JP2004235137A

JP2004235137A - Method of manufacturing fuel cell separator and molding

Info

Publication number: JP2004235137A
Application number: JP2003199291A
Authority: JP
Inventors: Takashi Gonda; 貴司権田; Nobuhiro Shimane; 伸浩島根
Original assignee: Shin Etsu Polymer Co Ltd; Shin Etsu Chemical Co Ltd
Current assignee: Shin Etsu Polymer Co Ltd; Shin Etsu Chemical Co Ltd
Priority date: 2002-12-04
Filing date: 2003-07-18
Publication date: 2004-08-19

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive method of manufacturing a fuel cell separator and a molding, whereby there is no possibility of burrs produced at the joint of a die, and electrical characteristics for practical use can be obtained. <P>SOLUTION: This method is provided with a process to fill a mixed molding material 1 in a preforming die 10 and to preform an intermediate article 20 by compressing it, and a process to provide a plurality of grooves side by side in the molding by actually molding the intermediate article 20 by an actual molding die. When a region with grooves and a region without grooves in the molding are made of the same material, the rate of a mass per the unit area of the region with grooves to a mass per the unit area of the region without grooves in the molding is defined as R0, and the rate of a mass per the unit area of a region with expected grooves to a mass per the unit area of a region without expected grooves in the intermediate article 20 is defined as R1, the value of R1/R0 is not less than 0.8 but not more than 1.3. Since the molding is obtained by applying primary molding by using the mixed molding material 1, and by applying secondary molding to the intermediate article 20 processed in advance by the actual molding die, a work time can be shortened, and the availability factor of the actual molding die can be enhanced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電気、電子、半導体の分野等で使用される燃料電池用セパレータ及び成形品の製造方法に関するものである。
【０００２】
【従来の技術】
従来、板形の成形品４０Ａを製造する場合には、図１９に示す所定の材料６０を金型６１に充填して圧縮加熱（図２０参照）し、板形の成形品４０Ａを成形して取り出す（図２１参照）ようにしている。
しかしながら、板形の成形品４０Ａを単に成形するだけでは、品質の不安定化を招くという問題がある。すなわち、成形品４０Ａが横長の断面略Ｕ字形でその周縁部と非周縁部との断面が相違する場合等には、例え成形品４０Ａの肉厚が同一でも、密度が一定しないので、品質が安定しないこととなる。この問題を解消する手段として、成形品４０Ａの厚みに応じて材料６０を充填する技術が提案されている（特許文献１参照）。
また、板形の成形品４０Ａが燃料電池用セパレータの場合には、様々な製造方法により製造されている（特許文献２、３参照）。
【０００３】
【特許文献１】
特開２００２−１９２３９３号公報
【０００４】
【特許文献２】
特開２００２−２９４０２４号公報
【０００５】
【特許文献３】
特開２００２−２３１２６１号公報
【０００６】
【発明が解決しようとする課題】
しかし、上記文献の技術を採用する場合、材料６０が飛散して金型６１の接合部等にバリの生じるおそれが少なくない。また、特許文献２の製造方法により、燃料電池用セパレータからなる板形の成形品４０Ａを製造する場合、実用に耐えることのできる電気的特性を得ることができない。さらに、特許文献３の製造方法を採用する場合、実用に耐える電気的特性を得るには、炭化焼成が必要となるので、価格の増大を招くという問題がある。
【０００７】
本発明は、上記に鑑みなされたもので、金型の接合部等にバリの生じるおそれがなく、実用の電気的特性を得ることのできる安価な燃料電池用セパレータ及び成形品の製造方法を提供することを目的としている。
【０００８】
【課題を解決するための手段】
本発明者等は、鋭意研究した結果、特定の分子量、粒子形状、粒子径を有するフェノール樹脂に着目し、このフェノール樹脂と黒鉛との混合物を融点（ＤＳＣにおける吸熱ピーク温度をいう）以下の温度で圧縮成形して中間品を予備成形し、この中間品を融点以上の温度で本成形すれば、上記課題を達成することができることを見出し、本発明を完成させた。
すなわち、本発明においては、上記課題を達成するため、フェノール樹脂１００質量部に対して黒鉛９００〜２０００質量部が添加された混合成形材料により略板体に成形され、両面に複数の凹凸がそれぞれ配列されていることを特徴としている。
なお、フェノール樹脂を、自己硬化性を有するフェノール・ホルムアルデヒド系樹脂とすることができる。
【０００９】
また、本発明においては、上記課題を達成するため、熱硬化性樹脂と導電性材料とからなる混合成形材料を使用して成形品を製造するものの製造方法であって、
混合成形材料を使用して成形品と略同様の外形を有する中間品を成形する予備成形工程と、この中間品を成形してその成形品の少なくとも一面に複数の溝を配列する本成形工程とを含んでなることを特徴としている。
なお、フェノール樹脂１００質量部に対して黒鉛９００〜２０００質量部を添加して混合成形材料とし、成形品を燃料電池用セパレータとすることができる。
【００１０】
また、成形品を板体としてその両面には複数の溝をそれぞれ所定のピッチで並べ設け、成形品の一面における溝の位置と、成形品の他面における溝の位置とを配列方向にずらして相互に相違させることができる。
また、予備成形時に用いる予備成形金型、及び又は本成形時に用いる本成形金型の一の型の形成部を分割して開閉方向にスライド可能とすることができる。
また、本成形金型を熱硬化性樹脂の硬化温度に保持することができる。
また、成形品における溝無し領域の単位面積当たりの質量に対する溝領域の単位面積当たりの質量の比率をＲ０、中間品における溝無し予定領域の単位面積当たりの質量に対する溝予定領域の単位面積当たりの質量の比率をＲ１とし、Ｒ１／Ｒ０の値を０．８〜１．２の範囲とすることができる。
【００１１】
また、成形品における溝領域の密度／溝無し予定領域の密度を０．８〜１．２の範囲とすることができる。
また、本成形金型の形成部における立面壁の少なくとも開口側を外側に傾斜させると良い。
さらに、予備成形時に融点以下の温度で成形品の９５〜１００％以下の面積を有する中間品を成形し、本成形時に中間品を融点以上の温度で加熱加圧成形することが好ましい。
さらにまた、本成形時に、本成形金型に中間品をガス抜きせずにセットすることが好ましい。
【００１２】
ここで特許請求の範囲における混合成形材料は、粉末の熱硬化性樹脂と導電性材料とからなり、金型内での材料移動がきわめて少ないものが主ではあるが、特に限定されるものではない。この混合成形材料は、例えば導電性材料と熱硬化性樹脂とが混合・混練されることにより調製される。具体的には、例えばカーボンや黒鉛等の無機材料からなる導電性材料と、フェノール樹脂やエポキシ樹脂等の粉末からなり、バインダー機能を有する熱硬化性樹脂とが混合・混練されることにより所定質量部（例えば５０質量部以上、好ましくは８０質量部以上）調製される。混合成形材料は、その粘性や流動性が高くても低くても良い。また、成形品は、その両面に複数の溝を並べ備えたものが主ではあるが、一面に複数の溝を並べ備えたものでも良い。成形品と略同様の外形には、成形品と同一の外形の他、成形品とおおよそ同一と認められる類似の外形が含まれる。
【００１３】
成形品は、その一面における溝の位置と他面における溝の位置とが配列方向にずれて相互に相違するのが主ではあるが、一面における溝の位置と他面における溝の位置とが配列方向にずれていなくても良い。成形品の一面の溝と他面の溝とは、形状、間隔、方向等が同一でもそうでなくても良い。また、成形品に単数複数の孔を成形により設ける場合、貫通孔部分がその周辺と表面が連なるものとして、換言すれば、貫通孔が存在しないものとして、領域の質量、密度を算出するものとする。さらに、本発明に係る成形品は、少なくとも電気、電子、電池、精密部品、自動車等の分野で利用することが可能である。
【００１４】
本発明によれば、フェノール樹脂に黒鉛を混合した混合成形材料を使用し、成形するだけで燃料電池用セパレータを得ることができるから、燃料電池用セパレータの抵抗値を低下させることができる。
また、フェノール樹脂を、自己硬化性を有するフェノール・ホルムアルデヒド系樹脂とすれば、硬化剤の分散性が不安定になるのを抑制することができる。すなわち、燃料電池用セパレータを製造する場合には、通常、硬化剤を混合する必要があるが、この硬化剤の量はフェノール樹脂よりも少ないので、黒鉛を含めた全体量に対して少ない量を混合することになり、硬化剤の分散性が不安定になる。しかしながら、フェノール樹脂を、自己硬化性のフェノール・ホルムアルデヒド系樹脂とすれば、硬化剤が不要となり、分散性が安定する。
【００１５】
また、本発明によれば、飛び散りやすい材料を使用して成形品を直ちに製造するのではなく、混合成形材料を使用して固形の中間品を予め成形し、この飛び散らない中間品に外力を加えて変形させ、成形品を製造するので、材料の飛び散りに伴うバリの発生を抑制することができる。
また、中間品と成形品の投影面積当たりの容積比率を略同等とするので、成形品の各部分の密度がおおよそ一定する。
【００１６】
【発明の実施の形態】
以下、図面を参照して本発明の好ましい実施形態を説明すると、本実施形態における燃料電池用セパレータの製造方法は、図１ないし図７に示すように、混合成形材料１を予備成形金型１０に充填・圧縮して燃料電池用セパレータの中間品２０を予備成形する工程と、この中間品２０を本成形金型３０で加熱加圧して複数の溝４１を並設する工程とを備え、燃料電池用セパレータである成形品４０の溝領域と溝無し領域とを同一の材料とし、成形品４０における溝無し領域の単位面積当たりの質量に対する溝領域の単位面積当たりの質量の比率をＲ０、中間品２０における溝無し予定領域の単位面積当たりの質量に対する溝予定領域の単位面積当たりの質量の比率をＲ１とした場合に、Ｒ１／Ｒ０の値を０．８以上１．２以下の値とするようにしている。
【００１７】
混合成形材料１は、フェノール樹脂１００質量部に対して黒鉛が９００〜２０００質量部添加され、タンブラーミキサー、ヘンシルミキサー、リボンブレンダー、ナウタミキサー等の攪拌機により混合調製される。フェノール樹脂としては、レゾール型、ノボラック型、フェノール類とホルムアルデヒドとの反応により生成されるフェノール樹脂、フェノール類とホルムアルデヒドとを少なくとも含窒素系化合物の存在下で反応させて得られる縮合物に親水性高分子化合物を添加し、反応させて得られるフェノール樹脂、及びフェノールとホルムアルデヒドとを塩基性水溶液中で反応させて得られるプレポリマーを保護コロイドと混合し、酸性下で不活性固形ビーズ状に凝固させて得られるもの等があげられる。
【００１８】
特に、特公昭６２−３０２１１号公報記載の方法により得られるフェノール樹脂は、レゾール型、ノボラック型のフェノール樹脂と比較して粒子形状が球状で高分子量であり、黒鉛の高充填化が可能であるとともに、成形時の溶融温度が高いので、黒鉛粒子の表面被覆が他のフェノール樹脂と比較して小さく、硬化反応も緩やかであるので最適である。
【００１９】
フェノール樹脂は、平均粒径が５〜１００μｍ以下の球状が好ましい。これは、平均粒径が５μｍ未満の場合には、フェノール樹脂が黒鉛との混合時に舞い上がり、作業環境が悪化するからである。逆に、平均粒径が１００μｍを超える場合には、黒鉛との混合の均一化が困難になり、成形した燃料電池用セパレータの表面に凹凸模様が生じて好ましくないからである。また、フェノール樹脂の分子量は、３，０００〜２０，０００以下、好ましくは４，０００〜１５，０００以下、より好ましくは５，０００〜１０，０００以下が良い。フェノール樹脂の分子量が３，０００以上を要するのは、分子量が３，０００未満の場合には、黒鉛の高充填化が困難となり、溶融温度が低下するので黒鉛粒子の表面被覆が大きくなり、電気的特性が低下して燃料電池用セパレータの電気的特性に問題が生じるからである。
【００２０】
黒鉛としては、鱗片状黒鉛、鱗状黒鉛、土壌黒鉛等の天然黒鉛あるいは天然コークス等を原料として成形、焼成し、さらに２５００℃以上の高温で黒鉛化した人造黒鉛、鱗片状黒鉛を濃硫酸と過酸化水素、過塩素酸塩、過マンガン酸塩等の強酸化剤で処理し黒鉛層間化合物を生成した後、水洗、乾燥して製造される膨張黒鉛、膨張黒鉛を９５０〜１１００℃の高温下で急激に加熱して得られる膨張化黒鉛等の人造黒鉛等、特に限定されるものではないが、かさ比重が０．１ｇ／ｃｃ以上の黒鉛が好ましい。かさ比重が０．１ｇ／ｃｃ以上を要するのは、かさ比重が０．１ｇ／ｃｃ未満の場合、中間品２０の成形が困難になったり、フェノール樹脂との均一な混合に問題が生じるからである。
【００２１】
黒鉛は、単独あるいは２種以上の混合物を使用することができる。この黒鉛は、平均粒径が５〜１００μｍ以下、好ましくは平均粒径が１０〜７０μｍ以下の鱗片状が好適である。これは、平均粒径が５μｍ未満の場合には、電気的特性の低下を招く他、フェノール樹脂との混合時に黒鉛が舞い上がり、作業環境が悪化するという理由に基づく。逆に、平均粒径が１００μｍを超える場合には、フェノール樹脂との混合の均一化が困難になり、成形した燃料電池用セパレータの機械的特性が低下するという理由に基づく。黒鉛は、平均粒径が同一のものでも良いし、異なるものを使用することも可能である。
【００２２】
なお、アセトアルコキシアルミニウムジイソプロピレート等のアルミネート系カップリング剤、イソプロピルトリイソステアロイルチタネート、ビス（ジオクチルバイロホスフェート）オキシアセテート、イソプロピルトリデシルベンゼンスルホニルチタネート等のチタネート系カップリング剤、γ−グリシドキシプロピルメチルジエトキシシラン、β−（３，４エポキシシクロヘキシル）エチルトリメトキシシラン、Ｎ−β（アミノエチル）γ−アミノプロピルトリメトキシシラン等のシランカップリング剤等の表面改質剤、あるいはアセチレンアルコール、アセチレングリコール、グリセリン脂肪族エステル、ソルビタン脂肪族エステル、ポリグリセリン脂肪族エステル、プロピレングリコール脂肪族エステル、高吸アルコール脂肪族エステル等の各種界面活性剤で表面処理された黒鉛も本発明の特性を失わない範囲で使用可能である。
【００２３】
フェノール樹脂と黒鉛との配合は、フェノール樹脂１００質量部に対して黒鉛が９００〜２０００質量部、好ましくはフェノール樹脂１００質量部に対して黒鉛１１００〜１９００質量部、より好ましくはフェノール樹脂１００質量部に対して黒鉛１２００〜１７００質量部が良い。これは、黒鉛の添加量がフェノール樹脂１００質量部に対して９００質量部未満の場合には、燃料電池用セパレータの電気的特性に支障を来たすからである。逆に、黒鉛の添加量がフェノール樹脂１００質量部に対して２０００質量部を超える場合には、実用に耐える燃料電池用セパレータの機械的特性を得ることができないからである。
【００２４】
混合成形材料１には、燃料電池用セパレータの特性を失わせない範囲において、炭酸カルシウム、タルク、カオリン、珪藻土、天然あるいは合成シリカ、ウォラストナイト、ベントナイト、セビオライト、マイカ、水酸化アルミニウム、酸化チタン、ガラスビーズ、ガラスバルーン、活性炭、木炭、竹炭、ガラス繊維、アラミド繊維、金属繊維等の充填剤、導電性オイルファーネスブラック、アセチレンブラック、サーマルブラック、ＰＡＮ系カーボン繊維、ピッチ系カーボン繊維等のカーボン系導電性充填剤、金、銀、銅、パラジウム、アルミニウム、ステンレス等の金属粉末を添加することができる。
【００２５】
予備成形金型１０は、図１等に示すように、相対向する凹字形の固定型１１とスライド可能な凸字形の可動型１２とを備える。固定型１１は、その凹んだ形成部１３が複数に分割されてその中央の一部が開閉方向（本実施形態では上下方向）に適宜スライド可能とされ、図３に示す底部の浅い横長で断面略Ｕ字形の中間品２０を予備成形したり、ハンドリング等に資するよう機能する。また、可動型１２の対向面周縁部には、略枠形の段差１４が切り欠かれる。
【００２６】
本成形金型３０は、図４や図５等に示すように、相対向する凹字形の固定型３１と凸字形の可動型３２とを備え、これら固定型３１とスライド可能な可動型３２との対向面には、中間品２０に製品形状を転写する複数の凹凸３３が略等間隔に並べて形成される。固定型３１の凹んだ形成部３４の各立面壁３５は、その開口側が徐々に外側に傾斜形成され、製造した成形品４０の脱型等を容易化する。
【００２７】
上記において、燃料電池用セパレータを製造する場合には、先ず、粉末状のフェノール樹脂と黒鉛とを混合・攪拌して混合成形材料１を調製し、この混合成形材料１を予備成形金型１０に充填（図１参照）して５〜１２０秒、好ましくは１０〜１００秒加圧（図２参照）し、成形品４０と略同様の外形寸法（厚さ寸法除く）を有する横長で断面略凹字形の中間品２０を略平板に予備成形（図３参照）し、その後、予備成形金型１０を型開きして固形物と化した中間品２０を取り出す。
【００２８】
混合成形材料１の充填に際しては、混合成形材料１の密度や深さ（高さ）を成形品４０の単位面積当たりの質量に応じて充填すると、密度にムラの少ない中間品２０を得ることができる。また、加圧時間が５〜１２０秒なのは、加圧時間が５秒未満の場合には中間品２０の成形が困難となり、逆に加圧時間が１２０秒を超える場合には成形サイクルが長くなり、成形効率の低下を招くからである。
【００２９】
成形温度は、混合成形材料１の融点以下であることが必要となる。これは、融点を超える場合には、フェノール樹脂が溶融し、予備成形金型１０から中間品２０を取り出す場合に中間品２０にそりが生じたり、変形や電気的特性の低下を招くからである。成形に要する成形圧力は０．１〜２ＭＰａの範囲が好ましい。これは、成形圧力が０．１ＭＰａ未満の場合には、中間品２０の成形が困難化し、予備成形金型１０から中間品２０を取り出す場合に中間品２０の破損するおそれがあるからである。逆に、成形圧力が２ＭＰａを超える場合には、フェノール樹脂が黒鉛の表面を覆い、電気的特性が低下するという理由に基づく。また、中間品２０は、融点以下の温度で成形品４０の９５〜１００％以下の面積を有するように成形される。
【００３０】
中間品２０を予備成形したら、この中間品２０を本成形金型３０にインサート（図４参照）して加熱加圧（図５参照）し、中間品２０の表裏両面に複数の溝４１をそれぞれ略等間隔のピッチで平行に並設して成形品４０を成形した後、加圧状態で硬化させて本成形金型３０を型開きし、硬化した成形品４０を取り出せば（図６参照）、燃料電池用セパレータである成形品４０を製造することができる。
なお、本実施形態においては、成形品４０の表面における溝４１の位置と裏面における溝４１の位置とは、図６に示すように、左右配列方向にずれて相互に相違する。
【００３１】
本成形に際しては、中間品２０と成形品４０の断面寸法が以下の関係となるよう留意するのが好ましい。すなわち、図３や図７において、成形品４０の幅寸法をｗＯ、中間品２０の相対的に突出した周縁部の幅寸法をｗＡ、中間品２０の周縁部以外の幅寸法をｗＣ、成形品４０の表面端部から直近の溝４１の上端部までの寸法をｍ１，ｍ２、成形品４０の裏面端部から直近の溝４１の下端部までの寸法をｎ１，ｎ２とすると、中間品２０と成形品４０とが、ｗＡ＝（ｍ１＋ｎ１）／２、ｗＣ＝（ｍ２＋ｎ２）／２の関係にあれば、良質の成形品４０を得ることができる。
【００３２】
本成形の加熱加圧時間は、１〜６０分以下、好ましくは３〜４０分以下、より好ましくは３〜３０分以下が良い。これは、１分未満の場合には、硬化が不十分になるので機械的特性が劣化したり、使用中に成形品４０にそりが発生するからである。逆に、６０分を超える場合には、成形サイクルの遅延化を来たすからである。成形温度は、混合成形材料１の融点〜３５０℃以下、好ましくは１５０℃〜２５０℃以下、より好ましくは１５０℃〜２００℃以下が良い。これは、成形温度が融点以下の場合には、フェノール樹脂が溶融硬化しないので成形品４０を得ることができなくなるという理由に基づく。逆に、成形温度が３５０℃を超える場合には、フェノール樹脂が分解するので、成形品４０の機械的特性が低下するという理由に基づく。
【００３３】
成形に要する成形圧力は、３〜２０ＭＰａの範囲、好ましくは５〜２０ＭＰａの範囲、換言すれば、１０〜２００ｋｇ／ｃｍ^２、好ましくは３０〜１５０ｋｇ／ｃｍ^２、より好ましくは５０〜１００ｋｇ／ｃｍ^２が良い。これは、成形圧力が３ＭＰａ未満の場合には、充填密度が低下するので、機械的、電気的特性が低下するからである。逆に、成形圧力が２０ＭＰａを超える場合には、フェノール樹脂が黒鉛の表面を覆い、電気的特性が低下するからである。
【００３４】
なお、中間品２０は、予備成形の段階で圧縮され、僅かな空気しか含有されていないので、一般的なプレス成形で必要なガス抜きが不要となる。したがって、本成形金型３０の型締め後にガス抜きすることなく、成形時間を短縮することができる。また、本成形した成形品４０には、１８０℃〜２５０℃以下の温度で必要に応じ、熱処理することもできる。
【００３５】
上記によれば、粉末状の混合成形材料１を用いて成形品４０を直ちに製造するのではなく、先ず、混合成形材料１を用いて一次成形し、この予め処理され、比較的簡単に崩れる中間品２０を本成形金型３０で二次成形して崩し、溝４１付きの成形品４０を得るので、作業時間を大幅に短縮することができ、本成形金型３０の稼働率を著しく向上させることができる。すなわち、精密な成形品４０を製造するためには、金型内の必要個所に混合成形材料１を過不足なく充填するのが必要不可欠となるが、この充填作業には、長時間を要することが少なくない。この点、本実施形態によれば、本成形金型３０に取り扱いの容易な中間品２０をインサートするだけで良い。したがって、準備時間を短縮（所定の条件下では、半分以下の時間となる）して本成形金型３０の稼働率を向上させることができる。
【００３６】
また、粒径が１０μｍに満たない微細の粉末を含む混合成形材料１を金型内に充填する場合には、高温加熱された金型に上昇気流が生じている関係上、混合成形材料１が飛散して形成部１３以外の個所に付着硬化し、バリの原因となって金型の寿命を縮める等の不具合を招くことが少なくない。また、金型内に粉末の混合成形材料１を充填すると、最初に金型に接触した混合成形材料１の硬化反応が始まるので、成形品４０の部分毎に硬化反応の進み方が異なり、加圧（圧縮）に基づく製品形状の転写にも悪影響を及ぼすこととなる。これに対し、本実施形態によれば、本成形金型３０に固形の中間品２０をインサートするので、バリの原因となることがなく、長期に亘り金型を使用することができ、しかも、加圧に基づく製品形状の転写にもなんら悪影響を及ぼすことがない。
【００３７】
また、肉厚が一定ではない成形品４０を成形する場合には、その肉厚に応じた材料を充填する必要があるが、粉末からなる混合成形材料１では肉厚に応じた充填が実に困難である。これに対し、本実施形態によれば、中間品２０を単なる平板に成形するのではなく、横長の断面略Ｕ字形に予備成形し、しかも、成形品４０における溝無し領域の単位面積当たりの質量に対する溝領域の単位面積当たりの質量の比率をＲ０、中間品２０における溝無し予定領域の単位面積当たりの質量に対する溝予定領域の単位面積当たりの質量の比率をＲ１とした場合に、Ｒ１／Ｒ０≒１とする。
【００３８】
換言すれば、成形品４０における溝領域の密度／溝無し予定領域の密度を０．８〜１．２の範囲とするので、部位毎に適正量の混合成形材料１を供給することができる。この結果、混合成形材料１の流動性にかかわりなく、成形品４０の密度が一定化し、良質の成形品４０を容易に得ることが可能となる。また、フェノール樹脂に黒鉛を混練溶融して粉砕し、これを予備成形、本成形するのではなく、フェノール樹脂に黒鉛を混練するだけで、実用的な燃料電池用セパレータを得ることができるから、燃料電池用セパレータの抵抗値の大幅な低下が期待できる。さらに、曲げ特性、電気的特性、厚み精度、優れた表面状態を得ることができ、しかも、製造コストを著しく削減することができる。
【００３９】
さらにまた、本成形金型３０を構成する固定型３１の形成部３４における各立面壁３５の開口側が徐々に外側に傾斜して中間品２０の周縁部との間にクリアランスを形成するので、図８のように脆い中間品２０が引っかかったり、破損する等、インサートに支障を来たすことがない。
【００４０】
次に、図９、図１０は本発明における第２の実施形態を示すもので、この場合には、予備成形金型１０を構成する可動型１２の段差１４を省略して平坦な成形面とし、この可動型１２を用いて面が平らな中間品２０を予備成形するようにしている。その他の部分については、上記実施形態と同様であるので説明を省略する。
本実施形態においても上記実施形態と同様の作用効果が期待でき、しかも、平坦な中間品２０を予備成形するので、溝４１を有しない複数の中間品２０同士の積層がきわめて容易となるのは明らかである。
【００４１】
次に、図１１は本発明における第３の実施形態を示すもので、この場合には、本成形金型３０を構成する固定型３１の形成部３４における各立面壁３５を徐々に外側に傾斜させて成形品４０の周縁部との間にクリアランスを形成し、中間品２０のインサートと成形品４０の離型とを容易化するようにしている。その他の部分については、上記実施形態と同様であるので説明を省略する。
本実施形態においても上記実施形態と同様の作用効果が期待でき、しかも、各立面壁３５の開口側だけではなく、開口側以外の領域をも一律に外側に傾斜させるので、固定型３１の設計・製造が容易化するのは明らかである。
【００４２】
次に、図１２ないし図１６は本発明における第４の実施形態を示すもので、この場合には、燃料電池セパレータの中間品２０を本成形金型３０に中間品用供給具５０により供給するようにしている。
本成形金型３０は、図１２等に示すように、中間品用供給具５０の開放された開口５２より中間品２０が落下して供給される固定型３１と、この固定型３１に対して開閉する可動型３２とを備えている。
【００４３】
固定型３１と可動型３２との対向面には、複数の凹凸３３が所定のピッチ・方向で並設され、この複数の凹凸３３が中間品２０の表裏面に複数の溝４１を所定のピッチ・方向で転写する。固定型３１は、中間品２０を囲む枠形の周壁３６と、この周壁３６の内底に嵌合されて可動型３２の開閉方向（本実施形態では上下方向）に往復動する底部３７と、これら周壁３６と底部３７とを搭載するベース板３８とに分割され、可動型３２の下方に位置する。固定型３１の周壁３６は、内周面下部が垂直に形成され、内周の立面壁３５が徐々に外方向に傾斜形成されており、この立面壁３５が成形品４０の脱型を容易化するよう機能する。この固定型３１の周壁３６の上部には、中間品用供給具５０を位置決めしたり、ガイドする機構（図示せず）が配設される。
【００４４】
中間品用供給具５０は、図１５や図１６に示すように、一対のガイドレール５１と、この一対のガイドレール５１の間の開口５２を開閉する搭載板５７とを備え、一対のガイドレール５１の間に搭載板５７を挿入し、一対のガイドレール５１の両端部間に連結板５４・５４Ａをそれぞれ架設するとともに、連結板５４Ａを着脱自在とするようにしている。
【００４５】
一対のガイドレール５１、搭載板５７、一対の連結板５４・５４Ａは、少なくとも中間品２０と接触する９０％以上の領域が繊維系、発泡プラスチック系、ガラスウール等の断熱材により形成され、中間品２０が本成形金型３０に供給される前に中間品２０に熱が伝わるのを抑制するよう機能する。一対のガイドレール５１は、図１５や図１６に示すように、それぞれ細長い薄板に形成され、間隔をおいて相互に対向して中間品２０よりも大きい平面矩形の開口５２を形成しており、この開口５２が中間品２０を落下させるよう機能する。各ガイドレール５１の対向面には、断面Ｕ字形の嵌合ガイド溝５３が長手方向に切り欠かれる。
【００４６】
一対のガイドレール５１の一端部間には連結板５４が一体形成され、この連結板５４の内周面には、ガイドレール５１の嵌合ガイド溝５３に連通する断面Ｕ字形の嵌合ガイド溝５３が切り欠かれる。また、一対のガイドレール５１の他端部間には、接続板５５が一体形成されるとともに、この接続板５５上に隙間を介して対向する連結板５４Ａがガイドレール５１内側の取付溝５６を介し着脱自在に装着され、この連結板５４Ａが搭載板５７の表面に接触し、かつ中間品２０のずれや損傷等を規制する。
【００４７】
搭載板５７は、ポリイミドフィルム等を使用して中間品２０よりも大きい平面矩形の薄板に形成される。そして、一対のガイドレール５１の間に嵌合ガイド溝５３を介しスライド可能・着脱可能に挿入支持され、開口５２を開閉するとともに、中間品２０を搭載するよう機能する。その他の部分については、上記実施形態と同様であるので説明を省略する。
【００４８】
上記において、燃料電池セパレータの成形品４０を本成形する場合には、先ず、混合成形材料１を調製し、この混合成形材料１を予備成形金型１０に充填して圧縮し、成形品４０と略同様の外形寸法を有する中間品２０を予備成形して脱型する。溝４１無しの中間品２０を成形したら、この取り扱いが容易になった単一の中間品２０を略枠形を呈した中間品用供給具５０の搭載板５７に載せ、この搭載板５７を一対のガイドレール５１間に嵌合ガイド溝５３を介し挿入して開口５２を閉塞し、連結板５４Ａをガイドレール５１の取付溝５６に嵌入して搭載板５７に接触させ、中間品２０の位置ずれや損傷等を規制するようにする。この際、一対のガイドレール５１上に、中間品２０を覆う蓋体（図示せず）をセットして本成形金型３０の可動型３２の輻射熱を防ぐようにしても良い。
【００４９】
次いで、予め加熱しておいた本成形金型３０を型開きしてその固定型３１と可動型３２との間に中間品用供給具５０を介在するとともに、固定型３１の周壁３６の上部に中間品用供給具５０を機構を介して位置決め固定（図１２参照）し、中間品用供給具５０の搭載板５７を引き抜いて開口５２を開放し、固定型３１内に中間品２０を落下供給（図１３参照）し、固定型３１から中間品用供給具５０を取り外す（図１４参照）。こうして中間品用供給具５０を取り外したら、固定型３１と可動型３２とを型締めして所定時間加熱加圧し、インサートされた中間品２０の表裏両面にそれぞれ複数の溝４１を転写して加圧状態で硬化させ、成形品４０を成形する。
【００５０】
この際、中間品２０は、予備成形の段階で圧縮され、僅かな空気しか含有されていないので、一般的なプレス成形で必要なガス抜きが不要となる。したがって、本成形金型３０の型締め後にガス抜きすることなく、成形時間を短縮することができる。
【００５１】
次いで、本成形金型３０を型開きして成形品４０を搭載した固定型３１の底部３７を上昇させ、固定型３１の周壁３６の内周面下部から成形品４０の周縁部を離隔させ、固定型３１の内周面中央付近に成形品４０の周縁部を支持させ、成形品４０から離れた固定型３１の底部３７を元の位置に下降復帰させる。成形品４０は、残留する内圧で外寸法が少々膨張拡大するので、固定型３１の周壁３６の内周面下部から立面壁３５の下端との境界付近まで移動すると、傾斜した立面壁３５に摩擦により支持されることとなる。また、固定型３１の底部３７の上下動に際しては、エジェクタロッドの駆動を利用することができる。その後、固定型３１の底部３７が元の位置に復帰したら、硬化した成形品４０を取り出し、成形品４０を得ることができる。
【００５２】
本実施形態においても上記実施形態と同様の作用効果が期待でき、しかも、中間品用供給具５０を利用して固定型３１内に中間品２０を供給するので、材料の投入から加圧開始までの時間を著しく短縮（所定の条件下では１０秒以下）することができ、セパレータとしての特性（体積抵抗率の減少）を大幅に向上させることができる。また、中間品用供給具５０の入る隙間があれば良いから、本成形金型３０の型開きストロークが僅かな量で済み、作業時間の大幅な短縮を図ることができる。
【００５３】
また、連結板５４Ａをガイドレール５１の取付溝５６に嵌入して搭載板５７に接触させるので、引き抜きに伴う搭載板５７上の中間品２０の移動できる範囲が制限され、位置ずれや損傷等を規制することができる。これにより、中間品２０の投入時間を短縮するため、例え水平方向に加速度を加えても、中間品２０の変形や損傷を抑制防止して安定した取り扱いが可能になる。また、成形品４０を搭載した固定型３１の底部３７を上昇させ、固定型３１の立面壁３５に成形品４０の周縁部を支持させるので、成形品４０の脱型が容易になり、自動化が可能になる。さらに、成形品４０の取り出しに必要な型開き量が減少し、成形の高速化が可能になる。
【００５４】
なお、上記各実施形態における成形品４０の各溝４１は、その立面が垂直でも良いが、図１７のように斜めに傾斜していても良い。また、成形品４０の複数の溝４１のピッチは、小さくても良いが、図１８のように大きくても良い。
【００５５】
【実施例】
以下、本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施例について比較例と共に説明する。
実施例１〜３、比較例１〜３で燃料電池用セパレータの成形品をそれぞれ成形し、この成形品の曲げ特性、電気的特性、厚み精度の測定を行い、成形品の表面状態を目視観察してその結果を表１にまとめた。
実施例１
先ず、重合度１００００，平均粒径２０μｍのフェノール樹脂〔カネボウ株式会社製商品名ベルパールＳ８９０〕１００質量部に対して平均粒径５０μｍの黒鉛〔中越黒鉛工業所製商品名ＨＧ−５０Ａ〕１０００質量部をタンブラーミキサーにより３０分間混合して混合成形材料を調製し、この混合成形材料を１５×１５ｃｍの予備成形金型に７７ｇ投入し、厚さ２ｍｍの中間品を圧縮成形した。中間品は、成形温度３０℃、加圧時間１０秒の条件で予備成形した。
【００５６】
中間品を予備成形したら、この中間品を１５０℃の温度に加熱した１５×１５ｃｍの本成形金型にインサートし、圧縮成形して成形品である燃料電池用セパレータを得た。成形品は、成形温度１５０℃、成形圧力５ＭＰａ、加熱加圧時間３０分間の条件で本成形した。成形品を得たら、この成形品の曲げ特性、電気的特性、厚み精度の測定を行い、成形品の表面状態を目視観察してその結果を表１にまとめた。成形品の電気的特性は、体積抵抗率により評価することとした。
【００５７】
実施例２
先ず、フェノール樹脂〔カネボウ株式会社製商品名ベルパールＳ８７０〕１００質量部に対して黒鉛〔中越黒鉛工業所製商品名ＨＧ−３０Ａ〕１５００質量部をタンブラーミキサーにより３０分間混合して混合成形材料を調製し、この混合成形材料を１５×１５ｃｍの予備成形金型に７７ｇ投入し、厚さ２ｍｍの中間品を圧縮成形した。中間品は、成形温度３０℃、加熱加圧時間１０秒の条件で予備成形した。
【００５８】
中間品を予備成形したら、この中間品を１９０℃の温度に加熱した１５×１５ｃｍの本成形金型にインサートし、圧縮成形して成形品である燃料電池用セパレータを得た。成形品は、成形温度１９０℃、成形圧力９ＭＰａ、加熱加圧時間５分間の条件で本成形した。成形品を得たら、この成形品の曲げ特性、電気的特性、厚み精度の測定を行い、成形品の表面状態を目視観察してその結果を表１にまとめた。
【００５９】
実施例３
先ず、フェノール樹脂〔カネボウ株式会社製商品名ベルパールＳ９９Ｗ〕１００質量部に対して黒鉛〔中越黒鉛工業所製商品名ＨＧ−３０Ａ〕１８００質量部をタンブラーミキサーにより３０分間混合して混合成形材料を調製し、この混合成形材料を１５×１５ｃｍの予備成形金型に７７ｇ投入し、厚さ２ｍｍの中間品を圧縮成形した。中間品は、成形温度３０℃、加熱加圧時間１０秒の条件で予備成形した。
【００６０】
中間品を予備成形したら、この中間品を２００℃の温度に加熱した１５×１５ｃｍの本成形金型にインサートし、圧縮成形して成形品である燃料電池用セパレータを得た。成形品は、成形温度２００℃、成形圧力１２ＭＰａ、成形時間３分間の条件で本成形した。成形品を得たら、この成形品の曲げ特性、電気的特性、厚み精度の測定を行い、成形品の表面状態を目視観察してその結果を表１にまとめた。
【００６１】
比較例１
実施例１のフェノール樹脂１００質量部に対して実施例１の黒鉛７００質量部をタンブラーミキサーにより３０分間混合して混合成形材料を調製し、この混合成形材料を１５×１５ｃｍの予備成形金型に７７ｇ投入し、厚さ２ｍｍの中間品を圧縮成形した。その他は実施例１と同様とした。
比較例２
実施例２のフェノール樹脂１００質量部に対して実施例２の黒鉛２２００質量部をタンブラーミキサーにより３０分間混合して混合成形材料を調製し、この混合成形材料を１５×１５ｃｍの予備成形金型に７７ｇ投入し、厚さ２ｍｍの中間品を圧縮成形した。その他は実施例１と同様とした。
【００６２】
比較例３
実施例３の混合成形材料を中間品に成形することなく、１９０℃の温度に加熱した１５×１５ｃｍの本成形金型に投入し、圧縮成形して厚さ２ｍｍで板状の成形品からなる燃料電池用セパレータを得た。成形品は、成形温度２００℃、成形圧力１２ＭＰａ、成形時間３分間の条件で本成形した。成形品を得たら、この成形品の曲げ特性、電気的特性、厚み精度の測定を行い、成形品の表面状態を目視観察してその結果を表１にまとめた。
【００６３】
・成形品の曲げ特性の測定方法
曲げ特性の測定方法は、ＪＩＳＫ７１７１に準じて測定した。
・体積抵抗率の測定方法
１５×１５ｃｍの成形品を５×５ｃｍのサイズに４枚切り出し、この成形品の厚みを測定して四探針法により体積抵抗率を測定した。測定器としては、ＬＯＲＥＳＴＡ・ＨＰＭＣＰ−Ｔ４１０〔三菱化学株式会社製商品名〕を使用した。
・厚み精度の測定
成形品の縦横方向共、２．５ｃｍ間隔で２５箇所の厚みを測定し、レンジにより評価した。
【００６４】
【表１】

【００６５】
結果
実施例１〜３によれば、曲げ特性、電気的特性、厚み精度、表面状態に優れた成形品を得ることができた。
【００６６】
【発明の効果】
以上のように本発明によれば、金型の接合部等にバリの生じるおそれがなく、実用の電気的特性を得ることのできる安価な燃料電池用セパレータ、及び成形品の製造方法を提供することができるという効果がある。
【図面の簡単な説明】
【図１】本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施形態における混合成形材料を予備成形金型に充填する状態を示す模式断面説明図である。
【図２】図１の予備成形金型を型締めして圧縮する状態を示す断面説明図である。
【図３】本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施形態における成形品と略同様の外形寸法を有する中間品を示す模式断面説明図である。
【図４】本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施形態における本成形金型を示す模式断面説明図である。
【図５】図４の本成形金型を型締めする状態を示す模式断面説明図である。
【図６】本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施形態における成形品を示す模式断面説明図である。
【図７】本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施形態における中間品と成形品の寸法関係を示す模式説明図である。
【図８】本発明に係る燃料電池用セパレータ及び成形品の製造方法の実施形態における立面壁の傾斜しない本成形金型の問題点を示す模式断面説明図である。
【図９】本発明に係る燃料電池用セパレータ及び成形品の製造方法の第２の実施形態における予備成形金型を示す模式断面説明図である。
【図１０】図９の予備成形金型を型締めして圧縮する状態を示す断面説明図である。
【図１１】本発明に係る燃料電池用セパレータ及び成形品の製造方法の第３の実施形態における本成形金型を示す模式断面説明図である。
【図１２】本発明に係る燃料電池用セパレータ及び成形品の製造方法の第４の実施形態における本成形金型を型開きしてその固定型と可動型との間に中間品用供給具を介在した状態を示す断面説明図である。
【図１３】図１２の中間品用供給具の搭載板を引き抜いて固定型内に予備成形品を供給する状態を示す断面説明図である。
【図１４】図１３の固定型から中間品用供給具を取り外した状態を示す断面説明図である。
【図１５】本発明に係る燃料電池用セパレータ及び成形品の製造方法の第４の実施形態における中間品用供給具を示す斜視説明図である。
【図１６】図１５の分解斜視説明図である。
【図１７】本発明に係る燃料電池用セパレータ及び成形品の製造方法の他の実施形態における成形品を示す部分拡大断面図である。
【図１８】本発明に係る燃料電池用セパレータ及び成形品の製造方法の他の実施形態における成形品を示す部分拡大断面図である。
【図１９】所定の材料を金型に充填する状態を示す模式断面説明図である。
【図２０】図１９の金型を型締めして加熱加圧した状態を示す模式断面説明図である。
【図２１】図２０の金型から脱型した薄い平板の成形品を示す模式断面説明図である。
【符号の説明】
１混合成形材料
１０予備成形金型
１１固定型（一の型）
１２可動型
１３形成部
２０中間品
３０本成形金型
３１固定型（一の型）
３２可動型
３３凹凸
３４形成部
３５立面壁
４０成形品
４１溝
５０中間品用供給具[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell separator used in the fields of electricity, electronics, semiconductors, and the like, and a method for producing a molded article.
[0002]
[Prior art]
Conventionally, when manufacturing a plate-shaped molded product 40A, a predetermined material 60 shown in FIG. 19 is filled in a mold 61, compression-heated (see FIG. 20), and the plate-shaped molded product 40A is formed. It is taken out (see FIG. 21).
However, there is a problem in that simply molding the plate-shaped molded product 40A causes unstable quality. In other words, when the molded product 40A has a horizontally long cross-section of substantially U-shape and the peripheral portion and the non-peripheral portion have different cross sections, even if the molded product 40A has the same thickness, the density is not constant. It will not be stable. As a means for solving this problem, a technique of filling the material 60 in accordance with the thickness of the molded article 40A has been proposed (see Patent Document 1).
When the plate-shaped molded product 40A is a fuel cell separator, it is manufactured by various manufacturing methods (see Patent Documents 2 and 3).
[0003]
[Patent Document 1]
JP 2002-192393 A
[0004]
[Patent Document 2]
JP-A-2002-294024
[0005]
[Patent Document 3]
JP-A-2002-231261
[0006]
[Problems to be solved by the invention]
However, when the technique of the above-mentioned document is adopted, there is not a small possibility that the material 60 is scattered and burrs are formed at a joint portion of the mold 61 or the like. Further, in the case where the plate-shaped molded product 40A made of the fuel cell separator is manufactured by the manufacturing method of Patent Document 2, it is not possible to obtain electrical characteristics that can withstand practical use. Furthermore, when the manufacturing method of Patent Document 3 is employed, carbonization and sintering are required to obtain practically usable electrical characteristics, which causes a problem of increasing the price.
[0007]
The present invention has been made in view of the above, and provides an inexpensive fuel cell separator and a method of manufacturing a molded product that can obtain practical electric characteristics without the risk of generating burrs at a joint portion of a mold or the like. It is intended to be.
[0008]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have focused on a phenol resin having a specific molecular weight, particle shape, and particle diameter, and set a mixture of the phenol resin and graphite at a temperature below the melting point (referred to as an endothermic peak temperature in DSC). It was found that if the intermediate product was preformed by compression molding at a temperature higher than the melting point, the above object could be achieved, and the present invention was completed.
That is, in the present invention, in order to achieve the above object, a substantially plate body is formed from a mixed molding material in which 900 to 2,000 parts by mass of graphite is added to 100 parts by mass of a phenol resin, and a plurality of irregularities are formed on both surfaces. It is characterized by being arranged.
Note that the phenol resin can be a phenol / formaldehyde resin having self-curability.
[0009]
Further, in the present invention, in order to achieve the above object, a method for manufacturing a molded article using a mixed molding material consisting of a thermosetting resin and a conductive material,
A preforming step of forming an intermediate product having substantially the same outer shape as the molded product using the mixed molding material, and a main forming process of forming the intermediate product and arranging a plurality of grooves on at least one surface of the molded product; .
In addition, 900 to 2000 parts by mass of graphite is added to 100 parts by mass of the phenol resin to form a mixed molding material, and the molded product can be used as a fuel cell separator.
[0010]
Further, the molded article is a plate body, and a plurality of grooves are provided on both surfaces thereof at a predetermined pitch, and the position of the groove on one surface of the molded article and the position of the groove on the other surface of the molded article are shifted in the arrangement direction. They can be different from each other.
In addition, the forming part of the preforming die used in the preforming and / or the one forming part of the main forming die used in the main forming can be divided so as to be slidable in the opening and closing direction.
Further, the molding die can be maintained at the curing temperature of the thermosetting resin.
Further, the ratio of the mass per unit area of the groove region to the mass per unit area of the non-groove region in the molded product is R0, and the ratio per unit area of the planned groove region to the mass per unit area of the planned non-groove region in the intermediate product is R0. The mass ratio can be R1, and the value of R1 / R0 can be in the range of 0.8 to 1.2.
[0011]
In addition, the density of the groove area / the density of the non-groove scheduled area in the molded product can be in the range of 0.8 to 1.2.
Further, it is preferable that at least the opening side of the vertical wall in the forming portion of the main mold is inclined outward.
Further, it is preferable to mold an intermediate product having an area of 95 to 100% or less of the molded product at a temperature lower than the melting point at the time of preforming, and to heat and press mold the intermediate product at a temperature higher than the melting point at the time of main molding.
Furthermore, it is preferable to set the intermediate product in the main molding die without degassing during the main molding.
[0012]
Here, the mixed molding material in the claims is composed of a powdery thermosetting resin and a conductive material, and is mainly one in which material movement in the mold is extremely small, but is not particularly limited. . This mixed molding material is prepared, for example, by mixing and kneading a conductive material and a thermosetting resin. Specifically, for example, a predetermined mass is obtained by mixing and kneading a conductive material made of an inorganic material such as carbon or graphite, and a thermosetting resin made of a powder such as a phenol resin or an epoxy resin and having a binder function. Parts (for example, 50 parts by mass or more, preferably 80 parts by mass or more). The mixed molding material may have high or low viscosity or fluidity. Further, the molded product is mainly provided with a plurality of grooves arranged on both surfaces thereof, but may be provided with a plurality of grooves arranged on one surface. The outer shape substantially similar to the molded product includes, in addition to the same outer shape as the molded product, a similar outer shape recognized to be approximately the same as the molded product.
[0013]
In the molded product, the position of the groove on one surface and the position of the groove on the other surface are mainly different from each other because they are displaced in the arrangement direction, but the position of the groove on one surface and the position of the groove on the other surface are arranged. It does not have to be displaced in the direction. The grooves on one surface and the grooves on the other surface of the molded product may or may not have the same shape, interval, direction, and the like. In addition, when providing a plurality of holes in the molded product by molding, assuming that the through-hole portion is continuous with the periphery and the surface, in other words, assuming that there is no through-hole, the mass and density of the region are calculated. I do. Further, the molded article according to the present invention can be used at least in the fields of electricity, electronics, batteries, precision parts, automobiles and the like.
[0014]
According to the present invention, a separator for a fuel cell can be obtained only by molding using a mixed molding material in which graphite is mixed with a phenolic resin, so that the resistance value of the separator for a fuel cell can be reduced.
Further, when the phenol resin is a phenol-formaldehyde resin having self-curability, it is possible to suppress the dispersibility of the curing agent from becoming unstable. That is, when manufacturing a fuel cell separator, it is usually necessary to mix a curing agent, but since the amount of this curing agent is smaller than that of the phenolic resin, a smaller amount is required relative to the total amount including graphite. As a result, the dispersibility of the curing agent becomes unstable. However, if the phenol resin is a self-curing phenol-formaldehyde resin, a curing agent is not required and the dispersibility is stabilized.
[0015]
Further, according to the present invention, instead of immediately manufacturing a molded article using a material which is easily scattered, a solid intermediate product is preliminarily formed using a mixed molding material, and an external force is applied to the intermediate product which is not scattered. To produce a molded product, thereby suppressing the generation of burrs due to scattering of the material.
Further, since the volume ratio per projected area of the intermediate product and the molded product is substantially equal, the density of each part of the molded product is substantially constant.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. A method of manufacturing a fuel cell separator according to the present embodiment comprises, as shown in FIGS. And a step of preforming the intermediate product 20 of the fuel cell separator by heating and pressurizing the intermediate product 20 with a main molding die 30 to form a plurality of grooves 41 in parallel. The groove region and the non-groove region of the molded product 40 which is a battery separator are made of the same material, and the ratio of the mass per unit area of the groove region to the mass per unit area of the non-groove region in the molded product 40 is R0. When the ratio of the mass per unit area of the planned groove region to the mass per unit area of the planned groove-free region in the article 20 is R1, the value of R1 / R0 is set to a value of 0.8 or more and 1.2 or less. Like It is.
[0017]
The mixed molding material 1 is prepared by adding 900 to 2,000 parts by mass of graphite to 100 parts by mass of the phenol resin, and mixing and preparing the mixture with a stirrer such as a tumbler mixer, a Hensyl mixer, a ribbon blender, and a Nauta mixer. Phenol resins include resol type, novolak type, phenolic resin produced by the reaction of phenols and formaldehyde, and hydrophilicity to condensates obtained by reacting phenols and formaldehyde in the presence of at least a nitrogen-containing compound. Phenol resin obtained by adding and reacting a polymer compound, and prepolymer obtained by reacting phenol and formaldehyde in a basic aqueous solution are mixed with a protective colloid, and coagulated into inert solid beads under acidic conditions. And the like.
[0018]
In particular, the phenolic resin obtained by the method described in JP-B-62-30212 has a spherical particle shape and a high molecular weight as compared with resol-type and novolak-type phenolic resins, and can be highly filled with graphite. At the same time, since the melting temperature at the time of molding is high, the surface coating of the graphite particles is smaller than other phenolic resins, and the curing reaction is slow, which is optimal.
[0019]
The phenol resin is preferably spherical having an average particle size of 5 to 100 μm or less. This is because, when the average particle size is less than 5 μm, the phenolic resin flies up when mixed with graphite, and the working environment deteriorates. Conversely, if the average particle size exceeds 100 μm, it is difficult to make the mixture with graphite uniform, and an uneven pattern is formed on the surface of the formed fuel cell separator, which is not preferable. The molecular weight of the phenol resin is preferably 3,000 to 20,000 or less, preferably 4,000 to 15,000 or less, and more preferably 5,000 to 10,000 or less. The reason why the molecular weight of the phenol resin is required to be 3,000 or more is that if the molecular weight is less than 3,000, it becomes difficult to highly fill the graphite, and the melting temperature is lowered, so that the surface coating of the graphite particles becomes large, This is because the electrical characteristics of the fuel cell separator deteriorate, causing a problem in the electrical characteristics of the fuel cell separator.
[0020]
As the graphite, natural graphite such as flaky graphite, flaky graphite, soil graphite or natural coke is molded and calcined, and then artificial graphite and flaky graphite graphitized at a high temperature of 2500 ° C. or more are mixed with concentrated sulfuric acid. After being treated with a strong oxidizing agent such as hydrogen oxide, perchlorate, or permanganate to produce a graphite intercalation compound, it is washed with water and dried to produce expanded graphite and expanded graphite at a high temperature of 950 to 1100 ° C. There is no particular limitation on artificial graphite such as expanded graphite obtained by rapid heating, but graphite having a bulk specific gravity of 0.1 g / cc or more is preferred. The reason why the bulk specific gravity is required to be 0.1 g / cc or more is that if the bulk specific gravity is less than 0.1 g / cc, it becomes difficult to mold the intermediate product 20 or a problem occurs in uniform mixing with the phenol resin. is there.
[0021]
Graphite can be used alone or in combination of two or more. This graphite is preferably in the form of a flake having an average particle size of 5 to 100 μm or less, preferably 10 to 70 μm or less. This is based on the reason that, when the average particle size is less than 5 μm, the electrical properties are lowered and the graphite soars when mixed with the phenol resin, thereby deteriorating the working environment. On the other hand, when the average particle size exceeds 100 μm, it is difficult to make the mixture with the phenol resin uniform, and the mechanical properties of the molded fuel cell separator deteriorate. The graphite may have the same average particle size, or may have different average particle sizes.
[0022]
Note that aluminate-based coupling agents such as acetoalkoxyaluminum diisopropylate, titanate-based coupling agents such as isopropyltriisostearoyl titanate, bis (dioctylbylphosphate) oxyacetate, and isopropyltridecylbenzenesulfonyl titanate; Surface modifiers such as silane coupling agents such as xypropylmethyldiethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, or acetylene Alcohol, acetylene glycol, glycerin aliphatic ester, sorbitan aliphatic ester, polyglycerin aliphatic ester, propylene glycol aliphatic ester, superabsorbent alcohol aliphatic Surface-treated graphite with various surfactants such as Le can be used within a range which does not impair the characteristics of the present invention.
[0023]
The compounding of the phenolic resin and the graphite is such that the graphite is 900 to 2,000 parts by mass with respect to 100 parts by mass of the phenolic resin, preferably 1100 to 1900 parts by mass of graphite with respect to 100 parts by mass of the phenolic resin, more preferably 100 parts by mass of the phenolic resin The amount of graphite is preferably 1200 to 1700 parts by mass. This is because if the added amount of graphite is less than 900 parts by mass with respect to 100 parts by mass of the phenol resin, the electrical characteristics of the fuel cell separator will be impaired. Conversely, if the amount of graphite exceeds 2,000 parts by mass with respect to 100 parts by mass of the phenol resin, mechanical properties of a fuel cell separator that can be practically used cannot be obtained.
[0024]
The mixed molding material 1 includes calcium carbonate, talc, kaolin, diatomaceous earth, natural or synthetic silica, wollastonite, bentonite, sebiolite, mica, aluminum hydroxide, and titanium oxide as long as the properties of the fuel cell separator are not lost. Filler such as glass beads, glass beads, activated carbon, charcoal, bamboo charcoal, glass fiber, aramid fiber, metal fiber, conductive oil furnace black, acetylene black, thermal black, PAN-based carbon fiber, pitch-based carbon fiber, etc. A metal powder such as a system conductive filler, gold, silver, copper, palladium, aluminum, and stainless steel can be added.
[0025]
As shown in FIG. 1 and the like, the preforming mold 10 includes a concave fixed mold 11 and a slidable convex movable mold 12 facing each other. In the fixed mold 11, the recessed forming part 13 is divided into a plurality of parts, and a part of the center thereof can be slid appropriately in the opening and closing direction (vertical direction in the present embodiment), and has a shallow horizontal section at the bottom shown in FIG. It functions so as to preform the substantially U-shaped intermediate product 20 and to contribute to handling and the like. In addition, a substantially frame-shaped step 14 is cut out at the periphery of the opposing surface of the movable mold 12.
[0026]
As shown in FIG. 4 and FIG. 5, the main molding die 30 includes a concave fixed mold 31 and a convex movable mold 32 facing each other. A plurality of irregularities 33 for transferring the product shape to the intermediate product 20 are formed at substantially equal intervals on the facing surface of the intermediate product 20. Each of the vertical walls 35 of the recessed forming portion 34 of the fixed mold 31 is formed such that the opening side is gradually inclined outward, thereby facilitating the removal of the manufactured molded article 40 from the mold.
[0027]
In the above, when producing a fuel cell separator, first, a powdered phenol resin and graphite are mixed and stirred to prepare a mixed molding material 1, and this mixed molding material 1 is placed in a preforming mold 10. Fill (see FIG. 1) and pressurize (see FIG. 2) for 5 to 120 seconds, preferably 10 to 100 seconds, and have a laterally long and substantially concave cross-section having substantially the same external dimensions (excluding thickness dimensions) as the molded article 40 The letter-shaped intermediate product 20 is preformed into a substantially flat plate (see FIG. 3), and then the preformed mold 10 is opened to take out the solidified intermediate product 20.
[0028]
When filling the mixed molding material 1 with the density and the depth (height) of the mixed molding material 1 according to the mass per unit area of the molded product 40, the intermediate product 20 with less unevenness in density can be obtained. it can. Also, the pressurization time of 5 to 120 seconds means that if the pressurization time is less than 5 seconds, molding of the intermediate product 20 becomes difficult, and if the pressurization time exceeds 120 seconds, the molding cycle becomes longer. This is because the molding efficiency is reduced.
[0029]
The molding temperature needs to be lower than the melting point of the mixed molding material 1. This is because, if the melting point is exceeded, the phenolic resin is melted, and when the intermediate product 20 is taken out from the pre-molding mold 10, the intermediate product 20 may be warped, deformed, or deteriorated in electrical characteristics. . The molding pressure required for molding is preferably in the range of 0.1 to 2 MPa. This is because if the molding pressure is less than 0.1 MPa, the molding of the intermediate product 20 becomes difficult, and the intermediate product 20 may be damaged when the intermediate product 20 is taken out from the preforming mold 10. Conversely, when the molding pressure exceeds 2 MPa, it is based on the reason that the phenolic resin covers the surface of the graphite and the electrical characteristics are reduced. Further, the intermediate product 20 is molded so as to have an area of 95 to 100% or less of the molded product 40 at a temperature equal to or lower than the melting point.
[0030]
When the intermediate product 20 is preformed, the intermediate product 20 is inserted into the main molding die 30 (see FIG. 4), heated and pressed (see FIG. 5), and a plurality of grooves 41 are formed on the front and back surfaces of the intermediate product 20, respectively. After forming the molded products 40 in parallel at substantially equal pitches, the molded products 40 are cured in a pressurized state, the main molding die 30 is opened, and the cured molded products 40 are taken out (see FIG. 6). Thus, it is possible to manufacture a molded article 40 which is a fuel cell separator.
In the present embodiment, the position of the groove 41 on the front surface of the molded article 40 and the position of the groove 41 on the rear surface are different from each other, as shown in FIG.
[0031]
At the time of the main molding, it is preferable to take care that the cross-sectional dimensions of the intermediate product 20 and the molded product 40 have the following relationship. That is, in FIGS. 3 and 7, the width of the molded product 40 is wO, the width of the relatively protruding peripheral portion of the intermediate product 20 is wA, the width of the intermediate product 20 other than the peripheral edge is wC, and the molded product is wC. Assuming that the dimension from the front end of the groove 40 to the upper end of the nearest groove 41 is m1, m2, and the dimension from the rear end of the molded article 40 to the lower end of the nearest groove 41 is n1, n2, If the molded article 40 has a relationship of wA = (m1 + n1) / 2 and wC = (m2 + n2) / 2, a high quality molded article 40 can be obtained.
[0032]
The heating and pressurizing time of the main molding is 1 to 60 minutes or less, preferably 3 to 40 minutes or less, and more preferably 3 to 30 minutes or less. This is because if the time is less than 1 minute, the curing is insufficient, so that the mechanical properties are degraded and the molded product 40 is warped during use. Conversely, if it exceeds 60 minutes, the molding cycle will be delayed. The molding temperature is from the melting point of the mixed molding material 1 to 350 ° C or lower, preferably 150 ° C to 250 ° C or lower, more preferably 150 ° C to 200 ° C or lower. This is based on the reason that when the molding temperature is lower than the melting point, the phenolic resin does not melt and harden, so that the molded article 40 cannot be obtained. Conversely, if the molding temperature exceeds 350 ° C., the phenolic resin is decomposed, so that the mechanical properties of the molded article 40 are reduced.
[0033]
The molding pressure required for molding is in the range of 3 to 20 MPa, preferably in the range of 5 to 20 MPa, in other words, 10 to 200 kg / cm. ² , Preferably 30 to 150 kg / cm ² , More preferably 50-100 kg / cm ² Is good. This is because if the molding pressure is less than 3 MPa, the packing density is reduced, and the mechanical and electrical properties are reduced. Conversely, if the molding pressure exceeds 20 MPa, the phenolic resin covers the surface of the graphite, and the electrical characteristics deteriorate.
[0034]
Since the intermediate product 20 is compressed in the pre-molding stage and contains only a small amount of air, degassing required in general press molding is not required. Therefore, the molding time can be shortened without degassing after the main molding die 30 is closed. Further, the molded article 40 which has been fully molded can be subjected to a heat treatment at a temperature of 180 ° C. to 250 ° C. or lower, if necessary.
[0035]
According to the above, instead of immediately manufacturing the molded article 40 using the powdery mixed molding material 1, first, the primary molding is performed using the mixed molding material 1, and this pre-processed, relatively easily broken intermediate Since the product 20 is subjected to secondary molding with the main molding die 30 and collapsed, and the molded product 40 with the groove 41 is obtained, the operation time can be greatly reduced, and the operation rate of the main molding die 30 is significantly improved. be able to. In other words, in order to manufacture a precise molded product 40, it is essential to fill the mixed molding material 1 in the required places in the mold without excess or deficiency, but this filling operation requires a long time. Is not few. In this regard, according to the present embodiment, it is only necessary to insert the easy-to-handle intermediate product 20 into the main molding die 30. Therefore, the preparation time can be reduced (the time is less than half under predetermined conditions), and the operation rate of the main molding die 30 can be improved.
[0036]
When the mixed molding material 1 containing a fine powder having a particle size of less than 10 μm is filled in a mold, the mixed molding material 1 is filled in due to an ascending air current generated in the high-temperature heated mold. It often scatters and adheres to and hardens at locations other than the formation portion 13, causing burrs and causing problems such as shortening the life of the mold. Further, when the mixed molding material 1 of powder is filled in the mold, the curing reaction of the mixed molding material 1 that first comes into contact with the mold starts. The transfer of the product shape based on the pressure (compression) is also adversely affected. On the other hand, according to the present embodiment, since the solid intermediate product 20 is inserted into the main mold 30, the mold can be used for a long time without causing burrs, and There is no adverse effect on the transfer of the product shape based on pressure.
[0037]
Further, when molding a molded article 40 having an irregular thickness, it is necessary to fill a material according to the thickness, but it is actually difficult to fill the mixed molding material 1 composed of powder according to the thickness. It is. On the other hand, according to the present embodiment, the intermediate product 20 is not simply molded into a flat plate, but is preliminarily molded into a substantially U-shaped cross section, and the mass per unit area of the grooveless region in the molded product 40. If the ratio of the mass per unit area of the groove region to the mass of the planned grooveless region in the intermediate product 20 is R0, the ratio of the mass per unit area of the planned groove region to the intermediate product 20 is R1 / R0. ≒ 1.
[0038]
In other words, since the density of the groove region / the density of the non-groove scheduled region in the molded article 40 is in the range of 0.8 to 1.2, it is possible to supply an appropriate amount of the mixed molding material 1 for each part. As a result, irrespective of the fluidity of the mixed molding material 1, the density of the molded article 40 is constant, and a high quality molded article 40 can be easily obtained. Also, rather than kneading and melting graphite into phenolic resin and pulverizing it, instead of preforming and main-forming the same, it is possible to obtain a practical fuel cell separator simply by kneading graphite into the phenolic resin, A significant decrease in the resistance value of the fuel cell separator can be expected. Further, bending characteristics, electrical characteristics, thickness accuracy, and excellent surface condition can be obtained, and further, manufacturing cost can be significantly reduced.
[0039]
Furthermore, since the opening side of each upright wall 35 in the forming portion 34 of the fixed mold 31 constituting the main molding die 30 is gradually inclined outward to form a clearance with the peripheral portion of the intermediate product 20, As shown in FIG. 8, the insert does not hinder the brittle intermediate product 20 from being caught or broken.
[0040]
Next, FIG. 9 and FIG. 10 show a second embodiment of the present invention. In this case, the step 14 of the movable die 12 constituting the preforming die 10 is omitted to form a flat molding surface. An intermediate product 20 having a flat surface is preformed using the movable mold 12. The other parts are the same as those in the above-described embodiment, and a description thereof will be omitted.
In this embodiment, the same operation and effect as the above embodiment can be expected, and since the flat intermediate product 20 is preformed, the lamination of the plurality of intermediate products 20 having no groove 41 becomes extremely easy. it is obvious.
[0041]
Next, FIG. 11 shows a third embodiment of the present invention. In this case, each vertical wall 35 in the forming portion 34 of the fixed die 31 constituting the main forming die 30 is gradually moved outward. The clearance is formed between the peripheral part of the molded article 40 by inclining, and the insert of the intermediate article 20 and the mold release of the molded article 40 are facilitated. The other parts are the same as those in the above-described embodiment, and a description thereof will be omitted.
In this embodiment, the same operation and effect as those of the above embodiment can be expected. Further, not only the opening side of each raised wall 35 but also the area other than the opening side is uniformly inclined outward, so that the fixed die 31 Obviously, the design and manufacturing will be easier.
[0042]
Next, FIGS. 12 to 16 show a fourth embodiment of the present invention. In this case, the intermediate product 20 of the fuel cell separator is supplied to the main molding die 30 by the intermediate product supply tool 50. Like that.
As shown in FIG. 12 and the like, the molding die 30 includes a fixed mold 31 to which the intermediate product 20 is supplied by dropping from the open opening 52 of the intermediate product supply tool 50, And a movable mold 32 that opens and closes.
[0043]
On the opposing surface of the fixed mold 31 and the movable mold 32, a plurality of irregularities 33 are arranged in parallel at a predetermined pitch and direction, and the plurality of irregularities 33 form a plurality of grooves 41 on the front and back surfaces of the intermediate product 20 at a predetermined pitch.・ Transfer in the direction. The fixed mold 31 has a frame-shaped peripheral wall 36 surrounding the intermediate product 20, a bottom portion 37 fitted to the inner bottom of the peripheral wall 36 and reciprocating in the opening and closing direction of the movable mold 32 (up and down direction in the present embodiment). It is divided into a base plate 38 on which the peripheral wall 36 and the bottom 37 are mounted, and is located below the movable mold 32. The peripheral wall 36 of the fixed die 31 has a vertically lower inner peripheral surface, and an inner raised wall 35 that is gradually inclined outwardly. Serves to facilitate. A mechanism (not shown) for positioning and guiding the intermediate product supply device 50 is disposed above the peripheral wall 36 of the fixed mold 31.
[0044]
As shown in FIGS. 15 and 16, the intermediate product supply device 50 includes a pair of guide rails 51 and a mounting plate 57 that opens and closes an opening 52 between the pair of guide rails 51. A mounting plate 57 is inserted between the pair of guide rails 51, connecting

plates

54 and 54A are provided between both ends of the pair of guide rails 51, and the connecting plate 54A is made detachable.
[0045]
In the pair of guide rails 51, the mounting plate 57, and the pair of connecting

plates

54, 54A, at least 90% or more of the regions that come into contact with the intermediate product 20 are formed of a heat insulating material such as a fibrous, foamed plastic, or glass wool. It functions to prevent heat from being transmitted to the intermediate product 20 before the product 20 is supplied to the main molding die 30. As shown in FIGS. 15 and 16, the pair of guide rails 51 are each formed in an elongated thin plate, face each other at intervals, and form a flat rectangular opening 52 larger than the intermediate product 20. The opening 52 functions to drop the intermediate product 20. On the opposing surface of each guide rail 51, a fitting guide groove 53 having a U-shaped cross section is cut out in the longitudinal direction.
[0046]
A connecting plate 54 is integrally formed between one end portions of the pair of guide rails 51, and a fitting guide groove having a U-shaped cross section communicating with the fitting guide groove 53 of the guide rail 51 is formed on an inner peripheral surface of the connecting plate 54. 53 is cut out. A connecting plate 55 is integrally formed between the other ends of the pair of guide rails 51, and a connecting plate 54A opposed to the connecting plate 55 via a gap forms a mounting groove 56 inside the guide rail 51. The connecting plate 54A comes into contact with the surface of the mounting plate 57 and regulates displacement, damage, and the like of the intermediate product 20.
[0047]
The mounting plate 57 is formed as a flat rectangular thin plate larger than the intermediate product 20 using a polyimide film or the like. It is slidably and detachably inserted and supported between the pair of guide rails 51 via a fitting guide groove 53, and functions to open and close the opening 52 and mount the intermediate product 20. The other parts are the same as those in the above-described embodiment, and a description thereof will be omitted.
[0048]
In the above, when the molded article 40 of the fuel cell separator is fully molded, first, a mixed molding material 1 is prepared, and the mixed molding material 1 is filled into a pre-molding mold 10 and compressed, and the molded article 40 is formed. The intermediate product 20 having substantially the same external dimensions is preformed and released. After the intermediate product 20 without the groove 41 is formed, the single intermediate product 20 that has been easily handled is placed on the mounting plate 57 of the intermediate product supply tool 50 having a substantially frame shape. The guide plate 51 is inserted between the guide rails 51 via the fitting guide groove 53 to close the opening 52, and the connecting plate 54A is fitted into the mounting groove 56 of the guide rail 51 and brought into contact with the mounting plate 57, so that the intermediate product 20 is displaced. And damage and so on. At this time, a lid (not shown) that covers the intermediate product 20 may be set on the pair of guide rails 51 to prevent the radiant heat of the movable mold 32 of the main molding die 30.
[0049]
Next, the pre-heated main molding die 30 is opened, the intermediate product supply tool 50 is interposed between the fixed die 31 and the movable die 32, and the upper part of the peripheral wall 36 of the fixed die 31 The intermediate product supply device 50 is positioned and fixed via a mechanism (see FIG. 12), the mounting plate 57 of the intermediate product supply device 50 is pulled out, the opening 52 is opened, and the intermediate product 20 is dropped and supplied into the fixed mold 31. (See FIG. 13), and then remove the intermediate product supply tool 50 from the fixed mold 31 (see FIG. 14). When the intermediate product supply tool 50 is removed in this way, the fixed mold 31 and the movable mold 32 are clamped and heated and pressurized for a predetermined time, and a plurality of grooves 41 are transferred to the front and back surfaces of the inserted intermediate product 20, respectively. The molded article 40 is molded by being cured in a pressure state.
[0050]
At this time, the intermediate product 20 is compressed in the pre-molding stage and contains only a small amount of air, so that degassing required for general press molding is not required. Therefore, the molding time can be shortened without degassing after the main molding die 30 is closed.
[0051]
Next, the main mold 30 is opened to raise the bottom 37 of the fixed mold 31 on which the molded article 40 is mounted, and the peripheral edge of the molded article 40 is separated from the lower portion of the inner peripheral surface of the peripheral wall 36 of the fixed mold 31. The peripheral portion of the molded product 40 is supported near the center of the inner peripheral surface of the fixed die 31, and the bottom 37 of the fixed die 31 separated from the molded product 40 is returned to the original position. Since the molded product 40 slightly expands and expands in outer dimensions due to the remaining internal pressure, when the molded product 40 moves from the lower portion of the inner peripheral surface of the peripheral wall 36 of the fixed die 31 to near the boundary with the lower end of the vertical wall 35, the inclined vertical wall 35 Will be supported by friction. In addition, when the bottom portion 37 of the fixed mold 31 moves up and down, the drive of the ejector rod can be used. Thereafter, when the bottom portion 37 of the fixed mold 31 returns to the original position, the cured molded product 40 can be taken out, and the molded product 40 can be obtained.
[0052]
In this embodiment, the same operation and effect as those in the above embodiment can be expected. Further, since the intermediate product 20 is supplied into the fixed mold 31 by using the intermediate product supply tool 50, from the input of the material to the start of pressurization. Can be significantly shortened (10 seconds or less under predetermined conditions), and the characteristics (decrease in volume resistivity) as a separator can be greatly improved. Further, since it is sufficient that there is a gap into which the intermediate product supply tool 50 enters, the opening stroke of the main molding die 30 can be a small amount, and the working time can be greatly reduced.
[0053]
Further, since the connecting plate 54A is fitted into the mounting groove 56 of the guide rail 51 and is brought into contact with the mounting plate 57, the movable range of the intermediate product 20 on the mounting plate 57 due to withdrawal is limited, and displacement and damage are prevented. Can be regulated. As a result, in order to shorten the charging time of the intermediate product 20, even if an acceleration is applied in the horizontal direction, the deformation and damage of the intermediate product 20 can be prevented and the stable handling can be achieved. In addition, since the bottom 37 of the fixed mold 31 on which the molded article 40 is mounted is raised, and the peripheral edge of the molded article 40 is supported by the vertical wall 35 of the fixed mold 31, the removal of the molded article 40 is facilitated and automation is achieved. Becomes possible. Further, the amount of mold opening required for taking out the molded product 40 is reduced, and the molding can be speeded up.
[0054]
In addition, although each groove 41 of the molded article 40 in each of the above embodiments may have a vertical surface, it may be inclined obliquely as shown in FIG. Further, the pitch of the plurality of grooves 41 of the molded product 40 may be small, but may be large as shown in FIG.
[0055]
【Example】
Hereinafter, examples of the method for producing a fuel cell separator and a molded article according to the present invention will be described together with comparative examples.
In each of Examples 1 to 3 and Comparative Examples 1 to 3, molded products of the fuel cell separator were molded, and the bending characteristics, electrical characteristics, and thickness accuracy of the molded products were measured, and the surface state of the molded products was visually observed. The results are summarized in Table 1.
Example 1
First, 100 parts by mass of a phenol resin having a degree of polymerization of 10,000 and an average particle size of 20 μm (trade name: Bellpearl S890, manufactured by Kanebo Co., Ltd.): 1000 parts by mass of graphite having an average particle size of 50 μm (trade name, HG-50A, manufactured by Chuetsu Graphite Industry Co., Ltd.) Was mixed by a tumbler mixer for 30 minutes to prepare a mixed molding material. 77 g of the mixed molding material was put into a 15 × 15 cm preforming mold, and an intermediate product having a thickness of 2 mm was compression-molded. The intermediate product was preformed under the conditions of a molding temperature of 30 ° C. and a pressing time of 10 seconds.
[0056]
After the intermediate product was preformed, the intermediate product was inserted into a 15 × 15 cm main molding die heated to a temperature of 150 ° C., and compression molded to obtain a molded fuel cell separator. The molded article was fully molded under the conditions of a molding temperature of 150 ° C., a molding pressure of 5 MPa, and a heating and pressing time of 30 minutes. After obtaining the molded product, the bending characteristics, electrical characteristics, and thickness accuracy of the molded product were measured, and the surface state of the molded product was visually observed. The results are shown in Table 1. The electrical characteristics of the molded article were evaluated based on volume resistivity.
[0057]
Example 2
First, 1500 parts by mass of graphite (trade name: HG-30A, manufactured by Chuetsu Graphite Industry Co., Ltd.) is mixed with 100 parts by mass of a phenol resin (trade name: Bellpearl S870, manufactured by Kanebo Co., Ltd.) by a tumbler mixer for 30 minutes to prepare a mixed molding material. Then, 77 g of this mixed molding material was put into a 15 × 15 cm preforming mold, and an intermediate product having a thickness of 2 mm was compression-molded. The intermediate product was preformed under the conditions of a molding temperature of 30 ° C. and a heating and pressing time of 10 seconds.
[0058]
After the intermediate product was preformed, the intermediate product was inserted into a 15 × 15 cm main molding die heated to a temperature of 190 ° C., and compression molded to obtain a molded fuel cell separator. The molded article was fully molded under the conditions of a molding temperature of 190 ° C., a molding pressure of 9 MPa, and a heating and pressing time of 5 minutes. After obtaining the molded product, the bending characteristics, electrical characteristics, and thickness accuracy of the molded product were measured, and the surface state of the molded product was visually observed. The results are shown in Table 1.
[0059]
Example 3
First, 100 parts by mass of a phenolic resin (trade name: Bellpearl S99W manufactured by Kanebo Co., Ltd.) is mixed with 1800 parts by mass of graphite (trade name: HG-30A manufactured by Chuetsu Graphite Industry Co., Ltd.) using a tumbler mixer for 30 minutes to prepare a mixed molding material. Then, 77 g of this mixed molding material was put into a 15 × 15 cm preforming mold, and an intermediate product having a thickness of 2 mm was compression-molded. The intermediate product was preformed under the conditions of a molding temperature of 30 ° C. and a heating and pressing time of 10 seconds.
[0060]
After the intermediate product was preformed, the intermediate product was inserted into a 15 × 15 cm main molding die heated to a temperature of 200 ° C., and compression molded to obtain a molded fuel cell separator. The molded article was fully molded at a molding temperature of 200 ° C., a molding pressure of 12 MPa, and a molding time of 3 minutes. After obtaining the molded product, the bending characteristics, electrical characteristics, and thickness accuracy of the molded product were measured, and the surface state of the molded product was visually observed. The results are shown in Table 1.
[0061]
Comparative Example 1
700 parts by mass of the graphite of Example 1 was mixed with 100 parts by mass of the phenolic resin of Example 1 for 30 minutes using a tumbler mixer to prepare a mixed molding material, and this mixed molding material was placed in a 15 × 15 cm preforming mold. 77 g was charged, and an intermediate product having a thickness of 2 mm was compression-molded. Others were the same as Example 1.
Comparative Example 2
100 parts by mass of the phenolic resin of Example 2 was mixed with 2200 parts by mass of the graphite of Example 2 using a tumbler mixer for 30 minutes to prepare a mixed molding material, and this mixed molding material was placed in a 15 × 15 cm preforming mold. 77 g was charged, and an intermediate product having a thickness of 2 mm was compression-molded. Others were the same as Example 1.
[0062]
Comparative Example 3
Instead of molding the mixed molding material of Example 3 into an intermediate product, it was put into a 15 × 15 cm main molding die heated to a temperature of 190 ° C., compression-molded and formed into a plate-like molded product having a thickness of 2 mm. A fuel cell separator was obtained. The molded article was fully molded at a molding temperature of 200 ° C., a molding pressure of 12 MPa, and a molding time of 3 minutes. After obtaining the molded product, the bending characteristics, electrical characteristics, and thickness accuracy of the molded product were measured, and the surface state of the molded product was visually observed. The results are shown in Table 1.
[0063]
・ Measuring method of bending characteristics of molded products
The bending characteristics were measured according to JIS K7171.
・ Method of measuring volume resistivity
Four molded articles of 15 × 15 cm were cut out to a size of 5 × 5 cm, the thickness of the molded articles was measured, and the volume resistivity was measured by a four probe method. As a measuring device, LORESTA HP MCP-T410 (trade name, manufactured by Mitsubishi Chemical Corporation) was used.
・ Measuring thickness accuracy
The thickness of the molded article was measured at 25 locations at 2.5 cm intervals in both the vertical and horizontal directions, and evaluated by the range.
[0064]
[Table 1]

[0065]
Result
According to Examples 1 to 3, molded products excellent in bending characteristics, electrical characteristics, thickness accuracy, and surface condition could be obtained.
[0066]
【The invention's effect】
As described above, according to the present invention, there is provided an inexpensive fuel cell separator capable of obtaining practical electric characteristics without the risk of generating burrs at a joint portion of a mold and the like, and a method of manufacturing a molded product. There is an effect that can be.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional explanatory view showing a state in which a mixed molding material is filled in a preforming mold in an embodiment of a method for producing a fuel cell separator and a molded product according to the present invention.
FIG. 2 is an explanatory cross-sectional view showing a state in which the preforming mold of FIG. 1 is clamped and compressed.
FIG. 3 is a schematic cross-sectional explanatory view showing an intermediate product having substantially the same outer dimensions as a molded product in an embodiment of a method for manufacturing a fuel cell separator and a molded product according to the present invention.
FIG. 4 is a schematic cross-sectional explanatory view showing a molding die according to an embodiment of the fuel cell separator and the method for producing a molded product according to the present invention.
FIG. 5 is a schematic cross-sectional explanatory view showing a state in which the main molding die of FIG. 4 is clamped.
FIG. 6 is a schematic sectional view showing a molded product in a fuel cell separator and a method for producing a molded product according to an embodiment of the present invention.
FIG. 7 is a schematic explanatory view showing a dimensional relationship between an intermediate product and a molded product in the embodiment of the fuel cell separator and the method for producing a molded product according to the present invention.
FIG. 8 is a schematic cross-sectional explanatory view showing a problem of the present molding die in which the vertical wall does not tilt in the embodiment of the fuel cell separator and the method of manufacturing a molded product according to the present invention.
FIG. 9 is a schematic sectional explanatory view showing a preforming die according to a second embodiment of the method for producing a fuel cell separator and a molded product according to the present invention.
10 is an explanatory sectional view showing a state in which the preforming mold of FIG. 9 is clamped and compressed.
FIG. 11 is a schematic cross-sectional explanatory view showing a molding die according to a third embodiment of the method for producing a fuel cell separator and a molded product according to the present invention.
FIG. 12 is a diagram showing a fourth embodiment of the method for producing a fuel cell separator and a molded product according to the present invention, in which the molding die is opened and an intermediate product supply tool is provided between the fixed mold and the movable mold. It is sectional explanatory drawing which shows the state which interposed.
13 is an explanatory cross-sectional view showing a state in which the mounting plate of the intermediate product supply tool of FIG. 12 is pulled out and a preform is supplied into the fixed mold.
FIG. 14 is an explanatory cross-sectional view showing a state in which an intermediate product supply tool is removed from the fixed mold shown in FIG. 13;
FIG. 15 is an explanatory perspective view showing a supply device for an intermediate product in a fourth embodiment of the method for producing a fuel cell separator and a molded product according to the present invention.
16 is an exploded perspective view of FIG.
FIG. 17 is a partially enlarged cross-sectional view showing a molded product according to another embodiment of the fuel cell separator and the method for producing a molded product according to the present invention.
FIG. 18 is a partially enlarged cross-sectional view showing a molded article according to another embodiment of the fuel cell separator and the method for producing a molded article according to the present invention.
FIG. 19 is a schematic cross-sectional explanatory view showing a state in which a mold is filled with a predetermined material.
FIG. 20 is a schematic cross-sectional explanatory view showing a state where the mold of FIG. 19 is clamped and heated and pressed.
FIG. 21 is a schematic cross-sectional explanatory view showing a thin flat molded product removed from the mold of FIG. 20;
[Explanation of symbols]
1 Mixed molding materials
10 Preforming mold
11 fixed type (one type)
12 Movable type
13 Formation
20 Intermediate products
30 Molds
31 Fixed type (one type)
32 movable type
33 irregularities
34 Formation
35 Elevated Wall
40 Molded product
41 grooves
50 Supplies for intermediate products

Claims

A separator for a fuel cell, which is formed into a substantially plate-shaped body by using a mixed molding material in which 900 to 2000 parts by mass of graphite is added to 100 parts by mass of a phenol resin, and a plurality of irregularities are arranged on both surfaces, respectively.

2. The fuel cell separator according to claim 1, wherein the phenol resin is a phenol-formaldehyde resin having self-curability.

A method for producing a molded article using a mixed molding material composed of a thermosetting resin and a conductive material, the method comprising:
A preforming step of forming an intermediate product having substantially the same outer shape as the molded product using the mixed molding material, and a main forming process of forming the intermediate product and arranging a plurality of grooves on at least one surface of the molded product; A method for producing a molded article, characterized by comprising:

The method for producing a molded article according to claim 3, wherein 900 to 2000 parts by mass of graphite is added to 100 parts by mass of the phenol resin to obtain a mixed molding material, and the molded article is used as a fuel cell separator.

A plurality of grooves are arranged at a predetermined pitch on both surfaces of the molded product as a plate body, and the position of the groove on one surface of the molded product and the position of the groove on the other surface of the molded product are mutually shifted in the arrangement direction. The method for producing a molded article according to claim 3 or 4, wherein the method is different.

The molded article according to claim 3, 4 or 5, wherein a preforming mold used in the preforming and / or a forming part of one of the main forming dies used in the main forming is divided so as to be slidable in the opening and closing direction. Production method.

The method for producing a molded product according to claim 6, wherein the molding die is maintained at a curing temperature of the thermosetting resin.

The ratio of the mass per unit area of the groove region to the mass per unit area of the non-groove region in the molded product is R0, and the ratio of the mass per unit area of the planned groove region to the mass per unit area of the planned non-groove region in the intermediate product. The method for producing a molded product according to claim 5, 6, or 7, wherein the ratio is R1, and the value of R1 / R0 is in the range of 0.8 to 1.2.

The method for producing a molded product according to any one of claims 5 to 8, wherein the density of the groove region / the density of the non-groove planned region in the molded product is in the range of 0.8 to 1.2.

The method for manufacturing a molded product according to any one of claims 6 to 9, wherein at least the opening side of the vertical wall in the forming portion of the main mold is inclined outward.

An intermediate product having an area of 95 to 100% or less of the molded product at a temperature lower than the melting point at the time of preforming, and the intermediate product is heated and pressed at a temperature higher than the melting point at the time of the main molding. A method for producing the molded article described above.