EP0374925B1 - High density graphite fiber and method of manufacture thereof - Google Patents
High density graphite fiber and method of manufacture thereof Download PDFInfo
- Publication number
- EP0374925B1 EP0374925B1 EP19890123668 EP89123668A EP0374925B1 EP 0374925 B1 EP0374925 B1 EP 0374925B1 EP 19890123668 EP19890123668 EP 19890123668 EP 89123668 A EP89123668 A EP 89123668A EP 0374925 B1 EP0374925 B1 EP 0374925B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- fiber
- graphite
- less
- weight
- manufacturing
- 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
Links
- 239000000835 fiber Substances 0.000 title claims description 103
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims description 69
- 229910002804 graphite Inorganic materials 0.000 title claims description 69
- 239000010439 graphite Substances 0.000 title claims description 69
- 238000000034 method Methods 0.000 title claims description 19
- 238000004519 manufacturing process Methods 0.000 title claims description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 19
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 19
- 239000004917 carbon fiber Substances 0.000 claims description 19
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 19
- 229920002972 Acrylic fiber Polymers 0.000 claims description 15
- 238000002441 X-ray diffraction Methods 0.000 claims description 10
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 239000013078 crystal Substances 0.000 claims description 7
- 238000005087 graphitization Methods 0.000 claims description 7
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 claims description 4
- 238000010000 carbonizing Methods 0.000 claims description 4
- 125000004432 carbon atom Chemical group C* 0.000 claims description 3
- 229920001577 copolymer Polymers 0.000 claims description 3
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- 125000004433 nitrogen atom Chemical group N* 0.000 claims description 3
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 2
- 239000002131 composite material Substances 0.000 description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 239000004593 Epoxy Substances 0.000 description 4
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000001307 helium Substances 0.000 description 3
- 229910052734 helium Inorganic materials 0.000 description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 description 2
- KUBDPQJOLOUJRM-UHFFFAOYSA-N 2-(chloromethyl)oxirane;4-[2-(4-hydroxyphenyl)propan-2-yl]phenol Chemical compound ClCC1CO1.C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 KUBDPQJOLOUJRM-UHFFFAOYSA-N 0.000 description 2
- LCFVJGUPQDGYKZ-UHFFFAOYSA-N Bisphenol A diglycidyl ether Chemical compound C=1C=C(OCC2OC2)C=CC=1C(C)(C)C(C=C1)=CC=C1OCC1CO1 LCFVJGUPQDGYKZ-UHFFFAOYSA-N 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- OSSNTDFYBPYIEC-UHFFFAOYSA-N 1-ethenylimidazole Chemical compound C=CN1C=CN=C1 OSSNTDFYBPYIEC-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- ZDHWTWWXCXEGIC-UHFFFAOYSA-N 2-ethenylpyrimidine Chemical compound C=CC1=NC=CC=N1 ZDHWTWWXCXEGIC-UHFFFAOYSA-N 0.000 description 1
- XEEYSDHEOQHCDA-UHFFFAOYSA-N 2-methylprop-2-ene-1-sulfonic acid Chemical compound CC(=C)CS(O)(=O)=O XEEYSDHEOQHCDA-UHFFFAOYSA-N 0.000 description 1
- AGBXYHCHUYARJY-UHFFFAOYSA-N 2-phenylethenesulfonic acid Chemical compound OS(=O)(=O)C=CC1=CC=CC=C1 AGBXYHCHUYARJY-UHFFFAOYSA-N 0.000 description 1
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 1
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 1
- 239000011825 aerospace material Substances 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 1
- 239000011976 maleic acid Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- FQPSGWSUVKBHSU-UHFFFAOYSA-N methacrylamide Chemical compound CC(=C)C(N)=O FQPSGWSUVKBHSU-UHFFFAOYSA-N 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- XAEFZNCEHLXOMS-UHFFFAOYSA-M potassium benzoate Chemical compound [K+].[O-]C(=O)C1=CC=CC=C1 XAEFZNCEHLXOMS-UHFFFAOYSA-M 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- UIIIBRHUICCMAI-UHFFFAOYSA-N prop-2-ene-1-sulfonic acid Chemical compound OS(=O)(=O)CC=C UIIIBRHUICCMAI-UHFFFAOYSA-N 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- NLVXSWCKKBEXTG-UHFFFAOYSA-N vinylsulfonic acid Chemical compound OS(=O)(=O)C=C NLVXSWCKKBEXTG-UHFFFAOYSA-N 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
Definitions
- the present invention relates to a graphite fiber derived from polyacrylic fiber which is useful for reinforcing a composite material, particularly useful for reinforcing a composite material in the aerospace industry.
- the invention further relates to a method of manufacturing a graphite fiber.
- the graphite fibers which have been used in the aerospace industry have a strand tensile modulus of 50x103 kgf/mm2 at the highest and a strand tensile strength of as low as 200 kgf/mm2. Accordingly, their use for members in the aerospace industry is limited to a very narrow range.
- the fibers, even when they are useful, have disadvantages in that they have to be used in a large amount or have to be used in combination with other materials, thus resulting in increased weight.
- Such graphite fibers have been made according to the methods disclosed, for example, in U.S. Patent 4,321,446.
- Aerospace materials which are repeatedly exposed to high temperatures and low temperatures are required to have high heat conductivity.
- graphite fibers need to have higher density which correlates with the heat conductivity.
- graphite fibers are desired to have a high density, a high strength, and a high tensile modulus. Additionally, the graphite fibers are desired to be capable of being used as pseudoisotropic composite material in use for members in the aerospace industry.
- the graphite fibers are desired to have a small filament diameter.
- a graphite fiber has long been desired which is composed of filaments of a small diameter, particularly not more than 7 »m in diameter, and which has a high density, a high strength and a high modulus.
- An object of the present invention is to provide a graphite fiber which is light in weight and has a high strand tensile modulus and a high strand tensile strength and further which has a high density which contributes to heat conductivity.
- Another object of the present invention is to provide a graphite fiber which is suitable for producing a pseudoisotropic composite material.
- graphite fiber derived from an acrylic fiber, which has a fiber density of not less than 1.93 g/cm3, a strand tensile strength of not less than 350 kgf/mm2, and a strand tensile modulus of not less than 53x103 kgf/mm2.
- the fiber density, the strand tensile strength, and the strand tensile modulus are measured according to JIS R7601, and the diameter of the filament is determined by measuring the sectional area of the filament employing scanning electromicroscopy and converting the obtained value to the true circle diameter.
- a graphite fiber having a fiber density of up to about 2.10 g/cm3, a strand tensile strength of up to about 550 kgf/mm2, and a strand tensile modulus of up to about 75 x 103 kgf/mm2 can be obtained.
- the graphite fiber of the present invention substantially consists of carbon atoms in an amount of 100% by weight.
- nitrogen atoms, oxygen atoms, and hydrogen atoms each may be present in an amount of from 0 to 0.1% by weight
- ash may be present in an amount of from 0 to 0.2% by weight based on the weight of the total weight of the grahite fiber (including such materials, when present).
- the ash content is the residue of the graphite fiber after heating the graphite fiber at 650°C in the air for 300 minutes. (The heating is repeatedly conducted until the weight of the residue becomes constant.) A fiber density of less than 1.93/cm3 leads to decrease in the heat conductivity.
- the graphite fiber of the present invention preferably is composed of a filaments of not more than 7 »m in diameter.
- the filament diameter of not more than 7 »m is desirable as mentioned above, an excessively small filament diameter (i.e., less than 0.1 »m), namely extreme fineness thereof, is undesirable because such causes a remarkable increase in fluffing of the strands in ultra-thin sheet materials.
- a preferred diameter is from 0.5 to 5 »m.
- the number of filaments constituting a graphite fiber strand obtained according on the method of the present invention is desirably not overly large, and is preferably from 50 to 15,000 because of the required fineness of the strand. Less than 50 filaments is undesirable since it causes frequent thread breakage rendering difficult the production of thin sheet materials.
- the filaments constituting the strand are preferably not interlocked but are parallel with each other for producing thinner sheets.
- the interlocking degree of the filaments in a strand is measured by vertically hanging 300 mm long strand with a load of 0.1 g/d at the lower end thereof, perpendicularly piercing the strand with a chromium plated pin of 1 mm diameter at around the middle of the strand breadth, and measuring the distance that the pin goes down by 10 g of load for 3 minutes.
- the interlocking degree of the strand is represented by this distance.
- the interlocking degree is preferably not less than 250 mm.
- the graphite fiber of the present invention can be prepared from an acrylic fiber, that is, a polyacrylonitrile fiber or a copolymer fiber composed of preferably about 90% by weight or more, and more preferably about 95% by weight or more, of acrylonitrile, and any vinyl monomers which are copolymerizable with acrylonitrile can be used as the comonomers.
- known comonomers can be used, including neutral monomers such as methyl acrylate, methyl methacrylate and vinyl acetate; acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid and metal salts thereof (such as the sodium salt and potassium salt) and ammonium salts; vinylimidazole, vinylpyrimidine and derivatives thereof; and acrylamide, methacrylamide, etc.
- the preferred molecular weight of the polymer is about 40,000 to 200,000, more preferably about 60,000 to 150,000 calculated using Staudinger's equation.
- the graphite fiber can be obtained by preoxidizing acrylic fiber, carbonizing the thus-obtained preoxidized fiber and the graphitizing the thus-obtained carbon fiber.
- Methods for producing carbon fiber are known, for example, in U.S. Patents 4,197,279, 4,397,831, 4,347,279, 4,474,906 and 4,522,801, and methods for producing graphite fibers are known, for example in U.S. Patent 4,321,446.
- the graphite fiber of the present invention can be obtained by using a specifically selected carbon fiber and by using precisely selected conditions for obtaining the graphite fiber.
- Such an acrylic fiber can be obtained referring to U.S. Patent Application Serial No. 845,167*
- the acrylic fiber is preoxidized by heating in air at a temperature below the heat decomposition temperature of the fiber (usually at from 200 to 350°C) under a tension preferably of from 70 to 200 mg/d (more preferably of from 100 to 150 mg/d) for preferably from 5 to 120 minutes (more preferably of from 10 to 60 minutes) to give a fiber density of from 1.32 to 1.40 g/cm3 (preferably from 1.32 to 1.37 g/cm3).
- the thus obtained carbon fiber is stretched at least 3% (preferably from 5 to 15%, more preferably 5 to 10%) during graphitizing in an inert gas atmosphere (argon, helium or nitrogen, preferably argon or helium) at a temperature of 2,400°C or higher (preferably of from 2,400 to 3,300°C, more preferably of from 2,600 to 3,300°C) to produce a graphite fiber.
- the time period for heating (graphitizing) is usually from about 0.1 to 10 minutes.
- the graphitization is conducted until the density of the fiber becomes at least 1.93 g/cm3.
- the fiber density of the preoxidized fiber, the nitrogen content, the orientation degree, the density of the carbon fiber, the graphitization temperature of 2,400°C or higher and the elongation ratio must be met to provide the intended graphite.
- the composite materials reinforced by the graphite fiber of the present invention will enable a weight reduction and thus a speed increase of flying objects, satellites, and space stations etc., in the aerospace field, and similar results with respect to rotating bodies, travelling bodies, etc., in other technical fields.
- a prepreg containing fiber in an amount of 150 g/m2 with a resin content of 37% (based on the weight of the prepreg) was prepared from the thus obtained graphite fiber and a resin component constituted of 50 parts of an epoxy resin: Epikote 828 ® (made by Yuka Shell Epoxy K.K., bisphenol A diglycidyl ether having an epoxy equivalent of from 184 to 194), 50 parts of Epikote 1002 ® (made by Yuka Shell Epoxy K.K., bisphenol A diglycidyl ether having an epoxy equivalent of from 600 to 700) and 3 parts of dicyandiamide, by arranging the graphite fiber unidirectionally.
- Epikote 828 ® made by Yuka Shell Epoxy K.K., bisphenol A diglycidyl ether having an epoxy equivalent of from 184 to 194
- Epikote 1002 ® made by Yuka Shell Epoxy K.K., bisphenol A diglycidyl ether having an epoxy equivalent of from 600 to 700
- the prepreg was laminated and compression molded at 130°C for 2 hours under a pressure of 7 kgf/cm2 to produce a composite material in the form of a plate.
Description
- The present invention relates to a graphite fiber derived from polyacrylic fiber which is useful for reinforcing a composite material, particularly useful for reinforcing a composite material in the aerospace industry. The invention further relates to a method of manufacturing a graphite fiber.
- The graphite fibers which have been used in the aerospace industry have a strand tensile modulus of 50x10³ kgf/mm² at the highest and a strand tensile strength of as low as 200 kgf/mm². Accordingly, their use for members in the aerospace industry is limited to a very narrow range. The fibers, even when they are useful, have disadvantages in that they have to be used in a large amount or have to be used in combination with other materials, thus resulting in increased weight.
- Such graphite fibers have been made according to the methods disclosed, for example, in U.S. Patent 4,321,446.
- Aerospace materials which are repeatedly exposed to high temperatures and low temperatures are required to have high heat conductivity. To meet this requirement, graphite fibers need to have higher density which correlates with the heat conductivity.
- Hence graphite fibers are desired to have a high density, a high strength, and a high tensile modulus. Additionally, the graphite fibers are desired to be capable of being used as pseudoisotropic composite material in use for members in the aerospace industry.
- Moreover, the graphite fibers are desired to have a small filament diameter. Thus, a graphite fiber has long been desired which is composed of filaments of a small diameter, particularly not more than 7 »m in diameter, and which has a high density, a high strength and a high modulus.
- An object of the present invention is to provide a graphite fiber which is light in weight and has a high strand tensile modulus and a high strand tensile strength and further which has a high density which contributes to heat conductivity.
- Another object of the present invention is to provide a graphite fiber which is suitable for producing a pseudoisotropic composite material.
- According to one aspect of the present invention, there is provided graphite fiber derived from an acrylic fiber, which has a fiber density of not less than 1.93 g/cm³, a strand tensile strength of not less than 350 kgf/mm², and a strand tensile modulus of not less than 53x10³ kgf/mm².
- According to another aspect of the present invention, there is provided a method for manufacturing a graphite fiber having a fiber density of not less than 1.93 g/cm³, a strand tensile strength of not less than 350 kgf/mm², and a strand tensile modulus of not less than 53x10³ kgf/mm², comprising carbonizing a preoxidized fiber derived from an acrylic fiber and having a fiber density of from 1.32 to 1.40 g/cm³ to obtain a carbon fiber having a nitrogen content of not less than 1.0% by weight based on the carbon fiber weight, a fiber density of not less than 1.79 g/cm³ and an orientation of not less than 79% at a maximum diffraction at 2ϑ=25.3±0.5° in X-ray diffraction angle of the (002) plane of the graphite crystal, and graphitizing the thus-obtained carbon fiber in an inert gas at a temperature of not lower than 2,400°C and under a tension to stretch the fiber at least 3% during the graphitization.
- In the present invention the fiber density, the strand tensile strength, and the strand tensile modulus are measured according to JIS R7601, and the diameter of the filament is determined by measuring the sectional area of the filament employing scanning electromicroscopy and converting the obtained value to the true circle diameter.
- According to the method of the present invention a graphite fiber having a fiber density of up to about 2.10 g/cm³, a strand tensile strength of up to about 550 kgf/mm², and a strand tensile modulus of up to about 75 x 10³ kgf/mm² can be obtained.
- The graphite fiber of the present invention substantially consists of carbon atoms in an amount of 100% by weight. However, nitrogen atoms, oxygen atoms, and hydrogen atoms each may be present in an amount of from 0 to 0.1% by weight, and ash may be present in an amount of from 0 to 0.2% by weight based on the weight of the total weight of the grahite fiber (including such materials, when present).
- The ash content is the residue of the graphite fiber after heating the graphite fiber at 650°C in the air for 300 minutes. (The heating is repeatedly conducted until the weight of the residue becomes constant.)
A fiber density of less than 1.93/cm³ leads to decrease in the heat conductivity. - The graphite fiber of the present invention preferably is composed of a filaments of not more than 7 »m in diameter. Although the filament diameter of not more than 7 »m is desirable as mentioned above, an excessively small filament diameter (i.e., less than 0.1 »m), namely extreme fineness thereof, is undesirable because such causes a remarkable increase in fluffing of the strands in ultra-thin sheet materials. A preferred diameter is from 0.5 to 5 »m.
- The number of filaments constituting a graphite fiber strand obtained according on the method of the present invention is desirably not overly large, and is preferably from 50 to 15,000 because of the required fineness of the strand. Less than 50 filaments is undesirable since it causes frequent thread breakage rendering difficult the production of thin sheet materials. The filaments constituting the strand are preferably not interlocked but are parallel with each other for producing thinner sheets. The interlocking degree of the filaments in a strand is measured by vertically hanging 300 mm long strand with a load of 0.1 g/d at the lower end thereof, perpendicularly piercing the strand with a chromium plated pin of 1 mm diameter at around the middle of the strand breadth, and measuring the distance that the pin goes down by 10 g of load for 3 minutes. The interlocking degree of the strand is represented by this distance. The interlocking degree is preferably not less than 250 mm.
- The graphite fiber of the present invention can be prepared from an acrylic fiber, that is, a polyacrylonitrile fiber or a copolymer fiber composed of preferably about 90% by weight or more, and more preferably about 95% by weight or more, of acrylonitrile, and any vinyl monomers which are copolymerizable with acrylonitrile can be used as the comonomers. For instance, known comonomers can be used, including neutral monomers such as methyl acrylate, methyl methacrylate and vinyl acetate; acrylic acid, methacrylic acid, itaconic acid, maleic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid and metal salts thereof (such as the sodium salt and potassium salt) and ammonium salts; vinylimidazole, vinylpyrimidine and derivatives thereof; and acrylamide, methacrylamide, etc. The preferred molecular weight of the polymer is about 40,000 to 200,000, more preferably about 60,000 to 150,000 calculated using Staudinger's equation.
- The graphite fiber can be obtained by preoxidizing acrylic fiber, carbonizing the thus-obtained preoxidized fiber and the graphitizing the thus-obtained carbon fiber. Methods for producing carbon fiber are known, for example, in U.S. Patents 4,197,279, 4,397,831, 4,347,279, 4,474,906 and 4,522,801, and methods for producing graphite fibers are known, for example in U.S. Patent 4,321,446.
- The graphite fiber of the present invention can be obtained by using a specifically selected carbon fiber and by using precisely selected conditions for obtaining the graphite fiber.
- The acrylic fiber suitably comprises 50 to 15,000 filaments of a diameter of not more than 13 »m (preferably from 0.1 to 13 »m, more preferably from 0.2 to 10 »m; 0.05 to 1.5d and 0.1 to 1.0d, respectively), having a tensile strength of not less than 3 g/d (preferably of from 3 to 20 g/d, more preferably of from 5 to 15 g/d), a tensile elongation of not less than 5% (preferably from 5 to 15%, more preferably from 7 to 12%), and an orientation degree of not less than 88% (preferably of from 88 to 95%, more preferably of from 90 to 95%) measured at the diffraction angle range of 2ϑ=17.3 ± 0.3° where the maximum diffraction intensity is exhibited in X-ray diffraction. Such an acrylic fiber, can be obtained referring to U.S. Patent Application Serial No. 845,167* The acrylic fiber is preoxidized by heating in air at a temperature below the heat decomposition temperature of the fiber (usually at from 200 to 350°C) under a tension preferably of from 70 to 200 mg/d (more preferably of from 100 to 150 mg/d) for preferably from 5 to 120 minutes (more preferably of from 10 to 60 minutes) to give a fiber density of from 1.32 to 1.40 g/cm³ (preferably from 1.32 to 1.37 g/cm³). Subsequently, the thus obtained preoxidized fiber is carbonized in an inert atmosphere (nitrogen, argon or helium) at a temperature preferably of from 1,100 to 1,430°C (more preferably of from 1,200 to 1,400°C) for preferably from 0.5 to 10 minutes (more preferably from 1 to 5 minutes) under a tension to stretch the fiber (in an extent preferably of from 5 to 20%, more preferably from 8 to 12%) so as to result in a nitrogen content of at least 1.0% (preferably of from 1.0 to 8%, more preferably of from 3 to 5%) by weight in the fiber, an orientation of not less than 79% (preferably of from 79 to 84%, more preferably of from 80 to 84%) measured at a maximum diffraction intensity at 2ϑ=25.3 ± 0.5° (X-ray diffraction angle of the (002) plane of graphite crystal), and a fiber density of at least 1.79 g/cm³ (preferably from 1.79 to 1.85 g/cm³, more preferably from 1.81 to 1.85 g/cm³).
*(corresponding to DE-A1 36 10 517) - Thereafter the thus obtained carbon fiber is stretched at least 3% (preferably from 5 to 15%, more preferably 5 to 10%) during graphitizing in an inert gas atmosphere (argon, helium or nitrogen, preferably argon or helium) at a temperature of 2,400°C or higher (preferably of from 2,400 to 3,300°C, more preferably of from 2,600 to 3,300°C) to produce a graphite fiber. The time period for heating (graphitizing) is usually from about 0.1 to 10 minutes. The graphitization is conducted until the density of the fiber becomes at least 1.93 g/cm³. The thus obtained graphite fiber has an orientation degree (measured as above at 2ϑ=25.3 ± 0.5°), preferably of from 85 to 98%, more preferably from 90 to 98%.
- Among the above manufacturing conditions, the fiber density of the preoxidized fiber, the nitrogen content, the orientation degree, the density of the carbon fiber, the graphitization temperature of 2,400°C or higher and the elongation ratio must be met to provide the intended graphite.
- By employing the graphite fiber of the present invention in combination with a known resin, unidirectional composite materials, textile composite materials, and pseudoisotropic composite materials by multidirectional lamination can be prepared.
- The composite materials reinforced by the graphite fiber of the present invention will enable a weight reduction and thus a speed increase of flying objects, satellites, and space stations etc., in the aerospace field, and similar results with respect to rotating bodies, travelling bodies, etc., in other technical fields.
- Examples are shown below together with comparative examples. Unless otherwise mentioned, "%" and "parts" are based on weight in the examples.
- Various graphite fibers were prepared from an acrylic fiber (filament: 0.5 denier, number of filaments: 6000, tensile strength: 6.8 g/d, tensile elongation: 11%, orientation degree: 90.5% at a diffraction angle of the diffraction peak at 2ϑ=17.3 ± 0.3° in X ray diffraction) composed of 98% of acrylonitrile, 1.5% of methyl acrylate (the molecular weight of the acrylonitrile copolymer was 75,000), and 0.5% of itaconic acid, under the conditions shown in Table 1 regarding the preoxidation treatment (in air, 250°C, tension: 150 mg/d), the carbonization (in nitrogen gas, 3 minutes), and the graphitization (in argon, 3 minutes).
- A prepreg containing fiber in an amount of 150 g/m² with a resin content of 37% (based on the weight of the prepreg) was prepared from the thus obtained graphite fiber and a resin component constituted of 50 parts of an epoxy resin: Epikote 828® (made by Yuka Shell Epoxy K.K., bisphenol A diglycidyl ether having an epoxy equivalent of from 184 to 194), 50 parts of Epikote 1002® (made by Yuka Shell Epoxy K.K., bisphenol A diglycidyl ether having an epoxy equivalent of from 600 to 700) and 3 parts of dicyandiamide, by arranging the graphite fiber unidirectionally.
- The prepreg was laminated and compression molded at 130°C for 2 hours under a pressure of 7 kgf/cm² to produce a composite material in the form of a plate.
- The tensile characteristics and heat conductivity of the plate were measured. Table 2 shows the results. Table 2 shows that the composite materials produced employing the graphite fiber of the present invention have high strength, high modulus and excellent heat conductivity.
TABLE 1 Sample No. 1* 2* 3** 4** 5** 6** Preoxidation Time (min.) 48 48 48 55 42 35 Preoxidized Fiber Density 1.32 1.32 1.32 1.35 (1.31) 1.30 Carbonization Conditions Temperature (°C) 1380 1380 1380 1380 1380 1450 Elongation (%) 8 8 1 8 8 8 Properties of Carbon Fiber Orientation (%) 82 82 (78) 81 80 80 Nitrogen Content (%) 3.5 3.5 3.5 3.5 3.5 (0.8) Density (g/cm³) 1.83 1.83 1.80 (1.78) 1.84 1.82 Graphitization Conditions Temperature (°C) 2880 2880 2880 2880 2880 2880 Elongation (%) 7 3 7 6 7 7 Properties of Graphite Fiber Tensile Strength(kgf/mm²) 380 355 (300) 383 (283) (305) Tensile Modulus (x10³ kgf/mm²) 58.5 53.0 57.3 56.8 56.9 57.7 Fiber Density (g/cm³) 1.96 1.96 1.96 (1.90) 1.96 1.96 Fiber diameter (»m) 4.6 4.7 4.8 4.5 5.3 4.5 Orientation (%) 93 92 89 91 90 90 1) Filament denier of the acrylic fiber used for preparation of Sample 5 was 0.65
2) Values in the parentheses in Tables 1 and 2 are outside the present invention.Notes:
* : Invention**: Comparative - The following conversions to SI Units apply:
To convert from To Multiply by kgf/mm² GPa 9.807 x 10⁻³ g/d cN/tex 8.826 d tex 0.1111 mg/d cN/tex 8.826 x 10⁻³ kgf/cm² MPa 9.807 x 10⁻²
Claims (21)
- A graphite fiber derived from an acrylic fiber, said graphite fiber having a fiber density of not less than 1.93 g/cm³, a strand tensile strength of not less than 3.43245 GPa (350 kgf/mm²), and a strand tensile modulus of not less than 519.771 GPa (53×10³ kgf/mm²).
- The graphite fiber as in Claim 1, wherein the graphite fiber has a filament diameter of not more than 7 »m.
- The graphite fiber as in claim 1, wherein said fiber density is from 1.93 to 2.10 g/cm³.
- The graphite fiber as in claim 1, wherein said strand tensile strength is from 3.43245 to 5.39385 GPa (350 to 550 kgf/mm²).
- The graphite fiber as in claim 1, wherein said strand tensile modulus is from 519.771 to 735.525 GPa (53 x 10³ to 75 x 10³ kgf/mm²).
- The graphite fiber as in claim 1, wherein the filament diameter is from 0.1 to 7 »m.
- The graphite fiber as in claim 1, wherein the graphite fiber consists of 99.5 to 100% by weight of carbon atoms, less than 0.1% by weight of each of nitrogen atoms, oxygen atoms, and hydrogen atoms, and less than 0.2% by weight of ash.
- The graphite fiber as in claim 1, wherein the graphite fiber has an orientation of from 85 to 98% at a maximum diffraction at 2ϑ=25.3±0.5°, X-ray diffraction angle, of (002) plane of the graphite crystal.
- The graphite fiber as in claim 1, wherein the density is from 1.93 to 2.10 g/cm³, the strand tensile strength is from 3.43245 to 5.39385 GPa (350 to 550 kgf/mm²), the strand tensile modulus is from 519.771 to 735.525 GPa (53 x 10³ to 75 x 10³ kgf/mm²), the graphite fiber consists of from 99.5 to 100% by weight of carbon atoms, less than 0.1% by weight of each of nitrogen atoms, oxygen atoms, and hydrogen atoms, and less than 0.2% by weight of ash, and the graphite fiber has an orientation of from 85 to 98% at a maximum diffraction at 2ϑ=25.3±0.5°, X-ray diffraction angle, of (002) plane of the graphite crystal.
- A method for manufacturing a graphite fiber having a fiber density of not less than 1.93 g/cm³, a strand tensile strength of not less than 3.43245 GPa (350 kgf/mm²), and a strand tensile modulus of not less than 519.771 GPa (53×10³ kgf/mm²), comprising carbonizing a preoxidized fiber derived from an acrylic fiber and having a fiber density of from 1.32 to 1.40 g/cm³ to obtain a carbon fiber having a nitrogen content of not less than 1.0% by weight based on the carbon fiber weight, a fiber density of not less than 1.79 g/cm³ and an orientation of not less than 79% at a maximum diffraction at 2ϑ=25.3±0.5° in X-ray diffraction angle of the (002) plane of the graphite crystal, and graphitizing the thus-obtained carbon fiber in an inert gas at a temperature of not lower than 2,400°C and under a tension to stretch the fiber at least 3% during the graphitization.
- The method for manufacturing a graphite fiber as in claim 10, wherein the carbon fiber is stretched by 3% to 15% during the graphitization.
- The method for manufacturing a graphite fiber as in claim 10, wherein the nitrogen content of the carbon fiber is from 1.0 to 8% by weight.
- The method for manufacturing a graphite fibers as in claim 10, wherein the carbon fiber has an orientation of from 79 to 84% at the maximum diffraction at 2ϑ=25.3±0.5°, X-ray diffraction angle, of (002) plane of the graphite crystal.
- The method for manufacturing a graphite fiber as in claim 10, wherein the fiber density of the carbon fiber is from 1.79 to 1.85 g/cm³.
- The method for manufacturing a graphite fiber as in claim 10, wherein the carbon fiber comprises a strand consisting of from 50 to 15,000 filaments.
- The method for manufacturing a graphite fiber as in claim 10, wherein the acrylic fiber is a polyacrylonitrile fiber or a copolymer fiber composed of not less than 90% by weight of acrylonitrile.
- The method for manufacturing a graphite fiber as in claim 10, wherein the acrylic fiber has a filament diameter of from 0.1 to 13 »m.
- The method for manufacturing a graphite fiber as in claim 10, wherein the carbon fiber is derived from an acrylic fiber having a tensile strength of not less than 26.478 cN/tex (3 g/d), a tensile elongation of not less than 5%, and an orientation degree of not less than 88% measured at the X-ray diffraction angle of 2ϑ=17.3 ± 0.3°.
- The method for manufacturing a graphite fiber as in claim 10, wherein the graphitizing temperature is from 2,400 to 3,300°C.
- The method for manufacturing a graphite fiber as in claim 18, wherein the carbon fiber is obtained by preoxidizing said acrylic fiber in air at a temperature of from 200 to 350°C under a tension of from 0.617 to 1.765 cN/tex (70 to 200 mg/d) until the fiber density reaches 1.33 to 1.40 g/cm³, and then the thus obtained preoxidized fiber is carbonized in an inert atmosphere at a temperature of from 1,100 to 1,430°C while under a stretching condition so as to result in the orientation degree of from 79% to 84% at the maximum diffraction at 2ϑ=25.3±0.5°, X-ray diffraction angle, of (002) plane of the graphite crystal, until the fiber density becomes least 1.79 to 1.85 g/cm³ and the nitrogen content of from 1.0 to 8% by weight.
- The method for manufacturing a graphite fiber as in claim 20, wherein carbonizing is conducted under a stretching condition to stretch the fiber in an extent of from 5 to 20%.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP32439788 | 1988-12-22 | ||
JP324397/88 | 1988-12-22 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0374925A2 EP0374925A2 (en) | 1990-06-27 |
EP0374925A3 EP0374925A3 (en) | 1991-09-25 |
EP0374925B1 true EP0374925B1 (en) | 1995-03-08 |
Family
ID=18165338
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19890123668 Expired - Lifetime EP0374925B1 (en) | 1988-12-22 | 1989-12-21 | High density graphite fiber and method of manufacture thereof |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0374925B1 (en) |
DE (1) | DE68921581T2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7939046B2 (en) | 2004-06-21 | 2011-05-10 | Raytheon Company | Microporous graphite foam and process for producing same |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
TW459075B (en) * | 1996-05-24 | 2001-10-11 | Toray Ind Co Ltd | Carbon fiber, acrylic fiber and preparation thereof |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1093084A (en) * | 1965-03-16 | 1967-11-29 | Union Carbide Corp | Manufactured graphite yarn |
JPS58214534A (en) * | 1982-06-09 | 1983-12-13 | Toray Ind Inc | Carbon fiber bundle having high strength and elongation and production thereof |
WO1985001752A1 (en) * | 1983-10-13 | 1985-04-25 | Mitsubishi Rayon Co., Ltd. | Carbon fibers with high strength and high modulus, and process for their production |
-
1989
- 1989-12-21 EP EP19890123668 patent/EP0374925B1/en not_active Expired - Lifetime
- 1989-12-21 DE DE1989621581 patent/DE68921581T2/en not_active Expired - Fee Related
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7939046B2 (en) | 2004-06-21 | 2011-05-10 | Raytheon Company | Microporous graphite foam and process for producing same |
US8051666B2 (en) | 2004-06-21 | 2011-11-08 | Raytheon Company | Microporous graphite foam and process for producing same |
Also Published As
Publication number | Publication date |
---|---|
EP0374925A3 (en) | 1991-09-25 |
EP0374925A2 (en) | 1990-06-27 |
DE68921581T2 (en) | 1995-08-17 |
DE68921581D1 (en) | 1995-04-13 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Ko | The influence of pyrolysis on physical properties and microstructure of modified PAN fibers during carbonization | |
EP2233616B1 (en) | Processes for producing flameproof fiber and carbon fiber | |
US4904424A (en) | Ceramic alloys from colloidal metal alloy suspensions | |
EP0402915A2 (en) | Hybrid carbon/carbon composite material | |
Tse-Hao et al. | The characterization of PAN-based carbon fibers developed by two-stage continuous carbonization | |
EP0297695B1 (en) | Process for fabricating carbon/carbon fibre composite | |
US3917776A (en) | Process for producing carbon fiber | |
US3723607A (en) | Surface modification of carbon fibers | |
US5167945A (en) | Method for producing graphite fiber | |
EP0644280B1 (en) | Milled carbon fiber and process for producing the same | |
US3556729A (en) | Process for oxidizing and carbonizing acrylic fibers | |
Dačić et al. | Kinetics of air oxidation of unidirectional carbon fibres/CVD carbon composites | |
EP0374925B1 (en) | High density graphite fiber and method of manufacture thereof | |
US3754957A (en) | Enhancement of the surface characteristics of carbon fibers | |
JP2630477B2 (en) | High density graphite fiber | |
US3723150A (en) | Surface modification of carbon fibers | |
US3972984A (en) | Process for the preparation of carbon fiber | |
EP0372931B1 (en) | Continuous, ultrahigh modulus carbon fiber | |
US3900556A (en) | Process for the continuous carbonization and graphitization of a stabilized acrylic fibrous material | |
JP2004003043A (en) | Flameproof fiber material, carbon fiber material, graphite fiber material and method for producing the same | |
CA2007067A1 (en) | Composite metal-loaded carbon fibers | |
US3547584A (en) | Graphitization of fibrous polyamide resinous materials | |
Ko | Characterization of PAN‐based nonburning (nonflammable) fibers | |
Curtis et al. | Hollow carbon fibres for high performance polymer composites | |
JP3303424B2 (en) | Method for producing acrylic carbon fiber |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE FR GB |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE FR GB |
|
17P | Request for examination filed |
Effective date: 19920318 |
|
17Q | First examination report despatched |
Effective date: 19940517 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB |
|
REF | Corresponds to: |
Ref document number: 68921581 Country of ref document: DE Date of ref document: 19950413 |
|
ET | Fr: translation filed | ||
PLBI | Opposition filed |
Free format text: ORIGINAL CODE: 0009260 |
|
PLBQ | Unpublished change to opponent data |
Free format text: ORIGINAL CODE: EPIDOS OPPO |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
26 | Opposition filed |
Opponent name: TORAY INDUSTRIES, INC. Effective date: 19951208 |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
PLBF | Reply of patent proprietor to notice(s) of opposition |
Free format text: ORIGINAL CODE: EPIDOS OBSO |
|
PLBL | Opposition procedure terminated |
Free format text: ORIGINAL CODE: EPIDOS OPPC |
|
PLBM | Termination of opposition procedure: date of legal effect published |
Free format text: ORIGINAL CODE: 0009276 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: OPPOSITION PROCEDURE CLOSED |
|
27C | Opposition proceedings terminated |
Effective date: 19970210 |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20071219 Year of fee payment: 19 Ref country code: FR Payment date: 20071210 Year of fee payment: 19 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20071213 Year of fee payment: 19 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20081221 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST Effective date: 20090831 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20090701 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20081221 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20081231 |