JP5711590B2 - Binder for alkaline battery positive electrode and alkaline battery - Google Patents

Description

  The present invention relates to a thickener for an alkaline battery positive electrode and an alkaline battery. More specifically, the present invention relates to an alkaline battery positive electrode binder used for a positive electrode binder of an alkaline battery mainly composed of a positive electrode active material and a conductive agent, and an alkaline battery using the binder.

  Conventionally, a positive electrode including a positive electrode active material (mainly manganese dioxide), a conductive agent (graphite), and a binder has been used for the positive electrode of an alkaline battery. In order to prevent a short circuit, the thing using polyacrylic acid and its salt as a binder is proposed (patent document 1).

JP 2009-87872 A

However, alkaline batteries have been required to have higher performance in recent years, 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. It is not always satisfactory in terms of maintenance. Furthermore, it cannot be satisfied in terms of increasing the production efficiency of the positive electrode.
Then, an object of this invention is to provide the binder for alkaline battery positive electrodes excellent in maintenance of the discharge characteristic (discharge amount and discharge time) over a long term, and an alkaline battery using the same.

The alkaline battery positive electrode binder (C) of the present invention comprises a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes (a1) by hydrolysis and a crosslinking agent (b) as essential constituent units. A binder comprising the polymer (A),
The crosslinking agent (b) comprises a hydrolyzable crosslinking agent (b1) that is alkaline and hydrolyzes,
The weight of the crosslinking agent (b) is 0.05 to 2% by weight based on the total weight of (a1) and (a2);
The hydrolyzable crosslinking agent (b1) has a weight of 0.01 to 2% by weight based on the total weight of (a1) and (a2);
The gist of the invention is that it satisfies the following requirements (1) and (2).
Requirement (1): The absorption capacity of 40% by weight potassium hydroxide aqueous solution of (C) is 5 to 80 g / g.
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 a binder, and the viscosity (25 ° C.) of the formulation (D) after being allowed to stand at 25 ° C. for 24 hours. 1 to 500 Pa · s.
The gist of the alkaline battery positive electrode of the present invention is that it contains the above-mentioned binder for alkaline battery positive electrode, 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 of the present invention and the alkaline battery positive electrode and alkaline battery using this binder have the following effects.
(1) When the binder of the present invention is used, it is possible to produce an alkaline battery with a very small amount of binder and a very long discharge duration over a long period of time.
(2) Since there is little variation in the amount of electrolyte absorbed, an alkaline battery having uniform quality can be produced even during mass production.

In the present invention, the water-soluble vinyl monomer 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) and / or the vinyl monomer (a2) that becomes the water-soluble vinyl monomer (a1) by hydrolysis are not particularly limited, and examples thereof include water-soluble radicals described in JP-A-2005-075982. A polymerization monomer is mentioned. Among these, from the viewpoint of discharge characteristics, the water-soluble vinyl monomer (a1) is preferable, more preferably an anionic vinyl monomer, and particularly preferably a C3-C30 vinyl group-containing carboxylic acid (salt) {unsaturated monocarboxylic acid. Acids (salts) (such as (meth) acrylic acid, crotonic acid, cinnamic acid and their salts); unsaturated dicarboxylic acids (salts) (such as maleic acid, fumaric acid, citraconic acid, itaconic acid and their salts); and Monoalkyl (carbon number 1 to 8) ester of unsaturated dicarboxylic acid (maleic acid monobutyl ester, fumaric acid monobutyl ester, maleic acid ethyl carbitol monoester, fumaric acid ethyl carbitol monoester, citraconic acid monoester Butyl ester and glycol itaconate monoester, etc.}, preferably unsaturated monocarbo 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 crosslinked polymer (A) is an anionic vinyl monomer, this is a neutralized product (water-soluble vinyl monomer salt unit) even if it is an unneutralized product. However, one unit of the water-soluble vinyl monomer (a1) unit may be used for the purpose of reducing the tackiness and dispersibility of the crosslinked polymer (A), improving workability in producing the crosslinked polymer (A), and the like. It is preferable to neutralize some or all of the water-soluble vinyl monomer salt units.

  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. On the other hand, since the alkaline non-hydrolyzed crosslinking agent (b2) described below has poor water solubility, a predetermined amount of the crosslinking agent (b2) is added when polymerized in a state where the water-soluble vinyl monomer (a1) is highly neutralized. However, the crosslinking agent (b2) may be separated from the monomer aqueous solution, and the predetermined crosslinking may not be performed, so that the crosslinked polymer (A) having specified physical properties may not be obtained. From the viewpoint of suppressing the separation of the cross-linking agent (b2), the degree of neutralization of the water-soluble vinyl monomer (a1) is set to 0 to 30 mol%, and after carrying out the polymerization by containing the cross-linking agent (b2), If necessary, it is more preferable to adjust the degree of neutralization by adding an alkali metal hydroxide to the hydrogel.

  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 neutralization degree of the anionic vinyl monomer {anionic vinyl The content (mol%) of the anionic base based on the total number of moles of the anionic group and the anionic base of the monomer is preferably 30 to 100, more preferably 40 to 90, and particularly preferably 50 to 90. Within this range, the discharge characteristics of the alkaline battery are further improved. The anionic base means a neutralized anionic group.

  The content of the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) is determined from the viewpoint of the absorbent capacity of the binder (a1), (a2), the alkaline hydrolyzing crosslinking agent (b1) and the alkaline hydrolyzing. Is preferably 98.0 to 99.90% by weight, more preferably 99.0 to 99.85% by weight, particularly preferably 99.2 to 99.83% by weight, based on the total weight of the crosslinking agent (b2) not to be used. It is.

  Each of the water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) may be a single structural unit or two or more structural units.

Of the water-soluble vinyl monomer (a1) and vinyl monomer (a2), (a1) is preferred from the viewpoint of the ability of the binder to absorb, and more preferably (a1) is used alone as a structural unit.
When both the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) are used as constituent units, the molar ratio {(a1) / (a2)} of these vinyl monomer units is determined from the viewpoint of the discharge characteristics of the alkaline battery. 75/25 to 99/1 is preferable, more preferably 85/15 to 98/2, and most preferably 90/10 to 95/5.

The crosslinked polymer (A) is crosslinked using the crosslinking agent (b). The crosslinking agent (b) includes an alkaline hydrolyzable crosslinking agent (b1) and an alkaline non-hydrolyzing crosslinking agent (b2). In the present invention, as the crosslinking agent (b), a hydrolyzable crosslinking agent (b1) that is alkaline and hydrolyzes is used as an essential crosslinking agent.
By using this hydrolyzable cross-linking agent (b1), the adhesiveness of the binder can be further improved and the strength of the alkaline battery positive electrode can be maintained, so that a long-term discharge can be maintained. Furthermore, since the amount of electrolyte absorbed is small and the variation is small, the deviation of the amount of electrolyte in the alkaline battery is also small, which is preferable.

In the hydrolyzable cross-linking agent (b1) that is hydrolyzed with alkali, “alkaline and hydrolyze” means that the unit derived from (b1) in the cross-linked polymer (A) has a hydrolyzable bond, The hydrolyzable bond may be a bond that the crosslinking agent (b1) originally has in the molecule or {the crosslinking agent in this case is defined as a crosslinking agent (b1-1) having a hydrolyzable bond in the molecule}. , A bond formed by a crosslinking reaction with another monomer {(a1) or (a2)} constituting the crosslinked polymer (A) may be hydrolyzed {crosslinking the crosslinking agent in this case The bond produced by the reaction is a hydrolyzable crosslinking agent (b1-2)}. From the viewpoint of viscosity stability of the binder, the hydrolyzable bond derived from the hydrolyzable crosslinking agent (b1) was added at 1% by weight to the 40% by weight potassium hydroxide aqueous solution at 25 ° C. for 1 hour. It is preferable that 50% by weight or more decomposes when stirred.
Examples of the hydrolyzable bond include an ester bond and an amide bond.

  The crosslinking agent (b1-1) 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′-methylene Bisacrylamide, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri ( And (meth) acrylate, pentaerythritol tetra (meth) acrylate and polyglycerin (degree of polymerization 3 to 13) polyacrylate.

  As a crosslinking agent (b1-2) having a hydrolyzable bond formed by a crosslinking reaction, when an anionic vinyl monomer having a carboxyl group or a carboxylate group is used as (a1), a carboxyl group derived from this monomer Or a reactive crosslinking agent that reacts with a carboxylate group, a polyvalent glycidyl compound (such as ethylene glycol diglycidyl ether), a polyvalent isocyanate compound (such as 4,4′-diphenylmethane diisocyanate), a polyvalent amine compound (such as ethylenediamine) ) And polyhydric alcohol compounds (such as glycerin). 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.

  Of the hydrolyzable crosslinking agents (b1) that are hydrolyzed with alkali, the crosslinking agent (b1-1) and the polyvalent glycidyl compound are preferable from the viewpoint of the viscosity stability of the binder, and more preferably N, N′-methylene. Bisacrylamide, 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 '-Methylenebisacrylamide, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and ethylene glycol diglycidyl ether, particularly preferably N, N'-methylenebi Acrylamide, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and ethylene glycol diglycidyl ether.

  When the cross-linking agent (b1-2) is used, it is preferable that the cross-linking reaction is caused to proceed at an arbitrary stage after the cross-linking agent is added, and more preferably 120-160 ° C. Allow the reaction to proceed. Moreover, you may use together a crosslinking agent (b1-2) with 2 or more types in the range of predetermined amount, and also a crosslinking agent (b1-1).

  The non-hydrolyzable crosslinking agent (b2) that is alkaline and does not hydrolyze is a crosslinking agent that 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 (b2-1) having two or more vinyl ether bonds and a crosslinking agent (b2-2) having two or more allyl ether bonds. From the viewpoint of reactivity and the like, a crosslinking agent having two or more allyl ether bonds is preferable.

  Examples of the crosslinking agent (b2-1) having two or more vinyl ether bonds include ethylene glycol divinyl ether, 1,4-butanediol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, and 1,6-hexanediol divinyl ether. Polyethylene glycol divinyl ether (polymerization degree 2 to 5), bisphenol A divinyl ether, pentaerythritol trivinyl ether, sorbitol trivinyl ether, polyglycerol (polymerization degree 3 to 13) polyvinyl ether, and the like.

  As a crosslinking agent (b2-2) having two or more allyl ether bonds, a crosslinking agent (b2-2-1) having two allyl groups in the molecule and not containing a hydroxyl group, an allyl group in the molecule A cross-linking agent (b2-2-2) having 2 and 1 to 5 hydroxyl groups, a cross-linking agent (b2-2-3) having 3 to 10 allyl groups and no hydroxyl groups in the molecule, Examples thereof include a crosslinking agent (b2-2-4) having 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule. When a hydroxyl group is contained in the molecule, the compatibility with the vinyl monomer (a1) and / or (a2) {especially (meth) acrylic acid (salt)} is improved, the uniformity of crosslinking is improved, and the adhesion of the binder is increased. And the strength of the alkaline battery positive electrode is further improved.

As a crosslinking agent (b2-2-1) having two allyl groups in the molecule and not containing a hydroxyl group, diallyl ether, 1,4-cyclohexanedimethanol diallyl ether, alkylene (having 2 to 5 carbon atoms) glycol diallyl Examples include ether and polyethylene glycol (weight average molecular weight: 100 to 4000) diallyl ether.
Examples of the crosslinking agent (b2-2-2) having 2 allyl groups and 1 to 5 hydroxyl groups in the molecule include glyceryl diallyl ether, trimethylolpropane diallyl ether, pentaerythritol diallyl ether, polyglycerin (degree of polymerization). 2-5) diallyl ether and the like.
As a crosslinking agent (b2-2-3) having 3 to 10 allyl groups in the molecule and not having a hydroxyl group, trimethylolpropane triallyl ether, glyceryl triallyl ether, pentaerythritol tetraallyl ether and tetraallyl Examples include oxyethane.
Examples of the crosslinking agent (b2-2-4) having 3 to 10 allyl groups and 1 to 3 hydroxyl groups in the molecule include pentaerythritol triallyl ether, diglyceryl triallyl ether, sorbitol triallyl ether, poly Examples include glycerin (degree of polymerization 3 to 13) polyallyl ether.

Two or more non-hydrolyzable crosslinking agents (b2) that are alkaline and do not hydrolyze may be used in combination.
Among the crosslinking agents (b2), a crosslinking agent (b2-2) having two or more allyl ether bonds is preferable, and more preferably a crosslinking agent having 1 to 5 hydroxyl groups and 2 to 10 allyl groups {(b2- 2-2) and (b2-2-4)}, particularly preferably a crosslinking agent (b2-2-2) having two allyl groups and 1 to 5 hydroxyl groups in the molecule, most preferably trimethylol. Propane 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 present invention, the content of the crosslinking agent (b) is 0.05 to 2% by weight based on the total weight of (a1) and (a2). However, it is preferably 0.05 to 1% by weight, more preferably 0.1 to 0.8% by weight, and particularly preferably 0.2 to 0.6% by weight from the viewpoint of the absorbent capacity of the absorbent resin. is there. When the content of (b) is less than 0.05% by weight, the amount of absorption under load exceeds 2% by weight, and the strength of the alkaline battery positive electrode is deteriorated.

  In the present invention, the content of the hydrolyzable crosslinking agent (b1) that is alkaline and hydrolyzes is 0.01 to 2% by weight with respect to the total weight of (a1) and (a2), and the crosslinking agent (b1 ) And the average degree of polymerization, but from the viewpoint of the absorption capacity of the absorbent resin, 0.05 to 1% by weight is preferable, more preferably 0.08 to 0.78% by weight, and particularly preferably 0.8. 17 to 0.57% by weight. When the content of (b) is less than 0.01% by weight, the amount of absorption under load is poor, and when it exceeds 2% by weight, the strength of the alkaline battery positive electrode is deteriorated.

  The content of the non-hydrolyzable cross-linking agent (b2) that is alkaline and does not hydrolyze in the cross-linked polymer (A) depends on the type of the cross-linking agent (b2), but is 0 from the viewpoint of the absorbent capacity of the absorbent resin. ˜1.99% by weight is preferable, more preferably 0 to 0.95% by weight, particularly preferably 0.02 to 0.72% by weight, and most preferably 0.03 to 0.54% 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 binder for an alkaline battery positive electrode of the present invention has the following requirements (1) and (2).
Requirement (1) is a requirement necessary to reduce the unevenness of the electrolyte amount of the alkaline battery.
Further, requirement (2) is a requirement necessary for improving the discharge characteristics.

Requirement (1): The absorption capacity of 40% by weight potassium hydroxide aqueous solution of the binder is 5 to 80 g / g.
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 a binder, and the viscosity (25 ° C.) of the formulation (D) after being allowed to stand at 25 ° C. for 24 hours. 1 to 500 Pa · s.

  In Requirement (1), the 40 wt% potassium hydroxide aqueous solution absorption capacity of the binder is 5 to 80 g / g, and preferably 8 to 70 g / g, more preferably 10 to 60 g from the viewpoint of alkaline battery productivity. / G. When the absorption ratio is less than 5 g / g, the strength of the positive electrode is weakened, and when it exceeds 80 g / g, the deviation in the amount of electrolyte in the alkaline battery is increased.

In addition, said 40 weight% potassium hydroxide aqueous solution absorption capacity | capacitance is measured with the following method.
<Measurement method of absorption capacity of 40 wt% potassium hydroxide aqueous solution>
Absorption capacity of 40 wt% potassium hydroxide aqueous solution in accordance with JIS K7223-1996, except that 40 wt% potassium hydroxide aqueous solution is used in place of the sodium chloride aqueous solution, the standing time is 24 hours, and the draining time is 30 minutes. Measure.

  As a method of adjusting the absorption ratio of 40 wt% potassium hydroxide aqueous solution to the range of the above requirement (1), the total weight of the crosslinking agent (b1) and the crosslinking agent (b2) is the total weight of (a1) and (a2). It is preferable to satisfy 0.05 to 2% by weight based on the weight. If the absorption rate is high, the amount of (b2) is increased within the range, and if the absorption rate is low, the amount of (b2) is decreased within the range to reduce the absorption rate to the above numerical range. can do.

  In requirement (2), the viscosity (25 ° C.) of the composition (D) is 1 to 500 Pa · s, and preferably 2 to 450 Pa · s, particularly preferably 3 to 400 Pa, from the viewpoint of improving the discharge characteristics of the alkaline battery. -S. When it exceeds 500 Pa · s, the dispersibility of the positive electrode active material and the conductive agent is deteriorated, and when it is less than 1 Pa · s, the strength of the alkaline battery positive electrode is deteriorated.

  The blend (D) 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 a binder, and allowed to stand at 25 ° C. for 24 hours.

The viscosity of the blend (D) is measured by the following method.
<Measurement method of viscosity of compound (D)>
Using a digital viscometer DV-II + Pro (manufactured by Brookfield), the viscosity of the compound (D) at a measurement temperature of 25 ° C. is measured according to JIS7117-1: 1999, and the viscosity of the compound (D) is measured. And The rotor No. 64 is used and measured at a rotational speed of 3 rpm.

  As a method for adjusting the viscosity of the blend (D) to the range of the above requirement (2), the total weight of the crosslinking agent (b1) and the crosslinking agent (b2) is based on the total weight of (a1) and (a2). It is good to satisfy 0.05 to 2% by weight. If the viscosity is high, the amount of (b2) can be increased within the previous period, and if the viscosity is low, it can be satisfied by decreasing the amount of (b2) within the previous range.

The amount of the 40 wt% potassium hydroxide aqueous solution absorbed under 20 g / cm ² load of the binder of the present invention is preferably 2 to 10 g / g, more preferably 2 to 8 g / g, particularly preferably 3 to 7 g / g, Most preferably, it is 3-6 g / g. Within this range, the discharge characteristics over a long period of time are further improved.

Note that the 20 g / cm ² load at 40% by weight aqueous potassium hydroxide solution absorption, under a load of 20 g / cm ^2, the absorption amount of the binding agent after 1 hour immersion in 40 wt% aqueous solution of potassium hydroxide (under load Absorption amount) and is measured as follows.

<Measurement method of absorption under load>
0.16 g of a measurement sample sieved to a particle diameter of 250 to 500 μm in a cylindrical plastic tube (inner diameter: 25 mm, height: 34 mm) having a nylon mesh of 63 μm (JIS Z8801-1: 2006) pasted on the bottom. Were weighed and the cylindrical plastic tube was placed vertically so that the measurement sample had a substantially uniform thickness on the nylon mesh, and then a weight (weight: 310.6 g, outer diameter: 24. 5mm,). After weighing the whole cylindrical plastic tube (M1), the cylindrical plastic tube containing the measurement sample and the weight was placed vertically in a petri dish (diameter: 12 cm) containing 60 ml of 40% by weight potassium hydroxide aqueous solution. Stand up and soak with the nylon mesh side down, and let stand for 60 minutes. After 60 minutes, pull up the cylindrical plastic tube from the petri dish, tilt it diagonally, remove the dripping water drops, weigh the entire cylindrical plastic tube containing the measurement sample and weight (M2), and Obtain the amount absorbed under load. In addition, the temperature of the 40 weight% potassium hydroxide aqueous solution and measurement atmosphere to be used is 25 degreeC +/- 2 degreeC.
Absorption under load (g / g) = {(M2)-(M1)} / 0.16

  As a method for adjusting the amount of absorption under load to the above range, the total weight of the crosslinking agent (b1) and the crosslinking agent (b2) is 0.05 to 2% by weight with respect to the total weight of (a1) and (a2). Satisfy. If the absorption amount under load is high, the amount of (b1) or (b2) is reduced within the previous period range, and if the absorption amount under load is low, the amount of (b1) or (b2) is within the previous period range. It can be satisfied by increasing the amount.

  The total content of the non-polymerized water-soluble vinyl monomer (a1), vinyl monomer (a2) and crosslinking agent (b) in the binder of the present invention is 10 to 500 ppm based on the weight of (C). More preferably, it is 20-400 ppm, Most preferably, it is 30-300 ppm, Most preferably, it is 40-200 ppm. Within this range, the discharge characteristics over a long period of time are further improved.

  The total content of unpolymerized (a1), (a2) and (b) means the total content of (a1), (a2) and (b) contained as a structural unit of the crosslinked polymer. Not to do. The total content of unpolymerized (a1), (a2) and (b) is measured and calculated by the following method described in JP-A-2006-219661.

<Method for measuring total content of unpolymerized (a1), (a2) and (b)>
In a 300 ml beaker, 1.0 g of a measurement sample and 249.0 g of 0.9 wt% saline are added and stirred at 20 to 30 ° C. for 3 hours, and then the insoluble matter is filtered off to obtain a filtrate. Using this calibration curve prepared by high performance liquid chromatography (under the following conditions) with a known concentration of vinyl monomer or crosslinking agent, the total content of (a1), (a2) and (b) Ask for.
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), (a2) and (b) into a range of 10 to 500 ppm based on the weight of (C), JP-A No. Examples include a method in which a reducing substance described in JP-A-62317, a water-soluble thiol compound described in JP-A-8-157737, and the like are added to and mixed with the crosslinked polymer (A) as an aqueous solution or an aqueous dispersion. 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 the total amount of the water-soluble vinyl monomer (a1), the vinyl monomer (a2) that becomes (a1) by hydrolysis, and the crosslinking agent (b). It is preferably 5.0% by weight, more preferably 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. It is good to meet the range.
If the total content of unpolymerized (a1), (a2) and (b) does not satisfy the above range, the addition method described in JP-A-1-62317 and JP-A-8-157737 In the above, it can be satisfied by mixing, as necessary, a reducing substance, a water-soluble thiol compound aqueous solution or an aqueous dispersion in the step of neutralizing the hydrous gel (A) described later with an alkali.

  In the case of reverse phase suspension polymerization, as a method for bringing the total content of unpolymerized (a1), (a2) and (b) to a range of 10 to 500 ppm based on the weight of (C), JP-A The method of adjusting the supply at the time of superposition | polymerization of (a1), (a2), and (b) as described in 2006-131767 is mentioned.

The supply of (a1), (a2) and (b) is preferably performed continuously at a constant speed, but the supply speed may be changed, and (a1), (a2) and (b) may be changed in the middle. The supply can be suspended. The supply rate of (a1), (a2) and (b) is preferably such that the entire amount is supplied in 30 to 180 minutes, more preferably 45 to 120 minutes, and particularly preferably 60 to 80 minutes. good.
If the total content of unpolymerized (a1), (a2) and (b) does not satisfy the above range, an aging step is performed as necessary in the polymerization method described in JP-A-2006-131767. Can be satisfied.

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

Among these polymerization methods, from the viewpoint of the absorption capacity of the absorbent resin, solution polymerization, suspension polymerization, reverse phase suspension polymerization and emulsion polymerization are preferable, and solution polymerization, reverse phase suspension polymerization and emulsion polymerization are more preferable. Particularly preferred are 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 cross-linking agent (b1) and a cross-linking agent (b2) are added and dissolved in an aqueous monomer solution mainly composed of (meth) acrylic acid (salt), and a hydrophobic organic compound in the presence of a dispersant. This is a reverse phase suspension polymerization method in which a similar aqueous monomer solution is dispersed and suspended in a 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, the initiator includes an azo compound [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.], redox initiators [alkali metal sulfites or bisulfites, ammonium sulfites, ammonium bisulfites, L- Reducing agents such as ascorbic acid, alkali metal persulfate, ammonium persulfate, hydrogen peroxide, etc. Combination etc. peroxides. Two or more of these may be used in combination.

The polymerization temperature varies depending on the type of initiator used, but is preferably -10 ° C to 100 ° C, more preferably -10 ° C to 80 ° C, from the viewpoint of increasing the degree of polymerization of the polymer.
The amount of the initiator is not particularly limited, but is preferably 0.000001 to 3.0% by weight from the viewpoint of increasing the polymerization degree of the polymer with respect to the total weight of the vinyl monomers (a1) and (a2). More preferably, it is 0.000001 to 0.5% by weight.

In the case of aqueous solution polymerization, the polymerization concentration (% by weight) of the monomer varies depending on other polymerization conditions, but (meth) acrylic acid (salt) increases the polymerization concentration when the polymerization concentration is increased. Crosslinking (self-crosslinking) is likely to occur, resulting in a decrease in the amount of absorption and a decrease in the average polymerization degree of the polymer, and it is difficult to control the temperature during polymerization, and a decrease in the average polymerization degree of the polymer and an increase in the oligomer component are likely to occur. Therefore, the polymerization concentration is preferably 10 to 40% by weight, more preferably 10 to 30% by weight. Moreover, regarding polymerization temperature, from a viewpoint of the average degree of polymerization of a polymer, -10-100 degreeC is preferable, More preferably, it is -10-80 degreeC. 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 crosslinked polymer (A) excellent in absorption capacity can be produced.

When (meth) acrylic acid is used, the degree of neutralization of (meth) acrylic acid during polymerization is such that a predetermined amount of hydrolyzable crosslinker (b1) and non-hydrolyzable crosslinker (b2) are completely in the monomer aqueous solution. (B2) is poorer in water solubility than (b1), and in particular, the solubility in (meth) acrylic acid (salt) aqueous solution is extremely low, and a predetermined amount of (b2) is added. However, (b2) may be separated from the aqueous monomer solution and the predetermined crosslinking may not be performed. From the viewpoint of the solubility of (b2), the degree of neutralization of (meth) acrylic acid at the time of polymerization is preferably 0 to 30 mol% and is preferably further neutralized after the polymerization if necessary, in an unneutralized state. It is more preferable to neutralize after polymerization after polymerization.
In addition, (meth) acrylic acid, when polymerized under the same conditions, tends to increase the degree of polymerization (absorption capacity) when the degree of neutralization is low. It is preferable to carry out the polymerization in a low state.

  Regarding the reverse phase suspension polymerization method, an aqueous solution of (meth) acrylic acid (salt) is suspended and dispersed in a hydrophobic organic solvent typified by hexane, toluene, xylene, etc. in the presence of a dispersant. In this polymerization method, the monomer concentration in the aqueous monomer solution is preferably 10 to 40% by weight, more preferably 10 to 30% by weight, in this polymerization method as well. Within this range, a crosslinked polymer (A) having a high degree of polymerization can be produced.

  In addition, regarding this reverse phase suspension polymerization method, you may use a dispersing agent at the time of superposition | polymerization. As the dispersing agent, known dispersing agents can be used, sorbitan fatty acid esters such as sorbitan monostearic acid ester having 3 to 8 HLB (Hydrophile-Lipophile Balance), glycerin fatty acid esters such as glycerin monostearic acid ester, and sucrose distearic acid. 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. When the polymer dispersant is used as the dispersant, it is easier to adjust the size of the suspended particles of the aqueous monomer solution in the solvent, and a hydrogel of the cross-linked polymer (A) having the required particle size can be prepared. Therefore, it is 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.
0.1-2.0 are preferable and, as for the weight ratio (W / O ratio) of the monomer aqueous solution and hydrophobic organic solvent in reverse phase suspension polymerization, 0.3-1.0 are more preferable. Within these ranges, the particle diameter of the crosslinked polymer (A) can be further easily adjusted.

In the production of the crosslinked polymer (A), the weight average molecular weight of the polymer is preferably 5,000 to 1,000,000 when the polymer is produced under exactly the same conditions except that no crosslinking agent is used. More preferably, it is 10,000-1,000,000.
When polymerization is carried out under conditions where the weight average molecular weight is 5,000 or more, the use of an appropriate amount of a crosslinking agent prevents a decrease in viscosity and / or an increase in spinnability of a high-concentration alkaline aqueous solution to which a binder has been added. I can do it. The weight average molecular weight is measured by a gel permeation chromatography method (GPC method).

The crosslinked 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 after drying.
Regarding the drying method of hydrous gel, in the case of aqueous solution polymerization, the hydrogel is subdivided to some extent with a meat chopper or cutter type crusher (the level of subdivision is about 0.5 to 20 mm square) or noodles, if necessary 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, the drying method of the hydrogel in the case of reverse phase suspension polymerization is carried out by solid-liquid separation of the polymerized hydrogel and the organic solvent by a method such as decantation, followed by drying under reduced pressure (degree of vacuum; about 100 to 50,000 Pa) Or it is common to perform ventilation drying.

  As another drying method of the hydrogel in aqueous solution polymerization, for example, there is a contact drying method in which the hydrogel is compressed and stretched on a drum dryer and the like. It is necessary to create a thin film of hydrogel on the drum or the like. However, since the materials of commercially available drum dryers are generally made of a metal that has a lower ionization tendency than zinc, such as iron, chromium, and nickel, the frequency of contact with the drum metal surface per hydrous gel is low. Further, since the water-containing gel is a poly (meth) acrylic acid (salt) water-containing gel, the content of metal elements having a lower ionization tendency than zinc in the binder is increased. Furthermore, since the contact frequency between the water-containing gel and the drum is extremely high, and the water-containing gel has high adhesiveness, it is necessary to bring a dried product from the drum dryer by bringing a knife-like material into contact with the drum dryer. Due to the mechanical wear of the knife, the metal surface of the drum or knife is worn, and the 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 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 considerably large amount of metal) ions and metal powder that 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 drying temperature at the time of drying the hydrogel varies depending on the dryer used, the drying time, and the like, 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 also varies depending on the model of the dryer to be used, the drying temperature, and the like, but is preferably 5 to 300 minutes, more preferably 5 to 120 minutes.

  The dried product of the crosslinked 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 crosslinked 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 alkaline battery to which the alkaline battery positive electrode using the binder of the present invention can be applied is not particularly limited, and an ordinary alkaline battery such as LR-20 (single 1 type alkaline battery), LR-6 type (single AA alkaline battery). ) And other various 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 method of filling the alkaline battery positive electrode with the alkaline battery positive electrode using the binder of the present invention is performed by previously adding the binder of the present invention, the positive electrode active material (for example, manganese dioxide), the conductive agent (for example, graphite), and other additives as required. After mixing, alkaline electrolyte (for example, potassium hydroxide aqueous solution) is mixed, a positive electrode mixture is produced, and the method of filling the positive electrode obtained by rolling and shape | molding in a container etc. can be illustrated here now.
The amount of the binder added 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, more preferably 0.1 to 0.5% by weight with respect to the positive electrode. 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.

In addition to the crosslinked polymer (A), the binder of the present invention may contain other additives as necessary for the purpose of improving fluidity at the time of producing a positive electrode, as long as no problem occurs in workability and battery characteristics. .
Examples of other additives include discharge characteristic improvers.

Examples of the discharge characteristic improver include known compounds such as silicon dioxide and potassium silicate.
The content in the case of containing a discharge characteristic improver is preferably 0 to 5.0% by weight, more preferably 0 to 3.0% by weight, based on the crosslinked polymer (A).

  The content in the case of containing other additives is preferably 0 to 5.0% by weight, more preferably 0 to 3.0% by weight, based on the crosslinked polymer (A).

  The method for adding the discharge characteristic improver is a method in which the binder of the present invention and the discharge characteristic improver are dry blended in advance and then blended with other positive electrode materials, and added and mixed separately from the binder of the present invention when producing the positive electrode. However, any method may be used as long as a predetermined amount of a binder can be added if necessary.

  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,% indicates% by weight, ultrapure water indicates water having an electric conductivity of 0.06 μS / cm or less, and ion exchange water indicates water having an electric conductivity of 1.0 μS / cm or less.

Example 1
In a 2-liter beaker, add 300 g of acrylic acid, 1.35 g of trimethylolpropane triacrylate (0.45% acrylic acid) and 700 g of ion-exchanged water, and mix by stirring to prepare an aqueous acrylic acid solution and cool to 4 ° C. did.
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, 4.0 g of 0.1% hydrogen peroxide solution, 4.0 g of 0.1% L-ascorbic acid aqueous solution and 10% 2,2′-azobis (2-amidinopropane) hydrochloride (Wako Pure) Yaku Kogyo Co., Ltd., trade name: V-50) 1.0 g of 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 carried out for 6 hours. When the temperature of the acrylic acid aqueous solution was measured with a hot spot thermometer, the maximum temperature reached was 97 ° C.
In addition, when the weight average molecular weight of the polymer polymerized under the same conditions except that the above-described polymerization was omitted, the polymer was measured using GPC, the weight average molecular weight of the polymer was about 27,000.
After removing the block-like crosslinked hydrous gel from the adiabatic polymerization tank and using a small meat chopper (Royal) to subdivide the gel into noodles with a thickness of 3 to 10 mm, 40% hydroxide 260 g of sodium (reagent special grade) aqueous solution (corresponding to a neutralization degree of acrylic acid of 75 mol%) was added to neutralize the hydrogel.
The neutralized water-containing gel is laminated on a SUS screen having an opening of 850 μm with a thickness of 5 cm, and hot air at 120 ° C. is applied for 1 hour using a small air-permeable dryer (manufactured by Inoue Metal Co., Ltd.). The water-containing gel was air-permeable and the water-containing gel was dried.
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.

Example 2
In Example 1, instead of 1.35 g of trimethylolpropane triacrylate (0.45% acrylic acid), the amount of N, N′-methylenebisacrylamide added was 0.6 g (0.2% acrylic acid). Except for this, the binder (2) of the present invention was obtained in the same manner as in Example 1.

Example 3
In Example 1, instead of 1.35 g of trimethylolpropane triacrylate (0.45% acrylic acid), 1.05 g of trimethylolpropane triacrylate (0.35% acrylic acid) was added, and pentaerythritol triacrylate was added. A binder (3) of the present invention was obtained in the same manner as in Example 1 except that the amount of allyl ether added was 0.36 g (0.12% with respect to acrylic acid).

Example 4
In Example 3, instead of trimethylolpropane triacrylate, the addition amount of triethylene glycol dimethacrylate was 1.71 g (0.57% of acrylic acid), and the addition amount of pentaerythritol triallyl ether was 0.09 g (vs. acrylic). The binder (4) of the present invention was obtained in the same manner as in Example 1 except that the acid was 0.03%.

Example 5
In Example 3, the binder (5) of the present invention was obtained in the same manner as in Example 3 except that the amount of pentaerythritol triallyl ether added was 0.24 g (0.08% acrylic acid). It was.

Example 6
In Example 3, the addition amount of trimethylolpropane triacrylate was 0.6 g (to 0.20% acrylic acid), and the addition amount of pentaerythritol triallyl ether was 0.75 g (to 0.25% acrylic acid). Except for this, the binder (6) of the present invention was obtained in the same manner as in Example 3.

Example 7
The binder (1) obtained in Example 1 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
A binder (8) of the present invention was obtained in the same manner as in Example 1 except that the amount of 0.1% hydrogen peroxide solution added was 8.0 g in Example 1.
When the weight average molecular weight of the polymer obtained by removing the cross-linking agent trimethylolpropane triacrylate was measured using GPC, the polymer weight average molecular weight was about 18,000.

Example 9
A binder (9) of the present invention was obtained in the same manner as in Example 1 except that the amount of 0.1% hydrogen peroxide solution added was 2.0 g in Example 1.
In addition, when the weight average molecular weight of the polymer obtained by removing the trimethylolpropane triacrylate which is a crosslinking agent was measured using GPC, the weight average molecular weight of the polymer was about 38,000.

Example 10
In Example 1, 45.2 g of an aqueous 10.0 wt% sodium sulfite solution (1.5 wt% with respect to the total weight of acrylic acid (salt) and the crosslinking agent) was added to the neutralized hydrogel, and the small size A binder (10) of the present invention was obtained in the same manner as in Example 1 except that the water-containing gel was uniformly kneaded with a meat chopper.

Example 11
Example 10 except that the amount of 10.0% by weight sodium sulfite aqueous solution added was 15.1 g {0.5% by weight based on the total weight of acrylic acid (salt) and the crosslinking agent} in Example 10. In the same manner as above, the binder (11) of the present invention was obtained.

Example 12
In Example 10, except that the addition amount of 10.0% by weight sodium sulfite aqueous solution was 90.4 g {3.0% by weight with respect to the total weight of acrylic acid (salt) and the crosslinking agent}, Example 10 In the same manner as above, a binder (12) of the present invention was obtained.

Example 13
The binder (10) obtained in Example 10 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 (13) of the present invention. It was.

Example 14
In Example 10, instead of 1.35 g of trimethylolpropane triacrylate (0.45% acrylic acid), 1.05 g of trimethylolpropane triacrylate (0.35% acrylic acid), pentaerythritol triallyl ether 15.0 g (with respect to acrylic acid 0.5%), the addition amount of 0.1% hydrogen peroxide water is 16.0 g, the addition amount of 10.0% by weight sodium sulfite aqueous solution is 1.5 g {acrylic acid ( The binder (14) of the present invention was obtained in the same manner as in Example 1 except that the total weight of the salt) and the crosslinking agent was 0.05% by weight}.
In addition, when the weight average molecular weight of the polymer which remove | excluded the trimethylol propane triacrylate and pentaerythritol triallyl ether which are crosslinking agents was measured using GPC, the weight average molecular weight of the polymer was about 12,000.

Example 15
In Example 14, the amount of pentaerythritol triallyl ether added was 0.36 g (based on acrylic acid 0.12%), the amount of 0.1% hydrogen peroxide added was 0.4 g, and 10.0 wt% sodium sulfite. The binder (15) of the present invention was prepared in the same manner as in Example 14 except that the addition amount of the aqueous solution was 60.3 g {2.0% by weight based on the total weight of acrylic acid (salt) and the crosslinking agent}. )
In addition, when the weight average molecular weight of the polymer which remove | excluded the trimethylol propane triacrylate and pentaerythritol triallyl ether which are crosslinking agents was measured using GPC, the weight average molecular weight of the polymer was about 75,000.

Comparative Example 1
Commercially available carboxymethyl cellulose (CMC2450, manufactured by Daicel Chemical Industries, Ltd.) was used as a binder for comparison (H1).

Comparative Example 2
In Example 1, the amount of pentaerythritol triallyl ether added to 9.0 g (vs. 3.0% acrylic acid) instead of trimethylolpropane triacrylate was the same as in Example 1 for comparison. A binder (H2) was obtained.

Comparative Example 3
In Example 1, the addition amount of the added polymerization initiator (hydrogen peroxide, ascorbic acid, V-50) was respectively increased 10 times, and instead of ion-exchanged water, a 20% ethanol aqueous solution {ethanol / water = 20/80 A comparative binder (H3) was obtained in the same manner as in Example 1 except that (weight ratio)}.
When the weight average molecular weight of the polymer obtained by removing the cross-linking agent trimethylolpropane triacrylate was measured using GPC, the polymer weight average molecular weight was about 1,700.

Comparative Example 4
In Example 1, a comparative binder (H4) was obtained in the same manner as in Example 1 except that trimethylolpropane triacrylate was not used.

  (1) Absorption capacity of binders (1) to (15) prepared in Examples 1 to 15 and comparative binders (H1) to (H4) prepared in Comparative Examples 1 to 4, (2) of the formulation Viscosity, (3) absorption under load, and (4) total content of unpolymerized (a1), (a2) and (b) were measured by the method described above. The results are shown in Table 1.

  Furthermore, using the binders (1) to (15) of the present invention and the comparative binders (H1) to (H4), (1) the breaking strength of the positive electrode and (2) the duration of the battery are as follows. It was measured. 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.

(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 15 of the present invention satisfy the requirements (1) and (2) of the present invention. On the other hand, Comparative Examples 1-4 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 the products 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 production 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.

Claims (5)

A binder comprising a water-soluble vinyl monomer (a1) and / or a vinyl polymer (a2) which becomes (a1) by hydrolysis and a crosslinked polymer (A) having a crosslinking agent (b) as essential constituent units. ,
Alkaline in which the crosslinking agent (b) is at least one selected from the group consisting of N, N′-methylenebisacrylamide, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate and ethylene glycol diglycidyl ether . Comprising a hydrolyzable cross-linking agent (b1) hydrolyzing with
The weight of the crosslinking agent (b) is 0.05 to 2% by weight based on the total weight of (a1) and (a2);
The hydrolyzable crosslinking agent (b1) has a weight of 0.01 to 2% by weight based on the total weight of (a1) and (a2);
And the binder (C) for alkaline battery positive electrodes which comprises the requirements of following requirements (1) and (2).
Requirement (1): The absorption capacity of 40% by weight potassium hydroxide aqueous solution of (C) is 5 to 80 g / g.
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 a binder, and the viscosity (25 ° C.) of the formulation (D) after being allowed to stand at 25 ° C. for 24 hours. 1 to 500 Pa · s. 2. The binder for an alkaline battery positive electrode according to claim 1, wherein the binder (C) has a 20 wt% potassium hydroxide aqueous solution absorption amount of 2 to 10 g / g under a load of 20 g / cm ² . In the binding agent (C), unpolymerized soluble vinyl monomer (a1), the total content of the vinyl monomer (a2) and the crosslinking agent (b), a 10~500ppm based on the weight of (C) according to Item 3. A binder for an alkaline battery positive electrode according to Item 1 or 2 . The alkaline battery positive electrode formed by containing the binder for alkaline battery positive electrodes in any one of Claims 1-3, manganese dioxide, and graphite. An alkaline battery comprising the positive electrode according to claim 4 , a negative electrode containing zinc or zinc powder, and an electrolytic solution containing an aqueous potassium hydroxide solution.