Raw material for coating material for secondary battery separator, coating material for secondary battery separator, secondary battery separator and secondary battery

Abstract

A starting material of a coating material for secondary battery separators according to the present invention comprises a water-soluble polymer. The water-soluble polymer comprises a first constituent unit that is derived from a reactive surfactant and a second constituent unit that is derived from an acidic group-containing vinyl monomer. The content ratio of the first constituent unit in the water-soluble polymer is 3% by mass to 30% by mass. The content ratio of the second constituent unit in the water-soluble polymer is 3% by mass to 19% by mass.

Description

Technical Field

[0001] The present invention relates to a coating material raw material for a secondary battery separator, a coating material for a secondary battery separator, a secondary battery separator, and a secondary battery. Specifically, the present invention relates to a coating material raw material for a secondary battery separator, a coating material for a secondary battery separator containing the coating material raw material for a secondary battery separator, a secondary battery separator provided with a coating film of the coating material for a secondary battery separator, and a secondary battery provided with the secondary battery separator.

Background Art

[0002] Conventionally, a separator for separating a positive electrode and a negative electrode and allowing ions in an electrolytic solution to pass therethrough has been provided in a secondary battery.

[0003] As such a separator, for example, a polyolefin porous membrane is known.

[0004] On the other hand, a coating layer may be provided on the surface of the separator from the viewpoint of imparting heat resistance. Such a coating layer contains a binder resin and inorganic particles.

[0005] Moreover, as the binder resin, an acrylic-based water-soluble polymer can be mentioned. And it is known to introduce a reactive surfactant unit into the acrylic-based water-soluble polymer from the viewpoint of dispersibility.

[0006] As such a binder resin, for example, a water-soluble polymer containing a reactive surfactant unit and having 1 part by weight of the reactive surfactant unit with respect to 101 parts by weight of the water-soluble polymer has been proposed (see, for example, Example 1 of Patent Document 1).

[0007] Also, a lithium-ion secondary battery binder composition containing a water-soluble polymer containing a reactive surfactant unit and a monomer unit containing an acid group in an amount of 20% by weight or more and 70% by weight or less has been proposed (see, for example, Patent Document 2).

Prior Art Documents

Patent Document

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, the coating layer is required to have heat resistance, breathability, and adhesion to the substrate (specifically, adhesion to a polyolefin porous membrane).

[0010] On the other hand, in Patent Document 1, since the amount of reactive surfactant units in the water - soluble polymer is small, there are problems such as a decrease in heat resistance, breathability, and adhesion.

[0011] Also, in Patent Document 2, since the amount of acid - group - containing monomer units in the water - soluble polymer is large, there are problems such as a decrease in heat resistance, breathability, and adhesion.

[0012] The present invention provides a coating material raw material for a secondary battery separator excellent in heat resistance, breathability, and adhesion, a coating material for a secondary battery separator containing the coating material raw material for a secondary battery separator, a secondary battery separator provided with a coating film of the coating material for a secondary battery separator, and a secondary battery provided with the secondary battery separator.

Means for Solving the Problems

[0013] The present invention [1] relates to a coating material raw material for a secondary battery separator, which contains a water-soluble polymer. The water-soluble polymer contains a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer. The content ratio of the first structural unit is 3% by mass or more and 30% by mass or less in the water-soluble polymer, and the content ratio of the second structural unit is 3% by mass or more and 19% by mass or less in the water-soluble polymer.

[0014] The present invention [2] includes the coating material raw material for a secondary battery separator according to [1] above, wherein the glass transition temperature of the water-soluble polymer is 150°C or higher.

[0015] The present invention [3] includes the coating material raw material for a secondary battery separator according to [1] or [2] above, wherein the water-soluble polymer further contains a third structural unit derived from an amide group-containing vinyl monomer, and the content ratio of the third structural unit is 51% by mass or more and 94% by mass or less in the water-soluble polymer.

[0016] The present invention [4] includes the coating material raw material for a secondary battery separator according to any one of [1] to [3] above, wherein the reactive surfactant is an ether sulfate type anionic reactive surfactant.

[0017] The present invention [5] includes the coating material raw material for a secondary battery separator according to [4] above, wherein the ether sulfate type anionic reactive surfactant is an ethylene oxide adduct.

[0018] The present invention [6] includes the coating material raw material for a secondary battery separator according to any one of [1] to [3] above, wherein the reactive surfactant is an ethylene oxide addition type nonionic reactive surfactant.

[0019] The present invention [7] includes the coating material raw material for a secondary battery separator according to [5] or [6] above, wherein the number of moles of ethylene oxide added is 5 moles or more and 30 moles or less.

[0020] The coating material raw material for a secondary battery separator of the present invention [8] includes a coating material for a secondary battery separator containing inorganic particles and the coating material raw material for a secondary battery separator according to any one of [1] to [7] above.

[0021] The secondary battery separator of the present invention [9] includes a porous membrane and a coating film of the coating material for a separator according to [8] above disposed on at least one side of the porous membrane.

[0022] The secondary battery of the present invention

[10] includes a positive electrode, a negative electrode, and the secondary battery separator according to [9] above disposed between the positive electrode and the negative electrode.

Advantages of the Invention

[0023] The coating material raw material for a secondary battery separator of the present invention includes a water-soluble polymer containing a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer at predetermined ratios, respectively. Therefore, it is excellent in heat resistance, air permeability, and adhesion.

[0024] The coating material for a secondary battery separator of the present invention includes the coating material raw material for a secondary battery separator of the present invention. Therefore, it is excellent in heat resistance, air permeability, and adhesion.

[0025] The secondary battery separator of the present invention includes a coating film of the coating material for a secondary battery separator of the present invention. Therefore, it is excellent in heat resistance, air permeability, and adhesion.

[0026] The secondary battery of the present invention includes the secondary battery separator of the present invention. Therefore 、 it is excellent in heat resistance, air permeability, and adhesion.

Embodiments for Carrying Out the Invention

[0027] <Coating Material Raw Material for Secondary Battery Separator> The coating material raw material for a secondary battery separator includes a water-soluble polymer.

[0028] The water-soluble polymer contains a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer.

[0029] Such a water-soluble polymer is a polymer obtained by polymerizing a water-soluble polymer raw material.

[0030] The water-soluble polymer is defined as a polymer in which, when a once-dried polymer is stirred and dissolved at 1 g per 100 ml of water for 24 hours and then filtered through a 300-mesh wire mesh, the residual solid content is 0.1% or less.

[0031] The water-soluble polymer raw material contains a reactive surfactant and an acidic group-containing vinyl monomer.

[0032] [Reactive Surfactant] The reactive surfactant is a surfactant copolymerizable with an acidic group-containing vinyl monomer. Specifically, the reactive surfactant is a surfactant having an ethylenically unsaturated group (for example, a vinyl group, a (meth)acryloyl group).

[0033] Examples of such a reactive surfactant include an anionic reactive surfactant and a nonionic reactive surfactant.

[0034] The anionic reactive surfactant is represented by, for example, the following formula (1). [Chemical Formula] In the above formula (1), R 1 represents a hydrogen atom or a methyl group. R 1 preferably represents a hydrogen atom.

[0035] Also, in the above formula (1), R 2represents an alkylene group having 1 to 4 carbon atoms. That is, the anionic reactive surfactant represented by the above formula (1) is an alkylene oxide adduct. Examples of the alkylene group having 1 to 4 carbon atoms include a methylene group, an ethylene group, a propylene group, and a butylene group. R 2 preferably represents an ethylene group from the viewpoint of improving heat resistance, air permeability, and adhesion (specifically, adhesion to a porous film (described later)). That is, the anionic reactive surfactant represented by the above formula (1) is preferably an ethylene oxide adduct.

[0036] Also, in the above formula (1), R 3 represents an alkyl group. Examples of the alkyl group include a linear alkyl group and a branched alkyl group. Examples of the linear alkyl group include linear alkyl groups having 1 to 20 carbon atoms. Examples of the linear alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group (lauryl group), a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an eicosyl group.

[0037] Examples of the branched alkyl group include branched alkyl groups having 3 to 16 carbon atoms. Examples of the branched alkyl group having 3 to 16 carbon atoms include an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, a 1-ethylpropyl group, a 1-methylbutyl group, a 1-methylpentyl group, a 1,1-dimethylpropyl group, a 1,1-dimethylbutyl group, a texyl group, a cyclohexyl group, a 1,1-dimethylpentyl group, a 1-methylhexyl group, a 1,1-dimethylhexyl group, a 1-methylheptyl group, a 2-methylbutyl group, a 2-ethylbutyl group, a 2,2-dimethylpropyl group, a cyclohexylmethyl group, a 2-ethylhexyl group, a 2-propylpentyl group, and a 3-methylpentyl group.

[0038] R 3preferably represents a linear alkyl group. R 3 more preferably represents a linear alkyl group having 8 to 20 carbon atoms. R 3 more preferably represents an undecyl group.

[0039] Further, in the above formula (1), R 4 represents an alkylene group. Examples of the alkylene group include a linear alkylene group and a branched alkylene group. Examples of the linear alkylene group include a linear alkylene group having 1 to 10 carbon atoms. Examples of the linear alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, and a decylene group.

[0040] Examples of the branched alkylene group include an alkylene group having 3 to 10 carbon atoms. Examples of the alkylene group having 3 to 10 carbon atoms include isopropylene, isobutylene, s-butylene, t-butylene, isopentylene, s-pentylene, 2-methylhexylene, and 2-ethylhexylene.

[0041] R 5 represents an anionic hydrophilic group. Examples of the anionic hydrophilic group include a carboxyl group, a sulfonic acid group, and a phosphate group. Further, these functional groups may form a salt (for example, sodium salt, potassium salt 、 calcium salt, magnesium salt, ammonium salt). R 5 preferably represents a salt of a sulfonic acid group (for example, -SO3X, where X represents a salt) from the viewpoint of improving heat resistance, air permeability, and adhesion. or That is, the anionic reactive surfactant is preferably an ether sulfate type anionic reactive surfactant. R 5 more preferably represents -SO3NH4.

[0042] m represents 0 or 1. m preferably represents 0.

[0043] n represents the number of moles of alkylene oxide (preferably ethylene oxide) added. For example, from the viewpoint of suppressing the copolymerization difficulty of the reactive surfactant due to the decrease in the solubility of the reactive surfactant in water and improving heat resistance and adhesion, n is preferably 4 or more, more preferably 5 or more, still more preferably 10 or more. Also, for example, n is 45 or less, preferably 40 or less, more preferably 35 or less, still more preferably 30 or less from the viewpoint of improving heat resistance, particularly preferably 25 or less, and most preferably 20 or less.

[0044] And the anionic reactive surfactant is preferably represented by the following formula (2) from the viewpoints of improving heat resistance, air permeability, and adhesion.

Chemical formula

[0045] In the above formula (2), the anionic reactive surfactant is such that in the above formula (1), R 1 represents a hydrogen atom, R 2 represents an ethylene group, R 3 represents an undecyl group, R 5 represents -SO3NH4, and m represents an anionic reactive surfactant showing 0.

[0046] Also, a commercially available product can be used as the anionic reactive surfactant. Examples of such commercially available products include ADEKA LIA SOAP SR series (an anionic reactive surfactant represented by the above formula (2), manufactured by ADEKA Corporation).

[0047] The nonionic reactive surfactant is, for example, represented by the following formula (3).

Chemical formula

[0048] In the above formula (3), R 1 ~R 4, m and n are the same as R in the above formula (1). 1 ~R 4 are synonymous with m and n.

[0049] In the above formula (3), R 1 preferably represents a hydrogen atom.

[0050] Also, in the above formula (3), R 2 preferably represents an ethylene group. That is, the nonionic reactive surfactant is preferably an ethylene oxide adduct (ethylene oxide-added type nonionic reactive surfactant) from the viewpoints of improving heat resistance, air permeability, and adhesion.

[0051] Also, in the above formula (3), R 3 preferably represents a linear alkyl group. R 3 more preferably represents an undecyl group. Also, in the above formula (3), R 4 preferably represents a linear alkylene group. R 4 more preferably represents an ethylene group. Also, in the above formula (3), m represents 1.

[0052] Also, in the above formula (3), n is, for example, 4 or more. From the viewpoint of suppressing the copolymerization difficulty of the reactive surfactant due to the decrease in the solubility of the reactive surfactant in water and improving heat resistance and adhesion, it is 5 or more, more preferably 10 or more. Also, for example, it is 45 or less, preferably 40 or less, more preferably 35 or less, and even more preferably 30 or less from the viewpoint of improving heat resistance, particularly preferably 25 or less, and most preferably 20 or less.

[0053] The nonionic reactive surfactant is preferably represented by the following formula (4).

Chemical formula

[0054] The nonionic reactive surfactant represented by the above formula (4) is, in the above formula (3), R 1 represents a hydrogen atom, R 2 represents an ethylene group, R 3 represents an undecyl group, R 4 represents an ethylene group, and m represents 1, which is a nonionic reactive surfactant.

[0055] Also, a commercially available product can be used as the nonionic reactive surfactant. Examples of such commercially available products include ADEKA LIA SOAP ER series (nonionic reactive surfactant represented by the above formula (4), manufactured by ADEKA Corporation), and AQUALON KH series (nonionic reactive surfactant represented by the above formula (4), manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0056] And the reactive surfactant is appropriately selected according to the type of the porous membrane (described later) and the type of the surface treatment applied to the porous membrane (described later).

[0057] The reactive surfactant can be used alone or in combination of two or more.

[0058] The content ratio of the reactive surfactant is, for example, 3% by mass or more, preferably 5% by mass or more, from the viewpoint of further improving the adhesion, with respect to the water-soluble polymer raw material, and, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, particularly preferably 9% by mass or less.

[0059] [Vinyl monomer containing an acidic group] Examples of the vinyl monomer containing an acidic group include a vinyl monomer containing a carboxy group, a vinyl monomer containing a sulfonic acid group, and a vinyl monomer containing a phosphoric acid group.

[0060] The vinyl monomer containing a carboxy group is copolymerizable with the reactive surfactant and is a vinyl monomer containing a carboxy group.

[0061] Examples of the vinyl monomer containing a carboxy group include monocarboxylic acids, dicarboxylic acids, or salts thereof. Examples of the monocarboxylic acid include (meth)acrylic acid. Examples of the dicarboxylic acid include itaconic acid, maleic acid, fumaric acid, itaconic anhydride, maleic anhydride, and fumaric anhydride. Note that (meth)acrylic refers to methacrylic and / or or acrylic.

[0062] Preferably, the vinyl monomer containing a carboxy group is a monocarboxylic acid. More preferably, the vinyl monomer containing a carboxy group is (meth)acrylic acid. Even more preferably, the vinyl monomer containing a carboxy group is methacrylic acid.

[0063] The vinyl monomer containing a sulfonic acid group is copolymerizable with a reactive surfactant and is a vinyl monomer containing a sulfonic acid group.

[0064] Examples of the vinyl monomer containing a sulfonic acid group include allyl sulfonic acid, methallyl sulfonic acid, and acrylamide t-butyl sulfonic acid. The vinyl monomer containing a sulfonic acid group also includes salts thereof. Examples of the salt of the vinyl monomer containing a sulfonic acid group include alkali metal salts (e.g., sodium salt, potassium salt), and ammonium salts. Specifically, examples include sodium allyl sulfonate, sodium methallyl sulfonate, and ammonium methallyl sulfonate.

[0065] The vinyl monomer containing a phosphate group is copolymerizable with a reactive surfactant and is a vinyl monomer containing a phosphate group.

[0066] Examples of the vinyl monomer containing a phosphate group include 2-meth Li acryloyloxyethyl acid phosphate.

[0067] As an acidic group-containing vinyl monomer, from the viewpoint of heat resistance, preferably, a carboxy group-containing vinyl monomer can be mentioned.

[0068] The acidic group-containing vinyl monomer can be used alone or in combination of two or more.

[0069] The content ratio of the acidic group-containing vinyl monomer is, for example, 3% by mass or more, preferably 5% by mass or more, and, for example, 19% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less from the viewpoint of further improving heat resistance and adhesion with respect to the water-soluble polymer raw material.

[0070] [Amide group-containing vinyl monomer] The water-soluble polymer raw material preferably contains an amide group-containing vinyl monomer. Although details will be described later, when the water-soluble polymer raw material contains an amide group-containing vinyl monomer, the water-soluble polymer contains a third structural unit derived from the amide group-containing vinyl monomer.

[0071] The amide group-containing vinyl monomer is copolymerizable with a reactive surfactant and an acidic group-containing vinyl monomer and is a vinyl monomer containing an amide group.

[0072] Examples of the amide group-containing vinyl monomer include methacrylamide and acrylamide.

[0073] Preferably, methacrylamide can be mentioned as the amide group-containing vinyl monomer.

[0074] The amide group-containing vinyl monomer can be used alone or in combination of two or more.

[0075] The content ratio of the amide group-containing vinyl monomer is, for example, 20% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, still more preferably 51% by mass or more, particularly preferably 60% by mass or more, most preferably 70% by mass or more, from the viewpoint of further improving heat resistance, air permeability, and adhesion, and, for example, 94% by mass or less, preferably 80% by mass or less, based on the water-soluble polymer raw material.

[0076] [Copolymerizable monomer] The water-soluble polymer raw material preferably contains a copolymerizable monomer. As will be described in detail later, when the water-soluble polymer raw material contains a copolymerizable monomer, the water-soluble polymer contains a fourth structural unit derived from the copolymerizable monomer.

[0077] The copolymerizable monomer is a monomer copolymerizable with a reactive surfactant, an acidic group-containing vinyl monomer, and an amide group-containing vinyl monomer.

[0078] Examples of the copolymerizable monomer include (meth)acrylic acid alkyl esters, functional group-containing vinyl monomers (excluding acidic group-containing vinyl monomers and amide group-containing vinyl monomers). ) vinyl esters, aromatic vinyl monomers, N-substituted unsaturated carboxylic acid amides, heterocyclic vinyl compounds, vinylidene halide compounds, α-olefins, dienes, and crosslinkable vinyl monomers.

[0079] Examples of the (meth)acrylic acid alkyl ester include alkyl (meth)acrylates having an alkyl moiety with 1 to 12 carbon atoms. Examples of the alkyl (meth)acrylates having an alkyl moiety with 1 to 12 carbon atoms include alkyl (meth)acrylates having an alkyl moiety with 1 to 4 carbon atoms and alkyl (meth)acrylates having an alkyl moiety with 5 to 12 carbon atoms. Examples of the alkyl (meth)acrylates having an alkyl moiety with 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate. Examples of the alkyl (meth)acrylates having an alkyl moiety with 5 to 12 carbon atoms include n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate.

[0080] Preferred examples of the (meth)acrylic acid alkyl ester include alkyl (meth)acrylates having an alkyl moiety with 1 to 4 carbon atoms.

[0081] Examples of the functional group-containing vinyl monomer (excluding the acidic group-containing vinyl monomer and the amide group-containing vinyl monomer) include a hydroxyl group-containing vinyl monomer, an amino group-containing vinyl monomer, a glycidyl group-containing vinyl monomer, a cyano group-containing vinyl monomer, and an acetoacetoxy group-containing vinyl monomer.

[0082] Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate. Preferred examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth)acrylate. More preferred examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl methacrylate.

[0083] Examples of the amino group-containing vinyl monomer include 2-aminoethyl (meth)acrylate, 2-(N-methylamino)ethyl (meth)acrylate, and 2-(N,N-dimethylamino)ethyl (meth)acrylate.

[0084] Examples of the glycidyl group-containing vinyl monomer include glycidyl (meth)acrylate.

[0085] Examples of the cyano group-containing vinyl monomer include (meth)acrylonitrile.

[0086] Examples of the acetoacetoxy group-containing vinyl monomer include acetoacetoxyethyl (meth)acrylate.

[0087] Examples of the vinyl esters include vinyl acetate and vinyl propionate.

[0088] Examples of the aromatic vinyl monomers include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and chlorostyrene.

[0089] Examples of the N-substituted unsaturated carboxylic acid amides include N-methylol (meth)acrylamide. Preferably, examples of the N-substituted unsaturated carboxylic acid amides include N-methylol acrylamide.

[0090] Examples of the heterocyclic vinyl compounds include vinyl pyrrolidone.

[0091] Examples of the vinylidene halide compounds include vinylidene chloride and vinylidene fluoride.

[0092] Examples of the α-olefins include ethylene and propylene.

[0093] Examples of the dienes include butadiene.

[0094] Examples of the crosslinkable vinyl monomer include vinyl monomers containing two or more vinyl groups. Examples of the vinyl monomers containing two or more vinyl groups include methylene bis(meth)acrylamide, divinylbenzene, polyethylene glycol chain-containing di(meth)acrylate, trimethylolpropane tetraacrylate, pentaery Li tol triacrylate, and pentaery Li tol tetraacrylate.

[0095] Preferred examples of the copolymerizable monomer include functional group-containing vinyl monomers. More preferred examples of the copolymerizable monomer include hydroxyl group-containing vinyl monomers.

[0096] The copolymerizable monomer can be used alone or in combination of two or more.

[0097] The content ratio of the copolymerizable monomer is, for example, 1% by mass or more, preferably 5% by mass or more, and, for example, 60% by mass or less, preferably 40% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, particularly preferably 10% by mass or less, based on the water-soluble polymer raw material.

[0098] [Method for producing water-soluble polymer] The water-soluble polymer can be obtained by polymerizing a water-soluble polymer raw material by a known method.

[0099] Specifically, for example, a water-soluble polymer raw material and a polymerization initiator are blended in water, the water-soluble polymer raw material is polymerized, and then, if necessary, aging is performed.

[0100] The polymerization initiator is not particularly limited, and examples thereof include water-soluble initiators, oil-soluble initiators, and redox initiators. Examples of the water-soluble initiators include persulfates (e.g., ammonium persulfate, potassium persulfate), hydrogen peroxide, organic hydroperoxides, and 4,4'-azobis(4-cyanovaleric acid) ) and the like. Examples of the oil-soluble initiators include benzoyl peroxide and azobisisobutyronitrile.

[0101] As the polymerization initiator, a water-soluble initiator is preferable, a persulfate is more preferable, and ammonium persulfate is even more preferable.

[0102] The blending ratio of the polymerization initiator is, for example, 0.01 part by mass or more, preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, even more preferably 0.5 part by mass or more, and, for example, 3 parts by mass or less, preferably 1 part by mass or less, based on 100 parts by mass of the water-soluble polymer raw material.

[0103] The polymerization initiator can be used alone or in combination of two or more.

[0104] The polymerization temperature is, under normal pressure, for example, 30°C or higher, preferably 50°C or higher, for example, 95°C or lower, preferably 85°C or lower. Also, the polymerization time is, for example, 0.5 hour or longer, preferably 1.5 hours or longer, and, for example, 20 hours or shorter, preferably 10 hours or shorter.

[0105] The aging time is, for example, 0.5 hour or longer, preferably 1.5 hours or longer, and, for example, 8 hours or shorter, preferably 6 hours or shorter.

[0106] In addition, in the above polymerization, from the viewpoint of improving production stability, known additives such as a pH adjuster, a sequestering agent (e.g., ethylenediaminetetraacetic acid and its salts), and, for example, a molecular weight regulator (chain transfer agent) (e.g., mercaptans, low molecular weight halogen compounds) can be blended at appropriate ratios.

[0107] Also, before or after the polymerization, a neutralizing agent such as ammonia can be added to adjust the pH to a range of 5 or more and 11 or less.

[0108] As a result, a water-soluble polymer is obtained as the polymer of the water-soluble polymer raw material, is and an aqueous solution containing the water-soluble polymer.

[0109] The solid content concentration of the aqueous solution containing the water-soluble polymer is, for example, 10% by mass or more and, for example, 50% by mass or less.

[0110] As described above, the water-soluble polymer is obtained by polymerizing a water-soluble polymer raw material containing a reactive surfactant and an acidic group-containing vinyl monomer.

[0111] Therefore, the water-soluble polymer contains a first structural unit derived from the reactive surfactant and a second structural unit derived from the acidic group-containing vinyl monomer.

[0112] The content ratio of the first structural unit is 3% by mass or more in the water-soluble polymer, preferably 5% by mass or more, more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 9% by mass or less, from the viewpoint of further improving the adhesion, and 30% by mass or less, preferably 20% by mass or less.

[0113] If the content ratio of the first structural unit is at least the above lower limit, the heat resistance, air permeability, and adhesion can be improved.

[0114] On the other hand, if the content ratio of the first structural unit is less than the above lower limit, the heat resistance, air permeability, and adhesion will decrease.

[0115] Also, if the content ratio of the first structural unit is at most the above upper limit, the heat resistance, air permeability, and adhesion can be improved.

[0116] On the other hand, when the content ratio of the first structural unit exceeds the above upper limit, the heat resistance, air permeability, and adhesion decrease.

[0117] Note that the content ratio of the first structural unit can be calculated from the charged amount of the reactive surfactant. That is, the content ratio of the first structural unit is synonymous with the content ratio of the reactive surfactant with respect to the above-mentioned water-soluble polymer raw material.

[0118] Also, the content ratio of the second structural unit in the water-soluble polymer is 3% by mass or more, preferably 5% by mass or more, and 19% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less from the viewpoint of further improving the heat resistance and adhesion.

[0119] When the content ratio of the second structural unit is at least the above lower limit, the heat resistance, air permeability, and adhesion can be improved.

[0120] On the other hand, when the content ratio of the second structural unit is less than the above lower limit, the heat resistance, air permeability, and adhesion decrease.

[0121] Also, when the content ratio of the second structural unit is at most the above upper limit, the heat resistance, air permeability, and adhesion can be improved.

[0122] On the other hand, when the content ratio of the second structural unit exceeds the above upper limit, the heat resistance, air permeability, and adhesion decrease.

[0123] Note that the content ratio of the second structural unit can be calculated from the charged amount of the acidic group-containing vinyl monomer. That is, the content ratio of the second structural unit is synonymous with the content ratio of the acidic group-containing vinyl monomer with respect to the above-mentioned water-soluble polymer raw material.

[0124] In the water-soluble polymer, the mass ratio of the first structural unit to the second structural unit (first structural unit / second structural unit) is, for example, 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more, and, for example, 15.0 or less, preferably 10.0 or less, more preferably 7.0 or less, still more preferably 5.0 or less.

[0125] If the above mass ratio is equal to or greater than the above lower limit and equal to or less than the above upper limit, heat resistance, air permeability, and adhesion can be improved.

[0126] When the water-soluble polymer raw material contains an amide group-containing vinyl monomer, the water-soluble polymer contains a third structural unit derived from the amide group-containing vinyl monomer.

[0127] The content ratio of the third structural unit in the water-soluble polymer is, for example, 20% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, still more preferably, from the viewpoint of further improving heat resistance, air permeability, and adhesion, 51% by mass or more, particularly preferably 60% by mass or more, most preferably 70% by mass or more, and, for example, 94% by mass or less, preferably 80% by mass or less.

[0128] If the content ratio of the third structural unit is equal to or greater than the above lower limit, heat resistance, air permeability, and adhesion can be improved.

[0129] If the content ratio of the third structural unit is equal to or less than the above upper limit, heat resistance, air permeability, and adhesion can be improved.

[0130] The content ratio of the third structural unit can be calculated from the charged amount of the amide group-containing vinyl monomer. That is, the content ratio of the third structural unit is synonymous with the content ratio of the amide group-containing vinyl monomer to the above-described water-soluble polymer raw material.

[0131] When the water-soluble polymer raw material contains a copolymerizable monomer, the water-soluble polymer contains a fourth structural unit derived from the copolymerizable monomer.

[0132] The content ratio of the fourth structural unit in the water-soluble polymer is, for example, 1% by mass or more, preferably 5% by mass or more, and, for example, 60% by mass or less, preferably 40% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, particularly preferably 10% by mass or less.

[0133] If the content ratio of the fourth structural unit is equal to or higher than the above lower limit, the heat resistance, air permeability, and adhesion can be improved.

[0134] Also, if the content ratio of the fourth structural unit is equal to or lower than the above upper limit, the heat resistance, air permeability, and adhesion can be improved.

[0135] Note that the content ratio of the fourth structural unit can be calculated from the charged amount of the copolymerizable monomer. That is, the content ratio of the fourth structural unit is synonymous with the content ratio of the copolymerizable monomer with respect to the above-described water-soluble polymer raw material.

[0136] The water-soluble polymer preferably contains the third structural unit and the fourth structural unit together with the first structural unit and the second structural unit.

[0137] Also, the glass transition temperature of the water-soluble polymer is, for example, 120°C or higher, preferably 150°C or higher, more preferably 180°C or higher, still more preferably 200°C or higher, particularly preferably 210°C or higher, most preferably 220°C or higher, and, for example, 300°C or lower, from the viewpoint of improving heat resistance.

[0138] The above glass transition temperature can be measured, for example, by Discovery DSC2500 manufactured by TA Instruments.

[0139] From the above, a raw material for a coating material for a secondary battery separator containing a water-soluble polymer is obtained.

[0140] And the coating material raw material for the secondary battery separator contains a water-soluble polymer containing a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer in predetermined proportions, respectively. Therefore, it is excellent in heat resistance, air permeability, and adhesion. And such a coating material raw material for the secondary battery separator can be preferably used particularly in the production of the coating material for the secondary battery separator.

[0141] <Coating Material for Secondary Battery Separator> The coating material for the secondary battery separator contains a coating material raw material for the secondary battery separator and inorganic particles.

[0142] Examples of the inorganic particles include oxides, nitrides, carbides, sulfates, hydroxides, and potassium titanate. Examples of the oxides include alumina, silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide. Examples of the nitrides include silicon nitride, titanium nitride, and boron nitride. Examples of the carbides include silicon carbide and calcium carbonate. Examples of the sulfates include magnesium sulfate and aluminum sulfate. Examples of the hydroxides include aluminum hydroxide and aluminum oxyhydroxide. Examples of the silicates include talc, kaolinite, dickite, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, silica sand, and glass. Preferably, the inorganic particles are hydroxides. More preferably, the inorganic particles are aluminum oxyhydroxide.

[0143] The average particle diameter of the inorganic particles is, for example, 0.1 μm or more, preferably 0.5 μm or more, and, for example, 5 μm or less, preferably 1 μm or less.

[0144] The average particle diameter of the inorganic particles can be determined by creating a particle size distribution curve using a laser diffraction / scattering particle size distribution measuring device and calculating the particle diameter corresponding to 50% by mass.

[0145] The inorganic particles can be used alone or in combination of two or more kinds.

[0146] The blending ratio of the inorganic particles is, for example, 1000 parts by mass or more, and, for example, 10000 parts by mass or less, preferably 5000 parts by mass or less, based on 100 parts by mass of the raw material for the coating material for the secondary battery separator.

[0147] To produce the coating material for the secondary battery separator, first, inorganic particles and, if necessary, a dispersant are blended in water to prepare an inorganic particle dispersion. When a dispersant is blended, the coating material for the secondary battery separator contains the dispersant.

[0148] Examples of the dispersant include ammonium polycarboxylate and sodium polycarboxylate. Preferably, ammonium polycarboxylate is mentioned as the dispersant.

[0149] The blending ratio of the dispersant is, for example, 0.5 part by mass or more, preferably 1 part by mass or more, and, for example, 10 parts by mass or less, preferably 5 parts by mass or less, based on 100 parts by mass of the inorganic particles.

[0150] The dispersant can be used alone or in combination of two or more kinds.

[0151] Next, the raw material for the coating material for the secondary battery separator is blended into the inorganic particle dispersion and stirred.

[0152] The stirring method is not particularly limited, and examples include ball mill, bead mill, planetary ball mill, vibration ball mill, sand mill, colloid mill, attritor, roll mill, high-speed impeller dispersion, disperser, homogenizer, high-speed impact mill, ultrasonic dispersion, and stirring blades.

[0153] In addition, if necessary, additives such as hydrophilic resins, wetting agents, defoaming agents, and pH adjusters can be blended into the coating material for the secondary battery separator at appropriate ratios. That is, the coating material for the secondary battery separator may contain additives if necessary. integral These additives can be used alone or in combination of two or more.

[0154] These additives can be used alone or in combination of two or more.

[0155] Furthermore, although details will be described later, in this coating material for the secondary battery separator, heat resistance and adhesion can be improved without blending a wetting agent. Therefore, preferably, no wetting agent is blended into the coating material for the secondary battery separator. In other words, the coating material for the secondary battery separator preferably does not substantially contain a wetting agent. That the coating material for the secondary battery separator does not substantially contain a wetting agent means that the content ratio of the wetting agent is, for example, 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.001% by mass or less with respect to the coating material for the secondary battery separator.

[0156] Thereby, a coating material for the secondary battery separator (an aqueous dispersion of the coating material for the secondary battery separator) is obtained.

[0157] The solid content concentration of the aqueous dispersion of the coating material for the secondary battery separator is, for example, 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and, for example, 50% by mass or less.

[0158] The coating material for the secondary battery separator contains the above-mentioned raw materials for the coating material for the secondary battery separator. Therefore 、 it is excellent in heat resistance, air permeability, and adhesion. And such a coating material for the secondary battery separator can be preferably used particularly in the manufacture of secondary battery separators.

[0159] <Secondary battery separator> The secondary battery separator includes a porous membrane and a coating film of the coating material for the secondary battery separator disposed on at least one side of the porous membrane.

[0160] [Porous membrane] Examples of the porous membrane include a polyolefin porous membrane and an aromatic polyamide porous membrane. Examples of the polyolefin porous membrane include a polyethylene porous membrane and a polypropylene porous membrane. Preferably, the porous membrane is a polyolefin porous membrane. The porous membrane may be surface-treated as necessary. Examples of the surface treatment include corona treatment and plasma treatment.

[0161] The thickness of the porous membrane is, for example, 1 μm or more, preferably 5 μm or more, and, for example, 40 μm or less, preferably 20 μm or less.

[0162] [Coated film] The coated film is a heat-resistant layer for imparting heat resistance to the porous membrane. The coated film is made of a coating material for a secondary battery separator.

[0163] The thickness of the coated film is, for example, 1 μm or more, preferably 3 μm or more, and, for example, 10 μm or less, preferably 8 μm or less.

[0164] [Method for manufacturing a secondary battery separator] The method for manufacturing a secondary battery separator includes a first step of preparing a porous membrane and a second step of applying a coating material for a separator to at least one side of the porous membrane.

[0165] (First step) In the first step, a porous membrane is prepared.

[0166] (Second step) In the second step, a coating material for a secondary battery separator (an aqueous dispersion of the coating material for a secondary battery separator) is applied to at least one side of the porous membrane, and then, if necessary, dried to obtain a coated film.

[0167] The coating method is not particularly limited, and examples thereof include a gravure coater method, a small-diameter gravure coater method, a reverse roll coater method, a transfer roll coater method, a kiss coater method, a dip coater method, a microgravure coat method, a knife coater method, an air doctor coater method, a blade coater method, a rod coater method, a squeeze coater method, a cast coater method, a die coater method, a screen printing method, and a spray coating method.

[0168] The drying temperature is, for example, 40°C or higher and, for example, 80°C or lower.

[0169] Thereby, a secondary battery separator is manufactured, which includes a porous membrane and a coating film of the above-described coating material for a secondary battery separator disposed on at least one side of the porous membrane.

[0170] In the above description, the coating film of the coating material for a secondary battery separator is disposed on at least one side of the porous membrane, but the above coating film can also be disposed on both sides of the porous membrane.

[0171] This secondary battery separator includes the coating film of the above-described coating material for a secondary battery separator. Therefore, it is excellent in heat resistance, air permeability, and adhesion. And such a secondary battery separator type can be preferably used, especially in the manufacture of secondary batteries.

[0172] <Secondary battery> A secondary battery includes a positive electrode, a negative electrode, the above-described secondary battery separator disposed between the positive electrode and the negative electrode, and an electrolyte impregnated in the positive electrode, the negative electrode, and the above-described secondary battery separator.

[0173] As the positive electrode, for example, a known electrode including a current collector for a positive electrode and a positive electrode active material laminated on the current collector for a positive electrode is used.

[0174] Examples of the current collector for a positive electrode include conductive materials such as aluminum, titanium, stainless steel, nickel, fired carbon, conductive polymers, and conductive glass.

[0175] The positive electrode active material is not particularly limited, and examples thereof include known positive electrode active materials such as lithium-containing transition metal oxides, lithium-containing phosphates, and lithium-containing sulfates.

[0176] These positive electrode active materials can be used alone or in combination of two or more.

[0177] As the negative electrode, for example, a known electrode including a current collector for the negative electrode and a negative electrode active material laminated on the current collector for the negative electrode is used.

[0178] Examples of the current collector for the negative electrode include conductive materials such as copper and nickel.

[0179] The negative electrode active material is not particularly limited, and examples thereof include carbon active materials. Examples of the carbon active materials include graphite, soft carbon, and hard carbon.

[0180] These negative electrode active materials can be used alone or in combination of two or more.

[0181] As the electrolyte, when a lithium ion battery is adopted as the secondary battery, for example, a solution in which a lithium salt is dissolved in a carbonate compound such as ethylene carbonate (EC), propylene carbonate (PC), or ethyl methyl carbonate (EMC) can be mentioned.

[0182] And to manufacture the secondary battery, for example, the separator of the secondary battery is sandwiched between the positive electrode and the negative electrode, these are housed in a battery case (cell), and the electrolyte is injected into the battery case. Thereby, a secondary battery can be obtained.

[0183] Since the above secondary battery includes the above secondary battery separator, it is excellent in heat resistance, air permeability, and adhesion.

[0184] <Function and Effect> The coating material raw material for the secondary battery separator contains a water-soluble polymer containing a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer, respectively, in a predetermined ratio. Therefore, it is excellent in heat resistance, air permeability, and adhesion.

[0185] Specifically, from the viewpoint of improving heat resistance and adhesion, it is considered to blend a wetting agent into the coating material for the secondary battery separator containing the above coating material raw material for the secondary battery separator.

[0186] As a result, the coating material for the secondary battery separator can be more firmly fixed on the surface of the porous membrane, and the heat resistance and adhesion can be improved. However, when a wetting agent is blended, the free wetting agent penetrates into the porous membrane, resulting in a decrease in air permeability.

[0187] On the other hand, the coating material raw material for the secondary battery separator contains a water-soluble polymer containing a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer, respectively, in a predetermined ratio.

[0188] As a result, the heat resistance and adhesion of the coating material for the secondary battery separator can be improved without blending a wetting agent. Moreover, since no wetting agent is blended, the decrease in air permeability due to the above-mentioned free wetting agent can be suppressed, and as a result, the air permeability can be improved.

[0189] The coating material for the secondary battery separator contains the above coating material raw material for the secondary battery separator. Therefore, it is excellent in heat resistance, air permeability, and adhesion.

[0190] The secondary battery separator includes a coating film of the above coating material for the secondary battery separator. Therefore, it is excellent in heat resistance, air permeability, and adhesion.

[0191] The secondary battery includes the above secondary battery separator. Therefore 、 it is excellent in heat resistance, air permeability, and adhesion.

Examples

[0192] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited by the following examples. In addition, "parts" and "%" are based on mass unless otherwise specified. Further, specific numerical values such as the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values (numerical values defined as "hereinafter" and "less than") or lower limit values (numerical values defined as "above" and "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above "Mode for Carrying Out the Invention".

[0193] <Details of Components> Details of the active ingredients used in the following examples and comparative examples are shown below. SR-10: Adeka Resope SR-10, the compound represented by the above formula (2) (n = 10), number of moles of ethylene oxide added: 10, manufactured by ADEKA SR-20: Adeka Resope SR-20, the compound represented by the above formula (2) (n = 20), number of moles of ethylene oxide added: 20, manufactured by ADEKA ER-10: Adeka Resope ER-10, the compound represented by the above formula (4) (n = 10), number of moles of ethylene oxide added: 10, manufactured by ADEKA ER-20: Adeka Resope ER-20, the compound represented by the above formula (4) (n = 20), number of moles of ethylene oxide added: 20, manufactured by ADEKA ER-30: Adeka Resope ER-30, the compound represented by the above formula (4) (n = 30), number of moles of ethylene oxide added: 30, manufactured by ADEKA ER-40: Adeka Resope ER-40, the compound represented by the above formula (4) (n = 40), number of moles of ethylene oxide added: 40, manufactured by ADEKA KH-05: Aqualon KH-05: the compound represented by the above formula (4) (n = 5), number of moles of ethylene oxide added: 5, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Mam: Methacrylic acid Mac: Methacrylamide HEMA: 2-Hydroxyethyl methacrylate

[0194] <Coating material raw material for secondary battery separator, coating material for secondary battery separator, and bit two manufacture of secondary battery separator> Example 1 [Manufacture of Coating Material Raw Material for Secondary Battery Separator] Separable flask equipped with a stirrer and reflux condenser device 392.0 parts by mass of distilled water was charged into a separable flask equipped with a stirrer and reflux condenser, replaced with nitrogen gas, and then heated to 80°C. Next, 0.6 parts by mass of ammonium persulfate was added, and then SR-10, Mac, Mam, and HEMA were dissolved in water so that the first to fourth structural units were in the ratios shown in Table 1, partially neutralized with aqueous ammonia, and continuously added over 3 hours, and further held for 3 hours to complete the polymerization. An appropriate amount of water was added to obtain an aqueous solution of a water-soluble polymer with a solid content of 15.0% by mass. The pH of the water-soluble polymer was 6.0. Thus, a coating material raw material for a secondary battery separator containing a water-soluble polymer was manufactured.

[0195] [Manufacture of Coating Material for Secondary Battery Separator] As inorganic particles, 100 parts by mass of aluminum hydroxide oxide (manufactured by Daimyo Chemical Co., Ltd., Boehmite Grade C06, particle size: 0.7 μm) and 3.0 parts by mass (in terms of solid content) of an aqueous ammonium polycarboxylate solution (manufactured by San Nopco Ltd., SN Dispersant 5468) as a dispersant were uniformly dispersed in 110 parts by mass of water to prepare an inorganic particle dispersion.

[0196] Next, 5 parts by mass of the above coating material raw material for a secondary battery separator was added to this inorganic particle dispersion in terms of solid content, water was added so that the solid content became 40% by mass, and the mixture was stirred for 15 minutes. Thus, a coating material for a secondary battery separator was manufactured.

[0197] [Manufacture of Secondary Battery Separator] (First Step) As the porous membrane, a polyolefin resin porous membrane was prepared. Specifically, as the polyolefin resin porous membrane, product number SW509C+ (membrane thickness 9.6 μm, porosity 40.6%, air permeability 158 g / 100 ml, areal density 5.5 g / m 2 , Changzhou Xingyuan New Energy Materials Co., Ltd.) was prepared. Next, the surface of the polyolefin resin porous membrane was cut to A4 size.

[0198] (Second step) On the surface (one side) of the polyolefin resin porous membrane, a coating material for a secondary battery separator (aqueous dispersion of the coating material for a secondary battery separator) was applied using a wire bar. Then, it was dried at 50 °C. As a result, a coating film (thickness 5 μm) was formed on the surface (one side) of the polyolefin resin porous membrane. Thereby, a secondary battery separator was manufactured.

[0199] Examples 2 to 20 and Comparative Examples 1 to 8 Based on the same procedure as in Example 1, a coating material raw material for a secondary battery separator, a coating material for a secondary battery separator, and a secondary battery separator were manufactured. However, the formulation of each component was changed so that the first to fourth structural units would be in the ratios described in Tables 1 to 3.

[0200] <Evaluation> [Glass transition temperature of water-soluble polymer] For the water-soluble polymers of each example and each comparative example, the glass transition temperature was measured. Specifically, using Discovery DSC2500 manufactured by TA Instruments, measurement condition 1; R.T / 300 °C (held for 1 minute) / -90 °C (held for 3 minutes); heating rate 50 °C / min, cooling rate 10 °C / min, second heating rate 10 °C / min, measured under a nitrogen atmosphere. The results are shown in Tables 1 to 3. [Heat resistance] The secondary battery separators of each example and each comparative example were cut out into 5 cm × 5 cm pieces, which were used as test pieces. After leaving these test pieces in an oven at 150 °C for 1 hour, the length of each side was measured and the heat shrinkage rate was calculated. Regarding heat resistance, evaluation was carried out according to the following criteria. The results are shown in Tables 1 to 3. (Standard) ◎: The heat shrinkage rate was less than 5%. ○: The heat shrinkage rate was 5% or more and less than 20%. △: The heat shrinkage rate was 20% or more and less than 50%. ×: The heat shrinkage rate was 50% or more.

[0201] [Air permeability] For the secondary battery separators of each example and each comparative example, the air permeability was measured in accordance with JIS-P-8117 using a Wang Research air permeability and smoothness tester manufactured by Asahi Seiko Co., Ltd. The smaller the air permeability, the better the air permeability can be evaluated. Regarding the air permeability, it was evaluated according to the following criteria. The results are shown in Tables 1 to 3. (Standard) ◎: The air permeability was less than 210 s / 100 ml. ○: The air permeability was 210 s / 100 ml or more and less than 250 s / 100 ml. ×: The air permeability was 250 s / 100 ml or more.

[0202] [Adhesion] For the secondary battery separators of each example and each comparative example, the adhesion was measured. Specifically, the coating film on the secondary battery separator was rubbed with an eraser. Regarding the adhesion, it was evaluated according to the following criteria. The results are shown in Tables 1 to 3. (Standard) ◎: It did not peel off even after rubbing 5 times with a weight of 400 g. load ○: It peeled off when rubbed less than 5 times with a weight of 400 g. ○: It peeled off when rubbed less than 5 times with a weight of 400 g. load ×: It peeled off when rubbed with a weight of 100 g. ×: It peeled off when rubbed with a weight of 100 g. load ×: It peeled off when rubbed with a weight of 100 g.

[0203]

Table 1

[0204]

Table 2

[0205]

Table 3

[0206] Note that the above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be construed in a limiting manner. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the claims described below.

Industrial Applicability

[0207] The raw material for the coating material for the secondary battery separator, the coating material for the secondary battery separator, and the secondary battery separator of the present invention can be suitably used, for example, in the manufacture of secondary batteries. The secondary battery of the present invention can be suitably used, for example, in various devices and automobiles.

Claims

1. It contains a water-soluble polymer, The water-soluble polymer contains a first structural unit derived from a reactive surfactant and a second structural unit derived from an acidic group-containing vinyl monomer, The content ratio of the first structural unit is 3% by mass or more and 30% by mass or less in the water-soluble polymer, A raw material for a coating material for a secondary battery separator, wherein the content ratio of the second structural unit is 3% by mass or more and 19% by mass or less in the water-soluble polymer.

2. The raw material for a coating material for a secondary battery separator according to Claim 1, wherein the glass transition temperature of the water-soluble polymer is 150 ° C or higher.

3. The water-soluble polymer further contains a third structural unit derived from an amide group-containing vinyl monomer, The raw material for a coating material for a secondary battery separator according to Claim 1, wherein the content ratio of the third structural unit is 51% by mass or more and 94% by mass or less in the water-soluble polymer.

4. The raw material for a coating material for a secondary battery separator according to Claim 1, wherein the reactive surfactant is an ether sulfate type anionic reactive surfactant.

5. The raw material for a coating material for a secondary battery separator according to Claim 4, wherein the ether sulfate type anionic reactive surfactant is an ethylene oxide adduct.

6. The raw material for a coating material for a secondary battery separator according to Claim 1, wherein the reactive surfactant is an ethylene oxide addition type nonionic reactive surfactant.

7. The raw material for a coating material for a secondary battery separator according to Claim 5, wherein the number of moles of ethylene oxide added is 5 moles or more and 30 moles or less.

8. A coating material for a secondary battery separator, comprising the raw material for a coating material for a secondary battery separator according to Claim 1 and inorganic particles.

9. A porous membrane, A secondary battery separator comprising a porous membrane and a coating film of the coating material for a separator according to Claim 8 disposed on at least one side of the porous membrane.

10. A secondary battery comprising a positive electrode, a negative electrode, and the secondary battery separator according to Claim 9 disposed between the positive electrode and the negative electrode.

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