Nitrile rubber

Abstract

Provided is a low ash-content nitrile rubber that: is easily hydrogenated; and, when hydrogenated, allows excellent peel strength of an electrode produced by using a conductive material dispersion liquid containing the hydrogenated nitrile rubber and excellent capacity characteristics and high-temperature storage characteristics of an electrochemical element containing the hydrogenated nitrile rubber. More specifically, the nitrile rubber contains acrylonitrile polymerization units and 1,3-butadiene polymerization units, has an ash content of 0.7 mass % or less, and the total amount (Ca + S) ratio of the calcium content (Ca) and the sulfur content (S) in the ash content, is 40 mass % or more.

Description

Nitrile rubber

[0001] The present invention relates to nitrile rubber and a method for producing the same, hydrogenated nitrile rubber obtained by hydrogenating nitrile rubber, and electrode materials, electrode binders, conductive material dispersions, electrode slurries, electrodes, and electrochemical elements using hydrogenated nitrile rubber.

[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] Patent Document 1 (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 ion-exchanged 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) adding dibutylhydroxytoluene (BHT) as an antioxidant to the obtained polymerization solution, and then (3) adding a 25% by mass aqueous solution of calcium chloride while stirring to coagulate the polymer, washing it with 50 times the volume of ion-exchanged 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 a Grubbs catalyst (bis(tricyclohexylphosphine)benzylideneruthenium chloride) is added to carry out a double decomposition reaction at 80°C and a stirring speed of 600 rpm. Then, (5) a Wilkinson catalyst and triphenylphosphine are added to carry out a hydrogenation reaction 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, improvements in the capacitance characteristics, cycle characteristics, and high-temperature storage characteristics of the electrochemical element, as well as low ash content of the hydrogenated nitrile rubber, are desired.

[0006] On the other hand, as a low-ash hydrogenated nitrile rubber, for example, Patent Document 2 (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 subjected to a centrifuge 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, an 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.

[0007] Furthermore, Patent Document 3 (Japanese Patent Publication No. 2018-145434) 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 to 0.88 in two separate steps), the 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 then (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 a solidification reaction to 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.

[0008] Further, as for low-ash nitrile rubber, for example, Patent Document 4 (Japanese Unexamined Patent Application Publication No. 2004-156011) discloses a method for producing an emulsion polymer of extremely high purity. Specifically, an aqueous dispersion of NBR latex having a Mooney viscosity of 80 MU (ML1+4 at 100°C), comprising 35% by mass of acrylonitrile and 65% by mass of butadiene, is coagulated with a 50% sulfuric acid solution, and the obtained coagulum is treated with an aqueous NaOH solution of pH 11.5 and a 50% sodium hydroxide solution to adjust the pH to 12. Then, the alkaline suspension is passed through a vibrating sieve, and wet polymer fragments are continuously conveyed to a dewatering screw equipped with a filter bar to adjust the residual humidity to 5%, thereby obtaining NBR having an ash content of <0.05%, a total sulfur content of 0.110%, an inorganic chlorine content of 0.009%, 208 mg / kg of Na, 149 mg / kg of K, 4 mg / kg of Ca and <1 mg / kg of Mg, or NBR having an ash content of <0.05%, a total sulfur content of 0.100%, an inorganic chlorine content of 0.011%, 150 mg / kg of Na, 62 mg / kg of K, 2 mg / kg of Ca and <1 mg / kg of Mg.

[0009] Patent Document 5 (Japanese Patent Publication No. 2010-528142) describes the following: (1) In an autoclave equipped with a stirrer, sodium salt of a mixture of monosulfonated and disulfonated naphthalene sulfonic acid containing isobutylene oligomer, sodium salt of methylenebisnaphthalene sulfonic acid, potassium salt of coconut oil fatty acid, and sodium hydroxide are placed in the autoclave with water as emulsifiers, and monomers of acrylonitrile and butadiene, a mixture of t-DDM:C12 mercaptan (0.24 parts + 0.24 parts) as a modifier, and aqueous solutions of tris(α-hydroxyethyl)amine, potassium peroxodisulfate, and sodium dithionite as polymerization initiators are added, and emulsion polymerization is carried out at 17°C until the conversion rate reaches 75%, (2) Before coagulation, an aqueous solution of 2,6-di-tert-butyl-p-cresol, an antioxidant, emulsified with alkylphenol polyglycol ether is added. (3) A coagulation reaction is carried out at 20-50°C with a 15-26% by weight concentration NaCl aqueous solution, and the resulting aggregates are washed with Ca-containing water at 20-40°C for 2.5-9 hours. Alternatively, a coagulation reaction is carried out at 20°C with a 0.3-1.2% by weight concentration CaCl2 aqueous solution, and the resulting aggregates are washed with deionized water at 20°C for 3.4-3.6 hours. (4) The washed rubber aggregates are pre-dried in a Welding screw to a residual moisture content of 5-10% by weight, and then vacuum-dried to obtain an NBR with Ca 325-1290 ppm, Na 6-625 ppm, and K 1-27 ppm.

[0010] However, even when these NBRs were hydrogenated and used as hydrogenated nitrile rubber in the manufacture of electrochemical elements, sufficient properties could not be obtained.

[0011] Publication No. WO2023 / 162835, Publication No. WO2007 / 049651, Japanese Patent Publication No. 2018-145434, Japanese Patent Publication No. 2004-156011, Japanese Patent Publication No. 2010-528142

[0012] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a low-ash nitrile rubber which is easily hydrogenated, and when hydrogenated, the resulting hydrogenated nitrile rubber provides an electrode produced from a conductive material dispersion that has excellent peel strength, and the electrochemical device fabricated therewith has excellent capacitance characteristics and high-temperature storage characteristics, a method for producing the same, a hydrogenated nitrile rubber obtained by hydrogenating the nitrile rubber, as well as an electrode material, an electrode binder, a conductive material dispersion, an electrode slurry, an electrode, and an electrochemical device using the hydrogenated nitrile rubber.

[0013] As a result of intensive studies conducted by the present inventors in view of the above problems, they have found that a low-ash hydrogenated nitrile rubber obtained by hydrogenating a nitrile rubber that contains acrylonitrile polymerized units and 1,3-butadiene polymerized units and has a reduced ash content which is high in calcium and sulfur is effective for solving the above problems.

[0014] In particular, the present inventors have found that a nitrile rubber that contains acrylonitrile polymerized units and 1,3-butadiene polymerized units, has an increased ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw), and has a reduced ash content which is high in calcium and sulfur, when hydrogenated into hydrogenated nitrile rubber, can improve the dispersibility and stability of a conductive material dispersion, enhance the peel strength of an electrode, and further improve the capacitance characteristics, resistance characteristics, cycle characteristics, and high-temperature storage characteristics of an electrochemical device.

[0015] Furthermore, the present inventors have particularly found that a low-molecular-weight, low-ash hydrogenated nitrile rubber obtained by hydrogenating a nitrile rubber that contains acrylonitrile polymerized units and 1,3-butadiene polymerized units, has a controlled ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw), contains an anti-aging agent, and has a reduced ash content which is high in calcium and sulfur, can improve the stability of a conductive material dispersion in the production of an electrochemical device, and significantly improve the peel strength of the produced electrochemical device, as well as the capacitance characteristics and high-temperature storage characteristics of the electrochemical device.

[0016] The present inventors have found that a low-molecular-weight, low-ash hydrogenated nitrile rubber can improve the dispersibility of a conductive material dispersion, and significantly enhance the capacitance characteristics, resistance characteristics, and high-temperature storage characteristics of an electrochemical device.

[0017] Furthermore, the inventors have discovered that it is difficult to remove ash from hydrogenated nitrile rubber that has a low molecular weight and high tackiness, or that hydrogenation of nitrile rubber is performed in an organic solvent such as monochlorobenzene and obtained in a cement state, and although it is possible to remove catalyst components dissolved in the organic solvent with ion exchange resins or activated carbon, it is difficult to remove salt compounds that are insoluble in organic solvents and have a high calcium and sulfur content. However, they have found that it is possible to easily produce hydrogenated nitrile rubber by reducing the ash content at the stage of high molecular weight nitrile rubber before hydrogenation, and then reducing the molecular weight by double decomposition before hydrogenation.

[0018] 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.

[0019] The inventors have discovered that differences in the ash composition of nitrile rubber result in completely different ease of removal, as well as significantly impacts the performance of hydrogenated nitrile rubber when used in the manufacture of electrochemical elements. The inventors have also found that controlling the total amount of sodium and potassium, as well as the total amount of calcium and sulfur, in the ash can dramatically improve the high-temperature storage characteristics of electrochemical elements.

[0020] The ash, which is rich in sodium and potassium, is contained within the water-containing crumb produced during solidification, due to the use of many sodium and potassium salts as polymerization auxiliary materials. Therefore, it cannot be removed by ordinary washing alone and remains in the nitrile rubber, and also remains in hydrogenated hydrogenated nitrile rubber. When used in the manufacture of electrochemical elements, it destroys the negative electrode active material, significantly reducing the capacitance characteristics of the electrochemical element and worsening its high-temperature storage characteristics. However, we have found that the water-containing crumb, which has the above-mentioned special shape and particle size distribution, can be easily removed by washing it with hot water and squeezing out the contained moisture through dehydration.

[0021] 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. When the amount of ash in nitrile rubber is reduced by washing and dehydrating the water-containing crumb with the above-mentioned special shape and particle size distribution, the sodium and potassium components decrease rapidly first, and most of the ash components are replaced by calcium and sulfur. Furthermore, by tracking the changes in data such as the ratio of the total amount of sodium and potassium (Na+K), the ratio of the total amount of calcium and sulfur (Ca+S), and the (Na+K) / (Ca+S) ratio in the ash, we found that the ash components change significantly as the amount of ash decreases.

[0022] One possible cause of sulfur content in 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 after polymerization in the form of S-alkyl groups, but in ash treatment, SO ２It is unlikely that these would be excreted. Therefore, it is highly probable that the ash, which is rich in calcium and sulfur, remains as salts of calcium and sulfur-containing acids. Sulfates and sulfonates are often used as polymerization auxiliary materials, and although these are readily soluble in water during the polymerization reaction, it is suspected that some of them undergo salt exchange with calcium salts during the coagulation reaction when calcium chloride is used as a coagulant, becoming sparingly soluble and remaining in the nitrile rubber. These salt exchanges can be seen from the fact that the mass ratio of calcium to sulfur (Ca / S) in the ash decreases, and the amount of acid containing sulfur as a counteranion to calcium increases. This can also be seen from the fact that the mass ratio of calcium to chlorine (Ca / Cl: calcium chloride = 0.565) increases from 3 or more, to 5 or more, and then to 50 or more, while the mass ratio of sulfur to chlorine (S / Cl) also increases from 3 or more, to 5 or more, and then to 50 or more. This can also be seen from the fact that the mass ratio of calcium to sulfur (Ca / S) in the ash decreases as the amount of ash decreases.

[0023] In their research, the inventors have produced nitrile rubber with low sodium and potassium content and high calcium and sulfur content, thereby reducing the ash content. They have also found that hydrogenated low-ash hydrogenated nitrile rubber, obtained by hydrogenating this low-ash nitrile rubber, enhances the stability of the conductive material dispersion, increases the peel strength of the electrodes, and improves the cycle characteristics and high-temperature storage characteristics of the electrochemical element when used in the manufacture of electrochemical elements. Furthermore, they have found that hydrogenated low-molecular-weight and low-ash hydrogenated nitrile rubber, obtained by hydrogenating low-ash nitrile rubber after reducing its molecular weight through a double decomposition reaction, enhances the dispersibility and stability of the conductive material dispersion, increases the peel strength of the electrodes, and significantly improves the capacitance characteristics, resistance characteristics, cycle characteristics, and high-temperature storage characteristics of the electrochemical element when used in the manufacture of electrochemical elements.

[0024] The inventors have found that increasing the Mz / Mw of nitrile rubber results in a high Mz / Mw being inherited by the hydrogenated nitrile rubber produced after double decomposition. This hydrogenated nitrile rubber exhibits excellent stability in conductive material dispersions, superior peel strength of electrodes, and excellent cycle characteristics of electrochemical elements, achieving a high balance of these properties. Furthermore, the inventors have found that increasing the Mz / Mw of nitrile rubber can be achieved by increasing the polymerization temperature during nitrile rubber emulsion polymerization and thereby increasing the polymerization conversion rate.

[0025] On the other hand, the inventors have also found that hydrogenated nitrile rubber, obtained by hydrogenating nitrile rubber having a specific ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw), can significantly improve the dispersibility of conductive material dispersions and the peel strength of electrodes in the manufacture of electrochemical elements. The inventors have found that while the Mz / Mw of nitrile rubber tends to decrease in double decomposition reactions and hydrogenation reactions, it can be controlled to a higher level by controlling the polymerization temperature and polymerization conversion rate in the manufacture of nitrile rubber.

[0026] The inventors have further discovered that by specifying the proportion of acrylonitrile polymerization units, the proportion of 1,2-bonding units in 1,3-butadiene polymerization units, weight-average molecular weight, antioxidant content, polymer pH, water content, and the total proportion of sodium and potassium in the ash, the mass ratio of the total amount of sodium and potassium to the total amount of calcium and sulfur, the mass ratio of calcium to chlorine, the mass ratio of calcium to sulfur, and the mass ratio of sulfur to chlorine, the dispersibility and stability of the conductive material dispersion, the peel strength of the electrodes, and the capacitance, resistance, cycle characteristics, and high-temperature storage characteristics of the electrochemical element, the inventors have found that these properties can be further improved.

[0027] Based on these findings, the inventors have completed the present invention.

[0028] According to one aspect of the present invention, the following [1] to

[40] are provided.

[0029] [1] Nitrile rubber containing acrylonitrile polymerization units and 1,3-butadiene polymerization units, with an ash content of 0.7% by mass or less and a total amount of calcium content (Ca) and sulfur content (S) in the ash (Ca + S) of 40% by mass or more.

[0030] [2] The nitrile rubber according to [1], wherein the ratio of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) (Mz / Mw) is 1.5 or more, and the mass ratio of the calcium content (Ca) to the sulfur content (S) in the ash (Ca / S) is 3 or less.

[0031] [3] The nitrile rubber according to [1], wherein the ratio of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) (Mz / Mw) is in the range of 1.5 or more and 7 or less, and further comprises an antioxidant.

[0032] [4] The nitrile rubber according to [1] or [3], wherein the mass ratio (Ca / S) of the calcium content (Ca) to the sulfur content (S) in the ash is 3 or less.

[0033] [5] Nitrile rubber according to any one of [1] to [4], wherein the weight-average molecular weight (Mw) is 10,000 or more and 5,000,000 or less.

[0034] [6] Nitrile rubber according to any one of [1] to [5], wherein the weight-average molecular weight (Mw) is 100,000 or more.

[0035] [7] Nitrile rubber according to any one of [1] to [6], wherein the ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) is in the range of 2.5 or more and 6 or less.

[0036] [8] The nitrile rubber according to any one of [1] to [7], wherein the ratio of the total amount (Na + K) of sodium content (Na) and potassium content (K) in the ash is 10% by mass or less.

[0037] [9] The nitrile rubber according to any one of [1] to [8], wherein the ash content is 0.01% by mass or more.

[0038]

[10] Nitrile rubber according to any one of [1] to [9], wherein the polymer pH is 4.5 or higher and 6 or lower.

[0039]

[11] The nitrile rubber according to any one of [1] to

[10] , wherein the mass ratio (Ca / Cl) of calcium content (Ca) to chlorine content (Cl) in the ash is 1.5 or more.

[0040]

[12] The nitrile rubber according to any one of [1] to

[11] , wherein the mass ratio (Ca / Cl) of the calcium content (Ca) to the chlorine content (Cl) in the ash is 3 or more.

[0041]

[13] The nitrile rubber according to any one of [1] to

[12] , wherein the mass ratio (S / Cl) of the sulfur content (S) to the chlorine content (Cl) in the ash is 1.5 or more.

[0042]

[14] The nitrile rubber according to any one of [1] to

[13] , wherein the mass ratio (S / Cl) of the sulfur content (S) to the chlorine content (Cl) in the ash is 3 or more.

[0043]

[15] The nitrile rubber according to any one of [1] to

[14] , wherein the mass ratio ((Na+K) / (Ca+S)) 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) is 0.5 or less.

[0044]

[16] The nitrile rubber according to any one of [1] to

[15] , wherein the mass ratio ((Na+K) / (Ca+S)) 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) is 0.3 or less.

[0045]

[17] The nitrile rubber according to any one of [1] to

[16] , wherein the proportion of 1,2-bonding units in the 1,3-butadiene polymerization unit is 5% by mass or more.

[0046]

[18] The nitrile rubber according to any one of [1] to

[17] , wherein the proportion of 1,2-bonding units in the 1,3-butadiene polymerization unit is 30% by mass or less.

[0047]

[19] The nitrile rubber according to any one of [1] to

[18] , wherein the proportion of 1,2-bonding units in the 1,3-butadiene polymerization unit is 12% by mass or more and 16% by mass or less.

[0048]

[20] The nitrile rubber according to any one of [1] to

[19] , wherein the proportion of the acrylonitrile polymerization units is 28% by mass or more and 40% by mass or less.

[0049]

[21] The nitrile rubber according to any one of [1] to

[20] , wherein the total ratio of the acrylonitrile polymerization units and the 1,3-butadiene polymerization units is 70 to 100% by mass.

[0050]

[22] Nitrile rubber according to any one of [1] to

[21] , wherein the content of the antioxidant is in the range of 0.001 to 2% by mass.

[0051]

[23] Nitrile rubber according to any one of [1] to

[22] , wherein the water content is less than 1% by mass.

[0052]

[24] The nitrile rubber according to any one of [1] to

[23] , which is a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride.

[0053]

[25] The nitrile rubber according to any one of [1] to

[24] , wherein acrylonitrile and 1,3-butadiene are emulsion polymerized using an alkali metal salt as a polymerization auxiliary material.

[0054]

[26] The nitrile rubber according to any one of [1] to

[25] , wherein acrylonitrile and 1,3-butadiene are emulsion polymerized using sulfate and / or sulfonate as polymerization auxiliary materials.

[0055]

[27] Nitrile rubber according to any one of [1] to

[26] , 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 acrylonitrile and 1,3-butadiene are emulsion polymerized and coagulated with calcium chloride.

[0056]

[28] A method for producing nitrile rubber, comprising emulsion polymerization of monomer components containing acrylonitrile and 1,3-butadiene, and contact with an aqueous calcium chloride solution to produce a water-containing crumb by contacting the emulsion polymerization solution with an aqueous calcium chloride solution, and then washing, dewatering, and drying the water-containing crumb, wherein 50% by mass or more of the water-containing crumb is water-containing crumb that passes through a JIS sieve with an opening of 8 mm but does not pass through a JIS sieve with an opening of 4.75 mm.

[0057]

[29] The method for producing nitrile rubber according to

[28] , wherein the nitrile rubber is the nitrile rubber described in any of [1], [2] and [5] to

[27] .

[0058]

[30] A method for producing nitrile rubber, comprising emulsion polymerization of monomer components containing acrylonitrile and 1,3-butadiene, contacting the emulsion polymerization solution to which an antioxidant has been added with an aqueous calcium chloride solution to produce a hydrated crumb that satisfies all of the following conditions (a) to (e), and then washing, dewatering, and drying the produced hydrated crumb. (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 a mesh size of 8 mm but do not pass through a JIS sieve with a mesh size of 1.7 mm is 50% by mass or more, (d) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 1.7 mm but do not pass through a JIS sieve with a mesh size of 0.43 mm is 25% by mass or less, and (e) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 0.43 mm is 10% by mass or less.

[0059]

[31] The method for producing nitrile rubber according to

[30] , wherein 30% by mass or more of the water-containing crumb produced 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.

[0060]

[32] The method for producing nitrile rubber according to

[30] or

[31] , wherein the nitrile rubber is the nitrile rubber described in any of [1] and [3] to

[27] .

[0061] Hydrogenated nitrile rubber having an iodine value of 100 mg / 100 mg or less, obtained by hydrogenating the nitrile rubber described in any of

[33] [1] to

[27] .

[0062] Hydrogenated nitrile rubber obtained by hydrogenating a nitrile rubber described in any of

[34] [1] to

[27] after double decomposition, having a weight-average molecular weight (Mw) of 100,000 or less and an iodine value of 100 mg / 100 mg or less.

[0063] An electrode material comprising the hydrogenated nitrile rubber described in

[35] ,

[33] , or

[34] .

[0064] An electrode binder obtained by dissolving the hydrogenated nitrile rubber described in

[36] ,

[33] , or

[34] in N-methylpyrrolidone (NMP).

[0065] A conductive material dispersion obtained by dissolving or dispersing the hydrogenated nitrile rubber and conductive material described in

[37] ,

[33] , or

[34] in N-methylpyrrolidone (NMP).

[0066]

[38] An electrode slurry obtained by dissolving or dispersing an electrode active material, a conductive material, and the hydrogenated nitrile rubber described in

[33] or

[34] in N-methylpyrrolidone (NMP).

[0067] An electrode comprising the hydrogenated nitrile rubber described in

[39] ,

[33] , or

[34] .

[0068] An electrochemical element comprising the hydrogenated nitrile rubber described in

[40] ,

[33] , or

[34] .

[0069] The present invention provides a low-ash nitrile rubber that is easy to hydrogenate, and the hydrogenated nitrile rubber after hydrogenation enhances the peel strength of electrodes manufactured with a conductive material dispersion, and also enhances the capacitance characteristics and high-temperature storage characteristics of electrochemical elements, as well as a method for producing the same, hydrogenated nitrile rubber obtained by hydrogenating nitrile rubber, and electrode materials, electrode binders, conductive material dispersions, electrode slurries, electrodes, and electrochemical elements using hydrogenated nitrile rubber.

[0070] This figure shows an example of a nitrile rubber manufacturing system according to an embodiment of the present invention.

[0071] Embodiments of the present invention will be described in detail below. In the following description, the positive electrode will be described as an example of an electrode according to the present invention.

[0072] The nitrile rubber of the present invention is characterized by containing acrylonitrile polymerization units and 1,3-butadiene polymerization units, and having reduced ash content with high calcium and sulfur content.

[0073] One embodiment of the nitrile rubber of the present invention is characterized by comprising acrylonitrile polymerization units and 1,3-butadiene polymerization units, having a ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) of 1.5 or more, an ash content of 0.7% by mass or less, a total amount of calcium content (Ca) and sulfur content (S) in the ash (Ca+S) of 40% by mass or more, and a mass ratio of calcium content (Ca) to sulfur content (S) (Ca / S) of 3 or less.

[0074] Another embodiment of the nitrile rubber of the present invention is characterized by comprising acrylonitrile polymerization units and 1,3-butadiene polymerization units, having a ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) in the range of 1.5 to 7, containing an antioxidant, having an ash content of 0.7% by mass or less, and a total amount of calcium content (Ca) and sulfur content (S) in the ash (Ca + S) of 40% by mass or more.

[0075] <Nitrile Rubber> (Repeating Units) The nitrile rubber of the present invention contains acrylonitrile polymerization units and 1,3-butadiene polymerization units.

[0076] The proportion of acrylonitrile polymerization units in the 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 nitrile rubber are within this range, the hydrogenated hydrogenated nitrile rubber can improve the dispersibility of the conductive material dispersion and improve the cycle characteristics and resistance characteristics of the electrochemical element.

[0077] The proportion of 1,3-butadiene polymerization units in the 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 80% by mass or less, more preferably 75% by mass or less, even more preferably 72% by mass or less, and most preferably 70% by mass or less.

[0078] The total ratio of acrylonitrile polymerization units and 1,3-butadiene polymerization units in the 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.

[0079] The proportion of 1,2-bonding units in the 1,3-butadiene polymerization units in the 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, and 12% by mass or more. The proportion of 1,2-bonding units in the 1,3-butadiene polymerization units of the nitrile rubber is also inherited in hydrogenated hydrogenated nitrile rubber, and is preferable when it is within this range because it can greatly enhance the capacitance characteristics of the electrochemical element. There is no particular limit to the upper limit of the total ratio of 1,2-bonding units and their hydride units in the 1,3-butadiene polymerization units in nitrile rubber, but it 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, 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 electrode from which the hydrogenated hydrogenated nitrile rubber is produced.

[0080] The 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 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.

[0087] (Anti-aging agent) The nitrile rubber of the present invention may contain an anti-aging agent.

[0088] There are no particular limitations on the anti-aging agents that can be included, but examples include amine-based anti-aging agents and phenol-based anti-aging agents, with phenol-based anti-aging agents being particularly preferred. There are no particular limitations on the phenol-based anti-aging agents, but for example, hindered phenol-based anti-aging agents are preferred because they remain in the hydrogenated hydrogenated nitrile rubber and can improve the stability of the conductive material dispersion and the electrode peel strength.

[0089] 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) butyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) hexyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) octyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) decyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) dodecyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) butyl propionate 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.

[0090] 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.

[0091] These antioxidants can be used individually or in combination of two or more. The content of the antioxidant in the 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 nitrile rubber is excessively low, the stability of the dispersion of hydrogenated hydrogenated nitrile rubber 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.

[0092] (Characteristics) One embodiment of the nitrile rubber of the present invention includes the above repeating units and has the characteristics of a specific ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) and a reduction in the ash content of a specific ash component.

[0093] Another aspect of the nitrile rubber of the present invention comprises the above-mentioned repeating units and an anti-aging agent, and has the properties of a specific ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) and a reduction in the ash content of a specific ash component.

[0094] The ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) of the nitrile rubber of the present invention 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, and 3 or higher, and 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, the 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, when hydrogenation is performed after double decomposition, the Mz / Mw after double decomposition will be smaller, so 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 of the hydrogenated nitrile rubber.

[0095] The weight-average molecular weight (Mw) of the nitrile rubber of the present invention is not particularly limited, but is usually 1,000 or more, preferably 10,000 or more and 30,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more and 120,000 or more, most preferably 150,000 or more, in the order of 180,000 or more and 200,000 or more, and usually 5,000,000 or less, preferably 3,500,000 or less and 2,000,000 or less, more preferably 1,000,000 or less, most preferably in the order of 500,000 or less, 400,000 or less and 300,000 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.

[0096] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) (Mw / Mn) of the nitrile rubber of the present invention is not particularly limited, but is usually 1.2 or higher, preferably 1.5 or higher, more preferably 2 or higher, or preferably in the order of 2.1 or higher, 2.2 or higher, 2.3 or higher, 2.4 or higher, 2.5 or higher, 2.6 or higher, 3 or higher, 3 or higher, 3.5 or higher, 3.6 or higher, 3.7 or higher, 3.8 or higher, 3.9 or higher, and 4 or higher, and is usually 8 or lower, preferably 7 or lower, more preferably 6.5 or lower, or preferably in the order of 6 or lower, 5.5 or lower, 5 or lower, and 4.5 or lower. When the Mw / Mn of the nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber can improve the output characteristics and cycle characteristics in electrochemical elements.

[0097] The ash content of the 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 nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber suppresses the increase in resistance during high-temperature storage of the electrochemical element, and also suppresses the deterioration of capacitance characteristics and cycle characteristics due to the destruction of the negative electrode active material, which is preferable. There is no particular limit to the lower limit of the ash content in 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. Hydrogenated hydrogenated nitrile rubber can increase the electrode peel strength at this time.

[0098] The total amount (Ca+S) of calcium content (Ca) and sulfur content (S) in the ash of the nitrile rubber of the present invention is 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, or preferably in the order of 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 amount (Ca+S) of calcium content (Ca) and sulfur content (S) in the ash of the nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber increases the electrode peel strength, suppresses the increase in resistance when the electrochemical element is stored at high temperatures, and suppresses the deterioration of capacity characteristics and cycle characteristics due to the destruction of the negative electrode active material, etc.

[0099] The total amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the 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, 7% 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 amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber can suppress the decrease in capacitance characteristics due to the destruction of the negative electrode active material of the electrochemical element, and can also suppress the increase in resistance during high-temperature storage.

[0100] The mass ratio ((Na+K) / (Ca+S)) of the total amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the nitrile rubber of the present invention to the total amount of calcium (Ca) and sulfur (S) content (Ca+S) is not particularly limited, but is usually 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less, or preferably in the order of 0.4 or less, 0.3 or less, 0.25 or less, 0.2 or less, 0.15 or less, 0.1 or less, 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. When the ratio is within this range, the hydrogenated hydrogenated nitrile rubber increases the electrode peel strength, suppresses the increase in resistance during high-temperature storage of the electrochemical element, and suppresses the deterioration of capacitance characteristics and cycle characteristics due to the destruction of the negative electrode active material, etc.

[0101] The mass ratio (Ca / S) of calcium content (Ca) to sulfur content (S) in the ash of the nitrile rubber of the present invention 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, 2.8 or less, 2.5 or less, 2.3 or less, 2 or less, 1.8 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, and 1.15 or less, and is 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, 0.9 or more, and 1 or more. When the mass ratio (Ca / S) of calcium content (Ca) to sulfur content (S) in the ash of nitrile rubber is within this range, hydrogenated hydrogenated nitrile rubber enhances the electrode peel strength, suppresses the increase in resistance of the resulting electrochemical element during high-temperature storage, and also suppresses the deterioration of capacitance characteristics due to the breakdown of the negative electrode active material.

[0102] The mass ratio (Ca / Cl) of calcium content (Ca) to chlorine content (Cl) in the ash of the nitrile rubber of the present invention is not particularly limited, but is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, or preferably in the order of 0.8 or more, 0.9 or more, 1 or more, 1.2 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.8 or more, 2 or more, 2.5 or more, 3 or more, 3.5 or more, 4 or more, 5 or more, 10 or more, 20 or more, and 50 or more, is usually 100 or less, preferably 90 or less, more preferably 80 or less, even more preferably 75 or less, and most preferably 70 or less. When the mass ratio (Ca / Cl) of calcium content (Ca) to chlorine content (Cl) in the ash of the nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber can enhance the viscosity characteristics of the conductive material dispersion and suppress the deterioration of the cycle characteristics of the resulting electrochemical element.

[0103] The mass ratio (S / Cl) of sulfur content (S) to chlorine content (Cl) in the ash of the nitrile rubber of the present invention is not particularly limited, but is usually 0.3 or more, preferably 0.5 or more, more preferably 0.7 or more, or preferably in the order of 1 or more, 1.5 or more, 2 or more, 2.5 or more, 3 or more, 3.5 or more, 4 or more, 4.5 or more, 5 or more, 10 or more, 30 or more, and 50 or more, is usually 100 or less, preferably 90 or less, more preferably 80 or less, even more preferably 75 or less, and most preferably 70 or less. When the mass ratio (S / Cl) of sulfur content (S) to chlorine content (Cl) in the ash of the nitrile rubber is within this range, the electrode peel strength of the hydrogenated hydrogenated nitrile rubber is increased, the increase in resistance during high-temperature storage of the electrochemical element is suppressed, and the decrease in capacity characteristics and cycle characteristics due to the destruction of the negative electrode active material is suppressed.

[0104] The calcium content (Ca) in the ash of the 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 nitrile rubber is within this range, the electrode peel strength of the hydrogenated hydrogenated nitrile rubber 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.

[0105] The sulfur content (S) in the ash of the 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 nitrile rubber is within this range, the electrode peel strength of the hydrogenated hydrogenated nitrile rubber 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.

[0106] The chlorine content (Cl) in the ash of the 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, the effects of the hydrogenated hydrogenated nitrile rubber, such as the cycle characteristics of the electrochemical element and the suppression of resistance increase during high-temperature storage, are improved.

[0107] The total amount of sodium (Na) and potassium (K) content (Na+K) in the ash of the 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 nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber can suppress the decrease in battery capacity and cycle characteristics due to the destruction of the negative electrode active material, etc.

[0108] The sodium content (Na) in the ash of the 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 nitrile rubber is within this range, the hydrogenated hydrogenated nitrile rubber can suppress the decrease in battery capacity and cycle characteristics due to the destruction of the negative electrode active material, etc.

[0109] The potassium content (K) in the ash of the 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 nitrile rubber is within this range, the hydrogenated nitrile rubber can suppress the decrease in battery capacity and cycle characteristics due to the destruction of the negative electrode active material, etc.

[0110] The nitrile rubber of the present invention is not limited by the manufacturing process, but is preferably a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using an alkali metal salt as a polymerization auxiliary material.

[0111] 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.

[0112] The nitrile rubber of the present invention is preferably a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene using sulfates and / or sulfonates as polymerization auxiliary materials.

[0113] 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 mass ratio of calcium to chlorine (Ca / Cl) of the calcium chloride used as a coagulant was 0.565, the mass ratio of calcium content (Ca) to chlorine content (Cl) in the ash (Ca / Cl) was much larger. It was inferred that during the coagulation reaction, some of the readily soluble calcium chloride was exchanged for acidic salts containing sparingly soluble sulfur and remained in the polymer. Although it is difficult to remove such sparingly soluble salts, by devising the coagulation reaction, washing, and dehydration processes described later, nitrile rubber with reduced sparingly soluble 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 sparingly soluble salts had the effect of increasing the peel strength of the electrodes. However, the effect of polymers with reduced levels of these poorly soluble 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.

[0114] The nitrile rubber of the present invention is preferably a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride. In particular, it is more preferable that the polymer is obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene and coagulation with calcium chloride, using at least one salt compound selected from the group consisting of alkali metal salts, sulfates, and sulfonates as polymerization auxiliary materials.

[0115] 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.

[0116] The nitrile rubber of the present invention is preferably a polymer obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene, followed by the addition of an antioxidant, particularly a phenolic antioxidant, and then coagulation with calcium chloride.

[0117] 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.

[0118] The polymer pH of the 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 3.5 or higher, 4 or higher, and 4.5 or higher in that order, and is usually 8 or lower, preferably 7 or lower, more preferably 6.5 or lower, even more preferably 6 or lower, and most preferably 5.8 or lower. When the pH of the nitrile rubber is within this range, the viscosity stability of the hydrogenated nitrile rubber slurry for the positive electrode can be increased, and the capacitance and resistance characteristics of the electrochemical element can be improved.

[0119] The water content of the 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.

[0120] <Method for Manufacturing Nitrile Rubber> The above method for manufacturing nitrile rubber is not particularly limited, but for example, monomer components containing acrylonitrile and 1,3-butadiene are emulsion polymerized, and then an anti-aging agent is added to the emulsion polymer solution, which is then brought into contact with an aqueous calcium chloride solution to produce a specific water-containing crumb, for example, a water-containing crumb that satisfies all of the following conditions (a) to (e). Then, the produced water-containing crumb is washed, dehydrated, and dried to easily produce the nitrile rubber. (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 a mesh size of 8 mm but do not pass through a JIS sieve with a mesh size of 1.7 mm is 50% by mass or more, (d) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 1.7 mm but do not pass through a JIS sieve with a mesh size of 0.43 mm is 25% by mass or less, and (e) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 0.43 mm is 10% by mass or less.

[0121] Furthermore, a nitrile rubber with even lower ash content can be produced when 30% by mass 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.

[0122] (Monomer Components) The monomer components used are the same as those described for the monomer components of the repeating units, and the amount used should be appropriately selected to match the monomer composition of the nitrile rubber.

[0123] (Emulsion polymerization process) There are no particular limitations on the emulsifier used in emulsion polymerization, and it is 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 and phosphate esters such as polyoxyalkylene alkyl ether phosphates; and alkyl sulfosuccinates. Among these, fatty acid salts, alkylbenzene sulfonates, and sulfate esters are preferred, and fatty acid salts and alkylbenzene sulfonates are particularly preferred.

[0124] 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.

[0125] 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 components.

[0126] 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 stirrer such as a homogenizer or 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.

[0127] Polymerization auxiliary materials refer to known materials used in emulsion polymerization, in addition to the emulsifiers mentioned above, which are appropriately optimized and used. Specifically, various polymerization regulators can be used, such as molecular weight regulators (chain transfer agents), pH adjusters, stabilizers, and reducing agents and chelating agents in redox catalysts.

[0128] 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.

[0129] Examples of radical generators include peroxides and azo compounds, with peroxides being preferred. Inorganic and organic peroxides are used. While inorganic peroxides are superior for increasing the number of 1,2-bonding units in the 1,3-butadiene polymerization units of nitrile rubber, organic peroxides are preferred for increasing the number of 1,2-bonding units in the 1,3-butadiene polymerization units and obtaining a stable weight-average molecular weight (Mw) for nitrile rubber.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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 can be increased. In addition, the ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) of the nitrile rubber can be increased.

[0135] 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 number of 1,2-bonding units in the 1,3-butadiene polymerization units of the nitrile rubber. It can also increase the ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) of the nitrile rubber. A polymerization inhibitor may be used to stop the polymerization.

[0136] (Addition of Anti-aging Agent) In one embodiment of the present invention, an anti-aging agent is added to the emulsion polymerization solution after the emulsion polymerization described above. Adding an 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.

[0137] The antioxidant used is the same as the example of the antioxidant contained in the 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.

[0138] The amount of antioxidant used can be appropriately selected to match the amount of antioxidant in the nitrile rubber of the present invention, but is usually 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.

[0139] (Coagulation process) In the coagulation reaction, an aqueous solution of calcium chloride is used as a coagulant and is brought into contact with the polymerization solution to which the above-mentioned antioxidant is added to produce a hydrated crumb.

[0140] The solid content concentration of the 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.

[0141] While there are no particular limitations on the concentration of the aqueous calcium chloride 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.

[0142] 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, when a uniform hydrated crumb is produced.

[0143] In the method for producing nitrile rubber of the present invention, it is preferable to add the polymerization solution to a 10-30% by mass aqueous calcium chloride solution that is vigorously stirred at 300 rpm or more. The water-containing crumb produced by this coagulation method can significantly improve the washing efficiency and dewatering efficiency of emulsifiers and coagulants.

[0144] There are no particular limitations on the rotation speed of the stirring blade, 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 stirring blade 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.

[0145] The peripheral velocity of the stirred solidified liquid is expressed as the linear velocity of the outer circumference of the stirring blade of the stirring device. It is preferable for the solidified liquid to be stirred 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 stirred solidified liquid, but typically it is 50 m / s or less, preferably 30 m / s or less, more preferably 25 m / s or less. Particularly preferable are 20 m / s or less, 15 m / s or less, 10 m / s or less, 5 m / s or less, and 4 m / s or less, in that order. When the velocity is within this range, it becomes easier to control the solidification reaction.

[0146] The resulting water-containing crumb is preferable when, after sieving (classification) using a JIS classification sieve, the proportion of water-containing crumb that passes through an 8 mm mesh JIS sieve but does not pass through a 4.75 mm mesh JIS sieve is 50% by mass or more, as this offers excellent operability and improved washing and dewatering efficiency.

[0147] Furthermore, there are no particular limitations on the type of water-containing crumb produced, but for example, when sieving (classification) is performed using a JIS classifying sieve under the conditions (a) to (g) below, the proportion of water-containing crumbs with a diameter of 3.35 to 4.75 mm is greatest, which is preferable because it provides a high balance between the efficiency of removal of emulsifiers and coagulants during washing and dewatering and the workability.

[0148] In the present invention, the resulting water-containing crumb is preferable if it satisfies all of the following conditions (a) to (e), as this significantly improves the efficiency of removing the emulsifier and coagulant 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 usually 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less. (b) The percentage 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 usually 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 a mesh size of 8 mm but do not pass through a JIS sieve with a mesh size of 1.7 mm is usually 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 sieve but not through a 0.43 mm mesh JIS sieve is usually 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 0.43 mm mesh JIS sieve is usually 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less.

[0150] In the present invention, it is further preferable that the resulting water-containing crumbs satisfy the following (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 usually 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 do not pass through a JIS sieve with a mesh size of 3.35 mm is usually 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 within 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] (Washing Process) In the present invention, it is preferable to use hot water as the washing method. The temperature of the hot water is usually 30°C or higher, preferably 35 to 100°C, more preferably 40 to 80°C, even more preferably 40 to 60°C, and most preferably 40 to 50°C, as this can significantly increase the washing efficiency. Calcium sulfate and calcium sulfonate salts are poorly soluble and have low solubility, but their solubility tends to increase at certain specific temperatures. By setting the temperature of the washing water above the aforementioned lower limit, emulsifiers and coagulants are released from the water-containing crumb, further improving the washing efficiency.

[0154] In the present invention, it is also effective to wash the hydrated crumb solidified with the above-mentioned high-concentration calcium chloride aqueous solution 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 the like 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 water-containing crumb after dewatering can be followed according to conventional methods. For example, it can be dried using a dryer such as a hot air dryer, vacuum dryer, expander dryer, kneader dryer, or screw extruder.

[0161] The shape of the dried rubber (polymer) is not particularly limited and can be, for example, crumb-like, powder-like, rod-like, or sheet-like. 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 is readily subject to hydrogenation, and hydrogenated nitrile rubber can be easily produced by carrying out this hydrogenation reaction.

[0163] <Hydrogenated Nitrile Rubber> The hydrogenated nitrile rubber of the present invention is obtained by hydrogenating the above-mentioned nitrile rubber to obtain an iodine value of 100 mg / 100 mg or less. The hydrogenated nitrile rubber of the present invention is also obtained by hydrogenating the above-mentioned nitrile rubber after a double decomposition reaction to obtain a weight-average molecular weight (Mw) of 100,000 or less and an iodine value of 100 mg / 100 mg or less.

[0164] The hydrogenated nitrile rubber of the present invention has the following properties: acrylonitrile polymerization unit ratio, 1,3-butadiene polymerization unit ratio, 1,2-bonding unit ratio (unhydrogenated unit + hydride unit) ratio in the 1,3-butadiene polymerization unit, other repeating unit ratios, ash content, ratio of the total amount of calcium content (Ca) and sulfur content (S) in the ash (Ca + S), ratio of the total amount of sodium content (Na) and potassium content (K) in the ash (Na + K), mass 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)), and the amount of calcium in the ash The mass ratio of sodium content (Ca) to sulfur content (S) (Ca / S), the mass ratio of sulfur content (S) to chlorine content (Cl) in the ash (S / Cl), the mass 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, as well as the repeating unit ratios, ash amount, and ash component amounts, are the same as those described for nitrile rubber, and the characteristic values ​​of nitrile rubber are inherited.

[0165] The type and content of the antioxidant in the hydrogenated nitrile rubber of the present invention are the same as those described for nitrile rubber, and the antioxidant content in the nitrile rubber is largely retained in the hydrogenated nitrile rubber. Furthermore, the polymer pH of the hydrogenated nitrile rubber of the present invention is the same as those described for nitrile rubber, and the polymer pH of the nitrile rubber is largely retained even after the hydrogenation reaction.

[0166] 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 in the order of 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, with the lower limit usually being 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 electrode, and the cycle characteristics of the electrochemical element can be greatly enhanced.

[0167] 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 1.3 or higher, preferably 1.4 or higher, more preferably 1.5 or higher, or preferably in the order of 1.6 or higher, 1.7 or higher, 1.8 or higher, 1.9 or higher, 2 or higher, 2.1 or higher, 2.2 or higher, 2.3 or higher, 2.4 or higher, and 2.5 or higher, and is usually 7 or lower, preferably 6 or lower, 5.5 or lower, more preferably 5 or lower, or preferably in the order of 4.5 or lower, 4 or lower, 3.5 or lower, 3 or lower, and 2.7 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.

[0168] The weight-average molecular weight (Mw) of the hydrogenated nitrile rubber obtained after the double decomposition reaction of the 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 weight-average molecular weight (Mw) is within this range, the dispersibility of the conductive material is significantly improved, and the resistance characteristics of the manufactured electrochemical element can be enhanced. On the other hand, there is no particular limit to the lower limit of the weight-average molecular weight (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. When the weight-average molecular weight (Mw) is within this range, the peel strength of the obtained electrode can be enhanced.

[0169] The weight-average molecular weight (Mw) of the hydrogenated nitrile rubber produced by hydrogenating nitrile rubber without the double decomposition reaction of the present invention is not particularly limited, but is usually 100,000 or more, preferably 150,000 or more, more preferably 180,000 or more, even more preferably 200,000 or more, most preferably 250,000 or more, and usually within the range of 5,000,000 or less, preferably 3,000,000 or less, 1,500,000 or less, more preferably 1,000,000 or less, and most preferably 500,000 or less. When the weight-average molecular weight (Mw) of the hydrogenated nitrile rubber is within this range, the electrode peel strength can be greatly increased.

[0170] In the hydrogenated nitrile rubber of the present invention, when the weight-average molecular weight (NMP-Mw) measured with N-methylpyrrolidone (NMP) as the solvent and the weight-average molecular weight (THF-Mw) measured with tetrahydrofuran (THF) as the solvent satisfy the relationship NMP-Mw ≥ THF-Mw, the dispersibility and stability of the conductive material dispersion using NMP as the solvent can be greatly improved.

[0171] 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 weight-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.

[0172] The weight-average molecular weight (Mw) of the nitrile rubber and hydrogenated nitrile rubber of the present invention were measured using tetrahydrofuran (THF) as the solvent, unless otherwise specified, by the method described in the examples below.

[0173] 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 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and most preferably 0.3% by mass or less.

[0174] 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, and most preferably 10% 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.

[0175] 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.

[0176] (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.

[0177] There are no particular limitations on the ruthenium-based catalyst used, and 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.

[0178] 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 having 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.

[0179] The amount of coolefin used is typically 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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 two hours. The progress of the double decomposition reaction can be monitored using standard analytical methods, such as GPC or solution viscosity.

[0184] (Hydrogenation reaction) The hydrogenation reaction can be carried out by dissolving nitrile rubber, or nitrile rubber that has undergone the double decomposition reaction as necessary, in a solvent (organic solvent) and adding a hydrogenation catalyst.

[0185] 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.

[0186] 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, the reaction vessel is subjected to hydrogen purging to produce a dihydrogen complex (PR), which is an olefin hydrogenation catalyst. ３ ) ２ RuCl ２ H ２ Since it is converted to , the process can be carried out continuously. In addition, dihydrogen complexes or other ruthenium-based catalysts can be used from the beginning. The hydrogenation reaction can be carried out according to a conventional method, for example, by the method described in Japanese Patent No. 6309634.

[0187] There are no particular limitations on hydrogenation catalysts other than ruthenium-based catalysts, but in particular, rhodium-based Wilkinson catalysts ((PPh ３ ) ３Known homogeneous hydrogenation catalysts such as RhCl are 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 a conventional method, for example, by the method described in Japanese Patent No. 6309634. In the case of the Wilkinson catalyst, examples of 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.

[0188] 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 and 0.01 to 0.05 parts by mass, based on 100 parts by mass of polymer before hydrogenation.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] (Catalyst removal and drying) After the hydrogenation reaction, the hydrogenation catalyst can be removed as needed, and then the area can be dried to obtain hydrogenated nitrile rubber.

[0194] The hydrogenation catalyst, if used as needed, can be removed by conventional methods, for example, by adsorbent treatment. The adsorbent is not particularly limited, but examples include activated carbon, ion exchange resin, and synthetic zeolite, with ion exchange resin being preferred.

[0195] 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.

[0196] After the adsorption treatment, the adsorbent can be removed by filtration or decantation, and the filtrate can be dried to obtain hydrogenated nitrile rubber.

[0197] <Positive electrode material and positive electrode binder> The positive electrode material of the present invention is characterized by using the above-mentioned hydrogenated nitrile rubber.

[0198] 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, for example, by adding an NMP solution to a hydrogenated nitrile rubber-containing monochlorobenzene solution obtained by hydrogenating nitrile rubber in monochlorobenzene, and then distilling off the monochlorobenzene solvent to perform solvent replacement.

[0199] 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 materials, 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.

[0200] 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.

[0201] The mixing method for hydrogenated nitrile rubber, NMP, and other components used as needed should follow conventional methods.

[0202] <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. The conductive material dispersion of the present invention can be manufactured, for example, by mixing the positive electrode binder and the conductive material of the present invention.

[0203] (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 type), 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.

[0204] 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.

[0205] 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, and the upper limit is 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.

[0206] 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.

[0207] <Slurry for Positive Electrode> The slurry for positive electrode of the present invention is obtained by dispersing or dissolving a positive electrode active material, a conductive material, and the hydrogenated nitrile rubber described above in N-methylpyrrolidone (NMP). Such a slurry for positive electrode can be produced by adding a solvent to the binder for positive electrode and the conductive material as needed, mixing them, and then mixing the positive electrode active material.

[0208] <Electrode for Electrochemical Device> The positive electrode of the present invention comprises the hydrogenated nitrile rubber described above, and for example, consists of a positive electrode mixture layer comprising a binder containing 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 binder for positive electrode and the conductive material as needed, mixing them, then mixing in the positive electrode active material to obtain the slurry for positive electrode described above, applying the slurry onto a current collector, and then drying the applied slurry.

[0209] (Positive Electrode Active Material) The positive electrode active material is not particularly limited, but when the electrochemical device is a lithium ion secondary battery, metal oxides containing lithium (Li) may be mentioned. As the positive electrode active material, a positive electrode active material containing, 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 a positive electrode active material include lithium-containing cobalt oxide (LiCoO ２ ), lithium manganate (LiMn ２ O ４ ), lithium-containing nickel oxide (LiNiO ２ ), 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 (LiMnPO ４ ), olivine-type lithium iron phosphate (LiFePO ４ ), Li １＋ｘ Mn ２－ｘ O ４ , a lithium-excess spinel compound represented by (0<X<2), Li[Ni ０．１７ Li ０．２ Co ０．０７ Mn ０．５６ O ２ , LiNi ０．５ Mn １．５ O ４, Li[Ni ０．５ Co ０．２ Mn ０．３ ]O ２ These are some examples. 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 two or more types may be used in any ratio.

[0210] 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.

[0211] (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 known current collectors can be used. For example, the current collector of 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 aluminum alloys of different types may be used. Aluminum and aluminum alloys are excellent current collector materials because they are heat resistant and electrochemically stable.

[0212] 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.

[0213] (Coating Process) The method for coating the positive electrode slurry onto the current collector is not particularly limited and any known method can be used. Specifically, the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, brush coating method, etc., can be used as coating methods. In this case, the positive electrode slurry may be coated on only one side of the current collector or on both sides. The thickness of the slurry film on the current collector before drying after coating can be appropriately set according to the thickness of the positive electrode composite layer obtained after drying.

[0214] (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 a current collector and a positive electrode composite layer can be obtained.

[0215] 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.

[0216] <Electrochemical Element> The electrochemical element of the present invention is characterized by containing the hydrogenated nitrile rubber of the present invention. The electrochemical element equipped with 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.

[0217] 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.

[0218] (Negative electrode) The negative electrode is not particularly limited and any known electrode can be used.

[0219] (Electrolyte) Typically, an organic electrolyte is used, which is an organic electrolyte in which a supporting electrolyte is dissolved in an organic solvent. For example, lithium salts are used as supporting electrolytes. For example, LiPF ６ LiAsF ６ LiBF ４ LiSbF ６ LiAlCl ４ LiClO ４ CF ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Examples include NLi. Among them, LiPF is particularly suitable because it is easily soluble in solvents and exhibits a high degree of dissociation. ６ LiClO ４ CF ３ SO ３ Li is preferred, LiPF ６ This is particularly preferable. 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.

[0220] 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.

[0221] 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.

[0222] (Separator) The separator is not particularly limited, and for example, those described in Japanese Patent Application 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.

[0223] (Method for manufacturing a lithium-ion secondary battery) 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.

[0224] <Applications> 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] <Configuration of the Nitrile Rubber Manufacturing System> The configuration of the nitrile rubber manufacturing system for manufacturing nitrile rubber according to the present invention will be described below. Figure 1 is a diagram showing an example of the nitrile rubber manufacturing system in an embodiment of the present invention.

[0229] Figure 1 schematically illustrates the apparatus configuration of a nitrile rubber manufacturing system according to an embodiment of the present invention, in accordance with the manufacturing process. The nitrile rubber manufacturing system shown in Figure 1 is generally configured to include an emulsion polymerization apparatus 10, a coagulation apparatus 30, a washing apparatus 50, and a squeezer 70.

[0230] (Emulsion polymerization apparatus 10) The emulsion polymerization apparatus 10 is configured to perform the processes related to the emulsion polymerization process. As shown in Figure 1, the emulsion polymerization apparatus 10 has a polymerization tank 11 and a stirring device 12 for copolymerizing monomer components such as acrylonitrile monomer and 1,3-butadiene monomer. The emulsion polymerization apparatus 10 may be batch type, semi-batch type, or chain type, and may be a tank reactor or a tubular reactor.

[0231] The polymerization vessel 11 is formed, for example, in a closed cylindrical shape so that it can store the emulsion polymerization liquid. The stirring device 12 is located inside the polymerization vessel 11 and includes a stirring blade 13 which is a member that rotates around a predetermined axis, a motor 14 that rotates the stirring blade 13, and a drive control unit (not shown) that controls the rotational number and rotational speed of the stirring blade 13.

[0232] A predetermined amount of acrylonitrile and 1,3-butadiene and water are placed in the polymerization vessel 11, polymerization auxiliary materials such as emulsifiers and molecular weight regulators are added, and nitrogen purging is performed to remove oxygen from the polymerization vessel 11. Then, a polymerization initiator is added while stirring to start the polymerization reaction.

[0233] The stirring device 12 is configured to rotate the stirring blades 13 at a predetermined rotational speed (stirring speed) inside the polymerization vessel 11, thereby enabling proper flow of the emulsion polymerization liquid. The stirring speed of the stirring blades 13, the shape and size of the stirring blades 13, the number of blades installed, etc., are determined appropriately considering the reaction conditions, etc.

[0234] The temperature of the emulsion polymerization solution inside the polymerization vessel 11 affects the reaction rate, molecular weight distribution, and molecular structure. For example, the proportion of 1,2-bond units in the polymerization units of 1,3-butadiene increases as the temperature of the emulsion polymerization solution increases and decreases as the temperature of the emulsion polymerization solution decreases, so this can be controlled by appropriately controlling the temperature of the emulsion polymerization solution.

[0235] When a predetermined polymerization conversion rate is reached, a polymerization stopper is added to the polymerization tank 11 to stop the polymerization reaction. The polymerization addition rate can be controlled to determine the molecular weight, molecular weight distribution, and the proportion of 1,2-bonding units in the 1,3-butadiene polymerization units of the nitrile rubber produced, so it can be appropriately selected according to the required properties. In addition, a process related to the addition of an anti-aging agent is carried out, and after the polymerization reaction is completed, the anti-aging agent is added to the polymerization tank 11. After that, the latex in the polymerization tank 11 is transferred to the solidification tank 31 of the solidification device 30.

[0236] (Solidification device 30) The solidification device 30 is configured to perform the processing related to the solidification process. As shown in Figure 1, the solidification device 30 has a solidification tank 31 and a stirring device 32 for solidifying the latex transferred from the emulsion polymerization device 10 and extracting crumb-shaped nitrile rubber (water-containing crumb).

[0237] The solidification tank 31 is formed, for example, in a closed cylindrical shape and is capable of storing a solidified liquid containing a solidifying agent (for example, calcium chloride). The stirring device 32 is located inside the solidification tank 31 and includes a stirring blade 33 which is a member that rotates around a predetermined axis, a motor 34 that rotates the stirring blade 33, and a drive control unit (not shown) that controls the rotational number and speed of the stirring blade 33.

[0238] In the coagulation apparatus 30, hydrated crumbs are generated by bringing the latex transferred from the emulsion polymerization apparatus 10 into contact with a coagulation solution containing a coagulant (e.g., calcium chloride). The method of contact between the latex and the coagulation solution is not particularly limited; for example, the latex may be added to the agitated coagulation solution, or the coagulation solution may be added to the agitated latex. In this embodiment, the coagulation apparatus 30 employs the method of adding the latex to the agitated coagulation solution. Adding the latex to the agitated coagulation solution concentrates the generated hydrated crumbs so that their shape and diameter are uniform, significantly improving the cleaning efficiency in the subsequent cleaning process.

[0239] The stirring device 32 is configured to rotate the stirring blades 33 at a predetermined rotational speed (stirring speed) within the solidification tank 31, thereby enabling proper flow of the solidified liquid. The stirring speed of the stirring blades 33, the shape and size of the stirring blades 33, the number of blades installed, etc., are determined appropriately considering the reaction conditions, etc., but it is preferable to configure the device to apply a strong shear force in order to generate smaller water-containing crumbs.

[0240] In the method of adding latex to a stirred solidifying solution, the solidifying solution and water (soft water) are filled into the solidifying tank 31 and stirred with the stirring blade 33, and the latex is added to the stirred solidifying solution. The latex that comes into contact with the solidifying solution solidifies and a water-containing crumb is formed.

[0241] The water-containing crumb generated in the solidification tank 31 is removed from the solidification tank 31 by overflowing it along with the solidification liquid and water-containing liquid. The water-containing crumb removed from the solidification tank 31 is transferred to the washing tank 51 of the washing device 50 via the dewatering machine 38.

[0242] As shown in Figure 1, a dewatering machine 38 is positioned between the solidification tank 31 and the washing tank 51. The dewatering machine 38 is configured to separate the water-containing crumb from the liquid (solidified liquid). A screen, wire mesh, electric sieve, etc., can be used for the dewatering machine 38.

[0243] (Washing device 50) The washing device 50 is configured to perform the processing related to the washing process. As shown in Figure 1, the washing device 50 has a washing tank 51 for receiving the water-containing crumb and washing water transferred from the solidification device 30, a stirring device 52, and a heating device 55.

[0244] The washing tank 51 is formed, for example, in a closed cylindrical shape and is capable of storing water-containing crumbs and washing water. The stirring device 52 is located inside the washing tank 51 and includes a stirring blade 53 which is a member that rotates around a predetermined axis, a motor 54 that rotates the stirring blade 53, and a drive control unit (not shown) that controls the rotational number and speed of the stirring blade 53. The heating device 55 includes a heating unit 56 that heats the inside of the washing tank 51, and a temperature control unit (not shown) that controls the temperature inside the washing tank 51.

[0245] The agitator 52 is configured to rotate the agitator blades 53 at a predetermined rotational speed (agitation speed) within the washing tank 51, thereby washing the water-containing crumbs by appropriately flowing the water-containing crumbs and washing water. The agitation speed of the agitator blades 53, the shape and size of the agitator blades 53, and the number of blades installed are determined appropriately considering the size of the water-containing crumbs and the washing efficiency.

[0246] The heating unit 56 of the heating device 55 sends steam to a jacket provided on the outer circumference of the washing tank 51, for example, and heats the washing liquid through heat exchange with the steam. The temperature of the washing water in the washing tank 51 is controlled to be, for example, 40°C or higher in order to improve the effect of releasing emulsifiers and coagulants from the water-containing crumb.

[0247] The water-containing crumb, washed in the washing tank 51, is removed from the washing tank 51 by overflowing with washing water. The water-containing crumb removed from the washing tank 51 is then transferred to the squeezer 70 via the dewatering machine 58.

[0248] (Squeezer 70) The squeezer 70 is configured to perform the dewatering process. In this embodiment, the squeezer 70 is used as the dewatering machine, but as a dewatering device for dewatering the water-containing crumb, for example, a screw-type extruder dryer that performs dewatering and drying can be used.

[0249] As shown in Figure 1, the squeezer 70 has a two-stage configuration in which an upstream heating mechanism 71 and a downstream pressurizing mechanism 72 are connected by a connecting part 73.

[0250] The heating mechanism 71 includes a chamber 71a and a roller 71b for heating the water-containing cramb, a motor (not shown) that generates rotational power to rotate the roller 71b, and a heating device 71c that supplies steam into the chamber 71a. The roller 71b is housed in the chamber 71a so as to extend in the direction of conveying the water-containing cramb. The shape of the roller 71b is not particularly limited, but for example, it is formed in a screw shape.

[0251] At the upstream end of the chamber 71a, a crumb supply unit 70a is provided for introducing water-containing crumbs transferred from the washing device 50 into the chamber 71a. The downstream end of the chamber 71a is connected to a connecting unit 73. Steam at a predetermined temperature and pressure is supplied into the chamber 71a by a heating device 71c. The steam temperature is set to, for example, 120°C. The steam pressure is set to, for example, 150 kPa. By heating the water-containing crumbs with steam in the heating mechanism 71, the dewatering efficiency in the subsequent pressurizing mechanism 72 can be improved.

[0252] The water-containing crambs fed into the cramb supply section 70a are heated while being pushed downstream by the rotation of the rollers 71b (roller transport), and then transferred through the connecting section 73 into the chamber 72a of the pressurizing mechanism 72.

[0253] The pressurizing mechanism 72 includes a chamber 72a and a roller 72b for pressurizing the water-containing cramb, and a motor (not shown) that generates rotational power to rotate the roller 72b. The roller 72b is housed in the chamber 72a so as to extend in the direction of conveying the water-containing cramb. The shape of the roller 72b is not particularly limited, but for example, it is formed in a screw shape.

[0254] The upstream end of chamber 72a is connected to a connecting portion 73. The downstream end of chamber 72a is provided with a crumb discharge portion 70b for discharging the water-containing crumb that has been dewatered in chamber 72a.

[0255] The pressurizing mechanism 72 is configured such that a roller 72b compresses the water-containing crumb within the chamber 72a, squeezing out the moisture from the crumb. The roller 72b may be single or two or more. The water-containing crumb is pushed downstream as moisture is squeezed out by the pressurizing effect of the rotation of the roller 72b, and is discharged from the crumb discharge section 70b. The dewatered water-containing crumb, dewatered by the squeezer 70, is transferred to the crushing device 75. The water content of the dewatered water-containing crumb is usually 35% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0256] (Crushing device 75) The crushing device 75 is configured to crush and pulverize the water-containing crumb transferred from the squeezer 70. The water-containing crumb discharged by the squeezer 70 after dewatering is uneven in size and shape. By crushing and pulverizing it in the crushing device 75, the drying efficiency in the subsequent drying process can be improved.

[0257] The crushing device 75 can be any device capable of crushing and pulverizing the crumb, such as a hammer-type crusher, a cutter-type crusher, a roller-type crusher, or a pin mill. In particular, considering that it can efficiently and continuously crush water-containing crumb that has elasticity and viscosity, it is preferable to use a hammer-type crusher that crushes and pulverizes the water-containing crumb by the impact of a hammer rotated at high speed.

[0258] The water-containing crumb, which is crushed after dehydration, is dried in a drying process to become dried rubber.

[0259] 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.

[0260] 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.

[0261] In the examples, reference examples, and comparative examples, various measurements and evaluations were carried out according to the following methods.

[0262] <Distribution of Moisture-Containing Crambs> The moisture-containing crambs produced by the coagulation reaction were classified using a JIS classification sieve. After that, each classified moisture-containing cramb was dried in a hot air dryer at 80°C for 3 hours, and the mass was measured to determine the proportion of each mass of cramb diameter (a) to (h). The JIS sieve conformed to the provisions of the Japanese Industrial Standard (JIS Z8801-1). (a) Does not pass through a JIS sieve with a mesh size of 9.5 mm, (b) 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) 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) 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) 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) 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) 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) Passes through a JIS sieve with a mesh size of 0.43 mm.

[0263] <Moisture Content> The moisture content of the water-containing crumb produced by the coagulation reaction after dehydration was determined according to the "oven method" specified in JIS K6238-1. Specifically, 10 g of water-containing crumb was placed in an oven at 105 ± 5°C and dried until the mass no longer changed substantially. The amount of mass loss before and after drying was determined, and the ratio of the mass loss to the mass of the dried crumb was calculated as the moisture content.

[0264] <Repeating Units> The acrylonitrile polymerization units and 1,3-butadiene polymerization units in the polymer (the sum of 1,2-bonding units, 1,4-bonding units, and their hydride units) 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 determined by converting this to a mass ratio.

[0265] The proportion of 1,2-bond units in the 1,3-butadiene polymerization units of the polymer is, １Using 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.

[0266] <Iodine Value> The iodine value of hydrogenated nitrile rubber was measured in accordance with JIS K6235.

[0267] <Molecular Weight> The weight-average molecular weight (Mw), Z-average molecular weight (Mz), and molecular weight distribution (Mz / Mw) 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 (Tosoh Corporation) • Detector: Differential refractometer detector RID-10A (Shimadzu Corporation) • Eluent flow rate: 0.6 mL / min • Column temperature: 40°C • Standard polymer: TSK Standard Polystyrene (Tosoh Corporation)

[0268] <Anti-aging agent content> The polymer was dissolved in a chlorobenzene solution and analyzed by gas chromatography to determine the percentage of anti-aging agent (BHT) content relative to the total mass of the polymer.

[0269] <Polymer pH> The pH of nitrile rubber or hydrogenated nitrile rubber was determined by adding 90 g of deionized water to 10 g of NMP solution (solid content concentration: 8%) of nitrile rubber or hydrogenated nitrile rubber, stirring and pressing with a spatula, and extracting the liquid contained within the solidified nitrile rubber or hydrogenated nitrile rubber 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) and was determined as the polymer pH.

[0270] <Water content of polymer> The water content of the polymer was measured in accordance with the "oven method" specified in JIS K6238-1.

[0271] <Ash Content> The amount of ash contained in the rubber was measured in accordance with JIS K6228A method.

[0272] <Ash Content> The amount of each component in the ash was 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 ZSX Primus (manufactured by Rigaku).

[0273] <Dispersibility of Conductive Material Dispersions> For the conductive material dispersions obtained in the examples, reference examples, and comparative examples, the viscosity 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 viscosity value indicates better dispersibility. ◎: 4 Pa·s or less 〇: Greater than 4 Pa·s and 6 Pa·s or less △: Greater than 6 Pa·s and 8 Pa·s or less ×: Greater than 8 Pa·s

[0274] <Stability of Conductive Material Dispersion Viscosity> The conductive material dispersions obtained in the examples, reference examples, and comparative examples were measured for viscosity (η0) and then stored in a sealed container at 25°C for 10 days. After that, the viscosity of the dispersion was measured again (η1), and the viscosity change rate was calculated. The viscosity retention rate Δη of the conductive material dispersion before and after storage was calculated as η1 / η0 × 100 (%), and the viscosity stability of the conductive material dispersion was evaluated according to the following criteria. The closer 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% 〇: 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

[0275] <Peel Strength> The positive electrodes prepared in the examples, reference examples, and comparative examples were cut into rectangles with a length of 100 mm and a width of 10 mm to serve as test pieces. Cellophane tape (compliant with JIS Z1522) was attached to the surface of the positive electrode composite layer with the side containing the positive electrode composite layer facing downwards. The stress was measured when the tape was peeled off by pulling one end of the current collector vertically at a speed of 100 mm / min (the cellophane tape was fixed to the test stand). Three measurements were taken, and the average value was calculated and defined as the peel strength, which was evaluated according to the following criteria. A higher peel strength value indicates that the positive electrode composite layer is firmly adhered to the current collector made of aluminum foil. ◎: Peel strength of 15 N / m or more ○: Peel strength of 10 N / m or more and less than 15 N / m ○ to △: Peel strength of 7 N / m or more and less than 10 N / m △: Peel strength of 5 N / m or more and less than 7 N / m ×: Peel strength of less than 5 N / m

[0276] <Flexibility> The positive electrodes prepared in the examples, reference examples, and comparative examples were wrapped around a 3.0 mm diameter stainless steel cylinder (with the current collector on the inside). The presence or absence of crack formation on the surface of the positive electrode composite layer after wrapping was visually confirmed. If no crack formation was confirmed, the diameter of the stainless steel cylinder was successively reduced to 2.5 mm and then 2.0 mm, and the same procedure was performed. The diameter of the cylinder at which the first crack was confirmed on the surface of the positive electrode composite layer (cylinder diameter at the time of crack formation) was recorded and evaluated according to the following criteria. A smaller cylinder diameter at the time of crack formation indicates superior flexibility of the positive electrode, and if no cracks are formed even when using a 2.0 mm diameter cylinder, it indicates extremely superior flexibility of the positive electrode. ◎: No crack formation was confirmed even with a cylinder diameter of 2.0 mm. ○: Cylinder diameter at the time of crack formation is 2.0 mm △: Cylinder diameter at the time of crack formation is 2.5 mm ×: Cylinder diameter at the time of crack formation is 3.0 mm

[0277] <Capacity Characteristics> The lithium-ion secondary batteries prepared in the Examples, Reference 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 (where C is a value expressed as rated capacity (mA) / 1h (hour)), and then aged 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. The discharge capacity of this third discharge was taken as the initial capacity, and the value of initial capacity / theoretical capacity was evaluated according to the following criteria. A larger value indicates a higher initial discharge capacity of the lithium-ion secondary battery. ◎: Initial capacity / theoretical capacity is 0.8 or higher 〇: Initial capacity / theoretical capacity is 0.78 or higher but less than 0.8 〇~△: Initial capacity / theoretical capacity is 0.76 or higher but less than 0.78 △: Initial capacity / theoretical capacity is 0.74 or higher but less than 0.76 ×: Initial capacity / theoretical capacity is 0.72 or higher but less than 0.74 ××: Initial capacity / theoretical capacity is less than 0.72

[0278] <Resistivity Characteristics> For the positive electrodes prepared in the Examples, Reference 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 resistivity was measured and evaluated according to the following criteria: ◎: Resistivity of 0.03 Ω·cm ２ Below, ○: Resistivity of 0.03 Ω·cm ２ Super 0.1Ω・cm ２ Below △: Resistivity is 0.1Ω・cm ２ Super 0.3Ω・cm ２ Below ×: Resistivity is 0.3Ω・cm ２ Super

[0279] <Cycle Characteristics> The lithium-ion secondary batteries prepared in the Examples, Reference Examples, and Comparative Examples were left standing 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 aged 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 0.2C charge-discharge process was repeated three times. Next, under conditions of 45°C, the charge-discharge operation was performed 300 times with a cell voltage of 4.35-3.00V and a charge-discharge rate of 1.0C. At that time, the discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 300th cycle was defined as X2. Using the 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 that the lithium-ion secondary battery has superior cycle characteristics. ◎: Capacity retention rate of 87% or more 〇: Capacity retention rate of 82% or more and less than 87% 〇~△: Capacity retention rate of 77% or more and less than 82% △: Capacity retention rate of 75% or more and less than 77% ×: Capacity retention rate less than 75%

[0280] <High-Temperature Storage Characteristics> The lithium-ion secondary batteries prepared in the Examples, Reference Examples, and Comparative Examples were left standing 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 aged 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, the lithium-ion secondary battery was charged to 50% of its State of Charge (SOC) at 1.0C in a 25°C atmosphere. 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 (upper limit cell voltage 4.35V) was performed at a constant current of 0.2C. Next, the lithium-ion secondary battery was stored for 4 weeks in an inert oven with a nitrogen atmosphere at 80°C. After storage, the IV resistance R2 after high-temperature storage was measured in the same way as the initial IV resistance R1. Using the obtained initial IV resistance R1 and the IV resistance R2 after high-temperature storage, the IV resistance increase rate was calculated using the following formula. IV resistance increase rate (%) = (R2 - R1) / R1 × 100 This IV resistance increase rate (%) and the IV resistance R2 after high-temperature storage were used to evaluate according to the following criteria. The smaller the IV resistance increase rate (%) and the IV resistance R2 (Ω) after high-temperature storage, the lower the internal resistance over the long term, indicating superior battery characteristics of the lithium-ion secondary battery. ◎: IV resistance increase rate less than 40% ◎~〇: IV resistance increase rate 40% or more and less than 45% 〇: IV resistance increase rate 45% or more and less than 50% 〇~△: IV resistance increase rate 50% or more and less than 55% △: IV resistance increase rate 55% or more and less than 60% ×: IV resistance increase rate 60% or more and less than 65% ××: IV resistance increase rate 65% or more

[0281] (Example 1) <Production of Nitrile Rubber> In a reactor with an internal volume of 10 liters, 100 parts of ion-exchanged 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, appropriate amounts of reducing agent, and chelating agent were added, and emulsion polymerization was carried out at a temperature of 30°C to copolymerize acrylonitrile and 1,3-butadiene. When the polymerization conversion rate reached 80%, 0.2 parts of hydroxylamine sulfate per 100 parts of monomer was added to stop the polymerization. Next, the mixture was heated and steam distilled under reduced pressure at approximately 90°C to recover the residual monomers. Then, 0.1 parts of dibutylhydroxytoluene (BHT), a phenolic antioxidant, was added, and the pH was adjusted to 5.5 with a pH buffer to obtain the polymerization solution.

[0282] 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.

[0283] Next, the filtered water-containing crumb was added to a washing tank equipped with a stirring device and filled with deionized water at 45°C. The water-containing crumb was washed by passing 50 times the amount of deionized water (45°C) relative to the polymer while stirring. The washed water-containing crumb was heated to 60°C, then dehydrated at over 100°C using a steam-injected squeezer until the water content was reduced to 7%, and then dried under reduced pressure at 90°C to obtain nitrile rubber A. The repeating unit ratio, molecular weight, molecular weight distribution, polymer pH, antioxidant content, water content, and ash content of the obtained nitrile rubber A were measured and are shown in Table 1. Furthermore, the sodium (Na), potassium (K), calcium (Ca), sulfur (S), and chlorine (Cl) content in the ash was measured, and the ratio of the total amount of sodium (Na) and potassium (K) (Na+K) to the total amount of ash, the ratio of the total amount of calcium (Ca) and sulfur (S) (Ca+S) to the total amount of ash, the mass ratio of the total amount of sodium (Na) and potassium (K) (Na+K) to the total amount of calcium (Ca) and sulfur (S) (Ca+S) ((Na+K) / (Ca+S)), the mass ratio of calcium (Ca) to sulfur (S) (Ca / S), the mass ratio of calcium (Ca) to chlorine (Cl) (Ca / Cl), and the mass ratio of sulfur (S) to chlorine (Cl) (S / Cl) were calculated, and these results are shown together in Table 1.

[0284] <Hydrogenation of Nitrile Rubber> (Double Decomposition Reaction) Next, 9 parts of the obtained nitrile rubber A were dissolved in 141 parts of monochlorobenzene, a halogenated hydrocarbon, and added to the 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 so that the amount of Grubbs catalyst relative to the polymer was 1000 ppm. Then, 4.4 parts of cis-2-butene-1,4-diol as a coolefin were added per 100 parts of nitrile rubber A, and the double decomposition reaction of the polymer was carried out at a stirring speed of 600 rpm. During the reaction, the temperature was kept constant using a cooling coil connected to a temperature control device and a heat sensor.

[0285] (Hydrogenation reaction) After that, while continuing to stir, the reactor is heated to 0.7 MPa. ２ The mixture was degassed three times. 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 of the polymer was carried out under a hydrogen pressure (gauge pressure) of 8.4 MPa.

[0286] (Catalyst Removal Process) After the hydrogenation reaction was complete, in order to remove the ruthenium catalyst, one part of aminopropyl group-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 filtered solution was dried under reduced pressure at 90°C until the monochlorobenzene content reached 50 ppm to isolate hydrogenated nitrile rubber A.

[0287] The iodine value of the obtained hydrogenated nitrile rubber A was measured and is shown in Table 2. The weight-average molecular weight (Mw) of hydrogenated nitrile rubber A was measured to be 48,000, and the Z-average molecular weight (Mz) was measured and the ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) was calculated to be 2.5, which was about "1" smaller than the Mz / Mw of the nitrile rubber before hydrogenation. In addition, the repeating unit ratio, antioxidant content, polymer pH, and ash content of the hydrogenated nitrile rubber were measured and confirmed to be unchanged from those properties of nitrile rubber. Furthermore, the sodium (Na), potassium (K), calcium (Ca), sulfur (S), ruthenium (Ru), rhodium (Rh), phosphorus (P), and chlorine (Cl) content in the ash were measured, and the ratio of the total amount of ruthenium (Ru) and rhodium (Rh) (Ru + Rh) to the total amount of ash, the ratio of phosphorus (P) to the total amount of ash, the ratio of the total amount of sodium (Na) and potassium (K) (Na + K) to the total amount of ash, and the calcium (Cl) content to the total amount of ash were measured. a) The ratio of the total amount of sodium (Na) and sulfur (S) content (Ca+S), the mass 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 mass ratio of calcium (Ca) content to sulfur (S) content (Ca / S), the mass ratio of calcium (Ca) content to chlorine (Cl) content (Ca / Cl), and the mass ratio of sulfur (S) content to chlorine (Cl) content (S / Cl) were calculated, and the results are shown in Table 2. It was confirmed that these values ​​were almost the same as the values ​​of nitrile rubber before hydrogenation. 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.

[0288] <Manufacturing of Lithium-ion Secondary Batteries> (Manufacturing of Positive Electrode Binder) After the above hydrogenation reaction, an appropriate amount of NMP was mixed with the filtered monochlorobenzene solution, and all of the chlorobenzene was evaporated under reduced pressure to obtain hydrogenated nitrile rubber positive electrode binder A (solid content concentration: 8%).

[0289] (Preparation of conductive material dispersion) 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, and 74.6 parts of NMP as an organic solvent were added and stirred with a disperser (3000 rpm, 10 minutes). Then, conductive material dispersion A was prepared by mixing for 1 hour at a peripheral speed of 8 m / s using a bead mill (manufactured by 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.

[0290] (Preparation of cathode slurry) In the conductive material dispersion described above, a ternary active material having a layered structure (LiNi) is added as the cathode active material. ０．５ Co ０．２ Mn ０．３ O ２ 98.5 parts of (average particle size: 10 μm), 1.0 part of polyvinylidene fluoride as a binder, 0.5 parts (solid content equivalent) of the above conductive material dispersion, and NMP were added and mixed in a planetary mixer (60 rpm, 30 minutes) to prepare cathode slurry A. 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.

[0291] (Preparation of the positive electrode) A 20 μm thick aluminum foil was prepared as the current collector. The above-mentioned slurry A for the positive electrode 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 a lithium-ion secondary battery. The peel strength and flexibility of the obtained positive electrode were measured, and the results are shown in Table 2.

[0292] (Preparation 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 added and thoroughly stirred, then heated to 50°C to start polymerization. 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 the binder for the negative electrode.

[0293] 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.

[0294] Next, a copper foil with a thickness of 15 μm 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.

[0295] (Fabrication of Lithium-ion Secondary Battery) The fabricated positive electrode A and negative electrode for the lithium-ion secondary battery were placed with their electrode mixture layers facing each other, and a 15 μm thick separator (microporous polyethylene membrane) was interposed between them. The materials were then wound around a 20 mm diameter core to obtain a wound body. The obtained 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.

[0296] Additionally, 1.0 M LiPF is used as the electrolyte. ６ A solution was prepared (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2% by volume of vinylene carbonate (solvent ratio)).

[0297] 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.

[0298] The capacity characteristics, resistance characteristics, cycle characteristics, and high-temperature storage characteristics of the obtained lithium-ion secondary battery A were evaluated, and the results are shown in Table 2.

[0299] (Example 2) Nitrile rubber B, hydrogenated nitrile rubber B, cathode binder B, conductive material dispersion B, cathode slurry B, cathode B, and lithium-ion secondary battery B were obtained in the same manner as in Example 1, except that the polymerization conversion rate was changed to 85%. The same evaluation as in Example 1 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber B were almost unchanged from the specific values ​​of nitrile rubber B before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of nitrile rubber B before hydrogenation.

[0300] (Example 3) Nitrile rubber C, hydrogenated nitrile rubber C, cathode binder C, conductive material dispersion C, cathode slurry C, cathode 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. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber C were almost unchanged from the specific values ​​of nitrile rubber C before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of nitrile rubber C before hydrogenation.

[0301] (Example 4) 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, except that the water content after dehydration of the water-containing crumb was changed to 25%. The same evaluation as in Example 1 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber D were almost unchanged from the specific values ​​of nitrile rubber D before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of nitrile rubber D before hydrogenation.

[0302] (Example 5) Nitrile rubber E, hydrogenated nitrile rubber E, cathode binder E, conductive material dispersion E, cathode slurry E, cathode E, and lithium-ion secondary battery E 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 35%. The same evaluation as in Example 1 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber E were almost unchanged from the specific values ​​of the nitrile rubber E before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber E before hydrogenation.

[0303] (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 polymerization conversion rate was changed to 75%. The same evaluation as in Example 5 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber F were almost unchanged from the specific values ​​of the nitrile rubber F before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber F before hydrogenation.

[0304] (Example 7) 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, except that the polymerization conversion rate was changed to 78%. The same evaluation as in Example 5 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber G were almost unchanged from the specific values ​​of the nitrile rubber G before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber G before hydrogenation.

[0305] (Example 8) 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, 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. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber H were almost unchanged from the specific values ​​of the nitrile rubber H before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber H before hydrogenation.

[0306] (Example 9) 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, except that the water content after dehydration of the water-containing crumb was changed to less than 1%. The same evaluation as in Example 5 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber I were almost unchanged from the specific values ​​of nitrile rubber I before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of nitrile rubber I before hydrogenation.

[0307] (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 1, except that the addition of the polymerization solution in the solidification reaction was changed to be performed from the middle of the solidification tank wall (1 / 2 outside) from the stirring blade of the stirred calcium chloride aqueous solution to the wall side. The same evaluation as in Example 1 was performed and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber J were almost unchanged from the specific values ​​of the nitrile rubber J before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber J before hydrogenation.

[0308] (Example 11) 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 10, except that the rotation speed of the solidification tank stirring blade was changed to 350 rpm (peripheral speed 1.8 m / s). The same evaluation as in Example 10 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber K were almost unchanged from the specific values ​​of the nitrile rubber K before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber K before hydrogenation.

[0309] (Example 12) Nitrile rubber L, hydrogenated nitrile rubber L, cathode binder L, conductive material dispersion L, cathode slurry L, cathode L, and lithium-ion secondary battery L were obtained in the same manner as in Example 11, 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 11 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber L were almost unchanged from the specific values ​​of the nitrile rubber L before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber L before hydrogenation.

[0310] (Example 13) Nitrile rubber M, hydrogenated nitrile rubber M, cathode binder M, conductive material dispersion M, cathode slurry M, cathode M, and lithium-ion secondary battery M were obtained in the same manner as in Example 11, except that the amount of acrylonitrile in emulsion polymerization was changed to 47 parts and the amount of 1,3-butadiene to 53 parts. The same evaluation as in Example 11 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber M were almost unchanged from the specific values ​​of the nitrile rubber M before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber M before hydrogenation.

[0311] (Reference Example 1) Nitrile rubber N, hydrogenated nitrile rubber N, positive electrode binder N, conductive material dispersion N, positive electrode slurry N, positive electrode N, and lithium-ion secondary battery N were obtained in the same manner as in Example 10, except that the rotation speed of the solidification tank stirring blade was changed to 100 rpm (peripheral speed 0.5 m / s) and the water content after dewatering was changed to 25%. The same evaluation as in Example 10 was performed and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber N were almost unchanged from the specific values ​​of nitrile rubber N before hydrogenation, the molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of nitrile rubber N before hydrogenation.

[0312] (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 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 10, and evaluated in the same manner as in Example 10, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber O were almost unchanged from the specific values ​​of the nitrile rubber O before hydrogenation, the molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber O before hydrogenation.

[0313] (Reference Example 3) Nitrile rubber, hydrogenated nitrile rubber, cathode binder, conductive material dispersion, cathode slurry, cathode, and 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 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 "×".

[0314] (Reference Example 4) Nitrile rubber, hydrogenated nitrile rubber, cathode binder, conductive material dispersion, cathode slurry, cathode, and lithium-ion secondary battery were obtained in the same manner as in Reference Example 2, except that the polymer pH of the nitrile rubber obtained by adjusting the pH of the emulsion polymerization solution after the addition of the antioxidant to 9 was set to 9. Evaluations were 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 capacity characteristics was "××".

[0315] (Comparative Example 1) Nitrile rubber P, hydrogenated nitrile rubber P, cathode binder P, conductive material dispersion P, cathode slurry P, cathode P, and lithium-ion secondary battery P were obtained in the same manner as in Reference Example 2, except that the rotation speed of the solidification tank stirring blade was changed to 100 rpm (peripheral speed 0.5 m / s) and dewatering was not performed. The same evaluation as in Reference Example 2 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber P were almost unchanged from the specific values ​​of the nitrile rubber P before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber P before hydrogenation.

[0316] (Comparative Example 2) Nitrile rubber Q, hydrogenated nitrile rubber Q, cathode binder Q, conductive material dispersion Q, cathode slurry Q, cathode Q, and lithium-ion secondary battery Q were obtained in the same manner as in Comparative Example 1, except that the Grubbs catalyst was not added in the hydrogenation reaction. The same evaluation as in Comparative Example 1 was performed, and the results are shown in Tables 1 and 2. The repeating unit ratio, antioxidant content, polymer pH, water content, ash content, and ash component content of the obtained hydrogenated nitrile rubber Q were almost unchanged from the specific values ​​of the nitrile rubber Q before hydrogenation. The molecular weight Mw was 48,000, and the molecular weight distribution Mz / Mw, which is mainly in the high molecular weight region, was about "1" smaller than the Mz / Mw of the nitrile rubber Q before hydrogenation.

[0317] (Comparative Example 2-2) Nitrile rubber Q-2, hydrogenated nitrile rubber Q-2, positive electrode binder Q-2, conductive material dispersion Q-2, positive electrode slurry Q-2, positive electrode Q-2, and lithium-ion secondary battery Q-2 were obtained in the same manner as in Comparative Example 1, except that an antioxidant (BHT) was not added after the emulsion polymerization reaction. The same evaluation as in Comparative Example 1 was performed, and the results are shown in Tables 1 and 2.

[0318]

[0319]

[0320]

[0321]

[0322]

[0323]

[0324]

[0325]

[0326]

[0327]

[0328] Tables 1 and 2 show that the nitrile rubbers A to M of the present invention, which contain acrylonitrile polymerization units and 1,3-butadiene polymerization units, have a ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) of 1.5 or more, an ash content of 0.7% by mass or less, a total amount of calcium content (Ca) and sulfur content (S) in the ash (Ca+S) of 40% by mass or more, and a mass ratio of calcium content (Ca) to sulfur content (S) (Ca / S) of 3 or less, achieve a good iodine value of hydrogenated nitrile rubber with a small amount of hydrogenation catalyst and are easy to hydrogenate. When hydrogenated nitrile rubbers A to M are used in the manufacture of electrochemical elements, the dispersibility and stability of the conductive material dispersion are excellent, the peel strength of the electrodes is excellent, and the capacitance characteristics, resistance characteristics, cycle characteristics, and high-temperature storage characteristics of the electrochemical elements are remarkably superior.

[0329] Furthermore, as can be seen from Tables 1 and 2, the nitrile rubbers A to M of the present invention contain acrylonitrile polymerization units and 1,3-butadiene polymerization units, have a ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) in the range of 1.5 to 7, contain an antioxidant, have an ash content of 0.7% by mass or less, and the total amount of calcium content (Ca) and sulfur content (S) in the ash (Ca + S) is 40% by mass or more. This allows for a sufficient reduction in the iodine value of the hydrogenated nitrile rubber even with a small amount of hydrogenation catalyst, and hydrogenation is easy. When hydrogenated nitrile rubbers A to M are used in the manufacture of electrochemical elements, the stability of the conductive material dispersion is enhanced, the electrode peel strength is increased, the capacitance characteristics and high-temperature storage characteristics of the electrochemical element are greatly improved, and furthermore, the dispersibility of the conductive material dispersion, electrode flexibility, and resistance characteristics and cycle characteristics of the electrochemical element are also excellent.

[0330] Table 1 shows that using cumene hydroperoxide as an organic polymerization initiator and maintaining a high polymerization temperature of 30°C can increase the Mz / Mw of the produced nitrile rubber (for all nitrile rubbers A to Q from Example 1 to Comparative Example 2). Furthermore, it can be seen that increasing the polymerization conversion rate further increases the Mz / Mw of the produced nitrile rubber (comparison of Examples 1-2 and Examples 6-8).

[0331] Table 1 shows that increasing the polymerization conversion rate can increase the proportion of 1,2-bonding units in the 1,3-butadiene polymerization units of nitrile rubber (comparison of Examples 1-2 and 6-8). On the other hand, although not shown in these examples, the proportion of 1,2-bonding units in nitrile rubber can be further increased by using an inorganic polymerization initiator.

[0332] Table 1 shows that the ash content of nitrile rubber with a high Mw varies depending on the conditions in the coagulation reaction (number of stirs of the coagulation solution and polymerization solution, coagulation method depending on whether polymerization solution or coagulation solution is added, and position of addition of polymerization solution), and that this can be reduced by improving washing efficiency and dewatering efficiency.

[0333] 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 above 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.

[0334] Table 1 shows that the water-containing crumbs produced by adding the polymerization solution to the coagulation solution vigorously stirred at 600 rpm in Examples 1 to 10 were mostly 3.35 to 4.75 mm in size. This size is easy to work with and also provides good washing and dewatering efficiency (Examples 1 to 10). Furthermore, when the polymerization solution is added to the center of the vigorously stirred coagulation solution (where the coagulation solution forms a vortex and the central stirring blade is visible, and the solution should be applied directly to the stirring blade), the water-containing crumbs produced tend to have a large hole shape in the center, and the ash content in the nitrile rubber after washing and dewatering can be reduced to 0.14% (Examples 1 and 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 coagulation solution), the particle size distribution does not change, but the water-containing crumbs with almost no hole shape are produced, and the ash content in the nitrile rubber can only be reduced to 0.5% (comparison between Example 1 and Example 10 under the same conditions).

[0335] Table 1 shows that when the rotation speed of the agitated coagulated liquid 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 11 to 13). Furthermore, even though the agitation speed is normally on the faster side, 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, is 8 to 9.5 mm, and the amount of ash in the nitrile rubber can only be reduced to about 1% (Reference Example 1).

[0336] 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 crumb size is divided into large and small crumbs, and the amount of ash remaining in the nitrile rubber differs by a factor of two (comparison between Example 10 and Reference Example 2). Furthermore, when the rotation speed of the polymerization solution is reduced to 100 rpm, the amount of ash remaining is nearly doubled (comparison between Reference Example 2 and Comparative Examples 1-2).

[0337] 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 greatly depending on the water content after dehydration (comparison between Example 1, Examples 3-5, and Example 9). Furthermore, although not shown in this example, the amount of ash in the nitrile rubber is greatly affected by the concentration of the coagulation solution (calcium chloride aqueous solution), the washing temperature, and the dehydration temperature, and it can be seen that the amount of ash in the nitrile rubber can be sufficiently reduced by controlling these coagulation, washing, and dehydration processes.

[0338] Table 1 shows that when the ash content in nitrile rubber is reduced to 0.5%, the sodium and potassium content in the ash decreases rapidly, improving the volume characteristics. Furthermore, as the ash content is reduced to 0.5% or less, the components of the ash become mostly calcium and sulfur, and the high-temperature storage characteristics improve with reduction (comparison between Examples 10-2 and Examples 1-9). On the other hand, when the ash content is reduced too much (Example 9), the electrode peel strength decreases, indicating that ash with a high content of calcium and sulfur enhances the electrode peel strength.

[0339] From Tables 1 and 2, it can be seen that the proportions of acrylonitrile polymerization units, 1,3-butadiene polymerization units, and 1,2-bonding units in nitrile rubbers A to M are inherited in hydrogenated nitrile rubbers A to M after double decomposition, and that the dispersibility of the conductive material dispersion, the flexibility of the electrodes, and the capacitance, resistance, and cycle characteristics of the electrochemical element can be greatly improved.

[0340] Tables 1 and 2 show that the phenolic antioxidant content in nitrile rubbers A to M is almost entirely retained in hydrogenated nitrile rubbers A to M after double decomposition and hydrogenation. Hydrogenated nitrile rubber, obtained by double decomposition and hydrogenation of nitrile rubber without antioxidants, reduces the stability and peel strength of the conductive material dispersion (Comparative Example 2-2).

[0341] Tables 1 and 2 show that the ash content and ash component content in nitrile rubbers A to M are inherited in hydrogenated nitrile rubbers A to M after double decomposition, significantly improving the peel strength, capacitance characteristics, and high-temperature storage characteristics of the electrochemical element. It can be seen that the capacitance characteristics of the electrochemical element can be significantly improved by reducing the ash content and the proportion of sodium and calcium in the ash. Furthermore, it can be seen that the high-temperature storage characteristics can be improved by reducing the ash content and eliminating sodium and potassium in the ash, leaving it almost entirely composed of calcium and sulfur, and that this calcium and sulfur-rich ash increases the peel strength of the electrochemical element.

[0342] Tables 1 and 2 show that high molecular weight, low ash nitrile rubber can be hydrogenated after double decomposition to produce low molecular weight, low ash hydrogenated nitrile rubber, which improves the dispersibility of conductive material dispersions and significantly enhances the resistance characteristics and high-temperature storage characteristics of electrochemical elements. Furthermore, although the Mz / Mw ratio of nitrile rubber is slightly reduced by double decomposition, it can be retained at a high level in the hydrogenated nitrile rubber, without reducing the electrode peel strength.

[0343] Table 2 shows that when nitrile rubber with reduced ash content is double-decomposed and hydrogenated, and then used in the manufacture of electrochemical elements, the capacitance characteristics and high-temperature storage characteristics of the electrochemical elements are improved. Capacitance characteristics can be greatly improved by reducing the ash content to 0.5% or less, and high-temperature storage characteristics can be greatly improved by reducing the ash content to 0.25% (comparison with Examples 1, 3-5, 9-11, Reference Examples 1-2, and Comparative Examples 1-2, which are under the same conditions).

[0344] In reducing the ash content of nitrile rubber, although not shown in this example, 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 was found that when the water-containing crumb is produced under the specific coagulation conditions described above, both washing efficiency 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 because the calcium salt is a salt of a sulfur (S)-containing acid. Since only calcium chloride is used as a coagulant, it is presumed that the chlorine in the calcium chloride was exchanged for a sulfur (S)-containing acid during the coagulation reaction. In other words, although many compounds such as sulfates and sulfonates are used as polymerization auxiliary materials, they suddenly become poorly soluble when they become calcium salts, 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 proportion of the total amount of calcium (Ca) and sulfur (S) in the ash (Ca+S), the sudden decrease in the mass ratio ((Na+K) / (Ca+S)) between the total amount of sodium (Na) and potassium (K) (Na+K) and the total amount of calcium (Ca) and sulfur (S) (Ca+S), the sudden increase in the mass ratio of calcium (Ca) to chlorine (Cl) (Ca / Cl) (Ca / Cl for calcium chloride is 0.565), and the sudden increase in the mass ratio of sulfur (S) to chlorine (Cl) (S / Cl).

[0345] Furthermore, as shown in Table 2, while most of the hydrogenation catalyst used could be removed by treating the monochlorobenzene (MCB) solution after the hydrogenation reaction with aminopropyl group-modified silica, an ion exchange compound, it was found that almost all of the ash in the nitrile rubber remained in the hydrogenated nitrile rubber. This indicates that although the hydrogenation catalyst dissolved in the cement (MCB solution) can be removed, almost all of the ash in the nitrile rubber, which is a precursor that does not dissolve, cannot be removed. Therefore, it was found that reducing the ash in the precursor nitrile rubber is necessary to reduce the ash content of hydrogenated nitrile rubber.

[0346] Regarding capacity characteristics, in addition to the ash content and ash components of the nitrile rubber mentioned above, the proportion of 1,2-bonding units in the 1,3-butadiene polymerization units also has an influence, and it can be seen that a higher proportion of 1,2-bonding units is preferable (comparison between Examples 1-2 and Examples 6-8). On the other hand, from Tables 1 and 2, it can be seen that when the proportion of 1,2-bonding units is excessively high, the electrode flexibility tends to decrease, and it can be seen that in order to achieve a high balance between electrode flexibility and the capacity characteristics of the electrochemical element, the proportion of 1,2-bonding units in the 1,3-butadiene polymerization units of the nitrile rubber before hydrogenation should be adjusted (comparison between Examples 1-2 and Examples 6-8). Furthermore, it can be seen that the proportion of 1,2-bonding units in the 1,3-butadiene polymerization units of nitrile rubber can be easily controlled by the polymerization temperature and polymerization conversion rate, and nitrile rubber with a high proportion of 1,2-bonding units can be manufactured (Examples 1-2 and Examples 6-8). Furthermore, regarding the capacity characteristics, as shown in Reference Example 4, they decrease when hydrogenated nitrile rubber, which is obtained by hydrogenating nitrile rubber with a high polymer pH of 9, is used.

[0347] Regarding the stability of conductive material dispersions, it can be seen that hydrogenation of nitrile rubber that does not contain an antioxidant deteriorates the stability (Comparative Example 2-2). If the stability of the conductive material dispersion is poor, various properties of the manufactured electrodes and electrochemical elements deteriorate, indicating that it is important to hydrogenate nitrile rubber that contains an antioxidant, especially a phenolic antioxidant.

[0348] Regarding the electrode peel strength, it was found that, in addition to the amount of ash containing large amounts of calcium and sulfur, the absence of an antioxidant in the nitrile rubber worsened the peel strength (Comparative Example 2-2). Although not shown in this example, if the ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the nitrile rubber (Mz / Mw) is excessively small, the electrode peel strength tends to decrease. Conversely, if Mz / Mw is excessively large, the dispersibility of the conductive material dispersion decreases, and the resistance characteristics of the electrochemical element tend to decrease. It was found that adjusting the Mz / Mw of the nitrile rubber before hydrogenation is necessary to achieve a high balance between the dispersibility of the conductive material dispersion, the electrode peel strength, and the resistance characteristics of the electrochemical element in the manufacture of electrochemical elements.

[0349] Furthermore, as can be seen from Tables 1 and 2, adjusting the proportion of acrylonitrile polymerization units in the nitrile rubber before hydrogenation is sufficient to achieve a high balance between the dispersibility of the conductive material dispersion and the resistance and cycle characteristics of the electrochemical element (comparison between Examples 1-10 and Examples 11 and 12). Also, regarding the resistance characteristics, as described in Reference Example 3, they decrease when using nitrile rubber with a low polymer pH of 3.5.

[0350] As shown in Tables 1 and 2 above, the hydrogenated nitrile rubbers A to M of the present invention, obtained by hydrogenating the nitrile rubbers A to M, exhibit excellent stability of conductive material dispersions, peel strength of electrodes, and capacitance characteristics and high-temperature storage characteristics of electrochemical elements. In addition, they also exhibit excellent dispersibility of conductive material dispersions, flexibility of electrodes, and low resistance and cycle characteristics of electrochemical elements, demonstrating a high degree of balance among these characteristics.

[0351] 10 Emulsion polymerization apparatus 11 Polymerization tank 12, 32, 52 Agitator 13, 33, 53 Agitator blade 14, 34, 54 Motor 30 Solidification apparatus 31 Solidification tank 38, 58 Drainer 50 Washing apparatus 51 Washing tank 55, 71c Heating apparatus 56 Heating section 70 Squeezer 70a Clam supply section 70b Clam discharge section 71 Heating mechanism 71a, 72a Chamber 71b, 72b Roller 72 Pressurization mechanism 73 Connecting section 75 Crushing apparatus

Claims

1. Nitrile rubber containing acrylonitrile polymerization units and 1,3-butadiene polymerization units, with an ash content of 0.7% by mass or less and a total amount of calcium (Ca) and sulfur (S) content in the ash (Ca + S) of 40% by mass or more.

2. The nitrile rubber according to claim 1, wherein the ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) is 1.5 or more, and the mass ratio of the calcium content (Ca) to the sulfur content (S) in the ash (Ca / S) is 3 or less.

3. The nitrile rubber according to claim 1, wherein the ratio of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz / Mw) is in the range of 1.5 or more and 7 or less, and contains an anti-aging agent.

4. A method for producing nitrile rubber, comprising emulsion polymerization of monomer components containing acrylonitrile and 1,3-butadiene, contacting the emulsion polymerization solution to which an antioxidant has been added with an aqueous calcium chloride solution to produce a hydrated crumb that satisfies all of the following conditions (a) to (e), and then washing, dewatering, and drying the produced hydrated crumb. (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 a mesh size of 8 mm but do not pass through a JIS sieve with a mesh size of 1.7 mm is 50% by mass or more, (d) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 1.7 mm but do not pass through a JIS sieve with a mesh size of 0.43 mm is 25% by mass or less, and (e) The percentage of water-containing crumbs that pass through a JIS sieve with a mesh size of 0.43 mm is 10% by mass or less.

5. The method for producing nitrile rubber according to claim 4, wherein the nitrile rubber is the nitrile rubber described in claim 3.

6. Hydrogenated nitrile rubber obtained by hydrogenating the nitrile rubber described in claim 3, having an iodine value of 100 mg / 100 mg or less.

7. Hydrogenated nitrile rubber obtained by hydrogenating the nitrile rubber described in claim 3 after double decomposition, wherein the weight-average molecular weight (Mw) is 100,000 or less and the iodine value is 100 mg / 100 mg or less.

8. An electrode material comprising the hydrogenated nitrile rubber described in claim 6.

9. An electrode material comprising the hydrogenated nitrile rubber described in claim 7.

10. An electrode binder obtained by dissolving the hydrogenated nitrile rubber described in claim 6 in N-methylpyrrolidone (NMP).

11. An electrode binder obtained by dissolving the hydrogenated nitrile rubber described in claim 7 in N-methylpyrrolidone (NMP).

12. A conductive material dispersion obtained by dissolving or dispersing the hydrogenated nitrile rubber and conductive material described in claim 6 in N-methylpyrrolidone (NMP).

13. An electrode slurry obtained by dissolving or dispersing an electrode active material, a conductive material, and the hydrogenated nitrile rubber described in claim 6 in N-methylpyrrolidone (NMP).

14. An electrode comprising the hydrogenated nitrile rubber described in claim 6.

15. An electrochemical element comprising the hydrogenated nitrile rubber described in claim 6.

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