JP2025017769A - Porous film and absorbent article - Google Patents

Abstract

To provide a porous film which has sufficient moisture permeability and excellent flexibility and suppresses the occurrence of blocking, and an absorbent article using the same.SOLUTION: The porous film of the present invention contains an olefinic resin composition, an inorganic filler, and a fatty acid. The porous film contains 50 pts.mass or more and 400 pts.mass or less of the inorganic filler based on 100 pts.mass of the olefinic resin composition and 0.5 pt.mass or more and 5 pts.mass or less of the fatty acid based on 100 pts.mass of the inorganic filler. The olefinic resin composition contains a first olefinic resin having a melting point of 50°C or higher and lower than 90°C and a second olefinic resin having a melting point of 90°C or higher and 108°C or lower.SELECTED DRAWING: Figure 1

Description

The present invention relates to a porous film and an absorbent article using the same.

Absorptive articles such as disposable diapers and sanitary napkins are known that have an absorbent body that absorbs and retains bodily fluids and a back sheet that is placed on the non-skin-facing side of the absorbent body. This back sheet is often made of a porous film. Absorbent articles that have a back sheet made of a porous film have the advantage that moisture generated by the wearer's body when worn is easily released to the outside through the back sheet, making the article less likely to become stuffy when worn.

As a porous film, a moisture-permeable film formed from a resin composition containing a thermoplastic resin such as an olefin resin and an inorganic filler is known (Patent Documents 1 and 2). For example, Patent Document 1 describes a porous film made of a resin composition containing 100 parts by weight of polyolefin, 50 to 400 parts by weight of barium sulfate having an average particle size of 0.3 to 5 μm, and 0.3 to 10 parts by weight of fatty acid zinc, and made porous by stretching, in which the polyolefin is made of polyethylene having a density of 0.89 to 0.94 g/cm ³ .
Patent Document 2 describes the use of a resin component consisting of 20 to 100 parts by weight of a crystalline low-density polyethylene having a density of 0.86 to 0.90 g/cm ³ , a melt index of 0.1 to 50 g/10 min, a weight-average molecular weight/number-average molecular weight of 3 or less, and containing 12% by weight or more of an α-olefin comonomer having 4 to 8 carbon atoms, and 80 to 0 parts by weight of polyethylene having a density of 0.915 to 0.950 g/cm ³ .

Japanese Patent Application Publication No. 11-116714 JP 2000-1557 A

Porous films are required to have flexibility in addition to moisture permeability. For example, using a porous film with excellent flexibility as the back sheet of an absorbent article is expected to improve the comfort of the absorbent article when worn.

In addition, from the viewpoint of ease of handling, porous films are required to be able to suppress blocking (self-adhesion) when wound into a long length, and to be able to easily peel the film surfaces from each other. If a large force is required to peel the film surfaces from each other, the film may stretch unintentionally or break when unrolled.

However, the inventors have found that there is room for improvement in that conventional porous films have sufficient moisture permeability, excellent flexibility, and suppression of blocking.

The present invention relates to a porous film that has sufficient moisture permeability, excellent flexibility, and suppresses the occurrence of blocking, and an absorbent article using the same.

The present invention relates to a porous film comprising an olefin-based resin composition, an inorganic filler, and a fatty acid.
In one embodiment of the porous film of the present invention, it is preferable that the inorganic filler is contained in an amount of 50 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the olefin-based resin composition, and the fatty acid is contained in an amount of 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the inorganic filler.
In one embodiment of the porous film of the present invention, the olefin-based resin composition preferably contains a first olefin-based resin having a melting point of 50°C or higher and lower than 90°C.
In one embodiment of the porous film of the present invention, the olefin-based resin composition preferably contains a second olefin-based resin having a melting point of 90°C or higher and 108°C or lower.

The present invention relates to an absorbent article containing the porous film of the present invention.
Other features, advantages and embodiments of the present invention are described below.

The present invention provides a porous film that has sufficient moisture permeability, excellent flexibility, and suppresses the occurrence of blocking, and an absorbent article using the same.

FIG. 1 is a plan view showing a schematic view of the non-skin-facing side of a sanitary napkin, which is one embodiment of an absorbent article of the present invention. FIG. 2 is a cross-sectional view that shows a schematic cross-section of the sanitary napkin shown in FIG. 1 taken along line II (a cross-section along the thickness direction and the lateral direction). FIG. 3 is a view corresponding to FIG. 1 showing another embodiment of the absorbent article of the present invention.

The porous film of the present invention will be described in detail below.
The porous film of the present invention has a large number of micropores. The porous film of the present invention has moisture permeability due to the micropores. The porous film of the present invention also has high water resistance and high leakproofness. Furthermore, the porous film of the present invention has high flexibility and requires a small load to deform. The porous film of the present invention also has excellent handling properties, as blocking is unlikely to occur during production. The porous film of the present invention contains at least an olefin resin composition, an inorganic filler, and a fatty acid. In addition to these components, the porous film of the present invention may contain various additives for the purpose of improving various properties of the porous film.

<Olefin-Based Resin Composition>
In this specification, the term "olefin resin composition" includes both the case where only one type of various olefin resins is contained and the case where two or more types are contained. In addition, the term "olefin resin composition" is a concept that consists of only various olefin resins and does not contain other resins or components other than resins. In addition, the porous film of the present invention may contain resins other than olefin resins.
The olefin resin composition used in the present invention is composed mainly of at least one selected from the group consisting of polymers and copolymers of monoolefins such as ethylene, propylene, butene, etc. Examples of such polymers include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, olefin elastomers, and mixtures of any two or more of these.

The present inventors have found that it is difficult for conventional porous films to achieve all of the effects of excellent flexibility and moisture permeability, and suppressing the occurrence of blocking when rolled and stored. As a result of further intensive research, they have found that by including an olefin-based resin composition containing both a first olefin-based resin having a melting point of 50°C or more and less than 90°C (hereinafter also referred to as "low melting point OR") and a second olefin-based resin having a melting point of 90°C or more and 108°C or less (hereinafter also referred to as "high melting point OR"), the film has excellent flexibility and moisture permeability, and effectively suppresses blocking when rolled and stored.

Furthermore, as shown in Comparative Example 1, for example, a porous film using an olefin resin with a melting point lower than the low melting point OR of the present invention instead of the low melting point OR of the present invention may have a reduced adhesiveness of the adhesive after storage of the absorbent article when used as a back sheet of an absorbent article in a form in which an adhesive is attached to the back sheet. The cause of this reduced adhesiveness is believed to be that when an olefin resin with a melting point lower than the low melting point OR is used as the olefin resin, low molecular weight components in the adhesive are absorbed by the olefin resin with a melting point lower than the low melting point OR of the porous film during storage. However, in the porous film of the present invention, which combines a low melting point OR with a specific melting point and a high melting point OR, the adhesive performance of the adhesive after storage is maintained when used as a back sheet of an absorbent article to which an adhesive is attached.

The low melting point OR will now be described in more detail.
In the porous film of the present invention, the melting point of the low melting point OR is preferably 50° C. or more, more preferably 55° C. or more, and even more preferably 60° C. or more, from the viewpoint of suppressing blocking when the film is rolled up and stored, and maintaining adhesive performance after storage when the film is used as a back sheet of an absorbent article to which an adhesive is attached. In addition, from the viewpoint of imparting excellent flexibility, the melting point of the low melting point OR is preferably less than 90° C., more preferably less than 85° C., and even more preferably less than 80° C. In summary, the melting point of the low melting point OR is preferably 50° C. or more and less than 90° C., more preferably 55° C. or more and less than 85° C., and even more preferably less than 60° C. and less than 80° C.

The melting point of the olefin resin contained in the porous film is measured by the following method. Approximately 2.0 mg of the porous film is used as a sample, and differential scanning calorimetry (DSC) is performed using a differential scanning calorimeter (DSC7000X, Hitachi High-Tech Science Corporation) under the following conditions: a measurement temperature range of 20°C to 260°C, a heating rate of 10°C/min, a heating rate of 50°C/min, two repeated measurements, and in an air environment. In the obtained DSC curve, an endothermic peak is observed when the olefin resin melts, and the melting point of the olefin resin is the temperature at the apex of the endothermic peak observed during the second heating process. For example, in the case of a low melting point OR, the endothermic peak is observed in a temperature range of 50°C or more and less than 90°C, and in the case of a high melting point OR, the endothermic peak is observed in a temperature range of 90°C or more and 108°C or less.

In addition, when the porous film contains components (e.g. additives) other than the melting point measurement target (olefin resin), the above-mentioned melting point measurement method may not be able to accurately measure the melting point of the measurement target. In such a case, the additives are collected from the porous film by the following method, and their melting points are measured, so that the melting point of the measurement target, which is measured separately, can be distinguished from the melting points of other components (e.g. additives).
First, the porous film is kneaded at 160° C. and 30 rpm for 10 minutes using a Labo Plastomill (manufactured by Toyo Seiki Co., Ltd.) to obtain a resin mass.
Next, using a lab press (manufactured by Toyo Seiki Seisakusho), the resin block is pressed at 150° C. and 13 MPa for 1 minute, and then cold pressed at room temperature and 13 MPa for 1 minute to obtain a pressed film with a thickness of approximately 0.5 mm.
Finally, the pressed film is stored in an environment of 50° C. for one week. By doing so, more additives bleed out on the surface of the pressed film than in the state of a porous film, so that the additives can be collected efficiently. Methods for collecting the additives from the surface of the pressed film include, for example, wiping them off with a wipe or scraping them off with a spatula.

In the porous film of the present invention, the density of the low-melting point OR is preferably 0.865 g/cm3 or more, more preferably 0.870 g/cm3 or ^more , and even more preferably 0.875 g/cm3 or more, from the viewpoints of more effectively suppressing blocking when the film is rolled up and stored, and of better maintaining adhesive performance after storage when the film is used ^as a back sheet of an absorbent article ^to which an adhesive is attached.
From the viewpoint of imparting even greater flexibility, the density of the low-melting-point OR is preferably less than 0.890 g/cm ³ , more preferably 0.889 g/cm ³ or less, and even more preferably 0.888 g/cm ³ or less.
Taking all of this into consideration, the density of the low melting point OR is preferably 0.865 g/cm3 ^or more and less than 0.890 g/ ^cm3 , more preferably 0.870 g/cm3 or ^more and 0.889 g/cm3 ^or less, and even more preferably 0.875 g/ ^cm3 or more and 0.888 g/cm3 or ^less .

The low melting point OR is preferably a copolymer of ethylene and an α-olefin (hereinafter also referred to as "ethylene-α-olefin copolymer"). Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 1-decene. α-olefins having 3 to 5 carbon atoms are preferred because of their excellent flexibility.

It is more preferable that the low-melting point OR is a copolymer of ethylene and an α-olefin polymerized by a metallocene catalyst, since the strength of the film against tearing, punch-through and the like is further improved.
The metallocene catalyst is a combination of a metallocene, which is a compound having a structure in which a transition metal such as titanium, zirconium, or hafnium is sandwiched between unsaturated cyclic compounds containing a π-electron system cyclopentadienyl group or a substituted cyclopentadienyl group, and a cocatalyst such as an aluminum compound. Examples of the metallocene include titanocene and zirconocene. Examples of the aluminum compound include alkylaluminoxane, alkylaluminum, aluminum halide, and alkylaluminum halide.

The olefin resin composition used in the present invention preferably contains 75 parts by mass or less of low-melting-point OR in 100 parts by mass of the olefin resin composition, from the viewpoint of effectively suppressing blocking in the porous film of the present invention and increasing moisture permeability. From the viewpoint of making these advantages more prominent, the low-melting-point OR is more preferably contained in 100 parts by mass of the olefin resin composition in 73 parts by mass or less, and more preferably contained in 70 parts by mass or less.
In addition, it is preferable that the low melting point OR is contained in an amount of 30 parts by mass or more in 100 parts by mass of the olefin resin composition in order to obtain excellent flexibility of the porous film of the present invention. In order to make this advantage more prominent, the low melting point OR is contained in an amount of 40 parts by mass or more, and more preferably 50 parts by mass or more in 100 parts by mass of the olefin resin composition.
Taking all of the above into consideration, the olefin-based resin composition used in the present invention preferably contains 30 parts by mass or more and 75 parts by mass or less of low-melting point OR per 100 parts by mass of the olefin-based resin composition, more preferably 40 parts by mass or more and 73 parts by mass or less, and even more preferably 50 parts by mass or more and 70 parts by mass or less.

The high melting point OR will now be described in more detail.
In the porous film of the present invention, in combination with the specific low-melting point OR, the high-melting point OR has a melting point of preferably 108° C. or less, more preferably 107° C. or less, and even more preferably 105° C. or less, in order to obtain the effect of suppressing blocking and maintaining the adhesiveness of the adhesive on the back sheet of the absorbent article while also obtaining excellent flexibility and moisture permeability. In addition, in order to realize high-speed molding of the porous film to be melt-molded, the high-melting point OR has a melting point of preferably 90° C. or more, more preferably 93° C. or more, and even more preferably 95° C. or more, in order to realize solidification in a short time. In summary, the high-melting point OR has a melting point of preferably 90° C. or more and 108° C. or less, more preferably 93° C. or more and 107° C. or less, and even more preferably 95° C. or more and 105° C. or less.

In order to achieve even better flexibility, moisture permeability, blocking inhibition, and the effect of maintaining the adhesiveness of the adhesive on the back sheet of the absorbent article, the difference (M2-M1) between the melting point M1 of the low melting point OR and the melting point M2 of the high melting point OR is preferably 10°C or more and 60°C or less, and more preferably 20°C or more and 40°C or less.

From the viewpoint of obtaining excellent flexibility and moisture permeability in the porous film of the present invention, the density of the high melting point OR is preferably less than 0.915 g/cm ³ , more preferably 0.913 g/cm ³ or less, and even more preferably 0.910 g/cm ³ or less. In addition, from the viewpoint of making blocking less likely to occur and of improving the effect of maintaining the adhesiveness of the adhesive on the back sheet of the absorbent article, the density of the high melting point OR is preferably 0.890 g/cm ³ or more, more preferably 0.895 g/cm ³ or more, and even more preferably 0.900 g/cm ³ or more.
Considering all of the above, the density of the high melting point OR is preferably 0.890 g/cm ³ or more and less than 0.915 g/cm ³ , more preferably 0.895 g/cm ³ or more and 0.913 g/cm ³ or less, and even more preferably 0.900 g/cm ³ or more and 0.910 g/cm ³ or less.

In order to suppress blocking and to further improve the effect of maintaining the adhesiveness of the adhesive on the back sheet of the absorbent article, the difference (D2-D1) between the density D1 of the low melting point OR and the melting point D2 of the high melting point OR is preferably 0.005 g/cm3 or ^more and 0.040 g/cm3 ^or less, and more preferably 0.010 g/cm3 or ^more and 0.027 g/cm3 or ^less .

As the high melting point OR, it is preferable to use polyethylene such as low density polyethylene or linear low density polyethylene.

When polyethylene is used as the high melting point resin, it is preferable to use an ethylene-α-olefin copolymer as the polyethylene. As the α-olefin in the ethylene-α-olefin copolymer used in the high melting point OR, an α-olefin having 5 to 8 carbon atoms, such as 1-pentene, 1-hexene, 1-heptene, and 1-octene, is preferable, as this further improves the strength of the film against tearing and punch-through.

In particular, it is preferable to use linear low-density polyethylene as the high-melting point OR, since this improves heat resistance during stretching and allows for uniform stretching. In particular, it is more preferable to use linear low-density polyethylene polymerized with a metallocene catalyst, since this further improves the strength of the film against tearing and puncture.

The olefin resin composition preferably contains 15 parts by mass or more of high-melting-point OR per 100 parts by mass of the olefin resin composition, from the viewpoint of further imparting moisture permeability, blocking suppression, and adhesion retention. From the viewpoint of making this advantage more prominent, the high-melting-point OR is more preferably contained in an amount of 18 parts by mass or more, and even more preferably contained in an amount of 20 parts by mass or more, per 100 parts by mass of the olefin resin composition.
In addition, the olefin resin composition used in the present invention preferably contains 70 parts by mass or less of the high melting point OR in 100 parts by mass of the olefin resin composition from the viewpoint of flexibility of the porous film. In order to make this advantage more prominent, the high melting point OR is more preferably contained in an amount of 60 parts by mass or less, and even more preferably contained in an amount of 50 parts by mass or less in 100 parts by mass of the olefin resin composition.
Taking all of the above into consideration, the olefin-based resin composition used in the present invention preferably contains 15 parts by mass or more and 70 parts by mass or less of high melting point OR per 100 parts by mass of the olefin-based resin composition, more preferably 18 parts by mass or more and 60 parts by mass or less, and even more preferably 20 parts by mass or more and 50 parts by mass or less.

In the olefin-based resin composition, the ratio C1/C2 of the amount C1 of low-melting point OR to the amount C2 of high-melting point OR is preferably 0.5 or more in terms of improving flexibility, more preferably 1.0 or more, and even more preferably 1.5 or more.
In the olefin-based resin composition, the ratio C1/C2 of the amount C1 of low-melting point OR to the amount C2 of high-melting point OR is preferably 5.0 or less in order to impart even better moisture permeability, more preferably 4.0 or less, and even more preferably 3.0 or less.
Taking the above into consideration, the olefin-based resin composition preferably has a ratio C1/C2 of the amount C1 of low-melting point OR to the amount C2 of high-melting point OR of 0.5 or more and 5.0 or less, more preferably 1.0 or more and 4.0 or less, and even more preferably 1.5 or more and 3.0 or less.

The porous film of the present invention is preferably high in melt tension because it is easy to increase moisture permeability. From this viewpoint, it is preferable that the olefin resin composition contains a branched low-density polyethylene. Branched low-density polyethylene is also called "LDPE", and low-density polyethylene having long chain branches produced by a general high-pressure method can be used. Hereinafter, branched low-density polyethylene is also referred to as "LDPE". The melt tension can be measured by the method described in the examples below. It is preferable that the olefin resin composition further contains a branched low-density polyethylene in addition to the low-melting point OR and the high-melting point OR. Herein, "further containing branched low-density polyethylene" means "containing a high-melting point OR other than LDPE and further containing LDPE", and does not mean containing LDPE with a melting point of more than 108 ° C. When the olefin resin composition further contains LDPE, it may contain it as part of the high-melting point OR, or it may contain LDPE with a melting point exceeding the upper temperature limit of the high-melting point OR. In the present invention, it is particularly preferable for the high melting point OR to contain linear low density polyethylene and for the olefin resin composition to contain LDPE, in terms of improving moisture permeability.

In terms of increasing the moisture permeability of the porous film and balancing it with flexibility, etc., the melting point of LDPE is preferably 105°C or higher, and preferably 120°C or lower, more preferably 118°C or lower, and even more preferably 115°C or lower. Taking all of the above into consideration, the melting point of LDPE is preferably 105°C or higher and 120°C or lower, more preferably 105°C or higher and 118°C or lower, and even more preferably 105°C or higher and 115°C or lower.

From the viewpoint of flexibility of the porous film, the density of the LDPE is preferably 0.925 g/cm3 ^or less. From the viewpoint of preventing blocking and moisture permeability, the density of the LDPE is preferably 0.910 g/ ^cm3 or more, more preferably 0.913 g/cm3 or ^more , and even more preferably 0.915 g/cm3 or ^more .
Considering all of the above, the density of LDPE is preferably 0.910 g/cm ³ or more and 0.925 g/cm ³ or less, more preferably 0.913 g/cm ³ or more and 0.925 g/cm ³ or less, and even more preferably 0.915 g/cm ³ or more and 0.925 g/cm ³ or less.

The olefin resin composition preferably contains 3 parts by mass or more of LDPE per 100 parts by mass of the olefin resin composition in order to further impart moisture permeability. From the viewpoint of making this advantage more prominent, the LDPE is more preferably contained in an amount of 5 parts by mass or more, and even more preferably contained in an amount of 8 parts by mass or more, per 100 parts by mass of the olefin resin composition.
In addition, the amount of LDPE in the olefin resin composition used in the present invention is preferably 20 parts by mass or less per 100 parts by mass of the olefin resin composition in order to maintain the flexibility of the porous film. In order to make this advantage more prominent, the amount of LDPE is more preferably 18 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the olefin resin composition.
In summary, the olefin resin composition used in the present invention contains LDPE in an amount of preferably 3 parts by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 18 parts by mass or less, and even more preferably 8 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the olefin resin composition.

In the olefin resin composition, the mass ratio (C1+C4)/(C2+C3+C5) of the total amount (C1+C4) of the amount C1 of the low-melting point OR and the amount C4 of the olefin resin having a melting point lower than the lower melting point limit of the low-melting point OR to the total amount (C2+C3+C5) of the amount C2 of the high-melting point OR, the amount C3 of LDPE, and the amount C5 of the olefin resin other than LDPE having a melting point higher than the upper melting point limit of the high-melting point OR is preferably 0.4 or more in terms of improving flexibility, more preferably 1.0 or more, and even more preferably 1.2 or more.
In the olefin resin composition, the mass ratio (C1+C4)/(C2+C3+C5) is preferably 3.0 or less in order to further impart moisture permeability, more preferably 2.5 or less, and even more preferably 2.0 or less.
Taking the above into consideration, the olefin resin composition preferably has a mass ratio (C1+C4)/(C2+C3+C5) of 0.4 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, and even more preferably 1.2 or more and 2.0 or less.

<Components other than olefin-based resin composition>
The inorganic filler used in the present invention is a substance that causes peeling at the interface with the olefin resin composition to form micropores. From this viewpoint, the inorganic filler has an average particle size _D50 of preferably 30 μm or less, more preferably 10 μm or less, and also preferably 0.5 μm or more, and even more preferably 1.0 μm or more. In this specification, the average particle size _D50 of the inorganic filler refers to the weight cumulative particle size at a cumulative weight of 50 mass% measured by a laser diffraction scattering type particle size distribution measurement method.

Examples of inorganic fillers include calcium carbonate, gypsum, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium phosphate, aluminum hydroxide, zinc oxide, titanium oxide, alumina, mica, zeolite, and carbon black, as well as mixtures thereof. In particular, it is preferable to use calcium carbonate, since it is easy to adjust the particle size to the above-mentioned size.

The inorganic filler is preferably contained in an amount of 50 parts by mass or more per 100 parts by mass of the olefin resin composition in order to form a sufficient amount of fine pores and sufficiently increase the moisture permeability of the porous film, more preferably 60 parts by mass or more, and even more preferably 80 parts by mass or more.
In addition, it is preferable for the inorganic filler to be contained in an amount of 400 parts by mass or less per 100 parts by mass of the olefin resin composition, from the viewpoint of sufficiently enhancing the leakproofness of the porous film, more preferably 350 parts by mass or less, and even more preferably 200 parts by mass or less.

The fatty acid used in the present invention is a substance that functions as a dispersant for inorganic fillers. From the viewpoint of fully exerting this function, a dispersant that can hydrophobize the surface of the inorganic filler is preferably used. From this viewpoint, it is preferable to use, for example, a fatty acid as a dispersant, and stearic acid is particularly preferable. Other fatty acids include, for example, caprylic acid, palmitic acid, capric acid, oleic acid, myristic acid, lauric acid, etc.

The porous film of the present invention preferably contains the above-mentioned fatty acid in an amount of 0.5 parts by mass or more relative to 100 parts by mass of inorganic filler in order to enhance the dispersibility of the inorganic filler. In order to make this advantage more prominent, the fatty acid is more preferably contained in an amount of 0.6 parts by mass or more, and even more preferably contained in an amount of 0.7 parts by mass or more relative to 100 parts by mass of inorganic filler.
In addition, the porous film of the present invention preferably contains the above-mentioned fatty acid in an amount of 5.0 parts by mass or less per 100 parts by mass of inorganic filler, from the viewpoint of not impairing the formability of the film. In order to make this advantage more prominent, the fatty acid is more preferably contained in an amount of 4.0 parts by mass or less, and even more preferably contained in an amount of 3.0 parts by mass or less per 100 parts by mass of inorganic filler.
Taking all of the above into consideration, the porous film of the present invention preferably contains 0.5 parts by mass or more and 5.0 parts by mass or less of the above-mentioned fatty acid per 100 parts by mass of inorganic filler, more preferably 0.6 parts by mass or more and 4.0 parts by mass or less, and even more preferably 0.7 parts by mass or more and 3.0 parts by mass or less.

The porous film preferably contains a triglyceride, which enhances the water repellency of the surface of the porous film and improves leak resistance.
When the triglyceride contained in the porous film of the present invention is used as a back sheet of an absorbent article to which an adhesive is attached, the ratio (A1/A2) of the mass A1 of the group derived from a saturated fatty acid having 18 to 22 carbon atoms to the mass A2 of the group derived from a saturated fatty acid having 16 carbon atoms is preferably 1.0 or more, and from the viewpoint of particularly high effect of maintaining the adhesiveness of the adhesive, it is preferably 5 or more, more preferably 10 or more, and particularly preferably 15 or more. The higher the ratio (A1/A2), the better, but for example, a ratio of 99 or less is preferable from the viewpoint of increasing the water repellency of the porous film surface and increasing leakproofness.

In terms of high leakproofing properties, the triglyceride preferably contains 28 to 96% by mass of groups derived from saturated fatty acids having 18 carbon atoms in the total amount of groups derived from fatty acids contained in all triglycerides, and more preferably contains 60 to 96% by mass of groups derived from saturated fatty acids having 18 carbon atoms in the total amount of groups derived from fatty acids contained in all triglycerides in terms of high adhesion maintenance effect.
In addition, with regard to the mass of the group derived from a saturated fatty acid having 16 carbon atoms, in terms of high leakproofing, it is preferable that the mass of the group derived from a saturated fatty acid having 16 carbon atoms is 1 to 50 mass% of the total amount of groups derived from fatty acids contained in all triglycerides, and further, in terms of high adhesiveness maintenance effect, it is more preferable that it is 1 to 30 mass%.
Furthermore, in terms of leakproofness, the total amount of groups derived from fatty acids contained in all triglycerides may not include groups derived from saturated fatty acids having 20 to 22 carbon atoms, and may amount to, for example, 10% or less. In view of the fact that the melting point of the triglyceride is increased, the adhesiveness-maintaining effect of the pressure-sensitive adhesive is high, the thermal stability of the molded product is increased, and contamination of the rolls of the processing machine can be reduced, it is preferable that the total amount of groups derived from fatty acids contained in all triglycerides includes groups derived from saturated fatty acids having 20 to 22 carbon atoms, and the mass of the groups is more preferably 1 to 10 mass%, and even more preferably 1 to 5 mass%.
However, the total proportion of groups derived from saturated fatty acids having 18 carbon atoms, the proportion of groups derived from saturated fatty acids having 16 carbon atoms, and the proportion of groups derived from saturated fatty acids having 20 to 22 carbon atoms does not exceed 100 mass%.

The proportion of groups derived from various fatty acids based on the total amount of groups derived from fatty acids contained in all triglycerides is measured by the following method.
A good solvent for triglycerides, such as toluene, is used to extract the triglycerides present on the surface of the porous film.
The ester bonds in the extracted triglycerides are hydrolyzed with alkali, and the methyl-esterified fatty acids are quantitatively analyzed by gas chromatography.

From the viewpoint of further increasing the leakproofness of the porous film of the present invention, it is preferable that the triglyceride of the present invention does not contain groups derived from unsaturated fatty acids. "Does not contain groups derived from unsaturated fatty acids" includes both cases where no groups derived from unsaturated fatty acids are contained at all, and cases where a small amount of unsaturated fatty acids is inevitably contained. "In the case where a small amount of unsaturated fatty acids is inevitably contained", the proportion of groups derived from unsaturated fatty acids is 2% by mass or less, based on the total amount of groups derived from fatty acids contained in all triglycerides contained in the porous film.

It is preferable that the triglyceride does not contain a group derived from a fatty acid having a hydroxyl group, from the viewpoint of further increasing the leakproofness of the porous film of the present invention. A fatty acid having a hydroxyl group is a fatty acid in which at least one hydrogen atom in the hydrocarbon group of the fatty acid is replaced with a hydroxyl group. "Does not contain a group derived from a fatty acid having a hydroxyl group" includes both a case in which no group derived from a fatty acid having a hydroxyl group is contained at all, and a case in which a group derived from a fatty acid having a hydroxyl group is inevitably contained in a small amount. A case in which a group derived from a fatty acid having a hydroxyl group is inevitably contained in a small amount is, for example, a case in which the proportion of groups derived from a fatty acid having a hydroxyl group is 2% by mass or less based on the total amount of groups derived from fatty acids contained in all triglycerides contained in the porous film. Similarly, it is preferable that the proportion of fatty acids having other substituents such as epoxy groups and amino groups contained in all triglycerides is 2% by mass or less.

The triglyceride is preferably a natural oil. For example, specific triglycerides of natural oils have diverse molecular structures and therefore provide higher liquid repellency than other specific triglycerides such as synthetic oils. One example of a natural oil is extremely hardened oil obtained by hydrogenating vegetable oils such as palm oil, rapeseed oil, and soybean oil, or animal oils such as lard.

From the viewpoint of making the advantage of using triglyceride more prominent, the content of triglyceride in the porous film of the present invention is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, per 100 parts by mass of the olefin-based resin composition. Also, from the viewpoint of film formability, the content of triglyceride is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the olefin-based resin composition. Taking the above into consideration, the content of triglyceride in the porous film of the present invention is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1.0 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the olefin-based resin composition.

The porous film of the present invention may contain additives in addition to the olefin resin, inorganic filler, fatty acid, and triglyceride. The additives used can impart various additional properties to the porous film. Examples of such additives include plasticizers, water repellents, antioxidants, ultraviolet absorbers, and colorants.

The porous film of the present invention may further contain a pore opening promoter in addition to the above-mentioned olefin resin composition, inorganic filler and fatty acid. The pore opening promoter is used for the purpose of smoothly stretching the resin film containing the olefin resin composition and inorganic filler to generate micropores. In the present invention, even if the pore opening promoter is not used, the interfacial peeling occurs between the olefin resin composition and the inorganic filler, and the film can have a predetermined moisture permeability, but the pore opening promoter may be used in order to further increase the moisture permeability.
As the pore opening promoter, a substance known as a release agent between metal and resin is preferably used. Specific examples include metal soap, silicone, fluororesin, fatty acid amide, and hydrocarbon paraffin wax. In particular, it is preferable to use a metal soap, since it can more smoothly form fine pores. As the metal soap, a metal salt of a saturated fatty acid or an unsaturated fatty acid is preferably used. As the fatty acid, for example, caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, lauric acid, etc. are included. As the metal salt, calcium, aluminum, magnesium, zinc, etc. salts of these fatty acids are included. As the metal soap, zinc stearate is particularly preferred.

Next, a preferred method for producing the porous film of the present invention will be described.
The method for producing a porous film of the present invention includes a step of stretching, at least in one direction, a resin sheet obtained by melt molding a compound containing at least an olefin resin composition, an inorganic filler, and a fatty acid.
The details of the olefin resin composition, inorganic filler and fatty acid contained in the compound are as described above.The amount of the olefin resin composition, inorganic filler and fatty acid contained in the compound is the same as the amount of these components contained in the porous film.Furthermore, the type and amount of optional components such as triglyceride contained in the compound are the same as the type and amount of optional components contained in the porous film.

The porous film of the present invention can be efficiently produced, for example, by the following method.
First, the components constituting the compound described above are premixed using a Henschel mixer, a super mixer, or the like, and then kneaded and pelletized using a single-screw or twin-screw extruder. The pellets are then used to form a film using a molding machine to obtain a resin sheet. For example, a T-die type or an inflation type molding machine can be used.

The dispersant may be used alone and mixed with the other components constituting the compound, but it is preferable to attach the dispersant to the surface of the inorganic filler in advance to produce a surface-modified inorganic filler, and then mix this surface-modified inorganic filler with the other components constituting the compound to prepare the compound. In this way, the resin sheet can be successfully stretched while suppressing the occurrence of unintended pinholes, and a porous film that combines high moisture permeability and high water resistance can be obtained.

The resin sheet described above is stretched uniaxially or biaxially, which causes interfacial peeling between the olefin resin composition and the inorganic filler, making the sheet porous. For this stretching, a roll method capable of stretching in the machine direction or a tenter method capable of stretching in the film width direction in addition to the machine direction is used. In this way, the porous film of the present invention is obtained. The resin sheet is stretched at least uniaxially, preferably 1.1 times or more, more preferably 1.5 times or more, and even more preferably 2.0 times or more, so that the area increases with stretching. In addition, from the viewpoint of avoiding a decrease in tear strength due to excessive molecular orientation caused by excessive stretching, the resin sheet is stretched preferably 5.0 times or less, more preferably 4.5 times or less, and even more preferably 4.0 times or less.

In both uniaxial and biaxial stretching, the temperature of the resin film during stretching is preferably set to 30°C or higher and 100°C or lower, more preferably 35°C or higher and 95°C or lower, and even more preferably 40°C or higher and 90°C or lower, from the viewpoint of being able to stretch the film uniformly without breaking the film.

As a measure against thermal shrinkage in the stretching direction of the porous film, annealing may be performed after stretching. Here, annealing refers to applying heat to the film in advance to intentionally heat shrink the film and suppress shrinkage of the product roll. In the case of the roll stretching method, the stretched film is heated by a heated roll (annealing roll) while the peripheral speed of the annealing roll is set to a value of the film transport speed immediately after the annealing roll/film transport speed immediately before the annealing roll less than 1. In the case of the tenter stretching method, the film can be heated near the tenter outlet and the clip width at both ends can be narrowed to be narrower than the width after stretching, thereby causing the film to self-shrink. The temperature of the annealing treatment is preferably higher than the stretching temperature and 70 to 100°C, or the shrinkage ratio during the annealing treatment (film transport speed immediately after annealing treatment/film transport speed immediately before the annealing roll)) is preferably 65 to 80%. If the annealing temperature and shrinkage ratio are within these ranges, there is an advantage in that the dimensional stability during long-term storage is improved.

The porous film produced by the above method has high flexibility and high breathability. When the degree of flexibility is expressed by deformation flexibility, the porous film of the present invention has a low deformation flexibility in the machine direction of preferably 0.060 N/(mm (g/ ^m2 )) or less, more preferably 0.057 N/(mm (g/ ^m2 )) or less, and even more preferably 0.055 N/(mm (g/ ^m2 )) or less. From the viewpoint of maintaining the strength of the porous film of the present invention, the lower limit of the deformation flexibility is preferably 0.005 N/(mm (g/ ^m2 )) or more.

The deformation flexibility of the porous film is measured by the following method.
The porous film to be measured is cut into three pieces measuring 150 mm in the machine direction and 30 mm in the width direction. The cut test pieces are fixed to a tensile tester (product name: AG-1S, manufactured by Shimadzu Corporation) so that the initial length _L0 of the test piece is 100 mm. After fixing, the load read by the tensile tester is set to zero, and the test piece is elongated to 1.3 times _L0 at a deformation rate of 200 mm/min, and then immediately contracted to _L0 at a deformation rate of 200 mm/min to perform a cycle test. From the obtained data, the load (F _3% ) at 1.03 times deformation during the elongation process is read, and the deformation flexibility (N/(mm·(g/m ² ))) is calculated from the following formula.
Deformation flexibility (N/(mm·(g/m ² )))=F _3% (N)/(0.03×30 (mm)×film basis weight (g/m ² ))

The moisture permeability of the porous film of the present invention is preferably 0.8 g/(100 ^cm2 ·h), more preferably 1.0 g/(100 ^cm2 ·h) or more, and even more preferably 1.2 g/(100 ^cm2 ·h) or more. This allows the porous film of the present invention to have high moisture permeability and to properly dissipate moisture inside the absorbent article to the outside. On the other hand, the upper limit of the moisture permeability of the porous film is preferably 4.5 g/(100 ^cm2 ·h) or less, more preferably 3.5 g/(100 ^cm2 ·h) or less, and even more preferably 3.0 g/(100 ^cm2 ·h) or less, so as not to lose the necessary leakproofness of the back sheet due to excessive porosity.

The moisture permeability of the porous film is measured by the following method in accordance with JIS L1099A-2.
Approximately 25 mL of ion-exchanged water is placed in a glass bottle (Labolan screw bottle No. 8, AS ONE) with a mouth diameter of 2.03 cm (area 3.23 ^cm2 ), the mouth of the glass bottle is covered with a single test piece (porous film to be measured) so that there are no gaps, and the test piece is fixed to the glass bottle with a rubber band to prepare an evaluation sample. After measuring the mass (W1) of the evaluation sample, the sample is stored in a thermostatic chamber controlled at 40°C and 20% RH for 10 to 15 hours. After storage, the mass (W2) of the evaluation sample is measured, the storage time (T1, unit: h) is recorded, and the moisture permeability is calculated using the following formula.
Moisture permeability (g/( ^100cm2・h))=(W1-W2)/(T1×3.23)
×100

The melt tension of the porous film measured at 200° C. is preferably 4.0 mN or more in terms of excellent moisture permeability, more preferably 4.5 mN or more, and even more preferably 5.0 mN or more.
The melt tension of the porous film can be measured by the method described in the Examples below.

The basis weight of the porous film of the present invention varies depending on its application, but for example, when used as a back sheet of an absorbent article, it is preferably 5 g/m2 or ^more , more preferably 10 g/m2 or ^more , and preferably 100 g/m2 or ^less , more preferably 50 g/m2 or ^less .
The thickness of the porous film of the present invention may vary depending on the application, but for example, when used as a back sheet of an absorbent article, it may be about 4 μm or more and 90 μm or less. The thickness of the porous film in each example described later satisfies this range.

The porous film of the present invention may be a single layer film or a laminated film in which multiple layers are laminated in the thickness direction. When the porous film of the present invention is a laminated film, at least one of the multiple layers constituting the laminated film may be a porous film having the above-mentioned configuration.

The porous film of the present invention has excellent flexibility, moisture permeability, and high leak-proofing against liquids, especially water, so that the porous film of the present invention can be used, for example, as leak-proof sheets for absorbent articles such as disposable diapers and sanitary napkins, and waterproof sheets for rain gear, etc.

In particular, when the porous film is used in an absorbent article of the type that is fixed to clothing such as shorts, such as a sanitary napkin, the following advantages are obtained. In such absorbent articles, an adhesive is often provided as a fixing means on the surface of the back sheet facing the clothing. The adhesive as the fixing means is required to stably exhibit a certain level of adhesive strength so that after the absorbent article is fixed to a predetermined position on the clothing via the adhesive, the absorbent article does not shift from the fixed position, or the absorbent article does not undergo unintended deformation such as twisting or rolling over. In this regard, as shown in the examples described below, when the porous film of the present invention is used, the adhesive strength of the adhesive is suppressed from decreasing after storage, so that the absorbent article is less likely to shift when fixed to clothing and has excellent wearing comfort and leak prevention properties.
The absorbent article of the present invention will be described below based on preferred embodiments with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. The drawings are basically schematic, and the ratio of each dimension may differ from the actual one.

Figures 1 and 2 show a sanitary napkin 1A, which is one embodiment of the absorbent article of the present invention. The napkin 1A is an absorbent article that is fixed to clothing (not shown) and has adhesives 7 and 8 attached to the surface 3a that faces the clothing.

As shown in FIG. 1, the napkin 1A has a longitudinal direction X that corresponds to the front-rear direction of the wearer and extends from the wearer's abdomen through the crotch area to the back, and a lateral direction Y that is perpendicular to the longitudinal direction X.
The napkin 1A is divided into three regions in the longitudinal direction X: a longitudinal central region M including an excretory part facing portion (excretion point) facing the wearer's excretory part such as the vaginal opening, a front region F located closer to the wearer's abdomen (front side) than the excretory part facing portion, and a rear region R located closer to the wearer's back (rear side) than the excretory part facing portion. The longitudinal central region M can be the region located in the middle when the napkin 1A in an unfolded and maximally stretched state is divided into three equal parts in the longitudinal direction X.

As shown in FIG. 2, the napkin 1A comprises an absorbent body 4 that absorbs and retains bodily fluids, a liquid-permeable top sheet 2 that is arranged on the skin-facing side of the absorbent body 4 and can come into contact with the wearer's skin, and a leak-proof back sheet 3 that is arranged on the non-skin-facing side of the absorbent body 4.

In this specification, the "skin-facing side" refers to the side of the absorbent article or its constituent member (e.g., absorbent body 4) that faces the wearer's skin when the absorbent article is worn, i.e., the side that is relatively closer to the wearer's skin, and the "non-skin-facing side" refers to the side of the absorbent article or its constituent member that faces the opposite side to the skin when the absorbent article is worn, i.e., the side that is relatively farther from the wearer's skin. Note that "when worn" here refers to the normal, appropriate wearing position, i.e., the state in which the absorbent article is maintained in the correct wearing position.

In the napkin 1A, the absorbent body 4 is composed of an absorbent core 40 mainly made of a water-absorbing material, and a liquid-permeable core wrap sheet 41 covering the outer surface of the absorbent core 40. Examples of the water-absorbing material that can be used include hydrophilic fibers such as pulp fibers, particles of water-absorbing polymers, and mixtures thereof. The absorbent core 40 has a shape that is long in the vertical direction X in a plan view as shown in FIG. 1, and the longitudinal direction of the absorbent core 40 coincides with the vertical direction X of the napkin 1A, and the width direction of the absorbent core 40 coincides with the horizontal direction Y of the napkin 1A. The absorbent core 40 and the core wrap sheet 41 may be bonded together with an adhesive such as a hot melt adhesive. The core wrap sheet 41 may not be required.

As shown in FIG. 2, the top sheet 2 covers the entire skin-facing surface of the absorbent body 4. Meanwhile, the back sheet 3 covers the entire non-skin-facing surface of the absorbent body 4 and further extends outward in the horizontal direction Y from both side edges of the absorbent body 4 along the vertical direction X to form side flap portions 5, 5 together with side sheets 6, which will be described later. The side flap portions 5 are portions of the napkin 1A that are made of members that extend outward in the horizontal direction Y from the absorbent body 4.

The napkin 1A has a pair of wing portions 5W, 5W in the vertical central region M. The wing portions 5W are portions of the side flap portion 5 that extend outward in the horizontal direction Y beyond the peripheral portions. The wing portions 5W are trapezoidal in plan view as shown in FIG. 1, and the length in the vertical direction X gradually decreases from the inside to the outside in the horizontal direction Y. When the napkin 1A is secured to clothing such as shorts, the wing portions 5W are folded back to the outer surface (non-skin-facing surface) of the crotch portion of the clothing.

The napkin 1A has a pair of side sheets 6, 6 which, together with the top sheet 2, form the skin-facing surface of the napkin 1A. The top sheet 2 forms the central region in the lateral direction Y of the skin-facing surface of the napkin 1A, and the side sheets 6 form the side regions of the skin-facing surface of the napkin 1A. The pair of side sheets 6, 6 are each joined to another member (the back sheet 3 in the illustrated embodiment) by a known joining means such as an adhesive at joining lines (not shown) extending in the longitudinal direction X.
As the top sheet 2 and the side sheet 6, various types of sheets conventionally used in absorbent articles such as sanitary napkins can be used without any particular restrictions. As the top sheet 2, a single-layer or multi-layer nonwoven fabric, a perforated film, etc. can be used. As the side sheet 6, a sheet having liquid impermeability (a property that does not allow liquid to pass through at all) or liquid-difficulty permeability (a property that does not necessarily mean that the sheet is liquid impermeable, but does not allow liquid to pass through easily) can be used.

The napkin 1A has a surface 3a facing clothing such as shorts. The facing surface 3a is a fixed surface that is not facing the skin of the backsheet 3, and is the outer surface of the napkin 1A. Adhesives 7 and 8 are attached to the facing surface 3a. The adhesive 7 is disposed in an area of the facing surface 3a that overlaps with the absorbent body 4 in a plan view. The adhesive 8 is disposed in an area of the facing surface 3a that does not overlap with the absorbent body 4, specifically, in the wing portions 5W. Both adhesives 7 and 8 are directly attached to the backsheet 3.
The adhesives 7 and 8 are means for fixing the napkin 1A to clothing, and are covered with a release sheet (not shown) made of film, nonwoven fabric, paper, or the like before use.

As shown in FIG. 1, in the napkin 1A, the adhesive 7 has a long shape in the horizontal direction Y in plan view, specifically a rectangular shape, and is arranged at intervals in the vertical direction X from the front region F to the rear region R of the area overlapping with the absorbent body 4 in plan view, with its longitudinal direction aligned with the horizontal direction Y. The adhesive 8 has a quadrangular shape in plan view, and is arranged on the non-skin-facing surface of the wing portion 5W. Note that, since the wing portion 5W is folded back toward the outer surface of the crotch portion of the garment when in use, the non-skin-facing surface of the wing portion 5W faces the wearer's skin during use (while the napkin 1A is being worn), and becomes the skin-facing surface.

In the absorbent article of the present invention, the arrangement pattern of the adhesives 7, 8 is not limited to the arrangement pattern shown in FIG. 1, and can be set appropriately taking into consideration the function as a fixing means, etc. In the napkin 1B shown in FIG. 3, the adhesive 7 is in the form of a long strip in the vertical direction X in a plan view, and is arranged intermittently in the horizontal direction Y in the area where it overlaps with the absorbent body 4 in a plan view, with its longitudinal direction aligned with the vertical direction X.

The adhesives 7 and 8 may be any adhesive capable of releasably fixing the napkin 1A to clothing such as shorts, and any adhesive conventionally used for such purposes in absorbent articles such as sanitary napkins may be used without any particular restrictions. A preferred example of the adhesives 7 and 8 is a hot melt adhesive containing a styrene elastomer. The base polymer of the hot melt adhesive containing a styrene elastomer may be, for example, a styrene-isoprene-styrene block copolymer (SIS), a styrene-butadiene-styrene block copolymer (SBS), or a styrene-ethylene-butylene-ethylene block copolymer (SEBS), and may be blended with, for example, a hydrogenated petroleum resin as a tackifier and, for example, paraffin oil as a plasticizer for adjusting the melt viscosity. In this composition, the tackifier and the plasticizer correspond to the low molecular weight components of the adhesive. The hot melt adhesive preferably contains a total of 30% by mass or more of the plasticizer and the tackifier, and more preferably contains a total of 40 to 85% by mass. The total amount of paraffin oil and hydrogenated petroleum resin used in the examples described below is within the range of 40 to 85 mass %.
The amount of hot melt adhesive applied to the porous film is preferably, for example, 30 to 100 g/m ² .

The napkins 1A and 1B are absorbent articles that are used by being fixed to clothing, and are characterized in that the back sheet 3, which forms the surface 3a facing the clothing and is a sheet to which the adhesives 7 and 8 are applied, is the porous film of the present invention described above. As described above, the porous film of the present invention contains low-melting point OR and high-melting point OR, and therefore has excellent flexibility, and even if an adhesive is attached, the adhesive strength of the adhesive is unlikely to deteriorate over time. Therefore, the adhesives 7 and 8 attached to the back sheet 3 are unlikely to decrease in adhesive strength over time, and can stably maintain adhesive strength sufficient for practical use for a long period of time. Therefore, the back sheet 3 of the napkins 1A and 1B is flexible, and when used by being fixed to clothing via the adhesives 7 and 8, inconveniences such as slippage, twisting, and turning over are unlikely to occur, and the napkins have excellent wearing comfort and leak prevention properties.

Although the present invention has been described based on the embodiment, the present invention is not limited to the embodiment and can be modified as appropriate.
The absorbent article of the present invention broadly includes articles used to absorb bodily fluids discharged from the human body (menstrual blood, urine, loose stool, sweat, etc.), and includes, in addition to the sanitary napkins mentioned above, panty liners, panty liners, incontinence pads, disposable diapers, etc.

In relation to the above-described embodiment, the present invention further discloses the following porous film and absorbent article.

＜1＞
A porous film comprising an olefin-based resin composition, an inorganic filler, and a fatty acid,
The inorganic filler is contained in an amount of 50 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the olefin-based resin composition, and the fatty acid is contained in an amount of 0.5 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the inorganic filler,
The olefin resin composition is a porous film comprising a first olefin resin having a melting point of 50°C or more and less than 90°C, and a second olefin resin having a melting point of 90°C or more and 108°C or less.
＜2＞
The porous film according to <1>, wherein the melt tension of the porous film measured at 200° C. is 4.0 mN or more.
＜3＞
The porous film according to <1> or <2>, further comprising a branched low-density polyethylene.
＜4＞
<1> to <3>, wherein the density of the first olefin resin is 0.865 g/ ^cm3 or more and less than 0.890 g/ ^cm3 .
＜5＞
<4> The porous film according to any one of <1> to <4>, wherein the density of the second olefin resin is 0.890 g/cm ³ or more and less than 0.915 g/cm ^{3 .}
＜6＞
The porous film according to any one of <1> to <5>, further comprising a triglyceride.
＜７＞
The triglyceride has a ratio (A1/A2) of the mass A1 of the group derived from a saturated fatty acid having 18 to 22 carbon atoms to the mass A2 of the group derived from a saturated fatty acid having 16 carbon atoms of 5 or more. The porous film according to <6>.
＜8＞
The porous film according to any one of <1> to <7>, having a moisture permeability of 0.80 g/(100 ^cm2 ·h) or more and 4.50 g/(100 ^cm2 ·h) or less.
＜9＞
The porous film according to any one of <1> to <8>, having a deformation flexibility of 0.060 N/(mm·(g/m ² )) or less.
＜10＞
The first olefin resin has a melting point of preferably 50°C or more and less than 90°C, more preferably 55°C or more and less than 85°C, and even more preferably 60°C or more and less than 80°C. The porous film according to any one of <1> to <9>.
<11>
The first olefin resin has a density of preferably 0.865 g/cm ³ or more and less than 0.890 g/cm ³ , more preferably 0.870 g/cm ³ or more and 0.889 g/cm ³ or less, and even more preferably 0.875 g/cm ³ or more and 0.888 g/cm ³ or less. The porous film according to any one of <1> to <10>.
＜12＞
<12> The porous film according to any one of <1> to <11>, wherein the first olefin-based resin is a copolymer of ethylene and an α-olefin.
＜13＞
The porous film according to <12>, wherein the first olefin resin is a copolymer of ethylene and an α-olefin polymerized by a metallocene catalyst.
＜14＞
The first olefin resin is preferably contained in an amount of 75 parts by mass or less, more preferably 73 parts by mass or less, and even more preferably 70 parts by mass or less in 100 parts by mass of the olefin resin composition. The porous film according to any one of <1> to <13>.
＜15＞
The first olefin resin is preferably contained in an amount of 30 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more in 100 parts by mass of the olefin resin composition. The porous film according to any one of <1> to <14>.
＜16＞
The second olefin resin has a melting point of preferably 90° C. or higher and 108° C. or lower, more preferably 93° C. or higher and 107° C. or lower, and even more preferably 95° C. or higher and 105° C. or lower. The porous film according to any one of <1> to <15>.
＜１７＞
The difference (M2-M1) between the melting point M1 of the first olefin resin and the melting point M2 of the second olefin resin is preferably 10°C or more and 60°C or less, more preferably 20°C or more and 40°C or less. The porous film according to any one of <1> to <16>.
＜18＞
The density of the second olefin resin is preferably 0.890 g/cm ³ or more and less than 0.915 g/cm ³ , more preferably 0.895 g/cm ³ or more and 0.913 g/cm ³ or less, and even more preferably 0.900 g/cm ³ or more and 0.910 g/cm ³ or less. The porous film according to any one of <1> to <17>.
＜19＞
The porous film according to any one of <1> to <18>, wherein the difference (D2-D1) between the density D1 of the first olefin resin and the melting point D2 of the second olefin resin is preferably 0.005 g/cm ³ or more and 0.040 g/cm ³ or less, more preferably 0.010 g/cm ³ or more and 0.027 g/cm ³ or less.
＜20＞
<19> The porous film according to any one of <1> to <19>, wherein the second olefin-based resin is at least one selected from the group consisting of polyethylene and copolymers of ethylene and α-olefin.
＜21＞
<20> The porous film according to any one of <1> to <20>, wherein the second olefin resin is a linear low-density polyethylene polymerized by a metallocene catalyst.
＜22＞
The second olefin resin is preferably contained in an amount of 15 parts by mass or more, more preferably 18 parts by mass or more, and even more preferably 20 parts by mass or more in 100 parts by mass of the olefin resin composition. The porous film according to any one of <1> to <21>.
＜23＞
The second olefin resin is preferably contained in an amount of 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, per 100 parts by mass of the olefin resin composition. The porous film according to any one of <1> to <22>.
＜24＞
The branched low-density polyethylene has a melting point of preferably 105° C. or more and 120° C. or less, more preferably 105° C. or more and 118° C. or less, and even more preferably 105° C. or more and 115° C. or less. The porous film according to any one of <3> to <23>.
＜25＞
The branched low-density polyethylene has a density of preferably 0.910 g/cm ³ or more and 0.925 g/cm ³ or less, more preferably 0.913 g/cm ³ or more and 0.925 g/cm ³ or less, and even more preferably 0.915 g/cm ³ or more and 0.925 g/cm ³ or less. The porous film according to any one of <3> to <24>.
＜26＞
The porous film according to any one of <1> to <25>, wherein the branched low-density polyethylene is preferably contained in an amount of 3 parts by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 18 parts by mass or less, and even more preferably 8 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the olefin-based resin composition.
＜27＞
The mass ratio (C1+C4)/(C2+C3+C5) is preferably 0.4 or more, more preferably 1.0 or more, and even more preferably 1.2 or more. The porous film according to any one of <3> to <26>.
Here, C1+C4 is the total amount (C1+C4) of the mass C1 of the first olefin resin and the mass C4 of the olefin resin having a melting point lower than the lower limit of the melting point of the first olefin resin,
C2+C3+C5 is the total of the mass C2 of the second olefin resin, the mass C3 of the branched low density polyethylene, and the mass C5 of the olefin resin other than the branched low density polyethylene whose melting point is higher than the upper melting point limit of the second olefin resin.
＜28＞
The triglyceride has a ratio (A1/A2) of the mass A1 of the group derived from a saturated fatty acid having 18 to 22 carbon atoms to the mass A2 of the group derived from a saturated fatty acid having 16 carbon atoms, preferably 1.0 or more, more preferably 5 or more, further preferably 10 or more, particularly preferably 15 or more, and also preferably 99 or less. The porous film according to any one of <1> to <27>.
＜29＞
The porous film according to any one of <6> to <28>, wherein the triglyceride preferably contains 1 to 50 mass% of a group derived from a saturated fatty acid having 16 carbon atoms, more preferably 1 to 30 mass%, of the total amount of groups derived from fatty acids.
＜30＞
In the triglyceride, the mass of the group derived from a saturated fatty acid having 20 to 22 carbon atoms is preferably 0 to 10 mass%, more preferably 1 to 10 mass%, and even more preferably 1 to 5 mass%, of the total amount of the groups derived from the fatty acid. The porous film according to any one of <6> to <29>.
＜31＞
The porous film according to any one of <6> to <30>, wherein the triglyceride does not contain a group derived from an unsaturated fatty acid.
＜32＞
The content of the triglyceride is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1.0 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the olefin-based resin composition. The porous film according to any one of <6> to <31>.
＜33＞
The porous film according to any one of <1> to <32>, further comprising a pore opening promoter in addition to the olefin resin composition, the inorganic filler, and the fatty acid.
＜34＞
An absorbent article comprising the porous film according to any one of <1> to <33>.
＜35＞
The absorbent article according to <34>, which is an absorbent article to be fixed to clothing, and has an adhesive applied to a surface facing the clothing, and the surface facing the clothing is made of the porous film.
＜36＞
<35> The pressure-sensitive adhesive is a hot-melt pressure-sensitive adhesive containing a styrene-based elastomer.
The absorbent article according to claim 1.

The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "parts" means "parts by mass."

[Examples 1 to 3, Comparative Examples 1 to 5]
A porous film was produced by the following procedure.
(1) Production of Compound Except for Comparative Examples 1 and 5 in Table 1 below, 100 parts of an olefin-based resin composition having the composition shown in the column "Olefin-based resin composition (parts)" was weighed out, 2.69 parts of a triglyceride shown in Table 1 (per 100 parts of the olefin-based resin composition), 158.25 parts of an inorganic filler (per 100 parts of the olefin-based resin composition), 1.52 parts of a fatty acid (per 100 parts of the inorganic filler), and 0.26 parts of an antioxidant (per 100 parts of the olefin-based resin composition) were weighed out.
For Comparative Example 1 in Table 1, 100 parts of an olefin-based resin composition having the composition shown in the "Olefin-based resin composition (parts)" column, 2.84 parts of triglyceride shown in Table 1 (per 100 parts of the olefin-based resin composition), 167.22 parts of inorganic filler (per 100 parts of the olefin-based resin composition), 1.52 parts of fatty acid (per 100 parts of the inorganic filler), and 0.26 parts of antioxidant (per 100 parts of the olefin-based resin composition) were weighed out.
For Comparative Example 5, 100 parts of an olefin-based resin composition having the composition shown in the "Olefin-based resin composition (parts)" column, 93.38 parts of an inorganic filler shown in Table 1 (per 100 parts of the olefin-based resin composition), 1.53 parts of a fatty acid (per 100 parts of the inorganic filler), and 0.19 parts of an antioxidant (per 100 parts of the olefin-based resin composition) were weighed out.

Details of the resins listed in Table 1 are shown below.
Olefin resin 1: Ethylene-α-olefin copolymer having a melting point of 41° C.: a copolymer of ethylene and 1-butene produced with a metallocene catalyst (density 0.864 g/cm ³ )
Low melting point OR1: Ethylene-α-olefin copolymer with a melting point of 50° C.: a copolymer of ethylene and 1-butene produced with a metallocene catalyst (density 0.870 g/cm ³ )
Low melting point OR2: Ethylene-α-olefin copolymer with a melting point of 71° C.: a copolymer of ethylene and 1-butene produced with a metallocene catalyst (density 0.885 g/cm ³ )
Low melting point OR3: Ethylene-α-olefin copolymer with a melting point of 80° C.: a copolymer of ethylene and 1-butene produced with a metallocene catalyst (density 0.885 g/cm ³ )

High melting point OR1: Linear low density polyethylene with a melting point of 102°C: a copolymer of ethylene and 1-hexene produced with a metallocene catalyst (density 0.903 g/cm ³ )
High melting point OR2: Linear low density polyethylene with a melting point of 108°C: a copolymer of ethylene and 1-hexene produced with a metallocene catalyst (density 0.913 g/cm ³ )
Branched low density polyethylene (LDPE): High pressure low density polyethylene by radical polymerization with a melting point of 109°C, density 0.923g/cm3 ⁾
Olefin resin 2: Linear low-density polyethylene with a melting point of 116°C: a copolymer of ethylene and 1-hexene produced with a metallocene catalyst (density 0.924 g/cm ³ )

Inorganic filler: calcium carbonate (average particle size _D50 is 1.8 μm)
・Fatty acid: stearic acid ・Water repellent (triglyceride)
Triglyceride A: Rapeseed extremely hardened oil (among the constituent fatty acids, the proportion of saturated fatty acids having 16 carbon atoms is 4% by mass, the proportion of saturated fatty acids having 18 carbon atoms is 93% by mass, the proportion of saturated fatty acids having 20 carbon atoms is 2% by mass, and the proportion of saturated fatty acids having 22 carbon atoms is 1% by mass)
Triglyceride B: Hardened palm oil (among the constituent fatty acids, the proportion of saturated fatty acids with 14 carbon atoms is 1 mass%, the proportion of saturated fatty acids with 16 carbon atoms is 42 mass%, and the proportion of saturated fatty acids with 18 carbon atoms is 57 mass%)

These were mixed in a Henschel mixer (manufactured by Kawata Co., Ltd.) The obtained mixture was kneaded using a twin-screw extruder under conditions of a set temperature of 180° C. and a screw rotation speed of 180 rpm, to obtain a pelletized compound.
(2) Production of resin sheet A film was formed from the compound using a T-die having a width of 400 mm and a slit clearance of 1.0 mm at the die discharge part. The molding conditions for Examples 1 to 3 and Comparative Examples 1 to 5 were a T-die set temperature of 200° C. and a cast roll peripheral speed of 20 m/min.
(3) Production of Porous Film The film was uniaxially stretched in the machine direction using a roll stretching machine. The stretching ratio and stretching temperature are shown in the table.
In addition, as a measure against thermal shrinkage in the stretching direction of the porous film, heat setting (annealing) was performed after stretching. The stretched film was heated by a heated roll (annealing roll). The draw ratio in the annealing roll (film conveying speed immediately after annealing treatment/film conveying speed immediately before the annealing roll) was set to less than 1, and the porous film was thermally shrunk in the stretching direction in the stretching process. The shrinkage ratio (film conveying speed immediately after annealing treatment/film conveying speed immediately before the annealing roll) is shown in Table 1.

[Evaluation test]
For the porous films of each Example and Comparative Example, the deformation flexibility in the machine direction and the moisture permeability were measured by the above-mentioned methods. In addition, for the porous films of each Example and Comparative Example, the blocking property and the adhesion after storage were evaluated by the following methods, and the melt tension was measured. The results are shown in Table 1.

<Method for evaluating blocking properties>
Two pieces of porous film were cut out from the porous film to be measured, 30 mm in the width direction and 150 mm in the machine direction. The cut porous film was laminated in two, and a region of 100 mm from one end in the machine direction was pressed at 0.95 MPa for 20 seconds with a lab press (manufactured by Toyo Seiki Co., Ltd.) heated to 50 ° C. to obtain a measurement sample. When pressing, a silicon plate with a thickness of about 1.0 mm was sandwiched between the two laminated porous films and the press plate of the lab press so that the entire porous film could be pressed uniformly. Note that the silicon plate was left on the press plate of the lab press for 1 minute before pressing the two laminated porous films, and preheated. The obtained measurement sample was cooled at room temperature. The measurement sample was subjected to a T-peel test using a tensile tester (product name: AG-1S, manufactured by Shimadzu Corporation), and the maximum peel strength at that time was read. For each type of porous film to be measured, prepare three samples as described above, measure the maximum peel strength for each sample by the above procedure, and take the average of these three measurements as the inter-film peel strength (blocking property) of the porous film to be measured. The smaller the inter-film peel strength, the smaller the degree of blocking. The conditions of the tensile tester are: chuck distance 30 mm, peel speed 200 mm/min, and atmospheric temperature 24°C.

<Method for measuring adhesive strength after storage>
(1. Preparation of Composite Film)
A composite film to be used for measuring the post-storage adhesive strength described below was prepared by the following procedure: A hot-melt adhesive containing a styrene-based elastomer was applied in a predetermined pattern to the release-treated surface of a release film, and the release film and the porous film to be measured were integrated via the adhesive to prepare a composite film.
As the release film, "One-sided release film PET25 2010" manufactured by Lintec Corporation was used. As the adhesive, a hot melt type adhesive was used, which uses a styrene-butadiene copolymer as a base polymer, and is blended with hydrogenated petroleum resin as a tackifier and paraffin oil as a plasticizer for adjusting the melt viscosity. In this composition, the hydrogenated petroleum resin and the paraffin oil correspond to the low molecular weight components of the adhesive. The coating pattern of the adhesive was such that the coated and non-coated parts of the adhesive were alternately arranged in the machine direction (MD) of the release film, and the coated and non-coated parts each had a length of 2 mm in the MD and extended over the entire length of the release film in the direction (CD) perpendicular to the MD. The coating amount of the coated part was 50 g/ ^m2 .
The release film and the porous film were integrated by the following procedure. That is, the release film was placed with its adhesive coated surface facing up, and the porous film to be measured was placed on the adhesive coated surface so that the MD/CD of the release film and the MD/CD of the porous film were aligned. Then, the rubber roller was moved along the MD of the porous film while contacting the circumferential surface of the rubber roller with the upper surface of the porous film (the surface opposite to the surface facing the release film), and the release film and the porous film were integrated via the adhesive to obtain the target composite film. By such an integration operation, the adhesive coated on the release film was transferred to the porous film while maintaining the coating pattern. The rubber roller was moved back and forth once on the upper surface of the porous film in the MD, and the linear pressure of the rubber roller was 800 N/m and the moving speed of the rubber roller was 5 mm/sec.

(2. Measurement of adhesive strength after storage)
The composite film was allowed to stand for one week in a thermostatic chamber with an internal temperature of 50° C. Then, an adhesive tape (Nichiban Co., Ltd., Cellotape (registered trademark), No. 405) was applied to the entire area of the uncoated surface of the adhesive in the composite film, and the composite film was allowed to stand for 10 minutes in an environment with an atmospheric temperature of 40° C., and then a rectangular shape in plan view with an MD length of 120 mm and a CD length of 20 mm was cut out from the composite film to prepare a measurement sample precursor.
Next, the measurement sample precursor was left to stand in an environment of 24°C and 50%RH for 30 minutes, and then the release film was peeled off from the measurement sample precursor, and in the same environment, a cotton cloth (Kanakin No. 3) was attached to the transfer surface of the adhesive in the porous film constituting the measurement sample precursor (the surface facing the release film) using a rubber roller to obtain a measurement sample. In the attachment of the cotton cloth, the rubber roller was moved back and forth in the MD of the porous film, and the linear pressure of the rubber roller was 300N/m and the moving speed of the rubber roller was 10mm/sec.
Then, using a tensile tester in an environment of an atmospheric temperature of 24°C and a relative humidity of 50% RH, the porous film and the cotton cloth in the measurement sample were T-shaped peeled along the MD of the porous film at a peeling speed of 5 mm/sec, and the peeling force at that time was measured. In the measurement sample, the adhesive-coated part with a length of 2 mm in the MD and the non-adhesive part with a length of 2 mm in the MD are alternately arranged in the MD, so that in the T-shaped peeling, a peak value of the peeling force appears every 2 mm. The five-point average value of the peak value of the peeling force is taken as the adhesive force of the measurement sample. For each type of porous film to be measured, three measurement samples were prepared, and the adhesive force of each was measured by the above procedure, and the average value of the three measured values was taken as the adhesive force after storage of the porous film to be measured. The larger the value of the adhesive force after storage, the less likely the adhesive force of the adhesive to deteriorate over time, and the higher the evaluation.

<Melt tension test>
[Melt tension measurement conditions]
The strand extruded from the capillary having a cylinder and a die at a constant extrusion speed was taken up at a predetermined speed through a load cell with a pulley, and the load value of the load cell was read. The porous film sample was cut into 30 g of 1.0 cm square and filled into a cylinder. The average value of the measurement number n=5 was taken as the melt tension. The specific conditions were as follows.
Measuring device: Capillograph (manufactured by Toyo Seiki Seisakusho Co., Ltd.)
Measurement temperature: 200°C (cylinder and die)
Die outlet hole: diameter 1.0 mm
Die flow path length: 10 mm
Cylinder diameter: 95mm
Cylinder extrusion speed: 10 mm/min
Take-up roller rotation speed: 10 m/min
Measurement range: average melt tension within the reading section The reading section was set between 5 seconds and 10 seconds.

[Degree of liquid seepage]
A porous film cut to 50 mm in the machine direction and 35 mm in the width direction was placed on a filter paper (No. 2, diameter 70 mm, manufactured by Advantec Toyo Co., Ltd.). A dry pulp sheet (Lead Healthy Cooking Paper Double (product name), basis weight 40 g/ ^m2 , manufactured by Lion Corporation) cut to 3 cm x 2.5 cm was placed on the porous film.
0.265 g of a wetting tension test liquid (surface tension at 25° C.: 35 mN/m, manufactured by Kanto Chemical Co., Ltd.) was poured into the center of the dry pulp sheet using a dropper. After the pouring, a cylindrical acrylic plate with a diameter of 60 mm and a thickness of 5 mm was placed on top of the sheet, and a 500 g weight was placed on top of the plate to apply pressure for 1 hour.
After one hour had passed, the weight was removed and the degree of seepage of the liquid into the filter paper was visually observed to judge whether or not there was any seepage. This evaluation was carried out three times for each level, and the degree of seepage was evaluated according to the following criteria.
No bleeding: No bleeding was observed on all three pieces of filter paper.
Bleeding: Bleeding is observed even on one sheet.

As shown in Table 1, the porous films of each Example have low blocking properties, high adhesive strength after storage, and excellent moisture permeability and flexibility. On the other hand, Comparative Examples 1, 3, and 4, which use an olefin resin with a melting point lower than that of the low melting point OR instead of the low melting point OR used in the present invention, have high blocking properties. In particular, in Comparative Example 1, the adhesive strength of the hot melt adhesive after high temperature storage is reduced.
Even if a low melting point OR is used as in Comparative Example 2, if the melting point of the olefin resin combined with the low melting point OR is higher than the high melting point OR used in the present invention, the moisture permeability is poor. Furthermore, when only one type of olefin resin is used as in Comparative Example 5, it is not possible to obtain good flexibility, moisture permeability, inhibition of blocking property, and adhesion after storage.
Therefore, according to the present invention, it is possible to obtain a porous film that is excellent in moisture permeability and flexibility, and that suppresses the occurrence of blocking even after storage at high temperatures in the form of a rolled raw film. Furthermore, by using the porous film, it is possible to obtain an absorbent article that is excellent in wearing comfort and leak prevention, and is less likely to suffer from problems such as slippage when fixed to clothing even after storage at high temperatures.

1A, 1B Sanitary napkins (absorbent articles)
2 Surface sheet 3 Back sheet 3a Surface facing clothing 4 Absorbent bodies 7, 8 Adhesive

Claims (12)

A porous film comprising an olefin-based resin composition, an inorganic filler, and a fatty acid,
The inorganic filler is contained in an amount of 50 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the olefin-based resin composition, and the fatty acid is contained in an amount of 0.5 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the inorganic filler,
The olefin resin composition is a porous film comprising a first olefin resin having a melting point of 50°C or more and less than 90°C, and a second olefin resin having a melting point of 90°C or more and 108°C or less. The porous film according to claim 1, wherein the melt tension of the porous film is 4.0 mN or more when measured at 200°C. The porous film according to claim 1 or 2, further comprising a branched low-density polyethylene. The porous film according to any one of claims 1 to 3, wherein the density of the first olefin resin is 0.865 g/ ^cm3 or more and less than 0.890 g/ ^cm3 . The porous film according to any one of claims 1 to 4, wherein the density of the second olefin resin is 0.890 g/ ^cm3 or more and less than 0.915 g/ ^cm3 . The porous film according to any one of claims 1 to 5, which contains a triglyceride. The porous film according to claim 6, wherein the triglyceride has a ratio (A1/A2) of the mass A1 of the group derived from a saturated fatty acid having 18 to 22 carbon atoms to the mass A2 of the group derived from a saturated fatty acid having 16 carbon atoms, that is 5 or more. The porous film according to any one of claims 1 to 7, having a moisture permeability of 0.80 g/(100 ^cm2 ·h) or more and 4.5 g/(100 ^cm2 ·h) or less. The porous film according to any one of claims 1 to 8, having a deformation flexibility of 0.060 N/(mm·(g/m ² )) or less. An absorbent article comprising the porous film according to any one of claims 1 to 9. The absorbent article according to claim 10, which is used by being fixed to clothing, has an adhesive applied to the surface facing the clothing, and the surface facing the clothing is made of the porous film. The absorbent article according to claim 11, wherein the pressure sensitive adhesive is a hot melt type pressure sensitive adhesive containing a styrene-based elastomer.

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