JP2011073277A - Laminated microporous film, method for manufacturing the same, and separator for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated microporous film having good gas permeability. <P>SOLUTION: A method for producing the laminated microporous film [wherein, T<SB>mA</SB>is a melting point (°C) of a first resin composition, and T<SB>mB</SB>is a melting point (°C) of a second resin composition] includes the following processes (1)-(5) in turn: a process (1) for annealing a first resin film made of the first resin composition; a process (2) in which the first resin film and a second resin film made of the second resin composition having the melting point T<SB>mB</SB>lower than the melting point T<SB>mA</SB>of the first resin composition are hot-pressed to form a laminate; a process (3) for annealing the laminate obtained in the process (2); a cold stretching process (4) in which the laminate obtained in the process (3) is cold-stretched 1.05-2.0 times in at least one direction; and a hot stretching process (5) in which the laminate obtained in the process (4), while being kept at a temperature higher than that in the process (4), is hot-stretched >1.0 and ≤5.0 times in at least one direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laminated microporous film, a method for producing the same, and a battery separator.

  Microporous films, particularly polyolefin-based microporous films, are used in microfiltration membranes, battery separators, capacitor separators, fuel cell materials, and the like, and are particularly preferably used as lithium ion battery separators. . In recent years, lithium-ion batteries have been used for small electronic devices such as mobile phones and notebook personal computers, while being applied to hybrid electric vehicles and the like.

Here, a lithium ion battery for a hybrid electric vehicle is required to have higher output characteristics for taking out a lot of energy in a short time. Moreover, since lithium ion batteries for hybrid electric vehicles are generally large and require high energy capacity, higher safety is required.
The battery separator provided in the lithium battery is also required to have a shutdown (SD) function in order to ensure safety. The SD function is a function that, when the temperature inside the battery rises excessively, stops the battery reaction by abruptly increasing the electric resistance of the battery separator and prevents further temperature rise. As a mechanism for expressing the SD function, for example, in the case of a battery separator made of a microporous film, when the internal temperature of the battery rises to a predetermined temperature, the porous structure is lost and becomes non-porous, and ion permeation is blocked. Can be mentioned. However, even if the pores are made non-porous in this way and the ion permeation is blocked, if the temperature further rises and the entire film melts and breaks, the electrical insulation cannot be maintained. The temperature at which the film cannot maintain its shape and cannot block ion permeation is called the membrane breaking temperature. The higher the membrane breaking temperature, the better the battery separator. Moreover, it can be said that it is excellent in safety, so that the difference of the said film breaking temperature and the temperature which SD starts is large.

  For the purpose of providing a microporous film serving as a separator that can cope with such circumstances, for example, Patent Document 1 discloses a laminated film having a high melting point resin layer and a low melting point resin layer by a coextrusion molding method. A method for producing a laminated microporous film by molding and stretching is proposed. Patent Document 2 discloses a method of producing a laminated microporous film having good air permeability by separately forming a polypropylene film and a polyethylene film, then laminating, annealing, and stretching. .

Japanese Patent No. 2883726 Japanese Patent No. 3003830

The battery separator obtained by the method of Patent Document 1 has a high air permeability because it is necessary to match the molding temperatures of the high-melting point resin and the low-melting point resin to some extent, and it is difficult to mold them under optimum conditions. It was difficult to obtain a laminated microporous film.
Also, the air permeability is not sufficient for the laminated microporous film produced by the method disclosed in Patent Document 2.
This invention is made | formed in view of such a situation, and makes it a subject to provide the separator for batteries using the laminated microporous film which has favorable air permeability, its manufacturing method, and it.

As a result of intensive studies to solve the above-mentioned problems, the present inventors annealed the first resin film and then thermocompression bonded the first resin film and the second resin film to form a laminate. Then, it was found that a laminated microporous film having good air permeability can be obtained by annealing the laminate, and the present invention has been completed.
That is, the present invention is as follows.
A method for producing a laminated microporous film comprising the following steps (1) to (5) in this order (where T _mA is the melting point (° C.) of the first resin composition, and T _mB is 2 is the melting point (° C.) of the resin composition):
(1) A step of annealing a first resin film composed of the first resin composition,
(2) a first resin film, the second resin film and a second resin composition having a first melting point T _mB than the melting point T _mA resin composition, and thermocompression Forming a laminate,
(3) A step of annealing the laminate obtained in the step (2),
(4) A cold stretching step of cold stretching the laminate obtained in the step (3) at least 1.05 times to 2.0 times in at least one direction;
(5) Heat that heat-stretches the laminate obtained in the step (4) at a temperature higher than that of the step (4) at a temperature exceeding 1.0 times and not more than 5.0 times in at least one direction. Stretching process.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated microporous film which has favorable air permeability, its manufacturing method, and the battery separator using the same can be provided.

It is the schematic of the measuring apparatus of a film breaking temperature.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiment, and can be implemented with various modifications within the scope of the gist.

The laminated microporous film produced by the production method of the present embodiment has a microporous layer formed from the first resin film composed of the first resin composition, and more than the first resin composition. It has a structure in which a microporous layer formed from a second resin film composed of a second resin composition having a low melting point is laminated.
The first resin composition and the second resin composition have a melting point (hereinafter, simply referred to as “melting point”) T _mA and T _mB measured by a method according to JIS K-7121 and satisfy T _mA > T _mB . If it does, the material may be the same or different.

Here, the difference between the melting point T _mA of the first resin composition and the melting point T _{mB of} the second resin composition is preferably 5 ° C. or more, more preferably 10 ° C. or more. When the difference in melting point is 5 ° C. or more, when the laminated microporous film is used as a battery separator, even when the low melting point resin layer melts when the internal temperature of the battery rises due to abnormal current, The melting point resin layer is easily held without melting. As a result, the film shape or sheet shape of the battery separator is maintained, and the safety tends to be improved.

  In the step (2) of the production method of the laminated microporous film of the present embodiment, a laminate of the first resin film and the second resin film is formed, but the manner of lamination is not particularly limited. As a specific example of the aspect, (a) a laminate composed of one first resin film and one second resin film, (b) one first resin film and the first laminated on both sides thereof A laminate composed of two resin films, (c) a laminate composed of one second resin film and first resin films laminated on both sides thereof, (d) a first resin film-second As the resin film-first resin film-second resin film, there may be mentioned a laminate in which the respective resin films are alternately arranged.

  In the method for producing a laminated microporous film of the present embodiment, a first resin film (hereinafter sometimes referred to as “high melting point resin film”) composed of a first resin composition, and a first. A second resin film (hereinafter sometimes referred to as “low melting point resin film”) composed of the resin composition 2 is prepared separately. The first and second resin films can be produced, for example, by extruding each of the first and second resin compositions. The draw ratio at this time, that is, the film winding speed (unit is m / min) is the extrusion speed of the resin composition (the linear speed in the flow direction of the molten resin passing through the die lip, and the unit is m / min). The value divided by is preferably 10 to 500, more preferably 100 to 400, and still more preferably 150 to 350. The film winding speed is preferably about 2 to 400 m / min, more preferably 10 to 200 m / min.

The manufacturing method of the laminated microporous film of this embodiment includes an annealing step (1) of the high melting point resin film before thermocompression bonding (step (2)) of the high melting point resin film and the low melting point resin film.
As an annealing method, for example, a method in which a film is brought into contact with a heating roll or a method in which the film is exposed to a heated gas phase, a method in which the film is wound on a core body and exposed to a heated gas phase or a heated liquid phase, The method of performing in combination is mentioned. The conditions for these heat treatments are appropriately determined depending on the type of material constituting the film.
The heating temperature when annealing the high melting point resin film is preferably (T _mA- 50) ° C. or more and (T _mA −2) ° C. or less, more preferably (T _mA ), which is suitable for crystallization of the high melting point resin film. It is −40) ° C. or higher and (T _mA −10) ° C. or lower.

In the prior art disclosed in Patent Document 2, since the films constituting each layer are laminated and then annealed, each film cannot be crystallized at an optimum temperature. However, it is difficult to obtain a laminated microporous film having good air permeability.
On the other hand, in this embodiment, the air permeability of the laminated microporous film can be improved by annealing the high melting point resin film alone at an optimum temperature before thermocompression bonding with the low melting point resin film. I found. The cause of this air permeability improvement has not been fully elucidated, but probably the crystallinity of the high-melting point resin film is improved, and there are more opportunities for opening, resulting in a later porous process (process). (4) and (5)) are presumed to be easier to open.

The high melting point resin film and the low melting point resin film are made porous by applying a predetermined stretching treatment after the lamination, and become a microporous layer.
The first resin film has an elastic recovery rate after heat treatment of preferably 80 to 95%, more preferably 84 to 92%. The second resin film preferably has an elastic recovery rate after heat treatment of 50 to 80%, more preferably 60 to 75%.
If the elastic recovery rate of each resin film is within these ranges, a laminated microporous film having a sufficient degree of porosity can be obtained.

Here, the “elastic recovery rate after heat treatment” of the high melting point resin film and the low melting point resin film is derived as follows, respectively.
The high melting point resin film is annealed in air at 130 ° C. for 1 hour, and then cut into a strip shape having a width of 10 mm and a length of 50 mm to obtain a test piece. The test piece is set in a predetermined position of a tensile tester and is 100% in the length direction at a speed of 50 mm / min under the conditions of 25 ° C. and 65% relative humidity (that is, until the length becomes 100 mm). Elongate. Thereafter, the test piece is immediately relaxed at the same speed (50 mm / min), and the length of the test piece when the load becomes zero is measured. And based on following formula (1), the "elastic recovery rate after heat processing" of a high melting point resin film is derived | led-out.
Elastic recovery rate after heat treatment (%) = ((length of test piece when 100% stretched) − (length of test piece when relaxed to zero load)) / (test piece before stretching) Length) x 100 (1)
Further, the low melting point resin film is annealed in air at 130 ° C. for 1 hour, and then cut into a strip shape having a width of 15 mm and a length of 2 inches (5.08 cm) to obtain a test piece. The specimen is set in place on a tensile tester and is up to 50% in length (ie, 3 inches long) at a speed of 2 inches / minute under conditions of 25 ° C. and 65% relative humidity. Elongate). The specimen is then held in its stretched state for 1 minute, and then the specimen is relaxed at the same speed (2 inches / minute) and the length of the specimen when the load becomes zero is measured. And based on following formula (2), the "elastic recovery rate after heat processing" of a low melting-point resin film is derived | led-out.
Elastic recovery rate after heat treatment (%) = ((length of test piece at 50% extension) − (length of test piece when relaxed and load becomes zero)) / ((at 50% extension) Test piece length) − (length of test piece before stretching)) × 100 (2)

  In the step (2), it is preferable that the high-melting point resin film and the low-melting point resin film are overlapped, passed between heated rolls, and thermocompression bonded. In this case, each resin film is unwound from the roll roll stand, and is laminated by being nipped and pressure-bonded between heated rolls. During lamination, it is preferable to perform thermocompression bonding so that the elastic recovery rate of each resin film does not substantially decrease. In particular, when the high melting point resin films are laminated so as to be sandwiched between two low melting point resin films, it is preferable to employ this method. Thereby, curl (curvature) of the obtained laminated film is suppressed, and it is difficult to receive damage, so that the finally obtained laminated microporous film has better heat resistance, mechanical strength, and the like. In addition, when the laminated microporous film is used as a battery separator, it is also preferable from the viewpoint of sufficiently satisfying its safety and reliability characteristics.

The thermocompression bonding temperature and the temperature of the heated roll in the above example are not limited, but are preferably 120 ° C. or higher and 140 ° C. or lower, more preferably 127 ° C. or higher and 132 ° C. or lower. When the thermocompression bonding temperature is 120 ° C. or higher, the peel strength between the laminated films increases, and there is a tendency that peeling does not easily occur in each subsequent stretching step. Moreover, if the thermocompression bonding temperature is 140 ° C. or lower, a laminated microporous film that satisfies the intended problem tends to be easily obtained without dissolving the low melting point resin film and reducing its elastic recovery rate. There is.
Although there is no limitation on the thermocompression bonding pressure, the nip pressure between heated rolls in the above example, 1 to 3 kg / cm ² is appropriate, and the unwinding speed of each resin film from the original roll 0.5 to 8 m / min is appropriate. Moreover, although there is no limitation in the peeling strength of a laminated body, the range of 3-60g / 15mm is suitable.

The manufacturing method of the laminated microporous film of this embodiment includes an annealing step (3) after thermocompression bonding. The heating temperature in the step (3) is preferably (T _mB −30) ° C. or higher and (T _mB −2) ° C. or lower, more preferably (T _mB −15), which is suitable for crystallization of the low melting point resin film. It is not lower than C and (T _mB -2) C. or lower. The heating time is preferably 10 seconds to 100 hours, more preferably 1 minute to 10 hours.

The manufacturing method of the lamination | stacking microporous film of this embodiment includes a cold drawing process (4) after thermocompression bonding. The stretching temperature for cold stretching is preferably −20 ° C. or higher and (T _mB −60) ° C. or lower, more preferably 0 ° C. or higher and 50 ° C. or lower. When stretched at −20 ° C. or higher, the film is difficult to break, and when stretched at (T _mB −60) ° C. or lower, the resulting laminated microporous film has a high porosity and tends to have low air permeability. There is. Here, the stretching temperature in the cold stretching step (4) is the surface temperature of the laminated film.
The draw ratio in the cold drawing step (4) is preferably 1.05 to 2.0 times, more preferably 1.1 to less than 2.0 times.
Cold stretching is performed in at least one direction, but may be performed in both the extrusion direction of each resin film (hereinafter referred to as “MD direction”) and the width direction (hereinafter referred to as “TD direction”). Preferably, it is preferable to perform uniaxial stretching only in the extrusion direction of each film constituting the laminate.

The manufacturing method of the laminated microporous film of the present embodiment is a hot stretching in which a stretched laminated film is obtained by performing a second stretching in a state of being held at a temperature higher than that in the step (4) after the cold stretching step (4). Including step (5). The stretching temperature in the heat stretching step (5) is preferably (T _mB -60) ° C. or higher and (T _mB −2) ° C. or lower, more preferably (T _mB −30) ° C. or higher (T _mB −2) ° C. It is as follows.
When stretched at (T _mB −60) ° C. or higher, the film can be easily stretched without breaking, and when stretched at (T _mB −2) ° C. or lower, the porosity is low and the air permeability is high. It is easy to obtain a porous film. Here, the stretching temperature in the thermal stretching step (5) is the surface temperature of the laminated film.
The draw ratio in the heat drawing step (5) is preferably 1.05 times or more and 5.0 times or less, more preferably 1.1 times to 5.0 times, more preferably 2.0 times to 5. 0 times.
The hot stretching may be performed in at least one direction and may be performed in both the MD and TD directions, but is preferably performed in the same direction as the cold stretching direction, and more preferably only in the same direction as the cold stretching direction. It is to perform uniaxial stretching.

  It is preferable that the manufacturing method of the lamination | stacking microporous film of this embodiment further includes the process (6) which performs heat setting after a heat | fever extending process. Providing such a heat setting step not only can suppress shrinkage in the stretching direction of the laminated microporous film due to residual stress acting during stretching, but also improves the delamination strength of the resulting laminated microporous film. It is also suitable from the viewpoint. As the heat setting method, a method of heat shrinking to the extent that the length of the laminated microporous film after heat setting is reduced by 10 to 50% (hereinafter, this method is referred to as “relaxation”), and the dimension in the stretching direction are as follows. The method of fixing so that it may not change is mentioned.

The heat _setting temperature is preferably (T _mB −30) ° C. or more and (T _mB −2) ° C. or less, and more preferably (T _mB −15) ° C. or more and (T _mB −2) ° C. or less. Here, the heat setting temperature is the surface temperature of the laminated film.
In the cold drawing step (4), the hot drawing step (5), the other drawing step and the heat setting step (6), the roll, tenter, autograph, etc. are used in one step or two or more steps and uniaxial. A method of stretching and heat setting in the direction and / or biaxial direction may be employed. Among these, from the viewpoint of physical properties and applications required for the laminated microporous film obtained in the present embodiment, two or more stages of uniaxial stretching and heat setting with a roll are preferable.

[First resin film (high melting point resin film)]
The first resin film in this embodiment is made of polyethylene (PE), polypropylene (PP), polybutene-1, poly-4-methylpentene, polyolefin such as ethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer. It is preferably formed from a first resin composition mainly composed of a polymer containing an olefin hydrocarbon such as a coalescence as a monomer component.
The first resin composition constituting the high melting point resin film has a higher melting point than that of the second resin composition, and the melting point T _mA is, for example, 150 ° C. to 280 ° C. This is preferable because the balance of film properties is improved.
If the first resin composition forming the high melting point resin film is a thermoplastic resin composition containing 100 parts by mass of polypropylene resin and 5 to 90 parts by mass of polyphenylene ether resin, the laminated Since a porous film is obtained, it is preferable.

Hereinafter, the thermoplastic resin composition will be described in detail.
[Polypropylene resin]
In the present embodiment, the polypropylene resin (hereinafter sometimes abbreviated as “PP”) is a polymer containing polypropylene as a monomer component, and may be a homopolymer or a copolymer. When it is a copolymer, it may be a random copolymer or a block copolymer. Moreover, when it is a copolymer, there is no limitation in a copolymerization component, For example, ethylene, butene, hexene, etc. are mentioned. When the polypropylene resin is a copolymer, the copolymerization ratio of propylene is preferably 50% by mass or more, 70% by mass or more, or 90% by mass or more. A polypropylene resin is used individually by 1 type or in mixture of 2 or more types. The polymerization catalyst used for obtaining the polypropylene resin is not particularly limited, and examples thereof include a Ziegler-Natta catalyst and a metallocene catalyst.
Further, the stereoregularity of the polypropylene resin is not particularly limited, and isotactic or syndiotactic polypropylene resin is used.

  The polypropylene resin may have any crystallinity or melting point. In addition, two or more kinds of polypropylene resins having different crystallinity and melting point may be blended at a specific blending ratio depending on the physical properties and applications of the obtained microporous film.

  The polypropylene resin used in this embodiment preferably has a melt flow rate (based on ASTM D1238, measured at 230 ° C. under a load of 2.16 kg, the same applies hereinafter), preferably 0.1 to 100 g / 10 minutes, more preferably It can be selected from the range of 0.1 to 80 g / 10 min.

  Polypropylene resins used in this embodiment are known as described in JP-A Nos. 44-15422, 52-30545, 6-313078, and 2006-83294. The modified polypropylene resin may be used. Furthermore, the polypropylene resin used in the present embodiment may be a mixture in any proportion of the above-described polypropylene resin and the modified polypropylene resin.

ここで、式（１）中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、それぞれ独立に、水素原子、ハロゲン原子、炭素数１〜７の低級アルキル基、フェニル基、ハロアルキル基、アミノアルキル基、炭化水素オキシ基、及び、少なくとも２個の炭素原子がハロゲン原子と酸素原子とを隔てているハロ炭化水素オキシ基、からなる群より選ばれる化学種を示す。 [Polyphenylene ether resin]
Examples of the polyphenylene ether resin (hereinafter sometimes abbreviated as “PPE”) that can be used in the present embodiment include those having a repeating unit represented by the following general formula (1).

Here, in formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, a lower alkyl group having 1 to 7 carbon atoms, a phenyl group, a haloalkyl group, or an aminoalkyl. A chemical species selected from the group consisting of a group, a hydrocarbonoxy group, and a halohydrocarbonoxy group in which at least two carbon atoms separate a halogen atom and an oxygen atom.

  Specific examples of PPE include poly (2,6-dimethyl-1,4-phenylene ether), poly (2-methyl-6-ethyl-1,4-phenylene ether), and poly (2-methyl-6). -Phenyl-1,4-phenylene ether) and poly (2,6-dichloro-1,4-phenylene ether). Further, as PPE, for example, polyphenylene ether copolymer such as a copolymer of 2,6-dimethylphenol and other phenols (for example, 2,3,6-trimethylphenol and 2-methyl-6-butylphenol). Examples include coalescence. Among these, poly (2,6-dimethyl-1,4-phenylene ether) and a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol are preferable, and poly (2 , 6-dimethyl-1,4-phenylene ether) is more preferable.

Moreover, it does not specifically limit regarding the manufacturing method of PPE, If it is PPE obtained by a well-known manufacturing method, it can be used for this embodiment.
As the PPE used in the present embodiment, the above-mentioned PPE and a styrenic monomer and / or an α, β-unsaturated carboxylic acid or a derivative thereof (for example, an ester compound, an acid anhydride compound) in the presence of a radical generator or It is also possible to use a known modified PPE obtained by reacting at a temperature of 80 to 350 ° C. in the absence, in the molten state, in the solution state or in the slurry state. Furthermore, the mixture of the above-mentioned PPE and this modified PPE in arbitrary ratios may be sufficient. The reduced viscosity of PPE used in the present embodiment is preferably 0.15 to 2.5, and more preferably 0.30 to 2.00.

The thermoplastic resin composition according to the present embodiment contains 5 to 90 parts by mass, preferably 10 to 80 parts by mass, more preferably 20 to 65 parts by mass of the polyphenylene ether resin with respect to 100 parts by mass of the polypropylene resin. Setting the content ratio of PPE within the above range is preferable from the viewpoint of stretchability of the obtained laminated microporous film.
As the PPE used in the present embodiment, in addition to the above-mentioned PPE, a so-called polymer obtained by adding other polymers such as polystyrene, high impact polystyrene, syndiotactic polystyrene and / or rubber reinforced syndiotactic polystyrene to the PPE. Alloys are also preferably used. In this case, the amount of PPE (5 to 90 parts by mass) includes the mass of other polymers.

[Admixture]
The first resin film in the present embodiment is a sea-island structure including a phase sea part including polypropylene resin (preferably included as a main component) and a phase island including polyphenylene ether resin, preferably included as a main component. It is preferable that it has. In this case, the PPE resin is dispersed in the PP resin matrix.
Preferably, the island portion has a particle size of 0.01 μm to 10 μm. In order to control the size (particle size) of the island part, the thermoplastic resin composition according to the present embodiment particularly preferably contains an admixture in addition to the polypropylene resin and the polyphenylene ether resin.
In the present specification, “including as a main component” and “mainly comprising” means that the specific component is preferably contained in a composition (matrix component) containing the specific component, preferably 50% by mass or more. It means that 80% by mass or more is preferably contained, and 100% by mass may be contained.

  The admixture used in the present embodiment acts as a dispersant for dispersing the polyphenylene ether resin in the above-described polypropylene resin matrix. Furthermore, the admixture has the effect of imparting good porosity and good air permeability to the microporous film according to the present embodiment.

  The admixture used in the present embodiment is preferably a hydrogenated block copolymer from the viewpoint of dispersibility of the polyphenylene ether resin. The hydrogenated block copolymer includes, for example, at least one polymer block A mainly composed of a structural unit derived from a vinyl aromatic compound and at least one structural unit mainly composed of a conjugated diene compound. Examples thereof include a block copolymer obtained by adding hydrogen to a block copolymer composed of the polymer block B.

  Examples of the conjugated diene compound that provides the structural unit of the polymer block B include one or two selected from the group consisting of butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. The above is mentioned. Among these, butadiene, isoprene and combinations thereof are preferable. The polymer block B mainly composed of a structural unit derived from a conjugated diene compound is preferably a polymer block containing at least 70% by mass or more of a structural unit derived from a conjugated diene compound, and is a homopolymer block of a conjugated diene compound. Or a copolymer block of a conjugated diene compound and a monomer copolymerizable with the conjugated diene compound. Regarding the microstructure (bonded form of the conjugated diene compound) in the polymer block B, the sum of the 1,2-vinyl bond amount and the 3,4-vinyl bond amount (hereinafter simply referred to as “vinyl bond amount”) is used. It is preferable that it is 40 to 90%, More preferably, it is 45 to 85%. Here, the “vinyl bond amount” is the number of 1,2-, 3,4-vinyl bonds remaining in the polymer block B after the polymerization relative to the total number of vinyl bonds that the conjugated diene compound had before the polymerization. The percentage of the total number. The bond form and “vinyl bond amount” of these conjugated diene compounds are derived from infrared spectroscopy. However, the “vinyl bond amount” derived using the NMR spectrum may be converted into a value derived from the infrared spectrum. The conversion can be carried out by deriving the “vinyl bond amount” from the infrared spectrum and the NMR spectrum for a polymer having the same vinyl bond amount, and creating a calibration curve between these measurement methods. it can. When the vinyl bond amount is 40% or more, the laminated microporous film of this embodiment is further excellent in the balance between porosity and permeability.

Examples of the vinyl aromatic compound that provides the structural unit of the polymer block A include one or more selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, p-tert-butylstyrene, and diphenylethylene. Is mentioned. Of these, styrene is preferred.
The polymer block A mainly composed of a structural unit derived from a vinyl aromatic compound is preferably a polymer block containing 70% by mass or more of a structural unit derived from a vinyl aromatic compound. Examples thereof include a coalescence block or a copolymer block of a vinyl aromatic compound and a monomer copolymerizable with the vinyl aromatic compound.
The number average molecular weight of the block copolymer having the above structure is preferably in the range of 5,000 to 1,000,000 when measured by gel permeation chromatography using polystyrene as a standard substance. The molecular weight distribution, which is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography using polystyrene as a standard substance, is preferably 10 or less. Furthermore, the molecular structure of this block copolymer may be any of linear, branched, radial, or any combination thereof.

The block copolymer having such a structure is obtained by adding hydrogen to an aliphatic double bond (vinyl bond) of the polymer block B contained therein, thereby obtaining a hydrogenated block copolymer, that is, a vinyl aromatic. It becomes a hydrogenated compound-conjugated diene compound block copolymer and is used as an admixture.
The hydrogenation rate of the block copolymer (the proportion of the aliphatic double bonds of the block copolymer that are hydrogenated (%)) is the aliphatic double of the block copolymer before hydrogenation. Based on the total amount of bonds, it is preferably 80% or more. This hydrogenation rate is derived from the infrared spectrum as in the case of the vinyl bond described above, but the value of the hydrogenation rate derived from the NMR spectrum is converted to a value derived from the infrared spectrum. May be.
The proportion of the admixture in the thermoplastic resin composition is preferably 1 to 20% by mass, more preferably 1 to 15% by mass, based on the total amount of the composition. As a result, the dispersibility of the polyphenylene ether resin and the porosity and air permeability of the laminated microporous film in the present embodiment resulting from the dispersibility become better.

  Further, the thermoplastic resin composition according to the present embodiment includes, in addition to the above components, additional components such as an olefin elastomer, an oxidation agent, and the like as long as the effects exhibited by the present invention are not impaired. Inhibitors, metal deactivators, heat stabilizers, flame retardants (organic phosphate ester compounds, ammonium polyphosphate compounds, aromatic halogen flame retardants, silicone flame retardants, etc.), fluoropolymers, plasticizers ( Low molecular weight polyethylene, epoxidized soybean oil, polyethylene glycol, fatty acid esters, etc.), flame retardant aids such as antimony trioxide, weathering (light) improvers, polyolefin nucleating agents, slip agents, inorganic or organic fillers And reinforcing materials (polyacrylonitrile fiber, carbon black, titanium oxide, calcium carbonate, conductive metal fiber, conductive carbon black, etc.), each Colorants, may be added a release agent or the like.

[Sea-island structure]
The high melting point resin film according to the present embodiment preferably has a sea-island structure including a sea part of a phase containing a polypropylene resin and an island part of a phase containing a polyphenylene ether resin.
In the present embodiment, the “sea-island structure” is a structure in which a skeleton of a phase including a polypropylene resin as a sea part is formed between island components composed of phase particles including a polyphenylene ether resin. In other words, it refers to a structure in which a polyolefin ether resin is dispersed in a plurality of islands in a matrix (matrix) made of polypropylene resin.
The sea-island structure (dispersed state) as described above can be easily measured and observed using a transmission electron microscope or the like. For example, after a high melting point resin film to be measured is loaded on a sample stage, the high melting point resin film is coated with an osmium coating with a thickness of about 3 nm and an acceleration voltage is set to 1 kV (HITACHI S-4700). ).

The particle size of the island is preferably 0.01 μm to 10 μm, more preferably 0.1 μm to 5 μm. Setting the particle size of the island part in such a range can contribute to more uniformly dispersing the pores of the finally obtained laminated microporous film in the film thickness direction and the film surface direction. . A laminated microporous film in which the apertures are uniformly dispersed is suitable as a battery separator.
In the present embodiment, the particle size of the island is measured as follows.
First, a transmission electron micrograph (magnification: 5,000 times) is obtained in the same manner as the measurement method when observing the sea-island structure for the high melting point resin film to be measured. Next, 100 particles of a phase (island part) containing a polyphenylene ether resin dispersed in a phase containing a polypropylene resin as a matrix (sea part) are arbitrarily selected from the photograph. Then, the maximum length of each selected particle is measured as the major axis diameter, and the minimum length is measured as the minor axis diameter. The particle diameter is defined as the major axis diameter. As for this particle size, the arithmetic average value for 100 particles is preferably in the above range, and more preferably in the above range for all 100 particles.

The ratio of the major axis diameter to the minor axis diameter (major axis diameter / minor axis diameter) is preferably 1 to 5, and more preferably 1 to 3. Setting the ratio of the major axis diameter to the minor axis diameter in such a range is preferable from the viewpoint of the openability of the laminated microporous film.
In addition, by appropriately selecting the polypropylene resin, polyphenylene ether resin, and admixture to be used, particles of the phase containing the polyphenylene ether resin having the above-mentioned particle diameter, ratio of major axis diameter to minor axis diameter (island part) ) Can be dispersed in a phase containing a polypropylene resin which is a matrix (sea part).

  In this embodiment, the laminated microporous film obtained by using a high melting point resin film formed from a specific thermoplastic resin composition containing a polypropylene resin and a polyphenylene ether resin can also be used for a lithium ion battery separator. It is a laminated microporous film having excellent porosity and air permeability. This laminated microporous film is formed from a thermoplastic resin composition having a polypropylene resin as a base material (matrix), but maintains a film form even at a temperature exceeding 200 ° C. of the polypropylene resin melting point. It is a laminated microporous film with improved heat resistance. This improvement in heat resistance is surprising, which could never have been predicted from the prior art.

When the laminated microporous film is applied to a battery separator, the improvement in heat resistance brings about an increase in the film breaking temperature as shown in a battery oven test or the like that has been carried out in recent years. As apparent from the above, the laminated microporous film produced by the production method of the present embodiment can achieve a film breaking temperature of 200 ° C. or higher. A laminated microporous film having a film breaking temperature of 200 ° C. or higher can dramatically improve the heat resistance as a battery separator.
Although it is not clear in detail about the mechanism that achieves such a high membrane breaking temperature in the laminated microporous film produced by the production method of this embodiment, it has a morphology with PP as the sea and PPE as the island. Thus, it is considered that a high melt viscosity can be maintained even after film formation, contributing to an improvement in the film breaking temperature.

[Second resin film (low melting point resin film)]
The second resin film in the present embodiment is, for example, a polyolefin resin that is a polymer containing an olefin hydrocarbon such as a polyethylene resin or a polypropylene resin as a monomer component, or a saturated polyester such as a polyethylene terephthalate resin or a polybutylene terephthalate resin. It is preferable to be comprised from the 2nd resin composition containing resin.
When the second resin composition constituting the low melting point resin film has a melting point of 100 ° C. to 150 ° C., the safety of the battery is dramatically improved when the laminated microporous film is used as a battery separator. Therefore, it is preferable. In order to obtain such a second resin composition, a resin having a melting point of 100 ° C. to 150 ° C. may be included in the resin composition. Examples of such resins include polyethylene resins, and more specifically, so-called high density polyethylene, medium density polyethylene, and low density polyethylene. Among these, a high density polyethylene resin is preferably used.
The MFR of the second resin composition is preferably 0.01 to 10 g / 10 minutes, more preferably 0.1 to 3 g / 10 minutes, and further preferably 0.8 to 2.0 g / 10 minutes. And most preferably 1.0 to 1.6 g / 10 min. If the MFR is 0.01 g / 10 min or more, it is difficult for fish eyes to occur in the low melting point resin film, and if it is 10 g / 10 min or less, drawdown is difficult to occur, and the film formability is improved.
The density of the second resin composition is preferably 945~970kg / ^{m 3,} more preferably from 955~970kg / ^{m 3,} more preferably from 960~967kg / ^{m 3,} most preferably 963 to 967 kg / m ³ . If the density is 945 kg / m ³ or more, a microporous film with better air permeability can be obtained, and if it is 970 kg / m ³ or less, the membrane is difficult to break during stretching.

[Physical properties of laminated microporous film]
The porosity of the laminated microporous film of the present embodiment is preferably 20% to 70%, more preferably 35% to 65%, and further preferably 45% to 60%. By setting the porosity to 20% or more, sufficient ion permeability can be ensured when the laminated microporous film is used for battery applications. On the other hand, by setting the porosity to 70% or less, the laminated microporous film can ensure sufficient mechanical strength. 5-40 micrometers is preferable and, as for the film thickness of the lamination | stacking microporous film of this embodiment, 10-30 micrometers is more preferable.
In addition, the porosity of the laminated microporous film of this embodiment can be adjusted to the above-mentioned range by appropriately setting the composition of the resin composition constituting each layer, the stretching temperature, the stretching ratio, and the like.
In addition, the porosity of the laminated microporous film is calculated by cutting a 10 cm × 10 cm square sample from the film and using the following formula from the volume and mass of the sample. Here, the volume is the apparent volume of the laminated microporous film (including the volume of pores in the film). For example, the volume of a 10 cm × 10 cm square sample is 10 cm × 10 cm × film thickness (cm) It is.
Porosity (%) = (Volume (cm ³ ) −Mass (g) / Density of resin composition constituting film (g / cm ³ )) / Volume (cm ³ ) × 100
Here, the density of the resin composition that constitutes the film is an average value obtained by dividing the density of the resin composition that constitutes each layer constituting the laminated microporous film according to the volume of each layer.

The air permeability of the laminated microporous film of the present embodiment is preferably 10 seconds / 100 cc to 5000 seconds / 100 cc, more preferably 50 seconds / 100 cc to 1000 seconds / 100 cc, and even more preferably 100 seconds / 100 cc to 500 seconds. / 100cc. Setting the air permeability to 5000 seconds / 100 cc or less can contribute to ensuring sufficient ion permeability of the laminated microporous film. On the other hand, setting the air permeability to 10 seconds / 100 cc or more is preferable from the viewpoint of obtaining a more uniform laminated microporous film having no defects.
In addition, the air permeability of the laminated microporous film of the present embodiment can be adjusted to the above range by appropriately setting the composition of the resin composition constituting each layer, the stretching temperature, the stretching ratio, and the like.
The air permeability is measured using a Gurley type air permeability meter according to JIS P-8117.

  The laminated microporous film produced by the production method of this embodiment is suitably used as a battery separator, for example, a lithium secondary battery separator. In addition, it is used as various separation membranes.

Next, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to the following examples unless it exceeds the gist. In addition, the raw material used and the evaluation method of various characteristics are as follows.
First, the melt flow rate (MFR) is a value measured in accordance with JIS K 7210 under conditions of 210 ° C. and 2.16 kg for polypropylene resin and 190 ° C. and 2.16 kg for polyethylene resin, The unit is g / 10 minutes.
The density of the polyethylene resin is a value measured according to JIS K 7112, and the unit is kg / m ³ .

The following were used as polypropylene resin, polyphenylene ether resin, admixture, and polyethylene resin.
1. Polypropylene resin (a-1) Propylene homopolymer, MFR = 0.4, melting point (T _mA ) 165 ° C.
2. Polyphenylene ether resin (b-1) PPE having a reduced viscosity of 0.54 obtained by oxidative polymerization of 2,6-xylenol

3. Admixture (c-1) Hydrogenated product of styrene-butadiene block copolymer having the structure of polystyrene (1) -hydrogenated polybutadiene-polystyrene (2), wherein the polymerization ratio of styrene is 43% by weight, The number average molecular weight is 95,000, and the hydrogenation rate is 99.9%.
The number average molecular weight of the polystyrene (1) block (polymer block A1) is 30,000, the number average molecular weight of the polystyrene (2) block (polymer block A2) is 10,000, and a polybutadiene block (polymer block). The total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in B) is 80%.

4). Polyethylene (d-1) Suntec HD S160S, Asahi Kasei Chemicals Corporation, melting point (T _mB ) 133 ° C

The characteristics of various films were measured as follows.
(1) Film thickness (μm)
It was measured with a dial gauge (manufactured by Ozaki Seisakusho, trade name “PEACOCK No. 25”).
(2) Porosity (%)
A 10 cm × 10 cm square sample was cut out from the film, and calculated from the volume and mass of the sample using the following formula.
Porosity (%) = (volume (cm ³ ) −mass (g) / density of resin composition (g / cm ³ )) / volume (cm ³ ) × 100
(3) Air permeability (sec / 100cc)
It measured with the Gurley type air permeability meter based on JIS P-8117. A value obtained by converting the film thickness to 20 μm was derived.

(4) Film breaking temperature (film resistance)
FIG. 1 shows a schematic diagram of a measuring device for the film breaking temperature. (A) is the whole figure, (B), (C) is a top view showing roughly the sample in the measuring device. First, as shown in (B), a laminated microporous film 1 is laminated on a nickel foil 2A having a thickness of 10 μm, and the longitudinal direction (MD direction) (direction X in the drawing) of the laminated microporous film 1 is shown. A Teflon (registered trademark) tape (shown by diagonal lines in the figure; the same applies hereinafter) was applied from above the part to fix the laminated microporous film 1 on the nickel foil 2A. Here, the laminated microporous film 1 is impregnated in advance with a 1 mol / L lithium borofluoride solution (solvent: propylene carbonate / ethylene carbonate / γ-butyllactone = 1/1/2 (mass ratio)) as an electrolytic solution. Used. On the other hand, as shown in (C), a Teflon (registered trademark) tape was bonded to the 10 μm thick nickel foil 2B for masking. However, a 15 mm × 10 mm window (opening) portion was left in the center of the nickel foil 2B.

  Next, as shown in (A), the nickel foil 2A and the nickel foil 2B processed as described above were superposed with the laminated microporous film 1 interposed therebetween. Furthermore, two nickel foils 2A and 2B were sandwiched between the glass plates 3A and 3B from both sides. At this time, it aligned so that the window part of nickel foil 2B and the lamination | stacking microporous film 1 might face. The two glass plates 3A and 3B were sandwiched and fixed by a commercially available double clip (not shown). These were accommodated in the oven 8.

Next, an electrical resistance measuring device (LCR meter manufactured by Ando Electric Co., Ltd., trade name “AG-4311”) 4 was connected to the nickel foils 2A and 2B. Moreover, the thermocouple 5 connected to the thermometer 6 was fixed to the glass plate 3A using Teflon (registered trademark). A data collector 7 for recording the measured electric resistance and temperature was connected to the electric resistance measuring device 4 and the thermometer 6.
Using such an apparatus, the electrical resistance between the nickel foils 2A and 2B was continuously measured while raising the temperature of the glass plate 3A from 25 ° C. to 200 ° C. at a rate of 2 ° C./min. The electrical resistance was measured with an alternating current of 1 kHz. The temperature at which the electrical resistance value between the nickel foils 2A and 2B once reached 10 ³ Ω and then the electrical resistance value again falls below 10 ³ Ω was defined as the film breaking (short) temperature. The case where the film breaking temperature was less than 180 ° C. was evaluated as “X”, the case where the film breaking temperature was 180 ° C. to less than 200 ° C. was evaluated as “◯”, and the case where the film breaking temperature was 200 ° C. or more was evaluated as “「 ”.

(5) Thermal contraction rate A sample of 12 cm x 12 cm square is cut out from the film, and two (total of four) marks are placed at 10 cm intervals in the MD and TD directions of the sample, and the sample is sandwiched between papers. And left in an oven at 100 ° C. or 140 ° C. for 60 minutes. After the sample was taken out from the oven and cooled, the length (cm) between the marks in the MD direction and the TD direction was measured, and the thermal shrinkage rate in the MD direction and the TD direction was calculated by the following formula.
MD direction thermal shrinkage (%) = (10−length in the MD direction after heating (cm)) / 10 × 100
Thermal contraction rate (%) in TD direction = (10−length in TD direction after heating (cm)) / 10 × 100

[Production Example 1] High melting point resin film (A-1)
Polypropylene resin (a-1) was introduced into a single screw extruder set at 20 mm in diameter, L / D = 30, and 260 ° C. via a feeder, and from a T die having a lip thickness of 3.0 mm installed at the tip of the extruder. Extruded. Immediately thereafter, 25 ° C. cold air was applied to the molten resin, and the cast roll cooled to 95 ° C. was wound up under a draw ratio of 250 times and a winding speed of 10 m / min to form a high melting point resin film (A-1). did. The elastic recovery rate after heat treatment of this high melting point resin film was 90%.

[Production Example 2] High melting point resin film (A-2)
100 parts by mass of polypropylene resin (a-1), 11 parts by mass of polyphenylene ether resin (b-1), and 3 parts by mass of admixture (c-1) were prepared. Moreover, the twin-screw extruder which has a 1st raw material supply port and a 2nd raw material supply port was prepared. The nuclear material port was located at the approximate center of the extruder. (A-1) component, (b-1) component, (c-1) component are supplied to the above twin screw extruder set at a temperature of 260 to 320 ° C. and a screw rotation speed of 300 rpm, and are melt-kneaded to produce a thermoplastic resin The composition was obtained as a pellet.
A high melting point resin film (A-2) was molded in the same manner as in Production Example 1 except that the thermoplastic resin composition pellets obtained as described above were used instead of the polypropylene resin (a-1). . The particle size of the island part which is a phase containing PPE in this high melting point resin film was 0.1 to 2.5 μm. Further, the elastic recovery rate after heat treatment of this high melting point resin film was 88%.
The particle size (μm) of the island portion was measured as described in the specification text, and the measured particle size range (maximum particle size to minimum particle size) was shown. As is clear from the measurement of the particle size, a sea-island structure was also observed.

[Production Example 3] Low melting point resin film (B-1)
A polyethylene resin (d-1) was introduced into a single-screw extruder set at 20 mm in diameter, L / D = 30, 220 ° C. via a feeder, and from a T-die having a lip thickness of 3.0 mm installed at the tip of the extruder. Extruded. Immediately after that, 25 ° C. cold air was applied to the molten resin, and the film was wound with a cast roll cooled to 95 ° C. under a draw ratio of 300 times and a winding speed of 10 m / min to form a low melting point resin film (B-1). did. The elastic recovery rate after heat treatment of this low melting point resin film was 72%.

[Example 1]
Two high melting point resin films (A-1) were prepared and annealed for 1 hour in a hot air circulating oven heated to 150 ° C. (step (1)). Next, the high melting point resin film (A-1) and the low melting point resin film (B-1) were each unwound at an unwinding speed of 4.0 m / min and led to a heating roll, where the thermocompression bonding temperature was 130 ° C., The film was thermocompression bonded at a linear pressure of 2.0 kg / cm, and then led to a 25 ° C. cooling roll at the same speed and wound to obtain a laminated film. (Step (2)) The laminated film was annealed for 1 hour in a hot air circulating oven heated to 130 ° C. (Process (3))
Next, the annealed laminated film was uniaxially stretched 1.3 times in the machine direction at a temperature of 25 ° C. to obtain a stretched laminated film (cold stretching step (4)). Next, the stretched laminated film was uniaxially stretched 3.0 times in the machine direction at a temperature of 130 ° C. to obtain a laminated microporous film (thermal stretching step (5)).
About the obtained laminated microporous film in which the first microporous layer derived from A-1 and the second microporous layer derived from B-1 were laminated, the film thickness, porosity, air permeability, heat shrinkage The rate and the film breaking temperature (film resistance) were measured. The results are shown in Table 1.

[Example 2]
A laminated microporous film was obtained in the same manner as in Example 1 except that the high melting point resin film (A-1) was used instead of the high melting point resin film (A-1). The resulting laminated microporous film was measured for film thickness, porosity, air permeability, heat shrinkage rate, and film breaking temperature (film resistance). The results are shown in Table 1.

[Example 3]
A laminated microporous film was obtained in the same manner as in Example 2 except that after the heat stretching step (5) of Example 2, the film was heat fixed by relaxing it at a temperature of 130 ° C. by a factor of 0.8. The resulting laminated microporous film was measured for film thickness, porosity, air permeability, heat shrinkage rate, and film breaking temperature (film resistance). The results are shown in Table 1.

[Comparative Example 1]
The high melting point resin film (A-1) and the low melting point resin film (B-1) are each unwound at an unwinding speed of 4.0 m / min and led to a heating roll, where the thermocompression bonding temperature is 130 ° C. and the linear pressure. The film was thermocompression-bonded at 2.0 kg / cm, then led to a 25 ° C. cooling roll at the same speed and wound to obtain a laminated film. This laminated film was annealed for 1 hour in a hot air circulating oven heated to 130 ° C.
Next, the annealed laminated film was uniaxially stretched 1.3 times in the machine direction at a temperature of 25 ° C. to obtain a stretched laminated film (cold stretching process). Subsequently, the stretched laminated film was uniaxially stretched 3.0 times in the machine direction at a temperature of 130 ° C. to obtain a laminated microporous film (thermal stretching step). The laminated microporous film was heat-fixed by relaxing it at a temperature of 130 ° C. by a factor of 0.8.
About the obtained laminated microporous film in which the first microporous layer derived from A-1 and the second microporous layer derived from B-1 were laminated, the film thickness, porosity, air permeability, heat shrinkage The rate and the film breaking temperature (film resistance) were measured. The results are shown in Table 1. The air permeability was high, and the results were inferior compared to the examples.

DESCRIPTION OF SYMBOLS 1 Laminated microporous film 2A Nickel foil 2B Nickel foil 3A Glass plate 3B Glass plate 4 Electrical resistance measuring device 5 Thermocouple 6 Thermometer 7 Data collector 8 Oven

Claims (14)

A method for producing a laminated microporous film comprising the following steps (1) to (5) in this order (where T _mA is the melting point (° C.) of the first resin composition, and T _mB is 2 is the melting point (° C.) of the resin composition):
(1) A step of annealing a first resin film composed of the first resin composition,
(2) a first resin film, the second resin film and a second resin composition having a first melting point T _mB than the melting point T _mA resin composition, and thermocompression Forming a laminate,
(3) A step of annealing the laminate obtained in the step (2),
(4) A cold stretching step of cold stretching the laminate obtained in the step (3) at least 1.05 times to 2.0 times in at least one direction;
(5) Heat that heat-stretches the laminate obtained in the step (4) at a temperature higher than that of the step (4) at a temperature exceeding 1.0 times and not more than 5.0 times in at least one direction. Stretching process. The manufacturing method of the lamination | stacking microporous film of Claim 1 whose annealing temperature is ( _TmA- 50) _degreeC or more and ( _TmA- 2) degrees C or less in the said process (1).   The manufacturing method of the lamination | stacking microporous film of Claim 1 or 2 whose thermocompression bonding temperature is 120 degreeC or more and 140 degrees C or less in the said process (2). The manufacturing method of the lamination | stacking microporous film of any one of Claims 1-3 whose annealing temperature is ( _TmB- 30) _degreeC or more and ( _TmB- 2) degrees C or less in the said process (3). . In the step (4), the cold drawing is performed in a state where the laminate obtained in the step (3) is held at -20 ° C or higher ( _TmB- 60) ° C or lower. A method for producing a laminated microporous film according to any one of the preceding claims. In the step (5), the thermal stretching is performed in a state in which the laminate obtained in the step (4) is held at ( _TmB- 60) ° C or higher and ( _TmB- 2) ° C or lower. The manufacturing method of the lamination | stacking microporous film of any one of -5. The method for producing a laminated microporous film according to any one of claims 1 to 6, further comprising the following step (6) after the step (5):
(6) The process of heat-setting the laminated body heat-stretched by process (5) at the temperature of ( _TmB- 30) _degreeC or more and ( _TmB- 2) degrees C or less. The first resin composition is a thermoplastic resin composition containing 100 parts by mass of a polypropylene resin and 5 to 90 parts by mass of a polyphenylene ether resin,
The 1st resin film comprised from the said 1st resin composition has a sea island structure which consists of the sea part of the phase containing the said polypropylene resin, and the island part of the phase containing the said polyphenylene ether resin. The manufacturing method of the laminated microporous film of any one of these.   The method for producing a laminated microporous film according to claim 8, wherein the thermoplastic resin composition further contains 1 to 20 parts by mass of an admixture with respect to 100 parts by mass of the polypropylene resin.   The admixture is mainly composed of at least one polymer block A mainly composed of a structural unit derived from a vinyl aromatic compound, and a structural unit derived from a conjugated diene compound. The hydrogenated block copolymer obtained by adding hydrogen to a block copolymer comprising at least one polymer block B having a total 4-vinyl bond content of 40 to 90%. A method for producing a laminated microporous film.   The manufacturing method of the lamination | stacking microporous film of any one of Claims 8-10 whose particle size of the said island part is 0.01 micrometer-10 micrometers.   The manufacturing method of the lamination | stacking microporous film of any one of Claims 1-11 whose said 2nd resin composition is a polyethylene-type resin composition.   A laminated microporous film produced by the production method according to claim 1.   A battery separator comprising the laminated microporous film according to claim 13.

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