JPH1053682A - Production of aqueous dispersion or organosol of fluorine-containing polymer and electric cell produced by using the aqueous dispersion or organosol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorine-containing polymer suitable as a binder or a water-repellent for an electric cell. SOLUTION: A reagent excluding ammonium salt or essentially free from ammonia is used as a reagent to be used in the emulsion polymerization of a monomer for forming a fluorine-containing polymer in an aqueous medium or as a reagent to be added to the produced polymer in the production of an aqueous dispersion of fine particles of at least one kind of a fluorine-containing polymer selected from tetrafluoroethylene, tetrafluoroethylene-perfluoro(alkylvinyl) ether copolymer and tetrafluoroethylene-hexafluoropropylene copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an aqueous dispersion of a fluoropolymer or an organosol and a battery produced using the dispersion or the organosol. More specifically, a method for producing an aqueous dispersion or organosol of fine particles of a fluoropolymer which does not substantially use an ammonium salt and / or ammonia when producing a fluoropolymer by emulsion polymerization, and an aqueous dispersion or organosol thereof. The present invention relates to a battery used as a binder and / or a water repellent.

[0002]

2. Description of the Related Art In recent years, small and portable precision electric and electronic devices such as audio tape recorders, camera-integrated video tape recorders, personal computers, and mobile phones have been increasingly used. Along with this,
The demand for a rechargeable so-called secondary battery that is small, lightweight, and has a high energy density as a power supply for driving these devices is rapidly increasing. Nickel-hydrogen secondary batteries and nickel-cadmium secondary batteries are typical ones.

[0003] It is the active materials of the positive and negative electrodes of the battery that greatly affect the performance of these secondary batteries. Examples of the positive electrode active material include manganese dioxide (MnO ₂ ), nickel hydroxide (Ni (OH) ₂ ), lithium cobalt oxide (L
iCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), vanadium pentoxide (V ₂ O ₅ ), niobium pentoxide (Nb ₂ O ₅ ), lithium manganate (LiMnO ₂ ), and the like. Is cadmium hydroxide (Cd (O
H) ₂ ), a hydrogen storage alloy (MH), graphite, and the like.

In the production of batteries, these electrode active materials and conductive carbonaceous materials (for example, carbon blacks such as acetylene black and Ketjen black and graphite) are used as a mixture to form a support (metal foil, metal net, etc.). ) To form an electrode. Conventionally, as a binder, a fluororesin material having excellent chemical resistance and heat resistance and having binding properties has been widely used as a suitable binder.

For example, in Japanese Patent Application Laid-Open No. 63-236258, a dispersion of polytetrafluoroethylene (PTFE) is used to bind MnO ₂ , acetylene black, graphite, etc., which are positive electrode materials of a lithium primary battery. ing. Japanese Patent Publication No. 6-10980 describes an example in which a manganese oxide, carbon black, and activated carbon are bound by PTFE dispersion in an air zinc battery. On the other hand, there is also known an example in which polyvinylidene fluoride (PVDF) is used as a binder. JP-A-6-44964 describes an electrode obtained by mixing an electrode material such as a hydrogen storage alloy or carbonyl nickel powder with a solution of PVDF and processing it into a sheet in a nickel-hydrogen battery. Also, in a lithium ion secondary battery, as in the example of JP-A-4-249860, a positive electrode material of lithium-containing oxide such as LiCoO ₂ and graphite and a negative electrode material of carbonaceous material are each provided with N- of PVDF. A methylpyrrolidone (NMP) solution is mixed and processed into a sheet to form an electrode.

On the other hand, the cycle life characteristic is adopted as one of the indexes of the performance of these secondary batteries. In a secondary battery using a nickel compound for the positive electrode, oxygen and hydrogen gas are generated from the positive electrode and the negative electrode, respectively, at the time of overcharge or rapid charging by a large current, and the internal pressure of the battery increases. This is a major cause and shortens the cycle life. In other words, when the internal pressure of the battery rises beyond a certain value and the attached safety valve operates, the electrolyte and oxygen gas are discharged to the outside of the battery,
This causes a decrease in discharge capacity and a liquid leakage phenomenon. As a result, the life is shortened.

One of the measures to solve this problem is to promptly diffuse the generated gas to the surface of the negative electrode to promote a reaction to return to water, oxide or hydride. Specific means include adjusting the capacity balance of the positive and negative electrodes to increase the negative electrode capacity, and adding a carbon-reducing catalyst to the negative electrode, and have already been implemented. As another means, the reaction that rapidly diffuses the generated gas and returns it to water, oxides or hydrides occurs at the three-phase interface between the gas phase, liquid phase, and solid phase in the electrode. Fine, dense and uniform distribution. Fluororesins have low surface energy and high water repellency, and thus have a feature of easily forming a three-phase interface. Therefore, in the nickel-hydrogen secondary battery and the nickel-cadmium secondary battery, among the properties of the fluororesin, not only the binding property but also the water repellency are utilized at the same time.

[0008] As described above, the fluororesin which is extremely useful in the electrode manufacturing process and the maintenance of battery performance is mainly used in an aqueous dispersion (dispersion) or the like in order to more efficiently bring out its performance in the battery electrode plate manufacturing process. It is used in the form of an organosol and is mainly produced by emulsion polymerization.

The aqueous dispersion is prepared, as is known, as follows. First, deoxygenated and deionized water is charged into a stainless steel or glass-lined autoclave having a stirrer. Next, a sufficient amount of a fluorinated polymerization emulsifier for stably presenting the colloidal fluoropolymer particles, and in some cases, a carbonization stabilizer for keeping the latex (colloidal fluoropolymer) stable during polymerization. A saturated hydrocarbon which is inactive for the substantial polymerization reaction which is liquid under the polymerization conditions and has a number of 12 or more is charged.

[0010] Examples of the fluorine-based polymerization emulsifier include the following compounds. General formula (1): X (CF ₂ ) _n COOY (1) wherein X is a hydrogen atom, a chlorine atom or a fluorine atom, n is an integer of 6 to 12, Y is a hydrogen atom, ammonium (NH)
₄ ) represents a group or an alkali metal atom. Or a salt thereof, represented by the general formula (2): Cl (CF ₂ CFCl) _m CF ₂ COOY (2) [wherein, m represents an integer of 6 to 12. Y is as defined above. Or a salt thereof, represented by the general formula (3): R _f ¹ (CFZCF ₂ O) _p CFZCOOY (3) wherein Y is as defined above. Z is a fluorine atom F or a lower (preferably 1 to 3 carbon atoms) perfluoroalkyl group (such as a trifluoromethyl group); p is an integer of 0 to 5; R _f ¹ is a perfluoroalkyl group; Represents a cycloalkyl group or a perfluoroalkyl ether group (for example, C ₃ F ₇ —, C ₃ F ₇ (CF ₂ CF ₂ CF ₂₀ ) ¹ —, etc.). Or a salt thereof, represented by the general formula (4): R _f ² SO ₃ Y (4) wherein R _f ² is a fluoroalkyl group contained in the formulas (1) to (3). . Y is as defined above. Or a salt thereof, and a mixture thereof.

The polymerization emulsifier is used in an amount of usually 10 ^{-4 to} 5% by weight based on water as a polymerization medium.

Specific examples of the polymerization stabilizer include hexadecane, tetradecane, paraffin wax and liquid paraffin, and are added in an amount of 1 to 20% by weight based on water.

After the space inside the polymerization vessel is replaced with an inert gas, a suitable monomer or monomer mixture is introduced into the vessel and pressurized to a predetermined pressure. As the pressure during polymerization,
Usually, 5 to 40 kg / cm ² is appropriate. Subsequently, the system is heated to a predetermined temperature (generally 5 to 95 ° C.) and kept at that temperature.

The polymerization reaction is started by adding a polymerization initiator to the system. As the polymerization initiator, usually, a ammonium persulfate salt or an alkali metal salt alone, or a water-soluble organic peroxide (for example, di-citrate peroxide, di-
Water-soluble aliphatic dibasic carboxylic acid peroxides such as glutaric acid peroxide) and their alkali metal salts alone, or a mixture of these organic peroxides and the above-mentioned persulfates are used. Further, the above-mentioned persulfate can be used as a redox system in combination with a suitable reducing agent (for example, a metal sulfite or an ammonium salt). The amount of the polymerization initiator ranges from 10 ^-6 to 10 ^-3 % by weight based on water. The polymerization reaction proceeds while continuously adding olefin monomer until a polymer of 15 to 45% by weight based on water is formed.

Since the aqueous fluoropolymer dispersion produced by the emulsion polymerization reaction tends to cause problems in the dispersion stability during transportation and operation as it is, a surfactant is generally added and the pH of the aqueous dispersion is adjusted to 7 to 11. Adjust to the alkali side and stabilize. The type of the surfactant is not particularly limited. At least one of anionic, cationic and nonionic surfactants can be used. Currently,
In most cases, a nonionic surfactant is used.
The type of the nonionic surfactant is not particularly limited, but a fatty acid ester type surfactant of a polyoxy compound (for example, glycol ester of fatty acid, fatty acid sorbitan and mannitol ester), a polyethylene oxide condensation type surfactant (for example, higher fatty acid) , Higher alcohols, and polyethylene oxide condensates such as alkylphenols). Also, a recent patent application (Japanese Unexamined Patent Publication No.
No. 0700) describes the use of sodium dialkyl sulfosuccinate or the like as an anionic surfactant.

As the pH adjusting agent, an aqueous solution of ammonium hydroxide or an alkali metal hydroxide is used.

Incidentally, the aqueous dispersion of the fluoropolymer obtained by emulsion polymerization may be concentrated to a higher concentration than usual. Concentration is particularly important when such aqueous dispersions are used for applications such as coating on metal substrates and impregnation into glass fibers. The concentration method is not limited, and includes a sedimentation concentration method (U.S. Pat. No. 3,379,953), an ultrafiltration concentration method (U.S. Pat. No. 4,369,266), an evaporative concentration method, an electrophoretic concentration method, and the like.

The organosol of the fluoropolymer is separated from the aqueous dispersion obtained by the above-mentioned emulsion polymerization by coagulation of polymer fine particles by a conventional method (for example, see US Pat. No. 2,953,583), and further dried. It can be easily produced by redispersing the obtained powder in a dispersion solvent mechanically or by ultrasonic waves. Alternatively, an organosol can be formed by a layer-transfer method as described in JP-B-49-17016 without a powdering step. The dispersion solvent used in the organosol may be any organic liquid that can wet the polymer fine particles, and is not particularly limited. They can be selected depending on the situation in which they are used.

Usually, due to the reagents used in the emulsion polymerization step and the subsequent post-treatment step, the aqueous dispersion or organosol of the fluoropolymer contains various impurities which adversely affect the performance of the battery. There are many. Examples of the impurities include ions of transition metals such as copper, lead, and iron, and oxidizing organic compounds.

In particular, ammonium compounds such as ammonium perfluoroalkylcarboxylate, ammonium persulfate, and aqueous ammonia are often used as emulsifiers and polymerization initiators required for emulsion polymerization and pH adjusters added in the post-treatment. You. Therefore, in many cases, the aqueous dispersion of the fluorine-containing polymer as a product contains the ammonium compound as described above, and all of them are not removed even after the electrode is prepared, and the electrode is not contained in the electrode. It is thought that it remains. When such an electrode is incorporated in a battery and comes into contact with an aqueous solution of potassium hydroxide as a strong base used as an electrolyte, ammonium ions are reduced to produce ammonia. In the case of nickel-metal hydride batteries, it is believed that this ammonia causes the following reactions at the positive and negative electrodes (M. Wada, Polymers for Advanced).
Technologies, 5 , 645 (1994)):

The positive _{electrode: NH 3 + 6NiOOH + H 2} O + OH - → 6Ni (OH) 2 + NO 2 - (i) NO 2 - + 2NiOOH + H 2 O → 2Ni (OH) 2 + NO 3 - (ii ) Negative electrode: NO ₃ ⁻ + MH _x → NO ₂ ⁻ + MH _x−2 + H ₂ O (iii) NO ₂ ⁻ + MH _x → NH ₃ + MH _x −6 + OH ⁻ + H ₂ O (iv)

During the reaction (i) to (iv), self-discharge occurs due to the repetition of so-called shuttle reactions, resulting in a decrease in battery performance. In the above document, the source of ammonia is a polyamide separator, and ammonia is generated by oxidation. To prevent this, a nonwoven polypropylene fabric is employed.

[0023]

SUMMARY OF THE INVENTION One object of the present invention is to provide a method for producing an aqueous dispersion or organosol of a fluorine-containing polymer which does not contain a source of ammonia which causes the above-mentioned deterioration in battery performance. It is to be. Another object of the present invention is to provide a battery manufactured using an aqueous fluoropolymer dispersion or an organosol that does not contain an ammonia generation source that causes the above-described deterioration in battery performance.

[0024]

SUMMARY OF THE INVENTION The above object is achieved by at least one selected from the group consisting of tetrafluoroethylene, tetrafluoroethylene-perfluoro (alkylvinyl) ether copolymer and tetrafluoroethylene-hexafluoropropylene copolymer. A method for producing an aqueous dispersion of one kind of fluoropolymer fine particles, wherein both a reagent used when emulsion-polymerizing a monomer forming the fluoropolymer in an aqueous medium and a reagent added after polymerization are used. Is not an ammonium salt or contains substantially no ammonia, a polymer fine particle is separated from the aqueous dispersion obtained by this manufacturing method by coagulation, and dried to obtain a polymer fine particle powder. The resulting polymer microparticle powder is re-mechanically or ultrasonically dispersed in a dispersion solvent. Selected from the group consisting of tetrafluoroethylene, tetrafluoroethylene-perfluoro (alkylvinyl) ether copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer, comprising dispersing or inverting the aqueous dispersion. A method for producing an organosol of at least one type of fluoropolymer obtained, and using an aqueous dispersion or organosol of a fluoropolymer obtained by such a production method as a binder and / or a water repellent The problem is solved by a battery manufactured by:

That is, the present invention focuses on potassium hydroxide used as an electrolyte of a battery, preferably a nickel-cadmium or nickel-hydrogen secondary battery, and uses a reagent used in a process for producing a fluoropolymer and a post-treatment process. Substituting an alkali metal ion such as potassium for the counter ion, that is, using an alkali metal persulfate alone as an initiator or in combination with a water-soluble organic peroxide containing no ammonium salt and ammonia, and polymerizing Polymerization is carried out using an alkali metal salt such as a carboxylic acid or sulfonic acid having a perfluoro group as an emulsifier, and further, in the case of an aqueous dispersion, a surfactant containing no ammonium salt and ammonia as a fine particle stabilizer in a post-treatment step. Using the agent,
Tetrafluoroethylene polymer, tetrafluoroethylene-perfluoro (alkylvinyl) ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer produced by adjusting the pH with an aqueous solution of an alkali metal hydroxide The object is achieved by an aqueous dispersion containing fine particles of coalescing (FEP) or an organosol.

In the production method of the present invention, an alkali metal persulfate is suitable as a polymerization initiator, and particularly, lithium, sodium and potassium salts having excellent solubility in water are preferable. Potassium salts are particularly preferred because the main component of the electrolyte in nickel-cadmium and nickel-hydrogen batteries is potassium hydroxide. The alkali metal persulfate may be used alone as a polymerization initiator, but may be a water-soluble organic peroxide (for example, a water-soluble aliphatic dibasic compound such as di-succinic acid peroxide and di-glytaric acid peroxide). Carboxylic acid peroxide) and their alkali metal salts. The polymerization initiator is used in an amount of 10 ^-6 to 10 ^-3 % by weight based on the aqueous dispersion.

As the polymerization emulsifier, an alkali metal salt of a carboxylic acid or a sulfonic acid containing a perfluoro group is preferable. Among them, potassium salts are more preferred.

For example, general formula (5): X (CF ₂ ) _n COOM (5) [wherein, a hydrogen atom, a chlorine atom or a fluorine atom, and n is 6 to
An integer of 12, M represents an alkali metal atom (Li, Na, K or Cs)],

General formula (6): Cl (CF ₂ CFCl) _n CF ₂ COOM (6) wherein M and n are as defined above. ],

Formula (7): R _f ¹ (CFY'CF ₂ O) _p CFY'COOM (7) wherein M is as defined above. Y ′ is a fluorine atom or a lower (preferably 1 to 3 carbon atoms) perfluoroalkyl group (for example, CF ₃ group), p is an integer of 0 to 5, R is
_f ¹ is a perfluoroalkyl group, a perfluorocycloalkyl group or a perfluoroalkyl ether group _{(e.g., C 3 F 7 -, C} 3 F 7 (CF 2 CF 2 CF 2 0) l - (l = 1
To 30). ],

Formula (8): R _f ² SO ₃ M (8) wherein R _f ² can be selected from fluoroalkyl groups contained in formulas (5) to (7). A compound represented by the formula:
And mixtures thereof. The polymerization emulsifier is used in an amount of 10 ^{-4 to} 5% by weight, preferably 10 ^{-2 to} 5 × 10 ^-1 % by weight, based on the aqueous dispersion.

The aqueous dispersion produced by emulsion polymerization tends to cause problems in dispersion stability during transportation and operation as it is. Therefore, a surfactant is added to the aqueous dispersion and the pH of the aqueous dispersion is adjusted to 7 to 11. It is desirable to stabilize by adjusting to the side. The type of surfactant used for stabilization is not particularly limited. At least one of anionic, cationic and nonionic surfactants can be used.

In order to prevent the stability of the aqueous dispersion from being impaired by the electrolyte used when forming the electrodes (a potassium hydroxide aqueous solution is mainly used in a nickel-hydrogen secondary battery), a nonionic interface is generally used. Activators are preferred.

The type of the nonionic surfactant is not particularly limited, but a fatty acid ester type surfactant of a polyoxy compound, for example, a fatty acid glycol ester, a fatty acid sorbitan and a mannitol ester, and a polyethylene oxide condensation type surfactant, for example, a higher fatty acid , Higher alcohols, and polyethylene oxide condensates such as alkylphenols.

The amount of the surfactant added is 1 to 20%, preferably 1%, based on the total weight of the fine particle polymer in the aqueous dispersion.
〜１０10%. If the amount is too small, the dispersion stability of the aqueous dispersion is not sufficient, and if the amount is too large, the battery performance is adversely affected.
For a battery, a surfactant is not essential, and it may be mixed with an electrode material without adding a surfactant.

As the pH adjusting agent, an aqueous solution of an alkali metal hydroxide (LiOH, NaOH, KOH, etc.) can be used. As described above, ammonium compounds such as ammonia increase self-discharge when present in a battery and cause a decrease in battery performance.However, by adjusting the pH with an alkali metal hydroxide, such a compound can be obtained. Problems are gone. Furthermore, it is free from the ammonia odor which is often a problem when using the conventional aqueous dispersion, and is advantageous in terms of working environment.

When the aqueous dispersion of the present invention is used as a binder or a water repellent for a battery, the concentration of the fine polymer particles in the aqueous dispersion is usually 5 to 70% by weight, preferably 10 to 65% by weight.
% By weight. If the concentration of the polymer fine particles is too high, the viscosity of the aqueous dispersion becomes high, resulting in poor workability. If the concentration is too low, it takes time and effort to remove excessive moisture, and the efficiency of electrode production is reduced.

The organosol of polymer fine particles of the present invention is separated from the aqueous dispersion obtained by emulsion polymerization by coagulation by a conventional method (for example, see US Pat. No. 2,953,583), and further dried. It can be easily produced by redispersing the obtained powder in a dispersion solvent mechanically or by ultrasonic waves. Alternatively, an organosol can be formed by a layer-transfer method as described in JP-B-49-17016 without a powdering step.

However, in the organosol, the polymer fine particles hardly exist in a finely dispersed state like an aqueous dispersion.
Some fine particles are agglomerated. Usually, aggregated particles are 1 to
It has a size of 3 μm. However, since the agglomerated particles are merely fused fine particles and are not fused, the specific surface area does not substantially change due to the aggregation. The average particle size as defined herein does not mean the average particle size of the aggregated particles, but the average particle size of the primary particles.

As the dispersion solvent for preparing the organosol, any organic liquid which can wet the polymer fine particles can be used, and is not particularly limited. For example, benzene, toluene,
Aromatic hydrocarbons such as xylene; halogenated hydrocarbons such as carbon tetrachloride and trichloroethylene; ketones and esters such as methyl isobutyl ketone (MIBK), diisobutyl ketone and butyl acetate; aqueous solutions such as methanol, ethanol and isopropanol (IPA) N-methylpyrrolidone (NMP) and the like are preferable. Organic solvent that is difficult to wet polymer particles by itself,
For example, when carbon tetrachloride, trichloroethylene, or diisobutyl ketone is used, the wetting of the fine particles can be improved by adding a small amount of an oil-soluble surfactant.
In view of the dispersibility of fine particles, workability of electrode preparation, or toxicity, particularly preferred organic liquids are IPA,
MIBK and NMP.

The concentration of the fluoropolymer in the organosol is usually 1 to 50% by weight, preferably 1 to 30% by weight. When the electrode material is subjected to water-repellent treatment using an organosol, there are advantages in that drying is easier than in the case of the aqueous dispersion, and that an adverse effect on the electrode due to a surfactant added to the aqueous dispersion can be reduced.

As described above, the fluoropolymer produced according to the present invention and used in the battery includes tetrafluoroethylene polymer (PTFE) (including modified PTFE) and tetrafluoroethylene-hexafluoropropylene copolymer ( PFA) and tetrafluoroethylene-
Perfluoro (alkyl vinyl) ether copolymer (F
EP). Depending on the average molecular weight or the composition of the copolymer, these fluorine-containing polymers have both functions of binding and water repellency (having a fiberizing ability), and those having poor binding power and only function of water repellency. (There is no fiberization ability).

In the case of PTFE, for example, when the average molecular weight is about 1,000,000 or less, it is said that the fiberizing ability is lost, and it is mainly used as a water repellent.
When it is not less than 0,000, it has a fiberizing ability, and is used mainly as a binder by using it, and it can impart a certain degree of water repellency.

Explaining PFA and FEP, the composition of perfluoro (alkyl vinyl) ether or hexafluoropropylene, which is a copolymer monomer, has a large difference in the fiberizing ability at about 1% by weight in the copolymer. . That is, when the amount is about 1% by weight or more, the fiberizing ability of the copolymer is significantly reduced, and almost no fiberizing ability is obtained. When the amount is less than 1% by weight, the copolymer still has the fiberizing ability. And can be used as a water repellent and a binder, respectively. Since the molecular weights of PFA and FEP cannot be measured accurately by the same method as that for PTFE, they cannot show a clearer boundary than PTFE.

Fluorine-containing polymers are disclosed in JP-A-64-649.
JP, JP-A-3-102767, JP-A-6-4
As described in Japanese Patent No. 4490, an aqueous dispersion is added to an electrode material (battery active material, conductive carbonaceous material, etc.) to form a paste, and the paste is formed around the current collector to form an electrode. Can be provided with binding properties and water repellency.

When used in batteries, it is desirable to use the fluoropolymer in the form of an aqueous dispersion. As the fluorine-containing polymer, a water-soluble polymer such as polyacrylate or carboxymethylcellulose (CMC) can be mixed and used. Also, after the electrode material is made into a paste without using the aqueous dispersion of the fluoropolymer, or after the paste is pressed against the current collector, the aqueous dispersion of the fluoropolymer is impregnated (the aqueous dispersion in the undried paste). Can the body be impregnated) or can be applied. In a state where the paste or the current collector to which the paste has been pressed is dried to a small extent and the water content is reduced, the fluoropolymer may be impregnated or applied in the form of an organosol.

[0047]

Next, the present invention will be described more specifically based on Preparation Examples and Examples. Example 1 A stainless steel (SUS) having an inner capacity of 6 liters and having a stainless steel anchor-type stirring blade and a jacket for temperature adjustment.
316) Add 2960m of deionized water to the autoclave
1, 3.8 g of potassium perfluorooctanoate, and paraffin wax (manufactured by Nippon Oil Co., Ltd.) as a stabilizer
After 120 g was charged, the atmosphere in the autoclave was replaced three times with nitrogen and twice with TFE to remove oxygen, the internal pressure was adjusted to 1.0 MPa with tetrafluoroethylene (TFE), the stirring speed was set to 250 rpm, and the internal temperature was reduced. Maintained at 70 ° C.

Next, as a chain transfer agent, 200 cc at normal pressure was used.
Ethane and potassium persulfate 300 as a polymerization initiator
A solution of 40 ml of water in which mg was dissolved was charged into the autoclave, and the reaction was started. During the reaction, the temperature in the system was set to 70
C., the stirring speed is maintained at 250 rpm, and the TFE is maintained so that the internal pressure of the autoclave is always maintained at 1.0 ± 0.05 MPa.
Was supplied continuously.

When the amount of TFE consumed in the reaction after the addition of the polymerization initiator reached 1500 g, the supply and stirring of TFE were stopped, and the TFE in the autoclave was discharged to normal pressure to terminate the reaction. . The total reaction time was 8 hours, the concentration of the solid content (approximately equal to the polymer concentration) determined by evaporating a portion of the obtained aqueous dispersion to dryness was 33.0% by weight, and the number average molecular weight of the polymer was It was about 200,000. Dilute nitric acid was added to a part of the obtained aqueous dispersion, and the mixture was coagulated with stirring, and the coagulated polymer was washed.
After drying for an hour, a powder polymer was obtained. This powder polymer did not contain nitrate ions.

Next, 10 parts by weight of the obtained powdery polymer was added to 100 parts by weight of isopropanol,
Ultrasonic waves of 0 watts were irradiated for 30 minutes to prepare an organosol of isopropanol (hereinafter referred to as "organosol 1").

On the other hand, Triton X-100 (Rohm & Haas) is used as a nonionic surfactant in the remaining aqueous dispersion.
(Manufactured by The Company) in an amount of 3.0% by weight based on the weight of the polymer contained, and p
After adjusting the H to 9.0, the water was evaporated under reduced pressure to concentrate the polymer solid content to 60% by weight (hereinafter, referred to as “polymer solid content”).
"Aqueous dispersion 1").

Example 2 Into the same autoclave used in Example 1, 2960 ml of deionized water and C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (C
F ₃ ) 3.0 g of COOK and 120 g of paraffin wax (manufactured by Nippon Oil Co., Ltd.) as a stabilizer, oxygen was removed from the atmosphere in the autoclave in the same manner as in Example 1, and the internal pressure was adjusted to 1.0 MPa with TFE. The stirring speed was kept at 250 rpm and the internal temperature was kept at 85 ° C.

Next, potassium persulfate 2 which is a polymerization initiator is used.
A solution of 20 mg of water in which 0 mg was dissolved and a solution of 20 ml of water in which 400 mg of disuccinic peroxide were dissolved were charged in an autoclave, and the reaction was started.
During the reaction, the temperature in the system was set to 85 ° C and the stirring speed was set to 250 rpm.
m, and keep the internal pressure of the autoclave at 1.0 ± 0.0
TFE was continuously supplied so as to keep the pressure at 5 MPa.

When the amount of TFE consumed in the reaction after the addition of the polymerization initiator reached 1200 g, the supply and stirring of TFE were stopped, and the TFE in the autoclave was discharged to normal pressure to terminate the reaction. . The total reaction time was 12 hours, the concentration of the solid content (approximately equal to the polymer concentration) determined by evaporating and drying a part of the obtained aqueous dispersion was 28.5% by weight, and the number average molecular weight was about 400%. It was 10,000. Dilute nitric acid was added to a part of the obtained aqueous dispersion, and it was coagulated while stirring.
After washing the coagulated polymer, it was dried at 130 ° C. for 16 hours to obtain a powdered polymer. This powder polymer did not contain nitrate ions.

On the other hand, Triton X-100 (Rohm & Haas) was used as a nonionic surfactant in the remaining aqueous dispersion.
6.0% by weight based on the weight of the polymer contained in the solution.
After adjusting the H to 9.0, the water was evaporated under reduced pressure to concentrate the polymer solid content to 60% by weight (hereinafter, referred to as “polymer solid content”).
"Aqueous dispersion 2").

Example 3 In the same autoclave used in Example 1, 2960 ml of deionized water and potassium perfluorooctanoate were used.
0 g and 120 g of paraffin wax (manufactured by Nippon Oil Co., Ltd.) as a stabilizer, and oxygen was removed from the atmosphere in the autoclave in the same manner as in Example 1;
The internal pressure is adjusted to 1.0 MPa with E, and the stirring speed is set to 280 rpm.
m, the internal temperature was kept at 85 ° C.

Next, as a chain transfer agent, 150 cc at normal pressure was used.
Of ethane, 5 g of perfluoro (propylvinyl) ether as a comonomer, and 40 ml of water in which 300 mg of potassium persulfate as a polymerization initiator were charged into the system, and the reaction was started. During the reaction, the temperature in the system was set to 70
C., the stirring speed is maintained at 280 rpm, and the TFE is maintained so that the internal pressure of the autoclave is always maintained at 1.0 ± 0.05 MPa.
Feeded continuously.

When the amount of TFE consumed in the reaction after the addition of the polymerization initiator reached 550 g, supply and stirring of TFE were stopped, and TFE in the autoclave was discharged to normal pressure to terminate the reaction. . The total reaction time was 6 hours, and the concentration of the solid content (approximately equal to the polymer concentration) determined by evaporating a part of the obtained aqueous dispersion to dryness was 15.0% by weight.

Dilute nitric acid was added to a part of the obtained aqueous dispersion and coagulated while stirring. The coagulated polymer was washed and dried at 130 ° C. for 16 hours to obtain a powdery polymer.
This powder polymer did not contain nitrate ions. According to the method described in JP-A-60-240713, the content of perfluoro (propylvinyl) ether in the copolymer was measured and found to be 2.5% by weight, indicating no fiberization ability.

To the remaining aqueous dispersion, 6.0% by weight based on the weight of the polymer containing Triton X-100 (manufactured by Rohm & Haas Company) as a nonionic surfactant was added, and the pH was further adjusted with an aqueous KOH solution. After adjusting to 9.0, water was evaporated under reduced pressure to reduce the polymer solid content to 6%.
0% by weight (hereinafter referred to as "aqueous dispersion 3").
Say).

Comparative Preparation Example 1 An aqueous solution was prepared in the same manner as in Example 2 except that 3.0 g of potassium perfluorooctanoate was replaced by 3.0 g of ammonium perfluorooctanoate and 10 mg of potassium persulfate was replaced by 10 mg of ammonium persulfate. A dispersion was obtained. The number average molecular weight was about 3.5 million. Further, "aqueous dispersion 4" was obtained in the same manner as in Example 1 except that ammonium hydroxide was used instead of potassium hydroxide.

[0062] Example 4 The average particle size 32μm of the hydrogen storage alloy (Santoku Metal Industry Co., _{Ltd., M m Ni 3.5 Al 0.5 Co} 0.7 Mn 0.3) with respect to 100 parts by weight, "aqueous dispersion of 5 parts by weight polymer content The mixture 1) and 15 parts by weight of the aqueous dispersion 2 were mixed and mixed at 10,000 rpm for 20 minutes while cooling with ice water using a homogenizer to prepare a paste. This paste was applied to both sides of a punched metal (made of nickel; thickness 0.07 mm, porosity 38%, hole diameter 1.5 mm) so that the amount of supported alloy was 0.5 g / cm ^2. Then, it was dried at 80 ° C. and pressed at a pressure of 1 ton / cm ² to obtain a sheet.

This sheet was cut into a 3 × 5 cm square, the lead wire was welded to form a negative electrode, combined with a sintered nickel positive electrode via a separator, and immersed in an 8 N aqueous potassium hydroxide solution to prepare a secondary battery. did. The discharge capacity (C ₀ ) after repeating charge and discharge three times was measured. 40
The discharge capacity after standing at 10 ° C. for 10 days was measured, and the ratio (remaining capacity) to C ₀ was determined to be 73%.

Example 5 For 100 parts by weight of the same hydrogen storage alloy as used in Example 1, 5 parts by weight of "Aqueous Dispersion 3" and 5 parts by weight of "Aqueous Dispersion 2" were added as polymer components. Mix and cool with ice water using a homogenizer at 10,000 rpm for 2 hours.
After mixing for 0 minutes, a paste was prepared. A battery was prepared using this paste in the same manner as in Example 4, and the remaining capacity was measured. As a result, it was 70%.

Example 6 To 100 parts by weight of the same hydrogen storage alloy as used in Example 4, 9 parts by weight of "aqueous dispersion 2" as a polymer was mixed, and the mixture was cooled with ice water using a homogenizer. The mixture was mixed at 10,000 rpm for 20 minutes to prepare a paste. This paste was applied on both sides of the same punched metal used in Example 4 as an alloy carrying amount of 0.5 g / cm.
² and then "Organosol 1" is applied so that the polymer content is 1 part by weight based on the alloy.
First, it was dried at room temperature and then at 80 ° C., and pressed at a pressure of 1 ton / cm ² to obtain a sheet. Using this sheet, a battery was prepared in the same manner as in Example 1, and the remaining capacity was measured. The result was 75%.

Comparative Example 1 A battery was prepared in the same manner as in Example 4 except that “aqueous dispersion 4” was used instead of “aqueous dispersion 2”. The remaining capacity of this battery was 53%.

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Claims (9)

[Claims] 1. Fine particles of at least one fluoropolymer selected from the group consisting of tetrafluoroethylene, tetrafluoroethylene-perfluoro (alkylvinyl) ether copolymer and tetrafluoroethylene-hexafluoropropylene copolymer Wherein the reagent used when emulsion-polymerizing the monomer forming the fluoropolymer in an aqueous medium and the reagent added after the polymerization are not ammonium salts or substantially non-ammonium salts. A production method characterized in that it does not contain ammonia. 2. The method according to claim 1, wherein the reagents used in the emulsion polymerization are a polymerization initiator, a polymerization emulsifier and a polymerization stabilizer, and the reagents added after the polymerization are a surfactant and a pH adjuster. Method. 3. The method according to claim 1, wherein an aqueous solution of an alkali metal hydroxide is used as the pH adjuster. 4. The method according to claim 1, wherein an alkali metal salt of an anionic fluorinated surfactant is used as the polymerization emulsifier. 5. A polymerization initiator containing an alkali metal persulfate as a main component as a polymerization initiator, an alkali metal salt of an anionic fluorinated surfactant as a polymerization emulsifier, and an alkali hydroxide as a pH adjuster. The method according to claim 1. 6. The method according to claim 3, wherein the alkali metal salt is a potassium salt. 7. A polymer fine particle powder obtained by separating polymer fine particles from the aqueous dispersion obtained by the production method according to claim 1 by coagulation and drying to obtain a polymer fine particle powder. Of tetrafluoroethylene, tetrafluoroethylene-perfluoro (alkylvinyl) ether copolymer and tetrafluoroethylene, which comprises redispersing the aqueous dispersion in a dispersing solvent mechanically or by ultrasonic waves, or transforming the aqueous dispersion. -A method for producing an organosol of at least one fluoropolymer selected from the group consisting of hexafluoropropylene copolymers. 8. An aqueous dispersion of a fluoropolymer obtained by the production method according to claim 1 or an aqueous dispersion of the fluoropolymer obtained by the production method according to claim 7, wherein the alkaline battery comprises a positive electrode, a negative electrode, and an electrolyte. A battery using a fluorine-containing polymer contained in an organosol obtained by the method as a binder and / or a water repellent for an electrode. 9. The battery according to claim 8, wherein the alkaline battery is a nickel-cadmium or nickel-hydrogen battery.