Porous film, method for manufacturing the same, and absorbent article provided with the same

Abstract

A porous film contains an olefin-based resin composition, an inorganic filler, a metal soap, and a fatty acid. The inorganic filler is contained at 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. The metal soap is contained at 0.5 parts by mass or more and 15 parts by mass or less relative to 100 parts by mass of the inorganic filler. The fatty acid is contained at 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-based resin composition contains a low-melting-point olefin-based resin. The metal soap has a melting point of 200°C or lower. The precipitation temperature of the metal soap is higher than the solidification temperature of the olefin-based resin composition.

Description

Technical Field

[0001] This invention relates to a porous membrane. Furthermore, this invention relates to a method for manufacturing a porous membrane and an absorbent article having the same. Background Technology

[0002] Porous membranes with high water pressure resistance and moisture permeability are known. These porous membranes are typically manufactured by uniaxially or biaxially stretching a resin membrane containing fillers and additives to form multiple micropores.

[0003] For example, Patent Document 1 describes a porous membrane comprising linear low-density polyethylene, branched low-density polyethylene, a filler, and a dispersant thereof. The dispersant is used to improve the uniform dispersion of the filler; specific examples include zinc stearate and calcium stearate.

[0004] Patent document 2 describes a porous membrane comprising polyolefin, barium sulfate, and zinc fatty acid. Zinc fatty acid is used to improve the dispersibility of barium sulfate.

[0005] Patent document 3 describes a porous membrane comprising crystalline low-density polyethylene containing α-olefin comonomers and an inorganic filler. The crystalline low-density polyethylene is used to impart elasticity to the porous membrane.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 01-144432

[0009] Patent Document 2: Japanese Patent Application Publication No. 11-116714

[0010] Patent Document 3: Japanese Patent Application Publication No. 2000-001557 Summary of the Invention

[0011] This invention provides a porous membrane comprising an olefinic resin composition, an inorganic filler, a metal soap, and fatty acids, and

[0012] The composition comprises an inorganic filler comprising 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap comprising 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid comprising 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler.

[0013] The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C.

[0014] The melting point of the metal soap is below 200°C.

[0015] The precipitation temperature of the metal soap is higher than the curing temperature of the olefin resin composition.

[0016] In addition, the present invention provides an absorbent article having the aforementioned porous membrane.

[0017] Furthermore, the present invention provides a method for manufacturing a porous membrane, comprising the following steps: melt-forming a composite comprising an olefinic resin composition, an inorganic filler, a metal soap, and a fatty acid to form a resin sheet, and stretching the resin sheet at least along a uniaxial direction.

[0018] The stretching is performed at a temperature above 30°C and below 100°C at a stretching ratio of 1.1 to 5.0 times.

[0019] The porous membrane comprises an inorganic filler in an amount of 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap in an amount of 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid in an amount of 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler.

[0020] The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C.

[0021] The melting point of the metal soap is below 200°C.

[0022] The precipitation temperature of the metal soap is higher than the curing temperature of the olefin resin composition. Detailed Implementation

[0023] Porous membranes are widely used as backing sheets for absorbent articles, primarily disposable diapers. To address the increasing demand for softer absorbent articles in recent years, backing sheets also require softening. Specifically, a backing sheet with low load-bearing capacity for deformation is needed. Softening of porous membranes used as backing sheets can be achieved, for example, by reducing the density of the resin constituting the porous membrane.

[0024] However, when using low-density resins, it is sometimes difficult to form micropores smoothly through stretching the resin film containing fillers. The reason is that low-density resins are soft, and when the resin film is stretched, interfacial delamination between the resin and the filler is not easily achieved.

[0025] Therefore, the present invention relates to a porous membrane that can eliminate the disadvantages of the prior art.

[0026] The present invention will now be described based on its preferred embodiments. The porous membrane of the present invention has a plurality of micropores. The porous membrane of the present invention is permeable to moisture through these micropores. Furthermore, the porous membrane of the present invention has high water resistance and high leak-proof performance. Moreover, the porous membrane of the present invention has high flexibility, requiring a small load for deformation. The porous membrane of the present invention comprises at least an olefin-based resin composition, an inorganic filler, a metal soap as a pore-opening promoter, and a fatty acid as a dispersant for the inorganic filler. In addition to these components, the porous membrane of the present invention may also contain various additives to enhance various properties of the porous membrane.

[0027] In this specification, "olefin resin composition" includes both cases containing only one type of olefin resin and cases containing two or more types of olefin resin. Furthermore, "olefin resin composition" refers to a concept consisting solely of various olefin resins, without any other resins or components other than resins. It should be noted that this does not preclude the inclusion of resins other than olefin resins in the porous membrane of the present invention.

[0028] The olefin-based resin compositions used in this invention are mainly composed of polymers and copolymers of monoolefins such as ethylene, propylene, and butene. Examples include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, and mixtures comprising any two or more of these.

[0029] In terms of imparting the required flexibility to the porous membrane of the present invention, the olefin resin composition used in the present invention preferably has a low density. From this perspective, the density of the olefin resin composition is preferably less than 0.900 g / cm³. 3 More preferably, it is 0.895 g / cm³. 3 The following is a further preferred value: 0.885 g / cm³ 3 the following.

[0030] Furthermore, the density of the olefin-based resin composition used in this invention is preferably 0.840 g / cm³. 3 The porous membrane of the present invention is less prone to adhesion, and more preferably has a density of 0.850 g / cm³. 3 The above is further preferred to be 0.860 g / cm³. 3 above.

[0031] In summary, the preferred density of the olefin-based resin composition is 0.840 g / cm³. 3 Above and less than 0.900 g / cm 3 More preferably, it is 0.850 g / cm³. 3 Above and 0.895 g / cm 3 The following is a further preferred value: 0.860 g / cm³ 3Above and 0.885 g / cm 3 the following.

[0032] To ensure the density of the olefin resin composition falls within the specified range, the olefin resin composition preferably comprises a low-melting-point olefin resin. Furthermore, the low-melting-point olefin resin is also used to impart flexibility to the porous membrane of the present invention. The low-melting-point olefin resin 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, and 1-hexene. In particular, copolymers of ethylene and α-olefins polymerized using a metallocene catalyst are more preferred as they further enhance the membrane's strength against tearing, puncture, etc.

[0033] From the viewpoint of imparting flexibility to the porous membrane of the present invention, the melting point of the low-melting-point olefin resin is preferably less than 90°C, more preferably less than 80°C, and even more preferably less than 70°C. Furthermore, to obtain morphological stability of the porous membrane, the melting point of the low-melting-point olefin resin is preferably 40°C or higher. The melting point of the low-melting-point olefin resin contained in the porous membrane with a melting point less than 90°C was determined by the following method. Approximately 2.0 mg of the porous membrane was used as a sample, and differential scanning calorimetry (DSC) was performed using a differential scanning calorimeter (DSC7000X, manufactured by Hitachi Advanced Technology & Science Co., Ltd.) under conditions of a measurement temperature range of 10°C to 260°C, a heating rate of 10°C / min, and an air environment. In the obtained DSC curve, an endothermic peak generated during the melting of the low-melting-point olefin resin was observed in the temperature region below 90°C, and the melting point of the low-melting-point olefin resin was the temperature at the peak of the observed endothermic peak.

[0034] It should be noted that the melting points of additives contained in porous membranes and low-melting-point olefin resins can be distinguished by collecting the additives that have seeped out of the porous membrane and measuring their melting points. The following methods can be used to efficiently collect additives from porous membranes.

[0035] First, a resin block was obtained by mixing the porous membrane at 160°C and 30 rpm for 10 minutes using a Labo Plastomill (manufactured by Toyo Seiki).

[0036] Then, using a Labo Press (manufactured by Toyo Seiki), the resin block is pressurized at 150°C and 13MPa for 1 minute, and then cooled and pressurized at room temperature and 13MPa for 1 minute to obtain a pressed film with a thickness of about 0.5mm.

[0037] Finally, the pressed membrane was stored at 50°C for one week. As a result, more additives seeped from the surface of the pressed membrane compared to a porous membrane, allowing for efficient additive collection. Methods for collecting additives from the pressed membrane surface include wiping with a cloth and scraping with a spatula.

[0038] From the viewpoint of further imparting flexibility to the porous membrane of the present invention, the density of the low-melting-point olefin resin is preferably 0.895 g / cm³. 3 The preferred value is 0.885 g / cm³. 3 The following is a further preferred value: 0.875 g / cm³ 3 From the viewpoint of maintaining the strength of porous membranes, the density of the low-melting-point olefin resin is preferably 0.840 g / cm³. 3 The above, more preferably 0.850 g / cm³ 3 The above is further preferred to be 0.860 g / cm³. 3 above.

[0039] In order to ensure that the low-melting-point olefin resin takes into account both the preferred density range and the preferred melting point range, the low-melting-point olefin resin is preferably a random copolymer.

[0040] In terms of imparting the required flexibility to the porous membrane of the present invention and minimizing residual strain after elongation deformation, the olefin resin composition used in the present invention preferably contains 30 or more parts by weight of the low-melting-point olefin resin in 100 parts by weight of the olefin resin composition. To further enhance this advantage, the low-melting-point olefin resin is more preferably contained in 35 or more parts by weight of the olefin resin composition in 100 parts by weight, and even more preferably in 40 or more parts by weight.

[0041] Furthermore, regarding the aspect that the porous membrane of the present invention is less prone to adhesion, the olefin resin composition used in the present invention preferably contains 95 parts by weight or less of the low-melting-point olefin resin in 100 parts by weight of the olefin resin composition. To make this advantage even more significant, the low-melting-point olefin resin is more preferably contained in 92 parts by weight or less in 100 parts by weight of the olefin resin composition, and even more preferably in 90 parts by weight or less.

[0042] In summary, the olefin resin composition used in this invention preferably contains 30 or more but less than 95 parts by mass of the low-melting-point olefin resin in 100 parts by mass, more preferably 35 or more but less than 92 parts by mass, and even more preferably 40 or more but less than 90 parts by mass.

[0043] In terms of further imparting heat resistance, morphological stability, and processability to the porous membrane of the present invention, the olefin resin composition used in the present invention preferably includes a high-melting-point olefin resin in addition to the aforementioned low-melting-point olefin resin. From the viewpoint of balancing the flexibility of the porous membrane, the density of the high-melting-point olefin resin is preferably relatively low, specifically, preferably 0.950 g / cm³. 3 The preferred value is 0.940 g / cm³. 3 The following is a further preferred value: 0.930 g / cm³ 3 the following.

[0044] Furthermore, from the viewpoint of minimizing adhesion, the density of the high-melting-point olefin resin is preferably 0.900 g / cm³. 3 The above, more preferably 0.905 g / cm³ 3 The above is further preferred to be 0.910 g / cm³. 3 above.

[0045] In summary, the preferred density of the high-melting-point olefin resin is 0.900 g / cm³. 3 Above and 0.950 g / cm 3 The following is more preferably 0.905 g / cm³. 3 Above and 0.940 g / cm 3 The following is a further preferred value: 0.910 g / cm³ 3 Above and 0.930 g / cm 3 the following.

[0046] The high-melting-point olefin resin having the aforementioned density is preferably polyethylene such as low-density polyethylene or linear low-density polyethylene, especially linear low-density polyethylene, which is preferred because its heat resistance during stretching is improved and it can be stretched uniformly. In particular, linear low-density polyethylene polymerized with a metallocene catalyst further improves the strength of the film against tearing, puncture, etc., and is therefore more preferred.

[0047] Metallocene catalysts are composed of metallocenes combined with cocatalysts such as aluminum compounds. The metallocenes are compounds with structures in which transition metals such as titanium, zirconium, and hafnium are encapsulated within unsaturated cyclic compounds containing π-electron groups or substituted cyclopentadienyl groups. Examples of metallocenes include titanocerocene and zirconium diacerocene. Examples of aluminum compounds include alkylaluminoxanes, alkylaluminum compounds, aluminum halides, and alkylaluminum halides.

[0048] In terms of further imparting heat resistance, morphological stability, and processability to the porous membrane, the olefin resin composition used in this invention preferably contains 5 or more parts by mass of a high-melting-point olefin resin having the aforementioned density, per 100 parts by mass of the olefin resin composition. To make this advantage even more pronounced, the high-melting-point olefin resin more preferably contains 8 or more parts by mass of the high-melting-point olefin resin per 100 parts by mass of the olefin resin composition, and even more preferably contains 10 or more parts by mass.

[0049] Furthermore, from the viewpoint of also maintaining the flexibility of the porous membrane, the olefin resin composition used in this invention preferably contains 70 parts by weight or less of the high-melting-point olefin resin in 100 parts by weight of the olefin resin composition. From the viewpoint of making this advantage even more significant, the high-melting-point olefin resin more preferably contains 65 parts by weight or less in 100 parts by weight of the olefin resin composition, and even more preferably contains 60 parts by weight or less.

[0050] In summary, the olefin resin composition used in this invention preferably contains 5 or more and 70 or less of a high-melting-point olefin resin having the aforementioned density in 100 parts by weight of the olefin resin composition, more preferably 8 or more and 65 or less by weight, and even more preferably 10 or more and 60 or less by weight.

[0051] To achieve high-speed molding of the porous membrane to be melt-formed and to enable short-time curing, the melting point of the high-melting-point olefin resin used in this invention is preferably 95°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. The melting point of the high-melting-point olefin resin contained in the porous membrane is determined by the following method: Approximately 2.0 mg of the porous membrane is used as a sample, and differential scanning calorimetry (DSC) is performed using a differential scanning calorimeter (DSC7000X, manufactured by Hitachi Advanced Technology & Science Co., Ltd.) under conditions of a measurement temperature range of 10°C to 260°C, a heating rate of 10°C / min, and an air environment. An endothermic peak generated during the melting of the high-melting-point olefin resin is observed in the temperature region above 95°C of the obtained DSC curve; the apex of this endothermic peak is the melting point of the high-melting-point olefin resin. It should be noted that the method for distinguishing the additives contained in the porous membrane from the high-melting-point olefin resin is the same as the method for distinguishing the additives contained in the porous membrane from the low-melting-point olefin resin.

[0052] As a preferred embodiment of the present invention, an example is provided: the olefin-based resin composition comprises an ethylene-α-olefin copolymer polymerized with a metallocene catalyst as a low-melting-point polyethylene resin, and a linear low-density polyethylene polymerized with a metallocene catalyst as a high-melting-point polyethylene resin. The porous membrane of this embodiment exhibits very high flexibility. Furthermore, by using it in conjunction with a metal soap as a pore-opening promoter, the porous membrane achieves very high moisture permeability and leak-proof properties.

[0053] The metal soap used in this invention as a pore-opening promoter is used to smoothly stretch a resin film containing an olefin resin composition and an inorganic filler to generate micropores. As described above, by making the olefin resin composition low-density, the porous membrane of this invention can be given flexibility, but low-density olefin resins tend to have a tendency to easily delaminate between the olefin resin composition and the inorganic filler. Therefore, in this invention, metal soap as a pore-opening promoter is used to promote the delamination between the olefin resin composition and the inorganic filler. As can be seen from the comparison between Comparative Example 1 and Comparative Example 3 below, even when metal soap is added to a high-density olefin resin composition, i.e., a hard olefin resin composition, the formation of micropores does not change. That is, the use of metal soap is effective for the formation of micropores only when a low-density, i.e., a soft olefin resin composition is used as the olefin resin composition.

[0054] As a metallic soap, metal salts of saturated or unsaturated fatty acids are preferred. Examples of fatty acids include caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, and lauric acid. Examples of metal salts include calcium, aluminum, magnesium, and zinc salts of these fatty acids.

[0055] Fatty acids themselves are known as substances similar to metal salts of fatty acids that can bind to porous membranes. As described below, fatty acids are used to improve the dispersibility of inorganic fillers. However, fatty acids do not have the function of promoting interfacial delamination between olefin-based resin compositions and inorganic fillers. Therefore, in this invention, metal salts of fatty acids are clearly distinguished from fatty acids in both substance and function.

[0056] From the viewpoint that the metal soap is fully melted and uniformly mixed in the molten resin during the compound mixing process in the manufacturing process of the porous membrane of the present invention, it is particularly preferable to use a metal soap with a melting point of 200°C or less. From this viewpoint, it is more preferable that the melting point of the metal soap is 180°C or less, and even more preferably 160°C or less.

[0057] Furthermore, regarding the metal soap, from the viewpoint that it can readily form micropores and obtain a porous membrane with high moisture permeability and high water resistance due to its relationship with the olefin resin composition, it is preferable to use a metal soap whose precipitation temperature is higher than the curing temperature of the olefin resin composition. Specifically, by setting the precipitation temperature of the metal soap higher than the curing temperature of the olefin resin composition, the metal soap precipitates faster than the curing temperature of the olefin resin composition, thus allowing it to readily transfer to the surface of the inorganic filler. As a result, the exfoliation properties between the inorganic filler and the olefin resin composition are good during stretching, and micropores are readily formed. From the viewpoint of further enhancing this advantage, when the precipitation temperature of the metal soap is set to Ts (°C) and the curing temperature of the olefin resin composition is set to Tp (°C), the value of Ts-Tp is preferably greater than 0°C, more preferably 1°C or more, and even more preferably 2°C or more. Furthermore, the value of Ts-Tp is preferably 50°C or less.

[0058] With the Ts-Tp value within the aforementioned range, the precipitation temperature Ts of the metal soap is preferably 80°C or higher and 180°C or lower, more preferably 90°C or higher and 170°C or lower, and even more preferably 100°C or higher and 160°C or lower.

[0059] On the other hand, provided that the Ts-Tp values ​​are within the aforementioned range, the curing temperature Tp of the olefin resin composition is preferably 60°C or higher and 130°C or lower, more preferably 70°C or higher and 120°C or lower, and even more preferably 80°C or higher and 115°C or lower.

[0060] The precipitation temperature Ts of the metallic soap was determined using a heating stirrer and thermocouples as follows: Using a heating stirrer, 0.43 g of metallic soap was added to 5.0 g of paraffin oil, and heated while stirring until the metallic soap dissolved. After stopping stirring, the temperature of the paraffin oil was decreased at a rate of 0.2 °C / min. The temperature of the paraffin oil at the point of precipitation was read using a thermocouple, and this temperature was taken as the precipitation temperature of the metallic soap. It should be noted that if the metallic soap does not dissolve in the paraffin oil even when heated to 210 °C, the precipitation temperature is defined as 210 °C.

[0061] On the other hand, the curing temperature Tp of the olefin resin composition was determined according to JIS K 7121 (method for extrapolating the end of crystallization temperature) and by the following method. Approximately 2.0 mg of porous membrane was used as a sample, and differential scanning calorimetry (DSC) was performed using a DSC7000X (manufactured by Hitachi Advanced Technology & Science Co., Ltd.) under the following conditions: a measurement temperature range of 30°C to 260°C, a heating rate of 10°C / min, a cooling rate of 50°C / min, in air, and a data sampling period of 0.5 s. The heat peak generated during the curing (crystallization) of the olefin resin composition was observed during the cooling process of the obtained DSC curve. The curing temperature of the olefin resin composition is the temperature at the intersection of a straight line drawn from the baseline on the lower side of the peak (where the heat generated during cooling is the greatest) extended towards the higher side, and an approximate straight line drawn between the two points with the steepest slope on the curve on the lower side of the peak. In cases where there are two or more overlapping heating peaks, the curing temperature can be determined by the method described above after peak separation, for example using software PeakFIT v4.12 (manufactured by HULINKS Inc.).

[0062] In the porous membrane of the present invention, in terms of the ability to smoothly generate micropores, it is preferable to include 0.5 parts by weight or more of metal soap relative to 100 parts by weight of the olefin resin composition. From the viewpoint of making this advantage even more significant, it is more preferable to include 1.0 parts by weight or more of metal soap relative to 100 parts by weight of the olefin resin composition, and even more preferably 2.0 parts by weight or more.

[0063] Furthermore, in the porous membrane of the present invention, in terms of maintaining good formability, it is preferable to contain 20 parts by weight or less of metal soap relative to 100 parts by weight of the olefin resin composition. From the viewpoint of making this advantage even more significant, it is more preferable to contain 15 parts by weight or less of metal soap relative to 100 parts by weight of the olefin resin composition, and even more preferably 10 parts by weight or less.

[0064] In summary, in the porous membrane of the present invention, it is preferable that, relative to 100 parts by weight of the olefinic resin composition, the metal soap comprises 0.5 parts by weight or more and 20 parts by weight or less, more preferably 1.0 parts by weight or more and 15 parts by weight or less, and even more preferably 2.0 parts by weight or more and 10 parts by weight or less.

[0065] The amount of metal soap contained in the porous membrane of the present invention is also related to the amount of inorganic filler contained in the porous membrane. Specifically, in the porous membrane of the present invention, for the purpose of smoothly generating micropores, it is preferable to contain 0.5 parts by mass or more of metal soap relative to 100 parts by mass of inorganic filler. From the viewpoint of making this advantage even more significant, it is more preferable to contain 1.5 parts by mass or more of metal soap relative to 100 parts by mass of inorganic filler, and even more preferably 2.0 parts by mass or more.

[0066] Furthermore, in the porous membrane of the present invention, in terms of maintaining good formability, it is preferable to include 15 parts by weight or less of metal soap relative to 100 parts by weight of inorganic filler. From the viewpoint of making this advantage even more significant, it is more preferable to include 10 parts by weight or less of metal soap relative to 100 parts by weight of inorganic filler, even more preferably 9.0 parts by weight or less, and still even more preferably 8.0 parts by weight or less.

[0067] In summary, in the porous membrane of the present invention, it is preferable that, relative to 100 parts by weight of the inorganic filler, the membrane contains 0.5 parts by weight or more and 15 parts by weight of the metal soap, more preferably 0.5 parts by weight or more and 10 parts by weight, even more preferably 1.5 parts by weight or more and 9.0 parts by weight, and even more preferably 2.0 parts by weight or more and 8.0 parts by weight.

[0068] The inorganic filler used in this invention is a substance that forms micropores by exfoliation at the interface with an olefin-based resin composition. From this perspective, the average particle size D of the inorganic filler... 50 Preferably, the particle size is 30 μm or less, more preferably 10 μm or less, and further preferably 0.5 μm or more, more preferably 1.0 μm or more. The average particle size D of the inorganic filler... 50 It is the cumulative particle size at 50% mass of cumulative weight obtained by laser diffraction particle size distribution determination method.

[0069] 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, aluminum oxide, mica, zeolite, and carbon black, as well as mixtures thereof. In particular, calcium carbonate is preferred for ease of adjustment to the stated particle size.

[0070] In terms of forming a sufficient number of micropores to adequately improve the moisture permeability of the porous membrane, it is preferable that the composition contains 50 parts or more of inorganic filler relative to 100 parts by weight of the olefin resin composition, more preferably 60 parts or more by weight, and even more preferably 80 parts or more by weight.

[0071] Furthermore, from the viewpoint of sufficiently improving the leak-proof properties of the porous membrane, it is preferable that the inorganic filler is 400 parts by weight or less, more preferably 350 parts by weight or less, and even more preferably 200 parts by weight or less, relative to 100 parts by weight of the olefin resin composition.

[0072] The porous membrane of the present invention contains a dispersant for an inorganic filler. As a dispersant, a substance that hydrophobizes the surface of the inorganic filler is preferably used. From this perspective, fatty acids are preferred, for example. Examples of fatty acids include: caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, lauric acid, etc.

[0073] In particular, if the chain length of the hydrocarbon chain in the fatty acid is the same as the chain length of the hydrocarbon chain in the fatty acid constituting the metal soap, the metal soap can be transferred more smoothly to the inorganic filler modified with fatty acid surface, which is therefore preferred. Particularly preferred is that both the fatty acid and the fatty acid constituting the metal soap are stearic acid.

[0074] In terms of improving the dispersibility of the inorganic filler, the porous membrane of the present invention preferably contains at least 0.5 parts by mass of the fatty acid relative to 100 parts by mass of the inorganic filler. From the viewpoint of making this advantage even more significant, it is more preferable to contain at least 0.8 parts by mass of the fatty acid relative to 100 parts by mass of the inorganic filler, and even more preferably at least 1.0 parts by mass.

[0075] Furthermore, in terms of not impairing the formability of the membrane, the porous membrane of the present invention preferably contains the fatty acid at a concentration of 5.0 parts by weight or less relative to 100 parts by weight of the inorganic filler. From the viewpoint of making this advantage even more significant, it is more preferable to contain 4.0 parts by weight or less of the fatty acid relative to 100 parts by weight of the inorganic filler, and even more preferably 3.0 parts by weight or less.

[0076] In summary, the porous membrane of the present invention preferably contains 0.5 parts by mass and 5 parts by mass or less of the fatty acid relative to 100 parts by mass of the inorganic filler, more preferably 0.8 parts by mass and 4.0 parts by mass or less, and even more preferably 1.0 parts by mass and 3.0 parts by mass or less.

[0077] The porous membrane of the present invention may also contain additives. The additives are substances that can impart various additional properties to the porous membrane. Examples of such additives include: plasticizers, water-repellent agents, antioxidants, ultraviolet absorbers, colorants, etc.

[0078] Plasticizers are used to impart softness and elasticity to the porous membrane of the present invention, or to prevent the porous membrane of the present invention from producing a rustling sound. Preferably, monoesters, polyesters, ethylene-α-olefin co-oligomers, low molecular weight polyethylene, olefin oligomers, liquid polyisoprene, liquid polybutadiene, etc., are used as plasticizers.

[0079] Monoesters are compounds obtained from monobasic acids and monohydric alcohols.

[0080] On the other hand, polyester is a compound obtained by any combination of a polybasic acid and a monohydric alcohol, a monohydric acid and a polyhydric alcohol, or a polybasic acid and a polyhydric alcohol.

[0081] Ethylene-α-olefin coolids are low molecular weight copolymers of α-olefins such as propylene, 1-butene, 1-pentene, and 1-hexene with ethylene.

[0082] As the monobasic acid, polybasic acid, monobasic alcohol and polyhydric alcohol, the following are preferred examples.

[0083] Examples of monocarboxylic acids include monocarboxylic acids of long-chain hydrocarbons with 10 to 22 carbon atoms.

[0084] Examples of polycarboxylic acids include dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids.

[0085] Examples of monohydric alcohols include monohydric alcohols of long-chain hydrocarbons with 10 to 22 carbon atoms.

[0086] Examples of polyols include diols, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, and sucrose.

[0087] Examples of particularly preferred polyesters include: polyesters formed by partially or completely capping the carboxylic acids or alcohols at both ends of a polyester of diethylene glycol and dimer acid using stearyl alcohol or stearic acid; polyesters of 1,3-butanediol and adipic acid; hexaesters formed from trimethylolpropane-adipic acid-stearic acid; octaesters formed from pentaerythritol-adipic acid-stearic acid; and dodecaesters formed from dipentaerythritol-adipic acid-stearic acid.

[0088] On the other hand, particularly preferred monoesters include, for example, esters with a total carbon number of 30 or more obtained by dehydration of monocarboxylic acids having 1 to 40 carbon atoms and monools having 1 to 40 carbon atoms. Among these, esters with a total carbon number of 30 or more obtained from monocarboxylic acids and monools are preferred, and monoesters with 38 or more carbon atoms and branched chains are more preferred. Specifically, examples include: isodecyl stearate, isodecyl behenate, isotriadecyl stearate, 2-octadecyl stearate, 2-decyl tetradecyl laurate, 2-decyl tetradecyl stearate, 2-octadecyl behenate, stearyl isostearate, esters of stearic acid and C20 Guerbert alcohol, and esters of α-branched fatty acids (18 to 40 carbon atoms) and monools (6 to 36 carbon atoms).

[0089] Triglycerides are preferably used as water-repellent agents. By using triglycerides, the water resistance and leakage prevention of the porous membrane surface are improved. In the field of porous membrane technology, triglycerides have been conventionally incorporated into porous membranes; however, the type of triglyceride used in this invention is preferably different from that conventionally used triglycerides. Specifically, the triglycerides suitably used in this invention comprise groups derived from fatty acids having 16 or more and 22 or fewer carbon atoms, and these groups are hydrocarbon groups without unsaturated bonds or substituents. The inventors' research results show that by using this triglyceride, the water resistance of the porous membrane surface containing this triglyceride is higher than before, and the leakage prevention of the porous membrane is also higher than before.

[0090] From the viewpoint that the aforementioned advantages are more significant, the amount of triglycerides in the porous membrane 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, relative to 100 parts by mass of the olefin resin composition.

[0091] Furthermore, from the viewpoint of film-forming properties, the amount of triglyceride incorporated is preferably 30 parts by weight or less, more preferably 25 parts by weight or less, and even more preferably 20 parts by weight or less, relative to 100 parts by weight of the olefin resin composition.

[0092] In summary, relative to 100 parts by weight of the olefin resin composition, the amount of the triglyceride is preferably 0.1 parts by weight or more and 30 parts by weight or less, more preferably 0.5 parts by weight or more and 25 parts by weight or less, and even more preferably 1.0 parts by weight or more and 20 parts by weight or less.

[0093] Furthermore, from the viewpoint of fully utilizing both the effects obtained from the metal soap used as a pore-opening promoter and the effects obtained from the water-repellent agent, and from the viewpoint of preventing deterioration of processability due to excessive additive content, the ratio of the triglycerides to the metal soap contained in the porous membrane of the present invention is preferably 30 parts by weight or more and 300 parts by weight or less relative to 100 parts by weight of the metal soap. From the viewpoint of making this advantage even more significant, it is more preferable to use 35 parts by weight or more and 250 parts by weight or less relative to 100 parts by weight of the metal soap, and even more preferably 40 parts by weight or more and 230 parts by weight or less relative to 100 parts by weight of the triglycerides.

[0094] The triglycerides used in this invention are represented by the following formula (1).

[0095] [Chemical Formula 1]

[0096]

[0097] In the formula, R 1 To R 3Indicates the same or different hydrocarbon groups. R 1 To R 3 At least one of the components is preferably a group derived from a fatty acid having 16 or more but less than 22 carbon atoms, and this group is a hydrocarbon group without unsaturated bonds or substituents. It should be noted that the alkyl group of palmitic acid, which is a fatty acid with 16 carbon atoms, has 15 carbon atoms.

[0098] "A hydrocarbon group without unsaturated bonds" refers to a hydrocarbon group that does not have either a carbon-carbon double bond or a triple bond. That is, it is an alkyl group. Furthermore, "a hydrocarbon group without substituents" means that the hydrogen atoms contained in the hydrocarbon group are not replaced by other atoms or groups of atoms (such as hydroxyl groups). Therefore, "a hydrocarbon group without unsaturated bonds and substituents" is synonymous with an unsubstituted alkyl group.

[0099] In the following description, for convenience, the triglycerides used in this invention will also be referred to as "the triglycerides of this invention".

[0100] In the triglycerides represented by formula (1), from the viewpoint of obtaining a porous membrane with higher leak-proof properties, R 1 To R 3 At least one of them is preferably a group derived from a fatty acid having 16 or more and 20 or fewer carbon atoms, and the group is a hydrocarbon group without unsaturated bonds and substituents. More preferably, it is a group derived from a fatty acid having 16 or more and 18 or fewer carbon atoms, and the group is a hydrocarbon group without unsaturated bonds and substituents.

[0101] Furthermore, in the triglycerides represented by formula (1), in R 1 To R 3 If any one or both of them are groups other than those derived from fatty acids with 16 or more but less than 22 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents), the groups can be derived from fatty acids and there is no particular limitation on their type. From the viewpoint of obtaining a porous membrane with higher leak-proof properties, the groups are preferably those without unsaturated bonds and substituents.

[0102] The triglycerides of the present invention preferably have an adjusted carbon number of fatty acid residues. Specifically, the following (a) or (b) are preferred as triglycerides.

[0103] (a) A triglyceride comprising a mixture of a triglyceride containing at least one group (a hydrocarbon group without unsaturated bonds and substituents) of a fatty acid (i.e., palmitic acid) having at least 16 carbon atoms and a triglyceride containing at least one group (a hydrocarbon group without unsaturated bonds and substituents) of a fatty acid (i.e., stearic acid) having at least 18 carbon atoms.

[0104] (b) A triglyceride comprising a molecule containing at least a group derived from a fatty acid with 16 carbon atoms and a group derived from a fatty acid with 18 carbon atoms.

[0105] As shown in case (a), in the case where the triglycerides of the present invention comprise multiple triglycerides, preferably at least one triglyceride contains at least one group derived from a saturated fatty acid having 16 carbon atoms within a molecule (the triglyceride is also referred to as "triglyceride 16"). Triglyceride 16 may contain one group derived from a saturated fatty acid having 16 carbon atoms within a molecule (the triglyceride is also referred to as "triglyceride P"), or two (the triglyceride is also referred to as "triglyceride PP"), or three (the triglyceride is also referred to as "triglyceride PPP").

[0106] It should be noted that there are no particular restrictions on the types of other fatty acid residues in triglyceride P and triglyceride PP. For example, they can be residues of saturated fatty acids with 12 or more carbons and less than 24 carbons.

[0107] Triglyceride 16 may consist only of triglyceride P, triglyceride PP, or triglyceride PPP.

[0108] Triglyceride 16 may be a combination of two or more selected from triglyceride P, triglyceride PP, and triglyceride PPP. For example, triglyceride 16 may be a combination of triglyceride P and triglyceride PP, a combination of triglyceride P and triglyceride PPP, a combination of triglyceride PP and triglyceride PPP, or a combination of triglyceride P, triglyceride PP, and triglyceride PPP.

[0109] As shown in case (a), when the triglycerides of the present invention comprise multiple triglycerides, it is also preferred that at least one triglyceride contains at least one group derived from a saturated fatty acid with 18 carbon atoms within a molecule (this triglyceride is also referred to as "triglyceride 18"). Triglyceride 18 may contain one group derived from a fatty acid with 18 carbon atoms within a molecule (this triglyceride is also referred to as "triglyceride S"), or two groups (this triglyceride is also referred to as "triglyceride SS"), or three groups (this triglyceride is also referred to as "triglyceride SSS").

[0110] It should be noted that there are no particular restrictions on the types of other fatty acid residues in triglycerides S and SS, such as residues of saturated fatty acids with 12 or more carbons and less than 24 carbons.

[0111] Triglyceride 18 may consist of only triglyceride S, only triglyceride SS, or only triglyceride SSS.

[0112] Triglyceride 18 may be a combination of two or more selected from triglyceride S, triglyceride SS, and triglyceride SSS. For example, triglyceride 18 may be a combination of triglyceride S and triglyceride SS, a combination of triglyceride S and triglyceride SSS, a combination of triglyceride SS and triglyceride SSS, or a combination of triglyceride S, triglyceride SS, and triglyceride SSS.

[0113] In case (a), the triglycerides of the present invention may consist only of triglycerides 16 and 18, or may be composed of other triglycerides in addition to triglycerides 16 and 18. Examples of other triglycerides include: triglycerides that do not have any groups derived from fatty acids having 16 or more but less than 22 carbon atoms, and triglycerides that contain groups derived from fatty acids having 16 or more but less than 22 carbon atoms (except for triglycerides 16 and 18).

[0114] When groups derived from saturated fatty acids with 16 carbon atoms are designated as "P", groups derived from saturated fatty acids with 18 carbon atoms are designated as "S", and groups derived from fatty acids other than saturated fatty acids with 16 and 18 carbon atoms are designated as "X" and "Y", examples of combinations of aliphatic groups constituting the triglycerides of the present invention include: PPP, SSS, PPX, SSX, PXY, SXY, PPS, PSS, and PSX. The structures of the triglycerides represented by PPX, SSX, PXY, SXY, and PSX are as shown in (A) to (M) below. It should be noted that the structures of PPS and PSS are not shown, but the structure of PPS follows the structure of PPX, and the structure of PSS follows the structure of SSX.

[0115] [Chemical Formula 2]

[0116]

[0117] [Chemical Formula 3]

[0118]

[0119] [Chemical Formula 4]

[0120]

[0121] [Chemical Formula 5]

[0122]

[0123] [Chemical Formula 6]

[0124]

[0125] The triglycerides of the present invention can be used alone. For example, in case (b), the triglycerides of the present invention can be used alone as triglycerides of PPS, PSS, and PSX. For example, the triglycerides of the present invention may contain a triglyceride comprising at least one group derived from a saturated fatty acid having 16 carbon atoms, at least one group derived from a saturated fatty acid having 18 carbon atoms, and no groups derived from fatty acids other than these. Alternatively, the triglycerides of the present invention may also contain a triglyceride comprising one group derived from a saturated fatty acid having 16 carbon atoms, one group derived from a saturated fatty acid having 18 carbon atoms, and one group derived from other fatty acids.

[0126] The triglycerides of the present invention may be combinations of two or more of the various triglycerides. For example, the triglycerides of the present invention may be a combination of (a) and (b). Alternatively, they may be combinations of two or more of (b).

[0127] Furthermore, the triglycerides of the present invention may also be a combination of one or more of the aforementioned triglycerides with other triglycerides. Examples of other triglycerides include, for instance, triglycerides comprising groups derived from fatty acids having 14 or more but less than 22 carbon atoms (except for triglycerides 16 and 18).

[0128] In this invention, from the viewpoint of further improving the leak-proof properties of the porous membrane of this invention, it is preferable to use the various triglycerides alone, or to use a combination of two or more of the various triglycerides alone.

[0129] From the viewpoint of obtaining a porous membrane with higher leak-proof properties, the triglycerides contained in the porous membrane of the present invention preferably contain 30% or more and 70% or less, particularly 35% or more and 70% or less, particularly 50% or more and 70% or less of fatty acid-derived groups contained in all triglycerides, of which groups are derived from fatty acids having 18 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents).

[0130] With regard to the same point described above, the triglycerides contained in the porous membrane of the present invention preferably comprise, relative to the total amount of fatty acid-derived groups contained in all triglycerides, at least 30% by mass and less than 70% by mass of groups derived from fatty acids with 18 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds or substituents), and at least 25% by mass and less than 50% by mass of groups derived from fatty acids with 16 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds or substituents). The condition is that the combined proportion of groups derived from fatty acids with 18 carbon atoms and the proportion of groups derived from fatty acids with 16 carbon atoms does not exceed 100% by mass.

[0131] In this case, the proportion of groups derived from fatty acids having 18 carbon atoms is preferably 35% by mass or more and 70% by mass or less, more preferably 50% by mass or more and 70% by mass or less.

[0132] On the other hand, the proportion of groups derived from fatty acids with 16 carbon atoms is preferably 25% by mass or more and 45% by mass or less, more preferably 35% by mass or more and 45% by mass or less.

[0133] The proportions of groups derived from 16-carbon fatty acids and groups derived from 18-carbon fatty acids in all triglycerides, based on the total amount of groups derived from fatty acids, were determined by the following method.

[0134] Triglycerides present on the surface of porous membranes are extracted using a good solvent for triglycerides, such as toluene.

[0135] The ester bonds in the extracted triglycerides are hydrolyzed using alkali, and the methylated fatty acids are quantitatively analyzed by gas chromatography.

[0136] It should be noted that the presence of alkyl chains with different carbon numbers within a single molecule of triglycerides can be determined using TOF-MS (Time-of-Flight Mass Spectrometry). Specifically, the molecular weight distribution of triglycerides is determined by TOF-MS, and the presence of alkyl chains with different carbon numbers within a single molecule is determined based on its molecular weight. For compounds with the same molecular weight, the presence of alkyl chains with different carbon numbers within a single molecule can be determined using a tandem mass spectrometer (MS / MS). This is achieved by selecting specific ions in the first mass separation section, colliding them with an inert gas to generate fragment ions, and then separating and detecting these fragment ions in the second mass separation section.

[0137] From the viewpoint of further improving the leak-proof properties of the porous membrane of the present invention, the triglycerides of the present invention preferably do not contain groups derived from unsaturated fatty acids. The absence of groups derived from unsaturated fatty acids includes both the case of completely lacking groups derived from unsaturated fatty acids and the case of unavoidably containing a small amount of unsaturated fatty acids. The case of unavoidably containing a small amount of unsaturated fatty acids is, for example, when the proportion of groups derived from unsaturated fatty acids is 2% by mass or less, based on the total amount of fatty acid-derived groups contained in all triglycerides contained in the porous membrane.

[0138] Similarly, from the viewpoint of further improving the leak-proof properties of the porous membrane of the present invention, the triglycerides of the present invention preferably do not contain groups derived from hydroxyl-containing fatty acids. A hydroxyl-containing fatty acid is a fatty acid in which at least one hydrogen atom in the hydrocarbon group is replaced by a hydroxyl group. The absence of groups derived from hydroxyl-containing fatty acids includes both the case of completely lacking groups derived from hydroxyl-containing fatty acids and the case of unavoidably containing a small amount of groups derived from hydroxyl-containing fatty acids. The case of unavoidably containing a small amount of groups derived from hydroxyl-containing fatty acids is, for example, when the proportion of groups derived from hydroxyl-containing fatty acids is less than 2% by mass, based on the total amount of fatty acid-derived groups contained in all triglycerides contained in the porous membrane.

[0139] The porous membrane of the present invention may contain only triglycerides as glycerides, or it may contain monoglycerides and / or diglycerides in addition to triglycerides, within the scope of achieving the intended effects of the present invention.

[0140] Next, a preferred method for manufacturing the porous membrane of the present invention will be described.

[0141] The method for manufacturing the porous membrane of the present invention includes the following steps: melting and forming a resin sheet by melting a composite comprising an olefinic resin composition, an inorganic filler, a metal soap and a fatty acid, and stretching the resin sheet at least along a uniaxial direction.

[0142] The details of the olefin resin composition, inorganic filler, metal soap, and fatty acid contained in the composite are as described above. Furthermore, the proportions of the olefin resin composition, inorganic filler, metal soap, and fatty acid contained in the composite are the same as those contained in the porous membrane. Moreover, the types and amounts of optional components contained in the composite are also the same as those of optional components contained in the porous membrane.

[0143] The porous membrane of the present invention can be manufactured efficiently, for example, by the following method.

[0144] First, the components constituting the composite are premixed using a Henschel mixer, high-speed mixer, or similar equipment, and then granulated by kneading using a single-shaft or twin-shaft extruder. The resulting granules are then used to form a film using a forming machine to obtain resin sheets. For example, a T-die type or blow molding machine can be used.

[0145] The dispersant can be used alone or mixed with other components constituting the composite. Preferably, it is pre-attached to the surface of the inorganic filler to prepare a surface-modified inorganic filler. This surface-modified inorganic filler is then mixed with the other components constituting the composite to prepare the composite. This process suppresses unintentional pinhole formation and allows for smooth stretching of the resin sheet, resulting in a porous membrane with both high moisture permeability and high water resistance.

[0146] Regarding the resin sheet, it is made porous by uniaxial or biaxial stretching, resulting in interfacial delamination between the olefin resin composition and the inorganic filler. This stretching can be performed using a roller stretching method that stretches along the mechanical direction, or a stretching method that stretches along the film width direction in addition to the mechanical direction. The porous membrane of the present invention is obtained in this manner. The resin sheet is preferably stretched at least 1.1 times in the uniaxial direction, more preferably 1.5 times or more, and even more preferably 2 times or more, so that the area increases with stretching. Furthermore, from the viewpoint of avoiding a decrease in tear strength due to excessive molecular orientation caused by excessive stretching, stretching of 5.0 times or less is preferred, more preferably 4.5 times or less, and even more preferably 4 times or less.

[0147] From the viewpoint that the film can be stretched uniformly without rupture, whether uniaxial stretching or biaxial stretching is performed, 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.

[0148] The porous membrane manufactured using the above method exhibits high flexibility and high air permeability. When flexibility is expressed as flexibility deformability, the mechanical flexibility deformability of the porous membrane of the present invention preferably shows 0.060 N / (mm·(g / m²)). 2 The lower value is preferred to be 0.057 N / (mm·(g / m). 2 The value is further preferably 0.055 N / (mm·(g / m)). 2 From the viewpoint of maintaining the strength of the porous membrane of the present invention, the lower limit of the flexibility is preferably 0.005 N / (mm·(g / m²)). 2 ))above.

[0149] The flexibility and deformability of the porous membrane were determined using the following method. Three pieces of the porous membrane were cut at a mechanical length of 150 mm and a width of 30 mm. The cut pieces were fixed to a tensile testing machine (trade name AG-1S, manufactured by Shimadzu Corporation) with an initial length L0 of 100 mm. After fixing, the load read by the tensile testing machine was set to zero, and a cyclic test was performed, that is, the piece was stretched to 1.3 times L0 at a deformation rate of 200 mm / min, and then immediately contracted back to L0 at a deformation rate of 200 mm / min. The load (F) at 1.03 times the deformation during the stretching process was recorded based on the obtained data. 3％ The degree of flexibility (N / (mm·(g / m)) is calculated according to the following formula. 2 ))).

[0150] Softness deformation (N / (mm·(g / m)) 2 )))=F 3％ (N) / (0.03×30(mm)×membrane unit area weight (g / m²) 2 ))

[0151] The preferred moisture permeability value of the porous membrane of the present invention is 0.8 g / (100 cm³). 2 ·h) or more, more preferably 1.0 g / (100cm) 2 ·h) or higher, more preferably 1.2g / (100cm) 2 •h) or above. Therefore, the porous membrane of the present invention has high moisture permeability, allowing appropriate dissipation of moisture from the interior of the absorbent article to the outside. On the other hand, to avoid losing the required leak-proof properties of the back sheet due to excessive porosity, the upper limit of the moisture permeability of the porous membrane is preferably 4.5 g / (100cm²). 2 ·h) or less, more preferably 3.5g / (100cm) 2 ·h) or less, more preferably 3.0 g / (100cm) 2 ·h) and below.

[0152] The water permeability of the porous membrane of the present invention was determined according to JIS L 1099A-2 and by the following method.

[0153] The diameter is 2.03 cm (area 3.23 cm²). 2Approximately 25 mL of ion-exchanged water was added to a glass bottle (Laboran screw bottle No. 8, manufactured by AS ONE). A test strip was used to cover the mouth of the glass bottle without gaps, and the test strip was 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 was stored in a constant temperature bath maintained at 40°C and 20% RH for 10–15 hours. After storage, the mass (W2) of the evaluation sample was measured, the storage time (T1, unit: h) was recorded, and the humidity permeability was calculated according to the following formula (1).

[0154] Moisture permeability (g / (100cm)) 2 ·h))=(W1―W2) / (T1×3.23)×100(1)

[0155] The weight per unit area of ​​the porous membrane of the present invention also depends on its application, and is preferably 5 g / m³. 2 The above, more preferably 10g / m 2 The above, and preferably 100g / m 2 The following is more preferably 50g / m 2 The thickness of the porous membrane of the present invention also depends on its application, and for example, it can be set to about 4 μm or more and about 90 μm or less.

[0156] The porous membrane of the present invention is permeable to moisture and has high leak-proof properties against liquids, especially water. Therefore, the porous membrane of the present invention can be used for leak-proof sheets for absorbent items such as disposable diapers and menstrual sanitary napkins, and waterproof sheets for rain gear.

[0157] The porous membrane of the present invention is particularly useful as a constituent component of absorbent articles. The present invention comprises absorbent articles having the porous membrane of the present invention.

[0158] The absorbent article of the present invention typically comprises a surface sheet forming a skin-facing side, a leak-proof sheet forming a non-skin-facing side, and a liquid-retaining absorbent disposed between these two sheets. The absorbent article may further have leak-proof flanges on both sides of the skin-facing side along its length.

[0159] The surface sheet is typically liquid permeable.

[0160] An absorber typically comprises an absorbent core and a coating material that encapsulates it.

[0161] The porous membrane of the present invention is particularly effective as a leak-proof sheet or leak-proof flange, and is therefore preferred.

[0162] When using the porous membrane of the present invention as a leak-proof sheet or leak-proof flange for absorbent articles, the porous membrane itself can be used as a leak-proof sheet, or the porous membrane can be used in combination with other sheet materials, such as non-woven fabrics.

[0163] It should be noted that "skin-facing side" refers to the side of the absorbent material or its constituent components (such as the absorbent core) that faces the wearer's skin when wearing absorbent materials, i.e., the side that is relatively close to the wearer's skin. "Non-skin-facing side" refers to the side of the absorbent material or its constituent components that faces away from the wearer's skin when wearing absorbent materials.

[0164] The surface sheet, absorbent core, and cladding material can be used without particular restriction by the usual users of such absorbent articles.

[0165] The absorbent articles of the present invention broadly include articles for absorbing bodily fluids (urine, feces, menstrual blood, sweat, etc.) excreted from the human body, such as disposable diapers, menstrual sanitary napkins, menstrual underwear, incontinence pads, etc.

[0166] In addition to the above-described embodiments, the present invention also discloses the following porous membrane, a method for manufacturing the porous membrane, and an absorbent article.

[0167] <1>

[0168] A porous membrane comprising an olefinic resin composition, an inorganic filler, a metal soap, and fatty acids, and

[0169] The composition comprises an inorganic filler comprising 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap comprising 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid comprising 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler.

[0170] The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C.

[0171] The melting point of the metal soap is below 200°C.

[0172] The precipitation temperature of the metal soap is higher than the curing temperature of the olefin resin composition.

[0173] <2>

[0174] The porous membrane described in <1> has a mechanical flexibility of 0.060 N / (mm·(g / m²)). 2 ))the following.

[0175] <3>

[0176] The porous membrane described in <1> or <2> preferably has a mechanically flexible deformability of 0.057 N / (mm·(g / m²)). 2 )) or less, more preferably 0.055 N / (mm·(g / m 2 The value is below 0.005 N / (mm·(g / m²)), and preferably 0.005 N / (mm·(g / m²)). 2 ))above.

[0177] <4>

[0178] The porous membrane described in any one of <1> to <3> comprises the metal soap in an amount of 0.5 parts by mass and 20 parts by mass relative to 100 parts by mass of the olefinic resin composition.

[0179] <5>

[0180] The porous membrane described in any one of <1> to <4> preferably contains 1.0 or more but less than 15 parts by weight of the metal soap relative to 100 parts by weight of the olefinic resin composition, more preferably 2.0 or more but less than 10 parts by weight.

[0181] <6>

[0182] The porous membrane described in any one of <1> to <5> comprises the metal soap in an amount of 0.5 parts by mass and 10 parts by mass relative to 100 parts by mass of the inorganic filler.

[0183] <7>

[0184] The porous membrane described in any one of <1> to <6> preferably comprises 1.5 parts by mass and 9.0 parts by mass or less of the metal soap relative to 100 parts by mass of the inorganic filler, and more preferably comprises 2.0 parts by mass and 8.0 parts by mass or less.

[0185] <8>

[0186] The porous membrane described in any one of <1> to <7>, wherein when the precipitation temperature of the metal soap is set to Ts (°C) and the curing temperature of the olefin resin composition is set to Tp (°C), the value of Ts-Tp is preferably greater than 0°C, more preferably 1°C or more, even more preferably 2°C or more, and preferably 50°C or less.

[0187] <9>

[0188] The porous membrane described in any one of <1> to <8>, wherein the precipitation temperature Ts of the metal soap is preferably 80°C or higher and 180°C or lower, more preferably 90°C or higher and 170°C or lower, and even more preferably 100°C or higher and 160°C or lower.

[0189] <10>

[0190] The porous membrane described in any one of <1> to <9>, wherein the curing temperature Tp of the olefin resin composition is preferably 60°C or higher and 130°C or lower, more preferably 70°C or higher and 120°C or lower, and even more preferably 80°C or higher and 115°C or lower.

[0191] <11>

[0192] The porous membrane described in any of <1> to <10>, wherein the chain length of the hydrocarbon chain in the fatty acid is the same as the chain length of the hydrocarbon chain in the fatty acid constituting the metal soap.

[0193] <12>

[0194] The porous membrane described in any one of <1> to <11>, wherein the density of the olefin-based resin composition is preferably less than 0.900 g / cm³. 3 More preferably, it is 0.895 g / cm³. 3 The following is a further preferred value: 0.885 g / cm³ 3 Below, and

[0195] The density of the olefin-based resin composition is preferably 0.840 g / cm³. 3 The above, more preferably 0.850 g / cm³ 3 The above is further preferred to be 0.860 g / cm³. 3 above.

[0196] <13>

[0197] The porous membrane described in any one of <1> to <12>, wherein the density of the low-melting-point olefin resin is preferably 0.895 g / cm³. 3 The preferred value is 0.885 g / cm³. 3 The following is a further preferred value: 0.875 g / cm³ 3 Below, and

[0198] The density of the low-melting-point olefin resin is preferably 0.840 g / cm³. 3 The above, more preferably 0.850 g / cm³ 3 The above is further preferred to be 0.860 g / cm³. 3 above.

[0199] <14>

[0200] The porous membrane described in any one of <1> to <13> preferably contains 30 parts by mass and 95 parts by mass of the low-melting-point olefin resin in 100 parts by mass of the olefin resin composition, more preferably 35 parts by mass and 92 parts by mass, and even more preferably 40 parts by mass and 90 parts by mass.

[0201] <15>

[0202] The porous membrane as described in any one of <1> to <14>, wherein the olefin resin composition comprises a high-melting-point olefin resin with a melting point of 95°C or higher, and

[0203] The density of the high-melting-point olefin resin is preferably 0.900 g / cm³. 3 Above and 0.950 g / cm 3 The following is more preferably 0.905 g / cm³. 3 Above and 0.940 g / cm 3 The following is a further preferred value: 0.910 g / cm³ 3 Above and 0.930 g / cm 3 the following.

[0204] <16>

[0205] The porous membrane described in <15>, wherein the high-melting-point olefin resin comprises polyethylene.

[0206] <17>

[0207] The porous membrane described in <16>, wherein the high-melting-point olefin resin comprises linear low-density polyethylene.

[0208] <18>

[0209] The porous membrane described in <17>, wherein the linear low-density polyethylene comprises linear low-density polyethylene polymerized by a metallocene catalyst.

[0210] <19>

[0211] The porous membrane described in any of <1> to <18>, wherein the low-melting-point olefin resin comprises an ethylene-α-olefin copolymer.

[0212] <20>

[0213] The porous membrane described in <19> includes an ethylene-α olefin copolymer comprising an ethylene-α olefin copolymer polymerized by a metallocene catalyst.

[0214] <21>

[0215] The porous membrane described in <17>, wherein the high-melting-point olefin resin comprises linear low-density polyethylene polymerized by a metallocene catalyst, and

[0216] The low-melting-point olefin resin comprises an ethylene-α-olefin copolymer polymerized by a metallocene catalyst.

[0217] <22>

[0218] As described in <17>, the porous membrane wherein the chain length of the hydrocarbon chain in the fatty acid is the same as the chain length of the hydrocarbon chain in the fatty acid constituting the metal soap.

[0219] The high-melting-point olefin resin comprises linear low-density polyethylene polymerized via a metallocene catalyst, and

[0220] The low-melting-point olefin resin comprises an ethylene-α-olefin copolymer polymerized by a metallocene catalyst.

[0221] <23>

[0222] The porous membrane described in any of <1> to <22>, wherein the fatty acid and the fatty acid constituting the metal soap are both stearic acid.

[0223] <24>

[0224] The porous membrane described in any one of <1> to <23> preferably contains 0.8 parts by mass and 4.0 parts by mass or less of the fatty acid relative to 100 parts by mass of the inorganic filler, and more preferably contains 1.0 parts by mass and 3.0 parts by mass or less.

[0225] <25>

[0226] The porous membrane as described in any one of <1> to <24> preferably contains 60 or more parts by weight of the inorganic filler relative to 100 parts by weight of the olefin resin composition, more preferably 80 or more parts by weight, and

[0227] Preferably, the inorganic filler is contained in 350 parts by weight or less, more preferably 200 parts by weight or less, relative to 100 parts by weight of the olefin resin composition.

[0228] <26>

[0229] The porous membrane described in any one of <1> to <25> comprises a triglyceride comprising 0.1 parts by mass and 30 parts by mass relative to 100 parts by mass of the olefinic resin composition.

[0230] <27>

[0231] The porous membrane described in <26> is wherein, relative to 100 parts by weight of the olefinic resin composition, the amount of triglyceride is preferably 0.5 parts by weight or more and 25 parts by weight or less, more preferably 1.0 parts by weight or more and 20 parts by weight or less.

[0232] <28>

[0233] The porous membrane described in <26> or <27>, wherein, regarding the ratio of the triglyceride to the metal soap, the metal soap is preferably 30 parts by mass or more and 300 parts by mass or less relative to 100 parts by mass of the triglyceride, more preferably 35 parts by mass or more and 250 parts by mass or less, and even more preferably 40 parts by mass or more and 230 parts by mass or less.

[0234] <29>

[0235] Porous membranes as described in any of <26> to <28>, wherein the triglycerides do not contain groups derived from unsaturated fatty acids.

[0236] <30>

[0237] Porous membranes as described in any of <26> to <29>, wherein the triglycerides do not contain groups derived from fatty acids having hydroxyl groups.

[0238] <31>

[0239] The porous membrane described in any of <26> to <30>, wherein the triglyceride comprises a group derived from a fatty acid having 16 or more and 22 or fewer carbon atoms, and the group is a hydrocarbon group without unsaturated bonds or substituents.

[0240] <32>

[0241] The porous membrane described in any of <26> to <31>, wherein the triglyceride is:

[0242] (a) A mixture of a triglyceride containing at least one group derived from a fatty acid having 16 carbon atoms and a triglyceride containing at least one group derived from a fatty acid having 18 carbon atoms; or

[0243] (b) A triglyceride containing at least one group derived from a fatty acid with 16 carbon atoms and one group derived from a fatty acid with 18 carbon atoms in one molecule.

[0244] <33>

[0245] The porous membrane described in any of <1> to <32> preferably has a water permeability of 0.80 g / (100 cm³) as determined by JIS L 1099. 2 •h) or more and 4.5g / (100cm) 2 ·h) or less, more preferably 1.0 g / (100cm) 2 • h) or more and 3.5 g / (100 cm 2 ·h) or less, more preferably 1.2g / (100cm) 2 • h) or more and 3.0 g / (100 cm 2 ·h) and below.

[0246] <34>

[0247] A porous membrane is manufactured by melt-forming a resin sheet from a composite containing an olefinic resin composition, an inorganic filler, a metal soap, and a fatty acid, and then subjecting the resin sheet to at least uniaxial stretching.

[0248] The composition comprises an inorganic filler comprising 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap comprising 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid comprising 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler.

[0249] The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C.

[0250] The melting point of the metal soap is below 200°C.

[0251] The precipitation temperature of the metal soap is higher than the curing temperature of the olefin resin composition.

[0252] <35>

[0253] The porous membrane described in <34> preferably has a mechanical flexibility of 0.060 N / (mm·(g / m²)). 2 )) or less, more preferably 0.057 N / (mm·(g / m 2 The value is further preferably 0.055 N / (mm·(g / m)). 2 ))the following.

[0254] <36>

[0255] The porous membrane described in any of <1> to <35>, wherein the melting point of the low-melting-point olefin resin is preferably less than 80°C, more preferably less than 70°C.

[0256] <37>

[0257] The porous membrane described in any of <1> to <36> is used for absorbent articles.

[0258] <38>

[0259] An absorbent article having a porous membrane as described in any one of <1> to <37>.

[0260] <39>

[0261] A method for manufacturing a porous membrane includes the following steps: melt-forming a composite containing a resin composition comprising an olefinic resin composition, an inorganic filler, a metal soap, and a fatty acid to form a resin sheet; and stretching the resin sheet at least along a uniaxial direction.

[0262] The stretching is performed at a temperature above 30°C and below 100°C, and at a stretching ratio of 1.1 times and below 5.0 times.

[0263] The porous membrane comprises an inorganic filler in an amount of 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap in an amount of 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid in an amount of 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler.

[0264] The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C.

[0265] The melting point of the metal soap is below 200°C.

[0266] The precipitation temperature of the metal soap is higher than the curing temperature of the olefin resin composition.

[0267] <40>

[0268] The manufacturing method described in <39> involves pre-attaching the fatty acid to the surface of the inorganic filler, pre-manufacturing a surface-modified inorganic filler, and mixing the surface-modified inorganic filler with other components constituting the complex to prepare the complex.

[0269] Example

[0270] The present invention will now be described in more detail through embodiments. However, the scope of the present invention is not limited to these embodiments. Unless otherwise specified, "parts" refers to "parts by weight".

[0271] [Examples 1 to 8 and Comparative Examples 1 to 6]

[0272] (1) Manufacturing of the complex

[0273] Weigh the components shown in Tables 1 and 2 below to the amounts indicated in those tables. Mix these components using a Henschel mixer (manufactured by Kawada Corporation). Knead the resulting mixture using a twin-screw extruder (manufactured by Toyo Seiki) at a set temperature of 180°C and a screw speed of 180 rpm to obtain a granulated composite.

[0274] The detailed information on the components shown in Tables 1 and 2 is presented in Table 3. Furthermore, the units for the components in Tables 1 and 2 are parts by mass.

[0275] (2) Manufacturing of resin sheets

[0276] Using a 150mm wide T-shaped die (manufactured by Toyo Seiki), composite resin sheets are formed.

[0277] The forming conditions for Examples 1 to 8, Comparative Examples 2 and 4 to 6 were set to a T-die temperature of 200°C and a casting roller speed of 3 m / min. The forming conditions for Comparative Examples 1 and 3 were set to a T-die temperature of 150°C and a casting roller speed of 3 m / min.

[0278] (3) Fabrication of porous membranes

[0279] The resin sheets obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were cut into sections of 120 mm in the mechanical direction and 60 mm in the width direction, with 10 mm at each end in the mechanical direction serving as the holding ends. Using a tenter frame (manufactured by IS Giken Co., Ltd.), with the initial length set to 100 mm, the resin sheets were uniaxially stretched along the mechanical direction by holding the holding ends, resulting in porous films with the unit area weights shown in Tables 1 and 2. At this time, the width direction of the resin sheets was not held. The stretching temperature and the stretching ratio set by the machine are shown in Tables 1 and 2.

[0280] [evaluate]

[0281] For the porous membranes obtained in the examples and comparative examples, the flexibility and moisture permeability in the mechanical direction were measured using the method described above. Furthermore, residual strain was measured using the following method. Furthermore, the degree of liquid leakage was evaluated using the following method. These results are shown in Table 1.

[0282] [Residual Strain]

[0283] The same measurement as that for the soft deformability of porous membranes was performed, and the strain that was less than 0.01 N under load during the process of shrinking the membrane to L0 at a deformation rate of 200 mm / min was taken as the residual strain.

[0284] [Degree of liquid seepage]

[0285] A porous membrane, cut to a size of 50mm or more in the mechanical direction and 35mm or more in the width direction, is placed on filter paper (manufactured by Advantech Toyo Co., Ltd., No. 2, 70mm in diameter). A sheet of dry pulp (manufactured by Lion Co., Ltd., Reed Healthy Cooking Paper Double, trade name, 40g / m²) is then placed on the porous membrane. 2 The result is obtained by cutting it into 3cm×2.5cm pieces.

[0286] 0.265g of wetting tension test solution (surface tension at 25°C: 35mN / m, manufactured by Kanto Chemical) was injected into the center of the dry pulp sheet using a dropper. After injection, a cylindrical acrylic sheet with a diameter of 60mm and a thickness of 5mm was overlapped, and a 500g weight was placed on it, and pressure was applied for 1 hour.

[0287] After one hour, the weights were removed, and the extent of liquid seepage to the filter paper was visually observed to determine whether any seepage had occurred. This evaluation was conducted in three groups for each level, and the degree of seepage was evaluated based on the following benchmarks.

[0288] A: No seepage was observed on any of the three filter papers.

[0289] B: Exudation was observed in at least one piece.

[0290] [Table 1]

[0291]

[0292] [Table 2]

[0293]

[0294] [Table 3]

[0295]

[0296] As shown in Tables 1 and 2, the porous membranes obtained in each embodiment have low flexibility and deformability, high moisture permeability, and high resistance to liquid leakage.

[0297] In particular, a comparison between Example 1 and Comparative Example 1 shows that, compared to Example 1 which uses a low-density olefin resin composition, Comparative Example 1, which uses a high-density olefin resin composition, has a higher softness deformability value.

[0298] Furthermore, regarding the film of Example 3, when uniaxially stretched at 40°C, the film ruptured immediately after stretching began. When uniaxially stretched at 23°C, due to the low stretching temperature, the film could not be uniformly stretched unless stretched to a 5.5-fold ratio. On the other hand, regarding the film of Example 1, when uniaxially stretched at 40°C, the film did not rupture and could be stretched to a 4.5-fold ratio; moreover, even at a 4.5-fold stretching ratio, the film was uniformly stretched. Therefore, based on the comparison between Example 1 and Example 3, it can be seen that if a combination of an ethylene-α-olefin copolymer polymerized by a metallocene catalyst and a linear low-density polyethylene polymerized by a metallocene catalyst is used as the olefin-based resin composition, stretching can be performed at a higher temperature, and a film uniformly stretched at a relatively small stretching ratio can be obtained.

[0299] Furthermore, a comparison between Example 3 and Comparative Example 5 shows that without the addition of fatty acids as a dispersant for the inorganic filler, the inorganic filler cannot be sufficiently dispersed in the olefin resin and thus cannot form a film.

[0300] Furthermore, a comparison between Comparative Example 1 and Comparative Example 3 shows that using a high-density resin (high-melting-point olefin resin 3, with a density of 0.922 g / cm³) is more effective. 3 In the case of olefin-based resin compositions, the moisture permeability value is substantially the same whether or not metal soap is added.

[0301] [Examples 9 to 12 and Comparative Examples 7 and 8]

[0302] (1) Manufacturing of the complex

[0303] For the components shown in Table 4 below, weigh them according to the amounts shown in the table. Otherwise, prepare the complex in the same manner as in Example 1.

[0304] (2) Manufacturing of resin sheets

[0305] A blow molding machine with a 100mm diameter slit and a 0.9mm gap at the mold outlet is used to form resin sheets from molten composite material. The mold temperature is set to 200℃, the draw speed to 10m / min, and the blow molding ratio to 2.5.

[0306] (3) Fabrication of porous membranes

[0307] The resin sheet was uniaxially stretched using a roller stretching machine to obtain porous membranes by weight per unit area as shown in Table 4. The stretching ratio and stretching temperature are shown in the table. The obtained porous membranes underwent the same measurements as in Example 1. The results are shown in Table 4.

[0308] [Table 4]

[0309]

[0310] As shown in Table 4, the porous membranes obtained in each embodiment have low flexibility and deformability, high moisture permeability, and high resistance to liquid leakage.

[0311] [Examples 13 to 15 and Comparative Examples 9 and 10]

[0312] The porous membrane was manufactured in the same manner as in Example 1, except that the components shown in Table 5 below were used. The stretching temperature and mechanical stretching ratio are shown in the table. In the table, the units of composition are parts by mass. The adhesion of the obtained porous membrane was evaluated using the following methods. The results are shown in Table 5.

[0313] [Adhesion Evaluation]

[0314] Two porous membranes were overlapped and pressurized at 50°C and 127 MPa for 1 minute using a Labo Press (manufactured by Toyo Seiki). Then, they were cooled at room temperature for 5 minutes to prepare a sample for adhesion evaluation. Adhesion evaluation involved manually peeling the two membranes of the prepared evaluation sample to confirm the presence or absence of adhesion. This evaluation was performed in three groups at each level, and adhesion was evaluated based on the following criteria.

[0315] A: All three pieces are easy to peel off by hand.

[0316] B: When peeling by hand, at least one piece is difficult to peel off, and the film is ruptured.

[0317] [Table 5]

[0318]

[0319] As shown in Table 5, the porous membranes obtained in each embodiment are not prone to adhesion.

[0320] [Refer to Example 1 and compare with Examples 1 to 3]

[0321] (1) Manufacturing of the complex

[0322] Weigh the components shown in Table 6 below to the amounts indicated in the table. Add these components to a Laboplastomill (manufactured by Toyo Seiki) and knead at 160°C and 30 rpm for 10 minutes to obtain a complex.

[0323] The detailed information on the components shown in Table 6 is shown in Table 7. Furthermore, the units for the components in Table 6 are parts by mass.

[0324] (2) Membrane manufacturing

[0325] Using a LaboPress (manufactured by Toyo Seiki), the composite was pressurized at 150°C and 13 MPa for 1 minute. Then, it was cooled at room temperature and pressurized at 13 MPa for 1 minute to produce a film (resin sheet). At this time, the thickness of the film was adjusted to 0.5 mm.

[0326] [evaluate]

[0327] The water resistance of the membranes obtained in Reference Example 1 and by comparing Reference Examples 1, 2 and 3 was evaluated using the following methods. The results are shown in Table 6 below.

[0328] [Membrane water resistance]

[0329] The prepared membrane was placed in an electric dryer and stored at 40°C for 7 days. After storage, the contact angle of the membrane surface was measured using a contact angle meter (DropMaster 500, manufactured by Kyowa Interface Science). Two evaluation solutions were used: one with a surface tension of 44.0 mN / m and the other with a surface tension of 35.0 mN / m.

[0330] • Measurement method: Droplet method

[0331] • Evaluation solution: Mixture for wetting tension test (surface tensions of 44.0 mN / m and 35.0 mN / m at 25°C, manufactured by Kanto Chemical)

[0332] • Droplet volume: 2μL

[0333] • For each test piece, the contact angle was measured at 5 locations 1 second after the drop was applied, and the average value of the 5 drops was taken as the contact angle value.

[0334] [Table 6]

[0335]

[0336] [Table 7]

[0337]

[0338] As shown in Tables 6 and 7, the membrane of Comparative Example 1 has a higher contact angle with the evaluation solution compared to the membrane of Comparative Example 1. This indicates that the liquid repellency is improved when both the metal soap and triglycerides are included in the membrane, compared to the case where only triglycerides are contained.

[0339] Industrial availability

[0340] As detailed above, according to the present invention, a porous membrane with high moisture permeability, leak-proof properties and flexibility is provided.

Claims

1. A porous membrane comprising an olefinic resin composition, an inorganic filler, a metal soap, and a fatty acid, and The composition comprises an inorganic filler comprising 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap comprising 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid comprising 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler. The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C. The olefin resin composition contains 40 parts by weight and 95 parts by weight of the low-melting-point olefin resin in 100 parts by weight. The density of the olefin-based resin composition is 0.840 g / cm³. 3 Above and less than 0.900 g / cm 3 , The melting point of the metal soap is below 200°C. The precipitation temperature of the metal soap is higher than the curing temperature of the olefin-based resin composition. The porous membrane, as measured according to JIS L 1099, has a water permeability of 0.80 g / (100 cm³). 2 •h) or more and 4.5g / (100 cm 2 ·h) and below, The porous membrane is used for absorbent articles.

2. The porous membrane according to claim 1 is manufactured by melt-forming a resin sheet from a composite containing a resin composition comprising an olefinic resin composition, an inorganic filler, a metal soap, and a fatty acid, and by subjecting the resin sheet to at least uniaxial stretching.

3. The porous membrane according to claim 1, wherein its mechanical flexibility is 0.060 N / (mm·(g / m²)). 2 ))the following.

4. The porous membrane according to claim 1, wherein its mechanical flexibility is 0.005 N / (mm·(g / m²)). 2 )) or above and 0.057 N / (mm·(g / m 2 ))the following.

5. The porous membrane according to claim 1, comprising the metal soap in an amount of 0.5 parts by weight or more and 20 parts by weight or less relative to 100 parts by weight of the olefinic resin composition.

6. The porous membrane according to claim 1, wherein, The composition comprises 1.0 part by weight and 15 parts by weight of the metal soap relative to 100 parts by weight of the olefin resin composition.

7. The porous membrane according to claim 1, comprising the metal soap in an amount of 0.5 parts by mass and 10 parts by mass relative to 100 parts by mass of the inorganic filler.

8. The porous membrane according to claim 1, wherein, When the precipitation temperature of the metal soap is set as Ts in °C and the curing temperature of the olefin resin composition is set as Tp in °C, the value of Ts-Tp is greater than 0 °C and less than 50 °C.

9. The porous membrane according to claim 1, wherein, The precipitation temperature Ts of the metal soap is above 80°C and below 180°C.

10. The porous membrane according to claim 1, wherein, The curing temperature Tp of the olefin-based resin composition is above 60°C and below 130°C.

11. The porous membrane according to claim 1, wherein, The chain length of the hydrocarbon chain in the fatty acid is the same as the chain length of the hydrocarbon chain in the fatty acid constituting the metal soap.

12. The porous membrane according to claim 1, wherein, The melting point of the low-melting-point olefin resin is less than 80°C.

13. The porous membrane according to claim 1, wherein, The density of the low-melting-point olefin resin is 0.895 g / cm³. 3 Below, and The density of the low-melting-point olefin resin is 0.840 g / cm³. 3 above.

14. The porous membrane according to claim 1, wherein, The olefin resin composition comprises a high-melting-point olefin resin with a melting point above 95°C, and The density of the high-melting-point olefin resin is 0.900 g / cm³. 3 Above and 0.950 g / cm 3 the following.

15. The porous membrane according to claim 14, wherein, The high-melting-point olefin resin includes polyethylene.

16. The porous membrane according to claim 15, wherein, The high-melting-point olefin resin includes linear low-density polyethylene.

17. The porous membrane according to claim 16, wherein, The linear low-density polyethylene comprises linear low-density polyethylene polymerized by a metallocene catalyst.

18. The porous membrane according to claim 1, wherein, The low-melting-point olefin resin includes an ethylene-α-olefin copolymer.

19. The porous membrane according to claim 18, wherein, The ethylene-α-olefin copolymer comprises an ethylene-α-olefin copolymer polymerized by a metallocene catalyst.

20. The porous membrane according to claim 16, wherein, The high-melting-point olefin resin comprises linear low-density polyethylene polymerized via a metallocene catalyst, and The low-melting-point olefin resin comprises an ethylene-α-olefin copolymer polymerized by a metallocene catalyst.

21. The porous membrane according to claim 16, wherein, The chain length of the hydrocarbon chain in the fatty acid is the same as the chain length of the hydrocarbon chain in the fatty acid constituting the metal soap. The high-melting-point olefin resin comprises linear low-density polyethylene polymerized via a metallocene catalyst, and The low-melting-point olefin resin comprises an ethylene-α-olefin copolymer polymerized by a metallocene catalyst.

22. The porous membrane according to claim 1, wherein, The fatty acid and the fatty acid constituting the metal soap are both stearic acid.

23. The porous membrane according to claim 1, comprising the fatty acid in an amount of 0.8 parts by mass or more and 4.0 parts by mass or less relative to 100 parts by mass of the inorganic filler.

24. The porous membrane according to claim 1, wherein, The inorganic filler comprises 60 parts by weight or more, relative to 100 parts by weight of the olefin-based resin composition. The inorganic filler is contained in 350 parts by weight or less relative to 100 parts by weight of the olefin resin composition.

25. A porous membrane comprising an olefinic resin composition, an inorganic filler, a metal soap, and a fatty acid, and The composition comprises an inorganic filler comprising 50 parts by weight or more and 400 parts by weight relative to 100 parts by weight of the olefin-based resin composition, a metallic soap comprising 0.5 parts by weight or more and 15 parts by weight relative to 100 parts by weight of the inorganic filler, and a fatty acid comprising 0.5 parts by weight or more and 5 parts by weight relative to 100 parts by weight of the inorganic filler. The olefin-based resin composition comprises a low-melting-point olefin-based resin with a melting point of less than 90°C. The olefin resin composition contains 40 parts by weight and 95 parts by weight of the low-melting-point olefin resin in 100 parts by weight. The density of the olefin-based resin composition is 0.840 g / cm³. 3 Above and less than 0.900 g / cm 3 , The melting point of the metal soap is below 200°C. The precipitation temperature of the metal soap is higher than the curing temperature of the olefin-based resin composition. The porous membrane contains triglycerides in an amount of 0.1 parts by weight or more and 30 parts by weight or less relative to 100 parts by weight of the olefinic resin composition.

26. The porous membrane according to claim 25, wherein its mechanical flexibility is 0.060 N / (mm·(g / m²)). 2 ))the following.

27. The porous membrane according to claim 25, wherein, The amount of triglyceride is 0.5 parts by weight or more and 25 parts by weight or less relative to 100 parts by weight of the olefin resin composition.

28. The porous membrane according to claim 25, wherein, The metallic soap comprises 30 to 300 parts by weight of the triglyceride, relative to 100 parts by weight of the triglyceride.

29. The porous membrane according to claim 25, wherein, The triglycerides do not contain groups derived from unsaturated fatty acids.

30. The porous membrane according to claim 25, wherein, The triglycerides do not contain groups derived from fatty acids with hydroxyl groups.

31. The porous membrane according to claim 25, wherein, The triglyceride contains a group derived from a fatty acid having 16 or more but less than 22 carbon atoms, and the group is a hydrocarbon group without unsaturated bonds or substituents.

32. The porous membrane according to claim 25, wherein, The triglyceride is: (a) A mixture of a triglyceride containing at least one group derived from a fatty acid having 16 carbon atoms and a triglyceride containing at least one group derived from a fatty acid having 18 carbon atoms; or (b) A triglyceride containing at least one group derived from a fatty acid with 16 carbon atoms and one group derived from a fatty acid with 18 carbon atoms in one molecule.

33. The porous membrane according to claim 25, used in absorbent articles.

Images