JP2014056675A - Sealant for secondary battery and sealant composition for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealant for a secondary battery capable of forming a sealant layer excellent in water resistance, moisture resistance, and heat resistance.SOLUTION: The sealant composition for secondary battery contains diene rubber and a polymer composed of an isobutylene block and a styrene block, and a weight ratio of the diene rubber to the polymer composed of the isobutylene block and the styrene block is 40/60 to 80/20 (the diene rubber/the polymer composed of the isobutylene block and the styrene block).

Description

  The present invention relates to a sealing material for a secondary battery and a sealing material composition for a secondary battery having high water resistance, moisture resistance and heat resistance.

  Lithium ion secondary batteries are often used as power sources for small electronic devices such as notebook computers, mobile phones, and PDAs, and in recent years, lithium ion secondary batteries have also been used for automotive applications. As the range of use of lithium ion secondary batteries widens, demands for the performance and safety of lithium secondary batteries (hereinafter sometimes simply referred to as batteries) are increasing. These batteries are usually used repeatedly by charging and discharging operations, but due to repeated charging and discharging, the internal pressure of the battery rises due to volume fluctuations and heat generation of the electrodes due to charging and discharging, and the electrolyte leaks to the outside. Sometimes. In this case, not only deterioration of battery characteristics occurs, but also dangers such as ignition and corrosion of equipment are problematic. For example, when an electrolytic solution is used for a lithium ion secondary battery, the electrolytic solution is organic and extremely dislikes water. Therefore, in such a lithium ion secondary battery, the penetration of water into the battery is completely prevented. A high sealing property is required to prevent the leakage of the electrolyte and completely prevent the electrolyte from leaking.

  For example, a lithium ion secondary battery is housed in a metal container in order to seal the power generation element, but in order to prevent a short circuit between the positive electrode and the negative electrode, it is necessary to insulate between the positive electrode terminal and the negative electrode terminal. . In general, a gasket made of an insulating material is used at the opening of a metal container containing a power generation element for insulation and sealing between the positive and negative electrodes. As an insulating material, it is known to use a resin insulating gasket (for example, refer to Patent Document 1).

  In order to further strengthen the sealing with such an insulating gasket, it has also been proposed to use an insulating gasket and a sealing material in combination (see, for example, Patent Documents 2 to 4). The sealing material is applied to an insulating gasket or a metal container, and the insulating gasket is attached to the metal container, thereby improving the sealing property between the insulating gasket and the metal container.

  Examples of such a sealing material include pitch materials such as coal tar and asphalt, and materials obtained by adding a polymer to the pitch materials as a modifier (see, for example, Patent Documents 5 to 9). In addition, butyl rubber (for example, see Patent Document 10), polyolefin adhesive (for example, see Patent Document 11), polyvinylidene fluoride resin (for example, see Patent Document 12), and the like have been proposed.

JP-A-53-084122 JP-A-55-030148 JP-A-55-016352 JP 59-111565 A JP 56-032671 A Japanese Patent Laid-Open No. 58-010365 JP 59-091660 A JP-A-6-124694 JP-A-6-005270 JP-A-55-030148 Japanese Patent Laid-Open No. 56-032672 JP-A-1-040469

  By the way, as the use range of the lithium ion secondary battery widens, a sealing material corresponding to the environment in which it is used is required. For example, in automobile applications and the like, further improvements in water resistance, moisture resistance and heat resistance of a sealing material layer formed of a sealing material are required.

  The objective of this invention is providing the sealing material for secondary batteries and the sealing material composition for secondary batteries which can form the sealing material layer excellent in water resistance, moisture resistance, and heat resistance.

As a result of intensive studies, the present inventor has found that the above object can be achieved by containing a polymer comprising a diene rubber, an isobutylene block and a styrene block in a predetermined ratio, and has completed the present invention.
That is, according to the present invention,

(1) A diene rubber and a polymer comprising an isobutylene block and a styrene block, wherein the weight ratio of the diene rubber and the polymer comprising the isobutylene block and the styrene block is (diene rubber / isobutylene). A polymer comprising a block and a styrene block) 40/60 to 80/20, a sealing material for a secondary battery,
(2) The diene rubber is a butadiene rubber having a 1,4-cis content of 90% or more, the sealing material for a secondary battery according to (1),
(3) The sealing material for a secondary battery according to (1) or (2) and an organic liquid material, wherein 1 to 30 wt% of the sealing material for the secondary battery is blended with respect to the organic liquid material. A sealing material composition for a secondary battery is provided.

  According to the sealing material for secondary batteries and the sealing material composition for secondary batteries according to the present invention, a sealing material layer having excellent water resistance, moisture resistance and heat resistance can be formed.

  Hereinafter, a sealing material for a secondary battery according to an embodiment of the present invention will be described. The sealing material for a secondary battery of the present invention comprises a diene rubber and a polymer comprising an isobutylene block and a styrene block, and a weight ratio of the diene rubber to a polymer comprising the isobutylene block and the styrene block. Is 40/60 to 80/20 (polymer comprising diene rubber / isobutylene block and styrene block).

(Diene rubber)
The diene rubber used for the sealing material for a secondary battery of the present invention is not particularly limited as long as it is a polymer containing a conjugated diene monomer unit obtained by polymerizing a diene monomer, but the conjugated diene homopolymer and At least one selected from the group consisting of conjugated diene copolymer is preferably used.

  The conjugated diene homopolymer may be a polymer obtained by polymerizing only a diene monomer, and those generally used industrially can be used without any particular limitation. Examples of the diene monomer forming the conjugated diene monomer unit of the conjugated diene homopolymer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1, Examples include 3-hexadiene chloroprene and cyanobutadiene. Among these, 1,3-butadiene and isoprene are preferable, and 1,3-butadiene is more preferable. These diene monomers can be used alone or in combination of two or more.

  Specific examples of the conjugated diene homopolymer include polybutadiene, polyisoprene, polychloroprene, polycyanobutadiene, and polypentadiene. Among these, polybutadiene and polyisoprene are preferable, and polybutadiene is more preferable. The polymerization mode of the conjugated diene homopolymer is not particularly limited, and may be appropriately selected depending on the purpose of use. Moreover, it does not specifically limit as a manufacturing method of a conjugated diene homopolymer, What is necessary is just to manufacture by a well-known method.

  The conjugated diene copolymer is not particularly limited as long as it is a copolymer containing at least a conjugated diene monomer unit. As the diene monomer forming the conjugated diene monomer unit of the conjugated diene copolymer, the same conjugated diene homopolymer as described above can be used.

  The monomer forming the monomer unit other than the conjugated diene monomer unit of the conjugated diene copolymer is not particularly limited as long as it is a monomer copolymerizable with the diene monomer. Examples thereof include a group-containing vinyl monomer, an amino group-containing vinyl monomer, a pyridyl group-containing vinyl monomer, an alkoxyl group-containing vinyl monomer, and an aromatic vinyl monomer. Among these, cyano group-containing vinyl monomers and aromatic vinyl monomers are preferable, and aromatic vinyl monomers are more preferable. These monomers copolymerizable with the diene monomer can be used alone or in combination of two or more.

  Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t. -Butyl styrene, 5-t-butyl-2-methyl styrene, N, N-dimethylaminoethyl styrene, N, N-diethylaminoethyl styrene and the like. Of these, styrene and α-methylstyrene are particularly preferable. These aromatic vinyl monomers can be used alone or in combination of two or more.

  The ratio of the diene monomer and the monomer copolymerizable with the diene monomer in the conjugated diene copolymer may be appropriately selected according to the purpose of use. The weight ratio of the “polymerizable monomer unit” is usually in the range of 5/95 to 95/5, preferably 10/90 to 90/10, more preferably 20/80 to 80/20.

  In addition, as the conjugated diene copolymer, either a random copolymer or a block copolymer can be used, but a block copolymer is preferable. The bonding mode of the conjugated diene block copolymer is appropriately selected according to the purpose of use, such as a diblock copolymer, triblock copolymer, tetrablock copolymer, and pentablock copolymer. Specific examples of the triblock copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, α-styrene-butadiene-α-styrene block copolymer, and the like. Among these, a styrene-butazine-styrene block copolymer is preferable. In addition, it does not specifically limit as a manufacturing method of a conjugated diene type copolymer, What is necessary is just to manufacture by a well-known method.

  In the present invention, the above-mentioned conjugated diene homopolymer and conjugated diene copolymer can be used alone or in combination of two or more as the diene rubber.

The amount of 1,2-vinyl bond in the conjugated diene part of the diene rubber used in the present invention is not particularly limited and may be appropriately selected according to the purpose of use, but is usually 5 mol% or more, preferably 40 mol% or more. More preferably, it is 60 mol% or more, and still more preferably 80 mol% or more.
The diene rubber used in the present invention is preferably a butadiene rubber having a 1,4-cis content of 90% or more.

  The molecular weight of the diene rubber used in the present invention is not particularly limited and may be appropriately selected depending on the purpose of use, but is a weight average molecular weight measured by gel permeation chromatography (polystyrene conversion, toluene eluent), Usually in the range of 500 to 5,000,000, preferably 1000 to 1,000,000.

  The molecular weight of the conjugated diene homopolymer when the conjugated diene homopolymer and the conjugated diene copolymer are used in combination as the diene rubber is measured by gel permeation chromatography (polystyrene conversion, toluene eluent). The weight average molecular weight is usually in the range of 500 to 500,000, preferably 1,000 to 10,000, more preferably 1,000 to 5,000. On the other hand, the molecular weight of the conjugated diene copolymer is a weight average molecular weight measured by gel permeation chromatography (polystyrene conversion, toluene eluent) and is usually 1,000 to 1,000,000, preferably 5,000. It is -500,000, More preferably, it is the range of 10,000-300,000.

Furthermore, when the conjugated diene homopolymer and the conjugated diene copolymer are used in combination, the ratio of these polymers is not particularly limited, and may be appropriately selected according to the purpose of use. The weight ratio of “conjugated diene copolymer” is usually in the range of 5/95 to 90/10, preferably 10/90 to 90/10, more preferably 30/70 to 80/20.
(Isobutylene block-polymer comprising styrene block)

  The polymer comprising the isobutylene block-styrene block used for the sealing material for secondary batteries of the present invention is a block copolymer obtained by copolymerizing a monomer composition containing an isobutylene monomer and a styrene monomer.

  The method for obtaining the block copolymer is not particularly limited, and examples thereof include radical polymerization, anionic polymerization, cationic polymerization, coordinated anionic polymerization, and coordinated cationic polymerization. When a method in which radical polymerization, anion polymerization, cation polymerization, or the like is performed by living polymerization, particularly a method in which living anion polymerization is performed, a polymerization operation and a hydrogenation reaction in a post process are facilitated.

  The polymerization is carried out in the presence of a polymerization initiator in a temperature range of usually 0 to 150 ° C, preferably 20 to 100 ° C, particularly preferably 10 to 80 ° C. In the case of living anionic polymerization, as a polymerization initiator, for example, monoorganolithium such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium; dilithiomethane, 1,4-diobane, 1, Polyfunctional organolithium compounds such as 4-dilithio-2-ethylcyclohexane can be used.

The polymerization reaction form may be any of solution polymerization, slurry polymerization, and the like, but if solution polymerization is used, the reaction heat can be easily removed. In this case, an inert solvent in which the polymer obtained in the block copolymer production process and the hydrogenated polymer production process described later is dissolved is used. Examples of the inert solvent used include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane and isooctane; cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane and decalin. , Alicyclic hydrocarbons such as bicyclo [4.3.0] nonane and tricyclo [4.3.0.1 ^2,5 ] decane; aromatic hydrocarbons such as benzene and toluene. Among these, alicyclic hydrocarbons are preferable because they can be used as they are as an inert solvent in the hydrogenation reaction described later and the solubility of the hydrogenated polymer is good. These solvents may be used alone or in combination of two or more. The amount of these solvents used is usually 200 to 2000 parts by mass with respect to 100 parts by mass of all monomers used.

  When two or more monomers are used in obtaining the block copolymer, a randomizer or the like can be used in order to prevent only a certain one-component chain from becoming long. In particular, when the polymerization reaction is performed by anionic polymerization, it is preferable to use a Lewis base compound or the like as a randomizer. Examples of the Lewis base compound include ether compounds such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, diphenyl ether, ethylene glycol diethyl ether, and ethylene glycol methyl phenyl ether; tetramethylethylenediamine, trimethylamine, triethylamine, pyridine Tertiary amine compounds; alkali metal alkoxide compounds such as potassium-t-amyl oxide and potassium-t-butyl oxide; phosphine compounds such as triphenylphosphine; and the like. These Lewis base compounds may be used alone or in combination of two or more.

The mode of the block copolymer is not particularly limited, and the [(A)-(B)] type diblock copolymer and the [(A)-(B)-(A)] type triblock copolymer. And block copolymers having more blocks.
In the present invention, it is preferable to use Shibster (manufactured by Kaneka Corporation) as a polymer comprising an isobutylene block-styrene block.

(Other ingredients)
The sealing material for a secondary battery of the present invention may further contain components such as a dispersant, an ultraviolet absorber and an anti-aging agent in addition to the above-mentioned conjugated diene polymer and cyclic olefin polymer. These are not particularly limited as long as they do not deteriorate the performance of an insulating gasket described later, do not react with the electrolytic solution, and do not dissolve in the electrolytic solution.

  Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. Among these, it is preferable to use a nonionic compound, and it is preferable to use a nonionic surfactant among nonionic compounds. The dispersant is selected according to the type of electrode active material and conductive agent used.

  Examples of ultraviolet absorbers include organic substances such as benzotriazole ultraviolet absorbers, bezoate ultraviolet absorbers, benzophenone ultraviolet absorbers, acrylate ultraviolet absorbers, metal complex ultraviolet absorbers, and salicylic acid esters, or fine particles. Inorganic materials such as zinc oxide, cerium oxide, and titanium oxide can be used. The content of the ultraviolet absorber in the sealing material is preferably 0.01 to 2 wt% from the viewpoint of preventing deterioration due to ultraviolet rays.

  Examples of the anti-aging agent include an antioxidant, a heat anti-aging agent, an anti-bending crack agent, and an ozone deterioration preventing agent. Among these, an antioxidant is preferable in that the sealing performance can be maintained for a longer period. When the present invention is applied to an organic electrolyte battery, among antioxidants, phenolic compounds and phosphite ester compounds do not dissolve in the electrolyte solution and do not adversely affect the electrolyte solution and function in a small amount. It is more preferable at the point which can exhibit.

(Sealant for secondary battery)
The sealing material for secondary batteries of the present invention comprises the above-mentioned diene rubber, a polymer comprising an isobutylene block-styrene block, and other components blended as necessary. The total amount of the diene rubber and the polymer comprising the isobutylene block-styrene block in the sealing material is 80 wt% or more, preferably 85 wt% or more, more preferably 90 wt% or more. When the total amount of the hydrogenated polymer and the conjugated diene-based polymer is too small, the electrolytic solution resistance and the sealing property of the obtained sealing material layer are lowered.

  The weight ratio of the diene rubber and the polymer comprising isobutylene block-styrene block contained in the sealing material for secondary battery of the present invention is (diene rubber / polymer comprising isobutylene block and styrene block). 40/60 to 80/20, preferably 50/50 to 70/30, more preferably 55/45 to 65/35. If the ratio of the diene rubber is too large, the acid resistance of the resulting sealing material layer will decrease, and if the ratio of the diene rubber is too small, the adhesion of the resulting sealing material layer to the metal container used in the secondary battery will decrease. As a result, the sealing performance decreases.

(Sealant composition)
The sealing material composition for a secondary battery of the present invention comprises the above-mentioned conjugated diene polymer, cyclic olefin polymer, organic liquid substance, and other components blended as necessary. It preferably contains a sealing material and an organic liquid material.

  The organic liquid substance is not particularly limited as long as it can dissolve the conjugated diene polymer and the cyclic olefin polymer, but in view of volatility and ease of drying, an organic solvent having 5 to 15 carbon atoms is preferable. An organic solvent having 6 to 12 carbon atoms is more preferable.

Examples of organic liquid substances include n-hexane, heptane, n-octane, isooctane, n-nonane, decane, decalin, α-pinene, β-pinene, δ-pinene, 1-chlorooctane, chlorodecane, cyclohexane, cycloheptane, Methylcyclopentane, 2-methylcyclohexane, 3-methylcyclohexanone, 4-methylcyclohexanone, 4-ethylcyclohexane, chlorocyclohexane, cyclohexene, cycloheptene, benzene, toluene, o-xylene, m-xylene, p-xylene, styrene, chlorobenzene O-chlorotoluene, m-chlorotoluene, p-chlorotoluene, ethylbenzene, propylbenzene, diisopropenylbenzene, butylbenzene, isobutylbenzene, n-amylbenzene, cumene, etc. Hydrocarbons; 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-octanol, 2-octanol, benzyl alcohol, 4-t-butylcatechol, Alcohols such as cyclopentanol, 2-pentanone, 2-hexanone, 3-hexanone, cyclopentanone, cyclohexanone, cycloheptanone, 2,6-dimethyl-4-heptanone, 4-methyl-2-pentanone, isophorone Ketones such as propyl ether, butyl ether, isobutyl ether, n-amyl ether, isoamyl ether, methyl n-amyl ether, ethyl butyl ether, ethyl isobutyl ether, ethyl n-amyl ether, ethyl isoamyl ether Esters such as butyl formate, pentyl formate, isopropyl acetate, n-propyl acetate, n-butyl acetate, s-butyl acetate, t-butyl acetate, ethyl lactate, butyl lactate, methyl benzoate, ethyl benzoate; -Amines such as toluidine, m-toluidine, p-toluidine, dimethylaniline, piperidine; amides such as N-methylpyrrolidone; sulfur-containing compounds; nitrile group-containing compounds such as adiponitrile; oxygen-containing heterocycles such as furfural Compounds; nitrogen-containing heterocyclic compounds such as pyridine; cellosolve acetates such as ethyl cellosolve acetate; glycols; diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol monobutyl ether, triethylene glycol dimethyl And ethylene glycol alkyl ethers such as ether; lactones such as γ-valerolactone and γ-caprolactone; lactams such as δ-valerolactam;
It is preferable that 1-30 wt% of sealing materials are contained in an organic liquid substance, and it is more preferable that 5-25 wt% is contained.

  Furthermore, you may add additives, such as a coloring agent, to the sealing material composition for secondary batteries of this invention as needed. The colorant that can be added is preferably one that does not react with the electrolyte and does not dissolve in the electrolyte, and includes various organic and inorganic pigments. Among these, carbon black, particularly carbon black having a particle size of 0.1 μm or less such as furnace black and channel black is preferable. When such a colorant is added, it must be dissolved or dispersed sufficiently uniformly in the composition. When using a granulated or agglomerated structure, a ball mill, a sand mill, an ultrasonic wave, etc. It is better to disperse with. The addition amount of such an additive such as a colorant may be any amount as necessary, but is usually 0.01% to 20% by weight with respect to the total amount of the conjugated diene polymer and the cyclic olefin polymer, Preferably they are 0.01 weight%-5 weight%, More preferably, they are 0.02 weight%-3 weight%. If the amount of additive added is too large, the sealing material becomes less flexible and may cause cracks.

  As a method for preparing the sealing material composition for a secondary battery of the present invention, a conjugated diene polymer and a cyclic olefin polymer previously kneaded are dissolved in an organic liquid substance, and then other components such as a dispersant are added. Method: Conjugated diene polymer and cyclic olefin polymer are sequentially added to an organic liquid substance and dissolved, and then other components such as a dispersant are added; conjugated diene polymer solution and cyclic olefin polymer solution are prepared. And a method of mixing them and then adding other components such as a dispersant.

(Secondary battery)
The secondary battery using the sealing material for a secondary battery and the sealing material composition for a secondary battery according to the present invention is provided between an insulating gasket attached to an opening of a metal container containing a power generation element and the metal container, and / or Or the sealing material layer formed with the above-mentioned sealing material composition is provided between an insulating gasket and a sealing body. The metal container material, power generation element, and insulating gasket used for the secondary battery may be those generally used. In this secondary battery, the power generation element is housed in a metal container and sealed.

  The power generation element is an electrolyte, an active material for positive and negative electrodes, a separator, and the like. As the electrolyte, a solid electrolyte is used in the case of an all-solid battery, and in the case of an organic electrolyte battery, an electrolyte solution (electrolytic solution) composed of a supporting electrolyte and an organic electrolyte solvent is used.

In an organic electrolyte battery, a supporting electrolyte constituting the electrolytic solution is a compound that easily reacts with water, such as a lithium-based compound such as LiPF ₆ , LiBF ₄ , LiClO ₄ , and the like. Moreover, as an organic electrolyte solution solvent, combustible organic compounds, such as propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC), are used, for example. As the insulating gasket, it is preferable to use polyolefin resins such as polyethylene, polypropylene, and ethylene copolymerized polypropylene, which are generally said to have high electrolytic solution resistance, and particularly ethylene copolymerized polypropylene because of a good balance between strength and elastic modulus. Further, as the polyolefin resin, one having a heat distortion temperature measured by JIS K7207 of 90 to 200 ° C., preferably 90 to 150 ° C., more preferably 95 to 130 ° C. may be used. If it is higher than 200 ° C, the bending elastic modulus at room temperature is too high, and deformation may occur when the insulating gasket is mounted, which may cause cracks and cracks. At temperatures below 90 ° C, the resistance of the insulating gasket at high temperatures Is inferior and the sealing performance is reduced.

  The sealing material layer of the secondary battery can be formed by the following procedure, for example. First, a predetermined amount of the sealing material composition is applied to the surface of the metal container and / or the insulating gasket by feeding a predetermined amount with a metering pump such as an air-driven metering dispenser, a roller pump, or a gear pump. After the application, natural drying is performed in a state where the sealing material composition is kept horizontal so that the sealing material composition is not displaced, and the organic liquid substance is removed to form a thin layer.

  The application is not limited to a method using a metering pump, and can be performed manually using a brush if the amount is small. In drying, instead of natural drying, forced drying using a heating device may be performed. In this case, drying can be performed in a short time, and the process can be industrially more suitable.

  What is necessary is just to select the thickness of the sealing material layer formed by the above-mentioned method arbitrarily according to the magnitude | size of a metal container and an insulation gasket, and is 0.1 micrometer-1000 micrometers normally. If the thickness of the layer is insufficient, problems such as electrolyte leakage and moisture intrusion may occur, or the layer may be cut. On the contrary, if the layer is thick, layer formation may be difficult.

  As the secondary battery using the sealing material for secondary battery and the sealing material composition for secondary battery of the present invention, a lithium ion secondary battery is preferable, and the lithium ion secondary battery may be an organic electrolyte battery, An all-solid battery may be used.

  The sealing material composition for a secondary battery of the present invention can be suitably used for electric and electronic parts such as electric field capacitors, electric double layer capacitors, and lithium ion capacitors.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the part and% in a present Example are a mass reference | standard. In Examples and Comparative Examples, the peel strength and the resistance to electrolytic solution were determined as follows.

(Peel strength)
The peel strength between the film 1 of the sealing material and the aluminum foil obtained in the examples and comparative examples was measured by a 180 ° peel method. An aluminum tape with an adhesive was bonded to a test piece cut into a ribbon shape having a width of 25 mm, and the peel strength was measured using a tensile tester. When peeled at the interface between the aluminum tape and the film 1 of the sealing material, the peel strength was measured when peeled off at the interface between the film 1 of the sealing material and the aluminum foil.

(Flexibility)
The films 1 obtained in the examples and comparative examples were folded outward at −20 ° C. The bent part was observed, and cracks, peeling, etc. were observed. Table 1 shows ◯ when no cracks, peeling, etc. were observed, and x when cracks, peeling, etc. were observed.

(Heat resistant acid water immersion)
The film 2 obtained in Examples and Comparative Examples was immersed in water adjusted to pH 3 with sulfuric acid (80 ° C., 240 hours), and after removing the droplets adhering to the surface of the film taken out, the appearance was observed. . The evaluation was performed according to the following criteria and is shown in Table 1.
A: No change B: Unevenness on the surface C: Large surface roughness (large unevenness on the whole, Ra> 100 μm)
The peel strength is shown in Table 1 as A when peeled at the interface between the PET film and the sealing material, and B when peeled at the interface between the sealing material and the PET film.

Example 1
(Polymerization of 1,3-butadiene polymer (diene rubber))
To a 10 liter autoclave equipped with a stirrer, 5000 g of toluene and 810 g of butadiene were added and sufficiently stirred. Then, 0.27 mol of diethylaluminum chloride and 0.6 mmol of chromium chloride / pyridine complex were added, and the mixture was polymerized while stirring at 60 ° C. for 3 hours. Thereafter, 100 ml of methanol was added to terminate the polymerization. After the polymerization was stopped, after cooling to room temperature, the polymerization solution was taken out. The resulting polymerization solution was steam-coagulated and then vacuum-dried at 60 ° C. for 48 hours to obtain 780 g of a solid polymer. Mw of the obtained polymer was 390,000.
From the result of ¹³ C-NMR spectrum, the cis-isomer content of this polymer was 94%.

(Test pieces)
50 parts by weight of the diene rubber obtained as described above, 50 parts by weight of Shibster and 900 parts by weight of an organic solvent (xylene) as a polymer comprising an isobutylene block-styrene block are heated to 50 ° C. in a flask equipped with a stirring blade. To obtain a homogeneous solution.
The obtained solution was cast on an aluminum foil (20 μm thick) with a doctor blade having a gap of 200 μm, and heat-dried at 80 ° C. for 20 minutes to obtain a film 1.

  The obtained solution was cast on a PET film (25 μm thick) with a doctor blade having a gap of 200 μm and dried by heating at 80 ° C. for 20 minutes to obtain a film 2.

(Example 2)
Film 1 and film 2 were obtained in the same manner as in Example 1 except that the polymer used in the solution prepared when obtaining the test piece was 55 parts by weight of diene rubber and 45 parts by weight of Shibster.

(Example 3)
Film 1 and film 2 were obtained in the same manner as in Example 1 except that the polymer used in the solution prepared when obtaining the test piece was 60 parts by weight of diene rubber and 40 parts by weight of Shibster.

(Comparative Example 1)
Film 1 and film 2 were obtained in the same manner as in Example 1 except that the polymer used in the solution to be prepared when obtaining the test piece was 30 parts by weight of diene rubber and 70 parts by weight of Shibster.

(Comparative Example 2)
Film 1 and film 2 were obtained in the same manner as in Example 1 except that 100 parts by weight of asphalt was used instead of the polymer used in the solution prepared when obtaining the test piece.

(Comparative Example 3)
Film 1 and film 2 were obtained in the same manner as in Example 1 except that the polymer used in the solution prepared when obtaining the test piece was 100 parts by weight of Shibster and no diene rubber was used.

As shown in Table 1, the weight ratio of the diene rubber and the block polymer comprising the isobutylene block and the styrene block, and the weight ratio of the diene rubber to the polymer comprising the isobutylene block and the styrene block is from 40/60 to In the case of 80/20, the peel strength, flexibility, and heat-resistant acidic water immersion were all good.

Claims (3)

A diene rubber and a polymer comprising an isobutylene block and a styrene block,
The weight ratio of the diene rubber to the polymer comprising the isobutylene block and the styrene block is 40/60 to 80/20 (the polymer comprising the diene rubber / isobutylene block and the styrene block). A sealing material for a secondary battery.   2. The sealing material for a secondary battery according to claim 1, wherein the diene rubber is a butadiene rubber having a 1,4-cis content of 90% or more. A sealing material for a secondary battery according to claim 1 or 2, and an organic liquid substance,
A sealing material composition for a secondary battery, wherein the sealing material for a secondary battery is blended in an amount of 1 to 30 wt% with respect to the organic liquid substance.