Adhesive composition, separator, and nonaqueous secondary battery

Abstract

To provide a separator, or an adhesive composition that has excellent adhesiveness in adhesion between a coating layer formed on the separator and an electrode, furthermore, solidification by adhesion between adhesion layers can be suppressed even when a coating layer is formed on the separator, wound and stored, and has excellent blocking resistance.SOLUTION: An adhesive composition including adhesive particles in which Young's modulus is continuously changing from the particle center toward a particle surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition containing adhesive particles, and a separator and a non-aqueous secondary battery using the same. [Background technology]

[0002] In recent years, devices with high-capacity electricity storage media, such as electric vehicles, have become increasingly popular. These devices often use secondary batteries, including lithium-ion secondary batteries, as their power sources. Lithium-ion secondary batteries generally include a separator to prevent short circuits between the positive and negative electrodes. If necessary, the separator may also include a different coating layer on its separator substrate. Known examples of such layers include a heat-resistant layer containing non-conductive particles, such as boehmite, and a binder that binds the non-conductive particles.

[0003] In the process of manufacturing secondary batteries equipped with separators and electrodes provided with a coating layer, it is necessary to achieve both the adhesive strength of the adhesive layer that bonds layers such as the electrode and separator inside the secondary battery and the blocking resistance that prevents self-adhesion when stored in the form of a coated separator, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 005145 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-219006 [Patent Document 3] International Publication No. 2018 / 096975 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, when uniform particles are used to improve adhesion, blocking (solidification due to adhesion between adhesive layers) occurs, making it impossible to ensure the shelf life of the coating film. To address this issue, methods have been proposed in which an adhesive is applied to the entire surface of the separator, or core-shell fine particles are distributed (Patent Documents 1 to 3). However, the former method has the problem of increasing battery resistance because the polymer is applied to the entire surface, and the latter method has the problem of insufficient adhesion.

[0006] An object of the present invention is to provide an adhesive composition and the like that has excellent adhesive properties when bonding a separator or a coating layer formed on a separator to an electrode, and further has excellent blocking resistance and can suppress solidification due to adhesion between adhesive layers even when a coating layer is formed on a separator and the separator is rolled up and stored. [Means for solving the problem]

[0007] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems of the present invention, they discovered that by using specific adhesive particles, an adhesive composition having excellent coating layer adhesion and blocking resistance can be obtained, and thus completed the present invention.

[0008] That is, the present invention is as follows. [1] An adhesive composition for bonding components constituting a non-aqueous secondary battery, the adhesive composition comprising adhesive particles whose Young's modulus changes continuously from the particle center to the particle surface. [2] The adhesive composition according to [1] above, wherein the maximum ratio of the higher Young's modulus to the lower Young's modulus at two adjacent measurement points is 290% or less when the Young's modulus is measured at 10 nm intervals from the center of the particle to the surface of the particle. [3] The adhesive composition according to [1] above, wherein the Young's modulus of the adhesive particles is higher at the particle surface than at the particle center. [4] The adhesive composition according to [1] above, wherein the adhesive particles have a structural unit derived from at least one monomer selected from the group consisting of monofunctional (meth)acrylate monomers, aromatic vinyl monomers, (meth)acrylonitrile monomers, and conjugated diene monomers. [5] The adhesive composition according to [1] above, wherein the adhesive particles have structural units derived from reactive monomers, and the content of the structural units derived from reactive monomers is 0.05% by mass to 5% by mass relative to the total mass of the adhesive particles. [6] The adhesive composition according to [5] above, wherein the reactive monomer comprises at least one selected from the group consisting of a polyfunctional (meth)acrylate monomer, an epoxy group-containing (meth)acrylate monomer, and a silanol group-containing (meth)acrylate monomer. [7] The adhesive composition according to [1] above, wherein the degree of swelling of the adhesive particles when immersed in a mixed electrolyte (ethylene carbonate / propylene carbonate = 1 / 1 (volume ratio)) containing 1 mol / L of LiPF6 is three times or more compared to before immersion. [8] The adhesive composition according to [1] above, further comprising at least one selected from the group consisting of a particulate binder having a glass transition temperature (Tg) of 30°C or less, a water-soluble polymer, and a preservative. [9] The adhesive composition according to the above [1], further comprising an inorganic filler.

[10] The adhesive composition according to [1] above, which contains water as a solvent, has a viscosity of 5 mPa·s to 1000 mPa·s at 25°C measured using a Brookfield viscometer at a rotor rotation speed of 60 rpm, and has a solids content of 5.0% by mass to 80.0% by mass, relative to 100% by mass of the adhesive composition.

[11] A separator comprising a substrate and an adhesive layer comprising the adhesive composition of claim 1.

[12] A non-aqueous secondary battery comprising the separator according to

[11] above.

[13] A method for producing a separator, comprising the steps of: filtering the adhesive composition according to any one of [1] to

[10] above using a magnetic separator and / or a filter; and forming an adhesive layer on a surface of a substrate using the filtered composition obtained in the step. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an adhesive composition and the like that has excellent adhesive properties when bonding a separator or a coating layer formed on a separator to an electrode, and further, that can suppress solidification due to adhesion between adhesive layers even when a coating layer is formed on a separator and the separator is rolled up and stored, and that also has excellent blocking resistance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a graph illustrating the relationship between the distance from the particle center and the Young's modulus of an adhesive particle whose Young's modulus changes continuously, and the ratio thereof. [Figure 2] FIG. 2 is a schematic diagram of a graph for explaining the relationship between the distance from the particle center of a conventional uniform particle and the Young's modulus and the ratio thereof. [Figure 3] FIG. 3 is a schematic diagram of a graph illustrating the relationship between the distance from the particle center of a conventional core-shell particle and the Young's modulus and the ratio thereof. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below with reference to preferred embodiments thereof. However, the present invention is not limited to the following embodiments and examples, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0012] In this specification, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the Examples. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, when there are multiple substances corresponding to each component, the amount of each component means the total amount of multiple substances, unless otherwise specified.

[0013] <Adhesive composition> The adhesive composition of the present invention is an adhesive composition for bonding components constituting a nonaqueous secondary battery together. The adhesive composition of the present invention contains adhesive particles (hereinafter simply referred to as "adhesive particles") whose Young's modulus changes continuously from the particle center to the particle surface. The Young's modulus of the adhesive particles tends to increase from the particle center to the particle surface, and it is preferable that the Young's modulus at the particle surface is higher than that at the particle center.

[0014] When the Young's modulus of an adhesive particle is measured at 10 nm intervals from the center to the surface of the particle, the maximum ratio of the higher Young's modulus to the lower Young's modulus at two adjacent measurement points is preferably 500% or less, more preferably 400% or less, even more preferably 350% or less, even more preferably 320% or less, and particularly preferably 290% or less, from the viewpoint of achieving higher adhesiveness.The lower limit of the maximum Young's modulus ratio is not particularly limited, but may be, for example, 101% or more, 102% or more, 105% or more, 110% or more, 120% or more, 130% or more, 140% or more, 150% or more, 160% or more, etc.

[0015] The maximum value of the Young's modulus ratio is calculated by measuring the Young's modulus at 10 nm intervals from the center of an adhesive particle to the particle surface, and calculating the ratio Y ratiois calculated according to the following formula (Y), and the maximum value among all the obtained ratio values ​​is extracted.

[0016]

number

[0017] [In formula (Y), Y L indicates the Young's modulus value (GPa) of the measurement point with the higher Young's modulus of the two adjacent measurement points, and Y S indicates the Young's modulus value (GPa) of the measurement point with the lower Young's modulus of the two adjacent measurement points.]

[0018] FIG. 1 is a schematic diagram illustrating the relationship between the distance from the particle center and the Young's modulus and its ratio for adhesive particles whose Young's modulus changes continuously. The circular plots in the diagram represent Young's moduli measured at 10 nm intervals from the particle center, plotted against the distance from the particle center, and the square plots represent the ratio of Young's moduli between adjacent measurement points. In this adhesive particle example, the Young's modulus ratio is within the range of 100-103% in all regions, with a maximum of approximately 103%. Therefore, the Young's modulus gradually increases from the particle center to the particle surface, and the Young's modulus at the particle surface is higher than that at the particle center. If the maximum Young's modulus ratio is 290% or less, it can be evaluated that there is no significant change in Young's modulus from the center to the surface, and that the Young's modulus changes continuously. In this specification, even if there is a region where the Young's modulus ratio is approximately 100%, if the maximum Young's modulus ratio is 290% or less and the Young's modulus changes overall, it is said to change continuously. By using such adhesive particles, it is possible to achieve both excellent blocking resistance and adhesiveness.

[0019] Fig. 2 is a schematic diagram of a graph illustrating the relationship between the distance from the particle center of a conventional uniform particle and the Young's modulus and its ratio. As shown in Fig. 2, in the case of a conventional uniform particle, the Young's modulus ratio is approximately 100% in all regions from the particle center to the particle surface, and the Young's modulus is constant. In this case, it cannot be said that the Young's modulus changes continuously. When conventional uniform particles are used, excellent blocking resistance cannot be obtained.

[0020] FIG. 3 is a schematic diagram of a graph illustrating the relationship between the distance from the particle center of a conventional core-shell particle and the Young's modulus and its ratio. In the case of conventional core-shell particles, as shown in FIG. 3, the Young's modulus ratio is approximately 100% from the particle center to a certain region, like a uniform particle, and the Young's modulus is also a constant value. However, in a certain region, the Young's modulus ratio exceeds 290%, and the Young's modulus suddenly increases. Then, from that region toward the particle surface, the Young's modulus ratio again falls to approximately 100%, and the Young's modulus also becomes a constant value. In this case, too, it cannot be said that the Young's modulus changes continuously. When conventional core-shell particles are used, excellent adhesiveness cannot be obtained.

[0021] The Young's modulus at 10 nm intervals from the particle center to the particle surface can be measured using an atomic force microscope (AFM). Specifically, the method described in Test Example 3 below can be used. The average Young's modulus at measurement points from the particle center to the particle surface of the adhesive particles is not particularly limited, but can be, for example, 0.5 to 4.0 GPa.

[0022] From the viewpoint of further improving oxidation resistance and adhesiveness, the adhesive particles preferably have a structural unit derived from at least one monomer selected from the group consisting of monofunctional (meth)acrylate monomers, aromatic vinyl monomers, (meth)acrylonitrile monomers, and conjugated diene monomers.

[0023] The monofunctional (meth)acrylate monomer refers to a monofunctional (meth)acrylic acid ester compound. However, the monofunctional (meth)acrylate monomer described here excludes epoxy group-containing (meth)acrylate monomers, silanol group-containing (meth)acrylate monomers, and acidic group-containing monomers. The term "(meth)acrylate" refers to acrylate, methacrylate, or both. Examples of the monofunctional (meth)acrylate monomer include compounds represented by the following formula (1). One type of monofunctional (meth)acrylate monomer may be used alone, or two or more types may be used in combination.

[0024] [ka]

[0025] [In formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents a monovalent hydrocarbon group which may have a substituent.]

[0026] In this specification, a monovalent hydrocarbon group refers to a monovalent group having only carbon atoms as skeleton atoms and having no ethylenically unsaturated groups, and may have a straight-chain structure, a branched-chain structure, and / or a cyclic structure, and may be a group containing or not containing an aromatic ring. The number of carbon atoms in the monovalent hydrocarbon group is preferably 1 to 14, more preferably 1 to 10, even more preferably 1 to 6, and particularly preferably 1 to 3. Examples of hydrocarbon groups include, but are not limited to, alkyl groups, aralkyl groups, aryl groups, aryl groups substituted with alkyl groups, and aryl groups substituted with aryl groups.

[0027] The alkyl group refers to a linear, branched, and / or cyclic monovalent aliphatic saturated hydrocarbon group. The alkyl group is preferably an alkyl group having 1 to 14 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, still more preferably an alkyl group having 1 to 6 carbon atoms, and particularly preferably an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a cyclopentyl group, a cyclohexyl group, a 4-methylcyclohexyl group, a 2,4-dimethylcyclohexyl group, a cyclopentylmethyl group, and a cyclohexylmethyl group.

[0028] The aryl group refers to a monovalent group formed by removing one hydrogen atom from an aromatic carbocyclic ring whose only ring constituent atoms are carbon atoms. The aryl group is preferably an aryl group having 6 to 14 carbon atoms, and particularly preferably an aryl group having 6 to 10 carbon atoms. Examples of the aryl group include a phenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0029] The aralkyl group refers to an alkyl group substituted with an aryl group. The aralkyl group is preferably an aralkyl group having 7 to 15 carbon atoms, and particularly preferably an aralkyl group having 7 to 11 carbon atoms. Examples of the aralkyl group include a benzyl group, a phenethyl group, and an α-methylbenzyl group.

[0030] The substituent of the monovalent hydrocarbon group is not particularly limited, but examples thereof include a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, -OR, -COR, -SR, -SOR, -SOR, -SOR, -NHR, -NR, -COOR, -OCOR, -CONHR, -CONR, and -NHCOR (wherein R represents a monovalent hydrocarbon group).

[0031] Specific examples of monofunctional (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, norbornyl (meth)acrylate, and isobornyl (meth)acrylate. aliphatic monofunctional (meth)acrylate monomers such as acrylate, adamantyl (meth)acrylate, lauryl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; hydroxyl group-containing monofunctional (meth)acrylate monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate; and halogen-containing monofunctional (meth)acrylate monomers such as 2,2,2-trifluoroethyl (meth)acrylate.

[0032] The content of the structural unit derived from the monofunctional (meth)acrylate monomer in the adhesive particles is preferably 0.1 mass% or more, more preferably 1 mass% or more, even more preferably 3 mass% or more, and particularly preferably 5 mass% or more, relative to the total mass of the adhesive particles, from the viewpoint of further improving oxidation resistance, and the upper limit is preferably 90 mass% or less, more preferably 60 mass% or less, even more preferably 50 mass% or less, and particularly preferably 40 mass% or less.

[0033] The aromatic vinyl monomer refers to a compound having a vinyl group or an isopropenyl group bonded to an aromatic carbon atom in the molecule. Examples of the aromatic vinyl monomer include compounds represented by the following formula (2). The aromatic vinyl monomer may be used alone or in combination of two or more.

[0034] [ka]

[0035] [In formula (2), R 3 represents a hydrogen atom or a methyl group, and R 4 each independently represents a substituent, and a represents an integer of 0 to 5.

[0036] R 4 The substituent represented by the formula (I) is not particularly limited, and examples thereof include a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, a carboxy group, -R, -OR, -COR, -SR, -SOR, -SOR, -SOR, -NHR, -NR, -COOR, -OCOR, -CONHR, -CONR, and -NHCOR (wherein R represents a monovalent hydrocarbon group).

[0037] Specific examples of aromatic vinyl monomers include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, and 2-hydroxymethylstyrene.

[0038] The content of structural units derived from aromatic vinyl monomers in the adhesive particles is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more, relative to the total mass of the adhesive particles, from the viewpoint of further improving blocking resistance; the upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less, from the viewpoint of further improving peel strength and adhesiveness.

[0039] The (meth)acrylonitrile monomer means (meth)acrylonitrile, that is, acrylonitrile or methacrylonitrile, or both. The (meth)acrylonitrile monomer may be used alone or in combination of acrylonitrile and methacrylonitrile.

[0040] The content of structural units derived from (meth)acrylonitrile monomers in the adhesive particles is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more, relative to the total mass of the adhesive particles, and the upper limit is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

[0041] The conjugated diene monomer refers to a compound having a conjugated diene structure in the molecule. The conjugated diene monomer may be used alone or in combination of two or more. Specific examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and piperylene.

[0042] The total content of the monofunctional (meth)acrylate monomer-derived structure, aromatic vinyl monomer-derived structure, (meth)acrylonitrile monomer-derived structure, and conjugated diene monomer-derived structure in the adhesive particles is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the total mass of the adhesive particles, and the upper limit is, for example, 100% by mass or less, preferably 99% by mass or less, more preferably 98% by mass or less, and particularly preferably 97% by mass or less.

[0043] The adhesive particles preferably have a structural unit derived from an acidic group-containing monomer from the viewpoints of suppressing sedimentation when left standing and improving storage stability.

[0044] The acidic group-containing monomer refers to a compound having a carboxyl group and an ethylenically unsaturated group. The acidic group-containing monomer may be used alone or in combination of two or more. Examples of the acidic group include a carboxyl group and a sulfonic acid group, and among these, a carboxyl group is preferred.

[0045] Specific examples of the acidic group-containing monomer include monocarboxylic acid monomers such as acrylic acid, methacrylic acid, monomethyl itaconate, monomethyl maleate, monomethyl fumarate, monomethyl mesaconic acid, monomethyl citraconic acid, monoethyl itaconate, monoethyl maleate, monoethyl fumarate, monoethyl mesaconic acid, and monoethyl citraconic acid; and dicarboxylic acid monomers such as itaconic acid, fumaric acid, maleic acid, mesaconic acid, and citraconic acid.

[0046] The content of structures derived from acidic group-containing monomers in the adhesive particles is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1% by mass or more, and particularly preferably 3% by mass or more, relative to the total mass of the adhesive particles, and the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 6% by mass or less, and particularly preferably 4% by mass or less.

[0047] From the viewpoint of further suppressing elution into the electrolyte solution, the adhesive particles preferably have a structural unit derived from a reactive monomer.

[0048] The reactive monomer preferably includes at least one selected from the group consisting of polyfunctional (meth)acrylate monomers, epoxy group-containing (meth)acrylate monomers, and silanol group-containing (meth)acrylate monomers.

[0049] The polyfunctional (meth)acrylate monomer refers to an ester compound of (meth)acrylic acid that is bifunctional or more (for example, bifunctional, trifunctional, or tetrafunctional, preferably bifunctional). However, the polyfunctional (meth)acrylate monomer described here excludes epoxy group-containing (meth)acrylate monomers, silanol group-containing (meth)acrylate monomers, and acidic group-containing monomers. Examples of the polyfunctional (meth)acrylate monomer include compounds represented by the following formula (3). One type of polyfunctional (meth)acrylate monomer may be used alone, or two or more types may be used in combination.

[0050] [ka]

[0051] [In formula (3), R 5 and R 6 each independently represents a hydrogen atom or a methyl group, and X represents a divalent hydrocarbon group in which the carbon atom CH2 bonded to two other carbon atoms may be replaced with an oxygen atom O and which may have a substituent.

[0052] The divalent hydrocarbon group in this specification refers to a divalent group having only carbon atoms as skeleton atoms and having no ethylenically unsaturated groups, and may have a straight-chain structure, a branched-chain structure, and / or a cyclic structure, and may be a group containing or not containing an aromatic ring. The number of carbon atoms in the divalent hydrocarbon group is preferably 2 to 50, more preferably 2 to 30, even more preferably 2 to 20, and particularly preferably 2 to 10.

[0053] The substituent of the divalent hydrocarbon group is not particularly limited, but examples thereof include a halogen atom, a nitro group, a cyano group, a hydroxy group, an amino group, -OCOCH=CH2, -OCOC(CH3)=CH2, -OR, -COR, -SR, -SOR, -SOR, -NHR, -NR2, -COOR, -OCOR, -CONHR, -CONR2, and -NHCOR (R represents a monovalent hydrocarbon group).

[0054] Specific examples of polyfunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 2,2-dimethylpropane-1,3-diol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, difunctional (meth)acrylate monomers such as dipentaerythritol penta(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate; trifunctional (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; tetrafunctional (meth)acrylate monomers such as pentaerythritol tetra(meth)acrylate; pentafunctional (meth)acrylate monomers such as dipentaerythritol penta(meth)acrylate; and hexafunctional (meth)acrylate monomers such as dipentaerythritol hexa(meth)acrylate, among which difunctional (meth)acrylate monomers are preferred.

[0055] The epoxy group-containing (meth)acrylate monomer refers to an ester compound of (meth)acrylic acid having an epoxy group in the molecule. The epoxy group-containing (meth)acrylate monomer may be used alone or in combination of two or more.

[0056] Specific examples of epoxy group-containing (meth)acrylate monomers include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and epoxycyclohexylmethyl (meth)acrylate.

[0057] The silanol group-containing (meth)acrylate monomer refers to an ester compound of (meth)acrylic acid having a silanol group in the molecule. Examples of the silanol group include a silanol group represented by the formula -Si(OR 8 ) s (R 9 ) 3-s (where each symbol is as explained below), and specific examples include a dimethylmethoxysilyl group, a dimethylethoxysilyl group, a methyldimethoxysilyl group, a methyldiethoxysilyl group, a trimethoxysilyl group, and a triethoxysilyl group. Examples of silanol group-containing (meth)acrylate monomers include compounds represented by the following formula (4): One type of silanol group-containing (meth)acrylate monomer may be used alone, or two or more types may be used in combination.

[0058] [ka]

[0059] [In formula (4), R 7 represents a hydrogen atom or a methyl group, and R 8 and R 9 each independently represents an alkyl group, Y represents a divalent hydrocarbon group in which the carbon atom CH2 bonded to two other carbon atoms may be replaced with an oxygen atom O and which may have a substituent, and s represents an integer of 1 to 3 (preferably 2 or 3).

[0060] Specific examples of silanol group-containing (meth)acrylate monomers include 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 4-(meth)acryloxybutyltrimethoxysilane, 5-(meth)acryloxypentyltrimethoxysilane, 6-(meth)acryloxyhexyltrimethoxysilane, 7-(meth)acryloxyheptyltrimethoxysilane, and 8-(meth)acryloxyoctyltrimethoxysilane.

[0061] The content of the structure derived from the reactive monomer in the adhesive particle is, for example, 0% by mass or more, preferably 0.005% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, relative to the total mass of the adhesive particle, and the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, and particularly preferably 5% by mass or less.

[0062] The adhesive particles have an appropriate swelling ratio, and therefore, in addition to ion permeability, they also have excellent adhesion after immersion in an electrolyte, resulting in excellent battery characteristics for the resulting nonaqueous secondary battery. For example, when adhesive particles are immersed in a mixed electrolyte (ethylene carbonate / propylene carbonate = 1 / 1 (volume ratio)) containing 1 mol / L of LiPF6, the swelling degree of the adhesive particles is preferably 1.5 times or more, more preferably 2 times or more, even more preferably 3 times or more, even more preferably 5 times or more, particularly preferably 7 times or more, and most preferably 10 times or more compared to the level before immersion. The upper limit of the swelling degree is preferably 50 times or less, more preferably 40 times or less, even more preferably 30 times or less, and particularly preferably 20 times or less compared to the level before immersion, from the viewpoint of suppressing a decrease in adhesion due to a decrease in the strength of the adhesive layer.

[0063] The average particle size of the adhesive particles is preferably 0.1 μm or more, more preferably 0.15 μm or more, even more preferably 0.2 μm or more, and particularly preferably 0.25 μm or more, from the viewpoint of preventing the adhesive particles from being embedded in other layers adjacent to the adhesive layer (e.g., heat-resistant layers). The upper limit of the average particle size of the adhesive particles is preferably 10.0 μm or less, more preferably 5.0 μm or less, even more preferably 1.0 μm or less, even more preferably 0.5 μm or less, and particularly preferably 0.4 μm or less, from the viewpoint of further improving peel strength. The average particle size refers to the 50% particle size D50 measured using a particle size analyzer based on the average particle size light scattering method (e.g., LEED & NORTHRUP, trade name "MICROTRAC UPA150").

[0064] The adhesive particles have a glass transition temperature of preferably 30° C. or higher, more preferably 40° C. or higher, and particularly preferably 50° C. or higher, from the viewpoint of further improving blocking resistance, and the upper limit is preferably 150° C. or lower, more preferably 130° C. or lower, even more preferably 100° C. or lower, and particularly preferably 80° C. or lower, from the viewpoint of further improving peel strength and wet adhesion. The glass transition temperature can be obtained by measuring a DSC curve and a DDSC curve in a nitrogen atmosphere using a DSC measuring device (Shimadzu Corporation, model number: DSC6220).

[0065] Adhesive particles can be produced, for example, by emulsion polymerization. For example, in a reaction system containing an emulsifier, a radical polymerization initiator, and optionally other additives, as well as a portion of the monomers to be added (hereinafter sometimes referred to as "first-stage monomers") in an aqueous medium (e.g., water, methanol, ethanol, or a mixture thereof), the first polymerization reaction is initiated. While the first polymerization reaction is in progress, the remaining monomers to be added (hereinafter sometimes referred to as "second-stage monomers") are added to initiate and complete the second polymerization reaction, thereby producing adhesive particles (polymerization reaction rate, e.g., 99% or higher). The polymerization reaction rate at the time the second-stage monomers are added and the second polymerization reaction is initiated is not particularly limited, but is preferably 50% or higher, more preferably 60% or higher, even more preferably 70% or higher, and particularly preferably 75% or higher. The upper limit is preferably 98% or lower, more preferably 95% or lower. It is preferred that the composition of the first-stage monomers and the second-stage monomers be different. The content of aromatic vinyl monomer in the first-stage monomer may be higher or lower than the content of aromatic vinyl monomer in the second-stage monomer, but is preferably lower. The content (mass%) of aromatic vinyl monomer in the second-stage monomer relative to the content (mass%) of aromatic vinyl monomer in the first-stage monomer may be set, for example, 10% or more, preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, and particularly preferably 45% or more lower. Specifically, the content of aromatic vinyl monomer in the first-stage monomer is preferably set to 10 to 70% by mass, more preferably 15 to 65% by mass, even more preferably 20 to 60% by mass, and particularly preferably 25 to 55% by mass, based on the total mass of all first-stage monomers, and the content of aromatic vinyl monomer in the second-stage monomer is preferably set to 45 to 99.9% by mass, based on the total mass of all second-stage monomers and all first-stage monomers.The above describes an example of a method in which polymerization is divided into two stages, the first and second stages, but the method for producing adhesive particles is not limited to this method, and polymerization may be divided into three or more stages, or they may be produced using different methods.

[0066] Examples of the emulsifier include anionic emulsifiers such as non-reactive alkyl sulfates (e.g., sodium lauryl sulfate), polyoxyethylene alkyl ether sulfate salts, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfosuccinates, alkyldiphenyl ether disulfonates, naphthalene sulfonate-formalin condensates, polyoxyethylene polycyclic phenyl ether sulfate salts, polyoxyethylene distyrenated phenyl ether sulfate salts, fatty acid salts, alkyl phosphates, and polyoxyethylene alkylphenyl ether sulfate salts; and nonionic emulsifiers such as non-reactive polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyethylene distyrenated phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, alkylalkanolamides, and polyoxyethylene alkylphenyl ethers. In addition to these, reactive emulsifiers having an ethylenic double bond introduced into the chemical structural formula of an emulsifier having a hydrophilic group and a lipophilic group may also be used. The emulsifiers may be used alone or in combination of two or more. The amount of emulsifier used is preferably 0.01% to 5.50% by mass, and particularly preferably 0.10% to 2.00% by mass, assuming that the total amount of added monomers is 100% by mass.

[0067] Radical polymerization initiators can initiate addition polymerization of monomers by radical decomposition using heat or a reducing substance. Both inorganic and organic radical polymerization initiators can be used as radical polymerization initiators. Water-soluble or oil-soluble radical polymerization initiators can be used as radical polymerization initiators. Examples of water-soluble radical polymerization initiators include peroxodisulfates, peroxides, water-soluble azobis compounds, and peroxide-reducing agent redox systems. Examples of peroxodisulfates include potassium peroxodisulfate (also known as potassium persulfate) (KPS), sodium peroxodisulfate (also known as sodium persulfate) (NPS), and ammonium peroxodisulfate (also known as ammonium persulfate) (APS). Examples of peroxides include hydrogen peroxide, t-butyl hydroperoxide, t-butyl peroxymaleic acid, succinic acid peroxide, and benzoyl peroxide. Examples of water-soluble azobis compounds include 2,2-azobis(N-hydroxyethylisobutyramide), 2,2-azobis(2-amidinopropane) dihydrogen chloride, and 4,4-azobis(4-cyanopentanoic acid). The peroxide in the peroxide-reducing agent redox system is not particularly limited. The reducing agent in the peroxide-reducing agent redox system is not particularly limited. Examples of reducing agents include sodium sulfoxylate formaldehyde, sodium bisulfite, sodium thiosulfate, sodium hydroxymethanesulfinate, L-ascorbic acid and its salts, cuprous salts, and ferrous salts. The radical polymerization initiators can be used alone or in combination of two or more. The amount of radical polymerization initiator used is preferably 0.10% to 8.00% by mass, and particularly preferably 0.50% to 3.00% by mass, based on 100% by mass of all monomers added.

[0068] The content of adhesive particles in the adhesive composition of the present invention is preferably 10% by mass or more, assuming that the total solid content of the adhesive composition is 100% by mass.

[0069] The adhesive composition of the present invention may further contain organic particles other than the adhesive particles described above. From the viewpoint of further improving electrolyte swelling resistance and adhesive strength, the adhesive composition of the present invention preferably further contains a particulate binder having a glass transition temperature (Tg) of 30°C or lower. Examples of particulate binders include, but are not limited to, acrylic latex, butadiene latex, and styrene-butadiene latex. One type of particulate binder can be used alone, or two or more types can be used in combination. The particle diameter (volume average particle diameter) of the particulate binder is preferably 10 nm or more and 1,000 nm or less, and more preferably 50 nm or more and 700 nm or less. The content of the particulate binder having a glass transition temperature (Tg) of 30°C or lower in the adhesive composition of the present invention is, for example, 0 to 10 mass%, preferably 1 to 5 mass%, relative to 100 mass% of the total solids content of the adhesive composition.

[0070] From the viewpoint of further improving storage stability, the adhesive composition of the present invention preferably further contains a water-soluble polymer. Examples of water-soluble polymers include polyvinyl alcohol, ammonium carboxymethylcellulose, sodium carboxymethylcellulose, polyethylene glycol, polypropylene glycol, polyvinyl ether, polymaleic acid copolymer, polyethyleneimide, polyvinylpyrrolidone, polyacrylamide, sodium polyacrylate, ammonium polyacrylate, dextrin and its hydrates, and guar gum. The water-soluble polymers can be used alone or in combination of two or more. The content of the water-soluble polymer in the adhesive composition of the present invention is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, based on 100% by mass of the total solids content of the adhesive composition.

[0071] The adhesive composition of the present invention preferably contains at least one selected from the group consisting of a particulate binder having a glass transition temperature (Tg) of 30° C. or lower, a water-soluble polymer, and a preservative.

[0072] From the viewpoint of further improving storage stability, the adhesive composition of the present invention preferably further contains a surfactant. Examples of surfactants include anionic surfactants, silicone surfactants, and nonionic surfactants. One surfactant may be used alone, or two or more surfactants may be used in combination. The content of the surfactant in the adhesive composition of the present invention is preferably 0.01 to 2% by mass, more preferably 0.1 to 1% by mass, relative to 100% by mass of the total solids content of the adhesive composition.

[0073] The adhesive composition of the present invention preferably further contains an inorganic filler to simultaneously impart heat resistance when formed into an adhesive layer. Examples of inorganic filler materials include oxide ceramics such as alumina, silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; ceramics such as silicon carbide, calcium carbonate, magnesium sulfate, aluminum sulfate, barium sulfate, aluminum hydroxide, aluminum oxide hydroxide, or boehmite, potassium titanate, talc, kaolinite, dickite, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fiber. Among these, at least one selected from the group consisting of alumina, boehmite, and barium sulfate is preferred from the viewpoint of stability in a secondary battery. The average primary particle diameter of the inorganic filler is preferably 0.10 μm to 6.00 μm, and more preferably 0.15 μm to 1.00 μm. The average primary particle diameter can be measured using a laser diffraction particle size distribution analyzer or the like. The inorganic fillers can be used alone or in combination of two or more. The content of the inorganic filler in the adhesive composition of the present invention can be set to 20% by mass or more, 40% by mass or more, 60% by mass or more, or 70% by mass or more, with the upper limit being, for example, 90% by mass or less, when the total solid content of the adhesive composition is 100% by mass.

[0074] The content of adhesive particles in the adhesive composition of the present invention is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, when the solid content excluding the inorganic filler of the adhesive composition is 100% by mass.

[0075] The adhesive composition of the present invention may further contain other additives such as an antifoaming agent, a pH adjuster, a dispersant, a lubricant, a thickener, a bactericide, etc. In order to maintain long-term dispersion stability, the pH of the adhesive composition of the present invention is preferably adjusted to a range of 5 to 12.

[0076] The adhesive composition of the present invention preferably contains a solvent. Specific examples of the solvent include aqueous solvents such as water and alcohols (e.g., methanol, ethanol, isopropanol), and non-aqueous solvents such as N-methylpyrrolidone. Among these, water is preferred from the viewpoint of reducing the environmental load.

[0077] The solid content of the adhesive composition of the present invention is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 20.0% by mass or more, relative to 100% by mass of the adhesive composition, and the upper limit is preferably 80.0% by mass or less, more preferably 70.0% by mass or less, and even more preferably 65.0% by mass or less.

[0078] The viscosity of the adhesive composition of the present invention at 25°C, measured using a Brookfield viscometer at a rotor rotation speed of 60 rpm, is preferably 5 mPa·s to 1000 mPa·s, more preferably 10 mPa·s to 500 mPa·s, and particularly preferably 15 mPa·s to 200 mPa·s.

[0079] <Separator> The separator of the present invention includes a substrate and an adhesive layer containing the adhesive composition of the present invention. Examples of materials for the substrate include polyolefin-based resins. Examples of polyolefin-based resins include homopolymers such as polyethylene and polypropylene, copolymers, and mixtures thereof. Examples of polyethylene include low-, medium-, and high-density polyethylenes, with high-density polyethylene being preferred from the viewpoints of puncture resistance and mechanical strength. Two or more of the above materials may be mixed together to form the substrate.

[0080] The thickness of the substrate is preferably 0.5 μm to 40 μm, more preferably 1 μm to 30 μm, and even more preferably 1 μm to 10 μm. When the thickness of the substrate is within the above range, the resistance caused by the separator in an electricity storage device such as a battery becomes smaller.

[0081] The separator may be produced by any method, including, for example, the method described in JP 2016-167455 A. The separator is preferably produced by a method including the steps of filtering the adhesive composition of the present invention, obtained by reacting and mixing the components described above, using a magnetic separator and / or a filter, and forming an adhesive layer on the surface of a substrate using the filtered composition.

[0082] ≪Nonaqueous secondary battery≫ The nonaqueous secondary battery of the present invention includes the separator of the present invention. The nonaqueous secondary battery may include a positive electrode and a negative electrode as electrodes. The adhesive layer of the separator may be bonded to either the positive electrode or the negative electrode.

[0083] The positive electrode material (positive electrode active material) is not particularly limited, but examples thereof include lithium-containing composite oxides such as LiCoO2, LiNiO2, spinel-type LiMnO4, and olivine-type LiFePO4. The negative electrode material (negative electrode active material) is not particularly limited, but examples thereof include carbon materials such as graphite, non-graphitizable carbonaceous materials, graphitizable carbonaceous materials, and composite carbon bodies; silicon, tin, metallic lithium, and various alloy materials. The positive electrode and negative electrode may each have a current collector; for example, an example of the positive electrode current collector is aluminum foil, and for example, an example of the negative electrode current collector is copper foil.

[0084] Non-aqueous secondary batteries contain a non-aqueous electrolyte. The non-aqueous electrolyte is not particularly limited, but may be an electrolyte solution in which an electrolyte is dissolved in an organic solvent. Examples of organic solvents include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of electrolytes include lithium salts such as LiClO4, LiBF4, and LiPF6.

[0085] There are no particular limitations on the method for producing a non-aqueous secondary battery, and for example, the method described in JP 2016-167455 A may be adopted. [Example]

[0086] The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples. In the following, "parts" representing amounts mean "parts by mass." Unless otherwise specified, the temperature conditions are room temperature (25°C), and unless otherwise specified, the pressure conditions are atmospheric pressure (1 atm).

[0087] Example 1: Production of adhesive particles A, adhesive composition slurry A, and separator A In a reactor equipped with a stirrer, 100 parts of ion-exchanged water, 0.05 parts of sodium lauryl sulfate as an emulsifier, and 0.3 parts of sodium persulfate as a radical polymerization initiator were added, and the gas phase in the reactor was replaced with nitrogen gas and heated to 70 ° C. In another vessel equipped with a stirrer, 100 parts of ion-exchanged water, 20.1 parts of 2-ethylhexyl acrylate (2-EHA), 6.0 parts of butyl acrylate (BA), 40.0 parts of styrene (ST), 3.5 parts of methacrylic acid (MAA), 10.0 parts of acrylonitrile (AN), and 0.3 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) as a reactive monomer were mixed and stirred to prepare emulsion A.

[0088] This emulsion A was continuously added to the reactor over 2.0 hours with continued stirring to initiate the reaction. 1.0 hour after the start of the reaction, the reaction rate was 81%. 1.0 hour after the start of the reaction, 20.0 parts of styrene (ST) and 0.1 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) were added to the reactor over 1.5 hours with stirring to emulsion A, and the reaction was continued. After the addition of emulsion A was completed, the mixture was stirred for an additional 2.0 hours at 80°C to terminate the reaction, yielding an aqueous dispersion containing adhesive particles A. The reaction rate at the end of the reaction was 99%.

[0089] The glass transition temperature (Tg) of the obtained adhesive particles A was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +34°C. Furthermore, the volume average particle diameter of the obtained adhesive particles A, measured as shown in Test Example 2 below, was 0.31 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 170%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 8 times larger.

[0090] A mixture of 95.5 parts of adhesive particles A (solids equivalent), 1.0 part of sodium polyacrylate (PAA-Na) as a water-soluble polymer, 3.0 parts of acrylic latex (Acl-Ltx) (BA / MMA / MAA copolymer latex, average particle size: 120 nm) with a Tg of -35°C as a particulate binder, 0.5 parts of SN Wet 126 (San Nopco) as a water-soluble silicone surfactant as a wetting agent, and 300 ppm of BIT (1,2-benzisothiazolin-3-one) as a preservative was added. Finally, ion-exchange water was added to achieve a solids concentration of 30%. The mixture was passed through a magnetic separator and then filtered through a #200 mesh filter. This produced adhesive composition slurry A for the adhesive layer.

[0091] A separator substrate made of a porous polyethylene substrate was prepared. The adhesive composition slurry A prepared by the above method was applied to one side of the separator substrate to a thickness of 0.5 μm and a basis weight of 0.4 g / m. 2 The adhesive composition slurry A was applied so that the adhesive layer formed a thickness of 31 mPa·s, and the adhesive layer was then dried with hot air for 10 minutes. This produced separator A equipped with an adhesive layer. The viscosity of adhesive composition slurry A, and the dry adhesive strength and blocking resistance of separator A were evaluated based on the following Test Examples 5 to 7. The viscosity was 31 mPa·s, the dry adhesive strength was rated "A", and the blocking resistance was rated "A".

[0092] Example 2: Production of adhesive particles B, adhesive composition slurry B, and separator B In a reactor equipped with a stirrer, 100 parts of ion-exchanged water, 0.05 parts of sodium lauryl sulfate as an emulsifier, and 0.3 parts of sodium persulfate as a radical polymerization initiator were added, and the gas phase in the reactor was replaced with nitrogen gas and heated to 70 ° C. In another vessel equipped with a stirrer, 100 parts of ion-exchanged water, 30.2 parts of 2-ethylhexyl acrylate (2-EHA), 10.0 parts of methyl methacrylic acid (MMA), 6.0 parts of butyl acrylate (BA), 20.0 parts of styrene (ST), 3.5 parts of methacrylic acid (MAA), 10.0 parts of acrylonitrile (AN), and 0.2 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) as a reactive monomer were mixed and stirred to prepare emulsion B.

[0093] This emulsion B was continuously added to the reactor over 1.5 hours while continuing to stir, and the reaction was initiated. After the addition of emulsion B, stirring was continued for an additional 0.5 hours, and the reaction rate was measured, which was 98%. Then, 10.0 parts of styrene (ST), 10.0 parts of acrylonitrile (AN), and 0.1 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) were added to the reactor over 0.5 hours, and the second stage of polymerization was carried out. After the addition was completed, the mixture was stirred for an additional 2 hours at 80°C to complete the reaction, yielding an aqueous dispersion containing adhesive particles B. The reaction rate at the end of the reaction was 99%.

[0094] The glass transition temperature (Tg) of the obtained adhesive particles B was measured as shown in Test Example 1 below, and it was confirmed that the glass transition temperature (Tg) was observed at only one point, +30°C. Furthermore, the volume average particle diameter of the obtained adhesive particles B, measured as shown in Test Example 2 below, was 0.28 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 200%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 8 times larger.

[0095] An adhesive composition slurry B for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles B were used instead of adhesive particles A, and a separator B equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry B, and the dry adhesive strength and blocking resistance of separator B were evaluated based on the following Test Examples 5 to 7. The viscosity was 35 mPa s, the dry adhesive strength was rated "B", and the blocking resistance was rated "A".

[0096] Example 3: Production of adhesive particles C, adhesive composition slurry C, and separator C Emulsion C was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 5.2 parts, the amount of styrene (ST) was changed from 40.0 parts to 55.0 parts, the amount of methacrylic acid (MAA) was changed from 3.5 parts to 3.4 parts, and the amount of acrylonitrile (AN) was changed from 10.0 parts to 20.0 parts. An aqueous dispersion containing adhesive particles C was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion C was used instead of emulsion A and 10.0 parts of 2-ethylhexyl acrylate (2-EHA) was used instead of 20.0 parts of styrene (ST). The reaction rate was 82% 1.0 hour after the start of the reaction with the addition of emulsion C. The reaction rate at the end of the reaction was 99%.

[0097] The glass transition temperature (Tg) of the obtained adhesive particles C was measured as shown in Test Example 1 below, and it was confirmed that the glass transition temperature (Tg) was observed at only one point, +37°C. Furthermore, the volume average particle diameter of the obtained adhesive particles C, measured as shown in Test Example 2 below, was 0.33 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 180%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 8 times larger.

[0098] An adhesive composition slurry C for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles C were used instead of adhesive particles A, and a separator C equipped with an adhesive layer was produced. The viscosity of the adhesive composition slurry C, and the dry adhesive strength and blocking resistance of the separator C were evaluated based on the following Test Examples 5 to 7. The viscosity was 31 mPa s, the dry adhesive strength was rated "A", and the blocking resistance was rated "C".

[0099] Example 4: Production of adhesive particles D, adhesive composition slurry D, and separator D Emulsion D was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 10.1 parts, the amount of styrene (ST) was changed from 40.0 parts to 30.0 parts, and 30.0 parts of methacrylonitrile (MAN) was used instead of 10.0 parts of acrylonitrile (AN). An aqueous dispersion containing adhesive particles D was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion D was used instead of emulsion A. The reaction rate was 81% 1.0 hour after the start of the reaction with the addition of emulsion D. The reaction rate at the end of the reaction was 99%.

[0100] The glass transition temperature (Tg) of the obtained adhesive particles D was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +59°C. Furthermore, the volume average particle diameter of the obtained adhesive particles D, measured as shown in Test Example 2 below, was 0.31 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 240%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 8 times larger.

[0101] An adhesive composition slurry D for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles D were used instead of adhesive particles A, and a separator D equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry D, and the dry adhesive strength and blocking resistance of separator D were evaluated based on the following Test Examples 5 to 7. The viscosity was 32 mPa s, the dry adhesive strength was rated "A", and the blocking resistance was rated "B".

[0102] Example 5: Production of adhesive particles E, adhesive composition slurry E, and separator E Emulsion E was prepared in the same manner as emulsion A in Example 1, except that the amount of styrene (ST) was changed from 40.0 parts to 30.0 parts and the amount of acrylonitrile (AN) was changed from 10.0 parts to 30.0 parts. An aqueous dispersion containing adhesive particles E was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion E was used instead of emulsion A and the amount of styrene (ST) was changed from 20.0 parts to 10.0 parts. The reaction rate was 87% 1.0 hour after the start of the reaction with the addition of emulsion E. The reaction rate at the end of the reaction was 99%.

[0103] The glass transition temperature (Tg) of the adhesive particles E obtained was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +45°C. Furthermore, the volume average particle diameter of the adhesive particles E obtained, measured as shown in Test Example 2 below, was 0.34 μm. When the Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum Young's modulus ratio between adjacent measurement points was 250%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 8 times larger.

[0104] An adhesive composition slurry E for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles E were used instead of adhesive particles A, and a separator E equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry E, and the dry adhesive strength and blocking resistance of separator E were evaluated based on the following Test Examples 5 to 7. The viscosity was 34 mPa s, the dry adhesive strength was rated "A," and the blocking resistance was rated "B."

[0105] Example 6: Production of adhesive particles F, adhesive composition slurry F, and separator F In a reactor equipped with a stirrer, 100 parts of ion-exchanged water, 0.05 parts of sodium lauryl sulfate as an emulsifier, and 0.3 parts of sodium persulfate as a radical polymerization initiator were added, and the gas phase in the reactor was replaced with nitrogen gas and the temperature was raised to 70° C. In another vessel equipped with a stirrer, 100 parts of ion-exchanged water, 0.5 parts of 2-ethylhexyl acrylate (2-EHA), 6.0 parts of butyl acrylate (BA), 30.0 parts of styrene (ST), 3.5 parts of methacrylic acid (MAA), and 30.0 parts of acrylonitrile (AN) were mixed and stirred to prepare emulsion F.

[0106] This emulsion F was continuously added to the reactor over 1.5 hours. The reaction rate at the end of the addition of emulsion F was 89%. Immediately after the addition of emulsion F was completed, 30.0 parts of styrene (ST) was added to emulsion F over 0.5 hours and polymerization was carried out. After the addition of styrene was completed, the mixture was stirred at 80°C for a further 2 hours to complete the reaction, yielding an aqueous dispersion containing adhesive particles F. The reaction rate at the end of the reaction was 99%.

[0107] The glass transition temperature (Tg) of the obtained adhesive particles F was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +59°C. Furthermore, the volume average particle diameter of the obtained adhesive particles F, measured as shown in Test Example 2 below, was 0.35 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum Young's modulus ratio between adjacent measurement points was 220%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 29 times.

[0108] An adhesive composition slurry F for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles F were used instead of adhesive particles A, and a separator F equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry F, and the dry adhesive strength and blocking resistance of separator F were evaluated based on the following Test Examples 5 to 7. The viscosity was 28 mPa s, the dry adhesive strength was rated "A," and the blocking resistance was rated "B."

[0109] Example 7: Production of adhesive particles G, adhesive composition slurry G, and separator G Emulsion G was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 10.35 parts, the amount of styrene (ST) was changed from 40.0 parts to 20.0 parts, the amount of acrylonitrile (AN) was changed from 10.0 parts to 20.0 parts, and the amount of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) was changed from 0.3 parts to 0.05 parts. An aqueous dispersion containing adhesive particles G was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion G was used instead of emulsion A and the amount of styrene (ST) was changed from 20.0 parts to 40.0 parts. The reaction rate after 1.0 hour of reaction with the addition of emulsion G was 87%. The reaction rate at the end of the reaction was 99%.

[0110] The glass transition temperature (Tg) of the adhesive particles G obtained was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +33°C. Furthermore, the volume average particle diameter of the adhesive particles G obtained, measured as shown in Test Example 2 below, was 0.34 μm. When the Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum Young's modulus ratio between adjacent measurement points was 290%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 18 times.

[0111] An adhesive composition slurry G for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles G were used instead of adhesive particles A, and a separator G equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry G, and the dry adhesive strength and blocking resistance of separator G were evaluated based on the following Test Examples 5 to 7. The viscosity was 31 mPa s, the dry adhesive strength was rated "B", and the blocking resistance was rated "A".

[0112] Example 8: Production of adhesive particles H, adhesive composition slurry H, and separator H Emulsion H was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 8.5 parts, the amount of styrene (ST) was changed from 40.0 parts to 30.0 parts, the amount of acrylonitrile (AN) was changed from 10.0 parts to 30.0 parts, and the amount of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) was changed from 0.3 parts to 1.9 parts. An aqueous dispersion containing adhesive particles H was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion H was used instead of emulsion A. The reaction rate was 78% 1.0 hour after the start of the reaction with the addition of emulsion H. The reaction rate at the end of the reaction was 99%.

[0113] The glass transition temperature (Tg) of the obtained adhesive particles H was measured as shown in Test Example 1 below, and it was confirmed that the glass transition temperature (Tg) was observed at only one point, +48°C. Furthermore, the volume average particle diameter of the obtained adhesive particles H, measured as shown in Test Example 2 below, was 0.29 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 190%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was found to be three times larger.

[0114] An adhesive composition slurry H for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles H were used instead of adhesive particles A, and a separator H equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry H, and the dry adhesive strength and blocking resistance of separator H were evaluated based on the following Test Examples 5 to 7. The viscosity was 30 mPa s, the dry adhesive strength was rated "B", and the blocking resistance was rated "A".

[0115] Example 9: Production of adhesive particles I, adhesive composition slurry I, and separator I Emulsion I was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 5.4 parts, the amount of styrene (ST) from 40.0 parts to 30.0 parts, the amount of acrylonitrile (AN) from 10.0 parts to 30.0 parts, and the amount of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) from 0.3 parts to 5.0 parts. An aqueous dispersion containing adhesive particles I was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion I was used instead of emulsion A. The reaction rate at the end of the reaction was 99%.

[0116] The glass transition temperature (Tg) of the obtained adhesive particles I was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +28°C. Furthermore, the volume average particle diameter of the obtained adhesive particles I, measured as shown in Test Example 2 below, was 0.28 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 210%, indicating that the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was found to be doubled.

[0117] An adhesive composition slurry I for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles I were used instead of adhesive particles A, and a separator I equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry I, and the dry adhesive strength and blocking resistance of separator I were evaluated based on the following Test Examples 5 to 7. The viscosity was 31 mPa s, the dry adhesive strength was rated "B", and the blocking resistance was rated "B".

[0118] Example 10: Production of adhesive particles J, adhesive composition slurry J, and separator J Emulsion J was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 9.9 parts, the amount of styrene (ST) was changed from 40.0 parts to 30.0 parts, and the amount of acrylonitrile (AN) was changed from 10.0 parts to 30.0 parts, and 0.5 parts of glycidyl methacrylate (GMA) was used instead of 0.3 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS). An aqueous dispersion containing adhesive particles J was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion J was used instead of emulsion A. The reaction rate at the end of the reaction was 99%.

[0119] The glass transition temperature (Tg) of the obtained adhesive particles J was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +37°C. Furthermore, the volume average particle diameter of the obtained adhesive particles J, measured as shown in Test Example 2 below, was 0.35 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 200%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 9 times.

[0120] An adhesive composition slurry J for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles J were used instead of adhesive particles A, and a separator J having an adhesive layer was produced. The viscosity of adhesive composition slurry J, and the dry adhesive strength and blocking resistance of separator J were evaluated based on the following Test Examples 5 to 7. The viscosity was 29 mPa s, the dry adhesive strength was rated "B", and the blocking resistance was rated "B".

[0121] Example 11: Production of adhesive particles K, adhesive composition slurry K, and separator K Emulsion K was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 9.9 parts, the amount of styrene (ST) was changed from 40.0 parts to 30.0 parts, and the amount of acrylonitrile (AN) was changed from 10.0 parts to 30.0 parts, and 0.5 parts of 1,9-nonanediol diacrylate (1,9-ND) was used instead of 0.3 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS). An aqueous dispersion containing adhesive particles K was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion K was used instead of emulsion A. The reaction rate at the end of the reaction was 99%.

[0122] The glass transition temperature (Tg) of the obtained adhesive particles K was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +37°C. Furthermore, the volume average particle diameter of the obtained adhesive particles K, measured as shown in Test Example 2 below, was 0.36 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 200%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 9 times.

[0123] An adhesive composition slurry K for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles K were used instead of adhesive particles A, and a separator K having an adhesive layer was produced. The viscosity of the adhesive composition slurry K, and the dry adhesive strength and blocking resistance of the separator K were evaluated based on the following Test Examples 5 to 7. The viscosity was 33 mPa s, the dry adhesive strength was rated "A", and the blocking resistance was rated "B".

[0124] Example 12: Production of adhesive particles L, adhesive composition slurry L, and separator L Emulsion L was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 9.9 parts, the amount of styrene (ST) from 40.0 parts to 30.0 parts, the amount of acrylonitrile (AN) from 10.0 parts to 30.0 parts, and the amount of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) from 0.3 parts to 0.25 parts, and 0.25 parts of 1,9-nonanediol diacrylate (1,9-ND) was used. An aqueous dispersion containing adhesive particles L was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion L was used instead of emulsion A. The reaction rate at the end of the reaction was 99%.

[0125] The glass transition temperature (Tg) of the obtained adhesive particles L was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +37°C. Furthermore, the volume average particle diameter of the obtained adhesive particles L, measured as shown in Test Example 2 below, was 0.30 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 210%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was 9 times.

[0126] An adhesive composition slurry L for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles L were used instead of adhesive particles A, and a separator L having an adhesive layer was produced. The viscosity of the adhesive composition slurry L, and the dry adhesive strength and blocking resistance of the separator L were evaluated based on the following Test Examples 5 to 7. The viscosity was 34 mPa s, the dry adhesive strength was rated "B", and the blocking resistance was rated "B".

[0127] Example 13: Production of adhesive particles M, adhesive composition slurry M, and separator M Emulsion M was prepared in the same manner as emulsion A in Example 1, except that the amount of 2-ethylhexyl acrylate (2-EHA) was changed from 20.1 parts to 10.1 parts, the amount of acrylonitrile (AN) was changed from 10.0 parts to 20.0 parts, and 0.3 parts of 1,9-nonanediol diacrylate (1,9-ND) was used instead of 0.3 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS). An aqueous dispersion containing adhesive particles M was obtained in the same manner as the aqueous dispersion in Example 1, except that emulsion M was used instead of emulsion A. The reaction rate at the end of the reaction was 99%.

[0128] The glass transition temperature (Tg) of the obtained adhesive particles M was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +76°C. Furthermore, the volume average particle diameter of the obtained adhesive particles M, measured as shown in Test Example 2 below, was 0.31 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum value of the Young's modulus ratio between adjacent measurement points was 180%, and the Young's modulus increased from the center to the surface. When the degree of swelling was measured as shown in Test Example 4 below, it was found to be 6 times larger.

[0129] An adhesive composition slurry M for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles M were used instead of adhesive particles A, and a separator M equipped with an adhesive layer was produced. The viscosity of the adhesive composition slurry M, and the dry adhesive strength and blocking resistance of the separator M were evaluated based on the following Test Examples 5 to 7. The viscosity was 33 mPa s, the dry adhesive strength was rated "C", and the blocking resistance was rated "B".

[0130] Example 14: Production of adhesive composition slurry N and separator N A mixture of 79.0 parts of a dispersion of alumina (average primary particle size: 0.58 μm), 15.0 parts of adhesive particles A obtained in Example 1, 2.0 parts of sodium polyacrylate (PAA-Na) as a water-soluble polymer, 3.0 parts of acrylic latex (Acl-Ltx) (BA / MMA / MAA copolymer latex, average particle size: 120 nm) with a Tg of -35°C as a particulate binder, 1.0 part of SN Wet 126 (manufactured by San Nopco) as a water-soluble silicone surfactant as a wetting agent, and 300 ppm of BIT (1,2-benzisothiazolin-3-one) as a preservative was added per 100 parts of the solids content. Finally, ion-exchanged water was added in an amount to achieve a solids concentration of 30%. The mixture was passed through a magnetic separator and then filtered through a #200 mesh filter. This produced adhesive composition slurry N for the adhesive layer.

[0131] A separator substrate consisting of a porous polyethylene substrate was prepared. The adhesive composition slurry prepared by the method described above was applied to one side of the separator substrate to a thickness of 1.0 μm on each side, and then dried with hot air for 10 minutes. This produced separator N equipped with an adhesive layer. The viscosity of adhesive composition slurry N, and the dry adhesive strength and blocking resistance of separator N were evaluated based on Test Examples 5 to 7 below. The viscosity was 78 mPa·s, the dry adhesive strength was rated "C," and the blocking resistance was rated "B."

[0132] Example 15: Production of adhesive composition slurry O and separator O An adhesive composition slurry O for an adhesive layer was prepared in the same manner as in Example 14, except that 79.0 parts (solids equivalent) of a dispersion of barium sulfate (average primary particle size 0.30 μm) was used instead of 79.0 parts of a dispersion of alumina (average primary particle size 0.58 μm), and a separator O equipped with an adhesive layer was fabricated. The viscosity of the adhesive composition slurry O, and the dry adhesive strength and blocking resistance of the separator O were evaluated based on Test Examples 5 to 7 below. The viscosity was 91 mPa s, the dry adhesive strength was rated "C", and the blocking resistance was rated "B".

[0133] (Example 16: Production of adhesive composition slurry P and separator P) An adhesive composition slurry P for an adhesive layer was prepared in the same manner as in Example 1, and a separator P equipped with an adhesive layer was produced, except that adhesive particles M produced in Example 13 were used instead of adhesive particles A, and the amount of Tg-35°C acrylic latex in the binder was changed from 3.0 parts to 0 part, and the amount of water-soluble polymer polyacrylate sodium (PAA-Na) was changed from 1.0 part to 4.0 parts. The viscosity of the adhesive composition slurry P, and the dry adhesive strength and blocking resistance of the separator P were evaluated based on the following Test Examples 5 to 7. The viscosity was 139 mPa s, the dry adhesive strength was rated "A", and the blocking resistance was rated "A".

[0134] Comparative Example 1: Production of Adhesive Particles Q, Adhesive Composition Slurry Q, and Separator Q Emulsion Q was prepared in the same manner as emulsion A in Example 1, except that the amount of styrene (ST) was changed from 40.0 parts to 60.0 parts and the amount of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) was changed from 0.3 parts to 0.4 parts. Emulsion Q was continuously added to the reactor over 2.0 hours with continued stirring to carry out polymerization. After the addition of emulsion Q was completed, the mixture was stirred at 80°C for an additional 2.0 hours to terminate the reaction, yielding an aqueous dispersion containing adhesive particles Q. The reaction rate at this time was 98%.

[0135] The glass transition temperature (Tg) of the obtained adhesive particles Q was measured as shown in Test Example 1 below, and it was confirmed that the glass transition temperature (Tg) was observed at only one point, which was +11°C. Furthermore, the volume average particle diameter of the obtained adhesive particles Q, measured as shown in Test Example 2 below, was 0.32 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum Young's modulus ratio between adjacent measurement points was 100%. When the degree of swelling was measured as shown in Test Example 4 below, it was 9 times.

[0136] An adhesive composition slurry Q for an adhesive layer was prepared in the same manner as in Example 1, except that adhesive particles Q were used instead of adhesive particles A, and a separator Q equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry Q, and the dry adhesive strength and blocking resistance of separator Q were evaluated based on the following Test Examples 5 to 7. The viscosity was 34 mPa s, the dry adhesive strength was rated "A", and the blocking resistance was rated "D".

[0137] Comparative Example 2: Production of Adhesive Particles R, Adhesive Composition Slurry R, ​​and Separator R In a reactor equipped with a stirrer, 100 parts of ion-exchanged water, 0.05 parts of sodium lauryl sulfate as an emulsifier, and 0.3 parts of sodium persulfate as a radical polymerization initiator were added, and the gas phase in the reactor was replaced with nitrogen gas and heated to 70 ° C. In another vessel equipped with a stirrer, 100 parts of ion-exchanged water, 20.1 parts of 2-ethylhexyl acrylate (2-EHA), 50.0 parts of methyl methacrylic acid (MMA), 6.0 parts of butyl acrylate (BA), 3.5 parts of methacrylic acid (MAA), and 0.3 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) as a reactive monomer were mixed and stirred to produce emulsion R.

[0138] This emulsion R was continuously added to the reactor over 2.0 hours. 1.5 hours after the addition of emulsion R was completed, a mixed monomer of 20.0 parts of styrene (ST) and 0.1 parts of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) was added to the reactor over 1.5 hours with stirring, and polymerization was carried out. After the addition of the mixed monomer was completed, the mixture was stirred at 80°C for an additional 2 hours to terminate the reaction, yielding an aqueous dispersion containing adhesive particles R. The reaction rate at this time was 87%.

[0139] The glass transition temperature (Tg) of the obtained adhesive particles R was measured as shown in Test Example 1 below, and it was confirmed that only one glass transition temperature (Tg) was observed, which was +34°C. Furthermore, the volume average particle diameter of the obtained adhesive particles R, measured as shown in Test Example 2 below, was 0.34 μm. When Young's modulus was measured at 10 nm intervals using an atomic force microscope (AFM) as shown in Test Example 3 below, the maximum Young's modulus ratio between adjacent measurement points was 520%. A single section of Young's modulus change, with a Young's modulus ratio of 520%, was observed in adhesive particles R, and adhesive particles R can be determined to be core-shell type particles bounded by this large Young's modulus change section. When the degree of swelling was measured as shown in Test Example 4 below, it was found to be 9 times larger.

[0140] Except for using adhesive particles R instead of adhesive particles A, adhesive composition slurry R for an adhesive layer was prepared in the same manner as in Example 1, and separator R equipped with an adhesive layer was produced. The viscosity of adhesive composition slurry R, ​​and the dry adhesive strength and blocking resistance of separator R were evaluated based on the following Test Examples 5 to 7. The viscosity was 33 mPa s, the dry adhesive strength was rated "D," and the blocking resistance was rated "C."

[0141] (Test Example 1: Measurement of Glass Transition Temperature of Adhesive Particles) An appropriate amount of the aqueous dispersion containing adhesive particles was placed in an aluminum dish and dried for 1 hour in a hot air dryer at 130°C. Approximately 10 mg of the dried film was placed in an aluminum container for measurement, and a DSC curve and a DDSC curve were obtained under a nitrogen atmosphere using a DSC measuring device (Shimadzu Corporation, model number: DSC6220). The glass transition temperature was determined from the obtained DSC curve and DDSC curve.

[0142] (Test Example 2: Measurement of the average particle size of adhesive particles) The 50% particle size (nm) of the adhesive particles based on volume was measured using a particle size measuring device using a light scattering method (manufactured by LEED & NORTHRUP, trade name "MICROTRAC UPA150"), and this was taken as the volume average particle size.

[0143] (Test Example 3: Analysis of adhesive particles by atomic force microscope (AFM)) An aqueous dispersion of adhesive particles was frozen with liquid nitrogen and then processed in a freeze dryer for 12 hours to obtain adhesive particle powder. Specifically, HERZOG Epo 1571 was used as the base resin and 1552-2 as the curing agent, and these were mixed in a 100:20 ratio. The adhesive particle powder was quickly dried before curing began, mixed, degassed under reduced pressure, and molded to embed and fix the adhesive particles. The embedded resin was cut using a cryomicrotome at -50°C to expose the particle cross-section. An atomic force microscope (AFM) (Oxford MPF-3D Origin+) was used in tapping mode to measure Young's modulus (GPa) in the peripheral field including the particle. Young's modulus values ​​were obtained at 10 nm intervals from the center of the particle to any surface portion, and the change in Young's modulus from the center to the surface was evaluated. Furthermore, the ratio Y of the Young's modulus between all adjacent measurement points was calculated. ratio was calculated according to the formula (Y) explained above, and the maximum value of all the obtained ratios was extracted. In Table 1 below, if the maximum value is 290% or less, there is no large change in Young's modulus from the center to the surface, and it can be evaluated that the Young's modulus changes continuously, and it is judged as "Good." If the maximum value exceeds 290%, it is judged as "Poor."

[0144] (Test Example 4: Evaluation of swelling degree of adhesive particles in electrolyte) The adhesive particles were heated at 100°C for 2 hours to remove the solvent and volatile components, resulting in a dried product. Next, 0.50 g of the dried product was weighed and used as a sample with a mass of W1. A sealable container was filled with 20 cc of an electrolyte solution containing 1.0 M LiPF6 in a 1 / 1 (v / v) ratio of ethylene carbonate (EC) to propylene carbonate (PC). The sample was then immersed in the solution. The solution was then left at 30°C for 48 hours to allow the sample to swell. After this time, a metal mesh with a mesh opening of 60-90 microns was weighed and recorded as the mass W2. The electrolyte and sample were filtered together using the mesh. The solution was left to stand for 10 seconds after filtration to allow excess electrolyte to drain. After this time, the mesh and the swollen sample were weighed and recorded as the mass W3. The swelling ratio S (times) was measured according to the following formula (S): The test was carried out with N=3, and the average value was recorded as the swelling degree (fold).

[0145]

number

[0146] (Test Example 5: Viscosity Measurement) Adhesive composition slurries were prepared using ion-exchanged water to a concentration of 30.0% by mass. Each sample was stirred at 1,000 rpm using a mixer, allowed to stand for 5 minutes, and then the apparent viscosity of the sample was measured using a viscometer (TV-10M rotational viscometer manufactured by Toki Sangyo Co., Ltd.) at 60 rpm for 60 seconds.

[0147] (Test Example 6: Evaluation of dry adhesive strength) The separator was cut into a 2 cm wide x 5 cm long test piece. A metal plate was prepared and a 2 cm wide double-sided tape was attached to it. The coated side of the test piece was attached to the other side of the double-sided tape, facing the other side. The metal plate was set in a peel tester and the test piece was fixed to a force gauge. Peeling was performed at a peel rate of 100 mm / min, and recording was performed at 0.05 sec intervals. 200 stable intervals were selected and the average of the measured values ​​was calculated. The test was performed with N=3, and the average value was recorded as adhesive strength (N / m). Evaluation was performed according to the following evaluation criteria. The calculated adhesive strength (dry adhesion) and evaluation results are shown in Table 1.

[0148] Evaluation criteria A:3.5N / m or more B: 3.0N / m or more, less than 3.5N / m C: 2.0N / m or more, less than 3.0N / m D: Less than 2.0N / m

[0149] (Test Example 7: Evaluation of blocking resistance) The separator was cut into a 5 cm wide x 5 cm long square to prepare a test piece. These were stacked with the coated surfaces facing each other to prepare a sample (unpressed sample), and a sample placed at 45°C and a pressure of 1.0 MPa after stacking (pressed sample). Each of these samples was left for 24 hours. After leaving the sample for 24 hours, the adhesion state (blocking state) of the stacked double-sided separators with porous membranes was visually inspected, and if possible, evaluated using the same method as for evaluating dry adhesive strength. In addition, samples that could not be subjected to a peel test were evaluated according to the following criteria. The evaluation results are shown in Table 1.

[0150] Evaluation criteria A: In the pressed sample, the separators do not block each other. B: In the pressed sample, the separators block each other, but peel off when one side is lifted. C: In the pressed sample, the separators are blocked together and do not peel off even when lifted. D: In the unpressed sample, the separators block each other.

[0151] The amounts of the components used to prepare the adhesive particles and adhesive compositions of the Examples and Comparative Examples, as well as the measured values, calculated values ​​and measurement results of the test examples, are summarized in Table 1 below.

[0152] [Table 1]

[0153] As shown in Table 1, Examples 1 to 16, which used adhesive particles in which the Young's modulus varied continuously with a maximum Young's modulus ratio of 290% or less, were excellent in both adhesive strength and anti-blocking strength. On the other hand, Comparative Example 1, which used uniform particles in which the Young's modulus ratio had a maximum value of 100%, exhibited poor anti-blocking strength, and Comparative Example 2, which used core-shell particles in which the Young's modulus ratio had a maximum value of 520%, exhibited poor adhesive strength.

[0154] The above results show that adhesive compositions containing adhesive particles in which the Young's modulus changes continuously from the particle center to the particle surface have excellent adhesion when bonding a separator or a coating layer formed on a separator to an electrode, and also have excellent blocking resistance, which prevents solidification due to adhesion between adhesive layers even when a coating layer is formed on a separator and stored rolled up.

Claims

1. An adhesive composition for bonding components constituting a non-aqueous secondary battery, the adhesive composition comprising adhesive particles whose Young's modulus changes continuously from the particle center to the particle surface.

2. 2. The adhesive composition according to claim 1, wherein, when the Young's modulus of the adhesive particles is measured at 10 nm intervals from the center of the particle to the surface of the particle, the maximum ratio of the higher Young's modulus to the lower Young's modulus between two adjacent measurement points is 290% or less.

3. The adhesive composition according to claim 1 , wherein the Young's modulus of the adhesive particles is higher at the particle surface than at the particle center.

4. 2. The adhesive composition according to claim 1, wherein the adhesive particles have a structural unit derived from at least one monomer selected from the group consisting of a monofunctional (meth)acrylate monomer, an aromatic vinyl monomer, a (meth)acrylonitrile monomer, and a conjugated diene monomer.

5. 2. The adhesive composition according to claim 1, wherein the adhesive particles have structural units derived from reactive monomers, and the content of the structural units derived from reactive monomers is 0.05% by mass to 5% by mass relative to the total mass of the adhesive particles.

6. 6. The adhesive composition according to claim 5, wherein the reactive monomer comprises at least one selected from the group consisting of a polyfunctional (meth)acrylate monomer, an epoxy group-containing (meth)acrylate monomer, and a silanol group-containing (meth)acrylate monomer.

7. LiPF 6 2. The adhesive composition according to claim 1, wherein the degree of swelling of the adhesive particles when immersed in a mixed electrolyte solution (ethylene carbonate / propylene carbonate=1 / 1 (volume ratio)) containing 1 mol / L of

8. The adhesive composition according to claim 1, further comprising at least one selected from the group consisting of a particulate binder having a glass transition temperature (Tg) of 30°C or less, a water-soluble polymer, and a preservative.

9. The adhesive composition according to claim 1 , further comprising an inorganic filler.

10. 2. The adhesive composition according to claim 1, which contains water as a solvent, has a viscosity of 5 mPa s to 1000 mPa s at 25°C measured using a Brookfield viscometer at a rotor rotation speed of 60 rpm, and has a solids content of 5.0 mass % to 80.0 mass %, relative to 100 mass % of the adhesive composition.

11. A separator comprising a substrate and an adhesive layer comprising the adhesive composition of claim 1.

12. A non-aqueous secondary battery comprising the separator of claim 11.

13. A method for producing a separator, comprising: a step of filtering the adhesive composition according to any one of claims 1 to 10 using either or both of a magnetic separator and a filter; and a step of forming an adhesive layer on a surface of a substrate using the filtered composition obtained in the step.

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