JP7169818B2 - absorbent article - Google Patents

Description

The present invention relates to an absorbent article in which a top sheet is composed of a plurality of layers, and among the plurality of layers, the layer located on the skin side does not contain acid, and the layer located on the back side contains acid. It is a thing.

Feces and urine excreted by the wearer of the absorbent article are absorbed by the absorbent article. The pH of the site where feces or urine is absorbed changes according to the elapsed time after excretion. For example, when urine is excreted, the pH at the absorption site immediately after excretion is often about 6.5. As time passes, urea in urine is decomposed by hydrolase (eg, urease) to produce ammonia. As a result, the pH of the absorption site inclines toward the alkaline side, sometimes reaching pH 11 or so.

Prolonged contact between the wearer's skin and alkaline absorbent sites is stressful to the skin. In particular, children who have just been born (children at a low age) have a thin skin layer, so the skin tends to be burdened more easily than adults.

There are prior arts in which an acidic component is added to the sheet on the skin side of an absorbent article to prevent excrement from tilting to the alkaline side due to ammonia generated after urination (Patent Documents 1 to 3 below).

In the absorbent article of Patent Document 1, the surface sheet is provided with projections, and the tops and side walls of the projections contain a weakly acidifying agent so that the fiber density of the side walls is lower than the fiber density of the tops. . According to this absorbent article, even when the weakly acidifying agent contained in the top and side wall portions is eluted into the excreted liquid, a certain amount of discharged liquid remains as residual liquid on the side wall portions where the fiber density is low. , the pH of the convex portion can be maintained at a weak acidity.

The absorbent article of Patent Document 2 includes a fumaric acid-containing sheet containing fumaric acid on a sheet base material mainly made of paper, and the fumaric acid content in the fumaric acid-containing sheet is 0.00015 mass. % to 1.5% by mass. According to this absorbent article, the wearer's skin rash can be prevented, and as a result of suppressing the propagation of germs after excretion and the generation of foul odors, the antibacterial and deodorizing effects can be maintained for a long time.

In the absorbent article of Patent Document 3, weakly acidic pulp is blended as a raw material of the absorbent body, antibacterial superabsorbent polymer is mixed with the absorbent body, citric acid consisting of granules is sprinkled on the absorbent body, and the absorbent body is mixed. A liquid-permeable sheet impregnated with malic acid is arranged above. According to this absorbent article, due to the synergistic effect of " weakly acidic pulp", "antibacterial super absorbent polymer", "citric acid" and "malic acid", it is possible to wear it for a long period of time, which cannot be obtained by using it alone or in partial combination. It is said that the deodorant effect can be dramatically enhanced at times.

Japanese Patent No. 6033981 JP 2017-184962 A JP 2014-079284 A

The following problems (A) to (C) arise when an acidic component is added to the skin-side sheet of the absorbent article.
(A) If the acidic component blended in the sheet runs off due to excretion, the effect of inhibiting alkalinization by the acidic component cannot be expected in the case of repeated excretion.
(B) When the wearer of the absorbent article does not excrete, the sheet containing an acidic component (for example, about pH 3) continues to touch the wearer's skin, which places a burden on the wearer's skin.
(C) In areas of the absorbent article that are subject to body pressure, there is a risk that acidic components that have not yet reacted with excrement will revert and come into contact with the wearer's skin.

Furthermore, Patent Documents 1 to 3 have the following problems.
In the absorbent article described in Patent Document 1, it is necessary to provide convex portions on the surface sheet, and the site where the weak acidifying agent is added is also limited, so the structure of the absorbent article is limited and the manufacturing method is simplified. There is a problem of difficulty.

The absorbent article described in Patent Document 2 uses a sheet impregnated with fumaric acid, but since fumaric acid is difficult to dissolve in water, it is difficult to apply fumaric acid to the fibers together with a hydrophilic agent. The problem is that it is difficult to manufacture.

The absorbent article described in Patent Document 3 uses a top sheet impregnated with malic acid, but there is a problem that malic acid tends to have relatively strong irritation to the skin.

Accordingly, an object of the present invention is to provide an absorbent article that can reduce the burden on the wearer's skin.

Various aspects of the tape-type disposable diaper that solves the above problems are as follows.
<First Aspect>
An absorbent article having a top sheet provided on the skin side and an absorbent body provided on the back side of the top sheet,
The topsheet is composed of a plurality of layers,
An absorbent article, wherein, of the plurality of layers, the layer located on the skin side does not contain acid, and the layer located on the back side contains acid.

(Effect)
In a first aspect, the topsheet contains an acid. Unlike the intermediate sheet and the packaging sheet, the top sheet has the particularity of being in direct contact with the wearer's skin. Therefore, it is particularly important to prevent the excreta adhering to the top sheet from tilting to the alkaline side. Therefore, by adding an acid to the top sheet, it is possible to prevent the inclination to the alkaline side and reduce the burden on the wearer's skin. For example, when the wearer urinates, urease breaks down urea in the urine to ammonia, which can be neutralized by the acid in the topsheet.

Since the top sheet is in contact with the wearer's skin, the acid contained in the top sheet may burden the wearer's skin. Therefore, by forming the top sheet from a plurality of layers and not containing acid in the layer located on the skin side, it is possible to prevent the wearer's skin from being burdened by the acid.

<Second Aspect>
The acid contained in the top sheet is a water-soluble acid,
The absorbent article according to the first aspect, wherein the top sheet contains a hydrophilic agent together with the water-soluble acid.

(Effect)
The acid contained in the top sheet is preferably a water-soluble acid. This is because the sparingly soluble acid has low affinity with the hydrophilic agent and is less likely to adhere to the fibers constituting the top sheet.

When the wearer of the absorbent article of this aspect excretes, the excrement comes into contact with the water-soluble acid contained in the top sheet, thereby suppressing the inclination of the excrement to the alkaline side.

In addition, due to the action of the hydrophilic agent contained in the top sheet, the water-soluble acid is less likely to run off from the top sheet. That is, in a state in which the water-soluble acid is chemically bonded to the hydrophilic agent, it becomes a structure that is held between the fibers that make up the top sheet. of acid becomes difficult to flow down. Such a topsheet can be produced, for example, by coating fibers constituting the topsheet with a water-soluble acid and a hydrophilic agent.

According to this embodiment, even if the wearer excretes a number of times, the top sheet retains the water-soluble acid. It is possible to continuously suppress the inclination to Since the hydrophilic agent prevents the water-soluble acid from flowing down from the top sheet due to excretion, the water-soluble acid and the hydrophilic agent are preferably provided at the same position on the top sheet in plan view.

In addition, when the top sheet is made of hydrophobic fibers, the water-repellent effect of the fibers causes excrement to stay on the skin surface of the top sheet, making it difficult for the excrement to reach the absorbent core. By including a hydrophilic agent in the top sheet as in this aspect, retention of such excrement is prevented, and the excrement can reach the absorbent body quickly.

<Third Aspect>
The absorbent article according to the second aspect, wherein the hydrophilic agent comprises a polyglycerin fatty acid ester, a polyether-polyester block copolymer, a polyether-modified silicone, a fatty acid ester of an ethylene oxide-added polyhydric alcohol, or a combination thereof. .

(Effect)
The hydrophilic agent contained in the top sheet preferably has a high effect of preventing water-soluble acid from running off. As hydrophilizing agents having such a high effect, polyglycerin fatty acid esters, polyether-polyester block copolymers, polyether-modified silicones, and fatty acid esters of ethylene oxide-added polyhydric alcohols may be used alone or in combination. You can use A combination of any of these substances and other known substances may also be used.

<Fourth Aspect>
The top sheet containing the water-soluble acid and the hydrophilic agent,
The second aspect or the third aspect, wherein the first measurement result is 10 points, the second measurement result is 10 points, and the third measurement result is 9 points or more in the artificial urine dropping test. Absorbent article according to.

(Effect)
The top sheet is composed of multiple layers, of which the layer located on the skin side does not contain a water-soluble acid, and the layer located on the back side contains a water-soluble acid. A top sheet is prepared, and an artificial urine drop test is performed on this top sheet. The first measurement result is 10 points, the second measurement result is 10 points, and the third measurement result is 9 points. It is preferable to use the top sheet having the above properties in an absorbent article. This is because even when the wearer excretes a number of times, the water-soluble acid and the hydrophilic agent are less likely to run off from the topsheet, so the burden on the wearer's skin can be reduced over a long period of time. . The number and thickness of layers of the top sheet used in the drip test of artificial urine, the material of the fiber of the top sheet, the manufacturing method, etc. are all the same as the top sheet actually mounted on the absorbent article. do.

The drip test of artificial urine is performed according to the following procedures (1) to (4).
<Drip test of artificial urine>
(1) The top sheet is placed on 10 layers of filter paper, and a metal jig with 10 holes is placed on the top sheet.
(2) Using a micropipette, 1 mL of artificial urine was dropped into each of the 10 holes of the metal jig, and the top sheet absorbed the artificial urine within 2 seconds after dropping. A hole that has been absorbed is counted as 1 point and a hole that is not absorbed as 0 point, and the total score of the 10 holes is recorded as the result of the first measurement.
(3) After 3 minutes have passed since the artificial urine was dripped in (2), 1 mL of artificial urine was dripped into each of the 10 holes of the metal jig using a micropipette, and then dripped. After that, within 2 seconds, check whether the top sheet has absorbed the artificial urine, count the absorbed holes as 1 point and the unabsorbed holes as 0 points, and count the total of 10 holes. Record the score as the result of the second measurement.
(4) After 6 minutes have passed since the artificial urine was dripped in (3), 500 μL of artificial urine was dripped into each of the 10 holes of the metal jig using a glass pipette and dripped. After that, within 2 seconds, check whether the top sheet has absorbed the artificial urine, count the absorbed holes as 1 point and the unabsorbed holes as 0 points, and count the total of 10 holes. Record the score as the result of the third measurement.

The artificial urine used in the artificial urine drip test contains 2 wt% urea, 0.8 wt% sodium chloride, 0.03 wt% calcium chloride dihydrate, 0.08 wt% magnesium sulfate heptahydrate, and ion 97.09 wt% of exchange water is mixed.

The metal jig used for the artificial urine drop test was a rectangle with a width of 210 mm, a length of 50 mm, and a thickness of 5 mm. are provided at regular intervals with a space between them, and the weight is 400 g.

<Fifth Aspect>
An intermediate sheet is provided between the top sheet and the absorbent body,
The absorbent article according to any one of the first to fourth aspects, wherein the intermediate sheet comprises a hydrophilic agent together with a water-soluble acid.

(Effect)
Although the intermediate sheet does not come into direct contact with the wearer's skin, excrement may remain in the intermediate sheet when the wearer excretes. When the excrement in the intermediate sheet becomes alkaline and returns to the skin surface side of the top sheet (excretion in the intermediate sheet moves to the skin surface side of the top sheet), it touches the wearer's skin, A burden is imposed on the wearer's skin. Therefore, by including a water-soluble acid in the intermediate sheet, it is possible to prevent the wearer's skin from being burdened.

In general, intermediate sheets are often bulkier than top sheets and packaging sheets. Therefore, the amount of excrement remaining inside the intermediate sheet tends to be greater than that of the top sheet or the packaging sheet. Therefore, when the reversion phenomenon is considered, the inclusion of a water-soluble acid in the intermediate sheet containing a large amount of excreta is more advantageous than the inclusion of a water-soluble acid in the packaging sheet. In addition, since the intermediate sheet is positioned closer to the skin than the packaging sheet, from this point as well, the inclusion of a water-soluble acid in the intermediate sheet close to the skin is better than the inclusion of a water-soluble acid in the packaging sheet. is also highly advantageous.

<Sixth Aspect>
A packaging sheet for wrapping the absorbent body is provided,
The absorbent article according to any one of the first to fifth aspects, wherein the packaging sheet contains a hydrophilic agent together with a water-soluble acid.

(Effect)
Although the packaging sheet does not come into direct contact with the wearer's skin, there is a possibility that excrement remains in the packaging sheet when the wearer excretes. When the excrement in the packaging sheet becomes alkaline and returns to the skin surface side of the top sheet (excretion in the packaging sheet moves to the skin surface side of the top sheet), it touches the wearer's skin, A burden is imposed on the wearer's skin. Therefore, by including a water-soluble acid in the packaging sheet, it is possible to prevent the wearer's skin from being burdened. Moreover, in general, the packaging sheet has many opportunities to come into contact with the absorbent body that retains the excrement. That is, since the water-soluble acid contained in the packaging sheet acts on the excrement retained by the absorbent body, the effect of suppressing the inclination of the excrement to the alkaline side is high.

<Seventh Aspect>
The absorbent article according to any one of the first to sixth aspects, wherein the top sheet has a fiber diameter of 4.0 dtex or more.

(Effect)
Excrement can be quickly absorbed by increasing the fiber diameter of the top sheet. Therefore, the time during which the wearer's skin is in contact with excrement can be reduced. At the same time, it is possible to prevent excrement from accumulating on the surface of the top sheet and spreading over a wide area, so that the area where the excrement adheres to the wearer's skin can be reduced. As a result, it is possible to reduce the burden on the skin due to the inclination of the excrement to the alkaline side. The fiber diameter of such a top sheet is preferably 4.0 dtex or more, more preferably 5.0 dtex or more.

<Eighth Aspect>
The absorbent according to any one of the first to seventh aspects, wherein, among the plurality of layers of the top sheet, the fiber diameter of the layer located on the skin side is smaller than the fiber diameter of the layer located on the back side. sexual goods.

(Effect)
By forming the top sheet from a plurality of layers and reducing the fiber diameter of the layer located on the skin side, the feel is improved, and the burden on the wearer's skin can be reduced. Further, by increasing the fiber diameter of the layer located on the back side, it is possible to obtain the same effects as those of the seventh aspect.

<Ninth Aspect>
The eighth aspect, wherein among the plurality of layers of the top sheet, the layer located on the skin side has a fiber diameter of 2.5 dtex or less, and the layer located on the back side has a fiber diameter of 4.0 dtex or more. Absorbent article according to.

(Effect)
By forming the top sheet from a plurality of layers and reducing the fiber diameter of the layer located on the skin side, the feel is improved, and the burden on the wearer's skin can be reduced. Further, by increasing the fiber diameter of the layer located on the back side, it is possible to obtain the same effects as those described in the seventh aspect.

Specifically, the fiber diameter of the layer located on the skin side is preferably 2.5 dtex or less, more preferably 1.7 dtex or less. Further, the fiber diameter of the layer positioned on the back side is preferably 4.0 dtex or more, more preferably 5.0 dtex or more. By setting the fiber diameter within the above range, the same function and effect as those described in the seventh aspect become significant.

<Tenth Aspect>
An intermediate sheet is provided between the top sheet and the absorbent body,
The absorbent article according to any one of claims 1 to 9, wherein the intermediate sheet has a basis weight of 20 gsm or more.

(Effect)
When the body pressure of the wearer is applied to the absorbent article, there is a possibility that the excrement retained by the absorbent body may move back toward the skin. Therefore, by making the weight of the intermediate sheet thicker, it is possible to reduce the amount of excrement that returns. In particular, when part of the acid contained in the top sheet runs off and is retained in the absorbent material, if the backflow occurs, the acid in the top sheet adheres to the wearer's skin, causing a burden on the wearer's skin. There is a risk of it. Such a burden can be alleviated by making the weight of the intermediate sheet thicker to prevent it from reverting. The basis weight of the intermediate sheet is preferably 20 gsm or more, more preferably 30 gsm or more.

<Eleventh Aspect>
A packaging sheet for wrapping the absorbent body is provided,
The absorbent article according to any one of the first to tenth aspects, wherein the packaging sheet has a basis weight of 20 gsm or more.

(Effect)
In the ninth aspect, reversion is prevented by making the weight of the intermediate sheet thicker, but the same effect can be obtained by making the packaging sheet thicker. The basis weight of the packaging sheet is preferably 20 gsm or more, more preferably 30 gsm or more.

<Twelfth Aspect>
The absorbent article according to any one of the first to tenth aspects, wherein said acid is citric acid.

(Effect)
Citric acid is suitable because it is safe enough to be used as a food additive and has a high effect of suppressing alkalinization.

ADVANTAGE OF THE INVENTION According to this invention, the burden on a wearer's skin can be reduced.

Fig. 2 is a plan view showing the inner surface of the tape-type disposable diaper when the diaper is unfolded; Fig. 2 is a plan view showing the outer surface of the tape-type disposable diaper when the diaper is unfolded; 6 is a cross-sectional view taken along line 6-6 of FIG. 1; FIG. FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 1; 1. (a) A cross-sectional view taken along the line 8-8 in FIG. 1, and (b) a cross-sectional view taken along the line 9-9 in FIG. It is the graph which showed the experimental result. It shows the change in pH when 100 μL of artificial urine was dripped three times at measurement points A to C and G to I. It is the graph which showed the experimental result. It shows the change in pH when 500 μL of artificial urine was dripped three times at measurement points D to F and J to L. (a) It is a top view of a metal jig. (b) It is a perspective view of a metal jig.

1 to 5 exemplify tape-type disposable diapers as absorbent articles, where X in the figures indicates the total width of the diaper excluding the connecting tape, and L indicates the total length of the diaper. there is Also, although not shown, the top sheet 30, the intermediate sheet 40, the packaging sheet 58, the absorbent body 56, the liquid impermeable sheet 11 and the exterior nonwoven fabric 12 are each bonded with a hot melt adhesive. The hot melt adhesive is applied by known methods such as slot coating, continuous line or dotted line bead coating, spiral or Z-shaped spray coating, or pattern coating (transfer of hot melt adhesive by letterpress method). can be applied. Alternatively or additionally, at the fixing portion of the elastic member, a hot melt adhesive can be applied to the outer peripheral surface of the elastic member to fix the elastic member to the adjacent member. Hot-melt adhesives include, for example, EVA-based, adhesive rubber-based (elastomer-based), olefin-based, and polyester-polyamide-based adhesives, and can be used without particular limitation. As a joining means for joining each constituent member, a means by material welding such as heat sealing or ultrasonic sealing can be used.

This tape-type disposable diaper has an abdominal portion F extending forward from the center in the front-rear direction LD and a back portion B extending rearward from the center in the front-rear direction LD. In addition, this tape-type disposable diaper includes an absorbent body 56 built in a region including the crotch portion, a liquid-permeable top sheet 30 covering the front side of the absorbent body 56, and a liquid-impermeable top sheet 30 covering the back side of the absorbent body 56. It has a sheet 11 and an exterior nonwoven fabric 12 that covers the back side of the liquid-impermeable sheet and constitutes the outer surface of the product.

The materials and characteristic parts of each part will be described in order below.
(Absorber)
The absorbent body 56 is a part that absorbs and retains the excreted fluid, and can be formed by an assembly of fibers. The filament assembly may be a filament assembly obtained by laminating short fibers such as cotton pulp or synthetic fibers, or by opening tows (fiber bundles) of synthetic fibers such as cellulose acetate as necessary. can also be used. The fiber basis weight can be, for example, about 100 to 300 g/m ² when piling up cotton-like pulp or short fibers, and for example, about 30 to 120 g/m ² for filament aggregates. can be done. The fineness of synthetic fibers is, for example, 1 to 16 dtex, preferably 1 to 10 dtex, more preferably 1 to 5 dtex. In the case of a filament assembly, the filaments may be non-crimped fibers, but crimped fibers are preferred. The degree of crimping of the crimped fibers can be, for example, about 5 to 75, preferably 10 to 50, more preferably 15 to 50 per 2.54 cm. Further, uniformly crimped crimped fibers can be used.

(superabsorbent polymer particles)
Absorbent body 56 may contain superabsorbent polymer particles in part or in its entirety. Superabsorbent polymer particles include "powder" in addition to "particles". As the superabsorbent polymer particles, those used in this type of absorbent article can be used as they are. Although the particle size of the superabsorbent polymer particles is not particularly limited, for example, sieving using a 500 μm standard sieve (JIS Z8801-1: 2006) (shaking for 5 minutes), and particles falling under the sieve in this sieving When sieving (shaking for 5 minutes) using a 180 μm standard sieve (JIS Z8801-1: 2006), the percentage of particles remaining on the 500 μm standard sieve is 30% by weight or less, and the 180 μm standard sieve It is desirable that the proportion of particles remaining on the top is 60% by weight or more.

Materials for the superabsorbent polymer particles may be used without any particular limitation, but those having a water absorption of 40 g/g or more are suitable. Superabsorbent polymer particles include starch-based, cellulose-based, and synthetic polymer-based particles. and acrylic acid (salt) polymers can be used. As for the shape of the superabsorbent polymer particles, the powder particles that are commonly used are suitable, but other shapes can also be used.

As the superabsorbent polymer particles, those having a water absorption rate of 70 seconds or less, particularly 40 seconds or less are preferably used. If the water absorption rate is too slow, the liquid supplied into the absorbent body 56 tends to return to the outside of the absorbent body 56, which is called reversion.

As the superabsorbent polymer particles, those having a gel strength of 1000 Pa or more are preferably used. As a result, even when the absorbent body 56 is bulky, it is possible to effectively suppress the feeling of stickiness after liquid absorption.

The basis weight of the superabsorbent polymer particles can be appropriately determined according to the absorption amount required for the use of the absorbent body 56 . Therefore, although it cannot be generalized, it can be 50 to 350 g/m ² . If the basis weight of the polymer is less than 50 g/m ² , it becomes difficult to secure the absorption capacity. If the amount exceeds 350 g/m ² , not only the effect is saturated, but also the excessive superabsorbent polymer particles give a gritty feeling of discomfort.

(packaging sheet)
In order to prevent the superabsorbent polymer particles from slipping out or to improve the shape retention of the absorbent body 56, the absorbent body 56 can be incorporated as an absorbent element 50 wrapped with a wrapping sheet 58. FIG. As the wrapping sheet 58, tissue paper, especially crepe paper, nonwoven fabric, poly-laminated nonwoven fabric, a sheet with small holes, or the like can be used. However, it is desirable that the sheet is such that the superabsorbent polymer particles do not escape. When non-woven fabric is used instead of crepe paper, hydrophilic SMMS (spunbond/meltblown/meltblown/spunbond) nonwoven fabric is particularly suitable, and polypropylene, polyethylene/polypropylene, etc. can be used as the material.

As shown in FIG. 3, the packaging sheet 58 may have a structure that wraps the entire absorber 56 with one sheet, or may wrap the entire absorber 56 with a plurality of sheets, such as two upper and lower sheets. The packaging sheet 58 can also be omitted.

The basis weight of the packaging sheet 58 is preferably 16 gsm or more, more preferably 20 gsm or more. By making the packaging sheet 58 thicker, it is possible to prevent excrement and acid retained by the absorbent body 56 from returning and adhering to the wearer's skin, thereby preventing the wearer's skin from being burdened.

(top sheet)
The top sheet 30 is liquid-permeable, and may be, for example, a perforated or non-perforated nonwoven fabric, a porous plastic sheet, or the like. In addition, among these, the nonwoven fabric is not particularly limited as to what the raw material fibers are. Examples include synthetic fibers such as olefins such as polyethylene and polypropylene, polyesters and polyamides, regenerated fibers such as rayon and cupra, and mixed fibers and composite fibers in which two or more of these are used. can. Furthermore, the nonwoven fabric may be manufactured by any processing. Examples of processing methods include known methods such as spunlace, spunbond, thermal bond, meltblown, needle punch, air through, and point bond methods. For example, if flexibility and drapeability are desired, the spunlace method is preferable, and if bulkiness and softness are desired, the thermal bond method is the preferable processing method.

The top sheet 30 extends from the front end to the rear end of the product in the front-rear direction, and extends laterally from the absorbent body 56 in the width direction WD. If necessary, such as when the top sheet 30 is located on the center side in the width direction, the width of the top sheet 30 may be made shorter than the total width of the absorbent body 56, and other suitable modifications may be made.

The fiber diameter of the top sheet 30 can be arbitrarily determined, but is preferably 4.0 dtex or more, more preferably 5.0 dtex or more. By increasing the fiber diameter of the top sheet 30 in this manner, excrement can be rapidly absorbed. As a result, it is possible to reduce the amount of time that excrement is in contact with the wearer's skin. In addition, since it is possible to prevent excrement from accumulating on the surface of the top sheet 30 and spreading over a wide area, the area where the excrement adheres to the wearer's skin can be reduced. As a result, it is possible to reduce the burden on the skin due to the inclination of the excrement adhering to the top sheet 30 to the alkaline side.

Moreover, it is preferable that the top sheet 30 is composed of a plurality of layers, and the fiber diameter of the layer positioned on the skin side is smaller than that of the layer positioned on the back side. By reducing the fiber diameter of the layer located on the skin side, the feel is improved, and the burden on the wearer's skin can be reduced. Further, by increasing the fiber diameter of the layer located on the back side, rapid absorption of excrement becomes possible.

Specifically, among the plurality of layers of the top sheet 30, the fiber diameter of the layer located on the skin side is preferably 2.5 dtex or less, more preferably 1.7 dtex or less. In addition, the fiber diameter of the layer positioned on the back side is preferably 4.0 dtex or more, more preferably 5.0 dtex or more. By setting the fiber diameter in such a range, the wearer can easily feel that the texture is good and the excrement can be quickly absorbed.

(intermediate sheet)
An intermediate sheet (also called a “second sheet”) 40 having a faster liquid permeation rate than the top sheet 30 can be provided in order to quickly transfer the liquid that has permeated the top sheet 30 to the absorbent body 56 . The intermediate sheet 40 is intended to quickly transfer the liquid to the absorbent body 56 to enhance the absorption performance of the absorbent body 56 and prevent the "return" phenomenon of the absorbed liquid from the absorbent body 56 . The intermediate sheet 40 can also be omitted.

Examples of the intermediate sheet 40 include materials similar to those of the top sheet 30, spunlace nonwoven fabric, spunbond nonwoven fabric, SMS nonwoven fabric, pulp nonwoven fabric, mixed sheet of pulp and rayon, pointbond nonwoven fabric, and crepe paper. In particular, an air-through nonwoven fabric is preferred because it is bulky. Composite fibers having a core-sheath structure are preferably used for the air-through nonwoven fabric. In this case, the resin used for the core may be polypropylene (PP), but polyester (PET) having high rigidity is preferable. The thickness of the raw fibers of the nonwoven fabric is preferably 2.0 to 10 dtex. In order to make the non-woven fabric bulky, it is also preferable to use eccentric fibers, hollow fibers, or eccentric and hollow fibers whose core is not in the center as mixed fibers of all or part of the raw material fibers.

The intermediate sheet 40 in the illustrated example is shorter than the width of the absorbent body 56 and arranged in the center, but it may be provided over the entire width. Further, the intermediate sheet 40 may be provided over the entire length of the diaper, or may be provided only in the intermediate portion including the excretion position as shown in the illustrated example.

The basis weight of the intermediate sheet 40 is preferably 20 gsm or more, more preferably 30 gsm or more. When the body pressure of the wearer is applied to the absorbent article, there is a possibility that the excrement retained by the absorbent body 56 may move back toward the skin. As described above, by making the weight of the intermediate sheet 40 thicker, it is possible to reduce the amount of excrement that returns. In particular, if part of the acid contained in the top sheet 30 flows down together with the excrement and is retained in the absorbent body 56, the acid in the top sheet 30 adheres to the wearer's skin, causing the wearer to wear the product. There is a risk of harming the skin of the person. Therefore, it is preferable to reduce such a burden by increasing the basis weight of the intermediate sheet 40 to prevent the backflow.

(liquid-impermeable sheet)
The liquid-impermeable sheet 11 is not particularly limited, but preferably has moisture permeability. As the liquid-impermeable sheet 11, for example, an inorganic filler is kneaded in an olefin resin such as polyethylene or polypropylene, the sheet is molded, and then the sheet is stretched in a uniaxial or biaxial direction. A sheet can be preferably used. Moreover, as the liquid-impermeable sheet 11, a non-woven fabric as a base material with improved waterproofness can also be used.

It is desirable that the liquid-impermeable sheet 11 extends in the same or wider range than the absorbent body 56 in the front-rear direction LD and the width direction WD. A structure in which the end portions of the absorber 56 are not covered in the front-rear direction LD and the width direction WD may also be employed.

(exterior non-woven fabric)
The exterior nonwoven fabric 12 covers the entire back side of the liquid-impermeable sheet 11 to give the outer surface of the product a cloth-like appearance. The exterior nonwoven fabric 12 is not particularly limited, and examples of raw material fibers include olefin-based, polyester-based, and polyamide-based synthetic fibers such as polyethylene or polypropylene, regenerated fibers such as rayon and cupra, and natural fibers such as cotton. A spunlace method, a spunbond method, a thermal bond method, an air through method, a needle punch method, or the like can be used as a processing method. However, spunbond nonwoven fabrics, SMS nonwoven fabrics, SMMS nonwoven fabrics, and other long-fiber nonwoven fabrics are suitable because they can achieve both good texture and strength. The non-woven fabric can be used singly or in multiple layers. In the latter case, it is preferable to bond the nonwoven fabrics together with a hot-melt adhesive or the like. When non-woven fabric is used, its fiber basis weight is preferably 10 to 50 g/m ² , particularly 15 to 30 g/m ² .

(Getting up gathers)
On both sides of the top sheet 30 in the width direction WD, rise gathers 60 standing up toward the wearer's skin are provided in order to prevent excrement from moving laterally along the top sheet 30 and prevent so-called side leakage. preferably. Of course, the rising gathers 60 can be omitted.

When adopting the rising gathers 60, the structure is not particularly limited, and any known structure can be adopted. The illustrated rising gathers 60 are composed of a gathering sheet 62 substantially continuous in the width direction WD, and an elongated gathering elastic member 63 fixed to the gathering sheet 62 in a stretched state along the front-rear direction LD. ing. As the gather sheet 62, a water-repellent nonwoven fabric can be used, and as the gather elastic member 63, thread rubber or the like can be used. The elastic member may be provided in a plurality of pieces as shown in FIGS. 1 and 2, or may be provided in a single piece.

The inner surface of the gather sheet 62 has a joining start end in the width direction WD on the side of the top sheet 30, and the portion outside the joining start end in the width direction is the inner surface of each side flap portion SF, that is, the liquid impermeable in the illustrated example. The nonwoven fabric 12 is bonded to the side of the adhesive sheet 11 and to the side of the exterior nonwoven fabric 12 positioned on the outside in the width direction thereof with a hot-melt adhesive or the like.

Around the legs, the width direction inner side from the joining start end of the rising gathers 60 is fixed on the top sheet 30 at both ends in the front and back direction of the product, but the portion in between is a non-fixed free portion. It rises due to the contractile force of the elastic member 63 and comes to adhere to the surface of the body.

(end flap part, side flap part)
The illustrated tape-type disposable diaper has a pair of end flap portions EF without the absorbent body 56 extending to the front side and the rear side of the absorbent body 56 respectively, It has a pair of side flap portions SF which do not have the absorber 56 and which extend from each other. The side flap portions SF may be made of a material (exterior nonwoven fabric 12 or the like) that continues from the portion having the absorber 56 as shown in the drawing, or may be formed by attaching another material.

(flat gather)
A side elastic member 64 made of an elongated elastic member such as rubber thread is fixed to each side flap portion SF while being stretched along the front-rear direction LD. is constructed as a planar gather. As shown in the figure, the leg elastic members 64 are provided between the gathered sheet 62 and the liquid-impermeable sheet 11 on the outside in the width direction near the joining start end of the joined portion of the gathered sheet 62. It can also be provided between the liquid-impermeable sheet 11 and the exterior nonwoven fabric 12 in the SF. A plurality of leg-surrounding elastic members 64 may be provided on each side as in the illustrated example, or only one leg-surrounding elastic member 64 may be provided on each side.

The planar gathers are portions on which the contractile force of the side elastic members 64 acts (portions where the side elastic members 64 are illustrated in the drawing). Therefore, in addition to the form in which the side elastic members 64 are present only in the planar gathers, the side elastic members 64 are present on the front side, the rear side, or both sides of the planar gathers, but the side elastic members 64 are present in areas other than the planar gathers. If the member is finely cut at one point or multiple points, or is not fixed to the sheet sandwiching the side elastic member 64, or both, the contractile force will not act on the part other than the planar gather. Also included is a structure in which the contractile force of the side elastic members 64 acts only on the plane gathers instead (substantially equivalent to not providing an elastic member).

(connecting tape)
The side flap portions SF of the dorsal portion B are provided with connecting tapes 13 that are detachably connected to the outer surface of the ventral portion F, respectively. When wearing the disposable diaper 10, the connecting tape 13 is wrapped around the outer surface of the abdominal portion F from both sides of the waist, and the connecting portions 13A of the connecting tape 13 are connected to the outer surface of the abdominal portion F at appropriate locations.

Although the structure of the connecting tape 13 is not particularly limited, in the illustrated example, it has a base end portion 13C fixed to the side flap portion SF and an extension portion 13B extending outward in the width direction WD from the base end portion 13C. The extension part 13B has a sheet base material and a connection part 13A provided in the widthwise middle part of the sheet base material and connected to the ventral outer surface. ing.

As the connection portion 13A, a hook member (male member) of a mechanical fastener (surface fastener) may be provided, or an adhesive layer may be provided. The hook material has a large number of engaging projections on its connection surface, and the shapes of the engaging projections are (A) square-shaped, (B) J-shaped, (C) mushroom-shaped, and (D). Although there are a T shape, (E) a double J shape (a shape in which two J shapes are joined back to back), and the like, any shape may be used.

Nonwoven fabrics, plastic films, polylaminated nonwoven fabrics, paper, and composite materials thereof can be used as the sheet base material forming the base end portion 13C to the extension portion 13B. A spunbond nonwoven fabric, an air-through nonwoven fabric, or a spunlaced nonwoven fabric having a weight of 20 to 100 g/m ² and a thickness of 1 mm or less is preferred.

(target sheet)
It is preferable to provide a target portion at a connecting portion of the connecting tape 13 in the ventral portion F. As shown in FIG. The target portion can be provided by attaching a target sheet 20 to the outer surface of the ventral portion F for facilitating connection, as shown in the illustrated example. When the connecting portion 13A is a hook material, the target sheet 20 may be one in which a large number of loop threads are provided on the surface of a sheet base material made of a plastic film or a non-woven fabric so that the engaging protrusions of the hook material can be entangled. Further, in the case of the adhesive layer, a sheet substrate made of a plastic film having a smooth surface and having high adhesiveness and having a release treatment applied to the surface thereof can be used. In addition, when the connecting portion of the connecting tape 13 in the ventral portion F is made of nonwoven fabric, for example, when the outer nonwoven fabric 12 is provided as shown in the figure, the target sheet 20 is omitted and the hook material is used as the fiber of the outer nonwoven fabric 12. It can also be tangled and connected. In this case, a target sheet 20 as a mark may be provided between the outer nonwoven fabric 12 and the liquid-impermeable sheet 11, or a mark may be printed on the outer surface of the outer nonwoven fabric 12 or the liquid-impermeable sheet 11.

(Wing part)
This tape-type disposable diaper has a crotch portion M extending from the midpoint of the abdominal portion F in the front-rear direction LD to the midpoint of the back portion B in the front-rear direction LD, as shown in FIGS. In addition, the ventral portion F and the dorsal portion B have wing portions WP that extend outward from the crotch portion M in the width direction WD. The lower edges 70 of the wing portions of the abdominal portion F extend forward from the front ends of the side edges of the crotch portion M so as to be positioned obliquely outward, and the lower edges 75 of the wing portions of the dorsal portion B It extends from the rear end of the side edge of the crotch portion M so as to be positioned obliquely outward toward the rear. Although the side edge of the wing portion WP is linear in the illustrated example, the shape is not limited to this, and other known shapes can be adopted. The dimension of the crotch portion M in the front-rear direction LD can be determined as appropriate, but it can be about 1.2 to 1.4 times the minimum width M _X of the crotch portion M. In the case of use for infants, the dimension M _Y in the front-rear direction LD of the crotch portion M is about 10 to 30 cm.

(Water-soluble acid and hydrophilic agent)
The topsheet 30 of the absorbent article contains a water-soluble acid. Preferably, the top sheet 30 further contains a hydrophilic agent. Moreover, it is preferable that not only the top sheet 30 but also one of the intermediate sheet 40 and the packaging sheet 58 or both the intermediate sheet 40 and the packaging sheet 58 contain a water-soluble acid. Also in this case, it is preferable to include a hydrophilic agent together with the water-soluble acid. In the following description, the water-soluble acid (and hydrophilic agent) contained in the top sheet 30 will be described, but the same applies to the intermediate sheet 40 and the packaging sheet 58 unless otherwise specified.

As the water-soluble acid, it can be used without any particular limitation, but those with a pH of 2 to 4 are suitable. If the pH value is less than 2, there is a disadvantage that when the acid adheres to the wearer's skin, the wearer's skin is burdened. On the other hand, if the pH value is greater than 4, there is a disadvantage that it is difficult to effectively suppress the inclination of the excrement to the alkaline side. Specific examples of water-soluble acids include citric acid, tartaric acid, malic acid, and lactic acid, and citric acid and lactic acid, which are used as food additives and are highly safe, are particularly preferred. The water-soluble acid is preferably applied to the fibers constituting the top sheet 30 to fix the acid components so that the acid component does not easily flow down to the absorbent body even when urination is repeated. Alternatively, it may be secured to the topsheet 30 by other methods such as in-line spray application during diaper manufacture. In general, the water-soluble acid is fixed in the interstices between the fibers forming the nonwoven fabric without chemical bonding. Therefore, when urinating, the urine will flow down from the nonwoven fabric together with the urine. Therefore, it is preferable to apply a water-soluble acid together with a hydrophilic agent to the non-woven fabric fibers so that even when urination is repeated, it will not run off.

Hydrophilic agents used for the above applications can be used without any particular limitation, and typical examples include various surfactants (anionic, cationic, amphoteric and nonionic). Specifically, for example, polyglycerin fatty acid ester, polyether-polyester block copolymer, polyether-modified silicone, fatty acid ester of ethylene oxide-added polyhydric alcohol, and the like can be used. In order to prevent acid from flowing down to the absorbent body 56 side when urinating repeatedly, the hydrophilizing agent is preferably applied to the fibers constituting the top sheet 30 for fixation. It may be secured to the topsheet 30 by other methods such as in-line spray application during diaper manufacture.

The top sheet 30 manufactured as described above is in a state in which water-soluble acid adheres to the outer surfaces of the fibers constituting the top sheet 30 . At the same time, the gaps between the plurality of fibers forming the top sheet 30 may be filled with a water-soluble acid. Furthermore, it is preferable to allow the water-soluble acid to permeate the interior of the fibers that constitute the top sheet 30, because the water-soluble acid is less likely to run off even after repeated excretion.

The following artificial urine drip test was performed on the top sheet 30 containing a water-soluble acid and a hydrophilic agent, and the first measurement result was 10 points, the second measurement result was 10 points, and the third It is preferable to mount the top sheet 30 having a measurement result of 9 points or more on the absorbent article.
(Dropping test method for artificial urine)
(1) A top sheet 30 containing a hydrophilic agent is placed on ten sheets of filter paper, and a metal jig 70 having ten holes is placed on the top sheet 30 . In addition, since this test is to confirm whether or not the hydrophilic agent contained in the top sheet 30 is difficult to run off when repeatedly excreted, the top sheet 30 used in this test was need not be included.
(2) (First measurement)
Using a micropipette, 1 mL of artificial urine (to which the colorant described below is added) is dropped into each hole (ie, a total of 10 mL of artificial urine is dropped into 10 holes). After dripping the artificial urine, confirm whether the nonwoven fabric has absorbed the artificial urine within 2 seconds. When the artificial urine remains on the nonwoven fabric (usually when the artificial urine is spherically placed on the nonwoven fabric), it is recorded that the nonwoven fabric does not absorb the artificial urine. On the other hand, when no artificial urine remains on the nonwoven fabric, it is recorded that the nonwoven fabric has absorbed the artificial urine. Do this recording operation for each of the 10 holes. That is, the number of places out of 10 that passed through the nonwoven fabric within 2 seconds is recorded. An absorbed hole is counted as 1 point, and an unabsorbed hole is counted as 0 point, and the total score of 10 holes is recorded.
(3) (Second measurement)
After dropping the artificial urine (with the following colorant added) in (2), wait for 3 minutes to pass, and after 3 minutes, again using a micropipette, each hole Instill 1 mL of artificial urine. Then, the total score is recorded in the same manner as in (2) above.
(4) (Third measurement)
After dropping the artificial urine (with the following coloring agent added) in (3) above, wait for 6 minutes, and after 6 minutes, use a glass pipette to add 500 μL per hole. Dripping artificial urine. Then, the total score is recorded in the same manner as in (2) above.
(5) In the recording results of (2) to (4) above, the first measurement result is 10 points, the second measurement result is 10 points, and the third measurement result is 9 points or more. It is preferable to mount the top sheet 30 on the absorbent article. This is because it can be determined that the hydrophilizing agent is less likely to run off even when urination is performed multiple times.
(filter paper)
As the filter paper used in the test, for example, FILTER PAPER 250 mm×250 mm square manufactured by ADVENTEC can be used.
(metal jig)
As the metal jig 70, the following is used.
It is rectangular with a width of 210 mm, a length of 50 mm, and a thickness of 5 mm, and ten holes 71 with a diameter of 15 mm are provided at regular intervals of 4 mm in the width and length directions. Weight is 400g.
(artificial urine)
As the artificial urine used in the test, the following are used.
A mixture of urea: 2 wt%, sodium chloride: 0.8 wt%, calcium chloride dihydrate: 0.03 wt%, magnesium sulfate heptahydrate: 0.08 wt%, and deionized water: 97.09 wt% (coloring agent)
Approximately 5 g of Brilliant Blue FCF (packaging: powder) manufactured by Kiriya is dissolved in approximately 300 ml of artificial urine.
(pipette)
Biohit Proline Pipette 100 to 1000 μl (model number: 720050), for example, can be used as a micropipette used in the artificial urine drop test. As the glass pipette used for the artificial urine dropping test, Maruem KOMA5 5 ml (model number: 0801-04), for example, can be used.

The hydrophilic agent adheres to the outer surface of the fibers forming the top sheet 30 together with the water-soluble acid. The gaps between the plurality of fibers forming the top sheet 30 may be filled with a hydrophilizing agent together with a water-soluble acid. In addition, when the water-soluble acid and the hydrophilic agent are impregnated inside the fibers constituting the top sheet 30, the water-soluble acid and the hydrophilic agent are less likely to run off even after repeated excretion. It is highly effective in continuously suppressing the inclination to the alkaline side.

When the wearer of the absorbent article excretes, the excrement comes into contact with the water-soluble acid contained in the top sheet 30 to prevent the excrement from tilting toward the alkaline side. For example, when the wearer urinates, the urea in the urine remaining on the top sheet 30 is hydrolyzed by urease over time to produce ammonia, but the water-soluble acid contained in the top sheet 30 reacts with this ammonia to prevent the pH of excreta from declining to the alkaline side. Specifically, the water-soluble acid suppresses the production of ammonia and neutralizes the produced ammonia. In this way, the water-soluble acid prevents the excrement from tilting to the alkaline side, so even if the excrement returns and continues to touch the wearer's skin, the burden on the skin is reduced.

If the water-soluble acid contained in the top sheet 30 runs down to the absorbent body 56 due to excretion, it is possible to effectively prevent the inclination of the excrement to the alkaline side during the second and subsequent excretion. Can not. In particular, disposable diapers that are worn at bedtime are expected to be excreted a number of times, so there is a strong need to prevent such problems from occurring. Therefore, the top sheet 30 according to the present invention contains a hydrophilic agent. This hydrophilic agent firmly fixes the water-soluble acid to the fibers that make up the top sheet 30, making it difficult for the water-soluble acid to run off even after repeated excretion, thereby keeping the excrement from tilting toward the alkaline side. can be deterred.

The content of the water-soluble acid in the top sheet 30 is preferably 0.02% to 0.07%, more preferably 0.03% to 0.05%. If the blending amount is more than 0.07%, there is a disadvantage that when the acid adheres to the wearer's skin, the wearer's skin is burdened. On the other hand, when the blending amount is less than 0.02%, there is a disadvantage that it is difficult to effectively suppress the inclination of excrement to the alkaline side. The amount of the hydrophilic agent to be added to the top sheet 30 is preferably 0.3% to 0.5%, more preferably 0.4% to 0.5%. If the blending amount is more than 0.5%, there is a disadvantage that the cost of the drug is high, the product cost is high, and the reversal is likely to occur when the wearer presses after urinating. On the other hand, if the blending amount is less than 0.3%, the bond between the water-soluble acid and the fibers constituting the top sheet 30 is weakened, and the water-soluble acid tends to run off after multiple excretion. , there is a risk that urine will not permeate the nonwoven fabric and lead to leakage. The mixing ratio of the water-soluble acid and the hydrophilic agent is preferably 1:7 to 1:20, more preferably 1:15. If this range is exceeded, there is a disadvantage that the hydrophilicity of the nonwoven fabric is affected.

When the top sheet 30 contains a water-soluble acid, it is highly effective in reducing the burden on the wearer's skin. Since the top sheet 30 is in direct contact with the wearer's skin (for example, the skin of the buttocks), if the excrement adhered to the top sheet 30 due to excretion leans toward the alkaline side, the skin and the excrement will continue to adhere to each other. The contact puts a strain on the skin. Therefore, by including a water-soluble acid in the top sheet 30, it is possible to suppress the inclination to the alkaline side and reduce the burden on the wearer's skin.

When the top sheet 30 contains a water-soluble acid, the acid contained in the top sheet 30 may burden the wearer's skin. It is possible to reduce the burden of acid on the skin by using a near-neutral acid or reducing the amount of acid added, but in this case, it is not possible to effectively suppress the inclination of excrement to the alkaline side. There is a drawback. Therefore, in order to solve such a problem, the top sheet 30 has a multi-layered structure, and the layer located on the skin side does not contain water-soluble acid (or, if it contains a small amount, it does). , the layer located on the back side preferably contains a water-soluble acid and a hydrophilic agent. For example, the top sheet 30 may have a two-layer structure in which the skin-side layer (upper layer) does not contain a water-soluble acid, and the back layer (lower layer) contains a water-soluble acid and a hydrophilic agent. When the top sheet 30 has a structure of three or more layers, the layer closest to the skin (top layer) does not contain a water-soluble acid, and any layer located on the back side of the top layer or All layers should contain a water-soluble acid and a hydrophilic agent. FIG. 3 exemplifies the top sheet 30 having a two-layer structure. The layer on the skin side (upper layer) is indicated by 30U, and the layer on the back side (lower layer) is indicated by 30D. The upper layer 30U does not contain a water-soluble acid and a hydrophilic agent, and the lower layer 30D contains a water-soluble acid and a hydrophilic agent. As described above, the upper layer 30U should not contain a water-soluble acid, but the hydrophilic agent may be contained in the upper layer 30U because it does not burden the skin. If the manufacturing process is simplified by including the hydrophilic agent in both the upper layer 30U and the lower layer 30D, it is preferable to include the hydrophilic agent in the upper layer 30U as well.

(delete)

However, when emphasis is placed on preventing alkalization of the portion of the top sheet 30 that comes into contact with the skin and reducing the burden on the skin due to ammonia, the layer positioned on the skin side of the top sheet 30 contains a water-soluble acid. It is also effective to intentionally include

In addition, the top sheet 30 having a special structure like the present invention, that is, the top sheet 30 in which the upper layer 30U does not contain a water-soluble acid and the lower layer 30D contains a water-soluble acid, for example, It can be produced by the method of (1) or (2).
(1) For example, first, raw cotton (raw material fibers; the same shall apply hereinafter), which is the raw material of the layer located on the skin side, is manufactured through the steps of raw material input, heating, melting, and extrusion. In addition, through the process of adding raw materials, heating, melting, extruding, cooling, and then applying acid, raw cotton that will be the raw material of the layer located on the back side is manufactured.
Then, a plurality of lines of a nonwoven fabric manufacturing apparatus (for example, when manufacturing a top sheet with a two-layer structure, there are two lines, a line for manufacturing a layer on the skin side and a line for manufacturing a layer on the back side). Raw cotton, which is the raw material for the layer located on the side, and raw cotton, which is the raw material for the layer located on the back side, are supplied separately. After that, each line separately performs primary defibration, weighing and blending, secondary defibration, tuft formation (the secondary defibrated raw cotton is evenly stored in a box), and web forming (using a card machine). , forming the raw cotton stored in the box into a sheet). Then, each sheet manufactured by web forming is superimposed to form a plurality of layers, and after being bonded by thermal fusion, the product is manufactured through processes such as inspection for inclusion of foreign matter and winding.
Although the above description exemplifies a method of manufacturing a multi-layered nonwoven fabric using the air-through manufacturing method, it can be manufactured in the same manner using other manufacturing methods in which the method of fusing the nonwoven fabric is different. Other manufacturing methods include the spunlace method, spunbond method, thermal bond method, meltblown method, needle punch method, point bond method, and the like.
In the above description, a hydrophilizing agent may be applied together with the acid when manufacturing the raw cotton that will be the raw material of the layer located on the back side. At the same time, the hydrophilizing agent may be applied at the timing after the cooling when manufacturing the raw cotton which is the raw material of the layer positioned on the skin side.
(2) For example, in the process of manufacturing a diaper using a diaper processing machine, only the lower layer side of the top sheet 30 before being attached to the main body of the diaper is provided with an acidic component by spray coating.

The intermediate sheet 40 can also contain a water-soluble acid. Since the intermediate sheet 40 does not come into direct contact with the wearer's skin, the intermediate sheet 40 containing a water-soluble acid can prevent the wearer's skin from being burdened by the acid. In addition, since the intermediate sheet 40 is generally bulky, when the excrement reaches the absorbent body 56, the amount of excrement remaining inside the intermediate sheet 40 may increase the amount of excrement remaining inside the top sheet 30 and the packaging sheet 58. This tends to be greater than the amount of excrement remaining in the body. Therefore, by impregnating the intermediate sheet 40 with a water-soluble acid to suppress the alkalinization of the excrement remaining on the intermediate sheet 40, the burden on the skin when the excrement remaining on the intermediate sheet 40 is reversed is reduced. can be mitigated.

The packaging sheet 58 can also contain a water-soluble acid. Since the packaging sheet 58 does not come into direct contact with the wearer's skin, the inclusion of water-soluble acid in the packaging sheet 58 can prevent the wearer's skin from being burdened by the acid. In addition, since the packaging sheet 58 wraps the absorbent body 56, there are many opportunities for contact with the absorbent body 56 holding the excrement. Therefore, the excrement retained by the absorber 56 can be acted on for a longer period of time by the acid contained in the packaging sheet 58, so that the excrement retained by the absorber 56 is effectively tilted toward the alkaline side. can be effectively deterred. In addition, the packaging sheet 58 may contain a water-soluble acid in the entire packaging sheet 58, but considering the purpose of reducing the burden on the wearer's skin, at least the absorbent body 56 in the packaging sheet 58 A water-soluble acid is preferably contained in the portion closer to the skin. Similarly, it is preferable to provide the hydrophilic agent in a portion closer to the skin than the absorber 56 .

It is important to include a water-soluble acid in the top sheet 30, which has a high impact on the wearer's skin. That is, since the top sheet 30 is in direct contact with the skin, it is effective to suppress the alkalinization of excrement adhering to the top sheet 30. From this point of view, at least the top sheet 30 contains a water-soluble acid. It is important to let However, in addition to this, any one sheet selected from the group of the intermediate sheet 40 and the packaging sheet 58 may contain a water-soluble acid, or all the sheets of these groups may contain a water-soluble acid. You may make it contain an acid. From the viewpoint of manufacturing cost, it is preferable to contain the water-soluble acid only in the top sheet 30, and it is easy to manufacture by containing the water-soluble acid especially in the intermediate sheet 40 as a sheet other than the top sheet 30. Therefore, it is advantageous in terms of cost. On the other hand, from the viewpoint of suppressing alkalinization, it is preferable that more sheets contain a water-soluble acid.

(Range to which acid is added)
In the top sheet 30, the intermediate sheet 40 and the packaging sheet 58, it is preferable that the plane area in which the water-soluble acid is contained is the area where excrement is expected to spread. When the absorbent article is the illustrated disposable diaper, it is preferable to apply acid to at least the crotch region M, considering the position of the wearer's excretory opening (urination opening, anus, etc.). When the amount of excrement is large or when excretion is performed multiple times, it is expected that the excrement will spread over a wide area. The intermediate sheet 40 and the packaging sheet 58 are preferably acid-applied to the same positions as the top sheet 30 . The hydrophilic agent is also preferably added to the same range as the acid.

(Experimental example)
The following two experimental materials were prepared.
(1) Material 1: An air-through nonwoven fabric (diaper top sheet) with a basis weight of 20 gsm, a two-layer structure with a skin surface of 2.0 dtex and a back surface of 3.3 dtex. Composite fibers of polyethylene and polyethylene terephthalate were used as the material of the nonwoven fabric. This air-through nonwoven fabric contains a nonionic surfactant as a hydrophilic agent. The content of hydrophilic agent is 0.4% based on the weight of the nonwoven fabric.
(2) Material 2: An air-through nonwoven fabric (diaper top sheet) with a basis weight of 20 gsm and a one-layer structure of 2.2 dtex. Composite fibers of polyethylene and polyethylene terephthalate were used as the material of the nonwoven fabric. This air-through nonwoven fabric contains a nonionic surfactant as a hydrophilic agent and citric acid as a water-soluble acid. The content of the hydrophilic agent is 0.4% and the content of the water-soluble acid is 0.05% based on the weight of the nonwoven fabric.

The experiment was conducted in a laboratory at 22.1° C. First, 10 sheets of filter paper (FILTER PAPER 250 mm×250 mm square, manufactured by ADVENTEC) were piled up, and the material 1 was placed on each of them. Then, a circle with a diameter of 20 mm was drawn on the material 1 with a marker, and the inside of the circle was used as a measurement point. More specifically, six circles were drawn on the material 1, and the inside of each circle was designated as measurement points A to F.

Next, material 2 was placed on 10 sheets of filter paper similar to the above. Then, a circle with a diameter of 20 mm was drawn on the material 2 with a marker, and the inside of the circle was used as the measurement point. More specifically, six circles were drawn on the material 2, and the inside of each circle was designated as measurement points G to L.

Next, 100 μL of artificial urine was dripped onto each of measurement points A to C of Material 1. The components of the artificial urine are urea: 2 wt%, sodium chloride: 0.8 wt%, calcium chloride dihydrate: 0.03 wt%, magnesium sulfate heptahydrate: 0.08 wt%, and deionized water. : 97.09 wt%. After 1 minute, the surface pH of the measurement points A to C of the material 1 was measured with a contact-type pH meter (manufactured by HORIBA, model #6261-10C) (first measurement).

After that, 100 μL of artificial urine was dropped on each of the measurement points A to C of the material 1, and after 1 minute, the pH of the surface of the measurement points A to C of the material 1 was measured using the contact-type pH meter. (second measurement). Furthermore, 100 μL of artificial urine was dropped on each of the measurement points A to C of the material 1, and after 1 minute, the pH of the surface of the measurement points A to C of the material 1 was measured using the contact-type pH meter. (Third measurement).

Next, the measurement points D to F of the material 1 were also measured under the same conditions as the first to third measurements. For measurement points D to F, the amount of artificial urine dripped each time was set to 500 μL instead of 100 μL.

Next, the measurement points G to I of the material 2 were also measured under the same conditions as the first to third measurements. For measurement points G to I, the amount of artificial urine dripped was set to 100 μL each time.

Furthermore, the measurement points J to L of the material 2 were also measured under the same conditions as the first to third measurements. For the measurement points J to L, the artificial urine was dripped in an amount of 500 μL each time.

The test results are shown in Table 1, FIG. 6 and FIG. 7 below.

(Discussion)
It was found that the pH values tended to be lower at measurement points G to L containing citric acid than at measurement points A to F not containing citric acid. In addition, it was found that at the measurement points G to L where the hydrophilizing agent was blended with citric acid, alkalinization hardly progressed even when artificial urine was dripped three times. This is probably because the citric acid is strongly retained in the fibers of the air-through nonwoven fabric by the hydrophilic agent and does not run off even after multiple times of urination.

(Effect of the present invention compared with the prior art)
According to the absorbent article of the present invention, acid tends to remain in the top sheet 30 even when the wearer excretes a number of times, so that the effect of suppressing alkalinization due to acid can be maintained. In addition, the water-soluble acid contained in the top sheet 30 should not continue to touch the wearer's skin in a state where the wearer of the absorbent article has not excreted even once (for example, the top sheet 30 may By blending an acid in the lower layer, the burden on the skin can be reduced. Further, by making at least one of the neutralizing sheet 40 and the packaging sheet 58 thick, excretions and acid are reversed and come into contact with the wearer's skin even at the site where body pressure is applied. can be less likely.

Since it is not necessary to provide the top sheet 30 with convex portions as in the above-mentioned Patent Document 1, the degree of freedom in designing the absorbent article is high. In addition, as in Patent Document 1, the part where the acid is added is not particularly limited, so production is easy. In addition, since a water-soluble acid is used instead of fumaric acid, which is difficult to dissolve in water, as in Patent Document 2, it is easy to apply it to the sheet together with the hydrophilic agent, and it is easy to manufacture. In addition, there is an advantage in that malic acid, which is more irritating to the skin than citric acid, is not used as in Patent Document 3 above.

(others)
Excrement inside the absorbent body 56 may also return. Considering this point, it is also effective to prevent alkalinization of excrement present inside the absorbent body 56 . Therefore, it is effective to reduce the burden on the skin by including a water-soluble acid in the absorber 56 itself (for example, SAP of the absorber).

(acid)
In the above description, the water-soluble acid is used as an example, but the acid contained in the top sheet 30 is not limited to the water-soluble acid. That is, the top sheet 30 may contain a sparingly soluble acid such as fumaric acid if affinity with the hydrophilic agent is not taken into consideration.

(Excretion)
Examples of excreta in the present invention include urine, defecation (particularly loose stool), menstrual blood, and the like. In particular, among excretions, it is effective in suppressing the alkalinization of excretions other than solid stool. In urine, the water-soluble acid inhibits degradative enzymes such as urease from hydrolyzing urea contained in urine into ammonia to alkalinize excreta. In loose stools, hydrolyzing enzymes such as urease hydrolyze urea contained in loose stools into ammonia to alkalinize excrement, which is inhibited by water-soluble acids.

<Description of terms in the specification>
The following terms in the specification have the following meanings unless otherwise specified in the specification.
・"Front-back direction" means the direction (longitudinal direction) indicated by symbol LD in the figure, and "width direction" means the direction (left-right direction) indicated by WD in the figure. are orthogonal.

- "Curve" means not including a straight line.

- "Unfolded state" means a flat unfolded state without contraction or slack.

- "Elongation rate" means a value when the natural length is taken as 100%. For example, an elongation rate of 200% is synonymous with an elongation ratio of 2 times.

- "Matsuke" is measured as follows. After pre-drying the sample or test piece, it is left in a test room or apparatus under standard conditions (test location: temperature 23±1° C., relative humidity 50±2%) to a constant weight. Pre-drying refers to making a sample or test piece constant weight in an environment at a temperature of 100°C. Fibers with an official moisture content of 0.0% do not need to be pre-dried. Using a sampling template (100 mm x 100 mm), a sample with dimensions of 100 mm x 100 mm is cut from the constant weight specimen. The weight of the sample is measured, multiplied by 100 to calculate the weight per square meter, and used as basis weight.

- "Thickness" is automatically measured using an automatic thickness gauge (KES-G5 handy compression tester) under the conditions of a load of 0.098 N/cm ² and a pressurized area of 2 cm ² .

・The “water absorption” is measured according to JIS K7223-1996 “Testing method for water absorption of super absorbent polymer”.

・"Water absorption rate" is "Time to end point" when JIS K7224-1996 "Test method for water absorption rate of superabsorbent polymer" is performed using 2g of superabsorbent polymer and 50g of physiological saline. and

・If there is no description about the environmental conditions for testing and measurement, the test and measurement shall be performed in a test room or equipment under standard conditions (test location: temperature 23±1°C, relative humidity 50±2%).

・Unless otherwise specified, the dimensions of each part mean the dimensions in the unfolded state, not in the natural length state.

The present invention can be applied to tape-type disposable diapers, as well as absorbent articles such as tape-type disposable diapers, pad-type disposable diapers, and napkins. In particular, application to each disposable diaper is suitable.

DESCRIPTION OF SYMBOLS 11... liquid impermeable sheet, 12... exterior nonwoven fabric, 13... connection tape, 13A... connection part, 13B... extension part, 13C... base end part, 20... target sheet, 30... top sheet, 40... intermediate sheet, 50... Absorption element, 56... Absorbent body, 58... Wrapping sheet, 60... Standing gather, 62... Gather sheet, 64... Side elastic member, 70... Metal jig, 71... Hole, B... Back part, F …abdominal portion, LD…front-back direction, M…crotch portion, SF…side flap portion, WD…width direction, WP…wing portion

Claims (6)

With the top sheet provided on the skin side ,
an absorbent provided on the back side of the top sheet ;
An absorbent article comprising an intermediate sheet provided between the top sheet and the absorbent body for preventing backflow of excreted liquid from the absorbent body ,
The topsheet is composed of a plurality of layers,
An absorbent article, wherein, of the plurality of layers, the layer located on the skin side does not contain acid, and the layer located on the back side contains acid. 2. The absorbent article according to claim 1, wherein, of the plurality of layers of said top sheet, the layer located on the skin side does not contain a hydrophilic agent, and the layer located on the back side contains a hydrophilic agent. 3. The absorbent article according to claim 2 , wherein the acid contained together with the hydrophilic agent in the layer positioned on the back side of the topsheet is lactic acid. The top sheet is a nonwoven fabric,
3. The absorbent article according to claim 2, wherein, in the layer positioned on the back side of said top sheet, said water-soluble acid and hydrophilic agent are applied to the raw fibers of said nonwoven fabric. 2. The absorbent article according to claim 1, wherein among the plurality of layers of the top sheet, the fiber diameter of the acid-free layer located on the skin side is smaller than the fiber diameter of the acid-containing layer located on the back side. 6. The method according to claim 5, wherein among the plurality of layers of the top sheet, the fiber diameter of the layer that is located on the skin side and does not contain an acid and a hydrophilic agent is smaller than the fiber diameter of the layer that is located on the back side and contains an acid and a hydrophilic agent. The absorbent article described.

Images