KR20210063328A - Method for producing flame-resistant fiber bundles and methods for producing carbon fiber bundles - Google Patents

Abstract

Acrylic fiber bundles 2 arranged by adjoining a plurality of bundles are conveyed by guide rollers 4 provided on both sides of the flame-resistant furnace 1, while running in a hot-air heating type flame-resistant furnace 1 A method for producing a flame-resistant fiber bundle subjected to heat treatment in an oxidizing atmosphere, wherein the direction of hot air in the flame-resistant furnace (1) is parallel to the running direction of the fiber bundle, and the contact ratio between adjacent fiber bundles defined by the following formula (1) A method for producing a flame-resistant fiber bundle in which P is 2 to 18%.
P=[1-p(x)｛-t<x<t｝]×100 (1)
where P is the contact rate (%) between adjacent fiber bundles, t is the gap between adjacent fiber bundles (mm), p(x) is ^{the probability density function of the normal distribution N(0,σ 2} ), σ is the standard deviation of the amplitude , x denotes a random variable with the center of the amplitude equal to zero. High-quality flame-resistant fiber bundles and carbon fiber bundles can be produced efficiently without operating problems.

Description

Method for producing flame-resistant fiber bundles and methods for producing carbon fiber bundles

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

Since carbon fiber has excellent specific strength, specific 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 uses, and general industrial purposes.

In general, as a method of manufacturing a carbon fiber bundle from an acrylic fiber bundle, a fiber bundle in which thousands to tens of thousands of short fibers of an acrylic polymer are bundled is fed into a flameproof furnace, and an oxidizing atmosphere such as air heated to 200 to 300°C After heat treatment (flammability treatment) by exposing to a hot air of a, the obtained flameproof fiber bundle is fed into a carbonization furnace and heat-treated (pre-carbonization treatment) in an inert gas atmosphere at 300 to 1000 ° C. Also known is a method of heat treatment (carbonization treatment) in a satisfactory carbonization furnace in an inert gas atmosphere of 1000°C or higher. In addition, flame-resistant fiber bundles, which are intermediate materials, are widely used as materials for flame-retardant woven fabrics by making use of their non-flammable performance.

In the carbon fiber bundle manufacturing process, the longest processing time and the largest amount of energy consumed is the flameproofing process. For this reason, productivity improvement in the flameproofing process becomes the most important in the manufacture of carbon fiber bundles.

In order to enable long-term heat treatment in the flameproofing process, an apparatus for flameproofing (hereinafter referred to as flameproofing furnace) uses a repeating roller disposed outside the flameproofing furnace to horizontally move the acrylic fiber. It is common to process while reciprocating several times with flameproofing. In order to improve productivity in the flameproofing process, it is effective to increase the density of the fiber bundles in the flameproof furnace by simultaneously conveying a large number of fiber bundles, and to increase the running 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 vibration of the fiber bundles increases. For this reason, the deterioration of the quality of the flame-resistant fiber due to frequent occurrence of mixed fibers of fiber bundles, breakage of single fibers, and the like is called.

In addition, in the case of increasing the running speed of the fiber bundle, it is necessary to increase the size of the flameproof 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 cost because it is necessary to divide the building hierarchy into a plurality of layers or to increase the load-bearing weight per unit area of the floor. Here, in order to suppress an increase in equipment cost and increase the size of the flameproof furnace, it is effective to decrease the size in the height direction by increasing the distance per pass in the horizontal direction (hereinafter, referred to as flameproof furnace length). However, by increasing the length of the flame-resistant furnace, the amount of suspension of the running fiber bundle increases, as in the case of increasing the density of the fiber bundle, contact between adjacent fiber bundles due to vibration, mixing of fiber bundles, , a decrease in the quality of the flame-resistant fiber caused by frequent breakage of short fibers and the like.

In order to solve the above problems, in Patent Document 1, the surface occupancy of the fiber bundle sheet-like material in the flameproofing step is stipulated, and the wind speed in the flameproofing furnace and the process tension in the flameproofing step are optimized. thing is being explained. In addition, in Patent Document 2, the surface occupancy of the fiber bundle sheet-like material in the flameproofing step, the wind speed in the flameproofing furnace, the fiber bundle density in the flameproofing furnace, specifically, the fineness per 1 mm of the width of the running fiber bundle is prescribed. doing is being explained. Moreover, in patent document 3, aiming at the optimization of the line speed of the flameproof process in the case where length becomes long by flameproofing, and the maximum amount of suspension of a fiber bundle is demonstrated. Patent Document 1: Japanese Patent Laid-Open No. 2000-160435 Patent Document 2: Japanese Patent Laid-Open No. 2011-127264 Patent Document 3: Japanese Patent Laid-Open No. Hei 11-61574

However, in Patent Document 1 and Patent Document 2, in the case of increasing the length of the flameproof furnace in order to improve productivity, the contact between adjacent fiber bundles cannot be avoided in the prescribed surface occupancy parameter. For this reason, there exists a possibility that high-quality flame-resistant fiber cannot be manufactured. Further, in Patent Document 3, the contact suppression between adjacent fiber bundles in the case of a large flameproof furnace length is considered by the regulation of the maximum suspension amount of the fiber bundles, but the density of the fiber bundles in the flameproof furnace is mentioned. It is not done, and productivity cannot be improved.

Accordingly, the problem to be solved by the present invention is to efficiently produce high-quality flame-resistant fiber bundles and carbon fiber bundles without operating troubles.

In order to solve the above problems, the method for producing a flame-resistant fiber bundle of the present invention has the following configuration. In other words,

A method for producing flame-resistant fiber bundles in which acrylic fiber bundles arranged adjacent to each other are transported by guide rollers installed on both sides of the flame-resistant furnace, while running in a hot-air heating type flame-resistant furnace and heat-treated in an oxidizing atmosphere As, the direction of the hot air in the flameproof furnace is parallel to the running direction of the fiber bundle, and the contact ratio P between adjacent fiber bundles defined by the following formula (1) is 2 to 18%. to be.

P=[1-p(x)｛-t<x<t｝]×100　　　(1)

where P is the contact rate (%) between adjacent fiber bundles, t is the gap between adjacent fiber bundles (mm), 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 denotes a random variable with the center of the amplitude equal to zero.

The "contact ratio P between adjacent fiber bundles" in the present invention means that, when a plurality of fiber bundles are run in parallel so that they are adjacent, the gap between adjacent fiber bundles is zero due to vibration (thread oscillation) in the width direction of the fiber bundles. indicates the probability of It is assumed that the amplitude of the vibration in the width direction of the fiber bundle follows a normal distribution N when the average of the amplitude of the fiber bundle is 0 and the standard deviation of the amplitude is σ, and the contact ratio P between adjacent fiber bundles is expressed in the formula (1) ) can be obtained from

Further, the method for producing a carbon fiber bundle of the present invention has the following configuration. In other words,

The flame-resistant fiber bundle produced by the method for producing the flame-resistant fiber bundle is pre-carbonized at a maximum temperature of 300 to 1,000° C. in an inert atmosphere to prepare a pre-carbonized fiber bundle, and the pre-carbonized fiber bundle is heated in an inert atmosphere. It is a method of manufacturing carbon fiber bundles that are carbonized at the highest temperature of 1,000 to 2,000 °C.

According to the manufacturing method of the flame-resistant fiber of this invention, high-quality flame-resistant fiber can be produced efficiently without an operation trouble.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic side view which shows a flameproof furnace.
FIG. 2 is an X-Y cross-sectional view of the flame-resistant furnace of FIG. 1 .
3 is an image diagram for explaining the contact ratio P between adjacent fiber bundles.

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

The present invention is a method for flame-resistant treatment of the acrylic fiber bundle in an oxidizing atmosphere, and is carried out in a flame-resistant furnace through which an oxidizing gas flows. As shown in FIG. 1 , the flame-resistant furnace 1 has a heat treatment chamber 3 in which a flame-resistant treatment is performed by blowing hot air to the acrylic fiber bundle 2 running while repeating a multi-stage running range. The acrylic fiber bundle 2 is fed into the heat treatment chamber 3 from an opening (not shown) provided on the side wall of the heat treatment chamber 3 of the flame resistant furnace 1 and travels in a straight line in the heat treatment chamber 3 . Then, it is once sent out of the heat treatment chamber 3 from the opening part of the side wall facing. Thereafter, it is repeatedly fed into the heat treatment chamber 3 again by the guide rollers 4 provided on the side walls outside the heat treatment chamber 3 . In this way, the acrylic fiber bundle 2 repeats the feeding and discharging in the heat treatment chamber 3 several times by repeating the running direction several times by the plurality of guide rollers 4, and the inside of the heat treatment chamber 3 is multi-stage. , as a whole moves from top to bottom in FIG. 1 . The direction of movement may be from bottom to top, and the number of repetitions of the acrylic fiber bundle 2 in the heat treatment chamber 3 is not particularly limited, and is appropriately designed depending on the scale of the flame-resistant furnace 1 and the like. In addition, you may provide the guide roller 4 inside the heat treatment chamber 3 .

The acrylic fiber bundle 2 is subjected to flame resistance treatment by the hot air flowing from the hot air outlet 5 toward the hot air outlet while traveling in the heat treatment chamber 3 while repeatedly running to form a flame resistant fiber bundle. In addition, as shown in FIG. 2, the acrylic fiber bundle 2 has a sheet-like shape with a wide width arranged in parallel in a plurality of directions perpendicular to the paper.

It is preferable to arrange|position the rectification|straightening member (not shown together), such as resistors, such as a perforated plate, and honeycomb, on the blowing surface at the hot air blower outlet 5, and give a pressure loss. The rectifying member can rectify the hot air blown into the heat treatment chamber 3 and blow the hot air with a uniform wind speed into the heat treatment chamber 3 .

In the hot air outlet 6 , similarly to the hot air outlet 5 , a resistor such as a perforated plate may be disposed on the blown-in surface to have a pressure loss, and it is determined appropriately as necessary.

The oxidizing gas flowing in the heat treatment chamber 3 may be air, and before entering the heat treatment chamber 3, it is heated to a desired temperature by the heater 7, the wind speed is controlled by the blower 8, and then hot air It blows into the heat treatment chamber 3 from the ejection port 5 . The oxidizing gas discharged from the hot air outlet 6 outside the heat treatment chamber 3 is released to the atmosphere after toxic substances are treated in the exhaust gas treatment furnace (not shown), but passes through the circulation path (not shown) and goes back to the hot air outlet ( You may blow into the heat treatment chamber 3 from 5).

Moreover, as the heater 7 used for the flameproof furnace 1, if it has a desired function, it will not specifically limit, For example, well-known heaters, such as an electric heater, may be used. It will not specifically limit as long as it has a desired function also about the blower 8, For example, well-known blowers, such as an axial fan, may be used.

In addition, by changing the rotation speed of each of the guide rollers 4, the running speed and tension of the acrylic fiber bundle 2 can be controlled, which is fixed according to the required properties of the flame-resistant fiber bundle or the throughput per unit time. .

In addition, a predetermined interval and a number of grooves are engraved on the surface layer of the guide roller 4, or a predetermined interval and number of comb guides (not shown) are placed right next to the guide roller 4 . By arranging a plurality of acrylic fiber bundles 3 running in parallel, it is possible to control the spacing and the number of bundles.

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

However, enlarging the yarn density means reducing the spacing between adjacent fiber bundles, and as described above, deterioration of quality due to mixing between fiber bundles due to vibration, etc. tends to occur.

In addition, when the traveling speed of the acrylic fiber bundle 2 is increased, the residence time in the flame-resistant heat treatment chamber becomes small and the amount of heat treatment is insufficient. Therefore, it is necessary to increase the total heat treatment length. To this end, it is good to increase the height of the flame-resistant furnace 1 to increase the number of repetitions of the acrylic fiber bundle, or to increase the distance (hereinafter referred to as the flame-resistant furnace length) L per pass to the flame-resistant furnace, In order to suppress the equipment cost, it is preferable to increase the length (L) of the flameproof furnace. However, this also increases the horizontal distance L' between the guide rollers 4, so that the fiber bundles are easily suspended, and contact between the fiber bundles due to vibration and deterioration of the quality due to the mixing of the fiber bundles are likely to occur.

In addition, the amplitude of the vibration of the fiber bundle causing contact between the fiber bundles is determined not only by the density of the yarns and the horizontal distance (L′) between the guide rollers 4, but also by the wind speed of the oxidizing gas flowing through the heat treatment chamber, and that of the traveling acrylic fiber bundle. is affected by tension. In addition, the frequency and degree of mixing even with the same amplitude is affected by the physical properties of the acrylic fiber bundle, ie, chemical properties, physical properties, dimensions, and the like.

The method for producing a flame-resistant fiber bundle of the present invention is to efficiently produce high-quality flame-resistant fibers without operating troubles regardless of the equipment specifications of the flame-resistant furnace, operating conditions, and physical properties of the acrylic fiber bundle.

Specifically, in the continuous heat treatment method in which a plurality of bundles are arranged adjacent to each other and heat-treated while running in a flame-resistant furnace 1 of a hot air heating type to obtain a flame-resistant fiber bundle, the acrylic fiber bundle (2) ) is conveyed by guide rollers 4 installed on both sides of the heat treatment chamber 3, the direction of the hot air in the flameproof furnace 1 is parallel to the yarn, and the contact ratio P between adjacent fiber bundles is 2 to 18. % or less, it is a method for producing a flame-resistant fiber. As described above, the contact ratio P between adjacent fiber bundles refers to the probability that the gap between adjacent fiber bundles becomes zero due to vibration in the width direction of the fiber bundles when a plurality of fiber bundles are run in parallel so as to be adjacent to each other. As for the vibration in the width direction of the fiber bundle, when the average amplitude of the fiber bundle is 0 and the standard deviation is σ, the contact ratio P between adjacent fiber bundles can be obtained from the following formula (1).

P=[1-p(x)｛-t<x<t｝]×100　　　(1)

where P is the contact rate (%) between adjacent fiber bundles, t is the gap between adjacent fiber bundles (mm), p(x) is ^{the probability density function of the normal distribution N(0,σ 2} ), and σ is the standard of amplitude The deviation, x, is a random variable with the center of the amplitude zero.

3 is an image diagram of the contact ratio P between adjacent fiber bundles, showing probability distributions of a plurality of fiber bundles with an upper end traveling and a lower end centered on the right end of the fiber bundle at the upper center. The acrylic fiber bundle 2 vibrates, and accordingly, the gap t between adjacent fiber bundles and the standard deviation sigma of the amplitude always change. 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 running fiber bundle.

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

Further, the amplitude of the fiber bundle and the width of the running fiber bundle can be measured, for example, by a high-precision two-dimensional displacement sensor on the upper surface or the lower surface of the running fiber bundle.

It is essential that the contact ratio P between adjacent fiber bundles is 2% or more and 18% or less, and is preferably 5 to 16%. When the contact ratio P between adjacent fiber bundles is less than 2%, the yarn density becomes too low and the production efficiency decreases. When the contact ratio P between adjacent fiber bundles exceeds 18%, mixed fibers between adjacent fiber bundles increase, and thus, it is impossible to suppress operation troubles such as deterioration of flame-resistant fibers such as fluffing and yarn breakage.

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

Moreover, it is preferable to make the wind speed of the hot air which flows through the inside of a flameproof furnace into 1.0-6.0 m/sec, More preferably, it is 2.0-5.0 m/sec. By making the wind speed of the hot air flowing through the flameproof furnace into this preferable range, the production cost can be advantageously reduced.

Moreover, it is preferable that the guide rollers on both sides of a flameproof furnace have a thread width regulation 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 the roller or right next to the roller. becomes For example, in the case of using a grooved roller with grooves engraved at regular pitch intervals on the guide roller (restricting the thread width on the roller), or in the case of using a guide roller with a constant pitch interval in the width direction at several cm in the direction from the guide roller to the flameproof furnace. When a comb guide is installed (the yarn width is regulated right next to the roller), unlike the case of using a flat roller that does not regulate the yarn width, the fiber bundle can be easily attached to the groove. When a fiber bundle is treated, it becomes difficult to entrap adjacent fiber bundles. In addition, even in the case of mixed fiber between adjacent fiber bundles, if the degree of mixed fiber is small, the fiber is again distributed in the groove portion of the roller, and the influence is less likely to spread to subsequent processes, and quality deterioration is small.

In addition, the short fibers of the acrylic fiber bundle have a surface uneven structure extending 2.0 µm or more in the longitudinal direction of the fibers in the range of 2.0 µm in the circumferential direction and 2.0 µm in the fiber axis direction of the surface of the single fiber, and the long diameter/ It is preferable that the ratio of the minor axis is 1.01 to 1.10, and in this case, the quality and operability of the flame-resistant fiber bundle are more superior. In general, pseudo-adhesion may occur between individual single fibers constituting the acrylic fiber bundle due to a rapid temperature rise in the flame-resistant step or the like. Similarly, even in the case of contact between fiber bundles, there is a risk of pseudo-adhesion between single fibers of adjacent fiber bundles. 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 entangle and it is difficult to spread to a large mixed island. Further, when the cross section of the single fibers approaches an ellipse, deflection of the single fibers occurs within the fiber bundle, and when the fiber bundles contact each other, they are likely to become entangled. Conversely, when the cross section of the single fiber is close to a perfect circle, since it is possible to suppress intermingling between fiber bundles, the ratio of the major axis / minor axis of the single fiber cross section is preferably 1.01 to 1.10, more preferably 1.01 to 1.05.

In addition, it is preferable that the hook drop length of the acrylic fiber bundle is 300 mm or less, and in this case, the quality and operability of the flame-resistant fiber bundle are more superior. The smaller the hook drop length, the larger the entanglement between the single fibers in the fiber bundle. If the entanglement between the single fibers is large, even if adjacent fiber bundles are mixed, the force to return the single fibers within the same fiber bundle is large, so that the mixed fiber of the fiber bundle is easily eliminated.

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

Moreover, it is preferable that the single fiber fineness of an acrylic fiber bundle is 0.05-0.22 tex, More preferably, it is 0.05-0.17 tex. By making the single fiber fineness of the acrylic fiber bundle into the above-mentioned preferred range, the quality and operability of the flame-resistant fiber bundle become more superior. If the single fiber fineness is within an appropriate range, the single fiber surface area to the same volume and mass of the single fiber does not become too large, and even when adjacent fiber bundles come into contact with each other, the single fiber becomes less likely to be related.

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

The maximum temperature of the inert atmosphere in the pre-carbonization treatment is preferably 550 to 800°C. As an inert atmosphere that satisfies the inside of the pre-carbonization furnace, a known inert atmosphere such as nitrogen, argon, or helium can be employed, but nitrogen is preferable from the viewpoint of economy.

The pre-carbonized fibers obtained by the pre-carbonization treatment are then fed into a carbonization furnace and subjected to carbonization treatment. In order to improve the mechanical properties of carbon fibers, it is preferable to perform carbonization treatment at a maximum temperature of 1,200 to 2,000° C. in an inert atmosphere.

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

The carbon fiber bundle obtained in this way may be provided with a sizing agent in order to improve handleability and affinity with the matrix resin. Although it will not specifically limit as a kind of sizing agent as long as a desired characteristic can be acquired, For example, the sizing agent which has an epoxy resin, a polyether resin, an epoxy-modified polyurethane resin, and a polyester resin as a main component is mentioned. A well-known method can be used for provision of a sizing agent.

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

As described above, the present invention provides heat treatment in an oxidizing atmosphere by traveling in a hot air heating type flameproof furnace while conveying the acrylic fiber bundles arranged by adjoining a plurality of bundles by guide rollers installed on both sides of the flameproof furnace. As a method for producing a flame-resistant fiber bundle, the direction of hot air in the flame-resistant furnace is parallel to the running direction of the fiber bundle, and the contact ratio P between adjacent fiber bundles is 2 to 18%, thereby producing high-quality flame-resistant fibers. It becomes possible to produce efficiently without operation trouble.

Example

Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these. In addition, the evaluation method and measurement method of each characteristic followed the method described below.

<Measuring method of single fiber fineness of acrylic fiber bundle>

It was performed based on JIS　L　1013.

<Measurement of surface uneven structure of short fibers of acrylic fiber bundles>

Both ends of the short fibers of the acrylic fiber bundle were placed on a metal sample stand (20 mm diameter) for SPA400 with a scanning probe microscope “Epolead Service Inc. Article, product number: K-Y10200167") was fixed with carbon paste, and measurement was performed under the following conditions.

(Scanning probe microscope measurement conditions)

Apparatus: "SPI4000 Probe Station, SPA400 (Unit)" SII NanoTechnology Inc. My

Scanning mode: Dynamic force mode (DFM) (shape measurement)

Probe: SII NanoTechnology Inc. Article, "SI-DF-20"

Scanning range: 2.0 μm×2.0 μm and 600 nm×600 nm

Rotation: 90° (Scan in the direction perpendicular to the fiber axis direction)

Scanning speed: 1.0Hz

The number of pixels: 512*512

Measurement environment: room temperature, in the air

About one single fiber, one image was obtained under the said conditions, and image analysis was performed for the obtained image on the following conditions using the image analysis software (SPIWin) attached to a scanning probe microscope.

(Image analysis conditions)

The obtained shape image was subjected to "flat processing", "median 8 processing", and "tertiary inclination correction" to obtain an image obtained by fitting the curved surface to a flat surface. _{The average surface roughness (R a} ) and the maximum in-plane height difference (R _max ) from the surface roughness analysis of the plane-corrected image were calculated|required. Here, the average surface roughness (R _a ) from the surface roughness analysis and the maximum in-plane height difference (R _max ) used data in a scanning range of 600 nm in circumference length × 600 nm in fiber axis direction. R _a is calculated by the following formula.

[Wed 1]

Central plane: A plane parallel to the plane in which the deviation in height from the real surface is minimized and dividing the real surface into two equal volumes

f(x, y): difference in elevation between the real surface and the center surface

Lx, Ly：Size of XY plane

For measurement, shape measurement of 10 single fibers with a scanning probe microscope for one sample, average surface roughness (R _a ) and maximum height difference (R _max ) are obtained for each measurement image, and the average value of the average value of the sample It was set as the surface roughness (R _a ) and the maximum height difference (R _max ). Regarding the presence or absence of a surface concavo-convex structure extending 2 μm or more in the longitudinal direction of the fiber on the surface of the single fiber, the range of 2.0 μm in the circumferential direction of the single fiber in the AFM (atomic force microscope) mode was set to 2.0 μm in the fiber axis direction. The scan was repeated over and over, slowly and slowly, and the presence or absence was judged from the obtained measurement image.

(flat processing)

This is a process that removes distortion and waves in the Z-axis direction that appear in image data due to lift, vibration, or scanner creep, etc., and removes data distortion due to device causes in SPM (Scanning Probe Microscope) measurement.

(Median 8 processing)

In a 3x3 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 By substituting for , to obtain the effect of a filter such as smoothing or noise removal.

The median 8 process calculates the median value of the Z data of 9 points of S and D1 to D8, and substitutes S.

(3rd order tilt correction)

In the tilt correction, a curved surface is obtained and fitted by least squares approximation from all data of the image to be processed, and the inclination is corrected. (1st order) (2nd order) (3rd order) indicates the degree of a curved surface to be fitted, and a cubic curved surface is fitted in the 3rd order. The tertiary inclination correction process removes the curvature of the fibers of the data to obtain a flat image.

<Evaluation of the cross-sectional shape of the short fibers of the acrylic fiber bundle>

The ratio of the major axis to the minor axis of the fiber cross section of the short fibers constituting the fiber bundle (major axis/minor axis) was determined as follows.

After passing the fiber bundle for measurement in a tube made of a vinyl chloride resin having an inner diameter of 1 mm, it is cut into rounds with a knife to prepare a sample. Next, the sample was adhered to the SEM sample stand with the fiber cross-section facing up, and Au was sputtered to a thickness of about 10 nm, and then operated with an XL20 scanning electron microscope manufactured by Philips, with an acceleration voltage of 7.00 kV, operated The fiber cross section was observed under the condition of a distance of 31 mm, the major and minor diameters of the fiber cross section of the short fibers were measured, and the ratio of the major axis/minor axis was evaluated.

<Measuring method of hook drop length of acrylic fiber bundle>

Take out the acrylic fiber bundle by 120 mm, attach it to the upper part of the unloading device and untwist, and then hang a weight of 200 g on the lower part of the fiber bundle. A hook (a stainless steel wire of φ 1 mm, R=5 mm of the hook) is inserted at a point 1 cm below the fiber bundle to divide the fiber bundle into three, and the hook is lowered. The hook is adjusted by adding a weight so that the total mass is 10 g. Find the descending distance of the hook to the point where the hook is stopped by the entanglement of the fiber bundle. The number of tests was set to N=50, and the average value was made into the hook drop length.

<Measuring method of wind speed in flameproof furnace>

ANEMOMASTER high temperature anemometer Model 6162 manufactured by KANOMAX JAPAN INC. was used, and the average value of 30 measured values per second was used. A measuring probe is inserted from a measuring hole (not shown) on the side of the heat treatment chamber 3 at a position corresponding to the center of the guide rollers 4 on both sides of the flame-resistant furnace 1, and the oxidizing gas flowing in the horizontal direction wind speed was measured. Five places were measured in the width direction, and the average value was used.

<Measuring method of yarn width and amplitude of a running fiber bundle>

Measurement was performed at a position corresponding to the center of the guide rollers 4 on both sides of the flame-resistant furnace 1 at which the amplitude of the running fiber bundle is maximized. Specifically, a laser displacement meter LJ-G200 manufactured by Keyence Corporation was installed above or below the traveling fiber bundle, and the specific fiber bundle was irradiated with a laser. The distance between both ends of the fiber bundle in the width direction was taken as the width of the fiber bundle, and the amount of variation in the width direction at one end in the width direction was taken as the amplitude. Each measurement was performed for 5 minutes at a frequency of 1 time/60 seconds or more and an accuracy of 0.01 mm or less, and the width (Wy) (average value) and standard deviation σ of the amplitude of the fiber bundle were obtained, and the contact ratio P between adjacent fiber bundles described above was obtained. calculated.

In Table 1, the results of operability, quality, and productivity in each Example and Comparative Example are shown qualitatively. Excellent, good, and bad were evaluated according to the following criteria.

(operability)

Excellent: A very good level with an average of zero troubles per day, such as mixed fibers or fiber bundle breakage.

Good: A level at which continuous operation can be continued sufficiently, with troubles such as strand breakage and fiber bundle breakage occurring an average of several times per day.

Impossible: A level where continuous operation cannot be continued due to an average of several dozen troubles per day, such as a single island or fiber bundle breakage.

(quality)

Excellent: The number of fluffs of 10 mm or more on the fiber bundle that can be visually confirmed after leaving the flame-resistant process is an average of several pieces/m or less, and the fluff quality does not affect the passability in the process or high-order processability as a product at all. .

Good: The number of fluffs of 10 mm or more on the fiber bundle that can be visually confirmed after exiting the flame-resistant process is 10 pieces/m or less on average, and the fluff quality hardly affects the passability in the process or high-order processability as a product. .

Impossible: A level at which the number of fluffs of 10 mm or more on the fiber bundle that can be visually confirmed after exiting the flame-resistant process is tens/m or more on average, and the fluff quality adversely affects passability in the process or high-order processability as a product.

(productivity)

Excellent: A level where the manufacturing cost is sufficiently low (80% or less compared to “good”) and the production per unit time is sufficiently large (120% or more compared to “good”).

Good: The manufacturing cost is relatively low, and the output per unit time is relatively large.

Impossible: A level with a high manufacturing cost (more than 150% for “good”) or low production per unit time (60% or less for “good”).

(Example 1)

Single fiber fineness 0.11 tex, the surface of the single fiber in the circumferential direction of 2.0 μm and the fiber axis direction of 2.0 μm The surface uneven structure extending in the longitudinal direction of the fiber in the four directions is 2.5 μm, the major/minor diameter of the single fiber cross section is 1.04 A flame-resistant fiber bundle was obtained by arranging 100 to 200 acrylic fiber bundles (2) consisting of 20,000 short fibers and heat-treating them in a flame-resistant furnace (1). The amount of the silicone oil agent adhering to the acrylic fiber bundle was 0.5%, and the hook drop length of the acrylic fiber bundle was 250 mm. In addition, the horizontal distance (L') between the guide rollers 4 on both sides of the heat treatment chamber 3 of the flame resistant furnace 1 is 20 m, and the guide roller 4 is spaced at a predetermined interval in the range of 3 to 15 mm ( The pitch interval to be physically regulated) Wp was used as a grooved roller. 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 wind speed in the horizontal direction of the oxidizing gas was set to 3 m/sec. The running speed of the yarn was adjusted in the range of 1 to 15 m/min according to the flameproof furnace length (L) so that the flame resistance treatment time was sufficiently taken, and the process tension was adjusted in the range of 0.5 to 2.5 g/tex. .

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

At this time, the width (Wy) of the fiber bundle running at the top of the heat treatment chamber 3 of the flame-resistant furnace 1 and the standard deviation σ of the amplitude at the center of the heat treatment chamber of the fiber bundle were measured and statistically calculated adjacent fibers The contact rate P between bundles was 6%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fibers or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with very good operability and production efficiency. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without 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 flameproof furnace 1 was 15 m, and the contact ratio P between adjacent fiber bundles was 10%. did the same

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fibers or fiber bundle breakage occurred due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with very good operability. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without 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 flameproof furnace 1 was 30 m, and the contact ratio P between adjacent fiber bundles was 15%. did the same

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fibers or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with very good operability and production efficiency. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without fluff or the like.

(Example 4)

The same procedure as in Example 1 was performed 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 fibers or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with very good operability and production efficiency. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without 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 flameproof furnace 1 was 10 m, and the contact ratio P between adjacent fiber bundles was 5%. did the same

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fibers or fiber bundle breakage occurred due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with very good operability. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without fluff or the like.

(Example 6)

The same procedure as in Example 1 was performed 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 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fibers or fiber bundle breakage occurred due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with very good operability. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without fluff or the like.

(Example 7)

The same procedure as in Example 1 was performed except that the guide rollers 4 on both sides of the heat treatment chamber 3 of the flameproof furnace 1 were used as flat rollers, and the contact ratio P between adjacent fiber bundles was set to 14%.

Under the above conditions, during the flame-resistance treatment of the acrylic fiber bundle, there was little mixed fiber or fiber bundle breakage due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability and more productively. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little fluff and the like.

(Example 8)

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

Under the above conditions, during the flame-resistance treatment of the acrylic fiber bundle, there was little mixed fiber or fiber bundle breakage due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability and more productively. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little fluff and the like.

(Example 9)

The same procedure as in Example 1 was performed except that the amount of silicone oil agent adhered to the acrylic fiber bundle used was 4.0%, and the contact ratio P between adjacent fiber bundles was 6%.

Under the above conditions, during the flame-resistance treatment of the acrylic fiber bundle, there were few mixed 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 productively. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little fluff and the like.

(Example 10)

The same procedure was performed as in Example 1, except that the silicone 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-resistance treatment of the acrylic fiber bundle, there was little mixed fiber or fiber bundle breakage due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability and more productively. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little fluff and the like.

(Example 11)

The same procedure as in Example 1 was performed 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-resistance treatment of the acrylic fiber bundle, there was little mixed fiber or fiber bundle breakage due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability and more productively. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little fluff and the like.

(Example 12)

The same procedure as in Example 1 was performed except that the single fiber fineness of the used acrylic fiber bundle was 0.18 tex, and the contact ratio P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistance treatment of the acrylic fiber bundle, there was little mixed fiber or fiber bundle breakage due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability and more productively. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little 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 used as flat rollers, and comb guides are further installed at a position of 30 mm from the flat roller to the flame-resistant furnace, and the comb guides has a gap at regular intervals in the range of 3 to 15 mm in the width direction, and the pitch interval of the fiber bundle, which is physically regulated by the passage of the fiber bundle through the gap, is a predetermined interval (Wp) in the range of 3 to 15 mm The same procedure as in Example 1 was performed except that the contact ratio P between adjacent fiber bundles was 14%.

Under the above conditions, during the flame-resistant treatment of the acrylic fiber bundle, no fibers or fiber bundle breakage due to contact between the fiber bundles occurred, and the flame-resistant fiber bundle was obtained with very good operability and production efficiency. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, they were of very good quality without fluff or the like.

(Comparative Example 1)

The same procedure as in Example 1 was performed except that the contact ratio P between adjacent fiber bundles was set to 24%, for example, by reducing the spacing 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, by improving the yarn density, the production volume itself could be increased, but during the flame-resistant treatment of the acrylic fiber bundles, there were many mixed fibers or breakage of the fiber bundles due to contact between the fiber bundles, making it difficult to continue the operation. . In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of poor quality with a lot of fluff and the like.

(Comparative Example 2)

The same procedure as in Example 1 was performed except that the contact ratio P between adjacent fiber bundles was set to 1% by, for example, increasing the spacing 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 mixed fiber or fiber bundle breakage due to contact between the fiber bundles, and a flame-resistant fiber bundle was obtained with good operability. In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, it was of good quality with little fluff and the like. However, as a result, the number of fiber bundles that can be fed into the flameproof furnace 1 decreased, and the productivity was greatly reduced.

(Comparative Example 3)

The same procedure as in Example 3 was performed except that the contact ratio P between adjacent fiber bundles was set to 28%, for example, by reducing the spacing between the grooves of the guide rollers 4 on both sides of the heat treatment chamber 3 of the flameproof furnace 1 .

Under the above conditions, by improving the yarn density, the production volume itself could be increased, but during the flame-resistant treatment of the acrylic fiber bundles, there were many mixed fibers or breakage of the fiber bundles due to contact between the fiber bundles, making it difficult to continue the operation. . In addition, as a result of visually confirming the obtained flame-resistant fiber bundle and carbon fiber bundle, fluff and the like were of poor quality.

(Comparative Example 4)

The same procedure as in Example 3 was performed 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 flame-resistance treatment of the acrylic fiber bundles, mixed fibers or breakage of the fiber bundles due to contact between the fiber bundles occurred frequently, making it difficult to continue the operation. In addition, as a result of visually confirming the obtained flame-resistant fiber and carbon fiber, fluff and the like were very poor quality. Moreover, by setting the wind speed to 8 m/sec, the equipment cost of the blower 8 which made this possible increased, and the production cost 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 uses such as pressure vessels and windmills, and sports applications such as golf shafts, but the scope of application is is not limited to

1 Flameproof furnace
2 Acrylic fiber bundle
3 Heat treatment room
4 guide roller
5 hot air vents
6 hot air outlet
7 burner
8 blower
L Flameproof furnace length (effective flameproofing length of 1 pass)
Horizontal distance between L' guide rollers
Wp physically regulated pitch spacing
Wy Width of the running fiber bundle
t Gap between adjacent fiber bundles

Claims (9)

A method for producing flame-resistant fiber bundles in which acrylic fiber bundles arranged adjacent to each other are transported by guide rollers installed on both sides of the flame-resistant furnace, while running in a hot-air heating type flame-resistant furnace and heat-treated in an oxidizing atmosphere As, the direction of the hot air in the flameproof furnace is parallel to the running direction of the fiber bundle, and the contact ratio P between adjacent fiber bundles defined by the following formula (1) is 2 to 18%. .
P=[1-p(x)｛-t<x<t｝]×100 (1)
where P is the contact rate (%) between adjacent fiber bundles, t is the gap between adjacent fiber bundles (mm), 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 denotes a random variable with the center of the amplitude equal to zero. The method of claim 1,
The horizontal distance between the guide rollers is 14.5 m or more, the method for producing a flame-resistant fiber bundle. The method according to claim 1 or 2,
A method for producing a flame-resistant fiber bundle, wherein the wind speed of the hot air flowing through the flame-resistant furnace is 1.0 to 6.0 m/sec. The method according to any one of claims 1 to 3,
The method for producing a flame-resistant fiber bundle, wherein the guide roller has a yarn width regulating mechanism. The method according to any one of claims 1 to 4,
The surface of the short fibers of the acrylic fiber bundle has a surface concavo-convex structure extending 2.0 μm or more in the longitudinal direction of the fiber in the circumferential direction of 2.0 μm and the fiber axis direction of 2.0 μm, and the major/minor diameter of the cross section of the single fiber The ratio of 1.01 to 1.10, the method for producing a flame-resistant fiber bundle. The method according to any one of claims 1 to 5,
The hook drop length of the acrylic fiber bundle is 300 mm or less, the method for producing a flame-resistant fiber bundle. The method according to any one of claims 1 to 6,
The method for producing a flame-resistant fiber bundle, wherein the amount of the silicone oil agent adhering to the acrylic fiber bundle is 0.1 to 3.0 mass%. The method according to any one of claims 1 to 7,
The single fiber fineness of the acrylic fiber bundle is 0.05 to 0.22 tex, a method for producing a flame resistant fiber bundle. 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 subjected to pre-carbonization treatment at a maximum temperature of 300 to 1,000° C. in an inert atmosphere to produce a pre-carbonized fiber bundle And, a method of producing a carbon fiber bundle for carbonizing the pre-carbonized fiber bundle at a maximum temperature of 1000 ~ 2000 ℃ in an inert atmosphere.

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