JP2014197541A - Coating material for lithium ion secondary battery separator, lithium ion secondary battery separator, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material excellent in adhesion between a porous substrate and inorganic particles, to provide a separator excellent in characteristics as a separator for a lithium ion secondary battery, excellent in adhesion between the porous substrate and the inorganic particles even when ambient pressure is changed, which is a usage condition unique to a vehicle, and to provide a lithium ion secondary battery.SOLUTION: The coating material for lithium ion secondary battery separator to be coated to a porous substrate is an aqueous dispersion body formed by dispersing into an aqueous medium a modified polyolefin resin (A) having an N-substituted maleimide unit whose N- substituent group is a substituent group represented by a specific formula and inorganic particles (B).

Description

  The present invention relates to a coating material for a lithium ion secondary battery separator that can be suitably used for a lithium ion secondary battery separator, a lithium ion secondary battery separator, and a lithium ion secondary battery obtained using the same.

  Main components of the lithium ion secondary battery are classified into positive and negative electrodes, an exterior material, an electrolytic solution, and a separator, and the separator that separates the positive electrode and the negative electrode is one of important components. The separator is required to have various performances such as heat resistance, air permeability, and shutdown performance. On the other hand, as a material used for the separator, a porous base material made of a thermoplastic resin excellent in cost, workability, and shutdown property is often used. However, in the case of a thermoplastic resin, there is a problem that the separator has insufficient heat resistance (such as dimensional stability at high temperature). Many proposals for solving this problem have been made, and among them, a method of adhering inorganic particles to the surface of a porous substrate made of a thermoplastic resin with a binder or the like has been proposed (Patent Documents 1 to 3).

  On the other hand, when lithium ion secondary batteries are classified by application, consumer, industrial equipment, and industrial robots used for power supplies such as personal computers, mobile phones, and home appliances that are often used by general consumers and households. It can be classified into industrial use, which is a power source, and in-vehicle use, which is mounted on a vehicle such as an electric vehicle and serves as a power source for power. Among them, the in-vehicle lithium ion secondary battery (sometimes referred to as “on-vehicle lithium ion secondary battery”) is expected to be widely used.

  However, since an in-vehicle lithium ion secondary battery is mounted on a vehicle and the vehicle moves under various conditions, unique performance different from that for consumer or industrial lithium ion secondary batteries may be required. Various conditions include, for example, conditions that apply a large centrifugal force when turning while moving at high speeds, vibrations coming from the road surface, etc., running in high altitude mountainous areas, and changes in atmospheric pressure when mounted on airplanes and so on. Even under such various use conditions, performance to ensure battery characteristics and safety is required. However, in-vehicle lithium-ion secondary batteries have a large output capacity, so the volume and mass of the battery body are large, and loads caused by disturbances such as stress, vibration, and atmospheric pressure change due to centrifugal force are large and have an adverse effect. It has a structure that is easy to receive.

JP 2012-190547 A JP 2012-138188 A JP 2011-110704 A

  However, Patent Documents 1 to 3 do not describe separator performance under conditions unique to the in-vehicle lithium ion secondary battery such as stress, vibration, and atmospheric pressure change due to centrifugal force. In addition, in a separator in which inorganic particles are adhered to the surface of the porous substrate with a binder or the like, the adhesiveness between the porous substrate and the inorganic particles may be lowered when the pressure change is repeated.

  The present invention solves the above-described problems, and is excellent in properties as a separator for a lithium ion secondary battery, and a coating material excellent in adhesion between a porous substrate and inorganic particles. An object of the present invention is to provide a separator and a lithium ion secondary battery that are excellent in adhesion between a porous substrate and inorganic particles even when there is a change in atmospheric pressure, which is a unique use condition.

  As a result of intensive studies to solve the above problems, the present inventors have found that an aqueous dispersion in which a specific modified polyolefin resin and inorganic particles are dispersed in an aqueous medium has improved adhesion to a porous substrate. As a result, the lithium ion secondary battery separator obtained by applying the aqueous dispersion to the surface of the porous substrate has been found to solve the above problems, and has reached the present invention.

  That is, the gist of the present invention is as follows.

(1) A modified polyolefin resin (A) having a N-substituted maleimide unit, which is a coating applied to a porous substrate and whose N-substituent is a substituent represented by the following formula (1), and inorganic particles A coating for a lithium ion secondary battery separator, wherein (B) is an aqueous dispersion dispersed in an aqueous medium.
^{_{- (CH 2) n NR 1}} R 2 (1)
(Wherein, R ¹ and R ² are alkyl groups of 1 to 5 carbon atoms, at least one selected from a hydroxyalkyl group having 1 to 5 carbon atoms or H,, n represents an integer of 1 to 5 )
(2) The lithium ion according to (1), wherein at least part of the N-substituent of the N-substituted maleimide unit of the modified polyolefin resin (A) is a substituent represented by the following formula (2) Paint for secondary battery separator.
^{_{- (CH 2) n N +}} R 1 R 2 R 3 · X - (2)
Wherein R ¹ and R ² are at least one selected from an alkyl group having 1 to 5 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, or H, and R ³ is H or a quaternization reaction. The residue of the quaternizing agent introduced by X, X ⁻ represents an anionic counterion, and n represents an integer of 1 to 5.)
(3) The N-substituted maleimide unit content of the modified polyolefin resin (A) is 0.1 to 5 mol%, and the paint for a lithium ion secondary battery separator according to (1) or (2) .
(4) The lithium ion secondary battery according to any one of (1) to (3), wherein the swelling ratio of the modified polyolefin resin (A) to the 50 ° C. electrolyte is in the range of 3 to 35%. Paint for separator.
(5) The coating material for a lithium ion secondary battery separator according to any one of (1) to (4), wherein the modified polyolefin resin (A) has a dissolution rate in an electrolyte solution of 50 ° C. of 5% or less. .
(6) The coating material for a lithium ion secondary battery separator according to any one of (1) to (5), which substantially does not contain a nonvolatile dispersion aid.
(7) The number average particle diameter of modified polyolefin resin (A) is 0.5 micrometer or less, The coating material for lithium ion secondary battery separators in any one of (1)-(6) characterized by the above-mentioned.
(8) The mass ratio of the modified polyolefin resin (A) to the inorganic particles (B) is in the range of (A) / (B) = 70/30 to 1/99, (1) to (7 ) The coating material for a lithium ion secondary battery separator according to any one of the above.
(9) The form of the porous substrate is at least one selected from a microporous film, a nonwoven fabric, a woven / knitted fabric, a nanofiber fabric, and paper, and is described in any one of (1) to (8) Paint for lithium ion secondary battery separator.
(10) The paint for a lithium ion secondary battery separator according to any one of (1) to (9), wherein the material of the porous substrate is a polyolefin resin.
(11) The paint for a lithium ion secondary battery separator according to any one of (1) to (10), which is applied to a vehicle-mounted lithium ion secondary battery separator.
(12) Lithium ion secondary in which a porous layer formed by applying the coating material for a lithium ion secondary battery separator according to any one of (1) to (11) is laminated on at least one surface of a porous substrate. Secondary battery separator.
(13) A lithium ion secondary battery comprising the lithium ion secondary battery separator according to (12).

  The coating material for a lithium ion secondary battery separator of the present invention has an adhesive property between a coating film obtained by coating (sometimes referred to as a porous layer) and a porous substrate serving as a base material for the lithium ion secondary battery separator. Excellent. Therefore, a lithium ion secondary battery separator in which a porous layer is laminated on a porous substrate is excellent in heat resistance, and the porous substrate and the porous layer are in close contact with each other even when used under conditions with changes in atmospheric pressure. The property is kept good. As a result, the lithium ion secondary battery provided with the lithium ion secondary battery separator is excellent in safety and battery characteristics even when mounted on a vehicle.

  Hereinafter, the present invention will be described in detail.

  The paint for a lithium ion secondary battery separator of the present invention is an aqueous dispersion in which a modified polyolefin resin (A) having an N-substituted maleimide unit and inorganic particles (B) are dispersed in an aqueous medium.

  Although the olefin unit which is the main component of the modified polyolefin resin (A) is not particularly limited, alkene having 2 to 6 carbon atoms such as ethylene, propylene, isobutylene, 2-butene, 1-butene, 1-pentene, 1-hexene and the like Preferably, a mixture of these may be used. Among these, from the viewpoint of improving adhesion and heat resistance, alkene having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene, and 1-butene is more preferable, ethylene and propylene are further preferable, and ethylene is most preferable.

In the present invention, the modified polyolefin resin (A) contains an N-substituted maleimide unit whose N-substituent is a substituent represented by the following formula (1) as a copolymerization component.
^{_{- (CH 2) n NR 1}} R 2 (1)

In the formula ^{(1), R 1, R} 2 is an alkyl group of 1 to 5 carbon atoms, at least one selected from a hydroxyalkyl group having 1 to 5 carbon atoms or H,, in view of stability of the paint To an alkyl group having 1 to 2 carbon atoms. Moreover, n is an integer of 1-5, and the integer of 2-4 is preferable from a heat resistant and adhesive viewpoint, and the integer of 2-3 is more preferable.

  Specific preferred N-substituents include N, N-dimethylaminoethyl group, N, N-dimethylaminopropyl group, N, N-dimethylaminobutyl group, N, N-diethylaminoethyl group, N, N- Examples thereof include a diethylaminopropyl group and an N, N-diethylaminobutyl group. Of these, an N, N-dimethylaminopropyl group is preferable.

  Specific examples of such a preferred N-substituted maleimide unit consisting of N-substituents include N, N-dimethylaminoethylmaleimide, N, N-dimethylaminopropylmaleimide, N, N-dimethylaminobutylmaleimide, N, Examples thereof include N-diethylaminoethylmaleimide, N, N-diethylaminopropylmaleimide, N, N-diethylaminobutylmaleimide and the like. Two or more of these may be copolymerized.

  The N-substituted maleimide unit may be copolymerized in the modified polyolefin resin, and its form is not limited. Examples of the copolymerization state include random copolymerization, block copolymerization, graft copolymerization (graft modification). ) And the like.

  The content of the N-substituted maleimide unit in the modified polyolefin resin (A) is preferably in the range of 0.1 to 5 mol%, and preferably 0.1 to 3 mol% from the viewpoint of easy adhesion and aqueous dispersion. More preferably, 0.2-2 mol% is further more preferable, 0.4-1 mol% is especially preferable, and 0.5-0.9 mol% is the most preferable. When the content is less than 0.1 mol%, the adhesion tends to be inferior, and further, the processing to an aqueous dispersion described later tends to be difficult. On the other hand, when it exceeds 5 mol%, the adhesion and the stability of the paint tend to be lowered.

  The modified polyolefin resin (A) preferably contains a (meth) acrylic acid ester unit as a copolymer component in order to obtain excellent adhesion to the porous substrate. Examples of the (meth) acrylic acid ester unit include an esterified product of (meth) acrylic acid and an alcohol having 1 to 30 carbon atoms. Among them, (meth) acrylic acid and carbon number 1 from the viewpoint of easy availability. Esterified products with ˜20 alcohols are preferred. Specific examples of (meth) acrylic acid ester units include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, (meth ) Octyl acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, and the like. Mixtures of these may be used. Among these, from the viewpoint of easy availability and adhesion, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl acrylate, octyl acrylate are more preferable, ethyl acrylate, More preferred is butyl acrylate, and particularly preferred is ethyl acrylate. ("(Meth) acrylic acid-" means "acrylic acid- or methacrylic acid-".

  The content of the (meth) acrylic acid ester unit in the modified polyolefin resin (A) is preferably 0.1 to 20 mol%, and preferably 1 to 15 mol% from the viewpoint of adhesion and heat resistance. More preferably, it is more preferably 2 to 10 mol%. When the content of the (meth) acrylic acid ester unit is less than 0.1 mol%, the adhesion tends to decrease, and when it exceeds 20 mol%, the heat resistance tends to deteriorate. Further, the (meth) acrylic acid ester unit may be copolymerized in the modified polyolefin resin, and the form thereof is not limited. Examples of the copolymerization state include random copolymerization, block copolymerization, and graft copolymerization. Examples thereof include polymerization (graft modification).

  Furthermore, the modified polyolefin resin (A) may contain an unsaturated carboxylic acid unit in order to further improve the adhesion. Examples of unsaturated carboxylic acid units include acrylic acid, methacrylic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, fumaric acid, crotonic acid, and the like, as well as unsaturated dicarboxylic acid half esters and half amides. Among these, acrylic acid, methacrylic acid, and (anhydrous) maleic acid are preferable from the viewpoint of adhesion to the porous substrate, and acrylic acid and (anhydrous) maleic acid are particularly preferable. The unsaturated carboxylic acid unit may be copolymerized in the modified polyolefin resin, and the form thereof is not limited. Examples of the copolymerization state include random copolymerization, block copolymerization, and graft copolymerization ( Graft modification). In addition, “(anhydrous) to acid” means “to acid or anhydrous to acid”. That is, (anhydrous) maleic acid means maleic acid or maleic anhydride.

  The content of the unsaturated carboxylic acid unit in the modified polyolefin resin (A) can be determined by measuring the acid value. The acid value (mgKOH / g) of the modified polyolefin resin (A) is obtained by dissolving the modified polyolefin resin (A) in a solvent of tetrahydrofuran / toluene / water = 20 / 4.8 / 0.2 (mass ratio). Is determined from the amount of KOH consumed when the color tone of the solution turns purple and the color tone does not change for 20 seconds. The acid value of the modified polyolefin resin (A) thus determined is preferably 0.1 to 50 mgKOH / g, more preferably 0.2 to 40 mgKOH / g. When the acid value of the modified polyolefin resin (A) exceeds 50 mgKOH / g, aqueous dispersion tends to be difficult. On the other hand, when it is less than 0.1 mgKOH / g, the content of unsaturated carboxylic acid is too small, and the effect of improving the adhesion tends to be low.

  The melt flow rate at 190 ° C. and 2160 g load, which is a measure of the molecular weight of the modified polyolefin resin (A), is preferably in the range of 0.01 to 300 g / 10 minutes, more preferably 0.1 to 200 g / 10 minutes, and 5 to 100 g / 10 min is more preferable, 1 to 80 g / 10 min is particularly preferable, and 1 to 50 g / 10 min is most preferable. When the melt flow rate exceeds 300 g / 10 minutes, the heat resistance tends to be reduced or the battery electrolyte tends to dissolve, and when it is less than 0.01 g / 10 minutes, aqueous dispersion tends to be difficult. .

  The swelling ratio of the modified polyolefin resin (A) in the 50 ° C. electrolytic solution is preferably in the range of 3 to 35%, more preferably 5 to 30%, and particularly preferably 7 to 25%. If the swelling rate is out of the above range, the adhesion when there is a change in atmospheric pressure may deteriorate.

  The dissolution rate of the modified polyolefin resin (A) in the 50 ° C. electrolytic solution is preferably 5% or less, more preferably 3% or less, particularly preferably 2% or less, and further preferably 1% or less. If the dissolution rate is out of the above range, the adhesion when there is a change in atmospheric pressure may deteriorate.

The dissolution rate and swelling rate of the modified polyolefin resin (A) in the 50 ° C. electrolyte solution are the type and content of components other than the olefin component contained in the modified polyolefin resin (A), and the melt flow rate of the modified polyolefin resin (A). It can be controlled by designing combinations such as the types of R ¹ and R ² of the substituent represented by the formula (1) of the modified polyolefin resin (A) and the number of n.

  The swelling rate and dissolution rate in the 50 ° C. electrolytic solution are the ratio of the weight increase of the modified polyolefin resin (A) when the modified polyolefin resin (A) is immersed in the 50 ° C. electrolytic solution (the swelling rate ( %), And the ratio of the weight loss of the modified polyolefin resin (A) is the dissolution rate (%).

  The melting point of the modified polyolefin resin (A) is preferably in the range of 60 to 140 ° C and more preferably in the range of 70 to 120 ° C from the viewpoint of improving battery performance.

  The hardness (Shore D) according to ISO-868 of the modified polyolefin resin (A) is preferably in the range of 10-50, more preferably in the range of 20-45, from the viewpoint of improving the adhesion.

  The bigat softening point according to ISO-306 of the modified polyolefin resin (A) is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 85 ° C, from the viewpoint of improving battery performance.

  The breaking strength according to ISO-R527 of the modified polyolefin resin (A) is preferably 6 MPa or more, more preferably in the range of 6 to 15 MPa from the viewpoint of improving battery performance.

  The breaking elongation according to ISO-R527 of the modified polyolefin resin (A) is preferably in the range of 500 to 900 MPa, and more preferably in the range of 600 to 800 MPa from the viewpoint of improving battery performance.

  The bending elastic modulus according to ISO-178 of the modified polyolefin resin (A) is preferably 150 MPa or less and more preferably in the range of 30 to 140 MPa from the viewpoint of improving battery performance.

  The method for producing the modified polyolefin resin (A) in the present invention is not particularly limited, but a polyolefin resin containing a maleic anhydride unit as a copolymerization component and an amino compound represented by the following formula (I) are heated. And a method of producing a modified polyolefin resin (A) by mixing and imidization reaction. In this method, the imidization reaction proceeds satisfactorily without adding a catalyst for promoting the imidization reaction.

The amino compound represented by the following formula (I) is an amine having a substituent represented by the formula (1).
_{H 2 N- (CH 2) n} NR 1 R 2 ( I)

In formula (I), R ¹ and R ² are at least one selected from alkyl groups having 1 to 5 carbon atoms, hydroxyalkyl groups having 1 to 5 carbon atoms, or H, and alkyl having 1 to 2 carbon atoms. Groups are preferred. n is an integer of 1 to 5, an integer of 2 to 4 is preferable, and an integer of 2 to 3 is more preferable.

  Preferable specific examples of the amino compound represented by the formula (I) include N, N-dialkylaminoalkylamine. Among them, N, N-dimethylaminoethylamine, N, N-dimethylaminopropylamine, N, N-dimethylaminobutylamine, N, N-diethylaminoethylamine, N, N-diethylaminopropylamine, N, N-diethylaminobutylamine, etc. N, N-dimethylaminopropylamine is preferable.

  Specific examples of polyolefin resins containing maleic anhydride units as raw materials for the modified polyolefin resin (A) as a copolymerization component (hereinafter referred to as “maleated polyolefin resin”) include ethylene- (maleic anhydride) copolymer. Polymer, propylene- (anhydride) maleic acid copolymer, ethylene-propylene- (anhydride) maleic acid copolymer, ethylene-propylene-1-butene- (anhydride) maleic acid copolymer, ethylene- (meth) acrylic acid Examples include ester- (anhydrous) maleic acid copolymers and propylene-1-butene- (anhydride) maleic acid copolymers. Among them, ethylene- (meth) acrylic acid ester- (anhydrous) maleic acid copolymer is used. preferable. The ethylene- (meth) acrylic acid ester- (anhydrous) maleic acid copolymer is described in, for example, British Patent No. 2911745, US Pat. No. 4,617,366 and US Pat. No. 4,644,044. By referring to these methods, those skilled in the art can easily produce them.

  In the present invention, the modified polyolefin resin (A) is used as an aqueous dispersion. Here, the aqueous dispersion of the modified polyolefin resin (A) will be described. The modified polyolefin resin (A) can be processed into an aqueous dispersion by dispersing it in an aqueous medium. As a dispersion method, a known dispersion method such as a self-emulsification method or a forced emulsification method may be employed.

The aqueous dispersion of the modified polyolefin resin (A) in the present invention is an amino acid having an N-substituent represented by the above formula (1) of the N-substituted maleimide unit contained in the modified polyolefin resin (A) in an aqueous medium. From the viewpoint of adhesion, it is preferable to use a cationic aqueous dispersion obtained by neutralizing a group with an acidic compound or quaternizing with a quaternizing agent. Among these, a cationic aqueous dispersion obtained by neutralization with an acidic compound is preferable because of excellent adhesion. As described above, the N-substituent of the N-substituted maleimide unit neutralized with an acidic compound or quaternized with a quaternizing agent is a substituent represented by the following formula (2). Therefore, the modified polyolefin resin (A) in the aqueous dispersion has a substituent in which at least a part of the N-substituent of the N-substituted maleimide unit contained as a copolymerization component is represented by the following formula (2). It is preferable.
^{_{- (CH 2) n N +}} R 1 R 2 R 3 · X - (2)

In the formula ^{(2), R 1, R} 2 is an alkyl group of 1 to 5 carbon atoms, at least one selected from a hydroxyalkyl group having 1 to 5 carbon atoms or H,, in view of stability of the paint To an alkyl group having 1 to 2 carbon atoms. Moreover, n is an integer of 1-5, and the integer of 2-4 is preferable from a heat resistant and adhesive viewpoint, and the integer of 2-3 is more preferable. R ³ is H or a residue of a quaternizing agent introduced by a quaternization reaction. Among them, H is preferable from the viewpoint of adhesion. X ⁻ represents an anionic counter ion.

  The aqueous medium used when the modified polyolefin resin (A) is dispersed in an aqueous solution may contain a neutralizing agent that contributes to stabilization of the dispersion, a water-soluble organic solvent, and the like.

  Examples of water-soluble organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, and tert-amyl alcohol. , Alcohols such as 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, cyclohexanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, cyclohexanone, isophorone; tetrahydrofuran, dioxane, etc. Ethers of ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-sec-butyl, acetic acid-3-methoxybutyl, propio Esters such as methyl acid, ethyl propionate, diethyl carbonate, dimethyl carbonate; ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol ethyl ether acetate, diethylene glycol, Glycol derivatives such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl ether acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol methyl ether acetate; Butoxy-3-methyl butanol, 3-methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate and the like. In addition, you may use these organic solvents in mixture of 2 or more types. Among these, it is preferable to use a volatile water-soluble organic solvent having a boiling point of 140 ° C. or less in order to reduce the residue when forming the porous layer. Specific examples include ethanol, n-propanol, isopropanol, and n-butanol.

  The acidic compound as a neutralizing agent used to neutralize the amino group of the N-substituent represented by the above formula (1) of the N-substituted maleimide unit contained in the modified polyolefin resin (A) is formic acid, acetic acid And organic acids such as propionic acid, butyric acid, valeric acid, lactic acid and citric acid, and inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. These may be used alone or in combination of two or more. Of these, organic acids are preferred because of excellent neutralization of amino groups, and formic acid and acetic acid are more preferred. The quaternizing agent used to quaternize the amino group of the N-substituent is not particularly limited; however, dialkyl sulfates such as dimethyl sulfate and diethyl sulfate; methyl chloride, ethyl chloride, benzyl chloride, methyl Alkyl halides such as bromide, ethyl bromide, benzyl bromide, methyl iodide, ethyl iodide, benzyl iodide; ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, allyl glycidyl ether, butyl glycidyl ether, 2- Epoxys such as ethyl hexyl glycidyl ether and phenyl glycidyl ether; alkyls such as methyl methanesulfonate and methyl p-toluenesulfonate, and arylsulfonic acid methyls It is below. Among these, dialkyl sulfates and alkyl halides are preferable because of excellent quaternization reactivity, and dialkyl sulfates are more preferable. These may be used alone or in combination of two or more.

  When the modified polyolefin resin (A) is dispersed in an aqueous solution, the use of a non-volatile dispersion aid as described below is not excluded, but it is stable in an aqueous medium without using a non-volatile dispersion aid. Can be dispersed. By using the aqueous dispersion of the modified polyolefin resin (A) substantially free of such a non-volatile dispersion aid, the non-volatile dispersion aid is substantially contained also in the coating for a lithium ion secondary battery separator of the present invention. Is obtained.

  The number average particle diameter of the modified polyolefin resin (A) contained in the aqueous dispersion of the modified polyolefin resin (A) is preferably 0.5 μm or less from the viewpoint of adhesion and dispersion stability, and is preferably 0.01 to 0. More preferably, it is in the range of 0.4 μm, particularly preferably 0.02 to 0.3 μm, further preferably 0.03 to 0.2 μm, and most preferably 0.04 to 0.1 μm.

  The pH of the aqueous dispersion of the modified polyolefin resin (A) is preferably in the range of pH 2 to 7, more preferably pH 2.5 to 4.5, from the viewpoint of dispersion stability.

Next, the inorganic particles (B) will be described. Examples of the inorganic particles (B) include electrically insulating metal oxides, metal nitrides, and metal carbides. Specifically, alumina (Al ₂ O ₃ ), magnesia (MgO), titania (TiO ₂ ), zirconia (ZrO ₂ ), silica (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), Boron nitride (BN), titanium nitride (TiN), silicon carbide (SiC), boron carbide (B ₄ C), a combination of kaolinite and amorphous quartz can be preferably used. These inorganic particles can be used alone or in admixture of two or more. Among these, alumina (Al ₂ O ₃ ) is preferable in consideration of heat resistance, adhesion when processed into a paint, and stability of the paint.

  The inorganic particles (B) can exhibit heat resistance, which cannot be achieved only with a porous substrate, by adhering to the surface of the porous substrate. In addition, the inorganic particles have oxidation resistance, and when used for battery applications, the inorganic particles have strong resistance to an oxidizing environment in the vicinity of the electrode, particularly the positive electrode during charging. For this reason, even if the separator incorporated in the lithium ion secondary battery is exposed to an oxidizing environment, it is possible to supplement the strength of the porous substrate and maintain the necessary strength as the whole separator.

  The shape of the primary particles of the inorganic particles (B) is not particularly limited, and is plate-shaped, spherical, elliptical, cubic, rectangular parallelepiped, rhombohedral, convex polyhedral, needle-shaped, rod-shaped, massive, Any of inorganic particles having shapes such as an indefinite shape, a fiber shape, and a random shape can be used. These shapes may be only the same shape or a combination of a plurality of shapes. In the case of a combination of a plurality of shapes, each may be combined. In addition, these shapes are not limited to primary particles, and the combination or aggregate of inorganic particles (B) may take the shape described above.

  The average particle size of the primary particles of the inorganic particles (B) is preferably in the range of 0.1 to 10 μm, more preferably 0.2 to 5 μm, and particularly preferably 0.5 to 4 μm. The average particle size of such primary particles can be measured by a method of analyzing a photograph obtained with an electron microscope with a particle size measuring instrument.

  The mass ratio of the modified polyolefin resin (A) and the inorganic particles (B) in the coating for a lithium ion secondary battery separator is preferably in the range of (A) / (B) = 70/30 to 1/99, 50 / 50 to 2/98 is more preferable, 40/60 to 5/95 is particularly preferable, and 30/70 to 5/95 is further preferable. When the mass ratio of (A) is more than 70% by mass with respect to the total amount of (A) and (B), the porous structure of the porous substrate cannot be maintained, and the amount of inorganic particles (B) is acid-modified polyolefin. Since there is little with respect to resin (A), it exists in the tendency which cannot form a uniform porous layer. Moreover, when the mass ratio of (A) is less than 1% by mass, the adhesion between the inorganic particles (B) and the porous substrate tends to deteriorate.

  The method for dispersing the inorganic particles (B) in the aqueous medium is not particularly limited, and the inorganic particles (B) are previously dispersed in the aqueous medium and then mixed with the aqueous dispersion of the modified polyolefin resin (A). The method, the method of mixing the powdered inorganic particles (B) with the aqueous dispersion of the modified polyolefin resin (A), and charging the inorganic particles (B) in the same system during the aqueous dispersion with the modified polyolefin resin (A) Examples include a method in which the (A) and (B) are dispersed all together.

  Here, the aqueous medium in the paint for a lithium ion secondary battery separator of the present invention is a medium made of water or a liquid containing water, and includes a neutralizing agent and a water-soluble organic solvent that contribute to dispersion stabilization. It may be included.

  The concentration of the modified polyolefin resin (A) and the inorganic particles (B) in the coating for a lithium ion secondary battery separator of the present invention is preferably in the range of 1 to 60% by mass with respect to the entire coating.

  The viscosity of the paint for a lithium ion secondary battery separator of the present invention measured with a B-type viscometer is preferably in the range of 1 to 500 mPa · S (25 ° C.) from the viewpoint of easy application.

  The paint for a lithium ion secondary battery separator of the present invention, that is, the aqueous dispersion in which the modified polyolefin resin (A) and the inorganic particles (B) are dispersed in an aqueous medium does not use a non-volatile dispersion aid. In addition, (A) and (B) can be stably dispersed in an aqueous medium. When the non-volatile dispersion aid is not substantially contained, a separator having excellent adhesion to a porous substrate, heat resistance, and battery characteristics can be obtained.

  Here, the “aqueous dispersion aid” is a drug or compound added for the purpose of promoting aqueous dispersion or stabilizing the aqueous dispersion in the production of the aqueous dispersion. Means that it does not have a boiling point at normal pressure or has a high boiling point (for example, 300 ° C. or higher) at normal pressure.

  The content of the non-volatile dispersion aid is 3 with respect to the total solid content <solid content (A) + (B)> of the acid-modified polyolefin resin (A) and the inorganic particles (B) in the coating for a secondary battery separator. The content is preferably not more than mass%. When a large amount of the non-volatile dispersion aid is contained, the battery characteristics and the like are deteriorated. Therefore, the content is more preferably 1% by mass or less, further preferably 0.5% by mass or less, and most preferably zero. is there.

  Examples of the non-volatile dispersion aid in the present invention include an emulsifier described later, a compound having a protective colloid effect, a modified wax, an acid-modified compound having a high acid value, and a water-soluble polymer.

  Examples of the emulsifier include a cationic emulsifier, an anionic emulsifier, a nonionic emulsifier, and an amphoteric emulsifier. In addition to those generally used for emulsion polymerization, surfactants are also included. For example, anionic emulsifiers include higher alcohol sulfates, higher alkyl sulfonates, higher carboxylates, alkyl benzene sulfonates, polyoxyethylene alkyl sulfate salts, polyoxyethylene alkyl phenyl ether sulfate salts, vinyl sulfosuccinates. Nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyethylene glycol fatty acid ester, ethylene oxide propylene oxide block copolymer, polyoxyethylene fatty acid amide, ethylene oxide-propylene oxide Compounds having polyoxyethylene structure such as copolymers and sorbitan derivatives such as polyoxyethylene sorbitan fatty acid esters Examples of cationic emulsifiers include quaternary ammonium salts such as alkyltrimethylammonium salts and dialkyldimethylammonium salts, and alkylamine salts. Examples of amphoteric emulsifiers include laurylbetaine and lauryldimethylamine oxide. Can be mentioned.

Compounds having protective colloid action, modified waxes, high amino modified compounds, acid modified compounds with high acid value, water-soluble polymers include polyvinyl alcohol, amino modified polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, modified starch, polyvinyl Pyrrolidone, polyacrylic acid and salts thereof, amino group-containing polyethylene wax, amino group-containing polypropylene wax, amino group-containing polyethylene-propylene wax and other amino-modified polyolefin waxes having a number average molecular weight of usually 5000 or less, and salts thereof, amino Examples thereof include water-soluble acrylic copolymers having groups, gelatin, gum arabic, and casein, which are generally used as fine particle dispersion stabilizers.
The amino-modified amount of the amino-modified polyolefin wax and its salt and the water-soluble acrylic copolymer having an amino group means that the content of the monomer unit having an amino group is 10 mol% or more.

  In addition to the modified polyolefin resin (A), the inorganic particles (B), and the aqueous medium, the paint for a lithium ion secondary battery separator according to the present invention does not impair the effects of the present invention depending on the required performance. Various additives can be added. Examples of the additive include resins other than (A) (hereinafter referred to as “other resins”), crosslinking agents, and the like.

  Specific examples of other resins include polyvinyl acetate, polyvinyl chloride, acrylic resin, acrylic silicon resin, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic copolymer, ethylene-aminoacrylamide copolymer, ethylene- Amino acrylate copolymer, polyvinylidene chloride, styrene-maleic acid resin, styrene-aminoalkylmaleimide copolymer, styrene-butadiene resin, styrene elastomer, butadiene resin, acrylonitrile-butadiene resin, poly (meth) acrylonitrile resin, ( (Meth) acrylamide resin, chlorinated polyethylene resin, chlorinated polypropylene resin, modified nylon resin, polyester resin, polyurethane resin, cellulose resin, phenol resin, silicone resin, epoxy resin, fluorine-containing resin, Li ethyleneimine, and the like UV-curable resin. These can be used individually or in mixture of 2 or more types. When these resins are added, it is preferable to use those in which an aqueous dispersion or an aqueous solution is used.

  The addition amount of the other resin may be appropriately designed according to the purpose, but is usually 0.1 to 300 parts by mass with respect to 100 parts by mass of the total of the modified polyolefin resin (A) and the inorganic particles (B). It is preferably 3 to 200 parts by mass, particularly preferably 5 to 100 parts by mass.

  The coating material for a lithium ion secondary battery separator of the present invention may contain a crosslinking agent.

  Examples of the crosslinking agent include a crosslinking agent having self-crosslinking property, a crosslinking agent having a plurality of functional groups that react with carboxyl groups in the molecule, a crosslinking agent having a plurality of functional groups that react with amino groups in the molecule, A metal complex having a coordination site or the like can be used. Specifically, a polyhydric hydrazide compound, a polyvalent isocyanate compound, a polyvalent blocked isocyanate compound, a polyvalent melamine compound, a polyvalent epoxy compound, a polyvalent carbodiimide compound, a polyvalent oxazoline group-containing compound, a polyvalent amine compound, a polyol, Zirconium salt compounds, silane coupling agents, organic peroxides and the like can be mentioned, and these crosslinking agents may be used in combination. The crosslinking agent may be a low molecular weight compound or a polymer type.

  Among these, a crosslinking agent having a plurality of functional groups that react with carboxyl groups in the molecule is more preferable. Examples of such crosslinking agents include polyvalent oxazoline compounds, polyvalent epoxy compounds, polyvalent carbodiimide compounds, polyvalent isocyanate compounds, polyvalent hydrazide compounds, polyvalent amine compounds, polyvalent melamine compounds, polyols, and the like. A polyvalent oxazoline compound, a polyvalent hydrazide compound, a polyvalent amine compound, a polyvalent carbodiimide compound, and a polyvalent isocyanate compound are preferable because of their excellent crosslinking effect. Compounds are particularly preferred.

  The addition amount of the crosslinking agent is 0.01 to 300 parts by mass as a solid content of the crosslinking agent with respect to 100 parts by mass of the modified polyolefin resin (A) in the coating from the viewpoint of sufficiently forming a crosslinked structure. Is preferably 0.1 to 100 parts by mass, more preferably 0.2 to 50 parts by mass, and particularly preferably 0.5 to 30 parts by mass.

  In the present invention, the crosslinking agent is preferably used as an aqueous solution or an aqueous dispersion in order to improve the miscibility with the aqueous dispersion. Therefore, the crosslinking agent is preferably water-soluble or water-dispersible. A method for processing the crosslinking agent into an aqueous solution or an aqueous dispersion is not particularly limited, and a known method can be adopted.

  Furthermore, the coating for a lithium ion secondary battery separator of the present invention includes a leveling agent, an antifoaming agent, an anti-waxing agent, a pigment dispersant, an ultraviolet absorber, a catalyst, a photocatalyst, a UV curing agent, as necessary. Various agents such as wetting agents, penetrating agents, softeners, thickeners, dispersants, water repellents, antistatic agents, anti-aging agents, vulcanization accelerators, pigments or dyes, carbon black, carbon nanotubes, glass fibers, An oxirane ring-containing compound, carboxymethyl cellulose, or the like may be added. These can be used alone or in combination of two or more.

  The paint for a lithium ion secondary battery separator of the present invention is a paint applied to a porous substrate. Next, the porous substrate will be described.

  The porous substrate is not particularly limited as long as it has a fine porous structure. Porous substrate strength, strength distribution profile, breaking strength, elongation, hardness, elongation retention under certain conditions, piercing elongation, breaking elongation, thermal shrinkage under certain conditions, certain ratio ( %) Shrinkage temperature, curvature, Young's modulus, tear strength, pore diameter, average pore diameter measured by silver press-in method, average fiber thickness, basis weight, fiber diameter, porosity, thickness, Thickness deviation, air permeability resistance, organic solvent permeability, organic solvent penetration rate, organic solvent penetration time change rate, solubility in organic solvent, swelling property in organic solvent, gel fraction, glass transition temperature, melt flow rate, Various properties such as intrinsic viscosity, molecular weight, molecular weight distribution, melting point, softening point, crystallinity, draw ratio, adhesive strength, dynamic friction coefficient, surface roughness, cushion ratio, loop stiffness, and combinations of various properties And its ratio, when processed under certain conditions Including retention of the various properties can be formed of the known. Furthermore, such various characteristics, combinations and ratios of various characteristics, retention ratio of various characteristics when processed under certain conditions, processing suitability to the separator, storage stability as a separator, stability, safety, Durability, adhesion, chemical resistance, flame resistance, heat resistance, shape retention, wrinkle suppression, breathability, electrolyte penetration, electrolyte resistance, shutdown, foreign matter resistance, piercing characteristics, separator Suitable for processing when incorporated in lithium ion secondary batteries, storage stability, stability, safety, durability, chemical resistance, flame resistance, heat resistance of lithium ion secondary batteries when made into lithium ion secondary batteries, What is necessary is just to design suitably considering various performances, such as shape retainability, shape retainability, an output characteristic, and a battery characteristic.

  In order to exhibit the effects of the present invention more remarkably, the form of the porous substrate is preferably a microporous film, a nonwoven fabric, a woven or knitted fabric, a nanofiber fabric, paper or the like, more preferably a microporous film or a nonwoven fabric, A microporous film is particularly preferred. These may be used alone or in combination. Examples of the material for the porous substrate include polyolefin resins, polyester resins, polyamide resins, aramid resins, polyarylene sulfide resins, and cellulose resins. Of these, polyolefin resins are preferred, and polypropylene resins are preferred. A resin is more preferable. Here, “˜resin” means a resin composition containing “˜resin”, “˜resin” alone, “˜resin” copolymerized resin composition, and “˜resin” are blended. Resin compositions and the like.

  Examples of the microporous film made of a polyolefin-based resin include, for example, polyolefin first and second microporous layers described in International Publication WO10 / 104077, microporous film containing polypropylene described in JP2013-023673, and JP Polyolefin microporous membrane described in 2011-233542, polyolefin microporous membrane described in International Publication WO10 / 070930, polyolefin microporous membrane described in International Publication WO09 / 136648, JP2013-032505A Porous polyolefin film, porous resin film containing polyolefin resin described in JP2012-229406, porous polypropylene film described in JP2012-177106, poly described in JP2012-131990 Refin-based porous film, porous polypropylene film described in JP2012-072380, polyolefin-based porous resin film described in JP2013-014103A, porous polypropylene film described in JP2012-007156A, No. 2011-171290, a porous polyolefin film containing a polypropylene resin described in JP 2011-168048 A, a polyolefin porous film described in International Publication No. WO 10/008003, and International Publication No. WO 07/046226 A microporous film mainly composed of the polypropylene described above, a polyolefin porous film described in JP2013-026165A, a polyolefin microporous film described in JP2011-065850A It is possible to use the known ones are exemplified etc.. Among these, a polypropylene microporous film having a high β crystal fraction obtained by using a β crystal method or a β crystal nucleating agent is preferable.

  Examples of the nonwoven fabric made of polyolefin resin include, for example, a polyolefin nonwoven fabric described in JP 2011-210701 A, a nonwoven fabric using polypropylene fibers described in JP 2011-070904 A, and a composite described in JP 2006-233691 A. It is possible to use known materials exemplified by non-woven fabrics in which the fusion component of high-strength polypropylene fibers is fused, non-woven fabrics described in International Publication WO 04/073094, and the like.

  Examples of the nonwoven fabric made of polyester resin include, for example, a wet nonwoven fabric described in JP2012-138235A, a nonwoven fabric containing polyester short fibers described in JP2010-238448A, and International Publication WO06 / 123811 It is possible to use known materials exemplified by non-woven fabric made of polyethylene terephthalate.

  Next, a method for laminating a porous layer by applying a coating for a lithium ion secondary battery separator on at least one surface of a porous substrate will be described. The coating material for a lithium ion secondary battery separator of the present invention is applied to at least one surface of a porous substrate and then dried by partially or entirely drying an aqueous medium in the applied coating material for a lithium ion secondary battery separator. A quality layer can be formed.

  As a method for applying and drying the separator paint, known methods such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating, etc. Uniform coating on the porous substrate surface, after setting at around room temperature as required, and then drying or partially heating the aqueous medium by subjecting it to heat treatment for drying. That is, the porous layer can be formed in close contact with the surface of the porous substrate. Although a drying temperature is not specifically limited, it can dry favorably in the range of 40-150 degreeC, and the range of 50-120 degreeC is more preferable. In drying, it is preferable to dry all of the aqueous medium from the viewpoint of improving adhesion and heat resistance. Further, after drying, an aging treatment such as an aging treatment may be performed.

  In addition, the surface activation process may be previously performed to the application surface of the porous base material before application | coating of a coating material. Examples of the surface activation treatment include corona discharge treatment, flame plasma treatment, atmospheric pressure plasma treatment, low pressure plasma treatment, ozone treatment, electron beam irradiation treatment, ultraviolet irradiation treatment, chemical treatment, solvent treatment, anchor coat treatment, and primer treatment. Etc.

  The lithium ion secondary battery separator of the present invention can be obtained by laminating the porous layer on at least one surface of the porous substrate by the method as described above. The thickness of the porous layer is preferably in the range of 0.5 to 10 μm, more preferably 1 to 9 μm, particularly preferably 2 to 8 μm, and further preferably 3 to 7 μm. . If the thickness is less than 0.5 μm, sufficient heat resistance tends not to be obtained. On the other hand, if the thickness exceeds 10 μm, the permeability and permeability of the electrolytic solution may deteriorate, and the battery performance tends to deteriorate.

  Young's modulus, tear strength, curvature, pore diameter, average pore diameter, porosity, thickness deviation, air permeability resistance, glass transition temperature (Tg), intrinsic viscosity, crystal in porous layer Various characteristics such as degree of conversion, draw ratio, adhesive strength, dynamic / static friction coefficient, surface roughness, cushion ratio, loop stiffness, etc., combinations and ratios of various characteristics, and various characteristics when processed under certain conditions Retention rate, etc., as separator, storage stability, stability, safety, durability, adhesion, chemical resistance, flame resistance, heat resistance, shape retention, wrinkle suppression, breathability, electrolyte penetration, Electrolytic solution resistance, shutdown property, foreign matter resistance, piercing properties, processing suitability when incorporating a separator into a lithium ion secondary battery, storage stability of lithium ion secondary battery when used as a lithium ion secondary battery, stability, Safety, resistance Gender, chemical resistance, flame retardancy, heat resistance, shape retention, shape retention, output characteristics, may be suitably designed in consideration of various properties such as cell characteristics.

  In the lithium ion secondary battery separator of the present invention, another functional layer other than the porous substrate or the porous layer may be provided on at least a part of the surface. As the functional layer, for example, a layer made of a known additive or stabilizer, an antistatic layer, an easy-adhesion layer, a sliding layer, a leveling layer, a flame retardant layer, a layer for improving compatibility with an electrolyte, an antioxidant layer , And a softening layer. The thickness of the functional layer may be determined in consideration of suitability as a packaging material and processability when laminated, and is not particularly limited.

  In the lithium ion secondary battery separator of the present invention, strength, strength distribution profile, breaking strength, elongation, elongation retention under certain conditions, piercing elongation, breaking elongation, Young's modulus, tear strength, constant ratio ( %) Shrinkage temperature, curvature, pore diameter, average pore diameter measured by silver press-in method, average fiber thickness, basis weight, fiber diameter, porosity, thickness, thickness deviation, air permeability resistance , Glass transition temperature (Tg), melt flow rate, intrinsic viscosity, molecular weight, molecular weight distribution, melting point, softening point, crystallinity, draw ratio, adhesive strength, dynamic / static coefficient of friction, surface roughness, cushion rate, Various characteristics such as loop stiffness, combinations and ratios of various characteristics, retention ratios of various characteristics when treated under certain conditions, combinations and ratios of various characteristics of porous substrate and various characteristics of porous layer, etc. , Separator Storage stability, stability, safety, durability, adhesion, chemical resistance, flame resistance, heat resistance, shape retention, wrinkle suppression, breathability, electrolyte penetration, electrolyte resistance, Shutdown, foreign matter resistance, piercing characteristics, proper processing when incorporating a separator into a lithium ion secondary battery, storage stability, stability, safety, durability of a lithium ion secondary battery It may be designed as appropriate in consideration of various performances such as chemical resistance, flame retardancy, heat resistance, shape retention, output characteristics, and battery characteristics.

  The lithium ion secondary battery separator of the present invention is excellent in the adhesion and heat resistance between the porous substrate and the porous layer, and even when used under conditions with changes in atmospheric pressure, Since it has the property which is excellent in adhesiveness with a porous layer, it can be used suitably as a vehicle-mounted lithium ion secondary battery separator. Here, the vehicle-mounted lithium ion secondary battery means a lithium ion secondary battery that is mounted on a vehicle and serves as a power source for functions and power of the vehicle. A vehicle refers to a vehicle body that is supported by wheels and is movable by rotation of the wheels, with all or a part of the vehicle body, and the wheels may be provided with tires, caterpillars, and the like. Specific examples of the vehicle include an electric automobile, an electric motorcycle, an electric bicycle, an electric bus, an electric truck, a train, an electric forklift, a reach forklift, a construction machine vehicle, and an airplane.

  The present invention will be specifically described by the following examples, but the present invention is not limited thereto.

1. Properties of modified polyolefin resin (1) Monomer composition
^It calculated | required from the <1> H-NMR analyzer (the JEOL company make, ECA500, 500MHz). Tetrachloroethane (d ₂ ) was used as a solvent and measurement was performed at 120 ° C.
(2) Melt flow rate (MFR)
According to the method described in JIS K7210: 1999, the measurement was performed at 190 ° C. under a load of 2160 g.
(3) Swelling rate and dissolution rate in 50 ° C. electrolyte solution 2 g of modified polyolefin resin (approximately 4 mm square pellet) dried in a vacuum at 50 ° C. for 24 hours in a 50 mL volume container, and 40 g of electrolyte solution (ethylene carbonate / (Liquid obtained by dissolving 1M lithium hexafluorophosphate in a mixed solution of diethyl carbonate / ethyl methyl carbonate = 1/1/1 (volume ratio), hereinafter, an electrolyte of the present composition is used in the comparative example) And the container was sealed, and this was placed in a thermostat set at 50 ° C. and kept warm for 14 days. After the heat retention, the modified polyolefin resin (A) was recovered from the container, and the surface electrolyte was lightly wiped with a paper cloth, and then the mass (g) of the modified polyolefin resin was quickly measured (this mass (g) was determined as X ). Subsequently, this modified polyolefin resin was vacuum-dried at 50 ° C. for 48 hours, and the mass (g) of the modified polyolefin resin after vacuum drying was measured (this mass (g) was defined as Y). From these values, the swelling rate was obtained from the following formula (I), and the dissolution rate was obtained from the following formula (II). The test was carried out 5 times and evaluated with an average of 5 times.
Swelling rate (%) = [(XY) / Y] × 100 (I)
Dissolution rate (%) = [(2-Y) / 2] × 100 (II)
(4) Melting point It measured by DSC method using Perkin Elmer DSC7.
(5) Hardness (Shore D)
The measurement was performed according to the method described in ISO-868.

2. Characteristics of modified polyolefin resin aqueous dispersion (1) pH
The pH at a temperature of 20 ° C. was measured using a pH meter (“F-52” manufactured by Horiba, Ltd.).
(2) Number average particle diameter of modified polyolefin resin It was determined using a Microtrac particle size distribution meter (manufactured by Nikkiso Co., Ltd., UPA150, MODEL No. 9340, dynamic light scattering method). The refractive index of the resin used for particle diameter calculation was 1.50.

3. Characteristics of inorganic particles (B) (1) Average particle size of primary particles The photograph obtained with an electron microscope was measured with a particle size measuring instrument.

4). Characteristics of lithium ion secondary battery separator (1) Heat resistance (125 ° C heat shrinkage)
A lithium ion secondary battery separator was cut into a rectangular shape with a length of 150 mm and a width of 10 mm in the MD direction and the TD direction to obtain a test piece. A marked line was drawn on the test piece at intervals of 100 mm, and a heat treatment was performed by placing it in a hot air oven heated to 125 ° C. with a 3.5 g weight suspended for 1 hour. After the heat treatment, the test piece was taken out and allowed to stand at room temperature for 24 hours, the distance between the marked lines was measured, the thermal shrinkage rate was calculated from the change in the distance between the marked lines before and after heating, and used as an index of dimensional stability. For each test piece, three samples were carried out in the MD direction and TD direction, and the average value was evaluated.

(2) Adhesiveness The entire 100 mm × 100 mm square lithium ion secondary battery separator was wound around a cylindrical metal rod having a diameter of 8 mm × 200 mm, and immediately unwound. After repeating this winding and unwinding operation 10 times, cellophane tape (manufactured by Nichiban Co., "TF-12") is applied to the surface of the porous layer of the lithium ion secondary battery separator, and the cellophane tape is peeled off at once. The peeled part of the cellophane tape was visually observed to evaluate the degree of migration of the porous layer to the cellophane tape. The test was conducted 10 times and evaluated according to the following criteria.
3: A porous layer cannot be confirmed at all in 10 tests.
2: A porous layer can be confirmed 1 or 2 times during 10 tests.
1: The porous layer can be confirmed 3 times or more during 10 tests.

(3) Resistance to atmospheric pressure change A 0.6 L electrolyte solution was charged into a sealable 1 L capacity vessel equipped with a vacuum gauge, and then a 70 mm × 70 mm square lithium ion secondary battery separator was charged. At this time, the four corners of the separator were fixed with weights made of polytetrafluoroethylene so that the entire lithium ion secondary battery separator was immersed in the electrolytic solution. The vessel was sealed except for a tube connected to the vacuum pump from the vessel (connected to the vacuum pump via a cooling trap), and in this state, the vessel was placed in a thermostat set at 45 ° C. and allowed to stand for 4 hours. Subsequently, the vacuum pump was operated, the inside of the container was reduced to 30 kPa (abs) and maintained for 5 minutes, and then released to atmospheric pressure (101.3 kPa (abs)). Thereafter, decompression and release under the same conditions were repeated 200 times continuously (approximately 22 hours were required to repeat 200 times). Next, the separator was collected from the container, dried at 80 ° C. for 3 hours, and then cellophane tape (manufactured by Nichiban Co., Ltd.) on the surface of the porous layer near the center of the separator (other than the portion fixed with a weight made of polytetrafluoroethylene). , "TF-12") was attached, the cellophane tape was peeled off at once, the peeled part of the cellophane tape was visually observed, and the degree of migration of the porous layer to the cellophane tape was evaluated. The test was conducted 10 times and evaluated according to the following criteria.
5: No porous layer can be confirmed even after 10 tests.
4: A porous layer can be confirmed once in 10 tests.
3: A porous layer can be confirmed twice during 10 tests.
2: A porous layer can be confirmed 3 times during 10 tests.
1: The porous layer can be confirmed 4 times during 10 tests.
0: The porous layer can be confirmed 5 times or more during 10 tests.

(4) Resistance to electrolytic solution 0.6 L of electrolytic solution was charged into a sealable 1 L capacity container, and then a 70 mm × 70 mm square lithium ion secondary battery separator was charged. At this time, the four corners of the separator were fixed with weights made of polytetrafluoroethylene so that the entire lithium ion secondary battery separator was immersed in the electrolytic solution. The container was sealed, and in this state, the container was placed in a thermostat set at 45 ° C. and allowed to stand for 26 hours. Next, the separator was collected from the container, dried at 80 ° C. for 2 hours, and then cellophane tape (manufactured by Nichiban Co., Ltd.) on the surface of the porous layer near the center of the separator (other than the portion fixed with a weight made of polytetrafluoroethylene). , "TF-12") was attached, the cellophane tape was peeled off at once, the peeled part of the cellophane tape was visually observed, and the degree of migration of the porous layer to the cellophane tape was evaluated. The test was carried out 10 times, and (3) evaluation was performed based on the same standard as the resistance to changes in atmospheric pressure.

(5) Battery characteristics A positive electrode in which an aluminum foil provided with lithium cobalt oxide (LiCoO ₂ ) with a thickness of 40 μm on one side is punched into a circle with a diameter of 15.9 mm, and copper with graphite provided on a side with a thickness of 50 μm A negative electrode obtained by punching a foil into a circular shape with a diameter of 16.2 mm and a lithium ion secondary battery separator punched with a diameter of 24 mm were prepared. Next, with the configuration in which the active material surface of the positive electrode faces the porous layer surface of the separator, and the porous base material surface of the separator faces the active material surface of the negative electrode, the positive electrode, the separator, and the negative electrode are stacked in this order, with a lid In a stainless steel container (HS cell manufactured by Hosen Co., Ltd.) with the negative electrode on the lower side and the positive electrode on the upper side. Lithium ion secondary battery in which an electrolytic solution is poured into this container and sealed with a lid (the lid and the container are insulated. The negative electrode copper foil and the container are in contact with the positive electrode aluminum foil and the lid). Was made. The manufactured lithium ion secondary battery was repeatedly charged and discharged 100 times in an atmosphere of 25 ° C., with charging at 0.3 mA up to 4.2 V for 12 hours and discharging at 3 mA up to 2.7 V. The capacity retention rate (%) was determined from the following formula (III). The test was performed 10 times, and the average of 10 capacity retention rates (%) was evaluated according to the following criteria.
Capacity retention (%) = [(100th discharge capacity) / (initial discharge capacity)] × 100 (III)
3: 85% or more 2: 80% or more and less than 85% 1: less than 80%

<Production of maleated polyolefin resins P1 to P8, P10, P11>
First, a maleated polyolefin resin as a raw material for the modified polyolefin resin (A) was produced with reference to British Patent No. 2911745, US Pat. No. 4,617,366 and US Pat. No. 4,644,044. The resulting maleated polyolefin resins were designated as “P1” to “P8”, “P10”, and “P11”. Table 1 shows the characteristics of “P1” to “P8”, “P10”, and “P11”.

<Manufacture of modified polyolefin resins PO1 to PO8, PO10, PO11>
Into a 1 liter separable flask equipped with a thermometer, a stirrer, a liquid injector, and a Dimroth, 250 g of the maleated polyolefin resin of any of the above “P1” to “P8”, “P10”, “P11”, toluene The flask was put into a 170 ° C. oil bath with the stirrer rotated at 100 rpm. After a few minutes, boiling of toluene was confirmed, but the generated steam was refluxed into the flask through the Dimroth. After a few minutes, it was confirmed that the maleated polyolefin resin was completely dissolved, and then N, N-dimethylaminopropylamine [[H ₂ N— (CH ₂ ) ₃ —N (CH ₃ ) ₂ ] as an amino compound. Then, 40 g of “DMAPA” is added. The temperature in the flask after the addition was 115 ° C., and this state was maintained to perform an imidization reaction. After 30 minutes, the mounting direction of the Dimroth was changed, and the pressure was further gradually reduced, and toluene and unreacted amino compound in the flask were removed by distillation. After confirming that no vapor of toluene and unreacted amino compound was generated from the inside of the flask, the pressure was further released for 10 minutes while maintaining the reduced pressure of 4 kPa (abs), the stirrer was stopped, the flask was taken out of the oil bath, An inner modified polyolefin resin (A) was obtained. The modified polyolefin resins (A) obtained using “P1” to “P8”, “P10”, and “P11” as raw materials were referred to as “PO1” to “PO8”, “PO10”, and “PO11”, respectively. Table 2 shows the characteristics of “PO1” to “PO8”, “P10”, and “P11”.

<Production of polyolefin copolymer P9 other than maleated polyolefin resin>
First, an ethylene-ethyl acrylate copolymer is obtained by subjecting an ethylene-ethyl acrylate copolymer to hydrolysis and thermal degradation treatment with reference to the method described in JP-A-60-79008. Manufactured. This polyolefin copolymer was designated as “P9”. The characteristics of “P9” are shown in Table 1.

<Manufacture of modified polyolefin resin PO9>
A 1 liter separable flask equipped with a thermometer, stirrer, and Dimroth was charged with 150 g of “P9”, 1 g of paratoluenesulfonic acid as a catalyst, 400 g of xylene, and 40 g of DMAPA as an amino compound. The flask was put into an oil bath at 170 ° C. while being rotated at 100 prm. After 10 minutes, “P9” in the flask was completely dissolved, and the temperature in the flask was 145 ° C. This state was maintained, and after 17 hours, the attachment direction of the Dimroth was changed, and the pressure was further gradually reduced. The xylene and the unreacted amino compound in the flask were removed by distillation. After confirming that the vapors of xylene and unreacted amino compound are no longer generated from the inside of the flask and holding the reduced pressure of 4 kPa (abs) for 10 minutes, release the pressure, stop the stirrer, take out the flask from the oil bath, An amino group-containing polyolefin resin was obtained. The obtained amino group-containing polyolefin resin was designated as “PO9”. The characteristics of “PO9” are shown in Table 2.

<Production of aqueous dispersion of modified polyolefin resins PO1 to PO9>
In a sealable pressure-resistant 1 liter glass container equipped with a heater equipped with a stirrer, 60 g of modified polyolefin resin of “PO1” to “PO9”, 90 g of isopropanol, 3 g of formic acid as a neutralizing agent and 147 g of distilled water When stirring was performed at a rotation speed of the stirring blade of 300 rpm, it was confirmed that no precipitation of resin particles was observed at the bottom of the container, and the mixture was in a floating state. Therefore, while maintaining this state, the heater was turned on and heated after 10 minutes. Then, the system temperature was kept at 140 to 145 ° C. and further stirred for 30 minutes. Thereafter, the glass container is placed in a water bath, cooled to room temperature (about 25 ° C.) with stirring at a rotational speed of 300 rpm, and then filtered under pressure through a 300 mesh stainless steel filter (wire diameter: 0.035 mm, plain weave). 2 MPa) to obtain an aqueous dispersion of a milky white uniform modified polyolefin resin. Table 2 shows the characteristics of the obtained aqueous dispersions of “PO1” to “PO9”.

<Production of aqueous dispersion of modified polyolefin resins PO10 and PO11>
The modified polyolefin resin “PO1” except that “PO10” and “PO11” were used as the modified polyolefin resins, the amount of formic acid as a neutralizing agent was changed from 3 g to 6 g, and the amount of distilled water was changed from 147 g to 144 g. ”To“ PO9 ”in the same manner as in the production of the aqueous dispersion, a milky white uniform modified polyolefin resin aqueous dispersion was obtained. The properties of the obtained aqueous dispersions of “PO10” and “PO11” are shown in Table 2.

<Manufacture of microporous film made of polypropylene resin>
93.7% by mass of homopolypropylene [MFR 15 g / 10 min (230 ° C., 2.16 Kg), density 0.9 g / cm ³ ], 6.0% by mass of ethylene-octene-1 copolymer [MFR 18 g / 10 min (190 ° C., 2.16 Kg)], a mixture obtained by dry blending 0.3% by mass of N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide was supplied to a twin screw extruder and melted at 290 ° C. It knead | mixed and pelletized. Next, this pellet is supplied to a single screw extruder and melt extruded at 210 ° C. After removing foreign matter with a 20 μm cut sintered filter, the pellet is discharged from a T die onto a cast drum whose surface temperature is controlled to 115 ° C. The unstretched sheet was obtained by indirect intrusion to the drum for 12 seconds (hereinafter, the surface in contact with the drum is referred to as “drum surface”).

  Next, the film was preheated with a 115 ° C. ceramic roll and stretched 5 times in the MD direction of the film. After cooling, the end was then held in a tenter type stretching machine with a clip and introduced into a tenter type stretching machine at 145 ° C. in the TD direction seven times. As it was, heat setting was carried out at 150 ° C. for 5 seconds while relaxing 10% in the TD direction to obtain a polypropylene-based resin microporous film (hereinafter sometimes referred to as “PP microporous”) having a thickness of 20 μm. The air permeability of the obtained microporous film was 210 s / 100 ml, the 125 ° C. heat shrinkage rate in the MD direction was 3.8%, and the 125 ° C. heat shrinkage rate in the TD direction was 12.0%.

<Manufacture of microporous film made of polyethylene resin>
5% by mass of an ultrahigh molecular weight polyethylene resin having a mass average molecular weight of 1.3 million and 95% by mass of a high density polyethylene resin having a mass average molecular weight of 250,000 were dry blended. This was supplied to a twin screw extruder set at 210 ° C., and liquid paraffin was supplied in an amount 2.4 times that of polyethylene resin from the side feeder of the twin screw extruder, and melt kneading was performed. Next, a composition composed of polyethylene resin and liquid paraffin was extruded through a T-die installed in an extruder to a 10 ° C. cooling roll to obtain a sheet (hereinafter referred to as “roll”). Surface "). This sheet was simultaneously biaxially stretched by a tenter stretching machine set at 115 ° C. so as to be 4.5 times in both the MD direction and the TD direction. The obtained stretched film was immersed in methylene chloride at 25 ° C., washed for 10 minutes, and then air-dried at 40 ° C. Subsequently, it extended | stretched again so that it might become 1.1 time in the TD direction using the batch-type extending | stretching machine set to 130 degreeC. In this state, heat setting was performed at 130 ° C. for 10 minutes to obtain a polyethylene resin microporous film having a thickness of 20 μm (hereinafter sometimes referred to as “PE microporous”). The air permeability of the obtained microporous film was 200 s / 100 ml, the 125 ° C. heat shrinkage rate in the MD direction was 4.2%, and the 125 ° C. heat shrinkage rate in the TD direction was 6.6%.

<Example 1>
An aqueous dispersion of “PO1” was used as the aqueous dispersion of the modified polyolefin resin, and alumina particles having an average primary particle diameter of 0.6 μm were used as the inorganic particles. The mass ratio between the solid content of the modified polyolefin resin in the aqueous dispersion of the modified polyolefin resin and the alumina particles as inorganic particles is the mass ratio shown in Table 3 (modified polyolefin resin / inorganic particles = 15/85). Further, distilled water was added so that the solid content concentration of the coating material was 10% by mass, and this was mixed and stirred at room temperature to obtain a coating material for a lithium ion secondary battery separator.

  Next, the obtained lithium ion secondary battery separator coating material was applied to the PP microporous drum surface using a wire bar so that the thickness of the porous layer after drying was 4 μm, and dried at 100 ° C. for 1 minute. Thus, a porous layer was formed to produce a lithium ion secondary battery separator.

<Examples 2-8, 12, 13, Comparative Example 1>
The same procedure as in Example 1 was conducted except that the aqueous dispersion of the modified polyolefin resin shown in Table 3 was used as the type of the aqueous dispersion of the modified polyolefin resin, and the paint for lithium ion secondary battery separator and the lithium ion secondary A battery separator was obtained.

<Examples 9 and 10>
The same operation as in Example 1 was performed except that the mass ratio of the solid content of the modified polyolefin resin and the alumina particles as inorganic particles was adjusted to the mass ratio shown in Table 3. A paint for a lithium ion secondary battery separator and a lithium ion secondary battery separator were obtained.

<Example 11>
Using the paint for a lithium ion secondary battery separator obtained in Example 1, this was applied to the PE microporous roll surface using a wire bar so that the thickness of the porous layer after drying was 4 μm. The porous layer was formed by drying at 100 ° C. for 1 minute to produce a lithium ion secondary battery separator.

<Reference Example 1>
Polyoxyethylene polyoxypropylene glycol (nonionic emulsifier), which is a non-volatile dispersion aid component, is added to the lithium ion secondary battery separator paint obtained in Example 1 with respect to the solid content in the paint. 0.07 mass% was added, mixed and stirred at room temperature to obtain a paint for a lithium ion secondary battery separator.

  Next, the obtained lithium ion secondary battery separator coating material was applied to the PP microporous drum surface using a wire bar so that the thickness of the porous layer after drying was 4 μm, and dried at 100 ° C. for 1 minute. Thus, a porous layer was formed to produce a lithium ion secondary battery separator.

  The evaluation results of the lithium ion secondary battery separators obtained in Examples 1 to 13, Comparative Example 1, and Reference Example 1 are shown in Table 3.

  Like Examples 1-13, the lithium ion secondary battery separator obtained by apply | coating the coating material for lithium ion secondary battery separators of this invention to a porous base material was excellent in various characteristics. On the other hand, since the modified polyolefin resin did not have the structure prescribed | regulated to this invention in the comparative example 1, those characteristics were inferior.

  In Examples 4 to 8, the swellability and solubility of the modified polyolefin resin (A) deviated from the optimum range of the present invention, and thus the resistance to changes in atmospheric pressure was slightly inferior.

  In the reference example, since the non-volatile dispersion aid was contained in the lithium ion secondary battery separator paint, there was a tendency to be slightly inferior to the examples.

Claims (13)

A modified polyolefin resin (A) having an N-substituted maleimide unit in which a N-substituent is a substituent represented by the following formula (1), and an inorganic particle (B), which is a coating applied to a porous substrate Is a water-based dispersion dispersed in an aqueous medium.
^{_{- (CH 2) n NR 1}} R 2 (1)
(Wherein, R ¹ and R ² are alkyl groups of 1 to 5 carbon atoms, at least one selected from a hydroxyalkyl group having 1 to 5 carbon atoms or H,, n represents an integer of 1 to 5 ) The lithium ion secondary battery according to claim 1, wherein at least a part of the N-substituent of the N-substituted maleimide unit of the modified polyolefin resin (A) is a substituent represented by the following formula (2). Paint for separator.
^{_{- (CH 2) n N +}} R 1 R 2 R 3 · X - (2)
Wherein R ¹ and R ² are at least one selected from an alkyl group having 1 to 5 carbon atoms, a hydroxyalkyl group having 1 to 5 carbon atoms, or H, and R ³ is H or a quaternization reaction. The residue of the quaternizing agent introduced by X, X ⁻ represents an anionic counterion, and n represents an integer of 1 to 5.)   3. The coating material for a lithium ion secondary battery separator according to claim 1, wherein the content of the N-substituted maleimide unit in the modified polyolefin resin (A) is 0.1 to 5 mol%.   4. The coating material for a lithium ion secondary battery separator according to claim 1, wherein the swelling ratio of the modified polyolefin resin (A) to the 50 ° C. electrolytic solution is in the range of 3 to 35%.   The paint for a lithium ion secondary battery separator according to any one of claims 1 to 4, wherein the modified polyolefin resin (A) has a dissolution rate in a 50 ° C electrolyte of 5% or less.   The coating material for a lithium ion secondary battery separator according to any one of claims 1 to 5, which is substantially free of a non-volatile dispersion aid.   The number average particle diameter of modified polyolefin resin (A) is 0.5 micrometer or less, The coating material for lithium ion secondary battery separators in any one of Claims 1-6 characterized by the above-mentioned.   The mass ratio of the modified polyolefin resin (A) and the inorganic particles (B) is in the range of (A) / (B) = 70/30 to 1/99, The coating material for lithium ion secondary battery separators as described.   The lithium ion secondary according to any one of claims 1 to 8, wherein the porous substrate has at least one type selected from a microporous film, a nonwoven fabric, a woven / knitted fabric, a nanofiber fabric, and paper. Battery separator paint.   The material for a porous substrate is a polyolefin-based resin, and the paint for a lithium ion secondary battery separator according to any one of claims 1 to 9.   The paint for a lithium ion secondary battery separator according to any one of claims 1 to 10, wherein the paint is applied to a vehicle-mounted lithium ion secondary battery separator.   The lithium ion secondary battery separator by which the porous layer formed by apply | coating the coating material for lithium ion secondary battery separators in any one of Claims 1-11 was laminated | stacked on the at least single side | surface of the porous base material. A lithium ion secondary battery comprising the lithium ion secondary battery separator according to claim 12.