Gel for alkaline battery

Abstract

Provided are: a gel for alkaline batteries, which has excellent impact resistance and heat resistance, while maintaining long-term discharge characteristics (discharge amount and discharge time); and an alkaline battery using the same. A gel for alkaline batteries, which contains a cross-linked polymer (A) that contains, as essential constituent units, a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes the water-soluble vinyl monomer (a1) by hydrolysis, and an internal cross-linking agent (b), and wherein a part of the cross-linked polymer (A) is neutralized with an alkali metal salt (c). The neutralization uniformity of the gel for the alkaline battery is 60 to 90 percent.

Description

Technical Field

[0001] The present invention relates to a gelling agent for alkaline batteries. Background Art

[0002] Conventionally, for the negative electrode of an alkaline battery, a mixture of a high-concentration alkaline electrolyte (an aqueous solution of high-concentration potassium hydroxide, a solution containing zinc oxide or the like as needed), zinc powder, and / or zinc alloy powder has been mainly used. From the viewpoints of preventing sedimentation of zinc powder in the alkaline electrolyte, preventing liquid leakage from the battery, and improving the production efficiency of the battery, a scheme has been proposed to use a water-absorbing resin obtained by insolubilizing poly(meth)acrylic acid and its salts with a crosslinking agent as a thickening agent for the purpose of suppressing drawability (Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-34379 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] However, in recent years, alkaline batteries have been required to have further high performance. For alkaline batteries using these gelling agents containing water-absorbing resins, it cannot be said that the sedimentation prevention of zinc powder and the like in the alkaline electrolyte is sufficient, and they may not be able to satisfy the requirements in terms of maintaining the long-term discharge characteristics (discharge capacity and discharge time) of the battery and shock resistance. In addition, when a strong shock is applied to the alkaline battery or in the case of accidental short circuit, a large current flows through the battery and generates heat, resulting in a decrease in discharge characteristics. Therefore, they may not be able to satisfy the requirements from the viewpoint of heat resistance.

[0008] Therefore, an object of the present invention is to provide a gelling agent for alkaline batteries and an alkaline battery using the same, which are excellent in maintaining long-term discharge characteristics (discharge capacity and discharge time), shock resistance, and heat resistance.

[0009] Technical Solution for Solving the Technical Problem

[0010] The inventors of the present invention conducted in-depth research to solve the above technical problems and as a result, completed the present invention. That is, the present invention is a gelling agent for alkaline batteries, which contains a crosslinked polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal crosslinking agent (b) as constituent monomers, a part of the crosslinked polymer (A) is neutralized with an alkali metal salt (c), and the neutralization uniformity of the gelling agent for alkaline batteries is 60 to 90%.

[0011] Advantages of the Invention

[0012] The gelling agent for alkaline batteries and the alkaline battery of the present invention exhibit the following effects.

[0013] (1) Since the gelling agent for alkaline batteries of the present invention has excellent anti-settling properties for zinc powder and the like in the negative electrode material, when used in alkaline batteries, it is possible to manufacture a battery that discharges for a long time with a small amount and has extremely excellent impact resistance.

[0014] (2) The negative electrode material added with the gelling agent for alkaline batteries of the present invention has a small viscosity change during heating, so it is possible to manufacture a battery with extremely excellent impact resistance, heat resistance and high safety.

[0015] (3) The viscosity of the negative electrode material added with the gelling agent for alkaline batteries of the present invention is in an appropriate range during filling, and the liquid breakage of the negative electrode material is good. As a result, the deviation of the filling amount of the negative electrode material per battery is small. Therefore, even in mass production, it is possible to produce batteries with uniform quality. In addition, even in small-sized batteries, the negative electrode material can be filled uniformly and at high speed, so it is possible to manufacture batteries with uniform quality. Detailed implementation mode

[0016] <Gelling agent for alkaline batteries>

[0017] The gelling agent (G) for alkaline batteries of the present invention contains a crosslinked polymer (A) composed of a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal crosslinking agent (b), and a part of the crosslinked polymer (A) is neutralized with an alkali metal salt (c). The neutralization uniformity of the gelling agent for alkaline batteries is 60 to 90%.

[0018] In the present invention, the water-soluble vinyl monomer refers to a vinyl monomer having the property of dissolving at least 100 g in 100 g of water at 25°C.

[0019] The water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) which becomes (a1) by hydrolysis are not particularly limited, and examples thereof include the water-soluble radical polymerization monomers described in JP-A-2005-075982. Among them, from the viewpoint of discharge characteristics, a water-soluble vinyl monomer (a1) is preferred, an anionic vinyl monomer is more preferred, and a vinyl group-containing carboxylic acid (salt) having 3 to 30 carbon atoms {unsaturated monocarboxylic acid (salt) [(meth)acrylic acid, crotonic acid, cinnamic acid and their salts, etc.]; unsaturated dicarboxylic acid (salt) (maleic acid, fumaric acid, citraconic acid, itaconic acid and their salts, etc.); and monoalkyl (having 1 to 8 carbon atoms) esters of the unsaturated dicarboxylic acid (monobutyl maleate, monobutyl fumarate, ethyl carbitol monoester of maleic acid, ethyl carbitol monoester of fumaric acid, monobutyl citraconate and diol monoester of itaconic acid, etc.} is particularly preferred, an unsaturated monocarboxylic acid (salt) is more preferred, and acrylic acid (salt) is most preferred.

[0020] In the present invention, (meth)acrylic acid means acrylic acid and / or methacrylic acid, and “… acid (salt)” means “… acid” and / or “… acid salt”. As the salt, it includes alkali metal salts such as potassium, sodium and lithium, and alkaline earth metal salts such as calcium.

[0021] The constituent monomer derived from the water-soluble vinyl monomer (a1) may be an unneutralized body or a neutralized body (constituent monomer of the water-soluble vinyl monomer salt). Further, from the viewpoints of reducing adhesiveness, improving dispersibility and operability in the production of the crosslinked polymer (A), it is preferred that a part or all of the crosslinked polymer (A) is neutralized.

[0022] When neutralizing the constituent monomer derived from the water-soluble vinyl monomer (a1) contained in the crosslinked polymer (A), usually an alkali metal hydroxide such as potassium hydroxide, sodium hydroxide or lithium hydroxide or an aqueous solution thereof may be added to the monomer stage before polymerization or the hydrogel after polymerization. However, since the crosslinking agent (b2) which is not hydrolyzed under alkaline conditions lacks water solubility, if polymerization is carried out in a state where the neutralization degree of the water-soluble vinyl monomer (a1) is high, sometimes even if a prescribed amount of the crosslinking agent (b2) is added, the crosslinking agent (b2) will be separated from the monomer aqueous solution and the prescribed crosslinking cannot be carried out, and the crosslinked polymer (A) cannot be obtained. More preferably, the neutralization degree of the water-soluble vinyl monomer (a1) is set to 0 to 30 mol%, polymerization is carried out while also containing the crosslinking agent (b2), and then, if necessary, an alkali metal hydroxide is added to the hydrogel to adjust the neutralization degree.

[0023] When an anionic vinyl monomer {most preferably acrylic acid (salt)} is used as the water-soluble vinyl monomer (a1) of the crosslinked polymer (A), the final degree of neutralization of the anionic vinyl monomer {the content (mol%) of the anionic base based on the total number of moles of the anionic groups and the anionic base of the anionic vinyl monomer} is preferably 10 to 90, more preferably 40 to 85, and particularly preferably 60 to 80. If it is within this range, the impact resistance and discharge characteristics of the negative electrode material become better. It should be noted that the anionic base refers to the anionic group that has been neutralized.

[0024] From the viewpoint of the absorption capacity of the gelling agent (G), the content of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) that becomes (a1) by hydrolysis is preferably 98.0 to 99.90% by weight, more preferably 99.0 to 99.85% by weight, and particularly preferably 99.2 to 99.83% by weight based on the total weight of (a1), (a2), the crosslinking agent (b1) hydrolyzed under alkaline conditions, and the crosslinking agent (b2) not hydrolyzed under alkaline conditions.

[0025] The water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) that becomes (a1) by hydrolysis can be used individually as one kind or in combination of two or more kinds.

[0026] Among the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) that becomes (a1) by hydrolysis, from the viewpoint of the discharge characteristics of the alkaline battery, it is preferable to use (a1) alone and in combination with (a2), and more preferably to use (a1) alone.

[0027] When both the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) that becomes (a1) by hydrolysis are used as the constituent monomers, from the viewpoint of the discharge characteristics of the alkaline battery, the molar ratio of the constituent monomers from these vinyl monomers {(a1) / (a2)} is preferably 75 / 25 to 99 / 1, more preferably 85 / 15 to 98 / 2, and most preferably 90 / 10 to 95 / 5.

[0028] In addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), the crosslinked polymer (A) can also use other vinyl monomers (a3) that can copolymerize with them as the constituent monomers. The other vinyl monomers (a3) can be used individually as one kind or in combination of two or more kinds.

[0029] As other vinyl monomers (a3) capable of copolymerization, there is no particular limitation, and known hydrophobic vinyl monomers (for example, the hydrophobic vinyl monomers disclosed in paragraphs

[0028] to

[0029] of Japanese Patent No. 3648553, the vinyl monomers disclosed in paragraph

[0025] of JP-A-2003-165883, and the vinyl monomers disclosed in paragraph

[0058] of JP-A-2005-75982, etc.) can be used. Specifically, for example, vinyl monomers such as the following (i) to (iii) can be used.

[0030] (i) Aromatic ethylenically unsaturated monomers having 8 to 30 carbon atoms

[0031] Styrene such as styrene, α-methylstyrene, vinyltoluene, and hydroxystyrene, vinylnaphthalene, and halogen-substituted styrenes such as dichlorostyrene.

[0032] (ii) Aliphatic ethylenically unsaturated monomers having 2 to 20 carbon atoms

[0033] Olefins (ethylene, propylene, butene, isobutene, pentene, heptene, diisobutene, octene, dodecene, octadecene, etc.); and diolefins (butadiene, isoprene, etc.).

[0034] (iii) Alicyclic ethylenically unsaturated monomers having 5 to 15 carbon atoms

[0035] Monounsaturated monomers (pinene, limonene, indene, etc.); and polyethylenic vinyl monomers [cyclopentadiene, dicyclopentadiene, ethylidene norbornene, etc.].

[0036] From the viewpoint of absorption performance and the like, the content (mol%) of the other vinyl monomer (a3) unit in the crosslinked polymer (A) is preferably 0 to 5, more preferably 0 to 3, particularly preferably 0 to 2, and most preferably 0 to 1.5, based on the total number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. From the viewpoint of absorption performance and the like, it is most preferred that the content of the monomer constituting the other vinyl monomer (a3) is 0 mol%.

[0037] The crosslinked polymer (A) is crosslinked using an internal crosslinking agent (b). As the internal crosslinking agent (b), crosslinking agents (b1) that hydrolyze in an alkaline medium and crosslinking agents (b2) that do not hydrolyze in an alkaline medium can be mentioned.

[0038] In the present invention, (b1) and (b2) are preferably used in combination. By using (b1) and (b2) in combination, the viscosity stability of the gelling agent (G) is further improved, the bleeding of the alkaline electrolyte can be prevented, and thus the long-term discharge of the battery can be maintained. Furthermore, when filling the battery, it can be uniformly injected, and the deviation in the injection amount of the electrolyte per cell also becomes smaller, so it is preferred. It should be noted that here, the "bleeding" of the alkaline electrolyte means that the substantially uniform mixing state of the gelling agent (G) and the alkaline electrolyte cannot be maintained, and the gelling agent (G) is separated from the alkaline electrolyte.

[0039] In the crosslinking agent (b1) that hydrolyzes under alkaline conditions, "hydrolyzes under alkaline conditions" means that in the crosslinked polymer (A), the constituent monomer derived from (b1) has a hydrolyzable bond. The hydrolyzable bond can be a bond originally possessed by the crosslinking agent (b1) in the molecule {the crosslinking agent at this time is the crosslinking agent (b11) having a hydrolyzable bond in the molecule}, or a hydrolyzable bond obtained by hydrolyzing a bond formed by a crosslinking reaction with other monomers {(a1) or (a2)} constituting the crosslinked polymer (A) {the bond formed by the crosslinking reaction of the crosslinking agent at this time is used as the hydrolyzable crosslinking agent (b12)}. Examples of the hydrolyzable bond include an ester bond and an amide bond.

[0040] Examples of the crosslinking agent (b11) having a hydrolyzable bond in the molecule include copolymerizable crosslinking agents having 2 to 10 ethylenically unsaturated bonds in the molecule, such as N,N'-methylenebisacrylamide, ethylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and polyglycerol (degree of polymerization 3 to 13) polyacrylate.

[0041] Examples of the crosslinking agent (b12) in which the bond formed by the crosslinking reaction is hydrolyzable include reactive crosslinking agents that react with carboxylic acids, such as polyglycidyl compounds (ethylene glycol diglycidyl ether, etc.), polyisocyanate compounds (4,4'-diphenylmethane diisocyanate, etc.), polyamine compounds (ethylenediamine, etc.), and polyol compounds (glycerol, etc.). The reactive crosslinking agent can react with (meth)acrylic acid (salt) to form an ester bond or an amide bond.

[0042] Among the crosslinking agents (b1) that hydrolyze under alkaline conditions, from the perspective of the viscosity stability of the negative electrode material to which the gelling agent (G) is added, polyacrylamide compounds and polyacrylate compounds are preferred, N,N'-methylenebisacrylamide, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate are more preferred, N,N'-methylenebisacrylamide, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and ethylene glycol diglycidyl ether are particularly more preferred, and N,N'-methylenebisacrylamide and trimethylolpropane tri(meth)acrylate are most preferred.

[0043] The crosslinking agent (b2) that does not hydrolyze under alkaline conditions is a crosslinking agent that does not have a hydrolyzable bond in the molecule and does not generate a hydrolyzable bond due to the crosslinking reaction. As such a crosslinking agent (b2), crosslinking agents (b21) having two or more vinyl ether bonds and crosslinking agents (b22) having two or more allyl ether bonds can be cited. From the perspective of reactivity and the like, a crosslinking agent having two or more allyl ether bonds is preferred.

[0044] As the crosslinking agent (b21) having two or more vinyl ether bonds, examples include: ethylene glycol divinyl ether, 1,4-butanediol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, 1,6-hexanediol divinyl ether, polyethylene glycol divinyl ether (degree of polymerization 2 - 5), bisphenol A divinyl ether, pentaerythritol trivinyl ether, sorbitol trivinyl ether, and polyglycerol (degree of polymerization 3 - 13) polyvinyl ether, etc.

[0045] As the crosslinking agent (b22) having two or more allyl ether bonds, examples include crosslinking agents (b221) having two allyls in the molecule and no hydroxyl group, crosslinking agents (b222) having two allyls in the molecule and 1 - 5 hydroxyl groups, crosslinking agents (b223) having 3 - 10 allyls in the molecule and no hydroxyl group, crosslinking agents (b224) having 3 - 10 allyls in the molecule and 1 - 3 hydroxyl groups, etc. When the molecule contains a hydroxyl group, the compatibility with the vinyl monomer (a1) and / or (a2) {especially (meth)acrylic acid (salt)} is good, the uniformity of crosslinking increases, the performance of the gelling agent (G) improves, and the long-term stability of the viscosity of the negative electrode material containing the gelling agent (G) is further excellent.

[0046] As the crosslinking agent (b221) having two allyls in the molecule and no hydroxyl group, examples include: 1,4-cyclohexanedimethanol diallyl ether, alkylene (2 - 5 carbon atoms) glycol diallyl ether, and polyalkylene (2 - 6 carbon atoms) glycol (weight average molecular weight: 100 - 4000) diallyl ether, etc.

[0047] Examples of the crosslinking agent (b222) having two allyl groups and 1 to 5 hydroxyl groups in the molecule include glycerol diallyl ether, trimethylolpropane diallyl ether, pentaerythritol diallyl ether, and polyglycerol (degree of polymerization: 2 to 5) diallyl ether.

[0048] Examples of the crosslinking agent (b223) having 3 to 10 allyl groups and no hydroxyl groups in the molecule include trimethylolpropane triallyl ether, glycerol triallyl ether, pentaerythritol tetraallyl ether, and tetraallyloxyethane.

[0049] Examples of the crosslinking agent (b224) having 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule include pentaerythritol triallyl ether, diglycerol triallyl ether, sorbitol triallyl ether, and polyglycerol (degree of polymerization: 3 to 13) polyallyl ether.

[0050] Two or more kinds of crosslinking agents (b2) that do not hydrolyze under alkaline conditions can be used in combination.

[0051] Among the crosslinking agents (b2), crosslinking agents (b22) having two or more allyl ether bonds are preferred, crosslinking agents {(b222) and (b224)} having 1 to 5 hydroxyl groups and 2 to 10 allyl groups are more preferred, crosslinking agents (b224) having 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule are particularly preferred, and pentaerythritol triallyl ether, diglycerol triallyl ether, and sorbitol triallyl ether are most preferred. When these crosslinking agents are used, the compatibility with the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) that becomes (a1) by hydrolysis is good, and efficient crosslinking can be carried out, so they are preferred.

[0052] The content of the crosslinking agent (b1) that hydrolyzes under alkaline conditions in the crosslinked polymer (A) of the present invention also depends on the type and average degree of polymerization of the crosslinking agent (b1). Based on the weight of the crosslinked polymer (A), it is preferably 0.05 to 1% by weight, more preferably 0.1 to 0.8% by weight, and particularly preferably 0.1 to 0.5% by weight. If it is within this range, excessive liquid loss of the alkaline electrolyte can be prevented, and thus the long-term discharge characteristics of the battery are further excellent.

[0053] The content of the crosslinking agent (b2) that does not hydrolyze under alkaline conditions in the crosslinked polymer (A) also depends on the type of the crosslinking agent (b2). Based on the weight of the crosslinked polymer (A), it is preferably 0.05 to 1% by weight, more preferably 0.05 to 0.5% by weight, and particularly preferably 0.1 to 0.3% by weight. If it is within this range, the long-term discharge characteristics of the battery are further excellent.

[0054] The total content of the crosslinking agent (b1) and the crosslinking agent (b2) is preferably 0.10 to 2.0% by weight, more preferably 0.30 to 1.0% by weight, and particularly preferably 0.40 to 0.8% by weight based on the weight of the crosslinked polymer (A). If it is within this range, excessive liquid separation of the alkaline electrolyte can be prevented, and thus the long-term discharge characteristics of the battery are further excellent. In addition, the stability of the gelling agent (G) is improved, and the long-term stability and temperature stability of the viscosity of the alkaline electrolyte containing the gelling agent (G) are further excellent.

[0055] The gelling agent (G) of the present invention may contain a surfactant (D) having an HLB of 1 to 12. Here, "HLB" is an index indicating the balance between hydrophilicity and lipophilicity, and can be calculated, for example, by the Oda method described on page 212 of "Introduction to Surfactants" [published by Sanyo Chemical Industries, Ltd. in 2007, written by Takehiko Fujimoto], from the ratio of the organic value to the inorganic value of the organic compound.

[0056] HLB = 10 × inorganicity / organicity

[0057] Regarding the organic value and inorganic value used to derive the HLB, the values in the table described on page 213 of the above-mentioned "Introduction to Surfactants" can be used for calculation.

[0058] As the surfactant (D), it includes an ionic surfactant and a nonionic surfactant.

[0059] As the ionic surfactant, it includes known anionic surfactants, amphoteric surfactants, and cationic surfactants. Specifically, the ionic surfactants described in WO99 / 03577 pamphlet, WO2002 / 005949 pamphlet, and USP4331447 specification can be mentioned. As the surfactant (D), from the viewpoints of the viscosity of the gel and the high-speed injectability of the negative electrode material, a nonionic surfactant is preferred.

[0060] A nonionic surfactant does not show ionic properties even when dissolved in water, but exhibits surface activity. In the present invention, the nonionic surfactant is not particularly limited, and from the viewpoints of the viscosity of the gel and the high-speed injectability of the negative electrode material, at least one selected from sucrose fatty acid esters, sorbitan fatty acid esters, glycerol fatty acid esters, and fatty acid amides is preferred.

[0061] As sucrose fatty acid esters, there are sucrose fatty acid esters in which fatty acids having 8 to 22 carbon atoms are ester-bonded to sucrose. Specifically, sucrose stearate can be cited [for example, sucrose stearate manufactured by Daiichi Kogyo Seiyaku Co., Ltd. {DKESTER F-50 (HLB = 6), F-70 (HLB = 8), and F-110 (HLB = 11), etc.}, sucrose stearate manufactured by Mitsubishi Chemical Foods Co., Ltd. {Ryoto Sugar Ester S-370 (HLB = about 3), S-770 (HLB = about 7), S-970 (HLB = about 9), S-1170 (HLB = about 11), and S-1170F (HLB = about 11), etc.}, etc.].

[0062] As sorbitan fatty acid esters, there are sorbitan fatty acid esters in which fatty acids having 8 to 22 carbon atoms are ester-bonded to sorbitan. Specifically, sorbitan palmitate can be cited [sorbitan palmitate manufactured by Kao Corporation {RHEODOL SP-P10 (HLB = 6.7), etc.} and sorbitan palmitate manufactured by Riken Vitamin Co., Ltd. {RIKEMAL P-300 (HLB = 5.6), etc.}, etc.].

[0063] As glycerol fatty acid esters, there are glycerol fatty acid esters in which fatty acids having 8 to 22 carbon atoms are ester-bonded to glycerol and / or a polymer of glycerol (degree of polymerization 2 to 20). Specifically, diglycerol monolaurate can be cited [diglycerol monolaurate manufactured by Riken Vitamin Co., Ltd. {POEM DL-100 (HLB = 9.4), etc.}, etc.], diglycerol monomyristate [diglycerol monomyristate manufactured by Riken Vitamin Co., Ltd. {POEM DM-100 (HLB = 8.7), etc.}, etc.], diglycerol monostearate [diglycerol monostearate manufactured by Riken Vitamin Co., Ltd. {POEM DS-100A (HLB = 7.7), etc.}, etc.], diglycerol monooleate [diglycerol monooleate manufactured by Riken Vitamin Co., Ltd. {POEM DO-100V (HLB = 7.3), RIKEMAL DO-100 (HLB = 7.4), etc.}, etc.], decaglycerol stearate [decaglycerol stearate manufactured by Riken Vitamin Co., Ltd. {POEM J-0081HV (HLB = 12), POEM J-0381V (HLB = 12), etc.}, etc.].

[0064] As the fatty acid amide, it includes a fatty acid amide formed by amide-bonding a fatty acid having 8 to 22 carbon atoms with ethanolamine. Specifically, examples include coconut oil fatty acid monoethanolamide [coconut oil fatty acid monoethanolamide manufactured by Sanyo Chemical Industries, Ltd. {PROFAN AB-20 (HLB = 11), etc.}], stearic acid monoethanolamide [stearic acid monoethanolamide manufactured by Sanyo Chemical Industries, Ltd. {PROFAN SME (HLB = 10), etc.}], and the like.

[0065] From the viewpoints of high-speed injectability of the negative electrode material and dehydration shrinkage of the negative electrode material, the HLB of the surfactant (D) is preferably 1 to 12, more preferably 3 to 11, and particularly preferably 5 to 9. In addition, as the surfactant (D), from the viewpoints of high-speed injectability of the negative electrode material and dehydration shrinkage of the negative electrode material, a nonionic surfactant is preferred, and at least one selected from sucrose fatty acid esters, sorbitan fatty acid esters, glycerol fatty acid esters, and fatty acid amides is more preferred.

[0066] In the gelling agent (G) of the present invention, based on the weight of the crosslinked polymer (A), from the viewpoints of high-speed injectability of the negative electrode material and dehydration shrinkage of the negative electrode material, the content of the surfactant (D) is preferably 0.001 to 2.0% by weight, more preferably 0.005 to 1.0% by weight, particularly preferably 0.01 to 0.8% by weight, and most preferably 0.01 to 0.5% by weight.

[0067] When the shape of the surfactant (D) is powdery, the particle size of the surfactant is not particularly limited. From the viewpoint of dry blending property in the crosslinked polymer (A), the volume average particle size is preferably 0.1 to 2000 μm, more preferably 0.5 to 1500 μm, and particularly preferably 1 to 1000 μm.

[0068] Next, a method for manufacturing the gelling agent (G) for an alkaline battery of the present invention will be described.

[0069] As a method for manufacturing the crosslinked polymer (A), an aqueous gel polymer (including a crosslinked polymer and water) obtained by known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc.; Japanese Patent Laid-Open No. 55-133413, etc.), known suspension polymerization method, inverse suspension polymerization (Japanese Patent Publication No. 54-30710, Japanese Patent Laid-Open No. 56-26909, Japanese Patent Laid-Open No. 1-5808, etc.) can be dried and pulverized to obtain it. The crosslinked polymer (A) may be a single type or a mixture of two or more types.

[0070] The crosslinked polymer (A) can be obtained by polymerizing a monomer composition containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal crosslinking agent (b) as essential components. As the polymerization method, solution polymerization is preferred. Since it is not necessary to use an organic solvent or the like, it is advantageous in terms of production cost. Therefore, aqueous solution polymerization is particularly preferred. From the aspect of not requiring temperature control during polymerization, aqueous solution adiabatic polymerization is most preferred.

[0071] The method of polymerizing the water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) which becomes (a1) by hydrolysis and the internal crosslinking agent (b) by aqueous solution polymerization can be a known method. For example, a method of polymerizing using a radical polymerization initiator, a method of irradiating radiation, ultraviolet rays, electron beams, etc. can be cited.

[0072] In the case of using a radical polymerization initiator, examples of such initiators include: azo compounds [azobisisovaleronitrile, azobisisobutyronitrile, 4,4′-azobis(4-cyanovaleric acid), 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide, 2,2′-azobis(2-amidinopropane) hydrochloride, etc.], inorganic peroxides [hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium persulfate, etc.], organic peroxides [di-tert-butyl peroxide, cumene hydroperoxide, etc.], redox initiators [combinations of reducing agents such as alkali metal salts of sulfite or bisulfite, ammonium sulfite, ammonium bisulfite, L-ascorbic acid, etc. and peroxides such as alkali metal salts of persulfate, ammonium persulfate, hydrogen peroxide water, etc.]. Two or more of them can be used in combination.

[0073] The polymerization temperature varies depending on the type of initiator used, etc. From the viewpoint of increasing the degree of polymerization of the polymer, it is preferably -10°C to 100°C, more preferably -10°C to 80°C.

[0074] Regarding the amount of the initiator, there is no particular limitation. From the viewpoint of increasing the degree of polymerization of the polymer, based on the total weight of the vinyl monomers (a1), (a2), the crosslinking agent (b) and other monomers (a3) used as required, it is preferably 0.000001 to 3.0% by weight, more preferably 0.000001 to 0.5% by weight.

[0075] In the case of aqueous solution polymerization, the polymerization concentration (wt%) of the monomer varies depending on other polymerization conditions. If the polymerization concentration of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) that becomes (a1) by hydrolysis is increased, pseudo-crosslinking (self-crosslinking) of the monomer itself easily occurs in parallel with the polymerization reaction, resulting in a decrease in the absorption amount and a decrease in the average degree of polymerization of the polymer. In addition, it is difficult to control the temperature during polymerization, which easily leads to a decrease in the average degree of polymerization of the polymer and an increase in the oligomer component. Therefore, the polymerization concentration is preferably 10 to 40 wt%, more preferably 10 to 30 wt%. In addition, regarding the polymerization temperature, it is preferably -10 to 100 °C, more preferably -10 to 80 °C. Regarding the dissolved oxygen amount during polymerization, although it also depends on the addition amount of the radical initiator, etc., it is preferably 0 to 2 ppm (2×10 -4 wt% or less), more preferably 0 to 0.5 ppm (0.5×10 -4 wt% or less). If it is within these ranges, a crosslinked polymer (A) with a high degree of polymerization can be produced.

[0076] The neutralization degree during polymerization is not particularly limited as long as the specified amount of the internal crosslinking agent (b) can be completely dissolved in the monomer aqueous solution. Compared with (b1), (b2) lacks water solubility. In addition, especially for monomers having an acid group, the solubility in the aqueous solution is extremely low. Even if a specified amount of (b2) is added, (b2) sometimes separates from the monomer aqueous solution and the specified crosslinking cannot be carried out. Therefore, the neutralization degree of the monomer having an acid group during polymerization is preferably polymerized at 0 to 30 mol%, and if necessary, it is further neutralized after polymerization. More preferably, it is polymerized in an unneutralized state and then neutralized as needed after polymerization. In addition, when monomers having an acid group are polymerized under the same conditions, the degree of polymerization is likely to increase when the neutralization degree is low. Therefore, in order to increase the degree of polymerization of the polymer, it is also preferably polymerized in a state of low neutralization degree.

[0077] In the production of the crosslinked polymer (A), except for not using a crosslinking agent, it is further preferred that the average degree of polymerization of the polymer when producing the polymer under exactly the same conditions is preferably 5000 to 1,000,000, more preferably 10,000 to 1,000,000.

[0078] If polymerization is carried out under the condition that the average degree of polymerization is 5000 or more, by using an appropriate amount of a crosslinking agent, it is possible to prevent a decrease in the viscosity and / or an increase in the drawability of a highly concentrated alkaline aqueous solution to which a gelling agent is added. The measurement of the above average degree of polymerization is carried out by gel permeation chromatography (GPC method).

[0079] In the present invention, the crosslinked polymer (A) obtained by aqueous solution polymerization is obtained in the form of a gel containing water (hydrogel). The hydrogel is used as a gelling agent after drying.

[0080] Regarding the method for drying the hydrogel, in the case of aqueous solution polymerization, the following methods can be exemplified: the hydrogel is divided to a certain extent (divided to a level of about 0.5 to 20 mm square) or strips using a meat grinder or a cutting type coarse chopper, and after neutralizing the hydrogel by adding an alkali metal hydroxide (c), the hydrogel is subjected to air drying (laminating the hydrogel on a perforated metal or a mesh, forcibly passing hot air at 50 to 150° C. to dry it, etc.) or ventilation drying (placing the hydrogel in a container, drying it by ventilation and circulation of hot air, and drying it while further dividing the gel into smaller pieces using a machine such as a rotary kiln). Among them, ventilation drying is preferred because it can efficiently dry the gel in a short time.

[0081] As another drying method of the hydrogel in aqueous solution polymerization, there is a contact drying method in which the hydrogel is compressed and stretched on a drum dryer and then dried. However, since the heat conductivity of the hydrogel is poor, a thin film of the hydrogel needs to be formed on the drum in order to dry it. However, the material of the commercially available drum dryer is usually formed of metals with a lower ionization tendency than zinc, such as iron, chromium, and nickel, so the frequency of each hydrogel contacting the metal surface of the drum is extremely high. In addition, the hydrogel is a hydrogel of polyacrylic acid (salt), so the content of metal elements with a lower ionization tendency than zinc dissolved in the gel increases. Furthermore, the contact frequency of the hydrogel with the drum is extremely high, and the hydrogel has high adhesion, so it is necessary to bring a knife or the like into contact with the drum dryer to peel the dried product from the drum dryer. Due to mechanical wear of the drum and the knife, the metal surface of the drum or the knife wears, and metal is mixed into the dried product. As described above, when a contact drying method such as a drum dryer is used, metal ions and metal powders are easily mixed into the gel, and a considerable amount of metal ions and metal powders having an ionization tendency lower than these zinc (metals represented by atomic symbols such as Cr, Fe, Ni, Sn, Pb, Cu, Hg, and Ag because they are metals having a lower standard electrode potential than zinc) are contained. When these gels are used as gels for alkaline batteries, zinc powder in the battery forms a cell with the metal ions or metal powders having an ionization tendency lower than zinc, so hydrogen gas is generated by electrolysis, thereby increasing the pressure inside the battery, which may cause the alkaline electrolyte to flow out, and in severe cases, cause the battery to be damaged. Furthermore, in the case of a film-like dried product obtained by compressing and stretching the hydrogel on a drum dryer or the like, even if the particle size of the dried product is adjusted to a desired particle size by pulverizing the dried product, the particles are flaky, and therefore, the strength is very weak compared to the pulverized product of a block-like dried product obtained by the air-permeable drying method or the ventilation drying method. If the hydrated gel is swollen in a high-concentration alkaline aqueous solution and mechanically stirred and mixed with zinc powder, the swollen gel is destroyed and the gel becomes smaller. Therefore, it is preferable not to use a contact drying method such as a drum dryer.

[0082] In the present invention, the drying temperature during the drying of the hydrogel varies depending on the dryer used, the drying time, etc., and is preferably 50 to 150 °C, more preferably 80 to 130 °C. If the drying temperature is 150 °C or lower, the polymer is not easily crosslinked by the heat during drying, the degree of crosslinking does not excessively increase due to thermal crosslinking, the absorption amount does not decrease, and the viscosity in the alkaline electrolyte does not decrease. If it is 50 °C or higher, the drying does not require a long time and is efficient. Regarding the drying time, it also varies depending on the type of dryer used and the drying temperature, etc., and is preferably 5 to 300 minutes, more preferably 5 to 120 minutes.

[0083] The dried product of the crosslinked polymer (A) thus obtained is pulverized into powder as needed. The pulverization method can be a known method, for example, it can be carried out using an impact pulverizer (pin mill, cutter mill, Skirel mill, ACM pulverizer, etc.), an air pulverizer (jet pulverizer, etc.).

[0084] The powdered crosslinked polymer (A) can be sieved using a sieve machine (vibrating sieve machine, centrifugal sieve machine, etc.) equipped with the required sieve as needed to collect the dried powder with the required particle size.

[0085] The volume average particle size of the gelling agent (G) in the present invention is preferably 20 to 500 μm, more preferably 30 to 400 μm, and particularly preferably 30 to 170 μm.

[0086] If the volume average particle size is within this range, the viscosity of the alkaline electrolyte added with the gelling agent (G) becomes an appropriate range, the liquid breaking of the negative electrode material becomes good, so that a battery with stable quality can be manufactured, and the sedimentation of zinc powder in the negative electrode material can be prevented, so that a battery with excellent discharge characteristics over time can be produced.

[0087] It should be noted that the above-mentioned volume average particle size is measured by the following method.

[0088] <Measurement method of volume average particle size of gelling agent (G)>

[0089] The gelling agent (G) of the present invention is dispersed in methanol and measured using a laser diffraction particle size distribution measuring device [Microtrac (manufactured by Nikkiso Co., Ltd.)]. It should be noted that the volume average particle size of the gelling agent (G) in the following examples is measured according to the above method.

[0090] The crosslinked polymer (A) can be reacted with a surface crosslinking agent as needed to perform surface crosslinking treatment.

[0091] As the surface crosslinking agent, known surface crosslinking agents can be used, such as those described in Japanese Patent Laid-Open No. 2003-225565.

[0092] Among these surface crosslinking agents, from the viewpoint of the discharge characteristics of alkaline batteries, crosslinking agents having at least two or more functional groups capable of reacting with the carboxyl group of acrylic acid (a1) are preferred, polyglycidyl groups are more preferred, ethylene glycol diglycidyl ether and glycerol diglycidyl ether are particularly preferred, and ethylene glycol diglycidyl ether is most preferred.

[0093] From the viewpoint of the discharge characteristics of alkaline batteries, the content (mol%) of the surface crosslinking agent is preferably 0.001 to 0.30, more preferably 0.005 to 0.25, and particularly preferably 0.010 to 0.20 based on the number of moles of the constituent monomers.

[0094] Methods for the surface crosslinking reaction can be applied to known methods {such as Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883, Japanese Patent Laid-Open No. 2005-75982, Japanese Patent Laid-Open No. 2005-95759}.

[0095] From the viewpoint of high-speed injection of the negative electrode material, the gelling agent (G) of the present invention preferably has a surfactant (D) near the surface of the crosslinked polymer (A). Examples of substances having a surfactant (D) near the surface of the crosslinked polymer (A) include substances obtained by the following methods.

[0096] (1) A method of directly mixing a solid surfactant (D) directly in the crosslinked polymer (A) by, for example, a dry mixing method;

[0097] (2) A method of dispersing the surfactant (D) in a slurry form in water or a hydrophilic organic solvent and mixing it with the crosslinked polymer (A);

[0098] (3) A method of dissolving the surfactant (D) in a hydrophobic organic solvent, impregnating the crosslinked polymer (A), and drying.

[0099] Among these mixing methods, (1) is preferred from the viewpoints of ease of drying and less residual solvent.

[0100] In the gelling agent (G) of the present invention, additives can be added as needed at any stage {during the polymerization process, chopping process, drying process, pulverization process, surface crosslinking process in the manufacturing process of the crosslinked polymer (A) and / or before and after these processes, and after the process of mixing (A) and (D), etc.}.

[0101] It should be noted that in the present invention, it is preferable to remove metal powders such as iron mixed in at any stage after drying using a magnetic iron remover. However, even if the iron removal is carried out quite precisely using an iron remover, it is difficult to remove non-magnetic metals using the iron remover. In addition, for magnetic metals, it is also impossible to remove the magnetic metals contained inside the dried polymer particles or the magnetic metals attached to the dried particles. Therefore, in order not to mix in these metals from the beginning, it is also desirable to fully consider the production equipment.

[0102] The neutralization uniformity of the gelling agent (G) in the present invention is 60 to 90%, preferably 65 to 85%, and more preferably 70 to 80%. If the neutralization uniformity is within the range of 60 to 90%, the viscosity of the alkaline electrolyte added with the gelling agent (G) becomes an appropriate range, the liquid breaking of the negative electrode material becomes good, so that a battery with stable quality can be manufactured, and the sedimentation of zinc powder in the negative electrode material can be prevented. Therefore, a battery with excellent discharge characteristics over time can be produced. On the other hand, if the neutralization uniformity is less than 60%, the liquid breaking of the negative electrode material of the alkaline battery added with the gelling agent (G) deteriorates, and a deviation in the filling amount occurs. When it exceeds 90%, the viscosity stability of the gelling agent (G) decreases, and the sedimentation of zinc powder occurs. Therefore, there is a tendency for the impact resistance and heat resistance to deteriorate.

[0103] The neutralization uniformity of the gelling agent (G) can be appropriately adjusted by the addition timing of the alkali metal hydroxide (c) during production, the subdivision and drying conditions of the hydrogel, or the mixing of crosslinked polymers (A) with different degrees of neutralization. As a method for reducing the neutralization uniformity, examples include not adding the alkali metal salt (c) during polymerization and adding the alkali metal salt (c) to the hydrogel after polymerization for neutralization, or mixing crosslinked polymers (A) with different degrees of neutralization. On the other hand, as a method for increasing the neutralization uniformity, examples include adding the alkali metal salt (c) for neutralization and then performing polymerization, or using a chopper to knead and chop the hydrogel after adding the alkali metal salt (c) to increase the contact frequency between the hydrogel and the alkali metal salt (c).

[0104] The neutralization uniformity of the gelling agent (G) is measured by the following method.

[0105] <Method for Measuring Neutralization Uniformity>

[0106] The sample piece for measurement is prepared by the following method.

[0107] Onto the surface of a substrate formed by pasting one side of a double-sided tape (4 cm × 4 cm: "NICETACK" manufactured by NICHIBAN Co., Ltd.) onto a polyethylene sheet (5 cm × 5 cm), the measurement sample was sprinkled in a manner of filling without gaps on the surface. Then, the substrate was turned over, and the excess unbonded measurement sample was shaken off. Towards the surface of the substrate, a BTB solution (bromothymol blue: a mixed solution of 400 mg, methanol: 200 mL, water: 200 mL) was sprayed onto the substrate at 0.2 g / second for 10 seconds. After standing for 20 seconds, it was further sprayed at 0.1 g / second for 10 seconds to prepare a sample sheet.

[0108] The neutralization uniformity was measured by the following method.

[0109] In a room with white illumination without sunlight entering, the background was unified, and a photo was taken with a pixel count of 8 megapixels or more. The sample sheet 20 seconds after spraying with the BTB solution was used during the photo shooting.

[0110] The photographed photo was analyzed using the image analysis software "WinROOF" for Windows. First, the total area (G1) of the sample was calculated. From the menu, [Image Processing], [Monochromatic Image Conversion] were selected to convert the image into monochromatic. Then, [Binary Processing], [Binary Thresholding Based on Two Thresholds] were selected, and the threshold was visually adjusted so that the boundary of the measurement area coincided with the boundary of the sample. Then, [Measurement], [Total Area · Number] were selected, and the calculated value was taken as the total area (G1) of the sample.

[0111] Next, the area (G2) of the specified color of the sample was calculated. The binary processing was set to the color extraction mode, and the range of hue 60 - 75, lightness 23 - 120, and chroma 40 - 255 was specified. The measurement was set to the total area · number mode, and the calculated value was taken as the area (G2) of the specified color. The neutralization uniformity was calculated as follows.

[0112] Neutralization uniformity (%) = (G2) / (G1) × 100

[0113] It should be noted that the neutralization uniformity of the gelling agent in the examples described later was measured according to the above method.

[0114] The viscosity (N1(40)) of the gel (GA) of the gelling agent (G) of the present invention is preferably 70 - 120 Pa·s, more preferably 80 - 110 Pa·s, and particularly preferably 90 - 100 Pa·s. If it is within this range, the long-term discharge characteristics are further excellent. Here, the gel (GA) is prepared by stirring and mixing 97 parts by weight of a 40% by weight aqueous potassium hydroxide solution and 3 parts by weight of the gelling agent (G) until uniform, and is the gel after standing at 40°C for 24 hours. The viscosity (N1(40)) of this gel (GA) was measured by the following method.

[0115] <Method for Measuring Viscosity (N1(40)) of Gel (GA)>

[0116] Using a digital B-type viscometer (manufactured by TOKIMEC Inc.), the viscosity of gel (GA) at a measurement temperature of 40°C was measured in accordance with JIS 7117-1:1999, and this was taken as the viscosity of gel (GA). It should be noted that a rotor No. 4 was used and the measurement was carried out at a rotational speed of 3 rpm. It should be noted that the viscosity of gel (GA) in the examples described later was measured according to the above method.

[0117] In addition, the ratio (N1(40) / N60(40)) of the viscosity (N1(40)) of gel (GA) of the gelling agent (G) of the present invention to the viscosity (N60(40)) after a further 59 days at 40°C is preferably 0.85 to 1.15, and more preferably 0.90 to 1.10. If it is within this range, the zinc powder in the electrolyte is less likely to settle, and thus the discharge characteristics and shock resistance are further excellent. The ratio (N1(40) / N60(40)) of the viscosity of gel (GA) is measured by the following method. It should be noted that the ratio (N1(40) / N60(40)) of the viscosity of gel (GA) in the examples described later was measured according to the following method.

[0118] <Method for Measuring Ratio (N1(40) / N60(40)) of Viscosity of Gel (GA)>

[0119] The sample after the measurement of the viscosity (N1(40)) of gel (GA) was sealed and further placed in a thermostat at 40°C for 59 days. The viscosity of gel (GA) measured under the same conditions as the viscosity (N1(40)) was taken as the viscosity (N60(40)) of gel (GA) after 60 days of placement. The ratio (N1(40) / N60(40)) of the viscosity of gel (GA) was calculated by the following formula.

[0120] Ratio (N1(40) / N60(40)) of viscosity (N1(40)) of gel (GA) to viscosity (N60(40)) after a further 59 days at 40°C = {viscosity (N1(40))} / {viscosity (N60(40))}

[0121] Furthermore, the ratio (N1(40) / N1(150)) of the viscosity (N1(40)) of the gel (GA) of the gelling agent (G) of the present invention to the viscosity (N1(150)) of the gel (GA) after temperature adjustment at 150°C is preferably 0.85 to 1.15, more preferably 0.90 to 1.10. If it is within this range, the zinc powder in the electrolyte under high-temperature conditions is less likely to settle, so the impact resistance and heat resistance are further excellent. The viscosity ratio (N1(40) / N1(150)) of the gel (GA) is measured by the following method. It should be noted that the viscosity ratio (N1(40) / N1(150)) during the temperature change of the gel (GA) in the examples described later is measured according to the following method.

[0122] <Measurement method of viscosity ratio (N1(40) / N1(150)) of gel (GA)>

[0123] Seal the sample after the measurement of (N1(40)) of the gel (GA), and adjust the temperature in a constant-temperature machine at 150°C for 10 minutes. After adjusting the temperature at 150°C for 10 minutes, adjust the temperature at 40°C for 1 hour. Measure the viscosity of the gel (GA) under the same conditions as the viscosity (N1(40)) as the viscosity (N1(150)) of the gel (GA) after temperature adjustment at 150°C. Calculate the viscosity ratio (N1(40) / N1(150)) of the gel (GA) by the following formula.

[0124] Viscosity ratio (N1(40) / N1(150)) of gel (GA) = {Viscosity (N1(40))} / {Viscosity (N1(150))}

[0125] <Alkaline battery>

[0126] The alkaline battery of the present invention has a gel-like negative electrode containing the gelling agent (G) and zinc powder. As an alkaline battery having a gel-like negative electrode containing the gelling agent (G) and zinc powder, there is no particular limitation, and it can be applied not only to general alkaline batteries, such as LR-20 (size D alkaline battery) and LR-6 type (size AA alkaline battery), but also to various other alkaline batteries. An alkaline battery generally has a structure in which a positive electrode agent, a current collector rod, and a gel negative electrode are sealed in an outer can, and the positive electrode agent and the gel negative electrode are separated by a separator or the like.

[0127] As a method of filling the gel-like negative electrode containing the gelling agent (G) and zinc powder into an alkaline battery, the following methods can be exemplified:

[0128] (1) A method of manufacturing a gel-like negative electrode by pre-mixing the gelling agent (G), an alkaline electrolyte (e.g., a high-concentration aqueous potassium hydroxide solution, containing zinc oxide, etc. as required), zinc powder (and / or zinc alloy powder), and other additives as required, and filling the mixture into the negative electrode container of the battery to form a gel-like negative electrode;

[0129] (2) A method such as filling the gelling agent (G), zinc powder (and / or zinc alloy powder), and other additives as required into the negative electrode container of the battery, and then filling the alkaline electrolyte to generate a gel-like negative electrode in the container.

[0130] Among them, the method of (1) in which the zinc powder can be uniformly dispersed in the negative electrode container of the battery is preferred. The addition amount of the gelling agent (G) varies depending on the structure of the negative electrode container, the particle size of the zinc powder, and the concentration of the alkaline electrolyte. Based on the weight of the alkaline electrolyte, it is preferably 0.5 to 10% by weight, and more preferably 1.0 to 5.0% by weight. If the addition amount is 0.5 to 10% by weight, the viscosity of the alkaline electrolyte containing the gelling agent becomes appropriate, which can prevent the sedimentation of the zinc powder and is also easy to operate.

[0131] The sedimentation property of the zinc powder of the gelling agent (G) is preferably less than 10 mm, and more preferably less than 5 mm. It should be noted that the sedimentation property of the zinc powder of the gelling agent (G) is measured by the method described in the examples.

[0132] Examples

[0133] Hereinafter, the present invention will be further described by way of examples and comparative examples, but the present invention is not limited thereto. Hereinafter, unless otherwise specified, ultrapure water means water with a conductivity of 0.06 μS / cm or less, and ion-exchanged water means water with a conductivity of 1.0 μS / cm or less.

[0134] <Example 1>

[0135] In a 3-L adiabatic polymerization tank, 280.0 g of acrylic acid, 0.50 g of pentaerythritol triallyl ether (0.18 wt% relative to acrylic acid), 0.45 g of trimethylolpropane triacrylate (0.16 wt% relative to acrylic acid), and 720 g of ion-exchanged water were added. After stirring and mixing to adjust the aqueous acrylic acid solution, the aqueous acrylic acid solution was cooled to 3°C. After cooling, nitrogen was introduced into the aqueous acrylic acid solution at a flow rate of 5 L / min to make the dissolved oxygen concentration in the aqueous acrylic acid solution 0.10 ppm or less. The dissolved oxygen concentration was measured using an oxygen concentration meter (ORBISPHERE 510, manufactured by HACH ULTRA) based on the diaphragm electrode method. After confirming that the aqueous acrylic acid solution was 3°C, while continuing to introduce nitrogen, 5.0 g of a 10 wt% aqueous solution of 2,2′-azobis(2-amidinopropane) hydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-50), 5.0 g of a 1.0 wt% aqueous hydrogen peroxide solution, 5.0 g of a 1.0 wt% aqueous L-ascorbic acid solution, and 5.0 g of a 0.1 wt% aqueous iron(III) sulfate solution were added as polymerization initiators to the adiabatic polymerization tank. After adding the polymerization initiators, nitrogen was introduced for another 25 minutes, then the introduction of nitrogen was stopped, and the mixture was allowed to stand for 16 hours for the polymerization reaction. After standing for 16 hours, the hydrogel obtained by the polymerization reaction was taken out from the polymerization reaction tank. The taken-out hydrogel was chopped at a gel temperature of 90°C using a chopper (12VR-400K manufactured by ROYAL, sieve plate diameter 8 mm). After adding 280.0 g of a 49 wt% aqueous sodium hydroxide (reagent special grade) solution to the subdivided hydrogel, the mixture was uniformly kneaded in the hydrogel using the above chopper for neutralization. After neutralization kneading, the hydrogel was then kneaded and chopped using the above chopper. The neutralized and kneaded hydrogel was stacked in layers with a thickness of 5 cm on a SUS sieve with a mesh size of 850 μm, and hot air at 150°C was passed through the hydrogel for 1 hour using a small air-permeable dryer (manufactured by Inoue Metal Co., Ltd.) to evaporate the moisture in the hydrogel, obtaining a dried gel. After pulverizing the dried gel using a cooking blender, the gel with a particle size of 75 μm (200 mesh) was collected using a sieve to obtain the gelling agent (G-1) of the present invention.

[0136] <Example 2>

[0137] In Example 1, the amount of acrylic acid added was 250.0 g, the amount of pentaerythritol triallyl ether added was 0.55 g (0.22 wt% relative to acrylic acid), the amount of trimethylolpropane triacrylate added was 0.45 g (0.18 wt% relative to acrylic acid), the amount of ion-exchanged water added was 750.0 g, and the amount of a 49 wt% aqueous sodium hydroxide (reagent special grade) solution added was 250.0 g. Otherwise, the same operations as in Example 1 were carried out to obtain the gelling agent (G-2) of the present invention.

[0138] <Example 3>

[0139] In Example 2, after adding 250.0 g of an aqueous solution of 49 wt% sodium hydroxide (special grade reagent) to the subdivided hydrogel for neutralization and kneading, 0.5 g of sucrose stearate (HLB: 7) was further added, and the hydrogel was uniformly kneaded and chopped using the above-mentioned chopper. Except for this, the same operations as in Example 2 were carried out to obtain the gelling agent (G-3) of the present invention.

[0140] <Example 4>

[0141] In Example 2, after adding 250.0 g of an aqueous solution of 49 wt% sodium hydroxide (special grade reagent) to the subdivided hydrogel for neutralization and kneading, the hydrogel was kneaded and chopped without using the above-mentioned chopper. Except for this, the same operations as in Example 2 were carried out to obtain the gelling agent (G-4) of the present invention.

[0142] <Comparative Example 1>

[0143] In Example 1, after neutralization and kneading, the hydrogel was kneaded and chopped using the above-mentioned chopper, and then the hydrogel was further kneaded and chopped using the above-mentioned chopper. Except for this, the same operations as in Example 1 were carried out to obtain the comparative gelling agent (H-1).

[0144] <Comparative Example 2>

[0145] In Example 4, the sieve plate diameter of the chopper (12VR-400K manufactured by ROYAL) used was 16 mm. Except for this, the same operations as in Example 4 were carried out to obtain the comparative gelling agent (H-2).

[0146] For the gelling agents (G-1) to (G-4) manufactured in Examples 1 to 4 and the comparative gelling agents (H-1) and (H-2) manufactured in Comparative Examples 1 and 2, the results of measuring the neutralization uniformity and the viscosity of the gel (GA) by the said method are shown in Table 1. It should be noted that the volume average particle diameters of the gelling agents (G-1) to (G-4) manufactured in Examples 1 to 4 and the comparative gelling agents (H-1) and (H-2) manufactured in Comparative Examples 1 and 2 are all 50 μm.

[0147] [Table 1]

[0148]

[0149] Furthermore, using the gelling agents (G-1) to (G-4) of the present invention and the comparative gelling agents (H-1) and (H-2), the results of measuring the sedimentation property of zinc powder and the deviation of the injection amount by the following method are shown in Table 2.

[0150] (1) Sedimentation property of zinc powder

[0151] In a 1-liter biaxial kneader (manufactured by Irie Shokai Co., Ltd., trade name: PNV-1), 150 g of a 40 wt% potassium hydroxide aqueous solution, 300 g of zinc powder (manufactured by UNION MINIERES.A.) with a volume average particle diameter of 200 μm, and 3.0 g of a gelling agent were added, and the mixture was mixed at 50 rpm for 60 minutes to produce a negative electrode material. 50 g of the produced negative electrode material was placed in a 50-ml sample bottle (diameter 34 mm, height 77 mm, made of polypropylene) that could be sealed, and the air bubbles that entered during mixing were degassed under reduced pressure. The sample bottle was sealed and placed in a constant temperature bath at 40 °C for 60 days. After that, using the device attached to a powder tester (manufactured by Hosokawa Micron Corporation), the sample bottle was tapped 300 times at a rate of 30 times per minute from a height of 3 cm to promote the sedimentation of the zinc powder. After the tapping was completed, the distance (mm) from the initial position of the zinc powder (the position of the upper end of the negative electrode material in the sample bottle) to the most sedimented position of the zinc powder was measured and used as the sedimentation property (mm) of the zinc powder. The sedimentation property of the zinc powder was evaluated according to the following evaluation criteria.

[0152] <Evaluation criteria>

[0153] ◎: Less than 5.0 mm

[0154] ○: 5.0 mm or more and less than 10.0 mm

[0155] ×: 10.0 mm or more

[0156] (2) Deviation of injection volume

[0157] In a 1-liter biaxial kneader, 150 g of a 40 wt% potassium hydroxide aqueous solution, 300 g of zinc powder (manufactured by UNION MINIERES.A.) with a volume average particle diameter of 200 μm, and 3.0 g of a gelling agent were added, and the mixture was mixed at 50 rpm for 60 minutes to produce a negative electrode material. The produced negative electrode material was transferred to a beaker, and the air bubbles that occurred during mixing were degassed under reduced pressure. The degassed negative electrode material was suctioned into a 10-ml syringe with an inner diameter of 2 mm at the injection port and having a scale in 0.1-ml units. From the height of the mouth of a 5-ml sample bottle (inner diameter 18 mm, height 40 mm), the syringe was pressed in by 5.0 ml to inject the negative electrode material into the sample bottle, and the weight of the negative electrode gel injected into the sample bottle was measured. The same operation was repeated 20 times in total, and the standard deviation (σ) of the injection volume was calculated as the deviation of the injection volume. The deviation of the injection volume was evaluated according to the following evaluation criteria.

[0158] <Evaluation criteria>

[0159] ◎: 0.02 or less

[0160] ○: 0.03 or more and -0.10 or less

[0161] ×: 0.11 or more

[0162] The evaluation results are shown in Table 2.

[0163] [Table 2]

[0164]

[0165] Industrial applicability

[0166] The gelling agent (G) of the present invention is useful not only as a cylindrical alkaline battery but also as a gelling agent for primary and secondary alkaline batteries such as alkaline button batteries, silver oxide batteries, nickel-cadmium storage batteries, and nickel-metal hydride storage batteries. In addition, the alkaline battery using the gelling agent of the present invention has excellent shock resistance and heat resistance, excellent maintenance of discharge characteristics, and excellent viscosity stability of the negative electrode material, and thus is useful as an alkaline battery with improved production efficiency and safety.

Claims

1. A gelling agent for alkaline batteries, characterized in that: A cross-linked polymer (A) containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal cross-linking agent (b) as constituent monomers, wherein a portion of the cross-linked polymer (A) is neutralized with an alkali metal salt (c), and the neutralization uniformity of the gelling agent for alkaline batteries is 60% to 90%.

2. The gelling agent for alkaline batteries according to claim 1, wherein The internal crosslinking agent (b) includes a crosslinking agent (b1) that can be hydrolyzed under alkali conditions, and a crosslinking agent (b2) that is not hydrolyzed under alkali conditions.

3. The gelling agent for alkaline batteries according to claim 1 or 2, wherein 97 parts by weight of a 40% by weight potassium hydroxide aqueous solution and 3 parts by weight of the alkaline battery gelling agent are stirred and mixed until uniform, and the viscosity N1(40) of the gel (GA) after being left at 40° C. for 24 hours is 70 Pa·s to 120 Pa·s.

4. The gelling agent for alkaline batteries according to any one of claims 1 to 3, wherein A gel (GA) is prepared by stirring and mixing 97 parts by weight of a 40% by weight potassium hydroxide aqueous solution and 3 parts by weight of the alkaline battery gelling agent until uniform, and the ratio of the viscosity N1(40) of the gel (GA) after being left at 40°C for 24 hours to the viscosity N60(40) after further being left at 40°C for 59 days is 0.85 to 1.

15.

5. The gelling agent for alkaline batteries according to any one of claims 1 to 4, wherein The preparation is prepared by stirring and mixing 97 parts by weight of a 40% by weight potassium hydroxide aqueous solution and 3 parts by weight of the gelling agent for alkaline batteries until they are uniformly mixed, and the ratio N1(40) / N1(150) of the viscosity of the gel (GA) after being left at 40°C for 24 hours to the viscosity of the gel (GA) after temperature adjustment at 150°C is 0.85 to 1.

15.

6. The gelling agent for alkaline batteries according to any one of claims 1 to 5, wherein The gelling agent for alkaline batteries further contains a surfactant (D) having an HLB of 1 to 12.

7. The gelling agent for alkaline batteries according to claim 6, wherein The surfactant (D) is at least one selected from the group consisting of sucrose fatty acid esters, sorbitan fatty acid esters, glycerol fatty acid esters and fatty acid amides.

8. An alkaline battery, characterized in that: The invention relates to a gelled negative electrode comprising a gelling agent for alkaline batteries and zinc powder, wherein the gelling agent for alkaline batteries comprises a crosslinked polymer (A) having as constituent monomers a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes the water-soluble vinyl monomer (a1) by hydrolysis, and an internal crosslinking agent (b), wherein a part of the crosslinked polymer (A) is neutralized with an alkali metal salt (c), and the neutralization uniformity of the gelling agent for alkaline batteries is 60% to 90%.

9. The alkaline battery according to claim 8, wherein The sedimentation of zinc powder in the gel for alkaline batteries is less than 10.0 mm.

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