EP0579879B1 - Production method of expanded graphite sheet and expanded graphite sheet obtained thereby - Google Patents

Production method of expanded graphite sheet and expanded graphite sheet obtained thereby Download PDF

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Publication number
EP0579879B1
EP0579879B1 EP92306679A EP92306679A EP0579879B1 EP 0579879 B1 EP0579879 B1 EP 0579879B1 EP 92306679 A EP92306679 A EP 92306679A EP 92306679 A EP92306679 A EP 92306679A EP 0579879 B1 EP0579879 B1 EP 0579879B1
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EP
European Patent Office
Prior art keywords
expanded graphite
sheet
graphite sheet
expanded
parts
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92306679A
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German (de)
English (en)
French (fr)
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EP0579879A1 (en
Inventor
Toshiki Kusuyama
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyo Tanso Co Ltd
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Toyo Tanso Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to JP3085713A priority Critical patent/JP2931882B2/ja
Application filed by Toyo Tanso Co Ltd filed Critical Toyo Tanso Co Ltd
Priority to EP92306679A priority patent/EP0579879B1/en
Priority to DE69205421T priority patent/DE69205421T2/de
Publication of EP0579879A1 publication Critical patent/EP0579879A1/en
Application granted granted Critical
Publication of EP0579879B1 publication Critical patent/EP0579879B1/en
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/36—Inorganic fibres or flakes
    • D21H13/46—Non-siliceous fibres, e.g. from metal oxides
    • D21H13/50—Carbon fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/10—Organic non-cellulose fibres
    • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H13/26—Polyamides; Polyimides

Definitions

  • the present invention relates to an expanded graphite and production method thereof and, more particularly, to a heat resistant and asbestos-free graphite sheet which is utilized in gasket or the like for sealing various joints of internal combustion engine and in other industrial purposes, and a production method thereof.
  • joint sheets and beater sheets mainly composed of asbestos have been used as conventional gasket or the like.
  • Use of asbestos has been increasingly regulated due to its harmfulness for the health.
  • the present invention was made to solve the above discussed problem pertinent to the graphite sheet, particulary, to expanded graphite sheet, and has an object of developing a novel asbestos-free expanded graphite sheet of superior mechanical strength.
  • a method for producing the asbestos-free expanded graphite sheet according to the invention comprises the steps of: compressing a graphite preliminaryly expanded to not less than 50 times as large as normal state in average so as to be 0.02 to 0.3 g/cm 3 in bulk density; grinding the compressed graphite: suspending the above ground graphite into water in the presence of a binder together with a reinforcing fiber formed by fibrilating an aramid pulp fiber so as to be not less than 3.0 m 2 /g in specific surface, thus obtaining a paper making slurry; and wet-processing the slurry to be formed into a sheet.
  • the expanded graphite is first compressed to a predetermined bulk density.
  • a graphite expanded to not less than 50 times as large as normal state in average is not uniformly suspended into water to be a slurry no matter how it is ground, and not made into a paper due to floating of graphite particles on the surface of the water.
  • a method of utilizing a small amount of hydrophilic solvent such as acetone is known, but graphite particles tend to still float on the water even if employing such solvent, and this method is not a definite means of solution to the problem.
  • the expanded graphite particles are first subject to compression to be 0.02 to 0.3 g/cm 3, preferably 0.05 to 0.15 g/cm 3, in bulk density.
  • the bulk density is smaller than 0.02 g/cm 3
  • expanded gas existing in the hollow pores of the expanded graphite particles is not discharged, but the graphite particles (i.e., material) remain floating no matter how they are ground and stirred in the water.
  • the bulk density is larger than 0.3 g/cm 3
  • the ground expanded graphite does not lose the required characteristics, and is successfully suspended into water and fixed to the aramid pulp fiber resulting in an ideal paper material.
  • any means may be employed in principle as far as a required bulk density is obtained thereby, and in particular it is preferable to employ compressive means capable of continuously compressing the material in combination of a horizontal conveyor and an inclined conveyor.
  • the compression for obtaining a bulk density of 0.05 to 0.1 g/cm 3 according to the invention may be achieved by the known method as disclosed in the Japanese Patent Publication No. 71694/1978 in which casing of wire gauze is used. In this known method, however, mass production is difficult.
  • an expanded graphite which has been expanded to not less than 50 times in average as large as normal state is employed. Accordingly, not only the graphite particles alone expanded to not less than 50 times but also a mixture of a graphite expanded to be less than 50 times with another graphite expanded to not less than 50 times so as to be not less than 50 times in its entirety may be employed in the invention.
  • expansion of less than 50 times in average brings about decline in flexibility and sealing performance of the sheet.
  • the compressed graphite is then ground in the invention.
  • either wet process or dry process can be employed.
  • the compressed graphite is ground in a state preliminarily mixed with water, and the ground objects thus obtained are used as they are to be prepared into slurry.
  • a customary mixer type grinder as grinder means.
  • a beater used in the field of paper making. Size of the ground objects is usually not larger than 50 meshes, preferably about 60 to 100 meshes.
  • the compressed graphite is ground to the same size as the foregoing wet process in the absence of water. It is preferable to employ a grinder utilizing shearing force such as high speed mixer, for example.
  • the objects ground by dry process may be mixed with water beforehand, then prepared into slurry. It is also preferable to make the ground objects directly into slurry.
  • the reinforcing fiber employed in the invention causes the expanded graphite particles to fix thereto in the water and be dispersed evenly without separation when diluted to a required concentration. This function of even or uniform dispersion is a key factor for obtaining an expanded graphite sheet of high strength. To satisfy such conditions without fail, the reinforcing fiber should be of following characteristics:
  • a reinforcing fiber composed of pulped para-aramid or meta-aramid fiber of superior heat resistance can satisfy the mentioned conditions most effectively.
  • Aramid fiber itself is well known, and various kinds of conventionally known aramid fibers can be used in the invention. Any of those aramid fibers is employed through fibrilation so as to be of a required specific surface. Means of fibrilation are not particularly defined and any known means can be employed. Specific surface is required to be not less than 3.0 m 2 /g , preferably 5.0 to 8.0 m 2 /g . If less than 3.0 m 2 /g , there arises a disadvantage of poor fixation of graphite particles.
  • aramid fiber As for amount of use of such aramid fiber in the slurry, 3 to 25 parts by weight of aramid fiber, preferably 5 to 15 parts by weight, are used.
  • a binder is also used in the invention.
  • Water-soluble binder, emulsion type binder and powder binder are all employable, and among them emulsion type is particularly preferable because this type of binder is composed of fine particles easy to be dispersed in water and fixed gradually.
  • Latex of NR, NBR, CR and acrylic rubber is preferably added according to specific use considering such characteristics as strength, heat resistance, oil resistance, etc. When a further high heat resistance is required, it is preferable to employ phenol resin and NBR latex together or emulsion of silicon rubber and fluoro-rubber and the like.
  • Each of the mentioned materials is then suspended into water to be made into a paper-making slurry in the following mix proportion: Expanded graphite particles 60 to 90 parts by weight Aramid pulp 3 to 25 parts by weight Binder 1 to 20 parts by weight For obtaining a sheet of superior strength and heat resistance having a tensile strength of not less than 1.0 kg/mm 2, a following mix proportion is preferable: Expanded graphite particles 70 to 85 parts by weight Aramid pulp 5 to 10 parts by weight Binder 3 to 10 parts by weight It is to be noted that, in the solution of mentioned material, the expanded graphite particles are fixed using the aramid pulp as a nucleus, and therefore no separation takes place but even diffusion is achieved without floating on the water when diluting the material solution to 1 to 2% in concentration. In this manner, a sheet of high strength can be obtained by means of a paper-making apparatus.
  • wet process For preparing a paper-making slurry into a paper, wet process is usually employed. Conventionally known conditions for such wet process itself and paper making apparatus can be appropriately utilized as they are.
  • the sheet thus obtained from an expanded graphite according to the invention is very high in mechanical strength, superior in heat resistance and sealing performance, sufficient in flexibility, and therefore quite preferably formed into gaskets for sealing various joint surfaces of internal combustion engine or for other industrial uses.
  • the specific surfaces are measured by BET method using a mixed gas of N2 (30%) and He (70%).
  • the sheet of above composition and function according to the present invention mechanical strength and flexibility are significantly improved as compared with the flexible expanded graphite sheet according to the prior art, and easy to handle in practical use. Furthermore, other characteristics such as water resistance, oil resistance are also improved thereby substantially satisfying JIS standard on asbestos joint sheet.
  • the sheet of the mentioned features according to the invention can be widely used not only as gasket for industries in general but also as gasket for sealing various joints in internal combustion engine.
  • Figures 1 and 2 are graphs respectively showing a relation between mix proportion of graphite sheet material and tensile strength, and a relation between mix proportion of graphite sheet material and stress relaxation.
  • the obtained product was then put in a tank equipped with a pickup net and dispersed uniformly, and drained, thus a sheet being obtained.
  • the obtained sheet was then subject to suction of water by a suction pump, and dewatering by wrapping it in a felt to be compressed by a press.
  • the sheet was then placed in an oven for drying at 120°C, and density of the sheet was adjusted to 1.3 g/cm 3 by passing through calender rollers. Finally crosslinking was carried out at 150°C for 20 minutes.
  • a sheet was formed in the same manner as the foregoing Example 1 except that 15 parts of aramid pulp, 75 parts of expanded graphite and 10 parts (calculated in solid) of NBR latex were used.
  • 15 parts of aramid pulp, 75 parts of expanded graphite and 10 parts (calculated in solid) of NBR latex were used.
  • a cationic flocculant such as aqueous solution of 0.1 part of Sanflock CH799P (produced by Sanyo Chemical Industries) was added.
  • a sheet was formed in the same manner as the foregoing Examples 1 and 2 except that mix proportion of expanded graphite, aramid pulp and NBR latex was varied as shown in Table 1.
  • Characteristics of the flexible expanded graphite sheet obtained in Examples 1 and 2 were measured according to JIS R 3453. Result of the measurement was compared with the standard values of Class 1, 2 and 3 prescribed in JIS R 3453, as shown in Table 2.
  • any required sheet can be formed by optionally selecting the addition amount of reinforcing agent and binder.
  • Table 1 NBR latex Expanded graphite Aramid pulp Example Group I 5 90 5 3 85 10 1 80 15 4 75 20 5 85 5 6 Group II 10 80 10 7 75 15 2 70 20 8
EP92306679A 1991-01-23 1992-07-21 Production method of expanded graphite sheet and expanded graphite sheet obtained thereby Expired - Lifetime EP0579879B1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP3085713A JP2931882B2 (ja) 1991-01-23 1991-01-23 膨張黒鉛シートの製造法
EP92306679A EP0579879B1 (en) 1991-01-23 1992-07-21 Production method of expanded graphite sheet and expanded graphite sheet obtained thereby
DE69205421T DE69205421T2 (de) 1991-01-23 1992-07-21 Verfahren zur Herstellung einer Bahn aus expandiertem Graphit und eine durch dieses Verfahren erhaltene expandierte Graphitbahn.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP3085713A JP2931882B2 (ja) 1991-01-23 1991-01-23 膨張黒鉛シートの製造法
EP92306679A EP0579879B1 (en) 1991-01-23 1992-07-21 Production method of expanded graphite sheet and expanded graphite sheet obtained thereby

Publications (2)

Publication Number Publication Date
EP0579879A1 EP0579879A1 (en) 1994-01-26
EP0579879B1 true EP0579879B1 (en) 1995-10-11

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP92306679A Expired - Lifetime EP0579879B1 (en) 1991-01-23 1992-07-21 Production method of expanded graphite sheet and expanded graphite sheet obtained thereby

Country Status (3)

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EP (1) EP0579879B1 (ja)
JP (1) JP2931882B2 (ja)
DE (1) DE69205421T2 (ja)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999010598A1 (fr) * 1997-08-26 1999-03-04 Toyo Tanso Kabushiki Kaisya Tole de graphite deploye pour blindage contre les ondes electromagnetiques et son procede de fabrication
KR100731967B1 (ko) * 1999-07-22 2007-06-25 토요 탄소 가부시키가이샤 발열체
US6451486B1 (en) 2000-05-01 2002-09-17 The Gillette Company Battery cathode including a mixture of manganese dioxide with carbon particles of expanded and non-expanded graphite
US6921610B2 (en) 2001-07-11 2005-07-26 The Gillette Company Battery
CA2518273C (en) * 2003-03-31 2010-10-05 Young Woo Shin Manufacturing method of expanded graphite products
EP1518842A1 (en) * 2003-09-23 2005-03-30 Advanced Energy Technology Inc. Reactive additive that promotes material flow for moulding compounds
JP4747131B2 (ja) * 2007-04-26 2011-08-17 日本ピラー工業株式会社 シートガスケット

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992002354A1 (en) * 1990-08-01 1992-02-20 Mcallister Richard G High modulus media of reinforcing materials and thermoplastic fibrets

Also Published As

Publication number Publication date
JPH04240295A (ja) 1992-08-27
EP0579879A1 (en) 1994-01-26
JP2931882B2 (ja) 1999-08-09
DE69205421T2 (de) 1996-06-05
DE69205421D1 (de) 1995-11-16

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