JP2008019526A - Method for producing carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing carbon fiber, by which the carbon fiber having good quality can be produced in high productivity while being a thick tow. <P>SOLUTION: The method for producing the carbon fiber has a step for carrying out flame retardant treatment of an acrylonitrile-based precursor fiber of a straight tow having a filament count of ≥49,000 and a crimp number of ≤5/25 mm in oxidative atmosphere at 200-300°C, and a step for carrying out carbonization treatment of the fiber subjected to the flame retardant treatment in an inert atmosphere at ≥1,000°C. The time for the flame retardant treatment is ≤100 min and the width W of the tow of the acrylonitrile-based precursor fiber under the flame retardant treatment is regulated according to the density of the acrylonitrile-based precursor fiber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing carbon fiber.

  In general, a carbon fiber is produced by making an acrylonitrile-based precursor fiber into a flame-resistant fiber by a flame-proofing process in which heat treatment is performed in an oxidizing atmosphere at 200 to 300 ° C. Carbon fibers are produced by a carbonization process in which heat treatment is performed in an active atmosphere. The carbon fiber thus obtained is widely used as a reinforcing fiber material for high-performance composite materials for aerospace use, sports / leisure use, etc. due to its excellent mechanical properties. In recent years, demands for applications in general industrial fields such as automobiles, ships, and building materials are increasing.

  However, the conventional small tow (total fineness less than 21,000 dtex) carbon fiber is excellent in physical properties and quality, but because of its high price, it can be fully used in industrial applications where cost is important. It was not possible. On the other hand, large tow carbon fiber, which is a thick tow, is set at a low price, but its use in the industrial application field is still limited in terms of performance and quality. Accordingly, carbon fibers that achieve both high quality and low price are desired in many markets.

  In order to reduce the cost of carbon fibers, it is necessary to improve the productivity of the flameproofing process having the longest processing time during the manufacturing process. However, in the flameproofing process, there is intense heat generation due to the oxidation reaction of the acrylonitrile precursor fiber, so heat is stored inside the acrylonitrile precursor fiber, and the temperature inside the acrylonitrile precursor fiber is extremely higher than the processing temperature. Get higher. For this reason, problems such as smoke are likely to occur, and production must be carried out at a reduced flameproofing temperature. Therefore, it takes time to obtain flameproofed fibers that have been sufficiently flameproofed.

  As a method for reducing the price of carbon fibers, it is possible to efficiently fire thick-type acrylic fibers. However, thick tow has more heat storage than small tow, so it must be produced at a lower flameproofing temperature than small tow, and in order to obtain sufficient flameproof fiber, it takes longer than 100 minutes. Time processing was needed. Therefore, it has been more difficult to fire thick tow efficiently than small tow.

  In order to solve such problems in the thick tow, Japanese Patent Application Laid-Open No. 10-266024 (Patent Document 1) describes the cross-sectional shape of the acrylonitrile-based precursor fiber at the time of the flameproofing treatment as the yarn width / yarn thickness ratio. Is disclosed, but the tensile strength obtained is low and it is difficult to say high performance.

In addition, in the production of carbon fiber, the equipment of the carbonization furnace that heat-treats at a temperature exceeding 1000 ° C., its maintenance cost, and the power cost are the major factors that increase the production cost, and the downsizing of the carbonization furnace is a cost. The reduction is considered to be very effective.
Japanese Patent Laid-Open No. 10-266024

  An object of this invention is to provide the manufacturing method of the carbon fiber which can obtain a high quality carbon fiber with sufficient productivity, though it is a thick tow.

The present invention includes a step of flameproofing an acrylonitrile-based precursor fiber composed of tow having a number of filaments of 49,000 or more and 5 threads / 25 mm or less in an oxidizing atmosphere at 200 to 300 ° C. A method for producing carbon fiber comprising a step of carbonizing the treated fiber at 1,000 ° C. or higher in an inert atmosphere,
The flameproofing treatment time is 100 minutes or less, and the control of the tow width W of the acrylonitrile precursor fiber during the flameproofing treatment, the density of the acrylonitrile precursor fiber is 1.15 to 1.25 g / cm. during a ³ controls according to the following formula (1), while a 1.25~1.30g / cm ³ controls according to the following formula (2), is 1.30~1.40g / cm ³ In the meantime, a method for producing a carbon fiber controlled according to the following formula (3) is provided.

0.065 × A ^1/2 ≦ W ≦ 0.083 × A ^1/2 Formula (1)
0.053 × A ^1/2 ≦ W ≦ 0.075 × A ^1/2 formula (2)
0.040 × A ^1/2 ≦ W ≦ 0.063 × A ^1/2 formula (3)
(In the formula, A represents the total fineness (dtex) of the acrylonitrile-based precursor fiber.)
The present invention also includes a step of flameproofing an acrylonitrile-based precursor fiber composed of tows having a number of filaments of 49,000 or more and 5 threads / 25 mm or less in an oxidizing atmosphere at 200 to 300 ° C., and flameproofing treatment. A method for producing carbon fiber comprising a step of carbonizing the produced fiber at 1,000 ° C. or higher in an inert atmosphere,
The flameproofing treatment time is 100 minutes or less, and the tow width W of the acrylonitrile precursor fiber during the flameproofing treatment is controlled by adjusting the density (ρ) of the acrylonitrile precursor fiber to 1.15 to 1.5. In the range of 40 g / cm ^3, the present invention provides a carbon fiber production method carried out according to the following formula (4).

(Where d is the single fiber fineness (dtex) of the acrylonitrile-based precursor fiber, A is the tow total fineness (dtex) of the acrylonitrile-based precursor fiber, and ρ is the density (g / cm ³ ) of the flameproofing process yarn. .)
Further, in the flameproofing treatment, the present invention allows a plurality of acrylonitrile-based precursor fibers arranged in parallel to pass through a plurality of flameproofing furnaces,
The ratio (Sw2 / Sw1) of the width Sw1 of the sheet material when initially introduced into the flameproofing furnace and the width Sw2 of the sheet material coming out of the final flameproofing furnace is in the range of the following formula (5). Any one of the manufacturing methods described above is provided.

0.50 ≦ Sw2 / Sw1 ≦ 0.85 Formula (5)
Furthermore, the present invention provides a method for producing any one of the above carbon fibers, wherein the CV value obtained by the following formula showing the uniformity of the tow width W is 10% or less in the flameproofing treatment.

        CV value (%) = (standard deviation / average value) × 100

  ADVANTAGE OF THE INVENTION According to this invention, although it is thick tow | toe (large tow), a high quality carbon fiber can be manufactured and the manufacturing method of carbon fiber with high productivity can be provided.

  In the acrylonitrile-based precursor fiber of the present invention, a polymer containing 90% by mass or more of acrylonitrile is preferably used as the acrylonitrile-based polymer. The acrylonitrile is more preferably 95% by mass or more. A homopolymer or copolymer of acrylonitrile or a mixture of these polymers can be used. The acrylonitrile copolymer is a copolymerized product of a monomer that can be copolymerized with acrylonitrile and acrylonitrile. Monomers that can be copolymerized with acrylonitrile include (meth) acrylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and hexyl (meth) acrylate. , Vinyl halides such as vinyl chloride, vinyl bromide, vinylidene chloride, acids having polymerizable double bonds such as (meth) acrylic acid, itaconic acid, crotonic acid and their salts, maleic acid imide, phenylmaleimide Imide unsaturated monomers such as (meth) acrylamide, styrene monomers such as styrene and α-methylstyrene, vinyl monomers such as vinyl acetate, Styrene sulfonic acid soda, allyl sulfonic acid soda, β-styrene sulfonic acid soda, methallyl sulphone Examples thereof include polymerizable unsaturated monomers containing a sulfone group such as sodium phonate, and polymerizable unsaturated monomers containing a pyridine group such as 2-vinylpyridine and 2-methyl-5-vinylpyridine. It is not limited to.

  Examples of the polymerization method include, but are not limited to, redox polymerization in an aqueous solution, suspension polymerization in a heterogeneous system, and emulsion polymerization using a dispersant.

  The acrylonitrile polymer solution can be produced by utilizing a known acrylonitrile precursor fiber spinning method such as wet spinning or dry wet spinning. For example, in normal wet spinning, after spinning, stretching, washing with water, oil agent treatment, and drying densification, post-stretching such as dry heat stretching and steam stretching is performed as necessary.

  The acrylonitrile-based precursor fiber in the present invention preferably has as few surface defects as possible such as impurities, internal voids, crazes and cracks.

  In addition, the acrylonitrile-based precursor fiber in the present invention uses a tow having a crimp of 5 peaks / 25 mm or less. When the crimp exceeds 5 crests / 25 mm, a buckling deformation called a crimp is imparted, and this buckling deformation essentially gives mechanical damage to the acrylonitrile-based precursor fiber. That is, crimping induces generation of fluff due to single yarn breakage in the carbon fiber production process, leading to troubles such as winding around a roll, and deterioration of the quality and performance of the obtained carbon fiber.

  The single yarn fineness (single fiber fineness) of the acrylonitrile-based precursor fiber in the present invention is preferably 0.5 to 1.3 dtex. If the single yarn fineness is too low, it becomes difficult to stably spin the acrylonitrile-based precursor fiber. On the other hand, if the single yarn fineness is too high, a double cross-sectional structure becomes remarkable and it is difficult to obtain high-performance carbon fibers. The range of a preferable single yarn fineness is 0.6-1.25 dtex, More preferably, it is 0.7-1.20 dtex.

  In the present invention, the number of filaments of the acrylonitrile-based precursor fiber needs to be 49,000 or more, which can improve productivity.

  In general, the speed of the process for producing acrylonitrile-based precursor fibers for producing carbon fibers is significantly different from the speed of the firing process for firing the acrylonitrile-based precursor fibers into carbon fibers. Is supplied to the firing process once wound up on the bobbin or in a state of being folded and stacked in a box (referred to as cans accommodation).

  The acrylonitrile-based precursor fiber in the present invention maintains the form of a single tow when containing cans, and has a splitting ability in the width direction that can be divided into a plurality of small tows when used by being pulled out from a container. Good.

  The acrylonitrile-based precursor fiber thus obtained is supplied to a flameproofing furnace composed of, for example, a hot air circulation type heating furnace in an oxidizing atmosphere and subjected to a flameproofing treatment. Since this flameproofing treatment takes the longest processing time in the production process of carbon fiber, in the present invention, in order to reduce the cost of carbon fiber production, the flameproofing treatment is carried out in a short time and further input into the treatment. The tow width of the precursor fiber was controlled in accordance with the density of the fiber being flame-resistant to improve productivity.

  In the flameproofing treatment, the fiber yarn being flameproofed itself generates heat so that heat is rapidly stored inside the fiber. Therefore, the temperature of the hot air applied to the fiber being flame-resistant must be controlled to be lower than the heat storage cutting temperature of the fiber yarn being flame-resistant so that the fiber being flame-resistant does not cut by this.

  On the other hand, the heat storage cutting temperature becomes higher as the fiber in which the flameproofing reaction has progressed, and the heat storage cutting temperature correlates with the density of the process yarn of the flameproofing treatment, and increases as the density increases. Furthermore, the heat storage cutting temperature of the fiber during flame resistance also depends on the input density (fineness per unit tow width) of the fiber, and the higher the input density, that is, the narrower the tow width, the lower the heat storage cutting temperature.

  As described above, the reaction rate of flame resistance increases as the temperature increases and increases as the input density increases. Therefore, in order to accelerate the flameproofing reaction and shorten the flameproofing time, it is lower than the thermal storage cutting temperature of the fiber being flameproofed, but at a temperature as high as possible, the input density is increased to make the fiber being flameproofed flameproof. It is important to process.

  The shortening of the flameproofing treatment time can be expected to have the effect of reducing the equipment of the flameproofing furnace and reducing the power cost, and is thought to contribute to the reduction of the manufacturing cost. However, it is also important in the performance of the carbon fiber. It is known that when the flameproofing treatment is too long, the strength of the carbon fiber is reduced. Since the thick tow has a large texture of filaments, it is easy to store heat, and as a result, the flameproof treatment time has to be set longer. From the viewpoint of performance development, the flameproofing treatment time is preferably 100 minutes or less, more preferably 95 minutes or less, more preferably 90 minutes or less.

  The present invention increases the density during flameproofing and increases the heat storage cutting temperature of the fiber being flameproofed, and at the same time increases the input density of the fiber being flameproofed, thereby improving productivity. In addition, the present inventors have found that acrylonitrile-based precursor fibers having a shape of thick tow having 49,000 or more filaments can be fired (flame-resistant) within a flame-proofing time in which the performance of carbon fibers is easy to develop.

While the density of the acrylonitrile-based precursor fiber during the flameproofing treatment is 1.15 to 1.25 g / cm ³ , the tow width W is controlled according to the following formula (1), and 1.25 to 1.30 g / while in cm ³ controls the tow width W according to the following equation (2), while a 1.30～1.40G / cm ³ for controlling tow width W according to the following equation (3).

0.065 × A ^1/2 ≦ W ≦ 0.083 × A ^1/2 Formula (1)
0.053 × A ^1/2 ≦ W ≦ 0.075 × A ^1/2 formula (2)
0.040 × A ^1/2 ≦ W ≦ 0.063 × A ^1/2 formula (3)
Here, in the formula, A represents the total fineness (dtex) of the acrylonitrile-based precursor fiber.

A ^1/2 in the formula is an index representing the size of the precursor fiber tow. The shape of the precursor fiber tow is a circle or an ellipse very close to the circle. That is, assuming that the density of the precursor fiber tow is ρ _PC , A / ρ _PC is a tow volume per 10,000 m, and this value is an index representing the cross-sectional area of the tow. Therefore, (A / ρ _PC ) ^1/2 is considered to be an index representing the size of the cross-section of the tow with the length as a dimension. In other words, A ^1/2 in the above expression is the dimension as a length. It can be said that it is an index representing the size of the cross section of the tow. For this reason, when considering an appropriate tow width in the flameproofing process, it makes sense to use A ^1/2 as an index, and as a result, limit the range for controlling the appropriate tow width. It can be a very effective index.

  If the tow width of the acrylonitrile-based precursor fiber in the flame resistance treatment in each density region is less than the left side, runaway reaction due to heat accumulation tends to cause yarn breakage, smoke, and the like. On the other hand, if the tow width exceeds the right side, the number of processing tows with respect to the flameproof furnace width decreases, the equipment productivity decreases, and it becomes impossible to obtain the intended effect of reducing the manufacturing cost.

Further, when the density (ρ) of the acrylonitrile-based precursor fiber during the flameproofing treatment is in the range of 1.15 to 1.40 g / cm ³ , the object can be achieved by controlling the tow width W by the following formula (4). can do.

d: Single fiber (filament) fineness (dtex) of acrylonitrile-based precursor fiber
A: Tow total fineness (dtex) of acrylonitrile-based precursor fiber
ρ: density of the flameproofing process yarn (g / cm ³ ).

  The variable of Formula (4) is demonstrated below.

(1) d ^{−1/2 The} flameproofing reaction proceeds by a cyclization reaction by heating with hot air heat transfer and an oxidation reaction caused by diffusion of oxygen into the filament. Therefore, the surface area per unit weight is very important in considering flame resistance reactivity. A precursor fiber having a smaller single fiber fineness has a larger surface area per unit weight, and as a result, an exothermic reaction tends to occur rapidly. Under such circumstances, it is considered to be very effective to use the ratio of the peripheral length of the filament cross section to the cross sectional area as an index of the heat generation property of the precursor fiber in the flameproofing process. Since the filament has a substantially round cross section, if the radius is r, the ratio of the circumference of the cross section to the cross sectional area can be expressed as 2r ^−1/2 . Here, d ^1/2 is a form factor of a filament having a primary length. Therefore, it is useful to use d ^−1/2 as an index of the exothermic property of the precursor fiber.

(2) About (A / ρ) ^1/2 As mentioned above, (A / ρ) ^1/2 is the size of the cross-section of the tow whose dimension is the length of the process yarn during the flameproofing treatment. It is an indicator to represent.

(3) About exp (-ρ) The thermal storage cutting temperature correlates with the density of the process yarn of the flameproofing treatment, and increases as the density increases. The correlation between flame resistance and density matches relatively well with the Aurenius type. Therefore, exp (−ρ) is used as an index of flame resistance reactivity.

  If the tow width of the acrylonitrile-based precursor fiber in the flame resistance treatment in each density region is less than the left side, runaway reaction due to heat accumulation tends to cause yarn breakage, smoke, and the like. On the other hand, if the tow width exceeds the right side, the number of treated tows with respect to the flameproof furnace width decreases, equipment productivity decreases, and a desired manufacturing cost reduction effect cannot be obtained.

  More preferable tow width W to be controlled is in the range of equation (6).

  A sheet width Sw1 when the sheet-like material in which a large number of acrylonitrile-based precursor fibers are arranged in parallel at a specific interval is first introduced into the flame-proofing furnace, and the width of the sheet-like material arranged in parallel from the final flame-proofing furnace In Sw2, it is preferable in commercial production that the value of Sw2 / Sw1 is in the range of the following formula (5). Here, the commercial production means that the capital investment is small, the running cost is small, and furthermore, high-quality carbon fibers can be produced with high production.

      0.50 ≦ Sw2 / Sw1 ≦ 0.85 Formula (5).

  The sheet in which the fibers exiting the flameproofing furnace are juxtaposed is subsequently processed in the carbonization furnace. In the production of carbon fiber, the equipment of the carbonization furnace that heat-treats at a temperature exceeding 1000 ° C., its maintenance cost, and the power cost are one of the major factors that increase the production cost. Very effective in reducing costs. Therefore, by reducing the width of the sheet material, it is possible to design the apparatus width of the carbonization furnace to be small. As a result, equipment costs and operating costs can be reduced, and the production cost of carbon fibers can be reduced. By making Sw2 / Sw1 0.85 or less, the cost reduction effect becomes remarkable. On the other hand, if Sw2 / Sw1 is too small, the entanglement between adjacent tows becomes large, the linearity of the yarn path on which the tows run cannot be maintained, and problems such as the inevitable mixing of twists and the like arise.

  More preferably, it is the range of 0.50 ≦ Sw2 / Sw1 ≦ 0.80. More preferably, it is 0.50 <= Sw2 / Sw1 <= 0.75.

  Sw2 / Sw1 control methods include, but are not limited to, a method of controlling the deflection of the roll by the tension of the fiber by a known technique, a method of controlling the acrylonitrile-based precursor fiber by entanglement treatment, and the like. It is not a thing. In the case where the entanglement process is performed and controlled, the entanglement condition is appropriately determined depending on the total fineness of the acrylonitrile-based precursor fiber.

In the flameproofing treatment, the fiber is subjected to 16 × 10 ⁻³ cN / dTex to 327 × 10 ⁻³ cN / dTex, preferably 32 × 10 ⁻³ cN / dTex to 261 × 10 ⁻³ cN / dTex, more preferably 65. It is desirable to apply a tension of × 10 ⁻³ cN / dTex to 229 × 10 ⁻³ cN / dTex. If the tension is too small, the fibers will loosen and the single yarn fluff will be easily taken up by the roll. If the tension is too high, some of the fibers that are flame resistant will start to cut, and the fluff and yarn breakage will easily occur .

  As a method for controlling the density of the fibers fed into the flameproofing furnace, there are a method of installing a grooved roll outside the flameproofing furnace and a method of installing a comb and a flat roll, both of which can be used.

  The grooved roll rarely generates so-called combined yarn due to fluff of fibers being flame-resistant, or interference between adjacent fibers, and so-called combined yarn is generated due to two spindles entering one groove. Since not only the charging density is increased but also twisting occurs, it is easy to cause yarn breakage, smoke, etc. due to heat removal failure.

  On the other hand, the use of a flat roll is preferable in terms of process stability because there is no occurrence of twisting and twisting due to groove jumping. In the case of a flat roll, it is preferable to control the acrylonitrile-based precursor fiber by subjecting it to entanglement by a known technique. The entanglement treatment condition is appropriately determined depending on the total fineness of the acrylonitrile-based precursor fiber. Flat rolls can be installed and used on both sides of the flameproofing furnace.

  Furthermore, it is desired to control the temperature as high as possible, although it is lower than that while controlling the tow width, and the heat storage cutting temperature of the fiber being flame-resistant increases. The flameproofing treatment is usually performed within a temperature range of 200 to 300 ° C, preferably 220 to 280 ° C. Such temperature control can be performed using a conventional flameproofing furnace divided into zones whose temperature can be individually adjusted.

  As the number of temperature controllable zones increases, the flameproofing time can be shortened, and when the number of zones is large, there is an allowance for the heat storage cutting temperature of the fiber being flameproofed compared to when the number of zones is small. Flame resistance can be achieved at a sufficiently high temperature, and operation with less trouble is possible with the same flame resistance time.

  However, as the number of zones increases, the price of the flameproofing furnace increases accordingly, and the effect of improving productivity decreases. From the viewpoint of enabling fine temperature control without impairing the effect of improving productivity, the number of zones is preferably 3 to 8, and more preferably 3 to 5.

  The passage path of the acrylonitrile-based precursor fiber in the flameproofing furnace is preferably provided in a plurality of stages in one flameproofing furnace, preferably 5 to 15 passes, and 7 to 11 passes. Further preferred. When there are few passage paths, a sufficient and reliable flameproofing reaction will proceed, but the number of flameproofing furnaces will increase the capital investment, or it will have a long-time flameproofing treatment, so high-performance carbon Fiber is difficult to obtain. When there are too many passage paths, the flameproofing furnace becomes large, so that not only the capital investment increases, but also the wind speed and temperature spots in the flameproofing furnace become large and yarn breakage, smoke, etc. are likely to occur.

  The length of one pass is preferably 5 to 30 m, and more preferably 10 to 25 m. If the length of one pass is too short, the number of passes or the number of flameproofing furnaces increases, so that the capital investment increases. If the length of one pass is too long, the wind speed and temperature spots in the flameproofing furnace increase, so that not only yarn breakage and smoke are likely to occur, but also high-performance carbon fibers are difficult to obtain.

  The direction of the wind in the flameproofing furnace is parallel to the plane formed by the multi-pyramidal fibers being flameproofed, and is parallel to the fibers being flameproofed, parallel flow perpendicular to the vertical, Examples thereof include, but are not limited to, a vertical flow that is perpendicular to the surface formed by the flame-resistant fiber and perpendicular to the flame-resistant fiber. The wind speed is preferably 0.3 to 5 m / sec. When the wind speed is too low, it becomes difficult to obtain a heat removal action by the wind in the flameproofing furnace, and smoke due to poor heat removal tends to occur. When the wind speed is too high, fluttering of the fibers being flame-resistant by the wind in the flame-proofing furnace becomes large, and single yarn breakage is likely to occur due to contact of the fibers being flame-resistant.

Density of oxidized fiber yarn after oxidization process is completed is preferably 1.33~1.40g / cm ^3, more preferably 1.34~1.37g / cm ^3. If this density is too low, the flame-resistant yarns are fused in the subsequent carbonization step and fluffing occurs, making it difficult to obtain high-performance and high-quality carbon fibers. If this density is too high, the strength tends to decrease due to excessive introduction of oxygen into the flame-resistant fiber yarn.

  In the flameproofing treatment, it is preferable that the CV value obtained by the following formula showing the uniformity of the tow width of the acrylonitrile-based precursor fiber is 10% or less.

CV value (%) = (standard deviation / average value) × 100
If this CV value is too large, the adjacent acrylonitrile-based precursor fibers being flame-resistant are merged, and not only fuzzing is likely to occur, but also yarn breakage, smoke, etc. are likely to occur. The CV value is more preferably 5% or less, still more preferably 3% or less.

  The flame resistant fiber yarn obtained by the above method is preferably carbonized in an inert atmosphere at 1,000 ° C. or higher. When the temperature is lower than 1,000 ° C., it is difficult to obtain high-performance carbon fibers.

  The flame-resistant fiber yarn obtained by the above method is preferably heat-treated in an inert atmosphere of 300 ° C. to 1,000 ° C. between the flame resistance treatment and the carbonization treatment, and is performed for 0.5 minutes or longer. It is preferable. This heat treatment can be carried out for the purpose of obtaining carbon fibers having high product quality and high performance by preventing fuzz and yarn breakage of the flame resistant fiber yarn.

  The carbon fiber thus obtained can be further subjected to surface treatment, sizing application, and the like by a conventionally known technique as necessary.

  Hereinafter, the manufacturing method of the carbon fiber of this invention is demonstrated concretely based on an Example.

  In addition, the tow | toe width | variety measured the acrylonitrile type | system | group precursor fiber on the roll in a flameproofing process 10 times in total for every 30 minutes with a ruler.

(Example 1)
By wet spinning, an acrylonitrile-based precursor fiber having a crimped crest / 25 mm, a single fiber fineness of 1.0 dtex, and a filament number of 60,000 was obtained.

This acrylonitrile-based precursor fiber was subjected to a flameproofing treatment continuously at a flameproofing treatment temperature of 220 ° C to 260 ° C. Density acrylonitrile based precursor fibers in oxidation step is 1.15~1.25g / cm ³ between the 17mm tow width, while a 1.25~1.30g / cm ³ 14mm tow width The density of 1.36 g / cm ³ while controlling the tow width at 11 mm while limiting the shrinkage to a process tension of 136 × 10 ⁻³ cN / dTex while 1.30 to 1.36 g / cm ^3. A cm ³ flame-resistant fiber yarn was obtained. The flameproofing treatment time is 90 minutes, Sw2 / Sw1 is 0.65, and the CV values of the tow width of the acrylic precursor fiber during the flameproofing process are 1.2%, 1.3% and 1.3%, respectively. there were. The rolls installed on both sides of the flameproofing furnace were flat rolls.

  The flame-resistant fiber yarn is passed through a pre-carbonization furnace comprising a nitrogen atmosphere having a temperature distribution of 300 to 700 ° C., and subsequently a carbonization furnace comprising a nitrogen atmosphere having a temperature distribution of 1,000 to 1,300 ° C. The carbon fiber was manufactured.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The carbon fiber had a strand strength of 4.8 GPa and an elastic modulus of 255 GPa.

(Example 2)
A carbon fiber was obtained in the same manner as in Example 1 except for the following items.

Acrylonitrile between the density of the precursor fiber is 1.15~1.25g / cm ³ is the toe width 19mm in oxidation step, while a 1.25~1.30g / cm ³ 17mm tow width The tow width was controlled at 14 mm while 1.30 to 1.36 g / cm ³ . The flameproofing treatment time was 80 minutes, Sw2 / Sw1 was 0.74, and the CV of the tow width of the acrylic precursor fiber during the flameproofing process was 1.2%, 1.3%, and 1.4%, respectively. It was.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The strand strength of this carbon fiber was 4.9 GPa and the elastic modulus was 260 GPa.

(Example 3)
By wet spinning, an acrylonitrile-based precursor fiber having a crimped crest / 25 mm, a single fiber fineness of 1.2 dtex, and a filament number of 50,000 was obtained.

  A carbon fiber was produced in the same manner as in Example 1 except that this acrylonitrile-based precursor fiber was used. Sw2 / Sw1 was 0.65, and the CV values of the tow width of the acrylic precursor fiber during the flameproofing process were 1.3%, 1.3%, and 1.3%, respectively.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The carbon fiber had a strand strength of 4.7 GPa and an elastic modulus of 235 GPa.

Example 4
A carbon fiber was obtained in the same manner as in Example 3 except for the following items.

Acrylonitrile between the density of the precursor fiber is 1.15~1.25g / cm ³ is the toe width 19mm in oxidation step, while a 1.25~1.30g / cm ³ 17mm tow width The tow width was controlled at 14 mm while 1.30 to 1.36 g / cm ³ . The flameproofing treatment time is 70 minutes, Sw2 / Sw1 is 0.74, and the CV values of the tow width of the acrylic precursor fiber during the flameproofing process are 1.2%, 1.3%, and 1.4%, respectively. there were.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The strand strength of this carbon fiber was 4.8 GPa and the elastic modulus was 240 GPa.

(Example 5)
Acrylonitrile-based precursor fibers having a crimped crest / 25 mm, a single fiber fineness of 1.0 dtex, and a filament number of 80,000 were obtained by a wet spinning method.

This acrylonitrile-based precursor fiber was subjected to a flameproofing treatment continuously at a flameproofing treatment temperature of 220 ° C to 260 ° C. Density acrylonitrile based precursor fibers in oxidation step is 1.15~1.25g / cm ³ between the 23mm tow width, while a 1.25~1.30g / cm ³ 20mm tow width While controlling the tow width at 16 mm while 1.30 to 1.36 g / cm ³ , and limiting the shrinkage by setting the process tension to 136 × 10 ⁻³ cN / dTex, the density is 1.36 g / A cm ³ flame-resistant fiber yarn was obtained. The flameproofing treatment time is 85 minutes, Sw2 / Sw1 is 0.70, and the CV value of the tow width of the acrylic precursor fiber during the flameproofing process is 1.5%, 1.6%, and 1.5%, respectively. there were. The rolls installed on both sides of the flameproofing furnace were flat rolls.

  The flame-resistant fiber yarn is passed through a pre-carbonization furnace comprising a nitrogen atmosphere having a temperature distribution of 300 to 700 ° C., and subsequently a carbonization furnace comprising a nitrogen atmosphere having a temperature distribution of 1,000 to 1,300 ° C. The carbon fiber was manufactured.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The strand strength of this carbon fiber was 4.9 GPa and the elastic modulus was 255 GPa.

(Example 6)
Acrylonitrile-based precursor fibers having a crimped crest / 25 mm, a single fiber fineness of 0.8 dtex, and a filament number of 50,000 were obtained by a wet spinning method.

This acrylonitrile-based precursor fiber was subjected to a flameproofing treatment continuously at a flameproofing treatment temperature of 220 ° C to 260 ° C. Density acrylonitrile based precursor fibers in oxidation step is 1.15~1.25g / cm ³ between the 14mm tow width, while a 1.25~1.30g / cm ³ 12mm tow width While controlling the tow width at 9 mm while 1.30 to 1.36 g / cm ³ , and limiting the shrinkage by setting the process tension to 136 × 10 ⁻³ cN / dTex, the density is 1.36 g / A cm ³ flame-resistant fiber yarn was obtained. The flameproofing treatment time is 70 minutes, Sw2 / Sw1 is 0.64, and the CV values of the tow width of the acrylic precursor fiber during the flameproofing process are 1.4%, 1.6% and 1.5%, respectively. there were. The rolls installed on both sides of the flameproofing furnace were flat rolls.

  The flame-resistant fiber yarn is passed through a pre-carbonization furnace comprising a nitrogen atmosphere having a temperature distribution of 300 to 700 ° C., and subsequently a carbonization furnace comprising a nitrogen atmosphere having a temperature distribution of 1,000 to 1,300 ° C. The carbon fiber was manufactured.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The strand strength of this carbon fiber was 5.1 GPa, and the elastic modulus was 255 GPa.

(Example 7)
A carbon fiber was obtained in the same manner as in Example 6 except for the following items.

Acrylonitrile between the density of the precursor fiber is 1.15~1.25g / cm ³ is the toe width 19mm in oxidation step, while a 1.25~1.30g / cm ³ 17mm tow width While being 1.30 to 1.36 g / cm ³ , flame resistant fiber yarns were obtained while controlling the tow width at 14 mm. The flameproofing treatment time was 60 minutes, Sw2 / Sw1 was 0.74, and the CV of the tow width of the acrylic precursor fiber during the flameproofing process was 1.2%, 1.3%, and 1.4%, respectively. It was.

  The flameproofing process passability was very good, and the fiber opening and quality were very good even in higher processing. The strand strength of this carbon fiber was 5.2 GPa and the elastic modulus was 260 GPa.

(Comparative Example 1)
Carbon fibers were produced in the same manner as in Example 1 by acrylonitrile-based precursor fibers having a crimped crest of 10/25 mm, a single fiber fineness of 1.0 dtex, and a filament number of 60,000 by the wet spinning method.

  Although the flame resistance process passability was good, the strand strength of this carbon fiber was 3.9 GPa and the elastic modulus was 250 GPa.

(Comparative Example 2)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 12mm tow width, while a 1.25~1.30g / cm ³ 10mm tow width, When carbon fiber was produced in the same manner as in Example 1 except that the tow width was controlled at 8 mm while being 1.30 to 1.36 g / cm ³ , yarn breakage occurred in the flameproofing treatment, and carbon was produced. The fiber could not be manufactured.

(Comparative Example 3)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 12mm tow width, while a 1.25~1.30g / cm ³ 10mm tow width, While being 1.30 to 1.36 g / cm ³ , the tow width was controlled at 8 mm, the flameproofing treatment temperature was 220 ° C. to 250 ° C., and the flameproofing treatment time was 110 minutes, as in Example 1. Carbon fiber was produced.

  Although the flame resistance process passability was favorable, the strand strength of this carbon fiber was 4.5 GPa and the elastic modulus was 245 GPa.

(Comparative Example 4)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 14mm tow width, while a 1.25~1.30g / cm ³ 12mm tow width, When carbon fiber was to be produced in the same manner as in Example 1 except that the tow width was controlled at 9 mm while it was 1.30 to 1.36 g / cm ³ , fluff was produced in the flameproofing treatment.

(Comparative Example 5)
During density acrylonitrile based precursor fiber in oxidation step is 1.15~1.25g / cm ³ 33mm tow width, while a 1.25~1.30g / cm ³ 23mm tow width, When carbon fiber was to be produced in the same manner as in Example 1 except that the tow width was controlled at 15 mm while it was 1.30 to 1.36 g / cm ³ , fluff was produced in the flameproofing treatment.

(Comparative Example 6)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 20mm tow width, while a 1.25~1.30g / cm ³ 17mm tow width, While trying to produce carbon fiber in the same manner as in Example 1 except that the tow width was controlled at 9 mm while being 1.30 to 1.36 g / cm ³ , yarn breakage occurred in the flameproofing treatment, Carbon fiber could not be manufactured.

(Comparative Example 7)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 25mm tow width, while a 1.25~1.30g / cm ³ 12mm tow width, Carbon fibers were produced under the same conditions as in Example 1 except that the tow width was controlled at 15 mm while it was 1.30 to 1.36 g / cm ³ .

  The CV values of the tow width of the acrylic precursor fiber during the flameproofing process were 10.2%, 111.5%, and 11.3%, respectively. In the flameproofing process, twisting was clearly observed, the passage was unstable, and the fiber opening was unstable even in higher processing.

(Comparative Example 8)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 14mm tow width, while a 1.25~1.30g / cm ³ 12mm tow width, While trying to produce carbon fibers in the same manner as in Example 5 except that the tow width was controlled at 10 mm while being 1.30 to 1.36 g / cm ³ , yarn breakage occurred in the flameproofing treatment, Carbon fiber could not be manufactured.

(Comparative Example 9)
In oxidation step density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ between the tow width 16 mm, while a 1.25~1.30g / cm ³ 14mm tow width, When carbon fiber was to be produced in the same manner as in Example 5 except that the tow width was controlled at 11 mm while it was 1.30 to 1.36 g / cm ³ , fluff was produced in the flameproofing treatment.

(Comparative Example 10)
During density acrylonitrile based precursor fiber is 1.15~1.25g / cm ³ in the oxidation step 11mm tow width, while a 1.25~1.30g / cm ³ 9mm tow width, While carbon fiber was to be produced in the same manner as in Example 6 except that the tow width was controlled at 7 mm while it was 1.30 to 1.36 g / cm ³ , fluff was produced in the flameproofing treatment.

Claims (4)

A step of flameproofing an acrylonitrile-based precursor fiber composed of tows having a number of filaments of 49,000 or more and 5 threads / 25 mm or less in an oxidizing atmosphere at 200 to 300 ° C. A carbon fiber manufacturing method comprising a step of carbonizing at 1,000 ° C. or higher in an active atmosphere,
The flameproofing treatment time is 100 minutes or less, and the control of the tow width W of the acrylonitrile precursor fiber during the flameproofing treatment, the density of the acrylonitrile precursor fiber is 1.15 to 1.25 g / cm. ^{While being 3} , the tow width W is controlled according to the following formula (1), and while being 1.25 to 1.30 g / cm ³ , the tow width W is controlled according to the following formula (2), and 1.30 A carbon fiber manufacturing method in which the tow width W is controlled in accordance with the following formula (3) while it is 1.40 g / cm ³ .
0.065 × A ^1/2 ≦ W ≦ 0.083 × A ^1/2 Formula (1)
0.053 × A ^1/2 ≦ W ≦ 0.075 × A ^1/2 formula (2)
0.040 × A ^1/2 ≦ W ≦ 0.063 × A ^1/2 formula (3)
(In the formula, A represents the total fineness (dtex) of the acrylonitrile-based precursor fiber.) A step of flameproofing an acrylonitrile-based precursor fiber composed of tows having a number of filaments of 49,000 or more and 5 threads / 25 mm or less in an oxidizing atmosphere at 200 to 300 ° C. A carbon fiber manufacturing method comprising a step of carbonizing at 1,000 ° C. or higher in an active atmosphere,
The flameproofing treatment time is 100 minutes or less, and the tow width W of the acrylonitrile precursor fiber during the flameproofing treatment is controlled by adjusting the density (ρ) of the acrylonitrile precursor fiber to 1.15 to 1.5. The manufacturing method of the carbon fiber performed according to following formula (4) in the range of 40 g / cm < ³ >.

(Where d is the single fiber fineness (dtex) of the acrylonitrile-based precursor fiber, A is the tow total fineness (dtex) of the acrylonitrile-based precursor fiber, and ρ is the density (g / cm ³ ) of the flameproofing process yarn. .) In the flameproofing treatment, a plurality of sheets of acrylonitrile-based precursor fibers arranged in parallel are passed through a plurality of flameproofing furnaces,
The ratio (Sw2 / Sw1) of the width Sw1 of the sheet-like material when initially introduced into the flame-proofing furnace and the width Sw2 of the sheet-like material exiting from the final flame-proofing furnace is in the range of the following formula (5). A method for producing a carbon fiber according to claim 1 or 2.
0.50 ≦ Sw2 / Sw1 ≦ 0.85 Formula (5) The method for producing carbon fiber according to any one of claims 1 to 4, wherein, in the flameproofing treatment, a CV value obtained by the following formula showing uniformity of tow width W is 10% or less.
CV value (%) = (standard deviation / average value) × 100