellent fiber treating agent on the surface of the fiber has 0.4% by mass of the fiber mass attached thereto. A fiber of a fiber treating agent for a potassium salt of a C16 alkyl phosphate. The contact angle is 112.3°.

The water-repellent fiber 2 is a single fiber composed of a polypropylene having a fiber diameter of 15.7 μm and a fiber length of 38 mm (melting point: 159 ° C), and the water-repellent fiber treating agent on the surface of the fiber is 0.4% by mass based on the fiber mass. A fiber of a fiber treating agent for a potassium salt of a C16 alkyl phosphate. The contact angle is 116.3°.

Water-repellent fiber 3: a core material having a fiber diameter of 30.8 μm and a fiber length of 64 mm is a crystalline polypropylene (melting point: 160 ° C), a sheath component of high-density polyethylene (melting point: 132 ° C), and a core component and a sheath component in the fiber cross section. Concentrically arranged core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40), the water-repellent fiber treatment agent on the fiber surface is 0.4% by mass of potassium C16 alkyl phosphate attached to the fiber mass. A fiber of a salt fiber treatment agent (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (H)). The contact angle was 109.6°.

Water-repellent fiber 4: A solvent-spun cellulose fiber having a fiber diameter of 12.1 μm and a fiber length of 38 mm, and a fiber having a water-repellent fiber treating agent adhered to the surface of the fiber (trade name: TENCEL (registered trademark) Biosoft) manufactured by LENZING Co., Ltd.

Water-repellent fiber 5: a single fiber composed of polypropylene having a fiber diameter of 30.8 μm and a fiber length of 64 mm (melting point: 160 ° C), and 0.4% by mass of a fiber treating agent having a potassium C16 alkylate salt adhered to the fiber mass. Fiber. The contact angle was 113.2°.

Fiber 1: The core component of the fiber diameter of 19.4 μm and the fiber length of 51 mm is polyethylene terephthalate (melting point 260 ° C), the sheath component is high density polyethylene (melting point 132 ° C), and the core component and sheath of the fiber section. The composition is a concentrically arranged core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40), and the hydrophilic fiber treating agent on the fiber surface is 0.35 mass% of phosphoric acid-containing C12 alkane attached to the fiber mass. A fiber of a water-resistant hydrophilic fiber treating agent of an ester potassium salt (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)). The contact angle is 53.3°.

Fiber 2: The core component of the fiber diameter of 21.6 μm and the fiber length of 51 mm is polyethylene terephthalate (melting point 260 ° C), the sheath component is high density polyethylene (melting point 132 ° C), and the core component and sheath of the fiber section The composition is a core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40) in a concentric arrangement, and the hydrophilic fiber treatment agent on the surface of the fiber is 0.34% by mass of a C12 alkane-containing phosphate attached to the fiber mass. A fiber of a water-resistant hydrophilic fiber treating agent of an ester potassium salt (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)). The contact angle was 52.9°.

Fiber 3: The core component of the fiber diameter of 15.6 μm and the fiber length of 45 mm is polyethylene terephthalate (melting point 260 ° C), the sheath component is high density polyethylene (melting point 132 ° C), and the core component and sheath of the fiber section The composition is a concentrically arranged core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40), and the hydrophilic fiber treating agent on the fiber surface is 0.35 mass% of phosphoric acid-containing C12 alkane attached to the fiber mass. A fiber of a non-water-resistant hydrophilic fiber treating agent of an ester potassium salt (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)). The contact angle is 60.2°.

Fiber 4: The core component having a fiber diameter of 19.4 μm and a fiber length of 51 mm is polyethylene terephthalate (melting point: 260 ° C), the sheath component is high-density polyethylene (melting point: 132 ° C), and the core component and sheath of the fiber cross section. The composition is a concentrically arranged core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40), and the hydrophilic fiber treating agent on the fiber surface is 0.35 mass% of phosphoric acid-containing C12 alkane attached to the fiber mass. A fiber of a non-water-resistant hydrophilic fiber treating agent of an ester potassium salt (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)). The contact angle is 60.5°.

In addition, the fiber diameter of each fiber was obtained by the following method: The side surface of the fiber was observed using a scanning electron microscope (SEM, manufactured by Hitachi, Ltd., trade name "S-3500N", magnification: 50 to 500 times), and any 100 was measured. The fiber diameter of the fiber is calculated and its average value is calculated.

(Examples 1 to 8 and Comparative Examples 2 to 4)

The fibers shown in Tables 1 to 3 were used as the water-repellent fibers, the first fibers, the second fibers, and other fibers, and the first fiber web to be the first fiber layer and the second fiber layer were produced by using a parallel carding machine. 2 fiber mesh. The target unit weights of the fiber web are shown in Tables 1 and 2, respectively. The first fiber web and the second fiber web were superposed to form a laminated fiber web, and the laminated fiber web was heat-treated for 12 seconds in a hot air-through heat treatment machine set to a temperature of 135 ° C, and the first fiber web and the second fiber were used. The polyethylene resin component of the fiber 1 and/or the fiber 2 contained in the net and the fibers are respectively obtained, and a nonwoven fabric composed of the first fiber layer and the second fiber layer is obtained. Further, since the unit weight of the actually manufactured non-woven fabric is not necessarily the target unit weight due to the error, the unit weight (measured unit weight) of the actually obtained non-woven fabric is also shown in Tables 1 to 3 in several examples and comparative examples.

(Comparative Example 1)

Only fiber 1 was used and a web was made using a parallel card. The target weight per unit of the fiber web is 50 g/m ² . The obtained fiber web was heat-treated for 12 seconds in a hot air through heat treatment machine set to a temperature of 135 ° C, and a non-woven fabric having a single-layer structure was obtained by the polyethylene resin component of the fiber 1 and the fibers. In Table 2, the column of the second fiber layer is conveniently referred to as the type, ratio, and unit weight of the fiber used in Comparative Example 1.

The thickness and specific volume of the non-woven fabrics obtained in Examples 1 to 8 and Comparative Examples 1 to 4, the tensile strength in the longitudinal direction (machine direction, also referred to as MD direction) of the nonwoven fabric, and the stress at 10% elongation were measured, and the liquid absorption performance was evaluated. Touch. These results are shown in Tables 1 and 2. Further, these measurements and evaluations were carried out according to the following methods.

(thickness, specific volume)

The thickness measurement system thickness (trade name THICKNESS GAUGE MODEL CR-60A, Daiei Kagaku Seiki Seisakusho Co., Ltd.), was measured in a state where a load of 2.94cN sample is applied per 1cm ^2. The specific volume is calculated from the unit weight and thickness.

(tensile strength, stress at 10% elongation)

According to the JIS L 10966.12.1A method (striping method), a tensile test was carried out using a constant-speed tensile tester with a width of 5 cm of the test piece, a clamp interval of 10 cm, and a tensile speed of 30 ± 2 cm/min. Elongation stress at 10% elongation and strength at break. The tensile test was carried out in the longitudinal direction of the nonwoven fabric in the direction of stretching.

(liquid absorption performance: the first evaluation method)

 <Production of surface sheet>  

In an absorbent article (for example, a disposable diaper or the like) for absorbing a liquid having a low viscosity such as urine, in order to evaluate the liquid absorbing performance when the intermediate sheet is used, the suction is evaluated in a state where the sample is placed under the surface sheet. Liquid properties. The surface sheets used for evaluating the liquid absorption performance were produced in the following order.

Prepare the following two types of fibers.

Fiber A: a core component having a fiber diameter of 15 μm and a fiber length of 45 mm is polyethylene terephthalate (melting point: 260° C.), a sheath component is high-density polyethylene (melting point: 132° C.), and a core component and a sheath component in the fiber cross section. The core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40) which is concentrically arranged is a water-resistant hydrophilicity containing 0.40% by mass of a potassium C12 alkyl phosphate salt adhered to the fiber surface with respect to the fiber mass. Fiber of fiber treatment agent (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)).

Fiber B: The core component having a fiber diameter of 19.2 μm and a fiber length of 51 mm is polyethylene terephthalate (melting point: 260 ° C), the sheath component is high-density polyethylene (melting point: 132 ° C), and the core component and sheath of the fiber cross section. The composition is a concentrically arranged core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40), which is a water-resistant hydrophilic substance containing a potassium C12 alkylate salt of 0.40% by mass attached to the fiber surface with respect to the fiber mass. Fiber of the fiber treatment agent (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)).

Using the fiber A, a web A having a unit weight of about 8 g/m ^{2 was} produced using a parallel card. Using fiber B, a web of B having a basis weight of about 12 g/m ^{2 was} produced using a parallel card. The laminated fiber web was produced by superimposing the fiber web A and the fiber web B, and the laminated fiber web was heat-treated in a hot air-through heat treatment machine set at 135 ° C for 12 seconds to obtain a nonwoven fabric having a unit weight of 18.2 g/m ² and a thickness of 1.32 mm. This non-woven fabric was used as the surface sheet.

<Evaluation of liquid absorption speed and prevention of liquid reflowability>

(1) In order to measure the liquid absorption time and the liquid return flow rate, the following items were prepared.

Absorber: As the absorber, three sheets of the product name ListerPaper (Grade 989, 10 cm × 10 cm) manufactured by MEZGER Inc. were used.

Physiological saline: An aqueous sodium chloride solution prepared so as to have a sodium chloride concentration of 0.9% by weight was used as physiological saline. The viscosity is 0.7 mPa‧s.

Filter paper: manufactured by Toyo Filter Co., Ltd., trade name ADVANTEC (registered trademark) No. 2, 10 cm × 10 cm.

Weight: 5kg.

Plate: made of acrylic resin, 125 mm × 125 mm, thickness 5 mm.

Measuring machine: Lister manufactured by Lenzing Instruments Co., Ltd. (hereinafter referred to as Lister tester only.)

(2) Method

The liquid absorption time and the liquid return flow rate were measured in the following order.

(i) The surface sheet and the non-woven fabric (the nonwoven fabric of the embodiment or the comparative example) cut into 10 cm × 10 cm (the longitudinal direction × the transverse direction) are placed on the absorbent body, and are attached to the measuring device in this state. The nonwoven fabric is disposed such that the second fiber layer is in contact with the absorber.

(ii) Into the installed non-woven fabric, 5 ml of physiological saline was dropped using a Lister tester. At this time, the time from the non-woven fabric surface to the physiological saline solution (the physiological saline solution was transferred from the non-woven fabric to the absorbent body under the non-woven fabric, and the liquid physiological saline was not confirmed on the surface of the non-woven fabric) was measured by a Lister tester (liquid absorption time). . The shorter the aspiration time, the higher the pipetting speed.

(iii) After measuring the liquid absorption time, the plate of the Lister tester was taken out, three pieces of filter paper were placed, and the weight was placed thereon for 20 seconds.

(iv) After 2 minutes, the filter paper was taken out, the mass of the filter paper absorbing physiological saline was measured, and the mass of the filter paper placed on the non-woven fabric was subtracted, and the liquid return flow was calculated. The smaller the liquid return flow rate, the higher the liquid reflow resistance is prevented.

<Preventing liquid retention>

(1) A non-woven fabric (non-woven fabric of the example or the comparative example) was cut into 10 cm × 10 cm (vertical direction × transverse direction), and completely immersed in a physiological saline solution (30 cm × 25 cm × 8 cm) in a container for 15 minutes.

(2) Remove the non-woven fabric and air dry for 5 minutes in the air.

(3) Calculate the liquid holding amount of the non-woven fabric from the quality of the non-woven fabric after air drying and the quality of the non-woven fabric before impregnation.

(4) The liquid holding amount was divided by the unit weight, and the liquid holding amount per unit weight was calculated, and the liquid retention resistance was evaluated by the value thereof. The smaller the liquid holding amount per unit weight, the higher the liquid retention property is prevented.

(liquid absorption performance: the second evaluation method)

The wicking properties were evaluated using actual diapers sold.

(1) A surface sheet of a diaper (manufactured by Kao Co., Ltd., trade name merries) and two sheets of the sheet under the surface sheet were exposed to expose the absorber, and the absorbent body was cut to have a size of 240 mm × 72 mm ( Non-woven fabric in the longitudinal direction × transverse direction) (non-woven fabric of the embodiment or the comparative example). The nonwoven fabric is placed so that the second fiber layer is in contact with the absorber. The surface sheet which is the same as the user of the first evaluation method as the surface sheet is provided thereon, and the nonwoven fabric of the embodiment or the comparative example functions as an intermediate sheet. A glassware for liquid passage (a cylindrical shape having a height of 75 mm, an inner diameter of 25 mm, and a thickness of 5 mm) was placed on the surface sheet, and 50 ml of ion-exchanged water was poured into the glassware for liquid passage. The time required for the liquid to be seen from the surface of the non-woven fabric (liquid absorption time) was measured. The shorter the aspiration time, the higher the pipetting speed.

(2) After measuring the liquid absorption time, 30 pieces of filter paper (manufactured by Toyo Filter Co., Ltd., trade name: ADVANTEC (registered trademark) No. 2, 10 cm × 10 cm) were placed, and a weight of 5 kg was placed on the filter paper. After the weight was placed for 20 seconds, the filter paper was taken out, the mass of the filter paper absorbing the physiological saline solution was measured, and the mass of the filter paper before the non-woven fabric was placed was measured, and the liquid return flow rate was calculated. The smaller the liquid return flow rate, the higher the liquid reflow resistance is prevented.

(3) After (1) measuring the liquid absorption time, the above (1) and (2) were further repeated after 30 minutes, and the second and third liquid absorption time and liquid return flow rate were obtained. The second and third aspiration time measurement intervals were all 30 minutes.

(touch)

A sensory evaluation was performed to evaluate the touch of the non-woven fabric. The evaluation criteria are as follows.

+++: Soft and tingling.

++: Soft but tingling.

+: Hard and tingling.

As shown in Tables 1 to 3, when the liquid absorption performance evaluated by the first evaluation method was observed, compared with Comparative Example 1, any of Examples 1 to 6 showed almost no difference in the liquid absorption speed, and liquid reflux was compared. Less, showing better resistance to liquid reflow. Further, compared with Comparative Example 1, any of Examples 1 to 6 had a small amount of liquid retention per unit weight, and showed better liquid retention resistance. Compared with Comparative Example 1, Examples 7 and 8 exhibited less liquid backflow and showed better liquid recirculation resistance. These results are considered to be because Examples 1 to 8 have the first fibrous layer containing the water repellent fiber and the first fiber.

As is clear from the results of Examples 1 to 5, the liquid recirculation flow rate tends to be small as the ratio of the water-repellent fibers in the first fiber layer is larger, and the liquid retention amount per unit weight is small, indicating better retention of liquid retention. . However, the greater the proportion of the water-repellent fibers in the first fiber layer, the lower the tensile strength and the stress at the 10% elongation. This phenomenon is considered to be due to the fact that the ratio of the first fibers which function as the fibers to each other becomes smaller, and the number of points decreases.

When the liquid absorption performance evaluated by the second evaluation method was observed, the liquid absorption speeds of Examples 2 and 4 were higher than those of Comparative Examples 2 and 3, and the liquid return flow rate was less, indicating better liquid recirculation resistance. In the combination of Example 2 and Comparative Example 2, and the combination of Example 4 and Comparative Example 3, only the fiber diameter of the water-repellent fiber used was different, and the other structures were the same. In this case, the fiber diameter of the water-repellent fiber affects the liquid absorption performance, and the water-repellent fiber using the larger fiber diameter improves the liquid absorption performance. The reason why the liquid return flow becomes large when the fiber diameter of the water-repellent fiber is small is considered to be that the liquid is held in the space between the fine fibers formed by the finely-drawn water-containing fibers, and the retained liquid permeates the surface due to the pressurization. Therefore. Further, as is clear from the results of Examples 2 and 3, the larger the ratio of the water-repellent fibers in the first fiber layer, the smaller the liquid return flow rate tends to be.

In Example 6, the fiber diameter of the first fiber was larger than the fiber diameter of the first fiber used in the other examples. However, the liquid reflux flow rate was the same as that of the other examples, and was smaller than that of Comparative Example 1, and Example 6 also showed good prevention of liquid reflowability.

In the seventh embodiment, the core-sheath combination is a core-sheath type composite fiber of crystalline polypropylene/high-density polyethylene as the water-repellent fiber, and therefore the sheath component of the water-repellent fiber also functions as a bonding component. Therefore, in Example 4, which is the same as the ratio of the water-repellent fiber and the first fiber, the number of points in the seventh embodiment is large. This can be confirmed by observing the surface of the nonwoven fabric with an electron microscope. The electron micrographs (60 times) of the nonwoven fabric surfaces of Example 4 and Example 7 are shown in Fig. 1 and Fig. 2, respectively. Then, the difference in the number of points was expressed by the touch, and the touch of Example 7 was inferior to that of Example 4.

In Comparative Example 4, a solvent-spun cellulose fiber to which a water-repellent fiber treating agent was attached was used as the water-repellent fiber. In Comparative Example 4, the liquid return flow rate evaluated by the first evaluation method was larger than that of the respective examples. This phenomenon is considered to be that the cellulose fibers used in Comparative Example 4 exhibit the original hydrophilicity if the water-repellent fiber treatment agent is not attached.

(Examples 9 to 14)

Using the fibers shown in Tables 4 and 5 as the water-repellent fibers, the first fibers, and the second fibers, a first fiber web constituting the first fiber layer and a second fiber web constituting the second fiber layer were produced using a parallel carding machine. The target unit weights of the fiber web are shown in Tables 4 and 5, respectively. The first fiber web and the second fiber web were superposed to form a laminated fiber web, and the laminated fiber web was heat-treated at a temperature of 135 ° C for 12 seconds, and the first fiber web and the second fiber web were respectively subjected to heat treatment. The polyethylene resin component containing the fiber 3 or the fiber 4 is followed by the fibers to obtain a nonwoven fabric composed of the first fiber layer and the second fiber layer. Further, the unit weight of the non-woven fabric actually produced is not necessarily the target unit weight due to an error, and the unit weight (measured unit weight) of the nonwoven fabric actually obtained in each of the examples and the comparative examples is also shown in Tables 4 and 5.

(Comparative examples 5 to 8)

Fibers 3 and fibers 4 were used, respectively, and a web was produced using a parallel carding machine. The target weight per unit of the fiber web is 30 g/m ² . The obtained fiber web was heat-treated for 12 seconds in a hot air-through heat treatment machine set to a temperature of 135 ° C, and a non-woven fabric having a single-layer structure was obtained by the polyethylene resin component of the fiber 3 and the fiber 4 and the fibers. In Table 5, the types, ratios, and unit weights of the fibers used in Comparative Examples 5 to 8 are shown in the column of the second fiber layer.

The thickness and specific volume of the nonwoven fabric obtained in Examples 9 to 14 and Comparative Examples 5 to 8 were measured, and the liquid absorption performance was evaluated. These results are shown in Tables 4 and 5. Further, the thickness and specific volume were evaluated by the methods described in Examples 1 to 8 and Comparative Examples 1 to 4. The liquid absorption performance was evaluated according to the following method.

(liquid absorption performance: the third evaluation method)

In an absorbent article (for example, a sanitary napkin or the like) for absorbing a liquid having a high viscosity such as menstrual blood, in order to evaluate the liquid absorbing performance when used as an intermediate sheet, the sample is placed under the surface sheet. Evaluation of the liquid absorption performance. The two types of surface sheets used for evaluating the liquid absorption performance were produced in the following order.

[Surface Sheet A]

Prepare the following two types of fibers.

Fiber α: a core component having a fiber diameter of 16.0 μm and a fiber length of 45 mm is polyethylene terephthalate (melting point: 260° C.), a sheath component is high-density polyethylene (melting point: 132° C.), and a core component and sheath in the fiber cross section. The composition is a concentrically arranged core-sheath type composite fiber (composite ratio (core/sheath, mass ratio) 60/40), which is a non-water resistant material containing 0.40% by mass of a potassium C12 alkyl phosphate salt adhered to the fiber surface with respect to the fiber mass. A fiber of a hydrophilic fiber treating agent (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (SH)).

Fiber β: The core component of the fiber diameter of 19.1 μm and the fiber length of 38 mm is polyethylene terephthalate (melting point 260 ° C), and the sheath component is linear low-density polyethylene (melting point 120 ° C) and low-density polyethylene. (melting point: 106 ° C) (mass ratio (linear low-density polyethylene / low-density polyethylene) is 85/15), and the core component and the sheath component are eccentric core sheaths with an eccentricity of 25% in the eccentric arrangement. Composite fiber (composite ratio (core/sheath, volume ratio) 50/50) is a fiber having a water-resistant hydrophilic fiber treatment agent containing 0.40% by mass of a potassium C12 alkyl phosphate salt adhered to the fiber surface with respect to the fiber mass ( Made by Daiwabo Polytec Co., Ltd., trade name NBF (SL) V).

The fiber α was mixed at 60% by mass and the fiber β was 40% by mass, and a parallel carding web was produced using a parallel card at a target unit weight of 25 g/m ² .

The parallel carding web was heat-treated at 132 ° C for about 15 seconds using a hot air through heat treatment machine to thermally fuse the fiber α and the sheath component of the fiber β to obtain a nonwoven fabric.

The nonwoven fabric was subjected to thickness processing for 10 days at a load of 2,400 kg per 1 m ² to obtain a surface sheet A for evaluation. The surface sheet A had a basis weight of 23.0 g/m ² and a thickness of 0.53 mm.

[Surface Sheet B]

The following fiber γ was prepared.

Fiber γ: a core component having a fiber diameter of 14.8 μm and a fiber length of 38 mm is polypropylene (melting point: 160° C.), a sheath component is high-density polyethylene (melting point: 132° C.), and a core component and a sheath component are concentrically arranged in the fiber cross section. The sheath-type composite fiber (composite ratio (core/sheath, mass ratio) 60/40) is a non-water-resistant hydrophilic fiber treatment agent containing 0.40% by mass of a potassium C12 alkyl phosphate salt adhered to the fiber surface with respect to the fiber mass. Fiber (manufactured by Daiwabo Polytec Co., Ltd., trade name NBF (H)).

The surface sheet for evaluation B was produced in the same order as the production order of the surface sheet A for evaluation, except that the fiber γ was mixed at 60% by mass and the fiber β used for producing the surface sheet A was mixed at 60% by mass. The surface sheet B had a basis weight of 22.3 g/m ² and a thickness of 0.53 mm.

(liquid absorption performance: the third evaluation method)

The liquid absorbing performance was evaluated using physiological cotton wool which was actually sold.

(1) The surface sheet of the sanitary napkin (manufactured by Kimberly-Clark, trade name "Super Suck") and the two sheets under the surface sheet are exposed to the absorber, and the absorbent body is cut to 240 mm. ×72 mm (longitudinal direction × transverse direction) non-woven fabric (non-woven fabric of the example or the comparative example). The nonwoven fabric is disposed such that the second fiber layer is in contact with the absorber. In Examples 9 to 11 and Comparative Examples 5 to 6, the surface sheet for evaluation A was provided as a surface sheet, and in Examples 12 to 14 and Comparative Examples 7 to 8, an evaluation surface was provided thereon. The sheet B was used as a surface sheet, and the nonwoven fabric of the example functions as an intermediate sheet. On the surface sheet, a plate with a note into the cylinder (having a height of 75 mm, an inner diameter of 25 mm at the upper portion of the cylinder, and a cylindrical portion having an inner diameter of 10 mm at the lower portion of the cylinder) was placed, and 6.0 cc was injected into the injection cylinder of the sheet into the cylinder. Artificial menstrual blood (viscosity 8mPa‧s, temperature 37 °C). The time required for the liquid to be seen from the surface of the non-woven fabric (liquid absorption time) was measured. The shorter the aspiration time, the higher the pipetting speed. Further, the composition of the artificial menstrual blood is 12.30% by mass of glycerin, 85.18% by mass of ion-exchanged water, 0.45 mass% of CMC (sodium carboxymethylcellulose), 0.97 mass% of NaCl (sodium chloride), and Na ₂ CO ₃ (sodium carbonate). 1.04% by mass and Qinghai moss powder 0.06% by mass.

(2) When the above-described liquid absorption time was measured, the artificial menstrual blood was injected for 5 minutes, and the length of the artificial menstrual blood absorbed in the longitudinal direction of the non-woven fabric of the example was measured as the diffusion length. The smaller the value of the diffusion length, the less the color of the menstrual blood in the sanitary napkin is, and the higher the concealability.

(3) When the time of the above-mentioned liquid absorption was measured, 10 minutes after the artificial menstrual blood was injected, a filter paper (manufactured by Toyo Filter Co., Ltd., trade name: ADVANTEC (registered trademark) No. 2, 10 cm × 10 cm) was placed on the non-woven fabric of the example. A weight of 1 kg (shape: square, 10 cm × 10 cm) was placed on the filter paper. After the weight was placed for 20 seconds, the filter paper was taken out, the mass of the filter paper absorbing artificial menstrual blood was measured, and the mass of the filter paper before being placed on the non-woven fabric was subtracted, and the liquid return flow was calculated. The smaller the liquid return flow rate, the higher the liquid reflow resistance and the higher the liquid retention property.

(4) Before the measurement of the liquid reflux flow rate, the surface of the surface sheet A for evaluation or the sheet B was observed, and the masking property (concealability) was evaluated according to the following criteria.

The "menstrual expansion" and "menstrual blood concentration" when the absorbent article was observed from the top sheet were scored by the following points.

 "menstrual expansion"  

2 points: The diffusion length is less than 4.0 cm.

1 point: The diffusion length is 4.0 cm or more and less than 6.0 cm.

0 point: The diffusion length is 6.0 cm or more.

 "menstrual blood concentration"  

2 points: The overall color is lighter.

1 point: The central color is darker and the surrounding color is lighter.

0: The overall color is thicker.

In each of the examples, two samples were observed, and the menstrual blood area and the menstrual blood concentration points were counted, and the corresponding points (the highest point of 8 points and the lowest point of 0 points) were evaluated for the masking property as follows. The evaluation was A with the highest masking property, and the evaluation was C with the lowest masking property.

A: 8~7.

B: 6~5 points.

C: 4~0 points.

As shown in Tables 4 and 5, in the comparison between Example 9 and Comparative Example 5, Examples 10 to 11 and Comparative Example 6, Example 12, Comparative Example 7, Example 13 to 14 and Comparative Example 8, Examples Either one of them has a small liquid return flow and shows better liquid recirculation resistance. Further, any of the examples showed better masking properties than the comparative examples. The reason for this is considered to be as follows: The nonwoven fabric of the embodiment has a first fibrous layer containing a water-repellent fiber having a large fineness and a fiber having a low water-repellent degree, so that the liquid is less likely to remain in the vicinity of the surface of the nonwoven fabric.

Examples 9 and 10 show a diffusion length less than that of Example 11, and Examples 12 and 13 show a diffusion length smaller than that of Example 14. The water-repellent fibers of Examples 9, 10, 12 and 13 were small in content, so that the liquid was strongly inhaled into the second fiber layer, and as a result, it was considered that the liquid diffusion of the first fiber layer was suppressed. Comparing Example 11 with Comparative Example 6, and Example 14 and Comparative Example 8, Example 11 and Example 14 each showed a smaller diffusion length, which is considered to be because the first fibrous layer contained water-repellent fibers. This results in a higher retention of liquid retention.

The nonwoven fabric of this embodiment includes the following aspects.

 (Speech 1)  

A sheet for an absorbent article comprising a first fibrous layer and a second fibrous layer on a main surface of the first fibrous layer, wherein the nonwoven fabric comprises a water-repellent fiber treating agent. a synthetic fiber (hereinafter referred to as "water-repellent fiber") and a fiber having a water-repellent degree lower than the water-repellent fiber (hereinafter referred to as "first fiber"), and the second fiber layer includes a low water-repellent degree In the fiber of the water-repellent fiber (hereinafter referred to as "second fiber"), the fiber diameter of the water-repellent fiber is 23.5 μm or more and 42 μm or less, and the fiber diameter of the first fiber is smaller than the fiber diameter of the water-repellent fiber, The ratio (% by mass) of the second fibers contained in the second fiber layer is larger than the ratio (% by mass) of the water-repellent fibers contained in the first fiber layer.

 (Surface 2)  

The sheet for an absorbent article according to aspect 1, wherein the fiber diameter of the second fiber is smaller than the fiber diameter of the water-repellent fiber.

 (Speech 3)  

The sheet for an absorbent article according to aspect 1 or 2, wherein the first fibrous layer contains the water-repellent fiber in a ratio of 5 mass% or more and 50 mass% or less.

 (Speech 4)  

The sheet for an absorbent article according to any one of the aspects 1 to 3, wherein the first fiber is a synthetic fiber containing a hydrophilic fiber treating agent.

 (Surface 5)  

The sheet for an absorbent article according to any one of the first aspect, wherein the constituent fibers are followed by a component constituting the first fiber and a component constituting the second fiber.

 (state 6)  

The sheet for an absorbent article according to the aspect 5, wherein the first fiber is a composite fiber comprising two or more components, and a component having the lowest melting point (hereinafter referred to as a "low melting component") constitutes at least a part of the surface of the fiber, and the low portion The melting point component has a melting point lower than a melting point of at least a component constituting the surface of the water-repellent fiber, and the constituent fibers are bonded to each other by the low-melting component.

 (Surface 7)  

The sheet for an absorbent article according to any one of the aspects 1 to 6, wherein the component constituting the water-repellent fiber does not have a function as a component of the fibers.

 (8)  

The sheet for an absorbent article according to any one of the aspects 1 to 7, wherein the water-repellent fiber is selected from the group consisting of a polyolefin resin, a polyester resin, an acrylic resin, and a polyamide resin. A single fiber made of one or more resins.

 (state 9)  

The sheet for an absorbent article according to any one of the first aspect, wherein the second fiber layer contains 50% by mass or more of the second fiber.

 (state 10)  

The sheet for an absorbent article according to any one of the first aspect, wherein the first fiber and the second fiber are the same fiber.

 (state 11)  

The sheet for an absorbent article according to any one of the aspects 1 to 10, wherein the first fibrous layer is disposed on a side close to a user's skin.

 (state 12)  

The sheet for an absorbent article according to any one of the aspects 1 to 11, which is an intermediate sheet, wherein the intermediate sheet has a surface sheet, a back sheet, and an absorption disposed between the surface sheet and the back sheet. The absorbent article of the body is disposed between the surface sheet and the absorber.

 (state 13)  

An absorbent article comprising a top sheet, a back sheet, an absorbent disposed between the top sheet and the back sheet, and an intermediate sheet disposed between the top sheet and the absorbent body, wherein the intermediate sheet The sheet is a sheet for an absorbent article according to any of the aspects 1 to 11.

 (State 14)  

The absorbent article according to aspect 13, wherein the absorbent article is a disposable diaper.

 (Figure 15)  

The absorbent article according to the aspect 13, wherein the absorbent article is a sanitary napkin.

 (industrial use)  

The sheet for absorbent articles of the present embodiment is excellent in balance, such as a liquid absorption rate, liquid reflow prevention, and liquid retention prevention. Therefore, the sheet for absorbent articles of the present embodiment is suitably used as an absorbent article having a surface sheet, a back sheet, and an absorbent member disposed between the top sheet and the back sheet, and is disposed on the surface sheet. Intermediate sheet between the body and the absorbent body.

Claims (15)

 A sheet for an absorbent article comprising a first fibrous layer and a second fibrous layer located on a main surface of one of the first fibrous layers, wherein the first fibrous layer comprises a water-repellent fiber treating agent a synthetic fiber (hereinafter referred to as "water-repellent fiber") and a fiber having a water-repellent degree lower than the water-repellent fiber (hereinafter referred to as "first fiber"), and the second fiber layer includes: a water-repellent degree a fiber lower than the water-repellent fiber (hereinafter referred to as "second fiber"), wherein the fiber diameter of the water-repellent fiber is 23.5 μm or more and 42 μm or less, and a fiber diameter of the first fiber is smaller than a fiber diameter of the water-repellent fiber, The ratio (% by mass) of the second fibers contained in the second fiber layer is larger than the ratio (% by mass) of the water-repellent fibers contained in the first fiber layer.    The sheet for absorbent articles according to claim 1, wherein the second fiber has a fiber diameter smaller than a fiber diameter of the water-repellent fiber.    The sheet for an absorbent article according to the first aspect of the invention, wherein the first fibrous layer contains the water-repellent fiber in a ratio of 5% by mass or more and 50% by mass or less.    The sheet for absorbent articles according to any one of claims 1 to 3, wherein the first fiber is a synthetic fiber containing a hydrophilic fiber treating agent.    The sheet for absorbent articles according to any one of claims 1 to 4, wherein the constituent fibers are followed by a component constituting the first fiber and a component constituting the second fiber.    The sheet for an absorbent article according to claim 5, wherein the first fiber is a composite fiber comprising two or more components, and a component having the lowest melting point (hereinafter referred to as "low melting component") constitutes a fiber surface. At least a part of the melting point of the low-melting component is lower than a melting point of at least a component constituting the surface of the water-repellent fiber, and the constituent fibers are bonded to each other by the low-melting component.    The sheet for absorbent articles according to any one of claims 1 to 6, wherein the components constituting the water-repellent fibers do not have a function as a component of the fibers.    The sheet for absorbent articles according to any one of claims 1 to 7, wherein the water-repellent fiber is a polyolefin resin, a polyester resin, an acrylic resin, and a polyamide resin. A single fiber composed of one or more resins selected in the group.    The sheet for absorbent articles according to any one of claims 1 to 8, wherein the second fiber layer contains 50% by mass or more of the second fiber.    The sheet for an absorbent article according to any one of claims 1 to 9, wherein the first fiber and the second fiber are the same fiber.    The sheet for absorbent articles according to any one of claims 1 to 10, wherein the first fibrous layer is disposed on a side close to a user's skin.    The sheet for absorbent articles according to any one of claims 1 to 11, which is an intermediate sheet, the intermediate sheet having a surface sheet, a back sheet, and a surface sheet disposed thereon The absorbent article of the absorbent material between the material and the back sheet is disposed between the surface sheet and the absorbent body.    An absorbent article comprising a top sheet, a back sheet, an absorbent disposed between the top sheet and the back sheet, and an intermediate sheet disposed between the top sheet and the absorbent body, wherein the intermediate sheet The sheet for an absorbent article according to any one of claims 1 to 11 of the invention.    The absorbent article of claim 13, wherein the absorbent article is a disposable diaper.    The absorbent article of claim 13, wherein the absorbent article is a sanitary napkin.