JP5697328B2 - Multilayer porous film, battery separator, and battery - Google Patents

Description

  The present invention relates to a laminated porous film, which can be used as a packaging, sanitary, livestock, agricultural, architectural, medical, separation membrane, light diffusion plate, battery separator, and particularly as a separator for non-aqueous electrolytic batteries. It can be used suitably.

  The polymer porous body with many fine communication holes is used for separation membranes used for the production of ultrapure water, purification of chemicals, water treatment, waterproof and moisture-permeable films used for clothing and sanitary materials, and batteries. It is used in various fields such as battery separators.

  In particular, secondary batteries are widely used as power sources for portable devices such as OA, FA, household electric appliances, and communication devices. In particular, portable devices using lithium ion secondary batteries are increasing because they have a high volumetric efficiency when mounted on devices, leading to a reduction in size and weight of the devices. On the other hand, large-sized secondary batteries are being researched and developed in many fields related to energy / environmental issues, including road leveling, UPS, and electric vehicles, and are excellent in large capacity, high output, high voltage, and long-term storage. Therefore, the use of lithium ion secondary batteries, which are a kind of non-aqueous electrolyte secondary battery, is expanding.

  The working voltage of a lithium ion secondary battery is usually designed with an upper limit of 4.1V to 4.2V. At such a high voltage, the aqueous solution causes electrolysis and cannot be used as an electrolyte. Therefore, so-called non-aqueous electrolytes using organic solvents are used as electrolytes that can withstand high voltages. As the solvent for the non-aqueous electrolyte, a high dielectric constant organic solvent capable of allowing more lithium ions to be present is used, and organic carbonate compounds such as propylene carbonate and ethylene carbonate are mainly used as the high dielectric constant organic solvent. It is used. As a supporting electrolyte that becomes a lithium ion source in the solvent, a highly reactive electrolyte such as lithium hexafluorophosphate is dissolved in the solvent and used.

  In the lithium ion secondary battery, a separator is interposed between the positive electrode and the negative electrode from the viewpoint of preventing an internal short circuit. Of course, the separator is required to have insulating properties due to its role. Moreover, it is necessary to have a microporous structure in order to provide air permeability as a lithium ion passage and a function of diffusing and holding the electrolyte. In order to satisfy these requirements, a porous film is used as a separator.

  With the recent increase in battery capacity, the importance of battery safety has increased. As a characteristic that contributes to the safety of the battery separator, there is a shutdown characteristic (hereinafter referred to as “SD characteristic”). This SD characteristic is a function that can prevent a subsequent increase in temperature inside the battery because the micropores are closed when the temperature is about 100 to 150 ° C., and as a result, ion conduction inside the battery is cut off. At this time, the lowest temperature among the temperatures at which the micropores of the laminated porous film are blocked is referred to as a shutdown temperature (hereinafter referred to as “SD temperature”). When used as a battery separator, it is necessary to have this SD characteristic.

  However, with the recent increase in energy density and power of lithium ion secondary batteries, the normal shutdown function does not function sufficiently, and the temperature inside the battery exceeds 150 ° C., the melting point of polyethylene, and further increases. There has been an accident where the separator breaks down and ignites. About this cause, it is said that foreign matters, such as metal powder mixed in the manufacturing process, are triggered, and sudden heat generation occurs locally due to an internal short circuit. Therefore, in order to ensure safety, a separator having both current SD characteristics and heat resistance is required.

  In response to the demand, a separator (Patent Document 1) including a porous film having a shutdown function and a porous layer made of a heat-resistant resin, and a heat-resistant porous layer laminated on a porous layer mainly composed of a thermoplastic resin Separator (Patent Document 2), a separator formed by laminating a porous film of a water-soluble polymer and a porous film of polyolefin (Patent Document 3), and a porous material containing an inorganic filler and a resin binder on at least one side of the polyolefin resin porous film A laminated porous film having a layer (Patent Document 4) has been proposed.

Further, slipperiness is required as a characteristic required for the separator. One of them is the pin detachability in battery assembly. In cylindrical and square wound lithium-ion secondary batteries, the separator and positive and negative electrodes are overlapped, a metal pin is used as the shaft core, and the end of the separator is inserted into the slit provided in the pin. After winding, the positive electrode plate and the negative electrode plate may be overlapped and wound with the separator interposed therebetween . Thereafter, the battery is assembled through a process of removing the spiral battery element from the pin. At this time, if the slipperiness of the separator in contact with the pin is bad, the battery element cannot be pulled out from the pin. Moreover, if it was difficult to pull out, it had a problem of affecting production. In addition, if the slipperiness is poor, there is a problem that the workability is deteriorated, for example, it causes a wrinkle when the film is wound during film formation. In order to improve the pin pull-out property, the pin is subjected to a surface treatment to reduce the friction coefficient of the pin. (Patent Document 5)

JP 2000-223107 A Japanese Patent No. 3756815 JP 2004-227972 A JP 2009-26733 A JP 2009-70726 A

In Patent Documents 1 to 4, pin detachability and pin wearability are not considered, and since harder alumina (Mohs hardness 9.0) is used, the pin is scraped, metal is mixed, and the interior There was a risk of short circuits and even local heating, leading to serious accidents. Further, blades used for slitting and the like, gravure rolls used for coating on a film, and the like are worn by alumina, and there is a risk of metal contamination and workability.
Moreover, in patent document 5, although the pin pull-out property has been improved, it does not lead to improvement in workability, which is not preferable from the viewpoint of productivity.

  An object of the present invention is to solve the above-described problems. In other words, it is a porous film that has both air permeability and heat resistance, and has a heat-resistant layer that not only has excellent slipperiness and pin-out properties when used as a battery separator, but also prevents metal contamination in the manufacturing process. An object of the present invention is to provide a laminated porous film.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that this can be achieved by the following laminated porous film. That is, the present invention is as follows.
[1] A heat-resistant layer containing a filler and a resin binder is laminated on at least one surface of a polyolefin-based resin porous film having β activity, and the filler is barium sulfate having a Mohs hardness of 6 or less, and laminated porous film which is a resin binder Gapo polyvinyl alcohol (PVA).
[2 ] The laminated porous film according to [1 ], wherein the air permeability is 2000 seconds / 100 ml or less.
[ 3 ] The laminated porous film according to [1] or [ 2], wherein a shrinkage rate at 150 ° C. is 10% or less.
[ 4 ] A battery separator using the laminated porous film according to any one of [1] to [ 3 ].
[ 5 ] A battery in which a part is wound around one end of a slit of a pin and then sandwiched between a positive electrode plate and a negative electrode plate to form a spiral wound body, and the battery is accommodated in a cylindrical electrode case with the pin removed. Separator for
Two pins of the laminated porous film cut out in a length of 5000 mm and a width of 580 mm are overlapped, and one end is a slit portion, with the pin detachable from the wound body wound by bringing the heat-resistant layer into contact with the outer peripheral surface of the pin A 4.3N weight is hung on the opposite end, the laminated porous film is fixed, and the laminated porous film is wound around a pin at a speed of 0.6 m / min so that the heat-resistant layer is on the inner side. [ 4 ] The battery separator according to [ 4 ], wherein after fixing, the pin is taken out from the apparatus, and the laminated porous film attached to the pin with a scissors is pulled out three times or more in four times.
[ 6 ] A battery using the battery separator according to [ 4 ] or [ 5 ].

INDUSTRIAL APPLICABILITY The present invention provides a laminated porous film having a heat-resistant layer that has both air permeability and slipperiness and can avoid metal contamination in the production process, and can be suitably used as a battery separator. In particular, when the battery is assembled, the heat-resistant layer containing the filler and the resin binder in contact with the pin has a good sliding property in the step of removing the pin after being wound spirally around the pin as a battery separator during battery assembly. The pin can be pulled out smoothly and is suitably used as a battery separator.

It is a partially broken perspective view of the battery which accommodates the lamination | stacking porous film of this invention. It is a figure explaining the pin used at a winding process. It is a figure explaining the measuring apparatus for measuring pin pull-out property. It is a figure explaining the fixation method of the lamination | stacking porous film in SD characteristic and an X-ray-diffraction measurement.

Hereinafter, embodiments of the laminated porous film of the present invention will be described in detail.
In the present invention, the expression “main component” includes the intention to allow other components to be contained within a range that does not interfere with the function of the main component, unless otherwise specified. The content ratio of the components is not specified, but the main component includes 50% by mass or more, preferably 70% by mass or more, particularly preferably 90% by mass or more (including 100%) in the composition. It is.
In addition, when described as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” and “preferably smaller than Y” together with the meaning of “X to Y” unless otherwise specified. Is included.

  Below, each component which comprises the laminated porous film of this invention is demonstrated.

(Polyolefin resin porous film)
Examples of the polyolefin resin used in the polyolefin resin porous film include homopolymers or copolymers obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexane, and the like. Among these, a polypropylene resin and a polyethylene resin are preferable.

(Polypropylene resin)
Examples of polypropylene resins include homopropylene (propylene homopolymer), or propylene and ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, etc. Examples thereof include random copolymers with α-olefins and block copolymers. Among these, homopolypropylene is more preferably used from the viewpoint of maintaining the mechanical strength and heat resistance of the laminated porous film.

Moreover, as a polypropylene resin, it is preferable that the isotactic pentad fraction (mmmm fraction) which shows stereoregularity is 80 to 99%. More preferably 83-98%, still more preferably 85-97%. If the isotactic pentad fraction is too low, the mechanical strength of the film may be reduced. On the other hand, the upper limit of the isotactic pentad fraction is defined by the upper limit that can be obtained industrially at the present time, but this is not the case when a more regular resin is developed in the industrial level in the future. is not.
The isotactic pentad fraction (mmmm fraction) is the same direction for all five methyl groups that are side chains with respect to the main chain of carbon-carbon bonds composed of arbitrary five consecutive propylene units. Means the three-dimensional structure located at or its proportion. Signal assignment of the methyl group region is as follows. It conformed to Zambelli et al (Macromolecules 8,687, (1975)).

  Moreover, as a polypropylene resin, it is preferable that Mw / Mn which is a parameter which shows molecular weight distribution is 2.0-10.0. More preferably, 2.0 to 8.0, and still more preferably 2.0 to 6.0 is used. This means that the smaller the Mw / Mn is, the narrower the molecular weight distribution is. However, when the Mw / Mn is less than 2.0, problems such as a decrease in extrusion moldability occur, and it is difficult to produce industrially. . On the other hand, when Mw / Mn exceeds 10.0, low molecular weight components increase, and the mechanical strength of the laminated porous film tends to decrease. Mw / Mn is obtained by GPC (gel permeation chromatography) method.

  Further, the melt flow rate (MFR) of the polypropylene-based resin is not particularly limited, but usually the MFR is preferably 0.5 to 15 g / 10 minutes, and 1.0 to 10 g / 10 minutes. It is more preferable. When the MFR is 0.5 g / 10 min or more, the resin has a high melt viscosity at the time of molding, and sufficient productivity can be ensured. On the other hand, the mechanical strength of the obtained laminated porous film can be sufficiently maintained by setting it to 15 g / 10 min or less. MFR is measured according to JIS K7210 under conditions of a temperature of 230 ° C. and a load of 2.16 kg.

  The method for producing the polypropylene resin is not particularly limited, and a known polymerization method using a known polymerization catalyst, for example, a multisite catalyst represented by a Ziegler-Natta type catalyst or a metallocene catalyst. And a polymerization method using a single site catalyst.

  Examples of the polypropylene resin include trade names “Novatech PP” “WINTEC” (manufactured by Nippon Polypro), “Versify” “Notio” “Tafmer XR” (manufactured by Mitsui Chemicals), “Zeras” “Thermolan” (Mitsubishi Chemical) Manufactured by Sumitomo Chemical Co., Ltd.), “Sumitomo Noblen” “Tufselen” (manufactured by Sumitomo Chemical Co., Ltd.), “Prime TPO” (manufactured by Prime Polymer Co., Ltd.), “Adflex”, “Adsyl”, “HMS-PP (PF814)” (manufactured by Sun Aroma) Commercially available products such as “Inspire” (Dow Chemical) can be used.

As described above, the laminated porous film of the present invention has β activity .
The β activity can be regarded as an index indicating that the polypropylene resin has produced β crystals in the film-like material before stretching. If the polypropylene resin in the film-like material before stretching produces β crystals, fine pores can be easily formed by stretching even when additives such as fillers are not used. A laminated porous film having characteristics can be obtained.

In the laminated porous film of the present invention, the presence or absence of “β activity” is determined when the crystal melting peak temperature derived from the β crystal is detected by a differential scanning calorimeter described below and / or the X-ray diffractometer described below. When a diffraction peak derived from the β crystal is detected by the measurement used, it is judged to have “β activity”.
Specifically, the laminated porous film is heated from 25 ° C. to 240 ° C. at a heating rate of 10 ° C./min for 1 minute with a differential scanning calorimeter, and then cooled from 240 ° C. to 25 ° C. at a cooling rate of 10 ° C./min. Was maintained for 1 minute after the temperature was lowered, and when the temperature was raised again from 25 ° C. to 240 ° C. at a heating rate of 10 ° C./min, a crystal melting peak temperature (Tmβ) derived from the β crystal of the polypropylene resin was detected. In the case, it is determined to have β activity.

In addition, the β activity of the laminated porous film is calculated by the following formula using the crystal heat of fusion derived from the α crystal of the polypropylene tree (ΔHmα) and the crystal heat of heat derived from the β crystal (ΔHmβ). .
β activity (%) = [ΔHmβ / (ΔHmβ + ΔHmα)] × 100
For example, when the polypropylene resin is homopolypropylene, the amount of heat of crystal melting derived from the β crystal (ΔHmβ) detected mainly in the range of 145 ° C. or higher and lower than 160 ° C., and mainly detected at 160 ° C. or higher and 170 ° C. or lower. It can be calculated from the heat of crystal melting (ΔHmα) derived from the α crystal. Further, for example, in the case of random polypropylene copolymerized with 1 to 4 mol% of ethylene, the crystal melting heat amount (ΔHmβ) derived from the β crystal detected mainly in the range of 120 ° C. or more and less than 140 ° C., and mainly 140 It can be calculated from the crystal melting calorie (ΔHmα) derived from the α crystal detected in the range of from 0 ° C. to 165 ° C.

The laminated porous film preferably has a higher β activity, and the β activity is preferably 20% or more. More preferably, it is 40% or more, and particularly preferably 60% or more. If the laminated porous film has a β activity of 20% or more, it indicates that a large amount of β crystals of polypropylene resin can be formed even in the film-like material before stretching, and there are many fine and uniform pores by stretching. As a result, a separator for a lithium ion lithium battery having high mechanical strength and excellent air permeability can be obtained.
The upper limit of β activity is not particularly limited, but the higher the β activity, the more effective the effect is obtained.

The presence or absence of the β activity can also be determined from a diffraction profile obtained by wide-angle X-ray diffraction measurement of a laminated porous film subjected to a specific heat treatment.
Specifically, wide-angle X-ray measurement was performed on a laminated porous film that was subjected to heat treatment at 170 ° C. to 190 ° C., which is a temperature exceeding the melting point of the polypropylene resin, and was slowly cooled to generate and grow β crystals. When the diffraction peak derived from the (300) plane of the β crystal is detected in the range of 2θ = 16.0 ° to 16.5 °, it is determined that there is β activity.
Details on the β crystal structure and wide angle X-ray diffraction of polypropylene resins can be found in Macromol. Chem. 187, 643-652 (1986), Prog. Polym. Sci. Vol. 16, 361-404 (1991), Macromol. Symp. 89, 499-511 (1995), Macromol. Chem. 75, 134 (1964), and references cited therein. A detailed evaluation method of β activity using wide-angle X-ray diffraction will be described in the examples described later.

The β activity can be measured in the state of the entire laminated porous film even in the case where the laminated porous film of the present invention has a single-layer structure or any other porous layer laminated. .
Further, if a layer containing a polypropylene resin other than the layer made of polypropylene resin is laminated, it is preferable that both layers have β activity.

  As a method for obtaining the β activity described above, as described in Japanese Patent No. 3739481, a method of adding polypropylene subjected to a treatment for generating a peroxide radical, a method of adding a β crystal nucleating agent to the composition, etc. Is mentioned.

(Β crystal nucleating agent)
Examples of the β crystal nucleating agent used in the present invention include those shown below, but are not particularly limited as long as they increase the formation and growth of β crystals of polypropylene resin, and two or more types are mixed. May be used.
Examples of the β crystal nucleating agent include amide compounds; tetraoxaspiro compounds; quinacridones; iron oxides having a nanoscale size; potassium 1,2-hydroxystearate, magnesium benzoate or magnesium succinate, magnesium phthalate, etc. Alkali or alkaline earth metal salts of carboxylic acids represented by: aromatic sulfonic acid compounds represented by sodium benzenesulfonate or sodium naphthalenesulfonate; di- or triesters of dibasic or tribasic carboxylic acids; phthalocyanine blue Phthalocyanine pigments typified by: a two-component compound comprising component A which is an organic dibasic acid and a component B which is an oxide, hydroxide or salt of a Group IIA metal of the periodic table; a cyclic phosphorus compound; Made of magnesium compound Such as the formation thereof. In addition, specific types of nucleating agents are described in JP-A No. 2003-306585, JP-A Nos. 06-228966, and JP-A Nos. 09-194650.

  As a commercial product of β crystal nucleating agent, β crystal nucleating agent “NJESTER NU-100” manufactured by Shin Nippon Rika Co., Ltd., as a specific example of polypropylene resin to which β crystal nucleating agent is added, polypropylene manufactured by Aristech “Bepol B -022SP ", polypropylene manufactured by Borealis" Beta (β) -PP BE60-7032 ", polypropylene manufactured by Mayzo" BNX BETAPP-LN ", and the like.

The ratio of the β-crystal nucleating agent added to the polypropylene resin needs to be appropriately adjusted depending on the type of the β-crystal nucleating agent or the composition of the polypropylene-based resin. 0.0001 to 5.0 parts by mass of the agent is preferred. 0.001-3.0 mass parts is more preferable, and 0.01-1.0 mass part is still more preferable. If it is 0.0001 part by mass or more, β crystals of polypropylene resin can be sufficiently produced and grown at the time of production, and sufficient β activity can be secured even when used as a separator, and the desired air permeability performance can be obtained. can get. Addition of 5.0 parts by mass or less is preferable because it is economically advantageous and there is no bleeding of the β crystal nucleating agent on the surface of the laminated porous film.
Further, when a layer containing a polypropylene resin other than the layer made of polypropylene resin is laminated, the amount of β crystal nucleating agent added to each layer may be the same or different. The porous structure of each layer can be appropriately adjusted by changing the addition amount of the β crystal nucleating agent.

(Other ingredients)
In the present invention, in addition to the components described above, additives generally added to the resin composition can be added as appropriate within a range that does not significantly impair the effects of the present invention. Examples of the additive include recycling resin, silica, talc, kaolin, calcium carbonate, and the like, which are added for the purpose of improving and adjusting molding processability, productivity, and various physical properties of the laminated porous film. Inorganic particles such as, pigments such as titanium oxide and carbon black, flame retardants, weathering stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, Examples thereof include additives such as antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, antiblocking agents, slip agents, and coloring agents. Specifically, the interfaces as antioxidants described in P154 to P158 of PLASTICS compounding agents, UV absorbers described in P178 to P182, and antistatic agents described in P271 to P275 Activators, lubricants described in P283 to P294, and the like.

(Polyethylene resin)
Specific examples of the polypropylene resin include ultra low density polyethylene, low density polyethylene, high density polyethylene, linear low density polyethylene, and homopolymer polyethylene such as ultra high molecular weight polyethylene characterized by molecular weight, as well as ethylene propylene. A copolymer or a copolymer polyethylene of a polyethylene resin and another polyolefin resin may be mentioned. Among these, homopolymer polyethylene or copolymer polyethylene having an α-olefin comonomer content of 2 mol% or less is preferable, and homopolymer polyethylene is more preferable. There is no restriction | limiting in particular about the kind of alpha-olefin comonomer.

Density of the polyethylene resin is preferably 0.910~0.970g / cm ^3, more preferably 0.930~0.970g / cm ^3, 0.940~0.970g / cm ³ is more preferable. A density of 0.910 g / cm ³ or more is preferable because it can have appropriate SD characteristics. On the other hand, 0.970 g / cm ³ or less is preferable in that it can have an appropriate SD characteristic and can maintain stretchability. The density can be measured according to JIS K7112 using a density gradient tube method.

Further, the melt flow rate (MFR) of the polyethylene resin is not particularly limited, but usually the MFR is preferably 0.03 to 30 g / 10 minutes, and preferably 0.3 to 10 g / 10 minutes. It is more preferable. If the MFR is 0.03 g / 10 min or more, the melt viscosity of the resin during the molding process is sufficiently low, which is excellent in productivity and preferable. On the other hand, if it is 30 g / 10 minutes or less, since sufficient mechanical strength can be obtained, it is preferable.
MFR is measured in accordance with JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg.

  The polymerization catalyst for the polyethylene resin is not particularly limited, and may be any Ziegler type catalyst, Philips type catalyst, Kaminsky type catalyst or the like. As a polymerization method of the polyethylene resin, there are a one-stage polymerization, a two-stage polymerization, or a multistage polymerization more than that, and any method of the polyethylene resin can be used.

(Porosification promoting compound)
It is preferable to add the porosity promoting compound X to the polyethylene resin. By adding the porosity promoting compound X, a porous structure can be obtained more efficiently, and the shape and diameter of the pores can be easily controlled.
The porosity promoting compound X is not particularly limited. Specifically, the porosity promoting compound X is selected from a modified polyolefin resin, an alicyclic saturated hydrocarbon resin or a modified product thereof, an ethylene copolymer, or a wax. It is preferable that at least one of them is included. Among these, an alicyclic saturated hydrocarbon resin or a modified product thereof, an ethylene copolymer, or a wax, which is more effective when made porous, is more preferable, and a wax is more preferable from the viewpoint of moldability.

  Examples of alicyclic saturated hydrocarbon resins and modified products thereof include petroleum resins, rosin resins, terpene resins, coumarone resins, indene resins, coumarone-indene resins, and modified products thereof.

  The petroleum resin in the present invention is a C4 to C10 aliphatic olefin or diolefin obtained from a by-product of naphtha pyrolysis or the like, or a C8 or higher aromatic compound having an olefinically unsaturated bond. An aliphatic, aromatic and copolymer petroleum resin obtained by singly or copolymerizing one or two or more of the compounds contained in the above.

  Examples of petroleum resins include aliphatic petroleum resins mainly containing C5 fraction, aromatic petroleum resins mainly containing C9 fraction, copolymer petroleum resins thereof, and alicyclic petroleum resins. . Examples of terpene resins include terpene resins and terpene-phenol resins derived from β-pinene, and examples of rosin resins include rosin resins such as gum rosin and utdrodine, and esterified rosin resins modified with glycerin and pentaerythritol. The alicyclic saturated hydrocarbon resin and the modified product thereof have relatively good compatibility when mixed with a polyethylene resin, but a petroleum resin is more preferable in terms of color tone and thermal stability, and a hydrogenated petroleum resin is used. More preferably.

  Hydrogenated petroleum resin is obtained by hydrogenating petroleum resin by a conventional method. Examples thereof include hydrogenated aliphatic petroleum resins, hydrogenated aromatic petroleum resins, hydrogenated copolymer petroleum resins and hydrogenated alicyclic petroleum resins, and hydrogenated terpene resins. Among hydrogenated petroleum resins, hydrogenated alicyclic petroleum resins obtained by copolymerizing and hydrogenating a cyclopentadiene compound and an aromatic vinyl compound are particularly preferable. Examples of commercially available hydrogenated petroleum resins include “ALCON” (manufactured by Arakawa Chemical Industries).

  The ethylene copolymer in the present invention is a compound obtained by copolymerizing ethylene and one or more of vinyl acetate, unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, or carboxylic acid ester. It is.

  The ethylene copolymer preferably has an ethylene monomer unit content of 50% by mass or more, more preferably 60% by mass or more, and still more preferably 65% by mass or more. On the other hand, regarding the upper limit, the content of ethylene monomer units is preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less. If the content of the ethylene monomer unit is within a predetermined range, a porous structure can be formed more efficiently.

  As the ethylene copolymer, those having an MFR (JIS K7210, temperature: 190 ° C., load: 2.16 kg) of 0.1 g / 10 min to 10 g / 10 min are preferably used. When the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, when the MFR is 10 g / 10 min or less, the strength of the film is hardly lowered, which is preferable.

  The ethylene-based copolymer includes “EVAFLEX” (Mitsui / DuPont Polychemical Co., Ltd.), “Novatech EVA” (Nihon Polyethylene Co., Ltd.) as an ethylene-vinyl acetate copolymer, and “NUC as an ethylene-acrylic acid copolymer. Copolymer ”(Nippon Unicar), Everflex-EAA (Mitsui / DuPont Polychemical),“ REXPEARL EAA ”(Japan Ethylene),“ ELVALOY ”(Mitsui) as an ethylene- (meth) acrylic acid copolymer -DuPont Polychemical Co., Ltd.), "REXPEARL EMA" (Nippon Ethylene Co., Ltd.), ethylene-ethyl acrylate copolymer as "REXPEARL EEA" (Nihon Ethylene Co., Ltd.), ethylene-methyl (meth) acrylic acid copolymer "Aclift" (manufactured by Sumitomo Chemical), "Bondyne" (manufactured by Sumitomo Chemical Co., Ltd.) as an ethylene-vinyl acetate-maleic anhydride terpolymer , "Bond first" (manufactured by Sumitomo Chemical Co., Ltd.) as ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer, ethylene-ethyl acrylate-glycidyl methacrylate terpolymer Are commercially available.

The wax in the present invention is an organic compound that satisfies the following properties (a) and (b).
(A) The melting point is 40 ° C to 200 ° C.
(A) The melt viscosity at a temperature 10 ° C. higher than the melting point is 50 Pa · s or less.

  For waxes, polar or nonpolar waxes, polypropylene waxes, polyethylene waxes and wax modifiers are included. Specifically, polar wax, nonpolar wax, Fischer-Tropsch wax, oxidized Fischer-Tropsch wax, hydroxy stearamide wax, functionalized wax, polypropylene wax, polyethylene wax, wax modifier, amorphous wax, carnauba wax , Castor oil wax, microcrystalline wax, beeswax, carnauba wax, castor wax, plant wax, candelilla wax, Japanese wax, ouricury wax, douglas fur bark wax, rice bran wax, jojoba wax, bay wax, montan wax, ozono Kelite wax, ceresin wax, petroleum wax, paraffin wax, chemically modified hydrocarbon wax, substituted amide wax, and combinations and derivatives thereof Body, and the like. Among these, paraffin wax, polyethylene wax, and microcrystalline wax are preferable from the viewpoint of efficiently forming a porous structure, and microcrystalline wax that can further reduce the pore diameter is more preferable from the viewpoint of SD characteristics. Examples of commercially available polyethylene wax include “FT-115” (manufactured by Nippon Seiwa), and examples of microcrystalline wax include “Hi-Mic” (manufactured by Nippon Seiwa).

  The blending amount of the porosity promoting compound X is set as a lower limit with respect to 100 parts by mass of the polyethylene resin contained in one layer when the microporous is formed by peeling the interface between the polyethylene resin and the porosity promoting compound X. 1 part by mass or more is preferable, 5 parts by mass or more is more preferable, and 10 parts by mass or more is still more preferable. On the other hand, the upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. By setting the blending amount of the porosity promoting compound X to 1 part by mass or more with respect to 100 parts by mass of the polyethylene-based resin, an effect of expressing a desired good porous structure is sufficiently obtained. Moreover, the more stable moldability is securable because the compounding quantity of the said porosity promotion compound X shall be 50 mass parts or less.

  If necessary, in addition to the polyethylene resin and the porosity promoting compound X, a thermoplastic resin may be used as long as the thermal characteristics of the porous film, specifically, the porosity is not impaired. Examples of other thermoplastic resins that can be mixed with the polyethylene resin include styrene resins such as styrene, AS resin, and ABS resin: polyvinyl chloride, fluorine resin, polyethylene terephthalate, polybutylene terephthalate, and polycarbonate. Or ester resins such as polyarylate; ether resins such as polyacetal, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone or polyphenylene sulfide; polyamides such as 6 nylon, 6-6 nylon and 6-12 nylon Examples thereof include thermoplastic resins such as resins.

  Moreover, what is called rubber components, such as a thermoplastic elastomer, may be added as needed. Examples of the thermoplastic elastomer include styrene / butadiene, polyolefin, urethane, polyester, polyamide, 1,2-polybutadiene, polyvinyl chloride, and ionomer.

In addition to the polyethylene-based resin and the porosity promoting compound X, additives or other components that are generally blended in the resin composition may be included. Examples of the additive include recycling resin, silica, talc, kaolin, carbonic acid, etc., which are added for the purpose of improving / adjusting the processability, productivity, and various physical properties of the laminated porous film. Inorganic particles such as calcium, pigments such as titanium oxide and carbon black, flame retardants, weathering stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents And additives such as antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, antiblocking agents, slip agents, and coloring agents.
Among them, the nucleating agent is preferable because it has an effect of controlling the crystal structure of the polyethylene resin and reducing the porous structure at the time of stretching and opening. Examples of commercially available products include “Gelall D” (manufactured by Shin Nippon Chemical Co., Ltd.), “Adeka Stub” (manufactured by Asahi Denka Kogyo Co., Ltd.), “Hyperform” (manufactured by Milliken Chemical Co., Ltd.), or “IRGACLEAR D” (Ciba Special Chemicals). Etc.). Moreover, as a specific example of the polyethylene resin to which the nucleating agent is added, “Rike Master” (manufactured by Riken Vitamin Co., Ltd.) and the like are commercially available.

(Layer structure of polyolefin resin porous film)
In the present invention, the polyolefin-based resin porous film may be a single layer or a laminate, but is preferably laminated in two or more layers. Especially, what laminated | stacked the layer containing a polypropylene resin and the layer containing a polyethylene resin is more preferable.
The layer structure of the polyolefin resin porous film is not particularly limited as long as at least one layer containing a polypropylene resin (hereinafter referred to as “A layer”) is present. In addition, other layers (hereinafter referred to as “B layer”) can be laminated as long as they do not interfere with the function of the polyolefin resin porous film. The structure which laminated | stacked the intensity | strength maintenance layer, the heat-resistant layer (high melting temperature resin layer), the shutdown layer (low melting temperature resin layer), etc. are mentioned. For example, when using as a separator for a lithium ion battery, a low melting point resin layer that ensures the safety of the battery is laminated by closing the hole in a high temperature atmosphere as described in JP-A No. 04-181651. Is preferred.
Specific examples include a two-layer structure in which A layers / B layers are stacked, a three-layer structure in which A layers / B layers / A layers, or B layers / A layers / B layers are stacked. In addition, it is possible to adopt a form of three types and three layers in combination with layers having other functions. In this case, the order of stacking with layers having other functions is not particularly limited. Further, the number of layers may be increased as necessary to 4 layers, 5 layers, 6 layers, and 7 layers.

  The physical properties of the polyolefin resin porous film of the present invention can be freely adjusted by the layer constitution, lamination ratio, composition of each layer, and production method.

(Manufacturing method of polyolefin resin porous film)
Next, although the manufacturing method of the polyolefin resin porous film of this invention is demonstrated, this invention is not limited only to the lamination | stacking porous film manufactured by this manufacturing method.

The method for producing the non-porous film is not particularly limited, and a known method may be used. For example, a method of melting a thermoplastic resin composition using an extruder, extruding from a T die, and cooling and solidifying with a cast roll. Is mentioned. Moreover, the method of cutting open the film-like thing manufactured by the tubular method and making it planar is also applicable.
There are methods for stretching the nonporous film-like material, such as a roll stretching method, a rolling method, a tenter stretching method, and a simultaneous biaxial stretching method, and these methods are used alone or in combination of two or more to perform uniaxial stretching or biaxial stretching. . Among these, sequential biaxial stretching is preferable from the viewpoint of controlling the porous structure.

Moreover, in this invention, when making a polyolefin resin porous film into a lamination, a manufacturing method is divided roughly into the following four according to the order of porous formation and lamination.
(A) A method of laminating each porous layer after laminating each porous layer or bonding with an adhesive or the like.
(B) A method of laminating each layer to produce a laminated nonporous film-like material and then making the nonporous film-like material porous.
(C) A method in which one of the layers is made porous and then laminated with another layer of a nonporous film to make it porous.
(D) A method of forming a laminated porous film by preparing a porous layer and then applying a coating such as inorganic / organic particles or depositing metal particles.
In the present invention, it is preferable to use the method (b) from the viewpoint of the simplicity of the process and productivity, and in particular, in order to ensure the interlayer adhesion between the two layers, a laminated nonporous film-like material is obtained by coextrusion. A method of forming a porous layer after preparing is particularly preferable.

Below, the detail of a manufacturing method is demonstrated.
First, a mixed resin composition of a polypropylene resin and, if necessary, a thermoplastic resin and additives is prepared. For example, raw materials such as polypropylene resin, β crystal nucleating agent, and other additives as required, preferably using Henschel mixer, super mixer, tumbler type mixer, etc., or by hand-blending all ingredients in a bag After mixing, the mixture is melt-kneaded with a single-screw or twin-screw extruder, a kneader or the like, preferably a twin-screw extruder, and then cut to obtain pellets.

The pellets are put into an extruder and extruded from a T-die extrusion die to form a film.
The type of T die is not particularly limited. For example, when the laminated porous film of the present invention has a laminated structure of two types and three layers, the T die may be a multi-manifold type for two types and three layers or a feed block type for two types and three layers.
The gap of the T die to be used is determined from the final required film thickness, stretching conditions, draft rate, various conditions, etc., but is generally about 0.1 to 3.0 mm, preferably 0.5. -1.0 mm. If it is less than 0.1 mm, it is not preferable from the viewpoint of production speed, and if it is more than 3.0 mm, it is not preferable from the viewpoint of production stability because the draft rate increases.

In extrusion molding, the extrusion temperature is appropriately adjusted depending on the flow characteristics and moldability of the resin composition, but is generally preferably 180 to 350 ° C, more preferably 200 to 330 ° C, and further preferably 220 to 300 ° C. A temperature of 180 ° C. or higher is preferable because the viscosity of the molten resin is sufficiently low and the moldability is excellent and the productivity is improved. On the other hand, by setting the temperature to 350 ° C. or lower, it is possible to suppress the deterioration of the resin composition, and hence the mechanical strength of the laminated porous film obtained.
The cooling and solidification temperature by the cast roll is very important in the present invention, and the ratio of the β crystal of the polypropylene resin in the film can be adjusted. The cooling and solidification temperature of the cast roll is preferably 80 to 150 ° C, more preferably 90 to 140 ° C, and still more preferably 100 to 130 ° C. It is preferable to set the cooling and solidification temperature to 80 ° C. or higher because the ratio of β crystals in the film can be sufficiently increased. Further, it is preferable to set the temperature to 150 ° C. or lower because troubles such as the extruded molten resin sticking to and wrapping around the cast roll hardly occur and the film can be efficiently formed into a film.

It is preferable to adjust the β crystal ratio of the polypropylene resin of the film-like material before stretching to 30 to 100% by setting a cast roll in the temperature range. 40-100% is more preferable, 50-100% is still more preferable, and 60-100% is the most preferable. By setting the β crystal ratio in the film-like material before stretching to 30% or more, a polyolefin-based resin porous film having good gas permeability can be obtained because it is easily made porous by the subsequent stretching operation.
The β crystal ratio in the film before stretching is detected when the film is heated from 25 ° C. to 240 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter. It is calculated by the following formula using the crystal melting calorie (ΔHmα) derived from the α crystal and the crystal melting calorie (ΔHmβ) derived from the β crystal of the polypropylene resin (A).
β crystal ratio (%) = [ΔHmβ / (ΔHmβ + ΔHmα)] × 100

In the stretching step, uniaxial stretching may be performed in the longitudinal direction or the transverse direction, or biaxial stretching may be performed. Moreover, when performing biaxial stretching, simultaneous biaxial stretching may be sufficient and sequential biaxial stretching may be sufficient. When producing the polyolefin resin porous film of the present invention, sequential biaxial stretching is more preferable because the stretching conditions can be selected in each stretching step and the porous structure can be easily controlled.
Next, it is more preferable to stretch the obtained nonporous film-like material at least biaxially. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching, but the stretching conditions (magnification, temperature) can be easily selected in each stretching step, and the porous structure can be easily controlled. Biaxial stretching is more preferable. The longitudinal direction of the film and the film is referred to as “longitudinal direction”, and the direction perpendicular to the longitudinal direction is referred to as “lateral direction”. In addition, stretching in the longitudinal direction is referred to as “longitudinal stretching”, and stretching in the direction perpendicular to the longitudinal direction is referred to as “lateral stretching”.

  When sequential biaxial stretching is used, the stretching temperature needs to be appropriately selected depending on the composition of the resin composition to be used and the crystallization state, but is preferably selected within the range of the following conditions.

When using sequential biaxial stretching, the stretching temperature needs to be changed from time to time depending on the composition of the resin composition to be used, the crystal melting peak temperature, the degree of crystallinity, etc., but the stretching temperature in the longitudinal stretching is preferably about 0 to 130 ° C. More preferably, it is controlled in the range of 10 to 120 ° C, and more preferably 20 to 110 ° C. The longitudinal draw ratio is preferably 2 to 10 times, more preferably 3 to 8 times, still more preferably 4 to 7 times. By performing longitudinal stretching within the above range, it is possible to develop an appropriate pore starting point while suppressing breakage during stretching.
On the other hand, the stretching temperature in transverse stretching is generally 100 to 160 ° C, preferably 110 to 150 ° C, and more preferably 120 to 140 ° C. Moreover, a preferable lateral stretch ratio is 2 to 10 times, more preferably 3 to 8 times, and still more preferably 4 to 7 times. By transversely stretching within the above range, the pore starting point formed by longitudinal stretching can be appropriately expanded, and a fine porous structure can be expressed.
The stretching speed in the stretching step is preferably 500 to 12000% / min, more preferably 1500 to 10,000% / min, and further preferably 2500 to 8000% / min.

  The laminated porous film thus obtained is preferably subjected to heat treatment for the purpose of improving dimensional stability. In this case, the effect of dimensional stability can be expected by setting the temperature to preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and still more preferably 140 ° C. or higher. On the other hand, the heat treatment temperature is preferably 170 ° C. or lower, more preferably 165 ° C. or lower, and further preferably 160 ° C. or lower. When the heat treatment temperature is 170 ° C. or lower, it is preferable because the heat treatment hardly melts polypropylene and maintains a porous structure. Moreover, you may perform a 1-20% relaxation process as needed during the heat processing process. In addition, the laminated porous film of this invention is obtained by uniformly cooling and winding up after heat processing.

(Heat resistant layer)
In the present invention, a heat-resistant layer containing a filler and a resin binder is laminated on at least one surface of a polyolefin resin porous film.

(Filler)
Examples of the filler that can be used in the present invention include an inorganic filler and an organic filler, but are not particularly limited. From the viewpoint of heat resistance, it is preferable to use an inorganic filler.

In the present invention, it is important that the filler has a Mohs hardness of 6 or less, preferably 4 or less. If the value of Mohs hardness is greater than 6, when used as a battery separator, after winding on the pin, the pin will wear out when the pin is pulled out from the battery element, or the blade will be damaged during slitting and other cutting processes There is a risk of metal contamination in the battery. The metal contamination may cause an internal short circuit and further local heating, leading to a serious accident. On the other hand, if the Mohs hardness is 6 or less, when the battery element is pulled out after being wound around the pin, the pin is pulled out without being worn, or used for coating on a blade or a film used for slitting or the like. Since the gravure roll or the like is not damaged, there is no possibility of metal contamination and there is no possibility of serious accidents associated with local heating.
Here, the Mohs hardness is the following 10 kinds of minerals (Mohs hardness 1: talc, Mohs hardness 2: gypsum, Mohs hardness 3: calcite, Mohs hardness 4: fluorite Mohs hardness 5: apatite, Mohs hardness 6: positive This is a method for evaluating hardness in comparison with feldspar, Mohs hardness 7: quartz, Mohs hardness 8: topaz, Mohs hardness 9: corundum, Mohs hardness 10: diamond) as standard materials. Scratch the reference material and the sample, and determine that the scratched surface is low in hardness. In addition, when it is difficult to directly measure the Mohs hardness, the composition can be obtained from composition analysis, and can be determined from the Mohs hardness of substances having the same composition.

  Examples of inorganic fillers include carbonates such as calcium carbonate (Mohs hardness: 3), magnesium carbonate (Mohs hardness: 3.5 to 4.5), barium carbonate (Mohs hardness: 3 to 3.5); calcium sulfate (Mohs hardness: 2), sulfates such as magnesium sulfate (Mohs hardness: 2-3), barium sulfate (Mohs hardness: 3-3.5); sodium chloride (Mohs hardness: 2-2.5), calcium chloride , Chlorides such as magnesium chloride, talc (Mohs hardness: 1), clay, silicates such as mica (Mohs hardness: 2.5 to 3), boehmite (Mohs hardness: 3.5 to 4), magnesium oxide ( Examples include Mohs hardness: 4), zinc oxide (Mohs hardness: 4 to 5), calcium oxide (Mohs hardness: 4), anatase-type titanium oxide (Mohs hardness: 5.5 to 6), and the like. Among these, barium sulfate, boehmite, or anatase-type titanium oxide is preferable from the viewpoints of hardness and electrochemical stability.

  Examples of organic fillers include ultra high molecular weight polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polytetrafluoroethylene, polyimide, polyether. Examples thereof include thermoplastic resins such as imide, melamine, and benzoguanamine, and thermosetting resins. Among these, cross-linked polystyrene and the like are particularly preferable.

The average particle size of the filler is preferably 0.1 μm or more, more preferably 0.2 μm or more, still more preferably 0.3 μm or more, and the upper limit is preferably 3.0 μm or less, more preferably 1.5 μm or less. It is. By setting the average particle size to 0.1 μm or more, it is preferable from the viewpoint of reducing the shrinkage rate of the laminated porous film and making it difficult to break the film, and achieving heat resistance. On the other hand, when the average particle size is 3.0 μm or less, it is preferable from the viewpoint of reducing the shrinkage rate of the laminated porous film and making it difficult to break the membrane. Moreover, it is more preferable that an average particle diameter shall be 1.5 micrometers or less from a viewpoint of forming the heat resistant layer with small layer thickness favorably, and the viewpoint of the dispersibility in the heat resistant layer of an inorganic filler.
In the present embodiment, the “average particle diameter of the filler” is a value measured according to a method using SEM.

  In the heat-resistant layer, the ratio of filler to the total amount of filler and resin binder (hereinafter referred to as “F%”) is preferably 92% by mass or more, more preferably 95% by mass or more, and 98% by mass or more. Further preferred. If the F% is 92% by mass or more, it is preferable because a laminated porous film having connectivity can be produced and excellent air permeation performance can be exhibited.

(Resin binder)
Resin binder that can be used in the present invention, the filler and the polyolefin resin porous film can satisfactorily adhere, electrochemically stable, and when using the laminated porous film as a battery, an organic electrolyte solution Those that are stable are used . Specifically, ethylene-acrylic acid copolymer such as ethylene-vinyl acetate copolymer (EVA, structural unit derived from vinyl acetate is 20 to 35 mol%), ethylene-ethyl acrylate copolymer, fluorine, etc. Resins [polyvinylidene fluoride (PVDF), etc.], fluorinated rubber, styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), polybutadiene rubber (BR), polyacrylonitrile (PAN), polyacrylic acid (PAA), carboxy One or more from the group consisting of methyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), poly N-vinylacetamide, cross-linked acrylic resin, polyurethane, epoxy resin But Barrel. These organic binders may be used alone or in combination of two or more. Among these, polyvinyl alcohol, polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, and polyacrylic acid are preferable.

(Method for producing heat-resistant layer)
The laminated porous film of the present embodiment is obtained by applying a filler-containing resin solution (dispersion) in which the filler and the resin binder are dissolved or dispersed in a solvent to at least one surface of the polyolefin-based resin porous film. It can be produced by forming a heat-resistant layer on the surface of the porous resin porous film.

  As the solvent, it is preferable to use a solvent in which the filler and the resin binder can be dissolved or dispersed uniformly and stably. Examples of such a solvent include N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, water, ethanol, toluene, hot xylene, and hexane. Further, in order to stabilize the filler-containing resin solution (dispersion) or to improve the coating property to the polyolefin resin porous film, the dispersion contains a dispersant such as a surfactant, a thickener, Various additives such as a wetting agent, an antifoaming agent, and a pH adjusting agent including an acid and an alkali may be added. These additives are preferably those that can be removed upon solvent removal or plasticizer extraction, but are electrochemically stable in the range of use of the lithium ion secondary battery, do not inhibit the battery reaction, and are up to about 200 ° C. If stable, it may remain in the battery (in the laminated porous film).

  Examples of a method for dissolving or dispersing the filler and the resin binder in a solvent include, for example, a ball mill, a bead mill, a planetary ball mill, a vibrating ball mill, a sand mill, a colloid mill, an attritor, a roll mill, a high-speed impeller dispersion, a disperser, a homogenizer, and a high-speed impact mill. , Ultrasonic dispersion, mechanical stirring method using stirring blades, and the like.

  The method for applying the dispersion to the surface of the polyolefin resin porous film is not particularly limited as long as it can realize the required layer thickness and application area. Examples of such coating methods include gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air doctor coater method, blade coater method, rod Examples include a coater method, a squeeze coater method, a cast coater method, a die coater method, a screen printing method, and a spray coating method. Moreover, the said dispersion liquid may be apply | coated to only one side of the polyolefin resin porous film in light of the use, and may be applied to both surfaces.

  The solvent is preferably a solvent that can be removed from the dispersion applied to the polyolefin resin porous film. As a method for removing the solvent, any method that does not adversely affect the polyolefin resin porous film can be adopted without any particular limitation. As a method for removing the solvent, for example, a method in which a polyolefin resin porous film is fixed and dried at a temperature below its melting point, a method in which drying is performed at a low temperature under reduced pressure, or a resin binder is solidified by being immersed in a poor solvent for the resin binder. And a method of extracting the solvent at the same time.

  In addition, the laminated porous film of this Embodiment can also be manufactured using the method different from the manufacturing method mentioned above. For example, the raw material for polyolefin resin porous film is introduced into one extruder, the raw material for the heat-resistant layer is introduced into the other extruder, integrated with a single die, and a laminated film is formed. It is also possible to adopt a processing method.

(Shape and physical properties of laminated porous film)
The film thickness of the laminated porous film of the present invention is preferably 5 to 100 μm. More preferably, it is 8-50 micrometers, More preferably, it is 10-30 micrometers. When it is used as a battery separator, if it is 5 μm or more, substantially necessary electrical insulation can be obtained. For example, even when a large force is applied to the protruding portion of the electrode, the battery separator is broken and short-circuited. It is difficult and safe. Moreover, since the electrical resistance of a laminated porous film can be made small if a film thickness is 100 micrometers or less, the performance of a battery can fully be ensured.

  The heat-resistant layer is preferably 0.5 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more, and particularly preferably 4 μm or more from the viewpoint of improving heat resistance. The upper limit is preferably 90 μm or less, more preferably 50 μm or less, still more preferably 30 μm or less, and particularly preferably 10 μm or less from the viewpoint of permeability and high battery capacity.

In the laminated porous film of the present invention, the porosity is preferably 30% or more, more preferably 35% or more, and further preferably 40% or more. If the porosity is 30% or more, it is possible to obtain a laminated porous film that ensures communication and has excellent air permeability.
On the other hand, the upper limit is preferably 70% or less, more preferably 65% or less, and still more preferably 60% or less. If the porosity is 70% or less, the strength of the laminated porous film is hardly lowered, which is preferable from the viewpoint of handling. The porosity is measured by the method described in the examples.

The air permeability of the laminated porous film of the present invention is preferably 2000 seconds / 100 ml or less, more preferably 10 to 1000 seconds / 100 ml, still more preferably 50 to 800 seconds / 100 ml. An air permeability of 2000 seconds / 100 ml or less is preferable because it indicates that the laminated porous film has communication properties and can exhibit excellent air permeability.
The air permeability represents the difficulty in passing through the air in the film thickness direction, and is specifically expressed by the number necessary for 100 ml of air to pass through the film. Therefore, it means that the smaller the numerical value is, the easier it is to pass through, and the higher numerical value is, the more difficult it is to pass. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means poor communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the air permeability of the laminated porous film of the present invention is low, it can be used for various applications. For example, when used as a battery separator, a low air permeability means that lithium ions can be easily transferred, which is preferable because battery performance is excellent.

  The laminated porous film of the present invention preferably has SD characteristics when used as a battery separator. Specifically, the air permeability after heating at 135 ° C. for 5 seconds is preferably 10,000 seconds / 100 ml or more, more preferably 25000 seconds / 100 ml or more, and further preferably 50000 seconds / 100 ml or more. By setting the air permeability after heating at 135 ° C for 5 seconds to 10000 seconds / 100ml or more, the holes are quickly closed and the current is cut off during abnormal heat generation, thus avoiding problems such as battery rupture. be able to.

In the laminated porous film of the present invention, the tensile elastic modulus at 3% elongation in the longitudinal direction of the film is preferably 400 MPa or more, more preferably 450 MPa or more, and further preferably 500 MPa or more. On the other hand, the upper limit is not particularly limited, but is preferably 1000 MPa or less, more preferably 900 MPa or less, and still more preferably 800 MPa or less. If the tensile elastic modulus at the time of 3% elongation is 400 MPa or more, the laminated porous film is stretched and wrinkled when it is used as a battery separator, for example, when the laminated porous film is wound or conveyed. There is no problem and a laminated porous film can be suitably used. On the other hand, 1000 MPa or less is preferable from the viewpoint of flexibility and handling.
In addition, the measuring method is described in the below-mentioned Example about the tensile elasticity modulus at the time of the said 3% expansion | extension.

  The shrinkage rate at 150 ° C. of the laminated porous film is preferably 15% or less, more preferably 12% or less, and still more preferably 10% or less. When the shrinkage rate at 150 ° C. is 15% or less, even when abnormal heat is generated when used as a battery separator, it has good dimensional stability, can prevent film breakage, and can improve internal short circuit temperature. . Although it does not limit as a minimum, 1% or more is more preferable.

(battery)
Next, a nonaqueous electrolyte battery containing the laminated porous film of the present invention as a battery separator will be described with reference to FIG.
Both electrodes of the positive electrode plate 21 and the negative electrode plate 22 are wound in a spiral shape so as to overlap each other via the battery separator 10, and the outside is stopped with a winding tape to form a wound body.
The winding process will be described in detail. One end of the battery separator is passed between the slits 1 of the pin (FIG. 2), and the pin is slightly rotated to wind one end of the battery separator around the pin. At this time, the surface of the pin is in contact with the heat-resistant layer of the battery separator. Thereafter, the positive electrode and the negative electrode are arranged so as to sandwich the battery separator, and the pins are rotated by a winding machine to wind the positive and negative electrodes and the battery separator. After winding, the pin is pulled out of the wound object.

  A wound body in which the positive electrode plate 21, the battery separator 10 and the negative electrode plate 22 are integrally wound is housed in a bottomed cylindrical battery case and welded to the positive and negative electrode lead bodies 24 and 25. Next, the electrolyte is injected into the battery can, and after the electrolyte has sufficiently penetrated into the battery separator 10 or the like, the positive electrode lid 27 is sealed around the opening periphery of the battery can via the gasket 26, and precharging and aging are performed. A cylindrical non-aqueous electrolyte battery is manufactured.

As the electrolytic solution, an electrolytic solution in which a lithium salt is used as an electrolytic solution and is dissolved in an organic solvent is used. The organic solvent is not particularly limited, but for example, propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, esters such as dimethyl carbonate, methyl propionate or butyl acetate, and nitriles such as acetonitrile. 1,2-dimethoxyethane, 1,2-dimethoxymethane, dimethoxypropane, 1,3-dioxolane, ethers such as tetrahydrofuran, 2-methyltetrahydrofuran or 4-methyl-1,3-dioxolane, or sulfolane These may be used alone or in combination of two or more.
Among them, an electrolyte obtained by dissolving lithium hexafluorophosphate (LiPF ₆₎ at a rate of 1.0 mol / L in a solvent obtained by mixing 2 parts by mass of methyl ethyl carbonate relative to ethylene carbonate 1 part by weight is preferred.

As the negative electrode, an alkali metal or a compound containing an alkali metal integrated with a current collecting material such as a stainless steel net is used. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the compound containing an alkali metal include an alloy of an alkali metal and aluminum, lead, indium, potassium, cadmium, tin or magnesium, a compound of an alkali metal and a carbon material, a low potential alkali metal and a metal oxide, and the like. Or a compound with a sulfide or the like.
When a carbon material is used for the negative electrode, the carbon material may be any material that can be doped and dedoped with lithium ions, such as graphite, pyrolytic carbons, cokes, glassy carbons, a fired body of an organic polymer compound, Mesocarbon microbeads, carbon fibers, activated carbon and the like can be used.

  In this embodiment, as a negative electrode, a carbon material having an average particle size of 10 μm is mixed with a solution in which vinylidene fluoride is dissolved in N-methylpyrrolidone to form a slurry, and this negative electrode mixture slurry is passed through a 70-mesh net. After removing the large particles, uniformly apply to both sides of the negative electrode current collector made of a strip-shaped copper foil having a thickness of 18 μm and dry, and then compression-molded with a roll press machine, cut, strip-shaped negative electrode plate and We use what we did.

  As the positive electrode, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, manganese dioxide, metal oxide such as vanadium pentoxide or chromium oxide, metal sulfide such as molybdenum disulfide, etc. are used as active materials. , These positive electrode active materials are combined with conductive additives and binders such as polytetrafluoroethylene as appropriate, and finished with a current collector material such as a stainless steel mesh as a core material. It is done.

In the present embodiment, a strip-like positive electrode plate produced as follows is used as the positive electrode. In other words, lithium graphite oxide (LiCoO ₂ ) was added with phosphorous graphite as a conductive additive at a mass ratio of 90: 5 (lithium cobalt oxide: phosphorous graphite) and mixed, and this mixture and polyvinylidene fluoride were mixed with N -Mix with a solution dissolved in methylpyrrolidone to make a slurry. This positive electrode mixture slurry is passed through a 70-mesh net to remove large particles, and then uniformly applied to both sides of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm, dried, and then compressed by a roll press. After forming, it is cut into a strip-like positive electrode plate.

  Examples and Comparative Examples are shown below, and the laminated porous film of the present invention will be described in more detail. However, the present invention is not limited to these. The longitudinal direction of the laminated porous film is referred to as “longitudinal direction”, and the direction perpendicular to the longitudinal direction is referred to as “lateral direction”.

(1) Film thickness Using an 1/1000 mm dial gauge, 30 in-plane measurements were made unspecified, and the average value was taken as the film thickness.

(2) F%
In the heat-resistant layer, the ratio of filler to the total amount of filler and resin binder was F%.

(3) SUS test A4 size stainless steel plate (material: SUS304, Mohs hardness: 6) is fixed, and the laminated porous film is wound around a round bar so that the heat-resistant layer is on the outside. The stainless plate and the heat-resistant layer were rubbed for 10 seconds. The state of the heat-resistant layer after rubbing was evaluated based on the following criteria.
X : The laminated porous film is discolored black and wear is recognized.
○ : The laminated porous film does not change color

(4) Pin detachability Using the apparatus shown in FIG. 3, two laminated porous films cut into a length of 5000 mm and a width of 580 mm are stacked, one end is sandwiched between the slit portions 1 in FIG. 3, and a weight of 4.3 N is placed on the opposite end. 7 was hung and the laminated porous film was fixed. Next, the laminated porous film was wound around the pin 2 at a speed of 0.6 m / min so that the heat-resistant layer was inside, and fixed with a cellophane tape. The pin 2 was taken out from the apparatus, and the laminated porous film attached to the pin 2 with the scissors 3 was pulled out. This was repeated four times, and the pin pull-out property was evaluated based on the following criteria, and the laminated porous film that was “◎” was accepted.
◎: The number of withdrawals is 3 times or more △: The number of withdrawals is 2 times ×: The number of withdrawals is 1 time or less

(5) Air permeability (Gurley value)
The air permeability (second / 100 ml) was measured according to JIS P8117.

(6) SD characteristics (air permeability after heating at 135 ° C for 5 seconds)
The laminated porous film was cut into a 60 mm vertical and 60 mm wide square, and an aluminum plate (material: JIS A5052, size: ø40 mm in the center as shown in FIG. 4A).
It was sandwiched between two sheets (length 60 mm, width 60 mm, thickness 1 mm), and the periphery was fixed with clips as shown in FIG. 4 (B). Next, glycerin (manufactured by Nacalai Tesque, grade 1) was filled up to 100 mm from the bottom, and was fixed to the center of a 135 ° C. oil bath (manufactured by ASONE, OB-200A) with two aluminum plates. The film in the state was immersed and heated for 5 seconds. Immediately after heating, it is immersed in a separately prepared cooling bath filled with 25 ° C. glycerin and cooled for 5 minutes, and then washed with 2-propanol (manufactured by Nacalai Tesque, special grade) and acetone (manufactured by Nacalai Tesque, special grade). And dried in an air atmosphere at 25 ° C. for 15 minutes. The air permeability of the dried film was measured according to the method (5).

(7) Shrinkage rate at 150 ° C. A sample obtained by cutting a laminated porous film into a length of 150 mm and a width of 30 mm square is marked so that the distance between chucks is 100 mm, and the sample is sandwiched with aluminum foil so that the wind does not directly hit, and 150 ° C. The sample was placed in an oven (Tabai Espec Corp., Tabai Gear Oven GPH200) set for 1 hour and allowed to stand for 1 hour. After the sample was taken out of the oven and cooled, the length was measured, and the shrinkage in the vertical direction (MD) and the horizontal direction (TD) was calculated by the following formulas.
Shrinkage rate (%) = {(100−length after heating) / 100} × 100

Further, the obtained laminated porous film was evaluated for β activity as follows.
(8) Differential scanning calorimetry (DSC)
The obtained laminated porous film was heated from 25 ° C. to 240 ° C. at a scanning speed of 10 ° C./min for 1 minute using a differential scanning calorimeter (DSC-7) manufactured by Perkin Elmer, and then held for 240 minutes. The temperature was lowered from 10 ° C. to 25 ° C. at a scanning speed of 10 ° C./min and held for 1 minute, and then heated again from 25 ° C. to 240 ° C. at a scanning speed of 10 ° C./min. The presence or absence of β activity was evaluated according to the following criteria depending on whether or not a peak was detected at 145 to 160 ° C., which is a crystal melting peak temperature (Tmβ) derived from the β crystal of the polypropylene resin at the time of reheating.
○: When Tmβ is detected within the range of 145 ° C to 160 ° C (with β activity)
X: When Tmβ is not detected within the range of 145 ° C to 160 ° C (no β activity)
The β activity was measured with a sample amount of 10 mg under a nitrogen atmosphere.

(9) Wide angle X-ray diffraction measurement (XRD)
The laminated porous film was cut into a 60 mm vertical and 60 mm horizontal square, and as shown in FIG. 4 (A), an aluminum plate having a circular hole with a central portion of 40 mmφ (material: JIS A5052, size: vertical 60 mm, horizontal 60 mm, (Thickness 1 mm) was sandwiched between two sheets, and the periphery was fixed with clips as shown in FIG. 4 (B).
A sample in which the laminated porous film is constrained to two aluminum plates is placed in a ventilation constant temperature thermostat (Yamato Scientific Co., Ltd., model: DKN602) having a set temperature of 180 ° C. and a display temperature of 180 ° C., and then set for 3 minutes. The temperature was changed to 100 ° C., and the mixture was gradually cooled to 100 ° C. over 10 minutes or more. When the display temperature reaches 100 ° C., the sample is taken out and cooled for 5 minutes in an atmosphere of 25 ° C. while being restrained by two aluminum plates. Wide-angle X-ray diffraction measurement was performed on a 40 mmφ circular portion.
-Wide-angle X-ray diffraction measurement device: manufactured by Mac Science, model number: XMP18A
X-ray source: CuKα ray, output: 40 kV, 200 mA
Scanning method: 2θ / θ scan, 2θ range: 5 ° to 25 °, scanning interval: 0.05 °, scanning speed: 5 ° / min
About the obtained diffraction profile, the presence or absence of β activity was evaluated as follows from the peak derived from the (300) plane of β crystal of the polypropylene resin.
○: When a peak is detected in the range of 2θ = 16.0 to 16.5 ° (with β activity)
X: When no peak was detected in the range of 2θ = 16.0 to 16.5 ° (no β activity)
In addition, when a laminated porous film piece cannot be cut out to 60 mm length and 60 mm square, it may adjust so that a laminated porous film may be installed in the circular hole of 40 mmphi in the center part, and may produce a sample.

(10) Comprehensive evaluation A laminated porous film satisfying all of the following conditions was marked with ◎, even if none was satisfied.
1. Air permeability: 1-2000 seconds / 100ml
2. SD characteristics: 10000 seconds / 100 ml or more 3. Shrinkage at 150 ° C .: 10% or less in both the vertical and horizontal directions Pin-out property: ◎
5. SUS test: ○

[Example 1]
(Polyolefin resin film)
As the A layer, polypropylene resin (manufactured by Prime Polymer Co., Ltd., 300 SV, density: 0.90 g / cm ³ , MFR: 3.0 g / 10 min, Tm: 167 ° C.) and β crystal nucleating agent, N, N ′ -Dicyclohexyl-2,6-naphthalenedicarboxylic acid amide was prepared. Each raw material is blended at a ratio of 0.2 part by mass of β crystal nucleating agent with respect to 100 parts by mass of polypropylene resin, and a twin-screw extruder manufactured by Toshiba Machine Co., Ltd. (caliber: 40 mmφ, L / D: 32) After melting and mixing at a set temperature of 300 ° C., the strand was cooled and solidified in a water tank, and the strand was cut with a pelletizer to produce a polypropylene resin composition pellet. The β activity of the polypropylene resin composition was 80%.

Next, as a mixed resin composition constituting the B layer, glycerin is added to 100 parts by mass of high-density polyethylene (manufactured by Nippon Polytechnic Co., Ltd., Novatec HD HF560, density: 0.963 g / cm ³ , MFR: 7.0 g / 10 min). Add 0.04 parts by mass of monoester and 10 parts by mass of microcrystalline wax (Hi-Mic 1080, manufactured by Nippon Seiwa Co., Ltd.), melt and knead at 220 ° C. using the same type twin screw extruder, and pellets A resin composition processed into a shape was obtained.

Using the two kinds of raw materials, using a separate extruder so that the outer layer is A layer and the intermediate layer is B layer, it is extruded from a die for lamination molding through a feed block of two kinds and three layers, By cooling and solidifying with a casting roll, a two-layered / three-layered film-like product of A layer / B layer / A layer was produced.
The laminated film-like product is stretched 4.6 times in the longitudinal direction using a longitudinal stretching machine, and then stretched 1.9 times in the transverse direction at 98 ° C. by a transverse stretching machine, and then subjected to heat setting / relaxation treatment. It was. As a result, a porous film having a film thickness of 20 μm and an air permeability of 450 seconds / 100 ml was obtained.

  The obtained polyolefin resin porous film was subjected to corona surface treatment with a corona treatment apparatus (manufactured by Kasuga Denki Co., Ltd., line speed: 50 m / min, treatment output: 2 kW).

(Heat resistant layer)
Barium sulfate (manufactured by Sakai Chemical Industry Co., Ltd., B-35T, average particle size: 0.6 μm, Mohs hardness: 3.5) 25.5 parts by weight, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA120, degree of saponification: 98.0 99.0, average degree of polymerization: 2000) A dispersion in which 0.5 part by weight was dispersed in a mixture of 66.6 parts by weight of water and 7.4 parts by weight of 2-propanol was obtained. The obtained dispersion was applied to the corona-treated surface of the polyolefin resin porous film using a gravure coater and then dried at 75 ° C.
The physical properties of the obtained laminated porous film were evaluated, and the results are summarized in Table 1.

[Example 2]
Barium sulfate (manufactured by Sakai Chemical Industry Co., Ltd., B-35T, average particle size: 0.3 μm, Mohs hardness: 3.5) 24.7 parts by weight, polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA120, saponification degree: 98.0 99.0, average degree of polymerization: 2000) A dispersion was obtained by dispersing 1.3 parts by weight in a mixture of 66.6 parts by weight of water and 7.4 parts by weight of 2-propanol. The obtained dispersion was applied to the corona-treated surface of the polyolefin resin porous film produced in Example 1 using a gravure coater, and then dried at 75 ° C.
The physical properties of the obtained laminated porous film were evaluated, and the results are summarized in Table 1.

[Comparative Example 1]
Alumina (Sumitomo Chemical Co., Sumiko Random AA-03, average particle size: 0.3 μm, Mohs hardness: 9.0) 39.2 parts by weight, polyvinyl alcohol (Kuraray Co., Ltd., PVA120, saponification degree: 98.0) 99.0, average degree of polymerization: 2000) A dispersion in which 0.8 part by weight was dispersed in 60.0 parts by weight of water was obtained. The obtained dispersion was applied to the corona-treated surface of the polyolefin resin porous film produced in Example 1 using a gravure coater, and then dried at 75 ° C.
The physical properties of the obtained laminated porous film were evaluated, and the results are summarized in Table 1.

[Comparative Example 2]
Alumina (Sumitomo Chemical Co., Sumiko Random AA-03, average particle size: 0.6 μm, Mohs hardness: 9.0) 39.2 parts by weight, polyvinyl alcohol (Kuraray Co., Ltd., PVA120, degree of saponification: 98.0) 99.0, average degree of polymerization: 2000) A dispersion in which 0.8 part by weight was dispersed in 60.0 parts by weight of water was obtained. The obtained dispersion was applied to the corona-treated surface of the polyolefin resin porous film produced in Example 1 using a gravure coater, and then dried at 75 ° C.
The physical properties of the obtained laminated porous film were evaluated, and the results are summarized in Table 1.

[Comparative Example 3]
The physical properties of the polyolefin resin porous film produced in Example 1 were evaluated, and the results are summarized in Table 1.

Table 1 shows the physical property values obtained in each Example and Comparative Example. The laminated porous film of the example configured within the range specified in the present invention does not wear SUS and is superior to the polyolefin resin porous film of Comparative Example 3 configured in the range other than specified in the present invention. It can be seen that it has pin-out properties and air permeability.
On the other hand, when a filler with a high Mohs hardness is used from Comparative Examples 1 and 2, it is suggested that even if the pin pull-out property is good, SUS is worn and metal may be mixed in during the manufacturing process. doing.

  The laminated porous film of the present invention can be applied to various uses that require air permeability. Separators for lithium batteries; sanitary materials such as disposable paper diapers and pads for absorbing body fluids such as sanitary items or bed sheets; medical materials such as surgical clothing or base materials for hot compresses; for clothing such as jumpers, sportswear or rainwear Materials: Architectural materials such as wallpaper, roof waterproofing material, heat insulating material, sound absorbing material, etc .; Desiccant; Dampproofing agent; Deoxygenating agent; Disposable body warmer; Used as packaging materials such as freshness preservation packaging or food packaging, etc. it can.

DESCRIPTION OF SYMBOLS 1 Slit part 2 Pin 3 鍔 5 Rotating roll part 6 Sample 7 Weight 10 Battery separator 20 Secondary battery 21 Positive electrode plate 22 Negative electrode plate 24 Positive electrode lead body 25 Negative electrode lead body 26 Gasket 27 Positive electrode cover 31 Aluminum plate 32 Separator 33 Clip 34 Film length direction 35 Film width direction

Claims (6)

A heat-resistant layer containing a filler and a resin binder is laminated on at least one surface of a polyolefin resin porous film having β activity, and the filler is barium sulfate having a Mohs hardness of 6 or less, and the resin binder is laminated porous film, which is a port polyvinyl alcohol (PVA). Air permeability is 2000 second / 100ml or less, The laminated porous film of Claim 1 characterized by the above-mentioned. 3. The laminated porous film according to claim 1, wherein the shrinkage rate at 150 ° C. is 10% or less. The battery separator using the laminated porous film of any one of Claims 1-3 . A battery separator that is wound around a pin slit through one end and then sandwiched between a positive electrode plate and a negative electrode plate to form a spiral wound body and is housed in a cylindrical electrode case with the pin removed. There,
Two pins of the laminated porous film cut out in a length of 5000 mm and a width of 580 mm are overlapped, and one end is a slit portion, with the pin detachable from the wound body wound by bringing the heat-resistant layer into contact with the outer peripheral surface of the pin A 4.3N weight is hung on the opposite end, the laminated porous film is fixed, and the laminated porous film is wound around a pin at a speed of 0.6 m / min so that the heat-resistant layer is on the inner side. 5. The battery separator according to claim 4 , wherein after fixing, the pin is taken out from the apparatus, and the number of times of pulling out the laminated porous film attached to the pin with a scissors is 3 times or more in 4 times. Battery using the battery separator of claim 4 or 5.

Images