JP5751414B2 - Slurry composition for secondary battery porous membrane - Google Patents

Description

  The present invention relates to a slurry composition for a secondary battery porous membrane, and more specifically, a secondary battery that is formed on the surface of an electrode or separator of a lithium ion secondary battery and has high flexibility and can contribute to improvement of battery cycle characteristics. The present invention relates to a slurry composition for a secondary battery porous membrane for producing a porous membrane. The present invention also relates to a secondary battery electrode, a secondary battery separator and a secondary battery provided with such a secondary battery porous membrane.

  Among batteries in practical use, lithium ion secondary batteries exhibit the highest energy density, and are often used particularly for small electronics. In addition to small-sized applications, development for automobiles is also expected. Among them, there is a demand for extending the life of lithium ion secondary batteries and further improving safety.

  A lithium ion secondary battery generally includes a positive electrode and a negative electrode including an electrode active material layer carried on a current collector, a separator, and a non-aqueous electrolyte. The electrode active material layer usually contains an electrode active material having an average particle diameter of about 5 to 50 μm and a binder for the electrode active material layer. The electrode is usually produced by applying an electrode active material layer slurry containing a powdered electrode active material on a current collector to form an electrode active material layer. Moreover, as a separator for isolating a positive electrode and a negative electrode, the very thin separator about 10-50 micrometers in thickness is normally used. A lithium ion secondary battery is manufactured through a lamination process of an electrode and a separator, a cutting process of cutting into a predetermined electrode shape, and the like.

  However, while passing through this series of manufacturing steps, the electrode active material may be detached from the electrode active material layer, and a part of the detached electrode active material may be contained in the battery as foreign matter. Such a foreign substance has a particle diameter of about 5 to 50 μm and is about the same as the thickness of the separator, and thus may penetrate the separator in the assembled battery and cause a short circuit.

  Further, heat is generated when the battery is operated. As a result, the organic separator made of a stretched resin such as a stretched polyethylene resin is also heated. An organic separator made of a stretched resin generally tends to shrink even at a temperature of 150 ° C. or lower, and easily causes a battery short circuit. In addition, when a sharply shaped protrusion such as a nail penetrates the battery (for example, during a nail penetration test), there is a tendency that a short circuit occurs instantaneously, reaction heat is generated, and the short circuit part expands.

  Therefore, in order to solve such problems, it has been proposed to provide a porous film for a secondary battery including non-conductive particles such as an inorganic filler on the surface of the electrode or the organic separator or inside the organic separator. By providing such a porous film, the strength of the organic separator or electrode is increased, and safety is improved.

  As a technique related to the porous film as described above, for example, techniques described in Patent Document 1 and Patent Document 2 are known. Patent Document 1 describes a porous membrane for a secondary battery composed of alumina and an acrylonitrile-modified rubber binder. Patent Document 2 describes a porous film for a secondary battery containing polyacrylonitrile.

JP 2005-190912 A JP 2003-59480 A

The porous film is usually obtained by preparing a slurry composition in which the material of the porous film is dispersed, and applying and drying the slurry composition. However, according to the study of the present inventor, the porous membrane for a secondary battery described in Patent Document 1 does not have sufficient strength, and the alumina powder may be detached (powder off). As a result, the high-temperature cycle characteristics of the secondary battery may be deteriorated. Moreover, since the porous film for secondary batteries described in Patent Document 2 is inferior in flexibility, the high-temperature cycle characteristics of the secondary battery may be deteriorated.
Then, an object of this invention is to provide the slurry composition for secondary battery porous films used in order to manufacture the secondary battery excellent in the high temperature cycling characteristic.

The gist of the present invention aimed at solving such problems is as follows.
(1) consisting of non-conductive particles and a binder containing a hydrogenated nitrile polymer and polyacrylonitrile,
A slurry composition for a secondary battery porous membrane, wherein the hydrogenated nitrile polymer has an iodine value of 3 to 60 mg / 100 mg.

(2) The slurry composition for a secondary battery porous membrane according to (1), wherein the hydrogenated nitrile polymer is polymerized and hydrogenated using water as a solvent.

(3) The secondary battery porous membrane according to (1) or (2), wherein the hydrogenated nitrile polymer includes a linear alkylene polymer unit obtained by hydrogenating a polymer unit derived from a conjugated diene monomer having 4 or more carbon atoms. Slurry composition.

(4) The slurry composition for a secondary battery porous membrane according to any one of (1) to (3), wherein the binder further comprises a polymer unit having a hydrophilic group.

(5) The slurry composition for a secondary battery porous film according to any one of (1) to (4), wherein the nonconductive particles are inorganic oxide particles or organic particles.

(6) A secondary battery porous membrane obtained by forming the slurry composition for a secondary battery porous membrane according to any one of (1) to (5) above into a film shape and drying.

(7) A secondary battery electrode, wherein a current collector, an electrode active material layer, and a porous film are laminated in this order, and the porous film is the secondary battery porous film according to (6) .

(8) A secondary battery separator, wherein an organic separator and a porous film are laminated, and the porous film is the secondary battery porous film according to (6).

(9) A secondary battery including a positive electrode, a negative electrode, an organic separator, and an electrolyte solution,
A secondary battery in which the secondary battery porous film according to (6) is laminated on any of the positive electrode, the negative electrode, and the organic separator.

  According to the slurry composition for a secondary battery porous membrane of the present invention, since a specific binder is included, it is excellent in dispersibility of non-conductive particles, and a homogeneous and uniform porous membrane can be formed. Since the porous film contains a specific binder, there is almost no detachment (powder off) of non-conductive particles, and as a result, a secondary battery excellent in high-temperature cycle characteristics and reliability can be obtained.

[Slurry composition for secondary battery porous membrane]
The slurry composition for a secondary battery porous membrane of the present invention (hereinafter sometimes referred to as “porous membrane slurry”) may be described as a secondary battery porous membrane (hereinafter referred to as “porous membrane”). .) Is a slurry composition. The porous film slurry is composed of non-conductive particles and a binder having a specific composition, and the non-conductive particles, the binder and optional components are uniformly dispersed in a solvent as a solid content.

(Non-conductive particles)
It is desired that the non-conductive particles used in the present invention exist stably in a use environment of a secondary battery (such as a lithium ion secondary battery or a nickel hydride secondary battery) and are electrochemically stable.

As the non-conductive particles, for example, various inorganic particles, organic particles, and other particles can be used. Among these, inorganic oxide particles or organic particles are preferable, and organic particles are more preferably used because there are few contaminations such as metal ions in the particles (hereinafter sometimes referred to as “metal foreign matter”). The metal ions in the particles may form a salt in the vicinity of the electrode, which may cause an increase in the internal resistance of the electrode and a decrease in the cycle characteristics of the secondary battery. In addition, as other particles, the surface of conductive metal such as carbon black, graphite, SnO ₂ , ITO, metal powder and fine powder of conductive compound or oxide is surface-treated with a non-electrically conductive substance. By doing so, particles having electrical insulation properties can be mentioned. In the present invention, two or more of the above particles may be used in combination as non-conductive particles.

Examples of inorganic particles include inorganic oxide particles such as aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, BaTiO ₂ , ZrO, and alumina-silica composite oxide; inorganic nitride particles such as aluminum nitride and boron nitride; silicone Covalent crystal particles such as diamond, sparingly soluble ionic crystal particles such as barium sulfate, calcium fluoride, and barium fluoride; clay fine particles such as talc and montmorillonite are used. These particles may be subjected to element substitution, surface treatment, solid solution, or the like, if necessary, or may be a single or a combination of two or more. Among these, inorganic oxide particles are preferable from the viewpoints of stability in an electrolytic solution and potential stability.

  The shape of the inorganic particles is not particularly limited, and may be a needle shape, a rod shape, a spindle shape, a plate shape, or the like. In particular, the shape of the inorganic particles may be a plate shape from the viewpoint of effectively preventing the needle-like material from penetrating. preferable.

  When the inorganic particles are plate-like, it is preferable to orient the inorganic particles in the porous film so that the flat plate surface is substantially parallel to the surface of the porous film. Thus, occurrence of a short circuit of the battery can be suppressed more favorably. This is because the inorganic particles are oriented as described above so that the inorganic particles overlap with each other on a part of the flat plate surface, so that the voids (through holes) from one side of the porous film to the other side are linear. It is thought that it is formed in a bent shape (that is, the curvature is increased) instead of being able to prevent lithium dendrite from penetrating the porous film, and the occurrence of a short circuit is suppressed better. It is guessed.

Examples of the plate-like inorganic particles preferably used include various commercially available products, for example, “Sun Lovely” (SiO ₂ ) manufactured by Asahi Glass S-Tech, and pulverized products (TiO ₂ ) of “NST-B1” manufactured by Ishihara Sangyo Co., Ltd. Barium sulfate plate “H series” and “HL series” manufactured by Sakai Chemical Industry Co., Ltd. “Micron White” (talc) manufactured by Hayashi Kasei Co., Ltd. “Bengell” (bentonite) manufactured by Hayashi Kasei Co., Ltd. “BMM” manufactured by Kawai Lime Co., Ltd. ”Or“ BMT ”(Boehmite),“ Cerasure BMT-B ”[Alumina (Al ₂ O ₃ )] manufactured by Kawai Lime Co.,“ Seraph ”(alumina) manufactured by Kinsei Matec Co., Ltd.,“ Yodogawa Mica Z- ”manufactured by Yodogawa Mining 20 "(sericite) etc. are available. In addition, SiO ₂ , Al ₂ O ₃ , and ZrO can be produced by the method disclosed in Japanese Patent Application Laid-Open No. 2003-206475.

  The average particle diameter of the inorganic particles is preferably 0.005 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.3 to 2 μm. When the average particle diameter of the inorganic particles is within the above range, the dispersion state of the porous film slurry can be easily controlled, and thus the production of a porous film having a uniform predetermined thickness is facilitated. Furthermore, the adhesiveness with the binder is improved, and even when the porous film is wound, the inorganic particles are prevented from peeling off, and sufficient safety can be achieved even if the porous film is thinned. Moreover, since it can suppress that the particle filling rate in a porous film becomes high, it can suppress that the ionic conductivity in a porous film falls. Furthermore, the porous membrane of the present invention can be formed thin.

  The average particle diameter of the inorganic particles is determined as an average value of the equivalent circle diameter of each particle by arbitrarily selecting 50 primary particles in an arbitrary field of view from an SEM (scanning electron microscope) image and performing image analysis. be able to.

  The particle size distribution (CV value) of the inorganic particles is preferably 0.5 to 40%, more preferably 0.5 to 30%, and particularly preferably 0.5 to 20%. By setting the particle size distribution of the inorganic particles in the above range, it is possible to maintain a predetermined gap between the non-conductive particles, thereby inhibiting the movement of lithium and increasing the resistance in the secondary battery of the present invention. Can be suppressed. The particle size distribution (CV value) of the inorganic particles is obtained by observing the inorganic particles with an electron microscope, measuring the particle size of 200 or more particles, and obtaining the average particle size and the standard deviation of the particle size. Standard deviation) / (average particle diameter). It means that the larger the CV value, the larger the variation in particle diameter.

Further, the BET specific surface area of the inorganic particles used in the present invention is specifically 0.9 to ²⁰⁰ m ² / g from the viewpoint of suppressing the aggregation of the inorganic particles and optimizing the fluidity of the porous membrane slurry described later. It is preferable that it is 1.5 to 150 m ² / g.

As the organic particles, organic particles having a functional group capable of crosslinking with a functional group of a binder described later (for example, a hydrophilic group in a hydrogenated nitrile polymer described later) are preferable. By using such organic particles, the reactivity with the binder can be increased, so that the dispersibility of non-conductive particles (organic particles) in the porous film slurry is improved.

In the organic particles used in the present invention, the functional group that can be crosslinked with the functional group of the binder refers to a functional group that can form a chemical bond with an anion derived from the functional group of the binder. Include an epoxy group, an N-methylolamide group, an oxazoline group, an allyl group, an isocyanate group, an oxetanyl group, and an alkoxysilane group. Above all, the reactivity with the functional group of the binder is high, so it can be easily crosslinked, and the crosslinking density can be easily controlled by changing the temperature and time during crosslinking. Epoxy groups are preferred and most preferred. In addition, the kind of said functional group may be one type, and may be two or more types.
By using a monomer having a functional group capable of crosslinking with the functional group of the binder when producing the organic particles, the polymerized unit having the functional group can be introduced into the organic particles.

Examples of the monomer having an epoxy group include a monomer containing a carbon-carbon double bond and an epoxy group, and a monomer containing a halogen atom and an epoxy group.
Examples of the monomer containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether; butadiene monoepoxide, Diene or polyene monoepoxides such as chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene; -Alkenyl epoxides such as epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate Glycidyl esters of unsaturated carboxylic acids such as glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid, etc. Can be mentioned.
Examples of the monomer containing a halogen atom and an epoxy group include epihalohydrins such as epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, β-methylepichlorohydrin; p-chlorostyrene oxide; Dibromophenyl glycidyl ether; and the like.

  Examples of the monomer having an N-methylolamide group include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide.

  Examples of the monomer having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline. 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like.

  Examples of the monomer having an allyl group include allyl acrylate, allyl methacrylate, and allyl glycidyl ether.

  Examples of the monomer having an isocyanate group include vinyl isocyanate, allyl isocyanate, (meth) acrylic isocyanate, 2- (meth) acryloyloxyethyl isocyanate, 2-isocyanatoethyl (meth) acrylate, m-isopropenyl-α, α. -Dimethyl methyl benzyl isocyanate etc. are mentioned.

  Examples of the monomer having an oxetanyl group include 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) acryloyloxymethyl) -2-trifluoromethyloxetane, and 3-((meth) acryloyloxymethyl). -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, 2-((meth) acryloyloxymethyl) -4-trifluoromethyloxetane, and the like.

  Examples of the monomer having an alkoxysilane group include vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropyltriethoxysilane, 3- And methacryloxytriethoxysilane.

  The content of the functional group in the organic particles is preferably 0.003 to 0.08 mmol / g, more preferably 0.005 to 0.05 mmol / g with respect to the organic particles. By making the amount of functional groups in the organic particles in the above range, the mobility of the functional groups in the organic particles is sufficiently maintained, so that the reactivity with the binder is improved. As a result, the strength of the porous film can be improved.

  It is preferable that the organic particles further include a polyfunctional (meth) acrylate polymer unit. The content ratio of the polyfunctional (meth) acrylate polymer units in the total monomer weight in the organic particles is preferably 50 to 95% by mass, more preferably 60 to 95% by mass, and particularly preferably 70 to 95% by mass. is there. By including polyfunctional (meth) acrylate polymer units in the organic particles, the crosslink density of the organic particles is increased, so that the heat resistance of the organic particles is improved, and the reliability of the resulting secondary battery porous membrane is also improved.

  Polyfunctional (meth) acrylates include polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, neopentyl glycol diacrylate, polypropylene glycol diacrylate, 2,2′-bis ( Diacrylate compounds such as 4-acryloxypropyloxyphenyl) propane and 2,2′-bis (4-acryloxydiethoxyphenyl) propane; trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate, etc. Triacrylate compounds; tetraacrylate compounds such as tetramethylolmethane tetraacrylate; ethylene glycol dimethacrylate, diethylene glycol dimethyl Chrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate Examples include dimethacrylate compounds such as methacrylate, polypropylene glycol dimethacrylate, and 2,2′-bis (4-methacryloxydiethoxyphenyl) propane; and trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate. Among these, it is preferable to use ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate, and it is particularly preferable to use ethylene glycol dimethacrylate. By using ethylene glycol dimethacrylate, the number of crosslinking points increases, so that organic particles having excellent heat resistance can be obtained. As a result, the high-temperature cycle characteristics of the secondary battery are improved. These are preferably used in combination with other crosslinkable monomers such as divinylbenzene and ethylvinylbenzene, and the crosslink density of the organic particles can be further improved by using in combination with the crosslinkable monomer.

  The organic particles may contain an arbitrary polymer unit in addition to the two polymer units. As a monomer (arbitrary monomer) constituting an arbitrary polymerization unit, an aromatic monovinyl compound, a (meth) acrylic acid ester monomer, a conjugated diene monomer, a vinyl ester compound, an α-olefin compound, a cationic monomer Body and a hydroxyl group-containing monomer. Two or more kinds of polymer units derived from these monomers may be contained in the organic particles.

  Examples of the aromatic monovinyl compound include styrene, α-methylstyrene, fluorostyrene, and vinylpyridine.

  Examples of the acrylate monomer include butyl acrylate, 2-ethylhexyl ethyl acrylate, N, N′-dimethylaminoethyl acrylate, and the like.

  Examples of the methacrylic acid ester monomer include butyl methacrylate, 2-ethylhexyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, N, N′-dimethylaminoethyl methacrylate and the like.

  Examples of the conjugated diene monomer include butadiene and isoprene.

  Examples of the vinyl ester compound include vinyl acetate.

  Examples of the α-olefin compound include 4-methyl-1-pentene.

  Examples of the cationic monomer include dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylate.

Examples of the hydroxyl group-containing monomer include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-buten-1-ol, and 5-hexen-1-ol; acrylate-2-hydroxyethyl, acrylate-2- Ethylenic solvents such as hydroxypropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate and di-2-hydroxypropyl itaconate alkanol esters of saturated carboxylic acids; formula ^{_{CH 2 = CR 1 -COO- (C}} n H 2n O) m -H (m is 2 to 9 integer, n represents 2 to 4 integer, ^{R 1} is hydrogen or An ester of a polyalkylene glycol represented by a methyl group) and (meth) acrylic acid; Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as lu-2 ′-(meth) acryloyloxyphthalate, 2-hydroxyethyl-2 ′-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl ether; Vinyl ethers such as 2-hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2- Mono (meth) allyl ethers of alkylene glycols such as hydroxybutyl ether, (meth) allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, (meth) allyl-6-hydroxyhexyl ether Polyoxyalkylene glycol (meth) monoallyl ethers such as diethylene glycol mono (meth) allyl ether and dipropylene glycol mono (meth) allyl ether; glycerin mono (meth) allyl ether, (meth) allyl-2-chloro-3- Mono (meth) allyl ethers of halogens and hydroxy-substituted products of (poly) alkylene glycol, such as hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; polyphenols such as eugenol, isoeugenol Mono (meth) allyl ether and its halogen-substituted product; (meth) allylthioe of alkylene glycol such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether Ethers; and the like.

  Any one of the above monomers can be used alone or in combination of two or more. Among the above optional monomers, styrene, methyl methacrylate, or a combination thereof is particularly preferable from the viewpoint of reactivity with a crosslinkable monomer such as divinylbenzene or ethylvinylbenzene.

  The content ratio of arbitrary polymerization units in the total monomer weight in the organic particles is preferably 3 to 80% by mass, more preferably 4 to 70% by mass, and particularly preferably 5 to 60% by mass. In particular, when styrene and / or methyl methacrylate is included as an optional monomer, the preferable content ratio is 4.5 to 76.5% by mass based on the total amount of monomers constituting the organic particles. In the case where both styrene and methyl methacrylate are contained, it is preferable that the sum thereof is within this range. By setting the content ratio of styrene and / or methyl methacrylate to 76.5% by mass or less, it is possible to prevent the dispersibility of the organic particles from being lowered, increase the strength of the porous film, and obtain film uniformity. be able to. On the other hand, by setting the content ratio of styrene and / or methyl methacrylate to 4.5% by mass or more, the heat resistance of the organic particles can be improved, so that the heat resistance of the porous film can be improved, and thus at a high temperature. Generation | occurrence | production of the short circuit of a battery can be reduced.

(Method for producing organic particles)
The method for producing the organic particles is not particularly limited, and the above-described monomers constituting the organic particles and other optional components as necessary are dissolved or dispersed in a dispersion medium, and an emulsion polymerization method or a soap-free polymerization method. The method of superposing | polymerizing in this dispersion liquid is mentioned.

  In emulsion polymerization, it is preferable to carry out the polymerization in a plurality of stages in order to obtain a desired particle diameter and average circularity. For example, a seed polymer particle is formed by first polymerizing a part of the monomer constituting the organic particle, and then the other polymer is absorbed by the seed polymer particle and polymerization is performed in that state. Organic particles can be produced (seed polymerization method). Furthermore, when forming the seed polymer particles, the polymerization can be further divided into a plurality of stages.

  More specifically, for example, the seed polymer particle A is formed using a part of the monomer constituting the organic particle, and the seed polymer particle A and another monomer constituting the organic particle are used. A seed polymer particle B having a larger particle size, and further using the seed polymer particle B and the remaining monomer constituting the organic particle and other optional components as necessary, Organic particles having a large particle size can be formed. Thus, there is an advantage that a desired particle diameter and average circularity can be stably obtained by forming seed polymer particles by a two-step reaction and further forming organic particles. In this case, a part or all (preferably all) of monomers having functional groups capable of crosslinking with the functional groups of the binder among the monomers constituting the organic particles are converted into seed polymer particles A and seed polymer particles B. It is preferable to use it in forming the particles in order to ensure the stability of the particles. Furthermore, in this case, it is possible to use styrene, which is an arbitrary monomer, as the monomer for forming the seed polymer particles A. When forming the seed polymer particles B and the non-conductive particles, the seed polymer particles It is preferable in order to ensure the absorbability of the monomer.

  Since the case where the polymerization is performed in a plurality of stages as described above is also included, the monomers constituting the organic particles may not be in a state where all the monomers are mixed in the polymerization. . When the polymerization is performed in a plurality of stages, in the finally obtained organic particles, the composition of the monomer derived from the polymerization unit constituting the organic particle is the composition of the monomer constituting the organic particle described above. The ratio is preferably satisfied.

  Examples of the medium that can be used for the polymerization of monomers constituting the organic particles include water, organic solvents, and mixtures thereof. As the organic solvent, those which are inert to radical polymerization and do not inhibit the polymerization of monomers can be used. Specific examples of the organic solvent include alcohols such as methanol, ethanol, propanol, cyclohexanol and octanol, esters such as dibutyl phthalate and dioctyl phthalate, ketones such as cyclohexanone, and mixtures thereof. Preferably, an aqueous medium such as water is used as a dispersion medium, and emulsion polymerization can be performed as polymerization.

  These amount ratios when the seed polymer particles and the monomer are reacted are preferably 2 to 19 parts by mass, more preferably 3 to 16 parts by mass as the amount of the monomer used with respect to 1 part by mass of the seed polymer particles. Even more preferably, it is 4 to 12 parts by mass. By making the usage-amount of a monomer 2 mass parts or more with respect to 1 mass part of seed polymer particles, the mechanical strength and heat resistance of the organic particle obtained can be improved. Moreover, since the monomer can be efficiently absorbed into the seed polymer particle by setting the amount of the monomer used to 19 parts by mass or less with respect to 1 part by mass of the seed polymer particle, a single amount that is not absorbed by the seed polymer particle. The body weight can be kept in a small range. In addition, since the particle size of the organic particles can be controlled well, the generation of coarse particles having a wide particle size distribution and a large amount of fine particles can be prevented.

Specific operations for the polymerization include a method in which a monomer is added to an aqueous dispersion of seed polymer particles at a time, and a method in which the monomer is divided or continuously added while performing polymerization. It is preferred that the monomer be absorbed by the seed polymer particles before polymerization is initiated and substantial crosslinking occurs in the seed polymer particles.
If a monomer is added after the middle of the polymerization, the monomer is not absorbed by the seed polymer particles, so a large amount of fine particles are generated, the polymerization stability is deteriorated, and the polymerization reaction may not be maintained. Therefore, it is preferable to add all the monomers to the seed polymer particles before the start of polymerization, or to finish adding all the monomers before the polymerization conversion rate reaches about 30%. In particular, it is preferable to start the polymerization after the monomer is added to the aqueous dispersion of seed polymer particles and stirred before the polymerization starts, and the seed polymer particles absorb this.

An optional component can be added to the polymerization reaction system in addition to the monomer constituting the organic particles and the dispersion medium. Specifically, components such as a polymerization initiator, a surfactant, and a suspension protective agent can be added. As the polymerization initiator, a general water-soluble radical polymerization initiator or oil-soluble radical polymerization initiator can be used, but a monomer that is not absorbed by the seed polymer particles rarely initiates polymerization in the aqueous phase. In view of this, it is preferable to use a water-soluble radical polymerization initiator. Examples of the water-soluble radical polymerization initiator include potassium persulfate, sodium persulfate, cumene hydroperoxide, hydrogen peroxide, or a water-soluble initiator or a reducing agent such as an oil-soluble initiator and sodium bisulfite described later. Redox initiators in combination are mentioned. Examples of the oil-soluble radical polymerization initiator include benzoyl peroxide, α, α′-azobisisobutyronitrile, t-butylperoxy-2-ethylhexanoate, 3,5,5-trimethylhexanoyl A peroxide etc. can be mentioned. Of the oil-soluble radical polymerization initiators, α, α′-azobisisobutyronitrile can be preferably used. In the polymerization reaction, it is preferable to add a small amount of a water-soluble polymerization inhibitor such as potassium dichromate, ferric chloride, or hydroquinone because generation of fine particles can be suppressed.
As the surfactant, a normal one can be used, and examples thereof include anionic emulsifiers such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dialkylsulfosuccinate, and a formalin condensate of naphthalenesulfonic acid. Furthermore, nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyethylene glycol monostearate, sorbitan monostearate can be used in combination. Preferred examples of the suspension protective agent include polyvinyl alcohol, carboxymethyl cellulose, sodium polyacrylate, and a fine powder inorganic compound.

  In the present invention, the most preferable combination of a polymerization initiator and a stabilizer for obtaining organic particles having a target particle size and a narrow particle size distribution with good reproducibility while ensuring the stability of the system during polymerization, A water-soluble radical polymerization initiator is used as the polymerization initiator, and C.I. M.M. C. A surfactant having a concentration equal to or lower than the concentration (critical micelle concentration) and in the vicinity thereof (specifically, 0.3 to 1.0 times the CMC concentration) is used.

(Properties of organic particles)
The shape of the organic particles used in the present invention is not particularly limited to a spherical shape, a needle shape, a rod shape, a spindle shape, a plate shape, or the like, but a spherical shape, a needle shape, or a spindle shape is preferable. It is preferable that the organic particles have high heat resistance from the viewpoint of imparting heat resistance to the porous membrane and improving the reliability of the secondary battery electrode and the secondary battery separator described later. Specifically, the temperature at which the weight loss rate of the organic particles reaches 10% by mass when heated at a heating rate of 10 ° C./min in a nitrogen atmosphere by thermobalance analysis is preferably 250 ° C. or more, more preferably 300 ° C. As described above, the temperature is particularly preferably 360 ° C. or higher. On the other hand, the upper limit of the temperature is not particularly limited, but can be, for example, 450 ° C. or less.

  The average particle diameter of the organic particles is preferably 0.005 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.3 to 2 μm. By controlling the average particle diameter of the organic particles in the above range, it becomes easy to control the dispersion state of the porous film slurry, so that it is easy to produce a porous film having a uniform predetermined thickness. Moreover, since it can suppress that the particle filling rate in a porous film becomes high, it can suppress that the ionic conductivity in a porous film falls, and can implement | achieve the outstanding cycling characteristics. It is particularly preferable that the average particle diameter of the organic particles be in the range of 0.3 to 2 μm because it is excellent in dispersion, ease of application, and control of voids. The average particle diameter can be obtained from an average value obtained by observing an electron microscope and calculating (a + b) / 2 by taking the longest side of the particle image as a and the shortest side as b for 100 or more particles. .

  The average circularity of the organic particles is preferably 0.900 to 0.995, more preferably 0.91 to 0.98, and particularly preferably 0.92 to 0.97. By setting the average circularity of the organic particles in the above range, the contact area between the organic particles can be maintained moderately, so that the strength and heat resistance of the porous film can be improved. As a result, the reliability of the secondary battery using the porous film can be improved.

Further, the BET specific surface area of the organic particles used in the present invention is specifically 0.9 to ²⁰⁰ m ² / g from the viewpoint of suppressing the aggregation of the organic particles and optimizing the fluidity of the porous membrane slurry. Is preferable, and it is more preferable that it is 1.5-150 m < ² > / g.

  The particle size distribution of the organic particles is preferably 1.00 to 1.4, more preferably 1.00 to 1.3, and particularly preferably 1.00 to 1.2. By setting the particle size distribution of the organic particles within the above range, it is possible to maintain a predetermined gap between the organic particles, thereby inhibiting lithium migration and increasing resistance in the secondary battery of the present invention. be able to. The particle size distribution of the organic particles is obtained by measuring the particle size with a laser diffraction scattering particle size distribution measuring device (LS230) manufactured by Beckman Co., Ltd., and then obtaining the volume average particle size V and the number average particle size N. The ratio V / N can be obtained.

  Moreover, in the organic particle used for this invention, it is preferable to use the organic particle whose content of a metal foreign material is 100 ppm or less from a viewpoint of reducing the metal foreign material which has a bad influence on the performance of a battery. When organic particles containing a large amount of metal foreign matter or metal ions are used, the metal foreign matter (metal ions) is eluted in the porous membrane slurry, which causes ionic crosslinking with the polymer in the porous membrane slurry, and the porous membrane slurry aggregates. As a result, the porosity of the porous film is lowered. Therefore, there is a possibility that the rate characteristic (output characteristic) of the secondary battery using the porous film is deteriorated. As the metal, it is most preferable to contain Fe, Ni, Cr and the like which are particularly easily ionized. Therefore, the metal content in the organic particles is preferably 100 ppm or less, more preferably 50 ppm or less. The smaller the content, the less likely the battery characteristics will deteriorate. The term “metal foreign matter” as used herein means a simple metal other than organic particles. The content of the metal foreign matter in the organic particles can be measured using ICP (Inductively Coupled Plasma).

  The content of non-conductive particles with respect to 100 parts by mass of the total solid content of the porous membrane slurry is preferably 70 to 99 parts by mass, more preferably 75 to 98 parts by mass, and particularly preferably 80 to 98 parts by mass. By setting the content of non-conductive particles in the above range, a porous film exhibiting high thermal stability can be obtained. Further, desorption (powder off) of non-conductive particles from the porous film can be suppressed, and a porous film having high strength can be obtained, and deterioration of battery characteristics such as cycle characteristics can be prevented. .

(binder)
The binder in the present invention includes a hydrogenated nitrile polymer and polyacrylonitrile. Hereinafter, the hydrogenated nitrile polymer and polyacrylonitrile will be described.

Hydrogenated nitrile polymer The hydrogenated nitrile polymer used in the present invention preferably contains a polymer unit having a nitrile group and a linear alkylene polymer unit having 4 or more carbon atoms. The linear alkylene polymer unit is preferably formed by hydrogenation after obtaining a polymer having a polymer unit having an unsaturated bond. The hydrogenated nitrile polymer used in the present invention is a polymer different from polyacrylonitrile described later.

  By having a polymer unit having a nitrile group in the polymer constituting the hydrogenated nitrile polymer, the dispersibility of non-conductive particles in the porous membrane slurry is improved, and the slurry can be stored in a stable state for a long period of time. it can. As a result, a uniform porous film can be easily manufactured. Moreover, since the lithium ion conductivity is good, the internal resistance in the battery can be reduced, and the output characteristics of the battery can be improved.

  The hydrogenated nitrile polymer preferably contains 5 to 25% by mass, more preferably 9 to 25% by mass, of polymerized units having a nitrile group, based on the total polymerized units. By making the content rate of the polymerization unit which has a nitrile group into the said range, it is excellent in the dispersion stability and adhesive force of a porous membrane slurry.

  Moreover, it is preferable that the hydrogenated nitrile polymer used for this invention has a linear alkylene polymer unit. Carbon number of a linear alkylene polymer unit is 4 or more, Preferably it is 4-16, More preferably, it is the range of 4-12.

  By introducing non-polar linear alkylene polymer units into the polymer constituting the hydrogenated nitrile polymer, the dispersibility of the non-conductive particles in the porous membrane slurry is improved, and the slurry is stored in a stable state for a long period of time. can do. As a result, a uniform porous film can be easily manufactured. Further, by introducing a linear alkylene polymer unit having a chain length of a predetermined length or more, the swellability of the porous membrane with respect to the electrolytic solution is optimized, and the battery characteristics are improved.

  The hydrogenated nitrile polymer preferably contains 50 to 98% by mass, more preferably 50 to 80% by mass, and particularly preferably 50 to 70% by mass of linear alkylene polymer units based on the total polymerized units.

  The hydrogenated nitrile polymer used in the present invention preferably has a polymerized unit having a hydrophilic group. In the present invention, the hydrophilic group means a functional group that liberates protons in an aqueous solvent and a salt in which the proton is substituted with a cation, and specifically includes a carboxylic acid group, a sulfonic acid group, and phosphoric acid. Groups, hydroxyl groups and salts thereof.

  By introducing a hydrophilic group into the polymer constituting the hydrogenated nitrile polymer, the adhesion between the non-conductive particles and between the non-conductive particles and the base material to be described later is improved, and the production process of the porous film The non-conductive particles falling off (powder falling) can be reduced.

  The hydrogenated nitrile polymer is preferably 0.2 to 10% by mass, more preferably 0.5 to 8% by mass, particularly preferably 1 to 6% of polymerized units having a hydrophilic group based on the total polymerized units. Contains by mass%. By making the content rate of the polymerization unit which has a hydrophilic group into the said range, the adhesive force and stability of a binder can be improved.

  The iodine value of the hydrogenated nitrile polymer in the present invention is 3 to 60 mg / 100 mg, preferably 3 to 30 mg / 100 mg, more preferably 8 to 10 mg / 100 mg. When the iodine value exceeds 60 mg / 100 mg, the stability at the oxidation potential is low due to the unsaturated bond contained in the hydrogenated nitrile polymer, and the high-temperature cycle characteristics of the battery are inferior. On the other hand, if the iodine value is less than 3 mg / 100 mg, the flexibility of the binder is lowered due to the lowered flexibility of the hydrogenated nitrile polymer. As a result, part of the non-conductive particles may be detached due to chipping of the porous film, powder falling, or the like when the electrode is wound or pressed. When powder falling or the like occurs, the detached lump (non-conductive particles) causes damage to the separator, a short circuit between the positive electrode and the negative electrode, and is inferior in safety and long-term characteristics. When the iodine value of the hydrogenated nitrile polymer is included in the above range, the hydrogenated nitrile polymer is chemically structurally stable with respect to a high potential, and the electrode structure can be maintained even in a long-term cycle. Excellent. The iodine value is determined according to JIS K 6235;

  The weight average molecular weight in terms of polystyrene by gel permeation chromatography of the hydrogenated nitrile polymer used in the present invention is preferably 50,000 or more, more preferably 100,000 to 500,000, and particularly preferably 100,000 to 300,000. By setting the weight average molecular weight of the hydrogenated nitrile polymer in the above range, a binder having excellent adhesion can be obtained, so that non-conductive particles are prevented from falling off the porous film, and the cycle characteristics of the secondary battery Can be suppressed. Further, the porous membrane can be made flexible, and the viscosity can be easily adjusted to be easily applied during the production of the porous membrane slurry.

  As described above, the polymer constituting the hydrogenated nitrile polymer preferably contains a polymer unit having a nitrile group, a linear alkylene polymer unit, and a polymer unit having a hydrophilic group in the same molecule. Such a polymer is obtained by polymerizing a monomer that leads to a polymer unit having a nitrile group, a monomer that leads to a linear alkylene polymer unit, and a monomer that leads to a polymer unit having a hydrophilic group. The linear alkylene polymer unit can be formed by obtaining a polymer having a polymer unit having an unsaturated bond and then hydrogenating it.

Hereinafter, a method for producing a hydrogenated nitrile polymer will be described.
Examples of the monomer for deriving a polymer unit having a nitrile group include α, β-unsaturated nitrile monomers. The α, β-unsaturated nitrile monomer is not particularly limited, and examples thereof include acrylonitrile; α-halogenoacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile; . Among these, acrylonitrile and methacrylonitrile are preferable. These can be used individually by 1 type or in combination of multiple types.

  The method for introducing the linear alkylene polymer unit into the hydrogenated nitrile polymer is not particularly limited, but a method in which a polymer unit derived from a conjugated diene monomer is introduced and then hydrogenated is simple and preferable.

  The conjugated diene monomer is preferably a conjugated diene having 4 or more carbon atoms, and examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like. Of these, 1,3-butadiene is preferred. These can be used individually by 1 type or in combination of multiple types.

  Introduction of the hydrophilic group into the hydrogenated nitrile polymer is carried out by polymerizing a monomer containing a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group and a salt thereof.

  Examples of the monomer having a carboxylic acid group include monocarboxylic acids and derivatives thereof, dicarboxylic acids, and derivatives thereof. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid, and the like. Can be mentioned. Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like. Dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid and the like methyl allyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, And maleate esters such as octadecyl maleate and fluoroalkyl maleate. Moreover, the acid anhydride which produces | generates a carboxyl group by hydrolysis can also be used. Examples of the acid anhydride of dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.

  Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, ethyl (meth) acrylic acid-2-sulfonate, 2-acrylamido-2-methylpropane sulfone. Acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and the like.

  Examples of the monomer having a phosphate group include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, and ethyl phosphate- (meth) acryloyloxyethyl phosphate.

Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-buten-1-ol, 5-hexen-1-ol; 2-hydroxyethyl acrylate, 2-hydroxy acrylate Ethylenic unsaturation such as propyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, di-2-hydroxypropyl itaconate alkanol esters of carboxylic acids; formula ^{_{CH 2 = CR 1 -COO- (C}} n H 2n O) m -H (m is 2 to 9 integer, n represents 2 to 4 integer, ^{R 1} is hydrogen or methyl Ester of polyalkylene glycol and (meth) acrylic acid represented by 2-hydride; Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as xylethyl-2 ′-(meth) acryloyloxyphthalate, 2-hydroxyethyl-2 ′-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl ether; Vinyl ethers such as 2-hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2- Mono (meth) allyl ethers of alkylene glycols such as hydroxybutyl ether, (meth) allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, (meth) allyl-6-hydroxyhexyl ether Ters; polyoxyalkylene glycol (meth) monoallyl ethers such as diethylene glycol mono (meth) allyl ether and dipropylene glycol mono (meth) allyl ether; glycerin mono (meth) allyl ether, (meth) allyl-2-chloro Mono (meth) allyl ethers of halogen and hydroxy-substituted products of (poly) alkylene glycols such as -3-hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; eugenol, isoeugenol Mono (meth) allyl ethers of monohydric phenols and halogen-substituted products thereof; (meth) ants of alkylene glycols such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether Thioethers; and the like.

  Among these, the hydrophilic group is preferably a carboxylic acid group or a sulfonic acid group because it has excellent adhesion to an electrode active material layer or an organic separator, which will be described later, and in particular a transition that may be eluted from the positive electrode active material. A carboxylic acid group is particularly preferred because it efficiently captures metal ions. Accordingly, among the monomers having a hydrophilic group, among the above, two monocarboxylic acids having 5 or less carbon atoms having a carboxylic acid group such as acrylic acid and methacrylic acid, and two carboxylic acid groups such as maleic acid and itaconic acid are used. A dicarboxylic acid having 5 or less carbon atoms is preferred. Furthermore, acrylic acid and methacrylic acid are particularly preferable from the viewpoint of high storage stability of the produced porous membrane slurry.

  Moreover, the hydrogenated nitrile polymer used in the present invention may contain polymerized units of other monomers copolymerizable with the monomers forming these polymerized units in addition to the polymerized units of the above monomers. The content ratio of the polymerization units of such other monomers is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less with respect to the total polymerization units.

  Examples of such other copolymerizable monomers include aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene; fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethyl styrene, pentafluorobenzoic acid. Fluorine-containing vinyl compounds such as vinyl, difluoroethylene, and tetrafluoroethylene; non-conjugated diene compounds such as 1,4-pentadiene, 1,4-hexadiene, vinylnorbornene, and dicyclopentadiene; ethylene, propylene, 1-butene, 4- Α-olefin compounds such as methyl-1-pentene, 1-hexene, 1-octene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. Α, -Ethylenically unsaturated monocarboxylic acid alkyl ester; monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, fumaric acid Monoesters and diesters of α, β-ethylenically unsaturated polyvalent carboxylic acids such as dicyclohexyl, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, dibutyl itaconate; methoxyethyl (meth) acrylate, (meth) acrylic acid Alkoxyalkyl esters of α, β-ethylenically unsaturated carboxylic acids such as methoxypropyl and butoxyethyl (meth) acrylate; divinyl compounds such as divinylbenzene; ethylene di (meth) acrylate and die Polyfunctional ethylenic unsaturation such as di (meth) acrylic acid esters such as lenglycol di (meth) acrylate and ethylene glycol di (meth) acrylate; trimethacrylic acid esters such as trimethylolpropane tri (meth) acrylate; In addition to the monomer, self-crosslinking compounds such as N-methylol (meth) acrylamide and N, N′-dimethylol (meth) acrylamide;

  Furthermore, the hydrogenated nitrile polymer used in the present invention may contain a monomer copolymerizable with these in addition to the monomer components described above. Monomers that can be copolymerized with these include halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, and vinyl butyrate; methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, and the like. Vinyl ethers; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine, and vinyl imidazole. The hydrogenated nitrile polymer used in the present invention can be obtained by graft copolymerizing these monomers by an appropriate technique.

  The hydrogenated nitrile polymer used in the present invention is used in the form of a dispersion or dissolved solution dispersed in a dispersion medium (water or organic solvent) (hereinafter collectively referred to as “hydrogenated nitrile polymer dispersion”). "). In the present invention, it is preferable to use water as a dispersion medium from the viewpoints of excellent environmental viewpoint and high drying speed. When an organic solvent is used as the dispersion medium, an organic solvent such as N-methylpyrrolidone (NMP) is used.

  In the case where the hydrogenated nitrile polymer is dispersed in the dispersion medium in the form of particles, the average particle diameter (dispersed particle diameter) of the hydrogenated nitrile polymer dispersed in the form of particles is preferably 50 to 500 nm, and preferably 70 to 400 nm. More preferably, it is 100 to 250 nm. When the average particle size of the hydrogenated nitrile polymer is within this range, the strength and flexibility of the porous film obtained are good.

  In the case where the hydrogenated nitrile polymer is dispersed in the dispersion medium in the form of particles, the solid content concentration of the dispersion is usually 15 to 70% by mass, preferably 20 to 65% by mass, and more preferably 30 to 60% by mass. preferable. When the solid content concentration is within this range, workability in producing the porous membrane slurry is good.

  The glass transition temperature (Tg) of the hydrogenated nitrile polymer used in the present invention is preferably −50 to 25 ° C., more preferably −45 to 15 ° C., and particularly preferably −40 to 5 ° C. When the Tg of the hydrogenated nitrile polymer is in the above range, the porous film of the present invention has excellent strength and flexibility, so that the output characteristics of a secondary battery using the porous film can be improved. The glass transition temperature of the hydrogenated nitrile polymer can be adjusted by combining various monomers.

  The production method of the hydrogenated nitrile polymer used in the present invention is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used. Examples of the polymerization initiator used for polymerization include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Organic peroxides, azo compounds such as α, α′-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like.

  When a linear alkylene polymer unit is formed by hydrogenation after the introduction of a polymer unit derived from a conjugated diene monomer, the method of hydrogenation is not particularly limited, and an ordinary method can be used. For example, an organic solvent solution of a polymer containing a polymer unit derived from a conjugated diene monomer may be reacted with hydrogen gas in the presence of a hydrogenation catalyst such as Raney nickel, a titanocene compound, or an aluminum-supported nickel catalyst. In the present invention, the hydrogenated nitrile polymer is preferably polymerized and hydrogenated in an aqueous solvent. Specifically, a polymer containing a polymer unit derived from a conjugated diene monomer is prepared by emulsion polymerization, and a hydrogenation catalyst such as palladium acetate is added to the polymerization reaction solution to bring it into contact with hydrogen gas in an aqueous emulsion state. React. By the hydrogenation reaction, the iodine value of the hydrogenated nitrile polymer containing the polymerized unit derived from the conjugated diene monomer can be within the above-described range. The hydrogenated nitrile polymer used in the present invention is preferably a hydrogenated acrylonitrile-butadiene copolymer having a hydrophilic group (hereinafter sometimes referred to as “hydrogenated NBR”).

  The method for producing a hydrogenated nitrile polymer is particularly preferably a method in which hydrogenation is carried out in two or more stages. Even when the same amount of hydrogenation catalyst is used, the hydrogenation efficiency can be increased by carrying out the hydrogenation in two or more stages. That is, when the polymerized unit derived from the conjugated diene monomer is converted into a linear alkylene polymerized unit, the iodine value can be further reduced.

  In addition, when hydrogenation is performed in two or more stages, it is preferable to achieve hydrogenation of 50% or more, more preferably 70% or more at the hydrogenation rate (hydrogenation rate) (%) in the first stage. . That is, when the numerical value obtained by the following formula is the hydrogenation rate (%), this numerical value is preferably 50% or more, and more preferably 70% or more.

Hydrogenation rate (hydrogenation rate) (%)
= 100 × (carbon-carbon double bond amount before hydrogenation-carbon-carbon double bond amount after hydrogenation) / (carbon-carbon double bond amount before hydrogenation)
In addition, the amount of carbon-carbon double bonds can be analyzed using ¹³ C-NMR.

  The hydrogenation catalyst is a hydrogenation catalyst containing a platinum group element (ruthenium, rhodium, palladium, osmium, iridium or platinum). As the hydrogenation catalyst, a palladium compound and a rhodium compound are preferable from the viewpoint of catalytic activity and availability, and a palladium compound is more preferable. Two or more platinum group element compounds may be used in combination, but in this case as well, it is preferable to use a palladium compound as the main catalyst component. Specific examples thereof include palladium salts of carboxylic acids such as formic acid, acetic acid, propionic acid, lauric acid, succinic acid, oleic acid, stearic acid, phthalic acid, benzoic acid; palladium chloride, dichloro (cyclooctadiene) palladium, dichloro (Norbornadiene) palladium, dichloro (benzonitrile) palladium, dichlorobis (triphenylphosphine) palladium, hexachloropalladium (IV) ammonium ammonium and other chlorinated products; iodinated products such as palladium iodide; palladium sulfate dihydrate, etc. Can be mentioned. Of these, palladium salts of carboxylic acids, dichloro (norbornadiene) palladium, ammonium hexachloropalladium (IV), and the like are particularly preferable. Although the usage-amount of a hydrogenation catalyst should just be determined suitably, Preferably it is 5-6,000 ppm per polymer weight, More preferably, it is 10-4,000 ppm.

  The reaction temperature at the time of hydrogenation is 0 to 300 ° C, preferably 20 to 150 ° C. The hydrogen pressure is 0.1 to 30 MPa, preferably 0.5 to 20 MPa, and more preferably 1 to 10 MPa. The reaction time for hydrogenation is selected in consideration of the reaction temperature, hydrogen pressure, target hydrogenation rate, etc., but preferably 1 to 10 hours.

  After completion of the hydrogenation reaction, the hydrogenation catalyst in the hydrogenated nitrile polymer dispersion is removed. As the method, for example, an adsorbent such as activated carbon or ion exchange resin can be added to adsorb the hydrogenation catalyst with stirring, and then the hydrogenated nitrile polymer dispersion can be filtered or centrifuged. It is also possible to leave the hydrogenated catalyst in the hydrogenated nitrile polymer dispersion without removing the hydrogenated catalyst.

  The hydrogenated nitrile polymer used in the present invention is obtained through a particulate metal removal step of removing particulate metal contained in the hydrogenated nitrile polymer dispersion in the production step of the hydrogenated nitrile polymer. preferable. When the content of the particulate metal component contained in the hydrogenated nitrile polymer is 10 ppm or less, it is possible to prevent metal ion crosslinking over time between the polymers in the porous film slurry described later, and to prevent an increase in viscosity. Furthermore, there is little concern about self-discharge increase due to internal short circuit of the secondary battery or dissolution / precipitation during charging, and the cycle characteristics and safety of the battery are improved.

  The method for removing the particulate metal component from the hydrogenated nitrile polymer dispersion in the particulate metal removal step is not particularly limited. For example, the removal method by filtration using a filtration filter, the removal method using a vibrating screen, or centrifugation. Examples thereof include a removal method and a removal method using magnetic force. Especially, since the removal object is a metal component, the method of removing by magnetic force is preferable. The method for removing by magnetic force is not particularly limited as long as it is a method capable of removing a metal component. However, in consideration of productivity and removal efficiency, a magnetic filter is preferably arranged in the production line of the hydrogenated nitrile polymer. Done in

  In the production process of the hydrogenated nitrile polymer used in the present invention, the dispersant used in the above polymerization method may be one used in ordinary synthesis. Specific examples include sodium dodecylbenzenesulfonate, dodecylphenylethersulfone. Benzene sulfonates such as sodium sulfate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecyl sulfate; sulfosuccinates such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate; fatty acid salts such as sodium laurate; polyoxyethylene lauryl Ethoxysulfate salts such as ether sulfate sodium salt, polyoxyethylene nonylphenyl ether sulfate sodium salt; alkane sulfonate salt; alkyl ether phosphate ester sodium Nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan lauryl ester, polyoxyethylene-polyoxypropylene block copolymer; gelatin, maleic anhydride-styrene copolymer, polyvinylpyrrolidone, poly Examples thereof include water-soluble polymers such as sodium acrylate and polyvinyl alcohol having a polymerization degree of 700 or more and a saponification degree of 75% or more, and these may be used alone or in combination of two or more. Among these, benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecylsulfate are preferable, and oxidation resistance is more preferable. From this point, it is a benzenesulfonate such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate. The addition amount of a dispersing agent can be set arbitrarily, and is about 0.01-10 mass parts normally with respect to 100 mass parts of monomer total amounts.

  The pH when the hydrogenated nitrile polymer used in the present invention is dispersed in the dispersion medium is preferably 5 to 13, more preferably 5 to 12, and most preferably 10 to 12. When the pH of the hydrogenated nitrile polymer is in the above range, the storage stability of the binder is improved, and further, the mechanical stability is improved.

  PH adjusters that adjust the pH of hydrogenated nitrile polymers include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, and alkaline earth metals such as calcium hydroxide, magnesium hydroxide, and barium hydroxide. Hydroxides such as hydroxides of metals belonging to Group IIIA in the long periodic table such as oxides and aluminum hydroxides; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkaline earth metal carbonates such as magnesium carbonate Examples of the organic amine include alkylamines such as ethylamine, diethylamine and propylamine; alcohol amines such as monomethanolamine, monoethanolamine and monopropanolamine; ammonia such as aqueous ammonia And so on. Among these, alkali metal hydroxides are preferable from the viewpoints of binding properties and operability, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are particularly preferable.

Polyacrylonitrile In the present invention, polyacrylonitrile is a polymer containing 70% by mass or more of polymer units having a nitrile group based on the total polymer units.
The polyacrylonitrile in the present invention includes a polymer unit having a nitrile group and a polymer unit derived from an ethylenically unsaturated compound.

  Examples of the monomer for deriving the polymerization unit having a nitrile group include an α, β-unsaturated nitrile monomer, and the α, β-unsaturated nitrile monomer exemplified in the hydrogenated nitrile polymer described above can be used. Among these, acrylonitrile is preferable from the viewpoint of the balance between ease of polymerization reaction, cost performance, flexibility and flexibility of the porous film, and resistance to swelling to the electrolytic solution. The α, β-unsaturated nitrile monomer may be used alone or in combination of two or more at any ratio. Moreover, the polyacrylonitrile may contain the polymer unit which has a nitrile group individually by 1 type, and may contain it combining 2 or more types by arbitrary ratios.

  The polyacrylonitrile is a polymer unit having a nitrile group with respect to all the polymer units, usually 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and usually 99.9% by mass or less. , Preferably it contains 99 mass% or less. By making the content rate of the polymerization unit which has a nitrile group into the said range, the adhesive strength (peel strength) of the porous film with respect to an electrode active material layer or an organic separator can be made high. Moreover, since the tolerance with respect to the electrolyte solution of polyacrylonitrile can be improved by making the content rate of the polymerization unit which has a nitrile group below the upper limit of the said range, for example, a binder melt | dissolves with respect to electrolyte solution, or electrolyte solution As a result, the binding property gradually decreases due to the swelling of the binder, and the non-conductive particles can be stably prevented from peeling off.

  Moreover, as an ethylenically unsaturated compound, the compound which has an unsaturated hydrocarbon chain containing a carbon-carbon double bond and can superpose | polymerize with an (alpha), (beta)-unsaturated nitrile monomer is used normally. Examples include vinyl halides and vinylidene halides such as vinyl chloride, vinyl bromide, vinyl fluoride, and vinylidene chloride; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and the like. Salts: Acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, methoxyethyl acrylate, phenyl acrylate, cyclohexyl acrylate, etc .; methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacryl Methacrylic acid esters such as octyl acid, methoxyethyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate; Unsaturated ketones such as methyl vinyl ketone, methyl phenyl ketone, methyl isopropenyl ketone; Vinyl formate, vinyl acetate Vinyl esters such as vinyl propionate, vinyl butyrate and vinyl benzoate; vinyl ethers of methyl vinyl ether and ethyl vinyl ether; acrylic amides and alkyl substituted products thereof; vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, p -Unsaturated sulfonic acids such as styrene sulfonic acid and salts thereof; styrene such as styrene, α-methylstyrene, chlorostyrene and alkyl or halogen substituted products thereof; allyl alcohol and esters or ethers thereof; vinyl pyridine, vinyl imidazole, And basic vinyl compounds such as dimethylaminoethyl methacrylate; vinyl compounds such as acrolein, methacrolein, vinylidene cyanide, glycidyl methacrylate, and methacrylonitrile;

  Especially, as an ethylenically unsaturated compound, the unsaturated compound which has a carboxyl group (-COOH group) is preferable. By using an unsaturated compound having a carboxyl group, the peel strength can be increased and the cycle characteristics of the battery can be stably improved. Among these, unsaturated carboxylic acid is particularly preferable, and acrylic acid and methacrylic acid are particularly preferable. In addition, an ethylenically unsaturated compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Polyacrylonitrile is usually 0.1 mass of polymer units derived from ethylenically unsaturated compounds (hereinafter sometimes referred to as “ethylenically unsaturated compound polymerized units”) with respect to all polymerized units. % Or more, preferably 1% by mass or more, and usually 10% by mass or less, preferably 6% by mass or less. The porous film can be stably formed by setting the content ratio of the ethylenically unsaturated compound polymerization unit in the polyacrylonitrile to be equal to or higher than the lower limit of the above range, and by increasing the content of the porous film slurry to the upper limit of the above range or less. And the manufacture of the porous membrane is facilitated.

  In addition, the polyacrylonitrile used in the present invention may contain a polymer unit other than a polymer unit having a nitrile group or an ethylenically unsaturated compound polymer unit unless the effects of the present invention are significantly impaired. These polymerized units may contain one kind alone, or may contain two or more kinds in combination at an arbitrary ratio.

The polyacrylonitrile has a weight average molecular weight Mw of usually 500,000 or more, preferably 750,000 or more, and usually 2 million or less, preferably 1.5 million or less. Polyacrylonitrile has a molecular weight distribution (Mw / Mn) of usually 13 or less, preferably 10 or less, and usually 3 or more. Here, Mn represents a number average molecular weight.
The weight average molecular weight Mw and the number average molecular weight Mn can be measured by gel permeation chromatography (GPC). Specifically, as a GPC eluent, a polar solvent such as N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) is used, and a polar polymer column is used. What is necessary is just to measure at 0 degreeC etc. and to obtain | require as a conversion value of standard polystyrene.

  Polyacrylonitrile is produced by a polymerization method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method using the above monomers. As the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used. Examples of the polymerization initiator used for polymerization include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Organic peroxides, azo compounds such as α, α′-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like.

(Binder production method)
The binder is produced by mixing the above hydrogenated nitrile polymer and polyacrylonitrile. Examples of the mixing means include mixing equipment such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer.

  The mass ratio (hydrogenated nitrile monomer / polyacrylonitrile) of the hydrogenated nitrile monomer and polyacrylonitrile in the binder used in the present invention is preferably 97/3 to 40/60, more preferably 95/5 to 50/50, particularly preferably. Is 93/7 to 70/30. By setting the mass ratio within the above range, a uniform porous film can be obtained. Further, since a binder having excellent adhesive strength can be obtained, non-conductive particles can be prevented from falling off, and as a result, a secondary battery having excellent cycle characteristics can be obtained.

  The binder used in the present invention is used in the form of a dispersion or a solution in which the hydrogenated nitrile monomer and polyacrylonitrile are dispersed in a dispersion medium (water or an organic solvent) (hereinafter collectively referred to as these). May be referred to as “binder dispersion”). In the present invention, it is preferable to use water as a dispersion medium from the viewpoints of excellent environmental viewpoint and high drying speed. When an organic solvent is used as the dispersion medium, an organic solvent such as N-methylpyrrolidone (NMP) is used.

  The binder is contained in an amount of preferably 0.5 to 20 parts by mass, more preferably 1 to 18 parts by mass, and particularly preferably 3 to 15 parts by mass with respect to 100 parts by mass of the total solid content of the porous membrane slurry. By making the content ratio of the binder within the above range, the above-mentioned non-conductive particles are prevented from detaching (powder falling) from the porous film produced using the porous film slurry of the present invention, and flexibility An excellent porous film can be obtained, and the cycle characteristics of a secondary battery using the porous film can be improved.

(Optional ingredients)
The porous membrane slurry of the present invention may contain an isothiazoline-based compound. By containing an isothiazoline-based compound, it is possible to suppress the growth of fungi, so it is possible to prevent the generation of off-flavors and thickening of the slurry in the porous membrane slurry for forming the porous membrane, and long-term storage stability Excellent.

  The porous membrane slurry of the present invention may contain a chelate compound. By adding a chelate compound, it is possible to capture transition metal ions that elute in the electrolyte during charge / discharge of a secondary battery using the porous film formed by the slurry. It is possible to prevent deterioration of the cycle characteristics and safety of the secondary battery.

  The porous membrane slurry may contain a pyrithione compound. Since pyrithione compounds are stable even when alkaline, they can be used in combination with isothiazoline-based compounds to extend the antiseptic performance effect even under alkaline conditions and to obtain a high antibacterial effect due to a synergistic effect.

  In addition to the above components, the porous membrane slurry has functions such as a dispersant, a leveling agent, an antioxidant, a binder other than the above binder, a thickener, an antifoaming agent, and electrolyte decomposition inhibition. An electrolytic solution additive or the like may be included. These are not particularly limited as long as they do not affect the battery reaction.

  Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. A dispersing agent is selected according to the nonelectroconductive particle to be used. By adding the dispersant, the coating property of the porous membrane slurry of the present invention is good, and a uniform porous membrane can be obtained.

  Examples of the leveling agent include surfactants such as alkyl surfactants, silicone surfactants, fluorine surfactants, and metal surfactants. By adding the surfactant, it is possible to prevent the repelling that occurs when the porous film slurry of the present invention is applied to the substrate described later, and to improve the smoothness of the porous film.

  Examples of the antioxidant include a phenol compound, a hydroquinone compound, an organic phosphorus compound, a sulfur compound, a phenylenediamine compound, and a polymer type phenol compound. The polymer type phenol compound is a polymer having a phenol structure in the molecule, and a polymer type phenol compound having a weight average molecular weight of 200 to 1000, preferably 600 to 700 is preferably used. By adding an antioxidant, the cycle life of the battery is excellent.

  Examples of binders other than the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyacrylic acid derivatives used in binders (electrode binders) used in electrodes described later. A soft polymer or the like can be used. By adding the binder, the adhesion between the porous membrane of the present invention and the electrode active material layer and organic separator described later is good. Moreover, it can suppress that resistance increases by inhibiting the movement of lithium ion, maintaining the softness | flexibility of a porous film.

  Examples of thickeners include cellulosic polymers such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, and ammonium salts and alkali metal salts thereof; (modified) poly (meth) acrylic acid and ammonium salts and alkali metal salts thereof; ) Polyvinyl alcohols such as polyvinyl alcohol, copolymers of acrylic acid or acrylate and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified Examples include polyacrylic acid, oxidized starch, phosphate starch, casein, and various modified starches. By adding the thickener, the coating property of the porous membrane slurry of the present invention and the adhesion between the porous membrane of the present invention and the electrode active material layer and organic separator described later are good. In the above, “(modified) poly” means “unmodified poly” or “modified poly”, and “(meth) acryl” means “acryl” or “methacryl”.

  As the antifoaming agent, metal soaps, polysiloxanes, polyethers, higher alcohols, perfluoroalkyls and the like are used. By adding an antifoaming agent, the defoaming step of the binder can be shortened.

  As the electrolytic solution additive, vinylene carbonate used in an electrode slurry and an electrolytic solution described later can be used. By adding the electrolytic solution additive, the cycle life of the battery is excellent.

  Other examples include nanoparticles such as fumed silica and fumed alumina. By mixing the nano fine particles, the thixotropy of the porous membrane slurry can be controlled, and the leveling properties of the porous membrane obtained thereby can be improved.

  The above optional components are preferably added to the porous membrane slurry within a range that does not affect the battery characteristics, and preferably 10 parts by mass or less of each component with respect to 100 parts by mass of the total solid content of the porous membrane slurry. The total of arbitrary components is preferably 40 parts by mass or less, more preferably 20 parts by mass or less. However, when the total of the non-conductive particles, the binder, and any components (excluding the binder) is less than 100 parts by mass, the content of the binder as the optional component may be appropriately increased. .

(Method for producing slurry composition for secondary battery porous membrane)
The porous film of the present invention is a slurry composition for a porous film of a secondary battery (porous film slurry) comprising non-conductive particles, a binder, an optional component added as necessary, and an appropriate dispersion medium. Is applied and dried on a predetermined base material to be described later.

  The porous membrane slurry of the present invention is a slurry for forming a porous membrane, and the above-mentioned non-conductive particles, a binder, and optional components added as necessary to a dispersion medium described later as a solid content. Uniformly dispersed. The dispersion medium is not particularly limited as long as it can uniformly disperse solid contents (binder, non-conductive particles, and optional components).

  As the dispersion medium used for the porous membrane slurry, either water or an organic solvent can be used. Examples of organic solvents include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, ethylmethylketone, diisopropylketone, cyclohexanone, methylcyclohexane, and ethylcyclohexane. Chlorinated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; Esters such as ethyl acetate, butyl acetate, γ-butyrolactone and ε-caprolactone; Acylonitriles such as acetonitrile and propionitrile; Tetrahydrofuran and Ethylene Ethers such as glycol diethyl ether; alcohols such as methanol, ethanol, isopropanol, ethylene glycol and ethylene glycol monomethyl ether; N-methyl Amides such as pyrrolidone and N, N-dimethylformamide may be mentioned.

  These dispersion media may be used alone, or two or more of these dispersion media may be mixed and used as a mixed solvent. Among these, a dispersion medium having excellent dispersibility of non-conductive particles and having a low boiling point and high volatility is preferable because it can be removed at a low temperature in a short time. Specifically, acetone, toluene, cyclohexanone, cyclopentane, tetrahydrofuran, cyclohexane, xylene, water, or N-methylpyrrolidone, or a mixed solvent thereof is preferable, and water is particularly preferable.

  The solid content concentration of the porous membrane slurry is not particularly limited as long as the slurry can be applied and immersed, and has a fluid viscosity, but is generally about 10 to 60% by mass.

  Components other than the solid content are components that volatilize in the drying step, and include, in addition to the dispersion medium, for example, a medium in which these are dissolved or dispersed when preparing and adding non-conductive particles and a binder.

  Since the porous film slurry of the present invention is for forming the porous film of the present invention, the content ratio of the non-conductive particles and the binder in the porous film is naturally the solid content of the porous film slurry of the present invention. It is said that the total amount is as per minute. That is, the content ratio of the nonconductive particles in the porous film is preferably 70 to 99 parts by mass, and the content ratio of the binder is preferably 0.5 to 20 parts by mass.

  The method for producing the slurry for the porous membrane is not particularly limited, and can be obtained by mixing the non-conductive particles, the binder, the dispersion medium and any components added as necessary.

  In the present invention, a porous film slurry in which non-conductive particles are highly dispersed can be obtained regardless of the mixing method and mixing order by using the above components. The mixing device is not particularly limited as long as it can uniformly mix the above components, and a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and the like can be used. In particular, it is particularly preferable to use a high dispersion apparatus such as a bead mill, a roll mill, or a fill mix that can add a high dispersion share.

  The viscosity of the porous membrane slurry is preferably 10 to 10,000 mPa · s, more preferably 50 to 500 mPa · s, from the viewpoint of uniform coating properties and slurry aging stability. The viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.

[Secondary battery porous membrane]
The secondary battery porous membrane of the present invention (hereinafter sometimes referred to as “porous membrane”) is formed by forming the above-mentioned slurry composition for a secondary battery porous membrane into a film and drying it. The porous film is used by being laminated on an organic separator or an electrode, or used as an organic separator itself.

  As a method for producing the porous membrane of the present invention, (I) a porous membrane slurry containing the above non-conductive particles, a binder, the optional components and a dispersion medium is applied on a predetermined substrate (positive electrode, negative electrode or organic separator). (II) A method in which the porous film slurry is immersed in a substrate (positive electrode, negative electrode or organic separator) and then dried; (III) The porous film slurry is removed from the release film. And a method of transferring the resulting porous film onto a predetermined substrate (positive electrode, negative electrode or organic separator). Among these, (I) The method of applying the porous film slurry to the substrate (positive electrode, negative electrode or organic separator) and then drying is most preferable because the film thickness of the porous film can be easily controlled.

  The porous film of the present invention is manufactured by the above-described methods (I) to (III), and the detailed manufacturing method will be described below.

  In the method (I), the porous membrane slurry of the present invention is produced by applying a porous membrane slurry onto a predetermined substrate (positive electrode, negative electrode or organic separator) and drying.

  The method for applying the slurry onto the substrate is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. Among these, the gravure method is preferable in that a uniform porous film can be obtained.

  Examples of the drying method include drying by warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying temperature can vary depending on the type of solvent used. In order to completely remove the solvent, for example, when a low-volatility solvent such as N-methylpyrrolidone is used, it is preferably dried at a high temperature of 120 ° C. or higher with a blower-type dryer. Conversely, when a highly volatile solvent is used, it can be dried at a low temperature of 100 ° C. or lower. When forming a porous film on the organic separator mentioned later, since it is necessary to dry without causing shrinkage of the organic separator, drying at a low temperature of 100 ° C. or lower is preferable.

In the method (II), the porous membrane of the present invention is produced by immersing the porous membrane slurry in a substrate (positive electrode, negative electrode or organic separator) and drying. The method for immersing the slurry in the substrate is not particularly limited, and for example, the slurry can be immersed by dip coating with a dip coater or the like.
Examples of the drying method include the same methods as the drying method in the method (I) described above.

  In the method (III), a porous film slurry is applied on a release film and formed into a film, thereby producing a porous film formed on the release film. Subsequently, the porous film of this invention is manufactured by transcribe | transferring the obtained porous film on a base material (a positive electrode, a negative electrode, or an organic separator).

  As the coating method, the same method as the coating method in the above-mentioned method (I) can be mentioned. The transfer method is not particularly limited.

  The porous film obtained by the methods (I) to (III) is then subjected to pressure treatment using a die press or a roll press, if necessary, and a substrate (positive electrode, negative electrode or organic separator) and porous film. It is also possible to improve the adhesion. However, at this time, if the pressure treatment is excessively performed, the porosity of the porous film may be impaired, so the pressure and the pressure time are controlled appropriately.

  The film thickness of the porous film is not particularly limited and is appropriately set according to the use or application field of the porous film. However, if the film is too thin, a uniform film cannot be formed. Since the capacity per volume (weight) decreases, 0.5 to 50 μm is preferable, and 0.5 to 10 μm is more preferable.

  The porous film of the present invention is formed on the surface of a substrate (positive electrode, negative electrode or organic separator) and is particularly preferably used as a protective film or separator for an electrode active material layer described later. The porous film of the present invention may be formed on any surface of the positive electrode, negative electrode or organic separator of the secondary battery, or may be formed on all of the positive electrode, negative electrode and organic separator.

[Secondary battery]
The secondary battery of the present invention includes a positive electrode, a negative electrode, an organic separator, and an electrolytic solution, and the above-described porous film is laminated on any of the positive electrode, the negative electrode, and the organic separator.

  Examples of the secondary battery of the present invention include a lithium ion secondary battery and a nickel hydride secondary battery. Among these, the lithium ion secondary battery is preferable because safety improvement is most demanded and the effect of introducing a porous film is the highest, and in addition, improvement of cycle characteristics is cited as a problem. The case where it uses for a battery is demonstrated.

(Positive electrode and negative electrode)
The positive electrode and the negative electrode are generally formed by attaching an electrode active material layer containing an electrode active material as an essential component to a current collector.

  A positive electrode or a negative electrode (hereinafter sometimes referred to as “secondary battery electrode”) used in the secondary battery of the present invention is formed by laminating a current collector, an electrode active material layer, and a porous film in this order. Therefore, the porous membrane is preferably the above-described secondary battery porous membrane. The electrode active material layer includes an electrode active material and an electrode binder. That is, in the secondary battery electrode of the present invention, the electrode active material layer containing the electrode active material and the electrode binder is attached to the current collector, and the above-mentioned second active electrode layer is formed on the surface of the electrode active material layer. A secondary battery porous membrane is preferably laminated.

(Electrode active material)
The electrode active material used for the electrode for the lithium ion secondary battery is not particularly limited as long as it can reversibly insert and release lithium ions by applying a potential in the electrolyte, and can be an inorganic compound or an organic compound.

Electrode active materials (positive electrode active materials) for lithium ion secondary battery positive electrodes are broadly classified into those made of inorganic compounds and those made of organic compounds. Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, composite oxides of lithium and transition metals, and transition metal sulfides. As the transition metal, Fe, Co, Ni, Mn and the like are used. Specific examples of the inorganic compound used for the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO _4, and other lithium-containing composite metal oxides; TiS ₂ , TiS ₃ , non- Transition metal sulfides such as crystalline MoS ₂ ; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ It is done. These compounds may be partially element-substituted. As the positive electrode active material made of an organic compound, for example, a conductive polymer such as polyacetylene or poly-p-phenylene can be used. An iron-based oxide having poor electrical conductivity may be used as an electrode active material covered with a carbon material by allowing a carbon source material to be present during reduction firing. These compounds may be partially element-substituted.

  The positive electrode active material for a lithium ion secondary battery may be a mixture of the above inorganic compound and organic compound. The particle diameter of the positive electrode active material is appropriately selected in consideration of the arbitrary constituent requirements of the battery. From the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, the 50% volume cumulative diameter is usually 0.1. -50 μm, preferably 1-20 μm. When the 50% volume cumulative diameter is within this range, a secondary battery having a large charge / discharge capacity can be obtained, and handling of the slurry for electrodes and the electrodes is easy. The 50% volume cumulative diameter can be determined by measuring the particle size distribution by laser diffraction.

  Examples of electrode active materials (negative electrode active materials) for negative electrodes of lithium ion secondary batteries include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, pitch-based carbon fibers, and high conductivity such as polyacene. Molecular compounds and the like. In addition, as the negative electrode active material, metals such as silicon, tin, zinc, manganese, iron, nickel, alloys thereof, oxides or sulfates of the metals or alloys are used. In addition, lithium alloys such as lithium metal, Li—Al, Li—Bi—Cd, and Li—Sn—Cd, lithium transition metal nitride, silicone, and the like can be used. As the electrode active material, a material obtained by attaching a conductivity imparting material to the surface by a mechanical modification method can also be used. The particle size of the negative electrode active material is appropriately selected in consideration of the other structural requirements of the battery. From the viewpoint of improving battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics, a 50% volume cumulative diameter is usually The thickness is 1 to 50 μm, preferably 15 to 30 μm.

(Binder for electrode)
In the present invention, the electrode active material layer includes a binder (hereinafter sometimes referred to as “electrode binder”) in addition to the electrode active material. By including a binder for the electrode, the binding property of the electrode active material layer in the electrode is improved, the strength against the mechanical force applied during the process of winding the electrode is increased, and the electrode active material in the electrode is increased. Since the material layer is less likely to be detached, the risk of a short circuit due to the desorbed material is reduced.

  Various resin components can be used as the electrode binder. For example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, and the like can be used. These may be used alone or in combination of two or more. Moreover, the binder used for the porous film of this invention can also be used as a binder for electrodes.

Furthermore, the soft polymer illustrated below can also be used as a binder for electrodes.
Acrylic or methacrylic acid such as polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer An acrylic soft polymer which is a homopolymer of a derivative or a copolymer of a monomer copolymerizable therewith;
Isobutylene-based soft polymers such as polyisobutylene, isobutylene-isoprene rubber, isobutylene-styrene copolymer;
Polybutadiene, polyisoprene, butadiene / styrene random copolymer, isoprene / styrene random copolymer, acrylonitrile / butadiene copolymer, acrylonitrile / butadiene / styrene copolymer, butadiene / styrene / block copolymer, styrene / butadiene / Diene-based soft polymers such as styrene block copolymer, isoprene / styrene block copolymer, styrene / isoprene / styrene block copolymer;
Silicon-containing soft polymers such as dimethylpolysiloxane, diphenylpolysiloxane, dihydroxypolysiloxane;
Liquid polyethylene, polypropylene, poly-1-butene, ethylene / α-olefin copolymer, propylene / α-olefin copolymer, ethylene / propylene / diene copolymer (EPDM), ethylene / propylene / styrene copolymer, etc. Olefinic soft polymers of
Vinyl-based soft polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, vinyl acetate / styrene copolymer;
Epoxy-based soft polymers such as polyethylene oxide, polypropylene oxide, epichlorohydrin rubber;
Fluorine-containing soft polymers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber;
Examples thereof include other soft polymers such as natural rubber, polypeptide, protein, polyester-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer. These soft polymers may have a cross-linked structure or may have a functional group introduced by modification.

  The amount of the electrode binder in the electrode active material layer is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and particularly preferably 0.00 with respect to 100 parts by mass of the electrode active material. 5 to 3 parts by mass. When the amount of the electrode binder in the electrode active material layer is within the above range, it is possible to prevent the active material from being detached from the electrode without inhibiting the battery reaction.

  The electrode binder is prepared as a solution or a dispersion for producing an electrode. The viscosity at that time is usually in the range of 1 to 300,000 mPa · s, preferably 50 to 10,000 mPa · s. The viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.

(Optional additive)
In the present invention, the electrode active material layer may contain an optional additive such as a conductivity-imparting material or a reinforcing material in addition to the electrode active material and the electrode binder. As the conductivity-imparting material, conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor-grown carbon fiber, and carbon nanotube can be used. Moreover, carbon powders such as graphite, fibers and foils of various metals can be used. As the reinforcing material, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used. By using the conductivity imparting material, the electrical contact between the electrode active materials can be improved, and the discharge rate characteristics can be improved when used in a lithium ion secondary battery. The usage-amount of an electroconductivity imparting material or a reinforcing material is 0-20 mass parts normally with respect to 100 mass parts of electrode active materials, Preferably it is 1-10 mass parts. Further, an isothiazoline-based compound or a chelate compound may be included in the electrode active material layer.

(Method for producing secondary battery electrode)
The secondary battery electrode of the present invention is manufactured by laminating the secondary battery porous film of the present invention on the surface of the electrode active material layer of the current collector in which the electrode active material layer is bound in layers. The electrode active material layer can be formed by attaching a slurry containing an electrode active material, an electrode binder, and a solvent (hereinafter also referred to as “electrode slurry”) to a current collector. The method for laminating the porous film on the surface of the electrode active material layer is not particularly limited, and examples thereof include the methods (I) to (III) described in the above method for producing a porous film.

  Any solvent may be used as long as it dissolves or disperses the electrode binder, but a solvent that dissolves is preferable. When a solvent that dissolves the electrode binder is used, the electrode binder is adsorbed on the surface of the electrode active material or any additive, thereby stabilizing the dispersion of the electrode active material.

  As the solvent used for the electrode slurry, either water or an organic solvent can be used. Examples of the organic solvent include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, γ-butyrolactone, ε -Esters such as caprolactone; acylonitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether; alcohols such as methanol, ethanol, isopropanol, ethylene glycol and ethylene glycol monomethyl ether; N-methyl Amides such as pyrrolidone and N, N-dimethylformamide are exemplified. These solvents may be used alone or in admixture of two or more and appropriately selected from the viewpoint of drying speed and environment.

  The electrode slurry may further contain additives that exhibit various functions such as a thickener. As the thickener, a polymer soluble in the solvent used for the electrode slurry is used. Specifically, the thickener exemplified in the porous membrane slurry of the present invention can be used. As for the usage-amount of a thickener, 0.5-1.5 mass parts is preferable with respect to 100 mass parts of electrode active materials. When the use amount of the thickener is within the above range, the coating property of the electrode slurry and the adhesion to the current collector are good.

  Furthermore, in addition to the above components, the electrode slurry contains trifluoropropylene carbonate, vinylene carbonate, catechol carbonate, 1,6-dioxaspiro [4,4] nonane-2,7 in order to increase the stability and life of the battery. -Dione, 12-crown-4-ether, etc. can be used. These may be used by being contained in an electrolyte solution described later.

  The amount of the solvent in the electrode slurry is adjusted so as to have a viscosity suitable for coating depending on the type of the electrode active material, the electrode binder and the like. Specifically, the solid content concentration of the electrode active material, the electrode binder, and the conductive additive in the electrode slurry is preferably 30 to 90% by mass, more preferably Is used by adjusting to an amount of 40 to 80% by mass.

  The electrode slurry is obtained by mixing an electrode active material, an electrode binder, an optional additive such as a conductivity imparting agent added as necessary, and a solvent using a mixer. Mixing may be performed by supplying the above components all at once to a mixer. When using electrode active materials, electrode binders, conductivity-imparting materials and thickeners as constituents of electrode slurries, conductivity is imparted by mixing the conductivity-imparting materials and thickeners in a solvent. It is preferable to disperse the material in the form of fine particles, and then add a binder for the electrode and an electrode active material and further mix, since the dispersibility of the slurry is improved. As the mixer, a ball mill, sand mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, Hobart mixer, etc. can be used. It is preferable because aggregation of the resin can be suppressed.

  The particle size of the electrode slurry is preferably 35 μm or less, more preferably 25 μm or less. When the particle size of the slurry is in the above range, the conductivity imparting material is highly dispersible and a homogeneous electrode can be obtained.

  The current collector is not particularly limited as long as it is an electrically conductive and electrochemically durable material. From the viewpoint of having heat resistance, for example, iron, copper, aluminum, nickel, stainless steel, etc. Metal materials such as titanium, tantalum, gold, and platinum are preferable. Among these, aluminum is particularly preferable for the positive electrode of the lithium ion secondary battery, and copper is particularly preferable for the negative electrode of the lithium ion secondary battery. The shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 to 0.5 mm is preferable. In order to increase the adhesive strength of the electrode active material layer, the current collector is preferably used after roughening in advance. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, an abrasive cloth paper with a fixed abrasive particle, a grindstone, an emery buff, a wire brush provided with a steel wire or the like is used. Further, an intermediate layer may be formed on the surface of the current collector in order to increase the adhesive strength and conductivity of the electrode active material layer.

  The method for producing the electrode active material layer may be any method in which the electrode active material layer is bound in layers on at least one side, preferably both sides of the current collector. For example, the electrode slurry is applied to a current collector and dried, and then heat-treated at 120 ° C. or higher for 1 hour or longer to form an electrode active material layer. The method for applying the electrode slurry to the current collector is not particularly limited. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. Examples of the drying method include drying by warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams.

  Next, it is preferable to lower the porosity of the electrode active material layer by pressure treatment using a mold press or a roll press. The preferable range of the porosity is 5 to 15%, more preferably 7 to 13%. If the porosity is too high, charging efficiency and discharging efficiency are deteriorated. When the porosity is too low, there are problems that it is difficult to obtain a high volume capacity, or that the electrode active material layer is easily peeled off and is likely to be defective. Further, when a curable polymer is used, it is preferably cured.

  The thickness of the electrode active material layer is usually 5 to 300 μm, preferably 10 to 250 μm, for both the positive electrode and the negative electrode.

  The secondary battery separator used in the secondary battery of the present invention is preferably formed by laminating an organic separator and a porous film, and the porous film is the above-described secondary battery porous film. That is, the secondary battery separator of the present invention is preferably formed by laminating the above-described secondary battery porous film on an organic separator.

(Organic separator)
As an organic separator for a lithium ion secondary battery, known ones such as a polyolefin resin such as polyethylene and polypropylene and a separator containing an aromatic polyamide resin are used.

  As the organic separator used in the present invention, a porous membrane having a fine pore size, having no electron conductivity and ionic conductivity and high resistance to organic solvents is used. For example, polyolefin-based (polyethylene, polypropylene, polybutene, polychlorinated) Vinyl), and a microporous film made of a resin such as a mixture or a copolymer thereof, polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, polyimide, polyimide amide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene Examples thereof include a microporous membrane made of a resin such as the above, or a woven fabric of polyolefin fibers, a nonwoven fabric thereof, an aggregate of insulating substance particles, or the like. Among these, since the coating property of the porous membrane slurry of the present invention is excellent, the film thickness of the entire separator can be reduced and the active material ratio in the battery can be increased to increase the capacity per volume. A microporous membrane is preferred.

  The thickness of the organic separator is usually 0.5 to 40 μm, preferably 1 to 30 μm, and more preferably 1 to 10 μm. Within this range, the resistance due to the organic separator in the battery is reduced. Moreover, the workability | operativity at the time of coating the porous membrane slurry of this invention to an organic separator is good.

  In the present invention, examples of the polyolefin-based resin used as the material for the organic separator include homopolymers such as polyethylene and polypropylene, copolymers, and mixtures thereof. Examples of the polyethylene include low density, medium density, and high density polyethylene, and high density polyethylene is preferable from the viewpoint of piercing strength and mechanical strength. These polyethylenes may be mixed in two or more types for the purpose of imparting flexibility. The polymerization catalyst used for these polyethylenes is not particularly limited, and examples thereof include Ziegler-Natta catalysts, Phillips catalysts, and metallocene catalysts. From the viewpoint of achieving both mechanical strength and high permeability, the viscosity average molecular weight of polyethylene is preferably 100,000 to 12 million, more preferably 200,000 to 3 million. Examples of polypropylene include homopolymers, random copolymers, and block copolymers, and one kind or a mixture of two or more kinds can be used. The polymerization catalyst is not particularly limited, and examples thereof include Ziegler-Natta catalysts and metallocene catalysts. The stereoregularity is not particularly limited, and isotactic, syndiotactic or atactic can be used. However, it is desirable to use isotactic polypropylene because it is inexpensive. Furthermore, an appropriate amount of a polyolefin other than polyethylene or polypropylene, and an additive such as an antioxidant or a nucleating agent may be added to the polyolefin as long as the effects of the present invention are not impaired.

  As a method for producing a polyolefin-based organic separator, a publicly known one is used. For example, after forming a melt-extruded film of polypropylene and polyethylene, annealing is performed at a low temperature to grow a crystal domain, and in this state, stretching is performed. A dry method of forming a microporous film by extending the amorphous region; mixing a hydrocarbon solvent or other low molecular weight material with polypropylene or polyethylene, forming a film, and then forming a solvent or low molecular weight into the amorphous phase A wet method in which a microporous film is formed by removing the film that has started to form an island phase by using this solvent or low-molecular solvent with another volatile solvent is selected. Among these, a dry method is preferable in that a large void can be easily obtained for the purpose of reducing the resistance.

  The organic separator used in the present invention may contain any filler or fiber compound for the purpose of controlling strength, hardness, and heat shrinkage. In addition, when laminating the porous membrane of the present invention, a low molecular compound or the like may be used in advance for the purpose of improving the adhesion between the organic separator and the porous membrane or improving the liquid impregnation property by lowering the surface tension with respect to the electrolytic solution. A coating treatment with a polymer compound, an electromagnetic radiation treatment such as ultraviolet rays, or a plasma treatment such as corona discharge / plasma gas may be performed. In particular, the coating treatment is preferably performed with a polymer compound containing a polar group such as a carboxylic acid group, a hydroxyl group, and a sulfonic acid group from the viewpoint that the impregnation property of the electrolytic solution is high and the adhesion with the porous film is easily obtained.

(Method for manufacturing secondary battery separator)
The secondary battery separator of this invention is manufactured by laminating | stacking the secondary battery porous film of this invention on said organic separator. Although the lamination | stacking method is not specifically limited, The method of (I)-(III) demonstrated by the manufacturing method of the above-mentioned porous film is mentioned.

(Electrolyte)
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is used. A lithium salt is used as the supporting electrolyte. The lithium salt is not particularly _{limited, LiPF 6, LiAsF 6, LiBF} 4, LiSbF 6, LiAlCl 4, LiClO 4, CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) ₂ NLi, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable. Two or more of these may be used in combination. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

  The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, but dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate. Carbonates such as (BC) and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; Are preferably used. Moreover, you may use the liquid mixture of these solvents. Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. Since the lithium ion conductivity increases as the viscosity of the solvent used decreases, the lithium ion conductivity can be adjusted depending on the type of the solvent.

  The density | concentration of the supporting electrolyte in electrolyte solution is 1-30 mass% normally, Preferably it is 5-20 mass%. Further, it is usually used at a concentration of 0.5 to 2.5 mol / L depending on the type of the supporting electrolyte. If the concentration of the supporting electrolyte is too low or too high, the ionic conductivity tends to decrease. Since the degree of swelling of the binder increases as the concentration of the electrolytic solution used decreases, the lithium ion conductivity can be adjusted by the concentration of the electrolytic solution.

(Method for manufacturing secondary battery)
As a specific method for producing a lithium ion secondary battery, a positive electrode and a negative electrode are stacked with an organic separator interposed therebetween, and this is wound or folded in accordance with the battery shape and put into a battery container. The method of injecting and sealing is mentioned. The porous film of the present invention is laminated on any one of the positive electrode, the negative electrode, and the organic separator. The method of laminating the porous film of the present invention on the positive electrode, the negative electrode, and the organic separator is as described in the method (I) or (II). Moreover, it is also possible to laminate | stack only a porous film on a positive electrode, a negative electrode, or an organic separator independently as the above-mentioned method of (III). If necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like can be inserted to prevent an increase in pressure inside the battery and overcharge / discharge. The shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.

  In the secondary battery of the present invention, the porous film of the present invention is preferably laminated on the surface of the positive electrode or negative electrode active material layer. By laminating the porous film of the present invention on the surface of the electrode active material layer, even if the organic separator is contracted by heat, a short circuit between the positive electrode and the negative electrode is not caused, and high safety is maintained. In addition, by laminating the porous membrane of the present invention on the surface of the electrode active material layer, the porous membrane can function as a separator without an organic separator, and a secondary battery can be produced at low cost. become. In addition, even when an organic separator is used, since the holes formed on the separator surface are not filled, higher high-temperature cycle characteristics can be expressed.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the part and% in a present Example are a mass reference | standard. In the examples and comparative examples, various physical properties are evaluated as follows.

<Dispersibility of nonconductive particles in porous membrane slurry>
Using a laser diffraction particle size distribution measuring device, the dispersed particle size of the non-conductive particles in the porous membrane slurry is measured to determine the volume average particle size D50. Dispersibility is judged according to the following criteria. The closer the dispersed particle diameter is to the primary particles (volume average particle diameter of non-conductive particles), the smaller the cohesiveness is, and the more the dispersion is proceeding.
(Evaluation criteria)
A: Less than 0.4 μm B: 0.4 μm or more but less than 0.8 μm C: 0.8 μm or more but less than 1.8 μm D: 1.8 μm or more but less than 4.8 μm E: 4.8 μm or more

<Reliability test of secondary battery separator (organic separator with porous membrane)>
A secondary battery separator (organic separator with a porous film) was punched into a circle having a diameter of 19 mm, immersed in a 3 wt% methanol solution of a nonionic surfactant (manufactured by Kao Corporation; Emulgen 210P), and air-dried. This circular secondary battery separator is impregnated with an electrolytic solution and sandwiched between a pair of circular SUS plates (diameter 15.5 mm), and the structure is (SUS plate) / (circular secondary battery separator) / (SUS plate). A laminate was obtained. Here, the electrolytic solution is LiPF ₆ in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C.) at a concentration of 1 mol / liter. The solution dissolved in was used.

The laminate was sealed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. While applying an alternating current with an amplitude of 10 mV and a frequency of 1 kHz, the temperature was raised to 200 ° C. at a rate of temperature rise of 1.6 ° C./min, and the cell resistance during this time was measured to confirm the occurrence of a short circuit. In this test, increased the resistance value by shutting down with increasing temperature, becomes at least 1000 [Omega] / cm ² or more, then a short circuit when dropped sharply to 10 [Omega / cm ² or less was assumed to have occurred. This test was conducted 20 times and evaluated according to the following criteria. The smaller the number of short circuits, the better the reliability.
(Evaluation criteria)
A: Number of short-circuit occurrences 0 B: Number of short-circuit occurrences 1 C: Number of short-circuit occurrences 2 to 3 D: Number of short-circuit occurrences 4 or more

<Reliability test of secondary battery electrode (electrode with porous film)>
An organic separator (single-layer polypropylene separator, porosity 55%, thickness 25 μm, the same as that used in Example 1 as “organic separator”) is punched into a circle having a diameter of 19 mm, and a nonionic surfactant It was immersed in a 3% by weight methanol solution (manufactured by Kao Corporation; Emulgen 210P) and air-dried. On the other hand, the secondary battery electrode (electrode with porous film) to be measured was punched into a circle having a diameter of 19 mm. These are impregnated with an electrolytic solution, and these are overlapped and sandwiched between a pair of circular SUS plates (diameter 15.5 mm), and (SUS plate) / (circular organic separator) / (circular secondary battery electrode) / ( (SUS plate) was obtained. The circular secondary battery electrode was arranged such that the surface on the porous membrane side was the organic separator side. Here, the electrolytic solution is LiPF ₆ in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C.) at a concentration of 1 mol / liter. The solution dissolved in was used.

The laminate was sealed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. While applying an alternating current with an amplitude of 10 mV and a frequency of 1 kHz, the temperature was raised to 200 ° C. at a rate of temperature rise of 1.6 ° C./min, and the cell resistance during this time was measured to confirm the occurrence of a short circuit. In this test, increased the resistance value by shutting down with increasing temperature, becomes at least 1000 [Omega] / cm ² or more, then a short circuit when dropped sharply to 10 [Omega / cm ² or less was assumed to have occurred. This test was conducted 20 times and evaluated according to the following criteria. The smaller the number of short circuits, the better the reliability.
(Evaluation criteria)
A: Number of short-circuit occurrences 0 B: Number of short-circuit occurrences 1 C: Number of short-circuit occurrences 2 to 3 D: Number of short-circuit occurrences 4 or more

<Powder fall off of secondary battery electrode (electrode with porous film)>
A secondary battery electrode (electrode with a porous film) was cut out at 5 cm square, put into a 500 ml glass bottle, and allowed to stand for 3 hours at 300 rpm with a machine. The mass of the fallen powder is a, the mass of the secondary battery electrode before the b is b, the mass of the electrode before laminating the porous film is c, and only the electrode not laminating the porous film has fallen The mass of the powder was d, and the ratio X [mass%] of the fallen powder was calculated by the following formula and evaluated according to the following criteria. The smaller the fallen powder ratio X, the better the high-temperature cycle characteristics of the secondary battery.
X = (ad) / (bca) × 100 [mass%]
(Evaluation criteria)
A: Less than 2% by mass B: 2% by mass or more and less than 5% by mass C: 5% by mass or more

<Powder removal property of secondary battery separator (organic separator with porous membrane)>
A secondary battery separator (organic separator with a porous film) was cut out in a 5 cm square, placed in a 500 ml glass bottle, and allowed to stand for 3 hours at 300 rpm with a knitting machine. The mass of the secondary battery separator before the mating was a, the mass of the secondary battery separator after the mating was b, and the ratio X [% by mass] of the fallen powder was calculated by the following formula and evaluated according to the following criteria. The smaller the fallen powder ratio X, the better the high-temperature cycle characteristics of the secondary battery.
X = (ab) / a * 100 [mass%]
(Evaluation criteria)
A: Less than 1% by mass B: 1% by mass or more and less than 3% by mass C: 3% by mass or more and less than 5% by mass D: 5% by mass or more and less than 10% by mass E: 10% by mass or more and less than 15% by mass F: 15% by mass %that's all

<High-temperature cycle characteristics of secondary batteries>
With respect to the full-cell coin type lithium ion secondary battery, charging and discharging of charging from 3 V to 4.3 V at 60 ° C. and 0.1 C and then discharging from 4.3 V to 3 V at 0.1 C were repeated 50 cycles. A value obtained by calculating the percentage of the 0.1C discharge capacity at the 50th cycle with respect to the 0.1C discharge capacity at the 5th cycle as a percentage was determined as the capacity maintenance rate, and the following criteria were used. The larger this value, the less the discharge capacity is reduced, and the high temperature cycle characteristics are excellent.
(Evaluation criteria)
A: 60% or more B: 50% or more and less than 60% C: 30% or more and less than 50% D: 10% or more and less than 30% E: Less than 10%

<Measurement of iodine value>
100 g of an aqueous dispersion of hydrogenated nitrile polymer used for the porous membrane binder was coagulated with 1 liter of methanol and then vacuum dried at 60 ° C. overnight. The iodine value of the dried polymer was measured according to JIS K6235;

Example 1
<1-1. Production of non-conductive particles>
In a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.2 part of sodium dodecylbenzenesulfonate, 0.5 part of ammonium persulfate and sodium lauryl sulfate as an emulsifier (product name “ Emar 2F ") 0.15 parts, respectively, the gas phase part was replaced with nitrogen gas, and the temperature was raised to 60 ° C.

  On the other hand, in a separate container, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate, 94.8 parts of n-butyl acrylate as a polymerizable monomer, 2 parts of acrylonitrile, 2 parts of methacrylic acid, N- A monomer mixture was obtained by mixing 1.2 parts of methylolacrylamide and 1 part of allyl glycidyl ether (AGE). This monomer mixture was continuously added to the reactor over 4 hours for polymerization. During the addition, the reaction was carried out at 60 ° C. After completion of the addition, the reaction was terminated by further stirring at 70 ° C. for 3 hours to obtain an aqueous dispersion of seed polymer particles. The polymerization conversion rate was 99% or more.

  In a reactor equipped with a stirrer, 10 parts of the above seed polymer particle aqueous dispersion, 90 parts of monomer (ethylene glycol dimethacrylate), sodium dodecylbenzenesulfonate (manufactured by Kao Chemical Co., Neopelex) 1 part of G-15), 4 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, perbutyl O) as a polymerization initiator, and 520 parts of ion-exchanged water were added at 90 ° C. For 5 hours. Thereafter, steam was introduced to remove unreacted monomers to obtain an aqueous dispersion of non-conductive particles having an average particle diameter of 0.7 μm.

  The composition of the monomer used from the formation of the seed polymer particles to the production of the non-conductive particles is n-butyl acrylate / acrylonitrile / methacrylic acid / N-methylol acrylamide / allyl glycidyl ether / ethylene glycol dimethacrylate = 9. It was 38 / 0.2 / 0.2 / 0.12 / 0.1 / 90 (mass ratio).

<1-2. Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 35 parts of acrylonitrile and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 60 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400ml of nitrile polymer (total solid content 48g) with total solid content adjusted to 12% was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was passed for 10 minutes to remove dissolved oxygen in the nitrile polymer. did. Thereafter, 75 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymerized units having a nitrile group were 35%, and the polymerized units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 7 mg / 100 mg.

<1-3. Production of polyacrylonitrile>
A pressure-resistant vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normal pressure with nitrogen gas were applied. Repeatedly, it was confirmed using a dissolved oxygen meter that the oxygen concentration in the gas phase portion of the reaction vessel was 1% or less and that the dissolved oxygen in water was 1 ppm or less. Thereafter, 0.2 parts of partially saponified polyvinyl alcohol (“GOHSENOL GH-20” (saponification degree: 86.5 to 89.0 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd.) was gradually added and dispersed well as a dispersant. Stirring was continued while gradually raising the temperature to 60 ° C. and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.

  Subsequently, under conditions of nitrogen gas flow rate of 0.5 ml / min, 85 parts of acrylonitrile as an α, β-unsaturated nitrile monomer, 5 parts of methacrylic acid as an ethylenically unsaturated compound, and t-dodecyl mercaptan as a chain transfer agent 0 2 parts were charged, mixed with stirring and kept at 60 ± 2 ° C. Here, 0.4 parts of 1,1-azobis (1-acetoxy-1-phenylethane) (Otsuka Chemical Co., Ltd. “OTAZO-15”; abbreviated OTazo-15), which is an oil-soluble polymerization initiator, was added to acrylonitrile 10 The solution dissolved in the part was added to start the reaction. After proceeding for 3 hours at 60 ± 2 ° C., the reaction was continued for further 2 hours at 70 ± 2 ° C., and further for 2 hours at 80 ± 2 ° C. Then, it cooled to 40 degrees C or less, and obtained the polymer particle. The obtained turbid particles of the polymer were collected on a 200-mesh filter cloth and washed three times with 100 parts of ion-exchanged water to obtain an aqueous dispersion of polyacrylonitrile. Thereafter, the aqueous dispersion was dried under reduced pressure at 70 ° C. for 12 hours and isolated and purified to obtain polyacrylonitrile (yield: 70%). In the obtained polyacrylonitrile, the proportion of polymerized units having a nitrile group was 95%, and the proportion of polymerized units derived from the ethylenically unsaturated compound was 5%.

  Moreover, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn and Mn are number average molecular weights) of the obtained polyacrylonitrile were measured by GPC (gel permeation chromatography). GPC was performed by the following method using methylformamide (DMF) as an eluent. The measured weight average molecular weight Mw was 1.3 million, and the molecular weight distribution Mw / Mn was 8.

<Molecular weight measurement (GPC measurement)>
(Sample preparation for measurement)
In about 5 mL of the eluent, the polyacrylonitrile obtained above is added so that the solid content concentration is about 0.5 g / L, and it is gently dissolved at room temperature. After visually confirming dissolution, it is added to a 0.45 μm filter. The sample for measurement was prepared by gently filtering.

(Measurement condition)
The following measuring device was used.
Column: TSKgel α-M × 2 (φ7.8 mm ID × 30 cm × 2 manufactured by Tosoh Corporation)
Eluent: Dimethylformamide (50 mM lithium bromide, 10 mM phosphoric acid)
Flow rate: 0.5 mL / min Sample concentration: About 0.5 g / L (solid content concentration)
Injection volume: 200 μL
Column temperature: 40 ° C
Detector: Differential refractive index detector RI (HLC-8320 GPC RI detector manufactured by Tosoh Corporation)
Detector conditions: RI: Pol (+), Res (1.0 s)
Molecular weight marker: Tosoh standard polystyrene kit PStQuick Kit-H

<1-4. Adjustment of porous membrane binder>
The aqueous dispersion of the hydrogenated nitrile polymer obtained above and the aqueous dispersion of polyacrylonitrile were mixed using a disper to obtain an aqueous dispersion of a binder for a porous membrane. The mass ratio (hydrogenated nitrile monomer / polyacrylonitrile) of the hydrogenated nitrile monomer and polyacrylonitrile in the porous membrane binder was 90/10.

<1-5. Production of porous membrane slurry>
As a thickener, 1% aqueous solution was prepared using carboxymethyl cellulose (Daicel Chemical Industries, Ltd. Daicel 1220) having a degree of etherification of 0.8 to 1.0 and a 1% aqueous solution viscosity of 10 to 20 mPa · s. Prepared.

  Solid content weight ratio of aqueous dispersion of non-conductive particles obtained in step <1-1>, aqueous dispersion of porous membrane binder obtained in step <1-4>, and 1% aqueous solution of carboxymethyl cellulose Was mixed in water to obtain 83.1: 12.3: 4.6 to obtain a porous membrane slurry.

<1-6. Production of positive electrode>
To 95 parts of lithium manganate having a spinel structure as a positive electrode active material, PVDF (polyvinylidene fluoride, manufactured by Kureha Chemical Co., Ltd., trade name: KF-1100) as a binder is added to 3 parts in terms of solid content. Furthermore, 2 parts of acetylene black and 20 parts of N-methylpyrrolidone were added and mixed with a planetary mixer to obtain a slurry composition for a positive electrode active material layer. The slurry composition for positive electrode active material layer is applied to one side of an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll-pressed to form a positive electrode having a positive electrode active material layer having a total thickness of 100 μm. Obtained.

<1-7. Production of negative electrode>
98 parts of graphite having a particle diameter of 20 μm and a specific surface area of 4.2 m ² / g as a negative electrode active material, and 1 part of solid content equivalent of SBR (styrene-butadiene rubber, glass transition temperature: −10 ° C.) as a binder The mixture was further mixed with 1.0 part of carboxymethylcellulose, water was added as a solvent, and these were mixed with a planetary mixer to obtain a slurry composition for a negative electrode active material layer. This negative electrode active material layer slurry composition was applied to one side of a 18 μm thick copper foil, dried at 120 ° C. for 3 hours, and then roll-pressed to form a negative electrode having a negative electrode active material layer with a total thickness of 60 μm. Obtained.

<1-8. Production of organic separator with porous membrane>
A single-layer polypropylene organic separator (porosity 55%, thickness 25 μm) produced by a dry method was prepared as an organic separator. On one surface of this organic separator, the porous membrane slurry obtained in step <1-5> was applied using a wire bar so that the thickness after drying was 5 μm to form a slurry layer. The slurry layer was dried at 50 ° C. for 10 minutes to form a porous film. Subsequently, a porous film was similarly formed on the other surface of the organic separator, and an organic separator with a porous film having a porous film on both surfaces was obtained.

<1-9. Production of secondary battery having organic separator with porous membrane>
The positive electrode obtained in step <1-6> was cut into a circle having a diameter of 13 mm to obtain a circular positive electrode. The negative electrode obtained in step <1-7> was cut into a circle having a diameter of 14 mm to obtain a circular negative electrode. Moreover, the organic separator with a porous film obtained in the step <1-8> was cut out into a circle having a diameter of 18 mm to obtain a circular organic separator with a porous film.

  A circular positive electrode is placed on the inner bottom surface of a stainless steel coin-type outer container provided with a polypropylene packing, a circular organic separator with a porous film is placed thereon, and a circular negative electrode is placed thereon. Were placed in a container. The circular positive electrode was placed so that the surface on the aluminum foil side faced toward the bottom surface side of the outer container and the surface on the positive electrode active material layer side faced upward. The circular negative electrode was placed so that the surface on the negative electrode active material layer side faced toward the organic separator with a circular porous film and the surface on the copper foil side faced upward.

Inject the electrolyte into the container so that no air remains, fix the outer container with a 0.2 mm thick stainless steel cap through a polypropylene packing, seal the battery can, and 20 mm in diameter. A lithium ion secondary battery (coin cell CR2032) having a thickness of about 3.2 mm was manufactured. As an electrolytic solution, LiPF ₆ is mixed at a concentration of 1 mol / liter in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C.). The dissolved solution was used.

<1-10. Evaluation>
The reliability of the porous film of the obtained organic separator with a porous film, powder fall-off property, and the high temperature cycle characteristic of the secondary battery obtained by process <1-9> were evaluated. The results are shown in Table 1.

(Example 2)
A porous membrane slurry is produced by performing the same operation as in Example 1 except that the following non-conductive particles are used in place of the non-conductive particles obtained in Step <1-1> of Example 1. Then, an organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Manufacture of non-conductive particles>
A reactor equipped with a stirrer was distilled and purified, and 99 parts of styrene having a purity of 99%, 1.0 part of sodium dodecylbenzenesulfonate, 100 parts of ion-exchanged water, and 0.5 part of potassium persulfate were placed at 80 ° C. Polymerized for 8 hours. As a result, an aqueous dispersion of seed polymer particles A having an average particle diameter of 60 nm was obtained.

In a reactor equipped with a stirrer, 2 parts of an aqueous dispersion of the seed polymer particles A described above on a solid basis (that is, based on the weight of the seed polymer particles A), 0.2 parts of sodium dodecylbenzenesulfonate, potassium persulfate 0.5 part and 100 parts of ion-exchanged water were added and mixed to obtain a mixture, which was heated to 80 ° C. Meanwhile, in another container, 97 parts of styrene, 3 parts of methacrylic acid, 4 parts of t-dodecyl mercaptan, 0.5 part of sodium dodecylbenzenesulfonate, and 100 parts of ion-exchanged water are mixed to disperse the monomer mixture. The body was prepared. The monomer mixture dispersion was continuously added to the mixture for 4 hours to polymerize. The reaction was carried out while maintaining the temperature of the reaction system at 80 ° C. during continuous addition of the dispersion of the monomer mixture. After completion of the continuous addition, the reaction was further continued at 90 ° C. for 3 hours.
Thereby, an aqueous dispersion of seed polymer particles B having an average particle diameter of 200 nm was obtained.

Next, in a reactor equipped with a stirrer, 10 parts of the aqueous dispersion of the seed polymer particles B on the basis of the solid content (that is, based on the weight of the seed polymer particles B) and 84 parts of divinylbenzene monomer having a purity of 99%. , 1.0 part of sodium dodecylbenzenesulfonate, 5 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: perbutyl O) as a polymerization initiator, and 200 parts of ion-exchanged water A portion of the mixture was stirred at 35 ° C. for 12 hours to completely absorb the monomer mixture and the polymerization initiator in the seed polymer particles B. Thereafter, this was polymerized at 90 ° C. for 4 hours, 1.5 parts of glycidyl methacrylate was added while maintaining the temperature at 90 ° C., and left for 15 minutes. Subsequently, 2,2′-azobis- [2-methyl-N- [1,1-bis (hydroxymethyl) 2-hydroxyethyl] propionamide] (manufactured by Wako Pure Chemical Industries, Ltd., product) dissolved in 10 parts of ion-exchanged water Name: VA-086) 0.1 part was added as an initiator, and the polymerization was further continued for 3 hours.
Thereafter, steam was introduced to remove unreacted monomers to obtain an aqueous dispersion of non-conductive particles having an average particle size of 0.3 μm.
The composition of the monomer used from the formation of the seed polymer particles to obtaining the non-conductive particles was styrene / methacrylic acid / divinylbenzene / ethylvinylbenzene / glycidyl methacrylate = 9.7 / 0.3 / 53.1. /35.4/1.5 (mass ratio).

(Example 3)
Instead of the non-conductive particles obtained in step <1-1> of Example 1, plate-like alumina (Seraph 0670 manufactured by Kinsei Tech Co., Ltd., average particle size 0.6 μm) as inorganic oxide particles was used. In the step <1-5> of Example 1, the above plate-like alumina, the aqueous dispersion of the porous membrane binder obtained in the step <1-4>, and a 1% aqueous solution of carboxymethyl cellulose were mixed in a solid weight ratio. Was 94.79: 3.79: 1.42 and mixed in water to obtain a porous membrane slurry. Except having used the said porous membrane slurry, operation similar to Example 1 was performed, the organic separator with a porous membrane, and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

Example 4
Instead of the non-conductive particles obtained in the step <1-1> of Example 1, tetrapot alumina (AKP-3000 manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.5 μm), which is inorganic oxide particles, is used. Except for the above, the same operation as in Example 3 was performed to produce a porous membrane slurry. Except having used the said porous membrane slurry, operation similar to Example 1 was performed, the organic separator with a porous membrane, and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 5)
Other than using non-conductive particles obtained in step <1-1> of Example 1 as titanium oxide (CR-EL manufactured by Ishihara Sangyo Co., Ltd., average particle size: 2.0 μm) which is inorganic oxide particles. Performed the same operation as in Example 3 to produce a porous membrane slurry. Except having used the said porous membrane slurry, operation similar to Example 1 was performed, the organic separator with a porous membrane, and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 6)
In step <1-5> of Example 1, an aqueous dispersion of non-conductive particles obtained in step <1-1>, and an aqueous dispersion of a porous membrane binder obtained in step <1-4>; A 1% aqueous solution of carboxymethylcellulose was mixed in water so that the solid content weight ratio was 91.6: 3.31: 5.09 to obtain a porous membrane slurry. Except having used the said porous membrane slurry, operation similar to Example 1 was performed, the organic separator with a porous membrane, and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 7)
In step <1-5> of Example 1, an aqueous dispersion of non-conductive particles obtained in step <1-1>, and an aqueous dispersion of a porous membrane binder obtained in step <1-4>; A 1% aqueous solution of carboxymethylcellulose was mixed in water such that the solid content weight ratio was 79.3: 16.3: 4.4 to obtain a porous membrane slurry. Except having used the said porous membrane slurry, operation similar to Example 1 was performed, the organic separator with a porous membrane, and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 8)
A porous membrane binder was prepared in the same manner as in Example 1 except that the following hydrogenated nitrile polymer was used instead of the hydrogenated nitrile polymer obtained in Step <1-2> of Example 1. A porous membrane slurry was produced, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 35 parts of acrylonitrile and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 60 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 90 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water to which nitric acid of 4 times moles of Pd was added, and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 10 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold molar nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymerized units having a nitrile group were 35%, and the polymerized units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 18 mg / 100 mg.

Example 9
A porous membrane binder was prepared in the same manner as in Example 1 except that the following hydrogenated nitrile polymer was used instead of the hydrogenated nitrile polymer obtained in Step <1-2> of Example 1. A porous membrane slurry was produced, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 35 parts of acrylonitrile and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 60 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 95 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 5 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water to which 4 times moles of nitric acid had been added to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymerized units having a nitrile group were 35%, and the polymerized units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 25 mg / 100 mg.

(Example 10)
A porous membrane binder was prepared in the same manner as in Example 1 except that the following hydrogenated nitrile polymer was used instead of the hydrogenated nitrile polymer obtained in Step <1-2> of Example 1. A porous membrane slurry was produced, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 35 parts of acrylonitrile and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 60 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 100 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water to which nitric acid of 4 times moles of Pd was added and added to the autoclave. After the inside of the system was replaced with hydrogen gas twice, the content of the autoclave was heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and subjected to hydrogenation reaction for 6 hours.

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymerized units having a nitrile group were 35%, and the polymerized units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 35 mg / 100 mg.

(Example 11)
A porous membrane binder was prepared in the same manner as in Example 1 except that the following hydrogenated nitrile polymer was used instead of the hydrogenated nitrile polymer obtained in Step <1-2> of Example 1. A porous membrane slurry was produced, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 10 parts of acrylonitrile and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen, and then 1,3-butadiene 85 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 75 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymer units having a nitrile group were 10%, and the polymer units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 7 mg / 100 mg.

(Example 12)
A porous membrane binder was prepared in the same manner as in Example 1 except that the following hydrogenated nitrile polymer was used instead of the hydrogenated nitrile polymer obtained in Step <1-2> of Example 1. A porous membrane slurry was produced, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 20 parts of acrylonitrile and 5 parts of methacrylic acid were placed in this order, and the inside of the bottle was replaced with nitrogen. 75 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was performed at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400ml of nitrile polymer (total solid content 48g) with total solid content adjusted to 12% was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was passed for 10 minutes to remove dissolved oxygen in the nitrile polymer. did. Thereafter, 75 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymer units having a nitrile group were 20%, and the polymer units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 7 mg / 100 mg.

(Example 13)
Instead of the hydrogenated nitrile polymer obtained in step <1-2> of Example 1, the following hydrogenated nitrile polymer was used. Moreover, the following polyacrylonitrile was used instead of the polyacrylonitrile obtained by process <1-3> of Example 1. Except that the hydrogenated nitrile polymer and polyacrylonitrile were used, the same operation as in Example 1 was performed to produce a porous membrane binder and a porous membrane slurry, to obtain an organic separator with a porous membrane and a secondary battery, Evaluation was performed. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 36 parts of acrylonitrile and 2 parts of methacrylic acid were placed in this order, and the inside of the bottle was replaced with nitrogen, and then 1,3-butadiene 62 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 75 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was Polymerized units having a nitrile group were 36%, and polymerized units having a carboxylic acid group were 2%. The iodine value of the hydrogenated nitrile polymer was 7 mg / 100 mg.

<Manufacture of polyacrylonitrile>
A pressure-resistant vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normal pressure with nitrogen gas were applied. Repeatedly, it was confirmed using a dissolved oxygen meter that the oxygen concentration in the gas phase portion of the reaction vessel was 1% or less and that the dissolved oxygen in water was 1 ppm or less. Thereafter, 0.2 parts of partially saponified polyvinyl alcohol (“GOHSENOL GH-20” (saponification degree: 86.5 to 89.0 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd.) was gradually added and dispersed well as a dispersant. Stirring was continued while gradually raising the temperature to 60 ° C. and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.

  Subsequently, under conditions of nitrogen gas flow rate of 0.5 ml / min, 85 parts of acrylonitrile as an α, β-unsaturated nitrile monomer, 5 parts of methacrylic acid as an ethylenically unsaturated compound, and t-dodecyl mercaptan as a chain transfer agent 0 2 parts were charged, mixed with stirring and kept at 60 ± 2 ° C. Here, 0.4 parts of 1,1-azobis (1-acetoxy-1-phenylethane) (Otsuka Chemical Co., Ltd. “OTAZO-15”; abbreviated OTazo-15), which is an oil-soluble polymerization initiator, was added to acrylonitrile 10 The solution dissolved in the part was added to start the reaction. After proceeding at 60 ± 2 ° C. for 3 hours, the reaction was further continued at 70 ± 2 ° C. for 2 hours. Then, it cooled to 40 degrees C or less, and obtained the polymer particle. The obtained turbid particles of the polymer were collected on a 200-mesh filter cloth and washed three times with 100 parts of ion-exchanged water to obtain an aqueous dispersion of polyacrylonitrile. Thereafter, the aqueous dispersion was dried under reduced pressure at 70 ° C. for 12 hours and isolated and purified to obtain polyacrylonitrile (yield: 70%). In the obtained polyacrylonitrile, the proportion of polymerized units having a nitrile group was 95%, and the proportion of polymerized units derived from the ethylenically unsaturated compound was 5%.

  Moreover, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn and Mn are number average molecular weights) of the obtained polyacrylonitrile were measured by GPC (gel permeation chromatography). GPC used methylformamide (DMF) as an eluent. The measured weight average molecular weight Mw was 1.3 million, and the molecular weight distribution Mw / Mn was 3.

(Example 14)
Instead of the hydrogenated nitrile polymer obtained in step <1-2> of Example 1, the following hydrogenated nitrile polymer was used. Moreover, the following polyacrylonitrile was used instead of the polyacrylonitrile obtained by process <1-3> of Example 1. Except that the hydrogenated nitrile polymer and polyacrylonitrile were used, the same operation as in Example 1 was performed to produce a porous membrane binder and a porous membrane slurry, to obtain an organic separator with a porous membrane and a secondary battery, Evaluation was performed. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 32 parts of acrylonitrile and 14 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen, and then 1,3-butadiene 54 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 75 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymer units having a nitrile group were 32%, and the polymer units having a carboxylic acid group were 14%. The iodine value of the hydrogenated nitrile polymer was 7 mg / 100 mg.

<Manufacture of polyacrylonitrile>
A pressure-resistant vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normal pressure with nitrogen gas were applied. Repeatedly, it was confirmed using a dissolved oxygen meter that the oxygen concentration in the gas phase portion of the reaction vessel was 1% or less and that the dissolved oxygen in water was 1 ppm or less. Thereafter, 0.2 parts of partially saponified polyvinyl alcohol (“GOHSENOL GH-20” (saponification degree: 86.5 to 89.0 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd.) was gradually added and dispersed well as a dispersant. Stirring was continued while gradually raising the temperature to 60 ° C. and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.

  Subsequently, under conditions of nitrogen gas flow rate of 0.5 ml / min, 85 parts of acrylonitrile as an α, β-unsaturated nitrile monomer, 5 parts of methacrylic acid as an ethylenically unsaturated compound, and t-dodecyl mercaptan as a chain transfer agent 0 2 parts were charged, mixed with stirring and kept at 60 ± 2 ° C. Here, 0.4 parts of 1,1-azobis (1-acetoxy-1-phenylethane) (Otsuka Chemical Co., Ltd. “OTAZO-15”; abbreviated OTazo-15), which is an oil-soluble polymerization initiator, was added to acrylonitrile 10 The solution dissolved in the part was added to start the reaction. After proceeding the reaction at 60 ± 2 ° C. for 3 hours, the reaction was further continued at 70 ± 2 ° C. for 2 hours, and further at 80 ± 2 ° C. for 4 hours. Then, it cooled to 40 degrees C or less, and obtained the polymer particle. The obtained turbid particles of the polymer were collected on a 200-mesh filter cloth and washed three times with 100 parts of ion-exchanged water to obtain an aqueous dispersion of polyacrylonitrile. Thereafter, the aqueous dispersion was dried under reduced pressure at 70 ° C. for 12 hours and isolated and purified to obtain polyacrylonitrile (yield: 70%). In the obtained polyacrylonitrile, the proportion of polymerized units having a nitrile group was 95%, and the proportion of polymerized units derived from the ethylenically unsaturated compound was 5%.

  Moreover, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn. Mn is a number average molecular weight) of the obtained polyacrylonitrile were measured by GPC (gel permeation chromatography). GPC used methylformamide (DMF) as an eluent. The measured weight average molecular weight Mw was 1.3 million, and the molecular weight distribution Mw / Mn was 10.

(Example 15)
The following polyacrylonitrile was used instead of the polyacrylonitrile obtained in the step <1-3> of Example 1. Except having used the said polyacrylonitrile, operation similar to Example 1 was performed, the binder for porous membranes and the porous membrane slurry were manufactured, the organic separator with a porous membrane, and the secondary battery were obtained and evaluated. The results are shown in Table 1.

<Manufacture of polyacrylonitrile>
A pressure-resistant vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normal pressure with nitrogen gas were applied. Repeatedly, it was confirmed using a dissolved oxygen meter that the oxygen concentration in the gas phase portion of the reaction vessel was 1% or less and that the dissolved oxygen in water was 1 ppm or less. Thereafter, 0.2 parts of partially saponified polyvinyl alcohol (“GOHSENOL GH-20” (saponification degree: 86.5 to 89.0 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd.) was gradually added and dispersed well as a dispersant. Stirring was continued while gradually raising the temperature to 60 ° C. and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.

  Subsequently, under conditions of nitrogen gas flow rate of 0.5 ml / min, 65 parts of acrylonitrile as the α, β-unsaturated nitrile monomer, 25 parts of methacrylic acid as the ethylenically unsaturated compound, and t-dodecyl mercaptan as the chain transfer agent 0 2 parts were charged, mixed with stirring and kept at 60 ± 2 ° C. Here, 0.4 parts of 1,1-azobis (1-acetoxy-1-phenylethane) (Otsuka Chemical Co., Ltd. “OTAZO-15”; abbreviated OTazo-15), which is an oil-soluble polymerization initiator, was added to acrylonitrile 10 The solution dissolved in the part was added to start the reaction. After proceeding for 3 hours at 60 ± 2 ° C., the reaction was continued for further 2 hours at 70 ± 2 ° C., and further for 2 hours at 80 ± 2 ° C. Then, it cooled to 40 degrees C or less, and obtained the polymer particle. The obtained turbid particles of the polymer were collected on a 200-mesh filter cloth and washed three times with 100 parts of ion-exchanged water to obtain an aqueous dispersion of polyacrylonitrile. Thereafter, the aqueous dispersion was dried under reduced pressure at 70 ° C. for 12 hours and isolated and purified to obtain polyacrylonitrile (yield: 70%). In the obtained polyacrylonitrile, the proportion of polymerized units having a nitrile group was 75%, and the proportion of polymerized units derived from the ethylenically unsaturated compound was 25%.

  Moreover, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn. Mn is a number average molecular weight) of the obtained polyacrylonitrile were measured by GPC (gel permeation chromatography). GPC used methylformamide (DMF) as an eluent. The measured weight average molecular weight Mw was 1.3 million, and the molecular weight distribution Mw / Mn was 8.

(Example 16)
The following polyacrylonitrile was used instead of the polyacrylonitrile obtained in the step <1-3> of Example 1. Except having used the said polyacrylonitrile, operation similar to Example 1 was performed, the binder for porous membranes and the porous membrane slurry were manufactured, the organic separator with a porous membrane, and the secondary battery were obtained and evaluated. The results are shown in Table 1.

<Manufacture of polyacrylonitrile>
A pressure-resistant vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normal pressure with nitrogen gas were applied. Repeatedly, it was confirmed using a dissolved oxygen meter that the oxygen concentration in the gas phase portion of the reaction vessel was 1% or less and that the dissolved oxygen in water was 1 ppm or less. Thereafter, 0.2 parts of partially saponified polyvinyl alcohol (“GOHSENOL GH-20” (saponification degree: 86.5 to 89.0 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd.) was gradually added and dispersed well as a dispersant. Stirring was continued while gradually raising the temperature to 60 ° C. and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.

  Subsequently, under conditions of nitrogen gas flow rate of 0.5 ml / min, 75 parts of acrylonitrile as an α, β-unsaturated nitrile monomer, 15 parts of methacrylic acid as an ethylenically unsaturated compound, and t-dodecyl mercaptan 0 as a chain transfer agent 2 parts were charged, mixed with stirring and kept at 60 ± 2 ° C. Here, 0.4 parts of 1,1-azobis (1-acetoxy-1-phenylethane) (Otsuka Chemical Co., Ltd. “OTAZO-15”; abbreviated OTazo-15), which is an oil-soluble polymerization initiator, was added to acrylonitrile 10 The solution dissolved in the part was added to start the reaction. After proceeding for 3 hours at 60 ± 2 ° C., the reaction was continued for further 2 hours at 70 ± 2 ° C., and further for 2 hours at 80 ± 2 ° C. Then, it cooled to 40 degrees C or less, and obtained the polymer particle. The obtained turbid particles of the polymer were collected on a 200-mesh filter cloth and washed three times with 100 parts of ion-exchanged water to obtain an aqueous dispersion of polyacrylonitrile. Thereafter, the aqueous dispersion was dried under reduced pressure at 70 ° C. for 12 hours and isolated and purified to obtain polyacrylonitrile (yield: 70%). In the obtained polyacrylonitrile, the proportion of polymer units having a nitrile group was 85%, and the proportion of polymer units derived from the ethylenically unsaturated compound was 15%.

  Moreover, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn. Mn is a number average molecular weight) of the obtained polyacrylonitrile were measured by GPC (gel permeation chromatography). GPC used methylformamide (DMF) as an eluent. The measured weight average molecular weight Mw was 1.3 million, and the molecular weight distribution Mw / Mn was 8.

(Example 17)
The following polyacrylonitrile was used instead of the polyacrylonitrile obtained in the step <1-3> of Example 1. Except having used the said polyacrylonitrile, operation similar to Example 1 was performed, the binder for porous membranes and the porous membrane slurry were manufactured, the organic separator with a porous membrane, and the secondary battery were obtained and evaluated. The results are shown in Table 1.

<Manufacture of polyacrylonitrile>
A pressure-resistant vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas introduction pipe was charged with 400 parts of ion-exchanged water, and while rotating the stirrer gently, reduced pressure (-600 mmHg) and normal pressure with nitrogen gas were applied. Repeatedly, it was confirmed using a dissolved oxygen meter that the oxygen concentration in the gas phase portion of the reaction vessel was 1% or less and that the dissolved oxygen in water was 1 ppm or less. Thereafter, 0.2 parts of partially saponified polyvinyl alcohol (“GOHSENOL GH-20” (saponification degree: 86.5 to 89.0 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd.) was gradually added and dispersed well as a dispersant. Stirring was continued while gradually raising the temperature to 60 ° C. and kept for 30 minutes to dissolve the partially saponified polyvinyl alcohol.

  Subsequently, under the condition of a nitrogen gas flow rate of 0.5 ml / min, 85 parts of acrylonitrile as the α, β-unsaturated nitrile monomer, 5 parts of acrylic acid as the ethylenically unsaturated compound, and t-dodecyl mercaptan as the chain transfer agent 0 2 parts were charged, mixed with stirring and kept at 60 ± 2 ° C. Here, 0.4 parts of 1,1-azobis (1-acetoxy-1-phenylethane) (Otsuka Chemical Co., Ltd. “OTAZO-15”; abbreviated OTazo-15), which is an oil-soluble polymerization initiator, was added to acrylonitrile 10 The solution dissolved in the part was added to start the reaction. After proceeding for 3 hours at 60 ± 2 ° C., the reaction was continued for further 2 hours at 70 ± 2 ° C., and further for 2 hours at 80 ± 2 ° C. Then, it cooled to 40 degrees C or less, and obtained the polymer particle. The obtained turbid particles of the polymer were collected on a 200-mesh filter cloth and washed three times with 100 parts of ion-exchanged water to obtain an aqueous dispersion of polyacrylonitrile. Thereafter, the aqueous dispersion was dried under reduced pressure at 70 ° C. for 12 hours and isolated and purified to obtain polyacrylonitrile (yield: 70%). In the obtained polyacrylonitrile, the proportion of polymerized units having a nitrile group was 95%, and the proportion of polymerized units derived from the ethylenically unsaturated compound was 5%.

  Moreover, the weight average molecular weight Mw and molecular weight distribution (Mw / Mn. Mn is a number average molecular weight) of the obtained polyacrylonitrile were measured by GPC (gel permeation chromatography). GPC used methylformamide (DMF) as an eluent. The measured weight average molecular weight Mw was 800,000, and the molecular weight distribution Mw / Mn was 8.

(Example 18)
In the process <1-4> of Example 1, the mass ratio of the hydrogenated nitrile polymer to polyacrylonitrile (hydrogenated nitrile polymer / polyacrylonitrile) was set to 80/20 to obtain a binder for a porous membrane. Except having obtained the porous film slurry using the said binder for porous films, operation similar to Example 1 was performed and the organic separator with a porous film and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 19)
In step <1-4> of Example 1, a porous membrane binder was obtained with a mass ratio of hydrogenated nitrile polymer to polyacrylonitrile (hydrogenated nitrile polymer / polyacrylonitrile) of 70/30. Except having obtained the porous film slurry using the said binder for porous films, operation similar to Example 1 was performed and the organic separator with a porous film and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 20)
In step <1-4> of Example 1, a porous membrane binder was obtained with a mass ratio of hydrogenated nitrile polymer to polyacrylonitrile (hydrogenated nitrile polymer / polyacrylonitrile) of 50/50. Except having obtained the porous film slurry using the said binder for porous films, operation similar to Example 1 was performed and the organic separator with a porous film and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 21)
In step <1-4> of Example 1, a porous membrane binder was obtained with a mass ratio of hydrogenated nitrile polymer to polyacrylonitrile (hydrogenated nitrile polymer / polyacrylonitrile) of 30/70. Except having obtained the porous film slurry using the said binder for porous films, operation similar to Example 1 was performed and the organic separator with a porous film and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

(Example 22)
The negative electrode active material layer completely covers the porous film slurry obtained in step <1-5> of Example 1 on the surface of the negative electrode active material layer side of the negative electrode obtained in Step <1-7> of Example 1. The slurry was applied so that the porous film thickness after drying was 5 μm to obtain a slurry layer. The slurry layer was dried at 50 ° C. for 10 minutes to form a porous film, and a negative electrode with a porous film was obtained. The obtained negative electrode with a porous film had a layer structure of (porous film) / (negative electrode active material layer) / (copper foil). The reliability and powder fall-off property of the obtained negative electrode with a porous film were evaluated. The results are shown in Table 1.

  Instead of the organic separator with a porous membrane obtained in step <1-8> of Example 1, an organic separator (single-layer polypropylene separator, porosity 55%, thickness 25 μm, step <1-8 of Example 1) > Is the same as that used as an organic separator).

  Moreover, except having used the said negative electrode with a porous film instead of the negative electrode obtained at process <1-7> of Example 1, operation similar to Example 1 was performed, and a secondary battery was obtained and evaluated. Went. The results are shown in Table 1. In placing the negative electrode with a circular porous film in the outer container, the negative electrode was placed so that the porous film side faced to the circular organic separator side and the copper foil side faced to the upper side.

(Comparative Example 1)
In step <1-4> of Example 1, a porous membrane binder was produced without mixing the hydrogenated nitrile polymer. Except having used the said porous membrane binder, operation similar to Example 1 was performed, the porous membrane slurry was manufactured, the organic separator with a porous membrane, and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Comparative Example 2)
In Step <1-4> of Example 1, a porous membrane binder was produced without mixing polyacrylonitrile. Except having used the said porous membrane binder, operation similar to Example 1 was performed, the porous membrane slurry was manufactured, the organic separator with a porous membrane, and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Comparative Example 3)
Example 1 except that PVDF (polyvinylidene fluoride, manufactured by Kureha Chemical Co., Ltd., trade name: KF-1100) was used instead of the hydrogenated nitrile polymer obtained in the step <1-2> of Example 1. A porous membrane slurry was produced by performing the same operation as in Example 1, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Comparative Example 4)
A porous membrane slurry was produced by performing the same operation as in Example 1 except that the following hydrogenated nitrile polymer was used instead of the hydrogenated nitrile polymer obtained in Step <1-2> of Example 1. Then, an organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

<Production of hydrogenated nitrile polymer>
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 35 parts of acrylonitrile and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 60 parts were injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a nitrile polymer. The polymerization conversion rate was 85%.

  400 ml of a nitrile polymer adjusted to a total solid content concentration of 12% by weight (48 g of total solids) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to dissolve dissolved oxygen in the nitrile polymer. Removed. Thereafter, 75 mg of palladium acetate as a hydrogenation catalyst was dissolved in 180 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first stage hydrogenation reaction”) was performed for 3 hours. )

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate as a hydrogenation catalyst was dissolved in 60 ml of water added with 4-fold mol of nitric acid with respect to Pd and added to the autoclave. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 3 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain an aqueous dispersion of a hydrogenated nitrile polymer. From the aqueous dispersion of hydrogenated nitrile polymer, a dried product was obtained in the same manner as described in “Measurement of iodine value” and analyzed by NMR. As a result, the hydrogenated nitrile polymer was The polymerized units having a nitrile group were 35%, and the polymerized units having a carboxylic acid group were 5%. The iodine value of the hydrogenated nitrile polymer was 40 mg / 100 mg.

  From the above, the porous film slurry using a specific binder is excellent in dispersibility of non-conductive particles. Moreover, the reliability of the organic separator with a porous film and electrode with a porous film which are obtained by using a specific binder improves, and powder fall-off is also prevented. Furthermore, it turns out that the cycling characteristics at the high temperature of a secondary battery improve by using this separator or electrode.

Claims (9)

Consisting of non-conductive particles and a binder comprising a hydrogenated nitrile polymer and polyacrylonitrile,
A slurry composition for a secondary battery porous membrane, wherein the hydrogenated nitrile polymer has an iodine value of 3 to 30 mg / 100 mg .   The slurry composition for a secondary battery porous film according to claim 1, wherein the hydrogenated nitrile polymer is polymerized and hydrogenated using water as a solvent.   The slurry composition for a secondary battery porous film according to claim 1 or 2, wherein the hydrogenated nitrile polymer includes a linear alkylene polymer unit obtained by hydrogenating a polymer unit derived from a conjugated diene monomer having 4 or more carbon atoms.   The slurry composition for a secondary battery porous film according to any one of claims 1 to 3, wherein the binder further comprises a polymer unit having a hydrophilic group.   The slurry composition for a secondary battery porous film according to any one of claims 1 to 4, wherein the non-conductive particles are inorganic oxide particles or organic particles.   The secondary battery porous film formed by forming the slurry composition for secondary battery porous films in any one of Claims 1-5 into a film | membrane form, and drying.   A secondary battery electrode, wherein the current collector, the electrode active material layer, and the porous film are laminated in this order, and the porous film is the secondary battery porous film according to claim 6.   An organic separator and a porous membrane are laminated, and the porous membrane is the secondary battery porous membrane according to claim 6. A secondary battery including a positive electrode, a negative electrode, an organic separator, and an electrolyte solution,
A secondary battery in which the secondary battery porous film according to claim 6 is laminated on any of the positive electrode, the negative electrode, and the organic separator.