JPH0614947B2 - Absorbent article - Google Patents

Description

TECHNICAL FIELD The present invention relates to absorbent articles such as sanitary napkins and disposable diapers. More specifically, the present invention relates to an absorbent article that uses, as a leak-proof layer, a sheet-like material that is impermeable to human body secretions and vapor-permeable, and that also has an appropriate waist.

[Conventional technology and problems]

Conventionally, absorbent articles such as sanitary napkins and disposable diapers basically have an absorbent layer 6 and a leakproof layer 7 as shown in FIG.
Is covered with the surface material 8, and the leak-proof layer is required to prevent leakage of human secretions such as menstrual blood, urine, and feces as its function. . Therefore, conventionally, a so-called poly-laminate waterproof paper in which a resin such as polyethylene is laminated on a base such as paper or a non-woven fabric, or simply a thin film of resin such as polyethylene has been used as the leak-proof layer.

However, since the leakproof layer does not have vapor permeability, once the human body secretory liquid is absorbed in the absorbent article, it may increase until it is replaced, but there is no decrease due to transpiration.

This means that if human body secretions evaporate, they will evaporate only from the point of use of the absorbent article (actually, it is quite difficult), and thus the user often feels "unevenness" or discomfort. Further, the rash during use may cause diseases such as "rash" and "inflammation".

This is an essential problem in that a polymer absorbent is used as a material for an absorbent layer of an absorbent article in recent years, and even if the absorbent performance is improved and improved, the occurrence cannot be prevented.

On the other hand, as a measure for preventing such "smoothing", it has recently been proposed to use a porous film or the like, which has been subjected to a stretching treatment after blending a filler and a liquid rubber with a polyolefin resin, as a leak-proof layer.

However, these porous films have the following drawbacks.

High precision control is required in the manufacturing process.

Since it is a stretched film, it has a large strength-to-width ratio and is easy to tear.

The film itself is thin and stiff. Therefore, an absorbent article using this as a leak-proof layer (especially in the case of a sanitary napkin) has a narrow central portion at the crotch portion when worn. That is, there is a tendency for the liquid to leak, and the human body secretory liquid tends to leak laterally.

[Means for solving problems]

The present inventors eliminate the drawbacks of these conventional absorbent articles,
Further, as a result of earnest research to provide a useful absorbent article to the user, as a leak-proof layer, a sheet-like material impermeable to human secretions and having vapor permeability is used. The inventors have found that the above-mentioned problems can be solved by using a sheet-like material obtained by subjecting the foamed sheet-like material that has been subjected to a compression treatment or a needle punching treatment, as a leak-proof layer, and arrived at the present invention.

That is, the present invention is an absorbent article having an absorbent layer and a leakproof layer located below the absorbent layer, wherein the leakproof layer is made of a foam having a closed cell structure, and at least one of the closed cells adjacent to the foam is The present invention relates to an absorbent article in which the upper surface and the lower surface of the foam body communicate with each other by communicating the parts.

Hereinafter, the present invention will be described in detail.

The leak-proof layer of the present invention is obtained by subjecting a foam 1 having closed cells 3 such as polyethylene foam or polybutadiene foam as shown in FIG. 1 to compression treatment or needle punching treatment. As shown in FIG. 3, FIG. 4 and FIG. 5, at least a part of the closed cells 3 are ruptured and at least a part of the adjacent closed cells are made to communicate with each other by the fine holes, and as a result, the foam is finely divided from the upper surface to the lower surface. The holes are communicated. As a method of communicating adjacent independent bubbles with each other through fine holes, any method may be used as long as this object is achieved, but if productivity or accuracy control is taken into consideration, a pressure roll is used. An example of the compression processing method can be used.

Taking the case of performing compression processing using a pressure roll as an example, since the surface skin layer 2 is generally formed on the foam 1 having a closed cell structure as shown in FIG. 1, the compression processing is performed by a smooth surface roll. If so, the bubbles inside the foam will burst, and even if they communicate with each other, since the surface skin layer has a thickness, they do not burst, and communication is blocked at that portion. Therefore, when the compression treatment is performed using a roll, it is important in the present method that the compression treatment is performed using an embossing roll having irregularities on the roll surface, rather than simply using a smooth roll. In order to further improve the effect, it is desirable that the convex portion of the embossing has a relatively sharp blade. In this way, the surface skin layer 2 is opened, and further the closed cells 3 are ruptured to obtain a foamed sheet having complicated communicating holes as shown in FIG.

As a method slightly different from the above method, it is conceivable to slice the surface skin layer 2 of the foam 1 having the surface skin layer 2 as shown in FIG. 1 and use it as shown in FIG. In this case, even if it is not an embossing roll, the object of the present invention can be achieved by simply compressing with a smooth roll.

The material used for the leak-proof layer of the present invention is basically not particularly limited as long as it is a foam having a closed cell structure,
For example, it is possible to use polyethylene foam, polypropylene foam, polystyrene foam, polyurethane foam, polybutadiene foam, silicone rubber foam, or a resin blend containing these as one component, but it is flexible and easy to rupture closed cells. Considering size and the like, polyethylene foam and polybutadiene foam are preferable.

The thickness of the foam is preferably 0.5 to 5 mm, more preferably 1 to 2 mm, from the viewpoint of its performance of human body liquid impermeable vapor permeability, and twisting during use.

The expansion ratio depends on the foam material, but
It is preferably -50 times, more preferably 15-35 times.

An important factor that affects the vapor permeability is the porosity of the surface skin layer of the foam, and the higher the porosity, the more preferable the tendency. The porosity of the surface skin layer is determined by the occupied area (number of pins) of the convex portion of the embossing roll when compression treatment is performed with a pressure roll.

〔Example〕

 Next, the present invention will be described in more detail with reference to Examples.

Example 1 Polyethylene foam (thickness: 2 mm, foaming ratio: 25 times) was used as a foam having a closed cell structure, and the surface skin layer was compression-treated with an embossing roll having a porosity of 10% (pressure 5 kg / cm ² ), and a test piece as shown in FIG. 2 was obtained. At this time, the sound of the closed bubbles exploding due to pressure was heard,
This proves that the bubbles are communicating with each other.

Example 2 Next, the same material as in Example 1 was used to perform compression treatment (pressure 5 kg / cm ² ) with an embossing roll such that the porosity of the surface skin layer was 50% to obtain a test piece.

Example 3 A polyethylene film (thickness: 1 mm, expansion ratio: 25 times) was used as a foam having a closed cell structure, and compression treatment was performed with an embossing roll such that the porosity of the surface skin layer was 50% (pressure 5 kg / cm ² ), a test piece was obtained.

Example 4 1,2-polybutadiene foam (thickness: 2 mm, foaming ratio: 15 times) was used as a foam having a closed cell structure, and compression treatment was performed with an embossing roll such that the surface skin layer had a porosity of 50%. (Pressure 15 kg / cm ² ) A test piece was obtained.

Example 5 1,2-polybutadiene foam (thickness 1 mm, foaming ratio 15 times) was used as a foam having a closed cell structure, and compression treatment was performed with an embossing roll such that the surface skin layer had a porosity of 50%. (Pressure 15 kg / cm ² ) A test piece was obtained.

Example 6 Polyethylene foam (thickness 10 mm, foaming ratio 30 times) was used as a foam having a closed cell structure, and a surface skin layer was sliced to prepare a 2 mm thick closed cell sheet having no skin layer. . This sample was compressed with a smooth roll (pressure 5 kg / cm ² ) to obtain a test piece as shown in FIG.

Example 7 As a foam having a closed cell structure, 1,2-polybutadiene foam (thickness: 2 mm, foaming ratio: 20 times) was used, and as shown in FIG. Needle-punching with a needle 4 so that the porosity of the surface skin layer 2 is 30% on one side (needle diameter 0.3 m
m), a test piece was obtained.

At this time, care was taken so that the needle 4 did not penetrate to one surface.

Example 8 The same material as in Example 7 was used, and as shown in FIG. 5, needles were arranged so that the porosity of the surface skin layer 2 was 30% from one side in the direction perpendicular to the sample as indicated by arrow 5. 4 was needle-punched (needle diameter: 0.3 mm) to obtain a test piece.

At this time, the needle 4 penetrated the foam.

The test pieces obtained in Examples 1 to 8 and the untreated polyethylene foam of Example 3 as a comparative product (Comparative Example 1),
The performance of the untreated polybutadiene foam of Example 5 (Comparative Example 2) and the conventional polyethylene laminated paper (Comparative Example 3) were evaluated. The results are shown in Table-1. still,
The characteristics were evaluated by the following methods.

Vapor transmission rate: JIS Z 0208 was applied mutatis mutandis, and the transmission rate in the initial 1 hour was measured.

Leakage prevention effect 8 pieces of absorbent paper of approximately the same size and basis weight of 30 g / m ² were placed on a test piece of 200 mm in length and 100 mm in width, and 10 g of defibrinated horse blood was dropped and absorbed as a test solution from above. Then, apply a load from above. It was measured leak, a load of up to bleeding is observed from the test piece back surface when changing to ^{5g / cm 2 ~150g / cm 2} . The measurement was performed for 3 minutes under one condition, and the load was increased one after another only when there was no leakage or bleeding.

[Effects of the Invention] As is clear from the results of Table 1, the untreated foamed sheets of Comparative Examples 1 and 2 are natural because they have a closed cell structure, but the leakage preventing effect is sufficiently recognized. There is no vapor transmission rate.

Similarly, the polyethylene laminate paper and the polyethylene film which are commonly used in Comparative Example 3 have a sufficient leakproof effect as well, but have almost no vapor permeation amount, which is a cause of the above-mentioned "smoothness" and "rash". The cause is clear.

As described above, no conventional leak preventive layer simultaneously satisfies these two requirements.

On the other hand, the product of the present invention is a method of compressing a foam having a closed cell structure with a pressure roll as in Examples 1 to 6,
Alternatively, a simple method such as the method of performing needle punching as in Examples 7 and 8 causes the closed cells to rupture and at least a part of the adjacent closed cells communicate with each other through the fine holes. As described above, the vapor permeability is exhibited, and the leakproof effect can be further exhibited.

As a standard of vapor permeability, at least by this test method
If it has a vapor permeation rate of 0.5 g / 100 cm ² · 1 Hr or more, an effect against stuffiness and rash can be recognized when actually used for sanitary napkins.

In addition, as a standard of the leakproof effect, when a sanitary napkin is used, a pressure of around 50 g / cm ² is applied, so that the leakproof effect is sufficient if no leakage is observed under a load of 110 g / cm ² .

Therefore, it can be said that Examples 1 to 8 of the product of the present invention simultaneously satisfy the vapor permeability, the leakproof effect, and these two required characteristics.

Although the foams of Examples 2, 3 and 4 have different thicknesses, a thinner thickness is preferable from the viewpoint of vapor permeability.

Further, as the foam material, a material having rubber elasticity, such as the 1,2-polybutadiene foam of Examples 4 and 5, is less likely to burst than the polyethylene foam of Examples 1, 2 and 3 because the foam is less likely to burst. Vapor permeability tends to be low. However, even if the material has rubber elasticity, it is possible to improve the vapor permeability to the same level as that of polyethylene foam by stricting the processing conditions.

Regarding the relationship between the porosity of the surface skin layer and the vapor permeability,
From the comparison of Examples 1 and 2 and the result of the foamed sheet having no surface skin layer of Example 6, it can be said that the vapor permeation amount tends to increase as the porosity increases.

Further, in the case where the needle punching treatment of FIGS. 4 and 5 is performed, particularly when the method as shown in FIG. 5 is selected, depending on the material, the portion punched by the needle punching tends to recover to the original shape. Therefore, it is preferable to use a material having rubber elasticity as much as possible.

As the effect of the product of the present invention, in addition to having the above-mentioned liquid-impermeable vapor permeability, to describe the effect in the case of being used in a sanitary napkin, one of the problems of conventional sanitary napkins is described. , Lateral leakage of menstrual blood from the sanitary napkin can be mentioned. This is because the constituent material of the napkin does not have a waist, so it is twisted during use and leaks from the place where a space is created by the twist. . However, such a leak phenomenon is more flexible than any material such as absorbent paper, pulp sheet, polymer absorbent sheet, etc. currently constituting the sanitary napkin when using the product of the present invention, so that the fitting property is high and leakage occurs. Can be prevented.

As described in detail above, the leak-proof layer according to the present invention has vapor permeability that is impermeable to human body secretions, so that it does not leak and does not feel "mottle", and it also has a moderate waist that has never been seen before. Since it is provided with the spring, it can prevent lateral leakage of menstrual blood from the sanitary napkin, for example, when it is used for a sanitary napkin.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a foam used in the leakproof layer of the present invention, and FIGS. 2, 3, 4, and 5 are various leakproof layers of the absorbent article of the present invention. Sectional view showing an embodiment,
FIG. 6 is a sectional view showing an example of a conventional absorbent article. 1: Foamed body, 2: Skin layer 3: Closed cells, 4: Needle 5: Arrow indicating the direction of needle punching 6: Absorbing layer, 7: Leak-proof layer 8: Surface material

Claims (1)

[Claims] 1. An absorbent article having an absorbent layer and a leakproof layer located below the absorbent layer, wherein the leakproof layer is made of a foam having a closed cell structure, and at least a part of the closed cells adjacent to the foamed body. The upper surface and the lower surface of the foam body communicate with each other by communicating with the absorbent article.