JP4540567B2 - Leak-proof sheet and absorbent article - Google Patents

Description

  The present invention relates to a leak-proof sheet having moisture permeability. Moreover, this invention relates to the absorbent article provided with this leak-proof sheet.

  Absorbent articles such as panty liners (sheets for measures against vaginal discharge) and side pads have been worn for about half a day due to the recent increase in the employment rate of women and longer hours of going out. . In these articles, even if worn for a long time, neither steaming nor stickiness occurs, and maintaining a feeling of sarat for a long time is one of important functions.

  For example, a panty liner has been proposed in which a liquid permeation resistant and air permeable intermediate layer sheet is interposed between a top sheet having through holes and a breathable back sheet (see Patent Document 1). According to this panty liner, it is said that excellent air permeability can be maintained even after body fluid absorption. However, in this panty liner, since the absorbed body fluid does not pass through the intermediate layer sheet and does not reach the back sheet, the rate at which the body fluid evaporates from the back sheet as water vapor is not sufficient. I can't say that. Therefore, even if the sticky feeling due to the body fluid coming into direct contact with the wearer's skin is improved, the feeling of stuffiness caused by water vapor generated by warming the entire absorbent article at body temperature is still likely to occur for a long time. It is difficult to maintain the feeling of sarat when worn.

JP-A-11-28222

  The purpose of the present invention is to comfortably use the sarat feeling until the end of use, without feeling of stuffiness or stickiness even when worn for a long time to absorb small quantities of body fluids such as caged goods, sweat, breast milk etc. It is in providing the absorbent article which can be done. Moreover, the objective of this invention is providing the leak-proof sheet | seat used suitably for this absorbent article.

  The present invention provides the above-mentioned object by providing a leak-proof sheet having a permeation layer capable of penetrating liquid and a liquid-impervious or liquid-impervious leak-proof layer and having moisture permeability as a whole. Achieved.

  The present invention also includes the leakproof sheet, wherein the leakproof sheet is provided with an absorbent article that is arranged so that the permeation layer of the leakproof sheet faces the skin side of the wearer. The goal has been achieved.

The leak-proof sheet of the present invention is compatible with the contradictory functions of moisture transfer: (i) exhausting moisture to the outside and not steaming and (b) preventing moisture from oozing out to the clothing side. According to the present invention, as a result of the moisture being easily infiltrated into the permeation layer on the side facing the wearer's skin in the leakproof sheet of the absorbent article, a large moisture discharge effect is obtained by the following two effects. It is done.
(A) As a result of allowing moisture to penetrate into the leak-proof sheet while being in a liquid state, an overwhelming difference occurs in the moisture content on the back and front of the sheet. That is, the moisture content on the side facing the wearer's skin is overwhelmingly larger than that on the side facing the underwear. The difference in the amount of moisture becomes a driving force, and the effect of transpiring the permeated moisture directly as water vapor increases.
(B) Since water permeation and diffusion occur in the leak-proof sheet portion, the evaporation area of the body fluid is increased, and water vapor is released more rapidly. As a result, it is difficult for moisture to accumulate inside the absorbent article, and it is difficult for the feeling of stuffiness due to water vapor to occur, and the feeling of slatting continues throughout the wear.
In particular, a liquid-permeable layer formed of a plurality of fiber assemblies in which the fiber density is denser in the layer facing the leak-proof sheet than on the layer in contact with the wearer's skin is disposed on the leak-proof sheet. In this case, the body fluid absorbed by the liquid permeable layer quickly moves to the vicinity of the leak-proof layer. As a result, no liquid remains on the skin contact surface of the liquid-permeable layer, and stickiness on the skin contact surface is difficult to occur.

  On the other hand, conventional leak-proof sheets have a film with extremely fine holes, or a polymer having a bulky molecular structure and appropriately high polarity segments by various methods as described later. (Non-perforated) film is mainly used. These films are materials that allow water vapor (gas) to pass through but not allow body fluid (liquid) to pass through or penetrate. Therefore, the mechanism for discharging water vapor to the outside is that the water vapor pressure generated exclusively inside the absorbent is higher than the water vapor pressure on the clothing side, that is, the water vapor pressure on the body side and the underwear side across the leak-proof sheet. It depends on gas diffusion due to the difference. In this case, the body fluid absorbed in the absorbent article cannot directly participate in water discharge. That is, unless the body fluid evaporates and the water vapor pressure is sufficiently increased, the moisture is not discharged to the outside. Further, the conventional leak-proof sheet has no moisture permeability, and furthermore, the thermoplastic resin itself as a main component is hydrophobic, so that the contact property with water is low.

  Hereinafter, an absorbent article of the present invention will be described based on a preferred embodiment thereof with reference to the drawings. As shown in FIGS. 1 and 2, a panty liner 1 as an embodiment of the absorbent article of the present invention includes a liquid-permeable layer 2 formed from a plurality of fiber assemblies, a moisture-permeable leak-proof sheet 3, and the like. Is provided. The liquid-permeable layer 2 is bonded to the leak-proof sheet 3 through an adhesive (not shown) with the bottom surface 22 facing the leak-proof sheet 3.

  FIG. 3 schematically shows the structure of the longitudinal section of the leak-proof sheet 3. The leak-proof sheet 3 has a first surface 31 and a second surface 32. The first surface 31 is a surface facing the wearer's skin. The second surface 32 is a surface facing underwear such as shorts.

  The leak-proof sheet 3 as a whole has moisture permeability and is liquid-impermeable or liquid-impermeable. The leak-proof sheet 3 can be said to be liquid-impermeable or liquid-impermeable if the following two requirements (a) and (b) are satisfied.

(A) The water pressure resistance measured by the method defined in JIS L 1092-1977 (Method B (high water pressure) described in “Waterproof test method for textile products”) is 0.18 kg / cm ² or more.

(B) In the following waterproof test as stipulated in the sanitary products voluntary standards, no bleeding should occur.
The body side of the leak-proof sheet is placed on the filter paper, and two sheets of leaching confirmation filter paper (manufactured by ADVANTEC, No. 2) having a diameter of 50 mm are stacked on the leak-proof sheet. After 1 mL of Congo Red solution (0.2 g of Congo Red dissolved in ion-exchanged water and adjusted to 100 mL in total volume) was gently allowed to flow down using a dropper or the like at about the center of the filter paper, Let stand for a minute. When a load having a diameter of 50 mm and a weight of 200 g is applied to the portion, it is confirmed whether or not the solution has oozed out on the leaching confirmation filter paper through the leak-proof sheet.

Moreover, if the moisture permeability (JIS Z0208) of the leak-proof sheet 3 is 2400 g / m ² · 24 h (1.0 g / 100 cm ² · hr) or more, the leak-proof sheet 3 has practically effective moisture permeability. Can do. In order to effectively release moisture inside the absorbent article, it is more preferable that the moisture permeability of the leak-proof sheet 3 is 3600 g / m ² · 24 h (1.5 g / 100 cm ² · hr) or more. On the other hand, if the water vapor transmission rate is extremely increased, there is a possibility that water oozes in the waterproof test. From this point of view, a preferable moisture permeability range is 2400 to 9600 g / m ² · 24 h (1.0 to 4.5 g / 100 cm ² · hr), particularly 3600 to 7200 g / m ² · 24 h (1.5 to 3.0 g). / 100 cm ² · hr).

The leak-proof sheet 3 shown in FIGS. 3 and 4 has a two-layer structure having a permeation layer 3 a including a first surface 31 and a leak-proof layer 3 b including a second surface 32. The penetration layer 3a is a layer facing the wearer's skin. The leak-proof layer 3b is a layer facing the underwear side. The permeation layer 3a is a layer capable of penetrating liquid (water). On the other hand, the leak-proof layer 3b has extremely low liquid (moisture) permeability and is liquid-impermeable or liquid-impermeable. In other words, the leak-proof layer 3b is a layer that satisfies the liquid-impermeable and breathable both requirements, osmotic layer 3 a, when causing exudation of water waterproof tests the same time high moisture permeability It is a layer which shows. Since both layers 3a and 3b are integrally formed as will be described later, the difference in liquid permeability can be confirmed by the method described below.

  The measuring method uses various colored liquids having different surface energies (that is, different penetrable diffusivities), and by dropping colored liquids having lower surface energy in order from colored liquids having higher surface energy onto the sheet surface, waterproofing of the leak-proof sheet. This is a method for evaluating sex. It is considered that the coloring liquid having a lower surface energy has higher waterproofness. Instead of the Congo red colored ion exchange water used in the waterproof test described above, a mixed liquid for wet tension test (colored in blue) manufactured by Wako Pure Chemical Industries, Ltd. is used as a colored liquid.

In a conventional moisture-permeable and leak-proof sheet that has been used in the past, the liquid permeation on both sides of the front and back surfaces does not change, so the surface energy of the liquid that causes coloring is the same on both sides. On the other hand, in the leak-proof sheet of this embodiment, the permeation layer 3a is colored with a liquid having a higher surface energy. Specifically, a conventional moisture-permeable leak-proof sheet that has been used in the past is not colored on both the front and back sides of the liquid No. 40 (surface tension 40.0 mN / m) for wet tension test, but No. 31. When the liquid is 0 (31.0 mN / m), both sides are colored. This is practically used as a guideline, and when a colored test liquid (mixture No. 40 for wetting tension test) having a surface tension of 40.0 mN / m is dropped, the test liquid is applied to the leak-proof sheet 3. When the leak-proof sheet 3 is infiltrated and colored, it can be said that the layer including the surface is the permeation layer 3a. On the other hand, the surface of the barrier sheet 3, be added dropwise colored test liquid has a surface tension of 40.0 mN / m to (get wet Re Tsutomu Cho test mixture No.40), the barrier sheet 3 colored If not, it can be said that the layer including the surface is the leak-proof layer 3b.

  The whole of the leak-proof sheet 3 is composed of a porous film having a large number of micropores. This porous film has a fine hole formed by uniaxially or biaxially stretching a sheet obtained by melt-kneading a resin composition containing a thermoplastic resin and an inorganic filler incompatible with the thermoplastic resin at a predetermined magnification. Is. Accordingly, both the permeation layer 3a and the leak-proof layer 3b constituting the leak-proof sheet 3 are obtained by uniaxially or biaxially stretching a molten extrudate of a resin composition containing a thermoplastic resin and an inorganic filler that is not compatible with the thermoplastic resin. Will be obtained. That is, the permeation layer 3a and the leak-proof layer 3b are made of a thermoplastic resin layer having a large number of fine holes.

In the permeation layer 3a and the leak-proof layer 3b, the opening state of the micropores is different on each surface. In particular,
a) The aperture size is larger on the penetration layer 3a side than the leak-proof layer 3b, and / or
b) The amount of fine openings is larger on the permeation layer 3a side than the leak-proof layer 3b.

  First, a specific example of a) is shown. In FIG. 3, the size of the micropores in the permeation layer 3a is large enough to allow penetration of both liquid and water vapor. On the other hand, the size of the micropores in the leak-proof layer 3b is small enough to allow water vapor to pass therethrough and prevent liquid penetration. As a result, the moisture derived from the body fluid sufficiently penetrates and spreads to the inside of the first surface 31 side, which is the surface facing the wearer's skin side. Therefore, there is a large difference in moisture content between the inside and outside of the leak-proof sheet 3, and the difference becomes a driving force. Further, the liquid spreads in the vicinity of the surface of the leak-proof sheet and the evaporation area is increased. Moisture accumulated inside is easily evaporated as water vapor. In particular, as will be described later, when moisture is retained in the lowermost layer (lower layer 42) of the liquid-permeable layer 2, transpiration of moisture from the leak-proof sheet 3 is further promoted.

  In order to make the size of the micropores in the osmotic layer 3a larger than the size of the micropores in the leakage preventing layer 3b, the particle size of the inorganic filler in the osmotic layer 3a is made larger than the particle size of the inorganic filler in the leakage preventing layer 3b. It is preferable to enlarge it. Specifically, the particle size of the inorganic filler in the permeation layer 3a is preferably 7 to 80 μm, and particularly preferably 12 to 55 μm, and the particle size of the inorganic filler in the leakage preventing layer 3b is 0.8 to 60 μm, particularly 1 to 25 μm. It is preferable that This particle size is measured by observing each surface with an electron microscope and averaging the diameters of particles observable from the surface by 20 points.

  Next, a specific example of b) is shown. In FIG. 4, the amount of micropores in the permeation layer 3a is large enough to allow permeation of both liquid and water vapor. On the other hand, the amount of micropores in the leak-proof layer 3b is small enough to allow water vapor to pass therethrough and prevent liquid penetration. As a result, the same water movement effect as in a) is obtained, and the water trapped inside the panty liner is easily evaporated as water vapor.

  In order to change the amount of micropores in the permeation layer 3a and the leak-proof layer 3b, it is preferable that the amount of the inorganic filler in the permeation layer 3a is larger than the amount of the inorganic filler in the leak-proof layer 3b. Specifically, the blending amount of the inorganic filler in the permeation layer 3a is preferably 45% by weight or more, more preferably 55 to 85% by weight with respect to the weight of the entire sheet. Since the excessive compounding of the inorganic filler affects the extrudability of the sheet, the most preferable compounding range that can be produced is 55 to 75% by weight. On the other hand, the blending amount of the inorganic filler in the leak-proof layer 3b is preferably 35% by weight or more, more preferably 45 to 65% by weight with respect to the weight of the entire sheet.

  In both cases a) and b), the preferred production form of the leak-proof sheet is as follows. Two types of mixtures are prepared in which the composition of the base thermoplastic resin (for example, polyethylene resin) is the same, and the particle size and / or amount of the inorganic filler to be blended is adjusted to a predetermined preferred range. Each of these mixtures is melt-kneaded and co-extruded (film extrusion with two layers from the same die), or immediately after either one is extruded to form a film, the second layer is directly extruded. Thereafter, the film is stretched at a predetermined stretching ratio to produce a large number of micropores.

  The opening state (opening diameter and opening amount) can be changed by the stretching ratio of the sheet. For example, a film in which inorganic fillers having the same particle diameter are blended in the same blending amount is stretched 4.5 times for the penetration layer 3a and 2.3 times for the leak-proof layer 3b, for example, and then both layers are coated with various adhesives. Can be attached as appropriate. However, the two methods described above are more advantageous in terms of both the fact that the two layers are fused and securely adhered, and that the stretching operation is only required once.

  As described above, the permeation layer 3a and the leak-proof layer 3b have different micropore opening states. That is, the permeation layer 3a clearly has (a) a larger opening size, (b) a larger amount of opening, or (c) both, compared to the leak-proof layer 3b. Whether such a device has been made can be confirmed by observing the first surface 31 and the second surface 32 with an electron microscope (SEM). In a conventional moisture-permeable and leak-proof film used conventionally, the open state observed with an electron microscope is the same on both sides.

  Regardless of the form of the leak-proof sheet 3, the inorganic filler contained in the leak-proof sheet 3 includes, for example, calcium carbonate, barium sulfate, zinc oxide, talc, zeolite, carbon, silica, and silicate. Minerals are used. In particular, since the particle surface is always exposed in the fine pores, it is preferable to use calcium carbonate, which is a highly hydrophilic filler, from the viewpoint that the liquid permeability in the permeation layer 3a can be further improved. Further, since calcium carbonate is an inexpensive material, it is economically advantageous. On the other hand, as the thermoplastic resin constituting the leak-proof sheet 3, for example, a polyolefin resin such as polyethylene or polypropylene is used. The kind of the inorganic filler contained in the permeation layer 3a and the inorganic filler contained in the leak-proof layer 3b may be the same or different. The thermoplastic resin constituting the permeation layer 3a and the thermoplastic resin constituting the leak-proof layer 3b may be the same or different.

In order to impart sufficient moisture permeability to the leak-proof sheet 3, the basis weight of the thermoplastic resin and the blending amount of the inorganic filler may be appropriately balanced. In order to achieve both high moisture permeability and strength that is not torn even when using a slip-fixing adhesive for fixing clothes, the preferred basis weight of the leak-proof sheet 3 (total basis weight of thermoplastic resin and inorganic filler) Is 18 to 70 g / m ² , more preferably 25 to 60 g / m ² . The basis weight of each of the permeation layer 3a and the leak-proof layer 3b in the leak-proof sheet 3 takes into consideration the liquid permeability in the permeation layer 3a, the prevention of liquid permeation by the leak-proof layer 3b, and the moisture permeability of the leak-proof sheet 3 as a whole. To be determined. The basis weight (total basis weight of the thermoplastic resin and the inorganic filler) of the osmotic layer 3a is preferably 8 to 30 g / m ² , particularly preferably 10 to 25 g / m ² . On the other hand, the basis weight (total basis weight of the thermoplastic resin and the inorganic filler) of the leak-proof layer 3b is preferably 10 to 60 g / m ² , particularly preferably 15 to 50 g / m ² .

  In addition to the leak-proof sheet shown in FIGS. 3 and 4, the leak-proof sheet 3 shown in FIG. 5 can also be used. In the leak-proof sheet 3 shown in FIG. 5, the permeation layer 3a is made of a porous film having a large number of micropores, and the leak-proof layer 3b is made of a water-repellent fiber assembly. The permeation layer 3a has the same configuration as the permeation layer 3a in the leak-proof sheet described so far. On the other hand, as the leak-proof layer 3b, a nonwoven fabric or a web is used, for example. It is preferable to use a water-repellent nonwoven fabric as the leak-proof layer 3b from the viewpoint that the liquid is difficult to penetrate.

Examples of the water-repellent nonwoven fabric include spunbond nonwoven fabric, meltblown nonwoven fabric, spunbond-meltblown-spunbond (SMS) nonwoven fabric, spunbond-meltblown-meltblown-spunbond (SMMS) nonwoven fabric, and the like. The basis weight of these nonwoven fabrics, 12~60g / m ² from the viewpoint of prevention of penetration of permeable and liquid vapor, particularly preferably 16~40g / m ^2.

  The leak-proof sheet 3 of the present embodiment is a porous sheet obtained by uniaxially or biaxially stretching a molten extrudate of a resin composition for an infiltration layer containing a thermoplastic resin and an inorganic filler that is not compatible with the thermoplastic resin. And a water-repellent fiber assembly, and the two are integrated by heat embossing, bonding with an adhesive, or a combination thereof.

  By using the leak-proof sheet 3 according to each embodiment having the above features in place of the conventional moisture-permeable leak-proof sheet, an absorptive article is obtained in which the feeling of sultry is further reduced and a slatted feel can be enjoyed for a long time. be able to. Basically, in the absorbent article, moisture evaporation at the leak-proof sheet is the biggest obstacle to the release of humidity. Therefore, the leak-proof sheet 3 according to each embodiment in which moisture transpiration is promoted in the leak-proof sheet part further reduces the feeling of stuffiness regardless of the device part of the absorbent article (for example, the surface sheet or the absorbent layer). And the feeling of sarato lasts for a long time. However, it is preferable to devise a moisture transfer immediately above the leak-proof sheet in order to achieve more improved humidity release. The most effective embodiment is shown below.

  The liquid-permeable layer 2 disposed on the leak-proof sheet 3 is composed of a multi-layer fiber assembly. The liquid-permeable layer 2 has a denser fiber density in the layer facing the leak-proof sheet 3 (hereinafter also referred to as “lowermost layer”) than in the layer in contact with the skin (hereinafter also referred to as “uppermost layer”). It is preferable. The “fiber density” here means the volume density of the constituent fibers in each layer of the liquid-permeable layer 2. In each layer, the fact that the ratio P of the total volume of the constituent fibers to the volume of the entire layer is large is called “fiber density is dense”. On the contrary, the fact that the ratio P is small is referred to as “sparse fiber density”. In the present embodiment, the liquid permeable layer 2 includes two layers, an upper layer 41 that is the uppermost layer and a lower layer 42 that is the lowermost layer.

  In order to increase the fiber density, for example, the gap between constituent fibers in the layer may be set small. In the present embodiment, the gap between the constituent fibers in the lower layer 42 is set smaller than the gap between the constituent fibers in the upper layer 41. Thus, when the fiber density of the upper layer 41 is made sparse and the fiber density of the lower layer 42 is set densely, the lower layer 42 has a greater capillary force than the upper layer 41. In the present embodiment, the liquid permeable layer 2 may be formed of three or more fiber assemblies. The liquid permeable layer 2 composed of three or more layers of fiber aggregates can be configured so that the fiber density becomes denser in order from the uppermost layer to the lowermost layer. In addition, even if it does not have such a sparse / dense relationship, the fiber density (sparse) of the uppermost layer <the fiber density (dense) of the lowermost layer, and the body fluid absorbed by the uppermost layer is in the lowermost layer. If it can be transferred, there is no limitation on the density relationship of the fiber density of the intermediate layer (one layer or two or more layers) between the uppermost layer and the lowermost layer. A particularly preferable form is to configure the fiber density so as to increase in order from the uppermost layer to the lowermost layer.

  In order to form the sparse / dense relationship as described above, the fineness of the fiber assembly is changed as described later (the uppermost layer is made thinner and the lowermost layer is made thicker). Change the ratio (the lower layer has more heat-sealing amount), change the crimping degree of the fibers in the upper layer and lower layer (the lower layer has more crimps and the fiber assembly is sparse), and the fiber assembly is on the lower side And hot pressing (concentrated crushing of the lowermost layer) can be used. As in the last of these methods, the fiber density is not clearly different between the layers, but a sparse / dense relationship in which the fiber density increases continuously (or stepwise) from the top layer to the bottom layer is also preferably selected. Is possible.

The fiber density can be calculated by measuring the basis weight (weight per m ² ) of each layer of the corresponding fiber assembly, further measuring the thickness of each layer, and the ratio (basis weight / thickness). Thickness is based on the concept of fabric compression test (initial thickness) ["Standardization and analysis of texture evaluation (2nd edition)", written by Toshio Kawabata, Japan Textile Machinery Society, Texture Measurement and Standardization Research Committee (Showa 55 (Issued July 10, 2010)] was applied mutatis mutandis, and the thickness under a load of 0.5 g / cm ² was used as a representative value. For measurement, a KES-FB3 compression tester manufactured by Kato Tech was used. When each layer has an uneven structure, the same measurement is performed and the maximum thickness is used as a representative value.

When the layers were in close contact and the thickness changed due to peeling, the thickness of each layer was measured as follows.
(1) As described above, the total thickness is measured with the compression tester.
(2) While holding the fiber assembly so as to have this thickness, the cross section is enlarged and observed, and the thickness of each layer is measured. The thickness of each layer is measured at the point where the cross-sectional thickness is maximum.
(3) The above measurement was performed at 20 locations, and the average value was used as the representative value.

  As shown in FIGS. 1 and 2, the liquid permeable layer 2 preferably has a large number of recesses 52 for locally concentrating body fluid over the entire layer. More specifically, in the liquid permeable layer 2, the upper layer 41 and the lower layer 42 are laminated and partially bonded by a large number of bonding portions 43 having a predetermined pattern. The joint portions 43 are formed in a discontinuous shape in a circular shape in plan view, and are arranged in a staggered pattern. The joint portion 43 is consolidated and has a smaller thickness and a higher density than other portions of the liquid permeable layer 2. The joining portion 43 is formed by various joining means such as heat embossing, ultrasonic embossing, and adhesion using an adhesive. The shape of the joint portion 43 may be an ellipse, a triangle, a rectangle, or a combination thereof in addition to a circle. Further, the joint portion 43 may be formed in a continuous shape, for example, a linear shape such as a straight line or a curve, or a lattice shape.

  In the upper layer 41, portions other than the joint portion 43 joined to the lower layer 42 protrude in a convex shape, whereby a large number of convex portions 51 are formed on the upper layer 41 side of the liquid-permeable layer 2. The inside of each convex portion 51 is filled with fibers constituting the upper layer 41. The shape of the convex portion 51 is mainly determined by the form of the upper layer 41 and the pattern of the joint portion 43. And between the convex parts 51 is the recessed part 52. FIG. The joint 43 is located at the bottom of the recess 52. When viewed as the entire liquid-permeable layer 2, the bottom surface (surface facing the leak-proof sheet 3) 22 is flat, and the top surface (skin contact surface) 21 has a concavo-convex structure.

  Thus, by forming a large number of recesses 52 over the entire layer of the liquid permeable layer 2, all the layers of the liquid permeable layer 2 (two layers in this embodiment) are integrated and directed toward the recess 52. The body fluid will concentrate. As a result, the body fluid does not easily move in the surface direction of the liquid permeable layer 2, and moves along the depth direction of the recess 52. That is, the directionality of the body fluid from the uppermost layer (upper layer 41) to the lowermost layer (lower layer 42) occurs. Moreover, since the liquid-permeable layer 2 has an uneven structure, the skin of the wearer and the upper surface (skin contact surface) 21 of the liquid-permeable layer 2 are difficult to adhere to each other. As a result, air permeability is improved.

  Furthermore, the liquid-permeable layer 2 is preferably configured such that the lowermost layer (lower layer 42) is more hydrophilic than the uppermost layer (upper layer 41). With this configuration, the capillary force gradient from the uppermost layer (upper layer 41) to the lowermost layer (lower layer 42) is further improved. In the case where the liquid-permeable layer 2 is composed of three or more fiber assemblies, the hydrophilic magnitude relationship of the intermediate layer (one layer or two or more layers) between the uppermost layer and the lowermost layer is as follows. This is the same as the density-dense relationship of the fiber density for the intermediate layer in the case where is composed of three or more fiber assemblies.

  In addition, when it has such a concavo-convex structure, the maximum thickness is measured by the convex portion 51 as described above, and the total fiber density including the concave portion 52 is represented by this maximum thickness (apparent density is used).

  As a method of hydrophilizing the constituent fibers of each layer of the liquid permeable layer 2, a method commonly used in the technical field can be appropriately used. For example, it is possible to improve the hydrophilicity of the entire fiber assembly by mixing a hydrophilic fiber such as rayon or pulp fiber at a predetermined ratio to obtain a nonwoven fabric. A more general method is to make a thermoplastic fiber typically used as a constituent fiber hydrophilic before forming a web.

  Specifically, polyethylene, polypropylene, polyester, nylon, or a composite fiber thereof is produced, and various hydrophilic treatment agents are applied to the composite fiber at a stage before forming a staple by cutting the composite fiber into a predetermined length. Apply. Examples of hydrophilizing agents include various alkyl sulfonates represented by α-olefin sulfonates, acrylates, acrylate / acrylamide copolymers, ester amides, ester amide salts, polyethylene glycol and derivatives thereof, Hydrophilic treatment agents known to those skilled in the art such as water-soluble polyester resins, various silicone derivatives, various saccharide derivatives, and mixtures thereof can be used.

  At this time, it is more effective to increase the hydrophilicity of the lower layer than the upper layer in order to promote the movement of body fluid between the upper and lower layers. For example, (b) coating a larger amount of the hydrophilic treatment agent on the lower layer, (b) increasing the hydrophilicity of the lower layer hydrophilic treatment agent, and (c) improving the hydrophilic durability of the lower layer hydrophilic treatment agent. It is possible to change the degree of hydrophilization treatment of each layer, such as increasing. Specifically, the hydrophilic treatment of each layer is performed by using a hydrophilic treatment agent having low solubility in body fluids, or by fixing the hydrophilic treatment agent to the fiber surface, from the uppermost layer toward the lowermost layer. There is a method of selecting a hydrophilic treatment agent so as to increase hydrophilicity and guiding it to the lowermost layer without changing the properties of the body fluid from the uppermost layer to the lowermost layer.

  Further, as another method of hydrophilizing the liquid permeable layer 2, in order to reduce the surface tension of the bodily fluid and promote the transition of the bodily fluid to the lowermost layer (lower layer 42), the hydrophilization in the uppermost layer (upper layer 41) There is a method of using a treatment agent having high solubility in the liquid and dissolving the hydrophilic treatment agent in the body fluid so that the surface tension of the body fluid is easily lowered.

  The liquid permeable layer 2 has a flat bottom surface 22. The term “flat shape” as used herein means that the shape is planar when viewed macroscopically, and includes cases where the bottom surface 22 has some irregularities and the bottom surface 22 is slightly wavy. As a method of flattening the bottom surface 22 of the liquid permeable layer 2, for example, a calendar process (that is, a method of passing the fiber aggregate of the liquid permeable layer between pressure rolls with a smooth surface and crushing it flatly). Can be mentioned.

  The calendering process is performed, for example, by bringing a metal roll having a flat surface and a rubber roll having a flat surface into contact with each other at the same peripheral speed, and passing the fiber aggregate of the liquid-permeable layer therebetween. At this time, the flatness of the bottom surface of the liquid-permeable layer can be improved by making the metal roll face the lowermost layer side of the liquid-permeable layer. Moreover, the flatness of the bottom face of a liquid-permeable layer can further be improved by heating a metal roll suitably. At this time, the density structure of the liquid-permeable layer 2 can be controlled by the relationship between the design of the thermoplastic fiber and the metal roll temperature.

  Specifically, core-sheath fibers having a core of polyethylene terephthalate (PET) and a sheath of polyethylene (PE, melting point 110 ° C.) are used for the entire liquid-permeable layer, and the surface temperature of the metal roll is set to 110 ° C. or higher. If it does in this way, the core-sheath fiber of the lowest layer will be heat-seal | fused, and a fiber density will become dense, and heat | fever fusion will weaken continuously as it goes to an upper layer, and a fiber density will become sparse. In addition, a large amount of the above-mentioned core-sheath fiber is blended in the lowermost layer of the liquid-permeable layer, and a higher-melting core-sheath fiber (for example, the core is PET, the sheath is about 124 ° C., PE having a high melting point, etc.) If a metal roll having a surface temperature of around 110 ° C. is used, the difference in density of the fiber density becomes stronger. As described above, the calendering process can contribute to the formation of a dense structure of the liquid-permeable layer as well as to improve the flatness of the bottom surface of the liquid-permeable layer.

  In order to promote the transpiration of moisture from the leak-proof sheet 3, it is preferable that the lowermost layer (lower layer 42) serving as a temporary moisture retaining layer is concentrated as close as possible to the leak-proof sheet 3. That is, the lowermost layer (lower layer 42) is preferably thinner. Similarly, in order to promote the transpiration of moisture from the leak-proof sheet 3, it is preferable that the evaporation area is wide. In other words, it is preferable that the body fluid spreads in the lowest layer as much as possible. On the other hand, in order to prevent the body fluid from adhering to the skin to feel wet or moist, it is preferable that the body fluid on the surface side of the liquid-permeable layer 2 that contacts the skin is less wet. That is, it is desirable that the body fluid does not spread out in the uppermost layer, but spreads out sufficiently in the lowermost layer, and is concentrated in the vicinity of the leak-proof sheet 3 in the lowermost layer as a whole. From this viewpoint, the ratio (t1 / t0) of the thickness (t1) of the lowermost layer (lower layer 42) to the thickness (t0) of the entire liquid-permeable layer 2 is preferably 5% to 40%, more preferably 7% to 30. %.

  The most ideal embodiment is a form in which wetting and spreading of bodily fluids on the surface of the liquid-permeable layer in contact with the skin are prevented by a large number of recesses, and the wetting and spreading of bodily fluids in the lowermost layer is not affected by the recesses. For this purpose, it is most preferable that the fiber density of the liquid-permeable layer is “uppermost layer << recessed portion ≦ lowermost layer”. From this point of view, the thickness ratio (t1 / t0) is such that the thickness on the upper layer side is 60% to 85%, the thickness of the recess is 5 to 40%, and the thickness of the lowermost layer is 5 to 40% as described above. It is preferable that the thickness of the lowermost layer is substantially the same as the feasible form. As described above, these thicknesses can be measured by using both the compression test and the magnification observation.

  The constituent fibers of the liquid permeable layer 2 have the liquid retention by the fibers themselves so that the absorbed body fluid is transferred and concentrated to the lowermost layer (the lower layer 42) and further propagated to the leak-proof sheet 3 to be quickly evaporated. It is preferable that the main component is fibers that do not substantially have. Examples of such fibers include hydrophobic fibers and chemically treated pulp. Particularly preferred fibers include fibers obtained by hydrophilizing thermoplastic fibers that are inherently hydrophobic and heat-fusible with a hydrophilizing agent.

  Among the hydrophilizing agents described above, those that have low solubility in bodily fluids or those that are fixed to the fiber surface have little change in the properties of the bodily fluid reaching the bottom layer, which is prevented by suppressing planar diffusion. Increases the chance of contact with leaking layers and increases the efficiency of transpiration. Further, when a hydrophilic treatment agent having high solubility in body fluid is used, the body fluid can be appropriately diffused in the lowermost layer to increase the efficiency of transpiration. Furthermore, when a fiber layer that is inherently hydrophilic and has low absorbability such as acetate tow and fiber orientation in the longitudinal direction is disposed in the lowermost layer, diffusion in the longitudinal direction can be selectively caused.

  The liquid-permeable layer 2 may contain a hydrophilic and liquid-retaining fiber in a part thereof. However, in order to ensure a sufficient capillary force, it is preferable that the ratio of the fibers that do not substantially have liquid retention to the entire liquid-permeable layer 2 is 70% by weight or more. Examples of the hydrophilic and liquid-retaining fibers include pulp, rayon, and other various natural fibers, as well as water-absorbing resin fibers (that is, fibers made of crosslinked acrylic acid or acrylate polymer). These fibers are effective especially in the intensive blending of the lowermost layer in order to promote the intensive transfer of body fluids. From the viewpoint of rapid transpiration, it is preferably within 10% by weight (as a ratio to the fiber amount of the entire lowermost layer), more preferably within 5% by weight. It is also preferable to promote the transfer of body fluids by not using these fibers and using another device.

The basis weight of the whole liquid-permeable layer, from the viewpoints of and twist prevention which can temporarily hold without liquid leakage, preferably 50 to 150 g / m ^2, more preferably at 60 to 100 / m ^2. The basis weight of the upper layer 41 is preferably 25 to 80 g / m ² from the viewpoint of not spreading the body fluid excessively, being difficult to sway, and maintaining a soft feel. The basis weight of the lower layer 42 is preferably 25 to 70 g / cm ² from the viewpoint of expressing a sufficient capillary force even if it is thin. Further, the fineness of the constituent fibers of the upper layer 41 is preferably 2.2 to 6.0 dtex because the capillary force is not so large (low liquid retention) and has a high touch (not rough and smooth). The fineness of the constituent fibers of the lower layer 42 is preferably smaller than that of the upper layer 41 from the viewpoint of sufficiently high capillary force. More preferably, it is 4.0 dtex or less, and it is 1.8-4.0 dtex in the more preferable range which can actually be obtained.

  The bottom surface 22 of the liquid-permeable layer 2 is bonded to the upper surface (surface facing the liquid-permeable layer 2) 31 of the leak-proof sheet 3 with an adhesive (not shown). If the adhesive is entirely applied to the contact surface between the liquid-permeable layer 2 and the leak-proof sheet 3, it becomes difficult for moisture to transfer from the liquid-permeable layer 2 to the leak-proof sheet 3. It is preferable that the coating is applied.

  It is preferable that the liquid-permeable layer 2 and the leak-proof sheet 3 are in close contact with each other in a region where the adhesive is not applied. The liquid-permeable layer 2 and the leak-proof sheet 3 are usually in close contact if the adhesive is thinly applied and the bottom surface 22 of the liquid-permeable layer 2 and the upper surface 31 of the leak-proof sheet 3 are flat.

As a method for applying the adhesive, for example, a hot melt adhesive having a wire diameter (60 to 120 μm) thinner than usual (140 to 200 μm) is applied in a spiral pattern with a density finer than at least the pattern density of the recesses 52. The method of doing is mentioned. According to such a coating method, the adhesion between the liquid-permeable layer 2 and the leak-proof sheet 3 is improved. Examples of the hot melt adhesive coating pattern include a dot pattern, an Ω-shaped pattern, and a linear pattern in addition to the spiral pattern. These patterns can be formed by spiral spray coating, slot spray coating, control weave coating, gravure coating or the like of a hot melt adhesive. In particular, spiral spray coating and control weave coating are preferably used from the viewpoints of ease of control, small damage to the leak-proof sheet 3, and the like. The coating amount of the hot melt adhesive is preferably ^{2 to} 15 g / m ² , more preferably 3 to 10 g / m ² .

  As shown in FIGS. 1 and 2, the panty liner 1 of the present embodiment includes a liquid-permeable layer 2 composed of a plurality of fiber assemblies, a moisture-permeable leak-proof sheet 3, and an adhesive (see FIG. (Not shown) is particularly preferable, but is not limited thereto. The term “only” as used herein refers to the effect of the present invention that even if the absorbed moisture is temporarily retained, it is not permanently retained in the absorbent article and is quickly discharged to the outside as water vapor. It means that it does not have an absorbent body or the like having a high liquid retention property that inhibits it. Therefore, the form in which the member which does not inhibit the effect of the present invention is not excluded, for example, an adhesive for fixing to clothes (usually on the second surface 32 side in the leak-proof sheet 3). Etc.) may be provided.

  The panty liner 1 of this embodiment includes a plurality of liquid-permeable layers 2 and a moisture-permeable leak-proof sheet 3, and a bottom surface 22 of the liquid-permeable layer 2 is bonded to the leak-proof sheet 3. Since the layer 41 in contact with the skin has a denser fiber density than the layer 42 facing the leak-proof layer, the body fluid absorbed by the liquid-permeable layer 2 quickly moves to the vicinity of the leak-proof sheet 3, The skin contact surface (upper surface) 21 of the liquid layer 2 does not remain and stickiness on the skin contact surface 21 is difficult to occur. Further, in the leak-proof sheet 3, the amount of moisture on the first surface 31 side facing the liquid-permeable layer 2 is very large (humidity is high), and the amount of moisture on the second surface 32 side facing the underwear is small. Moisture trapped inside the panty liner 1 is driven by the humidity difference (difference in equilibrium vapor pressure) between the inside and outside of the leak-proof sheet 3 (the humidity is low and almost the same as the humidity in the outside air). The effect of transpiration as water vapor increases. As a result, it is difficult for moisture to accumulate inside the panty liner 1, and it is difficult for the feeling of stuffiness due to water vapor to occur, and the feeling of slatting continues throughout the wear.

  Moreover, since it has many recessed parts 52 for making a body fluid concentrate locally over all the layers of the liquid permeable layer 2, all the layers of the liquid permeable layer 2 are integrated in the thickness direction, and toward the recessed part 52 The body fluid will concentrate. Therefore, the body fluid does not easily move in the surface direction of the liquid permeable layer 2, and moves along the depth direction of the recess 52. As a result, the direction of the body fluid from the upper layer 41 to the lower layer 42 is generated, so that the transferability of the body fluid in the liquid permeable layer 2 is improved. In addition, since the liquid-permeable layer 2 has higher hydrophilicity in the layer 42 facing the leak-proof sheet 3 than the layer 41 in contact with the skin, the fluid permeability of the liquid-permeable layer 2 is high. Is further improved.

  Furthermore, since the bottom surface 22 of the liquid-permeable layer 2 is flat and the bottom surface 22 is in close contact with the leak-proof sheet 3, the transfer of moisture from the liquid-permeable layer 2 to the leak-proof sheet 3 is improved. ing. Moreover, since the leakage preventing sheet 3 has improved hydrophilicity on the surface 31 side facing the wearer's skin, the water temporarily retained in the lower layer 42 of the liquid permeable layer 2 is easily compatible with the leakage preventing sheet 3, The transpiration of moisture from the leakage sheet 3 is promoted.

  The absorbent article and leak-proof sheet of the present invention are not limited to the above-described embodiment, and can be variously modified without departing from the spirit of the present invention. For example, the absorbent article and leak-proof sheet of the present invention can be applied to side pads, breast milk pads, light incontinence pads, sanitary napkins, diapers and the like in addition to the panty liner described above. Moreover, it is not necessary to provide a large number of recesses for locally concentrating body fluid in the liquid permeable layer.

  Moreover, the structure of a liquid-permeable layer is not restricted to the said embodiment, For example, the thing of a single layer structure can be used as a liquid-permeable layer.

Fig.1 (a) is a perspective view which shows the panty liner as one Embodiment of this invention, FIG.1 (b) is a partial expanded longitudinal cross-sectional view. FIG. 2 is a partially longitudinally cut perspective view showing the panty liner shown in FIG. FIG. 3 is a schematic diagram showing the structure of the longitudinal section of the leak-proof sheet 3 in the panty liner shown in FIG. FIG. 4 is a schematic diagram showing the structure of the longitudinal section of another leakproof sheet 3 in the panty liner shown in FIG. FIG. 5 is a schematic view showing the structure of a longitudinal section of still another leak-proof sheet 3 in the panty liner shown in FIG.

Explanation of symbols

1 Panty liner (absorbent article)
2 Liquid-permeable layer 21 Upper surface (skin contact surface)
22 bottom surface 3 leak-proof sheet 3a permeation layer 3b leak-proof layer 31 first surface 32 second surface 41 upper layer (layer in contact with skin)
42 Lower layer (layer facing the leak-proof layer)
51 Convex part 52 Concave part

Claims (5)

Has a permeation layer capable penetration of liquid, and a liquid-impermeable or Ekinan permeable leakproof layer, a barrier sheet having a moisture permeability as a whole,
The leak-proof sheet, wherein the leak-proof sheet is made of a porous film having a large number of micropores, and the size of the micropores in the penetration layer is larger than the size of the micropores in the leak-proof layer . The leakage preventing sheet is made of a porous film having a large number of fine pores, the pore number of the fine pores in the penetration layer, the leakproof layer in the proof of claim 1 has become larger than the number of holes micropores Leakage sheet. Both the permeation layer and the leak-proof layer are obtained by uniaxially or biaxially stretching a molten extrudate of a resin composition containing a thermoplastic resin and an inorganic filler that is not compatible therewith,
The particle size or blending amount of the inorganic filler in the resin composition used for forming the permeation layer is greater than the particle size or blending amount of the inorganic filler in the resin composition used for forming the leak-proof layer. The leak-proof sheet according to claim 1 , wherein the leak-proof sheet is larger or larger. An absorbent article comprising the leak-proof sheet according to any one of claims 1 to 3 , wherein the leak-proof sheet is arranged so that the permeation layer of the leak-proof sheet faces the skin side of the wearer. The absorbent article is composed of a liquid-permeable layer formed of at least a plurality of layers of fiber assemblies, and the leak-proof sheet,
The liquid-permeable layer is bonded to the leak-proof sheet via an adhesive, with the bottom surface facing the leak-proof sheet,
The absorbent article according to claim 4 , wherein the plurality of liquid-permeable layers have a denser fiber density in the layer facing the leak-proof sheet than in the layer contacting the skin.

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