JP4294512B2 - Method for producing raw material powder for gas diffusion electrode - Google Patents
Method for producing raw material powder for gas diffusion electrode Download PDFInfo
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- JP4294512B2 JP4294512B2 JP2004041895A JP2004041895A JP4294512B2 JP 4294512 B2 JP4294512 B2 JP 4294512B2 JP 2004041895 A JP2004041895 A JP 2004041895A JP 2004041895 A JP2004041895 A JP 2004041895A JP 4294512 B2 JP4294512 B2 JP 4294512B2
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- 239000000843 powder Substances 0.000 title claims description 91
- 238000009792 diffusion process Methods 0.000 title claims description 52
- 239000002994 raw material Substances 0.000 title claims description 40
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 239000006229 carbon black Substances 0.000 claims description 41
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 34
- 239000002245 particle Substances 0.000 claims description 33
- 239000004094 surface-active agent Substances 0.000 claims description 28
- 239000003795 chemical substances by application Substances 0.000 claims description 27
- 239000011259 mixed solution Substances 0.000 claims description 23
- 238000001035 drying Methods 0.000 claims description 20
- 239000007921 spray Substances 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 14
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 13
- 238000001694 spray drying Methods 0.000 claims description 13
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 claims description 12
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 12
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 claims description 8
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 7
- 239000004744 fabric Substances 0.000 claims description 4
- 229940035429 isobutyl alcohol Drugs 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 48
- 239000000463 material Substances 0.000 description 37
- 235000019241 carbon black Nutrition 0.000 description 36
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 32
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- 239000006185 dispersion Substances 0.000 description 29
- 239000007788 liquid Substances 0.000 description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 239000000693 micelle Substances 0.000 description 14
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- 239000011261 inert gas Substances 0.000 description 5
- GPRLSGONYQIRFK-MNYXATJNSA-N triton Chemical compound [3H+] GPRLSGONYQIRFK-MNYXATJNSA-N 0.000 description 5
- 241000872198 Serjania polyphylla Species 0.000 description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 4
- 230000000994 depressogenic effect Effects 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
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- 238000010298 pulverizing process Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 229910001873 dinitrogen Inorganic materials 0.000 description 3
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000013504 Triton X-100 Substances 0.000 description 2
- 229920004890 Triton X-100 Polymers 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- 239000000126 substance Substances 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
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- 239000007772 electrode material Substances 0.000 description 1
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Description
本発明は、ガス拡散電極用原料粉の製造方法に関し、より詳細には食塩電解用に使用するガス拡散電極のガス拡散層や反応層用の原料粉の製造方法に関する。 The present invention relates to a method for producing a raw material powder for a gas diffusion electrode, and more particularly to a method for producing a raw material powder for a gas diffusion layer or a reaction layer of a gas diffusion electrode used for salt electrolysis.
近年、食塩のイオン交換膜法電解において、従来の水素発生を伴う金属系陰極に代えて、酸素還元を行うガス拡散電極の利用が試みられている。この電極は陰極反応を水素発生から酸素還元に代えることによって理論的には電解電圧を約１Ｖ低減でき、大きな省エネルギープロセスとして期待されている。
従来からガス拡散電極の一種としてガス拡散層及び反応層の積層構造から成るものがあり、このガス拡散電極は、各々の材料を予め作製してから、材料粉を水や有機溶媒によって混練し、ロール法や塗工法により銀網等の集電体を介在して反応層とガス拡散層を積層し、ホットプレスで一体成形して製造されている。
Conventionally, there is a gas diffusion electrode and a reaction layer having a laminated structure as a kind of gas diffusion electrode. This gas diffusion electrode is prepared in advance after each material is kneaded with water or an organic solvent, It is manufactured by laminating a reaction layer and a gas diffusion layer through a current collector such as a silver net by a roll method or a coating method, and integrally forming with a hot press.
このガス拡散電極作製に使用する材料粉は、水にカーボンブラックと界面活性剤を加えて分散させ、更にポリテトラフルオロエチレン（ＰＴＦＥ）ディスパージョンを混合して、カーボンブラックとＰＴＦＥを高分散させた後に、界面活性剤のミセル構造を破壊するミセル破壊剤としての低級アルコール又は高水溶性のケトンを添加し、ＰＴＦＥの凝集体を
形成し、濾過し易い混合液の形で得ていた。この混合液を濾過して得られるガス拡散電極用原料は、数十〜数百μｍ径のＰＴＦＥ凝集体であり、このＰＴＦＥ凝集体の形成によって、添加されたＰＴＦＥの全てがバインダーとして有効に生かされず加熱加圧成形後のシートの引張強度の低下を引き起こしていた。更に粒子径がばらついているため、ガス拡散電極のガス拡散層や反応層の材料と使用してもガス拡散電極の性能が一定せず、高性能のガス拡散電極が製造できなくなるという問題点があった。
The material powder used for producing the gas diffusion electrode was dispersed by adding carbon black and a surfactant to water, and further mixing polytetrafluoroethylene (PTFE) dispersion to highly disperse carbon black and PTFE. Later, a lower alcohol or a highly water-soluble ketone as a micelle disrupting agent that destroys the micelle structure of the surfactant was added to form PTFE aggregates, which were obtained in the form of a liquid mixture that was easy to filter. The gas diffusion electrode raw material obtained by filtering this mixed liquid is a PTFE aggregate having a diameter of several tens to several hundreds of μm. By the formation of this PTFE aggregate, all of the added PTFE is effectively utilized as a binder. This has caused a decrease in the tensile strength of the sheet after heat and pressure forming. Furthermore, since the particle diameter varies, the performance of the gas diffusion electrode is not constant even if it is used as a material for the gas diffusion layer or reaction layer of the gas diffusion electrode, making it impossible to produce a high-performance gas diffusion electrode. there were.
又前記凝集操作には大量の有機溶媒が必要であり、更に例えばアルコールと水を混合した凝集液を工業的に濾過・乾燥する場合には、ヘリカルフィルター等が使用されてきたが、濾過時間が６時間程度、乾燥には更に２日間を要し、濾過・乾燥工程だけで長時間を要していた。これに加えて、乾燥の際には乾燥排気中に含まれるエタノール濃度を爆発限界濃度以下にするために、大量の不活性ガスで希釈する必要があり、高価な不活性ガスを大量に消費するために、製造コストが高くなるという問題があった。
特許文献１には、ＰＴＦＥディスパージョンを含むガス拡散電極用材料粉末の分散液に、アルコールなどの自己組織化剤を加えて粘度があまり高くならない段階で噴霧して乾燥する方法が開示されている。この方法は、材料粉末に自己組織化剤を加えて十分に自己組織化（塊状化）した後、濾過し、乾燥し更に粉砕するという、多数の工程を要し過度の凝集が進行する従来技術の欠点を解消するために、自己組織化剤を加えて粘度があまり高くならない段階で噴霧乾燥を行う点に特徴がある。しかしこの方法でも凝集の程度は低くなるにしても凝集は進行し、均一粒子径の高分散粉末は得られない。
In addition, a large amount of organic solvent is required for the agglomeration operation. Further, for example, when agglomerated liquid obtained by mixing alcohol and water is filtered and dried industrially, a helical filter or the like has been used. About 6 hours, it took another two days for drying, and it took a long time only for the filtration and drying process. In addition to this, when drying, it is necessary to dilute with a large amount of inert gas in order to keep the ethanol concentration contained in the dry exhaust below the explosion limit concentration, which consumes a large amount of expensive inert gas Therefore, there is a problem that the manufacturing cost becomes high.
Patent Document 1 discloses a method in which a self-organizing agent such as alcohol is added to a dispersion of gas diffusion electrode material powder containing PTFE dispersion and sprayed and dried at a stage where the viscosity does not become too high. . In this method, a self-organizing agent is added to the material powder and sufficiently self-organized (agglomerated), followed by filtration, drying, and further pulverization. In order to eliminate the disadvantages of the above, it is characterized in that spray drying is performed at a stage where the viscosity does not become so high by adding a self-organizing agent. However, even with this method, aggregation proceeds even if the degree of aggregation decreases, and a highly dispersed powder with a uniform particle size cannot be obtained.
従って本発明は、これらの問題点を解決し、分散状態の良好なガス拡散電極用原料粉を、比較的短時間で製造できる方法を提供することを目的とする。 Accordingly, an object of the present invention is to solve these problems and to provide a method capable of producing a gas diffusion electrode raw material powder having a good dispersion state in a relatively short time.
本発明は、カーボンブラックとフッ素樹脂を分散状態で含み、界面活性剤を含有し、メタノール、エタノール、ｎ−プロパノール、イソブチルアルコール、アセトン及びメチルエチルケトンから成る全てのミセル破壊剤を含有しない混合液を噴霧乾燥して乾燥粉末を形成することを特徴とするガス拡散電極用原料粉の製造方法である。
The present invention sprays a mixed solution containing carbon black and fluororesin in a dispersed state, containing a surfactant, and not containing all micelle breaking agents composed of methanol, ethanol, n-propanol, isobutyl alcohol, acetone and methyl ethyl ketone. A method for producing a raw material powder for a gas diffusion electrode, comprising drying to form a dry powder.
以下本発明を詳細に説明する。
本発明方法は、従来のアルコール等のミセル破壊剤の使用による材料粉末の凝集を行わせないために、ミセル破壊剤を含まない材料粉末の混合液を噴霧乾燥してガス拡散電極用原料粉を製造することを特徴とする。
ガス拡散電極用原料粉中のフッ素樹脂ディスパージョンは界面活性剤によりフッ素樹脂微粒子が親水コロイドを形成して溶液中に分散しているが、アルコールのような脱水剤（ミセル破壊剤）によって親水層が破壊されてフッ素樹脂微粒子同士が凝集し、巨大粒子が形成される。更にフッ素樹脂微粒子、特に親水化していないフッ素樹脂微粒子は攪拌のようなせん断力が加わると、フッ素樹脂の分子同士が絡まり合って繊維化が起こる。本発明における「ミセル破壊剤」は繊維化以前のフッ素樹脂微粒子同士の凝集を生じさせる化合物であるメタノール、エタノール、ｎ−プロパノール、イソブチルアルコール、アセトン及びメチルエチルケトンを意味する。
従来技術における自己組織化剤は、材料粉末を凝集させて粒子径を大きくして、濾過の際の濾紙や濾布の目詰まりを防止し短時間で濾過を終了させるために添加されるが、特許文献１では自己組織化剤添加による凝集の程度を抑制して濾過を行わずに噴霧乾燥を行っている。この方法では濾過に要する時間は省略できるが、前述の通り均一な高分散粉末が得られず、更に高価なエタノールを消費し、噴霧乾燥後のエタノール処理にも不活性ガスが必要になる。特許文献１における自己組織化剤は、前述したフッ素樹脂微粒子の凝集だけでなく、繊維化も含めているように解釈できるが、本発明のミセル破壊剤は前述の通りフッ素樹脂微粒子同士の凝集を生じさせる化合物を意味する。
The present invention will be described in detail below.
In the method of the present invention, in order not to cause aggregation of the material powder due to the use of a conventional micelle disrupting agent such as alcohol, a mixture of the material powder not containing the micelle disrupting agent is spray-dried to obtain the raw material powder for the gas diffusion electrode. It is characterized by manufacturing.
The fluororesin dispersion in the raw material powder for gas diffusion electrodes is composed of fluororesin fine particles that form a hydrocolloid with a surfactant and dispersed in the solution. However, a hydrophilic layer is formed by a dehydrating agent (micelle breaking agent) such as alcohol. Are destroyed and the fluororesin fine particles are aggregated to form giant particles. Furthermore, when the fluororesin fine particles, particularly the fluororesin fine particles not hydrophilized, are subjected to shearing force such as stirring, the fluororesin molecules are entangled with each other to cause fiberization. The “micelle breaking agent” in the present invention means methanol, ethanol, n-propanol, isobutyl alcohol, acetone and methyl ethyl ketone, which are compounds that cause aggregation of fluororesin fine particles before fiberization .
The self-organizing agent in the prior art is added to agglomerate the material powder to increase the particle diameter and prevent clogging of the filter paper and filter cloth during the filtration and finish the filtration in a short time. In Patent Document 1, spray drying is performed without performing filtration by suppressing the degree of aggregation due to the addition of the self-organizing agent. In this method, the time required for filtration can be omitted. However, as described above, a uniform highly dispersed powder cannot be obtained, more expensive ethanol is consumed, and an inert gas is also required for the ethanol treatment after spray drying. The self-organizing agent in Patent Document 1 can be interpreted as including not only the above-described aggregation of fluororesin fine particles but also fiberization, but the micelle-disrupting agent of the present invention causes aggregation of fluororesin fine particles as described above. Means the resulting compound.
本発明者らは、自己組織化剤を使用することを前提とする従来技術を根本から検討し直し、自己組織化剤、特にミセル破壊剤を使用しなくても所定のガス拡散電極用原料粉が得られること、及び該自己組織化剤、特にミセル破壊剤を使用しないことにより、他の効果も得られることを見出し、本発明に至ったものである。
本発明方法では、ガス拡散電極用原料粉の材料となるカーボンブラックとフッ素樹脂、及び界面活性剤を非有機系溶媒である水に分散又は溶解させて混合液とし、この混合液を噴霧乾燥してガス拡散電極用原料粉を製造する。
本発明では、ミセル破壊剤を使用して材料粉末を凝集させることがないため、材料粉末の粒子径が比較的均一で、この材料粉末を噴霧乾燥して得られる粉末の粒子径も比較的均一で、分散状態の良好なガス拡散電極用原料粉が得られる。この高分散原料粉は、従来の原料粉と比較して強度、特に引張強度が高く、高性能原料粉として得られる。
The inventors of the present invention have reexamined the prior art based on the premise that a self-organizing agent is used, and a predetermined raw material powder for a gas diffusion electrode without using a self-organizing agent, particularly a micelle-disrupting agent. Has been obtained, and other effects can be obtained by not using the self-organizing agent, in particular, the micelle-disrupting agent, and the present invention has been achieved.
In the method of the present invention, carbon black and fluororesin, which are raw material powders for gas diffusion electrodes, and a surfactant are dispersed or dissolved in water, which is a non-organic solvent, to obtain a mixed solution, and this mixed solution is spray-dried. The raw material powder for the gas diffusion electrode is manufactured.
In the present invention, since the material powder is not agglomerated using the micelle breaking agent, the particle size of the material powder is relatively uniform, and the particle size of the powder obtained by spray drying the material powder is also relatively uniform. Thus, a raw material powder for a gas diffusion electrode having a good dispersion state can be obtained. This highly dispersed raw material powder has higher strength, particularly tensile strength, compared to conventional raw material powder, and is obtained as a high-performance raw material powder.
更にエタノール等の高価なミセル破壊剤を使用しないため、製造コストが低減できる。又ミセル破壊剤として、メタノール、エタノール、ｎ−プロパノール及びイソブチルアルコールの低級アルコール及び／又はアセトンやメチルエチルケトンの高水溶性のケトンがあり、得られるガス拡散電極用原料粉中にこれらのミセル破壊剤が残存すると不活性ガス雰囲気での乾燥工程が必要になるが、本発明ではミセル破壊剤を使用しないため、乾燥時間を短縮できるとともに高価な不活性ガスの使用を回避できる。
Furthermore, since an expensive micelle disrupting agent such as ethanol is not used, the manufacturing cost can be reduced. Also as micelles breakers, methanol, ethanol, n- propanol and highly water-soluble ketones lower alcohols and / or acetone and methyl ethyl ketone of isobutyl alcohol there is, in the raw material powder for the resulting gas diffusion electrode these micelles destruction If the agent remains, a drying step in an inert gas atmosphere is required. However, in the present invention, since the micelle-disrupting agent is not used, the drying time can be shortened and the use of an expensive inert gas can be avoided.
本発明のガス拡散電極用原料粉は、ガス拡散電極のガス拡散層と反応層のいずれにも使用可能である。
ガス拡散層は、カーボンブラック、特に疎水性カーボンブラックとフッ素樹脂から構成され、反応層は通常疎水性カーボンブラック、親水性カーボンブラック、金属触媒粉末及びフッ素樹脂から構成される。
前述の混合液調製時には、これらの原料と界面活性剤を水に添加して水溶液とし、攪拌機、超音波分散機、ホモジナイザー等を使用して高度の分散混合液とする。この混合液の分散度は粒度分布計で評価できる。通常のカーボンブラックは約40nmの径の粒子として製造されるが、販売時には取扱い易さを考慮して１〜1.5mm径程度に造粒される。前記混合液の場合、攪拌のみの場合、カーボンブラックの平均粒子径は1.5μｍであるのに対し、前述の分散処理を行うと0.9μｍ以下になる。分散処理を行って作製した材料粉末を使用して製造されるガス拡散電極のガス拡散層や反応層は、分散処理を行わずに作製し材料粉末を使用する場合と比較して、比抵抗が小さく、引張強度が優り、更に耐水圧が大きくなる。
The raw material powder for a gas diffusion electrode of the present invention can be used for both a gas diffusion layer and a reaction layer of a gas diffusion electrode.
The gas diffusion layer is composed of carbon black, particularly hydrophobic carbon black and fluororesin, and the reaction layer is usually composed of hydrophobic carbon black, hydrophilic carbon black, metal catalyst powder and fluororesin.
When preparing the above-mentioned mixed solution, these raw materials and surfactant are added to water to form an aqueous solution, and a highly dispersed mixed solution is prepared using a stirrer, an ultrasonic disperser, a homogenizer, or the like. The degree of dispersion of this mixture can be evaluated with a particle size distribution meter. Ordinary carbon black is manufactured as particles having a diameter of about 40 nm, but is granulated to a diameter of about 1 to 1.5 mm in consideration of ease of handling at the time of sale. In the case of the above mixed solution, the average particle size of carbon black is 1.5 μm when stirring alone, whereas it becomes 0.9 μm or less when the above dispersion treatment is performed. The gas diffusion layer and reaction layer of the gas diffusion electrode manufactured using the material powder produced by the dispersion treatment have a specific resistance compared to the case of using the material powder produced without the dispersion treatment. Small, excellent tensile strength, and water pressure resistance increases.
混合液中のカーボンブラックは、乾燥処理速度を上げるためにはその量が多いことが望ましいが、多過ぎると均一に分散せずに沈殿を生じたり、又沈殿がなく均一に分散していても、長時間攪拌していると急激に粘度が上昇して流動性が悪化することがある。これを解消するためにはカーボンブラック量について適正範囲を設定することが望ましい。
前記混合液中には種々のカーボンブラックを存在させて実験を行ったところ、前記疎水性カーボンブラックの適正範囲はガス拡散層用の場合で100〜300ｇ／dm3、好ましくは100〜250ｇ／dm3であり、反応層用原料粉の場合で60〜180ｇ／dm3、好ましくは100〜150ｇ／dm3であった。
The amount of carbon black in the mixed solution is desirably large in order to increase the drying processing speed, but if it is too large, precipitation may occur without uniform dispersion, or even if there is no precipitation and even dispersion. If the mixture is stirred for a long time, the viscosity rapidly increases and the fluidity may deteriorate. In order to solve this problem, it is desirable to set an appropriate range for the amount of carbon black.
When an experiment was conducted in the presence of various carbon blacks in the mixed solution, the appropriate range of the hydrophobic carbon black was 100 to 300 g / dm 3 , preferably 100 to 250 g / dm for the gas diffusion layer. In the case of the raw material powder for the reaction layer, it was 60 to 180 g / dm 3 , preferably 100 to 150 g / dm 3 .
使用する前記フッ素樹脂はバインダーとしての機能を有し、通常はポリテトラフルオロエチレン（ＰＴＦＥ）が使用される。前記混合液には、ＰＴＦＥのディスパージョンとして添加される。
ＰＴＦＥを添加した混合液は十分に攪拌混合を行い、カーボンブラック及びＰＴＦＥを高分散化しても良いが、この攪拌混合の前後のカーボンブラックの平均粒子径には殆ど差異がないため、該攪拌混合は行わなくても良い。
反応層用の触媒金属は従来のものを制限なく使用できるが、銀触媒の使用が望ましい。
The fluororesin used has a function as a binder, and polytetrafluoroethylene (PTFE) is usually used. The mixture is added as a PTFE dispersion.
The mixed solution to which PTFE is added may be sufficiently stirred and mixed to highly disperse carbon black and PTFE. However, since there is almost no difference in the average particle diameter of carbon black before and after this stirring and mixing, the stirring and mixing Is not necessary.
Although the conventional catalyst metal for the reaction layer can be used without limitation, the use of a silver catalyst is desirable.
使用する界面活性剤は非イオン系界面活性剤が好ましく、この界面活性剤は界面活性剤として混合液中に添加しても、あるいは界面活性剤そのものを混合液中に添加せずＰＴＦＥディスパージョン中に含まれる界面活性剤を混合液中で使用しても良い。界面活性剤は使用時の安定性を考慮し、あるいはＰＴＦＥ中に含まれる界面活性剤と同じになるよう選択すれば良い。
混合液中に含まれる界面活性剤量は、カーボンブラックの分散に必要な最小量とすることが望ましい。これは界面活性剤が得られる原料粉中に残存し易いからである。つまり噴霧乾燥機による乾燥処理では水分だけが除去され、噴霧乾燥機の出口温度（約150℃）の熱で昇華又は分解しない混合液中の溶質は全て得られる製品粉末中に残存することになり、例えば一般的な非イオン系界面活性剤であるトライトンＸ−100の分解温度は約230℃であり、トライトンＸ−100も分解せずに製品粉末中に残留する。残留した界面活性剤はホットプレス成形時にガス発生を伴って分解するため、製造後の電極に剥離や割れ等の悪影響を及ぼし易い。
The surfactant to be used is preferably a nonionic surfactant, and even if this surfactant is added as a surfactant to the mixed solution, or in the PTFE dispersion without adding the surfactant itself to the mixed solution. May be used in the mixed solution. The surfactant may be selected in consideration of the stability during use or the same as the surfactant contained in PTFE.
It is desirable that the amount of the surfactant contained in the mixed solution be the minimum amount necessary for dispersing the carbon black. This is because the surfactant tends to remain in the raw material powder obtained. In other words, only the moisture is removed in the drying process by the spray dryer, and all the solutes in the mixed solution that are not sublimated or decomposed by the heat at the outlet temperature of the spray dryer (about 150 ° C) remain in the resulting product powder. For example, the decomposition temperature of Triton X-100, which is a general nonionic surfactant, is about 230 ° C., and Triton X-100 remains in the product powder without being decomposed. The remaining surfactant is decomposed with gas generation at the time of hot press molding, and thus tends to adversely affect the manufactured electrode such as peeling and cracking.
このため界面活性剤はホットプレス成形前に除去することが望ましく、従って添加量は少ないことが好ましい。一方カーボンブラックの分散にはある濃度以上の界面活性剤が必要で、不足するとカーボンブラックが塊で存在することになるため、最小限の界面活性剤の添加が必要である。
従って前記混合液中には適正な濃度範囲の界面活性剤を存在させることが望ましく、種々の組合わせで実験を行ったところ、前記適正範囲はガス拡散層用原料粉の場合で1.3〜3.0wt％、好ましくは1.7〜2.5wt％であり、反応層用原料粉の場合で2.0〜4.0wt％、好ましくは2.5〜3.5wt％であることが分かった。
For this reason, it is desirable to remove the surfactant before hot press molding, and therefore it is preferable that the amount added is small. On the other hand, a surfactant having a certain concentration or more is required for dispersion of carbon black, and if it is insufficient, carbon black is present in a lump, so that a minimum amount of surfactant needs to be added.
Accordingly, it is desirable that a surfactant having an appropriate concentration range be present in the mixed solution, and when experiments were conducted with various combinations, the appropriate range was 1.3 to 3.0 wt% in the case of the raw material powder for the gas diffusion layer. %, Preferably 1.7-2.5 wt%, and in the case of the reaction layer raw material powder, it was found to be 2.0-4.0 wt%, preferably 2.5-3.5 wt%.
このようにして準備した高分散混合液を噴霧乾燥機内に、例えば定量ポンプを使用して導入し、200〜250℃の熱風中に噴霧することにより乾燥を行う。噴霧乾燥機内に導入する前にミセル破壊剤による凝集を行っていないため、前記噴霧乾燥により粉末粒度分布の狭い製品粉末を得ることができる。
噴霧乾燥機のアトマイザは回転ディスク、圧力ノズル及び２流体ノズルの何れも使用可能であるが、粒度分布をより均一にできる回転ディスクの使用が望ましい。
噴霧乾燥機から乾燥粉末を取り出す場合、乾燥室底部やサイクロン捕集器から採取することになるが、前記乾燥粉末を移送する配管が長いと目詰まりを起こしたりする。更に微粉末である銀粉末を含む反応層用材料の場合、サイクロン捕集器でも捕集されずに排気ガスとともに排気されるため材料回収率が低下する。回収率を高くするためには、乾燥室が耐熱性濾布で形成されたスプレーバグドライヤー（バグ式噴霧乾燥機）の使用が最も適している。
Drying is performed by introducing the highly dispersed liquid mixture thus prepared into a spray dryer using, for example, a metering pump and spraying it in hot air at 200 to 250 ° C. Since agglomeration with a micelle disrupting agent is not performed before introduction into the spray dryer, a product powder having a narrow powder particle size distribution can be obtained by the spray drying.
The atomizer of the spray dryer can use any of a rotating disk, a pressure nozzle, and a two-fluid nozzle, but it is desirable to use a rotating disk that can make the particle size distribution more uniform.
When taking out the dry powder from the spray dryer, it is collected from the bottom of the drying chamber or the cyclone collector. However, if the pipe for transferring the dry powder is long, clogging may occur. Furthermore, in the case of a reaction layer material containing silver powder which is fine powder, the material recovery rate is lowered because it is exhausted together with exhaust gas without being collected by the cyclone collector. In order to increase the recovery rate, it is most suitable to use a spray bag dryer (bag type spray dryer) in which the drying chamber is formed of heat-resistant filter cloth.
このようにして製造されたガス拡散電極用原料粉を錠剤成型器で押し固め、ＳＥＭ（走査型電子顕微鏡）でフッ素樹脂凝集体の有無を観察しても通常凝集体は見出されない。
このガス拡散電極用原料粉を有機溶媒を用いてスラリー化し、ロール成型機を使用して薄いシートに成型し、金属メッシュ等の基材を介在させ塗工機によって前記基材表面にガス拡散層又は反応層を形成し、含有されている界面活性剤を溶媒抽出や加熱分解により除去し、加熱及び加圧して成形することによりガス拡散電極が得られる。
Even when the raw material powder for the gas diffusion electrode thus produced is pressed and compacted with a tablet molding machine and the presence or absence of the fluororesin aggregate is observed with an SEM (scanning electron microscope), no aggregate is usually found.
This raw material powder for gas diffusion electrode is slurried using an organic solvent, formed into a thin sheet using a roll molding machine, and a gas diffusion layer is formed on the surface of the base material by a coating machine with a base material such as a metal mesh interposed. Alternatively, a gas diffusion electrode can be obtained by forming a reaction layer, removing the contained surfactant by solvent extraction or thermal decomposition, and shaping by heating and pressurization.
本発明方法によるガス拡散電極用原料粉製造では、従来使用していたミセル破壊剤を使用せずに材料粉末の混合液を噴霧乾燥するため、ミセル破壊剤による材料粉末の凝集が抑制され、高分散状態で強度の強いガス拡散電極用原料粉が得られる。また、この高強度電極では長期使用による電極内部の抵抗上昇を抑えることができる。更にミセル破壊剤を使用しないため工程が簡略化でき、高価な薬剤やガスを使用することもなくなる。 In the production of the raw material powder for gas diffusion electrode according to the method of the present invention, the mixture of the material powder is spray-dried without using the conventionally used micelle-disrupting agent. A raw material powder for a gas diffusion electrode having a strong strength in a dispersed state is obtained. In addition, this high-strength electrode can suppress an increase in resistance inside the electrode due to long-term use. Furthermore, since no micelle disrupting agent is used, the process can be simplified, and expensive chemicals and gases are not used.
疎水性カーボンブラック（ＡＢ−６、電気化学工業株式会社製）100ｇを、1.5wt％に希釈した界面活性剤トライトン（Ｘ−100、ユニオン・カーバイド日本株式会社製）溶液400cm3中に添加し、ラボスターラー（ヤマト科学株式会社製）で攪拌しながら、超音波分散機（ＵＨ−600、株式会社エムエステー製）で30分間分散させた。
カーボンブラックの粒度分布を株式会社堀場製作所製ＬＡ−920で測定した結果、分散前の平均粒子径1.3μｍが分散後には平均粒子径0.8μｍまで減少していた。
100 g of hydrophobic carbon black (AB-6, manufactured by Denki Kagaku Kogyo Co., Ltd.) was added to 400 cm 3 of a surfactant Triton (X-100, manufactured by Union Carbide Japan Co., Ltd.) solution diluted to 1.5 wt%. While stirring with a lab stirrer (manufactured by Yamato Kagaku Co., Ltd.), the mixture was dispersed with an ultrasonic dispersing machine (UH-600, manufactured by MST Co., Ltd.) for 30 minutes.
As a result of measuring the particle size distribution of carbon black with LA-920 manufactured by HORIBA, Ltd., the average particle size of 1.3 μm before dispersion decreased to 0.8 μm after dispersion.
このカーボンブラックを含む液にＰＴＦＥディスパージョン（ＰＴＦＥ30Ｊ、三井・デュポンフロロケミカル株式会社製）80cm3を添加し、更に30分間攪拌を行い、高分散混合液を作製した。この混合液中のカーボンブラックの平均粒子径は攪拌前と同じであった。
この混合液を、入口送風温度を250℃に設定した噴霧乾燥機（Ｌ−８、大川原化工機株式会社製）内に定量ポンプを使用して導入し、これにより乾燥粉末が得られた。噴霧乾燥時の噴霧乾燥機の出口温度は150℃、乾燥処理時間は約15分とした。
得られた乾燥粉末は、球状もしくは一部が陥没した球状であり、実体顕微鏡で観察した粒子径は10〜60μｍ、120℃の恒温槽内に１時間保存して算出した含水率は1.5％で、材料回収率は80％であった。
To this liquid containing carbon black, 80 cm 3 of PTFE dispersion (PTFE 30J, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) was added, and further stirred for 30 minutes to prepare a highly dispersed mixed liquid. The average particle size of carbon black in this mixed solution was the same as that before stirring.
This mixed liquid was introduced into a spray dryer (L-8, manufactured by Okawahara Chemical Co., Ltd.) having an inlet blast temperature set to 250 ° C. using a metering pump, thereby obtaining a dry powder. At the time of spray drying, the outlet temperature of the spray dryer was 150 ° C., and the drying time was about 15 minutes.
The obtained dry powder has a spherical shape or a partially depressed spherical shape. The particle size observed with a stereomicroscope is 10 to 60 μm, and the water content calculated by storage in a constant temperature bath at 120 ° C. for 1 hour is 1.5%. The material recovery rate was 80%.
この材料粉末を錠剤成型器で整形した後、ＳＥＭで観察した結果、ＰＴＦＥの塊は観察されず、均質であった。
この材料粉末を25ｇ秤取り、50cm3のエタノールと混練して餅状のスラリーとした後、ロール機でＡ５版サイズの0.5mm厚みのシートを作製した。このシートをエタノール抽出して界面活性剤を除去した後、350℃、50kg／cm2で60秒間プレスして、得られたシートを評価した。その結果を表１に示した。更に得られた混合液から噴霧乾燥によりガス拡散電極用原料粉製造までに要した時間は表１及び２に示す通り、15分であった。
This material powder was shaped with a tablet molding machine and then observed with an SEM. As a result, no PTFE mass was observed and it was homogeneous.
25 g of this material powder was weighed and kneaded with 50 cm 3 of ethanol to form a bowl-like slurry, and then a 0.5 mm thick sheet of A5 size was produced with a roll machine. This sheet was extracted with ethanol to remove the surfactant and then pressed at 350 ° C. and 50 kg / cm 2 for 60 seconds to evaluate the obtained sheet. The results are shown in Table 1. Furthermore, as shown in Tables 1 and 2, the time required for producing the raw material powder for gas diffusion electrode by spray drying from the obtained mixed solution was 15 minutes.
なお各物性は次のようにして測定した。
(1)比抵抗・・・体積抵抗率を比抵抗として測定した。三菱化学株式会社製ロレスターＧＰを用い、ＪＩＳ Ｋ7194に準拠して測定を行った。
(2)耐水圧・・・φ43mmのシートサンプルに水圧を加え、破断した際の水圧を耐水圧値として測定した。
(3)ガス透過度・・・φ49mmのシートサンプルに0.01ＭＰａの酸素ガス圧を掛けた際のガス流量値として測定した。
(4)引張強度・引張展延・・・小型卓上試験器（ＥＺＴｅｓｔ、島津製作所製）を用い、ダンベル（評価部：５mm、巾×20mm）型に打ち抜き、引っ張り応力を逐次増加した際のそれぞれの破断応力と伸び率として測定した。
Each physical property was measured as follows.
(1) Specific resistance: Volume resistivity was measured as specific resistance. Measurement was performed according to JIS K7194 using a Lorester GP manufactured by Mitsubishi Chemical Corporation.
(2) Water pressure resistance: A water pressure was applied to a sheet sample of φ43 mm, and the water pressure at the time of fracture was measured as a water pressure resistance value.
(3) Gas permeability: Measured as a gas flow rate when an oxygen gas pressure of 0.01 MPa was applied to a sheet sample of φ49 mm.
(4) Tensile strength / tensile spread: Each time when the tensile stress was increased by punching into a dumbbell (evaluation part: 5mm, width x 20mm) using a small tabletop tester (EZTest, manufactured by Shimadzu Corporation) The rupture stress and elongation were measured.
疎水性カーボンブラック（ＡＢ−６）20ｇ及び親水性カーボンブラック（ＡＢ−12、電気化学工業株式会社製）40ｇを、３wt％トライトン溶液360 cm3中に添加し、ラボスターラー（ヤマト科学株式会社製）で攪拌しながら、超音波分散機（ＵＨ−600）で30分間分散させた。分散後のカーボンブラックの粒度分布を株式会社堀場製作所製ＬＡ−920で測定した結果、分散前の平均粒子径3.9μｍが分散後には平均粒子径0.6μｍまで減少していた。 20 g of hydrophobic carbon black (AB-6) and 40 g of hydrophilic carbon black (AB-12, manufactured by Denki Kagaku Kogyo Co., Ltd.) are added to 360 cm 3 of a 3 wt% Triton solution, and a laboratory stirrer (manufactured by Yamato Scientific Co., Ltd.). The mixture was dispersed with an ultrasonic disperser (UH-600) for 30 minutes while stirring. As a result of measuring the particle size distribution of carbon black after dispersion with LA-920 manufactured by Horiba, Ltd., the average particle diameter before dispersion was reduced to 3.9 μm after dispersion to an average particle diameter of 0.6 μm.
この液にＰＴＦＥディスパージョン（ＰＴＦＥ30Ｊ）32cm3と金属銀粉末を添加し、更に30分間攪拌を行い、高分散混合液を作製した。
この液を、入口送風温度を250℃に設定した噴霧乾燥機（Ｌ−８）内に定量ポンプを使用して導入し、これにより乾燥粉末が得られた。噴霧乾燥時の噴霧乾燥機の出口温度は150℃、乾燥処理時間は約12分とした。
得られた乾燥粉末は、球状もしくは一部が陥没した球状であり、実体顕微鏡で観察した粒子径は10〜60μｍ、120℃の恒温槽内に１時間保存して算出した含水率は0.9％で、材料回収率は86％であった。
To this solution, 32 cm 3 of PTFE dispersion (PTFE 30J) and metallic silver powder were added, and the mixture was further stirred for 30 minutes to prepare a highly dispersed mixed solution.
This liquid was introduced using a metering pump into a spray dryer (L-8) in which the inlet blast temperature was set to 250 ° C., whereby a dry powder was obtained. At the time of spray drying, the outlet temperature of the spray dryer was 150 ° C., and the drying time was about 12 minutes.
The obtained dry powder has a spherical shape or a partially depressed spherical shape. The particle size observed with a stereomicroscope is 10 to 60 μm, and the moisture content calculated by storing in a thermostatic bath at 120 ° C. for 1 hour is 0.9%. The material recovery rate was 86%.
この材料粉末を錠剤成型器で整形した後、ＳＥＭで観察した結果、ＰＴＦＥの塊は観察されなかった。
この材料粉末を実施例１と同一従来条件で評価した。その結果を表１に示した。更に得られた混合液から噴霧乾燥によりガス拡散電極用原料粉製造までに要した時間は表１及び２に示す通り、12分であった。
After this material powder was shaped with a tablet molding machine and observed with an SEM, no PTFE mass was observed.
This material powder was evaluated under the same conventional conditions as in Example 1. The results are shown in Table 1. Furthermore, as shown in Tables 1 and 2, the time required from the obtained mixed solution to the production of the raw material powder for gas diffusion electrode by spray drying was 12 minutes.
実施例１と同様にして高分散混合液を作製し、この液を、入口送風温度を220℃に設定しかつ乾燥室が濾布タイプの噴霧乾燥機（ＢＤＰ−15、大川原化工機株式会社製）内に定量ポンプを使用して導入し、乾燥粉末を作製した。噴霧乾燥時の噴霧乾燥機の出口温度は108℃、乾燥処理時間は約10分とした。
得られた乾燥粉末の実体顕微鏡で観察した平均粒子径は70μｍ、120℃の恒温槽内に１時間保存して算出した含水率は1.1％で、材料回収率は97％であった。
A highly dispersed mixed liquid was prepared in the same manner as in Example 1, and this liquid was set to an inlet blast temperature of 220 ° C. and the drying chamber was a filter cloth type spray dryer (BDP-15, manufactured by Okawara Kako Co., Ltd.). ) Using a metering pump to produce a dry powder. At the time of spray drying, the outlet temperature of the spray dryer was 108 ° C., and the drying time was about 10 minutes.
The average particle diameter of the obtained dry powder observed with a stereomicroscope was 70 μm, the moisture content calculated by storing in a constant temperature bath at 120 ° C. for 1 hour was 1.1%, and the material recovery rate was 97%.
この材料粉末を錠剤成型器で整形した後、ＳＥＭで観察した結果、ＰＴＦＥの塊は観察されなかった。
この材料粉末を実施例１と同一従来条件で評価した。その結果を表１に示した。更に得られた混合液から噴霧乾燥によりガス拡散電極用原料粉製造までに要した時間は表１及び表２に示す通り、10分であった。
After this material powder was shaped with a tablet molding machine and observed with an SEM, no PTFE mass was observed.
This material powder was evaluated under the same conventional conditions as in Example 1. The results are shown in Table 1. Further, as shown in Tables 1 and 2, the time required from the obtained mixed solution to the production of the raw material powder for gas diffusion electrode by spray drying was 10 minutes.
疎水性カーボンブラック（ＡＢ−６）100ｇを、2.5wt％に希釈した界面活性剤トライトン溶液2000cm3中に添加し、ラボスターラー（ヤマト科学株式会社製）で攪拌した。カーボンブラックの粒度分布を、株式会社堀場製作所製ＬＡ−920で測定した結果、平均粒子径は1.4μｍであった。 Hydrophobic carbon black (AB-6) 100 g was added to 2000 cm 3 of a surfactant Triton solution diluted to 2.5 wt%, and stirred with a laboratory stirrer (manufactured by Yamato Scientific Co., Ltd.). As a result of measuring the particle size distribution of carbon black with LA-920 manufactured by Horiba, Ltd., the average particle size was 1.4 μm.
このカーボンブラックを含む液にＰＴＦＥディスパージョン（ＰＴＦＥ30Ｊ）80cm3を添加し、更に30分間攪拌を行った。これにエタノール2000cm3を加えて15分間攪拌して凝集させた。凝集液中の粉末の平均粒子径は4.1μｍであった。この凝集液を0.2μｍのメンブレンフィルターを用い、0.18ＭＰａの窒素ガスで24分掛けて加圧濾過した。得られたペレット状の濾過物を80℃に設定した乾燥機内で７時間（420分）乾燥し、ブレードミルで20分掛けて粉砕し材料粉末を得た。この粉末の含水率は0.6％であった。
得られた材料粉末を錠剤成型器で整形した後、ＳＥＭで観察した結果、数μｍ〜80μｍ径のＰＴＦＥの塊が観察された。
この材料粉末を実施例１と同一従来条件で評価した。その結果を表１に示した。
更に濾過時間、乾燥時間、粉砕時間及び総時間を表２に纏めた。
［比較例２］
To this liquid containing carbon black, 80 cm 3 of PTFE dispersion (PTFE 30J) was added and further stirred for 30 minutes. Ethanol 2000 cm 3 was added thereto and stirred for 15 minutes for aggregation. The average particle size of the powder in the aggregated liquid was 4.1 μm. This agglomerated liquid was filtered under pressure using a 0.2 μm membrane filter for 24 minutes with 0.18 MPa of nitrogen gas. The obtained pellet-like filtrate was dried in a dryer set at 80 ° C. for 7 hours (420 minutes) and pulverized with a blade mill for 20 minutes to obtain a material powder. The water content of this powder was 0.6%.
After the obtained material powder was shaped with a tablet molding machine and observed with an SEM, a mass of PTFE having a diameter of several μm to 80 μm was observed.
This material powder was evaluated under the same conventional conditions as in Example 1. The results are shown in Table 1.
Further, the filtration time, drying time, pulverization time and total time are summarized in Table 2.
[Comparative Example 2]
疎水性カーボンブラック（ＡＢ−６）100ｇを、2.5wt％に希釈した界面活性剤トライトン溶液2000cm3中に添加し、ラボスターラー（ヤマト科学株式会社製）で攪拌しながら超音波分散機（ＵＨ−600）で30分間分散させた。
カーボンブラックの粒度分布をＬＡ−920で測定した結果、分散前の平均粒子径1.35μｍが分散後には平均粒子径0.8μｍまで減少していた。
Hydrophobic carbon black (AB-6) (100 g) was added to 2000 cm 3 of a surfactant Triton solution diluted to 2.5 wt%, and stirred with a lab stirrer (manufactured by Yamato Kagaku Co., Ltd.) with an ultrasonic disperser (UH- 600) for 30 minutes.
As a result of measuring the particle size distribution of the carbon black with LA-920, the average particle size of 1.35 μm before dispersion was reduced to 0.8 μm after dispersion.
このカーボンブラックを含む液にＰＴＦＥディスパージョン（ＰＴＦＥ30Ｊ）80cm3を添加し、更に30分間攪拌を行い高分散混合液を作製した。この混合液にエタノール2000 cm3を加えて15分間攪拌して凝集させた。凝集液中の粉末の平均粒子径は3.2μｍであった。この凝集液を0.2μｍのメンブレンフィルターを用い、0.18ＭＰａの窒素ガスで28分掛けて加圧濾過した。得られたペレット状の濾過物を80℃に設定した乾燥機内で７時間（420分）乾燥し、ブレードミルで20分掛けて粉砕し材料粉末を得た。この粉末の含水率は0.6％であった。
得られた材料粉末を錠剤成型器で整形した後、ＳＥＭで観察した結果、数μｍ〜80μｍ径のＰＴＦＥの塊が観察された。
この材料粉末を実施例１と同一従来条件で評価した。その結果を表１に示した。
更に濾過時間、乾燥時間、粉砕時間及び総時間を表２に纏めた。
［比較例３］
To this liquid containing carbon black, 80 cm 3 of PTFE dispersion (PTFE 30J) was added, and further stirred for 30 minutes to prepare a highly dispersed mixed liquid. To this mixture, 2000 cm 3 of ethanol was added and stirred for 15 minutes for aggregation. The average particle size of the powder in the aggregating liquid was 3.2 μm. This agglomerated liquid was filtered under pressure using a 0.2 μm membrane filter for 28 minutes with 0.18 MPa of nitrogen gas. The obtained pellet-like filtrate was dried in a dryer set at 80 ° C. for 7 hours (420 minutes) and pulverized with a blade mill for 20 minutes to obtain a material powder. The water content of this powder was 0.6%.
After the obtained material powder was shaped with a tablet molding machine and observed with an SEM, a mass of PTFE having a diameter of several μm to 80 μm was observed.
This material powder was evaluated under the same conventional conditions as in Example 1. The results are shown in Table 1.
Further, the filtration time, drying time, pulverization time and total time are summarized in Table 2.
[Comparative Example 3]
疎水性カーボンブラック（ＡＢ−６）100ｇを、2.5wt％に希釈した界面活性剤トライトン溶液2000cm3中に添加し、ラボスターラー（ヤマト科学株式会社製）で攪拌しながら超音波分散機（ＵＨ−600）で30分間分散させた。
カーボンブラックの粒度分布をＬＡ−920で測定した結果、分散前の平均粒子径1.3μｍが分散後には平均粒子径0.8μｍまで減少していた。
Hydrophobic carbon black (AB-6) (100 g) was added to 2000 cm 3 of a surfactant Triton solution diluted to 2.5 wt%, and stirred with a lab stirrer (manufactured by Yamato Kagaku Co., Ltd.) with an ultrasonic disperser (UH- 600) for 30 minutes.
As a result of measuring the particle size distribution of carbon black with LA-920, the average particle size of 1.3 μm before dispersion was reduced to 0.8 μm after dispersion.
このカーボンブラックを含む液にＰＴＦＥディスパージョン（ＰＴＦＥ30Ｊ）80cm3を添加し、更に30分間攪拌を行い高分散混合液を作製した。カーボンブラックの平均粒子径は0.8μｍでＰＴＦＥ添加前と同じであった。
この混合液を0.2μｍのメンブレンフィルターを用い、0.18ＭＰａの窒素ガスで45分掛けて加圧濾過した。得られた薄いペレット状の濾過物を80℃に設定した乾燥機内で７時間（420分）乾燥し、ブレードミルで20分掛けて粉砕し材料粉末を得た。この粉末の含水率は0.7％であった。
得られた材料粉末を錠剤成型器で整形した後、ＳＥＭで観察した結果、ＰＴＦＥの塊は観察されなかった。
この材料粉末を実施例１と同一従来条件で評価した。その結果を表１に示した。
更に濾過時間、乾燥時間、粉砕時間及び総時間を表２に纏めた。
［比較例４］
To this liquid containing carbon black, 80 cm 3 of PTFE dispersion (PTFE 30J) was added, and further stirred for 30 minutes to prepare a highly dispersed mixed liquid. The average particle size of carbon black was 0.8 μm, which was the same as before PTFE addition.
This mixed solution was subjected to pressure filtration using a 0.2 μm membrane filter with 0.18 MPa nitrogen gas over 45 minutes. The obtained thin pellet-like filtrate was dried in a dryer set at 80 ° C. for 7 hours (420 minutes) and pulverized with a blade mill for 20 minutes to obtain a material powder. The water content of this powder was 0.7%.
After the obtained material powder was shaped with a tablet molding machine and observed with SEM, no PTFE mass was observed.
This material powder was evaluated under the same conventional conditions as in Example 1. The results are shown in Table 1.
Further, the filtration time, drying time, pulverization time and total time are summarized in Table 2.
[Comparative Example 4]
比較例１と同一条件で凝集液を作製し、この凝集液を、実施例１における混合液と同様にして噴霧乾燥を行った。
得られた乾燥粉末は、球状もしくは一部が陥没した球状であり、実体顕微鏡で観察した粒子径は５〜50μｍ、120℃の恒温槽内に１時間保存して算出した含水率は1.5％で、材料回収率は75％であった。
［比較例５］
An aggregate liquid was produced under the same conditions as in Comparative Example 1, and this aggregate liquid was spray-dried in the same manner as the mixed liquid in Example 1.
The obtained dry powder has a spherical shape or a partially depressed spherical shape. The particle size observed with a stereomicroscope is 5 to 50 μm, and the water content calculated by storage in a constant temperature bath at 120 ° C. for 1 hour is 1.5%. The material recovery rate was 75%.
[Comparative Example 5]
エタノールの代わりにアセトンを使用して比較例４と同様にして噴霧乾燥を行った。
得られた乾燥粉末は、球状もしくは一部が陥没した球状であり、実体顕微鏡で観察した粒子径は５〜45μｍ、120℃の恒温槽内に１時間保存して算出した含水率は1.3％で、材料回収率は76％であった。
Spray drying was performed in the same manner as in Comparative Example 4 using acetone instead of ethanol.
The obtained dry powder has a spherical shape or a partially depressed spherical shape. The particle size observed with a stereomicroscope is 5 to 45 μm, and the water content calculated by storage in a constant temperature bath at 120 ° C. for 1 hour is 1.3%. The material recovery rate was 76%.
各実施例及び比較例を比較すると、ミセル破壊剤を使用せずにガス拡散電極用原料粉を製造することにより、比抵抗が小さく、耐水圧が高く、更に引張強度が大きく、引張圧延率の高いガス拡散電極用原料粉が得られたことが分かる。 Comparing each example and comparative example, by producing the raw material powder for gas diffusion electrode without using a micelle disrupting agent, the specific resistance is small, the water pressure resistance is high, the tensile strength is large, the tensile rolling rate is It turns out that the raw material powder for high gas diffusion electrodes was obtained.
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