JP4080095B2

JP4080095B2 - Manufacturing method of thick porous carbon material

Info

Publication number: JP4080095B2
Application number: JP05811999A
Authority: JP
Inventors: 明織井; 三男榎本
Original assignee: Tokai Carbon Co Ltd
Current assignee: Tokai Carbon Co Ltd
Priority date: 1999-03-05
Filing date: 1999-03-05
Publication date: 2008-04-23
Anticipated expiration: 2019-03-05
Also published as: JP2000256063A

Description

【０００１】
【発明の属する技術分野】
本発明は、気孔性状や材質性状の均一性に優れ、特に肉厚形状の多孔質炭素材の製造方法に関する。
【０００２】
【従来の技術】
軽量で耐熱性、耐蝕性、導電性などに優れる多孔質炭素材は、燃料電池や二次電池用の電極材、触媒担体、電気化学的水処理用電極材、フィルター、断熱材などの広い用途分野で各種工業用部材として有用されている。
【０００３】
多孔質炭素材の製造技術としては、炭素繊維をパルプとともに抄紙して得られるシートに熱硬化性樹脂液を含浸して積層成形し、焼成炭化する方法（例えば特開昭50−25808 号公報、同61−236664号公報など）が知られている。この方法は炭素繊維が補強骨格を形成するので材質強度の増大が図られるうえ、熱硬化性樹脂がガラス状カーボン組織に転化するため電気や熱に対する伝導性も向上する利点がある。
【０００４】
しかしながら、この方法は高価な炭素繊維を原料とする関係で製造コストが増大する欠点があり、また嵩密度、気孔径、気孔率などの制御性に難点がある。そこで、炭素繊維に代えて炭素繊維製造用の有機繊維を用い、これにパルプ、炭素質粉末などを配合して抄紙したシートに有機高分子物質あるいは炭素質粉末を懸濁した有機高分子物質を含浸したのち焼成処理する方法（特開昭61−236664号公報、同61−236665号公報）が提案されている。しかし、炭素繊維製造用有機繊維を原料とする方法では、組織内に局部的に閉塞された空隙部分が形成され易く、均質で制御された気孔構造を得るには困難性がある。
【０００５】
これらの難点を解消するために本出願人は、α−セルロースを主成分とする熱揮散性物質を抄紙してシート化する工程と、シートに残炭率40重量％以上の熱硬化性樹脂溶液を含浸する工程と、含浸処理後のシートを50〜150 ℃の温度で半硬化する工程と、半硬化シートを積層して全面を均一加熱しながらシート厚さが70〜20％になるように圧縮する工程と、圧縮シートを非酸化性雰囲気下で800 ℃以上の温度により焼成炭化する工程とからなることを特徴とするポーラスカーボン材の製造方法（特開平３−183672号公報）を開発した。
【０００６】
この製造方法によれば、良好な気孔性状と強度特性を備えたポーラスカーボン材を製造することができる。しかしながら、半硬化シートを積層して加熱しながら圧縮する工程において、積層シートによる圧力緩和が生じて加圧力が積層体内部にまで均一に伝達することが困難であり、積層体の表層部と内部では加圧力の相違により組織性状、特に気孔性状に差が生じ易い難点がある。また、加熱時にも熱エネルギーが均等に伝達され難いために積層体の表層部と内部とでは熱硬化性樹脂の硬化速度が異なることとなり、成形体の組織性状、気孔性状に差が生じることとなる。この現象は積層体が厚くなるほど著しくなり、したがって、均質な性状、特に気孔性状の均一性の高い肉厚のポーラスカーボン材を製造することが困難となる問題点がある。
【０００７】
そこで、本出願人は上記特開平３−１８３６７２号公報の技術を基に気孔性状が良好な肉厚形状のポーラスカーボン材の製造技術として、α−セルロースを主成分とする有機質物60〜90重量部と水溶性抄紙バインダー10〜40重量部を水に分散させて抄紙するシート成形工程、成形シートを残炭率40％以上の熱硬化性樹脂溶液に浸漬処理したのち半硬化し、該半硬化シートの所要枚数を加熱圧縮下に積層成形する一次成形工程、複数枚の一次成形体を前記工程と同一の半硬化シートを接合面に介在させて熱圧縮下に積層成形する二次成形工程、得られた二次成形体を非酸化性雰囲気下で 800℃以上の温度により焼成炭化する炭素化工程とからなる肉厚ポーラスカーボン材の製造方法（特開平５−51280 号公報）を開発提案した。
【０００８】
【発明が解決しようとする課題】
この特開平５−５１２８０号公報の方法によれば優れた気孔性状と組織強度を備え、50mmを超える肉厚形状のポーラスカーボン材を製造することができる。しかしながら、肉厚成形体である二次成形体は、半硬化シートを積層した一次成形体間に同一の半硬化シートを挟み、複数枚の一次成形体を積層成形することにより作製されるので手間がかかり、また半硬化シートによる一次成形体間の接合が充分でないという難点がある。
【０００９】
本発明者らは、上記の特開平５−５１２８０号公報の技術を基にさらに研究を進めた結果、積層体を加圧成形する際の加圧力は、主に積層体表面層の熱硬化性樹脂含浸シートにより圧力緩和されて積層体の表面層と内部とにおける組織性状の相違がもたらされること、更に、積層体を加熱する際の熱エネルギーは、表面層の熱硬化性樹脂含浸シートを急速に加熱することとなり、表層部の熱硬化性樹脂は一度軟化流動化して熱硬化性樹脂含浸シートの空隙を詰めたり、熱硬化性樹脂含浸シートの空隙を小さくしてから硬化すること、を確認した。
【００１０】
本発明はこれらの知見に基づいて開発されたものであって、その目的は気孔性状や材質性状の均一性に優れ、肉厚形状、例えば１０mmを超える肉厚形状の多孔質炭素材の製造方法を提供することにある。
【００１１】
【課題を解決するための手段】
上記の目的を達成するための本発明による肉厚多孔質炭素材の製造方法は、α―セルロースを主成分とする有機質物質と抄紙バインダーとを水に分散させ、水分散液を抄紙して得られた抄紙シートに熱硬化性樹脂溶液を含浸して半硬化し、半硬化した熱硬化性樹脂含浸シートを所定枚数積層し、積層体を熱圧成形した後、焼成炭化する多孔質炭素材の製造方法において、積層体の上下両面に少なくとも１枚の前記抄紙シートを積層した状態で熱圧成形し、熱圧成形後の積層体の上下両面に積層した各々の抄紙シートの厚みが０．５ｍｍ以上に設定することを構成上の特徴とする。
【００１２】
【発明の実施の形態】
α−セルロースを主成分とする有機質物質はシートのフィラー成分となる原料であって、好ましくはα−セルロース分を９０％以上含む木材パルプやレーヨンパルプなどのパルプ類が用いられ、パルプ性状としては抄紙成形性から太さ３〜１０デニール、長さ３〜１０mm程度の繊維形態のものが好ましい。抄紙バインダーは抄紙時に有機質物質のつなぎ材として機能するものであり、例えばアカマツ、エゾマツ、トドマツ、カラマツ、モミ、ツガなどの針葉樹系パルプ類が用いられる。
【００１３】
これらのα−セルロースを主成分とする有機質物質及び抄紙バインダーは抄紙性を考慮して適宜な量比に設定して水中に均一に分散させ、水分散液は長網式や丸網式などの抄紙機により抄紙してシート化する。形成されたシートは充分に乾燥したのち熱硬化性樹脂溶液が含浸される。含浸する熱硬化性樹脂は高残炭率、例えば残炭率が４０重量％以上のフェノール系、フラン系、ポリイミド系などの樹脂が単独または複数混合して用いられ、これらの熱硬化性樹脂はアセトン、エーテル、エタノールなどの低粘度で浸透性が高く、熱揮散性の有機溶媒に溶解し、熱硬化性樹脂溶液を調製してシートに含浸する。シートへの含浸は、シートを熱硬化性樹脂溶液に浸漬したり、シートに熱硬化性樹脂溶液を塗布するなどの方法で行うことができ、含浸した熱硬化性樹脂は焼成炭化時にガラス状カーボンに転化して多孔質炭素材の骨格を補強して強度向上に機能する。なお、熱硬化性樹脂溶液の樹脂濃度は、含浸性などを考慮して適宜設定する。
【００１４】
熱硬化性樹脂溶液を含浸したシートは５０〜１５０℃の温度に加熱して樹脂成分を半硬化する。この加熱処理時に有機溶媒の揮発性物質や半硬化時に生成した水分などが揮散除去されるとともに熱硬化性樹脂がシートに強固に付着保持される。半硬化した熱硬化性樹脂含浸シートは所定枚数を積層し、加熱しながら加圧して樹脂成分を硬化することにより積層体を一体化して成形する。この熱圧成形時の加熱温度は樹脂により異なるが、概ね８０〜２５０℃の温度で加熱硬化し、また圧力は気孔径や気孔率などの気孔性状との関係で適宜な圧縮比となるように設定する。
【００１５】
この熱圧成形時に、肉厚の多孔質炭素材を製造するために半硬化した熱硬化性樹脂含浸シートの積層枚数を多くして積層体の厚みを厚くすると、加熱エネルギー及び圧力の伝達が均等に伝わり難く、積層体の表面部と内部では温度および圧縮比が異なることになり、積層体の表面部は内部に比べて高温、高圧縮比の状態で熱圧成形されることとなる。その結果、得られた多孔質炭素材の組織性状は不均質化し易く、例えば表面部では内部に比べて組織性状が緻密化して、気孔径や気孔率が小さく、嵩密度が大きくなる傾向が生じる。
【００１６】
そこで、本発明は組織性状が不均質化し易い積層体の表面部に抄紙シートを介在させた状態で熱圧成形するものである。すなわち、積層体の上下両面に夫々少なくとも１枚の抄紙シートを積層した状態で熱圧成形することにより、温度及び圧力が不均等化し易い積層体の表面部を熱硬化性樹脂を含浸し半硬化したシート以外の樹脂含浸されていない抄紙シートで置換、代替させるのである。この積層する抄紙シートの材質は、熱圧成形時の温度、圧力に耐えるものであれば使用することができるが、熱硬化性樹脂が含浸される前の抄紙シート、すなわちα−セルロースを主成分とする有機質物質と抄紙バインダーとを抄紙したシートを用いることが作業上簡便であり、好ましい。
【００１７】
熱硬化性樹脂含浸シート積層体の上下両面に積層する抄紙シートの枚数は、積層する抄紙シート１枚当たりの厚さ、熱硬化性樹脂含浸シート積層体の厚さ、熱硬化性樹脂含浸シート積層体の熱圧成形時の圧縮比、多孔質炭素材の厚さなどにより異なるが、熱圧成形後の積層体の上下両面に積層した各々の抄紙シートの厚みが０．５ｍｍ以上となるように設定する。０．５ｍｍ未満より薄い場合には、多孔質炭素材の気孔性状や材質性状の均一性を保つことが困難となり易いからである。
【００１８】
所定の温度、圧力条件で熱圧成形したのち、積層体の上下両面に積層した抄紙シートは積層体の上下両面に積層した各１枚を残し、次いで熱圧成形体は常法により窒素、アルゴン、水素、アンモニアあるいは真空下などの非酸化性雰囲気に保持された加熱炉中で８００〜３０００℃の温度に加熱して焼成炭化され、肉厚多孔質炭素材が製造される。なお、熱圧成形体に積層した抄紙シートは必要に応じて熱圧成形体の上下両面を機械加工などの除去手段を用いて抄紙シートを除去してもよい。また焼成炭化後に機械加工を行って仕上げ除去することもできる。
【００１９】
【実施例】
以下、本発明の実施例を比較例と対比して具体的に説明する。
【００２０】
実施例１
太さ10デニール、長さ10mmのレーヨンパルプ〔大和紡績（株）製〕80重量部と晒し針葉樹パルプ(NBKP)20重量部を水 500重量部に加え、攪拌混合して均一な水分散液を作成し、長網式抄紙機を用いて抄紙、乾燥して厚さ0.35mm、坪量70g/m²、気孔径 150μm の抄紙シートを得た。この抄紙シートを残炭率45％のフェノール樹脂をメタノールに溶解したフェノール樹脂溶液（樹脂濃度30wt％）中に浸漬して樹脂溶液をシート組織内に充分に含浸し、次いで大気中80℃の温度で含浸樹脂を半硬化した。
【００２１】
この半硬化した熱硬化性樹脂含浸シートを 300mm角に裁断し、90枚を積層した積層体の上下両面に、裁断した上記の抄紙シート、すなわちフェノール樹脂溶液を含浸する前の抄紙シートを各6 枚づつ積層し、鉄板に挟持して 150℃に加熱したプレス盤に乗せて圧力 2kg/cm²で圧縮比（圧縮厚さ比）が70％となる熱圧条件下に4 時間保持して樹脂成分を硬化し熱圧成形体を得た。熱圧成形後の抄紙シート6 枚の厚さは1.5mm あった。次いで、上下両面に積層した抄紙シート各1 枚を残したのち、窒素雰囲気に保持した電気炉により2000℃の温度で焼成炭化して、厚さ14mmの多孔質炭素材を製造した。
【００２２】
実施例２
熱硬化性樹脂含浸シート積層体の上下両面に積層した抄紙シートを各12枚として、圧縮比（圧縮厚さ比）が70％となる熱圧条件下に4 時間保持して樹脂成分を硬化し熱圧成形体を得た。熱圧成形後の抄紙シート12枚の厚さは3.0mm あった。次いで、実施例１と同一の方法および条件により厚さ14mmの多孔質炭素材を製造した。
【００２３】
比較例１
実施例１において、積層体の上下両面に抄紙シートを積層しないほかは、全て実施例１と同一の方法および条件により多孔質炭素材を製造した。
【００２４】
実施例３
実施例１のレーヨンパルプの太さを 5デニール、長さを 5mmに変えて抄紙し、厚さ0.34mm、坪量70g/m²、気孔径 100μm のシートを得た。この抄紙シートをフェノール樹脂溶液（樹脂濃度20wt％）中に浸漬して実施例１と同一の方法、条件によって多孔質炭素材を製造した。
【００２５】
実施例４
熱硬化性樹脂含浸シート積層体の上下両面に積層した抄紙シートを各12枚として、圧縮比（圧縮厚さ比）が70％となる熱圧条件下に4 時間保持して樹脂成分を硬化し熱圧成形体を得た。熱圧成形後の抄紙シート12枚の厚さは3.0mm あった。次いで、実施例３と同一の方法および条件により厚さ14mmの多孔質炭素材を製造した。
【００２６】
比較例２
実施例３において、積層体の上下両面に抄紙シートを積層しないほかは、全て実施例３と同一の方法および条件により多孔質炭素材を製造した。
【００２７】
このようにして製造した多孔質炭素材について厚さ方向の表面から 2mmまでの表層部と厚さ方向の中心部 2mmの中央部を夫々機械加工により切り出し、表層部および中央部の平均気孔径、気孔率、嵩密度を測定し、また多孔質炭素材の曲げ強度を測定した。得られた結果を表１に示した。
【００２８】
【表１】

【００２９】
表１の結果から、実施例の肉厚多孔質炭素材は表層部と中央部における気孔径や気孔率の相違が少なく、また嵩密度の差も僅かであり、均一な気孔性状および材質性状を備えていることが判る。これに対して、比較例の肉厚多孔質炭素材は気孔径、気孔率、嵩密度の表層部と中央部における差が大きく、気孔性状および材質性状の均一性が実施例に比べて劣ることが明らかである。なお、実施例１、２と比較例１、実施例３、４と比較例２との対比から、曲げ強度は実質的に同等レベルにあることが認められる。
【００３０】
【発明の効果】
以上のとおり、本発明によれば表面部から内部まで気孔性状および材質性状の均一性が高く、均質な組織性状を備えた肉厚形状、例えば10mmを越える肉厚多孔質炭素材を製造することができる。したがって、電池用電極や電解用電極などに有用な多孔質炭素材の製造方法として極めて有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a porous carbon material having excellent porosity properties and material properties, and particularly a thick porous carbon material.
[0002]
[Prior art]
Lightweight, porous carbon materials with excellent heat resistance, corrosion resistance, conductivity, etc. are widely used for electrode materials for fuel cells and secondary batteries, catalyst carriers, electrode materials for electrochemical water treatment, filters, heat insulating materials, etc. It is useful as various industrial members in the field.
[0003]
As a technique for producing a porous carbon material, a sheet obtained by papermaking carbon fiber together with pulp is impregnated with a thermosetting resin solution, laminated and fired and carbonized (for example, JP-A-50-25808, No. 61-236664) is known. This method has the advantage that the strength of the material is increased because the carbon fiber forms a reinforcing skeleton, and the conductivity to electricity and heat is improved because the thermosetting resin is converted into a glassy carbon structure.
[0004]
However, this method has a drawback in that the production cost increases due to the use of expensive carbon fibers as a raw material, and there are difficulties in controllability such as bulk density, pore diameter, and porosity. Therefore, instead of carbon fiber, organic fiber for carbon fiber production is used, and an organic polymer substance or an organic polymer substance in which carbonaceous powder is suspended in a sheet made by mixing pulp and carbonaceous powder into paper. A method of firing after impregnation (JP-A 61-236664 and 61-236665) has been proposed. However, in the method using organic fibers for carbon fiber production as a raw material, a locally closed void portion is easily formed in the tissue, and there is a difficulty in obtaining a homogeneous and controlled pore structure.
[0005]
In order to solve these difficulties, the present applicant made a paper by making a heat-volatile material mainly composed of α-cellulose and formed a sheet, and a thermosetting resin solution having a residual carbon ratio of 40% by weight or more on the sheet. A step of impregnating the sheet, a step of semi-curing the sheet after the impregnation treatment at a temperature of 50 to 150 ° C., and laminating the semi-cured sheets so that the entire surface is uniformly heated so that the sheet thickness becomes 70 to 20%. Developed a method for producing a porous carbon material (Japanese Patent Laid-Open No. 3-183672) characterized by comprising a step of compressing and a step of firing and carbonizing a compressed sheet at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere. .
[0006]
According to this manufacturing method, a porous carbon material having good pore properties and strength characteristics can be manufactured. However, in the process of laminating the semi-cured sheets and compressing them while heating, it is difficult to uniformly transmit the pressure to the inside of the laminate due to pressure relaxation caused by the laminate sheets, However, there is a difficulty that a difference is easily caused in a tissue property, particularly a pore property due to a difference in pressure. Also, since it is difficult for heat energy to be transmitted evenly during heating, the curing rate of the thermosetting resin is different between the surface layer part and the inside of the laminate, and there is a difference in the texture and porosity properties of the molded body. Become. This phenomenon becomes more prominent as the laminate becomes thicker. Therefore, there is a problem that it becomes difficult to manufacture a porous carbon material having a uniform property, particularly a highly uniform porous property.
[0007]
Therefore, the applicant of the present invention, as a technique for producing a thick porous carbon material having good porosity, based on the technique of the above-mentioned Japanese Patent Application Laid-Open No. 3-183672, 60 to 90 weight of an organic substance mainly composed of α-cellulose. Molding process to make paper by dispersing 10 to 40 parts by weight of water-soluble papermaking binder in water, semi-cured after immersing the molded sheet in a thermosetting resin solution with a residual carbon ratio of 40% or more, and semi-cured A primary molding step of laminating and molding the required number of sheets under heat compression, a secondary molding step of laminating and molding a plurality of primary molded bodies under the thermal compression by interposing the same semi-cured sheet as in the above-mentioned step on the joining surface, Proposed the development of a method for producing a thick porous carbon material (Japanese Patent Laid-Open No. 5-51280) comprising a carbonization step of calcining and carbonizing the obtained secondary molded body at a temperature of 800 ° C. or higher in a non-oxidizing atmosphere. .
[0008]
[Problems to be solved by the invention]
According to the method of Japanese Patent Laid-Open No. 5-51280, a porous carbon material having excellent pore properties and tissue strength and having a wall thickness exceeding 50 mm can be produced. However, the secondary molded body that is a thick molded body is produced by sandwiching the same semi-cured sheet between the primary molded bodies in which the semi-cured sheets are laminated, and laminating a plurality of primary molded bodies. In addition, there is a problem that the joining between the primary molded bodies by the semi-cured sheet is not sufficient.
[0009]
As a result of further research based on the technique of the above-mentioned Japanese Patent Application Laid-Open No. 5-51280, the present inventors mainly applied the pressurizing force during pressure molding of the laminate to the thermosetting property of the laminate surface layer. The pressure is relaxed by the resin-impregnated sheet, resulting in a difference in texture between the surface layer and the inside of the laminate, and the thermal energy when heating the laminate rapidly increases the thermosetting resin-impregnated sheet of the surface layer. It is confirmed that the thermosetting resin in the surface layer is softened and fluidized once to fill the gaps in the thermosetting resin-impregnated sheet, or is cured after reducing the gaps in the thermosetting resin-impregnated sheet. did.
[0010]
The present invention has been developed on the basis of these findings, and the object thereof is excellent in uniformity of porosity and material properties, and a method for producing a porous carbon material having a thick shape, for example, a thick shape exceeding 10 mm. Is to provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a method for producing a thick porous carbon material according to the present invention is obtained by dispersing an organic substance mainly composed of α-cellulose and a papermaking binder in water, and papermaking an aqueous dispersion. The resulting papermaking sheet is impregnated with a thermosetting resin solution and semi-cured, a predetermined number of semi-cured thermosetting resin-impregnated sheets are laminated, and the laminate is hot-press molded, and then calcined and carbonized porous carbon material. In the manufacturing method, the thickness of each papermaking sheet laminated on the upper and lower surfaces of the laminate after hot-pressure forming is hot-press-molded in a state where at least one paper-making sheet is laminated on both upper and lower surfaces of the laminate. Setting as described above is a structural feature.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The organic substance mainly composed of α-cellulose is a raw material which becomes a filler component of the sheet, and preferably pulps such as wood pulp and rayon pulp containing 90% or more of α-cellulose content are used. A fiber form having a thickness of about 3 to 10 denier and a length of about 3 to 10 mm is preferable in terms of papermaking moldability. The papermaking binder functions as a binder for organic substances during papermaking. For example, softwood pulps such as red pine, spruce, todomatsu, larch, fir, and tsuga are used.
[0013]
These α-cellulose-based organic substances and papermaking binders are uniformly dispersed in water by setting an appropriate amount ratio in consideration of papermaking properties. Paper is made into a sheet by a paper machine. The formed sheet is sufficiently dried and then impregnated with a thermosetting resin solution. The thermosetting resin to be impregnated is a high residual carbon ratio, for example, phenolic, furan, polyimide, etc. resins having a residual carbon ratio of 40% by weight or more are used alone or in combination, and these thermosetting resins are Dissolve in a low-viscosity, high-penetration, heat-volatile organic solvent such as acetone, ether, ethanol, etc. to prepare a thermosetting resin solution and impregnate the sheet. The impregnation of the sheet can be performed by immersing the sheet in a thermosetting resin solution or applying a thermosetting resin solution to the sheet. The impregnated thermosetting resin is glassy carbon during calcination carbonization. It functions to improve the strength by reinforcing the skeleton of the porous carbon material. The resin concentration of the thermosetting resin solution is appropriately set in consideration of impregnation properties and the like.
[0014]
The sheet impregnated with the thermosetting resin solution is heated to a temperature of 50 to 150 ° C. to semi-cure the resin component. During the heat treatment, volatile substances of the organic solvent and moisture generated during the semi-curing are volatilized and removed, and the thermosetting resin is firmly attached and held on the sheet. A predetermined number of semi-cured thermosetting resin-impregnated sheets are laminated, and the laminate is integrated and molded by applying pressure while heating to cure the resin component. Although the heating temperature at the time of hot pressing varies depending on the resin, it is cured by heating at a temperature of about 80 to 250 ° C., and the pressure is set to an appropriate compression ratio in relation to the pore properties such as pore diameter and porosity. Set.
[0015]
If the number of laminated semi-cured thermosetting resin-impregnated sheets is increased to increase the thickness of the laminate during this hot pressing to produce a thick porous carbon material, the transmission of heating energy and pressure is even. Therefore, the temperature and compression ratio are different between the surface portion and the inside of the laminate, and the surface portion of the laminate is hot-press molded at a higher temperature and a higher compression ratio than the inside. As a result, the structural properties of the obtained porous carbon material are likely to be inhomogeneous. For example, in the surface portion, the structural properties become denser than the inside, and the pore diameter and porosity tend to be small, and the bulk density tends to increase. .
[0016]
In view of this, the present invention is to perform hot-pressure molding in a state in which a papermaking sheet is interposed on the surface of a laminated body in which the texture is likely to be heterogeneous. That is, by thermo-pressing in a state where at least one papermaking sheet is laminated on each of the upper and lower surfaces of the laminate, the surface portion of the laminate, which tends to have uneven temperature and pressure, is impregnated with a thermosetting resin and semi-cured. It is replaced with a papermaking sheet not impregnated with resin other than the prepared sheet. The material of the paper sheet to be laminated can be used as long as it can withstand the temperature and pressure at the time of hot pressing, but the paper sheet before impregnation with the thermosetting resin, that is, α-cellulose as a main component. It is preferable in terms of work to use a sheet made of the organic substance and a papermaking binder.
[0017]
The number of paper sheets to be laminated on the upper and lower surfaces of the thermosetting resin impregnated sheet laminate is the thickness per laminated paper sheet, the thickness of the thermosetting resin impregnated sheet laminate, and the thermosetting resin impregnated sheet lamination. Depending on the compression ratio at the time of hot pressing of the body, the thickness of the porous carbon material, etc., so that the thickness of each papermaking sheet laminated on the upper and lower surfaces of the laminated body after hot pressing is 0.5 mm or more Set. This is because when the thickness is less than 0.5 mm, it is difficult to maintain the porosity and material properties of the porous carbon material.
[0018]
After hot pressing under a predetermined temperature and pressure conditions, the paper sheets laminated on the upper and lower surfaces of the laminate remain one each laminated on the upper and lower surfaces of the laminate. Then, it is heated and calcined at a temperature of 800 to 3000 ° C. in a heating furnace maintained in a non-oxidizing atmosphere such as hydrogen, ammonia or under vacuum to produce a thick porous carbon material. In addition, as for the papermaking sheet laminated | stacked on the hot-press-molding body, you may remove a paper-making sheet using removal means, such as machining, on the upper and lower sides of a hot-pressing body. It can also be removed by machining after firing carbonization.
[0019]
【Example】
Examples of the present invention will be specifically described below in comparison with comparative examples.
[0020]
Example 1
Add 80 parts by weight of rayon pulp (manufactured by Daiwa Spinning Co., Ltd.) with a thickness of 10 denier and a length of 10 mm and 20 parts by weight of bleached softwood pulp (NBKP) to 500 parts by weight of water, stir and mix to obtain a uniform aqueous dispersion The paper sheet was prepared and dried using a long paper machine to obtain a paper sheet having a thickness of 0.35 mm, a basis weight of 70 g / m ² and a pore diameter of 150 μm. This paper sheet is immersed in a phenolic resin solution (resin concentration 30 wt%) in which a phenolic resin with a residual carbon ratio of 45% is dissolved in methanol to fully impregnate the resinous solution in the sheet structure, and then at a temperature of 80 ° C. in the atmosphere. The impregnated resin was semi-cured.
[0021]
This semi-cured thermosetting resin-impregnated sheet was cut into 300 mm square, and the above-mentioned cut paper-making sheet, that is, the paper-making sheet before impregnation with the phenol resin solution, was applied to each of the upper and lower surfaces of the laminate of 90 sheets. Laminated one by one, put on a steel plate sandwiched between iron plates and heated to 150 ° C, and held for 4 hours under a hot-pressing condition with a compression ratio (compression thickness ratio) of 70% at a pressure of 2kg / cm ² The components were cured to obtain a hot-pressed product. The thickness of the six papermaking sheets after hot pressing was 1.5 mm. Next, after leaving one paper sheet laminated on both upper and lower surfaces, it was calcined and carbonized at a temperature of 2000 ° C. in an electric furnace maintained in a nitrogen atmosphere to produce a porous carbon material having a thickness of 14 mm.
[0022]
Example 2
The paper components were laminated on the top and bottom surfaces of the thermosetting resin-impregnated sheet laminate, 12 sheets each, and held for 4 hours under hot-pressing conditions where the compression ratio (compression thickness ratio) was 70% to cure the resin component. A hot-pressed product was obtained. The thickness of 12 papermaking sheets after hot pressing was 3.0 mm. Next, a porous carbon material having a thickness of 14 mm was produced by the same method and conditions as in Example 1.
[0023]
Comparative Example 1
In Example 1, a porous carbon material was produced by the same method and conditions as in Example 1 except that the papermaking sheets were not laminated on the upper and lower surfaces of the laminate.
[0024]
Example 3
Paper making was performed by changing the thickness of the rayon pulp of Example 1 to 5 denier and the length to 5 mm to obtain a sheet having a thickness of 0.34 mm, a basis weight of 70 g / m ² and a pore diameter of 100 μm. This paper sheet was immersed in a phenol resin solution (resin concentration 20 wt%) to produce a porous carbon material by the same method and conditions as in Example 1.
[0025]
Example 4
The paper components were laminated on the top and bottom surfaces of the thermosetting resin-impregnated sheet laminate, 12 sheets each, and held for 4 hours under hot-pressing conditions where the compression ratio (compression thickness ratio) was 70% to cure the resin component. A hot-pressed product was obtained. The thickness of 12 papermaking sheets after hot pressing was 3.0 mm. Next, a porous carbon material having a thickness of 14 mm was produced by the same method and conditions as in Example 3.
[0026]
Comparative Example 2
In Example 3, a porous carbon material was produced by the same method and conditions as in Example 3 except that the papermaking sheets were not laminated on the upper and lower surfaces of the laminate.
[0027]
About the porous carbon material produced in this way, the surface layer part from the surface in the thickness direction to 2 mm and the center part of the center part 2 mm in the thickness direction are cut out by machining, respectively, the average pore diameter of the surface layer part and the center part, The porosity and bulk density were measured, and the bending strength of the porous carbon material was measured. The obtained results are shown in Table 1.
[0028]
[Table 1]

[0029]
From the results of Table 1, the thick porous carbon material of the example has little difference in pore diameter and porosity between the surface layer portion and the central portion, and also has a small difference in bulk density, and has uniform pore properties and material properties. You can see that it has. In contrast, the thick porous carbon material of the comparative example has a large difference in pore diameter, porosity, and bulk density between the surface layer portion and the central portion, and the uniformity of the porosity property and material property is inferior to the examples. Is clear. From the comparison between Examples 1 and 2 and Comparative Example 1, Examples 3 and 4, and Comparative Example 2, it is recognized that the bending strength is substantially at the same level.
[0030]
【The invention's effect】
As described above, according to the present invention, it is possible to produce a thick porous carbon material having a highly uniform porosity property and material property from the surface portion to the inside and having a homogeneous structure property, for example, a thick porous carbon material exceeding 10 mm. Can do. Therefore, it is extremely useful as a method for producing a porous carbon material useful for battery electrodes, electrolysis electrodes, and the like.

Claims

A paper sheet obtained by dispersing an organic substance mainly composed of α-cellulose and a paper-making binder in water, and making a paper with an aqueous dispersion is impregnated with a thermosetting resin solution, semi-cured, and semi-cured heat. In a method for producing a porous carbon material that is calcined and carbonized after laminating a predetermined number of curable resin-impregnated sheets and hot-pressing the laminate, in a state where at least one papermaking sheet is laminated on both upper and lower surfaces of the laminate. A method for producing a thick porous carbon material, characterized in that the thickness of each papermaking sheet laminated on both upper and lower surfaces of a laminate after hot pressing is set to 0.5 mm or more.