laminated film

Abstract

To provide a laminated film that is excellent in air permeability and bacteria separability.SOLUTION: This laminated film 10A has a polyolefin microporous membrane 20 and a porous support layer 30. The polyolefin microporous membrane 20 and the porous support layer 30 are bonded together by dispersed bonding sections 40 including a thermoplastic resin. The bubble point of the laminated film is 20 to 900 kPa.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a laminated film. [Background technology]

[0002] Patent Document 1 discloses a porous polyethylene membrane that can be used as a filtration medium. Patent Document 2 discloses a porous laminate having a polyolefin porous film and a polyolefin fiber layer, which is used as a medical sterilization packaging material. Patent Document 3 discloses a laminated filter made of polyolefin resin, which is useful as an industrial liquid filtration filter, and is formed by integrating a polyolefin nonwoven fabric and a polyolefin microporous membrane by heat calendering. Patent Document 4 discloses a method for producing a composite sheet in which an olefin-based porous film and a breathable reinforcing material are bonded together with a hot melt adhesive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2011-512252 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-163465 [Patent Document 3] Japanese Patent Application Publication No. 11-179120 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-114530 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, it has been difficult to achieve both breathability and bacteria separation performance in a laminated membrane formed by laminating a polyolefin microporous membrane and a porous support layer.

[0005] An object of the present disclosure is to provide a laminated film that is excellent in breathability and bacteria separation performance. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following aspects. <1> A laminated film having a microporous membrane containing a polyolefin and a porous support layer, wherein the microporous membrane and the porous support layer are bonded together with scattered adhesive parts containing a thermoplastic resin, and the film has a bubble point of 20 kPa to 900 kPa. <2> The microporous membrane comprises polyethylene. <1> The laminated film according to claim 1. <3> The weight-average molecular weight of the polyethylene contained in the microporous membrane is 800,000 to 2,800,000. <2> The laminated film according to claim 1. <4> The bubble point of the microporous membrane is 10 kPa to 800 kPa. <1> ~ <3> The laminated film according to any one of the preceding claims. <5> The porosity of the microporous membrane is 80% to 90%. <1> ~ <4> The laminated film according to any one of the preceding claims. <6> The microporous membrane has an average thickness of 10 μm to 110 μm. <1> ~ <5> The laminated film according to any one of the preceding claims. <7> The porous support layer is a polyester fiber structure. <1> ~ <6> The laminated film according to any one of the preceding claims. <8> The porous support layer has a basis weight of 50 g / m 2 ~150g / m 2 That is, <1> ~ <7> The laminated film according to any one of the preceding claims. <9> The porous support layer has a bulk density of 0.2 g / cm 3 ~0.5g / cm 3 That is, <1> ~ <8> The laminated film according to any one of the preceding claims. <10> The Gurley value of the laminated film is 5 seconds / 100 mL to 100 seconds / 100 mL. <1> ~ <9> The laminated film according to any one of the preceding claims. <11> Used to isolate bacteria, <1> ~ <10> The laminated film according to any one of the preceding claims. [Effects of the Invention]

[0007] According to the present disclosure, a laminated film having excellent breathability and bacteria separation performance is provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing an example of an embodiment of a laminated film. [Figure 2] FIG. 10 is a cross-sectional view showing another example of an embodiment of a laminated film. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0010] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0011] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0012] In the present disclosure, when referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified.

[0013] In this disclosure, MD (Machine Direction) refers to the longitudinal direction of a film or laminated film manufactured in a long shape, and TD (Transverse Direction) refers to the direction perpendicular to MD in the plane direction of the film or laminated film. In this disclosure, TD is also referred to as "Width Direction."

[0014] In the present disclosure, the side of the laminated film from which gas or liquid flows in is referred to as the "upstream" side, and the side from which gas or liquid flows out is referred to as the "downstream" side.

[0015] In this disclosure, a microporous membrane comprising a polyolefin is referred to as a "polyolefin microporous membrane." In the present disclosure, the term "porous support layer" does not include a "polyolefin microporous membrane." A "porous support layer" is a sheet-like object other than a "polyolefin microporous membrane."

[0016] In the present disclosure, the melting points of the polyolefin and thermoplastic resin of the polyolefin microporous film that constitutes the laminate film may be the melting points of the polyolefin and thermoplastic resin of the polyolefin microporous film that is the material used to produce the laminate film.

[0017] <Laminated film> The laminated film of the present disclosure has a polyolefin microporous film and a porous support layer, the polyolefin microporous film and the porous support layer being bonded together with scattered adhesive parts containing a thermoplastic resin, and has a bubble point of 20 kPa to 900 kPa.

[0018] In the laminated membrane of the present disclosure, the polyolefin microporous membrane and the porous support layer are bonded together at an adhesive joint containing a thermoplastic resin. The thermoplastic resin melts when heated to bond the polyolefin microporous membrane and the porous support layer, enabling bonding at a lower temperature than when the polyolefin microporous membrane and the porous support layer are directly bonded together by heat through a thermal calendaring process, and is less likely to clog the porous structures of the polyolefin microporous membrane and the porous support layer. Furthermore, in the laminated film of the present disclosure, the polyolefin microporous film and the porous support layer are bonded together at scattered adhesive joints, and therefore the breathability of the laminated film is good.

[0019] The laminated film of the present disclosure has a bubble point of 900 kPa or less. A laminated film with a bubble point of more than 900 kPa may have a pore size that is too small or some of the pores may be blocked, and such a laminated film does not have sufficient breathability. From the viewpoint of excellent breathability, the laminated film of the present disclosure has a bubble point of 900 kPa or less, preferably 850 kPa or less, more preferably 800 kPa or less, and even more preferably 700 kPa or less.

[0020] The laminated membrane of the present disclosure has a bubble point of 20 kPa or more. A laminated membrane with a bubble point of less than 20 kPa has a pore size that is too large and does not provide sufficient bacteria separation performance. From the viewpoint of excellent bacteria separation performance, the laminated membrane of the present disclosure has a bubble point of 20 kPa or more, preferably 40 kPa or more, more preferably 80 kPa or more, and even more preferably 100 kPa or more.

[0021] The bubble point of the laminated film is determined by the bubble point method (ASTM F316-86, JIS K3832:1990) using a Perm Porometer (PMI, model: CFP-1200-AEXL). The immersion liquid used during the test is Galwick (surface tension 15.9 dyn / cm) manufactured by PMI. The liquid temperature during the test is 24±2°C. When one exposed surface of the laminated film is a polyolefin microporous film and the other is a porous support layer, the surface with the exposed polyolefin microporous film is placed facing the pressure section of the Perm Porometer, and the measurement is performed.

[0022] From the viewpoint of enhancing bacteria separation performance, the Gurley value of the laminated film is preferably 5 seconds / 100 mL or more, more preferably 6 seconds / 100 mL or more, and even more preferably 7 seconds / 100 mL or more. From the viewpoint of improving breathability, the Gurley value of the laminated film is preferably 100 seconds / 100 mL or less, more preferably 90 seconds / 100 mL or less, and even more preferably 80 seconds / 100 mL or less. The Gurley value of the laminated film is a value measured in accordance with JIS P8117:2009.

[0023] [Applications of laminated film] The laminated membrane of the present disclosure is suitable for use in separating biological particles by passing a gas or liquid through it, and is particularly suitable for use in separating bacteria among biological particles. As used herein, biological particles include particles possessed by living organisms, particles released by living organisms, particles parasitic on living organisms, microorganisms, lipid-membrane vesicles, and fragments thereof. Biological particles as used herein include viruses, virus parts (e.g., particles obtained by removing the envelope from an enveloped virus), bacteriophages, bacteria, spores, fungi, molds, yeast, cysts, protozoa, unicellular algae, plant cells, animal cells, cultured cells, hybridomas, tumor cells, red blood cells, white blood cells (e.g., lymphocytes, monocytes, granulocytes), platelets, organelles (e.g., cell nuclei, mitochondria, vesicles), exosomes, apoptotic bodies, lipid bilayer particles, lipid monolayer particles, liposomes, enzymes, enzyme aggregates, proteins, protein aggregates, and fragments thereof. Biological particles as used herein also include artificial objects.

[0024] There is no limit to the size of biological particles to be separated by the laminated membrane of the present disclosure. The diameter or major axis length of the biological particles is, for example, 1 nm or more, 5 nm or more, 10 nm or more, or 20 nm or more, and is, for example, 100 μm or less, 50 μm or less, 10 μm or less, or 5 μm or less.

[0025] The laminated membrane of the present disclosure is preferably used to separate bacteria of nano- or micro-order size, with the diameter or major axis length of the bacteria preferably being 100 nm or more, more preferably 200 nm or more, even more preferably 300 nm or more, and preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less.

[0026] The laminated film of the present disclosure is suitable as a filter medium for air filters that prevent bacteria from entering. The air filters include, for example, dust masks, medical masks, coarse dust air filters, medium-performance air filters, high-performance air filters, and ultra-high-performance air filters.

[0027] The use of the laminated film of the present disclosure is not limited to air filter media. The laminated film of the present disclosure can also be used as a bag-shaped body for capturing functional particles. Examples of functional particles to be captured include biological particles, resin particles, metal particles, mineral particles, ceramic particles, pharmaceuticals, food, enzymes, catalysts, microorganisms, gas absorbents, dehumidifiers, deodorizers, and heat-generating agents. The bag-shaped body is produced, for example, by folding or overlapping a laminated film cut to a predetermined shape and size, and then gluing part or all of the outer periphery of the overlapped laminated film.

[0028] [Layer structure of laminated film] The laminated membrane of the present disclosure has at least one polyolefin microporous membrane and at least one porous support layer. The laminated membrane of the present disclosure may have multiple polyolefin microporous membrane layers, or may have multiple porous support layers. The laminated membrane of the present disclosure is preferably a laminated membrane having a layer structure in which at least one porous support layer is laminated on one side of a single polyolefin microporous membrane. The laminated membrane of the present disclosure may have other layers different from the polyolefin microporous membrane and the porous support layer.

[0029] The layer structure of the laminated film of the present disclosure will be described with reference to the drawings. Components indicated with the same reference numerals in each drawing are the same or similar components. The size of the components in each drawing is conceptual, and the relative relationship of the size between the components is not limited to this. The structure of the laminated film of the present disclosure is not limited to the structure shown in the drawings.

[0030] Fig. 1 is a cross-sectional view showing an example of an embodiment of a laminated membrane. The laminated membrane 10A shown in Fig. 1 has a polyolefin microporous membrane 20 and a porous support layer 30. The porous support layer 30 is disposed on one surface of the polyolefin microporous membrane 20.

[0031] In the laminated film 10A, the polyolefin microporous membrane 20 and the porous support layer 30 are bonded together by adhesive portions 40. The adhesive portions 40 are scattered at the interface between the polyolefin microporous membrane 20 and the porous support layer 30. When the interface is viewed from above, the adhesive portions 40 are scattered in the form of, for example, dots, lines, a lattice, or a net. The adhesive portions 40 contain a thermoplastic resin. Preferably, the adhesive portions 40 contain only a thermoplastic resin.

[0032] In use, the laminated film 10A is preferably such that the polyolefin microporous film 20 is on the upstream side and the porous support layer 30 is on the downstream side.

[0033] The laminated film 10A may have a reinforcing layer, an adhesive layer, a protective layer, etc. on the periphery of one or both exposed surfaces.

[0034] The laminated film 10A may be one unit, and a plurality of such units may be stacked to form a multi-layered film, which is an example of an embodiment of the laminated film of the present disclosure.

[0035] Fig. 2 is a cross-sectional view showing another example of an embodiment of the laminated membrane. The laminated membrane 10B shown in Fig. 2 has a polyolefin microporous membrane 20, a porous support layer 30a, and a porous support layer 30b. The porous support layer 30a is disposed on one side of the polyolefin microporous membrane 20, and the porous support layer 30b is disposed on the other side of the polyolefin microporous membrane 20. The porous support layers 30a and 30b may be the same type of porous support layer in terms of material, thickness, porosity, basis weight, etc., or may be different types of porous support layers.

[0036] In the laminated film 10B, the polyolefin microporous membrane 20 and the porous support layer 30a are bonded together by adhesive portions 40a, and the polyolefin microporous membrane 20 and the porous support layer 30b are bonded together by adhesive portions 40b. The adhesive portions 40a are scattered at the interface between the polyolefin microporous membrane 20 and the porous support layer 30a. The adhesive portions 40b are scattered at the interface between the polyolefin microporous membrane 20 and the porous support layer 30b. In a planar view of the interface, the adhesive portions 40a and 40b are each scattered in the form of, for example, dots, lines, a lattice, or a net. The adhesive portions 40a and 40b contain a thermoplastic resin. The adhesive portions 40a and 40b preferably contain only a thermoplastic resin. The adhesive portions 40a and 40b may be of the same or different types of thermoplastic resin. The adhesive portions 40a and the adhesive portions 40b may be the same type of adhesive portion or different types of adhesive portions in the scattered form.

[0037] The laminated film 10B may have a reinforcing layer, an adhesive layer, a protective layer, etc. on the periphery of one or both exposed surfaces.

[0038] The laminated film 10B may be one unit, and a plurality of such units may be stacked to form a multi-layered film, which is an example of an embodiment of the laminated film of the present disclosure.

[0039] Each layer of the laminated film of the present disclosure will be described in detail below.

[0040] [Polyolefin microporous membrane] In the present disclosure, a microporous membrane refers to a membrane having a structure in which a large number of micropores are internally connected, and which allows gas or liquid to pass from one surface to the other.

[0041] The microporous polyolefin membrane preferably has a three-dimensional network structure made of polyolefin fibrils.

[0042] Examples of polyolefins contained in the polyolefin microporous membrane include polyethylene, polypropylene, polybutylene, polymethylpentene, copolymers of polypropylene and polyethylene, etc. Among these, polyethylene is preferred, and high-density polyethylene, and mixtures of high-density polyethylene and ultra-high molecular weight polyethylene are also preferred.

[0043] An example of an embodiment of the polyolefin microporous membrane is a polyethylene microporous membrane containing only polyethylene as polyolefin.

[0044] An example of an embodiment of the polyolefin microporous film is a microporous film containing polypropylene, which has heat resistance such that it does not easily rupture when exposed to high temperatures.

[0045] An example of an embodiment of the microporous polyolefin membrane is a microporous polyolefin membrane containing at least a mixture of polyethylene and polypropylene.

[0046] An example of an embodiment of the microporous polyolefin membrane is a polyolefin microporous membrane having a laminate structure of two or more layers, at least one layer containing polyethylene and at least one layer containing polypropylene.

[0047] The thickness of the polyolefin microporous membrane is preferably 10 μm or more, more preferably 12 μm or more, and even more preferably 14 μm or more, from the viewpoint of increasing the strength of the polyolefin microporous membrane and increasing the separation rate of biological particles. The thickness of the polyolefin microporous film is preferably 110 μm or less, more preferably 105 μm or less, and even more preferably 100 μm or less, from the viewpoint of breathability of the laminated film. The thickness of the polyolefin microporous membrane is determined by measuring at 20 points with a contact type membrane thickness meter and averaging the measurements.

[0048] From the viewpoint of breathability of the laminated film, the porosity of the polyolefin microporous film is preferably 80% or more, more preferably 81% or more, even more preferably 82% or more, and even more preferably 83% or more. The porosity of the polyolefin microporous membrane is preferably 90% or less, more preferably 88% or less, and even more preferably 86% or less, from the viewpoint of increasing the separation efficiency of biological particles.

[0049] The porosity of the polyolefin microporous membrane is calculated by the following method. That is, for constituent material 1, constituent material 2, constituent material 3, ..., constituent material n of the polyolefin microporous membrane, the masses of the constituent materials are W1, W 2、 W3, …, W n (g / cm 2 ) and the true densities of the constituent materials are d1, d2, d3, ..., d n (g / cm 3 ) and when the membrane thickness is t (cm), the porosity ε (%) can be calculated by the following formula:

[0050]

number

[0051] The bubble point of the microporous polyolefin membrane is preferably 10 kPa or more, more preferably 50 kPa or more, and even more preferably 100 kPa or more, from the viewpoint of increasing the separation rate of biological particles. The bubble point of the polyolefin microporous film is preferably 800 kPa or less, more preferably 700 kPa or less, and even more preferably 600 kPa or less, from the viewpoint of breathability.

[0052] The bubble point of the polyolefin microporous membrane is determined by the bubble point method (ASTM F316-86, JIS K3832:1990) using a Perm Porometer (PMI, model: CFP-1200-AEXL). The immersion liquid used during the test is Galwick (surface tension: 15.9 dyn / cm) manufactured by PMI. The liquid temperature during the test is 24±2°C.

[0053] The Gurley value of the polyolefin microporous membrane is preferably 2 seconds / 100 mL or more, more preferably 3 seconds / 100 mL or more, and even more preferably 5 seconds / 100 mL or more, from the viewpoint of increasing the separation rate of biological particles. From the viewpoint of breathability, the Gurley value of the polyolefin microporous membrane is preferably 100 seconds / 100 mL or less, more preferably 90 seconds / 100 mL or less, and even more preferably 80 seconds / 100 mL or less. The Gurley value of the polyolefin microporous membrane is a value measured in accordance with JIS P8117:2009.

[0054] The weight average molecular weight (Mw) of the polyolefin contained in the polyolefin microporous membrane is preferably 500,000 to 5,000,000. When the Mw of the polyolefin is 500,000 or more, the microporous membrane can be imparted with sufficient mechanical properties. When the Mw of the polyolefin is 5,000,000 or less, the microporous membrane can be easily formed.

[0055] The weight average molecular weight (Mw) of the polyethylene contained in the polyolefin microporous film is preferably 800,000 or more, more preferably 1,000,000 or more, and even more preferably 1,100,000 or more, from the viewpoint of densifying the porous structure of the microporous film. The weight average molecular weight (Mw) of the polyethylene contained in the polyolefin microporous film is preferably 2.8 million or less, more preferably 2.5 million or less, and even more preferably 2.3 million or less, from the viewpoint of increasing the porosity of the microporous film.

[0056] The weight-average molecular weights of the polyolefin and polyethylene constituting the microporous polyolefin membrane are obtained by dissolving the microporous polyolefin membrane in o-dichlorobenzene under heating and measuring the molecular weight using gel permeation chromatography (Waters Alliance GPC 2000 system, GMH6-HT and GMH6-HTL columns) at a column temperature of 140°C and a flow rate of 1.0 mL / min. Monodisperse polystyrene (Tosoh Corporation) is used for molecular weight calibration.

[0057] An example of an embodiment of the polyolefin microporous membrane is a microporous membrane containing a polyolefin composition (which in the present disclosure refers to a polyolefin mixture containing two or more polyolefins, and when the polyolefin contained is only polyethylene, it is referred to as a polyethylene composition.) The polyolefin composition forms a network structure as it fibrillates during stretching, and has the effect of increasing the porosity of the polyolefin microporous membrane.

[0058] The polyolefin composition has a weight average molecular weight of 9 × 10 5 A polyolefin composition containing the above ultra-high molecular weight polyethylene in an amount of 5% by mass to 70% by mass relative to the total amount of polyolefins is preferred, more preferably 10% by mass to 60% by mass, and even more preferably 15% by mass to 50% by mass.

[0059] The polyolefin composition has a weight average molecular weight of 9×10 5 and ultra-high molecular weight polyethylene having a weight average molecular weight of 2×10 5 ~8×10 5 and density is 920 kg / m 3 ~960kg / m 3 and a high-density polyethylene in a mass ratio of 5:95 to 70:30 (more preferably 10:90 to 60:40, and even more preferably 15:85 to 50:50).

[0060] An example of an embodiment of the polyolefin microporous membrane is a polyolefin microporous membrane that has been hydrophilized. Examples of the hydrophilized polyolefin microporous membrane include a polyolefin microporous membrane whose surface is coated with a hydrophilic compound (e.g., ethylene-vinyl alcohol copolymer); a polyolefin microporous membrane whose surface is polymerized with a monomer having a hydrophilic group; and a polyolefin microporous membrane that has been subjected to plasma treatment or corona treatment. After the polyolefin microporous membrane and the porous support layer are laminated, the entire laminated membrane may be subjected to hydrophilization treatment.

[0061] [Method for producing polyolefin microporous membrane] The microporous polyolefin membrane can be produced, for example, by a production method including the following steps (I) to (IV).

[0062] Step (I): A step of preparing a solution containing a polyolefin composition and a volatile solvent having a boiling point of less than 210°C at atmospheric pressure. Step (II): A step of melt-kneading the solution, extruding the resulting melt-kneaded mixture through a die, and cooling and solidifying it to obtain a first gel-like molded product. Step (III): A step of stretching the first gel-like molding in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like molding. Step (IV): A step of stretching the second gel-like molding in at least one direction (secondary stretching).

[0063] Step (I) is a step of preparing a solution containing a polyolefin composition and a volatile solvent having a boiling point of less than 210°C at atmospheric pressure. The solution is preferably a thermoreversible sol-gel solution, and the polyolefin composition is dissolved in the solvent by heating to form a sol, thereby preparing the thermoreversible sol-gel solution. The volatile solvent having a boiling point of less than 210°C at atmospheric pressure is not particularly limited as long as it can sufficiently dissolve the polyolefin. Examples of the volatile solvent include tetralin (206°C to 208°C), ethylene glycol (197.3°C), decalin (decahydronaphthalene, 187°C to 196°C), toluene (110.6°C), xylene (138°C to 144°C), diethyltriamine (107°C), ethylenediamine (116°C), dimethylsulfoxide (189°C), and hexane (69°C). Decalin or xylene is preferred (the temperature in parentheses is the boiling point at atmospheric pressure). The volatile solvents may be used alone or in combination of two or more kinds.

[0064] The polyolefin composition (which in the present disclosure means a polyolefin mixture containing two or more polyolefins, and is referred to as a polyethylene composition when the only polyolefin contained is polyethylene) used in step (I) preferably contains polyethylene, and is more preferably a polyethylene composition.

[0065] From the viewpoint of controlling the porous structure of the polyolefin microporous membrane, the solution prepared in step (I) preferably has a polyolefin composition concentration of 10% by mass to 40% by mass, more preferably 15% by mass to 35% by mass. A polyolefin composition concentration of 10% by mass or more can suppress the occurrence of breakage during the polyolefin microporous membrane production process, and also increases the mechanical strength of the polyolefin microporous membrane, improving handleability. A polyolefin composition concentration of 40% by mass or less facilitates the formation of pores in the polyolefin microporous membrane.

[0066] Step (II) is a step of melt-kneading the solution prepared in step (I), extruding the resulting melt-kneaded mixture through a die, and cooling and solidifying it to obtain a first gel-like molded product. In step (II), for example, extrusion is performed through a die at a temperature range of the melting point of the polyolefin composition to the melting point + 65°C to obtain an extrudate, which is then cooled to obtain a first gel-like molded product. The first gel-like molded product is preferably shaped into a sheet. Cooling may be performed by immersion in water or an organic solvent, or by contact with a cooled metal roll, and is generally performed by immersion in the volatile solvent used in step (I).

[0067] Step (III) is a step of stretching the first gel-like molded product in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like molded product. The stretching step in step (III) is preferably biaxial stretching, and may be sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed separately, or simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed simultaneously. The stretching ratio in the primary stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is preferably 1.1 to 3 times, more preferably 1.1 to 2 times, from the viewpoint of controlling the porous structure of the polyolefin microporous membrane. The temperature during primary stretching is preferably 75°C or lower. The drying step in step (III) is carried out at any temperature that does not deform the second gel-like molded product, but is preferably carried out at 60°C or lower.

[0068] The stretching and drying steps in step (III) may be carried out simultaneously or stepwise. For example, the first stretching may be carried out while pre-drying and then main drying, or the first stretching may be carried out between pre-drying and main drying. The first stretching may also be carried out in a state where the drying is controlled and the solvent remains in a suitable state.

[0069] Step (IV) is a step of stretching the second gel-like molded product in at least one direction (secondary stretching). The stretching step in step (IV) is preferably biaxial stretching. The stretching step in step (IV) may be any of the following: sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed separately; simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed simultaneously; a step of stretching in the longitudinal direction multiple times and then stretching in the transverse direction; a step of stretching in the longitudinal direction and then stretching in the transverse direction multiple times; or a step of sequential biaxial stretching and then further stretching in the longitudinal and / or transverse directions once or multiple times.

[0070] From the viewpoint of controlling the porous structure of the polyolefin microporous membrane, the stretching ratio in the second stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is preferably 5 to 90, and more preferably 10 to 60. From the viewpoint of controlling the porous structure of the polyolefin microporous membrane, the stretching temperature in the second stretching is preferably 90°C to 135°C, and more preferably 90°C to 130°C.

[0071] Step (IV) may be followed by a heat setting treatment, which is preferably carried out at a heat setting temperature of 110°C to 160°C, more preferably 120°C to 150°C, from the viewpoint of controlling the porous structure of the polyolefin microporous membrane.

[0072] After the heat setting treatment, the polyolefin microporous membrane may be further subjected to an extraction treatment of the solvent remaining therein and an annealing treatment. The extraction treatment of the remaining solvent is carried out, for example, by immersing the heat-set sheet in a methylene chloride bath to dissolve the remaining solvent in the methylene chloride. After the polyolefin microporous membrane immersed in the methylene chloride bath is removed from the methylene chloride bath, the methylene chloride is preferably removed by drying. After the extraction treatment of the remaining solvent, the polyolefin microporous membrane is annealed by conveying it over rollers heated to, for example, 100°C to 140°C.

[0073] By controlling the conditions in steps (I) to (IV), the bubble point and porosity of the polyolefin microporous membrane can be adjusted.

[0074] [Porous support layer] The porous support layer is a layer that ensures the strength of the laminated film. The porous support layer has holes or voids therein, allowing gas or liquid to pass through from one surface to the other.

[0075] The porous support layer is preferably an organic or inorganic fiber structure. Examples of the organic fiber structure include nonwoven fabrics or woven or knitted fabrics mainly made of thermoplastic fibers. Examples of the inorganic fiber structure include electrospun fiber membranes made of glass fiber nonwoven fabrics, steel wool, ceramic fibers, etc. The nonwoven fabric, woven or knitted fabric, and fiber membrane may have a laminated structure of two or more layers. The nonwoven fabric, woven or knitted fabric, and fiber membrane may be of one type or two or more types in terms of material type, fiber thickness, cross-sectional shape, or basis weight.

[0076] As the porous support layer, a fiber structure mainly composed of thermoplastic fibers is suitable, and nonwoven fabric is particularly suitable. The fiber structure preferably contains 70% by mass or more of thermoplastic fibers. Examples of thermoplastic fibers include fibers made of resins such as polyester, polyolefin, polyamide, polyesteramide, acrylic resin, and polyvinyl alcohol, and mixtures of these fibers. Among these, from the viewpoints of achieving good bonding with the polyolefin microporous membrane and imparting mechanical strength, a structure made of at least one fiber selected from the group consisting of polyester fibers, polyolefin fibers, nylon, acrylic resin fibers, and polyvinyl alcohol-based resin fibers is preferred. Among these fiber structures, polyester fiber structures are more preferred. Examples of polyesters include polyethylene terephthalate (PET)-based resins, polybutylene terephthalate (PBT)-based resins, polytrimethylene terephthalate (PTT)-based resins, polyethylene naphthalate (PEN)-based resins, polytrimethylene naphthalate (PTN)-based resins, polybutylene naphthalate (PBN)-based resins, polyethylene isophthalate-based resins, and wholly aromatic polyester-based resins. Examples of polyolefins include polypropylene and polyethylene. Examples of nylons include nylon 6 and nylon 6,6. Examples of acrylic resins include polyacrylate and polymethyl methacrylate. Examples of polyvinyl alcohol resins include ethylene-vinyl alcohol copolymers.

[0077] When the porous support layer is an organic fiber structure, the melting point of the resin constituting the organic fibers is preferably 100° C. or higher, more preferably 150° C. or higher, and even more preferably 200° C. or higher, from the viewpoint of providing sufficient heat resistance to the porous support layer. Furthermore, the melting point of the resin constituting the organic fibers is preferably 300° C. or lower, more preferably 280° C. or lower, and even more preferably 260° C. or lower, from the viewpoint of ease of processing the resin into an organic fiber structure.

[0078] The basis weight of the porous support layer is set to 50 g / m from the viewpoint of high rigidity of the porous support layer. 2 More than 55g / m2 More preferably, 60 g / m 2 The above is more preferable. The basis weight of the porous support layer is set to 150 g / m2 from the viewpoint of excellent workability (bending and heat welding) of the porous support layer. 2 Preferably less than 120 g / m 2 Less than 100 g / m is more preferable. 2 The following is even more preferred:

[0079] The bulk density of the porous support layer is set to 0.2 g / cm3 in order to ensure high rigidity of the porous support layer. 3 More than 0.25 g / cm is preferable. 3 More preferably, 0.3 g / cm 3 The above is more preferable. The bulk density of the porous support layer is 0.5 g / cm from the viewpoint of excellent processability (bending and heat welding) of the porous support layer. 3 Preferably less than 0.48 g / cm 3 Less than 0.45 g / cm is more preferable. 3 The following is even more preferred:

[0080] The thickness of one porous support layer is preferably 100 μm or more, more preferably 120 μm or more, and even more preferably 140 μm or more, from the viewpoint of high rigidity of the porous support layer. The thickness of one porous support layer is preferably 240 μm or less, more preferably 220 μm or less, and even more preferably 200 μm or less, from the viewpoint of excellent processability (bending and thermal welding) of the porous support layer. The thickness of the porous support layer is determined by measuring 20 points with a film thickness meter and averaging the measurements.

[0081] Examples of methods for producing nonwoven fabrics include those that form a fiber web and bond the fibers within the fiber web to obtain a nonwoven fabric. Examples of methods for producing fiber webs include dry processes such as carding, air-laying, spunbonding, and meltblowing; wet processes such as wet papermaking; and electrospinning. In wet processes, fibers are dispersed in water to form a uniform papermaking slurry, and this papermaking slurry is used to obtain a fiber web using a papermaking machine with at least one of the following papermaking methods: cylinder, fourdrinier, and tilted. In methods for producing nonwoven fabrics from fiber webs, the fibers are bonded by a fiber bonding method selected from the group consisting of adhesion, fusion, and entanglement. It is also preferable to pass the nonwoven fabric between a heated metal roll and an elastic roll to subject it to a heat-and-pressure treatment (thermal calendering). As a method for producing woven or knitted fabrics, filaments or spun yarns are woven or knitted by a general method, as is done with general thermoplastic fibers.

[0082] [Adhesive part] The polyolefin microporous membrane and the porous support layer are bonded together by adhesive parts containing a thermoplastic resin. The adhesive parts containing a thermoplastic resin are scattered at the interface between the polyolefin microporous membrane and the porous support layer. The scattered adhesive parts at the interface between the polyolefin microporous membrane and the porous support layer ensure the breathability of the laminated membrane. Furthermore, the scattered adhesive parts at the interface between the polyolefin microporous membrane and the porous support layer prevent particles from clogging the interface.

[0083] In the present disclosure, "scattered" means that the thermoplastic resin constituting the adhesive part is continuously or discontinuously dispersed between the polyolefin microporous membrane and the porous support layer without covering the entire surface of the polyolefin microporous membrane. For example, this includes the thermoplastic resin being present in the form of dots, lines, fibers, strips, lattice, net, or three-dimensional network, and the like, which may be deformed by heat fusion and / or pressure.

[0084] The adhesive portion contains a thermoplastic resin, and preferably contains only a thermoplastic resin, that is, the adhesive portion is preferably made of a thermoplastic resin.

[0085] The melting point of the thermoplastic resin contained in the adhesive part is preferably lower than the melting point of the polyolefin contained in the polyolefin microporous membrane. When the porous support layer contains a resin, the melting point of the thermoplastic resin contained in the adhesive part is preferably lower than the melting point of the resin contained in the porous support layer.

[0086] When the polyolefin microporous membrane contains two or more types of polyolefins, the melting point of the thermoplastic resin contained in the adhesive part is preferably lower than the melting points of all the polyolefins contained in the polyolefin microporous membrane. When the adhesive part contains two or more types of thermoplastic resins, it is preferable that the melting points of all of these thermoplastic resins are lower than the melting point of the polyolefin contained in the microporous polyolefin membrane. When the polyolefin microporous membrane contains two or more types of polyolefins and the adhesive part contains two or more types of thermoplastic resins, it is preferable that the melting points of all the thermoplastic resins contained in the adhesive part are lower than the melting points of all the polyolefins contained in the polyolefin microporous membrane.

[0087] The melting point of the thermoplastic resin contained in the adhesive joint is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher, from the viewpoint of preventing deformation of the adhesive joint or elution of components contained in the adhesive joint due to the temperature of the gas or liquid being circulated. The melting point of the thermoplastic resin contained in the adhesive part is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower, from the viewpoint of suppressing the temperature of heat applied to bond the polyolefin microporous membrane and the porous support layer and suppressing deformation of the polyolefin microporous membrane and the porous support layer.

[0088] The melting point of a thermoplastic resin is the "melting peak temperature" of a DSC (Differential Scanning Calorimetry) curve obtained in accordance with JIS K7121:1987 "Method for measuring transition temperatures of plastics."

[0089] Examples of thermoplastic resins contained in the adhesive parts include polyolefins, polyesters, acrylic resins, and polyvinyl alcohols. Among these, polyolefins are preferred from the viewpoint of forming a good bond with at least the polyolefin microporous membrane. Examples of polyolefins include polyethylene, polypropylene, polybutylene, polymethylpentene, and copolymers of polypropylene and polyethylene. The thermoplastic resin contained in the adhesive parts is preferably the same type of polyolefin as the polyolefin contained in the polyolefin microporous membrane. For example, when the polyolefin microporous membrane is a polyethylene microporous membrane, the thermoplastic resin contained in the adhesive parts is preferably polyethylene.

[0090] When the interface between the polyolefin microporous membrane and the porous support layer is viewed in plan, the bonded areas are scattered in, for example, dots, lines, a lattice, or a net shape. The bonded areas may or may not be visible to the naked eye. When the bonded portions are dot-like, the number of bonded portions is preferably 3,000 to 15,000 per 10 cm square. When the interface between the polyolefin microporous membrane and the porous support layer is viewed from above, the total area of ​​the adhesive portions is preferably 5% to 80% of the area of ​​the interface.

[0091] [Method of manufacturing laminated film] The laminated film of the present disclosure is produced, for example, by a production method including the following steps (a) to (c).

[0092] Step (a): A step of disposing a thermoplastic resin in a scattered manner on one surface of a first layer included in a laminated film. Step (b): A step of forming a laminate by superposing a second layer contained in the laminate film on the thermoplastic resin scattered on the surface of the first layer. Step (c): A step of passing the laminate through a heating device to melt the thermoplastic resin and bond the first layer and the second layer together.

[0093] The first layer is either a microporous polyolefin membrane or a porous support layer. When the first layer is a microporous polyolefin membrane, the second layer is a porous support layer, and when the first layer is a porous support layer, the second layer is a microporous polyolefin membrane.

[0094] Steps (a) and (b) are performed once or multiple times depending on the number of layers in the laminated film. For example, if the laminated film consists of three layers, the second layer in the first step (b) is the first layer in the second step (a).

[0095] The thermoplastic resin used in step (a) functions as an adhesive that bonds the first layer and the second layer, and is preferably in the form of particles, lines, or fibers.

[0096] The amount of thermoplastic resin used is 1 g / m2 on the surface of the first layer. 2 ~20g / m 2 It is preferable that: The coverage rate of the thermoplastic resin on the surface of the first layer is preferably 5% to 80%.

[0097] The heating device in step (c) is, for example, a heating and pressure roll; a heating and pressure roll; or a heating furnace equipped with a pressure roll.

[0098] The temperature of the heating device is preferably higher than the melting point of the thermoplastic resin that functions as an adhesive by −10°C and lower than the melting point of the polyolefin contained in the polyolefin microporous membrane by +10°C. When the porous support layer contains a resin, the temperature of the heating device is preferably lower than the melting point of the resin contained in the porous support layer. The temperature of the heating device is preferably 50°C to 140°C, more preferably 60°C to 135°C, and even more preferably 70°C to 130°C. The time for applying heat by the heating device is set to a time required for the thermoplastic resin that functions as an adhesive to fully melt.

[0099] When the heating device includes a roll member, the pressure applied by the roll member is set within a range that does not clog the porous structure of the polyolefin microporous membrane. [Example]

[0100] The laminated film of the present disclosure will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the laminated film of the present disclosure should not be interpreted as being limited by the specific examples shown below.

[0101] In the following description, syntheses, treatments, manufacturing, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0102] <Measurement and evaluation methods> The measurement and evaluation methods used in the examples and comparative examples are as follows.

[0103] [Weight average molecular weight of polyolefin] The weight-average molecular weight of the polyolefin constituting the microporous polyolefin membrane was measured by dissolving the microporous polyolefin membrane in o-dichlorobenzene under heating using gel permeation chromatography (Waters Alliance GPC 2000 system, GMH6-HT and GMH6-HTL columns) at a column temperature of 140°C and a flow rate of 1.0 mL / min. Monodisperse polystyrene (Tosoh Corporation) was used to calibrate the molecular weight.

[0104] [Bubble point of polyolefin microporous membranes and laminated membranes] Measurements were taken using a PMI Perm Porometer (model: CFP-1200-AEXL) and a PMI Galwick (surface tension 15.9 dyn / cm) according to the bubble point method (ASTM F316-86, JIS K3832:1990). The liquid temperature during the test was 24±2°C. The bubble point of the laminated film was measured by placing the surface on which the polyolefin microporous film was exposed facing the pressure part of a perm porometer.

[0105] [Average thickness of polyolefin microporous membrane] The thickness was determined by averaging 20 measurements taken using a contact-type film thickness meter (Mitutoyo Corporation). The contact terminal used was a cylindrical terminal with a bottom diameter of 0.5 cm. The measurement pressure was 0.1 N.

[0106] [Porosity of polyolefin microporous membrane] The mass of each of the constituent materials of the polyolefin microporous membrane, W1, W2, W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14, W15, W16, W17, W18, W19, W19, W19, W20, W21, W22, W23, W24, W25, W26, W27, W28, W29, W30, W31, W32, W33, W34, W35, W36, W37, W38, W39, W40, W41, W42, W43, W44, W45, W46, W47, W48, W50, W51, W52, W53, W54, W55, W56, W57, W58, W59, W60, W61 2、 W3, …, W n (g / cm 2 ) and the true densities of the constituent materials are d1, d2, d3, ..., d n (g / cm 3 ) and the average thickness of the microporous polyolefin membrane is t (cm).

[0107]

number

[0108] [Weight per unit area of ​​porous support layer] The porous support layer before lamination was cut into a 10 cm x 10 cm square sample, and the mass of the sample was measured. 2 ) was calculated by dividing by

[0109] [Bulk density of porous support layer] The porous support layer before lamination was cut into a 10 cm x 10 cm square sample, and the mass and thickness of the sample were measured. The mass of the sample was calculated based on the thickness and area (100 cm 2 The thickness was calculated by dividing the measured value by the average value of 20 points using a Digimatic Micrometer (Mitutoyo Corporation, model number: MDC-25MJ).

[0110] [Gurley value of laminated film] Measurement was carried out using a Gurley densometer (Toyo Seiki Seisakusho Co., Ltd., model number: G-B2C) in accordance with JIS P8117:2009.

[0111] [Bacteria isolation performance] The following tools were prepared: Oil-free air compressor, model number: ACP-10A, Takagi Co., Ltd. (hereinafter referred to as "air compressor"). Lab test baby tank, model number: BT-700S, Advantech. hereinafter referred to as the "pressure tank." Stainless steel line holder, model number: KS-47, Advantech. Hereinafter referred to as "the holder." 0.22μm pore size membrane filter, model number: A020B025A, Advantech. Hereinafter referred to as "membrane filter".

[0112] The laminated membrane was cut into a circular shape with a diameter of 47 mm, which was used as a sample. The sample was immersed in ethanol, and then the ethanol-moistened sample was placed in a holder with the exposed surface of the polyolefin microporous membrane facing upstream.

[0113] The following steps (1) to (5) were carried out to determine the LRV (Logarithmic Reduction Value). (1) Preparation of test bacterial solution The test bacteria were inoculated onto TSA medium and cultured at 30°C for 24 hours. The grown colonies were suspended in 10 mL of TSB medium and cultured at 30°C for 24 hours. 2 mL of this culture was added dropwise to 1,000 mL of salted lactose broth medium and cultured at 30°C for 24 hours. This culture was diluted 10-fold with physiological saline and mixed well to prepare the test bacteria solution. (2) Measurement of the number of bacteria in the test solution The test bacterial solution was serially diluted 10-fold with physiological saline. 0.1 mL of the test bacterial solution or diluted solution was smeared on SA medium and cultured at 30°C for 48 hours, and the number of colonies that developed was counted. The number of bacteria per 500 mL of test bacterial solution was calculated from the number of colonies counted. (3) Bacterial isolation procedure An air compressor was connected to a pressure tank containing approximately 550 mL of test bacterial solution, and the valve was closed. Compressed air was sent from the air compressor, and the pressure inside the pressure tank was increased to 0.21 MPa. The valve was opened, and the entire test bacterial solution was passed through a holder containing a sample and collected in a water collection container. After the entire test bacterial solution had passed through the holder, the pressurization by the air compressor was stopped, and the pressure inside the pressure tank was returned to atmospheric pressure. Hereinafter, the liquid collected in the water collection container will be referred to as the "treated liquid." (4) Measurement of the number of bacteria in the treatment liquid 50 mL and 450 mL of the treatment solution were filtered through a membrane filter. Because the test bacteria were too large to pass through the membrane filter, most of them remained on the membrane filter. After filtering the treatment solution, the membrane filter was attached to SA medium and cultured at 30°C for 3 days, after which the number of colonies that grew was counted. The number of bacteria per 500 mL of treatment solution was calculated from the number of colonies counted. (5) Calculation of LRV The LRV was calculated using the following formula: LRV = log10 (number of bacteria per 500 mL of test solution / number of bacteria per 500 mL of treatment solution) LRV6 or higher was judged to be excellent for bacterial isolation performance.

[0114] [Initial pressure loss] The laminated membrane was cut out and placed in a holder with an effective opening diameter of 40 mm, with the exposed surface of the polyolefin microporous membrane facing upstream. Air was passed through the holder at a flow rate of 5.3 cm / sec, and the pressure difference (Pa) between the upstream and downstream sides of the laminated membrane was measured using a micro-differential pressure gauge. The measured pressure difference (Pa) was classified as follows: The practical acceptable range is a pressure difference of less than 40 kPa. A: Less than 10kPa B: 10kPa or more and less than 40kPa C: 40kPa or more

[0115] <Laminated film manufacturing> [Example 1] -Preparation of polyethylene microporous membrane- 12.5 parts by mass of ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE") with a weight average molecular weight of 4.6 million, and a weight average molecular weight of 560,000 and a density of 950 kg / m 3 A polyethylene composition was prepared by mixing the polyethylene composition with 12.5 parts by mass of high density polyethylene (hereinafter referred to as "HDPE"). A polyethylene solution was prepared by mixing the polyethylene composition with decalin so that the polymer concentration was 25% by mass.

[0116] The polyethylene solution was extruded from a die at a temperature of 153°C into a sheet, and the extrudate was then cooled in a water bath at a water temperature of 20°C to obtain a first gel-like sheet.

[0117] The first gel-like sheet was pre-dried for 10 minutes in an atmosphere at 70°C, then primarily stretched in the MD at 1.2 times its original size, and then finally dried for 5 minutes in an atmosphere at 57°C to obtain a second gel-like sheet (base tape). (The residual solvent in the second gel-like sheet was less than 1% by mass.) Next, as the secondary stretching, the second gel-like sheet (base tape) was stretched in the MD at 90°C at 3 times its original size, and then in the TD at 120°C at 10 times its original size, and then immediately heat-treated (heat-set) at 140°C.

[0118] The heat-set sheet was immersed in two separate methylene chloride baths for 30 seconds each to extract the decalin from the sheet. After removing the sheet from the methylene chloride bath, the methylene chloride was dried and removed in a 40°C atmosphere. A polyethylene microporous membrane was thus obtained.

[0119] -Laminated polyethylene microporous membrane and polyester nonwoven fabric- As a porous support layer, a polyester nonwoven fabric having the basis weight and bulk density shown in Table 1 was prepared. One side of the polyester nonwoven fabric was coated with 1 m of polyethylene powder having a melting point of 105°C. 2 A polyethylene microporous membrane was placed on top of the polyester nonwoven fabric, and a temperature of 100°C was applied using a heating and pressure roll to bond the polyethylene microporous membrane and polyester nonwoven fabric together.

[0120] [Examples 2 to 9, Comparative Examples 1 and 2] -Preparation of microporous polyolefin membranes- By changing the mixing ratio of UHMWPE and HDPE and controlling each production process condition so that the weight-average molecular weight of polyethylene measured by the above-mentioned method would be the value shown in Table 1, a polyethylene microporous membrane having the physical properties shown in Table 1 was produced. In Example 8, a polypropylene microporous membrane was produced using polypropylene instead of polyethylene.

[0121] -Lamination of polyolefin microporous membrane and nonwoven fabric- According to the specifications shown in Table 1, a polyethylene microporous membrane or a polypropylene microporous membrane was bonded to one side of a polyester nonwoven fabric or a polypropylene nonwoven fabric using polyethylene powder or a polyethylene web. The melting points of the polyethylene powder and the polyethylene web were 105°C. The polyethylene web had a basis weight of 12 g / m. 2 A web-like (nonwoven fabric) polyethylene was used.

[0122] [Table 1]

[0123] The abbreviations in Table 1 have the following meanings. ·Mw: Weight average molecular weight BP: Bubble point ·LRV:Logarithmic Reduction Value PE: Polyethylene PP: Polypropylene PET: Polyethylene terephthalate [Explanation of symbols]

[0124] 10A, 10B laminated film 20 Polyolefin microporous membrane 30,30a,30b Porous support layer 40,40a,40b Adhesive part

Claims

1. A microporous membrane comprising a polyolefin and a porous support layer, the microporous membrane and the porous support layer are bonded together by scattered adhesive parts containing a thermoplastic resin; the microporous membrane comprises at least one polyolefin selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and a polypropylene-polyethylene copolymer; the porous support layer is a fiber structure containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, polyesteramide, acrylic resin, and polyvinyl alcohol; the adhesive portion contains a thermoplastic resin selected from the group consisting of polyolefin, polyester, acrylic resin, and polyvinyl alcohol, the melting point of the thermoplastic resin contained in the adhesive portion is lower than the melting point of the polyolefin contained in the microporous membrane and lower than the melting point of the resin contained in the porous support layer; The bubble point is 20 kPa to 900 kPa, The Gurley value is 5 seconds / 100 mL to 100 seconds / 100 mL. Laminated film.

2. A microporous membrane comprising a polyolefin and a porous support layer, the microporous membrane and the porous support layer are bonded together by scattered adhesive parts containing a thermoplastic resin; the microporous membrane comprises polyethylene; the porous support layer is a fiber structure containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, polyesteramide, acrylic resin, and polyvinyl alcohol; the adhesive portion contains a thermoplastic resin selected from the group consisting of polyolefin, polyester, acrylic resin, and polyvinyl alcohol, the melting point of the thermoplastic resin contained in the adhesive portion is lower than the melting point of the polyolefin contained in the microporous membrane and lower than the melting point of the resin contained in the porous support layer; The bubble point is 20 kPa to 900 kPa, The weight-average molecular weight of the polyethylene contained in the microporous membrane is 800,000 to 2,800,000. Laminated film.

3. A microporous membrane comprising a polyolefin and a porous support layer, the microporous membrane and the porous support layer are bonded together by scattered adhesive parts containing a thermoplastic resin; the microporous membrane comprises at least one polyolefin selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and a polypropylene-polyethylene copolymer; the porous support layer is a fiber structure containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, polyesteramide, acrylic resin, and polyvinyl alcohol; the adhesive portion contains a thermoplastic resin selected from the group consisting of polyolefin, polyester, acrylic resin, and polyvinyl alcohol, the melting point of the thermoplastic resin contained in the adhesive portion is lower than the melting point of the polyolefin contained in the microporous membrane and lower than the melting point of the resin contained in the porous support layer; The bubble point is 20 kPa to 900 kPa, The porosity of the microporous membrane is 80% to 90%. Laminated film.

4. A microporous membrane comprising a polyolefin and a porous support layer, the microporous membrane and the porous support layer are bonded together by scattered adhesive parts containing a thermoplastic resin; the microporous membrane comprises at least one polyolefin selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and a polypropylene-polyethylene copolymer; the porous support layer is a fiber structure containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, polyesteramide, acrylic resin, and polyvinyl alcohol; the adhesive portion contains a thermoplastic resin selected from the group consisting of polyolefin, polyester, acrylic resin, and polyvinyl alcohol, the melting point of the thermoplastic resin contained in the adhesive portion is lower than the melting point of the polyolefin contained in the microporous membrane and lower than the melting point of the resin contained in the porous support layer; The bubble point is 20 kPa to 900 kPa, the porous support layer has a basis weight of 50 g / m 2 to 150 g / m 2 ; Laminated film.

5. A microporous membrane comprising a polyolefin and a porous support layer, the microporous membrane and the porous support layer are bonded together by scattered adhesive parts containing a thermoplastic resin; the microporous membrane comprises at least one polyolefin selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, and a polypropylene-polyethylene copolymer; the porous support layer is a fiber structure containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, polyesteramide, acrylic resin, and polyvinyl alcohol; the adhesive portion contains a thermoplastic resin selected from the group consisting of polyolefin, polyester, acrylic resin, and polyvinyl alcohol, the melting point of the thermoplastic resin contained in the adhesive portion is lower than the melting point of the polyolefin contained in the microporous membrane and lower than the melting point of the resin contained in the porous support layer; The bubble point is 20 kPa to 900 kPa, Used to isolate bacteria, Laminated film.

6. The laminate membrane of claim 1 , wherein the microporous membrane comprises polyethylene.

7. The laminated film according to claim 6, wherein the weight-average molecular weight of the polyethylene contained in the microporous film is 800,000 to 2,800,000.

8. The laminated film according to claim 1, wherein the microporous film has a bubble point of 10 kPa to 800 kPa.

9. The laminated film according to claim 1, wherein the microporous film has a porosity of 80% to 90%.

10. The laminated film according to claim 1, wherein the microporous film has an average thickness of 10 μm to 110 μm.

11. The laminate membrane of claim 1 , wherein the porous support layer is a polyester fibrous structure.

12. The porous support layer has a basis weight of 50 g / m ２ ~150g / m ２ The laminated film according to claim 1 ,

13. The porous support layer has a bulk density of 0.2 g / cm ３ ~0.5g / cm ３ The laminated film according to claim 1 ,

14. The laminated membrane of claim 1, which is used to separate bacteria.

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