JP2010275539A - Water permeable film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water permeable film which is produced with a convenient production process at high speed, with stability, and in large quantity, and which is excellent in water permeability and in tear resistance. <P>SOLUTION: The water permeable film includes a uniaxially stretched resin film which includes: 18-42 wt.% of a crystalline polyolefin-based resin (A); 5-15 wt.% of a thermoplastic elastomer (B); and 45-75 wt.% of inorganic fine powder (D) having surfaces subjected to hydrophilic treatment with a surface treating agent (C). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water permeable film that can easily allow liquid such as water or oil to pass from one surface to the other surface. The water-permeable film of the present invention can be used for various separators such as batteries and electrolytic capacitors, various separation membranes (filters), absorbent articles such as diapers, heat-sensitive receiving paper members, ink receptor members, and the like.

Conventionally, as a thin film material that can permeate water in the thickness direction, natural paper (pulp paper / paper filter), woven fabric (filtered fabric), non-woven fabric, porous film by oil removal or solvent extraction, ultra high molecular weight Porous films obtained by cutting from polyethylene sintered bodies, polytetrafluoroethylene, ultrahigh molecular weight polyethylene and polyamide resins, fibrillated porous films, physical foam films, sponges, wire mesh, etc. was there.
These materials include liquid absorbers, liquid-absorbing wiping materials, protective cushioning materials for packing and packaging, building materials, curing sheets and joint materials for civil engineering, anti-condensation materials, heat insulation materials for livestock houses, cushions, Applications such as padding for writing instruments, suction cores for fragrances, culture media for hydroponics, filter media such as filters, various microfiltration membranes, separators for batteries and electrolytic capacitors, members for heat-sensitive receiving paper, ink receptor members, etc. Has been used.

  Each of the above-described thin film materials has various advantages. For example, for natural paper and nonwoven fabric, the manufacturing process is simple and inexpensive. In addition, porous films obtained by solvent extraction, porous films obtained by cutting ultra-high molecular weight polyethylene sintered bodies, and porous films obtained by fibrillating various resin films by stretching are durable and empty. Since the pore diameter and distribution are uniform and precise, they are actually used in separators for batteries and electrolytic capacitors, and various microfiltration membranes (Patent Documents 1 to 9).

Japanese Patent No. 2814598 Japanese Patent No. 3055470 Japanese Patent No. 3121047 Japanese Patent No. 3455285 Japanese Patent No. 3067956 Japanese Patent No. 3502959 Japanese Patent No. 3533414 Japanese Patent No. 3378460 JP 2008-218085 A

  However, the above-mentioned porous resin film used particularly for separators for batteries and electrolytic capacitors, various microfiltration membranes, and the like have the following various problems. That is, the porous film obtained by solvent extraction has a problem of cost increase due to the treatment of the solvent waste liquid discharged in the process of extracting the solvent / plasticizer from the polymer and the low production rate. The porous film obtained from the sintering method of ultrahigh molecular weight polyethylene has many manufacturing processes and has a problem of cost increase. A porous film in which a resin film is fibrillated by stretching has a problem of cost increase due to precise temperature treatment and low production speed.

  Therefore, in order to solve the problems of the prior art, the present inventors have produced a water permeable film that can be stably manufactured in a large amount at a high speed with a simple manufacturing process and has excellent water permeability and tear resistance. It was an object of the present invention to provide.

The inventors of the present invention earnestly researched, melt-kneaded a resin composition highly filled with an inorganic filler (inorganic fine powder) in a polymer, and extruded the sheet with an extruder or the like connected to a T-die, By uniaxially stretching in the production line direction or in a direction perpendicular to the production line, a water-permeable film that can be easily formed at high speed has been completed by a production method in which a large number of fine communication holes are formed inside.
Conventionally, attempts to form a large number of fine communication holes with a filler as a core by stretching a sheet highly filled with an inorganic filler in the entire thickness direction is a process from stretching to winding of the sheet after stretching. In this case, the sheet is easily cut by the tension, and it is impossible to continuously and stably manufacture the sheet. In the present invention, this problem is solved by selecting a polymer, which enables simple and high-speed molding. In addition, the surface of the inorganic filler to be used was hydrophilized with a surface treatment agent to achieve extremely high water permeability while being a stretched resin film.

That is, the following present invention has been provided as means for solving the problems.
[1] A water-permeable film characterized by having a uniaxially stretched resin film having a water permeability measured in accordance with JIS-Z0221: 1976 of 0.1 to 2000 seconds and containing at least the following three components.
1) Crystalline polyolefin resin (A)
18-42% by weight
2) Thermoplastic elastomer (B)
5-15% by weight
3) Inorganic fine powder (D) whose surface is hydrophilized with the surface treatment agent (C)
45-75% by weight
[2] The thermoplastic elastomer (B) is one or more thermoplastic elastomers selected from the group consisting of a styrene-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, and an ester-based thermoplastic elastomer. Preferably,
[3] A styrene-based thermoplastic elastomer is particularly preferable.
[4] The styrenic thermoplastic elastomer is preferably hydrogenated styrene butadiene rubber (HSBR),
[5] Particularly preferred are those having a styrene content of 20% by weight or less.
[6] The crystalline polyolefin resin (A) includes 0.5 to 22 parts by weight of a high melt tension polypropylene having a melt tension of 10 to 60 g with respect to 100 parts by weight of the crystalline polyolefin resin having a melt tension of less than 10 g. Preferably
[7] In particular, the high melt tension polypropylene is preferably polypropylene (A ′) having a long chain branch in the main chain skeleton.
[8] The porosity of the uniaxially stretched resin film is preferably 28 to 64%.
[9] The surface treatment agent (C) is a water-soluble anionic surfactant having an average molecular weight of 1,000 to 15,000, a water-soluble cationic surfactant having an average molecular weight of 1,000 to 15,000, And a surface treatment agent selected from the group consisting of water-soluble nonionic surfactants having an average molecular weight of 1,000 to 15,000.
[10] The uniaxially stretched resin film preferably further contains a dispersant (E) that improves the dispersibility of the inorganic fine powder (D).
[11] Same as tear strength (kgf / mm) in the direction perpendicular to the film stretching axis measured based on JIS-K7128-3: 1998 right angle tearing method, test speed A of the uniaxially stretched resin film. Adjusting the composition of the resin composition so that the product of the displacement (mm) until the fracture of the test piece at the time of the tear test is 10 to 200 kgf can stably produce the uniaxially stretched resin film at a high speed. It is preferable from the viewpoint of facilitating.
[12] The water permeable film may be composed only of the uniaxially stretched resin film.
[13] The water-permeable film may have a multilayer structure in which the uniaxially stretched resin film is used as a base material layer and a surface layer is further provided on at least one surface thereof. A multilayer structure is included in the present invention as long as it includes the uniaxially stretched resin film and is within the specified range of water permeability.

[14] Crystalline polyolefin resin (A) 18 to 42% by weight, thermoplastic elastomer (B) 5 to 15% by weight, and inorganic fine powder (D) whose surface is hydrophilized with a surface treatment agent (C) ) A resin sheet is produced using a resin composition containing 45 to 75% by weight, and then the water permeability measured based on JIS-Z0221: 1976 is 0.1 by stretching the resin sheet uniaxially. The manufacturing method of the water-permeable film containing the said uniaxially stretched resin film characterized by including the process of manufacturing the uniaxially stretched resin film which is -2000 second.
[15] The thermoplastic elastomer (B) is preferably a styrenic thermoplastic elastomer,
[16] The styrenic thermoplastic elastomer is preferably a hydrogenated styrene butadiene rubber.
[17] The resin sheet is preferably stretched so that the porosity of the uniaxially stretched resin film produced by stretching is 28 to 64%.
[18] The resin sheet can be stretched by uniaxially stretching in the transport direction of the resin sheet.
[19] The resin sheet may be stretched by uniaxially stretching in a direction orthogonal to the resin sheet conveyance direction.
[20] The draw ratio of the resin sheet is preferably in the range of 4 to 10 times.
[21] The water-permeable film produced by the production method is also included in the present invention.

[22] The water-permeable film of the present invention can be used as a separator.
[23] The water-permeable film of the present invention can also be used as a microfiltration membrane.
[24] Furthermore, the water-permeable film of the present invention can also be used as a liquid absorbent article.

  The water-permeable film of the present invention can be produced at a high speed and at a low cost by a very simple production method such as formation of communication holes by uniaxial stretching. In addition, the water-permeable film of the present invention imparts water absorption and water permeability without plasma treatment or sputter etching treatment to impart hydrophilicity to the stretched resin film or use an expensive water-absorbing polymer. Can do.

  Below, the water-permeable film of this invention is demonstrated in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

Constituent material of water permeable film [crystalline polyolefin resin (A)]
The uniaxially stretched resin film constituting the water-permeable film of the present invention contains a crystalline polyolefin resin (A). In the present invention, the crystalline polyolefin resin (A) contributes to the film-forming property of the film as a matrix resin.
Examples of crystalline polyolefin resins that can be used in the present invention include high-density polyethylene, medium-density polyethylene, low-density polyethylene, crystalline ethylene resins such as ethylene / α-olefin copolymers, crystalline propylene resins, and polymethyl-1 -Crystalline polyolefin resin such as pentene. These may be used in combination of two or more.

The crystalline polyolefin resin exhibits crystallinity. The crystallinity of the resin by X-ray diffraction is usually preferably 20% or more, and more preferably 35 to 75%. Those not exhibiting crystallinity do not sufficiently form pores (openings) on the film surface due to stretching. The crystallinity here can be measured by methods such as X-ray diffraction and infrared spectrum analysis.
Among the crystalline polyolefin-based resins, it is more preferable to use a crystalline propylene-based resin from the viewpoint of stretch formation. As the crystalline propylene-based resin, it is preferable to use an isotactic polymer or a syndiotactic polymer obtained by homopolymerizing propylene. Copolymers mainly composed of propylene having various stereoregularities obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene and 4-methyl-1-pentene. Polymers can also be used. The copolymer may be a binary system or a ternary or higher multi-element system, and may be a random copolymer or a block copolymer.

The crystalline polyolefin resin (A) used in the present invention preferably contains high melt tension polypropylene in order to obtain stable stretch moldability. In particular, those having a melt tension measured using a capilograph manufactured by Toyo Seiki Seisakusho Co., Ltd. within a range of 10 to 60 g, preferably within a range of 20 to 50 g are preferable. By containing polypropylene having a melt tension in the range of 10 to 60 g, when casting the molten resin from the die to the cast roll by lateral drawing, the dripping phenomenon of the molten resin sheet is suppressed, In some cases, drawdown can be suppressed and cast sheet formability can be improved.
The high melt tension polypropylene is preferably polypropylene (A ′) having a long-chain branched structure in the main chain skeleton. If the crystalline polyolefin resin (A) contains polypropylene (A ′) having a long chain branch in the main chain skeleton, it is easy to improve the melt tension and the stretchability by strain hardening at the time of stretching. become.

Here, the polypropylene (A ′) having a long-chain branch in the main chain skeleton is a propylene-based resin having a propylene unit branch mainly in the molecular structure. Its existence can be confirmed by general analytical methods.
The Trouton ratio, which is an index indicating the structure of polypropylene having a long chain branch in the main chain skeleton, is determined by using the inflow pressure loss method, Coxwell's theory (Polymer Engineering Science, 12, P. 64-73 (1972). )) To obtain by measurement. The Troughton ratio is obtained from an elongation viscosity-elongation strain rate curve and a shear viscosity-shear strain rate curve approximated by an exponential function, and is a ratio of elongation viscosity to shear viscosity. Polypropylene having a long chain branch in the main chain skeleton has a high elongation viscosity instead of a shear viscosity. It can be said that the polypropylene (A ′) having a long chain branch in the main chain skeleton of the present invention corresponds to a trouton ratio of 30 or more.

ここで、［η］ＬＢは長鎖分岐を有するポリプロピレンの固有粘度であり、［η］Ｌｉｎは長鎖分岐を有するポリプロピレンと実質的に同一の重量平均分子量を有する直鎖状の結晶性ポリプロピレンの固有粘度である。
また、長鎖分岐を有するポリプロピレンの重量平均分子量は、Ｍ．Ｌ．ＭｃＣｏｎｎｅｌｌによってＡｍｅｒｉｃａｎ Ｌａｂｏｒａｔｏｒｙ，Ｍａｙ，６３−７５（１９７８）に記載されている低角度レーザー光散乱光度測定法で測定することができる。
これら主鎖骨格中に長鎖分岐を有するポリプロピレンの一般的な製造方法としては、放射線（高エネルギー）照射による架橋、パーオキサイド架橋、共重合等の方法が挙げられる。これらの主鎖骨格中に長鎖分岐を有するポリプロピレンの具体例としては、ダウケミカル日本製のインスパイア、ＢＯＲＥＡＬＩＳ社製のＤａｐｌｏｙ ＷＢ１３０ＨＭＳなどを挙げることができる。 An index value indicating the degree of long-chain branching of polypropylene includes a branching index g represented by the following formula (1).

Here, [η] LB is an intrinsic viscosity of polypropylene having a long chain branch, and [η] Lin is a linear crystalline polypropylene having substantially the same weight average molecular weight as the polypropylene having a long chain branch. Intrinsic viscosity.
In addition, the weight average molecular weight of polypropylene having a long chain branch is M.P. L. It can be measured by a low angle laser light scattering photometric method described by McConnell in American Laboratory, May, 63-75 (1978).
Examples of a general method for producing polypropylene having a long chain branch in the main chain skeleton include methods such as crosslinking by radiation (high energy) irradiation, peroxide crosslinking, and copolymerization. Specific examples of polypropylene having a long chain branch in these main chain skeletons include Inspire manufactured by Dow Chemical Japan, Daploy WB130HMS manufactured by BOREALIS.

In the uniaxially stretched resin film used in the present invention, the crystalline polyolefin resin (A) is added in a proportion of 18 to 42% by weight. This is preferably in the range of 22-37% by weight. If the crystalline polyolefin-based resin (A) is less than 18% by weight, the pore-forming property and stretchability are lowered, which is not preferable. On the other hand, when the crystalline polyolefin resin (A) exceeds 42% by weight, the number of pores formed and the tear strength of the stretched film are lowered, which is not preferable.
Regarding the blending of the crystalline polyolefin resin (A), more specifically, the high melt tension polypropylene having a melt tension in the range of 10 to 60 g with respect to 100 parts by weight of the crystalline propylene resin having a melt tension of less than 10 g. A mixture containing 0.5 to 22 parts by weight is preferred. More preferably, it is a mixture of 5 to 15 parts by weight of high melt tension polypropylene with respect to 100 parts by weight of the crystalline propylene resin.
If it is within the same range, when casting the cast resin from the die to the cast roll by lateral drawing, the dripping phenomenon of the molten resin sheet is suppressed, and in the case of vertical drawing, the drawdown is suppressed, and the cast sheet The formability can be improved, and the sheet can be prevented from cracking without impairing the stretch formability. Since the uniaxially stretched resin film of the present invention blends the inorganic fine powder (D) described later at a high concentration, the thermoplastic elastomer (B) described later is blended into the matrix resin so as to facilitate stretch molding. By adjusting the melt tension of the entire product with the crystalline polyolefin resin (A), stable stretch molding is facilitated while forming pores with the inorganic fine powder (D) as a core.

[Thermoplastic elastomer (B)]
The uniaxially stretched resin film constituting the water-permeable film of the present invention contains a thermoplastic elastomer (B). In the present invention, the thermoplastic elastomer (B) is added to improve the tear strength of the film, prevent tearing during the stretch molding, and impart characteristics such as production stability.
Examples of the thermoplastic elastomer (B) that can be used in the present invention include one or more thermoplastic elastomers selected from styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, and ester-based thermoplastic elastomers. can do. Among these, a styrene thermoplastic elastomer is preferable from the viewpoint of easy dispersion in the crystalline polyolefin resin (A) which is a matrix resin.

Styrene-based elastomers include styrene butadiene styrene block copolymer (SBS), styrene isoprene styrene block copolymer (SIS), styrene ethylene butylene styrene block copolymer (SEBS), and styrene ethylene propylene styrene block copolymer (SEPS). And hydrogenated styrene butadiene rubber (HSBR). Specific examples of these styrenic elastomers include Dynalon manufactured by JSR, Tuftec manufactured by Asahi Kasei, Kraton G manufactured by Kraton Polymer, Shibster manufactured by Kaneka, and Hibler manufactured by Kuraray. As the styrene elastomer, hydrogenated styrene butadiene rubber is particularly preferable, and Dynalon manufactured by JSR is particularly preferable. As hydrogenated styrene butadiene rubber, those having a styrene content of 20% by weight or less can be easily finely dispersed in the crystalline polyolefin resin (A) which is a matrix resin, and the stretch moldability is improved. Most preferred.
Examples of the olefin elastomer include ethylene propylene copolymer (EPM), ethylene propylene diene copolymer (EPDM), and those having structures such as blends of PP and PE, block copolymers, and graft copolymers. Specific examples of these olefin elastomers include Vistamax manufactured by Mitsui Chemicals, Notio manufactured by the company, Prime TPO manufactured by Prime Polymer, Versify manufactured by Dow Chemical Japan, and Zelas manufactured by Mitsubishi Chemical. .

As the urethane elastomer, a polymer chain composed of diisocyanate and short chain glycol (ethylene glycol, propylene glycol, 1,4-butanediol, bisphenol A, etc.) is used as a hard segment, and a polymer chain composed of diisocyanate and long chain polyol is used as a soft segment. The thing which has the structure to do can be mentioned. Specific examples of these urethane elastomers include elastollan manufactured by BASF Japan, texin manufactured by DIC Bayer Polymer, and milactolan manufactured by Nippon Polyurethane.
As the ester elastomer, polybutylene terephthalate (PBT) is a hard segment, and a polyether ester copolymer having a soft segment such as polytetramethylene glycol ether (PTMG) or PTMEG (condensate of PTMG and terephthalic acid), Mention may be made of those having a structure such as a polyester-ester copolymer. Specific examples of these ester elastomers include Byron manufactured by Toyobo Co., Ltd.

  In the uniaxially stretched resin film constituting the water-permeable film of the present invention, the thermoplastic elastomer (B) is added in a proportion of 5 to 15% by weight, and preferably in the range of 8 to 12% by weight. If the thermoplastic elastomer (B) is less than 5% by weight, the tear strength is undesirably lowered. On the other hand, the pore-forming property of the thermoplastic elastomer (B) exceeding 15% by weight is not preferable.

[Inorganic fine powder (D)]
The uniaxially stretched resin film constituting the water-permeable film of the present invention contains an inorganic fine powder (D) surface-treated with a surface treatment agent (C). In the present invention, the inorganic fine powder (D) is added for imparting water permeability to the water permeable film.
Examples of the inorganic fine powder (D) that can be used in the present invention include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, titanium oxide, barium sulfate, zinc oxide, magnesium oxide, diatomaceous earth, and silicon oxide. Examples thereof include a composite inorganic fine powder having aluminum oxide or hydroxide around the core of the inorganic fine powder, and hollow glass beads. Among these, heavy calcium carbonate, calcined clay, and diatomaceous earth are preferable because they are inexpensive and can form many pores during stretching, and the porosity can be easily adjusted. Heavy calcium carbonate and light calcium carbonate are preferable because the average particle size and particle size distribution can be easily obtained.

  In order to hydrophilize these inorganic fine powder (D), the surface treatment agent (C) for treating the surface of the inorganic fine powder (D) is water-soluble and has an average molecular weight of 1,000 to 150,000. A range of anionic or cationic or nonionic polymeric surfactants can be mentioned. Examples of these polymer surfactants include those described in JP-A-10-212367.

  The inorganic fine powder (D) hydrophilized with the surface treatment agent (C) is added to the uniaxially stretched resin film constituting the water-permeable film of the present invention at a ratio of 45 to 75% by weight. The proportion is preferably in the range of 50 to 70% by weight. If the inorganic fine powder (D) is less than 45% by weight, formation of communication holes (communication holes) becomes difficult, which is not preferable. On the contrary, film stretch molding in which the inorganic fine powder (D) exceeds 75% by weight becomes extremely difficult, which is not preferable. In addition to the inorganic fine powder (D), different inorganic fine powders may be combined and blended. Also in this case, when the total amount of the inorganic fine powder exceeds 75% by weight, the stretch moldability of the film deteriorates, which is not preferable.

[Inorganic fine powder (D) hydrophilized with surface treatment agent (C)]
In the present invention, the hydrophilic treatment of the inorganic fine powder (D) with the surface treatment agent (C) is an anionic system that is water-soluble and has an average molecular weight in the range of 1,000 to 150,000 when the inorganic particles are wet-ground. Alternatively, it can be carried out by introducing a cationic or nonionic polymer surfactant and subjecting it to a surface treatment while grinding. Moreover, when wet-grinding an inorganic compound, it can also carry out by surface-treating with an anionic, cationic or nonionic antistatic agent. Both of these processes may be performed individually. Preferable examples of the inorganic fine powder (D) subjected to the hydrophilization treatment include those described in JP-A-7-300568.
Specific examples of the inorganic fine powder (D) hydrophilized with the surface treatment agent (C) include AFF-Z manufactured by PMMA Tech.

[Dispersant (E)]
The uniaxially stretched resin film constituting the water-permeable film of the present invention may contain a dispersant (E). In the present invention, the dispersant (E) improves the dispersibility of the inorganic fine powder (D) in the water-permeable film, and imparts characteristics such as improved uniformity of pores and improved water permeability in the water-permeable film. To be added. As the dispersant (E) that can be used in the present invention, known ones can be used, but acid-modified polyolefin resins are particularly preferable, and specific examples include Umex 1001 manufactured by Sanyo Chemical Industries.
When using a dispersing agent (E) for the uniaxially stretched resin film which comprises the water-permeable film of this invention, it is preferable to add in the ratio of 0.01 to 10 weight%. If the dispersant (E) is less than 0.01% by weight, the original function of the dispersant cannot be sufficiently exhibited, which is not preferable. Conversely, if the dispersant (E) exceeds 10% by weight, the inorganic fine powder (D) may be aggregated, which is not preferable.

[Additive]
If necessary, the uniaxially stretched resin film of the present invention may be blended with known additives such as a heat stabilizer, an ultraviolet stabilizer, an antioxidant, an antiblocking agent, a nucleating agent, a lubricant, and a colorant. . These additives can be added to layers other than the uniaxially stretched resin film constituting the water-permeable film of the present invention. These additives are preferably blended in each layer in a proportion of 0.01 to 3% by weight.

The manufacturing method of a water-permeable film The water-permeable film of this invention can be manufactured by combining the various methods well-known to those skilled in the art. A water-permeable film produced by any method is included in the scope of the present invention as long as it satisfies the conditions described in the claims.

[Production method of the present invention]
The uniaxially stretched resin film constituting the water-permeable film of the present invention is preferably produced according to the production method of the present invention. Namely, 18 to 42% by weight of crystalline polyolefin resin (A), 5 to 15% by weight of thermoplastic elastomer (B), and inorganic fine powder (D) whose surface is hydrophilized with a surface treatment agent (C) A resin sheet is produced using a resin composition containing 45 to 75% by weight, and then the water permeability measured according to JIS-Z0221: 1976 is 0.1 to 0.1 by stretching the resin sheet uniaxially. It is preferable to produce a uniaxially stretched resin film that is 2000 seconds. The production method of the present invention includes a production process of such a uniaxially stretched resin film.

[Formation of resin sheet]
The method for producing a resin sheet using the resin composition is not particularly limited, and can be appropriately selected and employed from commonly used methods.
For example, the method of manufacturing a resin sheet can be mentioned by casting and cooling the molten resin composition. At this time, the resin composition melts at a temperature that is usually 30 to 110 ° C., preferably 50 to 90 ° C. higher than the melting temperature of the resin composition. When melting, it is preferable to knead simultaneously. The molten resin composition is cast into a sheet. At this time, for example, a method of melt-kneading the resin composition using an extruder or the like and extruding it from a T-die into a sheet can be preferably employed. The resin composition cast into a sheet is then cooled to a resin sheet using a cooling device or the like.

[Layer structure]
The water-permeable film of the present invention may have a single layer structure or a multilayer structure in which two or more layers are laminated. In the case of a single layer structure, a uniaxially stretched resin film obtained by stretching a resin sheet obtained by extruding the resin composition made of the above raw material in a sheet shape in a uniaxial direction can be used as it is as a water permeable film.
In the case of a multilayer structure, a uniaxially stretched resin film having a structure in which surface layers having different compositions are laminated on at least one surface can be used as the water permeable film. In the case of a multilayer structure, it may be produced by forming each layer separately and then laminating, or may be produced by stretching together after lamination.
When laminating after forming separately, the surface layer may be another stretched resin film, a woven fabric, a non-woven fabric, or a resin coating layer. Further, for example, another thermoplastic resin film layer or a nonwoven fabric layer may be further included as an intermediate layer between the uniaxially stretched resin film and the surface layer.
When extending | stretching collectively after lamination | stacking, it can obtain as a laminated structure orientated in the uniaxial direction of all the layers, for example by laminating | stacking a surface layer on one surface of a resin sheet, and extending | stretching after that in 1 axial direction. Alternatively, a resin sheet can be stretched in a uniaxial direction, and then a surface layer can be laminated to obtain a laminated structure. As described above, after laminating each layer, it is easier to stretch the layers together and the manufacturing cost is reduced.

The other layers (surface layer, intermediate layer) are provided for further improving the function of the water-permeable film of the present invention or adding a new function.
For example, if the water permeability and osmotic pressure of each layer are changed stepwise in the thickness direction, water and other liquids can be sucked up from one side, Although it is possible to contain a liquid inside and to release the liquid gradually from the other surface, it is possible to impart selectivity of the water permeation direction and the like in the opposite direction.
As said nonwoven fabric, the spun bond nonwoven fabric for improving physical strength, such as tear resistance at the time of use for a water-permeable film, etc. are mentioned, for example.
As said resin coating layer, the well-known recording layer for using a water-permeable film as an inkjet recording paper etc. are mentioned, for example.

[Stretching]
The water-permeable film of the present invention includes a uniaxially stretched resin film stretched in a uniaxial direction. Various known methods can be employed for stretching the film.
As a specific method of uniaxial stretching, stretching between rolls (hereinafter referred to as “longitudinal stretching” in the present invention) that stretches by utilizing the peripheral speed difference of the roll group in the transport direction of the resin sheet, in the transport direction of the resin sheet Examples thereof include clip stretching (hereinafter referred to as lateral stretching in the present invention) stretched using a tenter oven in an orthogonal direction (width direction), an inflation molding method utilizing a tubular method, and the like.
According to the longitudinal stretching method, it is easy to obtain a uniaxially stretched resin film having an arbitrary porosity, rigidity, opacity, smoothness, and glossiness by arbitrarily adjusting the stretching ratio.
In particular, the longitudinal stretching method is preferable because it is easy to obtain a water-permeable film having an arbitrary water permeability by arbitrarily adjusting the porosity. Accordingly, the draw ratio is not particularly limited, and is determined in consideration of the physical properties desired for the water-permeable film of the present invention and the properties of the thermoplastic resin used. The stretching ratio in the longitudinal stretching method is usually in the range of 3 to 11 times, preferably 4 to 10 times, and more preferably 5 to 7 times. Within the same range, a uniaxially stretched resin film having desired physical properties can be stably produced.

According to the transverse stretching method, the width of the obtained stretched film can be easily adjusted although there is no degree of freedom in stretching ratio as long as the longitudinal stretching method due to equipment limitations. If the stretched film width can be increased, the application can be easily expanded. The draw ratio of the transverse drawing method is usually 4 to 11 times, more preferably 4 to 10 times, and particularly preferably 5 to 9 times. By setting the draw ratio to 4 times or more, there is a tendency that communication holes are formed and it becomes easy to produce a uniaxially stretched resin film having a more uniform film thickness by preventing stretching unevenness. Moreover, by making it 11 times or less, there exists a tendency which becomes easy to prevent extending | stretching cut | disconnection and coarse perforation more effectively.
The stretching temperature is 5 ° C. or more lower than the melting point of the matrix resin, more preferably 5 ° C. or more lower than the melting point of the crystalline polyolefin resin (A) and higher than the softening temperature of the thermoplastic elastomer (B). preferable.

[Heat treatment]
The stretched film is preferably subjected to a heat treatment for the purpose of relaxing the tension of the polymer molecular chain accompanying the stretching. The temperature of the heat treatment is preferably selected within the range of a temperature 30 ° C. higher than the stretching temperature from the stretching temperature. The time of heat processing is 0.1 second-30 seconds normally, Preferably it is 0.5 second-20 seconds, More preferably, it is 1 second-10 seconds. By performing the heat treatment, the thermal shrinkage rate due to the stretching stress in the stretching direction is reduced, and sheet undulation and the like resulting from tightening during product storage and shrinkage due to heat are reduced. The heat treatment is generally performed by roll heating or a heat oven, but may be combined.
These heat treatments are preferably performed in a state where the stretched film is held under tension because a higher treatment effect can be obtained.

[Transport]
The water-permeable film of the present invention can be produced while conveying a resin film. That is, a water-permeable film can be efficiently manufactured by carrying out the uniaxial stretching, conveying the resin film formed from the resin composition, and performing heat processing as needed. In the case of longitudinal stretching, the conveying speed is usually 10 to 500 m / min, preferably 30 to 300 m / min, and more preferably 50 to 200 m / min. In the case of lateral stretching, it is usually 10 to 150 m / min, preferably 30 to 120 m / min, and more preferably 50 to 100 m / min. Moreover, if it manufactures conveying using a strip | belt-shaped resin sheet, the water-permeable film of this invention can also be manufactured continuously. A band-shaped water-permeable film continuously produced from a band-shaped resin sheet may be cut into a desired size during the production process, or once wound up in a roll and stored and transported as necessary. You may cut | judge to a desired size.
When a conventional water-permeable film is transported and stretched to be efficiently manufactured, the sheet is cut by tension, and it is difficult to continuously and stably manufacture the film. On the other hand, according to the present invention, it is possible to continuously and stably manufacture at high speed without cutting the sheet. Further, according to the present invention, the treatment of the solvent waste liquid and the precise temperature control required in the conventional method for producing a water-permeable film can be dispensed with according to the production method of the present invention. it can. Therefore, according to this invention, the functionally excellent water-permeable film can be manufactured efficiently.

Features of water-permeable film [thickness]
The thickness of the uniaxially stretched resin film constituting the water-permeable film of the present invention is not particularly limited, but is preferably 20 to 400 μm, more preferably 40 to 200 μm, and still more preferably 50 to 160 μm. When the water-permeable film of this invention is comprised only from a uniaxially stretched resin film, the preferable range of the total thickness of a water-permeable film is the same as the preferable range of the thickness of the said uniaxially stretched resin film. When the water-permeable film of the present invention has a structure in which a surface layer is laminated on at least one surface of a uniaxially stretched resin film, the thickness of the surface layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 3 to 30 μm. 10 μm is more preferable. When the water-permeable film of the present invention has a structure in which surface layers are laminated on both surfaces of a uniaxially stretched resin film, the thicknesses of the two surface layers are preferably the same from the viewpoint of preventing warping of the film. Moreover, when the intermediate layer is formed between the uniaxially stretched resin film and the surface layer, the thickness of the intermediate layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 5 to 30 μm, and further preferably 10 to 20 μm. preferable.

[Porosity]
The porosity of the uniaxially stretched resin film constituting the water-permeable film of the present invention is preferably 28 to 64%. It is more preferably 33 to 57%, particularly preferably 36 to 54%. When the porosity of the uniaxially stretched resin film is 28% or more, there is a tendency that pores communicating with the inside of the film are generated and desired water permeability is easily developed. Moreover, if the porosity is 64% or less, stretch cracks are unlikely to occur during film production, and therefore, more stable production tends to be performed. The porosity of the uniaxially stretched resin film can be controlled by adjusting the content of the thermoplastic elastomer (B) and the inorganic fine powder (D) and the stretch ratio.

The presence of pores inside can be confirmed by observing the cross section with an electron microscope. The porosity is obtained by taking an electron micrograph of a cross section and determining the area ratio (%) of the occupancy in the cross-sectional area taken in the photograph. Specifically, after embedding a uniaxially stretched resin film with an epoxy resin and solidifying it, using a microtome, for example, a cut surface parallel to the thickness direction of the film (that is, perpendicular to the surface direction) is produced. After the metallization of this cut surface, it is observed by enlarging to an arbitrary magnification (for example, 500 times to 2000 times) that is easy to observe with a scanning electron microscope, and further, the void portion is traced on the tracing film and painted. Is subjected to image processing with an image analysis apparatus (manufactured by Nireco Co., Ltd .: model Luzex IID), and the area ratio (%) of the holes occupying the measurement range can be obtained to obtain the porosity (%).
When the water permeable film has a multilayer structure, the porosity (%) can be determined for each layer by the above method.

[density]
Density of uniaxially stretched resin film constituting the water-permeable film of the present invention is preferably 0.5~1.1g / cm ^3, more preferably 0.6~1.0g / cm ³ 0.7 to 0.9 g / cm ³ is more preferable. When the density of the uniaxially stretched resin film is 0.5 g / cm ³ or more, there is a tendency that pores communicating with the inside of the film are generated and desired water permeability is easily developed. In addition, if the density is 1.1 g / cm ³ or less, stretch cracks are unlikely to occur during film production, so that more stable production tends to be performed. The density of the uniaxially stretched resin film can be controlled by adjusting the content of the thermoplastic elastomer (B) and the inorganic fine powder (D) and the stretch ratio.

[Water permeability]
Since the water-permeable film of the present invention has pores communicating in the thickness direction, liquid such as water and oil can be easily transmitted from one surface to the other surface. Specifically, the water permeability measured based on JIS-Z0221: 1976 is 0.1 to 2,000 seconds. The water permeability is preferably 1 to 1000 seconds, and more preferably 1 to 200 seconds. When the water permeability is 0.1 seconds or more, instantaneous water absorption / permeation is possible. Moreover, when the water permeability is 2,000 seconds or less, the function as a water-permeable film can be sufficiently exhibited.
The water-permeable film of the present invention can achieve the above water permeability from the structural features such as the degree of communication of pores inside the film, the size of the pores, the number of pores, and the like. Therefore, the water permeability of the water-permeable film of the present invention can be controlled by adjusting, for example, the particle diameter of the inorganic fine particle powder, the blending amount of the inorganic fine powder, the blending amount of the thermoplastic elastomer, the stretching temperature, the stretching ratio, and the like. it can.

  Battery and electrolytic capacitor separators are required to have high water permeability. Various filtration membranes require water permeability and filtration accuracy.

[Product of tear strength and displacement]
The water-permeable film of the present invention has the same tear strength (kgf / mm) in the direction perpendicular to the film stretching direction measured based on the right angle tearing method of JIS-K7128-3: 1998 and the test speed A. It is preferable that the product of the amount of displacement (tensile elongation, mm) until the test piece breaks during the test is 10 kgf or more. The product of tear strength and displacement represents the difficulty of tearing a water-permeable film, and is a measure of the ease of handling during manufacturing (sheet cracking difficulty) and the ease of handling during various processing. is there.

If the product of tear strength and displacement is large, the difficulty of tearing during film production can be avoided, but if the product is too large, it is difficult to form fine pores that communicate with each other, making it difficult to obtain the water permeability that is the gist of the present invention. There is a tendency to end up. Moreover, if the product of tear strength and displacement is small, sufficient pores can be obtained and the water permeability can be easily achieved. However, if the product is too small, the production stability tends to decrease.
For this reason, the product of tear strength and displacement is more preferably 10 to 200 kgf, and particularly preferably 15 to 100 kgf. If the product of tear strength and displacement is 10 kgf or more, it tends to be easy to avoid the occurrence of tearing during winding and various processing. Moreover, if it is 200 kgf or less, there exists a tendency for desired water permeability to be obtained easily.
The product of tear strength and displacement can be adjusted mainly by the blending ratio of thermoplastic elastomer (B) and inorganic fine powder (D) in terms of raw material composition, and mainly adjusted by the draw ratio and draw temperature in terms of manufacturing conditions. Is possible.

Use of water-permeable film The water-permeable film of the present invention is porous, can hold and absorb liquid in the entire thickness direction by osmotic pressure, and can be permeated by further applying pressure. Therefore, the water-permeable film of the present invention includes a liquid absorbent, a liquid absorbent wiping material, a protective cushioning material for packing and packaging, a building material, a curing sheet and a joint material for civil engineering, a dew condensation prevention material, and a heat insulation for livestock houses. Materials, cushions, padding for writing instruments, suction cores for fragrances, medium for hydroponics, filter media such as filters, various microfiltration membranes, separators for batteries and electrolytic capacitors, members for heat-sensitive paper, and ink receptors It can be used for applications such as members, outlets for liquid glue, microbubble generating members, synthetic seine leather substitutes, cell culture sheets and the like.
Since the water-permeable film of the present invention is a resin-made water-permeable film that is particularly durable and has a uniform and accurate pore size and distribution, the separator of a battery or electrolytic capacitor, It can be used appropriately for various microfiltration membranes and liquid absorbent articles.
When the water-permeable film of the present invention is used as a separator or various filtration membranes, unlike conventional products, a plasticizer and / or a solvent are added and eluted, or low molecular weight components are removed and high molecular weight polyolefin fibrils are used. It is not necessary to perform a heat treatment step for formation, and water permeability can be imparted without requiring hydrophilic treatment after film formation.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples and test examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the production examples and examples can be appropriately changed without departing from the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Production Example Using the raw materials listed in Table 1, resin compositions used for the production of uniaxially stretched resin films were prepared according to the blending amounts (% by weight) listed in Table 2 (Formulation Examples 1 to 35). Raw material No. described in Table 2 Is the raw material No. described in Table 1. It corresponds to. Here, regarding the crystalline polyolefin resin (A), a raw material measured using a capilograph manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of a temperature of 190 ° C., a capillary diameter of 2 mm, a piston speed of 10 mm / min, and a take-up speed of 10 m / min. No. No. 1 crystalline polypropylene has a melt tension of 12.2 g. 2 has a melt tension of 2 g. No. 3 crystalline polypropylene has a melt tension of 1.07 g. The melt tension of No. 4 long-chain branched polypropylene was 25 g. Moreover, No. which is a styrene-type elastomer. No. 5 has a styrene content of 10% by weight. The styrene content of 6 is 15% by weight.
Next, the uniaxially stretched resin film was manufactured according to the extending | stretching conditions of Table 3-Table 6 using the resin composition of the compounding example of Table 3-Table 6 (manufacture examples 1-84). The details of the manufacturing process are as follows. Formulation example No. of each layer described in Table 3 to Table 6. Is the formulation example No. described in Table 2. It corresponds to.

[Production Examples 1 to 18]
A resin composition having the composition shown in Table 2 is melt-kneaded with an extruder set at 250 ° C., extruded into a sheet form from a T-die, and cooled to 80 ° C. with a cooling device to be an unstretched resin. A sheet was obtained.
After heating the resin sheet to the stretching temperature described in Table 3, the resin sheet was uniaxially stretched at a stretching ratio described in Table 3 in the conveying direction (longitudinal direction) of the resin sheet by an inter-roll stretching method, and further at 160 ° C. Heat treatment was performed. Then, it cooled at 60 degreeC and slit the ear | edge part, and obtained the uniaxially stretched resin film. The conveyance speed of the resin sheet and the uniaxially stretched resin film in the region other than the stretching zone was controlled to be 20 m / min after stretching.
In addition, about manufacture example 12, 13 and manufacture example 18, it fractured | ruptured at the time of extending | stretching, and the uniaxially stretched resin film was not able to be obtained.
The physical properties (thickness, density, porosity) of these uniaxially stretched resin films were as shown in Table 3.

[Production Examples 19 to 36]
A resin composition having the composition shown in Table 2 is melt-kneaded with an extruder set at 250 ° C., extruded into a sheet form from a T-die, and cooled to 80 ° C. with a cooling device to be an unstretched resin. A sheet was obtained.
After heating this resin sheet to the stretching temperature described in Table 4, the resin sheet was uniaxially stretched at the stretching ratio described in Table 4 in the width direction (lateral direction) of the resin sheet by a clip stretching method using a tenter stretching machine. Further, heat treatment was performed at 160 ° C. Then, it cooled at 60 degreeC and slit the ear | edge part, and obtained the uniaxially stretched resin film. The conveyance speed of the resin sheet and the uniaxially stretched resin film in the region other than the stretching zone was controlled to 12 m / min. In addition, Production Examples 30, 31 and Production Example 36 were frequently broken during stretching, and a uniaxially stretched resin film could not be obtained.
The physical properties (thickness, density, porosity) of these uniaxially stretched resin films were as shown in Table 4.

[Production Examples 37 to 56, 58 to 61]
A resin composition having the composition shown in Table 2 is melt-kneaded with an extruder set at 250 ° C., extruded into a sheet form from a T-die, and cooled to 80 ° C. with a cooling device to be an unstretched resin. A sheet was obtained.
After heating this resin sheet to the extending | stretching temperature of Table 5, it is uniaxially stretched by the draw ratio of Table 5 in the conveyance direction (longitudinal direction) of the resin sheet by the stretching method between rolls, and a uniaxially stretched resin film Got. The conveyance speed of the resin sheet and the uniaxially stretched resin film in the region other than the stretching zone was controlled to be 20 m / min after stretching.
In addition, Production Example 43 and Production Example 61 were frequently broken during stretching, and a uniaxially stretched resin film could not be obtained.
The physical properties (thickness, density, porosity) of these uniaxially stretched resin films were as shown in Table 5.

[Production Example 57]
The resin composition of Formulation Example 18 shown in Table 2 was melt-kneaded with an extruder set at 250 ° C., extruded into a sheet form from a T-die, cooled to 80 ° C. with a cooling device, and unstretched. A resin sheet was obtained. Further, the resin composition having the composition of Formulation Example 35 shown in Table 2 was melted and kneaded with an extruder set at 250 ° C., extruded from a T-die into a sheet, and laminated on the front and back surfaces of the resin sheet, respectively. Thus, a resin sheet having a laminated structure of surface layer [b] / base material layer [a] / back surface layer [c] was obtained.
After heating this resin sheet to the extending | stretching temperature of Table 5, it is uniaxially stretched by the draw ratio of Table 5 in the conveyance direction (longitudinal direction) of the resin sheet by the stretching method between rolls, and a uniaxially stretched resin film Got. The conveyance speed of the resin sheet and the uniaxially stretched resin film in the region other than the stretching zone was controlled to be 20 m / min after stretching.
The physical properties (layer thickness, density, porosity) of this uniaxially stretched resin film were as shown in Table 5.

[Production Examples 62 to 79, 81 to 84]
A resin composition having the composition shown in Table 2 is melt-kneaded with an extruder set at 250 ° C., extruded into a sheet form from a T-die, and cooled to 80 ° C. with a cooling device to be an unstretched resin. A sheet was obtained.
After heating the resin sheet to the stretching temperature described in Table 6, the resin sheet was uniaxially stretched at the stretching ratio described in Table 6 in the width direction (lateral direction) of the resin sheet by a clip stretching method using a tenter stretching machine. A uniaxially stretched resin film was obtained. The conveyance speed of the resin sheet and the uniaxially stretched resin film in the region other than the stretching zone was controlled to 12 m / min. Note that Production Example 66 and Production Example 84 were frequently broken during stretching, and a uniaxially stretched resin film could not be obtained.
The physical properties (thickness, density, porosity) of these uniaxially stretched resin films were as shown in Table 6.

[Production Example 80]
The resin composition of Formulation Example 18 shown in Table 2 was melt-kneaded with an extruder set at 250 ° C., extruded into a sheet form from a T-die, cooled to 80 ° C. with a cooling device, and unstretched. A resin sheet was obtained. Further, the resin composition having the composition of Formulation Example 35 shown in Table 2 was melted and kneaded with an extruder set at 250 ° C., extruded from a T-die into a sheet, and laminated on the front and back surfaces of the resin sheet, respectively. Thus, a resin sheet having a laminated structure of surface layer [b] / base material layer [a] / back surface layer [c] was obtained.
After heating the resin sheet to the stretching temperature described in Table 6, the resin sheet was uniaxially stretched at the stretching ratio described in Table 6 in the width direction (lateral direction) of the resin sheet by a clip stretching method using a tenter stretching machine. A uniaxially stretched resin film was obtained. The conveyance speed of the resin sheet and the uniaxially stretched resin film in the region other than the stretching zone was controlled to 12 m / min.
The physical properties (thickness, density, porosity) of this uniaxially stretched resin film were as shown in Table 6.

Examples 1 to 56 and Comparative Examples 1 to 18
Production Examples 1 to 11, Production Examples 14 to 17, Production Examples 19 to 29, Production Examples 32 to 35, Production Examples 37 to 42, Production Examples 44 to 60, Production Examples 62 to 65, and Production Examples 67 to 83 are obtained. In addition, in each uniaxially stretched resin film, the following tests were carried out with the examples within the scope of the present invention as examples and the comparative examples as those outside the scope of the present invention. The test results are shown in Table 7 and Table 8.

[Water permeability]
The water permeability of the produced uniaxially stretched resin film was measured according to JIS-Z0221: 1976. The measurement was performed three times from the front side and the back side, respectively, and the average value of a total of six times was taken as the measured value. The quality of water permeability was determined according to the following criteria.
○: 0.1 to 2000 seconds ×: less than 0.1 seconds or more than 2000 seconds

[Extensible]
The number of film breaks when the uniaxially stretched resin film of each production example was continuously produced for 1 hour was counted, and the quality of stretchability was judged according to the following criteria.
○: 0 to 1 time ×: 2 times or more

[Right-angled tear strength and displacement to break]
The right-angled tear strength of the produced uniaxially stretched resin film and the amount of displacement up to the fracture were measured according to the test measure A of the right-angled tear method defined in JIS-K7128-3: 1998.
Test specimens from each uniaxially stretched resin film in the direction perpendicular to the stretching axis (in the case of longitudinal stretching in the horizontal direction of FIG. 1 of the same JIS and in the case of lateral stretching in the longitudinal direction of FIG. 1) of 5 test pieces. Collected.
The tensile tester (Orientec Co., Ltd., RTM-250) is attached with a tensile test knob, the test piece is attached, the test is performed at a speed of 200 mm per minute, and the maximum when the test piece is completely torn The load was the tear strength (kgf / mm).
The amount of displacement (mm) until breakage is the amount of movement of the crosshead (movable knob) of the tester at the moment of breakage after the test piece is no longer loosened and tension is applied to the test piece. It was.
The measurement was performed 5 times, and the average value was taken as the measurement value and used for product calculation. A uniaxially stretched resin film in which the product of the right-angled tear strength and the amount of displacement until breakage was less than 10 kgf was a film that was easily notched and easily torn, and was judged to have poor moldability. Conversely, if this exceeds 200 kgf, the moldability is good, but the required water permeability tends to be difficult to obtain. Therefore, the quality was determined according to the following criteria.
○: Product is 10-200kgf
X: Product is less than 10 kgf or more than 200 kgf

  The water-permeable film of the present invention can be produced in the same stretching process as a general porous film production method, and can be set to any water permeability, and is superior to conventional water-permeable films. It has performance. Therefore, the water-permeable film of the present invention has many industrial advantages and is extremely useful.

Claims (24)

A water-permeable film comprising a uniaxially stretched resin film having a water permeability measured in accordance with JIS-Z0221: 1976 of 0.1 to 2000 seconds and containing at least the following three components.
1) Crystalline polyolefin resin (A)
18-42% by weight
2) Thermoplastic elastomer (B)
5-15% by weight
3) Inorganic fine powder (D) whose surface is hydrophilized with the surface treatment agent (C)
45-75% by weight   The thermoplastic elastomer (B) is one or more thermoplastic elastomers selected from the group consisting of styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, and ester-based thermoplastic elastomers. The water-permeable film according to claim 1.   The water-permeable film according to claim 2, wherein the thermoplastic elastomer (B) is a styrene-based thermoplastic elastomer.   The water-permeable film according to claim 3, wherein the styrenic thermoplastic elastomer is hydrogenated styrene butadiene rubber.   The water-permeable film according to claim 4, wherein the hydrogenated styrene-butadiene rubber has a styrene content of 20% by weight or less.  The crystalline polyolefin resin (A) includes 0.5 to 22 parts by weight of high melt tension polypropylene having a melt tension of 10 to 60 g in 100 parts by weight of a crystalline polyolefin resin having a melt tension of less than 10 g. The water-permeable film according to claim 1.   The water permeable film according to claim 6, wherein the high melt tension polypropylene is a polypropylene (A ') having a long chain branch in the main chain skeleton.   8. The water permeable film according to claim 1, wherein the uniaxially stretched resin film has a porosity of 28 to 64%.   The surface treatment agent (C) is a water-soluble anionic surfactant having an average molecular weight of 1,000 to 15,000, a water-soluble cationic surfactant having an average molecular weight of 1,000 to 15,000, and an average molecular weight. Is a surface treatment agent selected from the group consisting of 1,000 to 15,000 water-soluble nonionic surfactants, The water-permeable film according to any one of claims 1 to 8, .   The water-permeable film according to any one of claims 1 to 9, wherein the uniaxially stretched resin film further contains a dispersant (E) of an inorganic fine powder.   The tear strength (kgf / mm) in the direction perpendicular to the film stretching axis measured based on the JIS-K7128-3: 1998 right angle tearing method, test speed A of the uniaxially stretched resin film, and the same tear The product with displacement (mm) until the fracture of the test piece at the time of the test is 10 to 200 kgf, The water permeable film according to any one of claims 1 to 10.   The water-permeable film according to claim 1, comprising only the uniaxially stretched resin film.   The water-permeable film according to claim 1, wherein the uniaxially stretched resin film has a structure in which a base layer is provided and a surface layer is further provided on at least one surface thereof.   18 to 42% by weight of crystalline polyolefin resin (A), 5 to 15% by weight of thermoplastic elastomer (B), and inorganic fine powder (D) 45 to 45 whose surface is hydrophilized with a surface treatment agent (C) A resin sheet is produced using a resin composition containing 75% by weight, and then the water permeability measured in accordance with JIS-Z0221: 1976 is 0.1 to 2000 seconds by uniaxially stretching the resin sheet. The manufacturing method of the water-permeable film containing the said uniaxially stretched resin film characterized by including the process of manufacturing the uniaxially stretched resin film which is.   The method for producing a water-permeable film according to claim 14, wherein the thermoplastic elastomer (B) is a styrene-based elastomer.   The method for producing a water-permeable film according to claim 15, wherein the styrene elastomer is hydrogenated styrene butadiene rubber.   The water permeable according to any one of claims 14 to 16, wherein the resin sheet is stretched so that a porosity of a uniaxially stretched resin film produced by stretching is 28 to 64%. For producing a conductive film.   The method for producing a water-permeable film according to any one of claims 14 to 17, wherein the resin sheet is stretched uniaxially in a transport direction of the resin sheet.   The method for producing a water-permeable film according to any one of claims 14 to 17, wherein the resin sheet is stretched uniaxially in a direction orthogonal to a conveyance direction of the resin sheet.   The method for producing a water-permeable film according to any one of claims 14 to 19, wherein the resin sheet is stretched 4 to 10 times.   The water-permeable film manufactured by the manufacturing method as described in any one of Claims 14-20.   The separator using the water-permeable film as described in any one of Claims 1-13 or 21.   The microfiltration membrane using the water-permeable film as described in any one of Claims 1-13 or 21.   The liquid absorbent article using the water-permeable film as described in any one of Claims 1-13 or 21.