JP2001110689A - Active carbon raw material for electric double-layer capacitor electrode, and activated carbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active carbon raw material for electric double-layer capacitor, which is suitable for obtaining a high capacitance and activated carbon using the raw material. SOLUTION: Activated carbon raw material for an electric double-layer capacitor electrode is vinylidene chloride copolymer, whose fine crystalline size S is not less than 150 Å and which contains polyvinylidene chloride or vinylidene chloride having a content of not less than 85 mol%. Active carbon for the electrode of an electric double-layer capacitor having high capacitance is obtained, by subjecting the activated carbon material to a carbonization treatment and/or an activation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated carbon raw material for an electric double layer capacitor electrode having a high capacitance and an activated carbon using the same.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been actively reduced in size, a small, highly reliable, high-capacitance capacitor used for a backup power supply has been adopted. In particular, recently, for the practical use of electric vehicles, an electric double-layer capacitor (ADP) has been developed as a new capacitor having a higher capacitance for the purpose of smoothing the load of an auxiliary power supply or a secondary battery for a power supply. (EDLC) is attracting attention.

An EDLC is a capacitor using an electric double layer generated at an interface between a solid and a liquid. The structure comprises a pair of polarizable electrodes sandwiching a separator, a case for accommodating them, an electrolytic solution and a current collector. Activated carbon having a large specific surface area (solidified powder,
Nonwoven fabric, sheet). Normally, as the activated carbon raw material, plant materials such as coconut shells and cellulose, petroleum materials such as coal and petroleum pitch, phenol resins, and resin materials such as polyacrylonitrile (PAN) are used.

On the other hand, as an electrolyte, an aqueous solution such as a sulfuric acid aqueous solution and a potassium hydroxide aqueous solution is used, and an organic solvent such as propylene carbonate (PC) in which a quaternary onium salt is dissolved is used. Often. An aqueous EDLC using an aqueous electrolyte is suitable for low equivalent series resistance (ESR) because of high conductivity of the electrolyte, and is excellent in environmental characteristics without being affected by humidity. Further, an organic EDLC using an organic electrolytic solution has a high withstand voltage, a high energy density, and a feature that it can be miniaturized.

In recent years, EDLC has been able to store a large capacitance or supply a large current, largely due to the use of activated carbon as an electrode material. The capacitance of EDLC greatly depends on the structure and physical properties of the activated carbon, which is the electrode material, and the required properties for the activated carbon include a large specific surface area, conductivity, low internal resistance, and low bulk density. It is big. It is considered that the pore structure such as the pore volume and pore diameter distribution of activated carbon has a great influence on these required characteristics.

As an example of the prior art for controlling the pore structure of activated carbon for the purpose of improving the capacitance of EDLC, Japanese Patent Application Laid-Open No. 7-220 is focused on the pore shape and pore diameter.
Japanese Patent Application Laid-Open No. 7-8598 focusing on activated carbon raw material
The technology of Japanese Patent Application Laid-Open No. 249551 and the technology of Japanese Patent Application Laid-Open No. 9-21589 have already been reported. JP-A-7-2209
According to the technique disclosed in Japanese Patent No. 85, the pores of activated carbon are slit-shaped or elliptical, and the aqueous electrolyte has a water molecule diameter of 1.5 to
An electrode material having pores with a slit width and a slit length that are three times as large is effective. In an organic electrolytic solution, an electrode material having pores having an ion diameter of a solvated ion of the electrolyte solution plus 0.2 nm or more is highly electrostatic. It has been shown to be optimal for high capacity EDLCs.

As a method for producing such activated carbon, there is disclosed a method for producing a porous body in which activated carbon fine particles are sintered with each other by a pulse impact current disclosed in Japanese Patent Application Laid-Open No. 3-78221. Is a special sintering method,
It is not preferable in terms of manufacturing cost and versatility. According to the technique disclosed in Japanese Patent Application Laid-Open No. 7-249551, polyvinylidene chloride resin is used as a raw material for activated carbon and heated at 800 to 1000 ° C. in a non-oxidizing atmosphere (under nitrogen gas N ↓ 2) to produce a large number of fine particles. It is shown that an activated carbon for an EDLC electrode having pores can be obtained. It is an excellent finding that a polyvinylidene chloride resin which easily provides a suitable field for the adsorption of a large number of electrolyte ions by an elimination reaction of hydrochloric acid from a side chain by heat treatment is used as an activated carbon raw material. However, JP-A-7-249551 does not disclose what kind of technique is used as the polyvinylidene chloride resin.

On the other hand, the technology disclosed in Japanese Patent Application Laid-Open No. Hei 9-21589 discloses various types of polyvinylidene chloride resins, specifically, vinylidene chloride homopolymer (described as polyvinylidene chloride or homo-PVDC), vinylidene chloride (VDC), and the like. Copolymer with comonomer (PVDC copolymer or VD
C / (comonomer name) copolymer), and it is important that the content of VDC with respect to the whole activated carbon raw material is 10 to 100% by weight, particularly 80 to 97% by weight. (Hereinafter referred to as Homo PV
DC and PVDC copolymers are collectively referred to as PVDC resins). However, even there, the VD
Only the content of C is specified, and nothing is specified about the definition of the crystallite size of the PVDC resin used as the activated carbon raw material for the electrode for EDLC.

According to the present invention, the crystallite size of the PVDC resin is found to have a great effect on the capacitance of the EDLC as a raw material of activated carbon for the EDLC together with the VDC content. Are polymerization methods, polymerization conditions (types and concentrations of initiators and additives, stirring conditions,
Polymerization temperature, polymerization time, etc.) and post-processing conditions (pulverization conditions, heat treatment, etc.) are greatly affected. As mentioned above,
In order to expand its applications as an auxiliary power supply for electric vehicles, including small backup power supplies for microcomputers and IC memories, EDLC (high capacitance) has a higher capacitance per unit weight or per unit volume. EDL
Despite the demand for (C), no technique has been developed to provide EDLC that satisfies the demand.

[0010]

SUMMARY OF THE INVENTION The present invention provides an activated carbon raw material for EDLC electrodes and an activated carbon for EDLC electrodes, which provide a high capacitance. In order to increase the capacitance of EDLC, it is important to obtain activated carbon having as many pore diameters as possible suitable for the electrolyte ion diameter. PVD
When C resin is used as a raw material for activated carbon, it is considered that if the VDC content in the PVDC resin is increased, the number of pores generated at the time of heating and carbonizing is also increased.
C is considered the best. However, in order to obtain activated carbon having a pore diameter suitable for the electrolyte ion diameter, know-how regarding not only the VDC content in the PVDC resin but also the crystallite size of the PVDC resin is required.

That is, R. A. Wessling, "P
oly Vinylidene Chloride ", G
orden and Break Science
Published by Publishers, pp. 158-172 (197
According to 7), the thermal decomposition process of the PVDC resin consists of the following four processes. These are a polychlorinated acetylene reaction process with dehydrochlorination, a cyclization reaction process by the Diels-Adler reaction between conjugated molecule sequences, a cyclization reaction process with dehydrochlorination, and a graphitization reaction process with dehydrochlorination. As the heating temperature increases, the process proceeds from the process to the process in the order, and carbonizes through the final process.

According to the process described above, the PVDC resin is
Dehydrochlorination in the solid state below the melting point of １９０190 ° C. gives an insoluble char,
It is shown that the pore diameter does not change significantly even when carbonized by heating at 900 ° C. Therefore, it is considered that the PVDC resin should be thermally decomposed as much as possible in this temperature range in order to leave as many fine pores formed by dehydrochlorination as possible. However, it takes a long time to dehydrochlorinate the PVDC resin by heating until an insoluble char is obtained in a solid state below the melting point, which is not industrial. On the other hand, if performed in a temperature range of 200 to 300 ° C. which is higher than the melting point and dehydrochlorination proceeds efficiently, the pore diameter generated in the process cannot be fixed at all, and the ionic diameter of the electrolytic solution,
It is very difficult to obtain activated carbon having a suitable pore size.

[0013]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the pores formed by dehydrochlorination in the above-mentioned polyacetylene conversion reaction, cyclization reaction and graphitization process of PVDC resin. In order to leave as many pore diameters and pore shapes as possible, it was found that (a) the VDC content in the PVDC resin should be increased and (b) the mobility of the PVDC resin molecules should be suppressed. Specifically, as (a), a PVDC resin having a VDC molar content of 85 mol% or more is used as a raw material for activated carbon, and preferably, homo-PVD is used.
C, and (b) using a crystalline PVDC resin having a crystallite size S of 150 ° or more, and finding that a PVDC resin that satisfies both conditions can be used as an activated carbon raw material for an EDLC electrode. The present invention has been completed.

That is, the present invention provides an ED that provides a high capacitance.
An object of the present invention is to provide an activated carbon material for an LC electrode and an activated carbon for an EDLC electrode using the same as a main material. Activated carbon for an electric double layer capacitor electrode, characterized in that it has a microcrystalline size S of 150 ° or more and contains polyvinylidene chloride or a vinylidene chloride copolymer having a molar content of vinylidene chloride of 85 mol% or more. Provide raw materials. Further, the present invention provides an activated carbon for an electrode of an electric double layer capacitor, which is obtained by carbonizing and / or activating the activated carbon material described above. Further, using a mixed solution of an organic solvent which swells or dissolves part or all of the activated carbon raw material described above, an aqueous solution of an alkali metal hydroxide or an alkaline earth hydroxide, and an alcohol and / or an ether at 100 ° C. The present invention provides an activated carbon for an electrode of an electric double layer capacitor, which is obtained by performing carbonization treatment and / or activation including a step of dehydrochlorination treatment below.

The details will be described below. (I) Activated carbon raw material for EDLC electrode The most important thing in the present invention is to use a PVDC resin satisfying both of the following two raw material conditions as a part, preferably all, as an activated carbon raw material. That is, the PVD of the present invention
The activated carbon raw material mixed with the C resin is not particularly limited as long as it is a carbon source usually used as an activated carbon raw material. For example, Kodansha, “New Activated Carbon-Basics and Applications”, by Yuzo Sanada, Motoyuki Suzuki, Kaoru Fujimoto, page 55 (1998), plant-based raw materials (wood, fruit shells, etc.), mineral-based Raw materials (peat, coal tar, coke, etc.), other raw materials (polyvinyl halide, polyvinylidene halide, rayon, phenol resin, acrylic resin, etc.) and their carbides, or those disclosed in JP-A-9-21589. Wood, wood flour, sawdust, sawdust dry distillate, charcoal,
Coconut coconut shell, palm coconut shell, walnut shell, fruit seed, by-products during pulp production, bacas, molasses, peat, peat coal, lignite, lignite, bituminous coal, anthracite, peat coal, petroleum distillate residue, petroleum pitch, coal pitch, Wood-based raw materials such as coke and coal tar, fossil-based raw materials, mineral-based raw materials and their carbonized and activated products;

Phenolic resin, polyvinyl chloride, melamine resin, urea resin, resorcinol resin, celluloid,
Epoxy resin, xylene resin, polysulfone, allyl resin, alkyd resin, fluororesin, silicon resin, polystyrene, polyamide, polyimide, polyamideimide, polyarylate, vinyl acetate resin, coumarone resin, ketone resin, phenoxy resin, butadiene resin, polycarbonate, Polyvinyl alcohol and their derivatives, polyphenylene oxide, polyphenylene sulfide,
Polymethylpentene, polysulfone, various ion exchange resins, various cellulose derivatives, polyglutamic acid, polyterpene, cellophane, poly-α-methylstyrene, cyclopentadiene-based resin, polybutylene, polybutadiene,
Polychloroprene, maleic acid resin, phthalic acid resin, fumaric acid resin, poly p-hydroxybenzoic acid, synthetic wood,
Synthetic resins such as synthetic pulp, carboxyvinyl polymer, polyacetylene, polyvinyl butyral, polyvinyl formal, methacrylic resin, acrylic resin, polyurethane, polyester, polyethylene, polypropylene, polyethylene glycol, polypropylene glycol, polytetraethylene glycol and polyhexaethylene glycol And the like.

(Raw material condition 1) As a PVDC resin, a homo PVDC or a PVDC having a VDC molar content of 85 mol% or more is used.
That is, it is a VDC copolymer. A PVDC copolymer having a VDC molar content of 90 mol% or more. It is particularly preferable to use homo-PVDC. In the raw material condition 1, the higher the VDC molar content in the PVDC resin,
This is a condition relating to a high possibility that the capacitance of the finally obtained EDLC is high because the number of pores generated by the dehydrochlorination reaction increases.

As a comonomer copolymerized with the VDC component of the PVDC copolymer (referred to as VDC / (comonomer name) copolymer), a comonomer copolymerized with VDC can be used. For example, ethylene, acetylene,
Propylene, butylene, butyne, butadiene, isoprene, isobutylene, vinyl chloride (VC), vinyl bromide,
Vinyl iodide, vinyl acetate, vinyl methyl ether, vinyl ethyl ether, vinyl isopropyl ether, vinyl propyl ether, vinyl isobutyl ether, vinyl normal amyl ether, vinyl isoamyl ether, vinyl-2-ethylhexyl ether, vinyl-n
Octadecyl ether,

Sodium vinyl sulfonate, divinylbenzene, vinyltoluene, acrylonitrile (AN),
Acrylic acid, acrylic acid chloride, acrylic acid bromide, acryloganamin, acryloylmorpholine,
Methyl acrylate (MA), ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate (BA), isobutyl acrylate, te acrylate
rt-butyl, hexyl acrylate, cyclohexyl acrylate, methylpropyl acrylate, lauryl acrylate, tridecyl acrylate, benzyl acrylate, n-amyl acrylate, isoamyl acrylate, tetrahydrofurfuryl acrylate, dimethylaminoethyl acrylate , Ethylene glycol ethoxylate acrylate, ethylene glycol methacrylate acrylate, diethylene glycol ethoxylate acrylate, diethylene glycol methoxy acrylate, ethylhexyl acrylate, epoxy acrylate, acrylates of pentaerythritol, n-stearyl acrylate, dipentaerythritol Acrylates of trimethylolpropane, caprolactone Acrylic acid esters, acrylic acid esters of neopentyl glycol, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 1,4
-Butanediol diacrylate, 1,6-hexanediol diacrylate, glycidyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, diacrylic acid
1,3-butylene glycol,

Sodium acrylate, potassium acrylate, aluminum acrylate, zinc acrylate, calcium acrylate, magnesium acrylate, acrylamide, N, N-dimethylacrylamide, N, N-dimethylpropylacrylamide, acrolein, methacrylic acid, methacrylic Acid chloride, methacrylic bromide, methyl methacrylate (MMA), ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, hexyl methacrylate,
Cyclohexyl methacrylate, methylpropyl methacrylate, lauryl methacrylate, tridecyl methacrylate, benzyl methacrylate, n-amyl methacrylate,
Isoamyl methacrylate, tetrahydrofurfuryl methacrylate, dimethylaminoethyl methacrylate,

Ethylene glycol methacrylate ethoxylate, ethylene glycol methacrylate methacrylate, diethylene glycol methacrylate methacrylate, diethylene glycol methacrylate methacrylate, ethylhexyl methacrylate, epoxy methacrylate, methacrylates of pentaerythritol, n-stearyl methacrylate, Pentaerythritol methacrylates, trimethylolpropane methacrylates, caprolactone-modified methacrylates, neopentyl glycol methacrylates, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate 1,4-butanediol dimethacrylate, 1 6- hexanediol dimethacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, dimethacrylate diethylene glycol, triethylene glycol dimethacrylate, dimethacrylate tetraethylene glycol dimethacrylate, -
1,3-butylene glycol,

Sodium methacrylate, potassium methacrylate, aluminum methacrylate, zinc methacrylate, calcium methacrylate, magnesium methacrylate, methacrylamide, N, N-dimethyl methacrylamide, N, N-dimethylaminopropyl methacrylamide, methacrolein , Sodium methallylsulfonate,
Potassium methallyl sulfonate, styrene, methyl styrene, vinyl pyridine, hydroxyethyl vinyl acetate, hydroxyethyl vinyl acetate ester, derivatives such as ether and urethane, allyl alcohol, allyl chloride, sodium allyl sulfonate, allylamine, allylaldehyde, allyl Bromide, allyl glycidyl ether, allyl caproate, allyl popper oil, allyl diglycol carbonate, allyl methacrylate, allyl adenine, allyl adenosine, allyl amino purine, allyl amino ribofuranosyl purine, glycerol diaryl ether, dicyclopentadiene,
Chloroprene, cyclohexene, α-methylstyrene,

Polymerizable silicon compounds, polymerizable fluorine compounds, maleic acid, maleic acid derivatives, fumaric acid, fumaric acid derivatives, crotonic acid, crotonic acid derivatives, oleic acid, oleic acid derivatives, itaconic acid, itaconic acid derivatives, crotonaldehyde , Chloroethyl vinyl ether, diallyldimethylammonium chloride, diallyldimethylammonium bromide, diallyldimethylammonium iodide, allylpyridinium chloride, allylpyridinium bromide, allylpyridinium iodide, diisobutylene, diethyleneglycolbisallylcarbonate, unsaturated carboxylic acids and derivatives thereof, Unsaturated aldehyde, unsaturated alkyls, N-phenylmaleimide, N-methylphenylmaleimide, N-
Cyclohexylmaleimide, other N-substituted maleimides and the like are mentioned as typical examples.

The PVDC resin may be in the form of a powder, an aqueous dispersion of the PVDC resin (latex), a solution of the PVDC resin dissolved in an organic solvent, or a cellulose or PAN impregnated with the latex or solution. Fiber or non-woven fabric may be dried. Preferably, 7
A fine powder state of 5 μm or less (particularly preferably 25 μm or less) or a fiber or nonwoven fabric state impregnated and dried with a PVDC resin is suitable from the viewpoint of suppression of foaming during heating carbonization, efficiency of carbonization treatment and the like. In addition, although there is no particular limitation on the molecular weight of the PVDC resin, polymerization of ordinary PVDC resin (emulsion polymerization,
Suspension polymerization, solution polymerization, etc.)
What is necessary is to use the thing of about 100,000.

(Raw material condition 2) The crystallite size S of the PVDC resin is 150 ° or more, preferably 200 ° or more, more preferably 300 ° or more. This raw material condition 2 is based on PV
This is a condition for suppressing the mobility of PVDC resin molecules in order to leave as many pore diameters and pore shapes as possible during heating carbonization and graphitization of pores generated in the process of dehydrochlorination of the DC resin.

(2) How to determine VDC molar content of PVDC resin VD in PVDC resin described in raw material condition 1 of the present invention
The method for determining the C mole content is described in the method described in “New Edition Polymer Analysis Handbook”, published by Kinokuniya Shoten, edited by the Japan Society for Analytical Chemistry and Polymer Analysis Research Council, pages 660-665 (1995) (oxygen flasks). Combustion method). That is, PV
After wrapping about 8 to 35 mg of the DC resin in a filter paper for quantitative measurement and attaching it to a platinum holder, the mixture is instantaneously and completely burned at about 950 ° C. under an oxygen atmosphere in a flask containing an absorbing solution to absorb generated hydrogen chloride. After that, nitric acid and sodium nitrate are added thereto, and the mixture is boiled. After allowing to cool, potentiometric titration is performed using a silver nitrate solution. However, when the PVDC resin is polymerized, if the polymerization yield is 99% or more, the composition ratio of the charged monomer may be the same as the result obtained by the above method.

(3) Method for Obtaining Fine Crystal Size S of PVDC Resin Next, a method for obtaining the fine crystal size S of the PVDC resin described in the raw material condition 2 of the present invention will be described below with reference to FIG. The crystallite size S of the PVDC resin referred to in the present invention is determined based on a crystallite size calculation method commonly used in crystal structure analysis of a crystalline polymer. That is, if the PVDC resin is crystalline, under the following X-ray diffraction measurement conditions, “Poly
mer Journal ", Volume 20, Issue 10, 883-8
Lattice constants a = 6.71 °, b = 4.68 °, c = 1 in the crystal structure of homo PVDC shown on page 93 (1988).
Under a monoclinic system of 2.51 ° and β = 123 degrees, the scattering angle 2θ = 15 to 17 degrees and the (100) plane and (−102) plane of the PVDC resin [(100) plane, hereinafter abbreviated. ). 2θ of scattering peak 1 = 9
A straight line connecting the low-angle valley A appearing at ~ 15 degrees and the high-angle valley B appearing at 2θ = 17-21 degrees is the baseline AB.
The spread of the scattering angle 2θ of the scattering peak 1 corresponding to の of the height of the scattering intensity (count) of the scattering peak 1 measured from the baseline AB is calculated as the half width W of the scattering peak 1.
(Calculation is performed in radians) and is calculated by the following equation (1). S = [0.9 × λ × (W ² −w ² ) ^0.5 ] / cos θ (1) [where λ is the wavelength of the characteristic X-ray CuKα ray used for measurement is 1.54 °, and W is W is the half width of the scattering peak 1 (in radians), w is the half width of the scattering peak of the (111) plane, which appears at 2θ = 28.4 degrees of the standard single crystal silicon powder Si used as the spread of the optical system. (Radian units), and θ is the black angle of scattering peak 1. ]

[X-ray Diffraction Measurement Conditions] As an X-ray diffractometer, a diffractometer system (with multiple peak separation software) equipped with a curved type monochromator of Rotaflex RU-200 manufactured by Rigaku Corporation was used. The measurement conditions were as follows: X-ray generator output, 40K using Cu-Kα ray.
V, 120 mA, divergence slit 1 degree, solar slit 1 / degree, light receiving slit 0.3 degree, measurement range 2θ = 5-3
The measurement is performed using the powdered PVDC resin under the condition of 0 degree (in the case where multiple components such as an amorphous PVDC resin and a carbide are mixed, the measurement range is 2θ = 5 to 60 degrees). In addition, PVD
In the case where scattering from other than the (100) plane of the PVDC resin appears in the measurement range 2θ = 5 to 30 degrees of the C resin (for example, when other substances are mixed or (10
(0) A scattering peak other than the plane or a scattering peak due to the amorphous phase of the PVDC resin appears), according to an analysis method usually performed in the measurement of the crystallite size, between the scattering peak 1 of the (100) plane and the other scattering peaks. After peak separation, PVD
What is necessary is just to calculate the crystallite size S based on the scattering peak 1 of the (100) plane of the C resin.

(4) Example of Method for Producing Activated Carbon Raw Material for EDLC Electrode A method for producing a PVDC resin as an activated carbon raw material for an EDLC electrode may be, for example, a suspension polymerization method or an emulsion polymerization method under the following conditions. . In addition, PV having a large crystallite size S
The suspension polymerization method is suitable from the viewpoint of producing DC resin powder, and the emulsion polymerization method tends to be suitable from the viewpoint of producing fine powdered PVDC resin powder having high carbonization efficiency. Hereinafter, an example of a polymerization method for obtaining a powdered PVDC resin will be described. When an aqueous dispersion state of the PVDC resin is used, a slurry or an aqueous dispersion obtained before drying in each polymerization method may be used. . When using a solution state or a state impregnated in a fiber or nonwoven fabric, tetrahydrofuran (THF), 1,4
Solvents for PVDC copolymers such as dioxane, cyclohexane, cyclopentanone, chlorobenzene, dichlorobenzene, dimethylformamide (DMF), methyl ether ketone (MEK), and ethyl acetate (homo-PVD
C swelling reagent), hexamethylphosphoramide, tetramethylene sulfoxide, N-acetylpiperidene, N
-Methylpyrrolidone, N-formylhexamethyleneimine, trimethylene sulfide, Nn-butylpyrrolidone, isopropylsulfoxide, N-formylpiperidin, N-acetylpyrrolidin, N, N-dimethylacetamide A powdered PVDC raw material obtained by the following polymerization method may be partially or entirely dissolved in a homo PVDC solvent such as cyclooctanone, cycloheptanone, n-butylsulfoxide and the like, and used.

Examples of Suspension Polymerization Method Examples of the suspension polymerization method include adding a suspending agent [eg, hydroxypropylmethylcellulose (HPMC)] to a glass-lined reactor equipped with a stirrer in an amount of 0.01 to 0.1 part. (A part used in the following description is a total polymerized monomer of 10 parts.
100 parts of deionized water in which each component is dissolved) is added.
Replace with nitrogen at ° C. Then, a polymerization initiator [for example, diisopropyl peroxydicarbonate (IPP)]
In the case of homo-PVDC, VDC alone was dissolved in 0.01 to 0.9 parts, and VDC and VDC were used in the case of PVDC copolymer.
A mixture of a comonomer copolymerized with C (the VDC molar content in the finally obtained PVDC copolymer is 85 mol%
100 parts of each monomer component is adjusted as described above), and the inside of the reactor is heated to a temperature at which the polymerization initiator reacts (for example, 30 to 80 ° C.) to start the polymerization reaction.
After the polymerization reaction is sufficiently performed under stirring (the polymerization reaction can be performed at several stages of temperature), the unreacted monomer is recovered,
After cooling, the slurry of the PVDC resin is taken out. The obtained slurry is subjected to a centrifugal dehydrator to dehydrate water, and then dried at 40 to 80 ° C. using a hot air drier to obtain a powdery PVDC resin.

Examples of Emulsion Polymerization On the other hand, examples of emulsion polymerization include, in a glass-lined pressure-resistant reactor equipped with a stirrer, 100 to 600 parts of water, a polymerization initiator [eg, sodium persulfate] 0.01 to 10
Parts, emulsifier [eg, sodium alkyl sulfonate]
After charging 0.1 to 1.0 part and degassing, the temperature of the content is raised to a temperature at which the polymerization initiator reacts (for example, 30 to 80 ° C.), and the temperature is maintained. The polymerized monomer is metered and mixed in a separate container to form a monomer mixture. 1 to 20 parts of the monomer mixture are added all at once into the pressure-resistant reactor, and the mixture is polymerized with stirring until the internal pressure of the reactor drops. Subsequently, the remaining amount of the monomer mixture is removed for a predetermined time (for example, 1 to 40).
A polymerization reaction (referred to as a seed addition polymerization) is performed while continuously adding a fixed amount over a period of time. Note that the entire amount of the monomer mixture may be added at once (called batch polymerization. In the case of a PVDC copolymer, the composition is difficult to be uniform depending on the combination of monomer types used). During the polymerization, the reaction temperature is maintained while stirring the contents, and the reaction is allowed to proceed until the internal pressure is sufficiently reduced, thereby obtaining an aqueous dispersion of a PVDC resin (PVDC resin latex). PVDC obtained
A powdery PVDC resin can be obtained by salting out the resin latex using a salting-out agent (for example, calcium chloride) to precipitate the PVDC resin, washing with water and drying.
However, there are no restrictions on the polymerization conditions, and a PVDC resin that satisfies both the raw material conditions 1 and 2 cannot be obtained only by performing polymerization as described above.

[Copolymer composition in case of PVDC copolymer]
For example, regarding the polymerization composition of the PVDC copolymer,
When a copolymer having a crosslinkability (for example, a comonomer having two or more unsaturated bonds such as divinylbenzene, acrylamide and glycidyl methacrylate) is reacted with 1 to 10 mol% as a copolymer to be copolymerized with In some cases, PVDC resin cannot be obtained.
Further, as a copolymer copolymerized with VDC, a comonomer having one unsaturated bond, for example, VC, AN, MM
Even when 1 to 10 mol% of A, MA, MAN or the like is reacted, a crystalline PVDC resin is obtained, but the raw material condition 2 may not be satisfied. Specific examples of polymerization conditions are shown in Examples, but the present invention is most characterized by using a PVDC resin that satisfies both raw material conditions 1 and 2 as a main activated carbon raw material.

(5) Activated carbon for EDLC electrode and method for producing the same [Activated carbon for EDLC electrode] An activated carbon raw material using a part, preferably all of a PVDC resin satisfying both of the raw material conditions described in (I) is as follows. Activated carbon for an electric double layer capacitor electrode obtained by carbonization (dehydrochlorination carbonization or heat carbonization and / or activation) according to [Activated carbon production process]. Particularly preferably, (a) the activated carbon for water-based EDLC is activated carbon obtained by subjecting homo PVDC satisfying the raw material conditions to carbonization according to the following [a or b in the activated carbon production process]. (b) The activated carbon for the organic EDLC is an activated carbon obtained by subjecting homo PVDC satisfying the raw material conditions to dehydrochlorination carbonization and heating carbonization according to the following [c of the activated carbon production process].

The activated carbon obtained as described above may be optionally coated with carbon black or vapor grown carbon fiber (VGC) in order to suppress the internal resistance and further increase the capacitance.
F) or other conductive fillers, additives containing transition metal ions, and noble metal oxides such as ruthenium oxide (RuO ₂ ) can be mixed. Such activated carbon is also included in the present invention.

[Example of Method for Producing Activated Carbon] In the method for producing activated carbon of the present invention, a PVDC resin satisfying both of the two raw material conditions of the present invention was obtained from Kodansha Publishing, "New Activated Carbon-Basic and Application", Yuzo Sanada. It is obtained by performing a carbonization treatment and / or an activation treatment according to a conventional activated carbon production method as shown in Motoyuki Suzuki and Kaoru Fujimoto, pp. 44-77 (1998). (i) Carbonization treatment For example, as the carbonization treatment, (a) a non-oxidizing atmosphere (N ₂ ,
Inert gas such as argon) or in an acidic atmosphere (water vapor H
₂ O, carbon dioxide gas CO ₂ etc.)
Min, 500-1000 ° C (preferably 600-900 ° C)
° C) for 1 minute to 120 minutes (preferably 30 minutes to 120 minutes)
Minutes), or (b) calcining and pulverizing the PVDC resin at 200 to 500 ° C. in a non-oxidizing atmosphere as described in JP-A-9-74053. After pressure molding, 500-900
It is obtained by performing a heating carbonization treatment at ℃.

As another method, (c) PV
A mixed solution of a DC copolymer solvent (homo-PVDC swelling reagent) or a homo-PVDC solvent, an aqueous solution of an alkali metal hydroxide or an alkaline earth hydroxide, and an alcohol (eg, methanol) and / or an ether. Using,
After performing a dehydrochlorination treatment (hereinafter simply referred to as an alkali solution treatment) once at 100 ° C. or lower for 1 minute to 2 weeks (at this time,
Alkali chloride and alkaline earth chloride generated by the dehydrochlorination reaction are formed on the surface and inside of the pores of the dehydrochlorinated product. If necessary, if these salts are left,
Organic EDL to act as activator during heat carbonization
An activated carbon having a high capacitance can be obtained as the activated carbon for the C electrode.) Then, the activated carbon may be obtained by further performing a heating carbonization treatment under the conditions (a) described above. In particular, according to the method for producing an activated carbon of a PVDC resin of (c), activated carbon for EDLC having an optimum pore diameter and pore distribution for an organic EDLC is 100%.
It can be easily obtained at a low temperature of not more than ℃. If necessary, the activated carbon obtained as in (a) to (c) may be further subjected to a normal activation treatment in order to optimize the ion diameter of the electrolytic solution used for EDLC.

(Ii) Activation Treatment As the activation treatment, (a) an activation gas such as H ₂ O, CO ₂ , hydrogen chloride, carbon monoxide, and O ₂ and a mixed gas containing these activation gases as main components are used. (B)
Activation treatment using alkali hydroxide, alkaline earth hydroxide, alkaline carbonate, alkaline earth carbonate, alkali salt, alkaline earth salt, boric acid, phosphoric acid, sulfuric acid, hydrochloric acid, zinc chloride, etc. Can be

(6) Method for Identifying Activated Carbon The method for identifying activated carbon of the present invention obtained according to the above-mentioned [Method for producing activated carbon] is a method for measuring pore distribution by a gas adsorption method which is widely used as an identification method for activated carbon. Method.
The pore distribution was measured by a constant volume gas adsorption method OMNISORP-100cx manufactured by COULTER (detection gas was CO ₂ , and degassing was performed at 250 ° C. for 3 hours as a pretreatment, and then measurement was performed. ). FIG. 2 shows a measurement example of the pore distribution of the activated carbon of Examples 1 and 4 of the present invention. The method of calculating the pore distribution is Horva.
Calculated using the th-Kawazoe method (HK method).
However, since there is no strict identification method for activated carbon, other identification methods such as an X-ray diffraction method and a transmission electron microscope (TEM) method can be used as necessary.

(7) Method for producing EDLC and method for measuring capacitance (i) [Method for producing EDLC] An EDLC for evaluation using the activated carbon of the present invention was produced by the following method. First, the PVDC resin shown in the present invention is calcined in a tubular furnace at 700 ° C. for 1 hour in a N ₂ atmosphere (heating rate: 10 ° C./min, cooling is natural cooling), and then using a pulverizing mill. It was pulverized to 75 μm or less. Next, 2% by weight of polytetrafluoroethylene (PTFE) latex was added as a binder to about 40 mg of the calcined fine powder, and the mixture was kneaded in an agate mortar, and then water was removed (dried at 120 ° C. for 2 hours with a hot air dryer). ), Then 40-50mg
(Per single pole) kneaded material using a tableting machine to about 2t /
Pressure molding (adjusting the molding pressure so that the specific gravity of the electrode is 0.9 to 0.6, particularly preferably 0.8 to 0.7) with a pressure of cm ² (per one side of the electrode) A tablet-like electrode for EDLC having a thickness of 10 mm and a thickness of about 1 mm was obtained. Subsequently, in the case of a water-based EDLC, the above-mentioned electrode for EDLC was placed in a 30% sulfuric acid aqueous solution having the same concentration as the electrolytic solution, subjected to boiling impregnation for 1 hour, and further vacuum impregnated using an aspirator for 24 hours. The boiling and vacuum impregnation were continued until the weight of the activated carbon after the electrolyte impregnation became about 1.6 times or more the weight before the impregnation. After vacuum impregnation, excess electrolyte was removed by filtration to obtain an electrode impregnated with the electrolyte.

Further, two electrodes impregnated with the electrolytic solution were
The separator was faced via a microporous polyethylene separator (H-1100A manufactured by Asahi Kasei Corporation) having a thickness of 0.1 μm.
Platinum plate (collector plate) with bipolar insulation at a pressure of / cm ²
The water-based EDLC was assembled. On the other hand, also in the case of an organic type, work was performed in an Ar box to prevent the adsorption of moisture, and 1M (C ₂ H ₅ ) ₄ NB was used as an electrolytic solution.
An organic EDLC was assembled in the same manner as the aqueous system except that a PC solution containing F ₄ as a solute was used.

(Ii) [Measurement Method of Capacitance] The capacitance was measured by a constant current discharging method in which the battery was discharged at a constant current and was determined from a change in voltage with respect to the charge amount. That is,
Water-based EDLC is a constant current charge of 20 mA at 0.8 V (about 5
After charging for 1 hour and holding the voltage for 1 hour, a constant current discharge at 20 mA was performed, and the terminal voltage at the time of discharging was 0.25 V
The capacitance was calculated by measuring the time required to reach. On the other hand, in the case of an organic EDLC, after performing a constant voltage charge at 2.5 V for 15 minutes, a constant current discharge at 3 mA is performed until the EDLC electrode terminal voltage at the time of discharge reaches 0.575 V. Was measured and the capacitance was calculated.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. [Polymerization of PVDC Resin] The PVDC resin as the activated carbon raw material used in the present Examples and Comparative Examples was polymerized as follows. Example by suspension polymerization method The PVDC resins of Examples 1 and 2 were produced by using the suspension polymerization method. That is, 100 parts of deionized water in which 0.03 part of a suspending agent HPMC was dissolved was charged into a glass-lined reactor equipped with a stirrer, and after stirring was started at a rotation speed of 60 rpm, the system was purged with nitrogen at 30 ° C in the system. Thereafter, 0.16 parts of a polymerization initiator IPP was dissolved. In the case of homo PVDC-a, VDC alone was used (Example 1), and in the case of a PVDC / VC copolymer, a mixed solution of VDC and VC was used (Example 2). After adjusting the amount of each monomer component so that the VDC molar content in the finally obtained PVDC resin was 85 mol% or more, 100 parts of all monomers were added. After stirring at 30 ° C. for 30 minutes, the temperature inside the reactor is raised to 45 ° C. at which the polymerization initiator reacts to start the polymerization reaction. After the polymerization reaction was carried out for 15 hours under stirring, the temperature inside the reactor was further raised to 55 ° C. (heating rate: 10 ° C./hour), and the polymerization reaction was carried out for 11 hours (since the polymerization yield was at least 99%). The resulting PVDC resin composition is
It may be the same as the charged monomer composition). After the completion of the polymerization reaction, the temperature was lowered and the slurry was taken out. The obtained slurry was subjected to a centrifugal dehydrator to dehydrate water, and then dried at 60 ° C. using a hot-air dryer to obtain a powdery PVDC resin (PVDC resins of Examples 1 and 2). . continue,
170 ° C. of the PVDC resin powder of Example 2 under N ₂ atmosphere
After heating and melting once in the same manner, the temperature was lowered under the same atmosphere, and the recrystallized product was freeze-pulverized, and had the same composition and molecular weight as those of Example 2, and differed only in the crystallite size S.
C resin powder was obtained.

Example Using Emulsion Polymerization On the other hand, an example using emulsion polymerization (homo-PVDC of Example 1)
-B, homo-PVDC-c of Comparative Example 1, Examples 3, 3, and 4) were 100 parts of water in a glass-lined pressure-resistant reactor with a stirrer (Example 3, Comparative Example 1). Example 3, Comparative Example 4) 550 parts (Homo PVDC-b of Example 1, homo PVDC-c of Comparative Example 1),
0.15 parts of polymerization initiator sodium persulfate (in the case of homo-PVDC-b of Example 1, Example 3, Comparative Example 3, Comparative Example 4), 0.87 parts (in the case of homo-PVDC-c of Comparative Example 1) ), 0.3 part of an emulsifier sodium alkyl sulfonate was charged, and after degassing, the temperature of the content was raised to 50 ° C. at which the polymerization initiator reacts, and the temperature was maintained. In a separate container, the polymerization monomer is weighed and mixed, and the monomer mixture 100
Prepare a copy. That is, in the case of homo PVDC-b, VDC
Alone (Example 1), PVDC / AN copolymer, VDC / MA copolymer and VDC / MAA copolymer in Example 3 for VDC and AN, VDC and MA, VDC and MM, respectively.
In the case of the PVDC / AN copolymer of Comparative Example 3, the monomer A is in a molar content ratio of 90 mol% and 10 mol%.
VDC / MA / BA / MMA of Comparative Example 4 at a molar content ratio of DC and AN monomer of 87 mol% and 13 mol%
In the case of a copolymer, the molar content ratio of monomers of VDC, MA, butyl acrylate (BA) and MMA is 45, respectively.
The amounts of the monomer components are adjusted in the proportions of mol%, 34 mol%, 10 mol%, and 11 mol%, and 100 parts of all monomers are prepared.

In the polymerization reaction, 7 parts of the monomer mixture were added all at once to the pressure-resistant reactor, and the mixture was polymerized under stirring until the internal pressure of the reactor dropped (nucleation). Subsequently, the polymerization reaction was carried out while continuously adding a fixed amount of 93 parts of the remaining amount of the monomer mixture over a predetermined period of 10 hours. During the reaction, the reaction temperature was maintained while stirring the contents, and the reaction was allowed to proceed until the internal pressure was sufficiently reduced, whereby an aqueous dispersion of a PVDC resin (PVDC resin latex) was obtained. The obtained PVDC resin latex was salted out using a salting-out agent and calcium chloride, and the PVDC resin was precipitated, washed with water, and dried at 60 ° C., whereby the homo-PVDC-b of Example 1, Comparative Example 3, Example 3, Comparative Example 4
(Polymerization yield of each PVDC resin is 99%, and the composition of the resulting PVDC resin may be the same as the charged monomer composition). Obtained
The crystallite sizes for all samples are shown in Table 1. In addition, the sample of Comparative Example 4 was amorphous and (10%) of PVDC resin.
Although there is no peak derived from the 0) plane, an area where 2θ is 5 to 60 degrees is measured and formally 5 to 30 degrees (peak 15.9).
Degrees), 10 to 40 degrees (peak 22.8 degrees), 15 to 55
The half value width of the peak at 5 to 30 degrees (peak 15.9 degrees) of the three peaks separated at 35.5 degrees (peak 35.5 degrees) is shown as a reference value.

[Alkaline solution treatment] Homo-PV of Example 1
DC-a and the PVDC resin of Comparative Example 1 were each treated with an alkaline solution to obtain a dehydrochlorination product of Example 4 and a dehydrochlorination product of Comparative Example 4. That is, as a dehydrochlorination carbonization treatment according to [c of the activated carbon production process], KOH, THF (Homo P
VDC swelling reagent), water, and methanol are 20% by weight, 20% by weight, 20% by weight, and 40% by weight, respectively.
About 20 using a homogeneous mixed solution of alkali metal hydroxides
C. (room temperature), dehydrochlorination carbonization was performed once in about 24 hours (at this time, according to electron beam microanalyzer analysis,
Potassium chloride (KCl) was formed on the pore surface and inside of the product obtained by the dehydrochlorination treatment).

[Carburizing treatment]

BEST MODE FOR CARRYING OUT THE INVENTION The PVDC resins obtained in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 obtained by [Polymerization of PVDC resin] Was treated with an alkaline solution, and the dehydrochlorinated product of Example 4 and the dehydrochlorinated product of Comparative Example 4 were subjected to N2 treatment using a tubular electric furnace.
_{In two} atmospheres, the temperature was raised to 700 ° C. at a rate of 10 ° C./min, kept at 700 ° C. for 30 minutes, carbonized, and then allowed to cool naturally to obtain the desired activated carbon.

[0047]

Example 1 and Comparative Example 1 As a PVDC resin used as a raw material for activated carbon, homo-PVDC-a having a crystallite size S = 271 ° was used.
The capacitance of the aqueous EDLCs produced using activated carbon obtained by carbonizing homo PVDC-b with S = 152 ° is 120
F / g and 105 F / g (Example 1). But,
The electrostatic capacity of the aqueous EDLC similarly manufactured using homo PVDC-c with S = 21 ° was 43 F / g (Comparative Example 1). Thus, it can be seen that even with EDLCs using the same homo PVDC, a large difference occurs in the capacitance obtained due to the difference in the crystallite size S.

[0048]

Example 2 and Comparative Example 2 A VDC / VC copolymer having a crystallite size S = 244 ° and a VDC molar content of 85 mol% was obtained by carbonization in the same manner as in Example 1 as a PVDC resin. The capacitance of the aqueous EDLC produced using activated carbon was 86 F / g (Example 2). However, S = 9
A water-based EDLC similarly prepared using a VDC / VC copolymer having a 2% VDC molar content of 85 mol% had a capacitance of 57 F / g (Comparative Example 2). Thus, PVD
Even in the case of the C copolymer, there is a large difference in the capacitance obtained due to the difference in the crystallite size S as in the relationship between Example 1 and Comparative Example 1, and the higher the VDC molar content is,
It can also be seen that the capacitance tends to increase.

[0049]

Example 3 and Comparative Example 3 As PVDC resin, VD having microcrystal size S of 155, 159, and 152, respectively.
A copolymer of VDC and a comonomer component of AN, MA, and MMA each having a C mole content of 90 mole% (VDC / An
And VDC / MA copolymer, VDC / MMA copolymer), and the water-based EDLC produced using activated carbon carbonized in the same manner as in Example 1 has a capacitance of 82 F /
g, 85 F / g and 81 F / g (Example 3). As described above, when the VDC molar content and the crystallite size S have substantially the same value, it is found that the capacitance hardly depends on the type of comonomer. Also, as PVDC resin, amorphous,
VDC having a VDC molar content of 45 mol% and MA, BA,
A water-based EDLC produced using an activated carbon carbonized in the same manner as in Example 1 using a copolymer of MMA (VDC / MA / BA / MMA copolymer) had a capacitance of 40 F / g (comparative). Example 3). As described above, the activated carbon obtained by carbonizing the PVDC resin having neither the VDC molar content nor the crystallite size S satisfy the raw material conditions of the present invention has no capacitance.

[0050]

Example 4 and Comparative Example 4 Homo PVDC-a of Example 1
And the dehydrochlorinated product of Example 4 and the dehydrochlorinated product of Comparative Example 4 obtained by treating the PVDC resin of Comparative Example 1 with an alkaline solution, respectively, and heated at 700 ° C. in an N ₂ atmosphere in the same manner as in Example 1. Activated carbon was obtained by carbonization. The capacitance of the organic EDLC produced using this activated carbon was 24 F / g.
(Example 4) and 13 F / g (Comparative Example 4). As described above, it can be seen that there is a large difference in the obtained capacitance due to the difference in the crystallite size S even in the organic EDLC and the EDLC using the same homo PVDC. The results of all Examples and Comparative Examples are shown in Table 1 below.

[0051]

[Table 1]

[0052]

According to the present invention, it is possible to provide an activated carbon raw material for an electric double layer capacitor electrode suitable for obtaining a high capacitance, and an activated carbon using the same.

[Brief description of the drawings]

FIG. 1 is a graph illustrating a method for obtaining a crystallite size S of a PVDC resin of the present invention. However, the scattering peak 1 is PV
Scattering peaks derived from the (100) plane reflection of the DC resin, A and B are valleys on the low angle side and valley on the high angle side of scattering peak 1, respectively, and C and D are baselines (straight line AB).
Are the point on the scattering profile on the low angle side and the point on the scattering profile on the high angle side corresponding to 1/2 of the height of the scattering intensity of the scattering peak 1 measured from, and W is the scattering peak 1
Is the half width.

FIG. 2 shows Embodiment 1 (1 in the drawing) and Embodiment 4 of the present invention.
The pore distribution curve of activated carbon (4 in the figure) is shown. Here, the horizontal axis is the pore diameter [unit nm], and the vertical axis is the differential pore volume [unit ml / (g · nm)].

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] October 6, 1999 (1999.10.
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

As a method for producing such activated carbon, there is disclosed a method for producing a porous body in which activated carbon fine particles are sintered with each other by a pulse impact current disclosed in Japanese Patent Application Laid-Open No. 3-78221. Is a special sintering method,
It is not preferable in terms of manufacturing cost and versatility. According to the technique disclosed in Japanese Patent Application Laid-Open No. 7-249551, a polyvinylidene chloride resin is used as a raw material for activated carbon, and heated at 800 to 1000 ° C. in a non-oxidizing atmosphere (nitrogen gas ₂ ) to have many pores. It is shown that activated carbon for EDLC electrodes can be obtained. It is an excellent finding that a polyvinylidene chloride resin which easily provides a suitable field for the adsorption of a large number of electrolyte ions by an elimination reaction of hydrochloric acid from a side chain by heat treatment is used as an activated carbon raw material. But,
JP-A-7-249551 does not disclose what kind of technique is used as polyvinylidene chloride resin.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G046 CA04 CB02 CB09 CC03 HA03 HC02 HC03 HC05 HC06 HC07 HC08 HC10 HC11 4J002 BD101 DA036 GQ00

Claims (3)

[Claims] 1. An electric double layer comprising microcrystalline size S of 150 ° or more and containing polyvinylidene chloride or a vinylidene chloride copolymer having a molar content of vinylidene chloride of 85 mol% or more. Activated carbon raw material for capacitor electrodes. 2. Activated carbon for an electrode of an electric double layer capacitor, obtained by carbonizing and / or activating the activated carbon raw material according to claim 1. 3. A mixed solution of an organic solvent for partially or entirely swelling or dissolving the activated carbon raw material according to claim 1, an aqueous solution of an alkali metal hydroxide or an alkaline earth hydroxide, and alcohol and / or ether. Using 10
Carbonization treatment including a step of dehydrochlorination treatment at 0 ° C. or lower and / or
The activated carbon for an electric double layer capacitor electrode according to claim 2, wherein the activated carbon is obtained by activation.