JPWO2020066653A1 - Method for manufacturing flame-resistant fiber bundle and method for manufacturing carbon fiber bundle - Google Patents

Abstract

Acrylic fiber bundles 2 in which a plurality of bundles are arranged adjacent to each other are conveyed by guide rollers 4 installed on both sides outside the flameproofing furnace 1 and run in a hot air heating type flameproofing furnace 1 for oxidation. A method for producing a flame-resistant fiber bundle that is heat-treated in a sexual atmosphere, in which the direction of hot air in the flame-resistant furnace 1 is parallel to the traveling direction of the fiber bundle and is adjacent as defined by the following equation (1). A method for producing a flame-resistant fiber bundle in which the contact ratio P between the fiber bundles is 2 to 18%.
P = [1-p (x) {-t <x <t}] x 100 (1)
Here, P is the contact rate (%) between adjacent fiber bundles, t is the gap (mm) between adjacent fiber bundles, p (x) is ^{the probability density function of the normal distribution N (0, σ 2} ), and σ is The standard deviation of the amplitude, x represents a random variable with the center of the amplitude as zero.
High-quality flame-resistant fiber bundles and carbon fiber bundles can be produced efficiently without operational troubles.

Description

The present invention relates to a method for producing a carbon fiber bundle. More specifically, the present invention relates to a method for producing a flame-resistant fiber bundle capable of efficiently producing a high-quality flame-resistant fiber bundle without operational trouble.

Since carbon fiber has excellent specific strength, specific elastic modulus, heat resistance, and chemical resistance, it is useful as a reinforcing material for various materials, and is used in a wide range of fields such as aerospace applications, leisure applications, and general industrial applications. Has been done.

Generally, as a method for producing a carbon fiber bundle from an acrylic fiber bundle, a fiber bundle in which thousands to tens of thousands of single fibers of an acrylic polymer are bundled is sent into a flameproof furnace and heated to 200 to 300 ° C. After heat treatment (flame resistance treatment) by exposing to hot air in an oxidizing atmosphere such as air, the obtained flame resistant fiber bundles are sent into a carbonization furnace in an inert gas atmosphere at 300 to 1000 ° C. There is known a method of heat-treating (pre-carbonizing) in the above, and then heat-treating (carbonizing) in a carbonization furnace filled with an inert gas atmosphere of 1000 ° C. or higher. Further, the flame-resistant fiber bundle, which is an intermediate material, is widely used as a material for flame-retardant woven fabrics by taking advantage of its non-flammable performance.

The flameproofing process has the longest processing time and the largest amount of energy consumed in the carbon fiber bundle manufacturing process. Therefore, improving productivity in the flame resistance process is of utmost importance in the production of carbon fiber bundles.

In order to enable long-term heat treatment in the flame-resistant process, the device for flame-resistant (hereinafter referred to as the flame-resistant furnace) uses a folding roller arranged outside the flame-resistant furnace to spread the acrylic fibers in the horizontal direction. It is common to reciprocate the fiber many times to make it flame resistant. In order to improve the productivity in the flameproofing process, it is effective to increase the density of the fiber bundles in the flameproofing furnace by transporting a large number of fiber bundles at the same time and to increase the traveling speed of the fiber bundles.

However, when the density of the fiber bundles in the furnace is increased, the frequency of contact between adjacent fiber bundles due to the vibration of the fiber bundles increases. Therefore, the quality of the flame-resistant fiber is deteriorated due to the frequent occurrence of mixed fibers of fiber bundles and breakage of single fibers.

Further, when increasing the traveling speed of the fiber bundle, it is necessary to increase the size of the flameproofing furnace in order to obtain the same amount of heat treatment. In particular, increasing the size in the height direction leads to an increase in equipment costs because it is necessary to divide the building floor into multiple parts and increase the load resistance per unit area of the floor surface. Therefore, in order to suppress the increase in equipment cost and increase the size of the flameproof furnace, it is effective to reduce the size in the height direction by increasing the distance per horizontal path (hereinafter referred to as the flameproof furnace length). Is. However, by increasing the flame-resistant furnace length, the amount of suspension of the traveling fiber bundles increases, and as in the case of increasing the density of the fiber bundles, contact between adjacent fiber bundles due to vibration and mixing of the fiber bundles Frequent breakage of fibers and single fibers causes deterioration of the quality of flame-resistant fibers.

In order to solve the above problems, Patent Document 1 defines the surface occupancy of the fiber bundle sheet-like material in the flameproofing process, and further optimizes the wind speed in the flameproofing furnace and the process tension in the flameproofing process. It is explained that the plan is to be taken.

Further, in Patent Document 2, the surface occupancy of the fiber bundle sheet-like material in the flame resistance step, the wind speed in the flame resistance furnace, the density of the fiber bundle in the flame resistance furnace, specifically, per 1 mm of the width of the traveling fiber bundle. It is explained that it defines the fineness.

Further, Patent Document 3 describes that the line speed of the flameproofing process and the maximum suspension amount of the fiber bundle are optimized when the flameproofing furnace length is lengthened.
Japanese Unexamined Patent Publication No. 2000-160435 Japanese Unexamined Patent Publication No. 2011-127264 Japanese Unexamined Patent Publication No. 11-61574

However, in Patent Document 1 and Patent Document 2, when the flame-resistant furnace length is also increased in order to improve productivity, it is not possible to avoid contact between adjacent fiber bundles with the specified surface occupancy parameter. Therefore, there is a concern that high-quality flame-resistant fibers cannot be produced. Further, in Patent Document 3, the maximum suspension amount of fiber bundles is specified to suppress contact between adjacent fiber bundles when the flame-resistant furnace length is large. However, regarding the density of fiber bundles in the flame-resistant furnace, Not mentioned and cannot improve productivity.

Therefore, the problem to be solved by the present invention is to produce high-quality flame-resistant fiber bundles and carbon fiber bundles with high production efficiency without operational troubles.

In order to solve the above problems, the method for producing a flame-resistant fiber bundle of the present invention has the following constitution. That is,
Acrylic fiber bundles in which a plurality of bundles are arranged adjacent to each other are conveyed by guide rollers installed on both sides outside the flame-resistant furnace, and the fibers are run in a hot-air heating type flame-resistant furnace to be heat-treated in an oxidizing atmosphere. This is a method for manufacturing a flame-resistant fiber bundle, in which the direction of hot air in the flame-resistant furnace is parallel to the traveling direction of the fiber bundle, and the contact rate between adjacent fiber bundles defined by the following equation (1). This is a method for producing a flame-resistant fiber bundle having P of 2 to 18%.

P = [1-p (x) {-t <x <t}] x 100 (1)
Here, P is the contact rate (%) between adjacent fiber bundles, t is the gap (mm) between adjacent fiber bundles, p (x) is ^{the probability density function of the normal distribution N (0, σ 2} ), and σ is The standard deviation of the amplitude, x represents a random variable with the center of the amplitude as zero.

The "contact rate P between adjacent fiber bundles" in the present invention means that when a plurality of fiber bundles are run in parallel so as to be adjacent to each other, the adjacent fiber bundles are caused by vibration (thread sway) in the width direction of the fiber bundles. Refers to the probability that the gap between the two will be zero. The amplitude of vibration in the width direction of the fiber bundle is assumed to follow a normal distribution N when the average amplitude of the fiber bundle is 0 and the standard deviation of the amplitude is σ. It can be obtained in 1).

Further, the method for producing a carbon fiber bundle of the present invention has the following constitution. That is,
The flame-resistant fiber bundle produced by the above method for producing a flame-resistant fiber bundle is precarbonized at a maximum temperature of 300 to 1,000 ° C. in an inert atmosphere to produce a precarbonized fiber bundle, and the precarbonized fiber bundle is produced. This is a method for producing a carbon fiber bundle, in which the chemical fiber bundle is carbonized at a maximum temperature of 1,000 to 2,000 ° C. in an inert atmosphere.

According to the method for producing flame-resistant fibers of the present invention, high-quality flame-resistant fibers can be produced efficiently without operational troubles.

It is a schematic side view which shows the flame-resistant furnace. FIG. 5 is a cross-sectional view taken along the line XY of the flameproofing furnace of FIG. It is an image figure for demonstrating the contact rate P between adjacent fiber bundles.

The acrylic fiber bundle used as the fiber bundle to be heat-treated in the method for producing a flame-resistant fiber bundle of the present invention is preferably composed of acrylic fiber containing 100% acrylonitrile or acrylic copolymer fiber containing 90 mol% or more of acrylonitrile. be. As the copolymerization component in the acrylic copolymer fiber, acrylic acid, methacrylic acid, itaconic acid, and alkali metal salts, ammonium metal salts, acrylamide, methyl acrylate and the like are preferable, but the chemical properties of the acrylic fiber bundle, The physical properties, dimensions, etc. are not particularly limited.

The present invention is a method for making the acrylic fiber bundle flame-resistant in an oxidizing atmosphere, and is carried out in a flame-resistant furnace in which an oxidizing gas flows inside. As shown in FIG. 1, the flame-resistant furnace 1 has a heat treatment chamber 3 for performing a flame-resistant treatment by blowing hot air on an acrylic fiber bundle 2 traveling while folding back a multi-stage traveling area. The acrylic fiber bundle 2 is fed into the heat treatment chamber 3 through an opening (not shown) provided on the side wall of the heat treatment chamber 3 of the flame resistant furnace 1, travels linearly in the heat treatment chamber 3, and then faces each other. It is once sent out of the heat treatment chamber 3 from the opening of the side wall. After that, it is folded back by the guide roller 4 provided on the side wall outside the heat treatment chamber 3 and is fed into the heat treatment chamber 3 again. In this way, the acrylic fiber bundle 2 is repeatedly sent in and out of the heat treatment chamber 3 a plurality of times by repeating the traveling direction a plurality of times by the plurality of guide rollers 4, and the heat treatment chamber 3 is divided into multiple stages as a whole. It moves from the top to the bottom of FIG. The moving direction may be from bottom to top, and the number of times the acrylic fiber bundle 2 is folded back in the heat treatment chamber 3 is not particularly limited, and is appropriately designed depending on the scale of the flameproofing furnace 1 and the like. The guide roller 4 may be provided inside the heat treatment chamber 3.

The acrylic fiber bundle 2 is subjected to flameproof treatment by hot air flowing from the hot air outlet 5 toward the hot air outlet 5 while traveling in the heat treatment chamber 3 while being folded back to become a flameproof fiber bundle. As shown in FIG. 2, the acrylic fiber bundle 2 has a wide sheet-like shape in which a plurality of acrylic fiber bundles 2 are aligned in parallel in a direction perpendicular to the paper surface.

It is preferable that the hot air outlet 5 is provided with a resistor such as a perforated plate and a rectifying member such as a honeycomb (both not shown) on the outlet surface to provide a pressure loss. The rectifying member can rectify the hot air blown into the heat treatment chamber 3 and blow hot air at a uniform wind speed into the heat treatment chamber 3.

Similar to the hot air outlet 5, a resistor such as a perforated plate may be arranged on the suction surface of the hot air outlet 6 to provide a pressure loss, which is appropriately determined as necessary.

The oxidizing gas flowing in the heat treatment chamber 3 may be air or the like, and is heated to a desired temperature by the heater 7 before entering the heat treatment chamber 3, the wind speed is controlled by the blower 8, and then from the hot air outlet 5. It is blown into the heat treatment chamber 3. The oxidizing gas discharged from the hot air outlet 6 to the outside of the heat treatment chamber 3 is released into the atmosphere after being treated with a toxic substance in an exhaust gas treatment furnace (not shown), but is released again through a circulation path (not shown). It may be blown into the heat treatment chamber 3 from the hot air outlet 5.

The heater 7 used in the flame-resistant furnace 1 is not particularly limited as long as it has a desired function, and for example, a known heater such as an electric heater may be used. The blower 8 is not particularly limited as long as it has a desired function, and a known blower such as an axial fan may be used.

Further, by changing the rotation speed of each of the guide rollers 4, the traveling speed and tension of the acrylic fiber bundle 2 can be controlled, which is required for the physical properties of the flame-resistant fiber bundle and the treatment per unit time. It is fixed according to the amount.

Further, by engraving a predetermined interval and a number of grooves on the surface layer of the guide roller 4, or by arranging a predetermined interval and a number of comb guides (not shown) in the immediate vicinity of the guide roller 4, a plurality of comb guides can be traveled in parallel. It is possible to control the interval and the number of bundles of the acrylic fiber bundles 3 to be formed.

In order to increase the production amount, the number of fiber bundles per unit distance in the width direction of the flameproof furnace 1, that is, the thread density may be increased, or the traveling speed of the acrylic fiber bundle 2 may be increased.

However, increasing the thread density means reducing the distance between adjacent fiber bundles, and as described above, quality deterioration due to mixing of fiber bundles due to vibration is likely to occur.

Further, when the traveling speed of the acrylic fiber bundle 2 is increased, the residence time in the flame-resistant heat treatment chamber is reduced and the amount of heat treatment is insufficient, so that the total heat treatment length needs to be increased. For that purpose, the height of the flame-resistant furnace 1 may be increased to increase the number of times the acrylic fiber bundle is folded back, or the distance L per pass of the flame-resistant furnace (hereinafter referred to as the flame-resistant furnace length) L may be increased. However, in order to reduce the equipment cost, it is preferable to increase the flameproof furnace length L. However, as a result, the horizontal distance L'between the guide rollers 4 becomes long, and the fiber bundles are likely to be suspended, so that contact between the fiber bundles due to vibration and deterioration of quality due to the mixing of the fiber bundles are likely to occur.

Further, the amplitude of the vibration of the fiber bundle that causes the contact between the fiber bundles is not only the above-mentioned thread density and the horizontal distance L'between the guide rollers 4, but also the wind speed of the oxidizing gas flowing through the heat treatment chamber and the traveling acrylic fiber. Affected by bundle tension. Further, even if the amplitude is the same, the frequency and degree of mixing are affected by the physical properties of the acrylic fiber bundle, that is, the chemical properties, physical properties, dimensions, and the like.

The method for producing a flame-resistant fiber bundle of the present invention efficiently produces high-quality flame-resistant fiber without operational trouble regardless of the equipment specifications, operating conditions, and physical characteristics of the acrylic fiber bundle. ..

Specifically, in the continuous heat treatment method of making a flame-resistant fiber bundle by heat-treating an acrylic fiber bundle 2 in which a plurality of bundles are arranged adjacent to each other while running in a hot-air heating type flame-resistant furnace 1. The acrylic fiber bundle 2 is conveyed by guide rollers 4 installed on both sides of the heat treatment chamber 3, the direction of hot air in the flameproof furnace 1 is parallel to the thread, and the contact ratio P between adjacent fiber bundles is 2 to 2. It is a method for producing a flame-resistant fiber, which comprises 18% or less. As described above, the contact ratio P between adjacent fiber bundles here means that when a plurality of fiber bundles are run in parallel so as to be adjacent to each other, the gap between the adjacent fiber bundles is caused by vibration in the width direction of the fiber bundles. Refers to the probability of becoming zero. The vibration in the width direction of the fiber bundle can be obtained by the following equation (1) when the amplitude average of the fiber bundle is 0 and the standard deviation is σ.

P = [1-p (x) {-t <x <t}] x 100 (1)
Here, P is the contact rate (%) between adjacent fiber bundles, t is the gap (mm) between adjacent fiber bundles, and p (x) is a random density function of the ^{normal distribution N (0, σ 2).} σ is the standard deviation of the amplitude, and x is a random variable with the center of the amplitude as zero.

FIG. 3 is an image diagram of the contact rate P between adjacent fiber bundles, and the upper row shows a plurality of running fiber bundles, and the lower row shows the probability distribution of the existence positions centered on the right end of the fiber bundle in the center of the upper row. The acrylic fiber bundle 2 vibrates, and the gap t between adjacent fiber bundles and the standard deviation σ of the amplitude always change accordingly. The gap t between adjacent fiber bundles can be expressed by the following formula.

t = (Wp-Wy) / 2
Here, Wp is a pitch interval physically regulated by a guide roller or the like, and Wy is the width of a traveling fiber bundle.

FIG. 3 is an image diagram when t <1σ, t = 1σ, and t> 1σ, respectively, from the left. P corresponds to the shaded area in the lower part of FIG. 3, assuming that the amplitude of the fiber bundle is a normal distribution, and is equal to or less than the running end position of the adjacent fiber bundle (the range of t when the reference fiber bundle position is zero). The cumulative probability of / or more is P, and it can be calculated statistically by actually measuring Wy and σ.

The amplitude of the fiber bundle and the width of the traveling fiber bundle can be measured, for example, from the upper surface or the lower surface of the traveling fiber bundle with a high-precision two-dimensional displacement sensor or the like.

The contact rate P between adjacent fiber bundles is essential to be 2% or more and 18% or less, preferably 5 to 16%. If the contact rate P between adjacent fiber bundles is less than 2%, the yarn density becomes too low and the production efficiency decreases. When the contact rate P between adjacent fiber bundles exceeds 18%, the mixed fibers between adjacent fiber bundles increase, and it is not possible to suppress operational troubles such as deterioration of flame-resistant fibers such as fluffing and thread breakage.

The horizontal distance between the guide rollers is preferably 14.5 m or more, and in this case, the production cost can be reduced more advantageously.

Further, the wind speed of the hot air flowing in the flameproof furnace is preferably 1.0 to 6.0 m / sec, more preferably 2.0 to 5.0 m / sec. By setting the wind velocity of the hot air flowing in the flameproof furnace within this preferable range, the production cost can be advantageously reduced.

Further, it is preferable that the guide rollers on both sides of the flameproof furnace have a yarn width regulating mechanism. The fact that the guide roller has a yarn width regulating mechanism means that the guide roller has a mechanism for regulating the yarn width on or in the immediate vicinity of the roller, and by having such a mechanism, the quality and operability of the flameproof fiber bundle Becomes more dominant. For example, when a groove roller in which grooves are carved at regular pitch intervals is used for the guide roller (the thread width is regulated on the roller), or when the guide roller is located several cm in the direction of the flameproof furnace and the pitch is constant in the width direction. When a comb guide with a gap is installed (the thread width is regulated in the immediate vicinity of the roller), unlike the case of using a flat roller that does not regulate the thread width, the fiber bundle can be easily grooved, so one broken fiber. It becomes difficult to involve adjacent fiber bundles when treating the bundles. Further, even in the case of mixing fibers between adjacent fiber bundles, if the degree of mixing is small, the fibers are separated again at the groove portion of the roller, the influence on the subsequent process is less likely to spread, and the deterioration of quality is small.

Further, the single fiber of the acrylic fiber bundle has a surface uneven structure extending 2.0 μm or more in the longitudinal direction of the fiber in the range of 2.0 μm in the circumferential direction and 2.0 μm in the fiber axis direction on the surface of the single fiber. The major axis / minor axis ratio of the single fiber cross section is preferably 1.01 to 1.10, and in this case, the quality and operability of the flame-resistant fiber bundle become more superior. In general, pseudo-adhesion may occur between individual single fibers constituting an acrylic fiber bundle due to a sudden temperature rise in the flame resistance process or the like. Similarly, in the contact between the fiber bundles, there is a concern that the single fibers of the adjacent fiber bundles may cause pseudo-adhesion. However, since the surface of the single fiber has fine irregularities, this pseudo-adhesion can be suppressed, and even if the contact ratio P between adjacent fiber bundles is the same, it is difficult to get entangled and spread to a large mixed fiber. Further, when the cross section of the single fiber approaches an ellipse, the short fibers are biased in the fiber bundle, and when the fiber bundles come into contact with each other, they are easily entangled. On the other hand, if the cross section of the single fiber is close to a perfect circle, it is possible to suppress the mixing of fibers between the fiber bundles. Therefore, the ratio of the major axis to the minor axis of the single fiber cross section is preferably 1.01 to 1.10, more preferably. It is 1.01 to 1.05.

Further, the hook drop length of the acrylic fiber bundle is preferably 300 mm or less, and in this case, the quality and operability of the flame-resistant fiber bundle become more superior. The smaller the hook drop length, the greater the entanglement between the single fibers in the fiber bundle. If the entanglement between the single fibers is large, even if the adjacent fiber bundles are mixed, the force for the single fibers to return to the same fiber bundle is large, so that the mixed fibers of the fiber bundles can be easily eliminated.

The amount of the silicon-based oil adhering to the acrylic fiber bundle is preferably 0.1 to 3.0% by mass, more preferably 0.1 to 1.5% by mass. By setting the amount of the silicone-based oil adhering to the acrylic fiber bundle within this preferable range, the quality and operability of the flame-resistant fiber bundle become more superior. It is common to suppress adhesion between single fibers by applying a silicone-based oil agent having a certain heat resistance to the single fibers of the acrylic fiber bundle.

The single fiber fineness of the acrylic fiber bundle is preferably 0.05 to 0.22 tex, more preferably 0.05 to 0.17 tex. By setting the single fiber fineness of the acrylic fiber bundle to the above-mentioned preferable range, the quality and operability of the flame-resistant fiber bundle become more superior. When the single fiber fineness is in an appropriate range, the surface area of the single fiber occupying the same volume and mass of the single fiber does not become too large, and the single fiber is less likely to be entangled even when adjacent fiber bundles come into contact with each other.

The flame-resistant fiber bundle produced by the above method is precarbonized at a maximum temperature of 300 to 1000 ° C. in an inert atmosphere to produce a precarbonized fiber bundle, and the maximum temperature in the inert atmosphere is 1,000 to 2, A carbon fiber bundle is produced by carbonization treatment at 000 ° C.

The maximum temperature of the inert atmosphere in the precarbonization treatment is preferably 550 to 800 ° C. As the inert atmosphere that fills the precarbonization furnace, a known inert atmosphere such as nitrogen, argon, or helium can be adopted, but nitrogen is preferable from the viewpoint of economy.

The pre-carbonized fiber obtained by the pre-carbonization treatment is then sent to a carbonization furnace for carbonization treatment. In order to improve the mechanical properties of the carbon fiber, it is preferable to carry out carbonization treatment at a maximum temperature of 1,200 to 2,000 ° C. in an inert atmosphere.

As the inert atmosphere that fills the inside of the carbonization furnace, a known inert atmosphere such as nitrogen, argon, or helium can be adopted, but nitrogen is preferable from the viewpoint of economy.

The carbon fiber bundle thus obtained may be provided with a sizing agent in order to improve the handleability and the affinity with the matrix resin. The type of sizing agent is not particularly limited as long as desired properties can be obtained, and examples thereof include sizing agents containing epoxy resin, polyether resin, epoxy-modified polyurethane resin, and polyester resin as main components. A known method can be used for applying the sizing agent.

Further, the carbon fiber bundle may be subjected to an electrolytic oxidation treatment or an oxidation treatment for the purpose of improving the affinity and adhesiveness with the fiber-reinforced composite material matrix resin, if necessary.

As described above, in the present invention, the inside of the hot air heating type flameproofing furnace is conveyed while the acrylic fiber bundles in which a plurality of bundles are arranged adjacent to each other are conveyed by the guide rollers installed on both sides outside the flameproofing furnace. A method for producing a flame-resistant fiber bundle that is run and heat-treated in an oxidizing atmosphere. The direction of hot air in the flame-resistant furnace is parallel to the running direction of the fiber bundle, and the contact rate between adjacent fiber bundles. By setting P to 2 to 18%, it becomes possible to efficiently produce high-quality flame-resistant fibers without operational troubles.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The evaluation method and measurement method for each characteristic were as described below.

<Measurement method of single fiber fineness of acrylic fiber bundle>
This was done in accordance with JIS L 1013.

<Measurement of surface uneven structure of single fiber of acrylic fiber bundle>
Both ends of the single fiber of the acrylic fiber bundle are fixed with carbon paste on a metal sample table for SPA400 (20 mm diameter) "Epolide Service Co., Ltd., product number: KY10200167" attached to the scanning probe microscope, and the following The measurement was performed under the conditions of.

(Scanning probe microscope measurement conditions)
Equipment: "SPI4000 probe station, SPA400 (unit)" SII Nanotechnology, Inc. Scanning mode: Dynamic force mode (DFM) (shape image measurement)
Needle: "SI-DF-20" manufactured by SII Nanotechnology Co., Ltd.
Scanning range: 2.0 μm × 2.0 μm and 600 nm × 600 nm
Rotation: 90 ° (scans perpendicular to the fiber axis direction)
Scanning speed: 1.0Hz
Number of pixels: 512 x 512
Measurement environment: One image is obtained for one single fiber in the air at room temperature under the above conditions, and the obtained image is imaged under the following conditions using the image analysis software (SPIWin) attached to the scanning probe microscope. The analysis was performed.

(Image analysis conditions)
The obtained shape image was subjected to "flat processing", "median 8 processing", and "third-order tilt correction" to obtain an image in which a curved surface was fitted and corrected to a flat surface. _{The average surface roughness (Ra} ) and the maximum in-plane height difference (R _max ) were obtained from the surface roughness analysis of the plane-corrected image. Here, as the average surface roughness ( _Ra ) and the maximum in-plane height difference (R _max ) from the surface roughness analysis, the data of the scanning range of the circumference length of 600 nm × the fiber axial length of 600 nm was used. Ra is calculated by the following formula.

Central plane: A plane parallel to the plane that minimizes the height deviation from the real surface and dividing the real surface into two with the same volume f (x, y): Height difference between the real surface and the central plane L _x , _Ly : In the size measurement of the XY plane, 10 single fibers are measured in shape with a scanning probe microscope for one sample, and the average surface roughness ( _Ra ) and maximum height difference (R _max ) are obtained for each measured image. , The average value was taken as the average surface roughness ( _Ra ) and the maximum height difference (R _max ) of the sample. Regarding the presence or absence of a surface uneven structure extending by 2 μm or more in the longitudinal direction of the single fiber on the surface of the single fiber, the length in the fiber axial direction is set in the range of 2.0 μm in the circumferential direction of the single fiber in AFM (atomic force microscope) mode. The presence or absence was determined from the obtained measured images by repeatedly scanning over a distance of 0.0 μm while shifting the particles little by little.

(Flat processing)
A process that removes distortion / waviness in the Z-axis direction that appears in image data due to lift, vibration, creep of a scanner, etc., and is a process that removes data distortion due to equipment factors in SPM (scanning probe microscope) measurement.

(Median 8 processing)
In a 3 × 3 window (matrix) centered on the data point S to be processed, an operation is performed between S and D1 to D8 (eight matrices surrounding S), and Z (height direction) data of S is performed. By replacing, you can get the effect of the filter such as smoothing and noise removal.

The median 8 process finds the median of the 9 points of Z data of S and D1 to D8 and replaces S.

(Third-order tilt correction)
In the tilt correction, a curved surface is obtained and fitted by the least squares approximation from all the data of the image to be processed, and the tilt is corrected. (Primary), (secondary), and (tertiary) indicate the order of the curved surface to be fitted, and the tertiary surface fits the cubic curved surface. The third-order tilt correction process eliminates the curvature of the fibers in the data to create a flat image.

<Evaluation of cross-sectional shape of single fiber of acrylic fiber bundle>
The ratio (major axis / minor axis) of the major axis to the minor axis of the fiber cross section of the single fiber constituting the fiber bundle was determined as follows.

A fiber bundle for measurement is passed through a tube made of vinyl chloride resin having an inner diameter of 1 mm, and then sliced into round slices with a knife to prepare a sample. Then, the sample was adhered to the SEM sample table with the fiber cross section facing upward, and Au was further sputtered to a thickness of about 10 nm, and then the acceleration voltage was 7.00 kV by an XL20 scanning electron microscope manufactured by Philips. The fiber cross section was observed under the condition of a working distance of 31 mm, the major axis and the minor axis of the fiber cross section of the single fiber were measured, and the ratio between the major axis and the minor axis was evaluated.

<Measuring method of hook drop length of acrylic fiber bundle>
The acrylic fiber bundle is pulled out by 120 mm, attached to the upper part of the hanging device, untwisted, and then a 200 g weight is hung from the lower part of the fiber bundle. A hook (made of φ1 mm stainless steel wire, hook R = 5 mm) is inserted so as to divide the fiber bundle into three at a point 1 cm below the upper part of the fiber bundle, and the hook is lowered. The hook is adjusted with a weight so that the total mass is 10 g. Find the descent distance of the hook to the point where the hook stopped due to the entanglement of the fiber bundles. The number of tests was N = 50, and the average value was taken as the hook drop length.

<Measurement method of wind speed in flameproof furnace>
An anemometer for high temperature, Model 6162 manufactured by Kanomax, was used, and the average value of 30 measured values per second was used. A measuring probe was inserted from a measuring hole (not shown) on the side surface of the heat treatment chamber 3 located at the center of the guide rollers 4 on both sides of the flameproofing furnace 1, and the wind speed of the oxidizing gas flowing in the horizontal direction was measured. Five points were measured in the width direction, and the average value was used.

<Measurement method of yarn width and amplitude of running fiber bundle>
The measurement was performed at a position corresponding to the center of the guide rollers 4 on both sides of the flameproofing furnace 1 in which the amplitude of the traveling fiber bundle was maximized. Specifically, a laser displacement meter LJ-G200 manufactured by KEYENCE CORPORATION was installed above or below a traveling fiber bundle to irradiate a specific fiber bundle with a laser. The distance between both ends in the width direction of the fiber bundle was defined as the width of the fiber bundle, and the amount of fluctuation in the width direction of one end in the width direction was defined as the amplitude. Measure once / 60 seconds or more with an accuracy of 0.01 mm or less for 5 minutes, obtain the standard deviation σ of the width Wy (average value) and amplitude of the fiber bundles, and obtain the standard deviation σ between the adjacent fiber bundles described above. The contact rate P was calculated.

Table 1 qualitatively shows the results of operability, quality, and productivity in each of the examples and comparative examples. Excellent, good, and unacceptable were evaluated according to the following criteria.

(Operability)
Excellent: The average number of troubles such as mixed fibers and broken fiber bundles is zero per day, which is an extremely good level.
Good: Problems such as mixed fibers and broken fiber bundles occur several times a day on average, and continuous operation can be continued sufficiently.
Impossible: Problems such as mixed fibers and broken fiber bundles occur dozens of times a day on average, and continuous operation cannot be continued.

(quality)
Excellent: The average number of fluffs of 10 mm or more on the fiber bundle that can be visually confirmed after the flame resistance process is several / m or less, and the fluff quality is excellent for passability in the process and high-order workability as a product. A level that does not affect at all.
Good: The average number of fluffs of 10 mm or more on the fiber bundle that can be visually confirmed after the flame resistance process is 10 pieces / m or less, and the fluff quality is excellent for passability in the process and high-order workability as a product. A level that has almost no effect.
Impossible: The average number of fluffs of 10 mm or more on the fiber bundle that can be visually confirmed after the flame resistance process is several tens / m or more, and the fluff quality is passability in the process and high-order workability as a product. Level that adversely affects.

(Productivity)
Excellent: The manufacturing cost is sufficiently low (80% or less compared to "good"), and the production volume per unit time is sufficiently large (120% or more compared to "good").
Good: The manufacturing cost is relatively low and the production volume per unit time is relatively large. Impossible: The manufacturing cost is high (150% or more compared to "good"), or the production volume per unit time is small ("" 60% or less compared to "good") level.

(Example 1)
Single fiber fineness 0.11tex, surface uneven structure extending in the longitudinal direction of the fiber in the range of 2.0 μm in the circumferential direction and 2.0 μm in the fiber axial direction of the surface of the single fiber is 2.5 μm, major axis / short of the single fiber cross section 100 to 200 acrylic fiber bundles 2 made of 20,000 single fibers having a diameter of 1.04 were aligned and heat-treated in the flame-resistant furnace 1 to obtain flame-resistant fiber bundles. The amount of the silicone-based oil adhering to the acrylic fiber bundle was 0.5%, and the hook drop length of the acrylic fiber bundle was set to 250 mm. Further, the horizontal distance L'between the guide rollers 4 on both sides of the heat treatment chamber 3 of the flameproof furnace 1 is 20 m, and the guide rollers 4 are grooved at a predetermined interval (pitch interval to be physically regulated) Wp in the range of 3 to 15 mm. It was a groove roller that was dug. At this time, the temperature of the oxidizing gas in the heat treatment chamber 3 of the flame-resistant furnace 1 was set to 240 to 280 ° C., and the horizontal wind speed of the oxidizing gas was set to 3 m / sec. The traveling speed of the yarn is adjusted in the range of 1 to 15 m / min according to the flameproof furnace length L so that the flameproofing treatment time can be sufficiently taken, and the process tension is in the range of 0.5 to 2.5 g / tex. It was adjusted.

The obtained flame-resistant fiber bundle is then fired in a pre-carbonization furnace at a maximum temperature of 700 ° C., then fired in a carbonization furnace at a maximum temperature of 1,400 ° C., and after electrolytic surface treatment, sizing is applied to carbon. A fiber bundle was obtained.

At this time, the standard deviation σ of the width Wy and the amplitude of the fiber bundle in the center of the heat treatment chamber of the fiber bundle running in the uppermost stage in the heat treatment chamber 3 of the flameproof furnace 1 was actually measured, and statistically calculated between the adjacent fiber bundles. The contact rate P was 6%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurs, and the operability is extremely good, and the flame-resistant fiber bundle is more production-efficient. Was acquired. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Example 2)
The same as in Example 1 except that the horizontal distance L'between the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1 was 15 m and the contact ratio P between adjacent fiber bundles was 10%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with extremely good operability. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Example 3)
The same as in Example 1 except that the horizontal distance L'between the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1 was 30 m and the contact rate P between adjacent fiber bundles was 15%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurs, and the operability is extremely good, and the flame-resistant fiber bundle is more production-efficient. Was acquired. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Example 4)
The same procedure as in Example 1 was carried out except that the horizontal wind speed of the oxidizing gas in the heat treatment chamber 3 of the flame-resistant furnace 1 was set to 5 m / sec and the contact rate P between adjacent fiber bundles was set to 7%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurs, and the operability is extremely good, and the flame-resistant fiber bundle is more production-efficient. Was acquired. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Example 5)
The same as in Example 1 except that the horizontal distance L'between the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1 was 10 m and the contact rate P between adjacent fiber bundles was 5%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with extremely good operability. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Example 6)
The same procedure as in Example 1 was carried out except that the horizontal wind speed of the oxidizing gas in the heat treatment chamber 3 of the flame-resistant furnace 1 was 8 m / sec and the contact rate P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with extremely good operability. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Example 7)
The same as in Example 1 except that the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1 were flat rollers and the contact ratio P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and the flame-resistant fiber bundle was obtained with good operability and more production efficiency. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like.

(Example 8)
The same procedure as in Example 1 was carried out except that the major axis / minor axis of the single fiber cross section of the acrylic fiber bundle used was 1.50 and the contact ratio P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and the flame-resistant fiber bundle was obtained with good operability and more production efficiency. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like.

(Example 9)
The same procedure as in Example 1 was carried out except that the amount of the silicone-based oil adhering to the acrylic fiber bundle used was 4.0% and the contact rate P between the adjacent fiber bundles was 6%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and the flame-resistant fiber bundle was obtained with good operability and more production efficiency. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like.

(Example 10)
The same as in Example 1 was carried out except that the silicone-based oil agent was not applied to the used acrylic fiber bundle and the contact ratio P between adjacent fiber bundles was set to 6%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and the flame-resistant fiber bundle was obtained with good operability and more production efficiency. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like.

(Example 11)
The same procedure as in Example 1 was carried out except that the hook drop length of the acrylic fiber bundle used was 350 mm and the contact ratio P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and the flame-resistant fiber bundle was obtained with good operability and more production efficiency. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like.

(Example 12)
The same as in Example 1 except that the single fiber fineness of the acrylic fiber bundle used was 0.18 tex and the contact rate P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and the flame-resistant fiber bundle was obtained with good operability and more production efficiency. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like.

(Example 13)
The guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1 are made into flat rollers, and a comb guide is installed at a position 30 mm in the direction of the flame-resistant furnace from the flat roller, and the comb guide is 3 to 15 mm in the width direction. The pitch interval of the fiber bundles, which has a gap of a certain interval in the range and is physically regulated by the fiber bundle passing through the gap, is set to a predetermined interval Wp in the range of 3 to 15 mm, and the contact rate between adjacent fiber bundles is set. This was the same as in Example 1 except that P was set to 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fiber mixing or fiber bundle breakage due to contact between the fiber bundles occurs, and the operability is extremely good, and the flame-resistant fiber bundle is more production-efficient. Was acquired. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was extremely good with no fluff or the like.

(Comparative Example 1)
The same as in Example 1 except that the contact ratio P between adjacent fiber bundles was set to 24% by reducing the distance between the grooves of the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1.

Under the above conditions, the production amount itself could be increased by improving the yarn density, but during the flameproofing treatment of the acrylic fiber bundles, mixed fibers and broken fiber bundles frequently occur due to contact between the fiber bundles. However, it became difficult to continue operations. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, there were many fluffs and the quality was poor.

(Comparative Example 2)
The same as in Example 1 except that the contact ratio P between adjacent fiber bundles was set to 1% by increasing the distance between the grooves of the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, there was little mixing of fibers or breakage of the fiber bundle due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, the quality was good with less fluff and the like. However, as a result, the number of fiber bundles that can be put into the flameproofing furnace 1 has decreased, and the productivity has greatly decreased.

(Comparative Example 3)
The same as in Example 3 except that the contact ratio P between adjacent fiber bundles was set to 28% by reducing the distance between the grooves of the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame-resistant furnace 1.

Under the above conditions, the production amount itself could be increased by improving the yarn density, but during the flameproofing treatment of the acrylic fiber bundles, mixed fibers and broken fiber bundles frequently occur due to contact between the fiber bundles. However, it became difficult to continue operations. Further, as a result of visually confirming the obtained flame-resistant fiber bundles and carbon fiber bundles, there were many fluffs and the quality was poor.

(Comparative Example 4)
The same as in Example 3 except that the horizontal wind speed of the oxidizing gas in the heat treatment chamber 3 of the flame-resistant furnace 1 was set to 8 m / sec and the contact rate P between adjacent fiber bundles was set to 19%.

Under the above conditions, during the flameproofing treatment of the acrylic fiber bundles, mixed fibers due to contact between the fiber bundles and broken fiber bundles frequently occurred, making it difficult to continue the operation. Further, as a result of visually confirming the obtained flame-resistant fibers and carbon fibers, the quality was inferior due to a large amount of fluff and the like. Further, by setting the wind speed to 8 m / sec, the equipment cost of the blower 8 that enables it has increased, and the production cost has deteriorated significantly.

The present invention relates to a method for producing a flame-resistant fiber bundle and a method for producing a carbon fiber bundle, and can be applied to aircraft applications, industrial applications such as pressure vessels and wind turbines, sports applications such as golf shafts, etc. It is not limited to these.

1 Flame-resistant furnace 2 Acrylic fiber bundle 3 Heat treatment chamber 4 Guide roller 5 Hot air outlet 6 Hot air outlet 7 Heater 8 Blower L Flame-resistant furnace length (1 pass flame-resistant effective length)
L'Horizontal distance between guide rollers Wp Physically regulated pitch interval Wy Width of traveling fiber bundle t Gap between adjacent fiber bundles

Claims (9)

Acrylic fiber bundles in which a plurality of bundles are arranged adjacent to each other are conveyed by guide rollers installed on both sides outside the flame-resistant furnace, and the fibers are run in a hot-air heating type flame-resistant furnace to be heat-treated in an oxidizing atmosphere. This is a method for manufacturing a flame-resistant fiber bundle, in which the direction of hot air in the flame-resistant furnace is parallel to the traveling direction of the fiber bundle, and the contact rate between adjacent fiber bundles defined by the following equation (1). A method for producing a flame-resistant fiber bundle having P of 2 to 18%.
P = [1-p (x) {-t <x <t}] x 100 (1)
Here, P is the contact rate (%) between adjacent fiber bundles, t is the gap (mm) between adjacent fiber bundles, p (x) is ^{the probability density function of the normal distribution N (0, σ 2} ), and σ is The standard deviation of the amplitude, x represents a random variable with the center of the amplitude as zero. The method for producing a flame-resistant fiber bundle according to claim 1, wherein the horizontal distance between the guide rollers is 14.5 m or more. The method for producing a flame-resistant fiber bundle according to claim 1 or 2, wherein the wind speed of the hot air flowing in the flame-resistant furnace is 1.0 to 6.0 m / sec. The method for producing a flame-resistant fiber bundle according to any one of claims 1 to 3, wherein the guide roller has a yarn width regulating mechanism. The surface of the single fiber of the acrylic fiber bundle has a surface uneven structure extending 2.0 μm or more in the longitudinal direction of the fiber in a range of 2.0 μm in the circumferential direction and 2.0 μm in the fiber axis direction, and the single fiber. The method for producing a flame-resistant fiber bundle according to any one of claims 1 to 4, wherein the ratio of the major axis to the minor axis of the fiber cross section is 1.01 to 1.10. The method for producing a flame-resistant fiber bundle according to any one of claims 1 to 5, wherein the hook drop length of the acrylic fiber bundle is 300 mm or less. The method for producing a flame-resistant fiber bundle according to any one of claims 1 to 6, wherein the amount of the silicon-based oil adhering to the acrylic fiber bundle is 0.1 to 3.0% by mass. The method for producing a flame-resistant fiber bundle according to any one of claims 1 to 7, wherein the single fiber fineness of the acrylic fiber bundle is 0.05 to 0.22 tex. The flame-resistant fiber bundle produced by the method for producing a flame-resistant fiber bundle according to any one of claims 1 to 8 is precarbonized by precarbonizing at a maximum temperature of 300 to 1,000 ° C. in an inert atmosphere. A method for producing a carbon fiber bundle, which comprises producing a fiber bundle and carbonizing the pre-carbonized fiber bundle at a maximum temperature of 1000 to 2000 ° C. in an inert atmosphere.

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