JP6108599B2 - Disposable diapers - Google Patents

Description

  The present invention relates to a disposable diaper.

Disposable diapers generally include a liquid-permeable surface sheet, a leak-proof sheet, and an absorbent body interposed between these two sheets. As the leak-proof sheet, a breathable film that is hardly permeable to liquid and has breathability is widely used from the viewpoint of prevention of stuffiness and the like.
Such a breathable film is obtained, for example, by adding filler fine particles to a polyolefin-based resin, kneading them, then melt-molding to form a film, and then making the film porous by uniaxial or biaxial stretching. It is manufactured. In the air-permeable film manufactured in this manner, air-permeable fine pores (microvoids) are generated from the interface between the polyolefin-based resin and the filler fine particles by stretching, and thereby fine pores having a pore diameter of several tens of microns or less Is formed.
However, there is a case where a hole called a pinhole of about 1 mm is generated during manufacturing. If such a hole is present, the liquid oozes out through the hole and causes the clothes on the outside of the diaper to become dirty.

Moreover, the diaper which laminated | stacked the outer layer nonwoven fabric of 1 sheet or 2 sheets on the outer surface of a breathable film, and raised the touch of the outer surface of a diaper is also proposed.
In addition, a technique has also been proposed in which an outer layer nonwoven fabric that is entirely water-repellent is provided on the outer surface of the breathable film to prevent the clothes from being soiled by the liquid that has oozed from the breathable film (see Patent Document 1).
Moreover, the technique which distribute | arranges the nonwoven fabric which has two layers of a hydrophilic layer and a hydrophobic layer on the outer surface of a breathable film is also known (patent document 2).

JP 2006-247909 A JP-A-10-272154

However, the technique described in Patent Document 1 was able to prevent adhesion to clothing when the amount of the liquid that exudes from the air permeable film was very small, but the liquid exuded from the air permeable film accumulated in the outer layer nonwoven fabric. As a result, when the nonwoven fabric is pressed and compressed by weight or the like, the liquid inside may ooze out on the surface of the nonwoven fabric and stain clothing.
Further, the technique described in Patent Document 2 uses a hydrophilic layer on the absorber side, a water repellent layer on the outer surface side, traps water vapor in the hydrophilic layer, and cannot reach the outer layer. Is different.

  Therefore, the subject of this invention is providing the disposable diaper which can eliminate the fault which the prior art mentioned above has.

  The present invention is a disposable diaper provided with a liquid-permeable surface sheet, a leak-proof sheet, and an absorbent body disposed between the two sheets, and the leak-proof sheet is liquid-permeable and breathable. It has a breathable film and an outer layer nonwoven fabric that covers the outer surface side of the breathable film, and the outer layer nonwoven fabric consists of a nonwoven fabric having a hydrophilic gradient in the thickness direction, in whole or in part in the thickness direction, The non-woven fabric has a surface located on the outer surface side of the diaper at the same position in the planar direction of the outer layer non-woven fabric 1 as P1, a surface located at the inner surface side of the diaper as P4, and two intermediate points located between them as P1. When it is set as P2 and P3 in order from the near side, the contact angle of the water with respect to the fiber taken out from each site | part P1-P4 is increasing in this order toward P1 from P4, and the disposable diaper is provided.

  Even when the disposable diaper of the present invention is pressurized by body pressure or the like, the liquid in the outer layer nonwoven fabric hardly oozes out on the outer surface of the diaper, and the clothes are not easily soiled or moistened.

FIG. 1 is a partially cutaway plan view showing an embodiment of the disposable diaper of the present invention. FIG. 2 is a partially enlarged sectional view of the disposable diaper shown in FIG. FIG. 3 is an enlarged cross-sectional view of a leak-proof sheet used in the disposable diaper shown in FIG. Figure 4 is a perspective view of the surface of the diaper outer surface side of the outer layer nonwoven fabric used in the barrier sheet shown in FIG. 3 from obliquely above. 5 (a) and 5 (b) are explanatory diagrams of the function and effect of the present invention, and FIGS. 5 (c) and 5 (d) are correspondence diagrams of the prior art. FIG. 6 is a cross-sectional view showing a leak-proof sheet in another embodiment of the present invention.

The present invention will be described below based on preferred embodiments with reference to the drawings.
As shown in FIG. 1, a disposable diaper 10 (hereinafter also simply referred to as a diaper 10) according to an embodiment of the present invention is disposed between a liquid-permeable top sheet 20, a leak-proof sheet 30, and both the sheets. An absorber 40 is provided.

Moreover, the diaper 10 has the back side part A distribute | arranged to a wearer's back side at the time of wear in the longitudinal direction, the crotch part B distribute | arranged to the crotch part, and the abdominal side part C distribute | arranged to the abdominal side. ing.
On both sides of the diaper 10 in the longitudinal direction, side sheets 70 made of a water-repellent nonwoven fabric are arranged so as to cover both side portions of the topsheet 20. The top sheet 20 and each side sheet 70 are joined to the leak-proof sheet 30 outside the periphery of the absorber 4. An elastic member 71 for forming leg gathers is disposed on the leg flap portion outside the side edge of the absorbent body 4, and the side edge on the center side in the diaper width direction of the side seat 70 is for forming a three-dimensional gather. An elastic member 72 is disposed.

  The diaper 10 is a so-called unfolded diaper, and fastening tapes 50 and 50 provided on both side edges of the back side A are fixed to a landing tape 60 provided on the outer surface of the ventral side C. By using it, wear it on your body. In addition, as the absorber 40, the fastening tape 50, the landing tape 60, the side sheet 70, and the elastic members 71 and 72, those used for this type of article can be used without any particular limitation. As the absorbent body 40, an absorbent core 41 made of a fiber aggregate made of a fiber material such as pulp fiber or made of fiber aggregate made by holding a water-absorbing polymer particle in a fiber material such as pulp fiber is used. The thing etc. which coat | cover with the core wrap sheet | seat 42 which consists of paper and a water-permeable nonwoven fabric can be used.

The leakproof sheet 30 of the diaper 10 will be described.
Further, as shown in FIGS. 2 and 3, the leak-proof sheet 30 includes a breathable film 3 that is hardly permeable and breathable, and an outer layer nonwoven fabric 1 that covers the outer surface side of the breathable film 3. Have.
The breathable film 3 is conventionally known as a moisture-permeable back sheet, a moisture-permeable back sheet, a moisture-permeable back material, etc., even in conventional disposable diapers, and various known materials can be used. . For example, after adding filler fine particles to a polyolefin-based resin, kneading them, melt-molding to form a film or a sheet, and then making it porous by uniaxial or biaxial stretching can be used. Such a breathable film is hardly permeable to liquids, has breathability, and allows water vapor to pass therethrough. The poor liquid permeability is a concept including a liquid impermeability other than a part where an unintended large hole is formed, a liquid impermeability as a whole, and the like.

The outer layer nonwoven fabric 1 used in this embodiment has a single layer structure as shown in FIGS. 3 and 4.
The outer layer nonwoven fabric 1 has a concavo-convex surface 1b having a concavo-convex shape on the non-skin surface side directed to the diaper outer surface side, and the skin surface side directed to the breathable film 3 side is flat or compared to the concavo-convex surface. Thus, the flat surface 1a has a small degree of unevenness.
The outer layer nonwoven fabric 1 is formed by embossing a web or nonwoven fabric produced by the card method or airlaid method and then heat-treating. As shown in FIG. 4, the outer layer nonwoven fabric 1 has a thin thickness formed by embossing. A plurality of portions 18 are dispersed and formed, and in the present embodiment, a plurality of scattered dots are formed. A relatively thick portion 19 is formed in a portion surrounded by the four thin portions 18. In the uneven surface 1b on the outer surface side of the outer layer nonwoven fabric 1, the thick portion 19 protrudes from the thin portion 18 to form a convex portion 119.

The outer layer nonwoven fabric 1 in the present embodiment has a hydrophilic gradient in the thickness direction, and the more hydrophilic side faces the diaper inner surface side. The inner surface side of the outer layer nonwoven fabric 1 is synonymous with the breathable film 3 side of the outer layer nonwoven fabric 1.
As shown in FIG. 3, the outer layer nonwoven fabric 1 has a hydrophilic gradient with the highly hydrophilic side facing the inner surface of the diaper. As shown in FIG. 3, both sides P1, P4 of the nonwoven fabric and a plurality of intermediate points P2, between them. The fiber is taken out from P3, and the contact angle of water with the fiber is measured and judged.
More specifically, as shown in FIG. 3, the surface located on the outer surface side of the diaper at the same position in the planar direction of the outer layer nonwoven fabric 1 is P1, the surface located on the inner surface side of the diaper is P4, and between them When the two intermediate points are P2 and P3 in order from the side closer to P1, the contact angles for the fibers taken out from the respective parts P1 to P4 increase in this order from P4 to P1, It is determined that the more hydrophilic side has a hydrophilic gradient facing the inner surface of the diaper. The two intermediate points P2 and P3 are preferably located at positions that divide the thickness t of the outer nonwoven fabric into three equal parts. In addition, the inner surface side is the surface side that is directed to the skin side of the wearer at the time of wearing out of both surfaces of the diaper or both components thereof, and the outer surface side is the both surfaces of the diaper or both surfaces of the component member, It is the surface side that is directed to the opposite side of the wearer's skin when worn.

The contact angle of water with respect to the fiber is measured by the following method.
As a measuring device, an automatic contact angle meter MCA-J manufactured by Kyowa Interface Science Co., Ltd. is used. Distilled water is used to measure the contact angle. The amount of liquid discharged from an ink jet type water droplet discharge part (manufactured by Cluster Technology, Inc., pulse injector CTC-25 having a discharge part pore diameter of 25 μm) is set to 20 picoliters, and a water drop is dropped directly above the fiber. The state of dripping is recorded on a high-speed recording device connected to a horizontally installed camera. The recording device is preferably a personal computer incorporating a high-speed capture device from the viewpoint of image analysis or image analysis later. In this measurement, an image is recorded every 17 msec. In the recorded video, the first image of water droplets on the fiber is attached to the attached software FAMAS (software version is 2.6.2, analysis method is droplet method, analysis method is θ / 2 method, image processing algorithm Is non-reflective, the image processing image mode is frame, the threshold level is 200, and the curvature is not corrected). Image analysis is performed to calculate the angle between the surface of the water droplet that touches the air and the fiber, and the contact angle And In addition, the measurement sample (fiber obtained by taking out from the nonwoven fabric) is cut from the nonwoven fabric with a fiber length of 1 mm, and the fiber is placed on the sample table of the contact angle meter and maintained horizontally. Measure the contact angle at the location. In each of the above-mentioned parts, N = 5 contact angles are measured to one decimal place, and a total of 10 measured values (rounded to the second decimal place) is calculated as the contact angle at each part. Define.

The moisture-permeable breathable film 3 is caused by unstable stress in film formability due to the addition of filling fine particles, and stress concentration on non-uniform portions on the film due to stretching for porous formation. As a result, pinholes 31 that are larger than other fine holes may be formed.
According to the diaper 10 of the present embodiment, as shown in FIG. 5A, in a state where the liquid U such as urine oozes out from the pinhole 31 generated in the breathable film 3 and accumulates in the outer nonwoven fabric 1. When the outer layer nonwoven fabric 1 is compressed by applying pressure due to body pressure or the like, as shown in FIG. 5 (b), the liquid U has a more hydrophilic plane direction than moving to the less hydrophilic clothing side. It is easy to spread. Moreover, in the outer layer nonwoven fabric 1 in this embodiment, since it has a hydrophilic gradient in the thickness direction, the effect that it is easy to spread in the plane direction from the clothing side occurs continuously in the thickness direction. Even if is compressed, the liquid U inside hardly reaches the outer surface of the diaper.

FIG.5 (c) and FIG.5 (d) are figures which show the case where an outer-layer nonwoven fabric is a water-repellent nonwoven fabric as a whole. When the whole is water-repellent, as shown in FIG. 5C, in the state where the liquid U such as urine that has oozed out from the pinhole 31 generated in the air permeable film 3 is accumulated in the outer layer nonwoven fabric. Even if 1 is compressed, as shown in FIG.5 (d), the effect that it is easy to spread in the plane direction rather than the clothing side with low hydrophilicity does not arise in the outer-layer nonwoven fabric. Therefore, the internal liquid U reaches the outer surface of the diaper along with the compression, and the clothes are soiled or wet.
In addition, when the outer layer nonwoven fabric is a nonwoven fabric having two layers of a hydrophilic layer and a hydrophobic layer, the liquid exuded from the breathable film is accumulated in the outer layer nonwoven fabric, and the outer layer nonwoven fabric is pressurized and compressed by weight or the like. In this case, the effect of spreading the liquid to the left and right only at the boundary between the hydrophilic layer and the hydrophobic layer can occur, and the liquid staying outside the diaper (hydrophobic layer) from the boundary between the hydrophilic layer and the hydrophobic layer is in a plane direction. Since the spreading force does not work, the liquid inside the hydrophobic layer once reaches the outer surface of the diaper easily.

  From the viewpoint of preventing oozing of the liquid to the outer surface of the diaper, the surface P4 on the inner surface side of the diaper is such that the contact angle of water with respect to the fiber measured by the method described above is preferably 80 ° or less, more preferably 75 ° or less. And preferably 60 ° or more, more preferably 65 ° or more. Further, from the same viewpoint, the surface P1 on the outer surface side of the diaper has a water contact angle with respect to the fiber measured by the method described above of preferably 70 ° or more, more preferably 75 ° or more, and more preferably 95 °. Hereinafter, it is more preferably 85 ° or less.

In the outer layer nonwoven fabric 1 in the diaper 10 of the present embodiment, the gap between fibers on the inner surface side of the diaper is narrower than the gap between fibers on the outer surface side of the diaper. That is, the porosity between fibers on the inner surface side of the diaper is smaller than the porosity between fibers on the outer surface side of the diaper.
Therefore, in the state where the liquid U such as urine oozes out from the pinhole 31 generated in the air permeable film 3 and is accumulated in the outer layer nonwoven fabric 1, when the outer layer nonwoven fabric 1 is compressed by applying pressure due to body pressure or the like, the outer layer The nonwoven fabric is first compressed from the outer surface side of the diaper having a wide gap between fibers. On the other hand, since the outer layer nonwoven fabric 1 is more hydrophobic on the outer surface side than the inner surface side at any position in the thickness direction as described above, the body fluid staying in the outer layer nonwoven fabric is more on the inner surface side than the outer surface side. Easy to stay. Therefore, the outer layer nonwoven fabric 1 according to this embodiment in which the gap between the fibers on the inner surface side of the diaper is narrower than the gap between the fibers on the outer surface side of the diaper and the outer surface side is easily compressed, However, it is difficult to reach the outer surface of the diaper.

Whether the gap between the fibers on the inner side of the diaper is narrower than the gap between the fibers on the outer side of the diaper, in other words, the porosity between the fibers on the inner side of the diaper is the porosity between the fibers on the outer side of the diaper. Whether or not it is smaller is determined by measuring the area ratio (%) in which the fiber occupies the space by the following method and subtracting the value from 100% to calculate the void ratio (%) between the fibers. That is, when the area ratio (%) for the fibers on the diaper inner surface side is higher than the area ratio (%) for the fibers on the diaper outer surface side, the void ratio between the fibers on the diaper inner surface side is on the diaper outer surface side. It is determined that the void ratio between the fibers is smaller.
<Measurement method of porosity>
The non-woven fabric is cut along two straight lines parallel to the direction along the longitudinal direction of the diaper so that the length in the direction along the width direction of the diaper is 0.5 to 1.0 mm to obtain a measurement sample. Then, the measurement sample is placed on a black mount horizontally arranged with the thickness direction of the cross section along the longitudinal direction of the cut diaper facing up and down in the vertical direction, and an enlarged photograph of the cross section along the longitudinal direction of the diaper Is obtained with a microscope (manufactured by Keyence Corporation, VHX-900). This data (jpeg) is subjected to image analysis using image analysis software (NexusNewQube). Specifically, binarization treatment was performed in the range of 0.2 mm in the thickness direction of the sample and 1 mm in the direction along the longitudinal direction of the diaper to obtain the area ratio occupied by the fiber, and this value was subtracted from 100%. A thing is made into the porosity (%) between the fibers in each position.

The non-woven fabric, the side disposed on the outer surface side of the diaper is defined as the upper side, the side disposed on the inner surface side of the diaper is defined as the lower side, and the porosity between the fibers is determined for each of the upper side and the lower side. The obtained non-woven fabric upper-side porosity X and non-woven fabric lower-side porosity Y, and the value calculated by the calculation formula X / Y is the density ratio. When the density ratio is larger than 1, it indicates that the porosity between fibers on the inner surface side of the diaper is smaller than the porosity between fibers on the outer surface side of the diaper. In addition, when a nonwoven fabric has an unevenness | corrugation, it measures just under the vertex of a convex part.
The porosity is preferably 20% or more, more preferably 30% or more, and 80% from the viewpoint of suppressing the body fluid U accumulated in the nonwoven fabric from exuding from the outer surface of the diaper. % Or more, more preferably 70% or less. The porosity of the lower side of the nonwoven fabric is preferably 15% or more, more preferably 25% or more, and preferably 75% or less, more preferably 65% or less.

  Further, the outer layer nonwoven fabric 1 has a thickness t in a non-pressurized state of preferably 0.5 mm or more, more preferably 1.0 mm or more, from the viewpoint of more efficiently suppressing the bleeding of the liquid U. Preferably it is 5.0 mm or less, More preferably, it is 3.0 mm or less, Preferably it is 0.5-5.0 mm, More preferably, it is 1.0-3.0 mm.

Further, the outer layer nonwoven fabric 1 preferably has a basis weight (weight per unit area) of 10 g / m ² or more from the viewpoint of preventing crushing at the time of compression due to a relatively low pressure and more effectively suppressing the bleeding of the liquid U. The amount is preferably 15 g / m ² or more, and preferably 50 g / m ² or less, more preferably 40 g / m ² or less, from the viewpoint of the appearance and texture of the diaper.

  For example, the outer layer nonwoven fabric 1 of the present embodiment forms a fiber web or a nonwoven fabric by using fibers whose hydrophilicity is lowered by heat treatment, and then produces an intermediate nonwoven fabric having one uneven surface by embossing, It is obtained by subjecting the intermediate nonwoven fabric to hot air passing from the uneven surface side to the flat surface side and subjecting it to an air-through heat treatment. The fiber whose hydrophilicity is lowered by heat treatment is a fiber whose length is increased by heating (hereinafter also referred to as a heat-extensible composite fiber), and is made hydrophilic by applying a hydrophilizing agent to the surface thereof. It is preferable. Examples of the heat-extensible fiber include a fiber that spontaneously extends as the crystal state of the resin changes due to heating. The heat-extensible fiber is present in the nonwoven fabric in a state where its length is extended by heating and / or in a state where it can be extended by heating. By using a heat-extensible fiber, a nonwoven fabric having a relatively large hydrophilic gradient using a single type of fiber can be obtained more easily.

A preferable heat-extensible conjugate fiber has a first resin component that constitutes a core portion and a second resin component that comprises a polyethylene resin and constitutes a sheath portion, and the first resin component is a second resin component. Has a higher melting point. A 1st resin component is a component which expresses the heat | fever extensibility of this fiber, and a 2nd resin component is a component which expresses heat-fusibility.
The melting points of the first resin component and the second resin component were determined by thermal analysis of a finely cut fiber sample (sample weight 2 mg) using a differential scanning calorimeter (DSC6200 manufactured by Seiko Instruments Inc.) at a heating rate of 10 ° C./min. The melting peak temperature of each resin is measured and defined by the melting peak temperature. When the melting point of the second resin component cannot be clearly measured by this method, the resin is defined as “resin having no melting point”. In this case, the temperature at which the second resin component is fused to such an extent that the strength of the fusion point of the fiber can be measured is used as the temperature at which the molecular flow of the second resin component begins, and this is used instead of the melting point.

  The preferred orientation index of the first resin component in the heat-stretchable conjugate fiber is naturally different depending on the resin used. For example, in the case of a polypropylene resin, the orientation index is preferably 60% or less, more preferably 40% or less. More preferably, it is 25% or less. When the first resin component is polyester, the orientation index is preferably 25% or less, more preferably 20% or less, and still more preferably 10% or less. On the other hand, the second resin component preferably has an orientation index of 5% or more, more preferably 15% or more, and still more preferably 30% or more. The orientation index is an index of the degree of orientation of the polymer chain of the resin constituting the fiber. And when the orientation index of a 1st resin component and a 2nd resin component is each said value, a heat | fever extensible composite fiber comes to expand | extend by heating.

The orientation index of the first resin component and the second resin component is expressed by the following formula (1), where A is the birefringence value of the resin in the heat-extensible conjugate fiber, and B is the intrinsic birefringence value of the resin. expressed.
Orientation index (%) = A / B × 100 (1)
Intrinsic birefringence refers to birefringence in the state where the polymer polymer chains are perfectly oriented. The values are, for example, the first edition of “Plastic Materials in Molding”, and the typical plastic materials used in molding processes (plastics). Edited by the Japan Society for Molding and Processing, Sigma Publishing, published on February 10, 1998).
The birefringence in the heat-extensible composite fiber is measured under polarization in a direction parallel to and perpendicular to the fiber axis by attaching a polarizing plate to an interference microscope. As the immersion liquid, a standard refraction liquid manufactured by Cargille is used. The refractive index of the immersion liquid is measured with an Abbe refractometer. From the interference fringe image of the composite fiber obtained by the interference microscope, the refractive index in the direction parallel and perpendicular to the fiber axis is obtained by the calculation method described in the following document, and the birefringence that is the difference between the two is calculated.
“Fiber structure formation in high-speed spinning of core-sheath type composite fiber”, page 408 (Journal of the Fiber Society, Vol. 51, No. 9, 1995)
In order to achieve the orientation index as described above for each resin component in the thermally stretchable conjugate fiber, for example, the first resin component and the second resin component having different melting points are used, and melt spinning is performed at a low speed of less than 2000 m / min. Then, after obtaining the composite fiber, the composite fiber may be heat-treated and / or crimped. In addition to this, the stretching process may be avoided.

In a preferred example, the thermally stretchable conjugate fiber exhibits thermal stretchability as a whole fiber by extending the first resin component (at this time, the first resin component is a thermal stretch component and the second resin is non-thermal stretch). Called ingredients). At that time, the film can be stretched by heat at a temperature lower than the melting point of the heat stretchable component. The heat-extensible composite fiber preferably has a fiber thermal elongation rate of 0.5 to 20% at a temperature 10 ° C. higher than the melting point of the non-heat-extensible component (softening point in the case of a resin having no melting point). More preferably, it is 3 to 20%, and still more preferably 5.0 to 20%. A nonwoven fabric containing fibers having such a thermal elongation rate becomes bulky due to the elongation of the fibers or has a three-dimensional appearance.
When the “thermal elongation rate of the fiber” is a positive value, the fiber is called “thermally extensible fiber”. The “fiber thermal elongation ratio” of the raw material of the nonwoven fabric is measured by the following method. A thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc. is used. As a sample, a sample obtained by collecting a plurality of fibers having a fiber length of 10 mm or more so that the total weight per 10 mm of the fiber length is 0.5 mg, and arranging the plurality of fibers in parallel, chuck It is mounted on the device at a distance of 10 mm. The measurement start temperature is 25 ° C., and the temperature is increased at a temperature increase rate of 5 ° C./min with a constant load of 0.73 mN / dtex applied. The amount of elongation of the fiber at that time is measured, and the amount of elongation X (mm) at a temperature 10 ° C. higher than the melting point of the non-thermally extensible component (in the case of a resin having no melting point) is read. Calculate the thermal expansion rate.
Fiber thermal elongation (%) = (X / 10) × 100
The reason for measuring the thermal elongation rate of the fiber at the above-mentioned temperature is that when the nonwoven fabric 10 is produced by thermally fusing the intersection of the fibers, the temperature is equal to or higher than the melting point or softening point of the second resin component and 10 ° C. from them. This is because it is usually produced in a range up to a high temperature.

[Evaluation of thermal extensibility of fibers in non-woven fabric]
Whether or not the fibers in the nonwoven fabric use heat-extensible composite fibers can be determined by measuring the “residual thermal elongation rate”. “Residual thermal elongation rate” means that when a heat-extensible fiber is made into a non-woven fabric, even if the fiber is heated to a certain temperature and heated to a temperature higher than that temperature, only the remaining thermal elongation This is because thermal expansion is possible.
The “remaining thermal elongation rate” is measured using the following method. First, fibers are collected from an arbitrary part of the nonwoven fabric. The length of the fiber to be collected is 1 mm or more and 5 mm or less. The collected fiber is sandwiched between preparations, and the total length of the sandwiched fiber is measured. The measurement is performed using a microscope VHX-900 and a lens VH-Z20R manufactured by KEYENCE, observing the fibers at a magnification of 50 to 100 times, and using a measurement tool incorporated in the apparatus for the observed image. . The length obtained by the measurement is defined as “the total length of fibers collected from the nonwoven fabric” Y. The fiber whose total length has been measured is placed in a DSC6200 sample container (product name: robot container 52-023P, 15 μL, aluminum) manufactured by SII Nano Technology. The container containing the fibers is placed in a sample place in a DSC 6200 heating furnace set in advance in the range of a temperature lower than the melting point of the first resin component by 30 ° C. Temperature set by a temperature measured by a thermocouple installed directly under the DSC6200 sample place (display name in measurement software: sample temperature) within a range of 30 ° C. lower than the melting point of the first resin component ± After reaching the range of 1 ° C., heat for 60 seconds and then quickly remove. The heat-treated fiber is taken out from the DSC sample container and sandwiched between preparations, and the total length of the sandwiched fiber is measured. For measurement, a microscope VHX-900 and a lens VH-Z20R manufactured by KEYENCE were used. The measurement was performed by observing the fiber at a magnification of 50 to 100 times and using a measurement tool incorporated in the apparatus for the observed image. The length obtained by the measurement is referred to as “full length of fiber after heat treatment” Z. The thermal elongation rate (%) remaining on the fibers in the nonwoven fabric is calculated from the following equation.
Residual thermal elongation (%) = (Z−Y) ÷ Y × 100 [%]
The above-mentioned “residual thermal elongation” is measured for any fiber, and when there is a fiber having a value of “residual thermal elongation” greater than 0, the heat-extensible composite fiber referred to in this application is used. It can be judged.
Here, when the first resin component of the fiber to be measured is a polyethylene terephthalate resin or a polypropylene resin, the temperature can be measured at a temperature 10 ° C. lower than the melting point.

  The ratio (mass ratio) of the first resin component and the second resin component in the heat-extensible composite fiber is 10:90 to 90: 10%, particularly 20:80 to 80: 20%, especially 50:50 to 70:30. % Is preferred. As the fiber length of the heat-extensible conjugate fiber, one having an appropriate length is used according to the method for producing the nonwoven fabric. For example, when the nonwoven fabric is manufactured by the card method as described later, the fiber length is preferably about 30 to 70 mm.

  The thickness of the heat-extensible composite fiber is preferably 1.0 dtex or more, more preferably 2.0 dtex or more, from the viewpoint of more easily holding the liquid U and more effectively suppressing the liquid U from exuding. In addition, from the viewpoint of keeping the touch of the diaper well, it is preferably 5.0 dtex or less, more preferably 4.2 dtex or less, and preferably 1.0 to 5.0 dtex, more preferably 2.0 to 4. 2 dtex.

  As the heat-extensible composite fiber, in addition to the above-described heat-extensible composite fiber, Japanese Patent No. 4131852, Japanese Patent Application Laid-Open No. 2005-350836, Japanese Patent Application Laid-Open No. 2007-303035, Japanese Patent Application Laid-Open No. 2007-204899, The fibers described in JP 2007-204901 A and JP 2007-204902 A can also be used.

As described above, the hydrophilic property of the heat-extensible composite fiber is enhanced by the hydrophilic agent adhering to the surface, and when the heat-extensible composite fiber is stretched by heating, the inside of the fiber becomes hydrophilic. The agent is taken in and the hydrophilicity decreases. Therefore, by blowing hot air from one side of the web or nonwoven fabric produced using the heat-extensible conjugate fiber, the hydrophilicity of the fiber on the side close to the one side is greatly reduced, while the side far from the other side is reduced. A decrease in the hydrophilicity of the fiber is suppressed, whereby a hydrophilic gradient is obtained in the thickness direction. From the viewpoint of making a difference in the heat treatment state of the fiber on the front and back sides and effectively obtaining a hydrophilic gradient, the preferred wind speed is preferably an ultra-fine wind of less than 0.4 m / sec.
The temperature of the hot air to be blown is set to a temperature equal to or higher than the melting point of the sheath resin component in the thermally extensible fiber. The temperature here refers to the temperature of hot air on the surface of the fiber web. In reality, however, the measurement of the hot air temperature at that position is technically very difficult, so in this patent, the temperature of the hot air is measured at a position 10 cm above the web, and the temperature is If the temperature is equal to or higher than the melting point of the two resin components, the temperature of the hot air on the surface of the web is also considered to be a temperature equal to or higher than the melting point of the second resin component. The temperature of the hot air at a position 10 cm above the web is preferably Mp or more and Mp + 50 ° C. or less, and preferably Mp or more and Mp + 30 ° C. or less, where the melting point of the second resin component is Mp (° C.). The temperature of the hot air is measured by, for example, a thermocouple.
As the hydrophilizing agent, various known ones conventionally used in the field of absorbent articles such as disposable diapers can be used without particular limitation. For example, the hydrophilizing agents A to R described in paragraph [0070] of JP2010-168715A can be used.

  As a method for attaching the hydrophilizing agent to the fiber surface, various known methods can be employed without any particular limitation. For example, application by spraying, application by slot coater, application by roll transfer, immersion in a hydrophilic oil, and the like can be mentioned. These treatments may be performed on the fibers before being formed into a web, or may be performed after the fibers are formed into a web by various methods. The fiber to which the hydrophilizing agent has adhered to the surface is dried at a temperature sufficiently lower than the melting point of the ethylene resin (for example, 120 ° C. or less) by, for example, a hot air blowing dryer.

  As described above, the outer-layer nonwoven fabric 1 used in the present embodiment, as shown in FIGS. 3 and 4, is embossed on the outer surface side of the diaper, as compared with the thin portion 18 and the portion 18. A relatively thick portion 19 is formed. As shown in FIG. 3 and FIG. 4, the thin portion 18 is formed in a dotted shape so as to have a space between each other, so that the pressure due to body pressure or the like is applied to the outer nonwoven fabric 1 in which the liquid U is accumulated. Is added to prevent the liquid U from spreading in the plane direction when the outer layer nonwoven fabric 1 is compressed. Further, the shortest distance between the thin portion 18 and the thinnest portion 18 is preferably 3 mm or more, more preferably 5 mm or more, and preferably 20 mm or less, more preferably 15 mm or less. It is preferably 3 to 20 mm, more preferably 5 to 15 mm.

Moreover, as shown in FIG. 3, the outer layer nonwoven fabric 1 is integrated with the outer layer nonwoven fabric 1 with the flat surface 1a side, which is a highly hydrophilic side, facing the breathable film 3 side.
Further, the outer layer nonwoven fabric 1 is preferably at least in contact with the outer surface of the breathable film 3, and the hot melt adhesive is between the outer layer nonwoven fabric 1 and the outer surface of the breathable film 3. It is preferable that it is partially joined by such as. Examples of the adhesive coating pattern in the case of partial bonding include a spiral pattern, a stripe pattern, and a lattice pattern.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to embodiment mentioned above.
For example, the outer layer nonwoven fabric may have a uniform thickness.
Moreover, the formation pattern of the embossed part in the case of forming an embossed part in a nonwoven fabric can be changed arbitrarily. As the shape of each embossed portion arranged in a scattered dot shape, a symbol shape of “+”, a circle, an ellipse, a triangle, a quadrangle, a hexagon, a heart shape, and an arbitrary shape can be used. In addition, a square or rectangular lattice shape, a multi-row stripe shape, a checkered pattern shape, a spiral shape or the like can be used.
Moreover, as shown in FIG. 6, the outer layer nonwoven fabric in the disposable diaper of this invention may be a multilayer nonwoven fabric in which a plurality of nonwoven fabrics are laminated. The disposable diaper may be a pants-type disposable diaper for infants or adults, in addition to an unfolded disposable diaper for infants or adults. Further, the outer layer nonwoven fabric 1 may cover the breathable film over the entire outer surface of the diaper, or only the outer surface side of the breathable film only at a part of the outer surface of the diaper, for example, at a portion overlapping the absorber. It may be coated.

  The outer layer nonwoven fabric 1 shown in FIG. 3 has a single layer structure, and the entire thickness direction is a portion having a hydrophilic gradient in the thickness direction, but the outer layer nonwoven fabric of the present invention is a part in the thickness direction. Only the part which has a hydrophilic gradient and the more hydrophilic side of the part may be directed to the inner surface of the diaper. For example, the outer layer non-woven fabric of the present invention has a hydrophilic gradient in the thickness direction, and a laminated layer composed of a non-woven fabric whose higher hydrophilic side is directed to the inner surface of the diaper and one or more other non-woven fabrics. It may be a non-woven fabric. When the outer nonwoven fabric is a laminated nonwoven fabric, the nonwoven fabric having a hydrophilic gradient in the thickness direction and having a more hydrophilic side directed toward the inner surface of the diaper is the outermost surface of the leak-proof sheet that forms the outer surface of the diaper. May be disposed adjacent to the breathable film, or may be disposed between another nonwoven fabric and the breathable film.

This invention discloses the following absorbent articles further regarding embodiment mentioned above.
<1> A disposable diaper provided with a liquid-permeable surface sheet, a leak-proof sheet, and an absorbent body disposed between the two sheets,
The leakproof sheet has a liquid-permeable and air-permeable breathable film, and an outer layer nonwoven fabric that covers the outer surface side of the gas-permeable film.
The outer layer non-woven fabric is made of a non-woven fabric having a hydrophilic gradient in the thickness direction in whole or in part, and the surface of the outer layer non-woven fabric 1 located on the outer surface side of the diaper at the same position in the plane direction is P1. When the surface located on the inner surface side is P4, and the two intermediate points located between them are P2 and P3 in order from the side close to P1, the contact angle of water with respect to the fibers taken out from each part P1 to P4 is The disposable diaper which is increasing in this order from P4 to P1.
<2> The outer layer non-woven fabric has a concavo-convex surface having a concavo-convex shape on the non-skin surface side directed to the diaper outer surface side, and the skin surface side directed to the breathable film side is flat or the concavo-convex surface. The disposable diaper as described in said <1> which is a flat surface where the degree of unevenness is small.
<3> The outer layer nonwoven fabric is an air-through nonwoven fabric using heat-extensible fibers, and a thin portion and a thick portion are formed by embossing, according to <1> or <2>. Disposable diapers.
<4> The disposable diaper according to <3>, wherein a plurality of the thin portions are formed by being dispersed in the planar direction of the outer layer nonwoven fabric.
<5> The heat-extensible conjugate fiber has a first resin component that constitutes a core portion, and a second resin component that comprises a polyethylene resin and constitutes a sheath portion. The disposable diaper according to <3> or <4>, which has a melting point higher than two resin components.
<6> The first resin component in the heat-extensible conjugate fiber is a polyester resin, and the orientation index of the first resin component is preferably 25% or less, more preferably 20% or less, and still more preferably. The disposable diaper according to any one of <3> to <5>, which is 10% or less.
<7> The second resin component preferably has an orientation index of 5% or more, more preferably 15% or more, and still more preferably 30% or more. The disposable diaper according to claim 1.
<8> The diaper inner surface of the outer layer nonwoven fabric has a water contact angle with respect to the fibers of preferably 80 ° or less, more preferably 75 ° or less, preferably 60 ° or more, more preferably 65 ° or more. The disposable diaper according to any one of <1> to <7>.
<9> The outer surface of the diaper of the outer layer nonwoven fabric has a water contact angle with respect to the fibers of preferably 70 ° or more, more preferably 75 ° or more, and more preferably 95 ° or less, more preferably 85 or less. The disposable diaper according to any one of <1> to <8>, wherein
<10> The disposable fabric according to any one of <1> to <9>, wherein the non-woven fabric having the hydrophilic gradient is such that a gap between fibers on the inner surface side of the diaper is narrower than a space between fibers on the outer surface side of the diaper. Diapers.
<11> The disposable diaper according to <10>, wherein a void ratio on an upper side of the outer layer nonwoven fabric is preferably 20% or more, more preferably 30% or more, and 80% or more, more preferably 70% or less.
<12> The porosity of the lower side of the outer layer nonwoven fabric is preferably 15% or more, more preferably 25% or more, and preferably 75% or less, more preferably 65% or less. 11> disposable diapers.
<13> The disposable diaper according to any one of <1> to <12>, wherein the outer-layer nonwoven fabric has a single-layer structure.
<14> The disposable diaper according to any one of <1> to <13>, wherein the outer layer nonwoven fabric uses a single type of fiber.
<15> The outer layer nonwoven fabric according to any one of <1> to <12>, wherein the outer nonwoven fabric is a laminated nonwoven fabric composed of the nonwoven fabric having the hydrophilicity gradient and one or more other nonwoven fabrics. Disposable diapers.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not restrict | limited at all by the following examples.

[Example 1]
Using the fibers shown in Table 1, a web was formed using a card machine, and the web was embossed. The fiber 1 is a heat-extensible core-sheath type composite fiber having a core PET and a sheath PE, and a hydrophilic agent 1 described later is attached to the surface of the fiber 1. The embossing is performed between an embossing roll having a convex portion corresponding to the shape of the embossed portion on the surface and an anvil roll having a smooth surface, and the embossed portion is formed in a cross-like pattern as shown in FIG. It was set as the pattern in which the embossed part 18 which was spaced apart was formed in a staggered pattern. The embossing processing temperature was 120 ° C. for both the embossing roll and the flat roll. Next, heat treatment was performed by an air-through method that penetrates hot air. The air-through heat treatment was performed once by blowing hot air from the embossed surface side of the unevenness. The heat treatment temperature for air-through processing was 133 ° C., and the wind speed was 0.4 m / sec.
The obtained non-woven fabric has a thin portion (embossed portion) 18 and a thick portion 19 other than that, and one surface is a rough surface 1b having a large undulation, and the other surface is a substantially flat flat surface 1a. It was.
[Example 2]
Nonwoven fabrics were made for each of the two types of fibers shown in Table 1, and were stacked to form an outer layer nonwoven fabric. The fiber 1 in Table 1 is a heat-extensible core-sheath type composite fiber having a PET core and a sheath PE, and a hydrophilic agent 1 described later attached to the surface. A nonwoven fabric was produced in the same manner. The fiber 2 in Table 1 is a core-sheath type composite fiber having a PET core and a PE sheath, and is TJ04CE SD2.0 × 44TG made by Teijin Fibers. A nonwoven fabric was produced in the same manner as in Example 1 except that this fiber was used, the basis weight was 15 gsm, and heat embossing was not performed. The above-mentioned two nonwoven fabrics were overlapped to form one nonwoven fabric so that the surface on the uneven surface 1b side of the nonwoven fabric using the fibers 1 of Table 1 formed the outer surface of the diaper.

[Comparative Example 1]
A nonwoven fabric was produced in the same manner as in Example 1 except that the fibers used were changed as shown in Table 1.
In Comparative Example 1, the heat-fusible core-sheath fiber is TJ04CE SD2.0 × 44TG manufactured by Teijin Fibers, which is a core-sheath type composite fiber having a core PET and a sheath PE.
[Comparative Example 2]
Two different types of fibers shown in Table 1 were used. The web was formed by stacking two different types of fibers separately formed using a card machine to form one web. Thereafter, a nonwoven fabric was produced in the same manner as in Example 1. The heat-fusible core-sheath fiber used for the layer forming the surface on the uneven surface 1b side of the web is a core-sheath type composite fiber having a core PET and a sheath PE, and the following hydrophilizing agent 1 is attached to the surface. It has been made. The heat-fusible core-sheath fiber used for the layer on the opposite side of the uneven surface 1b side of the web is TJ04CE SD2.0 × 44TG made by Teijin Fibers, which is a core-sheath type composite fiber having a core PET and a sheath PE. is there.
The fibers “J04CE SD2.0 × 44TG” used in Example 2, Comparative Example 1 and Comparative Example 2 were all treated with the following hydrophilizing agent 2.

Hydrophilizing agent 1: Alkyl phosphate dipotassium salt (Kao Corporation, neutralized potassium hydroxide of gripper 4131) 100% by weight Hydrophilizing agent 2: Polyoxyethylene alkylamine (Kao Corporation, Amit 302) and diglycerin laurate (Riken Vitamin Co., Ltd., Riquemar L-71-D) blended at 50% by weight: 50% by weight.

[Evaluation of non-woven fabric]
1. Presence / absence of hydrophilic gradient About the nonwoven fabrics obtained in Examples and Comparative Examples, a flat surface is formed from the surface P1 on the uneven surface 1b side in the central portion (the top position of the convex portion) of the thick portion 19 surrounded by the embossed portion. With respect to the four fibers over the surface P4 on the 1a side, the contact angle of water with respect to the fibers was measured by the method described above.
The results are shown in Table 1. As shown in Table 1, the nonwoven fabrics of Examples 1 and 2 have a hydrophilic gradient that is continuous in the thickness direction, whereas the nonwoven fabric of Comparative Example 1 does not have a hydrophilic gradient in the thickness direction. The non-woven fabric of No. 2 had a two-layer structure with different hydrophilicity.
2. Ratio of porosity of fibers For the nonwoven fabrics obtained in the examples and comparative examples, the ratio of the porosity between the fibers on the outer side of the diaper, the ratio between the fibers on the inner side of the diaper, and the ratio of the porosity are obtained by the method described above. Table 1 shows the results. As shown in Table 1, the porosity ratio of only the nonwoven fabric of Example 1 was higher than 1, and the porosity on the diaper inner surface side was smaller than the porosity on the diaper outer surface side. In Example 2, two nonwoven fabrics were overlapped to form one nonwoven fabric, and the porosity of the fibers was measured by measuring the porosity between the fibers on the outer surface side and the inner surface side of each nonwoven fabric.

[Evaluation of diapers]
About each nonwoven fabric of an Example and a comparative example, when it used as an outer-layer nonwoven fabric of a diaper, it was evaluated by the following method how much body fluid leakage prevention property was obtained.
That is, the nonwoven fabric was placed on the filter paper with the surface P1 on the uneven surface 1b side facing downward. Next, 1 μL of artificial urine was dropped thereon (in the center of the embossed pattern if embossed). Further, a liquid-impermeable and gas-permeable sheet was placed thereon, and then 35 g / cm ² load was applied. After leaving for 10 seconds, the presence or absence of artificial urine on the filter paper was visually confirmed.
Evaluation was made at N = 10, and C was assigned to all of them, B was assigned to 5 or more pieces, and A was attached to 4 or less pieces.

As can be seen from the results shown in Table 1, in the case of Comparative Examples 1 and 2, the body fluid leaked to the filter paper side, while the outer layer nonwoven fabric having a hydrophilic gradient was more hydrophilic. In the case of Examples 1 and 2 used on the inner surface side of the diaper, no leakage of body fluid to the filter paper side occurred.
From this, it can be seen that the disposable diaper of the present invention is difficult to ooze the liquid in the outer layer nonwoven fabric to the outer surface of the diaper even when pressurized by body pressure or the like, and it is difficult to soil or moisten clothing.

DESCRIPTION OF SYMBOLS 1 Outer layer nonwoven fabric 1b Uneven surface 1a Flat surface P1 Diaper outer surface side P2 Intermediate point 3 Breathable film 4 Absorbent body 10 Disposable diaper 20 Surface sheet 30 Leakproof sheet 1 Outer layer nonwoven fabric 18 Thin portion (embossed portion)
DESCRIPTION OF SYMBOLS 19 Thick part 119 Convex part 31 Pinhole 40 Absorber 41 Absorbent core 42 Core wrap sheet 50 Fastening tape 60 Landing tape 70 Side sheet

Claims (5)

A disposable diaper comprising a liquid-permeable surface sheet, a leak-proof sheet and an absorbent body disposed between the two sheets,
The leakproof sheet has a liquid-permeable and air-permeable breathable film, and an outer layer nonwoven fabric that covers the outer surface side of the gas-permeable film.
The outer layer non-woven fabric is made of a non-woven fabric having a hydrophilic gradient in the thickness direction in whole or in part in the thickness direction, and the non-woven fabric has a surface located on the outer surface side of the diaper at the same position in the plane direction of the outer layer non-woven fabric. When P1, the surface located on the inner surface side of the diaper is P4, and the two intermediate points located between them are P2, P3 in order from the side closer to P1, water for the fibers taken out from the respective parts P1 to P4 The contact angle increases in this order from P4 to P1 ,
The said nonwoven fabric which has the said hydrophilicity gradient is a disposable diaper whose space | gap between the fibers in a diaper inner surface side is narrower than the space | gap between the fibers in a diaper outer surface side .   The disposable diaper according to claim 1, wherein the outer layer nonwoven fabric is an air-through nonwoven fabric using heat-extensible fibers, and a thin portion and a thick portion are formed by embossing.   The disposable diaper according to claim 2, wherein a plurality of the thin portions are dispersed and formed in a planar direction of the outer layer nonwoven fabric. The disposable diaper according to any one of claims 1 to 3 , wherein the outer layer nonwoven fabric has a single-layer structure. The disposable diaper according to any one of claims 1 to 3 , wherein the outer layer nonwoven fabric is a laminated nonwoven fabric composed of the nonwoven fabric having the hydrophilicity gradient and one or more other nonwoven fabrics.

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