JP5148981B2 - Sanitary napkin - Google Patents

Description

  The present invention relates to a sanitary napkin.

  Some people typified by the Malay tribe, who live mainly in Indonesia, Malaysia, etc., have a habit of washing used sanitary napkins with water and washing off absorbed menstrual blood. Conventionally, sanitary napkins that have been mainly used in Malay ethnic spheres are composed of cloth napkins (for example, Patent Documents 1 to 3) and absorbent materials mainly composed of pulp fibers and containing no water-absorbing polymer. Therefore, it can be washed with water, and absorbed menstrual blood and the like can be washed away with water.

  However, such a sanitary napkin has poor menstrual blood absorption / retention performance, and may cause so-called liquid return in which, for example, body fluid absorbed on the surface of the absorbent material oozes out. Therefore, in a conventional sanitary napkin that can be washed with water and does not contain a water-absorbing polymer, the use of a large amount of pulp fibers compensates for the lack of absorption performance. However, such sanitary napkins become thick due to the bulkiness of the pulp fibers, are particularly bulky when folded and packaged, are inconvenient to carry, and have a poor fit.

  At present, the present applicant has not found any prior art documents that have raised the above-mentioned problems relating to water washing of napkins. However, people who have a habit of cleaning napkins are considered to exist in areas other than the above-mentioned residential areas, and sanitary napkins that contain a water-absorbing polymer and are easy to wash are widely used in women's lifestyles. It is considered that it has the potential to greatly affect

JP 2006-288681 JP 2001-353182 A JP 2004-337204 A

  Accordingly, an object of the present invention is to provide a sanitary napkin that contains a water-absorbing polymer and can be easily washed with water.

  The present invention is a sanitary napkin comprising a surface layer, a back layer, and an absorbent layer disposed between both layers and containing a water-absorbing material, wherein the water-absorbing material has a centrifugal retention amount of 5 to 25 g / g. The above-mentioned object is achieved by providing a sanitary napkin containing a water-absorbing polymer having a water absorption rate of 25 seconds or more by a vortex method.

  Although the sanitary napkin of the present invention contains a water-absorbing polymer, the napkin is hard to tear and easy to wash with water, and the redness of menstrual blood of the napkin can be removed, so the napkin after use is washed with water It is suitable for people who have a habit of disposing them. Moreover, since the sanitary napkin of the present invention contains a water-absorbing polymer, it has good absorption performance such that liquid return can be effectively suppressed. Furthermore, since the thickness can be designed to be thin, it is possible to obtain a napkin that is not bulky and has excellent portability and wearing feeling.

  Hereinafter, the sanitary napkin of the present invention will be described based on a preferred embodiment thereof with reference to the drawings. The top view of the sanitary napkin of this embodiment is shown by FIG. 2 is a cross-sectional view taken along line XX in FIG.

  The sanitary napkin 1 (hereinafter also referred to as napkin 1) of the present embodiment has a surface layer and a back layer, and an absorption layer containing a water-absorbing material is provided between both layers. More specifically, the napkin 1 has a vertically long shape as shown in FIG. 1, and includes a top sheet 2 as a liquid-permeable surface layer, a back sheet 3 as a liquid-impermeable back layer, and both sheets. Between 2 and 3, a liquid-retaining absorbent layer 4 is provided. In the present specification, the “absorbing layer” refers to a layer structure of one or a plurality of absorbing structures, and the absorbing layer itself or a structure in which the absorbing layer is wrapped with a covering sheet is also referred to as an absorber. Hereinafter, the phrase “absorber 40” may be used. The absorber 40 means a structure formed by wrapping substantially the entire absorbent layer 4 with a covering sheet.

As shown in FIG. 2, the top sheet 2 covers the entire skin contact surface (upper surface) of the vertically long absorbent layer 4, and the back sheet 3 covers the entire non-skin contact surface of the absorbent layer 4. ing. End seals are applied to the top sheet 2 and the back sheet 3 at portions extending outward from the peripheral edge of the absorbent layer 4, and end seal portions 6 are formed. An adhesive is applied on the non-skin contact surface of the back sheet 3 to form a fixing portion (not shown) for fixing the napkin 1 to shorts or the like.
The top sheet 2 can be made of the same material as that conventionally known. For example, a hydrophilic nonwoven fabric or a perforated film is used. The back sheet 3 is made of, for example, a liquid-impermeable film sheet, and the liquid-impermeable film sheet may have water vapor permeability.
In this specification, the “skin contact surface” is a surface directed toward the wearer's skin when the napkin is worn, and the “non-skin contact surface” is the underwear side (the wearer's skin side) when the napkin is worn. It is the surface that faces the other side. In addition, the “longitudinal direction” is a direction (vertical direction in FIG. 1) along the long side direction of the napkin or various members, and the “width direction” is a direction orthogonal to the longitudinal direction.

  The absorbent layer 4 of the present embodiment has a configuration in which thin absorbent sheets 4a and 4b containing water-absorbing polymers and fibers are laminated. More specifically, two absorbent sheets 4a are overlaid to form a laminated body, and another absorbent sheet 4b is overlaid on each of the upper and lower surfaces of the laminated body to laminate four absorbent sheets. An absorption layer 4 made of a body is formed. The absorbent sheet 4a and the absorbent sheet 4b have the same composition and differ only in dimensions, and the absorbent sheet 4a positioned inside the absorbent body 4 is more than the absorbent sheet 4b positioned outside. Also, the dimension (length in the longitudinal direction and the width direction) in plan view is small. Since the absorbent layer 4 has such a configuration, the absorbent body is difficult to twist while the napkin is worn, and the absorbent body is not easily biased when the napkin is washed, so that it is easy to squeeze.

  Examples of the absorbent sheet include the absorbent sheet described in [Embodiment of the invention] of JP-A-9-156014. In addition, a sheet in which a polymer is fixed between two sheets of paper by adhesive or adhesiveness when wet, a sheet in which a polymer is dispersed during the production of a melt blown nonwoven fabric, and the polymer is fixed at the same time as the nonwoven fabric. The sheet | seat etc. which superposed | polymerized and fix | immobilized are preferably used as a thin absorbent sheet.

The water-absorbing polymer contained in the absorbent layer 4 includes a water-absorbing polymer having a centrifugal retention amount of 5 to 25 g / g and a water absorption rate of 25 seconds or more by the vortex method (hereinafter also referred to as a low water-absorbing polymer). It is included. In addition, in this invention, since the evaluation of the water absorption rate by the vortex method is evaluated by measuring time, the longer the measurement time, the lower the water absorption rate.
If such a centrifugal retention amount is within a specific range and a low water-absorbing polymer having a relatively low water absorption rate is contained in the absorbent material, the water-absorbing polymer conventionally used in Indonesia is not included. Compared with a napkin, it is possible to obtain a thin napkin that has sufficiently good absorption performance, can be thinned, and can be easily removed by washing with water. The centrifugal retention amount and the water absorption speed are each measured by the following measurement methods.

<Measuring method of centrifugal retention>
The saturated water absorption is measured according to JIS K 7223 (1996). Nylon woven fabric (mesh opening 255, sold by Sanriku Manufacturing Co., Ltd., product name: nylon net, standard: 250 x mesh width x 30 m) is cut into a rectangle with a width of 10 cm and a length of 40 cm and folded in half at the center in the longitudinal direction. Both ends are heat-sealed to produce a nylon bag having a width of 10 cm (inner dimension: 9 cm) and a length of 20 cm. 1.00 g of the water-absorbing polymer as a measurement sample is precisely weighed and placed uniformly at the bottom of the produced nylon bag. The nylon bag containing the sample is immersed in physiological saline (0.9% by weight sodium chloride water) adjusted to 25 ° C. After 30 minutes from the start of immersion, the nylon bag is taken out from the physiological saline, suspended in a vertical state for 1 hour and drained, and then dehydrated using a centrifugal dehydrator (Kokusan Co., Ltd., model H-130C special model). The dehydration condition is 143 G (800 rpm) for 10 minutes. After dehydration, the weight of the sample is measured, and the target centrifugal retention amount is calculated according to the following formula.
Centrifugal retention amount (g / g) = (a′−bc) / c; where a ′ is the total weight (g) of the sample and nylon bag after centrifugal dewatering, and b is before the nylon bag is absorbed (dried). C) represents the weight (g) of the sample before water absorption (during drying). The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value.

<Measurement method of water absorption rate by vortex method>
A 100 mL glass beaker with 50 mL of physiological saline (0.9 wt% sodium chloride water) and a magnetic stirrer chip (center diameter 8 mm, both ends diameter 7 mm, length 30 mm, surface coated with fluororesin ) And place the beaker on a magnetic stirrer (HPS-100 manufactured by ASONE). The rotational speed of the magnetic stirrer is adjusted to 600 ± 60 rpm, and the physiological saline is stirred. 2.0 g of the water-absorbing polymer as a measurement sample is put into the liquid at the center of the vortex of the saline solution being stirred, and the water absorption rate (seconds) of the water-absorbing polymer is measured in accordance with JIS K 7224 (1996). taking measurement. Specifically, the stopwatch is started when the absorption of the water-absorbing polymer into the beaker is completed, and stopped when the stirrer tip is covered with the test liquid (when the vortex disappears and the liquid surface becomes flat). Stop the watch and record the time (in seconds) as the water absorption rate by vortex method. In the measurement, n = 5 was measured, the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value. These measurements are performed at 23 ± 2 ° C. and a humidity of 50 ± 5%, and the samples are stored for 24 hours or more in the same environment before the measurement.

  The centrifugal retention amount of the low water absorption polymer is 5 to 25 g / g. When the amount of centrifugal retention is within this range, menstrual blood is effectively absorbed during wearing, so that leakage can be effectively prevented even during long-time use, and the napkin can be made thinner. In particular, when it is 5 to 20 g / g, particularly 10 to 20 g / g, the balance between the absorption retention capacity of menstrual blood and the removal of redness after washing with water in the napkin 1 is further improved, and the absorption performance is high even when it is thin. It is easy to obtain a napkin that is hard to tear and easy to wash.

  The water absorption rate of the low water absorption polymer by the vortex method is 25 seconds or more. When a water-absorbing polymer having such a water-absorbing speed is used, it is possible to prevent breakage by preventing the water-absorbing polymer from swollen rapidly during washing with water. The water absorption speed is preferably 25 to 60 seconds, particularly preferably 30 to 60 seconds. When the water absorption speed is within the above range, menstrual blood leakage during wearing is more effectively prevented, and the redness of the napkin is easily removed without applying excessive force to the napkin during washing. Therefore, the napkin is not easily broken during washing with water.

  The low water-absorbing polymer in which the centrifugal retention amount and the water absorption rate by the vortex method are within the above ranges can be obtained, for example, by subjecting a conventional water-absorbing polymer to a treatment that moderately increases the degree of surface cross-linking. More specifically, the low water-absorbing polymer can be obtained by re-crosslinking the water-absorbing polymer produced in the same manner as before.

Examples of the material for the low water-absorbing polymer include sodium polyacrylate, (acrylic acid-vinyl alcohol) copolymer, crosslinked polyacrylic acid soda, (starch-acrylic acid) graft polymer, and (isobutylene-maleic anhydride). Copolymers and saponified products thereof, potassium polyacrylate, cesium polyacrylate and the like can be mentioned, and one of these can be used alone or two or more can be used in combination.
In addition, examples of the shape of the low water-absorbing polymer include particles and fibers. The particulate water-absorbing polymer includes an amorphous type, a block type, a bowl type, a spherical agglomeration type, a spherical type and the like due to the difference in shape, and any type can be used.

  The content of the low water-absorbing polymer is 80 with respect to the total mass of all the water-absorbing polymers contained in the absorbent layer 4 from the viewpoint of more surely exerting the action and effect of the low water-absorbing polymer. It is preferably at least 90% by mass, more preferably at least 90% by mass, especially 100% by mass. If all of the water-absorbing polymer contained in the napkin 1 is a low water-absorbing polymer, it is ideal in terms of action and effect.

  The water-absorbing polymer in the absorbent layer 4 (all the water-absorbing polymers in the absorbent layer including the low water-absorbing polymer) is also referred to as a liquid passing speed under a pressure of 2.0 kPa (hereinafter referred to as “liquid passing speed under pressure”). ) Is preferably 50 ml / min or more because it is easy to remove redness during washing with water. This is because the blood remaining between the water-absorbing polymers is less likely to occur during washing operations (for example, during repeated paddy washing) because the water-absorbing polymers saturated and swollen by the liquid absorption are less likely to interfere with each other. This is considered to be due to the promotion of the cleaning property. From the viewpoint of ease of redness removal and improvement in the absorption rate of menstrual blood, the liquid passing rate under pressure is particularly preferably 50 to 3000 ml / min, and more preferably 80 to 2500 ml / min. In particular, it is suitable for a thin napkin having a high ratio of water-absorbing polymer to pulp.

The liquid passing rate under pressure is measured at 2.0 kPa according to the following procedure. This measurement is performed at 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and the sample is stored after being stored in the same environment for 24 hours or more.
(Measurement method of liquid flow rate under pressure)
In a 100 mL glass beaker, a sufficient amount of physiological saline (0.9 wt% sodium chloride water) to swell the measurement sample water-absorbing polymer 0.32 ± 0.005 g, for example, the saturated absorption amount of the water-absorbing polymer Immerse it in 5 times more saline and leave it for 30 minutes.
Separately, at the lower end of an opening of a vertically standing cylinder (inner diameter 25.4 mm), a wire mesh (mesh opening 150 μm, biocolumn sintered stainless steel filter 30SUS sold by Sansho Co., Ltd.) and a capillary (with an inner diameter of 2 mm) ( A filtration cylindrical tube having an inner diameter of 4 mm and a length of 8 cm) is prepared, and the contents of the beaker including the swollen measurement sample are put into the cylindrical tube with the cock closed. Next, a cylindrical rod having a diameter of 2 mm with a wire mesh having an opening of 150 μm and a diameter of 25 mm is inserted into the filtration cylindrical tube so that the wire mesh and the measurement sample are in contact with each other. Place a weight so that the load of. After standing for 1 minute in this state, the cock is opened to flow the liquid, and the time until the liquid level in the filtration cylindrical tube reaches the 40 mL scale line from the 60 mL scale line (that is, 20 mL of liquid passes) (T1). (Seconds) is measured. Using the measured time T1 (seconds), the flow rate at 2.0 kPa is calculated from the following equation. In the formula, T0 (seconds) is a value obtained by measuring the time required for 20 ml of physiological saline to pass through the wire mesh without putting a measurement sample in the filtration cylindrical tube.
Flow rate (ml / min) = 20 × 60 / (T1-T0)
The value obtained by the above formula is divided by the thickness of the swollen water-absorbing polymer layer in the cylinder, and converted to a value per 20 mm to obtain a liquid passing speed under pressure. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value.
A more detailed method for measuring the flow rate is described in paragraphs 0008 and 0009 of JP-A-2003-235889. The measuring device is described in FIGS. 1 and 2 of the publication.

In the present specification, “mass” means “mass at the time of drying” unless otherwise specified. The “mass at the time of drying” of the napkin and the constituent members of the napkin is measured as follows.
Measuring method of mass at the time of drying: The object to be measured is left for 24 hours in a constant temperature and high humidity environment at a temperature of 25 ° C. and a humidity of 30%, then the mass is measured in the environment, and the measured value is measured. This is the “mass when dried” of the object.

The content of the low water-absorbing polymer in the absorbent layer 4 is 2 to 60% by mass, particularly 5 to 50% by mass, based on the total mass of the absorbent layer 4, and the softness during wearing of the napkin 1 It is preferable in terms of balance with absorption performance. In particular, when the napkin 1 is made ultrathin with a thickness (thickness under a load of 7 g / cm ² ) of 2.5 mm or less, the content of the low water-absorbing polymer is 20 to 60% by mass, particularly 30 It is preferable to set it to -55 mass% in terms of balance between thinness and water absorption performance.
The distribution amount of the water-absorbing polymer (all the water-absorbing polymers in the absorbing layer including the low water-absorbing polymer) in the absorbing layer 4 is preferably 5 to 180 g / m ² , more preferably 10 to 160 g / m ² . is there.

Of all the water-absorbing polymers contained in the absorbent layer 4, the content of the water-absorbing polymer having a particle size of less than 250 μm is less than 20% by mass, particularly less than 15% by mass, when worn for a long time. It is preferable because the absorption time of the liquid into the napkin 1 is short, leakage hardly occurs, and redness is easily removed.
Further, in addition to the content of the water-absorbing polymer having a particle size of less than 250 μm being in the above range, the content of the water-absorbing polymer having a particle size of less than 150 μm is less than 5% by mass, particularly less than 3% by mass. This is preferable because the above-described effect can be achieved more reliably.

  The “content of water-absorbing polymer having a particle size of less than 250 μm” and “content of water-absorbing polymer having a particle size of less than 150 μm” are measured by the following <Method for Measuring Particle Size Distribution>, respectively. As is apparent from the following measurement method, the “water-absorbing polymer having a particle size of less than 250 μm or less than 150 μm” is not limited to a water-absorbing polymer having a spherical shape or a nearly spherical shape. The shape of the water-absorbing polymer is not limited.

<Measuring method of particle size distribution>
All the water-absorbing polymers contained in the napkin 1 (absorbing layer 4) are divided into two types of standard sieves with openings 250 and 150 (for example, standard sieves manufactured by Tokyo Screen) defined in JIS Z8801, and a saucer. , With the sieve having a mesh opening of 250 as the uppermost position and arranged in this order in the vertical direction. On the sieve of the mesh opening 250, the water-absorbing polymer contained in the napkin 1 (absorbing layer 4) is placed and shaken ( For example, it is sieved using Lecce's AS200 type. The shaking condition is 50 Hz, the amplitude is 0.5 mm, and the shaking time is 10 minutes. After the sieving operation, the “absorbent polymer having a particle size of 250 μm or more” is placed on the sieve having an opening of 250, and the “water-absorbing polymer having a particle size of less than 250 μm” is screened under the sieve having an opening of 250, that is, a sieve having an opening of 150. On the upper and lower saucers, “water-absorbing polymer having a particle size of less than 150 μm” means what is on the saucer after passing through a sieve having 150 openings. The sieving was performed three times, and the average value of the three times was defined as the weight on each sieve. The weight on each obtained sieve was calculated as a weight percentage with respect to the total weight, and the abundance ratio of each particle size was calculated.

The napkin 1 can be thinned by containing the low water-absorbing polymer described above. The thickness of the napkin 1 is preferably 1 to 10 mm, particularly 1 to 7 mm, and more preferably 1.5 to 5.5 mm because it does not feel strange while preventing leakage during wearing and is convenient for carrying. The thickness of the napkin here means the thickness of the napkin under a load of 7 g / cm ^{2 and} is measured by the following method.

<Method for measuring thickness>
Place the entire product to be measured (napkins) on a flat surface with the top sheet side up, without wrinkles or bending, and place 7 g / cm ^{2 on} the upper surface of the area where the absorber is placed. Apply a load and measure the thickness under that condition. Thickness meter PEACOCK DIAL UPRIGHT GAUGES R5-C (manufactured by OZAKI MFG.CO.LTD.) Is used for thickness measurement. At this time, a plate (an acrylic plate having a thickness of about 5 mm) is disposed at the measurement portion between the tip of the thickness meter and the product, and the size of the plate is adjusted so that the load is 7 g / cm ² . The shape of the plate is circular or square.

  As the fiber contained in the absorbent layer 4, those usually used in the technical field can be appropriately used. For example, natural fibers such as wood pulp and plant pulp, regenerated fibers such as cupra and rayon, semi-synthetic fibers such as acetate, synthetic fibers such as polyolefins, polyamides and polyesters, etc. Or a mixture of two or more.

From the viewpoint that blood adhering to the napkin is likely to flow out quickly when the napkin is washed with water, as a fiber contained in the absorption layer 4, a synthetic fiber such as polyolefin is subjected to a hydrophilic treatment (hydrophilic synthetic fiber) or It is preferable that the natural fiber contains a crosslinked pulp subjected to a crosslinking treatment.
The total proportion of the hydrophilic synthetic fiber and the crosslinked pulp in the total fibers contained in the absorbent layer 4 is preferably 20 to 100% by weight, more preferably 35 to 80% by weight. Moreover, the content weight ratio (hydrophilic synthetic fiber / crosslinked pulp) of the hydrophilic synthetic fiber and the crosslinked pulp is preferably 100/0 to 20/80, and more preferably 90/10 to 35/65.
Examples of the method for hydrophilizing the synthetic fiber include a method of kneading a hydrophilic substance into the synthetic fiber and a method of hydrophilizing the surface of the synthetic fiber with a surfactant. In addition, when using the said hydrophilic synthetic fiber as a fiber contained in the absorption layer 4, compared with the case where all this fiber is the above-mentioned natural fiber or a reproduction | regeneration fiber, there exists a concern about a fall in absorption performance, Therefore, a water absorbing polymer It is preferable to take measures such as increasing the amount (preferably 1.2 to 2 times the content of the water-absorbing polymer when the fibers are all the above-mentioned natural fibers or regenerated fibers).

The fiber content in the absorbent layer 4 is preferably 40 to 98 mass%, more preferably 45 to 95 mass%, based on the total mass of the absorbent layer 4. In the case of an ultra-thin napkin with a thickness (thickness under a load of 7 g / cm ² ) of 2.5 mm or less, it is preferably 40 to 80% by mass, particularly 45 to 70% by mass.

The absorbent layer 4 is mainly composed of a water-absorbing material (in this embodiment, a water-absorbing polymer and fibers). The water-absorbing material includes not only a material that itself retains liquid but also a material that retains liquid in the gap. The content of the water-absorbing material in the absorbent layer 4 is preferably 90% by mass or more, and more preferably 95% by mass with respect to the total mass of the absorbent layer 4.
The content of the water-absorbing material in the absorbent layer 4 is preferably 100% by mass in terms of water-absorbing performance. In addition to the absorbent material, the absorbent layer 4 may contain a hygroscopic agent or a deodorant as necessary. It is possible to contain a metal ion scavenger and the like. Examples of the hygroscopic agent include silica gel, and examples of the deodorizer include activated carbon, activated clay, and a silver-containing compound. Among these, the metal ion scavenger is effective for removing redness caused by menstrual blood by washing the napkin with water. Hereinafter, the metal ion scavenger will be described.

  Examples of the metal ion scavenger include ethylenediaminetetraacetic acid (EDTA) tetrasodium, nitrilotriacetic acid (NTA) trisodium, diethylenetriaminepentaacetic acid (DTPA) pentasodium, hydroxyethylethylenediaminetriacetic acid (HEDTA) trisodium, L-glutamic acid. Aminocarboxylate-based metal ion scavengers such as tetraacetic acid (GLDA) tetrasodium; phosphonate metal ion scavengers such as hydroxyethylidene diphosphonic acid (HEDP) tetrasodium; sodium tripolyphosphate (STPP), sodium pyrophosphate (TSPP), polymer phosphate metal ion scavengers such as sodium hexametaphosphate; builders for polymer detergents such as sodium polyacrylate, acrylic acid / maleic acid copolymer; trisodium citrate, citric acid Other organic metal ion scavengers such as ammonium; inorganic metal ion scavengers such as zeolite (crystalline aluminosilicate), sodium silicate, and the like. These may be used alone or in combination of two or more. Can be used. Of these, tetrasodium ethylenediaminetetraacetate (EDTA), trisodium citrate, sodium tripolyphosphate, sodium acrylate, and zeolite are preferred. Especially, trisodium citrate is highly water-soluble, so It is easy to move to the location, has a high redness removal effect, and has excellent biodegradability. Trisodium citrate is preferable because it is effective in weakening the affinity between hemoglobin contained in menstrual blood and the water-absorbing polymer and has a high redness removal effect.

  Examples of the method of containing the metal ion scavenger in the napkin 1 include a method of spraying as a solid (powder); an aqueous solution obtained by dissolving or dispersing the metal ion scavenger in an appropriate solvent such as water, and the aqueous solution And a method of spraying or applying the sucrose onto a predetermined part of the napkin 1 (a part where the metal ion scavenger is desired to be contained).

  As the location where the metal ion scavenger is present, from the viewpoint of efficiently performing menstrual blood absorption, the inside of the absorption layer 4 and the peripheral portion thereof can be mentioned. The inside of the absorbent layer is preferably between the absorbent sheet 4b disposed at a position farthest from the skin (position closest to the back sheet 2) and the absorbent sheet 4a positioned immediately above. Examples of the peripheral portion of the absorbent layer 4 include 1) the skin contact surface side of the absorbent layer 4 (for example, between the topsheet 2 and the absorbent layer 4), and 2) the non-skin contact surface side of the absorbent layer 4 (For example, between the absorption layer 4 and the back surface sheet 3) 3) The area | region of the fixed width (preferably 3-15 mm width) along the periphery of the absorption layer 4 is contained. In the napkin 1, the metal ion scavenger may be present at one location or may be present at a plurality of locations.

  The “absorbing layer 4” in the above 1) to 3) can be replaced with an “absorbing body 40” formed by wrapping substantially the entire absorbing layer 4 with a covering sheet. That is, when substantially the entire absorbent layer 4 is covered with a covering sheet, the metal ion scavenger 10 may be covered with the covering sheet and disposed outside the covering sheet (outside the absorber 40). May be. As the covering sheet, for example, a hydrophilic fiber sheet, a perforated film, or the like is used. As the hydrophilic fiber sheet, for example, paper such as tissue paper or various non-woven fabrics can be used.

  A particularly preferable location of the metal ion scavenger is 2) a portion closer to the non-skin contact surface than the absorbent layer 4 (absorber 40). In this case, the absorbed menstrual blood and the like could be washed out with water most cleanly.

FIG. 3 shows an embodiment in which 2) is adopted as the location of the metal ion scavenger. In the embodiment shown in FIG. 3, the metal ion scavenger 10 exists between the inner sheet 11 and the back sheet 3 disposed adjacent to the non-skin contact surface of the absorbent layer 4 (absorber 40). . In FIG. 3, for ease of explanation, the metal ion scavenger 10 is described as if it forms a layer, but it does not necessarily form a layer in practice.
The presence of the inner sheet 11 separates the absorption layer 4 (absorber 40) from the metal ion scavenger, and prevents the metal ion scavenger from entering the absorber layer 4 (absorber 40) beyond the design value. it can. As the inner sheet 11, the same sheet as the covering sheet can be used. The basis weight of the inner sheet 11 is preferably 10 to 20 g / m ² and the thickness is 0.05 to 0.15 mm.

  The content of the metal ion scavenger in the napkin 1 is preferably 25 to 1200 parts by weight with respect to 100 parts by weight of the total water-absorbing polymer contained in the napkin 1 from the viewpoint of washing menstrual blood and the like more cleanly from the napkin. More preferably, it is 55-1000 mass parts, Most preferably, it is 100-1000 mass parts.

The napkin 1 can remove redness due to menstrual blood by simple water washing. The degree of redness removal can be evaluated by the redness degree a ^* value of the red portion stained red by blood in the napkin after blood is injected and washed in accordance with the following procedures 1 to 3. The smaller the a ^* value, the lower the degree of red in the red part, which means that the blood has been washed away with water. The napkin 1 having the above-described configuration can remove redness to an a ^* value of 7 or less, preferably 5 or less.

Procedure 1: Inject 12 g of blood into the sanitary napkin from the surface layer side of the sanitary napkin, leave it in an environment of 25 ° C. for 30 minutes, and then remove the sanitary napkin with water having a water temperature of 25 ° C. and a hardness of 5 ° DH. The sanitary napkin is squeezed by hand, and the water contained in the napkin is squeezed out as much as possible.
Procedure 2: On the surface layer side of the wet sanitary napkin obtained in the procedure 1, the red degree a ^* using a spectrocolorimeter for the five most reddish spots of the red part stained with blood ^. Measure the value.
Procedure 3: The average of the three measured values obtained by removing the maximum value and the minimum value from the five measured values obtained in the procedure 2 is defined as the red degree a ^* value of the sanitary napkin.

The a ^* value obtained according to the above procedures 1 to 3 is a measure for evaluating the superiority or inferiority of the water-washing ability that the napkin has due to the inclusion of the metal ion scavenger, and the a ^* value is small. The degree of red in the red part is low, which means that blood is washed away by washing. Even if the napkin contains a metal ion scavenger, if the a ^* value exceeds 7, the absorbed menstrual blood has not been washed away, and has a practically sufficient water washing ability. It's hard to say. On the other hand, the napkin 1 of the present embodiment having the above-described configuration has an a ^* value of 7 or less, and has a sufficient water washing ability for practical use.

In the procedures 1 to 3, horse blood is used as blood to be injected into the napkin. More specifically, equine defibrinated blood manufactured by Japan Biotest Laboratory Co., Ltd. is used. The viscosity of this horse defibrinated blood is less than 15 mPa · S as measured with a (B type) viscometer TVB-10M (measurement temperature 25 ° C., rotor L adapter) manufactured by Toki Sangyo Co., Ltd.
In the above procedures 1 to 3, water used for washing the napkin is water prepared by dissolving calcium chloride and magnesium chloride in ion-exchanged water having an electric conductivity of 1 μS / cm or less, and calcium ions and magnesium. Water having an ion content ratio (calcium ion: magnesium ion) of 7: 3 and a German hardness of 5 ° DH is used.
In addition, the water for domestic use in Indonesia, which is one of the countries that have a custom of washing used sanitary napkins, varies depending on the region, but water with a German hardness of 5 ° DH used in the above steps 1 to 3 It is almost the same as domestic water used in at least part of Indonesia.

In the procedure 1, the environment in which the napkin into which blood has been injected is allowed to stand for 30 minutes before washing is an air temperature of 25 ° C. and a humidity of 60%.
The napkin is washed by hand, and “the operation of putting about 100 g of water on the napkin with one hand and squeezing the napkin with the other hand” is repeated three times in 10 seconds. That is, the operation performed for 10 seconds is “sprinkle water → squeeze the napkin → spread water → squeeze the napkin → spread water → squeeze the napkin”. Accordingly, the amount of water used for washing the napkin for 3 minutes in the procedure 1 is about 100 g as described above because the amount of water used in one water application operation is about 100 g as described above. 3 =) 5400 g. In the above formula, 100 × 3 corresponds to the amount of water used for 10 seconds, and 100 × 3 × 6 corresponds to the amount of water used for 1 minute.
When watering the napkin, use a beaker or the like, and do not squeeze the napkin while watering.
In Procedure 1, the pressure when hand-squeezing the napkin after washing the napkin for 3 minutes, that is, the gripping force of the hand is usually about 10 to 15 kg.
When measuring the red degree a ^* value of the red part, the measurement sample and the spectral color difference meter are brought into close contact with each other so that external light does not enter. As the spectral color difference meter, a simple spectral color difference meter “NF333” (pen type detector) manufactured by JASCO Corporation can be used.

Hereinafter, the napkin 1 of the present embodiment will be described in detail.
On the skin contact surface side (surface sheet 2 side) of the napkin 1, leakage prevention grooves 5 and 5 extending in the longitudinal direction of the napkin 1 are formed on both left and right sides in the longitudinal direction. Each leak-proof groove 5 is formed by compacting and integrating the topsheet 2 and the absorbent layer 4 (absorber 40) from the topsheet 2 side by pressing means such as embossing. Each leak-proof groove 5 has a substantially symmetric shape with respect to the vertical center line of the napkin 1. The leakage prevention grooves 5 are connected to each other at their front and rear ends, thereby forming a closed shape as a whole. By forming the leak-proof grooves 5 and 5, body fluids flowing outward in the napkin width direction are blocked, and leakage (lateral leakage) from the side of the napkin 1 is effectively prevented and cleaning is performed. Since the decomposition of the napkin at the time can be suppressed, it is easy to perform the washing operation and blood can be easily washed away. Furthermore, the fact that the leak-proof grooves 5 and 5 reach the vicinity of the lower part of the absorbent layer 4 (absorber 40). During washing, water easily flows through the entire absorbent body, and the absorbent body is biased and blood remains. It is preferable in order to prevent this.

  On the peripheral edge of the napkin 1, an end seal portion 6 is formed at a position spaced outward from the absorbent layer 4 (absorber 40). The end seal portion 6 in the present embodiment is formed by integrating the top sheet 2 and the back sheet 3. More specifically, in the present embodiment, the top sheet 2 and the back sheet 3 extend from the peripheral edge portion of the absorption layer 4, and are joined to each other by a heat embossing process at the extended portions. Is formed. The end seal portion 6 has an effect of preventing the water-absorbing material constituting the absorbent layer 4 from flowing out when the napkin 1 is washed (when wet). It is preferable that the end seal portion 6 is not provided with a material that causes swelling or the like due to water used for the absorbent layer 4 from the viewpoint of not separating each sheet material that is a constituent material of the end seal portion during cleaning. Further, the end seal portion 6 is formed by heat embossing with an adhesive such as hot melt disposed at a predetermined portion of the sheet material, thereby improving and stabilizing the flexibility of the seal portion and the seal strength when wet. From the viewpoint of making it more preferable.

The napkin 1 of the present embodiment is used by being attached to an undergarment in the same manner as a normal sanitary napkin of this type.
Since the napkin 1 of the present embodiment contains the above-described specific water-absorbing polymer (low water-absorbing polymer), it can be easily washed with water while having practically sufficient absorption performance. It is easy to wash away the blood adhering to the napkin 1 with water. For this reason, it can be suitably used for people who have a habit of discarding the used napkin after washing with water.
In addition, since the napkin 1 of the present embodiment contains a water-absorbing polymer, the napkin 1 can be designed to have a small thickness, is not bulky, and has excellent portability and wearing feeling.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment.
For example, the sanitary napkin of the present invention may not include the leak-proof groove 5, the adhesive portion (not shown), the wing portion, the rear flap portion, and the like included in the embodiment. Both the wing part and the rear flap part are parts extending outward from the both side edges of the absorbent body 40 in the longitudinal direction, and the wing part is normally opposed to the excretion part that is disposed to face the excretion part of the napkin wearer. The rear flap part is located behind the wing part in the napkin longitudinal direction.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to such examples.

Hereinafter, a method for synthesizing the water-absorbing polymer used in this example will be described. The synthesis method includes a step of synthesizing a water-absorbing polymer and a step of subjecting the obtained water-absorbing polymer to a crosslinking treatment.
(Synthesis of water-absorbing polymer)
Polyoxyalkylene ether phosphate 0.1% [as opposed to acrylic acid weight] as a dispersant in a SUS304 5L reaction vessel (using anchor blades) equipped with a stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet tube, thermometer , As an active ingredient], and 1500 ml of normal heptane was added. The temperature was raised to 90 ° C. while stirring in an atmosphere of nitrogen gas.
On the other hand, in a 2 L three-necked flask, acrylic acid as a monomer aqueous solution from 80% acrylic acid (manufactured by Toagosei Co., Ltd., act. 80.6%), ion-exchanged water, 48% sodium hydroxide aqueous solution (manufactured by Asahi Glass Co., Ltd., act. 49.7%) 1000 g of sodium (72% neutralized product) was obtained. After adding 0.25 g of N-acylated glutamic acid soda (trade name: Amisoft PS-11) dissolved in ion-exchanged water 4.41 g to this monomer aqueous solution, 550 g (hereinafter referred to as monomer aqueous solution A). ), 250 g (hereinafter referred to as monomer aqueous solution B), and 250 g (hereinafter referred to as monomer aqueous solution C).
Next, 2,2′-azobis (2-amidinopropane) dihydrochloride (Wako Pure Chemical Industries, trade name V-50) 0.05 g, polyethylene glycol (Kao, K-PEG6000 LA) 0.5 g, citric acid 4 g of ammonium iron (III) (manufactured by Kanto Chemical) and 10 g of ion-exchanged water were mixed and dissolved to prepare an initiator (A) solution. Further, 0.6 g of sodium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 g of ion-exchanged water to prepare an initiator (B) solution. Further, a titanium citrate aqueous solution (50% citric acid and 7.6% (TiO ₂ ) titanyl sulfate aqueous solution mixed at a weight ratio of 20/27) was prepared.
To monomer aqueous solution A, 12 g of initiator (A) solution is added to prepare monomer A. To monomer aqueous solution B, 5 g of initiator (B) solution is added to prepare monomer B. To monomer aqueous solution C, initiator ( B) Monomer C was prepared by adding 5 g of the solution and 2 g of the aqueous titanium citrate solution.
A monomer A, a monomer B, and a monomer C, which were allowed to stand for 5 minutes or more, were dropped into the 5 L reaction vessel from the monomer dropping port using a microtube pump in this order for polymerization. After completion of monomer dropping, azeotropic dehydration was performed using a dehydrating tube to adjust the water content of the water-absorbing polymer (hydrogel), and then ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX- 810) A solution prepared by dissolving 0.4 g in 10 g of ion-exchanged water was added. Thereafter, 1.6 g of a 60% 1-hydroxyethylidene-1,1′-diphosphonic acid aqueous solution (trade name Bryce ADPA-60A, manufactured by Rhodia) was added. After cooling, normal heptane was removed and dried to obtain a water-absorbing polymer.

[Crosslinking treatment of water-absorbing polymer]
Into the same reaction vessel (using anchor blades) as used in [Synthesis of water-absorbing polymer], 500 parts by weight of the water-absorbing polymer obtained in [Synthesis of water-absorbing polymer] was charged, and sucrose was used as a dispersant. Fatty acid ester (trade name Ryoto Sugar Ester S-770, manufactured by Mitsubishi Chemical Foods) 2% [weight of water-absorbing polymer as an active ingredient] was charged, and 1600 ml of cyclohexane was added. While stirring in a nitrogen atmosphere, the temperature was raised to 75 ° C.
Thereafter, 300 ml of ion-exchanged water was dropped from the dropping port using a dropping funnel, and then 10 g of ion-exchanged water was charged with ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX, trade name Denacol EX-810) as a crosslinking agent. The dissolved one was added. After refluxing for 1.5 hours, cyclohexane was removed and dried to obtain a crosslinked water-absorbing polymer.

[Synthesis Examples 1 to 5]
In Synthesis Examples 1 to 5 according to [Synthesis of water-absorbing polymer] and [Crosslinking treatment of water-absorbing polymer], five types of water-absorbing polymers subjected to crosslinking treatment were obtained. Synthesis Examples 1 to 5 differ only in the amount of the crosslinking agent used in [Crosslinking of water-absorbing polymer], 1 g in Synthesis Example 1, 15 g in Synthesis Example 2, 2.5 g in Synthesis Example 3, and Synthesis Example 4 25 g, and in Synthesis Example 5, 0.25 g was used.

As a result of measuring the centrifugal retention amount of the water-absorbing polymer obtained in Synthesis Examples 1 to 5 according to the measurement method described above, Synthesis Example 1 was 18 g / g, Synthesis Example 2 was 11 g / g, and Synthesis Example 3 was 14 g / g. g, Synthesis Example 4 was 7.5 g / g, and Synthesis Example 5 was 26 g / g.
Moreover, as a result of measuring the water absorption rate by the vortex method of the water-absorbing polymers obtained in Synthesis Examples 1 to 5 according to the above-described measurement method, Synthesis Example 1 was 33 seconds, Synthesis Example 2 was 53 seconds, and Synthesis Example 3 was 54 seconds, Synthesis Example 4 was not measurable, and Synthesis Example 5 was 29 seconds. Here, inability to measure, in the method of measuring the water absorption rate by the above-described vortex method, the stirrer tip is not covered with the test liquid even after 90 seconds or more (the vortex disappears and the liquid surface does not become flat) It means that the water absorption rate could not be measured.
Moreover, as a result of performing the measurement of the liquid flow rate under the pressure of 2.0 kPa of the water-absorbing polymer obtained in Synthesis Examples 1 to 5 according to the measurement method described above, Synthesis Example 1 is 520 ml / min, Synthesis Example 2 is 2500 ml / min, Synthesis Example 3 was 1100 ml / min, Synthesis Example 4 was 15000 ml / min, and Synthesis Example 5 was 370 ml / min.

[Example 1]
70 parts by weight of a crosslinked pulp (“High Bulk Additive HBA-S” manufactured by Weyerhauser Paper) having a fiber roughness of 0.32 mg / m and a fiber cross-section of 0.30, and a fiber roughness of 0.18 and a fiber cross-section of 30 parts by weight of a softwood kraft pulp (Skeena Cellulose Co. “SKEENA PRIME”) having a roundness of 0.32 was dispersed and mixed in water, and a paper strength reinforcing agent (polyamide) was added to 100 parts by dry weight of the mixed pulp. Epichlorohydrin resin (manufactured by Nippon PMC Co., Ltd., Kaimen WS-570) was dispersed and mixed with 1 part by weight of resin components in water to obtain a predetermined concentration, and then this dispersed mixture was dried at the forming part of a wet paper machine. The fiber web was formed so that the amount was 25 g / m ² . Next, the fiber web was dehydrated with a suction box until the moisture content reached 100 parts by weight based on 100 parts by weight of the dry fiber web. Next, immediately before the press part, on the wet fiber web after dehydration, the water-absorbing polymer of Synthesis Example 1 [the low water-absorbing polymer, centrifugal retention amount 18 g / g, water absorption speed 33 seconds by vortex method, particle size 250 μm. The content of water-absorbing polymer of less than 11.5% by mass and the content of water-absorbing polymer of less than 150 μm in particle size of 2.5% by mass] was sprayed almost uniformly at a spraying basis weight of 30 g / m ² . Next, a pre-paper-absorbing absorbent paper (basis weight 25 g / m ² ) having the same composition as that of the fiber web as a fiber aggregate is superposed on the surface of the fiber web where the water-absorbing polymer is dispersed. The laminated body of the fiber web and the absorbent paper was introduced into a dryer, and dried and integrated at a temperature of 130 ° C. to obtain an absorbent sheet having a water-absorbing polymer fixed therein. After the two absorbent sheets (length 90 mm, width 35 mm) are overlaid, the two absorbent sheets (length 200 mm, width 75 mm) are placed on the top and bottom, and the longitudinal front and rear ends are curved. The absorbent layer was cut into a shape.

  An adhesive was applied to the non-skin contact surface side of the obtained absorbent layer, and a back sheet was fixed on the non-skin contact surface of the absorbent layer via the adhesive. Next, the entire skin contact surface of the absorbent layer is covered with a surface sheet, and further, the skin contact surface side of the surface sheet is embossed according to a conventional method to form a leak-proof groove, and a napkin precursor Got. An adhesive is applied to a predetermined portion of the non-skin contact surface (outer surface of the back sheet) of the napkin precursor obtained in this manner to form an adhesive part, and further, the extension from the peripheral part of the absorbent layer in each of the front and back sheets. The end portion was subjected to end sealing according to a conventional method to obtain a napkin. In this napkin, an air-through nonwoven fabric (a perforated sheet used for a Kao Co., Ltd. Laurier Super Slim Guard) was used as the top sheet, and a polyethylene film having a thickness of 25 μm was used as the back sheet. The napkin generally has the structure shown in FIGS. The napkin thus obtained was used as a sample of Example 1.

  In the napkin of Example 1, the content of the water-absorbing material (water-absorbing polymer and fiber) is 100% by mass with respect to the total mass of the absorbing layer, and the water-absorbing property contained in the napkin (absorbing layer). All the polymers were the said low water absorption polymer, and content of the said low water absorption polymer in an absorption layer was 40 mass% with respect to the total mass of this absorption layer.

[Examples 2 to 4]
In Example 1, a napkin was produced in the same manner as in Example 1 except that the water-absorbing polymer was changed to those shown in Table 1 (the water-absorbing polymers in Synthesis Examples 2 to 4). Samples of

Example 5
In Example 1, the napkin was prepared in the same manner as in Example 1 except that the absorption layer was replaced with the following, and the thickness of the napkin (thickness under 7 g / cm ² load) was 5.5 mm. A sample of Example 5 was obtained.
(Absorption layer of Example 5)
A hot-melt adhesive (P-618B manufactured by Toyo Petrolite) was applied separately at a coating amount of 5 g / m ² , and separately prepared on the adhesive coating surface of a tissue paper (upper covering sheet) having a basis weight of 16 g / m ^2. A pulp fiber fiber web (basis weight 240 g / m ² , width 7 cm, length 17 cm) was placed. This tissue paper has larger dimensions than the fiber web. Next, from the top of the fiber web, 0.13 g of the water-absorbing polymer shown in Table 1 (the water-absorbing polymer of Synthesis Example 2) was uniformly spread over the entire fiber web. Further, a tissue paper (basis weight 16 g / m ² ) as a lower covering sheet in which a hot-melt adhesive is applied at a coating amount of 5 g / m ² with the same size as the fiber web on the water-absorbing polymer spray surface of the fiber web. Are stacked so that the adhesive application surface faces the fiber web, and the portions extending from the fiber web in the upper coating sheet are wound up on the upper surface of the lower coating sheet, and then the upper and lower surfaces of the fiber web are Was inverted to obtain a rectangular absorbent layer in a plan view in which substantially the entire absorbent layer was covered with tissue paper (coating sheet). A schematic cross-sectional view (corresponding to FIG. 2) of the napkin of Example 5 is shown in FIG. In FIG. 4, reference numeral 40 is an absorbent body, reference numeral 41 is a water-absorbing polymer, reference numeral 42 is a fiber web, reference numeral 43 is an upper covering sheet, and reference numeral 44 is a lower covering sheet.

Example 6
In Example 2, 1 g of trisodium citrate (94 parts by mass with respect to 100 parts by mass of the total water-absorbing polymer contained in the napkin) was sprayed as a metal ion scavenger between the absorbent layer and the back sheet. A napkin was produced in the same manner as in Example 2, and this was used as the sample of Example 6. The thickness of the napkin of Example 6 (thickness under a load of 7 g / cm ² ) was 2.0 mm.

[Comparative Example 1]
In Example 1, the water-absorbing polymer was a commercially available water-absorbing polymer (manufactured by Nippon Shokubai Co., Ltd., trade name Aquaric CA-W4, the centrifugal retention amount was 36 g / g, the water absorption rate by vortex method was 12 seconds, and 2.0 kPa. A napkin was prepared in the same manner as in Example 1 except that the liquid flow rate under pressure was changed to 0.19 ml / min.

[Comparative Example 2]
In Example 1, a napkin was prepared in the same manner as in Example 1 except that no water-absorbing polymer was arranged, and this was used as a sample of Comparative Example 2. The thickness of the napkin of Comparative Example 2 (thickness under 7 g / cm ² load) was 1.3 mm.

[Comparative Example 3]
A napkin was prepared in the same manner as in Example 1 except that the water-absorbing polymer in Example 1 was changed to that shown in Table 1 (the water-absorbing polymer in Synthesis Example 5), and this was used as a sample of Comparative Example 3. .

[Reference example]
A sanitary napkin “Super Maxi” (manufactured by Kao Corporation) marketed in Indonesia was used as a sample for reference. This super maxi does not contain a water-absorbing polymer. The thickness of the napkin of the reference example (thickness under a load of 7 g / cm ² ) was 9.5 mm.

[Evaluation]
About the sanitary napkin of an Example, a comparative example, and a reference example, the red degree a ^* value was measured according to the said procedures 1-3. Further, the state of the napkin after completion of the procedure 3 was visually observed, and it was confirmed whether or not the napkin was broken (washing breakage) due to washing with water. Moreover, as evaluation of the absorption performance of these sanitary napkins, the absorption time and the liquid return amount were measured by the following methods. These results are shown in Table 1 below.

<Measurement method of absorption time>
With the sanitary napkin to be measured spread in a plane and fixed on a horizontal surface with the top sheet facing up, an acrylic plate with a cylindrical injection part is placed on the top sheet in the center of the absorber. Further, a weight is placed on the acrylic plate, and a load of 5 g / m ² is applied to the center of the absorber. The injection part provided on the acrylic plate has a cylindrical shape with an inner diameter of 10 mm, and the central axis of the cylindrical injection part coincides with the central axis in the longitudinal direction and the width direction of the acrylic plate, and the cylindrical injection part A through-hole having an inner diameter of 10 mm is formed so as to communicate between the inside and the surface sheet facing surface of the acrylic plate. Next, the acrylic plate is arranged so that the central axis of the cylindrical injection portion coincides with the central portion of the absorber in plan view, and 3 g of blood is injected from the cylindrical injection portion and absorbed by the sanitary napkin. The time (seconds) from when the blood reached the surface of the napkin until the total amount of 3 g was absorbed by the napkin was measured, and this was taken as the first absorption time. In addition, 3 minutes after the first blood injection, the above procedure is repeated until 3 g of blood is further injected (a total of 6 g of blood is injected) until the total amount of the reinjected blood is absorbed by the napkin. Time (seconds) was measured, and this was taken as the second absorption time. Also, 3 minutes after the second blood injection, the above procedure is repeated until 3 g of blood is further injected (a total of 9 g of blood is injected) until the total amount of the reinjected blood is absorbed by the napkin. Was measured as a second absorption time. The smaller the value of these absorption times, the faster the absorption speed and the higher the evaluation. In addition, in the 1st time and the 2nd time, when it exceeded 3 minutes until the total amount (3 g) of the injected blood was absorbed, the next 3 g was injected immediately after the total amount was absorbed.

<Measurement method of liquid return amount>
In <Measurement method of absorption time>, after 3 minutes from the third blood injection, the acrylic plate and the weight are removed, and the basis weight of 30 g / 7 cm × 7 cm is formed on the skin contact surface of the napkin (on the top sheet). Ten sheets of m ² absorbent paper (commercial tissue paper) were placed on top of each other, and a load of 68 g / cm ² was applied to the absorbent paper for 1 minute. After the loading, 10 sheets of absorbent paper were removed, and the weight of the 10 sheets of absorbent paper was measured. From this measured value and the measured value of the weight of 10 sheets of absorbent paper before the load obtained in advance, the weight (g) of blood absorbed in 10 sheets of absorbent paper is determined, and this weight is taken as the liquid return amount. did. The smaller the liquid return amount, the higher the napkin absorption performance and the higher the evaluation.

As is apparent from the results in Table 1, each of the napkins of Examples 1 to 6 has practically sufficient absorption performance and can sufficiently remove redness by washing with water, although it is thin. is there. In particular, since the napkin of Example 6 contains a metal ion scavenger, it can be seen that the a ^* value is smaller than that of the other examples, and the redness removal performance is excellent.

On the other hand, the napkins of Comparative Example 1 and Comparative Example 3 did not use the low water-absorbing polymer. Therefore, the a ^* value was large and the tearing occurred, and it was difficult to say that washing with water was easy.
Moreover, since the napkin of Comparative Example 2 did not contain a water-absorbing polymer, the result was inferior in absorption performance, particularly in terms of liquid return.
In addition, although the reference example does not contain a water-absorbing polymer, since the thickness of an absorption layer is large, it has practically sufficient absorption performance.

FIG. 1 is a plan view showing the skin contact surface side (surface sheet side) of one embodiment of the sanitary napkin of the present invention. 2 is a cross-sectional view schematically showing a cross section taken along line XX of FIG. FIG. 3 is a view corresponding to FIG. 2 showing another embodiment of the sanitary napkin of the present invention. 4 is a view corresponding to FIG. 2 of the sanitary napkin of Example 5. FIG.

Explanation of symbols

1 Sanitary napkin 2 Surface sheet (surface layer)
3 Back sheet (back layer)
4 Absorbing layers 4a, 4b Absorbent sheet 40 Absorber 5 Leak-proof groove 6 End seal part 10 Metal ion scavenger 11 Internal sheet

Claims (6)

A sanitary napkin comprising a surface layer, a back layer, and an absorbent layer disposed between both layers and containing a water-absorbing material, wherein the water-absorbing material has a centrifugal retention amount of 5 to 18 g / g, according to a vortex method A water-absorbing polymer having a water absorption speed of 25 seconds or more ,
A sanitary napkin having a red degree a * value of 7 or less in a red portion stained with red blood after blood is injected and washed according to the following procedures 1 to 3 .
Procedure 1: Inject 12 g of blood into the sanitary napkin from the surface layer side of the sanitary napkin, leave it for 30 minutes in an environment at room temperature of 25 ° C., and then use the sanitary napkin with water at a water temperature of 25 ° C. and a hardness of 5 ° DH. After washing for 3 minutes, the sanitary napkin is squeezed by hand, and the water contained in the napkin is squeezed out as much as possible.
Procedure 2: On the surface layer side of the wet sanitary napkin obtained in the procedure 1 above, the red degree a * using a spectrocolorimeter at five points with the strongest redness of the red part stained with blood. Measure the value.
Procedure 3: The average of the three measured values obtained by subtracting the maximum value and the minimum value from the five measured values obtained in the procedure 2 is defined as the red degree a * value of the sanitary napkin.   The sanitary napkin according to claim 1, wherein a centrifugal retention amount of the water-absorbing polymer is 5 to 14 g / g.   The sanitary napkin according to claim 1 or 2, wherein the content of the water-absorbing material is 90% by mass or more based on the total mass of the absorbent layer.   The physiology according to any one of claims 1 to 3, wherein a content of the water-absorbing polymer having a particle size of less than 250 µm is less than 20% by mass among all the water-absorbing polymers contained in the sanitary napkin. For napkins.   The sanitary napkin according to any one of claims 1 to 4, comprising a metal ion scavenger.   The sanitary napkin according to any one of claims 1 to 5, wherein the water-absorbing polymer in the absorbent layer has a liquid flow rate of 50 ml / min or more under a pressure of 2.0 kPa.

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