JP2019143285A - Nonwoven fabric for absorbent article and absorbent article - Google Patents

Abstract

To provide a nonwoven fabric for absorbent article exhibiting high diffusion preventing property along with high liquid-absorbing speed and high liquid-return preventing property with a good balance, and to provide an absorbent article using the same.SOLUTION: There is provided a nonwoven fabric for absorbent article, in which the nonwoven fabric comprises a first fiber and a second fiber. Initial contact angles A, B of surfaces of the first and the second fibers with water are 45 to 70° and 65 to 85° respectively, and the initial contact angle A is smaller than the initial contact angle B by 10° or more. Contact angles after permeation of water of surfaces of the first and the second fibers with water are 90 to 120° and 65 to 85° respectively. The nonwoven fabric comprises the first fiber of 30 mass% to 70 mass% and the second fiber of 70 mass% to 30 mass% based on the total weight of the nonwoven fabric. The absorbent article comprises the nonwoven fabric for absorbent article as a surface sheet.SELECTED DRAWING: None

Description

  The present disclosure relates to a nonwoven fabric for absorbent articles and an absorbent article including the nonwoven fabric.

  Nonwoven fabrics having various configurations have been proposed as sheets constituting absorbent articles such as disposable diapers, incontinence pads, sanitary napkins, panty liners (orimono sheets), that is, sheets for absorbent articles. For example, Patent Document 1 discloses a first layer that forms a skin contact surface and a second layer that is disposed on the absorber side for the purpose of providing a surface sheet that has a good touch in addition to excellent liquid return prevention properties. A top sheet having a two-layer structure is disclosed. For the purpose of providing a non-woven fabric having excellent bulk recoverability and a non-woven fabric having a liquid that quickly migrates to the absorbent and hardly leaves the liquid on the skin, Patent Document 2 Disclosed is a nonwoven fabric comprising an adhesive composite fiber.

JP 2006-305044 A JP 2011-127258 A

  The absorbent article generally includes a top sheet, a back sheet, and an absorbent body disposed between the top sheet and the back sheet, and further includes other members as necessary. The nonwoven fabric for absorbent articles may be required to have performance such as high liquid absorption speed and high liquid return prevention property depending on the mode in which it is used.

  A high liquid absorption rate is required for rapidly transferring excretory body fluids (hereinafter also simply referred to as “liquid”) such as urine or menstrual blood to the absorber. Therefore, “high liquid absorption speed” means that the liquid absorption time is shorter. In addition, since the absorbent article may be used continuously for a long time, it is required that the liquid absorption time is short not only in the initial stage (first absorption) but also in the second and subsequent absorptions. It is done.

  With respect to the absorbent article, “liquid return” means that the liquid that has once passed through the surface sheet and reached the absorber oozes again on the surface of the surface sheet. The greater the amount of liquid that oozes onto the surface due to such liquid return, that is, the greater the liquid return amount, the more uncomfortable the user is. Therefore, “high liquid return prevention” means that such a liquid return amount is smaller. The liquid return amount also includes the amount of liquid that oozes to the surface due to “liquid residue” in which the liquid does not reach the absorber and stays in the nonwoven fabric.

  Further, in some cases, the absorbent article requires not only a high liquid absorption rate and high liquid return prevention property, but also a high diffusion prevention property on the surface sheet. For example, in the case of a sanitary napkin or the like, when menstrual blood diffuses on the surface sheet, the color of blood becomes conspicuous, and the user feels uncomfortable. Therefore, “high diffusion preventing property” means that the diffusion length of the liquid measured on the top sheet is shorter. In addition to the initial (first absorption), the second and subsequent absorptions are required to have a short diffusion length.

  Then, this indication aims at provision of the nonwoven fabric for absorbent articles which has a high liquid absorption speed and high liquid return prevention property with high diffusion prevention property in good balance, and an absorbent article containing the same.

The present disclosure provides the following nonwoven fabric for absorbent articles.
A nonwoven fabric for absorbent articles, wherein the nonwoven fabric includes a first fiber and a second fiber,
The initial contact angle A between the fiber surface of the first fibers and water is 45 degrees to 70 degrees,
The initial contact angle B between the fiber surface of the second fiber and water is 65 degrees to 85 degrees,
The initial contact angle A is 10 degrees or more smaller than the initial contact angle B,
The contact angle after water permeation between the fiber surface of the first fiber and water is 90 degrees to 120 degrees,
The contact angle after water permeation between the fiber surface of the second fiber and water is 65 degrees to 85 degrees,
The non-woven fabric includes the first fibers in a proportion of 30% by mass to 70% by mass and the second fibers in a proportion of 70% by mass to 30% by mass based on the total mass of the non-woven fabric (however, The sum of the proportion of the first fibers and the proportion of the second fibers does not exceed 100% by mass),
Nonwoven fabric for absorbent articles.
Moreover, this indication provides the absorbent article containing said nonwoven fabric for absorbent articles as a surface sheet.

  According to the present disclosure, it is possible to obtain a nonwoven fabric for absorbent articles that has a high liquid absorption rate and high liquid return prevention property as well as a high anti-diffusion property and an absorbent article including the same.

FIG. 1 schematically shows a contact angle formed between a water droplet and a fiber (surface). FIG. 2 schematically shows a stainless steel plate for attaching water droplets to a nonwoven fabric sample in order to measure the contact angle after water permeation.

[Nonwoven fabric for absorbent articles]
The nonwoven fabric for absorbent articles of the present disclosure (hereinafter also simply referred to as “nonwoven fabric”) includes at least “first fibers” and “second fibers”. As described in detail below, the first fiber and the second fiber can be defined by the contact angle between the fiber surface and water. This is because the contact angle between the fiber surface and water represents the degree of hydrophilicity of the fiber surface (for example, the larger the contact angle, the lower the hydrophilicity of the fiber surface, and the smaller the contact angle). This indicates that the hydrophilicity of the fiber surface is higher), and the characteristics of the nonwoven fabric are closely related to properties such as “liquid absorption rate”, “liquid return prevention”, and “diffusion prevention”. Particularly in the nonwoven fabric for absorbent articles, the contact angle before and after water permeation, that is, the “initial contact angle” and the “contact angle after water permeation” described in detail below are important.

[Initial contact angle between fiber surface of first fiber and water and contact angle after water permeation]
The initial contact angle between the fiber surface of the first fibers and water (hereinafter referred to as “initial contact angle A”) is 45 degrees to 70 degrees. The angle is preferably 50 to 68 degrees, more preferably 55 to 65 degrees. When the initial contact angle A is within the above range, effects such as an improved liquid absorption speed can be obtained.
The contact angle after water permeation between the fiber surface of the first fiber and water is 90 to 120 degrees. Preferably it is 93 degrees-114 degrees, More preferably, it is 98 degrees-108 degrees. When the contact angle after water permeation is within the above range, effects such as reducing the liquid return amount by lowering the liquid residue or liquid return of the nonwoven fabric can be obtained.
As described above, the first fiber is characterized in that the contact angle value increases before and after permeation of water. Such a first fiber is preferably hydrophilic and non-durable (for example, a property in which the hydrophilicity is significantly reduced by contact with water (for example, as compared with the second fiber) as described in detail below. Case)) can be obtained by treating the fiber with the fiber treating agent. That is, in the first fiber, by using a non-durable fiber treatment agent, after water permeates, the hydrophilicity decreases and the value of the contact angle can be increased.
The increase in contact angle before and after water permeation is preferably, for example, 10 to 90 degrees. More preferably, it is 20 degrees to 70 degrees, and still more preferably 30 degrees to 50 degrees. When the increase in the contact angle is within the above range, effects such as reducing the liquid return amount by reducing the liquid residue or liquid return of the nonwoven fabric can be obtained.

[Initial contact angle between fiber surface of second fiber and water and contact angle after water permeation]
The initial contact angle between the fiber surface of the second fiber and water (hereinafter referred to as “initial contact angle B”) is 65 to 85 degrees. Preferably it is 67 degree-83 degree, More preferably, it is 69 degree-81 degree. When the initial contact angle B is within the above range, effects such as reducing the liquid return amount by reducing the liquid remaining property or liquid return property of the nonwoven fabric can be obtained.
The contact angle after water permeation between the fiber surface of the second fiber and water is 65 to 85 degrees. Preferably it is 67 degree-83 degree, More preferably, it is 69 degree-81 degree. When the contact angle after water permeation is within the above range, effects such as improvement in the liquid absorption speed during repeated liquid absorption can be obtained.
As described above, the second fiber is characterized in that the contact angle value is substantially the same before and after permeation of water. Such second fibers are obtained, for example, by treating the fibers with a hydrophilic and durable fiber treating agent, as will be described in detail below. That is, in the second fiber, the contact angle value can be made substantially the same even after water has permeated by using a durable fiber treatment agent. “The contact angle value is substantially the same” before and after water permeation means that the fluctuation of the contact angle value is within ± 5 degrees before and after water permeation. When the contact angle value is substantially the same before and after the permeation of water, effects such as an improvement in the liquid absorption speed during repeated liquid absorption can be obtained.

In the nonwoven fabric of the present disclosure, the initial contact angle A is 10 degrees or more smaller than the initial contact angle B. Preferably it is 11 to 20 degrees smaller, more preferably 12 to 18 degrees smaller. When the above difference is provided between the initial contact angles A and B, the liquid remaining property or liquid return property of the nonwoven fabric can be lowered while suppressing the decrease in the liquid absorption rate, and the liquid absorption rate and the liquid return prevention property And the like can be suitably achieved.
In order to make the initial contact angle A smaller than the initial contact angle B, for example, as described in detail below, the hydrophilicity that can be imparted by the fiber treatment agent used in the first fiber and the second contact fiber are used. It is conceivable to provide a difference in the hydrophilicity to be imparted so that the first fiber becomes more hydrophilic with the hydrophilicity that can be imparted by the fiber treatment agent. For example, the hydrophilicity of the first fiber may be higher than the hydrophilicity of the second fiber. For example, it is preferable to use a highly hydrophilic fiber treatment agent in the first fiber, or to use a low hydrophilic fiber treatment agent in the second fiber. Alternatively, it is particularly preferred to use both of them.

Furthermore, the nonwoven fabric of this indication is 30 mass%-70 mass% with respect to the total mass, Preferably it is 34 mass%-66 mass%, More preferably, it is a ratio of 38 mass%-62 mass%. And the second fiber is contained in an amount of 70% by mass to 30% by mass, preferably 66% by mass to 34% by mass, and more preferably 62% by mass to 38% by mass. However, the total of the ratio of the first fibers and the ratio of the second fibers does not exceed 100% by mass.
Moreover, the nonwoven fabric of this indication may contain the other fiber. The other fibers may be contained in an amount of, for example, 40% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total mass of the nonwoven fabric. Examples of the other fibers include fibers whose contact angle does not correspond to either the first fiber or the second fiber.
By blending the first fiber and the second fiber in the above ratio, the nonwoven fabric of the present disclosure may be provided with a high liquid absorption rate, a high diffusion prevention property, and a high liquid return prevention property in a balanced manner for the first time. it can.

[Measurement method of initial contact angle]
The initial contact angle between water and the fiber surface can be measured by the following method.
A measurement unit having a zoom lens (manufactured by Keyence Co., Ltd., model number: VH-Z100R) attached to the KEYENCE microscope VHX-1000 is fixed in a state where it is tilted horizontally. A non-woven fabric containing fibers that are objects of contact angle measurement is cut so that the length (MD direction) × width (CD direction) is 50 mm × 10 mm, and a measurement sample is prepared. With the measurement surface of the measurement sample facing upward, test the measurement sample so that the CD direction of the nonwoven fabric is perpendicular to the lens surface of the zoom lens (that is, the observation direction is parallel to the CD direction). Place it on the table and fix both ends with tape. Note that the observation direction (the direction in which the object is viewed through the zoom lens) is not particularly limited as long as the fiber is selected so as to extend in a direction orthogonal to the observation direction. Depending on the type of nonwoven fabric, the viewing direction may be a direction that forms an angle of 45 ° with the CD direction of the nonwoven fabric, for example.

  Next, water droplets of ion-exchanged water (water temperature of about 20 ° C.) are sprayed on the measurement sample using a spray that makes the mist size as constant and fine as possible. Within 5 seconds after spraying, a water droplet placed on the fiber surface is observed with a zoom lens at 50 to 1000 times depending on the fiber diameter of the fiber to be observed, and an image is captured. Spraying and image capture are repeated to obtain 20 images with clear water droplets. From the obtained images, select an image in which the fibers are horizontal. This is because the contact angle changes when the fiber is tilted. When the number of selected images is 10 or more, the contact angle is obtained using these images. If the number of images in which the fibers are leveled is less than 10, obtain 20 more images and select the image in which the fibers are leveled from among them. Repeat until the total number of images is 10 or more.

For example, as shown in FIG. 1, the contact angle is an angle formed by drawing a tangent line on the water drop at a position where the surface of the water drop that comes into contact with the air contacts the fiber, and the tangent line and the fiber. The contact angle is measured by image analysis processing software (for example, two-dimensional image analysis software “MicroMeasure” available from SCARA Co., Ltd.) or a protractor. The contact angle is measured in each of the selected images, and the average value (arithmetic average value) of them is obtained to obtain the contact angle of the fiber to be measured.
The contact angle may be measured by a method in which a target constituent fiber is taken out from the measurement surface and water droplets are sprayed on the constituent fiber without measuring using a nonwoven fabric.

Pay attention to the following points when measuring the contact angle.
(1) Measure the contact angle of a water drop placed on the fiber. The contact angle of water drops that hang down to the bottom of the fiber and water drops that span two or more fibers is not measured.
(2) When the fiber has a fine crimp such as a spiral shape, it is measured at a place where the crimp is small or the fiber is stretched to eliminate the crimped state.
(3) As described above, the measurement result of the contact angle is obtained by changing the place to be measured or the measurement sample, selecting 10 or more images in which the fibers are horizontal, and averaging the measured values. When the degree of hydrophilicity of the fiber is high, water droplets can move on the fiber when measuring the contact angle (ie, the shape of the water droplets can change). In this case, the “contact angle” is obtained in consideration of the movement situation.
Less than 40% of the total number of measurements (total number of measurement points where shooting of water droplets was attempted, total when water droplets moved during shooting and when they did not move) before reaching 20 contact angle measurement points When the water droplet moves, 10 or more images in which the fibers are horizontal are selected and the measured values are averaged to obtain the contact angle.
If the water droplets move at 40% or more of the total number of measurements before the contact angle is measured at 20 points, the contact angle is 20 ° or less.

[Measurement method of contact angle after water permeation]
The contact angle after water permeation is measured by the contact angle measurement method described above except that a non-woven fabric sample (measurement sample) is prepared as described below.
The nonwoven fabric is cut into a size of 22 cm in the vertical direction and 5 cm in the horizontal direction to produce a measurement sample. Next, a stainless plate shown in FIG. 2 in which holes with a diameter of 15 mm are formed at equal intervals (the distance between the centers of the holes is 20 mm) is prepared. Mark with 4 oily magic pens in the hole of the plate. Place the plate on the measurement surface of the measurement sample. While placing the stainless steel plate on the measurement sample, 0.04 ml of ion-exchanged water adjusted to about 20 ° C. is applied to the measurement surface of the measurement sample located at the center of the hole provided in the stainless steel plate, Drip using a burette. After the ion exchange water is dropped, the ion exchange water of the measurement sample is absorbed. After the dropped water droplets disappear from the surface of the measurement sample, the measurement sample is dried in an atmosphere of 20 to 50 ° C. In addition, after water droplets are dropped on the measurement sample, when the water droplets are absorbed, the portion where the water droplets remain may be sucked from the lower side to forcibly absorb the water in the lower layer.

  The dried measurement sample is cut along a straight line passing through points 1 and 2 of the stainless steel plate shown in FIG. From the cut surface of the measurement sample corresponding to the location where ion exchange water is dropped, ion exchange water of about 20 ° C. is sprayed by the above-described spraying, and water droplets are attached to the fibers of the measurement sample. Hereinafter, the contact angle after water permeation is measured by observing water droplets on the fibers of the measurement sample by the same method as the above-described contact angle measurement method.

[fiber]
There is no restriction | limiting in particular as a 1st fiber, a 2nd fiber, and another fiber, For example, the fiber demonstrated in detail below can be used without a restriction | limiting at all.

The raw material or material of the fiber is not particularly limited as long as the nonwoven fabric for absorbent articles targeted by the present disclosure can be obtained.
The fibers can include, for example, the following fibers: natural fibers such as cotton, silk, and wool; viscose rayon, cupra, and solvent-spun cellulose fibers (eg, Lenzungryocell® and Tencel®) Synthetic fibers such as polyolefin fibers, polyester fibers, polyamide fibers, (poly) acrylic fibers made of acrylonitrile, polycarbonate fibers, polyacetal fibers, polystyrene fibers, and cyclic polyolefin fibers. .
The fiber is not only a fiber made of a single type of resin but also a composite fiber made of two or more types of resins (for example, concentric or eccentric core-sheath type composite fiber, sea-island type composite fiber, side-by-side type composite fiber) ) Etc. can also be used.
In addition, when natural fiber is included, the fineness or the fiber diameter can be calculated according to the method of JIS L 1019 7.4.1 Micro Ney.

As the fibers, synthetic fibers are preferable, and polyester fibers, polyolefin fibers, and combinations thereof are more preferable. As long as the non-woven fabric targeted by the present disclosure can be obtained, the fibers can include regenerated fibers and / or natural fibers in the synthetic fibers.
The fiber is, for example, a polyester fiber such as polyethylene terephthalate; polyethylene (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene, ethylene-propylene copolymer, ethylene-butene-1-propylene ternary copolymer. Polyolefin fibers such as polymers; and combinations thereof can be included.

The polyethylene is more preferably high-density polyethylene because crimps can be easily imparted.
In the present disclosure, as will be described later, a fiber treatment agent can be used to impart hydrophilicity to the fiber.
These fibers can be used alone or in combination.

  When two kinds of fibers are combined, a fiber obtained by simply mixing the fibers or a core-sheath type composite fiber may be used. In the nonwoven fabric for absorbent articles of the present disclosure, it is preferable to use a composite fiber from the viewpoints of touch, texture, fluff, appearance, and the like. When the composite fiber is used, the touch feeling, texture, fluffing, appearance, and the like can be improved or appropriately adjusted depending on the degree of thermal bonding, for example. The composite fiber is not particularly limited, and a known composite fiber such as a concentric or eccentric core-sheath type composite fiber, a sea-island type composite fiber, or a split type composite fiber can be used.

  A composite fiber in which two different resin components constituting the composite fiber are arranged concentrically, so-called concentric core-sheath type composite fiber (also called a core-sheath type composite fiber having a concentric circular section), or a core component and a sheath component In the composite fiber, the center of gravity of the core component in the fiber cross section is preferably a so-called eccentric core-sheath type composite fiber in a position different from the center of gravity of the entire composite fiber.

  When the core component is 100% by mass of the fiber, the core component is, for example, 30% by mass or more, preferably 35% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. Resins (eg, polyester resins; polypropylene resins, ethylene-propylene copolymer resins, polyolefin resins including cyclic olefin resins; polyamide resins including 6,6-nylon resins and 6-nylon resins) A core-sheath type composite fiber including A core-sheath type composite fiber in which the core component includes a polyester-based resin such as polyethylene terephthalate or a polyolefin-based resin such as polypropylene resin, and the sheath component includes a polyolefin-based resin (for example, polyethylene resin) is more preferable. In addition, the sheath component may contain a plurality of resins.

  The fiber preferably contains 50% by mass or more of the core-sheath type composite fiber, more preferably 70% by mass or more, and the fiber is particularly preferably the core-sheath type composite fiber.

[First fiber]
As described above, the first fiber has an initial contact angle A of 45 to 70 degrees (where the initial contact angle A is 10 degrees or more smaller than the initial contact angle B) and after water permeation of 90 to 120 degrees. Contact angle.
Therefore, the first fibers have a tendency to decrease in hydrophilicity after permeation of water, and can influence the liquid absorption speed, diffusion preventing property, liquid returning preventing property and the like of the obtained nonwoven fabric.
Such a 1st fiber can be obtained by processing said fiber with the "fiber treatment agent" demonstrated in detail below, for example.

  The fineness of the fiber used in the first fiber can be, for example, 1.0 dtex to 4.4 dtex, 1.0 dtex to 3.8 dtex, 1.0 dtex to 3.5 dtex, 1.0 dtex to 2.6 dtex is preferred. More preferably, it is 1.1 dtex-2.4 dtex, More preferably, it is 1.2 dtex-2.2 dtex. When it is within the above range, effects such as improvement of the touch of the nonwoven fabric can be obtained.

  The first fiber is preferably a core-sheath type composite fiber from the viewpoint of, for example, producing a nonwoven fabric using thermal bonding. The core-sheath type composite fiber may be concentric or eccentric. More preferably, it is a concentric core-sheath type composite fiber. When the concentric core-sheath type composite fiber is used, advantages such as improvement in tactile sensation, particularly smoothness of the nonwoven fabric can be obtained. In particular, when the fineness of the first fiber is relatively small as described above (for example, when compared with the second fiber), the first fiber when the nonwoven fabric is viewed from the thickness direction as a concentric core-sheath composite fiber. Since the occupied area is increased, the smoothness can be further improved. The first fiber may be a combination of a concentric core-sheath type composite fiber and an eccentric core-sheath type composite fiber.

  When the first fiber is a core-sheath type composite fiber, the core component preferably contains polypropylene from the viewpoint of the smoothness of the nonwoven fabric. Moreover, it is preferable that a polyethylene terephthalate is included from a soft viewpoint of a nonwoven fabric. The sheath component preferably includes polyethylene, and more preferably includes high-density polyethylene, from the viewpoint of functioning as a thermal adhesive component. The melting point of the high density polyethylene is preferably 120 ° C. or higher and 140 ° C. or lower, and more preferably 125 ° C. or higher and 138 ° C. or lower. The melting point of the sheath component of the core-sheath composite fiber is preferably 120 ° C. or higher and 140 ° C. or lower, and more preferably 125 ° C. or higher and 135 ° C. or lower.

  The fiber length of the first fiber is not particularly limited, but considering the card passing property, the fiber length is preferably 25 mm or more and 65 mm or less, more preferably 30 mm or more and 55 mm or less, and 35 mm or more and 48 mm or less. More preferably it is.

  The first fiber may have an elliptical shape, a Y shape, an X shape, a well shape, a polygonal shape, a star shape, or the like in addition to the circular shape. The first fiber may be a so-called solid fiber that does not have a cavity portion that is continuous in the length direction in the fiber cross section, or a so-called hollow fiber that has one or more cavity portions that are continuous in the length direction. There may be.

  The first fiber can contain an additive such as titanium oxide in the fiber in order to improve the texture and feel. Such an additive is preferably contained in an amount of 0.1 to 10% by mass, more preferably 1 to 5% by mass, based on 100% by mass of the entire fiber including the additive and the like. Further, when the first fiber is a core-sheath type composite fiber, the additive is preferably contained in the core component in a larger amount, and is preferably contained only in the core component. When the additive is contained in the sheath component, a manufacturing apparatus such as a nonwoven fabric may be damaged.

  When the first fiber is a core-sheath type composite fiber and the core component is polypropylene, the core-sheath ratio (core component / sheath component volume ratio) between the core component and the sheath component is 55 / 45-80 / 20. Is preferable, 60/40 to 75/25 is more preferable, and 62/38 to 68/32 is particularly preferable. When the core-sheath ratio (volume ratio) is within this range, it is preferable because a soft nonwoven fabric can be obtained while fibers are appropriately bonded by a sheath component in which at least a part is melted during heat treatment. When the core-sheath ratio is outside the above range and the thermoplastic resin of the core component is too much, the first fiber becomes stiff, the texture of the nonwoven fabric becomes hard, or the sheath component is too few, resulting in thermal bonding There is a possibility that the strength of the fiber bonding point of the nonwoven fabric is weakened, the strength of the nonwoven fabric itself is reduced, and the surface of the nonwoven fabric is fluffed. On the contrary, when the core-sheath ratio is outside the above-described range and the sheath component is too much, the heat-bonded adhesion point between the fibers becomes too large when the heat treatment is performed, and the resulting nonwoven fabric becomes too hard. is there. In addition, since the core component is too small, the rigidity of the first fiber itself is insufficient, so that the fiber is excessively entangled in the carding process when manufacturing the nonwoven fabric, so-called nep is easily generated, and the fiber is soft. Therefore, there is a risk that the fiber may easily be in a so-called fly state in which the fiber does not pass through the card machine and flies in the card machine.

  When the first fiber is a core-sheath type composite fiber and the core component is polyethylene terephthalate, the core-sheath ratio between the core component and the sheath component (core component / sheath component volume ratio) is 30/70 to 75 / 25 is preferable, 35/65 to 70/30 is more preferable, and 40/60 to 60/40 is particularly preferable. When the core-sheath ratio (volume ratio) is within this range, the first fiber produced when the core component is too much and the sheath component is too small, as in the case of the core-sheath ratio in the case where the core component is polypropylene. Deterioration of the texture of the non-woven fabric and the fluffing of the non-woven fabric do not occur, and conversely, the deterioration of the card passing property of the first fiber caused by too much sheath component and too little core component, and excessive thermal bonding It is preferable because the texture of the nonwoven fabric does not deteriorate due to progress.

[Secondary fiber]
As described above, the second fiber has an initial contact angle B of 65 to 85 degrees (however, the initial contact angle B is greater than the initial contact angle A by more than 10 degrees) and 65 to 85 degrees. And contact angle after water permeation.
Therefore, the second fibers have substantially the same degree of hydrophilicity after permeation of water, and can influence the liquid absorption rate, the diffusion preventing property, the liquid return preventing property and the like of the nonwoven fabric.
Such a second fiber can be obtained, for example, by treating the above fiber with a “fiber treatment agent” described in detail below.

  The fineness of the second fiber can be, for example, 1.0 dtex to 4.4 dtex, 1.1 dtex to 4.4 dtex, 1.2 dtex to 4.4 dtex, and 2.2 dtex to 4.4 dtex. preferable. More preferably, it is 2.4 dtex-3.8 dtex, More preferably, it is 2.6 dtex-3.5 dtex. Within the above range, effects such as reducing the liquid residue of the nonwoven fabric and reducing the liquid return amount can be obtained. The fineness of the second fiber is preferably larger than the fineness of the first fiber, and the fineness of the second fiber is more preferably 0.5 to 3.4 dtex greater than the fineness of the first fiber, and 0.5 to 3.0 dtex is more preferable, 1.0 to 2.5 dtex is further preferable, and 1.0 to 2.0 dtex is more preferable.

The second fiber is preferably a core-sheath type composite fiber from the viewpoint of, for example, producing a nonwoven fabric using thermal bonding. The core-sheath type composite fiber may be concentric or eccentric. More preferably, it is an eccentric core-sheath type composite fiber. When an eccentric core-sheath type composite fiber is used, advantages such as improvement in tactile sensation, particularly softness, of the nonwoven fabric can be obtained. In particular, when the fineness of the second fiber is relatively large as described above (for example, when compared with the first fiber), the thickness of the nonwoven fabric increases when the fiber is an eccentric core-sheath type composite fiber, so the softness is further improved. Can be made. The second fiber may be a combination of a concentric core-sheath type composite fiber and an eccentric core-sheath type composite fiber.
One of the first fiber and the second fiber may be a concentric core-sheath type composite fiber, and the other may be an eccentric core-sheath type composite fiber.

  The second fiber preferably has a three-dimensional crimp. In this specification, the term “steric crimp” is used to distinguish it from a mechanical crimp in which the peak (or peak) of the crimp is an acute angle. The three-dimensional crimp includes, for example, a crimp in which a peak is curved (wave shape crimp), a crimp in which a peak is curved in a spiral (spiral crimp), and a combination of a wave crimp and a spiral crimp. A crimp in which an acute angle crimp of mechanical crimping and at least one of a wave crimp and a spiral crimp are mixed. By having the three-dimensional crimp, the inter-fiber gap can be made suitable, and the liquid absorption speed can be particularly reduced, which is preferable.

  When the second fiber is a core-sheath type composite fiber, the core component preferably contains polyethylene terephthalate from the viewpoint of increasing the thickness of the nonwoven fabric and improving the softness. Moreover, it is preferable that a sheath component contains polyethylene from a viewpoint of making it function as a heat bonding component, etc., and it is preferable that linear low density polyethylene and / or low density polyethylene are included. It is preferable that the sheath component contains linear low-density polyethylene and / or low-density polyethylene because a comfortable touch such as softness and smoothness can be imparted to the nonwoven fabric surface. The melting point of the sheath component is preferably 120 to 130 ° C, and more preferably 122 to 128 ° C.

  The fiber length of the second fiber may be selected in the same manner as the fiber length mentioned for the first fiber. The form in the fiber cross section of the second fiber may be selected similarly to the form in the fiber cross section mentioned in the first fiber. The second fiber may contain an additive in the same manner as the first fiber.

  When the second fiber is a core-sheath composite fiber, the core-sheath ratio between the core component and the sheath component (core component / sheath component volume ratio) is preferably 80/20 to 30/70, and 70 / It is more preferably 30 to 35/65, and particularly preferably 60/40 to 40/60. When the core-sheath ratio (volume ratio) is within this range, for example, a soft nonwoven fabric can be obtained while the fibers are appropriately bonded together by a sheath component in which at least a part is melted during heat treatment. When the core-sheath ratio is outside the above range and the thermoplastic resin of the core component is too much, the second fiber becomes stiff, the texture of the nonwoven fabric becomes hard, or the sheath component is too few, resulting in thermal bonding obtained There is a possibility that the strength of the fiber bonding point of the nonwoven fabric is weakened, the strength of the nonwoven fabric itself is reduced, and the surface of the nonwoven fabric is fluffed. On the contrary, when the core-sheath ratio is outside the above-described range and the sheath component is too much, the heat-bonded adhesion point between the fibers becomes too large when the heat treatment is performed, and the resulting nonwoven fabric becomes too hard. is there.

The fineness of the first fiber and the fineness of the second fiber are preferably different, and the difference is preferably 0.5 to 3.4 dtex, more preferably 0.5 to 3.0 dtex, More preferably, it is 1.0 to 2.5 dtex, and particularly preferably 1.0 to 2.0 dtex.
Moreover, it is preferable that one of the fineness of a 1st fiber and the fineness of a 2nd fiber is 1.0 dtex-2.6 dtex, and the other is 2.2 dtex-4.4 dtex, and one is 1.1 dtex-2 It is more preferable that the other is 2.4 dtex to 3.8 dtex, one is 1.2 dtex to 2.2 dtex, and the other is 2.6 dtex to 3.5 dtex. Is more preferable.

One of the first fiber and the second fiber is preferably a concentric core-sheath type composite fiber, and the other is an eccentric core-sheath type composite fiber. The core component of the concentric core-sheath composite fiber preferably includes polypropylene or polyethylene terephthalate, and the sheath component preferably includes polyethylene. Furthermore, it is more preferable that the sheath component of the concentric core-sheath composite fiber includes high-density polyethylene. The core component of the eccentric core-sheath composite fiber preferably includes polyethylene terephthalate, and the sheath component preferably includes polyethylene. Furthermore, it is more preferable that the sheath component of the eccentric core-sheath type composite fiber includes linear low density polyethylene and / or low density polyethylene.
Furthermore, the configuration and numerical values related to the first fiber and the second fiber described above may be interchanged (or interchanged).

[Fiber treatment agent]
The fiber treating agent can impart, for example, functions such as hydrophilicity and hydrophobicity to the fiber. As long as the target nonwoven fabric is obtained, the “initial contact angle” defined above is used in the first fiber and the second fiber. And “contact angle after water permeation” can be used without particular limitation.

  In each of the first fiber and the second fiber, it is preferable to use, for example, a fiber treatment agent that can impart hydrophilicity (hereinafter also referred to as “hydrophilic fiber treatment agent”).

  The kind of hydrophilic fiber treating agent is not specifically limited. The hydrophilic fiber treating agent may be a known one. As a hydrophilic fiber processing agent, the fiber processing agent containing surfactant etc. are mentioned, for example. As the surfactant, anionic, cationic, zwitterionic and nonionic surfactants can be used.

  Examples of anionic surfactants include alkyl phosphate sodium salt, alkyl ether phosphate sodium salt, dialkyl phosphate sodium salt, dialkyl sulfosuccinate sodium salt, alkylbenzene sulfonate sodium salt, alkyl sulfonate sodium salt, and alkyl sulfate sodium salt. Can do. In the anionic surfactant, any alkyl preferably has 6 to 22 carbon atoms. In these anionic surfactants, other alkali metal salts such as potassium salts and alkaline earth metal salts (for example, magnesium salts) can be used instead of sodium salts.

  Examples of the cationic surfactant include alkyl (or alkenyl) trimethyl ammonium halide, dialkyl (or alkenyl) dimethyl ammonium halide, alkyl (or alkenyl) pyridinium halide, and the like. The cationic surfactant preferably has an alkyl group or alkenyl group having 6 to 18 carbon atoms. Examples of the halogen in the halide compound include chlorine and bromine.

Examples of the zwitterionic surfactant include betaine-type amphoteric surfactants such as alkyldimethylbetaine, amino acid-type amphoteric surfactants, and aminosulfonic acid-type amphoteric surfactants.
Examples of nonionic surfactants include polyhydric alcohol fatty acid esters such as glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, alkylene oxide adducts of polyhydric alcohol fatty acid esters, polyoxyalkylene-modified silicones, amino-modified Examples include silicone.

  As the hydrophilic fiber treatment agent, a fiber treatment agent containing an anionic surfactant is preferable. More preferred is a fiber treatment agent containing an alkyl phosphate sodium salt or potassium salt, and even more preferred is a fiber treatment agent containing a C8-C16 alkyl phosphate sodium salt or potassium salt.

In the first fiber, it is more preferable to use a hydrophilic and non-durable fiber treatment agent. More preferably, a highly hydrophilic and non-durable fiber treatment agent is used. By using such a fiber treatment agent, the “initial contact angle” and the “contact angle after water permeation” can be adjusted to the above ranges.
In the second fiber, it is more preferable to use a hydrophilic and durable fiber treatment agent. More preferably, a fiber treatment agent having low hydrophilicity and durability is used. By using such a fiber treatment agent, the “initial contact angle” and the “contact angle after water permeation” can be adjusted to the above ranges.

In the present disclosure, “high hydrophilicity” and “low hydrophilicity” are hydrophilicity imparted by the fiber treatment agent used in the first fibers and hydrophilicity imparted by the fiber treatment agent used in the second fibers. It is a term used to indicate a relative relationship between them and should not be interpreted as an absolute meaning.
Similarly, regarding “durability” and “non-durability”, the hydrophilic durability imparted by the fiber treatment agent used in the first fiber and the hydrophilic property imparted by the fiber treatment agent used in the second fiber It is a term used to indicate the relative relationship between the durability of the and should not be interpreted in absolute terms. However, the first fiber and the second fiber imparted with hydrophilicity by the fiber treatment agent must satisfy the requirements of the “initial contact angle” and the “contact angle after water permeation”, respectively.

  In the first fiber and the second fiber, the form of the fiber treatment agent that can be applied is not particularly limited. The fiber treatment agent may be adhered to the surface of the fiber or may be dispersed in the fiber. The fiber treating agent can be attached to the surface of the fiber by spraying the surface of the fiber with a spray or the like, or by applying the fiber treating agent to the surface of the fiber by any method. Alternatively, the fiber treatment agent may be dispersed in the fiber by melt spinning a thermoplastic resin kneaded with the fiber treatment agent.

  The content of the fiber treatment agent may be, for example, 0.1% by mass to 2.0% by mass when the fiber mass (the mass of the fiber excluding the fiber treatment agent) is 100% by mass. Content of a hydrophilic fiber processing agent may be 0.15 mass%-1.0 mass%, for example, Preferably it may be 0.2 mass%-0.6 mass%.

[Method for producing nonwoven fabric]
The method for producing the nonwoven fabric is not particularly limited as long as a nonwoven fabric containing at least the first fiber and the second fiber in a prescribed ratio can be produced.

  The non-woven fabric can be manufactured by, for example, a manufacturing method including mixing a first fiber and a second fiber to produce a fiber web, and subjecting the fibers included in the fiber web to integration with each other. it can.

  The fiber web can be produced, for example, by a known method. The form of the fibrous web may be, for example, a card web such as a parallel web, a cross web, a semi-random web, and a random web.

  A fiber web is attached | subjected to the process which integrates the fibers contained in it, for example. The process for integrating the fibers may be a process for integrating the fibers by entanglement, for example, an entanglement process using a high-pressure fluid or a needle punch process, or a thermal bonding process or an adhesive process. Or the like.

  The nonwoven fabric may be bonded by a component constituting the first fiber and a component constituting the second fiber. In order to obtain such a nonwoven, the fibrous web is preferably subjected to a heat treatment. According to the heat treatment, the component constituting the first fiber (for example, the sheath component of the core-sheath type composite fiber) and the component constituting the second fiber (for example, the sheath component of the core-sheath type composite fiber) are heated during the heat treatment. The fibers constituting the fiber web can be bonded to each other by melting or softening. The heat treatment is, for example, hot air processing for blowing hot air, hot roll processing (hot embossing roll processing), heat treatment using infrared rays, or the like. The hot air processing may be performed using a device that blows hot air having a predetermined temperature onto the fiber web, for example, a hot air through heat treatment machine or a hot air blowing heat treatment machine. When bulkiness is required, the nonwoven fabric is preferably manufactured by performing hot air processing. According to the hot air processing, a decrease in specific volume can be relatively suppressed.

  The heat treatment temperature (for example, the temperature of hot air) is a temperature at which the component having the highest melting point among the components constituting the first fiber and the second fiber and functioning as the thermal bonding component is softened or melted. As good as For example, the heat treatment temperature may be a temperature equal to or higher than the melting point of the component. For example, when both the first fiber and the second fiber contain polyethylene as a component, and polyethylene is used as a heat bonding component, the heat treatment temperature may be 130 ° C. to 150 ° C. Further, when the melting point of the thermal bonding component of the first fiber is different from the melting point of the thermal bonding component of the second fiber, it is, for example, 5 to 30 ° C., preferably 5 to 5 ° C. than the temperature at which the component having the lowest melting point is softened or melted. It is preferable that the heat treatment temperature is 20 ° C., more preferably 5 to 10 ° C., because the nonwoven fabric surface can be provided with a comfortable touch such as softness and smoothness.

(Weight)
The basis weight of the non-woven fabric (including the non-woven fabric sample) is not particularly limited, and can be appropriately selected according to its use. Basis weight of the nonwoven fabric, for ^{example, 10g / m 2 ~50g / m} 2 is preferred. More preferably ^{15g / m 2 ~45g / m 2} , and even more preferably from ^{20g / m 2 ~40g / m 2} . If the basis weight of the nonwoven fabric is too small, the nonwoven fabric may be easily broken, twisted or damaged, and if it is too large, the air permeability may be lowered.

(thickness)
The thickness of the non-woven fabric (including the non-woven fabric sample) is not particularly limited, and can be appropriately selected according to its use. The thickness of the nonwoven fabric is preferably, for example, 0.10 mm to 1.5 mm. More preferably, it is 0.15 mm-1.0 mm, More preferably, it is 0.20 mm-0.80 mm. If the thickness of the nonwoven fabric is too small, the nonwoven fabric may be easily torn, twisted or damaged, and if it is too large, the air permeability may be reduced. The thickness of the nonwoven fabric can be measured, for example, using a thickness measuring machine (trade name THICKNESS GAUGE model CR-60A manufactured by Daiei Kagaku Seisakusho Co., Ltd.) with a load of 294 Pa applied to the nonwoven fabric. .

(Specific volume)
The specific volume of the nonwoven fabric (including the nonwoven fabric sample) can be obtained by calculation from the above-mentioned basis weight and thickness. The specific volume of the nonwoven fabric is not particularly limited, and can be appropriately selected according to its use. Specific volume of the nonwoven fabric, for ^example, 5cm ³ / ^g~90cm 3 / g are preferred. More preferably 10cm ³ / g~80cm ³ / g, even more preferably 15cm ³ / g~60cm ³ / g. If the specific volume is too small, the liquid is difficult to permeate and the liquid absorption speed may be reduced.

(Fiber surface area per 1 cm ³ nonwoven fabric)
About the 1st fiber and the 2nd fiber, fiber surface area S (cm < ² >) per 1 cm < ³ > of nonwoven fabric can be calculated from a following formula, respectively.
S = [weight per unit area (g / m ² ) × mixing rate (mass%) × fiber diameter (μm) × circumference π] / [fineness (dtex) × thickness (mm) × 1000]
For “weight per unit” and “thickness”, the value of the whole nonwoven fabric is substituted, and for “mixing ratio”, “fiber diameter” and “fineness”, the values of the first fiber and the second fiber are respectively substituted. Thus, the fiber surface area S (cm ² ) per 1 cm ³ of the nonwoven fabric for the first fiber and the second fiber can be respectively calculated.
About the 1st fiber, the fiber surface area per 1 cm < ³ > of nonwoven fabric is not restrict | limited, According to the use etc., it can select suitably. The fiber surface area per nonwoven 1 cm ³ of the first fibers, for ^example, preferably 24cm ² ~75cm 2. More preferably 29cm ² ~70cm ^2, even more preferably from 34cm ² ~65cm ^2. When the fiber surface area is within the above range, the first fiber contains a fiber having a relatively high hydrophilicity on the fiber surface (for example, when compared with the second fiber), so that an effect of improving the liquid absorption rate can be obtained. .
About the 2nd fiber, the fiber surface area per 1 cm < ³ > of nonwoven fabric is not restrict | limited, According to the use etc., it can select suitably. The fiber surface area per nonwoven 1 cm ³ of the second fiber, for ^example, preferably 10cm ² ~70cm 2. More preferably 15cm ² ~65cm ^2, even more preferably from 20cm ² ~60cm ^2. When the fiber surface area is within the above range, the second fiber contains fibers having a relatively low hydrophilicity on the fiber surface (for example, when compared with the first fiber). Effects such as reducing the amount of liquid return can be obtained.

(Total fiber surface area per 1 cm ³ nonwoven fabric)
The total fiber surface area per 1 cm ^{3 of the} nonwoven fabric is not particularly limited, and may be appropriately selected depending on the use and the like. The total fiber surface area per nonwoven 1 cm ^3, for ^example, 40cm ^{2 ~145cm} 2 is preferred. More preferably 50cm ² ~135cm ^2, even more preferably from 60cm ² ~125cm ^2. If the total fiber surface area per 1 cm ^{3 of the} nonwoven fabric is too large, the liquid may be difficult to permeate and the liquid absorption speed may decrease.

  Although the nonwoven fabric for absorbent articles of the present disclosure may be laminated with another nonwoven fabric on one surface of the nonwoven fabric, the nonwoven fabric for absorbent articles of the present disclosure has a single-layer structure including the first fiber and the second fiber. It is preferable that it is a nonwoven fabric.

(Use)
The nonwoven fabric for absorbent articles of the present disclosure includes, for example, a surface sheet (also referred to as a top sheet), an intermediate sheet, a sheet that covers the absorbent core (also referred to as an SAP sheet and a core wrap sheet), a back Although it can be used as a member constituting a sheet or the like, it can be suitably used as a surface sheet. In particular, it can be suitably used as a surface sheet for absorbent articles.

[Absorbent articles]
An absorbent article will be described as another embodiment of the present disclosure. The absorbent article of the present embodiment preferably includes at least the above-described nonwoven fabric for absorbent articles as a surface sheet. For example, the absorbent article includes a top sheet, a back sheet, and an absorbent body disposed between the top sheet and the back sheet.

  In this embodiment, a surface sheet is the nonwoven fabric for absorbent articles of embodiment described previously. The back sheet may be a sheet made of a liquid-impermeable material. The backsheet may or may not be breathable.

  The absorbent body is, for example, an absorbent core composed of one or more members selected from a polymer absorbent body (also referred to as SAP, which is generally a powder), pulverized pulp, a fiber assembly, and a film. It may be coated with a core wrap sheet selected from non-woven fabrics and films. Or an absorber may not be coat | covered with a core wrap sheet but may consist only of an absorption core.

  The absorbent article of the present embodiment includes, for example, absorbent articles such as disposable diapers, incontinence pads, light incontinence pads, sanitary napkins, panty liners (orimono sheets), postpartum pads, pet sheets, etc. The absorbent article of this embodiment is not limited to these.

  EXAMPLES Hereinafter, although an Example of this invention is given and this invention is demonstrated further in detail, this invention is not limited to a following example.

The materials used in the examples and comparative examples will be described in detail.
Fiber Fiber A: Polyethylene terephthalate (PET) (melting point 260 ° C.) is the core, high-density polyethylene (HDPE) (melting point 132 ° C.) is the sheath, and the composite ratio (core / sheath, volume ratio) is 40/60. Concentric core-sheath type composite fiber (trade name NBF (SH) manufactured by Daiwabo Polytech Co., Ltd.) having a fineness of 2.2 dtex (fiber diameter of 16.0 μm) and a fiber length of 45 mm (the melting point of the sheath component is the differential scanning calorific value) Using a meter (manufactured by Seiko Instruments Inc.), setting the sample amount to 5.0 mg, raising the temperature from normal temperature to 200 ° C. at a temperature increase rate of 10 ° C./min, melting the fiber, and obtaining the melt It was 127 degreeC when it calculated | required from the calorie | heat amount curve.)
Fiber B: Polypropylene (PP) (melting point 160 ° C.) is the core, high-density polyethylene (HDPE) (melting point 132 ° C.) is the sheath, and the composite ratio (core / sheath, volume ratio) is 65/35. Concentric core-sheath type composite fiber having a fineness of 1.6 dtex (fiber diameter: 14.8 μm) and a fiber length of 38 mm (trade name NBF (H) manufactured by Daiwabo Polytech Co., Ltd.) (the melting point of the sheath component is a differential scanning calorimeter (Seiko) From Instruments, Inc.), the sample amount was 5.0 mg, the temperature was increased from room temperature to 200 ° C. at a temperature increase rate of 10 ° C./min, and the fiber was melted. When calculated, it was 127 ° C.)
Fiber C: Polyethylene terephthalate (PET) (melting point 260 ° C.) is the core, linear low density polyethylene (LLDPE) (melting point 120 ° C.) and low density polyethylene (LDPE) (melting point 106 ° C.) (mass ratio (linear 85/15) is a sheath, and the composite ratio (core / sheath, volume ratio) is 50/50, fineness 3.3 dtex (fiber diameter 19.1 μm), fiber length Eccentric core-sheath type composite fiber (trade name NBF (SL) V, manufactured by Daiwabo Polytech Co., Ltd.) with 38 mm and eccentricity of 25% (the melting point of the sheath component is a differential scanning calorimeter (Seiko Instruments Co., Ltd.)) Then, when the sample amount is 5.0 mg, the temperature is raised from room temperature to 200 ° C. at a temperature rising speed of 10 ° C./min, the fiber is melted, and the obtained heat of fusion curve is used. It was 26 ℃.)
Fiber treatment agent Fiber treatment agent 1: Non-durable highly hydrophilic fiber treatment agent containing C12 alkyl phosphate potassium salt Fiber treatment agent 2: Durable low hydrophilic fiber treatment agent containing C12 alkyl phosphate potassium salt Fiber treatment agent 3: C12 alkyl Durable highly hydrophilic fiber treatment agent containing phosphate potassium salt

Example 1
60% by mass of fiber A to which fiber treatment agent 1 is applied and 40% by mass of fiber C to which fiber treatment agent 2 is applied are mixed with a parallel card machine at a target weight of 25 g / m ² . A parallel card web was manufactured.
This parallel card web was heat-treated at 132 ° C. for about 15 seconds using a hot-air through heat treatment machine, and the sheath components of the fibers A and C were thermally fused to obtain a thermal bond nonwoven fabric.
The thermal bond nonwoven fabric was subjected to thickness processing with a load of 2400 kg per m ² for 10 days to obtain a nonwoven fabric of Example 1.
The initial contact angle of the fiber A to which the fiber treatment agent 1 was applied was 60.2 degrees, and the contact angle after water permeation was 102.6 degrees.
The initial contact angle of the fiber C to which the fiber treatment agent 2 was applied was 75.6 degrees, and the contact angle after water permeation was 72.9 degrees.

Examples 2-4 and Comparative Examples 1-7
As shown in the following table | surfaces, the nonwoven fabric of Examples 2-4 and Comparative Examples 1-7 was obtained like Example 1 except having changed the fiber, the fiber processing agent, and the cotton blend rate.

  About the nonwoven fabric produced by the Example and the comparative example, the absorbent article for evaluation was produced and the absorptivity was evaluated. The evaluation results are shown in the following table.

[Manufacture of absorbent articles]
From the commercially available sanitary napkin (trade name “KOTEX Super Absorbent” manufactured by Kimberley Clark), the top sheet is peeled off to expose the second sheet. Instead of the top sheet, the nonwoven fabrics of the above-mentioned examples and comparative examples ( (Vertical 30 cm × width 10.5 cm) was laminated to obtain an absorbent article for evaluation. Using this absorbent article for evaluation, “liquid absorption time”, “diffusion length”, and “liquid return amount” were evaluated as the absorbent characteristics of the nonwoven fabrics of Examples and Comparative Examples.

[Liquid absorption time]
A plate with an injection cylinder (a two-stage cylindrical shape having a height of 75 mm, an inner diameter of 25 mm at the upper part of the cylinder, an inner diameter of 10 mm at the lower part of the cylinder, and a thickness of 5 mm) is placed on the nonwoven fabric of the examples and comparative examples. 6.0 cc of artificial menstrual blood (temperature: 37 ° C., viscosity: 8 mPa · s) was injected into the injection cylinder of the plate. The time required for the liquid to disappear from the nonwoven fabric surface (liquid absorption time (seconds)) was measured. The composition of artificial menstrual blood is 12.30% by mass of glycerin, 85.18% by mass of ion-exchanged water, 0.45% by mass of CMC (carboxymethylcellulose sodium), 0.97% by mass of NaCl (sodium chloride), Na _2. CO ₃ (sodium carbonate) 1.04 wt%, and the blue powder 0.06 wt%.
In addition, after 15 minutes had elapsed from the measurement of the liquid absorption time, a second liquid absorption time (second) was measured.
The evaluation criteria for the first and second liquid absorption times are as follows. The shorter the liquid absorption time, the higher the liquid absorption speed.

[Evaluation criteria for the first absorption time]
○: Less than 10.5 seconds ×: 10.5 seconds or more [Evaluation criteria for second liquid absorption time]
○: Less than 14.0 seconds ×: 14.0 seconds or more

[Diffusion length]
At the time of measuring the first liquid absorption time, 5 minutes after the injection of artificial menstrual blood, the length of the portion of the nonwoven fabric of Examples and Comparative Examples that absorbed artificial menstrual blood in the vertical direction was measured to obtain a diffusion length. .
In the measurement of the second liquid absorption time, the diffusion length was measured 5 minutes after the injection of artificial menstrual blood as in the first time.
The evaluation criteria for the first and second diffusion lengths are as follows. The smaller the diffusion length value, the better because the color of menstrual blood becomes less noticeable.

[First evaluation standard for diffusion length]
○: Less than 3.5 cm ×: 3.5 cm or more [second evaluation criteria for diffusion length]
○: Less than 4.0 cm ×: 4.0 cm or more

[Liquid return amount]
In the absorbent article for evaluation prepared separately, artificial menstrual blood was injected in the same manner as the measurement of the first liquid absorption time, and 10 minutes after the injection, the filter paper ( Ten sheets made by Toyo Roshi Kaisha, Ltd., trade name ADVANTEC (registered trademark) No. 2, 10 cm × 10 cm) were placed, and a weight of 1 kg (shape: square, 10 cm × 10 cm) was placed on the filter paper. 20 seconds after placing the weight, the filter paper was taken out, the mass of the filter paper that absorbed artificial menstrual blood was measured, the mass of the filter paper before being placed on the nonwoven fabric was subtracted, and the liquid return amount (g) was calculated.
The evaluation criteria for the liquid return amount are as follows. It can be said that the smaller the liquid return amount, the higher the liquid return prevention property.
[Evaluation criteria for liquid return amount]
○: Less than 0.10 g ×: 0.10 g or more

  In measuring the liquid absorption time, diffusion length, and liquid return amount, two samples were prepared for each of the nonwoven fabrics of the examples and comparative examples. The average values of the liquid absorption time, diffusion length, and liquid return amount measured for each of the two samples were taken as the liquid absorption time, diffusion length, and liquid return amount of the nonwoven fabrics of each Example and Comparative Example.

  The nonwoven fabrics of Examples 1 to 4 have the first fiber treated with the fiber treatment agent 1 (highly hydrophilic but non-durable) and the fiber treatment agent 2 (low hydrophilic but durable). ) Treated with the second fiber at a specific blending rate, so that “liquid absorption time” (both first and second times), “diffusion length” (both first and second times), “liquid return” All of the “quantity” showed a well-balanced and highly evaluated result. The non-woven fabric of Example 3 is a non-woven fabric in which the fiber configuration other than the fiber treatment agent of the first fiber and the second fiber in Example 2 is replaced. As in Example 2, “liquid absorption time” (first time, 2 The results of high evaluation in a well-balanced manner were shown for all of “diffusion length” (both times), “diffusion length” (both first time and second time), and “liquid return amount”.

  The nonwoven fabric of Comparative Example 1 shows good results in both “liquid absorption time” (both first and second times), “diffusion length” (both first and second times), and “liquid return amount”. Not shown at all. In particular, since the nonwoven fabric of Comparative Example 1 uses the fiber treatment agent 3 (highly hydrophilic and durable) as the first fiber, the “liquid return amount” result was not good.

  Since the nonwoven fabric of Comparative Example 2 does not include the first fiber, only the second fiber, and the fiber treatment agent 2 (low hydrophilicity but durability) is used in the second fiber, the “diffusion length” The result of (both the first time and the second time) was not good. Since the fiber treatment agent 2 has low hydrophilicity, it is considered that the liquid was difficult to permeate to the absorber and the liquid flowed sideways.

  By simply blending the same first fiber and second fiber as in Example 2 from the nonwoven fabrics of Comparative Examples 3 and 4, all of “Liquid absorption time”, “Diffusion length” and “Liquid return amount” are good. It was also found that the correct result was not obtained.

  The nonwoven fabric of Comparative Example 5 does not include the second fiber, includes only the first fiber, and uses the fiber treatment agent 1 (highly hydrophilic but non-durable) in the first fiber. The “quantity” result was not good.

  Moreover, from the nonwoven fabrics of Comparative Examples 3 to 5, due to the small fineness (1.6 dtex) of the first fibers (compared to the second fibers), the liquid becomes permeable to the absorber as the value of the specific volume decreases. The liquid absorption time became longer.

In the nonwoven fabric of Comparative Example 6, since the fiber treatment agent for the first fiber and the second fiber is both the fiber treatment agent 1, the result of “diffusion length” (second time) was not good.
In the nonwoven fabric of Comparative Example 7, since the fiber treatment agent of the first fiber and the second fiber is both the fiber treatment agent 2, the “liquid absorption time” (both first and second times) “diffusion length” (1 The results of both the second and second times were not good.

Embodiments of the present invention include the following aspects.
(Aspect 1)
A nonwoven fabric for absorbent articles, wherein the nonwoven fabric includes a first fiber and a second fiber,
The initial contact angle A between the fiber surface of the first fibers and water is 45 degrees to 70 degrees,
The initial contact angle B between the fiber surface of the second fiber and water is 65 degrees to 85 degrees,
The initial contact angle A is 10 degrees or more smaller than the initial contact angle B,
The contact angle after water permeation between the fiber surface of the first fiber and water is 90 degrees to 120 degrees,
The contact angle after water permeation between the fiber surface of the second fiber and water is 65 degrees to 85 degrees,
The non-woven fabric includes the first fibers in a proportion of 30% by mass to 70% by mass and the second fibers in a proportion of 70% by mass to 30% by mass based on the total mass of the non-woven fabric (however, The sum of the proportion of the first fibers and the proportion of the second fibers does not exceed 100% by mass),
Nonwoven fabric for absorbent articles.
(Aspect 2)
The difference between the fineness of the first fiber and the fineness of the second fiber is the nonwoven fabric for absorbent articles according to aspect 1, in which the difference is 0.5 dtex to 3.4 dtex.
(Aspect 3)
One for the fineness of the said 1st fiber and the fineness of the said 2nd fiber is 1.0 dtex-2.6 dtex, The other is 2.2 dtex-4.4 dtex, For absorbent articles of aspect 1 or 2 Non-woven fabric.
(Aspect 3-2)
The nonwoven fabric for absorbent articles according to any one of aspects 1 to 3, wherein the fineness of the first fibers is 1.0 dtex to 2.6 dtex.
(Aspect 3-3)
The fineness of a said 2nd fiber is a nonwoven fabric for absorbent articles of any one aspect | mode of aspects 1-3-2 which are 2.2 dtex-4.4 dtex.
(Aspect 4)
The nonwoven fabric for absorbent articles according to any one of aspects 1 to 3, wherein one of the first fiber and the second fiber is a concentric core-sheath composite fiber and the other is an eccentric core-sheath composite fiber. .
(Aspect 5)
The nonwoven fabric for absorbent articles according to aspect 4, wherein the core component of the concentric core-sheath composite fiber includes polypropylene or polyethylene terephthalate, and the sheath component includes polyethylene.
(Aspect 6)
The nonwoven fabric for absorbent articles according to aspect 4 or 5, wherein the core component of the eccentric core-sheath composite fiber includes polyethylene terephthalate, and the sheath component includes polyethylene.
(Aspect 7)
Specific volume is ^{5cm 3} / ^g~90cm 3 / g, for an absorbent article nonwoven fabric according to any one of Embodiments 1-6.
(Aspect 8)
An absorbent article comprising the nonwoven fabric for absorbent articles according to any one of aspects 1 to 7 as a surface sheet.

  The nonwoven fabric for absorbent articles of the present embodiment has a high anti-diffusion property in a well-balanced manner with a high liquid absorption rate and high anti-return property. Therefore, the nonwoven fabric for absorbent articles of the present embodiment is suitable as a top sheet in an absorbent article having, for example, a top sheet, a back sheet, and an absorbent body disposed between the top sheet and the back sheet. Can be used for

Claims (8)

A nonwoven fabric for absorbent articles, wherein the nonwoven fabric includes a first fiber and a second fiber,
The initial contact angle A between the fiber surface of the first fibers and water is 45 degrees to 70 degrees,
The initial contact angle B between the fiber surface of the second fiber and water is 65 degrees to 85 degrees,
The initial contact angle A is 10 degrees or more smaller than the initial contact angle B,
The contact angle after water permeation between the fiber surface of the first fiber and water is 90 degrees to 120 degrees,
The contact angle after water permeation between the fiber surface of the second fiber and water is 65 degrees to 85 degrees,
The non-woven fabric includes the first fibers in a proportion of 30% by mass to 70% by mass and the second fibers in a proportion of 70% by mass to 30% by mass based on the total mass of the non-woven fabric (however, The sum of the proportion of the first fibers and the proportion of the second fibers does not exceed 100% by mass),
Nonwoven fabric for absorbent articles.   The non-woven fabric for absorbent articles according to claim 1, wherein a difference between the fineness of the first fiber and the fineness of the second fiber is 0.5 dtex to 3.4 dtex.   The absorbent article according to claim 1 or 2, wherein one of the fineness of the first fiber and the fineness of the second fiber is 1.0 dtex to 2.6 dtex, and the other is 2.2 dtex to 4.4 dtex. Nonwoven fabric.   The absorbent article according to any one of claims 1 to 3, wherein one of the first fiber and the second fiber is a concentric core-sheath type composite fiber and the other is an eccentric core-sheath type composite fiber. Non-woven fabric.   The nonwoven fabric for absorbent articles according to claim 4, wherein the core component of the concentric core-sheath composite fiber includes polypropylene or polyethylene terephthalate, and the sheath component includes polyethylene.   The nonwoven fabric for absorbent articles according to claim 4 or 5, wherein the core component of the eccentric core-sheath composite fiber includes polyethylene terephthalate, and the sheath component includes polyethylene. Specific volume is ^{5cm 3} / ^g~90cm 3 / g, for an absorbent article nonwoven fabric according to any one of claims 1 to 6.   An absorptive article containing the nonwoven fabric for absorptive articles given in any 1 paragraph of Claims 1-7 as a surface sheet.