JP6223788B2 - Binder for alkaline battery positive electrode and alkaline battery - Google Patents

Description

  The present invention relates to a binder for an alkaline battery positive electrode and an alkaline battery.

  Conventionally, a positive electrode containing a positive electrode active material (mainly composed of manganese dioxide), a conductive agent (graphite) and a binder has been used for the positive electrode of an alkaline battery. The binder that is uniformly dispersed in the positive electrode is used for the purpose of preventing the precipitation of zinc oxide and the accompanying internal short circuit, and has been proposed using polyacrylic acid and its salt as a binder ( Patent Document 1).

JP 2009-87872 A

However, in recent years, alkaline batteries have been required to have higher performance, and alkaline batteries using this binder have long-term discharge characteristics (discharge amount and discharge time), which are the most important characteristics of alkaline batteries. ) Is not always satisfactory in terms of maintenance.
Then, an object of this invention is to provide the binder for alkaline battery positive electrodes excellent in the maintenance of the discharge characteristic (discharge amount and discharge time) over a long term, and an alkaline battery using the same.

The binder for alkaline battery positive electrode (B) of the present invention comprises a polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes (a1) by hydrolysis as an essential constituent unit. It is a binder (B) consisting of the following requirements (1) and (2).
Requirement (1): The water-soluble component amount of the binder (B) is 50 to 95% by weight based on the weight of the binder (B).
Requirement (2): prepared by stirring and mixing 98 parts by weight of a 40% by weight aqueous potassium hydroxide solution and 2 parts by weight of the binder (B), and leaving the mixture at 40 ° C. for 24 hours (25) ° C) (V24) is 5 to 50 Pa · s.
The alkaline battery positive electrode of this invention makes it a summary to contain said binder (B) for alkaline battery positive electrodes, manganese dioxide, and graphite.
The gist of the alkaline battery of the present invention is that it comprises the above positive electrode, a negative electrode containing zinc or zinc powder, and an electrolytic solution containing an aqueous potassium hydroxide solution.

The alkaline battery positive electrode binder (B) of the present invention and the alkaline battery positive electrode and alkaline battery using this binder (B) have the following effects.
When the binder (B) of this invention is used, a high intensity | strength positive electrode can be created with a small amount of binders. Moreover, the alkaline battery using the binder (B) of the present invention has a long discharge duration and can produce an extremely excellent alkaline battery.

It is sectional drawing which shows an example of the alkaline battery of this invention.

  The binder for alkaline battery positive electrode (B) of the present invention comprises a polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes (a1) by hydrolysis as an essential constituent unit. It is a binder (B) consisting of

In the present invention, the water-soluble vinyl monomer (a1) means a vinyl monomer having a property of dissolving at least 100 g in 100 g of water at 25 ° C.
The water-soluble vinyl monomer (a1) which is an essential constituent monomer of the polymer (A) and / or the vinyl monomer (a2) which becomes the water-soluble vinyl monomer (a1) by hydrolysis are not particularly limited. Examples thereof include water-soluble radical polymerization monomers described in JP-A-2005-075982. Among these, from the viewpoint of discharge characteristics, the water-soluble vinyl monomer (a1) is preferable, and more preferably an anionic vinyl monomer {vinyl monomer having an anionic group (carboxy group, sulfo group, phosphono group, hydroxyl group, etc.)}, Particularly preferably, the C3-C30 vinyl group-containing carboxylic acid (salt) {unsaturated monocarboxylic acid (salt) {(meth) acrylic acid, crotonic acid, cinnamic acid, and salts thereof}; unsaturated dicarboxylic acid ( Salt) (maleic acid, fumaric acid, citraconic acid, itaconic acid, and salts thereof); and monoalkyl (carbon number 1 to 8) ester of the unsaturated dicarboxylic acid (maleic acid monobutyl ester, fumaric acid monobutyl ester) , Ethyl carbitol monoester of maleic acid, ethyl carbitol monoester of fumaric acid, citraconic acid And butyl ester and itaconic acid glycol monoester}, then preferably the unsaturated monocarboxylic acid (salt), most preferably acrylic acid (salt).

  In addition, (meth) acrylic acid means acrylic acid and / or methacrylic acid, and "... acid (salt)" means "... acid" and / or "... acid salt". . Examples of the salt include alkali metal salts such as potassium, sodium and lithium, and alkaline earth metal salts such as calcium.

  When the water-soluble vinyl monomer (a1) unit contained in the polymer (A) is an anionic vinyl monomer, it may be an unneutralized product or a neutralized product (water-soluble vinyl monomer salt unit). Any or all of the water-soluble vinyl monomer (a1) units may be used for the purpose of reducing the tackiness and dispersibility of the polymer (A) and improving workability in producing the polymer (A). It is preferable to neutralize the water-soluble vinyl monomer salt unit.

When an anionic vinyl monomer is used as (a1), and an anion portion derived from the anionic vinyl monomer contained in (A) is desired to be a neutralized product, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc. An alkaline earth metal hydroxide such as an alkali metal hydroxide or calcium hydroxide or an aqueous solution thereof may be added to the monomer stage before polymerization or the hydrogel after polymerization.
However, in the polymer (A), since the water-solubility of the non-hydrolyzable cross-linking agent (b2) described later is poor, a predetermined amount of cross-linking is obtained when the water-soluble vinyl monomer (a1) is polymerized in a highly neutralized state. Even if the agent (b2) is added, the crosslinking agent (b2) is separated from the monomer aqueous solution and the predetermined crosslinking cannot be performed, and the polymer (A) having the prescribed physical properties may not be obtained. Therefore, from the viewpoint of suppressing the separation of the crosslinking agent (b2), the water-soluble vinyl monomer (a1) was subjected to polymerization by setting the neutralization degree to 0 to 30 mol% and containing the crosslinking agent (b2). Thereafter, it is more preferable to adjust the degree of neutralization by adding an alkali metal hydroxide to the hydrogel as necessary.

  When an anionic vinyl monomer {most preferably acrylic acid (salt)} is used as the water-soluble vinyl monomer (a1) of the polymer (A), the final neutralization degree of the anionic vinyl monomer {anionic vinyl monomer The anionic base content (mol%)} based on the total number of moles of the anionic group and anionic base is preferably 0 to 40, more preferably 0 to 35, and particularly preferably 0 to 30. Within this range, the discharge characteristics of the alkaline battery are further improved. The anionic base means a neutralized anionic group.

  In the polymer (A), the total weight of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) in the constituent monomers constituting (A) is determined from the viewpoint of the absorption capacity of the binder (B). 99.0-100.0 weight% is preferable with respect to the total weight of (a1), (a2), (a3) and a crosslinking agent (b) {(b1) and (b2)}, More preferably, 99. It is 2 to 99.95% by weight, particularly preferably 99.5 to 99.93% by weight.

  Each of the water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) may be a single constituent monomer, or two or more types may be a constituent monomer.

Of the water-soluble vinyl monomer (a1) and / or vinyl monomer (a2), (a1) is preferable from the viewpoint of the absorption capacity of the binder (B), and more preferably (a1) is used alone as a constituent monomer. It is to be.
When both the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) are used as constituent monomers, the molar ratio {(a1) / (a2)} of these vinyl monomer units is the viewpoint of the discharge characteristics of the alkaline battery. To 75/25 to 99/1, more preferably 85/15 to 98/2, and most preferably 90/10 to 95/5.

  As a constituent monomer of the polymer (A), in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable with these may be used. it can.

Other vinyl monomers (a3) that can be copolymerized are not particularly limited and are known {Patent No. 3648553, JP-A No. 2003-165883, JP-A No. 2005-75982, and JP-A No. 2005-95759} The following hydrophobic monomers can be used. For example, the following vinyl monomers (i) to (iii) can be used.
(I) C8-C30 aromatic ethylenic monomer Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted products of styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) C2-C20 aliphatic ethylenic monomer Alkene [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkadiene [butadiene, isoprene, etc.], etc.
(Iii) Aliphatic ethylenic monomer having 5 to 15 carbon atoms Monoethylenically unsaturated monomer [pinene, limonene, indene and the like]; Polyethylene vinyl polymerizable monomer [cyclopentadiene, bicyclopentadiene, ethylidene norbornene and the like] and the like.

  When other vinyl monomer (a3) is used as a constituent monomer, the proportion (mol%) of other vinyl monomer (a3) is based on the total number of moles of (a1) and (a2) from the viewpoint of reactivity. 0.01 to 5 is preferable, more preferably 0.05 to 3, then 0.08 to 2, particularly preferably 0.1 to 1.5. In view of absorption characteristics, the content of the other vinyl monomer (a3) is most preferably 0 mol%.

  In the present invention, the polymer (A) may contain a crosslinking agent (b) as a structural unit. In (A), the crosslinking agent (b) may be composed of one of the hydrolyzable crosslinking agent (b1) or the non-hydrolyzable crosslinking agent (b2) as a constituent monomer, from (b1) and (b2) Two or more selected from the group may be used as constituent monomers.

The hydrolyzable crosslinking agent (b1) is an alkaline and hydrolyzing crosslinking agent. “Alkaline and hydrolyzing” means that the unit derived from (b) in the polymer (A) has a hydrolyzable bond. The hydrolyzable bond may be a bond that the crosslinking agent (b1) originally has in the molecule {the crosslinking agent in this case is defined as a crosslinking agent (b11) having a hydrolyzable bond in the molecule}, The bond formed by cross-linking reaction with another monomer {(a1) or (a2)} constituting the union (A) may be hydrolyzed {by cross-linking the cross-linking agent in this case The resulting bond is a hydrolyzable crosslinking agent (b12)}. From the viewpoint of viscosity stability of the binder (B), the hydrolyzable bond derived from the hydrolyzable crosslinking agent (b1) is 1 weight of the binder (B) in a 40 wt% aqueous potassium hydroxide solution at 25 ° C. It is preferable that 50% by weight or more decomposes when 1% is added and stirred for 1 hour.
Examples of the hydrolyzable bond include an ester bond and an amide bond.

  The crosslinking agent (b11) having a hydrolyzable bond in the molecule includes a copolymerizable crosslinking agent having 2 to 10 ethylenically unsaturated bonds in the molecule. For example, N, N′-methylenebisacrylamide , Ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) Examples include acrylate, pentaerythritol tetra (meth) acrylate, and polyglycerin (degree of polymerization 3 to 13) polyacrylate.

  As the crosslinking agent (b12) in which the bond formed by the crosslinking reaction is hydrolyzable, when an anionic vinyl monomer having a carboxyl group and / or a carboxylate group is used as (a1), the carboxyl derived from this monomer Reactive crosslinkers that react with groups or carboxylate groups are included. Examples of (b2) include polyvalent glycidyl compounds (such as ethylene glycol diglycidyl ether), polyvalent isocyanate compounds (such as 4,4′-diphenylmethane diisocyanate), polyvalent amine compounds (such as ethylenediamine), and polyhydric alcohol compounds (glycerin). Etc.). The reactive crosslinking agent can react with an anionic vinyl monomer having a carboxyl group or a carboxylate group {(meth) acrylic acid (salt), etc.} to form an ester bond or an amide bond.

Two or more hydrolyzable crosslinking agents (b1) may be used in combination.
Of the hydrolyzable crosslinking agent (b1), from the viewpoint of viscosity stability of the binder (B), the crosslinking agent (b11) and the polyvalent glycidyl compound are preferable, and more preferably N, N′-methylenebisacrylamide, ethylene. Glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate and polyvalent glycidyl compounds, and more preferably N, N'- Methylene bisacrylamide, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and ethylene glycol diglycidyl ether, particularly preferably N, N′-methylenebisacrylic Amides, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and ethylene glycol diglycidyl ether.

  When the cross-linking agent (b12) is used, it is preferable to proceed to the cross-linking reaction by heating to 100 to 230 ° C. at any stage after the addition of the cross-linking agent, and more preferably to 120 to 160 ° C. Make it progress. In addition, the crosslinking agent (b12) may be used in combination of two or more in a predetermined amount range, and further in combination with the crosslinking agent (b11).

  The non-hydrolyzable crosslinking agent (b2) is a crosslinking agent that is alkaline and does not hydrolyze, does not have a hydrolyzable bond in the molecule, and does not generate a hydrolyzable bond by a crosslinking reaction. Examples of such a crosslinking agent (b2) include a crosslinking agent (b21) having two or more vinyl ether bonds and a crosslinking agent (b22) having two or more allyl ether bonds. From the viewpoint of reactivity and the like, the crosslinking agent (b22) having two or more allyl ether bonds is preferable.

  Examples of the crosslinking agent (b21) having two or more vinyl ether bonds include ethylene glycol divinyl ether, 1,4-butanediol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, 1,6-hexanediol divinyl ether, polyethylene Examples include glycol divinyl ether (polymerization degree 2 to 5), bisphenol A divinyl ether, pentaerythritol trivinyl ether, sorbitol trivinyl ether, polyglycerin (polymerization degree 3 to 13) polyvinyl ether, and the like.

  As the cross-linking agent (b22) having two or more allyl ether bonds, the cross-linking agent (b221) having two allyl groups and no hydroxyl group in the molecule, having two allyl groups in the molecule and A crosslinking agent (b222) having 1 to 5 hydroxyl groups, a crosslinking agent (b223) having 3 to 10 allyl groups in the molecule and having no hydroxyl groups, 3 to 10 allyl groups in the molecule, and And a crosslinking agent having 1 to 3 hydroxyl groups (b224). When a hydroxyl group is included in the molecule, the compatibility with the vinyl monomer (a1) and / or (a2) {especially (meth) acrylic acid (salt)} is improved and the cross-linking uniformity is increased, so that the binder (B) The adhesion of the alkaline battery positive electrode is further improved.

As the crosslinking agent (b221) having two allyl groups in the molecule and not having a hydroxyl group, diallyl ether, 1,4-cyclohexanedimethanol diallyl ether, alkylene (2 to 5 carbon atoms) glycol diallyl ether and polyethylene Examples include glycol (weight average molecular weight: 100 to 4000) diallyl ether and the like.
As a crosslinking agent (b222) having 2 allyl groups and 1 to 5 hydroxyl groups in the molecule, glycerin diallyl ether, trimethylolpropane diallyl ether, pentaerythritol diallyl ether and polyglycerol (degree of polymerization 2 to 5) Examples include diallyl ether.
Examples of the cross-linking agent (b223) having 3 to 10 allyl groups in the molecule and having no hydroxyl group include trimethylolpropane triallyl ether, glycerin triallyl ether, pentaerythritol tetraallyl ether, and tetraallyloxyethane. Can be mentioned.
As the crosslinking agent (b224) having 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule, pentaerythritol triallyl ether, diglyceryl triallyl ether, sorbitol triallyl ether and polyglycerol (degree of polymerization) 3-13) and polyallyl ether.

Two or more non-hydrolyzable crosslinking agents (b2) may be used in combination.
Among the crosslinking agents (b2), the crosslinking agent (b22) having two or more allyl ether bonds is preferable, and more preferably the crosslinking agent (b222) having two allyl groups and 1 to 5 hydroxyl groups in the molecule. ) And a cross-linking agent (b224) having 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule, particularly preferably 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule. One crosslinking agent (b224), most preferably sorbitol triallyl ether and pentaerythritol triallyl ether. Use of these cross-linking agents is preferable because they are compatible with the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) and can be efficiently cross-linked.

  In the case of using the crosslinking agents (b1) and (b2) in the polymer (A), the amount of (b2) needs to be smaller than the amount of (b1). The amount of the crosslinking agent (b2) used is preferably 0 to 49% by weight, more preferably 0 to 45% by weight, based on the total weight of the crosslinking agents (b1) and (b2), from the viewpoint of the strength of the alkaline battery positive electrode. Particularly preferably, it is 0 to 40% by weight.

  In the polymer (A), it is preferable not to use the cross-linking agent (b) from the viewpoint of the discharge characteristics (discharge sustainability) immediately after the production of the battery. In the polymer (A), when the crosslinking agent (b) is used, the total content of (b1) and (b2) in the constituent monomers is the kind of the crosslinking agents (b1) and (b2), Although depending on the weight average molecular weight, from the viewpoint of the absorption capacity of the binder (B), 0.01 to about the total weight of (a1), (a2), (a3), (b1) and (b2) The amount is preferably 1% by weight, more preferably 0.05 to 0.8% by weight, and particularly preferably 0.07 to 0.5% by weight.

The binder for an alkaline battery positive electrode (B) of the present invention contains the polymer (A) and has the following requirements (1) and (2).
The requirement (1) is a requirement necessary for improving the discharge characteristics.
The requirement (2) is a requirement necessary for increasing the strength of the positive electrode of the alkaline battery.

Requirement (1): The water-soluble component amount of the binder (B) is 50 to 95% by weight based on the weight of the binder (B).
Requirement (2): prepared by stirring and mixing 98 parts by weight of a 40% by weight aqueous potassium hydroxide solution and 2 parts by weight of the binder (B), and leaving the mixture at 40 ° C. for 24 hours (25) ° C) (V24) is 5 to 50 Pa · s.

  In the requirement (1), the amount of the water-soluble component of the binder (B) is 50 to 95% by weight based on the weight of the binder (B), preferably 55 to 90% by weight from the viewpoint of discharge characteristics. More preferably, it is 60 to 80% by weight. If the amount of water-soluble component is less than 50% by weight, the discharge characteristics (discharge sustainability) immediately after the production of the battery deteriorate, and if it exceeds 95% by weight, uniform mixing with manganese dioxide and graphite becomes difficult.

In addition, said water-soluble component amount is measured with the following method.
<Method for measuring the amount of water-soluble components>
In a 2000 ml beaker, about 1 g of the binder (B) {measured to 4 digits after the decimal point (W ₀ )} and 1000 g of ion-exchanged water were added and stirred for 24 hours at 300 rpm using a magnetic stirrer. The stirred solution was filtered with a filter paper (No. 2 type, manufactured by Toyo Roshi Kaisha, Ltd.), and the filtrate was collected. After the filtrate was concentrated with an evaporator, it was evaporated to dryness at 120 ° C. using a dryer, and the weight (W ₁ ) g of the evaporation residue was measured. The amount (%) of the water-soluble component in the ion-exchanged water of the binder (B) was calculated by the following formula-(1).

Water-soluble component amount (%) = (W ₁ ) × 100 / (W ₀ ) Formula- (1)

  As a method for adjusting the amount of the water-soluble component to the range of the above requirement (1), the amount of the radical polymerization initiator at the time of producing the polymer (A) is the sum of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2). It is good to satisfy | fill 0.001-3.0 weight% with respect to a weight. If the amount of the water-soluble component is high, the amount of the initiator is reduced within the above range, and if the amount of the water-soluble component is low, the amount of the initiator is increased within the above range. It can be a numerical range.

  In the requirement (2), the viscosity (25 ° C.) of the compound (C) is 5 to 50 Pa · s. However, from the viewpoint of improving the positive electrode strength of the alkaline battery, 10 to 45 Pa · s is preferable, and particularly preferably 15 to 40 Pa · s. When it exceeds 50 Pa · s, dispersibility with manganese dioxide and graphite is deteriorated, and when it is less than 5 Pa · s, bonding properties with manganese dioxide and graphite are deteriorated.

  The viscosity (V24) of the compound (C) was prepared by stirring and mixing 98 parts by weight of a 40% by weight aqueous potassium hydroxide solution and 2 parts by weight of the binder (B), and the mixture was allowed to stand at 40 ° C. for 24 hours. The viscosity at 25 ° C.

The viscosity (V24) of this blend (C) is measured by the following method.
<Measurement Method of Viscosity (V24) of Formulation (C)>
Using a digital viscometer DV-II + Pro (manufactured by Brookfield), the viscosity of the compound (C) after 24 hours at 40 ° C. was measured at 25 ° C. in accordance with JIS-K7117-1: 1999. The viscosity (V24) of the blend (C) is measured. The rotor No. 64 is used and measured at a rotational speed of 3 rpm.

  As a method of adjusting the viscosity (V24) of the blend (C) to the range of the requirement (2), when the viscosity is high, the viscosity can be adjusted by increasing the amount of the initiator within the range. When the viscosity is low, the viscosity can be adjusted by reducing the amount of initiator within the above range. Moreover, when using a crosslinking agent (b), it is good for the usage-amount of a crosslinking agent (b2) to satisfy | fill 0 to 49 weight% with respect to the total weight of a crosslinking agent (b1) and (b2).

  The viscosity ratio (V24) / (V1) of the blend (C) is preferably 0.3 to 20, more preferably 0.5 to 10, particularly preferably 0.6 to 8, and most preferably 0.8. 8-6. Within this range, since the strength of the alkaline battery positive electrode can be maintained, the discharge characteristics over a long period of time are further improved.

  Viscosity (V1) of the blend (C) was prepared by stirring and mixing 98 parts by weight of a 40% by weight aqueous potassium hydroxide solution and 2 parts by weight of the binder (B), and left at 40 ° C. for 1 hour. The viscosity at 25 ° C.

The viscosity (V1) of the blend (C) is measured by the following method <Measurement method of the viscosity (V1) of the blend (C)>
Using a digital viscometer DV-II + Pro (manufactured by Brookfield), the viscosity of the compound (C) after being allowed to stand at 40 ° C. for 1 hour is measured at a measurement temperature of 25 ° C. according to JIS 71117-1: 1999. And the viscosity (V1) of the blend (C). The rotor No. 64 is used and measured at a rotational speed of 3 rpm.

The viscosity ratio (V24) / (V1) of the blend (C) is calculated from the following formula (4).

Viscosity ratio (V24) / (V1) = Viscosity of formulation (C) (V24) / Viscosity of formulation (C) (V1) Formula- (4)

  As a method of setting the viscosity ratio (V24) / (V1) of the blend (C) in the above range, when the viscosity ratio is high, the initiator amount is increased within the above range, and when the viscosity ratio is low. The amount of the initiator can be adjusted within the above range. Moreover, when using a crosslinking agent (b), it is good for the usage-amount of a crosslinking agent (b2) to satisfy | fill 0 to 49 weight% with respect to the total weight of a crosslinking agent (b1) and (b2).

  The amount of the soluble component in the 10% aqueous potassium hydroxide solution of the binder (B) is preferably 50 to 100% by weight, more preferably 55 to 95% by weight, particularly preferably 60 to 95% by weight, most preferably Preferably it is 60 to 90% by weight. In this range, since the strength of the alkaline battery positive electrode can be maintained, the discharge characteristics over a long period of time are further improved.

The amount of soluble components in the 10% aqueous potassium hydroxide solution is measured by the following method.
<Method for measuring the amount of soluble components in 10% aqueous potassium hydroxide solution>
In a 500 ml beaker, about 1 g of binder (B) (measured to 4 digits after the decimal point (W ₀ )) and 200 g of 10% potassium hydroxide aqueous solution were added and stirred for 24 hours at 300 rpm using a magnetic stirrer. . The stirred solution was filtered with a Buchner glass filter (manufactured by Mutual Riken Glass Co., Ltd., No. 1 type), and the filtrate was collected. After adjusting the pH to 7.0 by adding 10% sulfuric acid aqueous solution to 20 g of the filtrate and concentrating with an evaporator, it was evaporated to dryness at 120 ° C. using a dryer, and the weight (W ₂ ) g of the evaporation residue was obtained. It was measured. As a blank, 10% sulfuric acid aqueous solution was added to 20 g of 10% potassium hydroxide aqueous solution used, and the blank solution adjusted to pH 7.0 was concentrated by an evaporator, and then evaporated to dryness at 120 ° C. using a dryer. The weight (W ₃ ) g of the evaporation residue was measured. The amount (%) of the soluble component in the 10% aqueous potassium hydroxide solution of the binder (B) was calculated by the following formula-(2).

Amount of soluble component in 10% aqueous potassium hydroxide solution (%) = {(W ₂ ) − (W ₃ )} × 100 / (W ₀ ) × D Formula- (2)

D: Dilution ratio (D = 200/20 = 10)

  As a method for adjusting the amount of the soluble component in the 10% aqueous potassium hydroxide solution to the above range, the amount of the radical polymerization initiator at the time of producing the polymer (A) is adjusted so that the water-soluble vinyl monomer (a1) and the vinyl monomer (a2 ) To the total weight of 0.001 to 3.0% by weight. If the amount of the soluble component in the 10% aqueous potassium hydroxide solution is large, the amount of the initiator is reduced within the above range, and the amount of the soluble component in the 10% aqueous potassium hydroxide solution is small, the above range. The amount of the soluble component in the 10% aqueous potassium hydroxide solution can be adjusted to the above numerical range by increasing the amount of the initiator.

  The total content of the unpolymerized water-soluble vinyl monomer (a1) and vinyl monomer (a2) in the binder (B) of the present invention is preferably 10 to 2000 ppm based on the weight of (B), and Preferably it is 20-1000 ppm, Most preferably, it is 30-500 ppm, Most preferably, it is 40-300 ppm. Within this range, the discharge duration (discharge characteristics over a long period) is further improved.

  The total content of unpolymerized (a1) and (a2) does not mean the total content of (a1) and (a2) contained as a constituent unit of the polymer (A). The total content of unpolymerized (a1) and (a2) is measured and calculated by the following method described in JP-A-2006-219661.

<Method for measuring the total content of unpolymerized (a1) and (a2)>
In a 300 ml beaker, 1.0 g of binder (B) and 249.0 g of 0.9 wt% saline solution are added and stirred at 20 to 30 ° C. for 3 hours, and then the insoluble matter is filtered off to obtain a filtrate. The total content of (a1) and (a2) is obtained from this filtrate using a calibration curve prepared by a high-performance liquid chromatography method (under the following conditions) using a vinyl monomer or a crosslinking agent having a known concentration.
Measurement conditions Column: SCR-101H (length 0.3 m × inner diameter 7.9 mm, manufactured by Shimadzu Corporation)
Developing solution: 0.015 wt% phosphoric acid aqueous solution Flow rate: 0.5 ml / min
Sample injection volume: 100 μl
Detector: UV detector, wavelength 195 nm
Column temperature: 40 ° C

  In the case of aqueous solution polymerization described later, as a method for bringing the total content of unpolymerized (a1) and (a2) in the binder (B) to a range of 10 to 2000 ppm based on the weight of (B), A reducing substance described in JP-A-1-62317 or a water-soluble thiol compound (for example, sodium sulfite) described in JP-A-8-157737 is used as an aqueous solution or dispersion as a polymer (A). The method of adding and mixing is mentioned. These may be only one type of method, or two or more types may be used in combination.

The addition amount of the reducing substance or the water-soluble thiol compound is 0.01 to 5.0% by weight based on the total amount of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) that becomes (a1) by hydrolysis. It is preferable to satisfy 0.02 to 4.0% by weight, particularly preferably 0.03 to 3.0% by weight, and most preferably 0.05 to 2.0% by weight.
If the total content of the unpolymerized (a1) and (a2) does not satisfy the above range, the addition method described in JP-A-1-62317 and JP-A-8-157737 may be used as necessary. It can satisfy | fill by mixing in the process of neutralizing the hydrous gel of below-mentioned (A) as an reducing substance or water-soluble thiol compound aqueous solution or water dispersion in the process of neutralizing with an alkali.

  In the case of the reverse phase suspension polymerization described later, as a method for bringing the total content of unpolymerized (a1) and (a2) into the range of 10 to 2000 ppm based on the weight of (B), JP-A-2006- The method of adjusting the supply at the time of superposition | polymerization of (a1) and (a2) as described in 131767 gazette is mentioned.

The supply of (a1) and (a2) is preferably performed continuously at a constant speed, but the supply speed may be changed, and the supply of (a1) and (a2) may be temporarily interrupted. it can. As for the supply rate of (a1) and (a2), it is preferable to supply the whole amount in 30 to 180 minutes, more preferably 45 to 120 minutes, and particularly preferably 60 to 80 minutes.
If the total content of unpolymerized (a1) and (a2) does not satisfy the above range, the polymerization method described in JP-A-2006-131767 can be satisfied by performing an aging step as necessary. Can do.

Next, the manufacturing method of the binder (B) of this invention is demonstrated.
As a polymerization method for obtaining the polymer (A), a known polymerization method can be applied. For example, any of solution polymerization, suspension polymerization, bulk polymerization, reverse phase suspension polymerization, and emulsion polymerization may be used.

Among these polymerization methods, solution polymerization, suspension polymerization, reverse phase suspension polymerization and emulsion polymerization are preferable from the viewpoint of the absorption capacity of the binder (B), and more preferably solution polymerization, reverse phase suspension polymerization and emulsion. Polymerization, particularly preferably solution polymerization and reverse phase suspension polymerization. For these polymerizations, known polymerization initiators, chain transfer agents and / or solvents can be used.
Most preferably, an aqueous solution polymerization method in which a crosslinking agent (b1) and / or a crosslinking agent (b2) is added and dissolved in an aqueous monomer solution mainly composed of (meth) acrylic acid (salt), and hydrophobic in the presence of a dispersing agent. This is a reverse-phase suspension polymerization method in which a similar aqueous monomer solution is dispersed and suspended in a basic organic solvent (for example, hexane, toluene, xylene, etc.). With these polymerization methods, a binder having excellent discharge characteristics can be obtained.

  A method of polymerizing (meth) acrylic acid (salt) by an aqueous solution polymerization method or a reverse phase suspension polymerization method may be a known method, for example, a method of polymerization using a radical polymerization initiator, radiation, ultraviolet rays, electron beam, etc. Can be used.

When a radical polymerization initiator is used, examples of the initiator 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-t-butyl peroxide, cumene hydroperoxide, etc.] and redox initiators [alkali metal sulfites or bisulfites, ammonium sulfites, ammonium bisulfites, L- Reducing agents such as ascorbic acid and alkali metal persulfate, ammonium persulfate, hydrogen peroxide Combination etc. peroxides and the like. Two or more of these may be used in combination.
From the viewpoint of long-term discharge characteristics, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (2-amidinopropane) hydrochloride, hydrogen peroxide , Potassium persulfate and redox initiators (L-ascorbic acid and hydrogen peroxide) are preferred.

  Although 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.

  The initiator is not particularly limited, but it is 0 from the viewpoint of sustaining discharge of the alkaline battery and increasing the degree of polymerization of the polymer with respect to the total weight of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2). 0.001 to 3.0% by weight is preferable, and 0.01 to 0.5% by weight is more preferable.

When polymerizing the polymer (A) by the aqueous solution polymerization method, the polymerization concentration (% by weight) of the monomer {total of (a1), (a2), (b1) and (b2)} in the aqueous solution is Although it varies depending on the polymerization conditions, when (a1) is (meth) acrylic acid (salt), if the polymerization concentration is increased, crosslinking of the monomer itself (self-crosslinking) is likely to occur in parallel with the polymerization reaction, and the absorption amount Of the polymer and the average degree of polymerization of the polymer, and it is difficult to control the temperature during the polymerization. For this reason, the polymerization concentration is preferably 10 to 40% by weight, more preferably 10 to 30% by weight.
Further, the polymerization temperature of the aqueous solution polymerization method is preferably −10 to 100 ° C., more preferably −10 to 80 ° C. from the viewpoint of the average degree of polymerization of the polymer.
The amount of dissolved oxygen at the time of polymerization is preferably 0 to 2 ppm (2 × 10 ⁻⁴ wt% or less), more preferably 0 from the viewpoint of the average degree of polymerization of the polymer, although it depends on the amount of radical initiator added. ˜0.5 ppm (0.5 × 10 ⁻⁴ wt% or less). Within these ranges, a polymer (A) excellent in absorption capacity can be produced.

When (meth) acrylic acid is used as (a1), the degree of neutralization of (meth) acrylic acid during polymerization is such that a predetermined amount of hydrolyzable crosslinking agent (b1) or non-hydrolyzable crosslinking agent (b2). A degree of neutralization that can be completely dissolved in the aqueous monomer solution is preferred. Compared with (b1), (b2) has poor water solubility, and in particular, its solubility in (meth) acrylic acid (salt) aqueous solution is extremely low. Therefore, when polymerizing the polymer (A), even if a predetermined amount of (b2) is added, (b2) may be separated from the aqueous monomer solution and the predetermined crosslinking may not be performed. Therefore, when polymerizing the polymer (A), from the viewpoint of the solubility of (b2), the degree of neutralization of (meth) acrylic acid at the time of polymerization is 0 to 30 mol%, and if necessary, further after polymerization. It is preferable to neutralize, more preferably after the polymerization in an unneutralized state, if necessary, after the polymerization.
In addition, when (meth) acrylic acid is polymerized under the same conditions, the degree of polymerization (absorption capacity) tends to increase when the degree of neutralization is low. Therefore, when polymerizing the polymer (A), it is preferable to carry out the polymerization in a state where the degree of neutralization is low in order to increase the degree of polymerization of the polymer.

  The reverse phase suspension polymerization method is a polymerization method in which a monomer-containing aqueous solution is suspended and dispersed in the presence of a dispersant in a hydrophobic organic solvent typified by hexane, toluene, xylene and the like. However, in this polymerization method, as in the aqueous solution polymerization method, the total concentration of monomers in the aqueous solution is preferably 10 to 40% by weight, more preferably 10 to 30% by weight. Within this range, a polymer (A) having a high degree of polymerization can be produced.

  In this reverse phase suspension polymerization method, a dispersant may be used during the polymerization. As the dispersant, known dispersants can be used, sorbitan fatty acid esters such as sorbitan monostearate having an HLB (Hydrophile-Lipophile Balance) of 3 to 8, glycerin fatty acid esters such as glycerol monostearate, and sucrose distearate. Surfactants such as sucrose fatty acid esters such as acid esters; molecules such as maleated ethylene / acrylic acid copolymer, maleated ethylene / vinyl acetate copolymer, styrene sulfonic acid (salt) / styrene copolymer A polymer dispersant having a hydrophilic group therein and soluble in a solvent for dispersing an aqueous monomer solution (hydrophilic group; 0.1 to 20% by weight, weight average molecular weight; 1,000 to 1,000,000) 000) and the like. As the dispersant, it is easier to adjust the size of the suspended particles of the monomer aqueous solution in the solvent and the polymer gel (A) containing the required particle size can be made by using a polymer dispersant. preferable.

The addition amount of the dispersant is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, based on the weight of the hydrophobic organic solvent, from the viewpoint of discharge characteristics of the alkaline battery.
The weight ratio (W / O ratio) between the aqueous monomer solution and the hydrophobic organic solvent in the reverse phase suspension polymerization is preferably from 0.1 to 2.0, more preferably from 0.3 to 1.0. It is easy to adjust the particle diameter of a polymer (A) as it is these ranges.

In the production of the polymer (A), when a crosslinking agent is used, the weight average molecular weight of the polymer (hereinafter abbreviated as Mw) when the polymer is produced under exactly the same conditions except that the crosslinking agent is not used, It is preferably 200,000 to 1,500,000, more preferably 400,000 to 1,200,000, still more preferably 700,000 to 1,000,000.
When the polymerization is carried out under the condition that the Mw is 200,000 or more, the dispersibility with the positive electrode active material (manganese dioxide) and the conductive agent (graphite) is good, and the strength of the alkaline battery positive electrode can be maintained. The discharge characteristics over the range are further excellent. Moreover, since the intensity | strength of an alkaline battery positive electrode can be maintained as said Mw is 1,500,000 or less, the discharge characteristic over a long term is further excellent.
In addition, when the water-soluble vinyl monomer (a1) which comprises a polymer (A) is acrylic acid, said Mw is calculated | required by the following.
<Measurement of Mw>
About a polymer (A), a polymer (X) is manufactured on the completely same conditions except not using a crosslinking agent.
The following amount of 40 wt% aqueous potassium hydroxide solution and the following amount of polymer (X) were prepared by stirring and mixing, and the mixture was allowed to stand at 40 ° C. for 24 hours. ℃).

Amount (parts by weight) of polymer (X) = 1.64 / 72 × [[72 × {1-0.01 × (neutralization rate of polymer (X) (%))}] + [94 × 0 .01 × {Neutralization rate of polymer (X) (%)}]]

Amount of 40 wt% potassium hydroxide aqueous solution (parts by weight) = 100− [Amount of polymer (X) (parts by weight)]

In addition, 98.36 parts by weight of 40% by weight potassium hydroxide aqueous solution and polyacrylic acid having a known Mw (polyacrylic acid manufactured by Wako Pure Chemical Industries, Ltd., Mw: 25,000, 250,000, 1,000,000) 1.64 parts by weight) was prepared by stirring and mixing, and a calibration curve was prepared from the viscosity (25 ° C.) of the formulation after standing at 40 ° C. for 24 hours, and the viscosity of the formulation (C ′) was determined. Mw is calculated by fitting to a calibration curve.

The polymer (A) obtained by aqueous solution polymerization or reverse phase suspension polymerization is obtained as a gel containing water (hydrous gel). The hydrogel is usually used as a binder (B) after drying.
In the case of aqueous solution polymerization, the water-containing gel is dried by subdividing the water-containing gel to a certain degree with a meat chopper or cutter type crusher (the level of subdivision is about 0.5 to 20 mm square) or noodles. After neutralizing the hydrous gel by adding an alkali metal hydroxide or the like, air-permeable drying (lamination of the hydrogel on a punching metal or a screen and forcing a hot air of 50 to 150 ° C. to dry Etc.) and ventilation drying (water gel is put in a container, hot air is aerated and circulated and dried, and the gel is further subdivided with a machine such as a rotary kiln). Among these, air drying is preferable because efficient drying can be performed in a short time.
On the other hand, as a drying method of the hydrogel in the case of reverse phase suspension polymerization, the polymerized hydrogel and the organic solvent are solid-liquid separated by a method such as decantation, and then dried under reduced pressure (degree of vacuum; pressure is 100 to 50, Generally, it is performed by air drying.

  Examples of the method for drying the hydrogel in aqueous solution polymerization other than the above include, for example, a contact drying method in which the hydrogel is compressed and stretched on a drum dryer, and the hydrogel has a poor thermal conductivity, so that it is dried. In addition, it is necessary to make a thin film of hydrogel on the drum. However, the material of a commercially available drum dryer is generally formed of a metal having a lower ionization tendency than zinc, such as iron, chromium and nickel. When the hydrogel is a thin film, the drum per hydrogel The frequency of contact with the metal surface is extremely high. Therefore, when the water-containing gel is a poly (meth) acrylic acid (salt) water-containing gel, the water-containing gel is highly sticky, so a knife-like object is brought into contact with the drum dryer and the dried product is peeled off from the drum dryer. Content of metal elements that have a lower ionization tendency than zinc in the binder because the metal surface of the drum or knife is worn due to mechanical wear of the drum and knife, and the metal is mixed into the dry matter. Will increase. As described above, when a contact drying method such as a drum dryer is used, metal ions and metal powder are likely to be mixed into the binder, and these metals have a lower ionization tendency than zinc (metals whose standard electrode potential is lower than zinc). Therefore, it contains a considerable amount of metal) ions and metal powder which can be expressed by atomic symbols such as Cr, Fe, Ni, Sn, Pb, Cu, Hg and Ag. When these binders are used as binders for alkaline batteries, the zinc powder in the battery forms a battery with metal ions or metal powder that has a lower ionization tendency than zinc, and hydrogen gas is generated by electrolysis. As a result, the internal pressure of the battery rises, and the alkaline electrolyte may flow out or be severely damaged. Furthermore, the thin film film-like dried product obtained by compressing and stretching the hydrogel on a drum dryer or the like is then crushed to adjust the particle size of the dried product to a desired particle size. Therefore, the strength is much weaker than the pulverized product of the block-like dried product by the air-drying method or the air-drying method, and it swells when it is swollen in a high concentration alkaline aqueous solution and mechanically mixed with zinc powder The gel is destroyed and the gel becomes smaller. Therefore, it is preferable not to use a contact drying method such as a drum dryer.

The water-containing gel of the polymer (A) may contain a drying aid as necessary during drying. There are no particular limitations on the drying aid, and hydrophobic substances having an HLB value of 1 to 10 described in known {JP-A-2006-160774, JP-A-2007-71415, JP-A-2010-185029, etc.} can be used. . The HLB value means a hydrophilic-hydrophobic balance (HLB) value, and is determined by the Oda method (new introduction to surfactants, page 197, Takehiko Fujimoto, Sanyo Chemical Industries, Ltd., published in 1981). .
The mixing method of the water-containing gel of the polymer (A) and the drying aid is not particularly limited as long as they are mixed. However, the drying aid is not the dried body of the polymer (A), but the water-containing gel of (A). Or it is preferable to mix with the polymerization liquid before superposing | polymerizing (A) from a viewpoint contained uniformly in (A), More preferably, it is mixing with the hydrous gel of (A). In addition, it is preferable to mix uniformly so that mixing may be carried out.

When the polymer (A) is obtained by the aqueous solution polymerization method, the timing for mixing or kneading the drying aid and (A) is not particularly limited, but during the polymerization process, immediately after the polymerization process, the hydrogel is crushed (mince). Examples include during and after drying of the hydrogel, after drying of the hydrogel. Among these, kneading is preferably performed immediately after the polymerization step and during the pulverization (mincing) step of the hydrogel, and more preferably during the pulverization (mincing) step of the hydrogel.
When the polymer (A) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing of mixing the drying aid and (A) is not particularly limited, but during the polymerization process, immediately after the polymerization process, during the dehydration process. (During the process of dehydrating to about 10% by weight of water), Immediately after the dehydration process, during the process of separating and distilling off the organic solvent used for polymerization, and during drying of the hydrogel. Among these, during the polymerization step, immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, and during the step of separating and distilling off the organic solvent used for the polymerization are preferable, and more preferably during the polymerization step and immediately after the polymerization step.
In addition, 20-100 are preferable, and, as for mixing temperature (degreeC), More preferably, it is 40-90, Most preferably, it is 50-80.

  The drying temperature at the time of drying the hydrogel varies depending on the dryer used, the drying time, etc., but is preferably 50 to 150 ° C, more preferably 80 to 130 ° C. When the drying temperature is 150 ° C. or lower, the polymer is not easily crosslinked by heat during drying, the degree of crosslinking is not increased excessively by thermal crosslinking, the amount of absorption does not decrease, and the strength of the alkaline battery positive electrode does not decrease. When the temperature is 50 ° C. or higher, it is efficient without requiring a long time for drying. The drying time varies depending on the model of the dryer used and the drying temperature, but is preferably 5 to 300 minutes, more preferably 5 to 120 minutes.

  The dried product of the polymer (A) thus obtained is pulverized and powdered as necessary. The pulverization method may be a normal method, and can be performed by, for example, an impact pulverizer (pin mill, cutter mill, skiller mill, ACM pulverizer, etc.) or an air pulverizer (jet pulverizer, etc.).

As for the powdered polymer (A), a dry powder having a desired particle diameter can be collected using a sieve (vibrating sieve, centrifugal sieve, etc.) equipped with a desired screen if necessary.
In addition, it is preferable to remove metal powders, such as iron mixed, using the iron removal machine using magnetism in the arbitrary steps after drying. However, even if iron removal is performed with high precision, it is difficult to remove metals that are not magnetic with iron removal machines, and magnetic metals are also contained inside dry polymer particles. It is desirable to give sufficient consideration to the production equipment so that these metals are not mixed from the beginning, since it cannot be removed.

  The particle diameter of the polymer (A) is not particularly limited, but from the viewpoint of the breaking strength of the positive electrode, the weight average particle diameter is preferably 1 to 500 μm, more preferably 5 to 450 μm, particularly preferably 10 to 400 μm, Most preferably, it is 15-350 micrometers.

The binder (B) of the present invention contains, in addition to the polymer (A), other additives as necessary for the purpose of improving fluidity at the time of production of the positive electrode, as long as no problem occurs in workability and battery characteristics. But it ’s okay.
Examples of other additives include discharge characteristic improvers.

Examples of the discharge characteristic improver include known compounds such as TiO ₂ , Bi ₂ O ₃ , CuO, In ₂ O ₂ , SnO ₂ , Nb ₂ O ₃ , silicon dioxide, potassium silicate, silicone, and fluorine compounds.
The content in the case of containing the discharge characteristic improver is preferably 0 to 5.0% by weight, more preferably 0 to 3.0% by weight, based on the total weight of the polymer (A).

  0 to 5.0 weight% is preferable with respect to the weight of a polymer (A), and, as for the total content in case of containing another additive, More preferably, it is 0 to 3.0 weight%.

  The method for adding the discharge characteristic improver can be exemplified by a method in which the binder (B) of the present invention and the discharge characteristic improver are dry blended in advance and then blended with another positive electrode material. Any method that can add the binder (B) may be used.

  When the alkaline battery positive electrode binder (B) of the present invention is used, a high strength positive electrode can be prepared with a small amount of binder. Moreover, the alkaline battery using the binder (B) of the present invention has a long discharge duration and can produce an extremely excellent alkaline battery. In addition, it is possible to produce an alkaline battery having a uniform quality with a small amount of electrolyte solution absorbed, little variation in the amount of electrolyte solution absorbed, and a small amount of electrolyte solution in the alkaline battery even during mass production.

The alkaline battery positive electrode of the present invention is an alkaline battery positive electrode that uses the alkaline battery positive electrode binder (B) and further contains manganese dioxide and graphite.
As a method for producing the alkaline battery positive electrode of the present invention, a normal production method for producing an alkaline battery positive electrode using a binder, manganese dioxide and graphite can be used. For example, the binder (B) of the present invention, a positive electrode active material (manganese dioxide), a conductive agent (graphite) and, if necessary, other additives (discharge characteristics improver) are premixed, and then an alkaline electrolyte (for example, hydroxylated) (Potassium aqueous solution) is mixed to prepare a positive electrode mixture, followed by rolling and molding. The prepared alkaline battery positive electrode is filled in an alkaline battery.

  The amount of the binder (B) used for the alkaline battery positive electrode varies depending on the type of the positive electrode active material and the conductive agent, but is preferably 0.03 to 1.0% by weight with respect to the weight of the positive electrode. -0.5 wt% is more preferred. When the addition amount is within this range, the strength of the alkaline battery positive electrode is increased, and the discharge characteristics are excellent over a long period of time.

  The alkaline battery to which the alkaline battery positive electrode using the binder (B) of the present invention can be applied is not particularly limited, and is an ordinary alkaline battery such as LR-20 (single type 1 alkaline battery), LR-6 type (single AA). The present invention can be applied to various types of alkaline batteries. The alkaline battery usually has a structure in which a positive electrode, a current collecting rod and a gel negative electrode are enclosed in an outer can, and the positive electrode and the gel negative electrode are separated by a separator or the like.

The alkaline battery of the present invention is an alkaline battery comprising the above alkaline battery positive electrode, a negative electrode containing zinc or zinc powder, and an electrolytic solution containing an aqueous potassium hydroxide solution.
As a method for producing an alkaline battery of the present invention, a normal production method for producing an alkaline battery using a positive electrode terminal plate, a shrinkable tube, a positive electrode, an outer can, a separator, a current collector rod, a gasket, a negative electrode terminal plate and a gel negative electrode Can be used.

A cross-sectional structure of a typical example of the alkaline battery of the present invention is shown in FIG. In FIG. 1, 1 is a positive electrode terminal plate, 2 is a shrinkable tube, 3 is a positive electrode, 4 is an outer can, 5 is a separator, 6 is a current collecting rod, 7 is a gasket, 8 is a negative electrode terminal plate, and 9 is a gel negative electrode. Yes. As described above, the outer can 4 has a structure in which the positive electrode 3, the current collector rod 6 and the gel negative electrode 9 are sealed, and the positive electrode 3 and the gel negative electrode 9 are separated by the separator 5.
Although it does not specifically limit, As a material of the positive electrode terminal board 1, a nickel plating steel plate etc. are mentioned, for example. Examples of the material of the shrinkable tube 2 include a tube of heat-shrinkable resin such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, or polyester resin. The positive electrode 3 is composed of the binder (B) of the present invention, a positive electrode active material (manganese dioxide), a conductive agent (graphite), an alkaline electrolyte (potassium hydroxide aqueous solution) and other additives (discharge characteristic improvers) as necessary. An added positive electrode material is used. Examples of the material of the outer can 4 include a nickel-plated steel plate. Examples of the material for the separator 5 include alkali-resistant cellulose, nylon, polyolefin, acrylonitrile-vinyl chloride copolymer, polyvinyl alcohol, and combinations thereof. Examples of the material of the current collecting rod 6 include a tin-plated brass rod and an iron rod. Examples of the material of the gasket 7 include nylon resin and polyolefin resin. Examples of the material of the negative electrode terminal plate 8 include a nickel-plated steel plate. For the gel negative electrode 9, an alkaline electrolyte (such as an aqueous potassium hydroxide solution), zinc powder or zinc powder, and a negative electrode material to which a gelling agent or a thickener is added as required are used.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, “part” means “part by weight”, “%” means “% by weight”, and “ion exchange water” means water having an electric conductivity of 1.0 μS / cm or less.

Example 1
[Production of polymer (A1)]
A 2 liter beaker was charged with 300 g of acrylic acid and 700 g of ion-exchanged water, stirred and mixed to prepare an aqueous acrylic acid solution, and cooled to 4 ° C.
The acrylic acid aqueous solution was put into a 1.5 liter adiabatic polymerization tank, and the dissolved oxygen amount in the acrylic acid aqueous solution was adjusted to 0.1 ppm or less through nitrogen in the aqueous solution. To this adiabatic polymerization layer, 8.0 g of 0.1% hydrogen peroxide solution, 8.0 g of 0.1% L-ascorbic acid aqueous solution and 2% 2,2′-azobis [2-methyl-N- (2-hydroxy Ethyl) -propionamide] (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086) 5.0 g of an aqueous solution was added, and nitrogen aeration into the aqueous solution was continued until polymerization started. After confirming that the polymerization started and the viscosity of the acrylic acid aqueous solution started to rise, the nitrogen aeration was stopped and the polymerization was performed for 6 hours to obtain a polymer (J1). In addition, when the temperature of the acrylic acid aqueous solution at the time of superposition | polymerization was measured with the hot spot thermometer, the highest reached temperature was 97 degreeC.
The water-containing gel of the block polymer (J1) is taken out from the adiabatic polymerization tank, and the gel is subdivided into a noodle shape with a thickness of 3 to 10 mm using a small meat chopper (manufactured by Royal), and the polymer ( A hydrogel of A1) was obtained.
A hydrous gel is laminated on a SUS screen having an aperture of 850 μm with a thickness of 5 cm, and hot air at 120 ° C. is applied to the hydrous gel for 1 hour using a small air-permeable dryer (manufactured by Inoue Metal Co., Ltd.). The water-containing gel was dried by air permeation.
The dried product was pulverized using a cooking mixer, and a particle having a particle size of 32 to 500 μm (400 mesh to 40 mesh) was collected using a sieve to obtain the binder (1) of the present invention.
In addition, when Mw was calculated | required according to the measurement of following Mw using the said polymer (A1) as a polymer (X1), Mw was about 700,000.

<Measurement of Mw>
The polymer (A1) was used as the polymer (X1).
A blend (C′1) was prepared by stirring and mixing 98.36 parts of a 40% aqueous potassium hydroxide solution and 1.64 parts of the polymer (X1), and the mixture (C′1) was allowed to stand at 40 ° C. for 24 hours. The viscosity (25 ° C.) of 1) was measured using a digital viscometer DV-II + Pro (manufactured by Brookfield) at a measurement temperature of 25 ° C. in accordance with JIS7117-1: 1999. The rotor No. No. 64 was used and measured at a rotation speed of 3 rpm.
Moreover, 1.64 of polyacrylic acid (polyacrylic acid made by Wako Pure Chemical Industries, Ltd., Mw: 25,000, 250,000, 1,000,000) having a known 40% potassium hydroxide aqueous solution of 98.36 parts and Mw. Parts were stirred and mixed, and in the same manner as described above, the viscosity (25 ° C.) of the blend after being allowed to stand at 40 ° C. for 24 hours was measured, a calibration curve was prepared, and the blend (C′1) Mw was calculated by fitting the viscosity to a calibration curve.

Example 2
In Example 1, instead of “300 g of acrylic acid and 700 g of ion exchange water”, “300 g of acrylic acid, 0.3 g of trimethylolpropane triacrylate (crosslinking agent, 0.1% of acrylic acid) and 700 g of ion exchange water” , Except that the hydrogel was neutralized by adding 125 g of 40% sodium hydroxide (reagent special grade) aqueous solution (equivalent to neutralization degree of acrylic acid of 30 mol%) to the gel fragmented using a small meat chopper (Royal) Produced a polymer (A2) in the same manner as in Example 1 to obtain the binder (2) of the present invention. Mw was about 700,000.

<Measurement of Mw>
In the production of the polymer (A2), a polymer (X2) was produced in the same manner except that no crosslinking agent was used.
In the measurement of Mw in Example 1, “98.21 parts” was used instead of “98.36 parts” of 40% potassium hydroxide aqueous solution, and “heavy weight” was used instead of “polymer (X1) 1.64 parts”. (C′2) was prepared in the same manner except that 1.79 parts of the union (X2) was used, and the viscosity (25 ° C.) was measured and applied to a calibration curve to calculate Mw.

Example 3
In Example 2, 45.2 g of 10.0 wt% sodium sulfite aqueous solution {1.5 wt% with respect to the total weight of acrylic acid (salt) and the cross-linking agent} was added to the neutralized hydrogel, and the small size was reduced. A polymer (A3) was produced in the same manner as in Example 2 except that the hydrogel was uniformly kneaded with a meat chopper to obtain the binder (3) of the present invention. Mw was about 650,000.

<Measurement of Mw>
In the production of the polymer (A3), a polymer (X3) was produced in the same manner except that no crosslinking agent was used.
In the measurement of Mw in Example 1, “98.21 parts” was used instead of “98.36 parts” of 40% potassium hydroxide aqueous solution, and “heavy weight” was used instead of “polymer (X1) 1.64 parts”. (C′3) was prepared in the same manner except that 1.79 parts of union (X3) was used, and the viscosity (25 ° C.) was measured and applied to a calibration curve to calculate Mw.

Example 4
In Example 1, “300 g of acrylic acid, 700 g of ion-exchanged water, 8.0 g of 0.1% hydrogen peroxide water, 8.0 g of 0.1% L-ascorbic acid aqueous solution and 2% 2,2′-azobis [2 -“Methyl-N- (2-hydroxyethyl) -propionamide” (trade name: VA-086, manufactured by Wako Pure Chemical Industries, Ltd., 5.0 g aqueous solution), “200 g acrylic acid, 800 g ion-exchanged water, 2.7 g of 0.1% hydrogen peroxide solution, 5.3 g of 0.1% L-ascorbic acid aqueous solution and 10% 2,2′-azobis (2-amidinopropane) hydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., A polymer (A4) was produced in the same manner as in Example 1 except that “trade name: V-50) 2.0 g of aqueous solution” was obtained, and the binder (4) of the present invention was obtained. Mw was about 1,200,000.

<Measurement of Mw>
The polymer (A4) was used as the polymer (X4).
(C′4) was prepared in the same manner as in the measurement of Mw in Example 1, and the viscosity (25 ° C.) was measured and applied to a calibration curve to calculate Mw.

Example 5
In Example 4, 40 g of 10.0% sodium sulfite aqueous solution {2.0% with respect to acrylic acid (salt)} was added to the hydrogel that had been finely divided, and the hydrogel was uniformly kneaded with the small meat chopper. Produced a polymer (A5) in the same manner as in Example 4 to obtain the binder (5) of the present invention. Mw was about 1,000,000.

<Measurement of Mw>
The polymer (A5) was used as the polymer (X5).
(C′5) was prepared in the same manner as in the measurement of Mw in Example 1, and the viscosity (25 ° C.) was measured and applied to a calibration curve to calculate Mw.

Example 6
In Example 1, “300 g of acrylic acid, 700 g of ion-exchanged water, 8.0 g of 0.1% hydrogen peroxide water, 8.0 g of 0.1% L-ascorbic acid aqueous solution and 2% 2,2′-azobis [2 -"Methyl-N- (2-hydroxyethyl) -propionamide" (Wako Pure Chemical Industries, Ltd., trade name: VA-086) 5.0 g of aqueous solution "," 200 g of acrylic acid, 0.1 g of methylenebisacrylamide (Crosslinking agent, 0.05% acrylic acid), 0.04 g of pentaerythritol triallyl ether (crosslinking agent, 0.02% acrylic acid), 800 g of ion-exchanged water, 2.7 g of 0.1% hydrogen peroxide solution 0.1% L-ascorbic acid aqueous solution 5.3 g and 10% 2,2′-azobis (2-amidinopropane) hydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name: V 50) Aqueous solution 2.0 g ", and 97 g of 40% sodium hydroxide (reagent special grade) aqueous solution (corresponding to 35 mol% neutralization degree of acrylic acid) on the gel subdivided using a small meat chopper (Royal) In addition, uniformly kneaded with the small meat chopper, neutralized the water-containing gel, and further added 40 g of 10.0% sodium sulfite aqueous solution (2.0% with respect to acrylic acid (salt)), and water-containing with the small meat chopper A polymer (A6) was produced in the same manner as in Example 1 except that the gel was uniformly kneaded to obtain the binder (6) of the present invention. Mw was about 1,000,000.

<Measurement of Mw>
In the production of the polymer (A6), a polymer (X6) was produced in the same manner except that no crosslinking agent was used.
In the measurement of Mw of Example 1, 40% potassium hydroxide aqueous solution was replaced with “98.18 parts” instead of “98.36 parts”, and “polymer (X1) 1.64 parts” was replaced with “heavy weight”. (C′6) was prepared in the same manner except that 1.82 parts of union (X6) was used, and the viscosity (25 ° C.) was measured and applied to a calibration curve to calculate Mw.

Example 7
The binder (6) obtained in Example 6 was pulverized using a cooking mixer, and a particle having a particle size of 45 μm or less (350 mesh) was collected using a sieve to obtain the binder (7) of the present invention. It was.

Example 8
The binder (6) obtained in Example 6 was pulverized using a cooking mixer, and a particle having a particle size of 20 μm or less (635 mesh) was collected using a sieve to obtain the binder (8) of the present invention. It was.

Example 9
In Example 6, 97 g of 40% sodium hydroxide (reagent special grade) aqueous solution (corresponding to a neutralization degree of acrylic acid of 35 mol%) was added to the gel subdivided using the small meat chopper (Royal). Uniformly knead with a small meat chopper to neutralize the hydrous gel, and then add 40 g of 10.0% sodium sulfite aqueous solution (2.0% with respect to acrylic acid (salt)) to the hydrogel with the small meat chopper. Example 6 except that 0.04 g of drying aid [Ryoto Sugar Ester S-770, HLB value 7, manufactured by Mitsubishi Chemical Foods Co., Ltd.] 0.04 g was added, and the mixture was uniformly kneaded into the water-containing gel using the small meat chopper. In the same manner as described above, a polymer (A9) was produced to obtain the binder (9) of the present invention. Mw was about 1,000,000.

Example 10
The binder (9) obtained in Example 9 was pulverized using a cooking mixer, and a particle having a particle size of 20 μm or less (635 mesh) was collected using a sieve to obtain the binder (10) of the present invention. It was.

Comparative Example 1
Commercially available polyacrylic acid (Mw: 25,000, manufactured by Wako Pure Chemical Industries, Ltd.) was used as a comparative binder (H1).

Comparative Example 2
In Example 2, in place of trimethylolpropane triacrylate, the amount of pentaerythritol triallyl ether was changed to 9.0 g (3.0% acrylic acid) in the same manner as in Example 2, except that the polymer ( A′1) was produced and a comparative binder (H2) was obtained.

  Binders (1) to (10) prepared in Examples 1 to 10 and (1) water-soluble component amounts of comparative binders (H1) to (H2) prepared in Comparative Examples 1 and 2, and (2) formulation Viscosity of product (C) (V24), (3) Viscosity ratio of compound (C) {(V24) / (V1)}, (4) Amount of soluble component in 10% aqueous potassium hydroxide and (4) polymerization The total content of (a1) and (a2) not measured was measured by the method described above. The results are shown in Table 1.

  Further, using the binders (1) to (10) of the present invention and the comparative binders (H1) to (H2), a positive electrode and a battery were respectively prepared. (1) Breaking strength of the positive electrode and (2) Battery The duration of was measured by the following method. The results are shown in Table 2.

(1) Measuring method of breaking strength of positive electrode 200 g of manganese dioxide, 10 g of graphite and 0.6 g of binder were added to a biaxial kneader (product name: PNV-1 manufactured by Irie Trading Co., Ltd.) having a capacity of 1 liter, and 50 rpm Mix for 60 minutes at rotational speed. Subsequently, 5.3 g of 40% potassium hydroxide aqueous solution was added to the mixture, and the mixture was again mixed for 60 minutes at a rotation speed of 50 rpm. Next, after rolling this mixture with a press machine, it grind | pulverized and screened to about 100-1000 micrometers of particle sizes with the grinder. Furthermore, it shape | molded cyclically | annularly with the press machine and obtained the positive electrode.
A pressure test was conducted on the created positive electrode, and the pressure at the time of breakage was measured. In Table 2, relative ratios with the breaking strength of Example 1 as 100 are shown.

(2) Measuring method of battery duration To a biaxial kneader (product name: PNV-1 manufactured by Irie Trading Co., Ltd.) with a capacity of 1 liter, 200 g of manganese dioxide, 10 g of graphite, and 0.6 g of a binder were added, and 50 rpm Mix for 60 minutes at rotational speed. Subsequently, 5.3 g of 40% potassium hydroxide aqueous solution was added to the mixture, and the mixture was again mixed for 60 minutes at a rotation speed of 50 rpm. Next, after rolling this mixture with a press machine, it grind | pulverized and screened to about 100-1000 micrometers of particle sizes with the grinder. Furthermore, it shape | molded cyclically | annularly with the press machine and obtained the positive electrode.
10 g of this positive electrode was injected into a positive electrode container of an LR-6 type model battery, thereby creating a model battery.
Here, the constituent materials of each part other than the positive electrode of the model battery are polyethylene as the material of the shrinkable tube, 4.0 g of zinc powder as the material of the gel negative electrode, 2.0 g of 40% potassium hydroxide aqueous solution, gel A composition comprising 0.04 g of a thickener and 0.04 g of a thickener, a nickel-plated steel plate as the material of the outer can, a polyolefin as the material of the separator, and a tin-plated brass bar as the material of the current collecting rod As the material for the gasket, a polyolefin-based resin was used, and as the material for the negative electrode terminal plate, a nickel-plated steel plate was used.
An external resistance of 2Ω was connected to the prepared model battery at room temperature (20 to 25 ° C.), the battery was continuously discharged, and the time until the voltage decreased to 0.9 V was defined as the battery duration (hour).
After the model battery was prepared, the same operation was performed on the model battery that was left in a constant temperature bath at 60 ° C. for 60 days, and the duration of the battery was measured.

As can be seen from the results in Table 1, the binders of Examples 1 to 10 of the present invention satisfy the requirements (1) and (2) of the present invention. On the other hand, the binders of Comparative Examples 1 and 2 do not satisfy at least one of requirement (1) and requirement (2) of the present invention.
From the results of Table 2 using these binders, it can be seen that those using the binder of the present invention are excellent in all the items of the strength of the positive electrode and the duration of the battery immediately after preparation and after 60 ° C. × 60 days. .
That is, it can be seen that the alkaline battery using the binder of the present invention is excellent in maintaining discharge characteristics.

  The binder of the present invention is useful not only as a cylindrical alkaline battery but also as a binder for primary and secondary alkaline battery positive electrodes such as an alkaline button battery, a silver oxide battery, a nickel cadmium storage battery, and a nickel hydride storage battery. Moreover, the alkaline battery using the binder of the present invention is useful as an alkaline battery excellent in maintaining discharge characteristics and improved in production efficiency.

DESCRIPTION OF SYMBOLS 1 Positive electrode terminal plate 2 Shrinkable tube 3 Positive electrode 4 Exterior can 5 Separator 6 Current collector rod 7 Gasket 8 Negative electrode terminal plate 9 Gel negative electrode

Claims (6)

A binder comprising a polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes (a1) by hydrolysis as an essential constituent unit,
Binder (B) for alkaline battery positive electrode comprising the following requirements (1) and (2).
Requirement (1): It follows water soluble components of the binder (B) is 50 to 95% by weight based on the weight of the binder (B).
<Method for measuring the amount of water-soluble components>
In a 2000 ml beaker, 1 g of the binder (B) {measured to 4 digits after the decimal point (W ₀ )} and 1000 g of ion-exchanged water are added and stirred for 24 hours at 300 rpm using a magnetic stirrer. The stirred solution is filtered through filter paper (No. 2 type, manufactured by Toyo Roshi Kaisha, Ltd.), and the filtrate is collected. After concentrating the filtrate with an evaporator, it is evaporated to dryness at 120 ° C. using a dryer, and the weight (W ₁ ) g of the evaporation residue is measured. The water-soluble component amount (%) is calculated by the following formula-(1).

Water-soluble component amount (%) = (W ₁ ) × 100 / (W ₀ ) Formula- (1)

Requirement (2): prepared by stirring and mixing 98 parts by weight of a 40% by weight aqueous potassium hydroxide solution and 2 parts by weight of the binder (B), and leaving the mixture at 40 ° C. for 24 hours (25) ° C) (V24) is 5 to 50 Pa · s. The binder (B) for alkaline battery positive electrodes according to claim 1, wherein the viscosity ratio (V24) / (V1) of the following viscosity (V24) and the following viscosity (V1) is 0.3 to 20.
Viscosity (V24): prepared by stirring and mixing 98 parts by weight of 40 wt% potassium hydroxide aqueous solution and 2 parts by weight of binder (B), and leaving the mixture at 40 ° C. for 24 hours (25) ° C).
Viscosity (V1): prepared by stirring and mixing 98 parts by weight of 40% by weight aqueous potassium hydroxide solution and 2 parts by weight of binder (B), and leaving the mixture at 40 ° C. for 1 hour (25) ° C). Binding agent (B) below 10 wt.% Alkaline battery positive electrode binding agent according to claim 1 or 2 soluble component amount is 50 to 100 wt% of the aqueous potassium hydroxide solution (B).
<Method for measuring the amount of soluble components in 10% by weight aqueous potassium hydroxide>
In a 500 ml beaker, add 1 g of binder (B) {measure to 4 digits after the decimal point (W ₀ )} and 200 g of 10 wt% aqueous potassium hydroxide solution and stir at 300 rpm for 24 hours using a magnetic stirrer. . The stirred solution is filtered with a Buchner type glass filter (manufactured by Mutual Riken Glass Co., Ltd., No. 1 type), and the filtrate is collected. 10% by weight sulfuric acid aqueous solution was added to 20 g of the filtrate to adjust the pH to 7.0, concentrated with an evaporator, evaporated to dryness at 120 ° C. using a dryer, and the weight of evaporation residue (W ₂ ) g. Measure. As a blank, 10% by weight sulfuric acid aqueous solution was added to 20 g of the 10% by weight potassium hydroxide aqueous solution used, the blank solution adjusted to pH 7.0 was concentrated with an evaporator, and then evaporated at 120 ° C. using a dryer. After drying, the evaporation residue weight (W ₃ ) g was measured. The amount (%) of a soluble component in a 10% by weight potassium hydroxide aqueous solution is calculated by the following formula-(2).

Amount of soluble component in 10 wt% potassium hydroxide aqueous solution (%) = {(W ₂ ) − (W ₃ )} × 100 / (W ₀ ) × D Formula- (2)

D: Dilution ratio (D = 200/20 = 10)   The total content of the non-polymerized water-soluble vinyl monomer (a1) and vinyl monomer (a2) in the binder (B) is 10 to 2000 ppm based on the weight of (B). The binder for alkaline battery positive electrodes (B) of crab.   An alkaline battery positive electrode comprising the alkaline battery positive electrode binder (B) according to any one of claims 1 to 4, manganese dioxide and graphite. An alkaline battery comprising the alkaline battery positive electrode according to claim 5, a negative electrode comprising zinc or zinc powder, and an electrolytic solution comprising an aqueous potassium hydroxide solution.

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