JP6503790B2 - Binder for non-aqueous secondary battery porous membrane, composition for non-aqueous secondary battery porous membrane, porous membrane for non-aqueous secondary battery, and non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous secondary battery porous membrane binder, a non-aqueous secondary battery porous membrane composition, a non-aqueous secondary battery porous membrane, and a non-aqueous secondary battery.

  Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as “secondary batteries”) are small and lightweight, have high energy density, and have characteristics of being capable of repeated charge and discharge. , Is used in a wide range of applications. The secondary battery generally includes a battery member such as an electrode (positive electrode, negative electrode), and a separator that separates the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode.

Here, in recent years, in secondary batteries, battery members provided with a porous film as a protective layer are used for the purpose of improving heat resistance and strength.
Specific examples of the porous film include those formed by binding non-conductive particles such as organic particles and inorganic particles with a binder. Such a porous film may be generally referred to as a slurry composition in which a porous film material such as non-conductive particles or a binder is dissolved or dispersed in a dispersion medium such as water (hereinafter referred to as "composition for porous film" ) And the composition for a porous membrane is formed by applying and drying this composition on an electrode base material or separator base material provided with an electrode mixture layer on a current collector.

In recent years, porous films have been actively improved for the purpose of further improving the performance of non-aqueous secondary batteries (see, for example, Patent Documents 1 and 2).
Specifically, for example, in Patent Document 1, a secondary including 50 to 99% by mass of non-conductive particles and 0.1 to 10% by mass of a graft polymer having a degree of swelling of 100% to 300% with respect to an electrolytic solution It has been proposed to improve the rate characteristics and high temperature characteristics of non-aqueous secondary batteries by using a porous film for battery.
Moreover, in patent document 2, 0.5-40 mass% of water-soluble polymers, such as sodium salt or ammonium salt of cellulosic semi-synthetic polymer, inorganic particles, and a monomer unit containing a hydrophilic group are included. It has been proposed to secure the adhesion of the porous film to the electrode and improve the cycle characteristics of the secondary battery by using the porous film containing the particulate polymer.

WO 2010/134501 WO 2009/123168

Here, in recent years, non-aqueous secondary batteries are required to further improve their performance. Specifically, non-aqueous secondary batteries exhibit excellent durability even under severe conditions of use, for example, when mounted on an electric vehicle that is subject to continuous large vibration during use. Is required. Therefore, the porous film is also required to further improve the durability in the electrolytic solution when mounted in the non-aqueous secondary battery.
However, in the above-described conventional techniques, the durability of the porous film is not sufficient, and the durability of the non-aqueous secondary battery can not be made high enough.

  In addition, when forming a porous film on a base material, the composition for a porous film used for forming a porous film is subjected to high shear force by rotation of a gravure roll, for example, when it is coated by a gravure coating device. However, the composition for a porous film used in the formation of the above-mentioned conventional porous film has low dispersion stability when subjected to high shear force, and therefore the composition for a porous film has a long period of porosity. There is also a problem that when the rotational speed of the gravure roll is increased to form a film or to form a film at a high speed, the components are aggregated to make it difficult to obtain a porous film having a uniform thickness.

Therefore, the present invention provides a binder for a non-aqueous secondary battery porous membrane capable of forming a porous membrane excellent in durability and capable of enhancing the stability of the composition for a porous membrane under high shear. The purpose is to
Another object of the present invention is to provide a composition for a non-aqueous secondary battery porous film, which is excellent in stability under high shear and capable of forming a porous film excellent in durability.
And this invention aims at providing the non-aqueous secondary battery provided with the porous film for non-aqueous secondary batteries which is excellent in durability, and the said porous film for non-aqueous secondary batteries.

  The present inventors diligently studied for the purpose of solving the above-mentioned problems. Then, the present inventors have found that a particulate polymer comprising a random copolymer containing a (meth) acrylic acid alkyl ester monomer unit and an aromatic monovinyl monomer unit in a ratio within a specific range, and a sulfone, Of a composition for a porous membrane under high shear by using a binder for a porous membrane which contains an acid salt compound and the blending ratio of the sulfonate compound to the particulate polymer is a specific value or more And, it has been found that it is possible to secure the durability of the porous membrane, and the present invention has been completed.

  That is, the present invention aims to advantageously solve the above-mentioned problems, and the binder for a non-aqueous secondary battery porous membrane of the present invention comprises a particulate polymer and a sulfonate compound, and the particles described above Polymer is a random copolymer containing 35% by mass or more of (meth) acrylic acid alkyl ester monomer units and 20% by mass or more and 65% by mass or less of aromatic monovinyl monomer units; A value obtained by dividing the compounding amount of the acid salt compound by the compounding amount of the particulate polymer is 0.005 or more. Thus, a particulate polymer comprising a random copolymer containing the (meth) acrylic acid alkyl ester monomer unit and the aromatic monovinyl monomer unit in the above-mentioned range, and the particulate polymer On the other hand, if a binder containing a sulfonate compound at an amount ratio of the above or more is used, the stability of the composition for a porous film using the binder under high shear can be improved, and the binder The durability of the porous film formed using the above can be made excellent.

  Here, in the binder for a non-aqueous secondary battery porous film of the present invention, the particulate polymer preferably further contains an acidic group-containing monomer unit in an amount of 0.1% by mass to 5% by mass. If the particulate polymer contains an acidic group-containing monomer unit within the above-mentioned range, the stability of the composition for a porous film under high shear while suppressing an increase in water carried into the secondary battery The durability of the porous membrane can be further enhanced. In addition, electrical characteristics such as the life characteristics of the secondary battery provided with the porous film can be improved.

  Furthermore, in the binder for a non-aqueous secondary battery porous membrane of the present invention, it is preferable that the acidic group-containing monomer unit is a monomer unit derived from an ethylenically unsaturated dicarboxylic acid. When the particulate polymer includes a monomer unit derived from an ethylenically unsaturated dicarboxylic acid as an acid group-containing monomer unit, the content ratio of the acid group-containing monomer unit is reduced to bring it into a secondary battery. Even when the increase of the water content is further suppressed, the stability of the composition for a porous film under high shear, the durability of the porous film, and the electrical characteristics of the secondary battery can be sufficiently enhanced.

  And as for the binder for non-aqueous secondary battery porous films of this invention, it is preferable that volume average particle diameter D50 of the said particulate-form polymer is 100 nm-500 nm. If the volume average particle diameter D50 of the particulate polymer is within the above range, the stability of the composition for a porous membrane under high shear and the durability of the porous membrane can be further enhanced.

  In addition, in the binder for a non-aqueous secondary battery porous membrane of the present invention, it is preferable that the swelling degree of the particulate polymer with respect to the non-aqueous electrolyte is more than 1 time and 2 times or less. If the degree of swelling of the particulate polymer with respect to the non-aqueous electrolyte is within the above range, the durability of the porous film is further enhanced, and the electrical characteristics such as the life characteristics of the secondary battery provided with the porous film are improved. Can.

  Moreover, this invention aims at solving the said subject advantageously, The composition for non-aqueous secondary battery porous films of this invention is for non-aqueous secondary battery porous films of any of the above-mentioned. It is characterized by containing a binder, nonconductive particles and water. By using the composition containing any one of the above-mentioned binders for non-aqueous secondary battery porous films for forming a porous film, a porous film excellent in durability can be obtained. Moreover, the composition containing any one of the above-mentioned binders for non-aqueous secondary battery porous films is excellent in stability under high shear, and does not easily aggregate at the time of formation of the porous film.

  Moreover, this invention aims at solving the said subject advantageously, The porous film for non-aqueous secondary batteries of this invention is formed from the above-mentioned composition for non-aqueous secondary battery porous films. It is characterized by The porous film is excellent in durability.

  Moreover, this invention aims at solving the said subject advantageously. The non-aqueous secondary battery of this invention is equipped with the porous film for non-aqueous secondary batteries mentioned above. The non-aqueous secondary battery is excellent in durability and high in performance.

According to the present invention, a non-aqueous secondary battery porous film binder is provided which can form a porous film excellent in durability and can also enhance the stability of the composition for a porous film under high shear. can do.
Further, according to the present invention, it is possible to provide a composition for a non-aqueous secondary battery porous film which is excellent in stability under high shear and is capable of forming a porous film excellent in durability.
And according to the present invention, it is possible to provide a non-aqueous secondary battery provided with a porous film for non-aqueous secondary battery with excellent durability and the porous film for non-aqueous secondary battery.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder for non-aqueous secondary battery porous membranes of this invention is used as a material at the time of preparing the composition for non-aqueous secondary batteries porous membrane. And the composition for non-aqueous secondary battery porous membranes of this invention is prepared using the binder for non-aqueous secondary battery porous membranes of this invention. Moreover, the porous film for non-aqueous secondary batteries of this invention is formed using the composition for non-aqueous secondary batteries porous films of this invention. In addition, the non-aqueous secondary battery of the present invention comprises the porous film for non-aqueous secondary battery of the present invention on the surface of at least one battery member.

(Binder for non-aqueous secondary battery porous membrane)
The binder for a porous membrane of the present invention is a composition containing a particulate polymer having binding ability and a sulfonate compound, and optionally containing other components and a dispersion medium such as water. And the said particulate-form polymer is at least following (1), (2):
(1) 35 mass% or more of (meth) acrylic acid alkyl ester monomer units and 20 mass% or more and 65 mass% or less of aromatic monovinyl monomer units,
(2) a random copolymer,
Have the following characteristics: In addition, the value obtained by dividing the compounding amount of the sulfonate compound by the compounding amount of the particulate polymer (the compounding ratio of the sulfonate compound to the particulate polymer) is 0.005 or more. It is one of the characteristics of the binder for porous membranes.
In the present invention, “containing a monomer unit” means that “a structural unit derived from a monomer is contained in a polymer obtained using the monomer”. In the present invention, "(meth) acrylic" means acrylic and / or methacrylic.
And the composition for porous films containing the binder for porous films of this invention is excellent in the stability under high shear. Moreover, the porous film formed using the binder for porous films of this invention is excellent in durability.

<Particulate polymer>
The particulate polymer secures the strength of the obtained porous membrane and holds the components contained in the porous membrane so as not to be detached from the porous membrane.
Here, in general, the particulate polymer is not a water-soluble polymer but is present in the form of particles in an aqueous medium.

[(Meth) acrylic acid alkyl ester monomer unit]
Examples of (meth) acrylic acid alkyl ester monomers capable of forming (meth) acrylic acid alkyl ester monomer units include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and t-butyl Alkyl acrylates such as acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate Ester; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate And methacrylic acid alkyl esters such as stearyl methacrylate and glycidyl methacrylate; and the like. Among these, 2-ethylhexyl acrylate, ethyl acrylate and butyl acrylate are preferable from the viewpoints of improving the durability of the porous film and the life characteristics of the secondary battery and reducing the water content of the porous film, 2-ethylhexyl Acrylate is more preferred. From the viewpoint of reducing the amount of water brought into the secondary battery due to the particulate polymer to suppress the decomposition of the electrolyte in the electrolytic solution and improving the electrical characteristics (particularly the life characteristics) of the secondary battery. Preferably, the (meth) acrylic acid alkyl ester monomer does not have a hydrophilic group such as an acidic group (eg, a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group, etc.).
These can be used alone or in combination of two or more.

  The content ratio of the (meth) acrylic acid alkyl ester monomer unit in the particulate polymer is required to be 35% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, and further Preferably it is 55 mass% or more, Preferably it is 80 mass% or less, More preferably, it is 70 mass% or less, More preferably, it is 60 mass% or less. The adhesiveness of a particulate-form polymer is impaired as the content rate of a (meth) acrylic-acid alkylester monomer unit is less than 35 mass%, and durability of a porous film can not be ensured. On the other hand, when the content ratio of the (meth) acrylic acid alkyl ester monomer unit is 80% by mass or less, the life characteristics of the secondary battery can be improved.

[Aromatic monovinyl monomer unit]
Examples of the aromatic monovinyl monomer capable of forming an aromatic monovinyl monomer unit include styrene, styrene sulfonic acid and salts thereof (eg, sodium styrene sulfonate etc.), α-methylstyrene, vinyl toluene, 4- (tert) -Butoxy) styrene etc. are mentioned. Among these, styrene and sodium styrene sulfonate are preferable, and styrene is more preferable. The amount of water brought into the secondary battery due to the particulate polymer is reliably reduced to suppress the decomposition of the electrolyte in the electrolytic solution, thereby improving the electrical characteristics (particularly the life characteristics) of the secondary battery. From the viewpoint, it is preferable that the aromatic monovinyl monomer does not have a hydrophilic group such as an acid group (for example, a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group, etc.). These can be used alone or in combination of two or more.

  The content ratio of the aromatic monovinyl monomer unit in the particulate polymer is required to be 20% by mass or more and 65% by mass or less, preferably 25% by mass or more, more preferably 30% by mass or more, and further The content is preferably 35% by mass or more, preferably 64.9% by mass or less, more preferably 55% by mass or less, and still more preferably 50% by mass or less. If the content of the aromatic monovinyl monomer unit is less than 20% by mass, the durability of the porous film can not be ensured, and the electrical characteristics such as the life characteristics of the secondary battery are degraded. On the other hand, if the content of the aromatic monovinyl monomer unit exceeds 65% by mass, the adhesion of the particulate polymer is impaired, and the durability of the porous film can not be secured.

[Other monomer unit]
The particulate polymer may contain other monomer units other than the (meth) acrylic acid alkyl ester monomer unit and the aromatic monovinyl monomer unit described above. Such other monomer units are not particularly limited, and include acid group-containing monomer units and crosslinkable monomer units.
As described above, the acidic group-containing monomer unit and the crosslinkable monomer unit are monomer units other than the (meth) acrylic acid alkyl ester monomer unit and the aromatic monovinyl monomer unit. Therefore, the (meth) acrylic acid alkyl ester monomer described above is used for the acid group-containing monomer capable of forming an acid group-containing monomer unit and the crosslinkable monomer capable of forming a crosslinkable monomer unit. And aromatic monovinyl monomers such as styrene sulfonic acid and salts thereof are not included.

[[Acid group-containing monomer unit]]
As an acidic group containing monomer which can form an acidic group containing monomer unit, a carboxylic acid group containing monomer, a sulfonic acid group containing monomer, a phosphoric acid group containing monomer etc. can be mentioned.

Examples of carboxylic acid group-containing monomers include ethylenically unsaturated monocarboxylic acids and their derivatives, ethylenically unsaturated dicarboxylic acids and their acid anhydrides, and their derivatives.
Examples of ethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid and the like. And as an example of the derivative of the ethylenically unsaturated monocarboxylic acid, 2-ethyl acrylic acid, isocrotonic acid, α-acetoxy acrylic acid, β-trans-aryloxy acrylic acid, α-chloro-β-E mono methoxy acrylic Acids, β-diaminoacrylic acid and the like can be mentioned.
Examples of ethylenically unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, mesaconic acid and the like. And as an example of the acid anhydride of ethylenically unsaturated dicarboxylic acid, maleic anhydride, an acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride etc. are mentioned. Furthermore, examples of derivatives of ethylenically unsaturated dicarboxylic acids include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate And dodecyl maleate, octadecyl maleate, fluoroalkyl maleate and the like.

Examples of sulfonic acid group-containing monomers include vinylsulfonic acid, methylvinylsulfonic acid, (meth) allylsulfonic acid, ethyl (meth) acrylic acid-2-sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3 -Allyloxy 2-hydroxypropane sulfonic acid etc. are mentioned.
In the present invention, "(meth) allyl" means allyl and / or methallyl.

Examples of the phosphoric acid group-containing monomer include phosphoric acid-2- (meth) acryloyloxyethyl, methyl-2- (meth) acryloyloxyethyl phosphate, and ethyl phosphate- (meth) acryloyloxyethyl phosphate.
In the present invention, “(meth) acryloyl” means acryloyl and / or methacryloyl.

And among these, as an acidic group containing monomer, the acidic group containing monomer which has 2 or more of acidic groups in 1 molecule is preferable. When the particulate polymer has an acidic group-containing monomer unit, the presence of the acidic group can further enhance the stability of the composition for a porous membrane under high shear and the durability of the porous membrane, as well as the particles. It is possible to improve the rate characteristics of the secondary battery by increasing the degree of swelling of the solid polymer with respect to the non-aqueous electrolyte solution. However, on the other hand, when the amount of the acidic group-containing monomer used in preparing the particulate polymer is increased, the amount of water brought into the secondary battery due to the particulate polymer is increased, and the secondary Battery life characteristics are reduced. Therefore, from the viewpoint of enhancing the stability of the composition for a porous film under high shear, the durability of the porous film, and the rate characteristics of the secondary battery while suppressing an increase in the amount of water carried into the secondary battery. It is preferable to use an acidic group-containing monomer having two or more acidic groups in one molecule.
Further, from the viewpoint of enhancing the stability under high shear of the composition for a porous film, the durability of the porous film and the rate characteristics of the secondary battery, as the acidic group-containing monomer, a carboxylic acid group-containing monomer Sulfonic acid group-containing monomers and phosphoric acid group-containing monomers are preferable, and carboxylic acid group-containing monomers are more preferable.
Therefore, from these viewpoints, a carboxylic acid group-containing monomer having two or more carboxylic acid groups as acidic groups in one molecule is preferable, and more specifically, the above-mentioned ethylenically unsaturated dicarboxylic acid is preferable. Among these, itaconic acid, maleic acid and fumaric acid are more preferable, and itaconic acid is further preferable.
That is, the particulate polymer preferably contains a monomer unit derived from an ethylenically unsaturated dicarboxylic acid, and a monomer unit derived from itaconic acid, a monomer unit derived from maleic acid and a single amount derived from fumaric acid It is more preferable to include at least any one selected from the group consisting of body units, and it is further preferable to include a monomer unit derived from itaconic acid.

The content ratio of the acidic group-containing monomer unit in the particulate polymer is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.3% by mass or more. Is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1.8% by mass or less, and particularly preferably 1.5% by mass or less. When the content of the acidic group-containing monomer unit is 0.1% by mass or more, the stability of the composition for a porous film under high shear and the rate characteristics of the secondary battery are improved. On the other hand, when the content ratio of the acidic group-containing monomer unit is 5% by mass or less, the elution of the particulate polymer into the non-aqueous electrolytic solution is suppressed, and the durability of the porous film is improved. Since the amount of water brought into the secondary battery due to the combination is reduced, the electrical characteristics (particularly the life characteristics) of the secondary battery are improved.
In addition, the composition for porous membranes using the binder for porous membranes containing the particulate polymer mentioned above is dispersible by the aromatic monovinyl monomer unit contained in the said particulate polymer by a comparatively high ratio. Improve and show good stability even under high shear. Therefore, in this particulate polymer, even when the improvement of the durability of the porous film and the reduction of the amount of water carried into the secondary battery are achieved by reducing the content ratio of the acidic group-containing monomer unit The composition for a film can fully exhibit stability under high shear.

[[Crosslinkable Monomer Unit]]
As a crosslinkable monomer which can form a crosslinkable monomer unit, the monomer which can form a crosslinked structure when it superposes | polymerizes can be used. Specifically, a monofunctional monomer having a thermally crosslinkable crosslinkable group and one ethylenic unsaturated bond per molecule, and a multifunctional having two or more ethylenic unsaturated bonds per molecule Monomers are mentioned. Examples of the thermally crosslinkable crosslinkable group contained in the monofunctional monomer include an epoxy group, an N-methylolamide group, an oxetanyl group, an oxazoline group, and a combination thereof. By including the crosslinkable monomer unit, the size of the degree of swelling of the particulate polymer to be described later with respect to the non-aqueous electrolyte can be made to be a suitable size while enhancing the durability of the porous film.

The crosslinkable monomer may be hydrophobic or hydrophilic.
In the present invention, that the crosslinkable monomer is "hydrophobic" means that the crosslinkable monomer does not contain a hydrophilic group, and the crosslinkable monomer is "hydrophilic". It means that the said crosslinkable monomer contains a hydrophilic group. Here, the “hydrophilic group” in the crosslinkable monomer refers to a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, an epoxy group, a thiol group, an aldehyde group, an amide group, an oxetanyl group, and an oxazoline group.

Examples of hydrophobic crosslinkable monomers include allyl (meth) acrylate, ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate and trimethylol. Multifunctional (meth) acrylates such as propane-tri (meth) acrylate; difunctional polyallyl / vinyl ethers such as dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane and the like And divinyl benzene and the like.
Examples of hydrophilic crosslinkable monomers include vinyl glycidyl ether, allyl glycidyl ether, methylol acrylamide, acrylamide, allyl methacrylamide and the like.
These can be used alone or in combination of two or more.
Among these, a hydrophobic crosslinkable monomer is preferable from the viewpoint of reducing the amount of water carried into the secondary battery and improving the electrical characteristics (particularly, the life characteristics) of the secondary battery, allyl methacrylate And ethylene dimethacrylate are more preferred. And, from the viewpoint of enhancing the stability under high shear of the composition for a porous membrane containing a porous membrane binder, ethylene dimethacrylate is particularly preferable.
In the present invention, "(meth) acrylate" means acrylate and / or methacrylate.

  The content of the crosslinkable monomer unit in the particulate polymer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, and preferably It is 5% by mass or less, more preferably 2% by mass or less, still more preferably 1.8% by mass or less, and particularly preferably 1.5% by mass or less. When the content of the crosslinkable monomer unit is 0.1% by mass or more, the elution of the particulate polymer into the electrolytic solution is suppressed, and the durability of the porous film is enhanced. In addition, the shape of the particulate polymer hardly deforms even under high shear, and the stability of the composition for a porous membrane under high shear can be enhanced. On the other hand, the adhesiveness of a particulate-form polymer can fully be ensured as the content rate of a crosslinkable monomer unit is 5 mass% or less, and the durability of a porous film can be improved.

[Preparation of Particulate Polymer]
And a particulate polymer is prepared by polymerizing the monomer composition containing the monomer mentioned above. The formation of block copolymers and graft copolymers is suppressed by initiating polymerization in the form of monomers rather than in the form of oligomers obtained by polymerizing the monomers in the monomer composition to some extent, thereby suppressing the formation of random co-polymers. The particulate polymer of the present invention which is a polymer can be obtained.
Here, the content ratio of each monomer in the monomer composition is generally the same as the content ratio of the monomer unit in the desired particulate polymer.
The polymerization mode of the particulate polymer is not particularly limited as long as the resulting particulate polymer is a random copolymer, and, for example, a solution polymerization method, a suspension polymerization method, a bulk polymerization method, an emulsion polymerization method, etc. Any method may be used. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, living radical polymerization and the like can be used. And as an emulsifier, a dispersant, a polymerization initiator, a polymerization auxiliary and the like used for the polymerization, those generally used can be used, and the amount thereof used is also the amount generally used.

[Properties of Particulate Polymer]
The particulate polymer of the present invention is required to be a random copolymer. Even when the particulate polymer has a core structure and a shell structure, it is included in the particulate polymer of the present invention when the shell structure is a random copolymer.

[[Random copolymer structure and glass transition temperature]]
When the particulate polymer is a random copolymer, the polymer can be homogenized, the durability of the polymer to the electrolytic solution can be enhanced, and the dispersibility in the composition for a porous film can also be enhanced. it can. Furthermore, since the viscosity of the composition for a porous membrane can be suppressed, water can be easily removed from the porous membrane at the time of drying.
In the present invention, it is judged by measuring the glass transition temperature whether or not the particulate polymer is a random copolymer.
Specifically, when the particulate polymer which is a copolymer has one glass transition temperature, the particulate polymer corresponds to a random copolymer. On the other hand, when the particulate polymer has two or more glass transition temperatures, the particulate polymer does not have a random copolymer structure, and corresponds to a block copolymer, a graft copolymer or the like.
In the present invention, the "glass transition temperature" of the particulate polymer can be measured using the measurement method described in the examples of this specification.

  And the glass transition temperature of the particulate polymer which is a random copolymer is preferably 10 ° C. or less, more preferably 5 ° C. or less, particularly preferably 0 ° C. or less. The lower limit of the glass transition temperature of the particulate polymer is not particularly limited, but is usually -100 ° C. or higher.

[[Swelling degree to non-aqueous electrolyte]]
In the present invention, the “swelling degree of the particulate polymer in the non-aqueous electrolyte solution” is the immersion when the film (binder film) formed by forming the particulate polymer is immersed in a specific non-aqueous electrolyte solution under predetermined conditions The subsequent weight can be determined as the value (fold) divided by the weight before immersion, and specifically, the binder film is formed using the method described in the examples of the present specification and described in the same examples. Measure using the measurement method of
Here, the degree of swelling of the particulate polymer with respect to the non-aqueous electrolyte is usually more than 1 time, preferably 2 times or less, more preferably 1.9 times or less, and still more preferably 1.8 times or less. When the degree of swelling of the particulate polymer with respect to the non-aqueous electrolytic solution is 2 times or less, elution of the particulate polymer into the electrolytic solution is suppressed, and the durability of the porous film and the life characteristics of the secondary battery are improved.
The degree of swelling of the particulate polymer in the non-aqueous electrolyte solution can be adjusted by changing the type and amount of the monomer used, for example, the amount of the aromatic monovinyl monomer or the crosslinkable monomer The swelling degree with respect to the non-aqueous electrolyte can be reduced by increasing the polymerization molecular weight by increasing the polymerization temperature, increasing the polymerization temperature, or prolonging the polymerization reaction time.

[[Contact angle with water]]
In the present invention, the "contact angle with water" of the particulate polymer means the water droplet contact angle of the film (binder film) formed by molding the particulate polymer, and specifically, it is measured by the following method can do.
An aqueous dispersion of particulate polymer is applied to an electrolytic copper foil (NC-WS (registered trademark) manufactured by Furukawa Electric Co., Ltd.) using a table coater, and dried at 50 ° C. for 20 minutes, at 120 ° C. for 20 minutes, with hot air drying The resultant was dried in an oven to prepare three 1 cm.times.1 cm binder films (500 .mu.m in thickness). A drop of distilled water is dropped on the film, and the contact angle of the formed drop is measured with a contact angle meter under an atmosphere temperature of 23 degrees and a RH of 50% (model CA-DT-A, mfd. Kyowa It measures by interface science company make. The contact angle is measured at two points for each of the three binder films, and the average value of the total of six measurements is taken as the contact angle. In addition, the diameter of the water droplet of distilled water is 2 mm, and the numerical value of the contact angle which appears on a measuring meter adopts the value measured one minute after dropping the water droplet of distilled water.
The contact angle of the particulate polymer with water is preferably more than 80 °, more preferably 85 ° or more, particularly preferably 90 ° or more, preferably 120 ° or less, more preferably 115 ° or less, particularly Preferably it is 110 degrees or less.

[[Particle size]]
The volume average particle diameter D50 of the particulate polymer is preferably 100 nm or more, more preferably 110 nm or more, still more preferably 120 nm or more, preferably 500 nm or less, more preferably 400 nm or less, still more preferably 300 nm or less . When the volume average particle diameter D50 of the particulate polymer is 100 nm or more, the aggregation of the particulate polymer is suppressed, and the stability of the composition for a porous film under high shear is improved. On the other hand, when the volume average particle diameter D50 of the particulate polymer is 500 nm or less, the adhesiveness of the porous film is secured, and the durability of the porous film can be improved.
The “volume average particle diameter D50” of the particulate polymer represents a particle diameter at which the cumulative volume calculated from the small diameter side in the particle size distribution (volume basis) measured by the laser diffraction method is 50%.

<Sulfonate Compound>
The sulfonate compound is not particularly limited as long as it is a salt of a compound having a sulfonic acid group (—SO ₃ H). By blending such a sulfonate compound into the binder for a porous membrane, it is presumed that the compound is for suppressing the aggregation of the particulate polymer etc., but the high content of the composition for a porous membrane to be obtained Stability under shear can be ensured. In addition, the sulfonate compound is less likely to adversely affect the electrical properties of the secondary battery, and is also suitable for blending into the porous membrane binder in this respect.
The form of the salt is not particularly limited, and examples thereof include alkali metal salts such as sodium salt and alkaline earth metal salts such as calcium salt. The sulfonate compound is preferably a nonpolymer and its molecular weight is preferably in the range of 100 or more and 1000 or less.
And as a sulfonate compound, a sulfonate type surfactant is preferable. Examples of sulfonate surfactants include sulfosuccinates exemplified by dialkyl sulfosuccinates such as sodium dioctyl sulfosuccinate, alkyl benzene sulfonates, and alpha olefin sulfonates. Among these, from the viewpoint of further improving the stability under high shear of the composition for a porous film and reducing the amount of water carried into the secondary battery, sulfosuccinate is preferred, and dialkyl sulfosuccinate is preferred. More preferred is sodium dioctyl sulfosuccinate.
In addition, a sulfonate compound may be used individually by 1 type, and may be used combining 2 or more types.

  Here, in the binder for a non-aqueous secondary battery porous membrane of the present invention, a value obtained by dividing the compounding amount of the sulfonate compound by the compounding amount of the particulate polymer (the compounding ratio of the sulfonate compound to the particulate polymer Is required to be 0.005 or more, preferably 0.008 or more, more preferably 0.01 or more, and preferably 0.05 or less, more preferably 0.04 or less, still more preferably 0. .03 or less. If the blending ratio of the sulfonate compound to the particulate polymer is less than 0.005, the stability of the composition for a porous membrane under high shear can not be ensured. In addition, the durability of the porous film is reduced, and the rate characteristics and the life characteristics of the secondary battery are reduced. On the other hand, if the blending ratio of the sulfonate compound to the particulate polymer is 0.05 or less, the amount of water carried into the secondary battery is reduced, and the rate characteristics and the life characteristics of the secondary battery are improved. Can.

<Preparation of Binder for Nonaqueous Secondary Battery Porous Film>
Although the preparation method of the binder for porous membranes is not specifically limited, For example, when preparation of a particulate-form polymer is implemented in an aqueous medium and a particulate-form polymer is obtained as a water dispersion, the water of a particulate-form polymer is carried out. A sulfonate compound may be added to the dispersion to be used as a binder for a porous membrane as it is, or a sulfonate compound may be added to an aqueous dispersion of a particulate polymer, and any other component may be further added to a binder for a porous membrane It may be Here, as the other components, the other components described in the section of “composition for non-aqueous secondary battery porous film” described later can be mentioned.

(Composition for non-aqueous secondary battery porous membrane)
The composition for a non-aqueous secondary battery porous membrane of the present invention is an aqueous slurry composition in which the above-mentioned particulate polymer and sulfonate compound, and non-conductive particles are dispersed in water as a dispersion medium. In addition, the particulate polymer and the sulfonate compound are contained in the binder for the non-aqueous secondary battery porous film of the present invention, and the preferable abundance ratio of them is preferable in the binder for the porous film. It is the same as the abundance ratio.
And the porous film formed using the composition for porous films of this invention is excellent in durability.

<Non-conductive particles>
The non-conductive particles have non-conductivity and do not dissolve in water used as a dispersion medium in the composition for a porous film and the non-aqueous electrolyte solution of a secondary battery, and their shape is maintained even in them. Particles. And since non-conductive particles are also electrochemically stable, they are stably present in the porous film under the use environment of the secondary battery. When the composition for a porous film contains nonconductive particles, the network structure of the obtained porous film is appropriately plugged up, lithium dendrites and the like are prevented from penetrating the porous film, and a short circuit of the electrode is suppressed. It is because it can be made more reliable. As the nonconductive particles, various inorganic particles and organic particles can be used, for example.

As the inorganic particles, for example, oxide particles such as aluminum oxide (alumina), silicon oxide, magnesium oxide, titanium oxide, BaTiO ₂ , ZrO, alumina-silicic composite oxide, and nitride particles such as aluminum nitride and boron nitride And covalent crystal particles such as silicon and diamond, poorly soluble ionic crystal particles such as barium sulfate, calcium fluoride and barium fluoride, and clay fine particles such as talc and montmorillonite.
Examples of organic particles include polyethylene, polystyrene, polydivinylbenzene, crosslinked products of styrene-divinylbenzene copolymer, and various crosslinked polymers such as polyimide, polyamide, polyamideimide, melamine resin, phenol resin, benzoguanamine-formaldehyde condensate, etc. Molecular particles, heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, thermoplastic polyimide and the like can be mentioned. Here, the organic particle and the above-mentioned particulate polymer differ in that the particulate polymer has a binding ability but the organic particle does not have a binding ability. Particulate polymer is not included.

Among these, from the viewpoint of improving the durability of the porous film and the electrical characteristics of the secondary battery provided with the porous film, inorganic particles are preferable as the nonconductive particles, and aluminum oxide is more preferable.
The particle size of the non-conductive particles is not particularly limited, and can be the same as non-conductive particles conventionally used.

<Compounding ratio of non-conductive particles and binder for porous film>
The compounding ratio of the nonconductive particles and the binder for the porous film in the composition for the porous film is not particularly limited. For example, in the composition for a porous membrane, the blending amount of the particulate polymer is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, particularly preferably 3 parts by mass, per 100 parts by mass of the nonconductive particles. The binder for a porous membrane is contained in an amount of 25 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 18 parts by mass or less, particularly preferably 15 parts by mass or less. If the blending amount of the particulate polymer is 0.1 parts by mass or more per 100 parts by mass of the nonconductive particles, the adhesiveness between the porous membrane and the electrode base material or the separator base material is secured to improve the durability of the porous membrane. If the amount is 25 parts by mass or less, the amount of water carried into the secondary battery due to the particulate polymer can be reduced, and the electrical characteristics of the secondary battery can be improved. Moreover, the stability under high shear of the composition for porous films can also be improved.

<Other ingredients>
The composition for porous membranes may contain other optional components in addition to the components described above. The optional component is not particularly limited as long as it does not excessively adversely affect the battery reaction in the secondary battery using the porous membrane. The type of the optional component may be one or two or more.
Examples of the optional components include wetting agents, leveling agents, electrolyte solution decomposition inhibitors, water-soluble polymers, and the like.

[Water-soluble polymer]
Among the other components described above, the composition for a porous membrane preferably contains a water-soluble polymer. Since the composition for porous films which is a water-based slurry composition contains a water-soluble polymer, the composition for porous films can be thickened and it can be adjusted to the viscosity which is easy to apply. In addition, since the water-soluble polymer has binding property and electrolyte resistance, in the secondary battery, the binding of the respective components in the porous film with the particulate polymer, the porous film and the base material It can play a role in assisting adhesion. Therefore, the durability of the porous film can be further improved by using a water-soluble polymer.
Here, that a substance in the present invention is "water-soluble" means that when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C, the insoluble content is less than 1.0% by mass. Say. In addition, about the substance to which solubility changes with pH of water, if it corresponds to the "water solubility" mentioned above in at least one of pH, the substance assumes that it is "water solubility".
And as a water soluble polymer, a natural polymer, a semi synthetic polymer, and a synthetic polymer can be mentioned, for example. The water-soluble polymer does not contain the above-mentioned sulfonate compound.

[Natural polymer]
Natural polymers include, for example, polysaccharides and proteins of plant or animal origin, and fermented products of these microorganisms and the like, and heat-treated products of these.
These natural polymers can be classified into plant-based natural polymers, animal-based natural polymers, microorganism-produced natural polymers, and the like.
Examples of plant-based natural polymers include gum arabic, tragacanth gum, galactan, guar gum, carob gum, karaya gum, carrageenan, pectin, cannan, quince seed (marcolo), alke colloid (a gossy extract), starch (rice, corn, potato, wheat) And glycyrrhizin). Animal-based natural polymers include collagen, casein, albumin and gelatin. Microorganism-produced natural polymers include xanthan gum, dextran, succinoglucan, and bluran.

[Semi-synthetic polymers]
Examples of semi-synthetic polymers include cellulosic semi-synthetic polymers. The cellulose semisynthetic polymers can be classified into nonionic cellulose semisynthetic polymers, anionic cellulose semisynthetic polymers and cationic cellulose semisynthetic polymers.

  Examples of nonionic cellulose-based semi-synthetic polymers include alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose and microcrystalline cellulose; hydroxyethyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxy And hydroxyalkyl celluloses such as propyl methyl cellulose stearoxy ether, carboxymethyl hydroxyethyl cellulose, alkyl hydroxyethyl cellulose, nonoxynyl hydroxyethyl cellulose and the like.

  As anionic cellulose semisynthetic polymers, there may be mentioned substitution products obtained by substituting the above-mentioned nonionic cellulose semisynthetic polymers with various derivative groups, and salts thereof (sodium salts, ammonium salts, etc.). Specifically, sodium cellulose sulfate, methyl cellulose, methyl ethyl cellulose, ethyl cellulose, carboxymethyl cellulose (CMC) and salts thereof can be mentioned.

  Examples of cationic cellulose-based semi-synthetic polymers include low nitrogen hydroxyethyl cellulose dimethyldiallyl ammonium chloride (polyquaternium-4), O- [2-hydroxy-3- (trimethylammonio) propyl chloride chloride (polyquaternium-10 O- [2-hydroxy-3- (lauryldimethylammonio) propyl] hydroxyethyl cellulose chloride (polyquaternium-24).

[Synthetic polymer]
Examples of synthetic polymers include polyacrylates such as sodium polyacrylate, polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, copolymers of acrylic acid or acrylate with vinyl alcohol, maleic anhydride or maleic acid or fumar Complete or partial saponification of acid / vinyl acetate copolymer, modified polyvinyl alcohol, modified polyacrylic acid, polyethylene glycol, polycarboxylic acid, ethylene-vinyl alcohol copolymer, vinyl acetate polymer, carboxylic acid group introduced Acrylamide polymers and the like.

Among these water-soluble polymers, from the viewpoint of imparting heat resistance to the porous film and suppressing heat shrinkage of the organic separator such as polypropylene, carboxyl methyl cellulose and its salt, an acrylamide polymer into which a carboxylic acid group is introduced is preferable. Furthermore, from the viewpoint of reducing the amount of water carried into the secondary battery and improving the electrical characteristics, an acrylamide polymer having a carboxylic acid group introduced is particularly preferable.
The content of the water-soluble polymer in the composition for a porous membrane is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the nonconductive particles, and preferably It is 10 parts by mass or less, more preferably 5 parts by mass or less. When the compounding amount of the water-soluble polymer is within the above range, an appropriate viscosity can be imparted to the composition for a porous film, and the durability of the resulting porous film can be improved.

<Preparation of composition for non-aqueous secondary battery porous film>
The method for preparing the composition for a porous membrane is not particularly limited, but usually, the binder for a porous membrane described above, non-conductive particles, water, and optional components used as needed are mixed. can get. The mixing method is not particularly limited, but in order to disperse each component efficiently, mixing is performed using a disperser as a mixing device.
The disperser is preferably an apparatus capable of uniformly dispersing and mixing the above components. Examples include ball mills, sand mills, pigment dispersers, grinders, ultrasonic dispersers, homogenizers, planetary mixers and the like. Among them, a high dispersion apparatus such as a bead mill, a roll mill, and a film mix is particularly preferable because a high dispersion share can be added.

  Then, the solid content concentration of the composition for a porous film may generally be set arbitrarily within the range that the slurry composition has a viscosity that does not impair the workability when producing the porous film. Specifically, the solid content concentration of the composition for a porous membrane can be usually 10 to 50% by mass.

(Porous membrane for non-aqueous secondary battery)
For example, the above-described composition for a secondary battery porous membrane is applied to the surface of a suitable substrate to form a coating film, and the formed coating film is dried to obtain a non-aqueous secondary battery on the substrate. A porous membrane can be formed. The porous film is excellent in durability, and the non-aqueous secondary battery provided with the porous film is excellent in durability.

Here, the base material which apply | coats the composition for porous films is a member used as the object which forms the coating film of the composition for porous films. There is no restriction on the base material, for example, a coating film of the composition for a porous film is formed on the surface of the release substrate, the coating film is dried to form a porous film, and the release substrate is peeled off from the porous film. You may The porous film thus peeled off from the release substrate can also be used as a self-supporting film in a secondary battery.
However, it is preferable to use a separator substrate or an electrode substrate as a substrate from the viewpoint of omitting the step of peeling the porous film and enhancing the production efficiency. The porous film provided on the separator substrate and the electrode substrate can be suitably used as a protective layer for improving the heat resistance, strength and the like of the separator and the electrode.

<Separator base material>
Although it does not specifically limit as a separator base material, Well-known separator base materials, such as an organic separator base material, are mentioned. Here, the organic separator substrate is a porous member made of an organic material, and examples of the organic separator substrate include a microporous film or non-woven fabric containing a polyolefin resin such as polyethylene or polypropylene, an aromatic polyamide resin, etc. It is preferable to use a microporous membrane or non-woven fabric made of polyethylene because it is excellent in strength. The thickness of the organic separator substrate can be any thickness, usually 0.5 μm or more, preferably 5 μm or more, and usually 40 μm or less, preferably 30 μm or less, more preferably 20 μm or less.

<Electrode base material>
Although it does not specifically limit as an electrode base material (a positive electrode base material and a negative electrode base material), The electrode base material in which the electrode compound material layer was formed on the collector is mentioned.
Here, the current collector, the electrode active material (positive electrode active material, negative electrode active material) in the electrode mixture layer, and the binder for the electrode mixture layer (binding agent for the positive electrode mixture layer, the binder for the negative electrode mixture layer) A known material can be used for the method of forming the electrode mixture layer on the current collector and the current collector, and examples thereof include those described in Japanese Patent Application Laid-Open No. 2013-145763.

<Method of forming porous film for non-aqueous secondary battery>
As a method of forming a porous film on base materials, such as a separator base material mentioned above and an electrode base material, the following method is mentioned.
1) A method of applying the composition for a porous film to the surface of the separator substrate or the electrode substrate (the surface on the electrode mixture layer side in the case of the electrode substrate, the same applies hereinafter) and then drying
2) A method of drying the separator substrate or the electrode substrate after immersing the separator substrate or the electrode substrate in the composition for a porous membrane;
3) A method of applying a composition for a porous film on a release substrate and drying to produce a porous film, and transferring the obtained porous film to the surface of a separator substrate or an electrode substrate;
Among these, the method 1) is particularly preferable because it is easy to control the thickness of the porous film. Specifically, in the method 1), the step of applying the composition for a porous membrane on a substrate (coating step), the composition for a porous membrane applied on a substrate is dried to form a porous membrane A process (porous membrane formation process) is provided.

In the coating step, the method for coating the composition for a porous film on a substrate is not particularly limited. For example, the doctor blade method, reverse roll method, direct roll method, gravure method, extrusion method, brushing method, etc. The method is mentioned. Among them, the gravure method is preferable in that a uniform porous film can be obtained.
In the porous film forming step, the method for drying the composition for a porous film on a substrate is not particularly limited, and any known method can be used. For example, drying with warm air, hot air, low humidity air, vacuum drying, The drying method by irradiation of infrared rays, an electron beam, etc. is mentioned. Although the drying conditions are not particularly limited, the drying temperature is preferably 50 to 150 ° C., and the drying time is preferably 5 to 30 minutes.

  In addition, the separator and the electrode may be provided with components other than the separator base or the electrode base and the above-mentioned porous film of the present invention as long as the effects of the present invention are not significantly impaired. For example, if necessary, another layer may be provided between the separator substrate or the electrode substrate and the porous membrane of the present invention. In this case, the porous film of the present invention is indirectly provided on the surface of the separator substrate or the electrode substrate. Further, another layer may be provided on the surface of the porous membrane of the present invention.

  The thickness of the porous film formed on the substrate is preferably 0.01 μm or more, more preferably 0.1 μm or more, particularly preferably 1 μm or more, preferably 20 μm or less, more preferably 10 μm or less, in particular Preferably it is 5 micrometers or less. When the thickness of the porous film is 0.01 μm or more, the strength of the porous film can be sufficiently secured, and by being 20 μm or less, the diffusibility of the electrolytic solution is secured, and the secondary using the porous film The rate characteristics of the battery can be improved.

(Non-aqueous secondary battery)
The non-aqueous secondary battery of the present invention comprises the above-described porous film for non-aqueous secondary battery of the present invention. More specifically, the non-aqueous secondary battery of the present invention comprises a positive electrode, a negative electrode, a separator, and an electrolytic solution, and the above-mentioned porous film for non-aqueous secondary battery is a battery member including a positive electrode, a negative electrode and a separator. Included in at least one.
The non-aqueous secondary battery of the present invention is provided with a porous film obtained from the composition for a porous film of the present invention, and thus has excellent durability and high performance.

<Positive electrode, negative electrode and separator>
At least one of the positive electrode, the negative electrode and the separator used in the secondary battery of the present invention includes a porous film. Specifically, as a positive electrode and a negative electrode having a porous film, an electrode in which a porous film is provided on an electrode base material formed by forming an electrode mixture layer on a current collector can be used. Moreover, as a separator which has a porous film, the separator which provides a porous film on a separator base material, and the separator which consists of porous films can be used. In addition, as an electrode base material and a separator base material, the thing similar to what was mentioned in the term of "the porous film for non-aqueous secondary batteries" can be used.
Moreover, as a positive electrode, a negative electrode, and a separator which do not have a porous film, it is not specifically limited, The electrode which consists of an electrode base material mentioned above, and the separator which consists of a separator base material mentioned above can be used.

<Electrolyte solution>
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As a supporting electrolyte, for example, a lithium salt is used in a lithium ion secondary battery. Examples of lithium salts include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , 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 them, LiPF ₆ , LiClO ₄ and CF ₃ SO ₃ Li are preferable because they are easily dissolved in a solvent and exhibit a high degree of dissociation. The electrolyte may be used alone or in combination of two or more. Usually, the lithium ion conductivity tends to be higher as the supporting electrolyte having a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of the supporting electrolyte.

The organic solvent used for the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in a lithium ion secondary battery, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC) Carbonates such as propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfolane Sulfur-containing compounds such as dimethyl sulfoxide; and the like are suitably used. Also, a mixture of these solvents may be used. Among them, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. In general, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be. Therefore, the lithium ion conductivity can be controlled by the type of the solvent.
The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. In addition, known additives may be added to the electrolytic solution.

<Method of manufacturing non-aqueous secondary battery>
In a non-aqueous secondary battery, for example, a positive electrode and a negative electrode are stacked via a separator, and this is wound or folded as needed into a battery container, and an electrolytic solution is injected into the battery container and sealed. Can be manufactured. Note that at least one member of the positive electrode, the negative electrode, and the separator is a member with a porous film. Here, an expanded metal, a fuse, an overcurrent preventing element such as a PTC element, a lead plate, or the like may be inserted into the battery container as necessary to prevent a pressure increase inside the battery and overcharge and discharge. The shape of the battery may be, for example, a coin, a button, a sheet, a cylinder, a square, or a flat.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto. In the examples, parts and% are based on mass unless otherwise specified.
In Examples and Comparative Examples, the glass transition temperature of the particulate polymer, the volume average particle diameter D50, the degree of swelling with respect to the non-aqueous electrolyte, the durability and the water content of the porous film, and the high shear of the composition for porous film The stability of the battery and the rate and life characteristics of the non-aqueous secondary battery were measured and evaluated by the following methods.

<Glass transition temperature>
The aqueous dispersion containing the particulate polymer was dried at 50% humidity and an environment of 23 to 25 ° C. for 3 days to obtain a film having a thickness of 1 ± 0.3 mm. The film was dried in a hot air oven at 120 ° C. for 1 hour. Thereafter, using a dried film as a sample, a differential scanning calorimeter (DSC 6220 SII, manufactured by Nano Technology Co., Ltd.) at a measurement temperature of −100 ° C. to 180 ° C. and a temperature rising rate of 5 ° C./minute according to JIS K7121. The glass transition temperature (° C.) was measured.
<Volume average particle diameter D50>
An aqueous dispersion containing the produced particulate polymer is diluted with ion-exchanged water to prepare a measurement sample having a solid content concentration of 2% by mass, and a laser diffraction / light scattering type particle size distribution measuring apparatus (LS230, manufactured by Beckman Coulter, Inc.) The volume average particle diameter D50 of the particulate polymer was measured using
<Swelling degree of particulate polymer to non-aqueous electrolyte>
The aqueous dispersion containing the particulate polymer is applied to an electrolytic copper foil (NC-WS (registered trademark) manufactured by Furukawa Electric Co., Ltd.) using a table coater, and heated at 50 ° C. for 20 minutes, 120 ° C. for 20 minutes. It was dried in a drier to prepare a 1 cm × 1 cm binder film (500 μm thick), and the weight M0 was measured. After that, the obtained film was immersed in a non-aqueous electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio), electrolyte: 1 M concentration LiPF ₆ ) at 60 ° C. for 72 hours . The non-aqueous electrolyte solution on the surface of the film after immersion was wiped off and the weight M1 was measured. And the swelling degree with respect to a non-aqueous electrolyte was computed according to the following formula.
Swelling degree for non-aqueous electrolyte = M1 / M0
<Durability of porous membrane>
The porous membrane-provided separator was cut into 5 cm × 5 cm, and the weight was measured, and the weight of the separator substrate was subtracted to calculate the weight M0 of the porous membrane. Subsequently, the separator with a porous membrane cut out was cut into a non-aqueous electrolyte solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio), electrolyte: 1 M concentration LiPF ₆ ) at 60 ° C. It was immersed and subjected to ultrasonic vibration of 30 kHz for 10 minutes. Thereafter, the porous membrane-provided separator was taken out, dried in an atmosphere of 60 ° C. for 10 hours, and the weight M1 of the porous membrane after drying was calculated in the same manner as the weight M0. And vibration drop-out rate (DELTA) M (%) was computed using the formula of (DELTA) M = {(M0-M1) / M0} x100, and it evaluated as follows. The smaller this value is, the better the durability is.
A: Vibration dropout rate ΔM is less than 20% B: Vibration dropout rate ΔM is from 20% to less than 40% C: Vibration dropout rate ΔM is from 40% to less than 60% D: Vibration dropout rate ΔM is at least 60% <porous film Water content>
The porous membrane-provided separator was cut into 10 cm × 10 cm and used as a test piece. The test piece is left to stand at a temperature of 25 ° C. and a humidity of 50% for 24 hours, and then, using a coulometric titration-type moisture meter, a test piece by the Karl Fischer method (JIS K-0068 (2001) moisture vaporization method, vaporization temperature 150 ° C. Water content W (ppm) was measured. The smaller this value is, the smaller the water content in the porous film, and the lower the water content carried into the secondary battery.
A: Water content W is 500 ppm or less B: Water content W is more than 500 ppm and 600 ppm or less C: Water content W is more than 600 ppm and 700 ppm or less D: Water content W is more than 700 ppm <high shear of composition for porous film Stability at>
The composition for a porous film is coated on a separator substrate (made of polyethylene) using a gravure roll (number of lines: 95) at a conveyance speed of 50 m / min and a gravure rotation ratio of 100%, and the separator group after application The material was cut out, and the application amount M0 (mg / cm ² ) per unit area was calculated. Moreover, 1 hour after the application start, the application amount M1 (mg / cm ² ) was similarly calculated. Then, using the formula of ΔM = (| M0−M1 |) / M0 × 100 (%), the application amount change rate ΔM (%) was calculated and evaluated as follows. The smaller this value is, the higher the stability of the composition for a porous membrane under high shear is.
A: Coating amount change rate ΔM is less than 5% B: Coating amount change rate ΔM is 5% or more and less than 10% C: Coating amount change rate ΔM is 10% or more and less than 20% D: Coating amount change rate ΔM is 20% or more <Rate characteristics>
The prepared secondary battery is allowed to stand in an environment of 25 ° C. for 24 hours, and then charging operation is performed at 4.2 V, 0.1 C for 5 hours in an environment of 25 ° C. V) was measured. Thereafter, discharge operation was performed at a discharge rate of 1 C under an environment of -10 ° C, and a voltage V1 (V) 15 seconds after the start of discharge was measured. The voltage change ΔV (mV) was calculated using the equation ΔV = {V0−V1} × 1000, and evaluated as follows. The smaller this value is, the better the rate characteristics (low temperature characteristics) are.
A: Voltage change ΔV is 500mV or less B: Voltage change ΔV is more than 500mV to 700mV C: Voltage change ΔV is more than 700mV to 900mV D: Voltage change ΔV is more than 900mV <Life characteristics>
The prepared secondary battery is allowed to stand at 25 ° C. for 24 hours, and then charged / discharged at 4.35 V, 0.1 C, 2.75 V, 0.1 C discharge at 25 ° C. I did the operation of. Thereafter, the battery was charged at 4.35 V and 0.1 C and left at 60 ° C. for 168 hours (7 days), and then the cell voltage V2 (V) was measured at 25 ° C. The voltage drop ΔV (mV) was calculated using the equation ΔV = {4.35-V2} × 1000 and evaluated as follows. The smaller the value, the better the life characteristics (self-discharge characteristics).
A: Voltage drop ΔV is 200mV or less B: Voltage drop ΔV is more than 200mV to 400mV C: Voltage drop ΔV is more than 400mV to 600mV D: Voltage drop ΔV is more than 600mV

Example 1
<Preparation of Binder for Nonaqueous Secondary Battery Porous Film>
In a reactor A equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of polyoxyethylene lauryl ether (manufactured by Kao Chemical Co., Ltd., "Emulgen (registered trademark) 120") as an emulsifier, and ammonium persulfate 0. Five parts were each supplied, the gas phase part was substituted by nitrogen gas, and it heated up at 60 degreeC.
On the other hand, 50 parts of ion-exchanged water in another container B, 0.5 parts of polyoxyethylene lauryl ether (manufactured by Kao Chemical Co., Ltd., "Emulgen (registered trademark) 120") as an emulsifier, and a single amount of (meth) acrylic acid alkyl ester 58.2 parts of 2-ethylhexyl acrylate (2-EHA), 40 parts of styrene (ST) as an aromatic monovinyl monomer, 0.8 parts of itaconic acid (IA) as an acid group-containing monomer, and a crosslinkable monomer A monomer composition was obtained by mixing 1.0 parts of ethylene dimethacrylate (EDMA) as a monomer. The monomer composition was continuously added to the reactor A over 4 hours to carry out polymerization. The reaction was carried out at 70 ° C. during the addition. After completion of the addition, the reaction was further completed by stirring at 80 ° C. for 3 hours to complete an aqueous dispersion containing a particulate polymer.
When the glass transition temperature of the obtained particulate polymer was measured, the observed glass transition temperature was only one point (-8 ° C.), and it was confirmed that the particulate polymer was a random copolymer. At the same time, the degree of swelling of the particulate polymer in the non-aqueous electrolyte and the volume average particle diameter D50 were measured. The results are shown in Table 1.
In an aqueous dispersion containing the obtained particulate polymer, 2 parts of a dioctyl sulfosuccinate sodium salt (DOSS, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., “NEOCOL® (registered trademark P)”) as a sulfonate compound (particulate polymer The ratio of the blending ratio of the sulfonate compound to 0.02) was added to prepare a non-aqueous secondary battery porous membrane binder.

<Preparation of composition for non-aqueous secondary battery porous film>
Relative to 100 parts of an alumina filler ("LS 256" manufactured by Nippon Light Metal Co., Ltd.) as nonconductive particles, the above-mentioned binder for a porous film containing a particulate polymer and a sulfonate compound in solid equivalent (6 parts of a particulate polymer, 0.12 parts of a sulfonate compound), an acrylamide polymer into which a carboxylic acid group has been introduced as a thickener (Arakawa Chemical Co., Ltd., "Polistron (registered trademark) 117"). 5 parts and 0.2 parts of polyethylene glycol type surfactant ("San Nopco (registered trademark) SN wet 366" manufactured by San Nopco) were mixed to prepare a composition for a porous membrane.
The stability under high shear was evaluated using the composition for porous films obtained. The results are shown in Table 1.

<Production of Porous Membrane and Separator with Porous Membrane>
An organic separator substrate (manufactured by Celgard, thickness 16 μm) made of a porous substrate made of polyethylene was prepared. The composition for a porous film obtained as described above was applied to one surface of the prepared organic separator substrate, and dried at 60 ° C. for 10 minutes. Thereby, a separator with a porous film with a thickness of 18 μm was obtained.
Durability and water content were evaluated using the obtained separator with a porous membrane. The results are shown in Table 1.

<Manufacture of negative electrode>
In a 5 MPa pressure-resistant container with stirrer, 33 parts of 1,3-butadiene, 3.5 parts of IA, 63.5 parts of ST, 0.4 parts of sodium dodecylbenzene sulfonate as an emulsifier, 150 parts of ion exchanged water, and potassium persulfate as a polymerization initiator After 0.5 parts were added and sufficiently stirred, the mixture was heated to 50 ° C. to start polymerization. When the polymerization conversion ratio reached 96%, the reaction was stopped by cooling to obtain a mixture containing a negative electrode mixture layer binder (SBR). A 5% aqueous solution of sodium hydroxide is added to the mixture containing the binder for the negative electrode mixture layer to adjust to pH 8, and after removing unreacted monomers by heating under reduced pressure distillation, to 30 ° C. or less The resultant was cooled to obtain an aqueous dispersion containing a desired binder for a negative electrode mixture layer.
100 parts of artificial graphite (average particle diameter: 15.6 μm) as a negative electrode active material, 1 part of a 2% aqueous solution of carboxymethylcellulose sodium salt (“MAC 350 HC” manufactured by Nippon Paper Industries Co., Ltd.) as a water-soluble polymer The mixture was mixed with deionized water to adjust the solid concentration to 68%, and then mixed at 25 ° C. for 60 minutes. Further, the solid concentration was adjusted to 62% with ion-exchanged water, and further mixed at 25 ° C. for 15 minutes. Add 1.5 parts of the above binder for the negative electrode mixture layer in solid equivalent equivalents and ion-exchanged water to the above mixed solution, and adjust the final solid concentration to 52%, and further for 10 minutes. Mixed. The slurry was defoamed under reduced pressure to obtain a slurry composition for a secondary battery negative electrode having good fluidity.
The obtained negative electrode slurry composition was applied by a comma coater on a 20 μm thick copper foil as a current collector such that the film thickness after drying was about 150 μm and dried. This drying was performed by conveying the copper foil at a speed of 0.5 m / min for 2 minutes in an oven at 60 ° C. Then, it heat-processed at 120 degreeC for 2 minutes, and obtained the negative electrode original fabric before a press. The negative electrode material sheet before this pressing was rolled by a roll press to obtain a negative electrode after pressing having a thickness of the negative electrode mixture layer of 80 μm (single-sided negative electrode).
Further, the same application is performed on the back surface of the negative electrode raw fabric before pressing, the negative electrode mixture layer is formed on both sides, and rolling is performed by a roll press, and the negative electrode after pressing has a thickness of 80 μm for each negative electrode mixture layer. (Both sides negative electrode).

<Manufacture of positive electrode>
100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as a positive electrode active material, ₂ parts of acetylene black ("HS-100" manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, as a binder for positive electrode mixture layer Polyvinylidene fluoride (Kureha Co., Ltd., "# 7208") was mixed with 2 parts by solid equivalent, and N-methyl pyrrolidone to make the total solid concentration 70%. These were mixed to prepare a slurry composition for a positive electrode.
The obtained positive electrode slurry composition was applied by a comma coater on an aluminum foil with a thickness of 20 μm, which is a current collector, to a film thickness after drying of about 150 μm and dried. This drying was performed by conveying the aluminum foil at a speed of 0.5 m / min for 2 minutes in an oven at 60 ° C. Then, it heat-processed at 120 degreeC for 2 minutes, and obtained the positive electrode original fabric before a press. The positive electrode material sheet before this pressing was rolled by a roll press to obtain a positive electrode after pressing having a thickness of the positive electrode mixture layer of 80 μm (single-sided positive electrode).
Further, the same application is performed on the back surface of the positive electrode raw fabric before the pressing, the positive electrode mixture layer is formed on both sides, and rolling is performed by a roll press, and the positive electrode after pressing has a thickness of 80 μm for each positive electrode mixture layer. (Both sides positive electrode).

<Manufacture of secondary battery>
The single-sided positive electrode obtained above is cut out to 5 cm × 15 cm, the separator with a porous membrane cut out to 6 cm × 16 cm is placed on it (the material layer side) so that the porous film faces the single-sided positive electrode, The double-sided negative electrode cut out into 5.5 cm × 15.5 cm was disposed thereon, to obtain a laminate A. A separator with a porous film cut out to 6 cm × 16 cm is disposed on the double-sided negative electrode side of this laminate A so that the separator substrate faces the double-sided negative electrode, and a double-sided positive electrode cut out to 5 cm × 15 cm thereon And then the separator with a porous membrane cut out to 6 cm × 16 cm is disposed so that the porous membrane faces the positive electrode on both sides, and finally, it is cut to 5.5 cm × 5.5 cm on one side The negative electrode was laminated such that the negative electrode mixture layer faced the separator base of the porous membrane-provided separator, to obtain a laminate B. This laminate B is wrapped with an aluminum packaging material as an exterior of a battery, and a non-aqueous electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio), electrolyte: concentration 1 M LiPF ₆ ) was injected without leaving air. Furthermore, after heat sealing at 150 ° C. to close the opening of the aluminum packaging material, flat plate pressing of the obtained battery outer package is performed at 100 Kg for 2 minutes at 100 ° C. to produce a 1000 mAh laminated lithium ion secondary battery did.
The lifetime characteristic and the rate characteristic were evaluated using the obtained secondary battery. The results are shown in Table 1.

(Examples 2 to 5)
The same as Example 1, except that the amount of DOSS used as the sulfonate compound was changed to 1.2 parts, 2.8 parts, 0.7 parts, and 4.8 parts, respectively, at the time of preparation of the binder for a porous membrane. A particulate polymer, a binder for a porous membrane, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 1.

(Example 6)
Example 1 except that DOSS as a sulfonate compound was changed to alkylbenzene sulfonic acid sodium salt (LAS, manufactured by Kao Chemical Co., Ltd., “Noperex® G-15”) at the time of preparation of the binder for a porous membrane. A particulate polymer, a binder for a porous membrane, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured in the same manner as in the above, and the same items were evaluated. The results are shown in Table 1.

(Examples 7 and 8)
A particulate polymer for a porous membrane in the same manner as in Example 1 except that, when preparing the particulate polymer contained in the binder for a porous membrane, the amounts of IA and 2-EHA used are changed as shown in Table 1. A binder, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 1.

(Example 9)
A particulate polymer in the same manner as in Example 1 except that maleic acid (MA) was used in place of IA as the acidic group-containing monomer when preparing the particulate polymer contained in the binder for a porous membrane. A binder for a porous membrane, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 1.

(Examples 10, 11, 15)
A particulate polymer for a porous membrane in the same manner as in Example 1 except that the amounts of ST and 2-EHA used are changed as shown in Table 1 when preparing the particulate polymer contained in the binder for a porous membrane. A binder, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 1.

(Examples 12, 13)
At the time of preparation of the particulate polymer contained in the binder for porous film, the addition amount of polyoxyethylene lauryl ether as an emulsifier to reactor A / container B is 0.25 / 0.4 parts and 0 / 0.65, respectively. A particulate polymer, a binder for a porous membrane, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery are manufactured in the same manner as in Example 1 except that Was rated. The results are shown in Table 2.

(Example 14)
A particulate polymer for a porous membrane in the same manner as in Example 1 except that the amounts of 2-EHA and EDMA used were changed as shown in Table 2 at the time of preparation of the particulate polymer contained in the binder for a porous membrane. A binder, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 2.

(Comparative example 1)
When preparing a binder for a porous membrane, in place of DOSS as a sulfonate compound, a water-soluble polymer sodium polyacrylate (SPA, manufactured by Toagosei Co., Ltd., "Aron (registered trademark) T50") was used. In the same manner as in Example 1, a particulate polymer, a binder for a porous membrane, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were produced, and the same items were evaluated. The results are shown in Table 2.

(Comparative example 2)
A particulate polymer for a porous membrane in the same manner as in Example 1 except that the amounts of ST and 2-EHA used were changed as shown in Table 2 at the time of preparation of the particulate polymer contained in the binder for a porous membrane. A binder, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode, and a secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 2.

(Comparative example 3)
A binder for a porous membrane, a composition for a porous membrane, a separator with a porous membrane, a negative electrode, a positive electrode in the same manner as in Example 1 except that a particulate polymer which is a graft copolymer prepared as follows is used. And secondary batteries were manufactured and evaluated on the same items. The results are shown in Table 2.
<Preparation of Particulate Polymer (Graft Copolymer)>
In a reactor equipped with a stirrer, 230 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate ("Emar (registered trademark) 2F" manufactured by Kao Chemical Co., Ltd.) as an emulsifier, 49.2 n-butyl acrylate (BA) Parts, 50 parts of styrene macromonomer (STMM, single-terminal methacryloylated polystyrene oligomer, “AS-6” manufactured by Toho Synthetic Chemical Industry Co., Ltd.), 0.8 parts of itaconic acid (IA), t-butylperoxy as a polymerization initiator After 1 part of 2-ethylhexanate was added and sufficiently stirred, the mixture was heated to 90 ° C. for polymerization to obtain an aqueous dispersion of a particulate polymer. When the glass transition temperature of the obtained particulate polymer was measured, two points (-40 degreeC and 97 degreeC) of glass transition temperature were confirmed, and it confirmed that a particulate polymer was a graft copolymer.

The random copolymer which contains a (meth) acrylic-acid alkylester monomer unit and an aromatic monovinyl monomer unit in the ratio within the specific range from Examples 1-15 of the above-mentioned table, and comparative examples 1-3 If a binder for a porous membrane is used, which comprises a particulate polymer comprising the compound and a sulfonate compound, the compounding amount of the sulfonate compound divided by the compounding amount of the particulate polymer is a specific value or more, It can be seen that a composition for a porous film having excellent stability under high shear, a porous film having excellent durability and a small water content, and a secondary battery having excellent rate characteristics and life characteristics can be obtained.
Here, from Examples 1 to 5 of the above-mentioned table, the stability of the composition for a porous film under high shear and the secondary battery by adjusting the blending ratio of the sulfonate compound to the particulate polymer It can be seen that the rate characteristics and the life characteristics of the porous film can be further improved, and the water content of the porous film can be further reduced.
Further, according to Examples 1 and 6 of the above-mentioned table, the high shear condition of the composition for a porous membrane can be further improved by changing the kind of the sulfonate compound, and the water content of the porous membrane can be further enhanced. It turns out that it can reduce.
And, by changing the composition of the particulate polymer according to Examples 1, 7 to 11, 14 and 15 in the above table, the stability of the composition for a porous membrane under high shear and the durability of the porous membrane Also, it is understood that the rate characteristics and the life characteristics of the secondary battery can be further improved, and the water content of the porous membrane can be further reduced. In particular, it is understood from Examples 1 and 14 that the durability of the porous film and the life characteristics of the secondary battery can be further improved by adjusting the degree of swelling of the particulate polymer in the non-aqueous electrolyte solution.
Furthermore, the stability under high shear of the composition for a porous film can be further improved by adjusting the volume average particle diameter D50 of the particulate polymer according to Examples 1, 12 and 13 of the above-mentioned table. I understand.

According to the present invention, a non-aqueous secondary battery porous film binder is provided which can form a porous film excellent in durability and can also enhance the stability of the composition for a porous film under high shear. can do.
Further, according to the present invention, it is possible to provide a composition for a non-aqueous secondary battery porous film which is excellent in stability under high shear and is capable of forming a porous film excellent in durability.
And according to the present invention, it is possible to provide a non-aqueous secondary battery provided with a porous film for non-aqueous secondary battery with excellent durability and the porous film for non-aqueous secondary battery.

Claims (8)

Containing particulate polymer and sulfonate compound,
The particulate polymer is a random copolymer containing 35% by mass or more of (meth) acrylic acid alkyl ester monomer units and 20% by mass or more and 65% by mass or less of aromatic monovinyl monomer units, The glass transition temperature of the particulate polymer is 10 ° C. or less (excluding 10 ° C.),
The binder for non-aqueous secondary battery porous membranes whose value which remove | divided the compounding quantity of the said sulfonate compound by the compounding quantity of the said particulate-form polymer is 0.005 or more.   The binder for non-aqueous secondary battery porous films according to claim 1, wherein the particulate polymer further contains 0.1% by mass or more and 5% by mass or less of an acidic group-containing monomer unit.   The binder for porous film for non-aqueous secondary batteries according to claim 2, wherein the acidic group-containing monomer unit is a monomer unit derived from an ethylenically unsaturated dicarboxylic acid.   The binder for non-aqueous secondary battery porous films in any one of Claims 1-3 whose volume average particle diameter D50 of the said particulate-form polymer is 100 nm-500 nm.   The binder for non-aqueous secondary battery porous films in any one of Claims 1-4 whose swelling degree with respect to the non-aqueous electrolyte solution of the said particulate-form polymer is more than 1 time and 2 times or less.   The composition for non-aqueous secondary battery porous films containing the binder for non-aqueous secondary battery porous films in any one of Claims 1-5, nonelectroconductive particle, and water.   A porous film for a non-aqueous secondary battery, formed from the composition for a non-aqueous secondary battery porous film according to claim 6.   A non-aqueous secondary battery comprising the porous film for non-aqueous secondary battery according to claim 7.