JPH0663137B2 - Carbon fiber manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is derived from a stabilized carbonaceous precursor material that imparts a morphology of a spring-like structure capable of reversible flexure of about 1.2 times the length of the fiber when in a relaxed state. Elastic fiber or fiber assembly.

The carbonaceous fibers of the present invention have a substantially permanent, non-linear, elastic, stretchable, spring-like structure morphology, eg, a sharp or sharp bend-free morphology in the fiber. The morphological and elastic stretchable features of the present invention include stretched, stretched, and substantially linear when the fiber is under tension from a relaxed (ie, spring-like) state. Allows fiber dimensional changes up to and including any degree therebetween. When under tension, the fibers are capable of stretching at least 1.2 times, typically 2 to 4 times the length of their relaxed, undeflected, spring-like fibers. Thus, the spring-like fibers can be deflected (stretched or stretched) into a substantially linear shape or configuration. The elastic modulus of the fiber itself is not reached,
Or, if this is not exceeded, i.e. the fiber is not under a tension above that required to be straightened into a substantially linear shape, the fiber will change its size or physical structure. It can return from a linear to its relaxed spring-like shape over multiple cycles of stress elongation and relaxation without breaking or substantially changing.

The prior art is generally directed to producing filaments from pitch-based (petroleum and / or coal tar) compositions by conventional techniques by melt spinning the composition to produce continuous filaments and then stabilizing it by oxidation. Is taught. Such filaments are taught to be useful by themselves. Alternatively, the continuous filaments may be cut or stretch broken into what are referred to in the art as "staple" fibers. Such "staple" fibers can be added to the yarn by drafting, drawing and / or twisting (referred to in the industry as spinning). The continuous filament can also be a tow formed from multiple continuous monofilaments. The resulting yarn or yarn is used on its own, or alternatively, woven into a textile article and used on its own. Alternatively, the woven article may be carbonized into graphite or a graphite-like cloth. Alternatively, the tow itself can be carbonized and subsequently used as a reinforcing agent for synthetic resin materials such as "prepreg" without weaving the tow into a cloth.

In a similar fashion, wet wet-spun polyacrylonitrile (PAN) into filaments, collect the filaments into tows, stabilize the filaments or tows by oxidation, and staple the filaments or tows by cutting or stretch breaking. It has been taught that the staples are spun into spun yarns, the yarns are knitted or woven into a cloth or fabric, and if desired, the resulting fabric is carbonized at temperatures above 1400 ° C. These materials are
In its pre-carbonized woven state it was used as a non-combustible reinforcing agent for metallized fire resistant clothing. In their non-woven carbonized form, these materials have also been used as stiffeners in synthetic resin materials such as golf club shafts.

In the manufacture of non-carbonized conventional polymer fiber yarns for the production of knits, fabrics or other fiber products, the fiber tows are pinched and crimped to sharply crimp set the individual fibers of the tow Or, it is a common practice in the industry to include around sharp angles.Treatment of such textiles has the same effect when used on stabilized carbonaceous precursor yarns or tows, that is to say A crimp is applied to the yarn to create entanglement between the individual fibers of the yarn, to hold or secure the short staple fibers in the yarn, and to impart bulk to the yarn.
When the usual textile yarn manufacturing process is used and the yarn made from the carbonaceous precursor material is crimped and then carbonized at a temperature of about 1000 ° C. or higher, and more substantially at 1400 ° C. and higher, the result is Carburized yarns become very brittle. That is, this yarn is subject to harsh handling or crimping, for example knitting or weaving, unless knitting or weaving is carried out with great care and under highly controlled process conditions. I can't. For the same reason, such knitted or woven yarns cannot be easily knitted, recycled or carded without breaking the fibers in the yarn into small pieces. As a result of such brittleness, knitted knitted fabrics cannot be unraveled without special care, and such knitted yarns are subsequently carded to produce severe fiber breaks or breaks. The fibers in the yarn cannot be converted to a fluffy, wool-like material without crimping.

The prior art also generally discloses carbonized filaments with high tensile strength or high surface area. Such filaments have a highly "graphitic" nature and, as a result, use high temperatures to obtain a high degree of carbonization. However, the filaments produced by such isothermal treatment are very brittle and cannot withstand the stresses of repeated bending of the filaments. This is especially true when these filaments are exposed to temperatures above about 1000 ° C and even more so when these filaments are exposed to temperatures above about 1400 ° C. An example of high temperature processing of filaments derived from stabilized interlayer pitch is U.S. Pat. No. 4,005,183.
Can be found in which the oxidation-stabilized fibers (at temperatures of 250-400 ° C.) have a low surface area (lower than ordinary absorbent carbon) and within the range of 1-55 million psi (7Gpa-380Gpa). It is made into a yarn with Young's modulus.

Fabric panel manufacturing techniques are described in U.S. Pat.No. 4,341,830, in which an acrylic filament tow
Oxidized under tension at a temperature of 200-300 ° C, the stuffer
Crimped in boxes (pinch crimped), stapled, fiberized, spun into yarn, then knitted into woven panels and heat treated or carbonized in an inert atmosphere at a temperature of 1400 ° C . The carbonized fabric panels in this manner are accumulated in a stack and the stack is placed in a carbon steam furnace to deposit carbon on and in the stack. This treatment involves passing a carbonaceous gas, or methane, through the stack, during which the stack is electrically inductively heated to a temperature of 2000 ° C. to deposit carbon on and in the stack, the matrix of the knitted panel. To produce a carbonaceous body having However, the yarns made by this method are very fragile, as will be shown in the comparative example below, and without the severe breakage of the fibers, such as those that occur when a woven panel is unraveled and subjected to carding. It cannot be bent under acute angle stress.

Definitions "Fiber" or "filament", as interchangeable terms, refers to a fine thread or structure of a natural or synthetic material in its normal application. Included in this are fibers made by wet spinning PAN.

The term "fiber assembly" as used herein refers to a large number of filaments commonly used in the textile industry such as tows or yarns. The fiber assembly is made from conventional polymeric woven fibers or filaments, but also applies to stabilized and treated carbonaceous fibers or filaments according to the description and examples set forth below.

The terms "spring-like", "spring-like structure" or "form of spring-like structure" are used interchangeably herein and are substantially linear to coil-like, sinusoidal without sharp bends. Required to refer to fibers or tows that are physically deformed into a shape (sinusoidal), or other multi-curve shape or form.

The term "tow" here is defined by the number of filaments
Refers to an assembly of multiple continuous filaments identified by nk (n is the numerical value in increments of 1000 filaments).

The term "staple" refers to a discontinuous strand of yarn or fiber that can be "spun" (drafted, drawn and / or twisted) into a yarn or yarn used in the textile industry to make woven and / or knitted articles. Say.

As used herein, the term "stabilize" applies to fibers or tows oxidized at a particular temperature, typically less than about 250 ° C for PAN. However, it should be understood that in some cases the fiber is oxidized at low temperature with a chemical oxidant.

The term "yarn" as used herein applies to a continuous strand of twisted filaments, threads or fibers. The term "spun yarn" refers to a continuous strand of staple fibers drafted, drawn and / or twisted into a yarn or yarn.

The term "carding" is used herein to at least partially align staple fibers to a tangled web or sliver by combing or brushing the yarn with a toothed device such as a wire brush. Refers to the operation.

The term "recycle (garnet)" as used herein refers to a method of returning various textile wastes to fibers by passing the textile wastes through a machine called a garnet similar to a guard.

"Knitting" here means simple jersey knit, rib knit, pearl knit, interlock knit,
Double knits and similar methods of knitting fibers, yarns or tows into fabrics are included.

"Reversible deflection" or "working flexibility" is used herein as applied to helical, sinusoidal (sinusoidal) compression springs. Mechanical Derigh-Theory and Practic (Mac Mil
lan Publ. Co, 1975) pp. 719-748, especially section 14-
2, pp. 721-724.

By "Hook's law" it is meant that the stress applied to pull or compress an object is proportional to the strain or length change applied, as long as the elastic limit is not exceeded.

The carbonaceous precursor starting material capable of making the spring-like structured fibers of the present invention is PAN (acrylic) fiber (trade name PANOX,
GRAFIL etc.).

According to the present invention, unique articles are made from such carbonaceous precursor materials. Such carbonaceous precursor materials are formed into fibers or tows of fibers, stabilized by oxidation, and then given a spring-like structural morphology that alters the spring-like structural morphology of the fiber over many cycles of elongation and contraction. The fibers are imparted with flexibility, elasticity, stretchability and deflectability without. Fibers made from PAN are typically 200-250
It is stabilized by oxidation at a temperature of ° C and typically has a nominal diameter of 10-20 microns.

A large number of continuous fibers are collected to make a tow, which is then stabilized by conventional oxidation. The stabilized tow is then and in accordance with the present invention formed into a coiled structure, for example by wrapping the tow on a cylindrical rod or mandrel, or by knitting the tow into a woven fabric or cloth in a sinusoidal shape (sinusoidal). Corrugated) or other curvilinear (it will be appreciated that other textile and coil forming methods may also be used). It is convenient to form the sinusoidal structure on a standard knitting machine (eg a flat bed or tubular knitting machine) or in a round tooth gear box that does not impart sharp or sharp bends to the fibers. The coiled or sinusoidal fibers, tows or knitted fabrics are then heat treated at a temperature of 150-1550 ° C. The fibers, tows or fabrics are heat treated in an inert atmosphere at temperatures above about 250 ° C. If the desired end product requires subsequent mechanical treatment, that is, carding or unraveling of the fabric, it is preferred to heat the fiber, tow or fabric to a temperature below about 550 ° C in an inert atmosphere.

At temperatures between 150 and 525 ° C., the fibers are given a tentative set, but the high degree of brittleness associated with “graphite” fibers has not yet been retained. However, the fibers were initially 550-1000 ° C.
When treated at a temperature in the upper limit of the range, the fiber is given a "permanent set".

When imparting a spring-like morphology to a fiber or fiber tow by a round tooth gear crimp or by wrapping around a rod or mandrel, the fiber should not be heated under tension to a temperature above about 250 ° C. Is especially important. Above this temperature, the fiber begins to lose weight and the coil diameter shrinks, and the tension resulting from such shrinkage and weight loss causes non-annealing stress cracks and weaknesses in the fiber.

As long as the fibers are in a relaxed state (spring-like form) and heat treated in an inert, non-oxidizing atmosphere, the fibers and tows initially have high temperatures (500-1000 ° C for staple yarn knitted fabrics). , For braided fabrics made from continuous filament tows, can be heat treated at 1500 ° C). As a result of the high temperature treatment, the fibers are given the morphology of a permanent set of spring-like structures. The resulting fibers, tows having such a spring-like structure morphology, can be used on their own or, in the case of knitted fabrics, knitted into sinusoidal or other curvilinear fibers or tows. You can also In each case, the fiber, tow or fabric is then treated by itself with any of the carding or garneting operations or a number of other mechanical treatments known in the art. The entangled woolen fluff in which the fibers are separated and the individual fibers retain their spring-like morphology.
Can be

The fibers of the present invention have densities of less than 2.5 g / cc and, for certain applications, preferably have a Young's modulus of 7 to 380 GPa.

Fibers, tows, or knitted fabrics or wool-like fluffy produced by heat treatment in a relaxed state (with a temporary set of spring-like morphology imparted to the fibers, tows or threads) at temperatures below about 525 ° C. The material is then further heat-treated in a relaxed state under a non-oxidizing atmosphere to a temperature of 550-1550 ° C. to give the fibers a permanent set of spring-like structure morphology. About 15
At temperatures of from greater to about 3000 ° C. than 50 ° C., the electrical resistance of the various positions of is applied to the fibers, such resistance is preferably less than about 10 ^{1 0} ohm-cm.
The fibers or tows formed into the spring-like structure form as described above are in their relaxed, unstretched, spring-like form 1.
2 times or more: 1, generally 2 times or more reversible deflection ratio. It is of course possible to allow greater elongation or extension of the spring-like fibers or tows by adjusting this structural form, for example by adjusting the number of loops per length or the number of turns on the rod or mandrel. Be understood by The tension or relaxation of a non-linear coil or curl in a fiber, such as the number of loops per centimeter in a knitted fabric of the fiber, governs the degree of elongation of the spring-like fiber or tow.

In a preferred embodiment, polyacrylonitrile is spun into fibers, the fibers are stabilized by oxidation, a large number of continuous filaments are collected into a tow, and the tow is knitted. After knitting, the fibers in the fabric are tentatively "fixed" (set) into a coiled or sinusoidal structure by first treating the fabric at 150-550 ° C. The fibers in the knitted fabric are then heat treated in an inert atmosphere in a relaxed state at the temperature at which the acrylic fibers carbonize. When the heat treatment temperature is 950 ° C. or less, a considerable amount of nitrogen atoms are present in addition to carbon, and the log resistivity is −2.84 or more, which is particularly excellent in heat insulation. When heated to a temperature higher than 950 ° C and subjected to heat treatment, the log resistivity is less than -2.84, which shows high electrical conductivity like ordinary carbon fibers.

Since both of them have reversible flexibility, they can be effectively used as a heat insulating material or a static electricity dissipating material in carpets.

Examples of products that can be produced by the techniques of the present invention are shown in the examples below.

Example 1 Oxidation-stabilized polyacrylonitrile PAN-OX (R.R.) having a nominal single fiber diameter of 12 microns (at a temperature of about 250 ° C).
K. Textiles) Continuous 3K or 6K (3000 or 6000 fibers) tows were knitted on a flat bed machine to make a fabric with 3-4 loops per centimeter. This cloth part was heat-treated at a temperature shown in Table 1 for 6 hours under an inert atmosphere of nitrogen. When I knit this cloth, it is 2
A tow with a reversible deflection ratio of more than twice (specifically 2.3 times) was produced. The knitted tow was cut into various lengths of 5 to 25 cm and fed to the Platts Shirley Analyzer. The tow fibers were separated by carding to give a wooly, fluffy material. That is, the resulting product is a entangled wooly mass or fluffy material, with the fibers in the material having a high clearance spacing and a high degree of overlap as a result of the coiled and spring-like morphology of the fibers. I was there. The length of each fiber of such treatment was measured and the results are shown in Table 1.

Example 2 3K or 6K PANOX (RK Texti on a singer flatbed machine
les) A woven fabric was knitted from tows of continuous oxidation-stabilized filaments and heat-treated at a temperature shown in Table II under an inert atmosphere of nitrogen. The fabric was then unraveled and the tows in the form of spring-like structures were fed directly into the coding machine.
The resulting wooly agglomerates were collected on a rotating drum and had sufficient integrity to allow for easy handling. The length of these fibers was in the range of 2-15 cm.
The wooly agglomerates treated at a temperature of 950 ° C were highly conductive and had a resistance of less than 75 ohms at any test length taken at widely separated distances up to 60 cm in the wooly agglomerates. log resistivity (logarithmic value of resistivity ohm-cm)-
At 2.84, the reversible deflection ratio was 2.3 times.

Example 3 Stabilized tow of 3K PANOX is knitted on a singer flatbed knitting machine at a rate of 4 knits per cm, then under an inert atmosphere of nitrogen.
It was heat treated at a temperature of 950 ° C. The fabric was knitted, and the tow (having a tensile elongation greater than 2: 1 or a reversible flex ratio) cut to a length of 7.5 cm was then carded on a Platt Minature Carding machine to 3.5-6.5 cm. Wool fluff with lengths in the range and average lengths of about 5 cm were obtained. This wooly fluff had high electrical conductivity over any length tested up to 60 cm.

Example 4 Similar to Example 3, a portion from the same knitted fabric was heat treated at a temperature of 1550 ° C. under a nitrogen specific activity atmosphere.
The fabric itself and the tow that was knitted from it had a very high electrical conductivity. A 15 cm length of cut tow was carded to give a fluffy material flower with a fiber length in the range of 2.5-9.5 cm and an average length of 5 cm. That is, it was found that the carding of a tow of knitted and unraveled continuous filaments exposed to temperatures above 1000 ° C. could still result in a wooly fluff.

COMPARATIVE EXAMPLE A Ten double-layer staple single stabilized polyacrylonitrile PANOX yarns were knitted into tubular socks at a rate of 4 loops per cm, followed by heat treatment at a temperature of 1550 ° C. under an inert atmosphere of nitrogen. The yarn was then cut to a length of 10 cm. The cut yarn was then carded in a carding machine. The product was difficult to collect. Short fibers with a length of 0.5-1.25 cm were obtained with a large amount of debris. Fiber recovery difficulties result from the high degree of twist and fiber entanglement typically found in spun yarns. Hysol
-Gra obtained from Grafil Ltd. (Coventry, UK)
Similar results were obtained when the above example was repeated using a similar spun yarn of fil-01 as the raw material.

Example 5 A series of experiments were conducted to investigate the effect of different heat treatment temperatures on the fibers. A significant property was the fiber resistivity. To investigate such properties, 1.35 to 1.38 g / c
Many samples of oxidation-stabilized PAN yarn with a density of m ³
And collected in 6K tow. This tow (called PANOX,
(Manufactured by RK Textiles of Heaton-Norris, Stockport, England) into a plain jersey flat cloth with 3 and 5 knits per cm, respectively. The fabric was then heat treated at various temperatures in an oxygen-free nitrogen atmosphere in an incrementally heat-controlled quartz tube furnace. The temperature of the furnace was gradually increased from room temperature to about 550 ° C. over a period of 3 hours, whereby the high temperature was increased at a rate of 50 ° C. every 10 to 15 minutes. The sample was held at the desired temperature for about 1 hour and allowed to cool with the furnace open and a nitrogen purge. Typical furnace temperatures for the above heating schedule are for 6K yarns and are shown in Table III below.

Table III Time Temperature ℃ 0720 200 0810 270 0820 300 0830 320 0840 340 0850 360 0900 370 0905 380 0935 420 0950 450 1005 500 1010 550 1025 590 1035 650 1045 700 1100 750 1400 750 The specific resistance of fiber is 6 pieces. Calculated from the measurements made for each sample using the average of the values. The six measurements are for those made from the fibers removed at each corner of the sample and at the center of the sample from the fibers removed from each edge. The results are shown in Table IV below.

Table IV Final temperature ℃ Weight loss% Specific resistance (logarithmic value) 500 − 4.849 550 33 − 600 2.010 650 34 − 700 − − 750 37 −1.21 850 38 −2.02 900 42 −2.54 950 45 −2.84 1000 48 −3.026 1800 51-3.295 Carbonized and permanent set fibers of the present invention are such that the fibers still exhibit elasticity, flexibility, reversible flexibility, and non-weakness at temperatures sufficient to impart electrical conductivity to the fibers. It is particularly suitable for mixing with standard carpet fibers or yarns to produce a static dissipative yarn when treated at sufficiently low temperatures. Such a carpet / yarn blend has at least 0 in the carpet yarn.
It may contain 25% by weight of carbonized fibers. The weight ratio of synthetic carpet fiber to carbonized fiber is preferably greater than 100: 1 and up to 200: 1. Carpets using the carbonized fibers of the present invention exhibited a static discharge which resulted in an applied electrostatic charge of 0% in less than 1 second.

Example 6 Monsanto's 1879 nylon (trilobal) staple was blended with 0.5% by weight of the electrically conductive fiber prepared according to the present invention. This electrically conductive fiber is made by heating the tow of oxidation-stabilized polyacrylonitrile multifilament fiber knitted into a cloth, heat-treating it at about 1500 ° C, knitting it and cutting it into staples with a length of about 18 cm. The reversible deflection ratio of the fiber was 3.9 times. Pin draft of selected sliver 3 times, carded with blended staples. Recombination ratios were 10: 1, 3: 1 and 5: 1 respectively. The resulting draft sliver was spun into a single ply yarn with an average twist of about 4.75. Most carbonaceous fibers were broken to a length much smaller than the original 18 cm length, resulting in a large amount of carbonaceous fiber loss from what was originally included in the single spinning process. The resulting carbonaceous fiber containing a single yarn was similarly prepared but overlaid on a nylon yarn containing no carbonaceous fiber. 3.00 / 2 lapped yarn heat-set on Suessen heat-set device was tufted into 1/8 gauge, 27.03 (765g), 9.5mm pile height carpet (cut loop type) about 3 pieces per cm Produced a carpet with knitting. The ratio of carbonaceous fiber / non-carbonaceous yarn during the tufting operation was 1: 5, respectively. A portion of this carpet was lined with a commercially available non-conductive latex carpet backing material. The resulting carpet was tested for its electrostatic discharge properties by charging it to 5000 volts in an atmosphere of less than 20% relative humidity. The electrostatic charge dissipated to 0% of its original charge in less than 1 second and in some samples discharged in less than 1/2 second. The industrial standard is 2
Release up to 0% within seconds.

This example shows that temperatures above about 1000 ° C. can be used to heat set the spring-like structural morphology to the carbonaceous fiber tow, but at temperatures above 1000 ° C. many weakenings occur,
The resulting fibers are used inefficiently, are lost as short fibers and are not incorporated into the yarn when drafted with ordinary carpet staples to make singles.

Example 7 In another example, 100 g of tow of the same precursor acrylonitrile fiber as described in Example 6 was used. However,
The precursor fibers were knitted and then heat treated at a temperature of 950 ° C. Everything else about handling carbonaceous material was the same. Carbonized fiber as in Example 6 from Monsanto 18
Blended with 45.3 kg of 79 nylon yarn. The obtained yarn contained 0.02% by weight of carbonized fiber, and the carbonized fiber was distributed substantially uniformly throughout the yarn.
This yarn was tufted into a carpet in the same manner as in Example 6. That is, each tufted end contained carbonized fibers. The results were similar to those obtained in Example 6.

Knitted yarns or fiber tows that have been heat treated to temperatures above 1000 ° C. and thus imparted with electrical conductivity are also disclosed in US Patent Application Serial No. 558,239 (filed Dec. 5, 1983;
Inventors F.P. McCullough and A.F. Beer Jr .; title of the invention "energy storage device" and No. 678,186 (filed on December 4, 1984; title of invention "secondary electric energy storage device and A special application has also been found in the manufacture of electrodes for non-aqueous secondary battery energy storage devices as described in (Electrodes therefor).

Example 8 In another experiment, a flat stock cloth was woven to make a tow. The tow was a stabilized polyacrylonitrile precursor with the indicated number of filaments heat set at the indicated temperature prior to knitting. The elastic deflection was measured by applying a known load to the tow section, and the intermediate and final deformation as well as the final inelastic elongation deflection was measured.
These decisions are shown in Table V.

Comparative Example B To demonstrate the effect of tension on the fibers in the spring-like morphology of the set, a 6K tow of Panox continuous fiber was rolled into an 8 mm push rod. Example 5 of this rolled tow
Heat treatment was carried out at a final temperature of 300 ° C. according to the schedule shown in Table III, while firmly holding the ends of the wrapped tow. This heat treatment fixed a spring-like morphology to the tow. However, the fibers were so stiff that it was difficult to remove the tow from the bar. Many of the fibers broke during removal. This tow was not as elastic as the heat set tow in a relaxed braided form. Using the same method except heating the spring-like tow to a temperature of 350 ° C. resulted in even more breaks even before removal.

The latter method was repeated and the heat treated material (350 ° C) was carefully removed from the bar and then slowly heated to a temperature of about 650 ° C in the relaxed state to see if annealing occurred. No annealing occurred. The generator coil was brittle and not elastic.

However, removing the coiled tow from the rod before reaching 275 ° C and inserting a rod with a smaller diameter to maintain the spring-like integrity and heating in this "relaxed" state,
A spring-like tow having substantially the same properties as the above-mentioned braided tow was obtained.

Comparative Example C An experiment was conducted on the technique disclosed in U.S. Pat. No. 4,193,252 (corresponding to JP-A-54-40885). First, an experiment was conducted on rayon, which is the only precursor specifically described therein.

(A) Using a single-ended jersey-style circular deflector, knit socks with a diameter of about 2 inches (about 2.5 cm) using 300 denier and 1650 denier rayon continuous tow yarns, and knitting socks with 4 Cut into two pieces,
Put three pieces of 300 denier socks from Yan Toe into the tube furnace, one at a time, closing the furnace in each case 15
Nitrogen was bubbled through for a minute and gradually heated. The first part is heated to 370 ° C in 1 hour 30 minutes, the second part is heated to 550 ° C in 1 hour 45 minutes, and the third part is heated to 1050 ° C in 1 hour 15 minutes. did.

The first part, heated to 370 ° C, is flexible and substantially electrically non-conductive, and this tow can be hand-knitted; it has a sinusoidal shape and is straight with almost no breakage of individual fibers. Stretched. However, when this tow is heated by wiping hot air with a heating gun (hair dryer), the sine waveform disappears, and the "fixed" (sine waveform or coil shape of the tow) is tentative, and the minimum weight reduction as a result of this heat treatment process. It turned out that it was seen (that is, not carbonized).

The second part heated to 550 ° C has a moderately flexible 7 × 1
It has an electrical resistance of ⁹ ohm / cm ² and is substantially electrically conductive. This tow can be carefully disassembled by hand, but is 2.5-5 cm.
Of the tow has a sinusoidal morphology, but it cannot be reversibly expanded without breaking, that is, the constituent fibers of the depolarized tow are stretched as much as possible. It was unavoidable that the tow sine wave morphology would be broken into small pieces no matter how long it was stretched to be linear. However, the fibers were broken by the hot air from the heating gun, and the yarn strands consisting of short fiber bundles were fragile and could not be separated into individual fibers with a length of about 1 cm or more even with the utmost care. It turned out that That is, there was no reversible flexibility.

The third part, heated to 1050 ° C, is much less flexible than the previous one, and this third part is less than 75% of its original dry weight.
%, Resulting in a significantly smaller fiber diameter, the third portion having an electrical resistance of 70 ohm / cm ² and being substantially electrically conductive, careful after heat treatment It was not possible to pull out the tow from the knitted fabric even by hand, the fibers were broken into small pieces each time the tow was tried to be pulled, and 1.25 cm when the unwoven fabric of the third part was tried.
Fiber tows of less than length were obtained, which were found to be non-stretchable because they had a sinusoidal morphology but the individual fibers in the tow were even smaller fractured. That is, there was no reversible flexibility.

(B) Next, 1200 denier spun yarn of oxidatively stabilized acrylic fiber was knitted using a single-ended jersey style circular knitting machine to make a 2 inch sock.

Cut this sock into four parts, one at a time
They were placed in individual tubular furnaces, the furnace was closed in each case and gradually heated for 15 minutes by passing nitrogen through. 50 minutes for the first part over 15 minutes
Heated to 0 ° C, the second part heated to 600 ° C over 15 minutes, and the third part heated to 950 ° C over 15 minutes.

Each part could be disassembled and had a sine wave form. However, each fiber was tested and found to be extremely brittle and its brittleness was due to the tensions that were inevitably applied to the fiber when it was spun yarn and during subsequent heat treatment. There was no reversible deflection.

The logarithmic value of the specific resistance of the fiber from the first part is +5,
The logarithmic resistivity of the fibers from the second part was +2.2 and the logarithmic resistivity of the fibers from the third part was -2.7.

When this fiber was passed through a carding machine, it was extremely fragile and was broken into small pieces to give a dust-like substance. There was no reversible flexibility.

The socks before heat treatment were unknitted and the resulting spun yarns were tested and found to be under tension caused by the twist imparted during the twisting process to hold the fibers together.

When knitting this yarn, it was found that the fibers contained in the spun yarn, not the yarn itself, are under tension and this tension increases due to the mass loss (loss) and shrinkage of the fibers in the carbonization process.

The sublime yarn structure also had some tensile strength, but the individual fibers were brittle and could not be made into wool-like fluff or batteins.

That is, in the conventional method, it is not possible to repeatedly draw (elongate) a non-linear carbonaceous fiber having multiple curves into a linear state without breaking the fiber. In other words, the reversible deflection ratio according to the present invention cannot be measured.

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Claims (5)

[Claims] 1. A non-linear spring-like shape is imparted to a tow comprising substantially continuous filaments of oxidation-stabilized acrylic fiber, and the stabilized acrylic fiber tow having the non-linear shape is stressed. A process for producing a carbonaceous fiber, which comprises heat-treating under a non-oxidizing condition under a non-oxidizing condition to carbonize the fiber to impart substantial permanent heat setting and reversible flexibility to the fiber. 2. The method according to claim 1, wherein the heat treatment temperature is 950 ° C. or lower. 3. The method according to claim 1, wherein the reversible deflection ratio of the carbonaceous fiber is 1.2 times or more. 4. The method according to claim 2, wherein the carbonaceous fiber obtained has a log resistivity of −2.84 or more. 5. The method according to claim 1, wherein the heat treatment temperature is higher than 950 ° C.