CA1291407C - Composite product comprising carbon materials mutually joined by tetrafluoroethylene resin or electroconductive tetrafluoroethylene resin and process for producing the same - Google Patents
Composite product comprising carbon materials mutually joined by tetrafluoroethylene resin or electroconductive tetrafluoroethylene resin and process for producing the sameInfo
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- CA1291407C CA1291407C CA000519027A CA519027A CA1291407C CA 1291407 C CA1291407 C CA 1291407C CA 000519027 A CA000519027 A CA 000519027A CA 519027 A CA519027 A CA 519027A CA 1291407 C CA1291407 C CA 1291407C
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Abstract
TITLE OF THE INVENTION: COMPOSITE PRODUCT COMPRISING CARBON MATERIALS MUTUALLY JOINED BY TETRAFLUOROETHYLENE RESIN OR ELECTROCONDUCTIVE TETRAFLUOROETHYLENE RESIN AND PROCESS FOR PRODUCING THE SAME Disclosed herein are a composite product produced by joining carbon materials by a tetrafluoroethylene resin or a tetrafluoroethylene resin mixed with highly electroconductive carbon black and a process for producing the composite product.
Description
BACKGROUND OF THE INVENTION~
The present invention relates generally to carbon-aceous materials (hereinafter referred to as "carbon materials") and composite products o~tained therefrom, and particularly relates to a composite product which comprises a carbon material and has been produced by joining the carbon materials mutually by a tetrafluoroethylene resin or a tetrafluoroethylene resin mixed with highly electroconductive carbon black and a process for producing the composi.te product.
In recent years, carbonaceous products using carbon materials such as carbon fiber, carbon particle, etc. as the aggregate have been used in various industrial fields and the higher re~uirements such as the improvement of the productivity and the physical specificities of the carbon-aceous products have been largely raised with the technical progress and the increase of the demand of such a productO
Although the carbon material is excellent in the physical properties as a raw material, for instance, heat-resistance, resistance to chemicals ! electroconductivity, mechanical strength, etc., a development of the carbonaceous composite material produced by joining the carbon materials of the same or the different quality has been promoted in order to make the most of the above-mentioned excellent physical properties. Although such a carbonaceous composite
The present invention relates generally to carbon-aceous materials (hereinafter referred to as "carbon materials") and composite products o~tained therefrom, and particularly relates to a composite product which comprises a carbon material and has been produced by joining the carbon materials mutually by a tetrafluoroethylene resin or a tetrafluoroethylene resin mixed with highly electroconductive carbon black and a process for producing the composi.te product.
In recent years, carbonaceous products using carbon materials such as carbon fiber, carbon particle, etc. as the aggregate have been used in various industrial fields and the higher re~uirements such as the improvement of the productivity and the physical specificities of the carbon-aceous products have been largely raised with the technical progress and the increase of the demand of such a productO
Although the carbon material is excellent in the physical properties as a raw material, for instance, heat-resistance, resistance to chemicals ! electroconductivity, mechanical strength, etc., a development of the carbonaceous composite material produced by joining the carbon materials of the same or the different quality has been promoted in order to make the most of the above-mentioned excellent physical properties. Although such a carbonaceous composite
- 2 ~
40~
material has been used as the carbon product produced by only sticking the raw materials with an adhesive, there has been a problem in the resistance to chemicals, electroconductivity, stability in dimensions, etc. thereof. Recently, a method for settling the above-mentioned problems has been conceived wherein the carbon materials are mutually joined by using an adhesive and the thus joined materials are calcined to obtain a composite carbon product of one body.
However, in the case of using the above-mentioned method, there are occasions of exfoliation of the carbon material on the adhered surface thereof and of forming cracks in the product during the step of calcination due to the difrerence of the rate of expansion and contraction between the carbon materials resulting frequently in the reduction of the productlve yield.
As has been described above, the composite carbon material has been severely burdened with the foIlowing requirements. Namely the exfoliation of the carbon material should not occur at the time of producing and using the composite carbon material and at the same time, the final product should preserve the original excellent properties of the carbon material itself, for instance, heat-resistance, resistance to chemicals, mechanical strength, electrical specificities, etc. and therefore, the production of such an excellent composite carbon material is accompanied by an extraordinary difficulty.
As a result of the present inventors' studies on the method of mutually joining the carbon materials for producing the composite carbonaceous material, it has been found by the present inventors that in the case of inter-posing a flexible graphite sheet between the carbon materials, the thus interposed graphite sheet acts as the buffer layer of the difference of expansion and contraction rate between the carbon materials on calcination thereof resulting in the production of the carbonaceous composite materlal with a favorable productivity, and the present inventors have filed a patent application on the basis of their finding (refer to Canadian Patent Application No. 498,544).
Further, a method of joining the porous electro conductive materials wherein the gas-impermeability between the porous electroconductive materials has been increased, has been proposed recently. According to the proposed method, the porous electroconductive material is impregnated with a fluorinated ethylene-propylene polymer, a polysulphone resin, etc., and the thus impregnated layer is joined as an inter-face to another electroconductive material by hot-pressing while maintaining electroconductivity through the gas imper~ious region (for instance, refer to U.S. Patent No.
4,505,992).
~ lowever, in the case of using the above-mentioned methods, although the passage of the gas between the two carbon materials is prevented by the thus resin-impregnated carbon layer, in the case where the electroconductive material is the porous carbon material, since such a fluorinated resin is low in melting viscosity, the usage of the thus obtained composite material impregnated with such a resin is limited.
As a result o the present inventors' studies on the method of overcoming the above-mentioned defect and joining the carbon materials which have a large mechanical strength and can be used in an atmosphere at a temperature as high as abo~lt 350C, it has been found by the present inventors that in the case of joining the carbon materials by melt-adhesion of tetrafluoroethylene resin interposed between the two carbon materials, a composite product which is excellent in heat-resistance and resistance to chemicals and has an improved bufEer action to thermal expansion and an improved adhesive strength can be obtained and that by further mixing a highly electroconductive carbon black with the above-mentioned tetrafluoroethylene resin, a composite product which is excellent in resistance to chemicals and at the same time, has a high electroconductivity can be obtained. On the basis of the above-menti.oned findinys, the present inventors have attained the present invention.
Namely, the objective of thé present invention is to provide a composite material and an electroconductive composite material both of which comprise a carbon material and have excellent specificities, particularly, for instance, improved heat-resistance, resistance to chemicals and adhesive strength.
Another objective of the present invention is to provide a process for producing a composite material and an electroconductive composite material both of which comprise a carbon material, have not the defects in the conventional techniques and have excellent specificities.
SUMMARY OF THE INVENTION:
In a first aspect of the present invention, there is provided a composite product which comprises carbon materials joined by the melt-adhesion of tetrafluoroethylene resin interposed between said carbon ~.aterials.
In a second aspect of the present inventlon, there is provided a process for producing a composi~e product comprising carbon materials, comprising ~1) inserting a tetrafluoroethylene resin between said carbon materials or (1') applying a dispersion of the tetraflucroethylene resin on the joining surfaces of the carbon materials and after drying the thus applied dispersion, piling the thus treated materials, and (2) press-joining the thus composed materials by heating under a pressure, thereby produclng said composite product wherein said carbon materials have been joined by the melt-adhesion of said resin.
~x9~
In a third aspect of the present inver.tion, there is provided a composite product comprising the carbon materials joined by the melt-adhesion of tetra~luoroethylene resin mixed with highly electroconductive carbon black and interposed between the carbon materials.
In a fourth aspect of the present invention, there is provided a process for producing a composite product comprising the carbon materials joined by the melt-adhesion of tetrafluoroethylene resin mixed with highly electro-conductive carbon black and interposed between the carbon materials, the process comprising (l) mixing highly electro-conductive carbon black with a dispersion of the tetrafluoro-ethylene resin by stirring, (2) applying the thus prepared dispersion of the tetrafluoroethylene resin mixed with the highly electroconductive carbon black on the joining surfaces of the carbon materials and (3) after drying the thus applied dispersion and piling the thus treated carbon materials, press-joining the thus composed materials by heating under pressure.
DETAILED _ESCRIPTION OF THE INVENTION:
The composite product according to the present invention is obtained by joininy the carbon materials together via a sheet or a dispersion of a tetrafluoroethylene resin interposed between the carbon materials. Furthermore, the electroconductive composite product is obtained by .
~ - 7 -9~ ~)7 joining the carbon materials together via a dispersion of a tetrafluoroethylene resin containing hiyhly electroconductive carbon black interposed between the carbon materials.
The fluorocarbon resin used according to the present invention is tetrafluoroethylene resin, preferably (hereinafter referred to as TFE resin). For instancel as TFE resins used in the present invention, a TFE resin having the melting point of 327C and the thermally deforming temperature of 121C under a pressure of 4.6 kgf/cm G may be mentioned. These TFE resins used in the present invention are commercialized, for instance, as the resin having the trade name of TEFLO ~
According to the present invention, the above-mentioned TFE resin is used as, for instance, a sheet of about 50 micrometers in thickness or a dispersion of ahout 60 % by weight. A small amount of a surfactant may be added to the above-mentioned dispersion.
In the case of producing an electroconductive composite material according to the present invention, highly electroconduc-tive carbon black is mixed with the above-mentioned dispersion of the TFE resin, and the thus treated dispersion is used. As the highly electroconductive carbon black, for instance, there are those having the trade name of VULCAN XC-72R manuactured by Cabot Corp., the trade name of KET3ENBL~CK EC manufactured by L.ion Akzo Co. Ltd., etc., and ~t may be selected rom those commercialized.
The mixing ratio of the TFE resin and the highly ~ ~9~7 electroconductive carbon black is from 1:9 to 9:1. In the case of mixing the highly electroconduc-tive carbon black with the TFE resin dispersion, although it is sufficient only to mix the both materials by stirring, it is preferable to apply the supersonic stirring.
The both carbon materials joined according to the present invention may be the same or different in the quality.
The carbon material having a bulk density of not less than 1.4~ g/cc is preferable.
As the example of the raw carbon material used in the present invention, the following materials may be mentioned, however, it is not limited to those mentioned as follows:
(1) A molded carbon material comprising a carbonaceous aggxegate selected from the group co~sisting of carbon fibers, carbon granules and oxidized pitch particles and a binder.
As the binder, various materials, for instance, one material or two or more combined materials selected from phenol resins, furan resins, epoxy resins and pitches of petroleum- or coal series are used, (2) A carbon material obtained by further calcining the molded carbon material of the above (1) at a temperature of not less than 800C under a reduced pressure and/or in an inert atmosphere,
40~
material has been used as the carbon product produced by only sticking the raw materials with an adhesive, there has been a problem in the resistance to chemicals, electroconductivity, stability in dimensions, etc. thereof. Recently, a method for settling the above-mentioned problems has been conceived wherein the carbon materials are mutually joined by using an adhesive and the thus joined materials are calcined to obtain a composite carbon product of one body.
However, in the case of using the above-mentioned method, there are occasions of exfoliation of the carbon material on the adhered surface thereof and of forming cracks in the product during the step of calcination due to the difrerence of the rate of expansion and contraction between the carbon materials resulting frequently in the reduction of the productlve yield.
As has been described above, the composite carbon material has been severely burdened with the foIlowing requirements. Namely the exfoliation of the carbon material should not occur at the time of producing and using the composite carbon material and at the same time, the final product should preserve the original excellent properties of the carbon material itself, for instance, heat-resistance, resistance to chemicals, mechanical strength, electrical specificities, etc. and therefore, the production of such an excellent composite carbon material is accompanied by an extraordinary difficulty.
As a result of the present inventors' studies on the method of mutually joining the carbon materials for producing the composite carbonaceous material, it has been found by the present inventors that in the case of inter-posing a flexible graphite sheet between the carbon materials, the thus interposed graphite sheet acts as the buffer layer of the difference of expansion and contraction rate between the carbon materials on calcination thereof resulting in the production of the carbonaceous composite materlal with a favorable productivity, and the present inventors have filed a patent application on the basis of their finding (refer to Canadian Patent Application No. 498,544).
Further, a method of joining the porous electro conductive materials wherein the gas-impermeability between the porous electroconductive materials has been increased, has been proposed recently. According to the proposed method, the porous electroconductive material is impregnated with a fluorinated ethylene-propylene polymer, a polysulphone resin, etc., and the thus impregnated layer is joined as an inter-face to another electroconductive material by hot-pressing while maintaining electroconductivity through the gas imper~ious region (for instance, refer to U.S. Patent No.
4,505,992).
~ lowever, in the case of using the above-mentioned methods, although the passage of the gas between the two carbon materials is prevented by the thus resin-impregnated carbon layer, in the case where the electroconductive material is the porous carbon material, since such a fluorinated resin is low in melting viscosity, the usage of the thus obtained composite material impregnated with such a resin is limited.
As a result o the present inventors' studies on the method of overcoming the above-mentioned defect and joining the carbon materials which have a large mechanical strength and can be used in an atmosphere at a temperature as high as abo~lt 350C, it has been found by the present inventors that in the case of joining the carbon materials by melt-adhesion of tetrafluoroethylene resin interposed between the two carbon materials, a composite product which is excellent in heat-resistance and resistance to chemicals and has an improved bufEer action to thermal expansion and an improved adhesive strength can be obtained and that by further mixing a highly electroconductive carbon black with the above-mentioned tetrafluoroethylene resin, a composite product which is excellent in resistance to chemicals and at the same time, has a high electroconductivity can be obtained. On the basis of the above-menti.oned findinys, the present inventors have attained the present invention.
Namely, the objective of thé present invention is to provide a composite material and an electroconductive composite material both of which comprise a carbon material and have excellent specificities, particularly, for instance, improved heat-resistance, resistance to chemicals and adhesive strength.
Another objective of the present invention is to provide a process for producing a composite material and an electroconductive composite material both of which comprise a carbon material, have not the defects in the conventional techniques and have excellent specificities.
SUMMARY OF THE INVENTION:
In a first aspect of the present invention, there is provided a composite product which comprises carbon materials joined by the melt-adhesion of tetrafluoroethylene resin interposed between said carbon ~.aterials.
In a second aspect of the present inventlon, there is provided a process for producing a composi~e product comprising carbon materials, comprising ~1) inserting a tetrafluoroethylene resin between said carbon materials or (1') applying a dispersion of the tetraflucroethylene resin on the joining surfaces of the carbon materials and after drying the thus applied dispersion, piling the thus treated materials, and (2) press-joining the thus composed materials by heating under a pressure, thereby produclng said composite product wherein said carbon materials have been joined by the melt-adhesion of said resin.
~x9~
In a third aspect of the present inver.tion, there is provided a composite product comprising the carbon materials joined by the melt-adhesion of tetra~luoroethylene resin mixed with highly electroconductive carbon black and interposed between the carbon materials.
In a fourth aspect of the present invention, there is provided a process for producing a composite product comprising the carbon materials joined by the melt-adhesion of tetrafluoroethylene resin mixed with highly electro-conductive carbon black and interposed between the carbon materials, the process comprising (l) mixing highly electro-conductive carbon black with a dispersion of the tetrafluoro-ethylene resin by stirring, (2) applying the thus prepared dispersion of the tetrafluoroethylene resin mixed with the highly electroconductive carbon black on the joining surfaces of the carbon materials and (3) after drying the thus applied dispersion and piling the thus treated carbon materials, press-joining the thus composed materials by heating under pressure.
DETAILED _ESCRIPTION OF THE INVENTION:
The composite product according to the present invention is obtained by joininy the carbon materials together via a sheet or a dispersion of a tetrafluoroethylene resin interposed between the carbon materials. Furthermore, the electroconductive composite product is obtained by .
~ - 7 -9~ ~)7 joining the carbon materials together via a dispersion of a tetrafluoroethylene resin containing hiyhly electroconductive carbon black interposed between the carbon materials.
The fluorocarbon resin used according to the present invention is tetrafluoroethylene resin, preferably (hereinafter referred to as TFE resin). For instancel as TFE resins used in the present invention, a TFE resin having the melting point of 327C and the thermally deforming temperature of 121C under a pressure of 4.6 kgf/cm G may be mentioned. These TFE resins used in the present invention are commercialized, for instance, as the resin having the trade name of TEFLO ~
According to the present invention, the above-mentioned TFE resin is used as, for instance, a sheet of about 50 micrometers in thickness or a dispersion of ahout 60 % by weight. A small amount of a surfactant may be added to the above-mentioned dispersion.
In the case of producing an electroconductive composite material according to the present invention, highly electroconduc-tive carbon black is mixed with the above-mentioned dispersion of the TFE resin, and the thus treated dispersion is used. As the highly electroconductive carbon black, for instance, there are those having the trade name of VULCAN XC-72R manuactured by Cabot Corp., the trade name of KET3ENBL~CK EC manufactured by L.ion Akzo Co. Ltd., etc., and ~t may be selected rom those commercialized.
The mixing ratio of the TFE resin and the highly ~ ~9~7 electroconductive carbon black is from 1:9 to 9:1. In the case of mixing the highly electroconduc-tive carbon black with the TFE resin dispersion, although it is sufficient only to mix the both materials by stirring, it is preferable to apply the supersonic stirring.
The both carbon materials joined according to the present invention may be the same or different in the quality.
The carbon material having a bulk density of not less than 1.4~ g/cc is preferable.
As the example of the raw carbon material used in the present invention, the following materials may be mentioned, however, it is not limited to those mentioned as follows:
(1) A molded carbon material comprising a carbonaceous aggxegate selected from the group co~sisting of carbon fibers, carbon granules and oxidized pitch particles and a binder.
As the binder, various materials, for instance, one material or two or more combined materials selected from phenol resins, furan resins, epoxy resins and pitches of petroleum- or coal series are used, (2) A carbon material obtained by further calcining the molded carbon material of the above (1) at a temperature of not less than 800C under a reduced pressure and/or in an inert atmosphere,
(3) A molded carbon material comprising graphite particles and/or carbon aggregate which is easily graphitizable carbon particle and a binder, for instance, pitch of coal series, phenol resin, furan resin, epoxy resin and pitch of petroleum series, and
(4) A carbon material obtained by calcining the molded carbon material of the above (3) under a reduced pressure and/or in an inert atmosphere.
According to the present invention, the above-mentioned carbon materials are used as the raw material in an optional combination thereof.
In the production o~ the composite material according to the present invention, for joining the carbon materials together by melt-adhesion of the TFE resin, the above-mentioned TFE resin is interposed between the two carbon materials and the thus composed materials are press-joined by heating under pressure.
For instance, in the case o~ using a sheet-like TFE resin, this sheet-like TFE resin is inserted between the two carbon materials, and the thus composed materials are press-joined b~ heating under pressure, and on the other hand, in ~he case of using a dispersion o the TFE resin, the dispersion is applied onto the joining surfaces o~ the carbon materials, and a~ter drying the thus applied dis-persion, and piling the thus treated materials, the obtained 4~7 composed materials are press-joined by heating under pressure.
In the case of joining the above-mentioned carbon materials together in the production of an electroconductive composite material according to the present invention, the above-mentioned dispersion of the TFE resin mixed with the above-mentioned carbon black is applied on the joining surfaces of the carbon materials, and af1:er drying the dis-persion and piling the thus treated materials, the obtained composed materials are press-joined by heating under pressure.
The temperature in the above-mentioned process is not lower than the temperature which is lower than the melting point of the TFE resin by 50C, and the pressure in such a process is not less than 2 kgf/cm2G. In the case where the pressure is less than the above, it is preferable to heat the composed material at a temperature of not lower than the melting point of the TFE resin and on the other hand, in the case where the pressure is more than the above, the junction thereof may be accomplished even at the tem-perature of not higher than the melting point of the TFE
resin. The predetermined pressure is kept for not less than lO min.after the TFE resin i3 heated to the predetermined joinin~-temperature. The thus heated composed material is released to ordinary pressure or cooled to room temperature while keeping the predetermined pressure.
The composite product obtained according to the -present invention shows the original excellent specificities possessed by the carbon materials, and at the same time, the TFE resin acts as the buffer material of the difference of the expansion and contraction rate between the carbon materials in the temperature range of 150 to 350C, thereby exhibiting the effects of (1) preventing the occurrence of exfoliation of the carbon material (the raw material) on the joining surface thereof, (2) preventing the occurrence of cracks in the product and (3) giving the product in a favorable productive yield, Pa~ticularly, the above-mentioned effects of the present invention are clearly seen in comparison to the case where the carbon materials are joined together only by using an adhesive.
In addition, the composite product according to .
the present invention is excellent in resistance to chemicals because of the use of the TFE resin as the adhesive.
Since the adhesive used in the conventional junction of the carbon materials is poor in resistance to chemicals, in the conventional composite product produced by joining with such an adhesive, there i5 a ear of exfoliation of the carbon materials from the joining surface when such a product is used in an environment wherein the product is exposed to chemicals.
Furthermore, in the case where the highly 9~07 electroconductive carbon black has been mlxed with the adhesive layer of the TFE resin according to the present invention, the electroconductivity is retained in the joining surface and in the adhesive layer. In addition, since the highly electroeonductive carbon black itself is resistant to chemicals, the resistance to chemicals of the joining part is retained.
Although the conventionally used adhesive can be used only at a temperature of not higher than about 160C, the eomposite produet aceording to the present invention can be used at a high temperature in the vicinity of the melting point of the TFE resin. In this connection, in the case where the operation of heating the composite product aeeord-ing to the present invention to the temperature of not less than the melting point of the TFE resin and cooling thereof was repeated several times, exfoliation.of the eaeh material of the eomposite material did not oeeur.
Furthermore, aeeording to the presenee of the TFE
resin, the eomposite produet of the present invention has a large adhesive strength of not less than 9~ kgf/em .
Hither~o, for instanee, in the eomposite earbon produet in whieh a ~lexible graphite sheet is interposed between the earbon materials (in the prior patent applieation No. 498,544 ~iled by the present applieant), the adhesive strength was from 2 to 3 kg/em2.
.~
Hitherto, in the case where a carbonaceous composite material is used in a chemical at a high temperature, there has been the necessity of, for instance, for endowing the material with resistance to chemicals and electroconductivity, calcining the composite material at a high temperature in an inert atmosphere, thereby carbonizing the whole material.
In such a case, for preventing the occurrence of exfoliation o the carbon material on the joining surEace thereof and of the cracks in the product due to calcination at a high temperature, the carbon materials are joined by using a flexible graphite sheet as the stress-relaxant material, for instance, in the prior patent application No. 498,544.
However, in the present invention wherein the carbon materials are joined by using a TFE resin or a TFE
resin mixed with highly electroconductive carbon black, since the joining temperature can be lowered differing from the hitherto used method, the absolute value o~ the thermal expansion becomes smaller, and therefore, the junction of the materials of different quality having the large difference of thermal expansion rate between the materials is possible.
In addition, since the calcination of the thus jo.inted material is not necessary, the energy cost and the instal-lation cost or production thereof can be largely economized.
In addition, the joined part in the composite product according to the present invention is excellent also in gas-lmpermeability, and in the case where the gas-impermeability (gas permeability coefficient) is repre-sented by the volume of the leaked gas per the peripheral length of the joined part under a definite differential pressure per unit time [hydrogen gas permeability co-efficient/(the side length)x(differential pressure)], for instance, in the case of Example 1, the amount of gas-leakage was 3 x 10 6 ml/cm.hour.mmAq and in the case of Example 2, the amount of gas-leakage was 2 x 10 4 ml/cm-hour-mmAq.
As has been described above, since the composite product comprising carbon materials according to the present invention is excellent in resistance to chemicals and heat, the product according to the present invention is suitable particularly as the composite carbon product used in the environment wherein the product is exposed to chemi-cals at a high temperature.
The present invention will be explained more in detail while referring to the non-limitative examples as follows:
EXA~PLE 1:
After inserting a sheet of tetrafluoroe-thylene resin (made by NICHIAS Co., Ltd.) of a thickness of 50 ~m between a carbon material (made by TOKAI Carbon Co., Ltd.
of a bulk density of 1.85 g/cc) of 30~ mm in width, 25 mm in length and 2 mm in thickness and a carbon material (made by SHOWA DENKO Co., Ltd., of a hulk density of 1.50 g/cc) .~,~..~
9~
of 300 mm in width, 300 mm in length and 0.8 mm in thickness, and after heating the thus composed materials to 350C, the thus heated materials were press-joined at the same tempera-ture under a pressure of 50 kgf/cm G.for 5 min. Thereafter, the thus hot-pressed materials were cooled to room temperature under normal pressure.
In order to determine the adhesive strength of the thus produced product, a jig was jointed to the both sides of the carbon composite material by using an epoxy resin, and the jig was pulled in the direction perpendicular to the surface of the carbon composite material. In the case of applying a force of 90 kgf/cm2, the sheet of the TFE resin was not exfoliated and the jointed part of the epoxy resin was broken. From the above-mentioned results, the adhesive strength due to the TFE resin was presumed to be not less than 90 kgf/cm2.
EXAMPLE 2:
After applying a dispersion of tetrafluoroethylene resin (made by MITSUI Fluorochemical Co., Ltd.) onto the each surface to be joined of the same both carbon materials as those used in Example 1 and drying the thus applied dis-persion, the surfaces thus applied with the dispersion were combined.
After heating the thus composed carbon materials to 350~C, the thus heated materials were press-joined for ~ 16 -~'~9~07
According to the present invention, the above-mentioned carbon materials are used as the raw material in an optional combination thereof.
In the production o~ the composite material according to the present invention, for joining the carbon materials together by melt-adhesion of the TFE resin, the above-mentioned TFE resin is interposed between the two carbon materials and the thus composed materials are press-joined by heating under pressure.
For instance, in the case o~ using a sheet-like TFE resin, this sheet-like TFE resin is inserted between the two carbon materials, and the thus composed materials are press-joined b~ heating under pressure, and on the other hand, in ~he case of using a dispersion o the TFE resin, the dispersion is applied onto the joining surfaces o~ the carbon materials, and a~ter drying the thus applied dis-persion, and piling the thus treated materials, the obtained 4~7 composed materials are press-joined by heating under pressure.
In the case of joining the above-mentioned carbon materials together in the production of an electroconductive composite material according to the present invention, the above-mentioned dispersion of the TFE resin mixed with the above-mentioned carbon black is applied on the joining surfaces of the carbon materials, and af1:er drying the dis-persion and piling the thus treated materials, the obtained composed materials are press-joined by heating under pressure.
The temperature in the above-mentioned process is not lower than the temperature which is lower than the melting point of the TFE resin by 50C, and the pressure in such a process is not less than 2 kgf/cm2G. In the case where the pressure is less than the above, it is preferable to heat the composed material at a temperature of not lower than the melting point of the TFE resin and on the other hand, in the case where the pressure is more than the above, the junction thereof may be accomplished even at the tem-perature of not higher than the melting point of the TFE
resin. The predetermined pressure is kept for not less than lO min.after the TFE resin i3 heated to the predetermined joinin~-temperature. The thus heated composed material is released to ordinary pressure or cooled to room temperature while keeping the predetermined pressure.
The composite product obtained according to the -present invention shows the original excellent specificities possessed by the carbon materials, and at the same time, the TFE resin acts as the buffer material of the difference of the expansion and contraction rate between the carbon materials in the temperature range of 150 to 350C, thereby exhibiting the effects of (1) preventing the occurrence of exfoliation of the carbon material (the raw material) on the joining surface thereof, (2) preventing the occurrence of cracks in the product and (3) giving the product in a favorable productive yield, Pa~ticularly, the above-mentioned effects of the present invention are clearly seen in comparison to the case where the carbon materials are joined together only by using an adhesive.
In addition, the composite product according to .
the present invention is excellent in resistance to chemicals because of the use of the TFE resin as the adhesive.
Since the adhesive used in the conventional junction of the carbon materials is poor in resistance to chemicals, in the conventional composite product produced by joining with such an adhesive, there i5 a ear of exfoliation of the carbon materials from the joining surface when such a product is used in an environment wherein the product is exposed to chemicals.
Furthermore, in the case where the highly 9~07 electroconductive carbon black has been mlxed with the adhesive layer of the TFE resin according to the present invention, the electroconductivity is retained in the joining surface and in the adhesive layer. In addition, since the highly electroeonductive carbon black itself is resistant to chemicals, the resistance to chemicals of the joining part is retained.
Although the conventionally used adhesive can be used only at a temperature of not higher than about 160C, the eomposite produet aceording to the present invention can be used at a high temperature in the vicinity of the melting point of the TFE resin. In this connection, in the case where the operation of heating the composite product aeeord-ing to the present invention to the temperature of not less than the melting point of the TFE resin and cooling thereof was repeated several times, exfoliation.of the eaeh material of the eomposite material did not oeeur.
Furthermore, aeeording to the presenee of the TFE
resin, the eomposite produet of the present invention has a large adhesive strength of not less than 9~ kgf/em .
Hither~o, for instanee, in the eomposite earbon produet in whieh a ~lexible graphite sheet is interposed between the earbon materials (in the prior patent applieation No. 498,544 ~iled by the present applieant), the adhesive strength was from 2 to 3 kg/em2.
.~
Hitherto, in the case where a carbonaceous composite material is used in a chemical at a high temperature, there has been the necessity of, for instance, for endowing the material with resistance to chemicals and electroconductivity, calcining the composite material at a high temperature in an inert atmosphere, thereby carbonizing the whole material.
In such a case, for preventing the occurrence of exfoliation o the carbon material on the joining surEace thereof and of the cracks in the product due to calcination at a high temperature, the carbon materials are joined by using a flexible graphite sheet as the stress-relaxant material, for instance, in the prior patent application No. 498,544.
However, in the present invention wherein the carbon materials are joined by using a TFE resin or a TFE
resin mixed with highly electroconductive carbon black, since the joining temperature can be lowered differing from the hitherto used method, the absolute value o~ the thermal expansion becomes smaller, and therefore, the junction of the materials of different quality having the large difference of thermal expansion rate between the materials is possible.
In addition, since the calcination of the thus jo.inted material is not necessary, the energy cost and the instal-lation cost or production thereof can be largely economized.
In addition, the joined part in the composite product according to the present invention is excellent also in gas-lmpermeability, and in the case where the gas-impermeability (gas permeability coefficient) is repre-sented by the volume of the leaked gas per the peripheral length of the joined part under a definite differential pressure per unit time [hydrogen gas permeability co-efficient/(the side length)x(differential pressure)], for instance, in the case of Example 1, the amount of gas-leakage was 3 x 10 6 ml/cm.hour.mmAq and in the case of Example 2, the amount of gas-leakage was 2 x 10 4 ml/cm-hour-mmAq.
As has been described above, since the composite product comprising carbon materials according to the present invention is excellent in resistance to chemicals and heat, the product according to the present invention is suitable particularly as the composite carbon product used in the environment wherein the product is exposed to chemi-cals at a high temperature.
The present invention will be explained more in detail while referring to the non-limitative examples as follows:
EXA~PLE 1:
After inserting a sheet of tetrafluoroe-thylene resin (made by NICHIAS Co., Ltd.) of a thickness of 50 ~m between a carbon material (made by TOKAI Carbon Co., Ltd.
of a bulk density of 1.85 g/cc) of 30~ mm in width, 25 mm in length and 2 mm in thickness and a carbon material (made by SHOWA DENKO Co., Ltd., of a hulk density of 1.50 g/cc) .~,~..~
9~
of 300 mm in width, 300 mm in length and 0.8 mm in thickness, and after heating the thus composed materials to 350C, the thus heated materials were press-joined at the same tempera-ture under a pressure of 50 kgf/cm G.for 5 min. Thereafter, the thus hot-pressed materials were cooled to room temperature under normal pressure.
In order to determine the adhesive strength of the thus produced product, a jig was jointed to the both sides of the carbon composite material by using an epoxy resin, and the jig was pulled in the direction perpendicular to the surface of the carbon composite material. In the case of applying a force of 90 kgf/cm2, the sheet of the TFE resin was not exfoliated and the jointed part of the epoxy resin was broken. From the above-mentioned results, the adhesive strength due to the TFE resin was presumed to be not less than 90 kgf/cm2.
EXAMPLE 2:
After applying a dispersion of tetrafluoroethylene resin (made by MITSUI Fluorochemical Co., Ltd.) onto the each surface to be joined of the same both carbon materials as those used in Example 1 and drying the thus applied dis-persion, the surfaces thus applied with the dispersion were combined.
After heating the thus composed carbon materials to 350~C, the thus heated materials were press-joined for ~ 16 -~'~9~07
5 min.under a pressure of 50 kgf/cm2G.at the same tempera-ture, and then cooled to room temperature under the same pressure.
In the case of determining the adhesive strength in the same manner as in Example 1, the same results as in Example 1 were obtained.
EXAMPLE 3:
__ After preparing a series of the joined composite materials by using the mixture of the same dispersion of tetrafluoroethylene resin as that used in Example 2 and carbon black (made by CABOT Co.) while changing the mixing ratio, the specific resistance of the thus prepared joining layers was determined and the results are shown as follows, the weight of the TFE resin being represented by the solid content of the TFE in the dispersion~
Weight ratio of TFE
: resin to carbon black S~ecific resistance (Qcm) - ..
1 :8 2.4 1 :4 2.6 1 :1 3.5 3 :1 4.7
In the case of determining the adhesive strength in the same manner as in Example 1, the same results as in Example 1 were obtained.
EXAMPLE 3:
__ After preparing a series of the joined composite materials by using the mixture of the same dispersion of tetrafluoroethylene resin as that used in Example 2 and carbon black (made by CABOT Co.) while changing the mixing ratio, the specific resistance of the thus prepared joining layers was determined and the results are shown as follows, the weight of the TFE resin being represented by the solid content of the TFE in the dispersion~
Weight ratio of TFE
: resin to carbon black S~ecific resistance (Qcm) - ..
1 :8 2.4 1 :4 2.6 1 :1 3.5 3 :1 4.7
6 :1 40 EXAMPLE 4:
A ~lixture of dispersion of tetrafluoroethylene resin and carbon black ~the mixing ratio 3/1) used in i Example 3 was applied on the each joining surface of the same both carbon materials (having the same dimensions) as those used in Example 1, and the thus applied dispersion of the mixture was d~ied.
After combinlng the thus treated carbon materials and heating the composed materials to 350C, they were press-joined for 5 min.at the same temperature under a pressure of 50 kgf/cm2G.and then cooled to room temperature under the same pressure.
The adhesive strength of the thus produced product due to the TFE resin mixed with carbon black was determined in the same manner as in Example 1. The result was quite the same as that in Example 1.
Accordingly, the adhesive strength due to the TFE
resin mixed with carbon black was presumed to be not less than 90 kgf/cm2.
A ~lixture of dispersion of tetrafluoroethylene resin and carbon black ~the mixing ratio 3/1) used in i Example 3 was applied on the each joining surface of the same both carbon materials (having the same dimensions) as those used in Example 1, and the thus applied dispersion of the mixture was d~ied.
After combinlng the thus treated carbon materials and heating the composed materials to 350C, they were press-joined for 5 min.at the same temperature under a pressure of 50 kgf/cm2G.and then cooled to room temperature under the same pressure.
The adhesive strength of the thus produced product due to the TFE resin mixed with carbon black was determined in the same manner as in Example 1. The result was quite the same as that in Example 1.
Accordingly, the adhesive strength due to the TFE
resin mixed with carbon black was presumed to be not less than 90 kgf/cm2.
Claims (13)
1. A composite product which comprises carbon materials joined by the melt-adhesion of tetrafluoroethylene resin interposed between said carbon materials.
2. A composite product according to claim 1, wherein said carbon material has been selected from the group consisting of ? a molded carbon material comprising a carbon aggregate and a binder, ? a carbon material obtained by calcining said molded carbon material of the above ? under a reduced pressure and/or in an inert atmosphere.
? a molded carbon material comprising a graphite aggregate and a binder and ? a carbon material obtained by calcining said molded carbon material of the above ? under a reduced pressure and/or in an inert atmosphere.
? a molded carbon material comprising a graphite aggregate and a binder and ? a carbon material obtained by calcining said molded carbon material of the above ? under a reduced pressure and/or in an inert atmosphere.
3. A composite product according to claim 1, wherein a highly electroconductive carbon black has been mixed with said tatrafluoroethylene resin.
4. A composite product according to claim 3, wherein the mixing ratio by weight of said tetrafluoroethylene resin and said highly electroconductive carbon black is in the range of 1:9 to 9:1.
5. A process for producing a composite product comprising carbon materials, comprising (1) interposing a tetrafluoroethylene resin between carbon materials and (2) press-joining the thus composed materials by heating under a pressure, thereby producing said composite product wherein said carbon materials have been joined by the melt-adhesion of said resin.
6. A process according to claim 5, wherein said carbon material is selected from the group consisting of ? a molded carbon material comprising a carbon aggregate and a binder, ? a carbon material obtained by calcining said molded carbon material of the above ? under a reduced pressure and/or in an inert atmosphere, ? a molded carbon material comprising a graphite aggregate and a binder and ? a carbon material obtained by calcining said molded carbon material of the above ? under a reduced pressure and/or in an inert atmosphere.
7. A process according to claim 5, wherein said press-joining of said carbon materials is carried out at a joining temperature of not lower than the temperature of lower than the melting point of said tetrafluoroethylene resin by 50°C under a pressure of not less than 2 kgf/cm2G.
for a time of not less than 10 sec.
for a time of not less than 10 sec.
8. A process according to claim 5, wherein said tetrafluoroethylene resin takes a form of a sheet.
9. A process according to claim 8, comprising (1) inserting said sheet of tetrafluoroethylene resin between said carbon materials and (2) press-joining the thus composed materials by heating under a pressure.
10. A process according to claim 5, wherein said tetrafluoroethylene resin takes a form of dispersion.
11. A process according to claim 10, comprising (l) applying said dispersion of tetrafluoroethylene resin onto the joining surfaces of said carbon materials and (2) after drying the thus applied dispersion and piling the thus treated carbon materials, press-joining the composed materials by heating under a pressure.
12. A process according to claim ll, comprising adding a highly electroconductive carbon black into said dispersion of tetrafluoroethylene resin, stirring the thus prepared mixture and applying the thus dipersion of tetra-fluoroethylene resin mixed with the highly electroconductive carbon black onto the joining surfaces of said carbon materials.
13. A process according to claim 12, wherein said stirring is carried out by supersonic waves.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP211797/85 | 1985-09-25 | ||
| JP21179785A JPS6271637A (en) | 1985-09-25 | 1985-09-25 | Composite product in which carbon material is fusion-bonded mutually by fluoroplastic and manufacture thereof |
| JP60213408A JPS6271638A (en) | 1985-09-26 | 1985-09-26 | Composite product in which carbon material is joined mutually by conductive fluoroplastic and manufacture thereof |
| JP213408/85 | 1985-09-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1291407C true CA1291407C (en) | 1991-10-29 |
Family
ID=26518846
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000519027A Expired - Fee Related CA1291407C (en) | 1985-09-25 | 1986-09-24 | Composite product comprising carbon materials mutually joined by tetrafluoroethylene resin or electroconductive tetrafluoroethylene resin and process for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1291407C (en) |
-
1986
- 1986-09-24 CA CA000519027A patent/CA1291407C/en not_active Expired - Fee Related
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