US3914393A - Process for the conversion of stabilized acrylic fibers to carbon fibers - Google Patents
Process for the conversion of stabilized acrylic fibers to carbon fibers Download PDFInfo
- Publication number
- US3914393A US3914393A US400829A US40082973A US3914393A US 3914393 A US3914393 A US 3914393A US 400829 A US400829 A US 400829A US 40082973 A US40082973 A US 40082973A US 3914393 A US3914393 A US 3914393A
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- Prior art keywords
- fibrous material
- hydrogen cyanide
- process according
- improved process
- heating zone
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- 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
- ABSTRACT An improved process is provided for the thermal transformation of stabilized acrylic fibers to carbon fibers in an inert gaseous atmosphere wherein the highly toxic hydrogen cyanide gas which is simultaneously evolved from the fibrous material is effectively controlled and converted to a less toxic compound.
- a gaseous mixture of the inert gas and hydrogen cyanide is withdrawn from the heating zone wherein the thermal transformation is conducted and is contacted with an aqueous solution of cupric sulfate wherein the hydrogen cyanide gas undergoes chemical reaction to form an insoluble precipitate.
- the resulting precipitate may be optionally recovered from the aqueous solution.
- carbon fibers is used herein in its generic sense and includes graphite fibers as well as amorphous carbon fibers.
- Graphite fibers are defined herein as fibers which consist substantially of carbon and have a predominant x-ray diffraction pattern characteristic of graphite.
- Amorphous carbon fibers are defined as fibers in which the bulk of the fiber weight can be attributed to carbon and which exhibit a substantially amorphous x-ray diffraction pattern.
- Graphite fibers generally have a higher Youngs modulus than do amorphous carbon fibers and in addition are more highly electrically and thermally conductive.
- the thermal stabilization of an acrylic fibrous material in an oxygen-containing atmosphere is well known in the art and involves l an oxidative cross-linking reaction of adjoining molecules as well as (2) a cyclization reaction of pendant nitrile groups to a condensed dihydropyridine structure.
- the cyclization reaction is exothermic in nature and must be controlled if the fibrous configuration of the acrylic material is to be preserved. Accordingly, stabilization procedures commonly proposed are conducted for many hours (e.g., at 220C. for 3 to 7 hours, or more).
- elements in the stabilized fibrous material other than carbon e.g., nitrogen, hydrogen, and oxygen, are expelled.
- carbon fibers and carbonized fibrous material as used herein are defined to be materials consisting of at least about 90 percent carbon by weight, and preferably at least about 95 percent carbon by weight. Depending upon the conditions under which the carbonized fibrous product is processed, substantial amounts of graphitic carbon may or may not be present in the same as determined by the characteristic x-ray diffraction pattern of graphite.
- the acrylic fibrous material which is carbonized in accordance with the present process be preliminarily stabilized to a heat-resistant form.
- the term stabilized acrylic fibrous material as used herein is defined as an acrylic fibrous material which is non-burning when subjected to an ordinary match flame and capable of undergoing carbonization while retaining its original fibrous configuration essential intact.
- the stabilization reaction may be conducted by heating the acrylic material at relatively moderate temperatures. Such a stabilization procedure is commonly conducted in the presence of oxygen and results in the formation of a cyclized and preoxidized product which exhibits thermal stability not exhibited by the unmodi fied acrylic material. Stabilization procedures in which the cyclization reaction is catalyzed optionally may be employed.
- the stabilized acrylic fibrous material is derived from a material formed primarily of recurring acrylonitrile units.
- the acrylic fibrous material should generally contain at least about 85 mol percent of acrylonitrile units and up to about mol percent of one or more monovinyl units copolymerized therewith, such as styrene, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl pyridine, and the like.
- the stabilized acrylic fibrous material is derived from an acrylonitrile homopolymer.
- Preferred acrylonitrile copolymers contain no more than about 5 mol percent of one or more monovinyl comonomers copolymerized with acrylonitrile.
- the stabilized acrylic fibrous material following stabilization in an oxygen-containing atmosphere commonly exhibits a carbon content of up to about 65 percent by weight, e.g., 50 to 65 percent by weight, a nitrogen content of at least about percent by weight (e.g., 20 to 30 percent by weight), and bound oxygen content of at least about 7 percent by weight (e.g., 7 to 12 percent by weight).
- the bound oxygen content may be determined by the Unterzaucher or other similar analysis.
- the stabilized acrylic fibrous material which serves as the starting material in the present process may be provided in any one of a variety of physical configurations.
- the fibrous starting material is preferably provided as a continuous length.
- continuous multifilament yarns, strands, cables, and tows may be selected.
- the stabilized acrylic fibrous material is a continuous multifilament yarn or a tow.
- the yarn may optionally be provided with a twist which improves its handling characteristics. For example, a twist of about 0.1 to 3 tpi, and preferably about 0.1 to 1.0 tpi, may be utilized.
- the stabilized acrylic fibrous material is heated in an inert gaseous atmosphere at a temperature in excess of 300C. to form a carbonaceous fibrous material which contains at least about 90 percent carbon by weight, and most preferably at least about 95 percent carbon by weight.
- the carbonization heat treatment may be conducted on either a batch or continuous basis in accordance with techniques known in the art.
- Suitable inert gaseous atmospheres include nitrogen, argon, and helium.
- a continuous length of the stabilized acrylic fibrous material is continuously passed through a heating zone containing an inert gaseous atmosphere provided with a temperature gradient wherein the continuous length of fibrous material is elevated from a temperature of about 300C. to a temperature of about l00OC. to form a continuous length of carbonaceous fibrous material containing at least about percent carbon by weight, and most preferably at least about percent carbon by weight.
- the temperature gradient may be subsequently more highly elevated to about 2000 to 3100C. whereby substantial amounts of graphitic carbon are produced within the carbonaceous fibrous material.
- the presence of graphitic carbon in the fibrous product may be detected by the characteristic x-ray diffraction pattern of graphitic carbon.
- the equipment utilized to produce the heating zone in which the carbonization reaction is conducted may be varied widely as will be apparent to those skilled in the art.
- induction furnaces wherein a graphite susceptor is encompassed by the windings of an induction coil, may be selected.
- Resistance heated furnaces may also be conveniently utilized.
- a gaseous mixture of the inert gas and the hydrogen cyanide gas evolved during the carbonization heating is withdrawn from the heating zone and contacted with an aqueous solution of cupric sulfate to form an insoluble precipitate.
- the hydrogen cyanide gas reacts with the cupric sulfate [CuSO to form a solid precipitate of cuprous cyanide [CuCN] and cupric cyanide [Cu(CN)
- the inert gas is continuously introduced into the heating zone, (2) at least one stream of a gaseous mixture of the inert gas and hydrogen cyanide gas evolved during the heating is continuously withdrawn from the heating zone, and (3) the stream of the gaseous mixture following withdrawal from the heating zone is contacted with the aqueous solution of cupric sulfate wherein the hydrogen cyanide undergoes reaction with the cupric sulfate to form the insoluble precipitate.
- the concentration of the cupric sulfate in the aqueous solution when contacted with the gaseous mixture may be varied widely, and is sufficient to at least substantially stoichiometrically react with the hydrogen cyanide present in the gaseous mixture.
- the aqueous solution of the cupric sulfate is preferably saturated, and provided ata temperature of about to 100C. (most preferably 50 to 95C.). If desired this cupric sulfate may be generated in situ through the reaction of sulfuric acid with metallic copper.
- the quantity of the gaseous mixture contacted with the aqueous solution of cupric sulfate is adjusted so that the hydrogen cyanide present therein is substantially completely reacted to form the solid precipitate, i.e., the quantity of hydrogen cyanide in the gaseous mixture should not stoichiometrically exceed the quantity of unreacted cu pric sulfate in the solution.
- the contact between the gaseous mixture and the aqueous solution of cupric sulfate is accomplished by countercurrent flow through a tower provided with baffles, e.g., a packed or scrubbing tower.
- the gaseous mixture may be introduced at the bottom of a tower while the aqueous solution of cupric sulfate is passed down the tower.
- the solid precipitate of cuprous cyanide and cupric cyanide produced in the present process is considerably less poisonous than the gaseous hydrogen cyanide evolved during the carbonization reaction and thereby substantially eliminates the acute hazard posed by the production of the gaseous hydrogen cyanide byproduct.
- the solid precipitate may be conveniently recovered from the aqueous solution, such as by decantation or centrifugation.
- the solid precipitate may be transported with considerably less danger than hydrogen cyanide.
- the cuprous cyanide precipitate may be used in double cyanide plating baths and as a catalyst in various organic reactions as known in the art. Upon contact of the precipitate with sulfuric acid, the hydrogen cyanide may be again regenerated immediately prior to its utilization in the production of acrylonitrile.
- the carbon fibers produced in the process may be utilized as a high strength, lightweight, fibrous reinforcement when incorporated in a suitable matrix ma terial, e.g., a thermosetting resin or a metallic matrix.
- a suitable matrix ma terial e.g., a thermosetting resin or a metallic matrix.
- the starting material selected for use in the process is a continuous length of a stabilized acrylonitrile homopolymer continuous filament yarn having a carbon content of about 62.6 percent by weight, a nitrogen content of about 24.5 percent by weight, a hydrogen content of about 2 percent and a bound oxygen content of about 1 1 percent by weight as determined by the Unterzaucher analysis.
- the stabilized acrylonitrile homopolymer yarn is non-burning when subjected to an ordinary match flame.
- the starting material is derived from an 800 f1] dry spun acrylonitrile homopolymer continuous filament yarn having a total denier of about 1 150.
- the acrylonitrile homopolymer yarn is oriented by hot drawing following its formation to a single filament tenacity of about 3.5 grams per denier, and twisted to improve its handling characteristics at a twist of about 0.5 tpi.
- the yarn is stabilized by continuous passage for 120 minutes through a muffle furnace containing an air atmosphere maintained at 270C. in accordance with the teachings of US. Ser. No. 749,957 filed Aug. 5, 1968 of Dagobert E. Stuetz (now abandoned). During the stabilization reaction no substantial amount of hydrogen cyanide gas is evolved from the fibrous material (i.e., about 2.3 percent by weight hydrogen cyanide gas).
- the stabilized acrylonitrile homopolymer yarn is provided upon rotating feed bobbin 1, and is continuously unwound from the same prior to continuously passing through a Lepel 450 KC induction furnace 2 wherein it undergoes carbonization and graphitization prior to being taken up on rotating takeup bobbin 4.
- a graphite tube susceptor 6 having a length of 8 /2 inches, an outer diameter of V2 inch, and an inner diameter of /8 inch is positioned within induction furnace 2 and is encompassed by a copper coil 8 having a length of one inch which is attached to a high frequency power source (not shown).
- the copper coil 8 which encompasses a portion of the hollow graphite tube susceptor 6 is positioned at a location substantially equidistant from the respective ends of the graphite tube susceptor 6.
- An enclosure 10 provided with appropriate entrance and exit openings surrounds the graphite tube susceptor 6 and the copper coil 8.
- the stabilized acrylonitrile homopolymer yarn is continuously passed from rotating feed bobbin 1 to rotating takeup bobbin 4 at a speed of 3 inches per minute.
- the yarn is at room temperature (i.e., 25C.) as it approaches the induction furnace 2 and while passing through the heating zone present therein is subjected to a circulating heated nitrogen atmosphere provided with a temperature gradient wherein it is heated to a maximum temperature of about 2800C. While passing through the temperature gradient of the heating zone, a substantial amount of hydrogen cyanide gas is evolved as the fibrous material undergoes carbonization and is heated from a temperature of about 300C. to a temperature of about 1000C. Substantial amounts of graphitic carbon are formed as the fibrous material is elevated to 2800C. The resulting graphitic carbon yarn contains in excess of 99 percent carbon by weight.
- a stream of nitrogen gas is continuously introduced into enclosure 10 via line 12.
- a stream ofa gaseous mixture of nitrogen and hydrogen cyanide is continuously withdrawn from induction furnace 2 via line 14 which passes through enclosure 10 and communicates with an opening in the wall of graphite tube susceptor 6.
- the gaseous mixture is discharged from line 14 into the bottom of scrubbing tower 16 which is packed with ceramic rings (not shown) along the length of its interior which are supported upon a series of slotted plates.
- a saturated aqueous solution 20 containing cupric sulfate which is provided at about C.
- a portion of cupric sulfate solution 20 is continuously withdrawn through line 22 and is introduced into the top of the packed tower 16 where it contacts the upwardly flowing gaseous mixture introduced via line 14.
- the hydrogen cyanide of the gaseous mixture undergoes chemical reaction to form a solid precipitate of cuprous cyanide and cupric cyanide.
- Nitrogen gas may be withdrawn from the tower 16 via line 17.
- the solid precipitate while suspended in the solution together with a sulfuric acid byproduct is withdrawn from the bottom of tower 16 via line 24 and returned to vessel 18.
- the solid precipitate 26 is allowed to settle to the bottom of vessel 18 and may be withdrawn through valve 28.
- Metallic copper rods 32 immersed in solution 20 make possible the regeneration of the cupric sulfate solution upon the reaction of the sulfuric acid by-product with the same.
- a stabilized acrylic fibrous material derived from an acrylonitrile homopolymer or an acrylonitrile copolymer containing at least about 85 mol percent of acrylonitrile units and up to about 15 mol percent of one or more monovinyl units copolymerized therewith is positioned in a heating zone containing an inert gaseous atmosphere at a temperature in excess of 300C. to form a carbonaceous fibrous material containing at least about 90 percent carbon by weight with the simultaneous evolution of hydrogen cyanide gas from said fibrous material; the improvement comprising:
- said stabilized acrylic fibrous material is derived from an acrylonitrile copolymer which contains at least about mol percent of acrylonitrile units and up to about 5 mol percent of one or more monovinyl units copolymerized therewith.
- said inert gas is selected from the group consisting of nitrogen, argon, helium.
- An improved process according to claim 6 which includes the additional step of (d) recovering said insoluble precipitate from said aqueous solution.
Abstract
Description
Claims (16)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US400829A US3914393A (en) | 1972-02-24 | 1973-09-26 | Process for the conversion of stabilized acrylic fibers to carbon fibers |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US22895972A | 1972-02-24 | 1972-02-24 | |
US400829A US3914393A (en) | 1972-02-24 | 1973-09-26 | Process for the conversion of stabilized acrylic fibers to carbon fibers |
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Publication Number | Publication Date |
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US3914393A true US3914393A (en) | 1975-10-21 |
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US400829A Expired - Lifetime US3914393A (en) | 1972-02-24 | 1973-09-26 | Process for the conversion of stabilized acrylic fibers to carbon fibers |
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Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4534919A (en) * | 1983-08-30 | 1985-08-13 | Celanese Corporation | Production of a carbon fiber multifilamentary tow which is particularly suited for resin impregnation |
US4714642A (en) * | 1983-08-30 | 1987-12-22 | Basf Aktiengesellschaft | Carbon fiber multifilamentary tow which is particularly suited for weaving and/or resin impregnation |
US4781223A (en) * | 1985-06-27 | 1988-11-01 | Basf Aktiengesellschaft | Weaving process utilizing multifilamentary carbonaceous yarn bundles |
US20050124246A1 (en) * | 2003-12-03 | 2005-06-09 | Feng Chia University | Method for making carbon fabric and product thereof |
US20130340483A1 (en) * | 2006-02-06 | 2013-12-26 | Furukawa Electric Co., Ltd. | Graphite heating furnace |
DE102012220341A1 (en) | 2012-11-08 | 2014-05-08 | Evonik Industries Ag | Carbon fiber production with improved hydrocyanic acid production |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1609872A (en) * | 1922-12-30 | 1926-12-07 | Standard Dev Co | Process of purifying gases |
US2088003A (en) * | 1935-03-09 | 1937-07-27 | Rohm & Haas | Recovery of hydrocyanic acid |
US2140605A (en) * | 1937-06-25 | 1938-12-20 | Rohm & Haas | Recovery of hydrocyanic acid |
US3539295A (en) * | 1968-08-05 | 1970-11-10 | Celanese Corp | Thermal stabilization and carbonization of acrylic fibrous materials |
US3607009A (en) * | 1969-07-07 | 1971-09-21 | Du Pont | Process for the preparation of copper cyanide |
-
1973
- 1973-09-26 US US400829A patent/US3914393A/en not_active Expired - Lifetime
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1609872A (en) * | 1922-12-30 | 1926-12-07 | Standard Dev Co | Process of purifying gases |
US2088003A (en) * | 1935-03-09 | 1937-07-27 | Rohm & Haas | Recovery of hydrocyanic acid |
US2140605A (en) * | 1937-06-25 | 1938-12-20 | Rohm & Haas | Recovery of hydrocyanic acid |
US3539295A (en) * | 1968-08-05 | 1970-11-10 | Celanese Corp | Thermal stabilization and carbonization of acrylic fibrous materials |
US3607009A (en) * | 1969-07-07 | 1971-09-21 | Du Pont | Process for the preparation of copper cyanide |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4534919A (en) * | 1983-08-30 | 1985-08-13 | Celanese Corporation | Production of a carbon fiber multifilamentary tow which is particularly suited for resin impregnation |
US4714642A (en) * | 1983-08-30 | 1987-12-22 | Basf Aktiengesellschaft | Carbon fiber multifilamentary tow which is particularly suited for weaving and/or resin impregnation |
US4781223A (en) * | 1985-06-27 | 1988-11-01 | Basf Aktiengesellschaft | Weaving process utilizing multifilamentary carbonaceous yarn bundles |
US20050124246A1 (en) * | 2003-12-03 | 2005-06-09 | Feng Chia University | Method for making carbon fabric and product thereof |
US7670970B2 (en) * | 2003-12-03 | 2010-03-02 | Feng Chia University | Method for making carbon fabric and product thereof |
US20100112206A1 (en) * | 2003-12-03 | 2010-05-06 | Feng Chia University | Method for making carbon fabric and product thereof |
US7927575B2 (en) | 2003-12-03 | 2011-04-19 | Feng Chia University | Method for making carbon fabric and product thereof |
US20130340483A1 (en) * | 2006-02-06 | 2013-12-26 | Furukawa Electric Co., Ltd. | Graphite heating furnace |
US9458051B2 (en) * | 2006-02-06 | 2016-10-04 | Furukawa Electric Co., Ltd. | Graphite heating furnace |
DE102012220341A1 (en) | 2012-11-08 | 2014-05-08 | Evonik Industries Ag | Carbon fiber production with improved hydrocyanic acid production |
WO2014072236A1 (en) * | 2012-11-08 | 2014-05-15 | Evonik Industries Ag | Carbon fibre production with improved hydrogen cyanide production |
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Legal Events
Date | Code | Title | Description |
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AS | Assignment |
Owner name: CCF, INC., Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CELANESE CORPORATION;REEL/FRAME:004413/0650 Effective date: 19850510 |
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AS | Assignment |
Owner name: BASF STRUCTURAL MATERIALS, INC., 1501 STEELE CREEK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INMONT CORPORATION, A CORP. OF DE.;REEL/FRAME:004540/0948 Effective date: 19851231 |
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AS | Assignment |
Owner name: INMONT CORPORATION Free format text: MERGER;ASSIGNORS:NARMCO MATERIALS, INC.;QUANTUM, INCORPORATED;CCF, INC.;REEL/FRAME:004580/0870 Effective date: 19860417 |
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AS | Assignment |
Owner name: SUBJECT TO AGREEMENT RECITED SEE DOCUMENT FOR DETA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BASF STRUCTURAL MATERIALS INC.;REEL/FRAME:004718/0001 Effective date: 19860108 Owner name: BASF AKTIENGESELLSCHAFT, D-6700 LUDWIGSHAFEN, GERM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:BASF STRUCTURAL MATERIALS INC.;REEL/FRAME:004718/0001 Effective date: 19860108 |