Hydrogenated nitrile rubber

Abstract

This invention provides a low-ash hydrogenated nitrile rubber that exhibits excellent dispersibility and stability of conductive material dispersions, as well as superior resistance characteristics, output characteristics, cycle characteristics, and high-temperature storage characteristics of electrochemical elements. [Solution] The hydrogenated nitrile rubber of the present invention contains acrylonitrile polymerization units and 1,3-butadiene polymerization units, wherein the 1,3-butadiene polymerization units consist of 1,2-bonding units, 1,4-bonding units and their hydride units, the weight-average molecular weight (Mw) is 100,000 or less, the ratio of polymerization average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) is 2.5 or more, the iodine value is 100 mg / 100 mg or less, the ash content is 0.7 mass% or less, and the ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)) is 0.2 or less.

Description

[Technical Field]

[0001] The present invention relates to hydrogenated nitrile rubber and a method for producing the same, as well as a positive electrode material, a positive electrode binder, a conductive material dispersion, a positive electrode slurry, a positive electrode, and an electrochemical element using hydrogenated nitrile rubber. [Background technology]

[0002] Electrochemical elements such as lithium-ion secondary batteries, lithium-ion capacitors, and electric double-layer capacitors are small, lightweight, have high energy density, and can be repeatedly charged and discharged, making them suitable for a wide range of applications. Therefore, in recent years, improvements to battery components such as electrodes have been considered to further enhance the performance of electrochemical elements.

[0003] Here, the electrodes used in electrochemical elements typically comprise a current collector and an electrode composite layer formed on the current collector. This electrode composite layer is formed, for example, by applying a slurry containing an electrode active material, a conductive material, and a binder onto the current collector and then drying the applied slurry.

[0004] Therefore, in recent years, attempts have been made to improve the binders used in forming electrode composite layers in order to achieve further performance improvements in electrochemical elements. For example, the use of hydrogenated nitrile rubber as a binder is being investigated.

[0005] For example, Patent Document 1 (WO2013 / 129658) discloses a lithium-ion secondary battery with excellent cycle characteristics, which contains a first polymer as a positive electrode active material, comprising polymer units having nitrile groups, polymer units having hydrophilic groups, (meth)acrylic acid ester polymer units, and linear alkylene polymer units having 4 or more carbon atoms, and a fluorine-containing polymer as a binder component. Specifically, the first polymer is obtained by (1) adding deionized water, sodium alkylbenzene sulfonate, acrylonitrile, butyl acrylate, methacrylic acid, 1,3-butadiene, and ammonium persulfate to an autoclave with a stirrer and carrying out emulsion polymerization at 40°C until the polymerization conversion rate reaches 85%, (2) adding palladium acetate to the obtained polymerization solution and carrying out a hydrogenation reaction twice at a hydrogen pressure of 3 MPa and 50°C for 6 hours, and then (3) coagulating with methanol, and (4) containing 20% ​​by mass of acrylonitrile polymerization units, 45% by mass of conjugated diene-derived polymerization units, 30% by mass of butyl acrylate polymerization units, and 5% by mass of methacrylic acid polymerization units, wherein the conjugated diene-derived polymerization units are formed from 38.8% by mass of hydrogenated linear alkylene structural units having 4 or more carbon atoms, 2.1% by mass of unhydrogenated butadiene polymerization units, and 4.1% by mass of 1,2-addition polymerization units, and obtaining hydrogenated NBR with an iodine value of 8 mg / 100 mg. In recent years, there has been a growing demand for further improvements in the dispersibility and stability of conductive material dispersions, as well as improvements in the flexibility of the manufactured electrodes, the capacitance characteristics, resistance characteristics, and high-temperature storage characteristics of electrochemical elements, and a reduction in the ash content of hydrogenated nitrile rubber.

[0006] Patent Document 2 (WO2022 / 163321) discloses a non-aqueous electrochemical element that has excellent suppression of DC resistance increase at low temperatures and high-temperature storage properties, comprising polymer A containing nitrile group-containing monomer units and alkylene structural units, and a specific ester solvent and a non-halogenated carbonate solvent. Specifically, polymer A is obtained by (1) charging an ion-exchanged water reactor with monomers such as acrylonitrile and 1,3-butadiene, sodium dodecylbenzenesulfonate as an emulsifier, and t-dodecyl mercaptan as a chain transfer agent, and then continuously adding cumene hydroperoxide as a polymerization initiator, a reducing agent, and a chelating agent to perform emulsion polymerization at 10°C until the polymerization conversion rate reaches 80%, and then (2) using a hydrogenation catalyst (3) A 1% palladium acetate acetone solution is added, and a hydrogenation reaction is carried out at a hydrogen pressure of 3 MPa and a temperature of 50°C for 6 hours. (4) NMP is added as an organic solvent to the aqueous dispersion after the hydrogenation reaction, and all water is removed under reduced pressure. (5) An 8% NMP solution of polymer A, consisting of 35% by mass of acrylonitrile, 65% by mass of butadiene, 18% by mass of hydrogenated 1,2-butadiene units, and a weight-average molecular weight of 150,000, is obtained. (6) Multiwall carbon nanotubes are added thereto to obtain a conductive material dispersion. On the other hand, there is a need to further improve the dispersibility and stability of the conductive material dispersion, and to improve the peel strength and warping characteristics of electrodes, the resistance characteristics, cycle characteristics and high-temperature storage characteristics of electrochemical elements, and there is also a need for lower ash content in hydrogenated nitrile rubber.

[0007] Patent Document 3 (WO2019 / 181869) discloses a conductive material dispersion with excellent dispersibility of carbon nanotubes, containing a binder containing a polymer containing carbon nanotubes, aromatic vinyl monomer units, and linear alkylene structural units having 4 or more carbon atoms, and a dispersion medium. Specifically, the polymer is prepared by (1) charging an ion-exchanged water reactor with an aqueous solution of sodium dodecylbenzenesulfonate as an emulsifier, styrene, acrylonitrile, methacrylic acid, 1,3-butadiene, and t-dodecyl mercaptan (2 parts) as a molecular weight modifier, and adding cumene hydroperoxide as a polymerization initiator while maintaining the temperature at 10°C, and emulsion polymerization until the conversion rate reaches 85% to obtain an aqueous dispersion of the precursor (particulate polymer). (2) Palladium acetate is added to the obtained aqueous dispersion of the precursor, and a hydrogenation reaction is carried out at a hydrogen pressure of 3 MPa and 50°C for 6 hours to produce a polymer with a styrene content of 33-48% by mass, acrylonitrile content of 10-21% by mass, conjugated diene (unhydrogenated) content of 4-6.5% by mass, linear alkylene structural units with 4 or more carbon atoms (conjugated diene hydrogenation content) of 22-43% by mass, a weight-average molecular weight (Mw) of 50,000 and an iodine value of 15-38. However, further improvements are desired, such as improved stability of the conductive material dispersion, improved peel strength and warping characteristics of electrodes, capacitance characteristics and cycle characteristics in electrochemical elements, and suppression of gas generation during high-temperature storage. Furthermore, low ash content of hydrogenated nitrile rubber is also desired.

[0008] Patent Document 4 (WO2023 / 162835) discloses an electrochemical element composition that is excellent in terms of electrode flexibility and suppression of cracking of electrode active material, comprising a polymer containing a nitrile group-containing monomer unit, a conjugated diene monomer unit and / or alkylene structural unit, and having a functional group such as a carboxyl group, a trimethoxysilyl group, or a hydroxyl group at at least one terminal. Specifically, the polymer is prepared by (1) charging a reactor with deionized water, monomer components of 33 parts acrylonitrile and 67 parts 1,3-butadiene, potassium oleate as an emulsifier, and tert-dodecyl mercaptan (0.3 parts) as a molecular weight modifier, and carrying out emulsion polymerization at 5°C in the presence of potassium persulfate as a polymerization initiator until the polymerization conversion rate reaches 89%. (2) After adding dibutylhydroxytoluene (BHT) as an antioxidant to the obtained polymerization solution, (3) adding a 25% by mass aqueous calcium chloride solution while stirring to coagulate the polymer, washing it with 50 times the volume of deionized water, and then drying it under reduced pressure at 90°C to obtain a precursor (nitrile rubber) with a weight-average molecular weight of 210,000. Next, (4) the obtained precursor is dissolved in monochlorobenzene, and after adding Grubbs catalyst and ((tricyclohexylphosphine)benzylidene ruthenium), a double decomposition reaction is carried out at 80°C and a stirring speed of 600 rpm. Then, (5) Wilkinson catalyst and triphenylphosphine are added, and a hydrogenation reaction is carried out at 138°C and a hydrogen pressure of 8.4 MPa. (6) After activating carbon treatment to adjust the concentration of divalent or higher metal ions and remove residual chain transfer agents, the material is filtered and dried to obtain (7) hydrogenated nitrile rubber with a weight-average molecular weight of 48,000, an iodine value of 13, and a concentration of divalent or higher metal ions of 200 ppm or less. However, further improvement of the capacitance characteristics, cycle characteristics, and high-temperature storage characteristics of the electrochemical element, as well as a reduction in the ash content in the hydrogenated nitrile rubber, is desired.

[0009] On the other hand, as a low-ash hydrogenated nitrile rubber, for example, Patent Document 5 (WO2007 / 049651) discloses a carboxyl group-containing nitrile rubber that provides crosslinked structures with low compression set and dynamic heat generation, and exhibits excellent processability as a material for rubber products for industrial and automotive use. This rubber has an α,β-ethylenically unsaturated nitrile monomer unit content of 10 to 60% by mass, an iodine value of 120 or less, and a total amount of magnesium, calcium, and aluminum of 2000 ppm or less. Specifically, (1) acrylonitrile, mono-n-butyl fumarate, butadiene, sodium dodecylbenzenesulfonate, t-dodecyl mercaptan (0.5 parts), and cumene hydroperoxide are added and emulsion polymerization is carried out at 5°C for 16 hours. Then (2) a palladium catalyst is added to the obtained polymerization solution to perform a hydrogenation reaction. A magnesium sulfate aqueous solution (pH 4) is added to the latex of the nitrile group-containing saturated copolymer rubber to perform a coagulation reaction. (3) After coagulation, the crumb is filtered and washed with water three times, then centrifuged to remove the magnesium sulfate aqueous solution contained in the rubber, and vacuum dried at 60°C for 12 hours. (4) A nitrile rubber is obtained with an acrylonitrile unit content of 34%, an iodine value of 9, a ML viscosity of 85, a magnesium content of 1-2 ppm, a calcium content of 1 ppm, and an aluminum content of 1 ppm or less. However, even when attempting to use the nitrile rubber obtained here for the manufacture of electrochemical elements, it was inferior in terms of the dispersibility and stability of the conductive material dispersion, the peel strength at the electrodes, and the battery capacity characteristics, battery resistance characteristics, and cycle characteristics of the electrochemical element. Furthermore, it exhibited an increase in resistance during high-temperature storage, making it unsuitable as an electrode binder for lithium-ion secondary batteries.

[0010] Furthermore, Patent Document 6 (JP 2018-145434 A) discloses a low-ash hydrogenated nitrile rubber useful for sealing materials, hose materials, and transmission belts in the automotive field. Specifically, (1) acrylonitrile and 1,3-butadiene are charged, and polymerization auxiliary materials such as the sodium salt of a mixture of mono- and di-sulfonated naphthalene sulfonic acid having isobutylene oligomer substituents, the sodium salt of methylenebis(naphthalene sulfonate), tert-dodecyl mercaptan (0.66-0.88 in two separate additions), potassium salt of coconut fatty acid, and potassium hydroxide are added, and potassium peroxodisulfate and tris(α-hydroxyethyl)amine are added as polymerization catalysts and emulsion polymerization is carried out at 20°C until the polymerization conversion rate reaches 75%, and (2) 4-methyl-2,6-tert-butylphenol (BHT) is added to the obtained polymerization solution, and then an aqueous sodium chloride solution or magnesium chloride solution is prepared with tap water containing calcium ions. After adding a calcium aqueous solution and allowing it to solidify, (3) it is washed at 60°C with tap water containing calcium ions, pre-dried with a welding screw to a residual moisture content of 15-25% by weight, and then vacuum-dried to obtain NBR with an acrylonitrile content of 38.6-38.8% by weight, a calcium content of 285-595 ppm, a chlorine content of 190-590 ppm, and a (calcium content / chlorine content) ratio of 0.95-1.87. Then, (4) the obtained NBR is dissolved in chlorobenzene and hydrogenated to a hydrogenation level of 99.4±0.2% with a rhodium-based catalyst, and (5) the chlorobenzene-polymer solution is diluted to remove the rhodium, and then a 2% calcium chloride aqueous solution and a dilute sodium hydroxide aqueous solution are continuously added by metering to carry out the solidification reaction and obtain hydrogenated nitrile rubber. However, even when the hydrogenated nitrile rubber obtained here was used in the manufacture of electrochemical elements, it exhibited poor dispersibility in conductive material dispersions, resulting in inferior battery capacity characteristics, battery resistance characteristics, and cycle characteristics of the electrochemical elements. Furthermore, it experienced an increase in resistance during high-temperature storage, making it unsuitable as an electrode binder for lithium-ion secondary batteries. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Publication WO2013 / 129658 Patent Document 2 Publication WO2022 / 163321 Patent Document 3 Publication WO2019 / 181869 Patent Document 4 Publication WO2023 / 162835 Patent Document 5 Publication WO2007 / 049651 Patent Document 6 Japanese Unexamined Patent Publication No. 2018-145434 Summary of the Invention Problems to be Solved by the Invention

[0012] The present invention has been made in view of such circumstances, and an object thereof is to provide a low-ash hydrogenated nitrile rubber that is excellent in the dispersibility and stability of a conductive material dispersion liquid, and provides an electrochemical element excellent in resistance characteristics, output characteristics, cycle characteristics and high-temperature storage characteristics, a method for producing the same, as well as a positive electrode material, a positive electrode binder, a conductive material dispersion liquid, a positive electrode slurry, a positive electrode and an electrochemical element using the hydrogenated nitrile rubber. Means for Solving the Problems

[0013] As a result of intensive research in view of the above problems, the present inventors have found that a hydrogenated nitrile rubber comprising acrylonitrile polymerized units and 1,3-butadiene polymerized units, having a reduced weight average molecular weight (Mw) and a reduced iodine value, an increased ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn), and a reduced ash content can improve the dispersibility and stability of the conductive material dispersion liquid in the production of an electrochemical element, and can significantly improve the resistance characteristics, output characteristics, cycle characteristics and high-temperature storage characteristics of the electrochemical element.

[0014] The present inventors have found that when the molecular weight of hydrogenated nitrile rubber is reduced to lower the iodine value, the resulting hydrogenated nitrile rubber is excellent in the dispersibility and stability of the conductive material dispersion liquid, and can significantly improve the resistance characteristics and cycle characteristics of the electrochemical element.

[0015] The inventors have also found that by reducing the molecular weight of hydrogenated nitrile rubber and increasing its Mw / Mn ratio, the dispersibility of the conductive material dispersion is improved, and the resistance and output characteristics of the electrochemical element can be significantly enhanced. The inventors have found that when hydrogenating nitrile rubber after double decomposition produces low molecular weight hydrogenated nitrile rubber, the Mw / Mn ratio decreases and the output characteristics of the electrochemical element deteriorate. However, they have found that by producing nitrile rubber with a high Mw / Mn ratio and then performing a double decomposition reaction and hydrogenating it, hydrogenated nitrile rubber with a low molecular weight and a high Mw / Mn ratio can be produced. The inventors have also found that the Mw / Mn ratio of nitrile rubber can be adjusted by increasing the polymerization temperature and polymerization conversion rate in the emulsion polymerization process.

[0016] The inventors have also found that low molecular weight, low ash hydrogenated nitrile rubber significantly improves the dispersibility of conductive material dispersions, and significantly improves the capacitance characteristics, resistance characteristics, and high-temperature storage characteristics of electrochemical elements. The inventors have found that low molecular weight, low ash hydrogenated nitrile rubber is difficult to produce because it is difficult to remove ash from hydrogenated nitrile rubber that has become low molecular weight and highly viscous. Furthermore, hydrogenation of nitrile rubber is performed in an organic solvent such as monochlorobenzene and obtained in a cement state. Although it is possible to remove catalyst components dissolved in the organic solvent using ion exchange resins or activated carbon, it is difficult to remove salt compounds with high calcium and sulfur content. However, they have found that it is possible to easily produce low-ash hydrogenated nitrile rubber by first reducing the ash content at the stage of high molecular weight nitrile rubber before hydrogenation, and then further reducing the molecular weight by double decomposition before hydrogenation.

[0017] The inventors have found that while the ash content in high molecular weight nitrile rubber can be reduced to some extent by known methods, further reduction becomes difficult once the ash content in nitrile rubber falls below 1% by mass. However, they have discovered that by adding the emulsion polymerized polymer to a rapidly rotating solidifying liquid during the solidification reaction after emulsion polymerization, particularly by adding the emulsion polymerized polymer directly to the central stirring blade rotating at high speed, the resulting water-containing crumbs facilitate the removal of ash during washing and dewatering processes at specific temperatures. In particular, dewatering to a water content of 10% by mass or less significantly reduces the ash content in the nitrile rubber. Furthermore, the inventors have found that the water-containing crumbs produced by the above specific solidification method have a specific particle size distribution, a complex shape, and often a large hollow structure in the center. This significantly improves washing and dewatering efficiency (ash removal from the crumbs), enabling the production of low-ash nitrile rubber.

[0018] The inventors also found that differences in the ash content of nitrile rubber have different effects on the performance of hydrogenated nitrile rubber when used in the manufacture of electrochemical elements.

[0019] We found that ash high in sodium and potassium cannot be removed by ordinary washing alone because it is inherent in the water-containing crumb produced during solidification, as many sodium and potassium salts are used as polymerization auxiliary materials. It remains in the nitrile rubber and also in hydrogenated nitrile rubber, and when used in the manufacture of electrochemical elements, it destroys the negative electrode active material and significantly reduces the capacitance characteristics of the electrochemical element.

[0020] We found that ash rich in calcium and sulfur remains until the end when the water-containing crumb with the above-mentioned special shape and particle size distribution is washed with hot water or dehydrated with a squeezer, but it has almost no effect on reducing the capacitance characteristics of the electrochemical element, and its effect on worsening high-temperature storage is smaller than that of ash rich in sodium and potassium, and moreover, it has the property of strengthening the peel strength of the electrode.

[0021] The inventors have also found that differences in the total ratio of calcium and sulfur in the ash content of hydrogenated nitrile rubber, the total ratio of sodium and potassium, the ratio of calcium to sulfur, the ratio of calcium to chlorine, the ratio of sulfur to chlorine, and the ratio of the total amount of sodium and potassium to the total amount of calcium and sulfur have different effects on the peel strength of electrodes, the capacitance characteristics of electrochemical elements, and the high-temperature storage characteristics. Furthermore, the inventors have found that when alkali metal salts such as sodium and potassium, sulfates, or sulfonates are used as polymerization auxiliary materials, the amount of ash remaining in the hydrogenated nitrile rubber differs, affecting the various characteristics of the electrochemical elements.

[0022] The inventors have further discovered that by specifying the proportion of acrylonitrile polymerization units, the proportion of 1,2-units in 1,3-butadiene polymerization units, the antioxidant content, polymer pH, water content, and the proportions of sodium and potassium, calcium and sulfur, rhodium and ruthenium, and phosphorus in the ash, the ratio of the total amount of sodium and potassium to the total amount of calcium and sulfur, the ratio of calcium to chlorine, the ratio of calcium to sulfur, and the ratio of sulfur to chlorine, the dispersibility and stability of the conductive material dispersion, and the resistance characteristics, cycle characteristics, and high-temperature storage characteristics of the electrochemical element, the dispersibility and stability of the conductive material dispersion can be further improved.

[0023] Based on these findings, the inventors have completed the present invention.

[0024] Thus, according to the present invention, a hydrogenated nitrile rubber is provided which comprises acrylonitrile polymerization units and 1,3-butadiene polymerization units, wherein the 1,3-butadiene polymerization units consist of 1,2-bonding units, 1,4-bonding units and their hydride units, the weight-average molecular weight (Mw) is 100,000 or less, the ratio of polymerization average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) is 2.5 or more, the iodine value is 100 mg / 100 mg or less, the ash content is 0.7 mass% or less, and the ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)) is 0.2 or less.

[0025] In the hydrogenated nitrile rubber of the present invention, it is preferable that the ash content is 0.5% by mass or less.

[0026] In the hydrogenated nitrile rubber of the present invention, it is preferable that the ash content is 0.01% by mass or more.

[0027] In the hydrogenated nitrile rubber of the present invention, it is preferable that the total ratio of acrylonitrile polymerization units and 1,3-butadiene polymerization units is 70 to 100% by mass.

[0028] In the hydrogenated nitrile rubber of the present invention, it is preferable that the proportion of the acrylonitrile polymerization units is 28% by mass or more and 45% by mass or less.

[0029] In the hydrogenated nitrile rubber of the present invention, it is preferable that the content of the antioxidant is in the range of 0.001 to 2% by mass.

[0030] In the hydrogenated nitrile rubber of the present invention, the polymer pH is preferably in the range of 4.5 to 6.

[0031] In the hydrogenated nitrile rubber of the present invention, it is preferable that the total ratio of calcium content (Ca) and sulfur content (S) in the ash (Ca+S) is 30% by mass or more.

[0032] In the hydrogenated nitrile rubber of the present invention, it is preferable that the total ratio of sodium content (Na) and potassium content (K) in the ash (Na+K) is 20% by mass or less.

[0033] In the hydrogenated nitrile rubber of the present invention, it is preferable that the ratio of calcium content (Ca) to chlorine content (Cl) in the ash (Ca / Cl) is 1.5 or more.

[0034] In the hydrogenated nitrile rubber of the present invention, it is preferable that the ratio of sulfur content (S) to chlorine content (Cl) in the ash (S / Cl) is 1.5 or more.

[0035] In the hydrogenated nitrile rubber of the present invention, it is preferable that the ratio of calcium content (Ca) to sulfur content (S) in the ash (Ca / S) is 3 or less.

[0036] In the hydrogenated nitrile rubber of the present invention, it is preferable that the weight-average molecular weight (Mw) is 10,000 or more.

[0037] In the hydrogenated nitrile rubber of the present invention, it is preferable that the ratio of the total amount (Rh+Ru) of rhodium content (Rh) and ruthenium content (Ru) in the ash is 10% by mass or less.

[0038] In the hydrogenated nitrile rubber of the present invention, it is preferable that the phosphorus content (P) ratio in the ash is 10% by mass or less.

[0039] In the hydrogenated nitrile rubber of the present invention, it is preferable that the water content is less than 1% by mass.

[0040] In the hydrogenated nitrile rubber of the present invention, it is preferable that the polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride is hydrogenated.

[0041] In the hydrogenated nitrile rubber of the present invention, it is preferable that the polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using an alkali metal salt as a polymerization auxiliary material is hydrogenated.

[0042] In the hydrogenated nitrile rubber of the present invention, it is preferable that a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene is hydrogenated using sulfate and / or sulfonate as polymerization auxiliary materials.

[0043] In the hydrogenated nitrile rubber of the present invention, it is preferable that at least one salt compound selected from the group consisting of alkali metal salts, sulfates, and sulfonates is used as a polymerization auxiliary material, and that the polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride is hydrogenated.

[0044] The present invention also provides a method for producing hydrogenated nitrile rubber, which comprises acrylonitrile polymerization units and 1,3-butadiene polymerization units, has a ratio of average polymerization molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) of 2.5 or more, an ash content of 0.7% by mass or less, and a ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)) of 0.2 or less.

[0045] In the method for producing hydrogenated nitrile rubber of the present invention, it is preferable that the shape of the nitrile rubber is veil-like.

[0046] In the method for producing hydrogenated nitrile rubber of the present invention, it is preferable to hydrogenate the nitrile rubber after double decomposition.

[0047] In the method for producing hydrogenated nitrile rubber of the present invention, it is preferable that the hydrogenated nitrile rubber is the above-mentioned hydrogenated nitrile rubber.

[0048] The present invention also provides a positive electrode material comprising the above-mentioned hydrogenated nitrile rubber.

[0049] The present invention also provides a positive electrode binder obtained by dissolving the above-mentioned hydrogenated nitrile rubber in N-methylpyrrolidone (NMP).

[0050] The present invention also provides a conductive material dispersion liquid obtained by dissolving or dispersing the above-mentioned hydrogenated nitrile rubber and conductive material in N-methylpyrrolidone (NMP).

[0051] The present invention also provides a slurry for a positive electrode obtained by dissolving or dispersing a positive electrode active material, a conductive material, and the above-mentioned hydrogenated nitrile rubber in N-methylpyrrolidone (NMP).

[0052] The present invention also provides a positive electrode comprising the above-mentioned hydrogenated nitrile rubber.

[0053] The present invention further provides an electrochemical element comprising the above-mentioned hydrogenated nitrile rubber. [Effects of the Invention]

[0054] The present invention provides a low-ash hydrogenated nitrile rubber that enhances the dispersibility and stability of conductive material dispersions and improves the resistance characteristics, output characteristics, cycle characteristics, and high-temperature storage characteristics of electrochemical elements, as well as a method for producing the same, and a positive electrode material, a positive electrode binder, a conductive material dispersion, a positive electrode slurry, a positive electrode, and an electrochemical element using hydrogenated nitrile rubber. [Brief explanation of the drawing]

[0055] [Figure 1] This figure shows an example of a hydrogenated nitrile rubber manufacturing system according to an embodiment of the present invention. [Modes for carrying out the invention]

[0056] Embodiments of the present invention will be described in detail below.

[0057] <Hydrogenated nitrile rubber> The hydrogenated nitrile rubber of the present invention is characterized by comprising acrylonitrile polymerization units and 1,3-butadiene polymerization units, wherein the 1,3-butadiene polymerization units consist of 1,2-bonding units, 1,4-bonding units and their hydride units, having a weight-average molecular weight (Mw) of 100,000 or less, a ratio of polymerization average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) of 2.5 or more, an iodine value of 100 mg / 100 mg or less, an ash content of 0.7 mass% or less, and a ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)) of 0.2 or less.

[0058] (Repeating unit) The hydrogenated nitrile rubber of the present invention comprises acrylonitrile polymerization units and 1,3-butadiene polymerization units, wherein the 1,3-butadiene polymerization units consist of 1,2-bonding units, 1,4-bonding units, and their hydride units. Such hydrogenated nitrile rubber is a component that can function as a binder in the electrode composite layer formed in an electrochemical element, holding electrode active materials and the like from the current collector without detaching them. Furthermore, such hydrogenated nitrile rubber can also function as a dispersant in a conductive material dispersion containing a conductive material, capable of dispersing the conductive material.

[0059] The proportion of acrylonitrile polymerization units in the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 10% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 28% by mass or more, most preferably 30% by mass or more, and usually 60% by mass or less, preferably 55% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, and most preferably 40% by mass or less. When the acrylonitrile polymerization units in the hydrogenated nitrile rubber are within this range, it is preferable because it improves the dispersibility of the conductive material dispersion and enhances the cycle characteristics of the electrochemical element.

[0060] The proportion of 1,3-butadiene polymerization units in the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, most preferably 60% by mass or more, and usually 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, most preferably 70% by mass or less. The 1,3-butadiene polymerization units in the hydrogenated nitrile rubber refer to the total number of unhydrogenated and hydrogenated units of 1,3-butadiene polymerization units, that is, the total number of 1,2-bonding units, 1,4-bonding units and their hydride units.

[0061] The total ratio of acrylonitrile polymerization units and 1,3-butadiene polymerization units in the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually in the range of 70 to 100% by mass, preferably 80 to 100% by mass, more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and most preferably 97 to 100% by mass.

[0062] The total ratio of 1,2-bonding units and their hydride units in the 1,3-butadiene polymerization unit of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, or preferably in the order of 7% by mass or more, 8% by mass or more, 9% by mass or more, 9.5% by mass or more, 10% by mass or more, 10.5% by mass or more, 11% by mass or more, 11.5% by mass or more, 12% by mass or more, 12.5% ​​by mass or more, and 13% by mass or more. When the ratio is within this range, the warpage characteristics of the electrode and the capacitance characteristics of the electrochemical element can be greatly improved.

[0063] The upper limit of the total ratio of 1,2-bonding units and their hydride units in the 1,3-butadiene polymerization unit of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, or preferably in the order of 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 19% by mass or less, 18% by mass or less, 17% by mass or less, 16% by mass or less, and 15% by mass or less, which can increase the flexibility of the manufactured electrode. The ratio of 1,2-bonding units and their hydride units in the 1,3-butadiene polymerization unit is not particularly limited and can be appropriately adjusted based on the iodine value of the hydrogenated nitrile rubber.

[0064] The hydrogenated nitrile rubber of the present invention may contain, as necessary, other repeating units in addition to the acrylonitrile polymerization units and 1,3-butadiene polymerization units described above. There are no particular limitations on the other repeating units, but for example, polar group-containing monomer units are preferably used.

[0065] There are no particular limitations on the polar group of the polar group-containing monomer unit, but examples include epoxy groups, acetoacetoxyalkyl groups, diester dicarboxylic acid groups, and acidic groups, with acidic groups being preferred.

[0066] Examples of epoxy group-containing monomers that can form epoxy group-containing monomer units include glycidyl methacrylate and glycidyl acrylate, with glycidyl methacrylate being preferred. Examples of acetoacetoxyalkyl group-containing monomers include acetoacetoxyethyl methacrylate. Examples of diester dicarboxylic acid group-containing monomers include dibutyl maleate.

[0067] Examples of acidic group-containing monomers that can form acidic group-containing monomer units include carboxylic acid group-containing monomers, sulfonic acid group-containing monomers, and phosphate group-containing monomers, among which carboxylic acid group-containing monomers are preferred.

[0068] Examples of monomers containing a carboxylic acid group include monocarboxylic acids, dicarboxylic acids and their acid anhydrides, with monocarboxylic acids being preferred. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, monobutyl maleate, and monododecyl maleate, with methacrylic acid, acrylic acid, and monobutyl maleate being preferred, and methacrylic acid being more preferred. Examples of dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid.

[0069] Examples of monomers containing sulfonic acid groups include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl 2-(meth)acrylate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-alyloxy-2-hydroxypropanesulfonic acid. Examples of monomers containing phosphate groups include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate.

[0070] These other repeating units can be used individually or in combination of two or more types. There are no particular limitations on the content of these other repeating units in the hydrogenated nitrile rubber, but it is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and most preferably 3% by mass or less.

[0071] (characteristic) The hydrogenated nitrile rubber of the present invention contains the above repeating units and has properties such as a specific weight-average molecular weight (Mw), a specific ratio of polymerization-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn), a specific iodine value, and reduced ash content of a specific component.

[0072] The weight-average molecular weight (Mw) of the hydrogenated nitrile rubber of the present invention is 100,000 or less, preferably 90,000 or less, more preferably 80,000 or less, even more preferably 70,000 or less, and most preferably 60,000 or less. When the Mw of the hydrogenated nitrile rubber is in this range, the dispersibility of conductive materials is significantly improved, and the resistance characteristics of the manufactured electrochemical elements can be enhanced. There is no particular lower limit to the Mw of the hydrogenated nitrile rubber, but it is usually 1,000 or more, preferably 5,000 or more, more preferably 10,000 or more, even more preferably 20,000 or more, and most preferably 30,000 or more, and when the weight-average molecular weight (Mw) is in this range, the peel strength of the obtained electrodes can be enhanced.

[0073] In the hydrogenated nitrile rubber of the present invention, when the weight-average molecular weight (NMP-Mw) measured using N-methylpyrrolidone (NMP) as a solvent and the weight-average molecular weight (THF-Mw) measured using tetrahydrofuran (THF) as a solvent satisfy the relationship NMP-Mw ≥ THF-Mw, the dispersibility and stability of the conductive material dispersion using NMP as a solvent can be greatly improved.

[0074] The ratio (NMP-Mw / THF-Mw) of the weight-average molecular weight (NMP-Mw) of the hydrogenated nitrile rubber of the present invention, measured using N-methylpyrrolidone (NMP) as a solvent, to the important average molecular weight (THF-Mw) measured using tetrahydrofuran (THF) as a solvent, is not particularly limited, but is usually 1 or more, preferably 1.01 or more, more preferably 1.02 or more, even more preferably 1.05 or more, and most preferably 1.1 or more. The upper limit is not particularly limited, but is usually 3 or less, preferably 2.5 or less, more preferably 2.2 or less, even more preferably 2 or less, and most preferably 1.5 or less. When the NMP-Mw / THF-Mw of the hydrogenated nitrile rubber is within this range, the dispersibility and stability of the conductive material dispersion using NMP as a solvent can be greatly improved.

[0075] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the hydrogenated nitrile rubber of the present invention is 2.5 or higher, preferably 2.6 or higher, more preferably 2.7 or higher, even more preferably 2.8 or higher, particularly preferably 2.9 or higher, and most preferably 3 or higher. When the ratio is within this range, the output characteristics of the electrochemical element can be significantly improved. There is no particular limit to the upper limit of the Mw / Mn of the hydrogenated nitrile rubber, but it is usually 7 or lower, preferably 6 or lower, more preferably 5 or lower, or preferably 4.7 or lower, 4.5 or lower, 4.3 or lower, 4 or lower, 3.9 or lower, 3.8 or lower, 3.7 or lower, 3.6 or lower, and 3.5 or lower in that order, which can improve the cycle characteristics of the electrochemical element.

[0076] The ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 1.5 or higher, preferably 1.6 or higher, more preferably 1.7 or higher, or preferably in the order of 1.8 or higher, 1.9 or higher, 2 or higher, 2.1 or higher, 2.2 or higher, and 2.3 or higher, and is usually 7 or lower, preferably 6 or lower, more preferably 5 or lower, or preferably in the order of 4.5 or lower, 4 or lower, 3.5 or lower, and 3 or lower. When the Mz / Mw of the hydrogenated nitrile rubber is within this range, the dispersibility of the conductive material dispersion, the peel strength of the electrode, and the resistance characteristics of the electrochemical element can be improved.

[0077] The iodine value of the hydrogenated nitrile rubber of the present invention is 100 mg / 100 mg or less, preferably 80 mg / 100 mg or less, more preferably 60 mg / 100 mg or less, and preferably 50 mg / 100 mg or less, 40 mg / 100 mg or less, 30 mg / 100 mg or less, 20 mg / 100 mg or less, and 10 mg / 100 mg or less, in that order. The lower limit is usually 0.1 mg / 100 mg or more, preferably 0.5 mg / 100 mg or more, more preferably 1 mg / 100 mg or more, even more preferably 1.5 mg / 100 mg or more, and most preferably 2 mg / 100 mg or more. When the iodine value of the hydrogenated nitrile rubber is within this range, the stability of the conductive material dispersion, the flexibility of the electrodes, and the cycle characteristics of the electrochemical element can be greatly enhanced.

[0078] The ash content of the hydrogenated nitrile rubber of the present invention is 0.7% by mass or less, preferably 0.65% by mass or less, more preferably 0.6% by mass or less, or preferably in the order of 0.55% by mass or less, 0.5% by mass or less, 0.45% by mass or less, 0.4% by mass or less, 0.35% by mass or less, 0.3% by mass or less, 0.25% by mass or less, and 0.2% by mass or less. When the ash content in the hydrogenated nitrile rubber is within this range, it is preferable because it suppresses the increase in resistance when the electrochemical element is stored at high temperatures, and also suppresses the deterioration of capacitance characteristics and cycle characteristics due to the destruction of the negative electrode active material, etc. There is no particular limit to the ash content in hydrogenated nitrile rubber, but it is usually 0.01% by mass or more, preferably 0.02% by mass or more, more preferably 0.03% by mass or more, or preferably in the order of 0.04% by mass or more, 0.05% by mass or more, 0.06% by mass or more, 0.07% by mass or more, 0.08% by mass or more, 0.09% by mass or more, and 0.1% by mass or more, and the hydrogenated nitrile rubber at this level can have its electrode peel strength increased.

[0079] The ratio ((Na+K) / (Ca+S)) of the total amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the hydrogenated nitrile rubber of the present invention to the total amount of calcium (Ca) and sulfur (S) content (Ca+S) is 0.2 or less, preferably 0.15 or less, more preferably 0.1 or less, or preferably 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, and 0.03 or less in that order. When the ratio is within this range, the electrode peel strength is increased, the increase in resistance during high-temperature storage of the electrochemical element is suppressed, and the deterioration of capacitance characteristics and cycle characteristics due to the breakdown of the negative electrode active material is suppressed.

[0080] The total ratio of calcium content (Ca) and sulfur content (S) (Ca+S) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 30% by mass or more, preferably 35% by mass or more, more preferably 40% by mass or more, or preferably in the order of 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, and 90% by mass or more. When the total ratio of calcium content (Ca) and sulfur content (S) (Ca+S) in the ash of the hydrogenated nitrile rubber is within this range, the electrode peel strength is increased, the increase in resistance during high-temperature storage of the electrochemical element is suppressed, and the deterioration of capacitance characteristics and cycle characteristics due to the destruction of the negative electrode active material is suppressed.

[0081] The total ratio of sodium content (Na) and potassium content (K) (Na+K) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, or preferably in the order of 25% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass, 2% by mass or less, and 1% by mass or less. When the total ratio of sodium content (Na) and potassium content (K) (Na+K) in the ash of the hydrogenated nitrile rubber is within this range, the decrease in capacitance characteristics due to the breakdown of the negative electrode active material of the electrochemical element can be suppressed, and the increase in resistance during high-temperature storage can be suppressed.

[0082] The ratio of calcium content (Ca) to sulfur content (S) in the ash of the hydrogenated nitrile rubber of the present invention (Ca / S) is not particularly limited, but is usually 10 or less, preferably 7 or less, more preferably 5 or less, or preferably in the order of 4.5 or less, 4 or less, 3.5 or less, 3 or less, 2.5 or less, 2 or less, 1.5 or less, 1.3 or less, 1.2 or less, and 1.15 or less, and usually 0.1 or more, preferably 0.3 or more, more preferably 0.5 or more, or preferably in the order of 0.6 or more, 0.7 or more, 0.8 or more, and 0.9 or more. When the ratio of calcium content (Ca) to sulfur content (S) in the ash of the hydrogenated nitrile rubber (Ca / S) is within this range, the electrode peel strength is increased, the increase in resistance when the resulting electrochemical element is stored at high temperatures is suppressed, and the decrease in capacitance characteristics due to the destruction of the negative electrode active material, etc., can be suppressed.

[0083] The ratio of calcium content (Ca) to chlorine content (Cl) in the ash of the hydrogenated nitrile rubber of the present invention (Ca / Cl) is not particularly limited, but is usually 0.5 or higher, preferably 0.6 or higher, more preferably 0.7 or higher, or preferably 0.8 or higher, 0.9 or higher, 1 or higher, 1.2 or higher, 1.4 or higher, 1.5 or higher, 1.6 or higher, 1.8 or higher, 2 or higher, 2.5 or higher, 3 or higher, 3.5 or higher, 4 or higher, 5 or higher, 10 or higher, 20 or higher, and 50 or higher in that order, and is usually 100 or lower, preferably 90 or lower, more preferably 80 or lower, even more preferably 75 or lower, and most preferably 70 or lower. When the ratio of calcium content (Ca) to chlorine content (Cl) in the ash of the hydrogenated nitrile rubber (Ca / Cl) is within this range, the electrode peel strength can be increased and the decrease in the cycle characteristics of the resulting electrochemical element can be suppressed.

[0084] The ratio of sulfur content (S) to chlorine content (Cl) in the ash of the hydrogenated nitrile rubber of the present invention (S / Cl) is not particularly limited, but is usually 0.3 or higher, preferably 0.5 or higher, more preferably 0.7 or higher, or preferably in the order of 1 or higher, 1.5 or higher, 2 or higher, 2.5 or higher, 3 or higher, 3.5 or higher, 4 or higher, 4.5 or higher, 5 or higher, 10 or higher, 30 or higher, and 50 or higher, and is usually 100 or lower, preferably 90 or lower, more preferably 80 or lower, even more preferably 75 or lower, and most preferably 70 or lower. When the ratio of sulfur content (S) to chlorine content (Cl) in the ash of the hydrogenated nitrile rubber is within this range, the electrode peel strength is increased, the increase in resistance during high-temperature storage of the electrochemical element is suppressed, and the decrease in capacitance characteristics and cycle characteristics due to the destruction of the negative electrode active material is suppressed.

[0085] The calcium content (Ca) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, most preferably 40% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and most preferably 50% by mass or less. When the calcium content (Ca) in the ash of the hydrogenated nitrile rubber is within this range, the electrode peel strength is increased, the increase in resistance during high-temperature storage of the electrochemical element is suppressed, and the deterioration of capacity characteristics and cycle characteristics due to the destruction of the negative electrode active material is suppressed.

[0086] The sulfur content (S) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, most preferably 25% by mass or more, and usually 80% by mass or less, preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, most preferably 45% by mass or less. When the sulfur content (S) in the ash of the hydrogenated nitrile rubber is within this range, the electrode peel strength is increased, the increase in resistance during high-temperature storage of the electrochemical element is suppressed, and the deterioration of capacity characteristics and cycle characteristics due to the destruction of the negative electrode active material is suppressed.

[0087] The chlorine content (Cl) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, or preferably in the order of 25% by mass or less, 20% by mass or less, 15% by mass or less, and 10% by mass or less. When the chlorine content (Cl) in the ash of the hydrogenated nitrile rubber is within this range, effects such as the cycle characteristics of the electrochemical element and the suppression of resistance increase during high-temperature storage are improved.

[0088] The total amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 1500 ppm or less, preferably 1000 ppm or less, more preferably 800 ppm or less, or preferably in the order of 700 ppm or less, 600 ppm or less, 500 ppm or less, 450 ppm or less, 400 ppm or less, 350 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, 150 ppm or less, and 100 ppm or less. When the total amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the hydrogenated nitrile rubber is within this range, the decrease in battery capacity and cycle characteristics due to the destruction of the negative electrode active material can be suppressed.

[0089] The sodium content (Na) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 700 ppm or less, preferably 500 ppm or less, more preferably 400 ppm or less, or preferably in the order of 350 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, 150 ppm or less, 100 ppm or less, 70 ppm or less, and 50 ppm or less. When the sodium content (Na) in the ash of the hydrogenated nitrile rubber is within this range, the decrease in battery capacity and cycle characteristics due to the destruction of the negative electrode active material can be suppressed.

[0090] The potassium content (K) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 700 ppm or less, preferably 500 ppm or less, more preferably 400 ppm or less, or preferably in the order of 350 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, 150 ppm or less, 100 ppm or less, 70 ppm or less, and 50 ppm or less. When the potassium content (K) in the ash of the hydrogenated nitrile rubber is within this range, the decrease in battery capacity and cycle characteristics due to the destruction of the negative electrode active material can be suppressed.

[0091] The total amount (Ru+Rh) of ruthenium content (Ru) and rhodium content (Rh) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, particularly preferably 0.3% by mass or less, and most preferably 0.1% by mass or less.

[0092] The phosphorus content (P) in the ash of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, particularly preferably 10% by mass or less, and most preferably 5% by mass or less. When the phosphorus content (P) in the ash of the hydrogenated nitrile rubber is within this range, the cycle characteristics of the resulting electrochemical element are improved and it is preferable.

[0093] The polymer pH of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually 2 or higher, preferably 2.5 or higher, more preferably 3 or higher, or preferably in the order of 3.5 or higher, 4 or higher, 4.5 or higher, 4.6 or higher, 4.7 or higher, 4.8 or higher, 4.9 or higher, and 5 or higher, and is usually 8 or lower, preferably 7.5 or lower, more preferably 7 or lower, even more preferably 6.5 or lower, and most preferably 6 or lower. When the pH of the hydrogenated nitrile rubber is within this range, the viscosity stability of the positive electrode slurry can be increased, and the capacitance and resistance characteristics of the electrochemical element can be improved.

[0094] The water content of the hydrogenated nitrile rubber of the present invention is not particularly limited, but is usually less than 1% by mass, preferably 0.8% by mass or less, more preferably 0.7% by mass or less, even more preferably 0.6% by mass or less, and most preferably 0.5% by mass or less.

[0095] The hydrogenated nitrile rubber of the present invention may optionally contain an antioxidant. Including an antioxidant in the hydrogenated nitrile rubber is preferable because it significantly enhances the stability of the conductive material dispersion and the peel strength of the electrodes in the manufacture of electrochemical elements.

[0096] There are no particular limitations on the type of antioxidant that can be included, but examples include amine-based antioxidants and phenol-based antioxidants, with phenol-based antioxidants being preferred. There are no particular limitations on the type of phenol-based antioxidant, but hindered phenol-based antioxidants are particularly preferred, as they can improve the stability of the conductive material dispersion and enhance the electrode peel strength.

[0097] Examples of hindered phenol-based antioxidants include 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-pentenyl-4-methylphenol, 2,2-methylenebis(4-methyl-6-t-butylphenol), 2,4-bis(octylthiomethyl)-6-methylphenol, 2,6-di-t-butyl-α-dimethylamino-p-cresol, and 3-(4-hydroxy-3,5 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate butyl, 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate hexyl, 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate octyl, 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate decyl, 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate dodecyl, 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate butyl Examples include octadecyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, heptyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, dodecyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, octadecyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, 4,4'-methylenebis(2,6-dibutylphenol), 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-ylamino)phenol, and preferably 2,6-di-t-butyl-4-methylphenol (dibutylhydroxytoluene = BHT), 2,2-methylenebis(4-methyl-6-t-butylphenol), and 2,4-bis(octylthiomethyl)-6-methylphenol, with BHT being the most preferred.

[0098] Examples of phenolic antioxidants other than hindered phenolic antioxidants include styrene-phenols such as mono(or di, or tri)(α-methylbenzyl)phenol, butylhydroxyanisole, 2,2'-methylene-bis(4-methyl-6-t-butylphenol), alkylated bisphenols, 2,4-bis[(octylthio)methyl]-6-methylphenol, 2,2'-thiobis-(4-methyl-6-t-butylphenol), and 4,4'-thiobis-(6-t-butyl-o-cresol), with styrene-phenols and 2,4-bis[(octylthio)methyl]-6-methylphenol being preferred.

[0099] These antioxidants can be used individually or in combination of two or more. The content of the antioxidant in the hydrogenated nitrile rubber is not particularly limited, but is usually in the range of 0.001 to 2% by mass, preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, even more preferably 0.1 to 0.5% by mass, and most preferably 0.1 to 0.3% by mass. If the content of the antioxidant in the hydrogenated nitrile rubber is excessively low, the stability of the dispersion with the conductive material and the peel strength of the electrode will be poor, and if it is excessively high, it will affect the cycle characteristics of the electrochemical element.

[0100] The hydrogenated nitrile rubber of the present invention is not limited by the manufacturing process, but it is preferably a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using an alkali metal salt as a polymerization auxiliary material, and then hydrogenated.

[0101] In this specification, polymerization auxiliary materials are materials other than monomers and polymerization initiators used to stably carry out emulsion polymerization, and examples include emulsifiers, pH adjusters, chain transfer agents (molecular weight adjusters), chelating agents, and reducing agents. There are no particular limitations on the alkali metal salts used as polymerization auxiliary materials, but typical examples include potassium fatty acid and sodium dodecylbenzenesulfonate as emulsifiers, as well as sodium salts of mono- and di-sulfonated naphthalene sulfonic acid mixtures having isobutylene oligomer substituents, sodium salts of methylenebis(naphthalene sulfonate), and sodium phosphate as stabilizers. When alkali metal salts such as sodium salts and potassium salts are used as polymerization auxiliary materials, a uniform micelle structure and a uniform polymer can be produced, and the dispersibility and stability of the conductive material dispersion are excellent. However, differences in polymer structure occur that cannot be explained by measurable characteristic values ​​alone, and it is not possible to measure what type or shape of residue remains in the polymer after the polymerization auxiliary materials react. Furthermore, the polymerization auxiliary materials used remain in the crumb formed during the solidification reaction after polymerization and are difficult to remove. However, those using alkali metal salts are preferable because, due to the special crumb shape described later, they are easily removed by washing and dewatering. On the other hand, while the reduction of alkali metal salts from the polymer can be measured by the sodium (Na) and potassium (K) content in the ash, the effect on the properties of hydrogenated hydrogenated nitrile rubber varies greatly depending not only on the amount of Na and K in the ash but also on the type of counteranion, and these cannot be identified.

[0102] The hydrogenated nitrile rubber of the present invention is preferably obtained by hydrogenating a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using sulfates and / or sulfonates as polymerization auxiliary materials.

[0103] Examples of sulfates or sulfonic acids used as polymerization auxiliary materials include emulsifiers such as sodium dodecylbenzenesulfonate, reducing agents such as iron sulfate, sodium salts of mono- and di-sulfonated naphthalene sulfonic acid mixtures having isobutylene oligomer substituents, and sodium salts of methylenebis(naphthalene sulfonate). Polymerization auxiliary materials using sulfates and / or sulfonates are preferred because they are easily removed by cramb washing and dehydration, resulting in minimal impact on the resulting polymer. On the other hand, when examining the ash content in the polymer, it was found that when sulfates and / or sulfonates were used as polymerization auxiliary materials and calcium chloride was used as a coagulant, the ratio of calcium content (Ca) to sulfur content (S) in the ash was high. Furthermore, although the calcium-to-chlorine ratio (Ca / Cl) of the calcium chloride used as a coagulant was 0.565, the ratio of calcium content (Ca) to chlorine content (Cl) in the ash was much larger. It was inferred that during the coagulation reaction, some of the readily soluble calcium chloride was exchanged for acidic salts containing poorly hydrophilic (poorly soluble) sulfur and remained in the polymer. Although it is difficult to remove such poorly hydrophilic salts, by devising the coagulation reaction, washing, and dewatering processes described later, nitrile rubber with reduced poorly hydrophilic salts was obtained. Hydrogenated nitrile rubber obtained by hydrogenating this nitrile rubber suppressed gas generation and deterioration of cycle characteristics due to active material destruction during high-temperature storage of electrochemical elements. It was also found that the presence of poorly hydrophilic salts had the effect of increasing the peel strength of the electrodes. However, the effect of polymers that reduce these poorly hydrophilic salts cannot be explained solely by the calcium (Ca) and sulfur (S) content in the ash, and it is not possible to measure which specific salts are affecting the stability, dispersibility, and various properties of the conductive material dispersion and electrochemical elements.

[0104] The hydrogenated nitrile rubber of the present invention is preferably obtained by hydrogenating a polymer formed by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride.

[0105] When obtaining polymers by coagulating an emulsion polymerization solution, the size, shape, and properties of the resulting water-containing crumbs vary considerably depending on the type of coagulant used. This results in differences in the polymerization auxiliary materials that can be removed in subsequent washing and dehydration steps, as well as the various auxiliary material residues from the coagulation process. Furthermore, it is impossible to identify all trace amounts of these auxiliary materials and their reaction products. In particular, when hydrogenated nitrile rubber is used in electrochemical elements, these small amounts of residue affect various properties. Therefore, for electrochemical element applications, a solution using calcium chloride as a coagulant is preferable because, even if ash remains in the nitrile rubber or hydrogenated nitrile rubber, it exhibits excellent electrode peel strength characteristics and suppresses gas generation during high-temperature storage of the electrochemical element. Additionally, hydrogenated nitrile rubber obtained by hydrogenating nitrile rubber using alkali metal salts, sulfates, or sulfonates (preferably sulfates or sulfonates) as polymerization auxiliary materials and calcium chloride as a coagulant exhibits excellent electrode peel characteristics for electrochemical elements such as lithium-ion secondary batteries, and suppresses deterioration of cycle characteristics and gas generation during high-temperature storage compared to solutions using other coagulants.

[0106] The hydrogenated nitrile rubber of the present invention is preferably obtained by further emulsion polymerization of acrylonitrile and 1,3-butadiene, adding a phenolic antioxidant, and then coagulating with calcium chloride to obtain a polymer, which is then hydrogenated.

[0107] The effectiveness of the above-mentioned specific antioxidant is far superior and preferable in nitrile rubber produced by adding it to an emulsion polymerization solution obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene, rather than by mixing it with the nitrile rubber after production. Although this cannot be measured, it is thought that the phenolic antioxidant exhibits a high effect when the emulsion polymerization solution, in which the phenolic antioxidant is uniformly dispersed, is coagulated with calcium chloride, resulting in uniform and fine dispersion within the resulting nitrile rubber. In this invention, the antioxidant effect of the phenolic antioxidant is higher when added in the polymerization solution containing nitrile rubber after emulsion polymerization, rather than in the reaction solution containing hydrogenated nitrile rubber after hydrogenation. However, it is not possible to measure the state in which the antioxidant is thought to be uniformly dispersed in the nitrile rubber or hydrogenated nitrile rubber.

[0108] <Method for manufacturing hydrogenated nitrile rubber> The method for producing hydrogenated nitrile rubber according to the present invention is not particularly limited, but for example, it can be easily produced by hydrogenating nitrile rubber that contains acrylonitrile polymerization units and 1,3-butadiene polymerization units, has a ratio of the average polymerization molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) of 2.5 or more, has an ash content of 0.7% by mass or less, and has a ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)) of 0.2 or less. In the present invention, the hydrogenation of low-ash nitrile rubber is particularly characterized, and it is preferable to hydrogenate the low-ash nitrile rubber after double decomposition.

[0109] (Nitrile rubber) The nitrile rubber used contains acrylonitrile polymerization units and 1,3-butadiene polymerization units, within a specific MwMn range, and with reduced ash content of specific components.

[0110] The nitrile rubber used has the following characteristics: proportion of acrylonitrile polymerization units, proportion of 1,3-butadiene polymerization units, proportion of 1,2-bonding units (unhydrogenated units + hydride units) in the 1,3-butadiene polymerization units, proportion of other repeating units, ash content, proportion of the sum of calcium content (Ca) and sulfur content (S) in the ash (Ca+S), proportion of sodium content (Na) and potassium content (K) in the ash (Na+K), ratio of the sum of sodium content (Na) and potassium content (K) in the ash (Na+K) to the sum of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)), and calcium content in the ash. The ratio of amount (Ca) to sulfur content (S) (Ca / S), the ratio of sulfur content (S) to chlorine content (Cl) in the ash (S / Cl), the ratio of calcium content (Ca) to sulfur content (S) in the ash (Ca / S), the percentage of calcium content (Ca) in the ash, the percentage of sulfur content (S) in the ash, the percentage of chlorine content (Cl) in the ash, the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K), the sodium content (Na) in the ash, and the potassium content (K) in the ash are the same as those described for hydrogenated nitrile rubber, and these properties of nitrile rubber are largely inherited by hydrogenated nitrile rubber.

[0111] The type and amount of antioxidants contained in the hydrogenated nitrile rubber used are the same as those described for the hydrogenated nitrile rubber, and the amount of antioxidants in the nitrile rubber is almost entirely carried over to the hydrogenated nitrile rubber.

[0112] The weight-average molecular weight (Mw) of the nitrile rubber used is not particularly limited, but is usually in the range of 1,000 or more, preferably 10,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, most preferably 150,000 or more, and 5,000,000 or less, preferably 3,500,000 or less, 2,000,000 or less, more preferably 1,000,000 or less, most preferably 500,000 or less. When the weight-average molecular weight (Mw) of the nitrile rubber is within this range, ash removal from the nitrile rubber becomes easier, and the molecular weight adjustment of the hydrogenated hydrogenated nitrile rubber also becomes easier.

[0113] Furthermore, while there are no particular limitations on the weight-average molecular weight (Mw) of the nitrile rubber that is hydrogenated after double decomposition, it is usually 100,000 or more, preferably 130,000 or more, more preferably 150,000 or more, even more preferably 170,000 or more, and most preferably 200,000 or more.

[0114] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the nitrile rubber used is preferably 2.5 or higher, more preferably 2.6 or higher, more preferably 2.7 or higher, or preferably 2.8 or higher, 2.9 or higher, 3 or higher, 3 or higher, 3.1 or higher. In order of preference, it is preferable to have a ratio of 3.2 or higher, 3.3 or higher, 3.4 or higher, 3.5 or higher, 3.6 or higher, 3.7 or higher, and 3.8 or higher. When the ratio is within this range, the output characteristics of the electrochemical element can be significantly improved. Since the Mw / Mn of nitrile rubber decreases after the double decomposition reaction, it is preferable to set it higher than the preferred Mw / Mn of hydrogenated nitrile rubber. There is no particular upper limit to the Mw / Mn of the nitrile rubber used, but it is usually 7 or lower, more preferably 6 or lower, more preferably 5 or lower, or preferably 4.7 or lower, 4.5 or lower, 4.3 or lower, and 4 or lower, in that order, which improves the cycle characteristics of the electrochemical element.

[0115] The ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) of the nitrile rubber used is not particularly limited, but is usually 1.5 or higher, preferably 1.6 or higher, more preferably 1.7 or higher, or preferably in the order of 1.8 or higher, 2 or higher, 2.3 or higher, 2.5 or higher, 2.8 or higher, 3 or higher, 3.1 or higher, 3.2 or higher, 3.3 or higher, 3.4 or higher, and 3.5 or higher, and is usually 7 or lower, preferably 6 or lower, more preferably 5.5 or lower, or preferably in the order of 5 or lower, 4.7 or lower, 4.5 or lower, 4.3 or lower, and 4 or lower. When the Mz / Mw of the nitrile rubber is within this range, hydrogenated hydrogenated nitrile rubber can improve the dispersibility of the conductive material dispersion, the peel strength of the electrode, and the resistance characteristics of the electrochemical element. Furthermore, if hydrogenation is performed after double decomposition, the Mz / Mw ratio after double decomposition will be smaller. Therefore, it is preferable to set the dispersibility of the conductive material dispersion, the peel strength of the electrode, and the resistance characteristics of the electrochemical element to be greater than the optimal Mz / Mw ratio of the hydrogenated nitrile rubber.

[0116] The polymer pH of the nitrile rubber used is not particularly limited, but is usually 2 or higher, preferably 2.5 or higher, more preferably 3 or higher, or preferably 3.5 or higher, 4 or higher, 4.5 or higher, 4.6 or higher, 4.7 or higher, 4.8 or higher, 4.9 or higher, and 5 or higher in that order, and is usually 8 or lower, preferably 7.5 or lower, more preferably 7 or lower, even more preferably 6.5 or lower, and most preferably 6 or lower. The change in polymer pH is small in the hydrogenation reaction carried out in an organic solvent, and the polymer pH of the nitrile rubber is inherited by the hydrogenated hydrogenated nitrile rubber. When the polymer pH of the nitrile rubber is within this range, the viscosity stability of the conductive material dispersion of the hydrogenated hydrogenated nitrile rubber is increased, and the capacitance characteristics and resistance characteristics of the electrochemical element can be improved.

[0117] There are no particular limitations on the water content of the nitrile rubber used, but it is usually less than 1% by mass, preferably 0.8% by mass or less, more preferably 0.7% by mass or less, even more preferably 0.6% by mass or less, and most preferably 0.5% by mass or less. When the water content of the nitrile rubber is within this range, the double decomposition reaction and hydrogenation reaction in the organic solvent can be carried out easily.

[0118] There are no particular limitations on the shape of the nitrile rubber used, but a veil shape is preferable because it offers excellent storage stability and the gelation inhibition effect is enhanced when an anti-aging agent is included. There are no particular limitations on the size of the veil-shaped nitrile rubber, but the width is usually in the range of 100 to 800 mm, preferably 200 to 500 mm, more preferably 250 to 450 mm; the length is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, more preferably 500 to 800 mm; and the height is usually in the range of 50 to 500 mm, preferably 100 to 300 mm, more preferably 150 to 250 mm.

[0119] When performing a hydrogenation reaction using bale-shaped nitrile rubber, it can be carried out by dissolving it in the solvent used for the hydrogenation reaction.

[0120] (Method of manufacturing nitrile rubber) The nitrile rubber used in the method for producing hydrogenated nitrile rubber of the present invention is not limited by the manufacturing method, but the nitrile rubber produced by the following manufacturing method is preferably used, and will be described in detail below.

[0121] The low-ash nitrile rubber used can be easily produced, for example, by emulsion polymerization of monomer components containing acrylonitrile and 1,3-butadiene, adding an antioxidant as needed to the emulsion polymerization solution, and then contacting it with an aqueous calcium chloride solution to produce a hydrated crumb that satisfies all of the following conditions (a) to (e). The produced hydrated crumb is then washed, dehydrated, and dried. (a) The percentage of water-containing crumbs that do not pass through a JIS sieve with a mesh size of 9.5 mm is 10% by mass or less. (b) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 9.5 mm but do not pass through a JIS sieve with a mesh size of 8 mm is 25% by mass or less. (c) The percentage of water-containing crumbs that pass through a JIS sieve with an 8 mm mesh opening but do not pass through a JIS sieve with an 1.7 mm mesh opening is 50% by mass or more. (d) The percentage of water-containing crumbs that pass through a 1.7 mm mesh sieve but not through a 0.43 mm mesh JIS sieve is 25% by mass or less, (e) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh opening of 0.43 mm is 10% by mass or less.

[0122] Furthermore, a nitrile rubber with even lower ash content can be produced when 30% or more of the generated water-containing crumb is (f) water-containing crumb that passes through a JIS sieve with a mesh size of 4.75 mm but does not pass through a JIS sieve with a mesh size of 2.36 mm.

[0123] —Monomer components— The monomer components used are the same as those described for the monomer components of the repeating units, and the amounts used should be appropriately selected to achieve the monomer composition described above.

[0124] -Emulsion polymerization process- There are no particular limitations on the emulsifiers used in emulsion polymerization; they are selected according to conventional methods. Examples include salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as dodecylbenzenesulfonic acid; sulfate esters such as sodium lauryl sulfate; phosphate esters such as polyoxyalkylene alkyl ether phosphates; and alkyl sulfosuccinates. Among these, fatty acid salts, alkylbenzene sulfonates, and sulfate esters are preferred, with fatty acid salts and alkylbenzene sulfonates being particularly preferred.

[0125] Examples of salts such as fatty acid salts, alkylbenzene sulfonates, sulfate esters, and phosphate esters mentioned above include alkali metal salts and ammonium salts, with alkali metal salts being preferred, and sodium salts and potassium salts being particularly preferred. Specific examples of emulsifiers include potassium oleate, sodium oleate, potassium palmitate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, sodium laureth sulfate, sodium polyoxyethylene alkyl sulfate, and sodium polyoxyethylene alkylaryl sulfate, with potassium oleate and sodium dodecylbenzenesulfonate being preferred.

[0126] These emulsifiers can be used individually or in combination of two or more, and the amount used is usually in the range of 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of monomer component.

[0127] The method for mixing the monomer component, emulsifier, and water can be done according to conventional methods, such as stirring the monomer, emulsifier, and water using a homogenizer or a stirrer such as a disk turbine. The amount of water used is usually in the range of 10 to 750 parts by mass, preferably 50 to 500 parts by mass, and more preferably 100 to 400 parts by mass, per 100 parts by mass of the monomer component.

[0128] In addition to the emulsifiers mentioned above, known polymerization auxiliary materials used in emulsion polymerization can be used after being appropriately optimized. Specifically, various polymerization regulators such as molecular weight regulators (chain transfer agents), pH regulators, stabilizers, and reducing agents and chelating agents in redox catalysts can be used.

[0129] There are no particular limitations on the polymerization initiator used in emulsion polymerization, as long as it is one that is commonly used in emulsion polymerization; for example, a radical generator can be used.

[0130] Examples of radical generators include peroxides and azo compounds, with peroxides being preferred. Inorganic or organic peroxides are used. Organic peroxides are preferred to increase the number of 1,2-bond units in the 1,3-butadiene polymerization units of nitrile rubber.

[0131] Examples of inorganic peroxides (inorganic polymerization initiators) include sodium persulfate, potassium persulfate, hydrogen peroxide, and ammonium persulfate. Among these, potassium persulfate, hydrogen peroxide, and ammonium persulfate are preferred, with potassium persulfate being particularly preferred.

[0132] As for organic peroxides (organic polymerization initiators), there are no particular limitations as long as they are known to be used in emulsion polymerization. For example, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, 1-di-(t-hexylperoxy)cyclohexane, 1,1-di-(t-butylperoxy)cyclohexane, 4,4-di-(t-butylperoxy)n-butyl valerate, 2,2-di-(t-butylperoxy)butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropyl Examples include pyrubenzene hydroperoxide, paramentane hydroperoxide, benzoyl peroxide, 1,1,3,3-tetraethylbutyl hydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, and dilauroyl peroxide.

[0133] These polymerization initiators can be used individually or in combination of two or more types, and the amount used is usually in the range of 0.0001 to 5 parts by mass, preferably 0.0005 to 1 part by mass, and more preferably 0.001 to 0.5 parts by mass, per 100 parts by mass of monomer component.

[0134] The amount of water used in the emulsion polymerization reaction may be limited to the amount used during the emulsion formation of the monomer components, but it is usually adjusted to be in the range of 10 to 1000 parts by mass, preferably 50 to 500 parts by mass, more preferably 80 to 400 parts by mass, and most preferably 100 to 300 parts by mass, per 100 parts by mass of the monomer components used for polymerization.

[0135] The emulsion polymerization reaction can be carried out according to conventional methods and may be batch, semi-batch, or continuous. The polymerization temperature and polymerization time are not particularly limited and can be appropriately selected depending on the type of polymerization initiator used. The polymerization temperature is usually in the range of 0 to 100°C, preferably 10 to 90°C, more preferably 20 to 80°C, even more preferably 25 to 70°C, and most preferably 30 to 60°C, and the polymerization time is usually 0.5 to 100 hours, preferably 1 to 10 hours. By setting the polymerization temperature higher, the number of 1,2-bonding units in the 1,3-butadiene polymerization units of the nitrile rubber, or the Mw / Mn ratio of the nitrile rubber, can be increased.

[0136] The polymerization conversion rate in the emulsion polymerization reaction is not particularly limited, but is usually 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. Setting a higher polymerization conversion rate can increase the 1,2-bonding units in the 1,3-butadiene polymerization units of the nitrile rubber, or the Mw / Mn ratio of the nitrile rubber. A polymerization inhibitor may be used to stop the polymerization.

[0137] —Anti-aging agent addition process— In this invention, an anti-aging agent is added to the emulsion polymerization solution after the emulsion polymerization described above. Adding the anti-aging agent to the emulsion polymerization solution is preferable because it allows for uniform dispersion of the anti-aging agent in the resulting nitrile rubber or hydrogenated nitrile rubber. Furthermore, adding the anti-aging agent at this stage is preferable because it prevents deterioration reactions during the drying of the nitrile rubber.

[0138] The antioxidant used is the same as the example of the antioxidant contained in the hydrogenated nitrile rubber, and the method of adding the antioxidant to the emulsion polymerization solution is not particularly limited and can be done according to conventional methods. For example, it may be added as is, or it may be added after being emulsified with an emulsifier.

[0139] The amount of antioxidant used can be appropriately selected to match the amount of antioxidant in the hydrogenated nitrile rubber of the present invention, but is typically in the range of 0.001 to 15 parts by mass, preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, particularly preferably 0.3 to 3 parts by mass, and most preferably 0.5 to 2 parts by mass per 100 parts by mass of monomer component.

[0140] -Coagulation process- In the coagulation reaction, an aqueous solution of calcium chloride is used as the coagulation solution, and it is brought into contact with an emulsion polymerization solution to which the above-mentioned antioxidant is added to produce a hydrated crumb.

[0141] The solid content concentration of the emulsion polymerization solution used is not particularly limited, but is usually adjusted to a range of 5 to 50% by mass, preferably 10 to 45% by mass, and more preferably 20 to 40% by mass.

[0142] While there are no particular limitations on the concentration of the coagulation solution used, it is generally preferable to use a concentration of 0.1 to 70% by mass, preferably 1 to 60% by mass, more preferably 5 to 50% by mass, and especially preferably 10 to 30% by mass, as this allows for the concentration of the water-containing crumb particle size within a specific range.

[0143] While there are no particular limitations on the temperature during the coagulation reaction, it is generally preferable to have a temperature of 0°C or higher, preferably 10 to 90°C, and more preferably 20 to 80°C, as this is when a uniform hydrated crumb is produced.

[0144] In this method, it is preferable to add the emulsion polymerization solution to the vigorously agitated coagulation solution to carry out the coagulation reaction, which significantly improves the washing and dewatering efficiency of the resulting water-containing crumb. Furthermore, it is preferable to add the emulsion polymerization solution to the coagulation solution by directly contacting the vigorously agitated blades with the elution process before adding it to the coagulation solution, which also significantly improves the washing and dewatering efficiency of the resulting water-containing crumb. The water-containing crumb produced by this coagulation method is preferable because it significantly improves the washing and dewatering efficiency of the emulsifier and coagulant.

[0145] There are no particular limitations on the rotation speed of the impeller, but it is usually 100 rpm or more, preferably 200 rpm or more, more preferably 300 rpm or more, or preferably 350 rpm or more, 400 rpm or more, 450 rpm or more, 500 rpm or more, and 550 rpm or more in that order, and usually 1000 rpm or less, preferably 900 rpm or less, more preferably 800 rpm or less, even more preferably 750 rpm or less, and most preferably 700 rpm or less. It is preferable that the rotation speed of the impeller is above a certain level and the solidified liquid is vigorously stirred so that the diameter of the water-containing crumbs generated can be made smaller and concentrated in a specific region.

[0146] The peripheral velocity of the agitated solidified liquid is expressed as the linear velocity of the outer circumference of the stirring blade of the agitator. It is preferable for the solidified liquid to be agitated vigorously to a certain extent, as this makes it possible to create smaller and more uniform water-containing cramb diameters. Typically, a peripheral velocity of 0.5 m / s or more is suitable, preferably 1 m / s or more, more preferably 1.5 m / s or more, particularly preferably 2 m / s or more, and most preferably 2.5 m / s or more. There is no particular upper limit to the peripheral velocity of the agitated solidified liquid, but it is generally easier to control the solidification reaction when the peripheral velocity is 50 m / s or less, preferably 30 m / s or less, more preferably 25 m / s or less, and particularly preferably 20 m / s or less.

[0147] As for the resulting water-containing crumbs, for example, when sieving (classification) is performed using a JIS classification sieve under the conditions (a) to (g) below, the proportion of water-containing crumbs with a crumb diameter of 3.35 to 4.75 mm is the highest, which is preferable because it provides a high balance between the efficiency of removal of emulsifiers and coagulants during washing and dewatering and workability.

[0148] As for the resulting water-containing crumb, those that satisfy all of the following conditions (a) to (e) are preferable because they significantly improve the efficiency of removing emulsifiers and coagulants during washing and dewatering.

[0149] (a) The percentage of water-containing crumbs that do not pass through a JIS sieve with a mesh size of 9.5 mm is 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less. (b) The proportion of relatively large water-containing crumbs that pass through a JIS sieve with a mesh size of 9.5 mm but do not pass through a JIS sieve with a mesh size of 8 mm is 25% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and most preferably 5% by mass or less. (c) The percentage of water-containing crumbs that pass through a JIS sieve with an 8 mm mesh opening but do not pass through a JIS sieve with an 1.7 mm mesh opening is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and most preferably 90% by mass or more. (d) The percentage of water-containing crumbs that pass through a 1.7 mm mesh opening but do not pass through a JIS sieve with a 0.43 mm mesh opening is 25% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and most preferably 5% by mass or less. (e) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh opening of 0.43 mm is 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less.

[0150] Furthermore, it is preferable that the resulting hydrated crumb satisfies the following conditions (f) and / or (g). (f) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 4.75 mm but do not pass through a JIS sieve with a mesh size of 2.36 mm is 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and most preferably 70% by mass or more. (g) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 4.75 mm but not through a JIS sieve with a mesh size of 3.35 mm is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and most preferably 30% by mass or more. Furthermore, there is no particular limit to the upper limit of water-containing crumbs in this range, but it is usually 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and most preferably 70% by mass or less.

[0151] The shape of the resulting water-containing crumbs is not particularly limited, but a perforated shape is preferred. In particular, adding the emulsion polymerization solution directly to the central rotating shaft and rotor blades in the vigorously rotating solidifying liquid increases the amount of perforated water-containing crumbs, which is preferable.

[0152] After the solidification process, the resulting water-containing crumb can be washed, dehydrated, and dried to obtain the polymer before hydrogenation.

[0153] -Cleaning process- Using warm water is preferable as a cleaning method. The ideal temperature for the hot water is typically 30°C or higher, preferably 35-100°C, more preferably 40-80°C, even more preferably 40-60°C, and most preferably 40-50°C, as this significantly improves cleaning efficiency. Calcium sulfate and calcium sulfonate salts, for example, are poorly soluble in water and have low solubility, but their solubility tends to increase at certain temperatures. By setting the cleaning water temperature above the aforementioned lower limit, emulsifiers and coagulants are released from the water-containing crumb, further improving cleaning efficiency.

[0154] The hydrated crumb, solidified in a high-concentration coagulation solution (aqueous calcium chloride solution) during the coagulation process, is effectively washed with a large amount of water. The amount of water used is typically 10 to 500 times, preferably 25 to 250 times, and more preferably 50 to 100 times, by mass per 100 parts by mass of polymer.

[0155] There are no particular limitations on the washing time, but it is usually in the range of 1 to 120 minutes, preferably 2 to 60 minutes, and more preferably 3 to 30 minutes.

[0156] -Dehydration process- Washed, water-containing crumb is preferable because dehydration removes polymerization auxiliary materials such as emulsifiers trapped inside the water-containing crumb.

[0157] The water content of the dehydrated crumb is not particularly limited, but is usually 35% by mass or less, preferably 30% by mass or less, more preferably 25% by mass or less, or preferably in the order of 20% by mass or less, 15% by mass or less, 14% by mass or less, 13% by mass or less, 12% by mass or less, 10% by mass or less, 8% by mass or less, and 7% by mass or less.

[0158] There are no particular limitations on the method for dehydrating water-containing crumb, but a method that compresses and dehydrates the crumb using a squeezer or similar device to extract the internal moisture is preferable. On the other hand, dehydration using a centrifuge or similar device is insufficient as it can only reduce the water content of the crumb to about 50-60% by mass.

[0159] The dehydration temperature is not particularly limited, but is usually 30°C or higher, preferably 40°C or higher, more preferably 50°C or higher, or preferably 60°C or higher, 70°C or higher, 80°C or higher, and 90°C or higher in that order. At this temperature range, the water-containing crumb becomes flexible, making it easier to remove moisture containing polymerization auxiliary materials, etc.

[0160] -Drying process- The drying method for the dehydrated crumb can follow conventional methods, and can be performed using dryers such as hot air dryers, vacuum dryers, expander dryers, kneader dryers, and screw extruders.

[0161] The shape of the dried rubber (polymer) is not particularly limited and can be, for example, crumb, powder, rod, or sheet. Furthermore, baling it according to a conventional method provides excellent storage stability and is therefore preferable. The water content of the dried rubber is not particularly limited, but is usually less than 1% by mass, preferably 0.9% by mass or less, more preferably 0.8% by mass or less, even more preferably 0.6% by mass or less, and most preferably 0.5% by mass or less.

[0162] The nitrile rubber thus obtained can, if necessary, be subjected to a double decomposition reaction followed by a hydrogenation reaction to produce hydrogenated nitrile rubber.

[0163] (Double decomposition reaction) The double decomposition reaction of nitrile rubber can be carried out using, for example, the ruthenium catalyst described in Japanese Patent No. 4509792.

[0164] There are no particular limitations on the ruthenium-based catalyst used; any known ruthenium-based catalyst can be used. In particular, it is preferable to use Grubbs catalysts such as bis(tricyclohexylphosphine)benzylideneruthenium dichloride or 1,3-bis(2,4,6-trimethylphenyl)-2-(imidazolidinylidene)(dichlorophenylmethylene)(tricyclohexylphosphine)ruthenium.

[0165] The double decomposition reaction is carried out by dissolving the substance in a solvent in the presence of a coolefin. Examples of coolefins include olefins with 2 to 16 carbon atoms such as ethylene, isobutane, styrene, and 1-hexane, as well as cis-2-butene-1,4-diol, 3-butene-1-amine, vinyltrimethoxysilane, methoxypolyalkylene glycol methacrylate, and 2-(methacryloyloxy)ethanesulfonic acid.

[0166] The amount of coolefin used is typically in the range of 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of polymer.

[0167] The reaction can be carried out in a solvent that does not inactivate the catalyst or interfere with the reaction. Preferred solvents are not limited to dichloromethane, but include, for example, dichloromethane, benzene, toluene, tetrahydrofuran, cyclohexane, and monochlorobenzene (MCB), with MCB being preferred. In some cases, the coolefin itself can act as a solvent, in which case no other solvent is required.

[0168] The polymer concentration in the double decomposition reaction is not particularly limited, but is usually in the range of 1 to 20% by mass, preferably 6 to 15% by mass.

[0169] The reaction solution in the double decomposition reaction is usually stirred vigorously, for example, in the range of 200 to 1000 rpm, preferably 300 to 900 rpm, and more preferably 500 to 800 rpm.

[0170] The temperature for the double decomposition reaction is typically in the range of 20 to 140°C, preferably 60 to 120°C. The reaction time depends on numerous factors, including the cement concentration, the amount of catalyst used, and the reaction temperature, but is usually completed within 2 hours. The progress of the double decomposition reaction can be monitored using standard analytical methods, such as GPC or solution viscosity.

[0171] (Hydrogenation reaction) The hydrogenation reaction can be carried out by dissolving nitrile rubber, or nitrile rubber that has undergone the double decomposition reaction as needed, in a solvent and adding a hydrogenation catalyst.

[0172] The solvent used in the hydrogenation reaction can be either an aqueous solvent or an organic solvent, but an organic solvent is preferred. Suitable organic solvents include, for example, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, 1,3-dioxane, benzene, toluene, methylene chloride, chloroform, monochlorobenzene (MCB), and dichlorobenzene. Among these, MCB is particularly suitable as it is a good solvent for both the nitrile group-containing nitrile rubber before hydrogenation and the hydrogenated nitrile rubber after hydrogenation.

[0173] There are no particular limitations on the hydrogenation catalyst, but it is usually carried out using a ruthenium-based catalyst. When the above double decomposition reaction is carried out using the Grubbs catalyst, it can be converted to the olefin hydrogenation catalyst dihydrogen complex (PR3) 2RuCl2H2 by hydrogen substitution in the reactor, and the reaction can be continued. Alternatively, a dihydrogen complex or other ruthenium-based catalyst can be used. The hydrogenation reaction can be carried out according to a conventional method, for example, by the method described in Japanese Patent No. 6309634.

[0174] While there are no particular limitations on hydrogenation catalysts other than ruthenium-based catalysts, known homogeneous hydrogenation catalysts such as rhodium-based Wilkinson catalysts ((PPh3)3RhCl) are particularly preferred because they can be used with the same solvent as ruthenium-based catalysts and can be carried out without changing the reaction vessel. The hydrogenation reaction can be carried out according to conventional methods, for example, using the method described in Japanese Patent No. 6309634. In the case of Wilkinson catalysts, co-catalysts include phosphine, diphosphine, and triphenylphosphine, with triphenylphosphine being preferred. The amount of these co-catalysts used is usually in the range of 0.01 to 15 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the polymer to be hydrogenated.

[0175] The amount of hydrogenation catalyst used can be appropriately selected according to the purpose of use and the iodine value, but is usually in the range of 0.001 to 0.5 parts by mass, preferably 0.005 to 0.1 parts by mass, or 0.01 to 0.05 parts by mass, based on 100 parts by mass of polymer before hydrogenation.

[0176] The polymer concentration in the hydrogenation reaction is not particularly limited as long as the polymer can be dissolved, but is usually in the range of 1 to 30% by mass, preferably 5 to 25% by mass, and more preferably 7 to 20% by mass.

[0177] The pressure for the hydrogenation reaction is not particularly limited, but is usually in the range of 0.1 to 30 MPa, preferably 1 to 20 MPa, and more preferably 5 to 15 MPa.

[0178] The hydrogenation reaction temperature is typically in the range of 30 to 200°C, preferably 50 to 170°C, and more preferably 100 to 150°C. The reaction time is typically 1 to 50 hours, preferably 2 to 25 hours.

[0179] The hydrogenation reaction can be stopped by reducing the pressure or cooling the reactor once the desired hydrogenation level is reached. Any remaining hydrogen is usually removed by nitrogen purging. The hydrogenation catalyst can also be removed before removing the solvent and isolating the hydrogenated nitrile rubber from the organic layer.

[0180] (Catalyst removal and drying) After the hydrogenation reaction, the hydrogenation catalyst can be removed as needed, and then the rubber can be dried to obtain hydrogenated nitrile rubber.

[0181] The hydrogenation catalyst can be removed by conventional methods, and for example, adsorbent treatment is preferred. The adsorbent is not particularly limited, but examples include activated carbon, ion exchange resin, and synthetic zeolite, with ion exchange resin being preferred.

[0182] The adsorbent treatment can be carried out by adding and mixing the adsorbent to the reaction solution containing hydrogenated nitrile rubber after hydrogenation. There are no particular limitations on the amount of adsorbent to add, but it is usually in the range of 0.001 to 1 part by mass, preferably 0.05 to 0.5 parts by mass, and more preferably 0.01 to 0.4 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber. The mixing temperature is usually in the range of room temperature to 80°C, preferably room temperature to 60°C, and the mixing time is usually 1 minute to 1 hour, preferably 20 to 40 minutes.

[0183] After the adsorption treatment, the adsorbent can be removed by filtration or decantation, and the filtrate can be dried to obtain hydrogenated nitrile rubber.

[0184] <Positive electrode materials and binders for positive electrodes> The positive electrode material of the present invention is characterized by using the hydrogenated nitrile rubber of the present invention.

[0185] The positive electrode binder of the present invention is obtained by dissolving the hydrogenated nitrile rubber in N-methylpyrrolidone (NMP), and is suitable as a material for manufacturing the positive electrode of an electrochemical element. Furthermore, the positive electrode binder of the present invention can be easily manufactured by adding an NMP solution to a hydrogenated nitrile rubber-containing monochlorobenzene solution after hydrogenating nitrile rubber in monochlorobenzene, and then removing the monochlorobenzene solvent by distillation and performing solvent replacement.

[0186] The positive electrode binder of the present invention may combine other components as needed, in addition to hydrogenated nitrile rubber and NMP. These other components are not particularly limited, but examples include binders other than hydrogenated nitrile rubber (such as polyvinylidene fluoride or polyacrylate), reinforcing agents, leveling agents, viscosity modifiers, and electrolyte additives. These are not particularly limited as long as they do not affect the battery reaction, and known components can be used. Furthermore, the positive electrode binder of the present invention may contain solvents other than NMP, to the extent that they do not impair the properties of the present invention. These other components may be used individually or in combination of two or more types.

[0187] The solid content concentration of the positive electrode binder of the present invention is not particularly limited, but is usually in the range of 0.1 to 40% by mass, preferably 0.5 to 20% by mass, and more preferably 1 to 10% by mass.

[0188] The mixing method for hydrogenated nitrile rubber, NMP, and other components used as needed should follow conventional methods.

[0189] <Conductive material dispersion> The conductive material dispersion of the present invention is obtained by dissolving or dispersing the hydrogenated nitrile rubber and the conductive material in NMP.

[0190] (Conductive material) The conductive material is a component that functions to ensure electrical contact between electrode active materials. Carbonaceous materials can be suitably used as the conductive material. Examples of such carbonaceous materials include carbon black (e.g., acetylene black, Ketjenblack®, furnace black, etc.), single-walled or multi-walled carbon nanotubes (multi-walled carbon nanotubes include cup-stacked types), carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by crushing polymer fibers after firing, single-walled or multi-walled graphene, and carbon nonwoven fabric sheets obtained by firing nonwoven fabrics made of polymer fibers. These may be used individually or in combination of two or more in any ratio. Among these, carbon nanotubes (CNTs) are preferred from the viewpoint of forming good conductive paths.

[0191] When mixing the positive electrode binder and the conductive material of the present invention, the ratio of the conductive material to the positive electrode binder is not particularly limited. For example, the resulting conductive material dispersion may contain hydrogenated nitrile rubber in an amount of 1 to 100 parts by mass, preferably 5 to 50 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of conductive material. Furthermore, when mixing the positive electrode binder and the conductive material, NMP can be added as needed to adjust the viscosity.

[0192] The solid content concentration when the positive electrode binder and conductive material of the present invention are mixed is usually 0.01% by mass or more, preferably 1.0% by mass or more, and more preferably 3.0% by mass or more, with an upper limit of usually 10.0% by mass or less, preferably 9.0% by mass or less, and more preferably 8.0% by mass or less. If the solid content concentration is above the lower limit, the coating properties of the conductive material dispersion can be improved. Furthermore, if the solid content concentration is below the upper limit, the rate characteristics of the resulting electrochemical element can be improved.

[0193] The method for mixing the positive electrode binder and conductive material of the present invention is not particularly limited, and can be used, for example, with known mixing equipment.

[0194] <Electrode for electrochemical device> The positive electrode slurry of the present invention is obtained by dispersing or dissolving a positive electrode active material, a conductive material, and the hydrogenated nitrile rubber in N-methylpyrrolidone (NMP). Such a positive electrode slurry can be prepared by adding a solvent to the aforementioned positive electrode binder and the conductive material as needed, mixing them, and then mixing the positive electrode active material.

[0195] The positive electrode of the present invention comprises the hydrogenated nitrile rubber, and consists of a positive electrode mixture layer containing a binder including the hydrogenated nitrile rubber, a conductive material, and a positive electrode active material, and a current collector. The positive electrode of the present invention can be produced by: adding a solvent to the aforementioned positive electrode binder and conductive material as needed and mixing them, then mixing the positive electrode active material to obtain the aforementioned positive electrode slurry, applying the slurry onto a current collector, and then drying the applied slurry.

[0196] (Positive Electrode Active Material) The positive electrode active material is not particularly limited. When the electrochemical device is a lithium ion secondary battery, examples of the positive electrode active material include lithium (Li)-containing metal oxides. As the positive electrode active material, a positive electrode active material that contains, in addition to lithium (Li), at least one selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe) is preferable. Examples of such positive electrode active materials include lithium-containing cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium-containing nickel oxide (LiNiO2), lithium-containing composite oxides of Co-Ni-Mn, lithium-containing composite oxides of Ni-Mn-Al, lithium-containing composite oxides of Ni-Co-Al, olivine-type lithium manganese phosphate (LiMnPO4), olivine-type lithium iron phosphate (LiFePO4), Li 1+x Mn 2-x O4 (0<X<2), which is a lithium-excess spinel compound represented by the formula, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4, Li[Ni 0.5 Co 0.2 Mn 0.3Examples include O2. The particle size of the positive electrode active material is not particularly limited and can be the same as that of conventionally used electrode active materials. The positive electrode active material may be used alone or in combination of two or more types in any ratio.

[0197] The above-mentioned positive electrode active material can be mixed with the mixture of the positive electrode binder and conductive material to form a positive electrode slurry. The mixing method is not particularly limited and can be carried out using known mixing equipment. The amount of positive electrode active material is not particularly limited and can be within the range of conventionally used amounts.

[0198] (Current collector) The current collector is made of a material that is electrically conductive and electrochemically durable. The current collector is not particularly limited, and any known current collector can be used. For example, the current collector in the positive electrode of a lithium-ion secondary battery may be made of aluminum or an aluminum alloy. In this case, a combination of aluminum and an aluminum alloy may be used, or a combination of different types of aluminum alloys may be used. Aluminum and aluminum alloys are excellent current collector materials because they are heat-resistant and electrochemically stable.

[0199] The positive electrode of the present invention can be manufactured by applying the above-described slurry for the positive electrode of the present invention to at least one surface of a current collector and drying it to form a positive electrode composite layer.

[0200] (Coating process) The method for applying the positive electrode slurry onto the current collector is not particularly limited, and known methods can be used. Specifically, application methods include the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, and brush application method. In this case, the positive electrode slurry may be applied to only one side of the current collector or to both sides. The thickness of the slurry film on the current collector before drying after application can be appropriately set according to the thickness of the positive electrode composite layer obtained after drying.

[0201] (drying process) The method for drying the positive electrode composite layer slurry on the current collector is not particularly limited and known methods can be used, such as drying with hot air, hot air, low-humidity air, vacuum drying, and drying by irradiation with infrared rays or electron beams. By drying the positive electrode composite layer slurry on the current collector in this way, a positive electrode composite layer is formed on the current collector, and a positive electrode comprising the current collector and the positive electrode composite layer can be obtained.

[0202] Furthermore, after the drying process, the electrode composite layer may be subjected to pressure treatment using a die press or roll press. Pressure treatment allows the positive electrode composite layer to adhere well to the current collector. In addition, if the positive electrode composite layer contains a curable polymer, the polymer may be cured after the formation of the positive electrode composite layer.

[0203] <Electrochemical elements> The electrochemical element of the present invention is characterized by containing the hydrogenated nitrile rubber of the present invention. The electrochemical element comprising the positive electrode of the present invention described above has excellent capacitance characteristics, resistance characteristics, cycle characteristics, and high-temperature storage characteristics, and is particularly preferably a lithium-ion secondary battery.

[0204] Herein, the configuration of a lithium-ion secondary battery as an example of the electrochemical element of the present invention will be described. This lithium-ion secondary battery comprises a positive electrode, a negative electrode, an electrolyte, and a separator, and the positive electrode is the electrode of the present invention.

[0205] (Negative electrode) The negative electrode is not particularly limited and any known electrode can be used.

[0206] (electrolyte) Typically, an organic electrolyte is used, which is obtained by dissolving a supporting electrolyte in an organic solvent. For example, lithium salts are used as supporting electrolytes. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred, with LiPF6 being particularly preferred, because they are easily soluble in the solvent and exhibit a high degree of dissociation. Note that one type of electrolyte may be used alone, or two or more types may be used in any ratio. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0207] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte, but suitable examples include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. A mixture of these solvents may also be used. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range, and a mixture of ethylene carbonate and diethyl carbonate is even more preferred.

[0208] The concentration of the electrolyte in the electrolyte solution can be adjusted as appropriate. For example, it is preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and even more preferably 5 to 10% by mass. In addition, known additives such as vinylene carbonate, fluoroethylene carbonate, and ethylmethyl sulfone may be added to the electrolyte solution.

[0209] (Separator) The separator is not particularly limited, and for example, those described in Japanese Patent Publication No. 2012-204303 can be used. Among these, a microporous membrane made of polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows for a thinner overall film thickness of the separator, thereby increasing the ratio of electrode active material in the lithium-ion secondary battery and thus increasing the capacity per unit volume.

[0210] (Manufacturing method for lithium-ion secondary batteries) A lithium-ion secondary battery according to the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent pressure rise inside the secondary battery, overcharge and discharge, etc., an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plates, etc. may be provided as needed. The shape of the secondary battery may be any of the following: coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc.

[0211] <Application> In addition to being used for hydrogenated nitrile rubber and electrochemical elements as described above, the nitrile rubber of the present invention can be used for a variety of other applications. For example, because the nitrile rubber of the present invention has excellent oil resistance, heat resistance, and abrasion resistance, it can be used for automotive parts such as oil seals, oil hoses, fuel hoses, and diaphragms; industrial packings such as gaskets, O-ring packings, and seals; exterior parts such as electric wires and cables; and adhesives.

[0212] The hydrogenated nitrile rubber of the present invention can exhibit its functionality and be effectively utilized in any electrochemical element other than the lithium-ion secondary battery described above. Examples of usable devices include non-aqueous electrolyte batteries such as lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, calcium-ion batteries, aluminum-ion batteries, lithium-sulfur batteries, and lithium-air batteries; inorganic solid electrolyte batteries such as sulfide-based solid electrolytes and oxide-based solid electrolytes; polymer solid electrolyte batteries such as polyethylene oxide-based batteries; and semi-solid batteries such as polymer gel electrolyte batteries in which electrolyte is impregnated into PVDF.

[0213] The hydrogenated nitrile rubber of the present invention can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous solution batteries. In fuel cells, it can be used in PEFCs, SOFCs, DMPCs, etc., and in particular, it can be used not only to impart conductivity to electrodes but also as a support for oxidation-reduction catalysts.

[0214] The hydrogenated nitrile rubber of the present invention can be used for applications other than electrochemical elements. Other suitable applications include, for example, seals, hoses, transmission belts, cable sheaths, roller covers, and vibration damping applications in the automotive sector; stators, well seals, and valve seals in the oil extraction sector; and various components in the aerospace, electrical, mechanical engineering, and shipbuilding industries.

[0215] <Equipment configuration of the hydrogenated nitrile rubber manufacturing system> The following describes the apparatus configuration of the hydrogenated nitrile rubber manufacturing system for producing hydrogenated nitrile rubber according to the present invention. Figure 1 shows an example of the hydrogenated nitrile rubber manufacturing system in an embodiment of the present invention.

[0216] Figure 1 schematically illustrates the apparatus configuration of a hydrogenated nitrile rubber manufacturing system according to an embodiment of the present invention, in accordance with the manufacturing process. The hydrogenated nitrile rubber manufacturing system shown in Figure 1 is generally configured to include a crushing device 10, a dissolving device 20, a hydrogenation reaction device 30, and a solidification device 50.

[0217] (Crushing device 10) The crushing device 10 is configured to process nitrile rubber, which is the raw material for hydrogenated nitrile rubber, into a size suitable for subsequent processing. As the nitrile rubber used as the raw material for hydrogenated nitrile rubber, for example, a nitrile rubber bale (dried rubber bale) in which nitrile rubber is baled is used.

[0218] The crushing device 10 can be any device capable of cutting the nitrile rubber bale to a predetermined size; for example, an extruder-equipped cutter and a crusher can be used. Specifically, the nitrile rubber bale is set in the extruder-equipped cutter. The nitrile rubber bale is extruded through a die to form a specific shape (rod-shaped, sheet-shaped, tube-shaped, etc.), and then cut off at the exit of the die by a cutter. It is then further crushed into smaller pieces using a crusher. The raw nitrile rubber (base rubber) obtained by crushing with the crushing device 10 is transferred to the dissolution device 20 by a conveyor 11.

[0219] (melting device 20) The dissolution apparatus 20 is configured to perform the dissolution process. As shown in Figure 1, the dissolution apparatus 20 includes a dissolution tank 21 for dissolving the base rubber in an organic solvent, a stirring device 22, and a heating device 25.

[0220] The dissolution tank 21 is formed, for example, in a closed cylindrical shape and is capable of storing the base rubber and organic solvent. The stirring device 22 is located inside the dissolution tank 21 and includes a stirring blade 23 which is a component that rotates around a predetermined axis, a motor 24 that rotates the stirring blade 23, and a drive control unit (not shown) that controls the rotational speed and rotational number of the stirring blade 23. The heating device 25 includes a heating device 26 that heats the inside of the dissolution tank 21, and a temperature control unit (not shown) that controls the temperature inside the dissolution tank 21.

[0221] The stirring device 22 is configured to rotate the stirring blades 23 at a predetermined rotational speed (stirring speed) within the dissolution tank 21, thereby dissolving the base rubber in the organic solvent by appropriately flowing the base rubber and organic solvent. The stirring speed of the stirring blades 23, the shape and size of the stirring blades 23, the number of blades installed, etc., are appropriately determined considering the dissolution efficiency of the base rubber, etc.

[0222] The heating equipment 26 of the heating device 25 is configured to heat the molten liquid inside the molten tank 21 by sending a heat transfer medium to a jacket provided on the outer circumference of the molten tank 21, for example, through heat exchange.

[0223] In the dissolution apparatus 20, a predetermined amount of base rubber and organic solvent are placed in the dissolution tank 21, and the base rubber is dissolved by stirring appropriately with the stirring blade 23 for a predetermined time or longer (for example, 2 hours or more). This yields a solution in which the base rubber is dissolved in the organic solvent. The solution obtained from the dissolution apparatus 20 is transferred to the hydrogenation reactor 30.

[0224] (Hydrogenation reactor 30) The hydrogenation reactor 30 is configured to perform the processes related to the hydrogenation step. As shown in Figure 1, the hydrogenation reactor 30 has a reaction tank (hydrogenation reaction tank) 31 for bringing nitrile rubber dissolved in an organic solvent into contact with hydrogen to perform a hydrogenation reaction, a stirring device 32, and a heating device 35.

[0225] The reaction tank 31 is formed, for example, in a closed cylindrical shape and is capable of storing the dissolved liquid transferred from the dissolution tank 21. The reaction tank 31 can also receive hydrogen from a hydrogen supply source 37 into the gas phase and a catalyst for the hydrogenation reaction from a catalyst supply source 38. The stirring device 32 is located inside the reaction tank 31 and includes a stirring blade 33 which rotates around a predetermined axis, a motor 34 which rotates the stirring blade 33, and a drive control unit (not shown) which controls the rotational speed and rotational number of the stirring blade 33. The heating device 35 includes a heating device 36 which heats the inside of the reaction tank 31 and a temperature control unit (not shown) which controls the temperature inside the reaction tank 31.

[0226] The stirring device 32 is configured to rotate the stirring blades 33 at a predetermined rotational speed (stirring speed) within the reaction tank 31, thereby appropriately flowing the solution and bringing it into contact with and reacting with hydrogen in the gas phase. The stirring speed of the stirring blades 33, the shape and size of the stirring blades 33, the number of blades installed, etc., are appropriately determined considering the reaction efficiency, etc. For example, multiple stirring blades 33 may be placed at different height positions, in which case it is preferable that one of the stirring blades 33 be positioned to shear the gas-liquid interface between the hydrogen in the gas phase and the solution in the liquid phase within the reaction tank 31.

[0227] The heating equipment 36 of the heating device 35 is configured to send a heat transfer medium to a jacket provided on the outer circumference of the reaction tank 31, for example, and heat the solubility in the corresponding reaction tank 31 through heat exchange. The temperature inside the reaction tank 31 is preferably set to a temperature at which the hydrogenation reaction is effectively promoted, for example, to 150°C.

[0228] In the hydrogenation reactor 30, a solution of nitrile rubber dissolved in an organic solvent is placed in the reaction tank 31, a catalyst is added, and hydrogen is supplied until a predetermined pressure is reached, bringing the solution into contact with hydrogen to hydrogenate the nitrile rubber. The catalyst used is one that selectively hydrogenates only the carbon double bonds in the main chain of the nitrile rubber polymer. Since the hydrogenation reaction takes place at the gas-liquid interface where gaseous hydrogen and liquid-phase solution come into contact, for example, by using a stirring blade 33 to flow the solution vertically, the gas-liquid interface is sheared while refreshing the solution in contact with the gas phase, thereby improving the contact efficiency of the nitrile rubber with hydrogen and promoting the hydrogenation reaction.

[0229] (Coagulation device 50) The solidification device 50 is configured to perform the processing related to the solidification process. The solidification device 50 replaces the organic solvent in the solution with soft water (solidification solution), which is a polar solvent, to solidify the hydrogenated nitrile rubber into a crumb-like form. In this embodiment, in order to efficiently solidify the hydrogenated nitrile rubber, the solidification device 50 has first and second solidification tanks 51a and 51b. As shown in Figure 3, the two solidification tanks, the first and second solidification tanks 51a and 51b, are connected in series, but the number of solidification tanks and the connection configuration are not particularly limited.

[0230] The first and second solidification tanks 51a and 51b are equipped with stirring devices 52a and 52b and a heating device 55a.

[0231] The stirring devices 52a and 52b are arranged inside each solidification tank and include stirring blades 53a and 53b, which are members that rotate around a predetermined axis, motors 54a and 54b that rotate the stirring blades 53a and 53b, and a drive control unit (not shown) that controls the rotational speed and rotational number of the stirring blades 53a and 53b. The heating device 55a includes a heating unit 56a that heats the inside of the first solidification tank 51a, and a temperature control unit (not shown) that controls the temperature inside the first solidification tank 51a. Here, the heating device 55a is installed in the first solidification tank 51a for heating, but the second solidification tank 51b may be heated in the same way.

[0232] The solidification apparatus 50 is configured to rotate the stirring blades 53a and 53b at a predetermined rotational speed (stirring speed) within the first and second solidification tanks 51a and 51b, thereby enabling proper flow of the fluid contained within the first and second solidification tanks 51a and 51b. The stirring speed of the stirring blades 53a and 53b, the shape and size of the stirring blades 53a and 53b, the number of blades installed, etc., are determined appropriately considering the reaction conditions, etc.

[0233] The fluids in the first and second solidification tanks 51a and 51b are transported sequentially from upstream to downstream by pumps 57a and 57b as a cramb-containing fluid containing cramb-shaped solidified hydrogenated nitrile rubber and solidification liquid. Pump 57a transports the liquid in the first solidification tank 51a to the second solidification tank 51b. Pump 57b transports the liquid in the second solidification tank 51b to the outside of the solidification device 50. The hydrogenated nitrile rubber is isolated and dried by a dewatering machine (not shown). The transport by pumps 57a and 57b is controlled by a pump drive control unit (not shown).

[0234] The dissolved solution transferred from the hydrogenation reactor 30 to the solidification reactor 50 is continuously supplied into the first solidification tank 51a. Steam and water (soft water) are supplied to the first solidification tank 51a. The temperature of the steam and water is adjusted so that the temperature inside the first solidification tank 51a is above the boiling point of the organic solvent. As the dissolved solution is stirred in the first solidification tank 51a, the organic solvent vaporizes (evaporates) and is replaced by highly polar water, causing the hydrogenated nitrile rubber in the organic solvent to precipitate.

[0235] Similarly, in the second solidification tank 51b, stirring the liquid inside the second solidification tank 51b promotes the vaporization of the organic solvent, causing hydrogenated nitrile rubber to precipitate from the organic solvent. The liquid discharged from the second solidification tank 51b is in the form of a crumb-containing slurry, in which the organic solvent has vaporized and crumb-shaped hydrogenated nitrile rubber is suspended in the liquid (water).

[0236] The solidification apparatus 50 is configured to precipitate and solidify the hydrogenated nitrile rubber dissolved in the solution as a solid by stirring the solution in an environment above the boiling point of the organic solvent, vaporizing the organic solvent, and replacing it with water, in which the hydrogenated nitrile rubber is insoluble. [Examples]

[0237] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%", "ppm", and "parts" used to express quantities refer to mass unless otherwise specified.

[0238] Furthermore, in polymers produced by copolymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer is, unless otherwise specified, usually equal to the ratio (starting ratio) of that particular monomer to the total monomers used in the polymerization of the polymer.

[0239] In the examples and comparative examples, various measurements and evaluations were carried out according to the following methods.

[0240] <Moisture content crumb distribution> The water-containing crumbs produced by the coagulation reaction were classified using a JIS classification sieve. Afterward, each classified water-containing crumb was dried in a hot air dryer at 80°C for 3 hours, and the mass was measured to determine the proportion of each crumb diameter's weight (a) to (h). The JIS sieve conformed to the specifications of the Japanese Industrial Standard (JIS Z8801-1). (a) It does not pass through a JIS sieve with a mesh size of 9.5 mm. (b) It passes through a JIS sieve with a mesh size of 9.5 mm but does not pass through a JIS sieve with a mesh size of 8.0 mm. (c) It passes through a JIS sieve with a mesh size of 8.0 mm but does not pass through a JIS sieve with a mesh size of 4.75 mm. (d) It passes through a JIS sieve with a mesh size of 4.75 mm but does not pass through a JIS sieve with a mesh size of 3.35 mm. (e) It passes through a JIS sieve with a mesh size of 3.35 mm but does not pass through a JIS sieve with a mesh size of 2.36 mm. (f) It passes through a JIS sieve with a mesh size of 2.36 mm but does not pass through a JIS sieve with a mesh size of 1.7 mm. (g) It passes through a JIS sieve with a mesh size of 1.7 mm but does not pass through a JIS sieve with a mesh size of 0.43 mm. (h) It passes through a JIS sieve with a mesh size of 0.43 mm.

[0241] <Water content> The water content of the hydrated crumb produced by the coagulation reaction after dehydration was determined according to the "oven method" specified in JIS K6238-1. Specifically, 10 g of hydrated crumb was placed in an oven at 105 ± 5°C and dried until the mass no longer changed substantially. The mass loss before and after drying was determined, and the ratio of the mass loss to the mass of the dried crumb was calculated to determine the water content.

[0242] <Repeat Unit> The acrylonitrile polymerization units and 1,3-butadiene polymerization units (the sum of 1,2-bonding units, 1,4-bonding units, and their hydride units) in the polymer are, 1 The intensity ratio of the peaks originating from each repeating unit was determined using 1H-NMR (nuclear magnetic resonance) spectroscopy, and the content ratio in the polymer was calculated by converting this to a mass ratio.

[0243] The proportion of 1,2-bond units in the 1,3-butadiene polymerization units of the polymer is, 1 Using 1H-NMR (nuclear magnetic resonance) spectroscopy, peak intensities originating from 1,2-bonding units, 1,4-bonding units, and their hydride units were determined, and the ratio of (total amount of 1,2-bonding units and their hydride units) / (total amount of 1,2-bonding units, 1,4-bonding units, and their hydride units) was calculated.

[0244] <Iodine value> The iodine value of hydrogenated nitrile rubber was measured in accordance with JIS K6235.

[0245] <Molecular weight> The number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the polymer were measured by gel permeation chromatography (GPC) using a tetrahydrofuran (THF) solution under the following measurement conditions. • Separation column: TSK-gel SuperHM-H (manufactured by Tosoh Corporation) • Detector: Differential refractometer detector RID-10A (manufactured by Shimadzu Corporation) • Eluent flow rate: 0.6 mL / min Column temperature: 40°C • Standard polymer: TSK standard polystyrene (manufactured by Tosoh Corporation)

[0246] <Polymer pH> To 10 g of NMP solution (solid content concentration: 8%) of hydrogenated nitrile rubber, 90 g of deionized water was added. The mixture was stirred and pressed with a spatula, and the liquid contained within the solidified hydrogenated nitrile rubber was extracted in the deionized water phase to obtain an extract. The pH of the extract was measured at 25°C in accordance with JIS Z8802 (2011).

[0247] <Anti-aging agent content> The polymer was dissolved in a chlorobenzene solution and analyzed by gas chromatography to determine the percentage of the antioxidant (BHT) content relative to the total mass of the polymer.

[0248] <Water content of polymer> The water content of the polymer was measured according to the "oven method" specified in JIS K6238-1.

[0249] <Ash content> The amount of ash contained in the rubber was measured in accordance with the JIS K6228A method.

[0250] <Ash content> The amounts of each component in the ash were determined by pressing the ash collected during the above ash content measurement onto a Φ20 mm titration filter paper and performing XRF measurement using a ZSXPrimus (manufactured by Rigaku).

[0251] <Dispersibility of conductive material dispersion> The viscosity of the conductive material dispersions obtained in the examples and comparative examples was measured for 120 seconds at a temperature of 25°C and a shear rate of 10¹ / s using a rheometer (Anton Paar, "MCR302"). The average viscosity measurement value from 61 seconds to 120 seconds was evaluated according to the following criteria. A smaller dispersion viscosity value indicates better dispersibility. ◎:4Pa·s or less 〇: More than 4Pa·s but less than 6Pa·s △: More than 6Pa·s but less than 8Pa·s ×: 8 Pa·s super

[0252] <Stability of Conductive Material Dispersion Viscosity> For the conductive material dispersions obtained in the Examples and Comparative Examples, after measuring the aforementioned dispersion viscosity (η0), the dispersion was stored in a sealed container at 25°C for 10 days. Thereafter, the dispersion viscosity was measured again (η1), and the rate of viscosity change was calculated. Then, the viscosity retention rate Δη=η1 / η0×100 (%) of the conductive material dispersion before and after storage was calculated, and the viscosity stability of the conductive material dispersion was evaluated according to the following criteria. The closer the value of the viscosity retention rate Δη is to 100%, the better the viscosity stability of the conductive material dispersion. ⊚: Viscosity retention rate Δη is 90% or more and less than 110% ○: Viscosity retention rate Δη is 110% or more and less than 130% △: Viscosity retention rate Δη is 130% or more and less than 140% ×: Viscosity retention rate Δη is 140% or more

[0253] <Peel Strength> The positive electrodes produced in the Examples and Comparative Examples were cut into rectangles with a length of 100 mm and a width of 10 mm to obtain test pieces. A cellophane tape (conforming to JIS Z1522) was attached to the surface of the positive electrode mixture layer with the side having the positive electrode mixture layer facing down. The stress was measured when one end of the current collector was pulled vertically at a pulling speed of 100 mm / min to peel it off (the cellophane tape was fixed to the test stand). The measurement was performed three times, and the average value was obtained as the peel strength, which was evaluated according to the following criteria. A larger peel strength indicates that the positive electrode mixture layer is more strongly adhered to the current collector made of aluminum foil. ⊚: Peel strength is 15 N / m or more ○: Peel strength is 10 N / m or more and less than 15 N / m ○~△: Peel strength is 7 N / m or more and less than 10 N / m △: Peel strength is 5 N / m or more and less than 7 N / m ×: Peel strength is less than 5 N / m

[0254] <Resistance Characteristics> For the positive electrodes prepared in the examples and comparative examples, the resistivity (Ω·cm) at the interface between the positive electrode composite layer and the current collector was measured at 25°C using an electrode resistance system (HIOKI E.E. CORPORATION "RM2610"). 2 The following criteria were used to measure and evaluate the following: ◎: Resistivity is 0.03 Ω·cm 2 below ○: Resistivity is 0.03 Ω·cm 2 Super 0.1Ω cm 2 below △: Resistivity of 0.1 Ω·cm 2 Super 0.3Ω cm 2 below ×: Resistivity is 0.3Ω·cm 2 super

[0255] <Output Characteristics> The lithium-ion secondary batteries prepared in the examples and comparative examples were left to stand at 25°C for 5 hours after electrolyte injection. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then subjected to an aging treatment at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.35V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times. Next, the battery was charged with a constant current of 0.2C at a temperature of 25°C until the battery voltage reached 4.35V, and then charged with a constant voltage until the charging current was reduced to 0.2C at 4.35V. Subsequently, it was discharged with a constant current of 0.2C until the battery voltage reached 3.0V. The discharge capacity at this time was defined as C0.2. Next, the capacity C2.0 at 2.0C discharge was determined by the same procedure except for discharge at 2.0C. Then, the capacity ratio (%) = C2.0 / C0.2 × 100 was calculated and evaluated according to the following criteria. A larger capacity ratio indicates that the lithium-ion secondary battery has superior output characteristics. ◎: Volume ratio of 87% or more ○: Volume ratio is 85% or more but less than 87% △: Volume ratio is between 80% and less than 85% ×: Volume ratio less than 80%

[0256] <Cycle Characteristics> The lithium-ion secondary batteries prepared in the examples and comparative examples were left to stand at 25°C for 5 hours after electrolyte injection. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then subjected to an aging treatment at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.35V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times. Next, 300 charge-discharge cycles were performed in an environment of 45°C with a cell voltage of 4.35-3.00V and a charge-discharge rate of 1.0C. The discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 300th cycle as X2. Using these discharge capacities X1 and X2, the capacity retention rate = (X2 / X1) × 100 (%) was calculated and evaluated according to the following criteria. A higher capacity retention rate indicates superior cycle characteristics of the lithium-ion secondary battery. ◎: Capacity retention rate of 87% or higher ○: Capacity retention rate is 82% or more but less than 87% ○~△: Volume retention rate is 77% or more but less than 82% △: Capacity retention rate is 75% or more but less than 77% ×: Volume retention rate is less than 75%

[0257] <High temperature storage characteristics> The lithium-ion secondary batteries prepared in the examples and comparative examples were left to stand at 25°C for 5 hours after electrolyte injection. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then subjected to an aging treatment at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.35V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times. Next, the initial IV resistance R1 was measured. Specifically, under a 25°C atmosphere, the battery was charged to 50% of the State of Charge (SOC) at 1.0C. Then, charging and discharging were performed for 20 seconds at 0.5C, 1.0C, 1.5C, and 2.0C, centered around 50% of the SOC. In each case (charging and discharging), the battery voltage after 20 seconds was plotted against the current value, and the slope was determined as the initial IV resistance R1 (Ω) (IV resistance during charging and IV resistance during discharging). Subsequently, CC-CV charging was performed at a constant current of 0.2C (maximum cell voltage 4.35V). Then, the lithium-ion secondary batteries were stored for 4 weeks in an inert oven with a nitrogen atmosphere at 80°C. After storage, the IV resistance R2 was measured using the same method as the initial IV resistance R1, after high-temperature storage. The initial IV resistance R1 and the IV resistance R2 after high-temperature storage were used to calculate the IV resistance increase rate using the following formula. IV resistance increase rate (%) = (R2 - R1) / R1 × 100 The IV resistance increase rate (%) and the IV resistance R2 after high-temperature storage were used for evaluation according to the following criteria. A smaller IV resistance increase rate (%) and a smaller IV resistance R2 (Ω) after high-temperature storage indicate that the internal resistance has been reduced over a long period, and that the battery characteristics of the lithium-ion secondary battery are superior. ◎: IV resistance increase rate is less than 35% ◎~〇: IV resistance increase rate is 35% or more but less than 40% ○: IV resistance increase rate is 40% or more but less than 45% ○~△: IV resistance increase rate is 45% or more but less than 50% △: IV resistance increase rate is 50% or more but less than 55% ×: IV resistance increase rate is 55% or more but less than 60% ××: IV resistance increase rate is 60% or more

[0258] (Example 1) <Nitrile rubber manufacturing> In a reactor with an internal volume of 10 liters, 100 parts of deionized water, 35 parts of acrylonitrile, and 65 parts of 1,3-butadiene were charged. 40 parts of a 10% aqueous solution of sodium dodecylbenzenesulfonate were added as an emulsifier, 0.1 parts of potassium phosphate as a stabilizer, and 0.27 parts of tert-dodecyl mercaptan (TDM) as a molecular weight modifier (chain transfer agent). 0.1 parts of cumene hydroperoxide (QHPO) as a polymerization initiator, along with appropriate amounts of reducing and chelating agents, were added. Emulsification polymerization was carried out at a temperature of 30°C to copolymerize acrylonitrile and 1,3-butadiene. When the polymerization conversion rate reached 80%, polymerization was stopped by adding 0.2 parts of hydroxylamine sulfate per 100 parts of monomer. Subsequently, the mixture was heated and steam distilled under reduced pressure at approximately 90°C to recover the residual monomer. Then, 0.1 parts of dibutylhydroxytoluene (BHT), a phenolic antioxidant, was added to obtain the polymerization solution.

[0259] In a solidification tank equipped with a thermometer and a central stirring blade device, 100 parts of the polymer solids from the obtained polymerization liquid were directly added to a 25% calcium chloride aqueous solution (4 parts as calcium chloride) heated to 45°C and vigorously stirred (600 rpm, peripheral speed 3.1 m / s). The polymer was then solidified by continuously rotating stirring blades (central part) to obtain a water-containing crumb. The obtained water-containing crumb was measured for each component using a JIS classification sieve, and the results are shown in Table 1. Note that Tables 1-1 to 1-6 below are divisions of a single table, and Tables 1-1 to 1-6 together are referred to as Table 1.

[0260] Next, the filtered wet crumb was added at 45°C to a washing tank equipped with a stirrer filled with ion-exchanged water, and 50 times the amount of ion-exchanged water (45°C) relative to the polymer was passed through while stirring to wash the wet crumb. The washed wet crumb was heated to 60°C, dehydrated using a squeezer with introduced steam until the water content reached 7%, and then dried under reduced pressure to obtain nitrile rubber A. The repeating unit ratio, molecular weight, molecular weight distribution, polymer pH, anti-aging agent content, water content and ash content of the obtained nitrile rubber A were measured, and the results are shown in Table 1. Further, the sodium content (Na), potassium content (K), calcium content (Ca), sulfur content (S) and chlorine content (Cl) in the ash were measured. The ratio of the total of sodium content (Na) and potassium content (K) (Na+K) relative to the total ash content, the ratio of the total of calcium content (Ca) and sulfur content (S) (Ca+S) relative to the total ash content, the ratio of the total amount of sodium content (Na) and potassium content (K) (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)), the ratio of calcium content (Ca) to sulfur content (S) (Ca / S), the ratio of calcium content (Ca) to chlorine content (Cl) (Ca / Cl) and the ratio of sulfur content (S) to chlorine content (Cl) (S / Cl) were calculated, and these results are shown in Table 1.

[0261] <Hydrogenation of Nitrile Rubber> (Metathesis Reaction) Next, 9 parts of the obtained nitrile rubber A was dissolved in 141 parts of monochlorobenzene, which is a halogenated hydrocarbon, and charged into a reactor. After heating the reactor to 80°C, 2 L of a monochlorobenzene solution containing bis(tricyclohexylphosphine)benzylideneruthenium dichloride as a Grubbs catalyst was added such that the amount of the Grubbs catalyst relative to the polymer was 1000 ppm. Then, 4.4 parts of cis-2-butene-1,4-diol as a co-olefin was added per 100 parts of nitrile rubber A, and a metathesis reaction of the polymer was carried out at a stirring speed of 600 rpm. During the reaction, the temperature was kept constant using a temperature controller and a cooling coil connected to a heat sensor.

[0262] (Hydrogenation reaction) Subsequently, the reactor was degassed three times with H2 at 0.7 MPa while stirring continued. Then, 2 L of a monochlorobenzene solution containing bis(tricyclohexylphosphine)benzylideneruthenium dichloride was added as a Grubbs catalyst so that the amount of Grubbs catalyst relative to the polymer was 1000 ppm. The temperature was then raised to 150°C, and the hydrogenation reaction was carried out under a hydrogen pressure (gauge pressure) of 8.4 MPa until the iodine value of the polymer reached 13 mg / 100 mg.

[0263] (Catalyst removal process) After the hydrogenation reaction was complete, to remove the ruthenium catalyst, 1 part of aminopropyl-modified silica (trade name "QuadraSil AP", manufactured by SIGMA-ALDRICH, silica with aminopropyl groups introduced on its surface, average particle size 54 μm) was added to the reactor and stirred for 30 minutes. Then, the mixture was filtered through a 5 μm pore size filter. The filtrate was dried under reduced pressure at 90°C until the monochlorobenzene content reached 50 ppm, and hydrogenated nitrile rubber A was isolated.

[0264] The repeating unit ratio, molecular weight, molecular weight distribution, antioxidant content, water content, polymer pH, and ash content of the obtained hydrogenated nitrile rubber A were measured and are shown in Table 2. Furthermore, the sodium (Na), potassium (K), calcium (Ca), sulfur (S), chlorine (Cl), ruthenium (Ru), rhodium (Rh), and phosphorus (P) content in the ash were measured. The ratio of the sum of sodium (Na) and potassium (K) content (Na+K) to the total ash content, the ratio of the sum of calcium (Ca) and sulfur (S) content (Ca+S) to the total ash content, and the sum of sodium (Na) and potassium (K) content (Na+K) were also measured. The ratio of the total amount of calcium (Ca) and sulfur (S) (Ca+S) ((Na+K) / (Ca+S)), the ratio of calcium (Ca) to sulfur (S) (Ca / S), the ratio of calcium (Ca) to chlorine (Cl) (Ca / Cl), the ratio of sulfur (S) to chlorine (Cl) (S / Cl), the percentage of the total amount of ruthenium (Ru) and rhodium (Rh) (Ru+Rh) and the percentage of phosphorus (P) relative to the total ash amount were calculated, and these results are shown in Table 2. Note that Tables 2-1 to 2-4 below are divisions of a single table, and Tables 2-1 to 2-4 together are referred to as Table 2.

[0265] <Manufacturing of lithium-ion secondary batteries> (Manufacturing of binder for positive electrodes) After the above hydrogenation reaction, an appropriate amount of NMP was mixed with the filtered monochlorobenzene solution, and the chlorobenzene was completely evaporated under reduced pressure to obtain hydrogenated nitrile rubber positive electrode binder A (solid content concentration: 8%).

[0266] (Preparation of conductive material dispersion) Conductive material dispersion A was prepared by adding 0.4 parts of TUBALL SWCNT (manufactured by OCSiAl, single-walled carbon nanotubes) as a conductive material, 25 parts (equivalent to 2 parts as solids) of a positive electrode binder composition with a solid content of 8% obtained according to the above method, and 74.6 parts of NMP as an organic solvent. The mixture was stirred using a disperser (3000 rpm, 10 minutes), and then mixed for 1 hour at a peripheral speed of 8 m / s using a bead mill (Ashizawa Finetech, "LMZ015") with 1 mm diameter zirconia beads. The dispersibility and stability of the prepared conductive material dispersion were evaluated, and the results are shown in Table 2.

[0267] (Preparation of slurry for positive electrode) In the conductive material dispersion described above, a ternary active material having a layered structure (LiNi 0.5 Co 0.2 Mn 0.3 A cathode slurry was prepared by adding 98.5 parts of O2 (average particle size: 10 μm), 1.0 part of polyvinylidene fluoride as a binder, 0.5 parts of the above conductive material dispersion (in terms of solid content), and NMP, and mixing them in a planetary mixer (60 rpm, 30 minutes). The amount of NMP added was adjusted so that the viscosity of the resulting cathode slurry (measured using a single cylindrical rotational viscometer in accordance with JIS Z8803:1991; temperature: 25°C, rotation speed: 60 rpm) was in the range of 4000 to 5000 mPa·s.

[0268] (Fabrication of the positive electrode) A 20 μm thick aluminum foil was prepared as the current collector. The above-mentioned positive electrode slurry was dried onto the aluminum foil using a comma coater, and the basis weight after drying was 20 mg / cm². 2 The material was applied to the surface, dried at 120°C for 5 minutes, then at 130°C for 5 minutes, and finally heat-treated at 60°C for 10 hours to obtain a cathode base. This cathode base was rolled using a roll press to obtain a density of 3.5 g / cm³. 3 A sheet-like positive electrode was fabricated consisting of a positive electrode composite layer and aluminum foil. This sheet-like positive electrode was cut to a width of 4.8 cm and a length of 50 cm to form positive electrode A for lithium-ion secondary batteries. The peel strength of the obtained positive electrode was measured, and the results are shown in Table 2.

[0269] (Fabrication of the negative electrode) In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid as a carboxylic acid group-containing monomer, 63.5 parts of styrene as an aromatic vinyl monomer, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized water, and 0.5 parts of potassium persulfate as a polymerization initiator were placed and thoroughly stirred. After heating to 50°C, polymerization was started. When the polymerization conversion rate reached 96%, the mixture was cooled to stop the polymerization reaction, and a mixture containing particulate binder (styrene-butadiene copolymer) was obtained. A 5% aqueous sodium hydroxide solution was added to the above mixture to adjust the pH to 8, and unreacted monomers were removed by heated vacuum distillation. The mixture was then cooled to below 30°C to obtain an aqueous dispersion containing a binder for the negative electrode.

[0270] Next, 48.75 parts of artificial graphite and 48.75 parts of natural graphite as negative electrode active materials, and 1 part of carboxymethylcellulose as a thickener were added to a planetary mixer. Furthermore, the mixture was diluted with deionized water to a solid content concentration of 60%, and then kneaded at a rotation speed of 45 rpm for 60 minutes. After that, 1.5 parts of the aqueous dispersion containing the negative electrode binder obtained as described above was added in terms of solid content, and kneaded at a rotation speed of 40 rpm for 40 minutes. Finally, deionized water was added to achieve a viscosity of 3000 ± 500 mPa·s (measured with a B-type viscometer at 25°C and 60 rpm) to prepare a slurry for the negative electrode composite layer.

[0271] Next, a 15 μm thick copper foil was prepared as the current collector. The above-mentioned negative electrode slurry was applied to both sides of the copper foil, with a dry coating amount of 10 mg / cm² on each side. 2 The material was applied to the surface and dried at 80°C for 5 minutes and then at 120°C for 5 minutes to obtain a negative electrode base. This negative electrode base was rolled using a roll press to obtain a density of 1.6 g / cm³. 3 A sheet-like negative electrode was fabricated consisting of a negative electrode composite layer (on both sides) and copper foil. The sheet-like negative electrode was then cut to a width of 5.0 cm and a length of 52 cm to be used as a negative electrode for a lithium-ion secondary battery.

[0272] (Manufacturing of lithium-ion secondary batteries) The fabricated positive electrode and negative electrode for lithium-ion secondary batteries were placed facing each other with their electrode mixture layers facing each other, and a 15 μm thick separator (microporous polyethylene membrane) was interposed between them. The mixture was then wound around a 20 mm diameter core to obtain a wound body. The resulting wound body was then compressed from one direction at a speed of 10 mm / second until its thickness reached 4.5 mm. The compressed wound body was elliptical in plan view, and its ratio of major axis to minor axis (major axis / minor axis) was 7.7.

[0273] In addition, a 1.0 M LiPF6 solution was prepared as the electrolyte (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2 vol% vinylene carbonate (solvent ratio)).

[0274] Subsequently, the compressed coil was placed in an aluminum laminate case along with 3.2 g of non-aqueous electrolyte. Nickel lead wires were then connected to designated locations on the negative electrode and aluminum lead wires to designated locations on the positive electrode. Finally, the opening of the case was sealed with heat to obtain lithium-ion secondary battery A. This lithium-ion secondary battery was a pouch of a predetermined size capable of housing the above-mentioned coil, and the nominal capacity of the battery was 700 mAh.

[0275] The resistance characteristics, output characteristics, cycle characteristics, and high-temperature storage characteristics of the obtained lithium-ion secondary batteries were evaluated, and the results are shown in Table 2.

[0276] (Example 2) Except for changing the polymerization conversion rate to 85%, nitrile rubber B, hydrogenated nitrile rubber B, positive electrode binder B, conductive material dispersion B, positive electrode slurry B, positive electrode B, and lithium-ion secondary battery B were obtained in the same manner as in Example 1, and the same evaluation as in Example 1 was performed, and the results are shown in Tables 1 and 2.

[0277] (Example 3) Nitrile rubber C, hydrogenated nitrile rubber C, positive electrode binder C, conductive material dispersion C, positive electrode slurry C, positive electrode C, and lithium-ion secondary battery C were obtained in the same manner as in Example 1, except that the water content after dehydration of the water-containing crumb was changed to 15%. The same evaluation as in Example 1 was performed, and the results are shown in Tables 1 and 2.

[0278] (Example 4) Except for changing the water content of the dehydrated crumb to 25%, nitrile rubber D, hydrogenated nitrile rubber D, cathode binder D, conductive material dispersion D, cathode slurry D, cathode D, and lithium-ion secondary battery D were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

[0279] (Example 5) Except for changing the water content of the dehydrated crumb to 35%, nitrile rubber E, hydrogenated nitrile rubber E, positive electrode binder E, conductive material dispersion E, positive electrode slurry E, positive electrode E, and lithium-ion secondary battery E were obtained in the same manner as in Example 1, and the same evaluation as in Example 1 was performed, and the results are shown in Tables 1 and 2.

[0280] (Example 6) Nitrile rubber F, hydrogenated nitrile rubber F, cathode binder F, conductive material dispersion F, cathode slurry F, cathode F, and lithium-ion secondary battery F were obtained in the same manner as in Example 5, except that the amount of Grubbs catalyst used was changed to 2000 ppm in the double decomposition reaction and not added in the hydrogenation reaction. The same evaluation as in Example 5 was performed, and the results are shown in Tables 1 and 2.

[0281] (Example 7) Except for changing the amount of Grubbs catalyst used to 700 ppm in the double decomposition reaction and 1300 ppm in the hydrogenation reaction, nitrile rubber G, hydrogenated nitrile rubber G, cathode binder G, conductive material dispersion G, cathode slurry G, cathode G, and lithium-ion secondary battery G were obtained in the same manner as in Example 5, and the same evaluation as in Example 5 was performed, and the results are shown in Tables 1 and 2.

[0282] (Example 8) Except for changing the polymerization conversion rate to 75%, nitrile rubber H, hydrogenated nitrile rubber H, cathode binder H, conductive material dispersion H, cathode slurry H, cathode H, and lithium-ion secondary battery H were obtained in the same manner as in Example 5, and evaluated in the same manner as in Example 5, and the results are shown in Tables 1 and 2.

[0283] (Example 9) Except for changing the polymerization conversion rate to 78%, nitrile rubber I, hydrogenated nitrile rubber I, cathode binder I, conductive material dispersion I, cathode slurry I, cathode I, and lithium-ion secondary battery I were obtained in the same manner as in Example 5, and evaluated in the same manner as in Example 5, and the results are shown in Tables 1 and 2.

[0284] (Example 10) Nitrile rubber J, hydrogenated nitrile rubber J, cathode binder J, conductive material dispersion J, cathode slurry J, cathode J, and lithium-ion secondary battery J were obtained in the same manner as in Example 5, except that the polymerization conversion rate was changed to 90%. The same evaluation as in Example 5 was performed, and the results are shown in Tables 1 and 2.

[0285] (Example 11) Except for changing the water content of the dehydrated crumb to less than 1%, nitrile rubber K, hydrogenated nitrile rubber K, positive electrode binder K, conductive material dispersion K, positive electrode slurry K, positive electrode K, and lithium-ion secondary battery K were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0286] (Example 12) Except for changing the method of adding the polymerization solution in the solidification reaction to the wall side (1 / 2 outside) from the middle of the stirring blade of the agitated calcium chloride aqueous solution to the wall of the solidification tank, nitrile rubber L, hydrogenated nitrile rubber L, positive electrode binder L, conductive material dispersion L, positive electrode slurry L, positive electrode L, and lithium-ion secondary battery L were obtained in the same manner as in Example 1, and the same evaluation as in Example 1 was performed and the results are shown in Tables 1 and 2.

[0287] (Example 13) Except for changing the rotation speed of the solidification tank agitator blade to 350 rpm (peripheral speed 1.8 m / s), nitrile rubber M, hydrogenated nitrile rubber M, positive electrode binder M, conductive material dispersion M, positive electrode slurry M, positive electrode M, and lithium-ion secondary battery M were obtained in the same manner as in Example 12, and the same evaluation as in Example 12 was performed, and the results are shown in Tables 1 and 2.

[0288] (Example 14) Nitrile rubber N, hydrogenated nitrile rubber N, cathode binder N, conductive material dispersion N, cathode slurry N, cathode N, and lithium-ion secondary battery N were obtained in the same manner as in Example 13, except that the amount of acrylonitrile in emulsion polymerization was changed to 23 parts and the amount of 1,3-butadiene to 77 parts. The same evaluation as in Example 13 was performed, and the results are shown in Tables 1 and 2.

[0289] (Example 15) Except for changing the amount of acrylonitrile to 47 parts and the amount of 1,3-butadiene to 53 parts in emulsion polymerization, nitrile rubber O, hydrogenated nitrile rubber O, positive electrode binder O, conductive material dispersion O, positive electrode slurry O, positive electrode O, and lithium-ion secondary battery O were obtained in the same manner as in Example 13, and evaluated in the same manner as in Example 13, and the results are shown in Tables 1 and 2.

[0290] (Reference example 1) Except for changing the rotation speed of the solidification tank agitator blade to 100 rpm (peripheral speed 0.5 m / s) and the water content after dewatering to 25%, nitrile rubber P, hydrogenated nitrile rubber P, positive electrode binder P, conductive material dispersion P, positive electrode slurry P, positive electrode P, and lithium-ion secondary battery P were obtained in the same manner as in Example 12, and the same evaluation as in Example 12 was performed, and the results are shown in Tables 1 and 2.

[0291] (Reference example 2) Except for changing the coagulation reaction to a method of adding an aqueous calcium chloride solution to the polymerization liquid being stirred in a coagulation tank and changing the water content after dehydration to 25%, nitrile rubber Q, hydrogenated nitrile rubber Q, positive electrode binder Q, conductive material dispersion Q, positive electrode slurry Q, positive electrode Q, and lithium-ion secondary battery Q were obtained in the same manner as in Example 12, and the same evaluation as in Example 12 was performed, and the results are shown in Tables 1 and 2.

[0292] (Reference example 3) Nitrile rubber, hydrogenated nitrile rubber, a binder for the positive electrode, a dispersion of conductive material, a slurry for the positive electrode, a positive electrode, and a lithium-ion secondary battery were obtained in the same manner as in Reference Example 2, except that the pH of the emulsion polymerization solution after the addition of an antioxidant was adjusted to 3.5 to obtain a polymer pH of 3.5. Evaluations were then performed in the same manner as in Reference Example 2. The results were the same as in Reference Example 2, except that the evaluation of the resistance characteristics was "×".

[0293] (Comparative Example 1) Except for changing the rotation speed of the solidification tank agitator blade to 100 rpm (peripheral speed 0.5 m / s) and not performing dewatering, nitrile rubber R, hydrogenated nitrile rubber R, positive electrode binder R, conductive material dispersion R, positive electrode slurry R, ​​positive electrode R, and lithium-ion secondary battery R were obtained in the same manner as in Reference Example 2, and the same evaluation as in Reference Example 2 was performed, and the results are shown in Tables 1 and 2.

[0294] (Comparative Example 2) Nitrile rubber S, hydrogenated nitrile rubber S, cathode binder S, conductive material dispersion S, cathode slurry S, cathode S, and lithium-ion secondary battery S were obtained in the same manner as in Comparative Example 1, except that the polymerization temperature of the emulsion polymerization reaction was changed to 10°C and the polymerization conversion rate to 75%. The same evaluation as in Comparative Example 1 was performed, and the results are shown in Tables 1 and 2.

[0295] (Comparative Example 3) Except for not adding a Grubbs catalyst in the hydrogenation reaction, nitrile rubber T, hydrogenated nitrile rubber T, cathode binder T, conductive material dispersion T, cathode slurry T, cathode T, and lithium-ion secondary battery T were obtained in the same manner as in Comparative Example 1, and evaluated in the same manner as in Comparative Example 1. The results are shown in Tables 1 and 2.

[0296] [Table 1-1]

[0297] [Table 1-2]

[0298] [Table 1-3]

[0299] [Table 1-4]

[0300] [Table 1-5]

[0301] [Table 1-6]

[0302] Table 1 shows that the Mw / Mn range of the nitrile rubber produced can be adjusted by controlling the polymerization temperature and polymerization conversion rate (comparison of Examples 1-2 and Examples 8-10).

[0303] Table 1 shows that the particle size distribution and particle shape of the resulting water-containing crumb differ greatly depending on the conditions in the solidification reaction (number of stirs of the solidification solution and polymerization solution, solidification method depending on whether polymerization solution or solidification solution is added, and the position of addition of the polymerization solution), and that this greatly affects the ash content of the nitrile rubber.

[0304] Table 1 shows that when the polymerization solution is added to a coagulated liquid vigorously stirred at 600 rpm, the resulting hydrated crumbs are mostly 3.35 to 4.75 mm in size. This size offers good workability and also provides good washing and dewatering efficiency (Examples 1-11). Furthermore, when the polymerization solution is added to the center of the vigorously stirred coagulated liquid (where the coagulated liquid forms a vortex and the central stirring blade is visible, and the solution should be applied directly to the stirring blade), the resulting hydrated crumbs often have a large hole in the center, and the ash content in the nitrile rubber after washing and dewatering can be reduced to 0.14% (Examples 1-2). On the other hand, when the addition position of the polymerization solution is changed to closer to the wall between the stirring blade and the tank wall (directly added to the coagulated liquid), the particle size distribution does not change, but the resulting hydrated crumbs have almost no holes, and the ash content in the nitrile rubber can only be reduced to 0.5% (comparison between Example 1 and Example 12 under the same conditions).

[0305] Table 1 shows that when the rotation speed of the agitated coagulation solution is reduced from 600 rpm to 350 rpm, the size of the generated water-containing crumbs is mainly 4.75 to 8 mm, and the amount of ash in the nitrile rubber can only be reduced to about 0.7% (Examples 13 to 15). Furthermore, if the agitation speed is reduced to 100 rpm, the amount of water-containing crumbs, which is nearly twice as large as when agitated at 600 rpm (8 to 9.5 mm), increases, and the amount of ash in the nitrile rubber can only be reduced to about 1% (Reference Example 1).

[0306] Table 1 shows that when the coagulation method is changed to adding the coagulation solution to the stirred polymerization solution, even with vigorous stirring at the same 600 rpm, the resulting water-containing crumbs are divided into large and small sizes, and the amount of ash remaining in the nitrile rubber also increases (Reference Example 2). Furthermore, when the rotation speed of the polymerization solution is reduced to 100 rpm, the amount of ash remaining nearly doubles (comparison of Reference Example 2 with Comparative Examples 1-3).

[0307] Table 1 shows that, in the dehydration process of the water-containing crumb produced by the coagulation reaction, the amount of ash remaining in the nitrile rubber differs significantly depending on the water content after dehydration (comparison of Example 1 with Examples 3-5 and Example 11). Furthermore, although not shown in this example, the ash content of nitrile rubber is greatly affected by the concentration of the coagulation solution (calcium chloride aqueous solution), the washing temperature, and the dehydration temperature, and the amount of ash in the nitrile rubber can be reduced by controlling these coagulation, washing, and dehydration processes.

[0308] Table 1 shows that when the ash content of nitrile rubber is reduced to 0.5%, the sodium and potassium content in the ash is almost eliminated, and most of the components in the ash become calcium and sulfur (comparison between Examples 12 to Comparative Example 3 and Examples 1 to 9).

[0309] In reducing the ash content of nitrile rubber, sodium and potassium, which are ash components, are used in many polymerization auxiliary materials, including emulsifiers. These ions become embedded in the water-containing crumb during the coagulation reaction and are difficult to remove by washing alone. However, it has been found that when the water-containing crumb is produced under the specific coagulation conditions described above, both washing and dewatering efficiency are significantly improved. On the other hand, as the ash content is reduced, only calcium and sulfur components remain in the ash. This is presumed to be because, since only calcium chloride is used as a coagulant, the chlorine in the calcium chloride is exchanged for a sulfur-containing acid during the coagulation reaction. In other words, many compounds such as sulfates and sulfonates are also used as polymerization auxiliary materials, but calcium salts suddenly become poorly hydrophilic, and it is thought that they could not be removed from the water-containing crumb by normal washing and dewatering. These can be inferred from the changes observed, such as the increase in the total ratio of calcium (Ca) and sulfur (S) content (Ca+S) in the ash, the sudden decrease in the ratio of the total amount of sodium (Na) and potassium (K) content (Na+K) to the total amount of calcium (Ca) and sulfur (S) content (Ca+S) ((Na+K) / (Ca+S)), the sudden increase in the ratio of calcium (Ca) to chlorine (Cl) content (Ca / Cl) (Ca / Cl for calcium chloride is 0.565), and the sudden increase in the ratio of sulfur (S) to chlorine (Cl) content (S / Cl).

[0310] One possible cause of the sulfur component in the ash is sulfur compounds such as t-dodecyl mercaptan, which are molecular weight regulators in polymerization auxiliary materials. However, molecular weight regulators remain at the polymer ends in the form of S-alkyl groups after the polymerization reaction, but are discharged as SO2 during ash treatment, so this is unlikely. Therefore, it is highly probable that the ash, which is rich in calcium and sulfur, remains as a salt of calcium and a sulfur-containing acid. Many polymerization auxiliary materials use sulfates and sulfonates, which are readily soluble in water during the polymerization reaction. However, when calcium chloride is used as a coagulation agent, some of these are converted to calcium salts during the coagulation reaction, becoming poorly hydrophilic and remaining in the nitrile rubber. These salt exchanges can be seen from the fact that the ratio of calcium to chlorine in the ash (Ca / Cl: calcium chloride = 0.565) increases from 1.5 to 2, 3, 5, and 50, while the ratio of sulfur to chlorine (S / Cl) also increases from 1.5 to 2, 3, 5, and 50.

[0311] [Table 2-1]

[0312] [Table 2-2]

[0313] [Table 2-3]

[0314] [Table 2-4]

[0315] Table 2 shows that while most of the hydrogenation catalyst used can be removed by treating the monochlorobenzene (MCB) solution after the hydrogenation reaction with aminopropyl group-modified silica, an ion exchange compound, almost all of the ash in the nitrile rubber remains in the hydrogenated nitrile rubber. This indicates that although the hydrogenation catalyst dissolved in the cement (MCB solution) can be removed, the ash in the nitrile rubber, which is a precursor that does not dissolve, cannot be removed at all. Therefore, reducing the ash content in the precursor nitrile rubber is necessary to reduce the ash content of hydrogenated nitrile rubber.

[0316] Tables 1 and 2 show that the Mw / Mn ratio of hydrogenated nitrile rubber decreases with double decomposition, but it is directly influenced by the Mw / Mn ratio of the nitrile rubber (the larger the Mw / Mn of the nitrile rubber, the larger the Mw / Mn of the hydrogenated nitrile rubber: comparison of Examples 1-2 and Examples 8-10). Furthermore, it can be seen that the larger the molecular weight in the double decomposition reaction, the smaller the Mw / Mn ratio of the hydrogenated nitrile rubber (comparison of Examples 5-7).

[0317] Tables 1 and 2 show that the properties of hydrogenated nitrile rubber, such as the repeat unit ratio, polymer pH, antioxidant content, ash content, the ratio of the total sodium (Na) and potassium (K) content (Na+K) in the ash, the ratio of the total calcium (Ca) and sulfur (S) content (Ca+S) in the ash ((Na+K) / (Ca+S)), the ratio of the total calcium (Ca) and sulfur (S) content (Ca / S) in the ash, the ratio of the calcium (Ca) and chlorine (Cl) content (Ca / Cl) in the ash, and the ratio of the sulfur (S) and chlorine (Cl) content (S / Cl) in the ash, are largely inherited from the properties of nitrile rubber before hydrogenation.

[0318] From Table 2, it contains acrylonitrile polymerization units and 1,3-butadiene polymerization units, the 1,3-butadiene polymerization units consist of 1,2-bonding units, 1,4-bonding units and their hydride units, the weight-average molecular weight (Mw) is 100,000 or less, the ratio of polymerization average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) is 2.5 or more, the iodine value is 100 mg / 100 mg or less, the ash content is 0.7 mass% or less, and the ash contains sodium The hydrogenated nitrile rubbers A to O of the present invention, in which the ratio ((Na+K) / (Ca+S)) of the total amount of potassium content (Na+K) to the total amount of calcium content (Ca) to sulfur content (S) is 0.2 or less, exhibit excellent dispersibility and stability of conductive material dispersions, superior peel strength of electrodes, and significantly improved resistance characteristics, output characteristics, cycle characteristics, and high-temperature storage characteristics of electrochemical elements.

[0319] Regarding the dispersibility of the conductive material dispersion, it can be seen that the hydrogenated nitrile rubbers A to O of the present invention all have a weight-average molecular weight (Mw) of 100,000 or less, indicating good dispersibility. On the other hand, when the Mw of the hydrogenated nitrile rubber is increased (Example 7), or when the proportion of acrylonitrile polymerization units is reduced (Example 14), there is a tendency for the dispersibility of the conductive material dispersion to decrease.

[0320] Regarding the stability of the conductive material dispersion, all of the hydrogenated nitrile rubbers A to O of the present invention exhibit good stability, however, this property deteriorates when the iodine value significantly exceeds 100 mg / 100 mg (Comparative Example 3). Poor stability of the conductive material dispersion leads to deterioration of various properties of the manufactured electrodes and electrochemical elements, necessitating an increase in the iodine value of the hydrogenated nitrile rubber. Furthermore, although not shown in this comparative example, using hydrogenated nitrile rubber that does not contain a phenolic antioxidant reduces the stability of the conductive material dispersion.

[0321] Regarding resistance characteristics, it can be seen that the hydrogenated nitrile rubbers A to O of the present invention show good results when Mw is 100,000 or less. On the other hand, when the Mw of the hydrogenated nitrile rubber increases (Example 7) or when the proportion of acrylonitrile polymerization units decreases (Example 14), the resistance tends to decrease, which is correlated with the dispersibility of the conductive material dispersion. Furthermore, as described in Reference Example 3, the resistance characteristics decrease when the polymer pH of the hydrogenated nitrile rubber becomes excessively low.

[0322] Regarding the output characteristics, it can be seen that the hydrogenated nitrile rubbers A to O of the present invention show sufficiently large Mw / Mn values ​​and good results. On the other hand, it can be seen that the Mw / Mn value of the hydrogenated nitrile rubber changes abruptly between 2 and 3 in terms of output characteristics.

[0323] Regarding the cycle characteristics, all of the hydrogenated nitrile rubbers A to O of the present invention show good results, but it can be seen that they deteriorate significantly when the iodine value exceeds 100 mg / 100 mg (Comparative Example 3). Furthermore, when the proportion of acrylonitrile polymerization units in the hydrogenated nitrile rubber becomes excessively high, the cycle characteristics tend to decrease. This indicates that in order to achieve a high balance between the dispersibility of the conductive material dispersion and the resistance and cycle characteristics of the electrochemical element, the proportion of acrylonitrile polymerization units in the nitrile rubber before hydrogenation should be adjusted.

[0324] Regarding high-temperature storage characteristics, the ash content of hydrogenated nitrile rubber has a significant impact, and it can be seen that the characteristics improve as the ash content is reduced. Furthermore, when the ash content of hydrogenated nitrile rubber is reduced to 0.5% by mass or less, the sodium and potassium content is almost eliminated, and the ash components consist almost entirely of calcium and sulfur. The impact on high-temperature storage characteristics is greater for sodium and potassium, while the ash content, which is high in calcium and sulfur, is smaller. In addition, as the ash content in hydrogenated nitrile rubber is reduced, there is a tendency for the peel strength of the electrode to decrease (Example 11), indicating that this ash content plays a beneficial role in electrode peel strength.

[0325] Regarding the electrode peel strength, all of the hydrogenated nitrile rubbers A to O of the present invention show good results. On the other hand, the electrode peel strength tends to decrease as the Mw of the hydrogenated nitrile rubber decreases (Example 6), and by adjusting the Mw of the hydrogenated nitrile rubber, the electrode peel strength, the dispersibility of the conductive material dispersion, and the resistance characteristics of the electrochemical element can be greatly improved and balanced. Furthermore, the electrode peel strength tends to decrease when the ash content of the specific ash component described later is excessively reduced (Example 11), indicating that the ash content of the specific component of the hydrogenated nitrile rubber improves the electrode peel strength.

[0326] As can be seen from Table 2 above, the hydrogenated nitrile rubbers A to O of the present invention are highly balanced, improving the dispersibility and stability of conductive material dispersions, the peel strength of electrodes, and the resistance characteristics, output characteristics, cycle characteristics, and high-temperature storage characteristics of electrochemical elements. [Explanation of symbols]

[0327] 10 Crushing device 11 Conveyor 20 Melting equipment 21 Dissolution Tank 22, 32, 52a, 52b Stirring device 23, 33, 53a, 53b stirring blade 24, 34, 54a, 54b motors 25, 35, 55a heating device 26, 36 Heating equipment 30 Hydrogenation reactor 31 reaction tanks 37. Hydrogen supply sources 38 Catalyst Source 50 Coagulation equipment 51a First solidification tank 51b Second solidification tank 57a, 57b pumps

Claims

1. Hydrogenated nitrile rubber comprising acrylonitrile polymerization units and 1,3-butadiene polymerization units, wherein the 1,3-butadiene polymerization units consist of 1,2-bonding units, 1,4-bonding units and their hydride units, having a weight-average molecular weight (Mw) of 100,000 or less, a ratio of polymerization average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) of 2.5 or more, an iodine value of 100 mg / 100 mg or less, an ash content of 0.7 mass% or less, and a ratio ((Na+K) / (Ca+S)) of the sum of sodium content (Na) and potassium content (K) in the ash to the sum of calcium content (Ca) and sulfur content (S) (Na+K) of the ash being 0.2 or less.

2. The hydrogenated nitrile rubber according to claim 1, wherein the ash content is 0.5% by mass or less.

3. The hydrogenated nitrile rubber according to claim 1, wherein the ash content is 0.01% by mass or more.

4. The hydrogenated nitrile rubber according to claim 1, wherein the total ratio of acrylonitrile polymerization units and 1,3-butadiene polymerization units is 70 to 100% by mass.

5. The hydrogenated nitrile rubber according to claim 1, wherein the proportion of the acrylonitrile polymerization units is 28% by mass or more and 45% by mass or less.

6. The hydrogenated nitrile rubber according to claim 1, containing a phenolic antioxidant in an amount ranging from 0.001% to 2% by mass.

7. The hydrogenated nitrile rubber according to claim 1, wherein the polymer pH is in the range of 4.5 to 6.

8. The hydrogenated nitrile rubber according to claim 1, wherein the total ratio of calcium content (Ca) and sulfur content (S) in the ash (Ca + S) is 30% by mass or more.

9. The hydrogenated nitrile rubber according to claim 1, wherein the ratio of the total amount (Na + K) of sodium content (Na) and potassium content (K) in the ash is 20% by mass or less.

10. The hydrogenated nitrile rubber according to claim 1, wherein the ratio of calcium content (Ca) to chlorine content (Cl) in the ash (Ca / Cl) is 1.5 or more.

11. The hydrogenated nitrile rubber according to claim 1, wherein the ratio of sulfur content (S) to chlorine content (Cl) in the ash (S / Cl) is 1.5 or more.

12. The hydrogenated nitrile rubber according to claim 1, wherein the ratio of calcium content (Ca) to sulfur content (S) in the ash (Ca / S) is 3 or less.

13. The hydrogenated nitrile rubber according to claim 1, wherein the weight-average molecular weight (Mw) is 10,000 or more.

14. The hydrogenated nitrile rubber according to claim 1, wherein the total ratio of rhodium content (Rh) and ruthenium content (Ru) in the ash (Rh + Ru) is 10% by mass or less.

15. The hydrogenated nitrile rubber according to claim 1, wherein the phosphorus content (P) ratio in the ash is 10% by mass or less.

16. The hydrogenated nitrile rubber according to claim 1, wherein the water content is less than 1% by mass.

17. The hydrogenated nitrile rubber according to claim 1, which is obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride, and then hydrogenating the polymer.

18. The hydrogenated nitrile rubber according to claim 1, wherein the polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using an alkali metal salt as a polymerization auxiliary material is hydrogenated.

19. The hydrogenated nitrile rubber according to claim 1, wherein a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using sulfate and / or sulfonate as polymerization auxiliary materials is hydrogenated.

20. The hydrogenated nitrile rubber according to claim 1, wherein at least one salt compound selected from the group consisting of alkali metal salts, sulfates, and sulfonates is used as a polymerization auxiliary material, and a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride is hydrogenated.

21. A method for producing hydrogenated nitrile rubber, wherein the nitrile rubber contains acrylonitrile polymerization units and 1,3-butadiene polymerization units, has a ratio of the average polymerization molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) of 2.5 or more, has an ash content of 0.7% by mass or less, and has a ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na+K) to the total amount of calcium content (Ca) and sulfur content (S) (Ca+S) ((Na+K) / (Ca+S)) of 0.2 or less.

22. The method for producing hydrogenated nitrile rubber according to claim 21, wherein the shape of the nitrile rubber is veil-like.

23. A method for producing hydrogenated nitrile rubber according to claim 21, wherein the nitrile rubber is hydrogenated after double decomposition.

24. The method for producing hydrogenated nitrile rubber according to claim 21, wherein the hydrogenated nitrile rubber is the hydrogenated nitrile rubber described in any one of claims 1 to 20.

25. A positive electrode material comprising hydrogenated nitrile rubber according to any one of claims 1 to 20.

26. A cathode binder obtained by dissolving the hydrogenated nitrile rubber described in any one of claims 1 to 20 in N-methylpyrrolidone (NMP).

27. A conductive material dispersion liquid obtained by dissolving or dispersing the hydrogenated nitrile rubber and conductive material described in any one of claims 1 to 20 in N-methylpyrrolidone (NMP).

28. A slurry for a positive electrode, comprising a positive electrode active material, a conductive material, and a hydrogenated nitrile rubber according to any one of claims 1 to 20, dissolved or dispersed in N-methylpyrrolidone (NMP).

29. A positive electrode comprising the hydrogenated nitrile rubber described in any one of claims 1 to 20.

30. An electrochemical element comprising the hydrogenated nitrile rubber described in any one of claims 1 to 20.

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