JP2831677B2 - Surface material for absorbent articles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface material that can be suitably used for absorbent articles such as sanitary articles and disposable diapers, and more specifically, sanitary napkins and the like. The present invention relates to a surface material that can be suitably used for an absorbent article.

[Problems to be solved by conventional technology and invention]

An absorbent article used to absorb and hold liquid from the human body has a structure in which an absorber that absorbs and holds liquid is interposed between a liquid-permeable surface material and a liquid-impermeable leakproof material. Being known is known. In this absorbent article, a liquid-permeable surface material (also referred to as an outer packaging material, a covering material, a top sheet, a cover stock, etc.) allows liquid to be absorbed to be promptly transferred to the absorber. (Hereinafter, referred to as liquid permeability) or to give the user a dry feeling without reversing the liquid transferred into the absorber (hereinafter, referred to as liquid return prevention), and diffused into the absorber. There is a demand for shielding the color of the liquid (hereinafter referred to as a shielding property), and further having good flexibility.

Recently, a hydrophobic film having a three-dimensional shape with openings is used instead of a nonwoven fabric, which is a fiber aggregate conventionally used in general, because it has excellent liquid return prevention and shielding properties. Technology used as material (Japanese Patent Publication 57-
17081, JP-A-60-259260, etc.).

Certainly, if such a perforated hydrophobic film is used as a surface material, retention of liquid in the surface material does not occur, so that the liquid return preventing property and the shielding property are considerably improved. But,
It is evident that these perforated hydrophobic films have the drawback that the properties such as liquid permeability deteriorate over time due to changes in properties due to the characteristic temperature change of the film, because the film is perforated. Was. This deterioration over time is typified by the case where the surface permeability is significantly reduced when the surface material is stored in a high-temperature atmosphere such as in summer or / and under a high-pressure condition such as roll winding. You. Therefore, it has been substantially impossible to produce an absorbent article having stable performance using this.

As described above, no conventional surface material is excellent in basic performances such as liquid return prevention and shielding properties, and has little performance deterioration over time. This has been a major obstacle to improving the performance of absorbent articles.

[Means for solving the problem]

The present inventors have conducted intensive studies to overcome such problems, and as a result, have completed the present invention.

That is, the present invention comprises a hydrophobic film having an opening, the opening being subjected to heat treatment during or / and after perforation, and in the thickness direction under a pressure of 50 g / cm ^2. It is intended to provide a surface material of an absorbent article, characterized in that the distortion is 34% or less.

As a result of systematic studies, the present inventors have found that the performance deterioration of a conventional hydrophobic film over time is due to its poor shape retention. That is, the conventional hydrophobic film easily loses its conventional shape under conditions such as high temperature or high pressure, so that the area of apertures effective for liquid permeation is greatly reduced, and as a result, liquid permeability is significantly deteriorated. I do.

Therefore, the present inventors have found that by improving the shape retention of a hydrophobic film, it is possible to obtain a surface material that is excellent in basic performance such as liquid return prevention and shielding properties, and that hardly deteriorates with time. Successful. This shape retention is quantified as a strain in the thickness direction under a pressure of 50 g / cm ² (hereinafter, referred to as a compressive strain; for the measuring method, refer to the examples). When used in an absorbent article, it is necessary that the compression strain is 34% or less in order to impart sufficient shape retention, but it exhibits sufficient shape retention under any conditions. For this purpose, the content is preferably 32% or less.

The surface material used in the present invention means a hydrophobic film alone or a hydrophobic film and a fiber layer integrated on at least one surface of the hydrophobic film. In the latter case, the surface material is used for forming an absorbent article as the surface material. Any layer may be used as the surface, that is, the surface in contact with the body surface, and it is also possible to integrate the fiber layer on both sides of the film layer, or to integrate the film layer on both sides of the fiber layer. In general, it is preferable to use a film layer on the surface in consideration of shielding.

Hereinafter, the hydrophobic film and the fiber layer will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a surface material of the present invention, and FIG. 2 is an enlarged view of an opening portion thereof. This surface material is obtained by integrating a fiber layer 2 on the lower surface of a film layer 1. . The shape of the film layer 1 is, as shown in FIG. 1 and FIG.
It has a bottom part 4 and a wall part 5 connecting them, and an opening 6 exists in at least a part of the wall part.
Is preferably not covered with the top portion 3 in consideration of the liquid return preventing property, the shielding property, and the like. In this case, the angle between the plane formed by the openings and the plane formed by the tops connected to the wall where the openings exist (hereinafter referred to as the inclination angle; see the examples for the measuring method). More preferably, it is 20 mm or more. If the inclination angle is smaller than 20 °, the surface material will not substantially have a three-dimensional shape, so that the shielding property and the liquid return prevention property will be undesirably reduced.

On the other hand, the surface material of the present invention may have a shape in which an opening 6 is provided only in the bottom portion 4 as shown in FIG. It is not preferable because a decrease in the properties and shielding properties cannot be avoided.

The thickness of the film layer is preferably large in order to provide sufficient shape retention, but considering the application to absorbent articles, if the thickness is too large, flexibility is lost. It is preferable to set the range within the range. Such a preferable range of the thickness varies depending on the composition of the film layer or the fiber layer, and is not uniquely defined.However, in general, when the film layer alone is used as the surface material, 50 to 100 μm is used. It is preferably 10 to 50 μm when used integrally with the fiber layer.

As the resin forming the film layer, any resin may be used as long as it is hydrophobic. For example, polyolefin, olefin and other monomers (vinyl acetate, ethyl acrylate, etc.)
And copolymer resins such as polyurethane, polyester, nylon, and acetate, and blended polymers thereof. In consideration of flexibility, low-density polyethylene, linear low-density polyethylene, ethylene-
Polyethylene resins such as vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, and blends thereof are preferred.

The film layer is preferably opaque in order to impart sufficient shielding properties to the surface material. If the film layer is opaque, the surface material of the present invention becomes opaque and can be preferably used as a surface material of an absorbent article that absorbs a colored liquid such as menstrual blood. There are various methods for improving the opacity. For example, a method in which a white pigment is added to a resin in a film production process, a method in which a white pigment is mixed with an appropriate binder on a film surface and applied, and the like, can be used as long as the desired opacity can be imparted. Any method may be used without limitation.

The shape of the aperture provided in the film layer can be freely set within a range in which the liquid permeability and the shielding property are balanced, but the aperture size is generally 0.1 to ² mm2, and It is preferable that the density of the holes is 10 to 100 holes / cm ² . However, the size and density of the openings need not always be constant, but can be changed regularly or irregularly as needed. For example, the size or density of the apertures can be increased in the central portion of an absorbent article that requires particularly high liquid permeability.

Furthermore, as means for controlling liquid permeability and liquid return prevention, blending of a hydrophilic agent to the film resin, application of a surfactant to the film surface, physical treatment such as plasma irradiation, or mineral acid treatment, etc. It is also possible to hydrophilize the surface of the film layer by chemical treatment of
Conversely, the surface of the film layer can be subjected to a water-repellent treatment by applying a silicone-based or fluorine-based agent or the like.

In addition, it is also possible to subject the film layer to a calendering treatment or a fine pattern embossing treatment as required for improving the texture.

On the other hand, the fibrous layer can be a so-called web composed of lightly entangled fibers, a so-called nonwoven fabric or paper in which the fibers are entangled or fixed by adhesion, but in consideration of liquid permeability, the nonwoven fabric or Paper is preferred,
Considering flexibility, nonwoven fabric is more preferable among them,
A so-called dry heat-bonded nonwoven fabric in which fibers are fixed to each other by heat fusion is more preferable. In the web, since the fibers are not fixed to each other and the fiber layer is easily broken by the movement of the user, the liquid permeability may decrease. Also,
Paper is hard to break because the fibers are fixed to each other, but generally has poor flexibility. On the other hand, in a nonwoven fabric, especially a dry heat-bonded nonwoven fabric, the fibers are firmly fixed to each other and have high flexibility, so that liquid permeability, liquid return prevention and flexibility are extremely excellent. A surface material is obtained.

In addition, the fiber layer can have a structure in which the composition is discontinuously different in the thickness direction.In this case, when the fibers are arranged so that the hydrophilicity increases as the distance from the film layer increases. It is more preferable because the liquid permeability and the shielding property are improved.

Various fibers can be used as the constituent fibers of the fiber layer. For example, hydrophilic fibers such as wood pulp, rayon, and vinylon, and hydrophobic fibers such as polyolefin, polyester, acryl, and polyamide can be used.However, in consideration of shielding properties, hydrophobic fibers are mainly used. preferable. Considering that the fiber layer is preferably a heat-bonded dry nonwoven fabric as described above, among these hydrophobic fibers, polyethylene / polypropylene composite fibers, polyethylene / polyester composite fibers, and low-melting polyester / polyester composite fibers , Etc. are more preferable, and in consideration of the adhesiveness to the film layer, polyethylene / polypropylene conjugate fibers and polyethylene / polyester conjugate fibers are more preferable. In the case of a hydrophobic fiber, an appropriate hydrophilization treatment can be performed when further improvement in liquid permeability is required. It is also possible to use fibers with irregular cross sections such as leaf shapes.

The fineness of the fiber, considering the liquid return prevention and texture,
Generally, it is more preferably in the range of 1 to 10 denier (d), and still more preferably 1.5 to 6 d.

The basis weight of the fiber layer also considering the liquid return preventive property and texture, it is preferred that generally is 10 to 50 g / m ^2, 15 to 35 g /
cm ² is more preferable.

Further, considering the liquid permeability, the density of the fibers in the fiber layer is preferably lower in the opening of the film layer than in the non-opening part. More preferably, it is absent.

It is preferable that the film layer and the fiber layer are integrated as tightly as possible in consideration of the liquid permeability and the property of preventing liquid return, and it is generally preferable that the peel strength between the film layer and the fiber layer is 50 g or more. In the case of performing integration by bonding, the bonding points may be uniformly distributed on the boundary surface or may be in a pattern.

A typical method of integrating a film layer and a fiber layer is roughly classified into the following two methods.

The first is a method in which a film layer having no holes and a fiber layer are integrated by heat bonding or an adhesive, and then a hole is formed. This method is advantageous in that the density of the fibers in the fiber layer in the open portions of the film layer is necessarily lower than that in the non-open portions, and in the step of melting and extruding the raw material resin to produce a film, The fact that a so-called laminated film obtained by integration can be used is also advantageous in terms of productivity as compared with the following method.

The second is a method in which a film having no holes is perforated by itself to form a perforated film, and then integrated with a fiber layer. As a method of integration, bonding can be performed by heat bonding or bonding with an adhesive, or by entanglement with an air flow or a high-pressure water flow when the density of the holes is relatively large.

When it is necessary to impart a particularly high liquid permeability, a sheet-like material such as a nonwoven fabric or a web made of hydrophilic fibers such as pulp or rayon is adhered to the back surface of the surface material by heat bonding or an adhesive. Alternatively, in the first method, the hydrophilic fiber sheet-like material can be integrated by superposing and perforating the surface material.

As mentioned above, the permeability of the liquid as the surface material has been described, but in order to prevent the performance deterioration over time, it is necessary that the compression strain under the pressure of 50 g / cm ² is 34% or less. . When the film is used alone, the compression strain can be reduced to 34% or less depending on the thickness of the film, and when the film and fiber are integrated, it is possible to reduce the compression strain to 34% or less depending on the thickness of the film. Is not always satisfactory. There is a negative correlation between so-called compression strain and hand.

In order to satisfy this phenomenon, sufficient heat retention can be imparted by heat-treating only the apertures, and the compression strain can be reduced to 34% or less without impairing the texture. The effect can be remarkably exhibited in the surface material which has been converted.

At the time of perforation or / and after perforation, shape retention can be imparted by heat-treating only the opening, but it is industrially advantageous to perform perforation while heating at the time of perforation. The heating temperature at that time varies depending on the components of the surface material, but is preferably a temperature at which the resin of the components is thermally softened. For example, when the surface material is mainly composed of a polyethylene resin, it is preferable to heat to 50 to 120 ° C, preferably 60 to 100 ° C.

In addition, the surface material of the absorbent article of the present invention is not limited to the example described in detail, but can be variously modified within the range specified above.

〔Example〕

Hereinafter, the usefulness of the present invention will be described with specific examples, but the present invention is not limited to these examples.

Examples 1 and 2 and Comparative Examples 1 to 4 Various surface materials according to the present invention having the configurations shown in Table 1 or comparative surface materials were produced.

That is, in Comparative Example 1 and Comparative Example 3, a surface material was manufactured by performing perforation processing on a film made of a predetermined resin using an embossing roll. In Examples 1 and 2 and Comparative Example 2, after a predetermined film resin was laminated on a fiber layer made of a predetermined heat-bonded nonwoven fabric, embossing was performed. However, in Examples 1 and 2, the embossing roll was heated to 80 ° C. to perform the perforation, whereas in Comparative Examples 1, 2, and 3, the perforation was performed without heating the embossing roll. Comparative Example 4
Then, only the fiber layer was used as a surface material without performing perforation processing.

The performance of the obtained surface material was evaluated by the following method.

 The results are shown in Table 1.

In the evaluation of the absorption time and the shielding property, the surface material of a commercially available sanitary napkin “Lorie” (manufactured by Kao Corporation) was removed, and each surface material was formed instead, and this was evaluated as an assumed napkin sample. . However, in Examples 1 and 2 and Comparative Example 2, the surface material was configured such that the fiber layer was in contact with the absorber side.

<Measurement method> Pore size: An enlarged photograph of the aperture surface viewed from the vertical direction was taken using an electron microscope, and the aperture size a on the photograph was measured using a planimeter. The actual aperture size A was calculated by the formula I).

A (mm ² ) = a (mm ² ) / x ² (I) where x is the magnification of the photograph with respect to the real thing. Density of holes: Measured by counting the number of holes per cm ^{2 of} surface material.

Angle of inclination and wall thickness: The cross section of the surface material was photographed as shown in FIG.
Was measured with a protractor, and this was defined as the inclination angle. In addition, the thickness t ₁ on the photograph was measured using a ruler, (I
I) was calculated the thickness T ₁ of the real thing by the formula. When the surface material has a curved shape, as shown in FIG.
The angle of intersection of the straight line l ₂ passing through the tangent l ₁ and opening ends at the top upper end and an inclination angle alpha.

T ₁ (μm) = 1000 t ₁ (mm) / x (II) Compressive strain: Test piece: A surface material was cut into a square of 100 mm square and subjected to measurement.

Measurement method: Tensilon RTM-25 type (manufactured by Toyo Baldwin Co., Ltd.) was used. First, as shown in FIG. 6 (a), a pressure receiving plate 8 having a diameter of 30 mm is attached to the tip of a 5 kg load cell 7 for compression (hereinafter referred to as a cell), and then as shown in FIG. 6 (b). Gently contact the sample table 9 and 5kg
Apply a load of. At this time, the distance between the pressure receiving plate and the sample stage is set to 0. Next, the cell is raised by 9 mm. Then, as shown in FIG. 6 (c), the test piece 10 is placed on the sample table 9 face up, the cell is lowered, and the load applied to the test piece is recorded on a recording paper. The measurement conditions are as follows.

Cell lowering speed: 3 mm / min Recording paper full scale: 500 g Recording paper scanning speed: 300 mm / min Calculation method: The compression load recorded on the recording paper is as shown in FIG. In this recording sheet, the cell lowering start time A
, The distance d ₁ (mm) from the point at which the cell comes into contact with the test piece and the load starts to be applied, and the load of 350 g (this is 50 g / cm ²
The distance d ₂ (mm) until the point C when the pressure
Is measured with a ruler, the apparent thickness t ₂ (mm) of the sample is calculated by the formula (III), and the compressive strain ε (%) at 50 g / cm ² is calculated by the formula (IV).

t ₂ = (900−d ₁ ) / 100… (III) ε = (d ₂ −d ₁ ) / t ₂ … (IV) This measurement was performed 10 times at different locations of the surface material, and the compression calculated for each was The average value of the strain was taken.

Absorption time: The following test was performed on the surface material immediately after production and the surface material left standing for 30 days under a pressure of 50 kg in a 50 ° C. constant temperature bath, and the former value was determined as the initial value, and the latter value was determined as after storage.

That is, the test solution was injected into the napkin assumed sample under pressure, and the time required for absorption was defined as the absorption time. Generally, the shorter the absorption time, the better the liquid permeability.

Flexibility: The feel when touching the surface material was classified into the following three categories.

Level 3: Flexible.

Level 2: Stiff.

Grade 1: Very rigid.

Shielding property: The state after blood was absorbed by the napkin assumed sample was classified into the following three categories.

Grade 3: No red blood is observed.

Second grade: Only a slight red color of blood is observed.

Grade 1: The red color of the blood is remarkably recognized with discomfort.

Note) LLDPE: Linear low-density polyethylene LDPE: Low-density polyethylene Fiber layer: Heat-bonded nonwoven fabric of the following composition However, NBF: Polyethylene / polypropylene composite fiber with surface hydrophilic treatment (manufactured by Daiwa Spinning Co., Ltd.) SH: Polyethylene / polyester composite fiber with surface hydrophilic treatment (manufactured by Daiwa Spinning Co., Ltd.) [Effects of the Invention] As shown in the surface material of the present invention,
As well as being excellent in basic performance such as flexibility and shielding properties, it has a small compressive strain and has sufficient shape-retaining property, so that deterioration with time in absorption time is small and stable performance is obtained. In particular, Example 1 in which the film layer has the shape shown in FIG. 2 and heat treatment was performed at the time of perforation processing was very excellent in all performances, and can be said to be a truly ideal surface material.

On the other hand, in Comparative Example 1, the feel when touching the surface material was slightly stiff due to the large thickness, and in Comparative Examples 2 and 3, the surface material having a large compressive strain was used. And the deterioration with time of the absorption time is large. In Comparative Example 4, the nonwoven fabric was used alone as the surface material, and although the absorption time was slightly deteriorated with time, the shielding property was extremely poor. Therefore,
It must be said that all of those shown as comparative examples are extremely insufficient as surface materials.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a surface material of the present invention, and FIG.
The figure is an enlarged view of the opening, FIG. 3 is an enlarged view of the opening of another embodiment of the surface material of the present invention, and FIGS. 4 and 5 are measurements of the inclination angle and wall thickness of the film layer. FIGS. 6 and 7 are diagrams showing a method of measuring compression strain. 1: Film layer, 2: Fiber layer 3: Top, 4; Bottom 5: Wall, 6: Opening 7: Cell, 8: Pressure plate 9: Sample table, 10: Specimen

Continuation of the front page (56) References JP-A-1-158953 (JP, A) JP-A-2-19153 (JP, A) JP-A-1-119251 (JP, A) JP-A-64-34365 (JP) JP-A-64-72745 (JP, A) JP-A-1-59121 (JP, U) JP-A-1-95920 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB A61F 13/15

Claims (3)

(57) [Claims] The present invention comprises a hydrophobic film having an opening, which is heat-treated at the time of perforation processing and / or after perforation processing, and has a thickness direction under a pressure of 50 g / cm ² . 34 distortion
% Or less of the surface material of the absorbent article. 2. The surface material of an absorbent article according to claim 1, wherein a fiber layer is integrated on at least one surface of the hydrophobic film. 3. The hydrophobic film has a top portion, a bottom portion, and a wall connecting them, and at least a part of the wall is provided with an opening, and the wall having the opening is provided at the top. The surface material of the absorbent article according to claim 1, wherein the surface material is not covered.