JP6331556B2 - Laminated porous film, method for producing the same, and separator for electricity storage device - Google Patents

Description

  The present invention relates to a laminated porous film that is excellent in slipperiness, permeability, and productivity when used as a separator for an electricity storage device, and improved in yield reduction due to dropout of particles.

  Porous films are being considered for use in a wide range of applications, such as separators for electricity storage devices and electrolytic capacitors, various separation membranes, clothing, moisture-permeable waterproof membranes for medical applications, reflectors for flat panel displays, and thermal transfer recording sheets. Yes. Among them, it is suitable as a separator for lithium ion batteries widely used in mobile devices such as notebook personal computers, mobile phones, and digital cameras, electric vehicles, and hybrid vehicles.

  In general, porous films have poor slipping properties, and there are cases in which it is difficult to convey during film formation and handle post-processing. As for improvement in handling property by improving slipperiness, an off-line coating method in which a particle layer is applied after forming a porous film has been proposed (see, for example, Patent Document 1). However, since this method performs coating after unwinding the wound film, the productivity is poor and the cost is disadvantageous. Moreover, there was a limit to the control of the coating film thickness, and it was difficult to reduce the film thickness. Furthermore, since the coating is performed after the film is made porous, the particles and the binder resin for binding the particles may enter into the pores of the porous film, the pores are blocked, and the permeability of the porous film is reduced. In some cases, it could be significantly reduced. In addition, there is a possibility of contamination of the processing process due to the dropping of the particles, and the possibility that the particles become foreign matters and the porous film is torn. Although a method of applying a particle layer to a porous film by in-line coating has been proposed (see, for example, Patent Document 2), although productivity, thinning, and pore clogging of the porous film are improved, the particles There is still a possibility of contamination of the processing process due to omission.

JP 2009-19118 A JP 2009-227819 A

  An object of the present invention is to provide a laminated porous film that is excellent in slipperiness, permeability, and productivity when used as a separator for an electricity storage device, and improved in yield reduction due to dropout of particles.

The above-described problem is a laminated porous film in which an easy-sliding layer substantially free of particles is provided on at least one surface of a porous film mainly composed of a polypropylene-based resin, and has an air resistance of 50 to 10, was 000 sec / 100 ml, Ri thickness 200nm less der than 1nm of lubricity layer, static friction coefficient μs of the lubricity layer can be achieved by the laminated porous film Ru der less than 0.6.

  When used as a separator for an electricity storage device, it is excellent in slipperiness, permeability, and productivity, and the reduction in yield due to particle dropping is improved. Therefore, it can be suitably used as a separator for an electricity storage device.

The laminated porous film of the present invention is a laminated porous film in which an easy-sliding layer substantially free of particles is provided on at least one surface of a porous film containing a polypropylene resin as a main component. Here, the main component refers to occupying 50% by mass or more of the raw material constituting the porous film. Preferably it is 70 mass% or more, More preferably, it is 80 mass% or more. In addition, substantially free of particles means that when a surface of 1 cm ² of the laminated porous film is observed in a reflection mode of a differential interference microscope at a magnification of 1,000 times, particles having a particle diameter of 0.3 μm or more. Say that it is 1 or less.

  As a polypropylene resin contained in the porous film of the present invention, homopolypropylene can be used, as well as from the viewpoint of stability in the film-forming process, film-forming properties, and uniformity of physical properties. A resin obtained by copolymerizing an ethylene component and an α-olefin component such as butene, hexene, and octene in a range of 5% by mass or less, more preferably 2.5% by mass or less can also be used.

  The porous film used in the present invention has pores that penetrate both surfaces of the film and have air permeability (hereinafter referred to as through-holes). The method for obtaining the porous film having through-holes is not particularly limited. For example, a dry method such as a β crystal method or a lamellar stretching method, an extraction method, or a physical method using a laser after film formation. For example, from the viewpoint of productivity and uniformity of physical properties in the longitudinal direction and the width direction, the β crystal method is preferable.

  Here, the β crystal method uses a polypropylene resin cast sheet having a β crystal as a crystal structure, and the cast sheet is longitudinally stretched to transfer the crystal structure of the β crystal to the α crystal and in the film forming direction. This is a method of obtaining a film having through-holes by forming an α-crystal fibril-like product oriented in the direction of cleaving and cleaving the fibril-like product in a transverse stretching step to form a network structure. Here, the cast sheet means an unstretched sheet obtained by molding a molten polypropylene resin into a sheet shape on a cast drum. In the β crystal method, in order to improve the physical properties of the porous film, it is preferable to add a β crystal nucleating agent to the polypropylene resin to enhance the β crystal forming ability. Since the β-crystal forming ability is high, the portion of the crystal structure that causes crystal transition to the α-crystal increases, and the number of voids formed in the film can be increased. In addition, by controlling the raw material containing the β crystal nucleating agent, the orientation and density of the polypropylene crystal are improved, and the pores are uniformly and densely opened, whereby the battery when the porous film is used as a separator for an electricity storage device A reduction in resistance can be achieved. Moreover, by improving the uniformity of the open state, coarse pores can be reduced, and mechanical properties such as elastic modulus and tensile elongation can be improved. The reduction of battery resistance and improvement of mechanical properties in these β crystal methods can be achieved by performing film formation under specific film formation conditions using raw materials described later.

  The porous film used in the present invention preferably has a β crystal forming ability of 40% or more and 95% or less. More preferably, it is 60-85%, More preferably, it is 65-80%. When the β crystal forming ability is less than 40%, the amount of β crystals is small, so the number of voids formed in the film using the transition to the α crystal is reduced. As a result, only a film with low permeability is obtained. There may not be. When the β crystal forming ability exceeds 95%, coarse pores are formed, and sufficient film strength may not be obtained. As a method of controlling the β crystal formation ability to 40% or more and 95% or less, a method using a polypropylene resin having a high isotactic index, a β crystal selected by adding to a polypropylene resin called a β crystal nucleating agent In the present invention, there is a method of using a β crystal nucleating agent described later, or a β crystal nucleating agent described later for a polypropylene resin having a high isotactic index. It is preferable to use a method in which is used as an additive.

  Examples of the β crystal nucleating agent used in the present invention include alkali or alkaline earth metal salts of carboxylic acids such as calcium 1,2-hydroxystearate and magnesium succinate, and N, N′-dicyclohexyl-2,6-naphthalene. Amide compounds represented by carboxyamide, tetraoxaspiro compounds such as 3,9-bis [4- (N-cyclohexylcarbamoyl) phenyl] -2,4,8,10-tetraoxaspiro [5.5] undecane Aromatic sulfonic acid compounds such as sodium benzene sulfonate and sodium naphthalene sulfonate, imide carboxylic acid derivatives, and quinacridone pigments, particularly amide compounds disclosed in JP-A-5-310665. It is preferable to use it. Further, the content of the β crystal nucleating agent varies depending on the β crystal nucleating agent to be used, but when the amide compound is used, it is 0.05 to 0.5 based on the whole polypropylene composition. The content is preferably 0.1% by mass, more preferably 0.1 to 0.3% by mass, and particularly preferably 0.22 to 0.3% by mass in order to have the effect described later. If it is less than 0.05% by mass, the formation of β crystals becomes insufficient, and the air permeability of the porous film may deteriorate. On the other hand, if it exceeds 0.5 mass%, coarse voids are formed in the film due to aggregation of the β crystal nucleating agent, and mechanical strength such as elastic modulus, puncture strength, and tensile strength may be lowered.

  In the present invention, an isotactic polypropylene resin having a melt flow rate (hereinafter referred to as MFR) of 2 to 30 g / 10 min is used as the polypropylene resin from the viewpoint of extrusion moldability and uniform pore formation. preferable. Here, MFR is an index indicating the melt viscosity of a resin defined in JIS K 7210 (1995), and is a physical property value indicating the characteristics of a polyolefin resin. In the present invention, it refers to a value measured at 230 ° C. and 2.16 kg. In the present invention, from the viewpoint of crystallinity, the isotactic index of the polypropylene resin is preferably in the range of 90 to 99.9%, more preferably 95 to 99%. When the isotactic index is less than 90%, the crystallinity of the resin is lowered, the air permeability and the film forming property may be lowered, and the elastic modulus of the film may be inferior.

  The polypropylene resin used in the present invention is 80 to 99.9 parts by mass of polypropylene from the viewpoint of improving void formation efficiency during biaxial stretching, uniform opening of pores, and improving air permeability by expanding the pore diameter. It is preferable to use a mixture of 20 to 0.1 parts by mass of ethylene / α-olefin copolymer. Here, examples of the ethylene / α-olefin copolymer include linear low-density polyethylene and ultra-low-density polyethylene, and among them, copolymerized octene-1 copolymerized polyethylene having a melting point of 60 to 90 ° C. A resin (copolymerized PE resin) can be preferably used. Examples of the copolymerized polyethylene include commercially available resins such as “Engage (registered trademark)” (type names: 8411, 8452, 8100, etc.) manufactured by Dow Chemical.

  The copolymer polyethylene resin contains less than 10% by mass when the total polypropylene resin constituting the porous film is 100% by mass, and the porosity and average through-hole diameter described below are controlled within a preferable range. This is preferable because it becomes easy. If it is 0.1-7 mass% from a viewpoint of the mechanical characteristic of a film, it is more preferable, and it is 1-7 mass% more preferably from a viewpoint of battery resistance.

  The polypropylene resin used in the present invention is a dispersing agent in addition to the above-mentioned ethylene / α-olefin copolymer from the viewpoint of homogenizing the pore structure, miniaturizing the fibrils, and reducing unevenness of heat shrinkage in the film surface. Is preferably added. Any dispersant may be used as long as it can increase the dispersibility of the ethylene / α-olefin copolymer in the polypropylene resin. However, as described in International Publication No. 2007/046225, the polypropylene resin and the ethylene / α-olefin copolymer may be used. The compatibility of the α-olefin copolymer is good. For example, an ethylene / propylene random copolymer generally used as a compatibilizing agent for polypropylene resin and polyethylene resin is dispersed for uniform pore structure in this embodiment. Does not function as an agent. As a dispersant preferably used in the present embodiment, a block copolymer having a highly compatible segment with polypropylene (for example, a polypropylene segment, an ethylene butylene segment) and a highly compatible segment with polyethylene (such as a polyethylene segment), respectively. Coalescence is preferred. As a resin having such a structure, a commercially available resin such as olefin crystal, ethylene butylene, olefin crystal block polymer (hereinafter referred to as CEBC) “DYNARON (registered trademark)” (type name) manufactured by JSR Corporation : 6100P, 6200P, etc.) and olefin block copolymer “INFUSE OBC (registered trademark)” manufactured by Dow Chemical Company. The addition amount of the dispersant is preferably 1 to 50 parts by mass, more preferably 5 to 33 parts by mass with respect to 100 parts by mass of the ethylene / α-olefin copolymer. From the viewpoint of improving the dispersibility of the ethylene / α-olefin copolymer in polypropylene resin and improving the uniformity of pore formation, the melting point of the dispersant is higher than the melting point of the ethylene / α-olefin copolymer. It is preferably 0 to 60 ° C. and more preferably 15 to 30 ° C.

  In the polypropylene resin that forms the porous film of the present invention, an antioxidant, a heat stabilizer, an antistatic agent, an antiblocking agent, a filler, an incompatible polymer, etc., as long as the effects of the present invention are not impaired. Various additives may be included. In particular, it is preferable to add an antioxidant for the purpose of suppressing oxidative deterioration due to the thermal history of the polypropylene resin. The addition amount of the antioxidant is preferably 2 parts by mass or less, more preferably 1 part by mass or less, still more preferably 0.5 parts by mass or less with respect to 100 parts by mass of the polypropylene resin.

  The polypropylene resin that forms the porous film of the present invention can contain a pore-forming aid made of inorganic or organic particles within a range that does not impair the effects of the present invention. When using a pore-forming aid, it is preferable that the porous film of the present invention has a laminated structure of three or more layers and is contained in the inner layer from the viewpoint of preventing the particles from falling off. The content is preferably 5 parts by mass or less with respect to 100 parts by mass of the polypropylene resin, more preferably 2 parts by mass or less, and still more preferably 1 part by mass or less. If it exceeds 5 parts by mass, the raw material cost may increase when used as a separator for an electricity storage device, and productivity may be reduced.

  In the laminated porous film of the present invention, the method for providing an easy-sliding layer on at least one surface of the porous film is not particularly limited, and the solution is attached to the porous film by dipping, spraying, or exposing to the atmosphere. Examples of the forming method include a vapor deposition method, a CVD method, a sputtering method, an in-line coating method, etc., but the in-line coating method is preferable from the viewpoint of air permeability and surface opening ratio of the laminated porous film and thinning of the easy-sliding layer. .

  As a method for producing a laminated porous film of the present invention, a coating agent for forming an easy-sliding layer is applied to at least one surface of a sheet mainly composed of a polypropylene resin melt-extruded from a die, and then dried and stretched. It is preferable to use a manufacturing method in which the easy-slip layer is formed at least once by heat treatment, and the above method is an in-line coating method. In other words, it refers to a method of coating at any stage from melt extrusion of a thermoplastic resin to biaxial stretching followed by heat treatment and winding up, usually a substantially amorphous state obtained after melt extrusion and rapid cooling Unstretched (unoriented) thermoplastic resin film (A film), then uniaxially stretched (uniaxially oriented) thermoplastic resin film (B film) stretched in the longitudinal direction, or further heat treated before stretching in the width direction It is applied to any film of biaxially stretched (biaxially oriented) thermoplastic resin film (C film).

  In the present invention, a coating agent is applied to any one of the A film and the B film, and then the polypropylene film is stretched uniaxially or biaxially and subjected to heat treatment at a temperature higher than the boiling point of the solvent. It is preferable to adopt a method of providing a layer (sliding layer). According to this method, the production of the porous film and the coating and drying of the resin composition (coating agent) (that is, the formation of the easy-sliding layer) can be performed at the same time. In addition, regarding the thickness control of the coating layer (coating layer), there is a limit to the thickness control by adjusting the coating concentration and coating viscosity in the offline coating, but the easy-sliding layer and the polypropylene film are stretched after application by the in-line coating method. It is possible to control the thickness of the easy-sliding layer. In addition, in the offline coating, since the coating agent is applied to the surface of the film after biaxial stretching, the crystallinity of the surface is high, so that the coating repels easily and it may be difficult to reduce the thickness. In addition, by adopting an appropriate coating formulation, which will be described later, the easy-slip layer follows the stretch of the porous film and the surface of the laminated porous film opens, thereby suppressing deterioration of air resistance after the easy-slip layer is applied. it can. Sputtering or vapor deposition may not provide sufficient adhesion. In addition, the offline coating method is not a continuous process as in the inline coating method, and thus the productivity may be lowered.

  In the present invention, the slippery layer is preferably provided by an in-line coating method from the various advantages described above. As a coating method, for example, an arbitrary method such as a reverse coating method, a gravure coating method, a rod coating method, a die coating method, a spray coating method, or a bar coating method can be used.

  The resin used in the easy-slip layer of the laminated porous film of the present invention is not particularly limited as long as it can be suitably applied to the porous film and easy-slip properties are obtained, but it is fluorine from the viewpoint of adhesiveness to the porous film. It is preferable that the main component is at least one resin selected from the group consisting of a series resin, an acrylic resin, a urethane resin, and a polyester resin. By using these resins, slipperiness can be imparted even though particles are not substantially contained. Of these, acrylic resins are preferred because they are highly slippery after being laminated on a porous film. In the present invention, the above-mentioned at least one resin and a coating agent containing a solvent as necessary are applied onto the porous film, and if necessary, the solvent is dried, whereby an easy-sliding layer is formed on the porous film. Can be formed.

  The fluororesin used in the easy-sliding layer of the laminated porous film of the present invention is not particularly limited, but tetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene- Examples include hexafluoropropylene copolymers and ammonium fluorophosphate esters.

  Examples of the acrylic resin used in the easy-sliding layer of the laminated porous film of the present invention include long-chain alkyl acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethoxyethyl acrylate, and 2-methoxyethyl acrylate. , 2-butoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile, methacrylonitrile, vinyl acetate, (meth) acrylic acid, styrene, itaconic acid, (meth) acrylamide, 2-hydroxyethyl (meth) acrylate , Diethylene glycol mono (meth) acrylate, N-methylol (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acryloyloxyethyl phosphate ester, vinyl sulfone Soda, can be exemplified sodium styrenesulfonate and maleic acid. Examples of the long chain alkyl acrylate include a copolymer acrylic resin of an acrylic monomer having an alkyl group having 12 to 25 carbon atoms in the side chain and a monomer copolymerizable with the acrylic monomer. The copolymerization ratio of the alkyl acrylate monomer having an alkyl group having 12 to 25 carbon atoms in the side chain in the copolymerized acrylic resin is preferably 35% by mass or more. The amount of copolymerization is preferably 35 to 85% by mass, and more preferably 60 to 80% by mass in terms of blocking resistance and copolymerization. Such an alkyl acrylate monomer may satisfy the above requirements, for example, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, octadecyl acrylate, Long-chain alkyl group-containing acrylic monomers such as nonadecyl acrylate, eicosyl acrylate, henecosyl acrylate, docosyl acrylate, tricosyl acrylate, tetracosyl acrylate, pentacosyl acrylate, dodecyl methacrylate, eicosyl methacrylate and pentacosyl methacrylate Can be used.

  The urethane resin used in the easy-sliding layer of the laminated porous film of the present invention is not particularly limited as long as it is a water-soluble or water-dispersible urethane resin having an anionic group, and a polyol compound or a polyisocyanate compound. Is obtained by copolymerization as a main constituent. As the urethane resin, a resin whose affinity for water is enhanced by a carboxylate group, a sulfonate group, or a sulfuric acid half ester base can be used. The content of the carboxylate group, sulfonate group, or sulfuric acid half ester base is preferably in the range of 0.5 to 15% by mass. Examples of the polyol compound include polyethylene glycol, polypropylene glycol, polyethylene / propylene glycol, polytetramethylene glycol, hexamethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, polycaprolactone. Polyhexamethylene adipate, polytetramethylene adipate, trimethylolpropane, trimethylolethane, glycerin, acrylic polyol, and the like can be used. Examples of the polyisocyanate compound include tolylene diisocyanate, hexamethylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, an adduct of tolylene diisocyanate and trimethylolpropane, an adduct of hexamethylene diisocyanate and trimethylolethane, and the like. . The urethane resin having an anionic group is, for example, a method using a compound having an anionic group together with a polyol compound, a polyisocyanate compound, a chain extender, etc., a compound having an unreacted isocyanate group and an anionic group of the produced urethane resin, Can be produced by using a method of reacting a group having active hydrogen of a urethane resin with a specific compound, but is not particularly limited.

  The polyester resin used in the easy-sliding layer of the laminated porous film of the present invention has an ester bond in the main chain or side chain, and is obtained by polycondensation from dicarboxylic acid and diol. As the carboxylic acid component constituting the polyester resin, aromatic, aliphatic, and alicyclic dicarboxylic acids and trivalent or higher polyvalent carboxylic acids can be used. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-p, p′-dicarboxylic acid, phenylindanedicarboxylic acid, and the like. These aromatic dicarboxylic acids preferably occupy 30 mol% or more, more preferably 35 mol% or more, and most preferably 40 mol% or more of the total dicarboxylic acid component in terms of the strength and heat resistance of the laminated film. desirable. Specific examples of the aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid 1,4-cyclohexanedicarboxylic acid and the like, and ester-forming derivatives thereof. Specific examples of the glycol component of the polyester resin include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5- Pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1 , 3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 1 2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4′-methylenediphenol, 4,4 ′-(2-norbornylidene) diphenol, 4,4′-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4′-isopropyl Examples include redenephenol, 4,4′-isopropylidenevindiol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, and cyclohexane-1,4-diol.

  In the present invention, the resin forming the slip layer preferably has a glass transition point (Tg) of 30 ° C. or higher and 100 ° C. or lower. More preferably, it is 50 degreeC or more and 100 degrees C or less. In general in-line coating in a film having no pores, it is preferable that the glass transition temperature is lower because the followability is higher when the film is stretched and a uniformly coated laminated porous film can be obtained. Since the resin that forms the slippery layer does not need to cover the entire surface of the porous film, a resin having a high glass transition point is preferably used. If it is lower than 30 ° C., the pores of the porous film may be blocked from the viewpoint of followability to the film, and sufficient air resistance may not be obtained. Moreover, when it exceeds 100 degreeC, the followable | trackability to a porous film is low and may break in film forming.

  In the present invention, an aqueous solvent is preferably used as the solvent. Here, the aqueous solvent is soluble in water such as water or water and alcohols such as methanol, ethanol, isopropyl alcohol and butanol, ketones such as acetone and methyl ethyl ketone, and glycols such as ethylene glycol, diethylene glycol and propylene glycol. A certain organic solvent is mixed at an arbitrary ratio. This is because by using an aqueous solvent, rapid evaporation of the solvent in the drying step can be suppressed, which is excellent in terms of environmental load.

  In the present invention, the coating agent for forming the slippery layer can be prepared by mixing and stirring a solvent and various additives in a desired mass ratio in any order. The method of mixing and stirring can be performed by shaking the container by hand, using a magnetic stirrer or stirring blade, irradiating with ultrasonic waves, vibrating and dispersing. Moreover, you may add various additives, such as surfactant and antioxidant, as needed as long as the characteristic of an easy-slip layer is not deteriorated.

  The laminated porous film of the present invention has an air resistance of 50 to 10,000 seconds / 100 ml. If the air permeation resistance is less than 50 seconds / 100 ml, the strength may decrease when a separator is used. On the other hand, if it exceeds 10,000 seconds / 100 ml, battery characteristics when used as a separator tend to deteriorate. The air resistance of the laminated porous film is more preferably 50 to 2,000 seconds / 100 ml, further preferably 60 to 500 seconds / 100 ml, and most preferably 70 to 230 seconds / 100 ml. As a method for controlling the air permeability resistance to such a preferable range, the above-described polypropylene resin added with the β crystal nucleating agent is stretched and made porous. It is effective to provide an easy-slip layer without reducing the air resistance of the conductive film.

  In the laminated porous film of the present invention, the surface opening ratio of the easy-slip layer is preferably 45% or more. The surface aperture ratio indicates the ratio of the lithium ion transmission region on the surface of the porous film during charge / discharge to the entire surface region, and was calculated by binarizing a surface SEM image at a magnification of 1,000 times. Value.

  The surface aperture ratio is more preferably 50% or more, and further preferably 60% or more. When the surface opening ratio is less than 45%, the air permeability resistance deteriorates and the surface opening property becomes non-uniform. When used as a separator for an electricity storage device, the output characteristics are deteriorated and the in-plane resistance at the interface between the separator and the electrode is not good. It becomes uniform, electrodeposition occurs, and battery life may be reduced. From the viewpoint of output characteristics, the higher the surface aperture ratio, the better. However, if the surface aperture ratio is too high, the strength of the film decreases, and the safety may decrease when used as a power storage device separator. It is preferable to be 95% or less. In order to increase the surface opening ratio to 45% or more, the porous film is prepared by adjusting the amount of β-crystal nucleating agent added in the raw material and the crystallization temperature, an ethylene / α-olefin copolymer or dispersant. The temperature of the cast drum, the stretching ratio and temperature in the longitudinal direction, the transverse stretching speed, the temperature and time in the heat treatment step, and the relaxation rate in the relaxation zone can be controlled within the ranges described below. it can. Moreover, when providing a slippery layer, it is preferable to provide a slippery layer by the in-line coating method, without reducing the surface opening rate of a porous film.

  The easy slip layer of the laminated porous film of the present invention has a thickness of 1 nm or more and less than 200 nm. If the thickness is less than 1 nm, it may be difficult to maintain sufficient slipperiness in the laminated porous film. Further, when the thickness is 200 nm or more, the surface opening ratio of the easy-sliding layer may be reduced and air permeability resistance may be deteriorated, or the coating amount of the coating agent may be increased, resulting in an increase in cost. The thickness of the easy-slip layer is more preferably 10 nm or more and 150 nm or less, and further preferably 20 nm or more and 100 nm or less. As a method for controlling the thickness of the slippery layer to such a preferable range, it is possible to control the coating conditions of the slippery layer by an in-line coating method, or to control the conditions for forming a laminated porous film after coating. It is effective.

The laminated porous film of the present invention preferably has a pore specific surface area of 30 to 100 m ² / g by a nitrogen adsorption method. When the pore specific surface area is less than 30 m ² / g, the output characteristics may be deteriorated particularly when used as a separator for a high-power battery. When the pore specific surface area exceeds 100 m ² / g, the strength of the film is lowered, and in the post-processing step, the film is deformed by the tension applied to the laminated porous film, and wrinkles or flatness may be lowered. . The pore specific surface area is more preferably 35 to 100 m ² / g, still more preferably 40 to 100 m ² / g, and most preferably 45 to 100 m ² / g. In order to set the pore specific surface area within the above range, it is preferable that the composition and film forming conditions of the porous film are within the ranges described later, and the composition and thickness of the easy-slip layer are within the above-described ranges.

  Below, the manufacturing method of the porous film of this invention and a laminated porous film is demonstrated based on a specific example. In addition, the manufacturing method of the porous film of this invention and a laminated porous film is not limited to this.

  99.5 parts by mass of a commercially available homopolypropylene resin with a MFR of 8 g / 10 min as a polypropylene resin, 0.3 parts by mass of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide as a β crystal nucleating agent, and as an antioxidant Irganox 1010 and Irgafos 168 are each mixed with 0.1 parts by weight and 0.05 parts by weight of calcium behenate as a lubricant are mixed at this ratio. Then, it is cooled and solidified in a water bath at 25 ° C. and cut into chips to prepare a polypropylene raw material (a). At this time, the melting temperature is preferably 280 to 310 ° C., and the cross-sectional shape of the chip may be any of a circle, an ellipse, and a rectangle. The crystallization temperature of the polypropylene β crystal of the produced polypropylene raw material is preferably 130 ° C. or higher and more preferably 130.5 ° C. or higher in order to control the air permeability within a preferable range. There is no particular upper limit for the crystallization temperature of polypropylene β crystal, but it is difficult to make it 140 ° C. or higher. Surprisingly, it has been found that by increasing the take-up speed of the strand after discharge and increasing the draft ratio, the crystallization temperature can be controlled within the above temperature range and the battery resistance can be reduced. . A preferred draft ratio is preferably 2 or more, more preferably 3 or more. If the draft ratio exceeds 10, the strands are likely to be broken, and gut breakage may easily occur, and chip productivity is likely to be reduced.

  Similarly, 59.8 parts by mass of the above-mentioned homopolypropylene resin, 30 parts by mass of a commercially available ultra-low density polyethylene resin ethylene / octene-1 copolymer of MFR 18 g / 10 min as an ethylene / α-olefin copolymer, dispersed As raw materials, 10 parts by weight of commercially available CEBC and 0.2 parts by weight of antioxidant are mixed at this ratio, and the raw material is supplied from the weighing hopper to the twin screw extruder, melt kneaded at 240 ° C. Discharge, solidify by cooling in a water bath at 25 ° C., and cut into chips to prepare a polypropylene raw material (b).

  80.0 parts by mass of the above-mentioned polypropylene raw material (a) and 20.0 parts by mass of the above-mentioned polypropylene raw material (b) are dry blended and supplied to a single-screw extruder, and melt extrusion is performed at 200 to 230 ° C. And after removing a foreign material, a modified polymer, etc. with the filter installed in the middle of the polymer pipe | tube, it discharges on a cast drum from die | dye, and an unstretched sheet is obtained. Here, when the film is made into a laminated structure by coextrusion, a plurality of extruders are used to form a laminated structure by a feed block method or a multi-manifold method, and then discharged onto a cast drum from a die, and a laminated unstretched sheet It can be. The cast drum preferably has a surface temperature of 105 to 130 ° C from the viewpoint of battery resistance control, and more preferably 120 to 130 ° C. At this time, particularly, the forming of the end portion of the sheet affects the subsequent stretchability, and therefore it is preferable that the end portion is sprayed with spot air to be in close contact with the drum. Further, air may be blown over the entire surface using an air knife as necessary from the state in which the entire sheet is in close contact with the drum.

  Next, the obtained cast sheet is biaxially oriented to form pores in the film. As a biaxial orientation method, the film is stretched in the longitudinal direction of the film and then stretched in the width direction, or the sequential biaxial stretching method in which the film is stretched in the width direction and then stretched in the longitudinal direction. The simultaneous biaxial stretching method can be used, but it is preferable to adopt the sequential biaxial stretching method in that it is easy to obtain a film having a good balance between air permeability and surface opening ratio and mechanical strength, After stretching in the direction, it is preferable to stretch in the width direction.

  As specific stretching conditions, first, stretching is performed in the longitudinal direction while controlling the temperature of the cast sheet. As a temperature control method, a method using a temperature-controlled rotating roll, a method using a hot air oven, or the like can be adopted. The stretching temperature in the longitudinal direction is preferably 90 to 140 ° C, more preferably 100 to 130 ° C, and particularly preferably 115 to 125 ° C, from the viewpoint of achieving both air permeability and mechanical strength. If it is less than 90 degreeC, a film may fracture | rupture. Moreover, when it exceeds 140 degreeC, air permeability may deteriorate. From the viewpoint of achieving both air permeability and mechanical strength, the draw ratio is preferably 3 to 10 times. More preferably, it is 4.5 to 6 times. As the draw ratio is increased, the battery resistance decreases. However, if the stretch exceeds 10 times, the film is liable to break in the next transverse stretching step, and the air permeability becomes too high and the mechanical strength may be lowered. .

  Next, the coating agent for forming a slippery layer is apply | coated on the longitudinally stretched film cooled after extending | stretching to the longitudinal direction. If necessary, the coating surface of the film may be subjected to a surface treatment of corona discharge treatment in air, nitrogen, or a mixed atmosphere of carbon dioxide and nitrogen before coating. As the coating agent, for example, an alkyl acrylate (solid content concentration of 8.6% by mass) of 5% by mass and a solid content concentration of 5% by mass of an acetylenic diol ethylene oxide adduct “Orphine” (registered trademark) EXP-4123 (day 0.1% by mass and 94.9% by mass of water are mixed, and the mixture is stirred for 10 minutes using a stirrer. The coating agent is applied by a bar coating method using a Mayer bar.

  Next, the end of the film is gripped and introduced into a tenter type stretching machine. The stretching preheating temperature in the width direction is preferably 5 ° C. to 15 ° C. higher than the stretching temperature in the width direction from the viewpoint of drying efficiency and stretch followability during the formation of the slip layer. If it is not within the above range, the film-forming property may be deteriorated and may be easily broken. It is preferable that the extending | stretching temperature of the width direction is 130-155 degreeC from a viewpoint of coexistence of a surface opening ratio and mechanical strength. If it is less than 130 degreeC, drying of a slippery layer may become inadequate or a film may fracture | rupture, and if it exceeds 155 degreeC, the fluidity | liquidity of the resin of a slippery layer may increase, and surface opening ratio may fall. . The draw ratio in the width direction is preferably 2 to 12 times from the viewpoint of improving the tensile strength. More preferably, it is 7-11 times, More preferably, it is 7-10 times. If it is less than 2 times, the air permeability and the surface aperture ratio may decrease, or the tensile strength in the width direction may decrease. If it exceeds 12 times, the film may break. The stretching speed in the width direction at this time is preferably 500 to 6,000% / min, more preferably 1,000 to 5,000% / min. From the viewpoint of improving the elastic modulus while controlling the air permeability and the surface opening ratio within a preferable range, the area magnification (stretching ratio in the longitudinal direction × stretching ratio in the width direction) is preferably high, specifically 20 times. The above is preferable, 30 times or more is more preferable, and 45 times or more is particularly preferable. When the area magnification is low, specifically, when it is less than 20 times, it is difficult to control the air permeability and the surface opening ratio and improve the elastic modulus. The upper limit of the area magnification is not particularly provided, but if it exceeds 60 times, the film forming property is deteriorated and may be easily broken.

  Following the stretching in the width direction, a heat treatment step is performed in the tenter. Here, the heat treatment step includes a heat setting zone (hereinafter referred to as HS1 zone) in which heat treatment is performed with the width after stretching in the width direction, and a relaxation zone (hereinafter referred to as Rx) in which the tenter is narrowed to relax the film. The zone is divided into three zones: a heat setting zone (hereinafter referred to as HS2 zone) in which heat treatment is performed with the width after relaxation, which is compatible with air permeability and mechanical strength, and further reduces the heat shrinkage rate. It is preferable from the viewpoint.

  The temperature of the HS1 zone is preferably 140 to 165 ° C, and more preferably 150 to 165 ° C, from the viewpoint of achieving both air permeability and mechanical strength. If it is lower than 140 ° C., the thermal shrinkage in the width direction may increase. When the temperature exceeds 165 ° C., the orientation relaxation of the film is too large, so that the relaxation rate cannot be increased in the subsequent Rx zone, and it may be difficult to achieve both air permeability and mechanical strength. In addition, the slippery layer and the polymer around the pores may melt at high temperatures, resulting in low air permeability and surface opening ratio.

  The heat treatment time in the HS1 zone is preferably 0.1 seconds or longer and 10 seconds or shorter from the viewpoint of achieving both a heat shrinkage ratio in the width direction and productivity.

  In the present invention, the relaxation rate in the Rx zone is preferably 5 to 35%, more preferably 5 to 30%, from the viewpoint of controlling the air permeability within a preferable range and reducing the heat shrinkage rate. If the relaxation rate is less than 5%, the thermal shrinkage rate may be small. If it exceeds 35%, air permeability may be deteriorated, and thickness unevenness and flatness in the width direction may be deteriorated.

  The temperature of the Rx zone is preferably 155 to 170 ° C., more preferably 160 to 165 ° C., from the viewpoint of battery resistance reduction and heat shrinkage reduction. When the temperature of the Rx zone is less than 155 ° C., the shrinkage stress for relaxation is lowered, and the above-described high relaxation rate may not be achieved, and the thermal shrinkage rate in the width direction may be increased. When the temperature exceeds 170 ° C., the polymer around the pores may be melted at a high temperature, and the air permeability and the surface opening ratio may be deteriorated.

  The relaxation rate in the Rx zone is preferably 100 to 1,000% / min, and more preferably 150 to 500% / min. When the relaxation rate is less than 100% / min, it is necessary to slow down the film forming rate or lengthen the tenter length, which may be inferior in productivity. If it exceeds 1,000% / min, the speed at which the film shrinks becomes slower than the speed at which the rail width of the tenter shrinks, the film flutters in the tenter and breaks, or the physical properties in the width direction are uneven and the flatness is lowered. There is a case.

  The temperature of the HS2 zone is preferably 155 to 165 ° C, more preferably 160 to 165 ° C, from the viewpoint of air permeability, surface aperture ratio and mechanical strength. When the temperature is lower than 155 ° C., the tension of the film after thermal relaxation becomes insufficient, which may cause uneven physical properties in the width direction and a decrease in flatness, or increase the heat shrinkage rate in the width direction. Also, the higher the HS2 temperature, the higher the mechanical strength. If it is lower than 155 ° C., the mechanical strength may be inferior. If the temperature exceeds 165 ° C., the polymer around the pores may melt at a high temperature, and the air permeability and the surface aperture ratio may deteriorate.

  In the present invention, the heat treatment time in the HS2 zone is preferably 0.1 seconds or more and 10 seconds or less from the viewpoint of physical property unevenness in the width direction and flatness and productivity. The film after the heat setting step is removed by slitting the end gripped by the clip of the tenter, and wound around a core with a winder to obtain a product.

  The laminated porous film of the present invention not only excels in slipperiness, permeability and productivity, but also improves the yield reduction due to dropout of particles, so that packaging products, hygiene products, agricultural products, building products, medical care Although it can be used in applications, separation membranes, light diffusion plates, and reflective sheets, it can be preferably used as a separator for power storage devices. Here, examples of the electricity storage device include a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery, and an electric double layer capacitor such as a lithium ion capacitor. Since such an electricity storage device can be repeatedly used by charging and discharging, it can be used as a power supply device for industrial devices, household equipment, electric vehicles, hybrid electric vehicles, and the like.

  Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) Thickness of porous film The thickness was measured with a contact-type film thickness meter, Lightmatic VL-50A (10.5 mmφ carbide spherical surface probe, measurement load 0.06 N) manufactured by Mitutoyo Corporation. The measurement was performed 10 times at different locations, and the average value was taken as the thickness of the porous film.

(2) Thickness of the slippery layer The thickness of the slippery layer on the porous film was measured by observing a cross-section using a transmission electron microscope (Hitachi model H-7100). The slippery layer was stained with RuO ₄ and photographed at an acceleration voltage of 100 kV at a magnification of 40,000 times, and the thickness of the slippery layer was read from the image. A total of 20 easy-sliding layer thicknesses was measured and used as an average value.

(3) Air resistance About the laminated porous film or the porous film, using a Gurley type air permeability measuring machine of JIS P 8155 (2010) Tester Sangyo Co., Ltd., at 23 ° C. and relative humidity 65%, The permeation time (seconds) of 100 ml of air was determined. The measurement was performed three times while changing the sample, and the average value of the permeation time was taken as the air resistance of the film.

(4) Surface aperture ratio Ion coating is applied to the easy-sliding layer surface of the laminated porous film or the cast drum ground surface of the porous film using an IB-5 type ion coater manufactured by Eiko Engineering Co., Ltd., and field emission scanning manufactured by JEOL Ltd. The film surface was observed at a photographing magnification of 1,000 using a microscope (JSM-6700F). The obtained image data (the image of only the observation part without the display of the scale bar or the like) was transferred to HALCON Ver. Image analysis was performed using 10.0, and the surface aperture ratio (%) was calculated. As an image analysis method, first, an 11-pixel average image A and a 3-pixel average image B were respectively generated for a 256-tone monochrome image, and the area (Area_all) of the entire image B was calculated.

  Next, the image A was removed from the image B as a difference, an image C was generated, and a region D where the luminance ≧ 10 was extracted. The extracted region D was divided into chunks, and a region E with an area ≧ 100 was extracted. For the region E, a region F subjected to a closing process with a circular element having a radius of 2.5 pixels is generated, and a region G subjected to an opening process with a rectangular element of 1 × 5 pixels is generated, whereby a vertical size <5 The pixel portion was removed. And the area | region G was divided | segmented for every lump and the fibril area | region was extracted by extracting the area | region H used as area> = 500.

  Further, a region I where the image ≧ 5 is extracted from the image C, the region I is divided into chunks, and a region J where the area ≧ 300 is extracted. An area K is subjected to an opening process with a circular element having a radius of 1.5 pixels and then subjected to a closing process with a circular element having a radius of 8.5 pixels. L was extracted. In the region L, an unopened region other than the fibrils was extracted by generating a region M in which a dark portion with an area ≧ 4,000 pixels was filled with a bright portion.

  Finally, the sum area N of the area H and the area M is generated, and the area of the sum area N (Area_closed) is calculated to obtain the area of the unopened portion. The surface aperture ratio was calculated by the following formula.

Surface aperture ratio (%) = (Area_all−Area_closed) / Area_all
By the above method, 10 points were measured in the same laminated porous film or porous film, and the average value was defined as the surface opening ratio (%) of the sample.

(5) β-crystal forming ability 5 mg of a porous film was taken as a sample in an aluminum pan and measured using a differential scanning calorimeter (Seiko Denshi Kogyo RDC220). First, under a nitrogen atmosphere, the temperature was raised from room temperature to 220 ° C. at 40 ° C./minute, held for 5 minutes, and then cooled to 20 ° C. at 10 ° C./minute (first run). About the melting peak observed when the temperature is raised (second run) again at 40 ° C./minute after holding for 5 minutes, the melting having a peak in the temperature range of 145 to 157 ° C. is the melting peak of β crystal, 158 ° C. The melting at which the peak is observed is defined as the melting peak of the α crystal, and the melting heat amount of the α crystal is obtained from the baseline and the area of the region surrounded by the peak drawn from the flat portion on the high temperature side. Is ΔHα, and the heat of fusion of β crystal is ΔHβ, the value calculated by the following formula is β crystal forming ability. The heat of fusion was calibrated using indium.

β crystal forming ability (%) = [ΔHβ / (ΔHα + ΔHβ)] × 100
However, in the above method, there is a melting peak having an apex at 140 to 160 ° C., but when it is unclear whether it is caused by melting of the β crystal, the apex of the melting peak exists at 140 to 160 ° C. A sample prepared under the following conditions is determined to have β-crystal forming ability when the K value calculated from each diffraction peak intensity of the diffraction profile obtained by the 2θ / θ scan is 0.3 or more.

  The sample preparation conditions and the measurement conditions of the wide angle X-ray diffraction method are shown below.

·sample:
The direction of the film is aligned, and the samples are stacked so that the sample thickness after hot press preparation is about 1 mm. This sample is sandwiched between two aluminum plates having a thickness of 0.5 mm, and is hot-pressed at 280 ° C. for 3 minutes to be melted and compressed to make the polymer chain substantially non-oriented. The obtained sheet is crystallized by being immersed in boiling water at 100 ° C. for 5 minutes immediately after being taken out together with the aluminum plate. Then, a sample obtained by cutting a sheet obtained by cooling in an atmosphere at 25 ° C. is used for measurement.

・ Wide-angle X-ray diffraction measurement conditions:
In accordance with the above conditions, an X-ray diffraction profile is obtained by 2θ / θ scanning.

  Here, the K value is observed in the vicinity of 2θ = 16 °, and is observed in the diffraction peak intensity of the (300) plane (referred to as Hβ1) due to the β crystal and in the vicinity of 2θ = 14, 17, 19 °, and α From the diffraction peak intensities (referred to as Hα1, Hα2, and Hα3, respectively) of the (110), (040), and (130) planes due to the crystal, it can be calculated by the following mathematical formula. The K value is an empirical value indicating the ratio of β crystals. For details of the K value, such as the calculation method of each diffraction peak intensity, see A. Turner Jones et al., “Macromoleculare Chemie” (Macromoleculare Chemie). ), 75, pages 134-158 (1964).

K = Hβ1 / {Hβ1 + (Hα1 + Hα2 + Hα3)}
The structure of the polypropylene crystal type (α crystal, β crystal), the obtained wide-angle X-ray diffraction profile, etc. are described in, for example, Edward P. Moore Jr. Written by "Polypropylene Handbook", Industrial Research Committee (1998), p. 135-163; Hiroyuki Tadokoro, “Structure of Polymer”, Kagaku Dojin (1976), p. 393; A. Turner Jones et al., “Macromoleculare Chemie”, 75, 134-158 (1964), and there are many reports including references cited therein. You can refer to it.

(6) Presence / absence of particles The easy slip layer surface of the laminated porous film was observed using a differential interference microscope (DMLB HC) manufactured by Leica Corporation. In the reflection mode, 1 cm ^{2 was} observed at a magnification of 1,000 times, the number of particles having a particle diameter of 0.3 μm or more was counted, and the presence or absence of particles was evaluated as follows.

Yes: 1 cm particle diameter is more than one 0.3μm particles during ² No: less than 1 particle diameter is 0.3μm in the particles in 1 cm ² (7) static friction coefficient (.mu.s)
Using a slip tester manufactured by Toyo Seiki Co., Ltd., according to JIS K 7125 (1999), the value when the film coating surface was rubbed on both sides was measured, and the initial rise resistance value was determined as the coefficient of static friction μs. did. The coefficient of static friction was evaluated as follows.

○: 0.4 or less Δ: More than 0.4 and less than 0.6 ×: 0.6 or more (8) Surface observation after measurement of static friction coefficient (μs) 40 cm ² of sample surface before and after measuring friction coefficient μs ( Using a differential interference microscope (BMLB HC) manufactured by Leica Co., Ltd., the surface property was evaluated as follows.

  ○: The sample after the static friction coefficient measurement, and the surface state is the same as the sample before the static friction coefficient measurement.

  X: In the sample after the measurement of the coefficient of static friction, the easy-sliding layer is peeled off or particles are dropped.

(9) Air permeability evaluation The air resistance of the porous film and the laminated porous film is measured by the method of (3), the air resistance of the porous film is G ₀ , and the air resistance of the laminated porous film is G _1. And using the rate of change G (%) of the air resistance calculated by the following equation, the following evaluation was made.

G (%) = (G ₁ -G ₀ ) / G ₀ × 100
○: G (%) is within 50% Δ: G (%) exceeds 50% and is 100% or less X: G (%) exceeds 100% (10) Pore specific surface area Using “Mini”, the specific surface area (specific surface area by BET method) was measured according to JIS Z8830 (2013) under the following conditions. The sample was measured after 0.4 g of a porous polyolefin film before coating the inorganic particle-containing layer was put in a glass cell and degassed at room temperature for about 5 hours.

・ Measurement method: Nitrogen gas adsorption method ・ Adsorbate: Nitrogen ・ Dead volume measurement gas: Helium ・ Measurement temperature: 77K
・ Saturated vapor pressure: 101.3kPa
Measurement relative pressure P / P ₀ : about 0 to 1
EXAMPLES Next, although this invention is demonstrated based on an Example, this invention is not limited to these. Moreover, it shows to a reference example about the adjustment method of the coating material of a slippery layer.

(Reference Example 1) Preparation of coating agent A 5% by mass of alkyl acrylate (solid content concentration: 8.6% by mass), ethylene oxide adduct “Orphine” (registered trademark) EXP of acetylenic diol having a solid content concentration of 5% by mass -4123 (manufactured by Nissin Chemical Industry Co., Ltd.) and 0.14.9% by mass of water and 94.9% by mass of water were mixed and stirred.

Reference Example 2 Preparation of Coating B 0.5% by mass of a fluororesin “Megafac” (registered trademark) F-477 (manufactured by DIC Corporation) having a solid content concentration of 96.5% by mass and a solid content concentration of 5 A 0.1% by mass of ethylene oxide adduct “Olfin” (registered trademark) EXP-4123 (manufactured by Nissin Chemical Industry Co., Ltd.) of 9% by mass of water and 99.4% by mass of water was mixed and stirred. Agent B was obtained.

(Reference example 3) Preparation of coating agent C 3% by mass of urethane-based resin “Hydran” (registered trademark) HW-350 (manufactured by DIC Corporation) having a solid content concentration of 25.1% by mass and a solid content concentration of 5% by mass. Ethylene oxide adduct “Orphine” (registered trademark) EXP-4123 (manufactured by Nissin Chemical Industry Co., Ltd.) of acetylene-based diol was mixed and stirred at 0.1% by weight and 96.9% by weight of water. did.

(Reference Example 4) Preparation of coating material D High Tg acrylic resin “Barnock” (registered trademark) WE-304 (manufactured by DIC Corporation) having a solid content concentration of 45% by mass and a solid content concentration of 5% by mass. Ethylene oxide adduct “Orphine” (registered trademark) EXP-4123 (manufactured by Nissin Chemical Industry Co., Ltd.) of acetylene-based diol was mixed and stirred at 0.1 mass% and water at 97.9 mass%. did.

(Reference Example 5) Preparation of coating agent E 2.5% by mass of alkyl acrylate (solid content concentration 8.6% by mass), 2.5% by mass of silica particles (particle size 1 μm), and 5% by mass of solid content concentration Ethylene oxide adduct “Orphine” (registered trademark) EXP-4123 (manufactured by Nissin Chemical Industry Co., Ltd.) of acetylene-based diol was mixed and stirred at 0.1 wt% and water at 94.9 wt%. did.

(Reference Example 6) Preparation of coating agent F Low Tg acrylic resin “Bernock” (registered trademark) WE-310 (manufactured by DIC Corporation) having a solid content concentration of 45 mass% is 2 mass%, and the solid content concentration is 5 mass%. Ethylene oxide adduct “Orphine” (registered trademark) EXP-4123 (manufactured by Nissin Chemical Industry Co., Ltd.) of acetylene-based diol was mixed and stirred at 0.1 mass% and 97.9 mass% of water. did.

(Reference Example 7) Preparation of Coating Material G Ethylene oxide adduct "Olfin" (registered trademark) EXP of 25% by mass of alkyl acrylate (solid content concentration 8.6% by mass) and 5% by mass of solid content concentration -4123 (manufactured by Nissin Chemical Industry Co., Ltd.) and 0.14.9% by mass of water and 74.9% by mass of water were mixed and stirred to obtain coating agent G.

Example 1
As the polypropylene resin, 99.7 parts by mass of Homopolypropylene FLX80E4 manufactured by Sumitomo Chemical Co., Ltd., melting point 165 ° C., MFR = 7.5 g / 10 min, N, N′-dicyclohexyl-2,6- 0.3 parts by weight of naphthalene dicarboxyamide (manufactured by Shin Nippon Rika Co., Ltd., NU-100), 0.05 parts by weight of calcium behenate, and IRGANOX 1010 and IRGAFOS 168 by BASF, which are antioxidants, are each 0 The raw material is supplied from the weighing hopper to the L / D = 41 twin screw extruder so that 1 part by mass is mixed at this ratio, melt kneaded at 300 ° C., discharged from the die, and the cross-sectional area of the chip. take-off as (cross-sectional area perpendicular to the flow direction during manufacture of the chip) is 0.9 mm ^2, then it cooled and solidified at 25 ° C. water bath, cut into chips To the crystallization temperature (Tc) was obtained chips polypropylene composition comprising a 130.6 ° C. (Oh).

  59.8 parts by mass of FLX80E4 manufactured by Sumitomo Chemical Co., Ltd., having a melting point of 165 ° C. and MFR = 7.5 g / 10 min as a polypropylene resin, and ethylene-octene-1 copolymer (engage 8411 manufactured by Dow Chemical) as a copolymerized PE resin. , Melt index: 18 g / 10 min), 30 parts by weight of CEBC (DYNARON 6200P manufactured by JSR Corporation) as a dispersant, and 0 IRGANOX 1010 and IRGAFOS 168 manufactured by BASF Corporation which are antioxidants. The raw material was supplied from the weighing hopper to the twin-screw extruder so as to be mixed at a ratio of 1 part by mass, and melt kneading was performed at 230 ° C. The melt-kneaded material is discharged from the die in the form of a strand, taken to a draft ratio of 1.9, cooled and solidified in a 25 ° C. water bath, cut into a chip and cut into a polypropylene composition (I )

  80 parts by mass of the obtained polypropylene composition (A) and 20 parts by mass of the polypropylene composition (I) were dry blended and supplied to a uniaxial melt extruder, melt extruded at 210 ° C., and baked in a 60 μm cut. After removing the foreign matter with a binding filter, the product was discharged onto a cast drum whose surface temperature was controlled at 120 ° C. with a T-die to obtain a cast sheet. Subsequently, it preheated using the ceramic roll heated at 123 degreeC, and stretched 5.2 times in the longitudinal direction of the film.

  After cooling, the end was then held by a clip with a tenter type stretching machine, preheated at 150 ° C., and stretched 7 times in the width direction at 150 ° C. Next, the film was heat-set at 160 ° C. while relaxing 5% in the width direction in the tenter, uniformly cooled, then cooled to room temperature and wound up to obtain a porous film (I). The evaluation results of the obtained porous film are shown in Table 1-1.

  Next, returning to the step after stretching in the longitudinal direction, after the film stretched in the longitudinal direction was once cooled, the film was transported to a bar coater and subjected to corona discharge treatment on one side of the film. Then, the coating agent A was applied to the corona discharge treated surface with a Mayer bar. Further, after coating, both ends of the film were introduced into a tenter while being held with clips, preheated at 150 ° C., and stretched 7 times in the width direction at 150 ° C. Next, heat-fixing was performed at 160 ° C. while giving 5% relaxation in the transverse direction in the tenter, and after uniform cooling, the film was cooled to room temperature and wound up to obtain a laminated porous film. The evaluation result of the obtained laminated porous film is shown in Table 1-2.

(Example 2)
A porous film and a laminated porous film were obtained in the same manner as in Example 1 except that the coating agent B of (Reference Example 2) was used as the coating agent. The evaluation results of the obtained film are shown in Table 1-1 and Table 1-2.

(Example 3)
A porous film and a laminated porous film were obtained in the same manner as in Example 1 except that the coating agent C of (Reference Example 3) was used as the coating agent. The evaluation results of the obtained film are shown in Table 1-1 and Table 1-2.

Example 4
A porous film and a laminated porous film were obtained in the same manner as in Example 1 except that the coating material D of (Reference Example 4) was used as the coating material. The evaluation results of the obtained film are shown in Table 1-1 and Table 1-2.

(Comparative Example 1)
The porous film (I) obtained in Example 1 was evaluated as it was. The coefficient of static friction deteriorated. The evaluation results of the obtained porous film are shown in Table 2-1 and Table 2-2.

(Comparative Example 2)
The porous film (I) obtained in Example 1 was coated with the coating E of (Reference Example 5) off-line using a Meyer bar, dried in a hot air oven heated to 100 ° C. for 1 minute, and laminated porous. A characteristic film was obtained. As a result of observing the surface after the measurement of the static friction coefficient, the slippery layer peeled off and the particles dropped off. The evaluation results of the obtained film are shown in Table 2-1 and Table 2-2.

(Comparative Example 3)
The porous film (I) obtained in Example 1 was coated with the coating agent A of (Reference Example 1) off-line using a Meyer bar, dried in a hot air oven heated to 100 ° C. for 1 minute, and laminated porous. A characteristic film was obtained. Evaluation of the slippery layer was difficult to remove and peeled off during the drying process. The evaluation results of the obtained film are shown in Table 2-1 and Table 2-2.

(Comparative Example 4)
A porous film and a laminated porous film were obtained in the same manner as in Example 1 except that the coating material G of (Reference Example 7) was used as the coating material. The coating thickness increased and the surface aperture ratio and air permeability deteriorated. The evaluation results of the obtained film are shown in Table 2-1 and Table 2-2.

(Comparative Example 5)
Engage 8411 (melt index: 18 g / 10 min, below) manufactured by Sumitomo Chemical Co., Ltd. as a raw material for porous film, manufactured by Sumitomo Chemical Co., Ltd., 94.45% by mass of FLX80E4, Dow Chemical Co., Ltd. N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide (manufactured by Shin Nippon Rika Co., Ltd., Nu-100), which is a β crystal nucleating agent, added to 5% by mass. In the following, 0.3 mass% is simply expressed as β crystal nucleating agent, and 0.15% and 0.1% by mass of IRGANOX1010 and IRGAFOS168 manufactured by BASF Corporation, which are antioxidants, are mixed in this ratio. The raw material is fed from the weighing hopper to the twin screw extruder, melt kneaded at 300 ° C, discharged from the die in a strand shape, and cooled in a 25 ° C water bath. It solidified, and the chip raw materials and cut into chips.

  This chip is supplied to a single screw extruder and melt extruded at 220 ° C. After removing foreign matter with a 25 µm cut sintered filter, it is discharged from a T-die to a cast drum whose surface temperature is controlled at 120 ° C and unstretched sheet Got. Next, preheating was performed using a ceramic roll heated to 120 ° C., and the film was stretched 4.8 times in the longitudinal direction of the film. After cooling, the end portion was introduced into a tenter type stretching machine by holding it with a clip, and stretched 6 times at 145 ° C. The porous film (II) was obtained by performing a heat treatment at 155 ° C. for 6 seconds while applying 16% relaxation in the width direction. The evaluation results of the obtained porous film are shown in Table 2-1.

  Next, returning to the step after stretching in the longitudinal direction, after the film stretched in the longitudinal direction was once cooled, the film was transported to a bar coater and subjected to corona discharge treatment on one side of the film. Then, the coating agent G of (Reference Example 7) was applied to the corona discharge treated surface with a Mayer bar. Further, after coating, the film was introduced into a tenter while holding both ends of the film with clips, and stretched 6 times at 145 ° C. As it was, heat treatment was performed at 155 ° C. for 6 seconds while relaxing 16% in the width direction, and the mixture was gradually cooled gradually, and then cooled to room temperature and wound up to obtain a laminated porous film. As a result of evaluating the obtained laminated porous film, the air permeability deteriorated. The evaluation results of the obtained laminated porous film are shown in Table 2-2.

(Comparative Example 6)
A porous film and a laminated porous film were obtained in the same manner as in Example 1 except that the coating agent F of (Reference Example 6) was used as the coating agent. Surface aperture ratio, air permeability and static friction coefficient deteriorated. The evaluation results of the obtained film are shown in Table 2-1 and Table 2-2.

  The laminated porous film of the present invention is excellent in slipperiness, permeability, and productivity, and can be suitably used as a separator for an electricity storage device because yield reduction due to dropout of particles is improved.

Claims (7)

A laminated porous film in which an easy-sliding layer substantially free of particles is provided on at least one surface of a porous film mainly composed of polypropylene resin, and has an air resistance of 50 to 10,000 seconds / 100 ml. , Ri thickness 200nm less der than 1nm of lubricity layer, laminated porous static friction coefficient of the lubricity layer μs is Ru der less than 0.6 film. The laminated porous film according to claim 1, wherein the easy-sliding layer contains as a main component at least one resin selected from the group consisting of a fluororesin, an acrylic resin, a urethane resin, and a polyester resin. The laminated porous film according to claim 1 or 2, wherein the easy-slip layer has a surface area ratio of 45% or more. The laminated porous film according to any one of claims 1 to 3, wherein the β-crystal forming ability of the porous film is 40% or more and 95% or less. Pore specific surface area by nitrogen adsorption method is 30 to 100 m ² / g, the laminated porous film according to claim 1. When providing the easy-slip layer of the laminated porous film according to any one of claims 1 to 5, for forming the easy-slip layer on at least one side of a sheet mainly composed of a polypropylene resin melt-extruded from a die. A method for producing a laminated porous film in which a coating agent is applied, followed by drying, stretching, and heat treatment at least once to form an easy-sliding layer. The separator for electrical storage devices which uses the laminated porous film in any one of Claims 1-5.