JP2017027856A - Binder composition for nonaqueous secondary battery porous film, composition for nonaqueous secondary battery porous film, nonaqueous secondary battery porous film, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition for a nonaqueous secondary battery porous film, by which the stability of a composition for a nonaqueous secondary battery porous film in shearing can be increased, and a nonaqueous secondary battery is allowed to exhibit superior battery characteristics.SOLUTION: A binder composition for a nonaqueous secondary battery porous film comprises: a particulate polymer including 0.1-5 mass% of a repeating unit expressed by the formula (I), 35 mass% or more of a (meth)acrylic acid alkyl ester monomer unit, and 20-60 mass% of an aromatic monovinyl monomer unit. In the formula (I), Rrepresents a hydrogen atom or methyl group; Rrepresents a phenyl group, an alkyl group with 1-6C, or a phenyl group having one to three alkyl groups with 1-6C; and "n" represents an integer of 3 or more.SELECTED DRAWING: None

Description

  The present invention relates to a binder composition for a nonaqueous secondary battery porous film, a composition for a nonaqueous secondary battery porous film, a porous film for a nonaqueous secondary battery, and a nonaqueous secondary battery.

  Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as “secondary batteries”) have the characteristics of being small and lightweight, having high energy density, and capable of repeated charge and discharge. Yes, it is used for a wide range of purposes. The secondary battery generally includes an electrode (positive electrode, negative electrode) and a battery member such as 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 including 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 is usually 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 “a composition for a porous film”). The composition for porous membrane is applied on an electrode base material or a separator base material provided with an electrode mixture layer on a current collector and dried.

And in recent years, the improvement of the binder used for formation of a porous film is performed actively for the purpose of the further performance enhancement of a secondary battery.
For example, in Patent Document 1, a first monomer containing an acidic functional group, a second monomer containing an amide group, and a predetermined third monomer are copolymerized to form glass. A binder including a plurality of particles composed of a polymer having a transition temperature of −60 ° C. to 60 ° C. is excellent in resistance to electrolyte, and if this binder is used, a porous film as a protective layer having excellent adhesion is formed. It has been reported that it can. Furthermore, according to Patent Document 1, by using a polyoxyalkylene group-containing monomer (for example, methoxypolyethylene glycol methacrylate having a molecular weight of about 200) as the third monomer, ions of the porous film as a protective layer are used. Conductivity is improved.

Japanese Patent Laying-Open No. 2015-88484

  Here, when the porous film composition used for forming the porous film is applied with, for example, a gravure coating apparatus when forming the porous film on the substrate, it receives a shearing force due to the rotation of the gravure roll. However, the composition for a porous membrane comprising the conventional binder described above has low dispersion stability when subjected to shearing force. Therefore, if the porous film composition is formed over a long period of time, or if the rotational speed of the gravure roll is increased for high-speed molding, the contained components aggregate to obtain a porous film with a uniform thickness. There was a problem that it became difficult.

  Moreover, even if the above conventional binder is used, it cannot be said that the ion conductivity of the porous membrane can be secured at a sufficiently high level. And due to insufficient ion conductivity of the porous membrane, it was still difficult to produce a secondary battery excellent in battery characteristics such as rate characteristics and life characteristics using the porous film. .

  Therefore, an object of the present invention is to provide means for advantageously solving the above-described improvements.

The present inventor has intensively studied for the purpose of solving the above problems. Then, the present inventor has disclosed a repeating unit having a polyoxyethylene group in which a predetermined number or more of oxyethylene structures (—CH ₂ CH ₂ O—) are connected, a (meth) acrylic acid alkyl ester monomer unit, and an aromatic When a particulate polymer containing a group of monovinyl monomer units at a predetermined ratio is used as a binder, it is possible to improve the stability of the composition for a porous membrane under shear, and to a secondary battery. The inventors have found that excellent battery characteristics can be exhibited, and have completed the present invention.

（式中、Ｒ¹は水素原子又はメチル基を表し、Ｒ²はフェニル基、炭素原子数１以上６以下のアルキル基、又は炭素原子数１以上６以下のアルキル基を１つ以上３つ以下有するフェニル基を表し、そしてｎは３以上の整数を表す。）で表される繰り返し単位を０．１質量％以上５質量％以下、（メタ）アクリル酸アルキルエステル単量体単位を３５質量％以上、および芳香族モノビニル単量体単位を２０質量％以上６０質量％以下含む粒子状重合体を含有することを特徴とする。このように、上述の式（Ｉ）の繰り返し単位、（メタ）アクリル酸アルキルエステル単量体単位、および芳香族モノビニル単量体単位をそれぞれ上述の範囲内の割合で含む粒子状重合体を含有するバインダー組成物を用いれば、多孔膜用組成物のせん断下での安定性を高めつつ、二次電池に優れた電池特性を発揮させることができる。 That is, this invention aims at solving the said subject advantageously, The binder composition for non-aqueous secondary battery porous films of this invention is the following formula (I):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a phenyl group, an alkyl group having 1 to 6 carbon atoms, or one to three alkyl groups having 1 to 6 carbon atoms. And n represents an integer of 3 or more.) A repeating unit represented by 0.1 to 5% by mass, and a (meth) acrylic acid alkyl ester monomer unit to 35% by mass. A particulate polymer containing 20% by mass or more and 60% by mass or less of an aromatic monovinyl monomer unit as described above is contained. Thus, the particulate polymer containing the repeating unit of the above-mentioned formula (I), the (meth) acrylic acid alkyl ester monomer unit, and the aromatic monovinyl monomer unit in a proportion within the above-mentioned range is contained. If the binder composition to be used is used, the battery characteristics excellent in the secondary battery can be exhibited while enhancing the stability of the porous membrane composition under shear.

The binder composition for a nonaqueous secondary battery porous membrane of the present invention preferably has a degree of swelling of the particulate polymer with respect to the nonaqueous electrolyte of more than 1 time and 3 times or less. If the degree of swelling of the particulate polymer with respect to the nonaqueous electrolytic solution is within the above range, the particulate polymer is good in the nonaqueous electrolytic solution (hereinafter sometimes simply referred to as “electrolytic solution”). By exerting the adhesive force, the porous film and the substrate can be brought into close contact with each other, and the peel strength after the porous film is immersed in the electrolytic solution can be ensured. In addition, the battery characteristics of the secondary battery can be further enhanced.
In the present invention, the “swelling degree with respect to the non-aqueous electrolyte solution” of the particulate polymer is the case where a film (binder film) formed from the particulate polymer is immersed in a predetermined non-aqueous electrolyte solution under a predetermined condition. It is possible to obtain a value (times) obtained by dividing the weight after immersion by the weight before immersion. Specifically, a binder film is formed by using the method described in the examples of the present specification. Measured using the measurement method described in 1.

  Moreover, this invention aims at solving the said subject advantageously, The composition for non-aqueous secondary battery porous films of this invention is for any of the above-mentioned non-aqueous secondary battery porous films. It contains a binder composition, non-conductive particles and water. A composition for a porous membrane comprising any of the above-described binder compositions is excellent in stability under shear and hardly aggregates during formation of the porous membrane. And the porous film obtained using the said composition for porous films can exhibit the battery characteristic excellent in the secondary battery.

  And it is preferable that the composition for non-aqueous secondary battery porous membranes of this invention contains 0.5 to 10 mass parts of the said particulate polymer per 100 mass parts of said nonelectroconductive particles. If the porous membrane composition contains the particulate polymer in an amount within the above range, the amount of moisture brought into the secondary battery is reduced, while the secondary battery rate characteristics and the porous membrane composition are under shear. It is possible to further improve the stability at the time. Moreover, not only the peel strength after immersion of the porous membrane in the electrolytic solution is improved, but also the peel strength of the porous membrane can be ensured even before the particulate polymer is immersed in the electrolytic solution and swells. In this way, the porous film having excellent peel strength before immersion in the electrolyte solution is in good contact with the porous film and the substrate before immersion in the electrolyte solution. It is possible to suppress powder falling (dropping of fine powder from the porous film) that occurs when the porous film is cut and curved during production.

  Furthermore, in the composition for a nonaqueous secondary battery porous membrane of the present invention, the proportion of the nonconductive particles in the total solid content is preferably 70% by mass or more. When the ratio of the nonconductive particles in the total solid content in the composition for a porous membrane is equal to or higher than the above value, the durability of the obtained porous membrane can be ensured.

  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 that. The said porous film can exhibit the battery characteristic excellent in the secondary battery.

  Moreover, this invention aims at solving the said subject advantageously, and the nonaqueous secondary battery of this invention is equipped with the porous film for nonaqueous secondary batteries mentioned above, It is characterized by the above-mentioned. The non-aqueous secondary battery is excellent in battery characteristics such as rate characteristics and life characteristics.

ADVANTAGE OF THE INVENTION According to this invention, the binder for nonaqueous secondary battery porous films which can improve the stability under the shear of the composition for nonaqueous secondary battery porous films, and can exhibit the battery characteristic excellent in the nonaqueous secondary battery. A composition can be provided.
In addition, according to the present invention, it is possible to provide a composition for a porous membrane of a nonaqueous secondary battery that is excellent in stability under shear and that can exhibit excellent battery characteristics in a nonaqueous secondary battery. .
According to the present invention, a nonaqueous secondary battery porous membrane capable of exhibiting excellent battery characteristics in a nonaqueous secondary battery, and a nonaqueous secondary battery comprising the porous membrane for a nonaqueous secondary battery and having excellent battery characteristics A secondary battery can be provided.

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

(Binder composition for nonaqueous secondary battery porous membrane)
The binder composition of the present invention comprises a polyoxyethylene group-containing repeating unit represented by the formula (I) described above in an amount of 0.1% by mass to 5% by mass, and a (meth) acrylic acid alkyl ester monomer unit in an amount of 35%. A composition in which a particulate polymer containing 20% by mass or more and 20% by mass or less and 60% by mass or less of an aromatic monovinyl monomer unit is dispersed in a dispersion medium such as water. Here, in the present invention, “comprising a monomer unit” means “a repeating unit derived from a monomer is contained in a polymer obtained using the monomer”. In the present invention, “(meth) acryl” means acrylic and / or methacrylic.
Note that the binder composition of the present invention optionally contains other components in addition to the particulate polymer and the dispersion medium described above.
The binder composition of the present invention comprises a repeating unit of formula (I) of 0.1% by mass or more and 5% by mass or less, a (meth) acrylic acid alkyl ester monomer unit of 35% by mass or more, and an aromatic monovinyl. Since the particulate polymer containing 20% by mass or more and 60% by mass or less of the monomer unit is contained, the use of the binder composition of the present invention increases the stability of the porous membrane composition under shear. The battery characteristic which was excellent in the secondary battery can be exhibited.

Thus, the reason why the stability under the shear of the porous membrane composition and the battery characteristics of the secondary battery can be improved by using the binder composition containing the predetermined particulate polymer as the binder is as follows. Although it is not certain, it is presumed that the reason is as follows.
That is, the particulate polymer has a repeating unit of the above-mentioned formula (I), that is, a polyoxyethylene group having a sufficient length as a side chain, and this polyoxyethylene group is present outside the particulate polymer. It is thought that it protrudes. This protruding polyoxyethylene group physically suppresses aggregation of the particulate polymers under shear, so that it is presumed that the stability of the porous membrane composition under shear is improved. And if the composition for porous films which is excellent in the stability under a shear is used, the porous film which has uniform thickness will be obtained and the local fall of ionic conductivity will be suppressed.
Moreover, it is thought that the outer edge part of low density compared with the inside exists near the surface of a particulate polymer because a polyoxyethylene group protrudes toward the outside of a particulate polymer. It is speculated that the ion conductivity of the porous membrane is increased by allowing the low-density outer edge to easily pass ions such as lithium ions. Furthermore, the present inventor can improve the peel strength before immersion of the porous membrane in the electrolyte solution if the particulate polymer has a polyoxyethylene group, while the polyoxyethylene group in the particulate polymer can be improved. If the amount is excessive, the peel strength after immersion of the porous membrane in the electrolyte will decrease, and the moisture content of the porous membrane will increase and the amount of moisture brought into the secondary battery will increase, so the battery characteristics will deteriorate. I found that I suffered a disadvantage.
In addition, the aromatic monovinyl monomer unit having a high rigidity contributes to improving the stability of the porous membrane composition under shear by suppressing deformation and aggregation due to shearing of the particulate polymer. In addition, the aromatic monovinyl monomer unit ensures the peel strength of the porous membrane after immersion in the electrolyte by suppressing the elution of the particulate polymer in the electrolyte, and improves the life characteristics of the secondary battery. It is presumed that this will also contribute. On the other hand, the (meth) acrylic acid alkyl ester monomer unit capable of imparting an adhesive force to the particulate polymer, particularly in a dry state, contributes to an improvement in peel strength of the porous membrane before immersion in the electrolyte solution. It is surmised that by suppressing powder omission, the defective portions of the porous film are reduced and the battery characteristics of the secondary battery are improved.
Therefore, the particulate polymer contains a repeating unit containing a polyoxyethylene group having a predetermined length, an aromatic monovinyl monomer unit, and a (meth) acrylic acid alkyl ester monomer unit, each in a predetermined ratio. It is presumed that the composition for porous membranes having excellent stability under shear can be obtained by making it exist in addition to improving ion conductivity of the porous membrane and improving the rate characteristics and life characteristics of the secondary battery.

（式中、Ｒ¹は水素原子又はメチル基を表し、Ｒ²はフェニル基、炭素原子数１以上６以下のアルキル基、又は炭素原子数１以上６以下のアルキル基を１つ以上３つ以下有するフェニル基を表し、そしてｎは３以上の整数を表す。）で表される繰り返し単位を０．１質量％以上５質量％以下、（メタ）アクリル酸アルキルエステル単量体単位を３５質量％以上、および芳香族モノビニル単量体単位を２０質量％以上６０質量％以下含む。ここで、粒子状重合体は、上述した式（Ｉ）で表される繰り返し単位、（メタ）アクリル酸アルキルエステル単量体単位、および芳香族モノビニル単量体単位以外の繰り返し単位を含んでいてもよい。そのようなその他の繰り返し単位としては、酸性基含有単量体単位、架橋性単量体単位などが挙げられる。 <Particulate polymer>
The particulate polymer is a component that functions as a binder, ensures 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, the particulate polymer exists in a particulate form in the dispersion medium. Specifically, the particulate polymer is usually a water-insoluble polymer and is present in particulate form in an aqueous medium. In the present invention, the polymer being “water-insoluble” means that at 25 ° C., when 0.5 g of the polymer is dissolved in 100 g of water, the insoluble content becomes 90% by mass or more. Say.
The particulate polymer has the following formula (I):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a phenyl group, an alkyl group having 1 to 6 carbon atoms, or one to three alkyl groups having 1 to 6 carbon atoms. And n represents an integer of 3 or more.) A repeating unit represented by 0.1 to 5% by mass, and a (meth) acrylic acid alkyl ester monomer unit to 35% by mass. As mentioned above, 20 to 60 mass% of aromatic monovinyl monomer units are contained. Here, the particulate polymer contains a repeating unit other than the repeating unit represented by the above formula (I), the (meth) acrylic acid alkyl ester monomer unit, and the aromatic monovinyl monomer unit. Also good. Examples of such other repeating units include acidic group-containing monomer units and crosslinkable monomer units.

[Repeating unit represented by formula (I)]
In the repeating unit represented by the formula (I), the value of n needs to be 3 or more, preferably 4 or more, more preferably 5 or more, and particularly preferably 7 or more. It is preferably 25 or less, more preferably 15 or less. When the value of n is less than 3, the stability of the porous membrane composition under shear is impaired, and the peel strength of the porous membrane before immersion in the electrolyte and the rate characteristics of the secondary battery are deteriorated. On the other hand, if the value of n is 25 or less, it is possible to secure the peel strength after immersion of the porous membrane in the electrolyte while reducing the water content of the porous membrane, and to improve the life characteristics of the secondary battery. Moreover, the increase in the viscosity of the binder composition due to the excessively long polyoxyethylene group can be suppressed, and the preparation and handling of the binder composition are facilitated.
The particulate polymer may contain only one type of repeating unit represented by the formula (I), or may contain two or more types of repeating units represented by the formula (I).

で表されるポリオキシエチレン基含有単量体が挙げられる。ここで、式(II)中、Ｒ¹およびＲ²の構造は、対応する式（Ｉ）のそれらと同一である。そしてｎの値は対応する式（Ｉ）のそれと同一であり、その好適な範囲も式（Ｉ）における範囲と同一である。
式(II)で表されるポリオキシエチレン基含有単量体としては、例えば、製品名「ＡＭ−９０Ｇ」、「ＡＭ−１３０Ｇ」、「Ｍ−９０Ｇ」、「Ｍ−２３０Ｇ」（何れも新中村化学社製）や、製品名「ブレンマー（登録商標）ＰＭＥ−２００」（日油社製）などのポリオキシエチレン基含有（メタ）アクリレートが挙げられる。これらは１種単独で、または、２種以上を組み合わせて用いることができる。そしてこれらの中でも、Ｍ−９０Ｇ、Ｍ−２３０Ｇ、ブレンマーＰＭＥ−２００などのポリエチレングリコールメタクリレートが好ましく、Ｍ−９０Ｇが好ましい。なお、本発明において「（メタ）アクリレート」とは、アクリレートおよび／またはメタクリレートを意味する。 And as a monomer which can form the repeating unit represented by Formula (I), the following formula (II):

The polyoxyethylene group containing monomer represented by these is mentioned. Here, in the formula (II), the structures of R ¹ and R ² are the same as those of the corresponding formula (I). The value of n is the same as that of the corresponding formula (I), and its preferred range is also the same as the range in formula (I).
Examples of the polyoxyethylene group-containing monomer represented by the formula (II) include product names “AM-90G”, “AM-130G”, “M-90G”, “M-230G” (all new Nakamura Chemical Co., Ltd.) and polyoxyethylene group-containing (meth) acrylates such as “Blemmer (registered trademark) PME-200” (manufactured by NOF Corporation). These can be used alone or in combination of two or more. Among these, polyethylene glycol methacrylates such as M-90G, M-230G, and Bremer PME-200 are preferable, and M-90G is preferable. In the present invention, “(meth) acrylate” means acrylate and / or methacrylate.

  The content of the repeating unit represented by the formula (I) in the particulate polymer needs to be 0.1% by mass or more and 5% by mass or less, and preferably 0.2% by mass or more. , 0.6% by mass or more, more preferably 3.0% by mass or less, and even more preferably 1.5% by mass or less. When the content ratio of the repeating unit represented by the formula (I) is less than 0.1% by mass, the stability of the porous membrane composition under shear is impaired, and the peel of the porous membrane before immersion in the electrolyte solution The strength and the rate characteristics of the secondary battery are degraded. On the other hand, if the content ratio of the repeating unit represented by the formula (I) is more than 5% by mass, the moisture content of the porous film increases, and the peel strength after immersion of the porous film in the electrolyte solution decreases. The life characteristics of the secondary battery are degraded. In addition, the viscosity of the binder composition increases excessively due to an increase in the number of polyoxyethylene groups, which may hinder the preparation and handling of the binder composition.

Here, as an index correlating with the abundance ratio of the polyoxyethylene chain portion in the particulate polymer, P calculated by the following formula can be mentioned.
P = n _AVE. × C
(In the formula, n _AVE. Is a weighted average value of n values of repeating units represented by the formula (I) in the particulate polymer, and C is a formula (I) in the particulate polymer. (This is the content (% by mass) of the repeating unit represented.)
The value of P is preferably 3 or more, more preferably 5 or more, still more preferably 7 or more, and is preferably 50 or less, more preferably 30 or less, More preferably, it is 20 or less. If the value of P is 3 or more, the stability of the composition for a porous membrane under shear, the peel strength before immersion of the porous membrane in the electrolyte solution, and the rate characteristics of the secondary battery can be improved. On the other hand, if the value of P is 50 or less, it is possible to secure the peel strength after immersion of the porous membrane in the electrolyte while reducing the moisture content of the porous membrane, and to improve the life characteristics of the secondary battery. Moreover, the increase in the viscosity of the binder composition due to the increased proportion of polyoxyethylene groups can be suppressed, and the preparation and handling of the binder composition becomes easy.

[(Meth) acrylic acid alkyl ester monomer unit]
Examples of (meth) acrylic acid alkyl ester monomers that can form (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 Esters: 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 , Methacrylic acid alkyl esters such as stearyl methacrylate and glycidyl methacrylate; These can be used alone or in combination of two or more. Among these, 2-ethylhexyl acrylate, ethyl acrylate, and butyl acrylate are preferable from the viewpoint of improving the peel strength before and after immersion of the porous membrane in the electrolytic solution. And 2-ethylhexyl acrylate is more preferable from the viewpoint of further improving the peel strength before and after the electrolytic solution immersion liquid of the porous film and reducing the water content of the porous film to improve the battery characteristics of the secondary battery.

  The content ratio of the (meth) acrylic acid alkyl ester monomer unit in the particulate polymer needs to be 35% by mass or more, preferably 45% by mass or more, and 55% by mass or more. More preferably, it is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less. When the content ratio of the (meth) acrylic acid alkyl ester monomer unit is less than 35% by mass, the peel strength of the porous membrane before immersion in the electrolyte cannot be ensured. Therefore, the powder falling of the porous film cannot be sufficiently suppressed, and the rate characteristic and life characteristic of the secondary battery are deteriorated due to the presence of the defective portion of the porous film. 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 that can form an aromatic monovinyl monomer unit include styrene, styrene sulfonic acid and salts thereof (for example, sodium styrene sulfonate, lithium styrene sulfonate, etc.), α-methyl styrene, p- Examples include tert-butoxystyrene and vinyltoluene. These can be used alone or in combination of two or more. Among these, styrene is preferable from the viewpoint of reducing the moisture content of the porous film while increasing the stability of the composition for the porous film under shear and the peel strength before immersion of the porous film in the electrolyte solution.

  The content of the aromatic monovinyl monomer unit in the particulate polymer needs to be 20% by mass or more and 60% by mass or less, preferably 25% by mass or more, and 50% by mass or less. It is preferable that the content is 40% by mass or less. When the content ratio of the aromatic monovinyl monomer unit is less than 20% by mass, the stability of the porous membrane composition under shearing is impaired, and the peel strength after immersion of the porous membrane in the electrolytic solution can be secured. Therefore, the life characteristics of the secondary battery are deteriorated. On the other hand, when the content ratio of the aromatic monovinyl monomer unit is more than 60% by mass, it is difficult to prevent the powder falling because the peel strength before immersion of the porous membrane in the electrolyte solution cannot be secured, and the battery characteristics of the secondary battery ( In particular, the rate characteristics are reduced.

[Other repeat units]
The particulate polymer may contain a repeating unit other than the repeating unit represented by the above formula (I), the (meth) acrylic acid alkyl ester monomer unit, and the aromatic monovinyl monomer unit. As such other repeating units, an acidic group-containing monomer unit and a crosslinkable monomer unit will be described below as examples, but the other repeating units are not limited to these examples.

[[Acid group-containing monomer unit]]
Examples of the acidic group-containing monomer unit include a carboxylic acid group-containing monomer unit, a sulfonic acid group-containing monomer unit, and a phosphoric acid group-containing monomer unit.

Examples of the carboxylic acid group-containing monomer that can form a carboxylic acid group-containing monomer unit include ethylenically unsaturated monocarboxylic acid and derivatives thereof, ethylenically unsaturated dicarboxylic acid and acid anhydrides thereof, and derivatives thereof. Can be mentioned.
Examples of the ethylenically unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid and the like. Examples of ethylenically unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E monomethoxyacrylic. Examples include acid and β-diaminoacrylic acid.
Examples of the ethylenically unsaturated dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, mesaconic acid and the like. Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and the like. In addition, examples of ethylenically unsaturated dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate , Dodecyl maleate, octadecyl maleate, fluoroalkyl maleate and the like.

Examples of the sulfonic acid group-containing monomer that can form a sulfonic acid group-containing monomer unit include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, Examples include 2-acrylamido-2-methylpropanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid.
In the present invention, “(meth) allyl” means allyl and / or methallyl.

Examples of the phosphoric acid group-containing monomer that can form a phosphoric acid group-containing monomer unit include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, and ethyl phosphate. -(Meth) acryloyloxyethyl etc. are mentioned.
In the present invention, “(meth) acryloyl” means acryloyl and / or methacryloyl.

  These acidic group-containing monomers can be used alone or in combination of two or more. Among these, from the viewpoint of ensuring the dispersibility of the particulate polymer and improving the stability of the composition for the porous membrane under shear, and improving the rate characteristics of the secondary battery, it contains a carboxylic acid group. Monomers are preferred, acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid are more preferred, acrylic acid, methacrylic acid and itaconic acid are more preferred, and acrylic acid is particularly preferred.

  The content ratio of the acidic group-containing monomer unit in the particulate polymer is preferably 0.1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more. It is preferably 7% by mass or less, more preferably 6% by mass or less, and further preferably 5% by mass or less. If the content ratio of the acidic group-containing monomer unit is 0.1% by mass or more, the dispersibility of the particulate polymer is ensured, and the stability of the composition for a porous membrane under shear is increased, and the secondary The rate characteristics of the battery can be improved. On the other hand, if the content ratio of the acidic group-containing monomer unit is 7% by mass or less, the moisture content in the secondary battery is reduced due to a decrease in the moisture content of the porous membrane. Life characteristics are improved.

[[Crosslinkable monomer unit]]
The crosslinkable monomer unit is a monomer unit that forms a crosslinked structure within the particulate polymer or between the particulate polymers, or between the particulate polymer and a water-soluble polymer described later. Specifically, a first crosslinkable monomer unit formed from a first crosslinkable monomer having two or more ethylenically unsaturated bonds per molecule, or one ethylenically unsaturated bond per molecule. And a second crosslinkable monomer unit formed from a second crosslinkable monomer having one or more thermally crosslinkable groups per molecule. Examples of the thermally crosslinkable group include an epoxy group, an N-methylolamide group, an oxetanyl group, and an oxazoline group.

-First crosslinkable monomer unit-
The first crosslinkable monomer unit mainly forms a crosslinked structure in the particulate polymer and / or between the particulate polymers during the polymerization reaction for preparing the particulate polymer, and the particulate weight in the electrolytic solution is increased. Excessive swelling of the coalescence can be suppressed.
As the first crosslinkable monomer capable of forming the first crosslinkable monomer unit, allyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) Polyfunctional (meth) acrylates such as acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane-tri (meth) acrylate; dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether And polyfunctional allyl / vinyl ethers such as tetraallyloxyethane; divinylbenzene, and the like. These can be used alone or in combination of two or more. Among these, from the viewpoint of suppressing excessive swelling of the particulate polymer in the electrolytic solution to increase the peel strength after immersion of the porous membrane in the electrolytic solution and improving the life characteristics of the secondary battery, allyl methacrylate, ethylene glycol Dimethacrylate is preferred and allyl methacrylate is more preferred.

  The content of the first crosslinkable monomer unit in the particulate polymer is preferably 0.1% by mass or more, more preferably 3% by mass or less, and preferably 2% by mass or less. More preferably, it is more preferably 1% by mass or less. If the content ratio of the first crosslinkable monomer unit is 0.1% by mass or more, excessive swelling of the particulate polymer in the electrolytic solution is suppressed, and the peel strength after immersion of the porous membrane in the electrolytic solution is increased. The life characteristics of the secondary battery are improved. On the other hand, if the content ratio of the first crosslinkable monomer unit is 3% by mass or less, the peel strength of the porous membrane before immersion in the electrolyte solution can be ensured.

-Second crosslinkable monomer unit-
The second crosslinkable monomer unit is a functional group in a water-soluble polymer (hydroxyl group, carboxylic acid) described later, for example, when the composition for a porous membrane is dried to form a porous membrane. And the like) can form a cross-linked structure and increase the strength of the porous membrane.
Examples of the second crosslinkable monomer that can form the second crosslinkable monomer unit include allyl glycidyl ether, vinyl glycidyl ether, N-methylolacrylamide, and the like. These can be used alone or in combination of two or more.
Among these, allyl glycidyl ether is preferable from the viewpoint of forming a good crosslinked structure and further enhancing the strength of the porous film.

  The content ratio of the second crosslinkable monomer unit in the particulate polymer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and 0.5% by mass or more. More preferably, it is 3% by mass or less, more preferably 2% by mass or less, and further preferably 1.8% by mass or less. If the content ratio of the second crosslinkable monomer unit is 0.1% by mass or more, the strength of the porous film can be increased, and if it is 3% by mass or less, excessive crosslinking is suppressed, Brittleness can be prevented.

[Properties of particulate polymer]
[[Random copolymer structure and glass transition temperature]]
The structure of the particulate polymer is not particularly limited and may be any of a block copolymer, a graft copolymer, a random copolymer, and the like, but a random copolymer is preferable. Here, even when the particulate polymer has a core structure and a shell structure, when the shell structure is a random copolymer, the particulate polymer of the present invention corresponds to a random copolymer. It shall be.

When the particulate polymer is a random copolymer, the polymer can be homogenized, the durability of the polymer with respect to the electrolytic solution can be increased, and the dispersibility in the composition for a porous membrane can be improved. it can. Furthermore, since the viscosity of the composition for porous membrane can be suppressed, it becomes easy to remove moisture from the porous membrane during drying. As a result, the peel strength before and after immersion of the porous membrane in the electrolyte can be increased, and the life characteristics of the secondary battery can be improved.
In the present invention, whether or not the particulate polymer is a random copolymer is determined by measuring the glass transition temperature.
Specifically, when the particulate polymer that 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 or a graft copolymer.
In the present invention, the “glass transition temperature” of the particulate polymer can be measured using the measuring method described in the examples of the present specification.

  And the glass transition temperature of a particulate polymer becomes like this. Preferably it is 10 degrees C or less, More preferably, it is 0 degrees C or less, More preferably, it is -5 degrees C or less. If the glass transition temperature of the particulate polymer is 10 ° C. or lower, it is possible to suppress the powder falling off of the porous film at the time of assembling the secondary battery and to secure the battery characteristics (particularly the life characteristics) of the secondary battery. . Moreover, although the minimum of the glass transition temperature of a particulate polymer is not specifically limited, Usually, it is -100 degreeC or more.

[[Swelling degree with respect to non-aqueous electrolyte]]
The swelling degree of the particulate polymer with respect to the nonaqueous electrolytic solution is preferably more than 1 time, more preferably 1.2 times or more, further preferably 1.5 times or more, and 3 times. Is preferably 2.5 times or less, more preferably 2.5 times or less, and even more preferably 2.3 times or less. If the degree of swelling of the particulate polymer with respect to the non-aqueous electrolyte exceeds 1 time, the rate characteristics of the secondary battery can be improved, and if it is 3 times or less, the peel strength after immersion of the porous membrane in the electrolyte The life characteristics of the secondary battery can be improved.
The degree of swelling of the particulate polymer with respect to the non-aqueous electrolyte can be adjusted by changing the type and amount of the monomer used. For example, the first crosslinkable monomer or aromatic monovinyl monomer can be adjusted. The degree of swelling with respect to the non-aqueous electrolyte can be reduced by increasing the amount of the polymer, increasing the polymerization temperature, or increasing the polymerization reaction time to increase the polymerization molecular weight.

[[Volume average particle size]]
The volume average particle diameter 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 of the particulate polymer is 100 nm or more, the aggregation of the particulate polymer is suppressed, and the stability of the porous membrane composition under shear is improved. On the other hand, if the volume average particle diameter of the particulate polymer is 500 nm or less, peel strength before and after immersion of the porous membrane in the electrolytic solution is secured.
The “volume average particle diameter” of the particulate polymer represents the particle diameter (D50) at which the cumulative volume calculated from the small diameter side is 50% in the particle size distribution (volume basis) measured by the laser diffraction method.

[Preparation of particulate polymer]
The particulate polymer is prepared by polymerizing a monomer composition containing the above-described monomer.
Here, the content ratio of each monomer in the monomer composition is usually the same as the content ratio of each corresponding repeating unit in the desired particulate polymer.
The polymerization mode of the particulate polymer is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method may be used. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used. And generally used emulsifiers, dispersants, polymerization initiators, polymerization aids and the like used for the polymerization can be used, and the amount used is also generally used.
Here, when preparing a particulate polymer made of a random copolymer, the polymerization is started not in the state of an oligomer obtained by polymerizing the monomer in the monomer composition to some extent but in the state of the monomer. Thus, the generation of the block copolymer and the graft copolymer may be suppressed.

<Preparation of binder composition for nonaqueous secondary battery porous membrane>
The method for preparing the binder composition of the present invention is not particularly limited. For example, when the particulate polymer is prepared in an aqueous medium and the particulate polymer is obtained as an aqueous dispersion, the particulate polymer The aqueous dispersion may be used as it is as a binder composition, or other components may be optionally added to the aqueous dispersion of the particulate polymer to form a binder composition. Here, as other components, other components described in the section “Composition for non-aqueous secondary battery porous membrane” described later can be given.

(Composition for non-aqueous secondary battery porous membrane)
The composition for a porous membrane of the present invention is an aqueous slurry composition in which the above-mentioned particulate polymer and non-conductive particles are dispersed in water as a dispersion medium.
And since the composition for porous films of this invention uses the particulate polymer mentioned above as a binder, it is excellent in stability under shear, and if the composition for porous films is used, a secondary battery It is possible to form a porous film that exhibits excellent battery characteristics.

<Non-conductive particles>
Here, the non-conductive particles are particles that do not dissolve in water and the non-aqueous electrolyte solution of the secondary battery, and maintain the shape thereof. And since a nonelectroconductive particle is electrochemically stable, it exists stably in a porous film under the use environment of a secondary battery.

As the nonconductive particles, for example, various inorganic fine particles and organic fine particles can be used.
Specifically, as the non-conductive particles, both inorganic fine particles and organic fine particles other than the particulate polymer described above can be used, but inorganic fine particles are usually used. Especially, as a material of nonelectroconductive particle, the material which exists stably in the use environment of a non-aqueous secondary battery and is electrochemically stable is preferable. From this point of view, preferable examples of the non-conductive particle material include aluminum oxide (alumina), hydrated aluminum oxide (boehmite), silicon oxide, magnesium oxide (magnesia), calcium oxide, titanium oxide (titania). Oxide particles such as BaTiO ₃ , ZrO, alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalently bonded crystal particles such as silicon and diamond; barium sulfate, calcium fluoride, barium fluoride Insoluble ion crystal particles such as; clay fine particles such as talc and montmorillonite; In addition, these particles may be subjected to element substitution, surface treatment, solid solution, and the like as necessary.
One type of non-conductive particles described above may be used alone, or two or more types may be used in combination. As the non-conductive particles, aluminum oxide and hydrated aluminum oxide are preferable, and aluminum oxide is more preferable. The particle size of the nonconductive particles is not particularly limited, and can be the same as that of the conventionally used nonconductive particles.

<Combination ratio of non-conductive particles and binder composition>
The compounding ratio of the non-conductive particles and the binder composition in the porous film composition is not particularly limited. For example, in the composition for a porous membrane, the amount of the particulate polymer is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and still more preferably 2 per 100 parts by mass of the non-conductive particles. The binder composition is included in an amount that is at least part by mass, preferably at most 10 parts by mass, more preferably at most 6 parts by mass, and even more preferably at most 5 parts by mass. If the compounding amount of the particulate polymer is 0.5 parts by mass or more per 100 parts by mass of the non-conductive particles, it is possible to ensure the peel strength both before and after immersion of the porous membrane in the electrolyte solution. On the other hand, if the blending amount of the particulate polymer is 10 parts by mass or less per 100 parts by mass of the non-conductive particles, the rate characteristics of the secondary battery can be improved. Moreover, the stability under shear of the composition for porous membranes can be improved while reducing the amount of moisture brought into the secondary battery due to the particulate polymer.

<Other ingredients>
The composition for porous films may contain other arbitrary components in addition to the components described above. The optional component is not particularly limited as long as it does not have an excessively unfavorable effect on the battery reaction in the secondary battery using the porous film. Further, the kind of the arbitrary component may be one kind or two or more kinds.
Examples of the optional component include a water-soluble polymer, a wetting agent, a leveling agent, an electrolytic solution decomposition inhibitor, and the like.
And it is preferable that the composition for porous films contains a water-soluble polymer. Here, as the water-soluble polymer, water-soluble polysaccharides such as carboxymethyl cellulose, xanthan gum, and salts thereof are preferable, and carboxymethyl cellulose is more preferable. In the present invention, the term “water-soluble” means that the insoluble content is less than 0.5% by mass when 0.5 g of the polymer is dissolved in 100 g of water at 25 ° C. Say.
The porous membrane composition is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and still more preferably 0.7 parts by mass or more, based on 100 parts by mass of the non-conductive particles. And preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and still more preferably 1.5 parts by mass or less. If the compounding quantity of the water-soluble polymer in the composition for porous membranes is 0.1 mass part or more per 100 mass parts of nonelectroconductive particles, the peel strength before electrolyte solution immersion of a porous membrane can be improved. When the particulate polymer contains a second crosslinkable monomer unit, the thermally crosslinkable group derived from the second crosslinkable monomer is a functional group (hydroxyl group, carboxylic acid group, etc.) of the water-soluble polymer. Since a cross-linked structure is formed by the reaction, a porous film having excellent strength can be obtained. On the other hand, if the blending amount of the water-soluble polymer in the composition for a porous membrane is 5 parts by mass or less per 100 parts by mass of the non-conductive particles, the rate characteristics of the secondary battery can be improved.

<Preparation of composition for nonaqueous secondary battery porous membrane>
The method for preparing the composition for the porous membrane is not particularly limited, but it is usually obtained by mixing the binder composition described above, non-conductive particles, water, and any components used as necessary. It is done. 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 a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer. Among them, a high dispersion apparatus such as a bead mill, a roll mill, or a fill mix is particularly preferable because a high dispersion share can be added.

  And normally, what is necessary is just to arbitrarily set the solid content density | concentration of the composition for porous films in the range which the composition for porous films has the viscosity of the range which does not impair workability | operativity, when manufacturing a porous film. Specifically, the solid content concentration of the composition for a porous membrane can usually be 10 to 50% by mass.

(Porous membrane for non-aqueous secondary batteries)
The porous membrane of the present invention can be formed by removing a dispersion medium such as water from the porous membrane composition described above. That is, the porous film of the present invention usually contains a particulate polymer and non-conductive particles, and optionally further contains other components. The abundance ratio of each component (excluding a dispersion medium such as water) contained in the porous membrane of the present invention is usually the same as the abundance ratio of each component contained in the above-described porous membrane composition. The suitable abundance ratio of each component in the same is the same as the preferred abundance ratio of each component in the composition for a porous membrane described above.
And the porous film of this invention is the composition for porous films by, for example, apply | coating the composition for porous films mentioned above to the surface of a suitable base material, forming a coating film, and drying the formed coating film. It can be obtained as a molded body made of a dried product. Since the porous film of the present invention is formed using the composition for porous film of the present invention, the battery characteristics excellent in the secondary battery can be exhibited.

<Base material>
Here, there is no limitation on the substrate on which the porous film composition is applied. For example, a coating film of the porous film composition is formed on the surface of the release substrate, and the coating film is dried to form the porous film. The release substrate may be peeled off from the porous film. Thus, the porous film peeled off from the mold release substrate can be used as a self-supporting film for forming a battery member of a secondary battery. Specifically, the separator having a porous film may be formed by laminating the porous film peeled off from the release substrate on the separator substrate, or the porous film peeled off from the release substrate may be used as the electrode substrate. An electrode provided with a porous film may be formed by laminating on the substrate.
However, from the viewpoint of improving the production efficiency of the battery member by omitting the step of peeling the porous film, it is preferable to use a separator substrate or an electrode substrate as the substrate. 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 and strength of the separator and the electrode.

[Separator substrate]
Here, although it does not specifically limit as a separator base material, Known separator base materials, such as an organic separator base material, are mentioned. The organic separator substrate is a porous member made of an organic material. Examples of the organic separator substrate include a microporous membrane or a nonwoven fabric containing a polyolefin resin such as polyethylene and polypropylene, an aromatic polyamide resin, and the like. From the viewpoint of excellent strength, a polyethylene microporous film or nonwoven fabric is preferred. In addition, the thickness of an organic separator base material can be made into arbitrary thickness, Usually, 0.5 micrometer or more, Preferably it is 5 micrometers or more, Usually, 40 micrometers or less, Preferably it is 30 micrometers or less, More preferably, it is 20 micrometers or less.

[Electrode substrate]
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 with which the electrode compound-material layer was formed on the electrical power collector is mentioned.
Here, the current collector, the electrode active material in the electrode mixture layer (positive electrode active material, negative electrode active material) and the binder for electrode mixture layer (binder for positive electrode mixture layer, binder for negative electrode mixture layer) As a method for forming the electrode mixture layer on the current collector and the current collector, known methods can be used, and examples thereof include those described in JP2013-145663A.

<Method for forming porous film for non-aqueous secondary battery>
Examples of a method for forming a porous film on a substrate such as the above-described separator substrate or electrode substrate include the following methods.
1) A method in which the composition for a porous membrane is applied to the surface of a separator substrate or an electrode substrate (in the case of an electrode substrate, the surface on the electrode mixture layer side, the same shall apply hereinafter) and then dried;
2) A method of drying a separator substrate or electrode substrate after immersing the separator substrate or electrode substrate in the composition for a porous membrane;
3) A method for producing a porous film by applying and drying a composition for a porous film on a release substrate, 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 the film thickness of the porous film can be easily controlled. Specifically, in the method 1), a porous film is formed by drying a porous film composition applied on a substrate (application step) and applying a porous film composition on the substrate. A process (porous film formation process) is provided.

[Coating process]
In the coating process, the method for coating the porous membrane composition on the substrate is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. A method is mentioned.

[Porous membrane formation process]
Further, in the porous film forming step, the method for drying the composition for the porous film on the substrate is not particularly limited, and a known method can be used, for example, drying with hot air, hot air, low-humidity air, or vacuum drying. And a drying method by irradiation with infrared rays or electron beams. The drying conditions are not particularly limited, but the drying temperature is preferably 50 to 100 ° C., and the drying time is preferably 5 to 30 minutes.

<Thickness of porous film>
The thickness of the porous film formed on the substrate is preferably 0.01 μm or more, more preferably 0.1 μm or more, still more preferably 1 μm or more, preferably 20 μm or less, more preferably 10 μm or less, and further 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 when it is 20 μm or less, the diffusibility of the electrolyte is ensured and the rate characteristics of the secondary battery are improved. Can be made.

(Battery member provided with porous film)
The battery member (separator and electrode) provided with the porous film of the present invention described above includes components other than the separator base material or the electrode base material and the porous film of the present invention described above unless the effects of the present invention are significantly impaired. You may have. Here, the constituent elements other than the porous film of the present invention are not particularly limited as long as they do not correspond to the porous film of the present invention, and are provided on the porous film of the present invention for bonding between battery members. Examples thereof include an adhesive layer used. Here, the adhesive layer is not particularly limited, and includes a core portion made of a polymer having an electrolyte solution swelling degree of 5 times or more and 30 times or less, and a polymer having an electrolyte solution swelling degree of more than 1 time and 4 times or less. An adhesive layer formed using a polymer having a core-shell structure having a shell portion, for example, an adhesive layer described in JP-A-2015-28842 can be used. Such an adhesive layer exhibits an excellent adhesive force in the electrolytic solution.

(Non-aqueous secondary battery)
The non-aqueous secondary battery of the present invention includes the above-described porous membrane for a non-aqueous secondary battery of the present invention. More specifically, the non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte, and the above-described porous film for a non-aqueous secondary battery is a battery member of a positive electrode, a negative electrode, and a separator. Included in at least one. And since the non-aqueous secondary battery of this invention is equipped with the porous film obtained from the composition for porous films of this invention, it exhibits the outstanding battery characteristic.

<Positive electrode, negative electrode and separator>
At least one of the positive electrode, the negative electrode, and the separator used for the secondary battery of the present invention includes the porous film of the present invention. Specifically, as a positive electrode and a negative electrode having a porous film, an electrode in which the porous film of the present invention is provided on an electrode substrate 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 the porous film of this invention on a separator base material can be used. In addition, as an electrode base material and a separator base material, the thing similar to the thing quoted by the term of the "porous film for non-aqueous secondary batteries" can be used.
Moreover, as a positive electrode which does not have a porous film, a negative electrode, and a separator, it does not specifically limit, 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>
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte, for example, a lithium salt is used in a lithium ion secondary battery. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable because they are easily dissolved in a solvent and exhibit a high degree of dissociation. In addition, electrolyte may be used individually by 1 type and may be used in combination of 2 or more types. Usually, the lithium ion conductivity tends to increase as the supporting electrolyte having a higher degree of dissociation is used, so that the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. 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), and 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; are preferably used. Moreover, you may use the liquid mixture of these solvents. Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. Usually, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted depending on the type of solvent.
The concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate. Moreover, you may add a known additive to electrolyte solution.

<Method for producing non-aqueous secondary battery>
In the non-aqueous secondary battery of the present invention described above, for example, a positive electrode and a negative electrode are overlapped via a separator, and this is placed in a battery container by winding or folding as necessary. It can be manufactured by pouring and sealing. Of the positive electrode, the negative electrode, and the separator, at least one member is a member with a porous film. In addition, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like may be placed in the battery container to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
In addition, in a polymer produced by copolymerizing a plurality of types of monomers, the proportion of the repeating unit formed by polymerizing a certain monomer in the polymer is usually, unless otherwise specified. This corresponds to the ratio of monomer corresponding to the repeating unit in all the monomers used for polymerization of the polymer (preparation ratio).
In Examples and Comparative Examples, the glass transition temperature of the particulate polymer, the degree of swelling and the volume average particle diameter with respect to the non-aqueous electrolyte, the stability of the porous membrane composition under shear, the moisture content of the porous membrane and the electrolysis The peel strength before and after immersion and the rate characteristics and life characteristics of the lithium ion secondary battery were measured and evaluated by the following methods.

<Glass transition temperature>
The aqueous dispersion of the particulate polymer was dried for 3 days in an environment of 50% humidity and 23 to 25 ° C. to obtain a film having a thickness of 1 ± 0.3 mm. The film was dried in a 120 ° C. hot air oven for 1 hour. Using the dried film as a sample, a glass using a differential scanning calorimeter (DSC6220SII, manufactured by Nanotechnology) at a measurement temperature of −100 ° C. to 180 ° C. and a heating rate of 5 ° C./min according to JIS K7121. The transition temperature (° C.) was measured.
<Swelling degree with respect to non-aqueous electrolyte>
The aqueous dispersion of the particulate polymer was dried for 3 days in an environment of 50% humidity and 23 to 25 ° C. to obtain a film having a thickness of 1 ± 0.3 mm. This film was cut into 1 cm × 1 cm to form a binder film, and the weight M0 was measured. Thereafter, the obtained film was placed in a nonaqueous electrolytic solution (solvent: EC / DEC / vinylene carbonate (VC) = 68.5 / 30 / 1.5 (volume ratio), electrolyte: LiPF _{6 having a} concentration of 1 M) at 60 ° C., Soaked 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 non-aqueous electrolyte solution was computed according to the following formula.
Swelling degree with respect to non-aqueous electrolyte = M1 / M0
<Volume average particle diameter>
Dilute the aqueous dispersion of the particulate polymer with ion-exchanged water to prepare a measurement sample with a solid content concentration of 2% by mass, and use a laser diffraction / light scattering particle size distribution analyzer (LS230, manufactured by Beckman Coulter). Then, the volume average particle diameter (D50) of the particulate polymer was measured.
<Stability of the porous membrane composition under shear>
The porous membrane composition was sheared at a shear rate of 500,000 sec ⁻¹ using a rheometer (“MCR502” manufactured by Anton Paar Co., Ltd.) equipped with a parallel plate with a diameter of 50 mm, and the shear viscosity 30 seconds after the start of shearing. η ₁ was read while continuing shearing. Then, a required time T from the start of shearing at which the shear viscosity becomes 3 times η ₁ was measured and evaluated as follows. The longer the required time T, the more stable the composition for a porous membrane under shear.
A: Required time T is 80 minutes or more B: Required time T is 60 minutes or more and less than 80 minutes C: Required time T is 20 minutes or more and less than 40 minutes D: Required time T is less than 20 minutes <Water content of porous membrane>
An organic separator substrate made of a polyethylene porous substrate (manufactured by Celgard, thickness 16 μm) was prepared. The porous membrane composition was applied to one side of the prepared organic separator substrate and dried at 50 ° C. for 2 minutes to obtain a separator having a thickness of 18 μm (porous membrane: 2 μm, organic separator substrate: 16 μm). The obtained separator was cut out into 10 cm x 10 cm, and it was set as the test piece. This test piece is left for 24 hours at a temperature of 25 ° C. and a humidity of 50%, and then a test piece is obtained by a Karl Fischer method (JIS K-0068 (2001) water vaporization method, vaporization temperature 150 ° C.) using a coulometric titration moisture meter. The water content W (ppm) was measured and evaluated as follows. The smaller this value, the smaller the water content in the porous film, and the smaller the amount of water brought into the secondary battery.
A: Water content W is less than 800 ppm B: Water content W is 800 ppm or more and less than 1300 ppm C: Water content W is 1300 ppm or more and less than 1700 ppm D: Water content W is 1700 ppm or more and less than 2200 ppm E: Water content W is 2200 ppm <Peel strength before immersion of electrolyte in porous membrane>
An organic separator substrate made of a polyethylene porous substrate (manufactured by Celgard, thickness 16 μm) was prepared. The porous membrane composition was applied to one side of the prepared organic separator substrate and dried at 50 ° C. for 2 minutes to obtain a separator having a thickness of 18 μm (porous membrane: 2 μm, organic separator substrate: 16 μm). The obtained separator was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece. A cellophane tape was fixed to the test stand in advance. As this cellophane tape, the one specified in JIS Z1522 was used. And the test piece cut out from the separator was affixed on the cellophane tape with the porous membrane surface down. Then, the stress when one end of the test piece was pulled in the vertical direction at a pulling speed of 100 mm / min and peeled was measured. The measurement was performed 3 times, the average value was calculated | required, this was made into peel strength (before immersion), and it evaluated as follows. It shows that a porous film is excellent in adhesiveness with the base material (separator base material) before electrolyte solution immersion, so that peel strength (before immersion) is large.
A: Peel strength (before immersion) is 70 N / m or more B: Peel strength (before immersion) is 50 N / m or more and less than 70 N / m C: Peel strength (before immersion) is 30 N / m or more and less than 50 N / m D: Peel Strength (before immersion) is less than 30 N / m <Peel strength after immersion of electrolyte in porous membrane>
An organic separator substrate made of a polyethylene porous substrate (manufactured by Celgard, thickness 16 μm) was prepared. The porous membrane composition was applied to one side of the prepared organic separator substrate, and the same organic separator substrate as described above was overlaid on the obtained coating film. Subsequently, it dried at 50 degreeC for 2 minute (s), and the 34-micrometer-thick laminated body was obtained (porous film: 2 micrometers, organic separator base material 16 micrometers x 2). The obtained laminate was cut into a rectangle having a length of 100 mm and a width of 10 mm to obtain a test piece. This test piece was immersed in a nonaqueous electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio), electrolyte: LiPF _{6 having a} concentration of 1 M) at 60 ° C. for 72 hours. The test piece after immersion in the electrolyte is pressed under conditions of 1 MPa and 80 ° C. for 2 minutes, and then the end of one organic separator substrate of the test piece is fixed, and the end of the other organic separator is fixed to the porous membrane. The stress was measured when the film was peeled off by pulling in the vertical direction at a pulling speed of 50 mm / min. The measurement was performed three times, the average value was obtained, and this was taken as the peel strength (after immersion) and evaluated as follows. It shows that a porous film is excellent in adhesiveness with the base material (separator base material) after electrolyte solution immersion, so that peel strength (after immersion) is large.
A: Peel strength (after immersion) is 7.0 N / m or more B: Peel strength (after immersion) is 6.0 N / m or more and less than 7.0 N / m C: Peel strength (after immersion) is 6.0 N / m <Rate characteristics of lithium ion secondary battery>
The prepared secondary battery was allowed to stand for 24 hours in a 25 ° C. environment, and then charged and discharged with a 4.35 V, 0.1 C charge, and a 2.75 V, 0.1 C discharge in a 25 ° C. environment. The initial capacity C0 was measured. Thereafter, in a 25 ° C. environment, 4.35 V, 0.1 C charge, 2.75 V, and 2 C discharge were performed, and the capacity C1 was measured. Then, ΔC = {C1 / C0} × 100 (%) was calculated and evaluated according to the following criteria. It shows that it is excellent in a rate characteristic, so that (DELTA) C is large.
A: ΔC is 90% or more B: ΔC is 85% or more and less than 90% C: ΔC is 80% or more and less than 85% D: ΔC is less than 80% <lifetime characteristics>
The prepared secondary battery was allowed to stand for 24 hours in an environment of 25 ° C., and then charged and discharged by charging at 4.35 V, 0.1 C, and discharging at 2.75 V, 0.1 C in an environment at 25 ° C. The operation was performed. Thereafter, the battery was charged at 4.35 V and 0.1 C, left as it was for 168 hours (7 days) at 60 ° C., and then the cell voltage V 1 (V) was measured at 25 ° C. The voltage drop ΔV (mV) was calculated using the equation: ΔV = {4.35−V1} × 1000 and evaluated as follows. It shows that it is excellent in the lifetime characteristic (self-discharge characteristic), so that this value is small.
A: Voltage drop ΔV is 200 mV or less B: Voltage drop ΔV is more than 200 mV to 400 mV or less C: Voltage drop ΔV is more than 400 mV to 600 mV or less D: Voltage drop ΔV is more than 600 mV to 800 mV or less E: Voltage drop ΔV is more than 800 mV

Example 1
<Preparation of binder composition for nonaqueous secondary battery porous membrane>
To a reactor equipped with a stirrer, 90 parts of ion-exchanged water and 0.5 part of ammonium persulfate were supplied, the gas phase part was replaced with nitrogen gas, and the temperature was raised to 80 ° C. On the other hand, 40 parts of ion-exchanged water, 0.8 part of sodium dodecylbenzenesulfonate as an emulsifier, and methoxypolyethylene glycol # 400 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., “M- 90G ", R ¹ is a methyl group, R ² is a methyl group, and corresponds to a compound of formula (II) where n = 9.) 1.0 part, 2-ethylhexyl acrylate as a (meth) acrylic acid alkyl ester monomer (2-EHA) 64.1 parts, 30 parts of styrene (ST) as an aromatic monovinyl monomer, 4.0 parts of acrylic acid (AA) as an acidic group-containing monomer, allyl as a first crosslinkable monomer A monomer composition was obtained by mixing 0.2 part of methacrylamide (AMA) and 0.7 part of allyl glycidyl ether (AGE) as the second crosslinkable monomer. This monomer composition was continuously added to the reactor over 4 hours for polymerization. The reaction was carried out at 80 ° C. during the addition. After completion of the addition, 0.5 part of ammonium persulfate was added, and the reaction was terminated by further stirring at 80 ° C. for 3 hours, and an aqueous dispersion of particulate polymer (binder composition for nonaqueous secondary battery porous membrane) was obtained. Manufactured. The obtained particulate polymer had a volume average particle size of 200 nm. Moreover, using this aqueous dispersion, the glass transition temperature of the particulate polymer and the degree of swelling with respect to the non-aqueous electrolyte were measured. The results are shown in Table 1. The glass transition temperature was one, and it was confirmed that the obtained particulate polymer was a random copolymer.
<Preparation of composition for nonaqueous secondary battery porous membrane>
3 parts of the above binder composition corresponding to the solid content with respect to 100 parts of alumina filler (Nippon Light Metal Co., Ltd., “LS256”) as non-conductive particles, sodium salt of carboxymethyl cellulose (CMC-) as a water-soluble polymer 1 part of Na, manufactured by Daicel FineChem, "Daicel (registered trademark) 1220"), 0.2 part of a polyethylene glycol type surfactant (manufactured by San Nopco, "San Nopco (registered trademark) SN Wet 366") is mixed and porous. A film composition was prepared.
Using the obtained porous membrane composition, the stability of the porous membrane composition under shear, the moisture content of the porous membrane, and the peel strength before and after immersion of the porous membrane in the electrolytic solution were evaluated. The results are shown in Table 1.

<Manufacture of porous membrane and separator>
An organic separator substrate made of a polyethylene porous substrate (manufactured by Celgard, thickness 16 μm) was prepared. The porous membrane composition obtained as described above was applied to one side of the prepared organic separator substrate and dried at 50 ° C. for 2 minutes to form a porous membrane. Further, a slurry for adhesive layer (manufactured by Zeon Corporation, “BM-2500M”) was applied on the porous membrane and dried at 50 ° C. for 2 minutes. Thereby, a separator having a thickness of 20 μm (adhesive layer: 2 μm, porous film: 2 μm, organic separator substrate: 16 μm) was obtained.

<Manufacture of negative electrode>
In a 5 MPa pressure vessel with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of IA, 63.5 parts of ST, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water and potassium persulfate as a polymerization initiator After adding 0.5 part and stirring sufficiently, it heated to 50 degreeC and superposition | polymerization was started. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the binder for negative electrode mixture layer (SBR). After adding a 5% aqueous sodium hydroxide solution to the mixture containing the binder for the negative electrode mixture layer and adjusting the pH to 8, the unreacted monomer is removed by heating under reduced pressure, and then up to 30 ° C. or lower. The mixture was cooled to obtain an aqueous dispersion containing the desired binder for the negative electrode mixture layer.
Next, 100 parts of artificial graphite (volume average particle diameter: 15.6 μm) as the negative electrode active material, carboxymethylcellulose sodium salt (“MAC350HC” manufactured by Nippon Paper Chemical Co., Ltd.) as the water-soluble polymer (thickener) A 2% aqueous solution was mixed with 1 part of solid content and ion-exchanged water to prepare a solid content concentration of 68%, and then mixed at 25 ° C. for 60 minutes. Further, ion exchange water was added to adjust the solid content concentration to 62%, and further mixed at 25 ° C. for 15 minutes to obtain a mixed solution. To this mixed solution, 1.5 parts of the above binder for the negative electrode mixture layer and an amount of ion-exchanged water corresponding to the solid content are added to adjust the final solid content concentration to 52% and mixed for 10 minutes. did. This was defoamed under reduced pressure to obtain a slurry composition for negative electrode having good fluidity.
The obtained negative electrode slurry composition was applied on a copper foil having a thickness of 20 μm, which was a current collector, with a comma coater so that the film thickness after drying was about 150 μm, and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode raw material before pressing. The negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode mixture layer thickness of 80 μm.

<Production of positive electrode>
100 parts of LiCoO ₂ (volume average particle diameter: 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, binder for positive electrode mixture layer Polyvinylidene fluoride (Kureha Co., Ltd., “# 7208”) in an amount corresponding to the solid content and N-methylpyrrolidone were mixed so that the total solid content was 70%. These were mixed by a planetary mixer to prepare a positive electrode slurry composition.
The obtained positive electrode slurry composition was applied onto a 20 μm-thick aluminum foil as a current collector by a comma coater so that the film thickness after drying was about 150 μm and dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material before pressing. The positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a positive electrode mixture layer thickness of 80 μm.

<Manufacture of lithium ion secondary batteries>
The positive electrode after pressing obtained above was cut into 49 cm × 5 cm and placed so that the surface on the positive electrode mixture layer side was on the upper side. On top of that, a separator (a separator having an adhesive layer and a porous film on one side) cut out to 120 cm × 5.5 cm is disposed so that the surface of the positive electrode mixture layer side of the positive electrode faces the adhesive layer of the separator. Was placed on the left side in the longitudinal direction of the separator. Furthermore, the negative electrode after pressing obtained above was cut out to 50 cm × 5.2 cm, and this was placed on the separator so that the surface on the negative electrode mixture layer side faced the organic separator substrate of the separator, and the negative electrode was It arrange | positioned so that it might be located in the longitudinal direction right side of a separator. This was wound with a winding machine around the center in the longitudinal direction of the separator to obtain a wound body. The wound body is pressed at 60 ° C. and 0.5 MPa to form a flat body, and then wrapped in an aluminum packaging exterior as the exterior of the battery, and an electrolytic solution (solvent: EC / DEC / VC (volume ratio) = 68. 5/30 / 1.5, electrolyte: LiPF ₆ ) with a concentration of 1M was injected so that no air remained. Further, in order to seal the opening of the aluminum packaging material exterior, heat sealing at 150 ° C. is performed to close the aluminum packaging material exterior, and then the wound body enclosed in the aluminum packaging material exterior is heated to a temperature of 80 with the aluminum packaging material exterior. The wound lithium ion secondary battery having a discharge capacity of 1000 mAh was manufactured as a non-aqueous secondary battery by pressing at a pressure of 1 ° C. for 2 minutes.
And the rate characteristic and lifetime characteristic were evaluated about the obtained secondary battery. The results are shown in Table 1.

(Examples 2 to 8)
A particulate polymer aqueous dispersion (binder composition), porous membrane in the same manner as in Example 1 except that the amount and type of monomer used for the preparation of the particulate polymer were changed as shown in Table 1. Compositions, separators, negative electrodes, positive electrodes, and lithium ion secondary batteries were manufactured, and the same items were evaluated. The results are shown in Table 1.
In Example 5, as a polyoxyethylene group-containing monomer, methoxypolyethylene glycol monomethacrylate (manufactured by NOF Corporation, “Blenmer PME-200”, R ¹ is a methyl group, R ² instead of M-90G) Corresponds to a methyl group and a compound of formula (II) with n = 4). In Example 6, as a polyoxyethylene group-containing monomer, methoxypolyethylene glycol # 1000 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., “M-230G” instead of M-90G, R ¹ is a methyl group, R ² Corresponds to a methyl group and a compound of formula (II) with n = 23).

Example 9
In the same manner as in Example 1 except that the amount of the particulate polymer was changed as shown in Table 1 when the porous membrane composition was prepared, an aqueous dispersion of the particulate polymer (binder composition) A porous membrane composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced, and the same items were evaluated. The results are shown in Table 1.

(Comparative Examples 1-3)
A particulate polymer aqueous dispersion (binder composition), porous membrane in the same manner as in Example 1 except that the amount and type of monomer used for the preparation of the particulate polymer were changed as shown in Table 1. Compositions, separators, negative electrodes, positive electrodes, and lithium ion secondary batteries were manufactured, and the same items were evaluated. The results are shown in Table 1.

From Examples 1 to 9 and Comparative Examples 1 to 3 in Table 1 above, the repeating unit represented by the formula (I), the (meth) acrylic acid alkyl ester monomer unit, and the aromatic monovinyl monomer unit When a particulate polymer containing a proportion within a predetermined range is used as a binder for a porous membrane, a composition for a porous membrane having excellent stability under shear can be obtained, and an excellent rate for a lithium ion secondary battery. It can be seen that the characteristics and life characteristics can be exhibited. Moreover, in Examples 1-9, it turns out that the moisture content of a porous film is low enough, and the peel strength before and behind electrolyte solution immersion of a porous film is excellent.
Here, from Examples 1 to 4 in Table 1 and Comparative Examples 1 and 2, by changing the content ratio of the repeating unit represented by the formula (I) in the particulate polymer, for the porous membrane It can be seen that the stability of the composition under shear, the peel strength before and after immersion of the porous membrane in the electrolyte, the rate characteristics and life characteristics of the secondary battery can be improved, and the moisture content of the porous film can be reduced.
And from Examples 1, 5, and 6 in Table 1 above, by changing the value of n in the repeating unit represented by the formula (I) of the particulate polymer, under the shear of the porous membrane composition It can be seen that the stability of the porous film, the peel strength before and after immersion in the electrolyte solution, the rate characteristics and the life characteristics of the secondary battery can be improved, and the water content of the porous film can be reduced. In particular, from Examples 1 and 5 in Table 1 above, even if the value of P (an index correlating with the abundance ratio of the polyoxyethylene chain portion in the particulate polymer) is similar, the value of n is It can be seen that by changing the stability of the composition for the porous membrane under shear, the peel strength before immersion of the porous membrane in the electrolyte, the rate characteristics and the life characteristics of the secondary battery can be improved.
Furthermore, from Examples 1 and 9 in Table 1 above, by changing the blending amount of the particulate polymer, the stability of the composition for porous membranes under shear and the rate characteristics of the secondary battery are improved, It can also be seen that the moisture content of the porous membrane can be reduced.

ADVANTAGE OF THE INVENTION According to this invention, the binder for nonaqueous secondary battery porous films which can improve the stability under the shear of the composition for nonaqueous secondary battery porous films, and can exhibit the battery characteristic excellent in the nonaqueous secondary battery. A composition can be provided.
In addition, according to the present invention, it is possible to provide a composition for a porous membrane of a nonaqueous secondary battery that is excellent in stability under shear and that can exhibit excellent battery characteristics in a nonaqueous secondary battery. .
According to the present invention, a nonaqueous secondary battery porous membrane capable of exhibiting excellent battery characteristics in a nonaqueous secondary battery, and a nonaqueous secondary battery comprising the porous membrane for a nonaqueous secondary battery and having excellent battery characteristics A secondary battery can be provided.

Claims (7)

The following formula (I):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a phenyl group, an alkyl group having 1 to 6 carbon atoms, or one to three alkyl groups having 1 to 6 carbon atoms. And n represents an integer of 3 or more.) A repeating unit represented by 0.1 to 5% by mass, and a (meth) acrylic acid alkyl ester monomer unit to 35% by mass. The binder composition for nonaqueous secondary battery porous films containing the particulate polymer which contains the above and the aromatic monovinyl monomer unit 20 mass% or more and 60 mass% or less.   The binder composition for non-aqueous secondary battery porous membrane according to claim 1, wherein the degree of swelling of the particulate polymer with respect to the non-aqueous electrolyte is more than 1 time and 3 times or less.   The composition for non-aqueous secondary battery porous films containing the binder composition for non-aqueous secondary battery porous films of Claim 1 or 2, a nonelectroconductive particle, and water.   The composition for a nonaqueous secondary battery porous membrane according to claim 3, comprising 0.5 to 10 parts by mass of the particulate polymer per 100 parts by mass of the nonconductive particles.   The composition for a non-aqueous secondary battery porous membrane according to claim 3 or 4, wherein a proportion of the non-conductive particles in the total solid content is 70% by mass or more.   A porous membrane for a non-aqueous secondary battery, formed from the composition for a secondary battery porous membrane according to any one of claims 3 to 5.   A non-aqueous secondary battery comprising the porous membrane for a non-aqueous secondary battery according to claim 6.