WO2022203046A1

WO2022203046A1 - Carbon fiber bundle

Info

Publication number: WO2022203046A1
Application number: PCT/JP2022/014411
Authority: WO
Inventors: 祐太郎中村; 究太田
Original assignee: 三菱ケミカル株式会社
Priority date: 2021-03-26
Filing date: 2022-03-25
Publication date: 2022-09-29
Also published as: MX2023011242A; JPWO2022203046A1; EP4317552A1; CN117120676A; US20240018695A1

Abstract

Provided is a carbon fiber bundle with total fineness of 2 g/m or more. The variation rate of the fiber bundle thickness in the width direction of the fiber bundle is 30% or less. Provided is a method for producing carbon fiber bundles, involving: applying a sizing agent to a carbonized fiber bundle; drying same; subsequently bringing one surface and the opposite surface of the widthwise surfaces of the carbonized fiber bundle alternatively into contact with two or more parallel bars and passing the carbonized fiber bundle through the bars; and winding the carbonized fiber bundle around a bobbin.

Description

carbon fiber bundle

TECHNICAL FIELD The present invention relates to a carbon fiber bundle that can be easily handled during advanced processing even if the carbon fiber bundle has a large total fineness, and that yields a molded product in which the carbon fibers are uniformly distributed.
This application claims priority based on Japanese Patent Application No. 2021-052932 filed in Japan on March 26, 2021, the content of which is incorporated herein.

Carbon fiber has excellent specific strength and specific modulus, so it is widely used from sports and leisure goods to aerospace applications. In addition to sports applications such as golf club shafts and fishing rods and aircraft applications, it has been developed into so-called general industrial applications such as windmill components for power generation, automobile components, CNG tanks, seismic reinforcement of buildings, and ship components. A carbon fiber bundle having a large mass per unit (total fineness) is required.

When a carbon fiber bundle with a large total fineness is processed into a prepreg by the drum winding method or various composite materials are molded by the filament winding method, resin is applied to the carbon fiber bundle by the touch roll method. In the technology, there are parts with a high fiber content and parts with a low fiber content in the molded product, and the part with a low fiber content sometimes becomes the starting point of early breakage.

One of the causes is thought to be thickness unevenness in the width direction of carbon fiber bundles having a large total fineness. For carbon fiber bundles with a large total fineness, during the production process of the carbon fiber precursor fiber bundle, the firing process, the process of applying a sizing agent, etc., the adjacent process fiber bundles are prevented from contacting, entangling or sticking together. Therefore, it is necessary to restrict the width using a width restriction guide or the like. When passing through the width regulating guide, the fiber bundle is pushed from both sides, and unevenness in thickness tends to occur.
In addition, when the carbon fiber bundle is wound, unevenness in thickness tends to occur because the width is narrowed by the concavely curved guide.

In Patent Document 1, when winding 60,000 carbon fiber bundles, the fiber bundles are twisted 90 degrees at the traversing location, twisted back, and wound with a concavely curved guide, so that the carbon fibers at the time of unwinding A method for producing a wide carbon fiber bundle with a uniform yarn width and a large total fineness is disclosed.

Patent Document 2 discloses a method of reducing variations in yarn width by using a guide that stabilizes the yarn path when winding 36,000 carbon fiber bundles.

In Patent Document 3, 24,000 fiber bundles are baked, impregnated with a sizing agent, and brought into contact with a heat roller having a surface temperature of 120 to 140° C. for 15 to 30 seconds, thereby reducing the flatness of the cross section of the fiber bundle (carbon fiber bundle (ratio of width to thickness) of 40-90 and a drape value (softness of the carbon fiber bundle) of 50-100 mm.

Japanese Unexamined Patent Application Publication No. 2011-11830 Japanese Unexamined Patent Application Publication No. 2012-154000 JP 2011-252264 A

However, in Patent Document 1, as shown in the comparative example of the present application, the variation rate of thickness is large.

Patent Literatures

2 and 3 do not describe the variation rate of the thickness of the carbon fiber bundles, and are not controlled.
In the process of applying the sizing agent, the fabric passes through the comb guide, dries with a large variation in thickness, and is wound up, so the variation in thickness remains large.

The present invention solves the conventional problems, and even if the carbon fiber bundle has a large total fineness, it can be easily handled during advanced processing, and the carbon fiber is uniformly distributed and a molded product with a uniform fiber content can be obtained. An object of the present invention is to provide a carbon fiber bundle that can be

The carbon fiber bundle of the present invention has the following features.
[1] A carbon fiber bundle having a total fineness of 2 g/m or more and a thickness variation rate of 30% or less in the width direction of the fiber bundle.
[2] The carbon fiber bundle according to [1], wherein the number of single fibers is 20000 or more.
[3] The carbon fiber bundle according to [1] or [2], wherein the fiber bundle has an average thickness of 0.18 to 0.28 mm.
[4] The carbon fiber bundle according to any one of [1] to [3], wherein the width variation rate of the fiber bundle in the length direction of the fiber bundle is 13% or less.
[5] The carbon fiber bundle according to any one of [1] to [4], wherein the width of the fiber bundle is 13 to 18 mm [6] The flatness (width/average thickness) of the fiber bundle is 60 to 70 The carbon fiber bundle according to any one of [1] to [5].
[7] The carbon fiber bundle according to any one of [1] to [6], which has a cantilever value of 210 to 250 mm and a sticking property of 0.18 m or less.
[8] The carbon fiber bundle according to any one of [1] to [7], wherein the sizing agent is applied in an amount of 0 to 20% by mass.
[9] The carbon fiber bundle according to any one of [1] to [8], which has an interfiber dynamic friction coefficient of 0.2 or less.
[10] The carbon fiber bundle according to any one of [1] to [9], which has a coefficient of dynamic friction between fibers and metals of 0.18 or less.
[11] In an averaging member having two or more parallel bars arranged between a sizing agent dryer and a winder or a transfer device, the surface A of the carbonized fiber bundle and the surface opposite to the surface A A method for producing a carbon fiber bundle, comprising contacting each of B with the rod one or more times and passing the carbonized fiber bundle through the averaging member.
[12] The method for producing a carbon fiber bundle according to [11], wherein the distance between adjacent parallel bars is 15 to 50 mm.
[13] In the above-mentioned passing, the carbonized fiber bundle is twisted by 90° in the plane direction of the carbon fiber bundle in contact with the roller immediately before the parallel rod. The method for producing a carbon fiber bundle according to [11] or [12], in which the carbon fiber bundle is passed in contact with the
[14] In the passing, the maximum width of the carbonized fiber bundle in contact with the parallel bars is relative to the width of the carbonized fiber bundle in contact with the roller immediately before the parallel bars. The method for producing a carbon fiber bundle according to any one of [11] to [13], wherein the carbon fiber bundle is passed through so as to be 5 to 20% wider.
[15] The roller is located upstream from the parallel rod in the running direction of the carbonized fiber bundle, and the length direction of the roller is substantially perpendicular to the length direction of the parallel rod. , [13] or [14].
[16] The distance from the center of the roller to the center of the parallel bar is preferably 200 to 1500 mm at the shortest position, more preferably 500 to 1000 mm, [13] to [15] ] The production method according to any one of the above.
[17] In the passing, the carbonized fiber bundle is flat, and one surface A of the carbonized fiber bundle is brought into contact with the parallel rod positioned upstream in the traveling direction of the carbonized fiber bundle. After that, the other surface B of the carbonized fiber bundle is brought into contact with the parallel rod located downstream in the running direction of the carbonized fiber bundle, and the carbonized fiber bundle is passed through the averaging member. , the method for producing a carbon fiber bundle according to any one of [11] to [16].
[18] Any one of [11] to [17], including changing the orientation of the surface of the carbonized fiber bundle about the length direction of the carbonized fiber bundle before the passing. A method for producing the described carbon fiber bundle.
[19] In changing the direction of the surface, it is preferable to tilt the surface of the carbonized fiber bundle in the width direction within a range of 30° to 150° with the length direction of the carbonized fiber bundle as an axis; It is more preferable to tilt the surface of the carbonized fiber bundle in the width direction within the range of 45° to 135° with the length direction of the carbonized fiber bundle as the axis; As, it is more preferable to tilt the surface of the carbonized fiber bundle in the width direction within the range of 60 ° to 120 °; The manufacturing method according to [18], wherein it is particularly preferable to incline at approximately 90° in the direction.
[20] Changing the direction of the surface includes a roller positioned upstream of the two or more parallel rods in the running direction of the carbonized fiber bundle, and a roller positioned most upstream of the two or more parallel rods in the running direction of the carbonized fiber bundle. The manufacturing method according to [18] or [19], performed between positioned parallel bars.
[21] The manufacturing method according to any one of [11] to [20], which is a method for manufacturing the carbon fiber bundle according to any one of [1] to [10].

The carbon fiber bundle of the present invention also has the following features.
[1a] contacting one surface A of the carbonized fiber bundle with a first rod; and contacting the other surface B of the carbonized fiber bundle with a second rod. Production method.
[2a] The manufacturing method according to [1a], including changing the orientation of the surface of the carbonized fiber bundle with the longitudinal direction of the carbonized fiber bundle as an axis.
[3a] In changing the orientation of the surface, it is preferable to tilt the surface of the carbonized fiber bundle in the width direction within a range of 30° to 150° with the length direction of the carbonized fiber bundle as an axis; It is more preferable to tilt the surface of the carbonized fiber bundle in the width direction within the range of 45° to 135° with the length direction of the carbonized fiber bundle as the axis; As, it is more preferable to tilt the surface of the carbonized fiber bundle in the width direction within the range of 60 ° to 120 °; The manufacturing method according to [2a], wherein it is particularly preferable to incline at approximately 90° in the direction.
[4a] The manufacturing method according to [2a] or [3a], wherein changing the orientation of the surface; contacting the first rod; and contacting the second rod are performed in this order. .
[5a] Changing the direction of the surface; contacting the first rod; and contacting the second rod in this order, so that the carbon fiber bundle before performing these steps The manufacturing method according to any one of [2a] to [4a], wherein the width of the carbon fiber bundle after these steps is widened to be within the range of 105 to 120% with respect to the width of 100%.
[6a] The manufacturing method according to any one of [1a] to [5a], which is a method for manufacturing the carbon fiber bundle according to any one of [1] to [10].

Even if the carbon fiber bundle of the present invention has a large total fineness, it is easy to handle during advanced processing, and a molded product in which the carbon fibers are uniformly distributed can be obtained.

FIG. 4 is a diagram showing a method of calculating a variation rate of thickness of a carbon fiber bundle; FIG. 4 is a diagram showing an example of an apparatus used for measuring the dynamic friction coefficient between fibers and the dynamic friction coefficient between fibers and metals of carbon fiber bundles. FIG. 4 is a diagram showing an example of an averaging member used for producing the carbon fiber bundles of the present invention; 1 is a perspective view showing an example of a state in which carbonized fiber bundles of the present invention pass through parallel bars. FIG. FIG. 4 is a top view showing an example of a state in which the carbonized fiber bundle of the present invention passes through parallel bars; It is a figure which shows an example of the arrangement place of the averaging member of this invention. It is a figure which shows an example of the winder of this invention.

The carbon fiber bundle of the present invention is a carbon fiber bundle having a total fineness of 2 g/m or more and a thickness variation rate of 30% or less in the width direction of the fiber bundle.

The carbon fiber bundle of the present invention is a carbon fiber bundle having a total fineness of 2.0 g/m or more. Since the productivity of carbon fiber bundles depends on the total fineness of the carbon fiber bundles, carbon fiber bundles having a large mass per unit length can be produced efficiently. More preferably, the total fineness is 2.5 g/m or more, and most preferably 3 g/m or more.
When the total fineness of 2.0 g/m is expressed in dtex, it is 20000 dtex.

The variation rate of the thickness of the carbon fiber bundle in the width direction of the fiber bundle of the present invention (hereinafter, "the variation rate of the thickness of the carbon fiber bundle in the width direction of the fiber bundle" is simply referred to as the "thickness variation rate". ) can be measured by the method described later.
The carbon fiber bundle of the present invention preferably has a variation rate of thickness of the carbon fiber bundle of 30% or less. By setting the variation rate of the thickness of the carbon fiber bundle to 30% or less, it is possible to produce a compact in which the carbon fibers are uniformly distributed. The variation rate of the thickness of the carbon fiber bundle is more preferably 20% or less, more preferably 15% or less.

The carbon fiber bundle of the present invention preferably has 20,000 or more single fibers.
As the number of single fibers increases, the productivity increases, which is preferable. In addition, the greater the number of single fibers, the greater the variation in thickness, so the carbon fiber bundle manufacturing method of the present invention can be easily applied. From these points of view, the number of single fibers is more preferably 30,000 or more, and even more preferably 40,000 or more.

The carbon fiber bundle of the present invention preferably has an average thickness of 0.18 to 0.28 mm.
If the average thickness of the fiber bundle is 0.18 mm or more, the width of the carbon fiber bundle having a large total fineness does not become too large, and the handleability tends to be good. can be made smaller.
From these points of view, the average thickness of the fiber bundle is more preferably 0.20 to 0.27 mm, still more preferably 0.21 to 0.25 mm.

The carbon fiber bundle of the present invention preferably has a width variation rate of 13% or less in the length direction of the fiber bundle. When the fluctuation rate of the width of the fiber bundle is 13% or less, it becomes easy to produce a molded body in which the carbon fibers are uniformly distributed. The variation rate of the thickness of the carbon fiber bundle is more preferably 12% or less, and even more preferably 11% or less.
The fluctuation rate of the width of the carbon fiber bundle in the length direction of the fiber bundle of the present invention can be measured by the method described later.

(Average value of carbon fiber bundle thickness, thickness variation rate and carbon fiber width, method of measuring width variation rate)
The measurement is performed under an environment of room temperature of 25° C. and humidity of 50%. With a tension of 0.40 cN/tex applied to the carbon fiber bundle, it is brought into contact with a free rotating roller with a diameter of 60 mm so that the embrace angle θ = π (rad), 10 m / min, and the rotation roller is in the middle of the embrace angle. A two-dimensional line laser displacement meter is installed on the point, and displacement data are simultaneously acquired in a row at equal intervals of 0.1 mm in the width direction of the carbon fiber bundle. Excluding the measurement points in the regions at both ends where the displacement is 5% or less of the maximum value, calculate the average value and standard deviation of the displacement (Fig. 1), and calculate the rate of variation from the ratio of the two. Let the average value of the said displacement be an average value of thickness. At that time, the width of the range for calculating the average value and standard deviation of the thickness is recorded as the width of the fiber bundle. The average value of the variation rate of each point obtained by measuring 300 points at intervals of 2 cm in the longitudinal direction of the carbon fiber bundle is referred to as the "thickness variation rate in the width direction of the carbon fiber bundle" of the carbon fiber bundle to be measured. do. In addition, the average value and standard deviation of the width of the 300 fiber bundles obtained at the same time are calculated, and the ratio of the two is defined as the "variation rate of the width in the length direction of the carbon fiber bundle" of the carbon fiber bundle to be measured, Let the average value of the width of the fiber bundle be the width of the carbon fiber.

The carbon fiber bundle of the present invention preferably has a width of 13 to 18 mm.
If the width of the carbon fiber is 13 mm or more, the thickness does not become too large, and the variation rate of the thickness can be easily reduced.
From these points of view, the width of the carbon fiber bundle is more preferably 13.5 to 16.5 mm, even more preferably 14 to 17 mm.

The flatness (width/average thickness) of the carbon fiber bundle of the present invention is preferably 60-70.
If the flatness of the carbon fiber bundle is 60 or more, the thickness of the carbon fiber bundle will not be too large, and if it is 70 or less, the width will not be too wide and the handleability will be good.
From these points of view, the flatness is more preferably 61-69, more preferably 62-68.

The carbon fiber bundle of the present invention preferably has a cantilever value of 210 to 250 mm.
If the cantilever value is 210 mm or more, the bundling property of the carbon fiber bundle running on the yarn path can be ensured during high-order processing, and resin impregnation is performed from the creel housing the carbon fiber bundle when the carbon fiber bundle is impregnated with resin. It is possible to prevent the occurrence of fluff on the yarn path leading to the process. If the cantilever value is 250 mm or less, it is possible to ensure good openability between the carbon fiber filaments during advanced processing. More preferably, the cantilever value is 220 mm or more and 240 mm or less.
The cantilever value of the carbon fiber bundle can be measured by the method described later.

(Method for measuring cantilever value of carbon fiber bundle)
The measurement is performed under an environment of room temperature of 25° C. and humidity of 50%. About 1 m of carbon fiber bundle is unwound from the carbon fiber bundle package without tension and cut out. In order to eliminate the influence of the curl of the cut carbon fiber bundle, one end of the carbon fiber bundle was fixed, the other end was attached with a weight of 13 mg / tex, and held in a vertically suspended state for 30 minutes. , and cut out 30 cm so as not to include the end, and use it as a carbon fiber bundle for testing. A state in which the test carbon fiber bundle is not twisted or disturbed on the horizontal surface of a measuring table having a horizontal surface and a slope with an inclination angle of 45 degrees that is inclined downward from one end (linear) of the horizontal surface. , and the end (linear) of the test carbon fiber bundle is aligned with the boundary line between the slope and the horizontal surface. A metal pressing plate is placed on the test carbon fiber bundle, and the edge (linear) of the pressing plate is aligned with the boundary line. Next, the holding plate is moved in the horizontal direction toward the slope at a speed of 0.5 cm/sec, and the movement of the holding plate is stopped when the end of the test carbon fiber bundle comes into contact with the slope. Measure the shortest distance between the point where the end of the bundle touches the slope and the boundary line. The measurement is performed once for each of the five test carbon fiber bundles, and the simple average value of the obtained numerical values is taken as the cantilever value of the carbon fiber bundle.

The carbon fiber bundle of the present invention preferably has stickiness of 0.18 m or less.
If the sticking property is 0.18 m or less, the bundling property of the carbon fiber bundle running on the yarn path can be ensured during high-order processing, and the carbon fiber bundle is accommodated when impregnating the carbon fiber bundle with the matrix resin. It is possible to prevent the occurrence of fluff on the yarn path from the creel to the resin impregnation step. The sticking property is more preferably 0.16 m or less.
The sticking property of the carbon fiber bundle can be measured by the method described later.

(Method for measuring sticking property of carbon fiber bundle)
The measurement is performed at room temperature of 25° C., humidity of 50%, and windless environment. A spool with a diameter of 20 to 25 cm on which the carbon fiber bundle is wound is kept so that its axial direction is horizontal, and the carbon fiber bundle is unwound without applying tension, and the height of the center of the shaft of the spool is 10 cm. Cut the carbon fiber bundle at the bottom position. Next, from the contact start point between the fiber bundle unwound by the unwinding of the carbon fiber bundle and the spool, the direction in which the carbon fiber bundle is wound obliquely around the spool advances upward, and the spool is vertically wound. Stand upright and hold without vibration. After holding for 10 minutes, the carbon fiber bundle is cut off at a position 10 cm from the contact start point with the spool, and the length of the carbon fiber bundle peeled off from the spool is measured. The measurement is performed three times, and the simple average value of the obtained numerical values is used as the measured sticking property of the carbon fiber bundle.

The carbon fiber bundle of the present invention preferably has a sizing agent adhesion amount of 0 to 20% by mass.
If the amount of the sizing agent adhered is 20% by mass or less, the fiber bundles are less likely to stick to each other, and the variation rate of the thickness can be easily reduced.
From this viewpoint, the adhesion amount of the sizing agent is more preferably 15% by mass or less, further preferably 10% by mass or less, and most preferably 5% by mass or less.
The lower limit value is preferably 0% by mass from the viewpoint of thickness unevenness, but is more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, from the viewpoint that the carbon fiber bundles are gathered together to improve handleability.

The carbon fiber bundle of the present invention preferably has a dynamic friction coefficient between fibers of 0.2 or less.
If the coefficient of dynamic friction between fibers is 0.2 or less, the frictional force between single yarns is reduced, so the occurrence of fluff due to friction between carbon fiber filaments is suppressed, and the fluff, called ringer, surrounds the bobbin to produce carbon fiber. It is possible to prevent the phenomenon that the bundle cannot be unwound. 0.17 or less is more preferable.
The dynamic friction coefficient between fibers can be measured by the method described later.

(Method for measuring dynamic friction coefficient between fibers)
An example of a measuring device is shown in FIG. A carbon fiber bundle 1 to be measured is tightly wound and fixed on a drive roller 1 having a diameter of 30 mm having a heating device, with a winding angle in the range of 0.1 to 0.5 mm so that the thickness is uniform. With the driving roller 1 stopped, the carbon fiber bundle 2 to be measured is arranged so that the embracing angle θ=π (rad) on the yarn path shown in FIG. The surface temperature of the driving roller 1 is set at 30°C. A weight 4 (T1=0.53 g/tex) is attached to one end of the carbon fiber bundle 2 placed on the yarn path, and a spring balance 5 is attached to the opposite end. The drive roller 1 is rotated at a rotation speed of 60 rpm, and the central value T2 (g) of the indicated value of the spring balance 5 after one minute is read. The measurement is performed twice, and the dynamic friction coefficient between fibers is calculated from the obtained average value of T2.
Dynamic friction coefficient between fibers = π ^-1 ln ((average value of T2) / (T1 x total fineness))

The carbon fiber bundle of the present invention preferably has a fiber-to-metal dynamic friction coefficient of 0.18 or less.
If the fiber-to-metal dynamic friction coefficient is 0.18 or less, the frictional force between the metal guide and the carbon fiber filament is reduced, so the abrasion resistance is improved. The coefficient of dynamic friction between fibers and metals is more preferably 0.16 or less.
The coefficient of dynamic friction between fibers and metals can be measured by the method described later.

(Method for measuring dynamic friction coefficient between fiber and metal)
An example of a measuring device is shown in FIG. With the driving roller 1 having a diameter of 30 mm having a heating device stopped, the carbon fiber bundle 2 to be measured is arranged so that the embrace angle θ=π (rad) on the yarn path shown in FIG. In the method for measuring the dynamic friction coefficient between fibers and metals, unlike the above-described method for measuring the dynamic friction coefficient between fibers, the carbon fiber bundle 2 to be measured is simply placed on the drive roller 1 and the carbon fiber bundle 1 is not wound. The driving roller 1 is a metal roller (material: S45C-H, mesh 400 with satin finish), and the surface temperature is 30°C. A weight 4 (T3=0.53 g/tex) is attached to one end of the carbon fiber bundle arranged on the yarn path, and a spring balance 5 is attached to the opposite end. The drive roller 1 is rotated at a rotation speed of 60 rpm, and the central value T4 (g) of the indicated values of the spring balance after 5 minutes is read. The measurement is performed twice, and the fiber-to-metal dynamic friction coefficient is calculated from the obtained average value of T4.
Fiber-to-metal dynamic friction coefficient = π ^-1 ln ((average value of T4) / (T3 x total fineness))

(Manufacturing method of carbon fiber bundle)
The method for producing the carbon fiber bundle of the present invention is not particularly limited, and for example, it can be produced by a method including the following steps (a) to (i).
(a) A step of spinning and solidifying the spinning dope to obtain a coagulated yarn.
(b) A step of washing and drawing the coagulated thread to obtain a precursor process thread.
(c) Precursor step A step of applying an oil agent to the yarn and drying and densifying it to obtain a precursor fiber bundle.
(d) A step of subjecting the precursor fiber bundle to a flameproof treatment to obtain a flameproof fiber bundle.
(e) A step of carbonizing the flameproof fiber bundle to obtain a carbonized fiber bundle.
(f) a step of subjecting the carbonized fiber bundle to a surface oxidation treatment;
(g) A step of applying a sizing agent to the carbonized fiber bundle after the surface oxidation treatment.
(h) A step of homogenizing the carbonized fiber bundle after applying the sizing agent.
(i) A winding step of winding around a bobbin to obtain a carbon fiber bundle.

FIGS. 6 and 7 show a general process diagram of the process transition for applying the sizing agent to the carbonized fiber bundles, and the averaging member in the present invention is arranged in the broken line portion indicated by A in FIG.

In the step (a), the raw spinning solution is spun and coagulated to obtain a coagulated yarn.
The spinning dope used in step (a) is not particularly limited. An organic solvent solution of an acrylonitrile copolymer is preferable from the viewpoint of developing mechanical properties such as strength of carbon fibers. The acrylonitrile copolymer is a polymer having 90% by mass or more of repeating units derived from acrylonitrile, preferably a copolymer having 95% by mass or more of repeating units derived from acrylonitrile.

In the acrylonitrile copolymer, repeating units derived from other than acrylonitrile (hereinafter referred to as "copolymerization component") include, for example, acrylic acid, methacrylic acid, itaconic acid, acrylic acid derivatives such as methyl acrylate, methacrylic acid Methacrylic acid derivatives such as methyl, acrylamide derivatives such as acrylamide, methacrylamide, N-methylolacrylamide and N,N-dimethylacrylamide, and vinyl monomers such as vinyl acetate can be mentioned. The copolymerization component may be one kind, or two or more kinds. A vinyl monomer having one or more carboxyl groups is preferred as the copolymer component.

The polymerization method for producing the acrylonitrile copolymer is not particularly limited, and examples thereof include solution polymerization in an organic solvent that dissolves the acrylonitrile copolymer and precipitation polymerization in water.

Examples of organic solvents used in the spinning dope include polar organic solvents such as dimethylacetamide, dimethylsulfoxide, and dimethylformamide. Since the spinning stock solution obtained using these polar organic solvents does not contain metal elements, the content of metal elements in the resulting carbon fiber bundle can be reduced. The solid content concentration of the spinning dope is preferably 20% by mass or more.

The spinning method may be either wet spinning or dry-wet spinning. For example, in wet spinning, a filament is spun into a temperature-controlled coagulating liquid from a spinneret having a large number of discharge holes and coagulated, and a large number of formed filaments are collectively collected as a coagulated yarn. As the coagulating liquid, a known one such as a mixed solution of a polar organic solvent used for the spinning dope and water can be used.

In step (b), the coagulated yarn obtained in step (a) is washed and drawn to obtain a precursor process yarn. Any known washing method may be used as long as the solvent can be removed from the coagulated yarn. A denser fibril structure can also be formed by drawing the fibers in the air or in an aqueous solvent solution having a lower solvent concentration and a higher temperature than the coagulated liquid before washing the coagulated yarn. After washing the coagulated yarn, the fibers are drawn in hot water to further enhance the orientation of the acrylonitrile copolymer in the fibers.

In the step (c), an oil agent is applied to the precursor process yarn obtained in the step (b), dried and densified to obtain a precursor fiber bundle. As the oil agent, a known one can be used, and examples thereof include an oil agent composed of a silicone compound such as silicone oil.

The method of drying and densification is not particularly limited, as long as the precursor process thread to which the oil agent is adhered is dried by a known drying method to be densified.

The fibers after drying and densification are drawn by 1.8 to 6 times in pressurized steam at 130 to 200 ° C., between heating rollers or on a heating plate, as necessary, to improve the orientation of the precursor fiber bundle. Further refinement and densification may be performed.

In step (d), the precursor fiber bundle obtained in step (c) is subjected to a flameproof treatment to obtain a flameproof fiber bundle.
As the flameproof treatment, for example, a method of passing through a hot blast oven set so that the temperature rises stepwise from 220 to 260° C. for 30 to 100 minutes can be mentioned. The fibers may be stretched during the flameproofing treatment. Moderate elongation in the flameproofing treatment can maintain or improve the orientation of the fibril structure forming the fibers, making it easier to obtain carbon fiber bundles with excellent mechanical properties. It is preferable that the density of the single fibers constituting the flameproof fiber bundle is 1.33 to 1.40 g/cm ³ .

In step (e), the flameproof fiber bundle obtained in step (d) is carbonized to obtain a carbonized fiber bundle. As the carbonization treatment, for example, a first carbonization treatment in which the maximum temperature is set to 600° C. to 800° C. in an inert atmosphere such as nitrogen, and a maximum temperature of 1200° C. to 2000° C. in an inert atmosphere such as nitrogen. A treatment including a second carbonization treatment in which heat treatment is performed as ° C. can be mentioned.

The treatment time for the first carbonization treatment is preferably 1 to 3 minutes. In the first carbonization treatment, it is preferable to perform an elongation operation of 1% to 5% from the viewpoint of promoting the regular orientation of the carbon structure.

The treatment time in the second carbonization treatment is preferably 1.3 to 5 minutes. The strength and elastic modulus of the carbon fiber bundle can be controlled by the temperature and treatment time in the second carbonization treatment. In the second carbonization treatment, a large shrinkage occurs in the fibers, so the elongation rate is preferably -5% to -2%. After the second carbonization treatment, a third carbonization treatment may be additionally performed as necessary.

In step (f), the carbonized fiber bundle obtained in step (e) is subjected to surface oxidation treatment. A known method can be employed for the surface oxidation treatment, and examples thereof include electrolytic oxidation, chemical oxidation, and air oxidation. Among them, electrolytic oxidation is preferred.

In step (g), a sizing agent is applied to the carbonized fiber bundle obtained in step (f). The sizing agent can be applied to the carbonized fiber bundle by applying a solution in which the sizing agent is dissolved in an organic solvent, or an emulsion in which the sizing agent is dispersed in water using an emulsifier or the like, to the carbonized fiber bundle and then drying.
Before and after applying the sizing agent, it is preferable to separate adjacent carbonized fiber bundles with a comb guide or the like so that they do not stick together.

A sizing agent is selected that has a dynamic friction coefficient between fibers of 0.20 or less and a dynamic friction coefficient between fibers of 0.18 or less, measured by the method described in the specification. There is no particular limitation as long as the sizing agent has a coefficient of dynamic friction between fibers of 0.20 or less and a coefficient of dynamic friction between fibers and metals of 0.18 or less.

The amount of sizing agent attached to the carbon fiber bundle can be adjusted by adjusting the concentration of the sizing agent in the solution or emulsion, or by adjusting the amount of squeezing after application of the solution or emulsion. The amount of the sizing agent attached to the carbon fiber bundle is preferably 0.4 to 2.0% with respect to the total mass of the carbon fiber bundle to which the sizing agent is attached. The method of drying after application of the solution or emulsion is not particularly limited, and can be carried out using, for example, hot air, a hot plate, a heating roller, an infrared heater, or the like.

In the step (h), before winding the carbonized fiber bundle obtained in the step (g), the carbonized fiber bundle is widened using a carbonized fiber bundle averaging member, and the fiber bundle is Uniform thickness.
It is preferable that the averaging member applies an external force to the fiber bundle to widen the width of the fiber bundle, thereby loosening the single fibers so that the single fibers can be easily moved. Friction between the fiber and the metal member, air flow, vibration, or the like is used as a means for applying an external force to the single fiber.
When producing a large number of carbon fiber bundles, it is preferable to spread in a direction to avoid contact with adjacent fiber bundles. The averaging member constantly applies a physical external force to the single fibers that make up the running fiber bundle, and the single fibers change their positions within the fiber bundle, resulting in a carbon fiber bundle with a good cantilever value and sticking properties. is obtained.

The averaging member used to produce the carbon fiber bundles of the present invention may be any means as long as it constantly applies a physical external force to single fibers. It is sufficient if the positions of the single fibers constituting the carbonized fiber bundle can be shifted with respect to each other by a physical external force while avoiding contact between them, so that the distribution can be made uniform.

The shape of the averaging member that applies an external force to the single fibers by the friction between the fibers and the metal member is not particularly limited. As the averaging member, a parallel-bar guide, a comb guide, or the like can be used, but a parallel-bar guide capable of efficiently applying an external force to single fibers and capable of adjusting the applied external force is preferable. An example of a parallel bar guide is shown in FIG. The parallel bar guide is preferably two straight bars with smooth surfaces held in parallel.

In the method for producing a carbon fiber bundle of the present invention, the surface of the carbonized fiber bundle is A and a surface B opposite said surface A are each brought into contact with said bar one or more times.
By doing so, the fiber bundle spreads in the width direction, and the sticking of the single fibers is easily loosened.
It is sufficient for the rod to have parallel surfaces with which the carbonized fiber bundles come into contact. The shape of the rod is not particularly limited, such as a round shape or a square shape. is preferred.
Since the fiber bundle is loosened when the surface A and the surface B come into contact with the bar once, respectively, the variation rate of the thickness can be easily reduced.
From the point of view of loosening the fiber bundle, the first rod contacts the surface A and the second rod contacts the surface B, so that the surface A, the surface B, the surface A, and the surface B are alternately contacted in this order. is preferred.

In the carbon fiber bundle manufacturing method of the present invention, it is preferable that the distance between adjacent parallel bars is 15 to 50 mm.
If the distance between the parallel bars adjacent to each other is 15 mm or more, the carbonized fiber bundle can be easily passed through, and if the distance is 50 mm or less, the effect of widening the width is likely to be obtained.
From these points of view, the distance between adjacent parallel bars is more preferably 17 to 45 mm, more preferably 19 to 40 mm.

In the method for producing a carbon fiber bundle of the present invention, the carbonized fiber bundle is twisted by 90° in the plane direction of the carbon fiber bundle in contact with the roller immediately before the parallel rod. It is preferable to let it pass through in contact with .
By twisting the carbonized fiber bundle by 90°, an external force is applied to the carbonized fiber bundle, and the width of the carbonized fiber bundle tends to widen. Moreover, when a plurality of carbonized fiber bundles are running in parallel, it is preferable because the adjacent carbonized fiber bundles do not come into contact with each other, which saves space.

In the method for producing a carbon fiber bundle of the present invention, the maximum width of the carbonized fiber bundle in contact with the parallel bars is the width of the carbonized fiber bundle in contact with the roller immediately before the parallel bars. 5-20% wider is preferred.
In addition, the rod is preferably fixed, but the resistance of the rod is such that the surface speed of the rod becomes slower than the speed of the fiber bundles so that frictional force is generated between the carbon fiber bundles and the fiber bundles and an external force is applied. , the rod may rotate.

In the winding process of step (i), the carbon fiber bundle is wound on the winding core while being traversed to obtain a spool of the carbon fiber bundle. The method of winding the carbon fiber bundle may be any method as long as it can wind the carbon fiber bundle onto the spool without twisting or the like. There is a free-roll guide 11 with a depression in front of the traverse, and although the fiber bundle narrows, the presence of the averaging member of the present invention does not cause thickness unevenness.
Also, instead of winding it on a spool, it may be transferred to a packing box or the like.

The present invention will be specifically described below with reference to examples, but the following examples are not intended to limit the scope of the present invention.

(Method for measuring amount of rubbed fluff)
The carbon fiber bundle was unwound from the bobbin with an unwinding tension of 0.40 cN/tex and a running speed of the carbon fiber bundle of 20 m/min. -mirror surface treatment) at an embrace angle of 15° and rubbed. After the carbon fiber bundle has passed 500 m, the running is stopped, and fluff deposited on the stainless rod is collected and measured for mass. The measurement was performed 3 times, and the simple average value of the obtained numerical values was taken as the rubbed fluff amount.

[Examples 1 to 10]
(Manufacture of carbon fiber bundles)
A precursor fiber bundle with a single fiber fineness of 1.33 dtex and a single fiber number of 50,000 is heated in air at 240°C to 260°C in a hot air circulation type flameproofing furnace at an elongation rate of -3.9% for 66 minutes. After obtaining a flame-resistant fiber bundle by performing flame-resistant treatment, pre-carbonization treatment is performed for about 1.5 minutes at an elongation rate of 1.5% in a heat treatment furnace with a maximum temperature of 700 ° C. in a nitrogen atmosphere. Then, carbonization treatment was carried out for about 1.5 minutes in a heat treatment furnace with a maximum temperature of 1350° C. in a nitrogen atmosphere at an elongation rate of −4.5% to obtain a carbonized fiber bundle.

Next, the carbonized fiber bundle is run in a 5% by mass aqueous solution of ammonium bicarbonate, and the carbonized fiber bundle is used as an anode, and an electric current is applied between the opposite electrode so that the amount of electricity is 30 coulombs per 1 g of the carbonized fiber bundle. After that, it was washed with hot water at 90°C and dried. Then, it was immersed in an aqueous dispersion containing 6.0% of a sizing agent containing bisphenol A type epoxy resin as a main component. Next, after passing through a nip roller, the carbonized fiber bundle was dried by contacting with a roller heated to 150° C. for 30 seconds to obtain a carbonized fiber bundle with a sizing agent of 1.6 wt % attached to the carbon fiber bundle. rice field.

The process of averaging the carbonized fiber bundles with the sizing agent attached was run. As the averaging member, parallel bars were used in which two cylinders with a diameter of 5 mm were arranged in parallel with a center-to-center distance of 30 mm, and the parallel bars were arranged perpendicular to the plane having the width direction of the fiber bundle. The installation angle of the parallel bars was adjusted so that the gap between the cylinders was 0 mm when viewed from the running direction of the carbonized fiber bundle. The carbonized fiber bundle is twisted 90° in the axial direction by the parallel rods, the width direction of the fiber bundle is set as the vertical direction, and the carbonized fiber bundle is passed in contact with the parallel rods, and then twisted back by 90° with the horizontal roller. , the carbon fiber bundle was wound onto 10 spools.

Various evaluations of the carbon fiber bundles thus obtained were performed. In order to measure the thickness of the carbon fiber bundle, a two-dimensional laser displacement meter (manufactured by KEYENCE CORPORATION, sensor head LJ-V7080, controller LJ-V7000) is used to measure the thickness data simultaneously in a row in the width direction of the carbon fiber bundle. obtained. Table 1 shows the results.
In the example, the variation rate of the thickness of the carbon fiber bundle was less than half that of the comparative example, which was a conventional process without the parallel bars as the averaging members, and the result was good.
In addition, the cantilever value and sticking property are lower than those of the comparative example, indicating that the fiber bundles are loosened.
Since the carbon fiber bundles obtained in these examples have a small variation in the thickness of the fiber bundle in the width direction of the fiber bundle, a fixed amount of resin is applied to a unit amount of carbon fiber by a touch roll method. Therefore, the fiber content in the molded product becomes uniform.

[Comparative Examples 1 to 4]
A carbon fiber bundle was obtained in the same manner as in Example 1, except that the carbon fiber bundle was wound on four spools at the winding unit without running the step of homogenizing the carbon fiber bundle after the sizing step. rice field. Various evaluation results are shown in Table 1. The resulting carbon fiber bundle was poor in that the thickness variation rate of the carbon fiber bundle was greater than 35%.

1: drive roller 2: carbon fiber bundle 3: free roller 4: weight 5: spring scale 6: parallel bars (averaging member)
7: carbonized fiber bundle 8: sizing agent bath 9: dryer 10: winder 11: free roll A: location of averaging member

Claims

A carbon fiber bundle having a total fineness of 2 g/m or more and a variation rate of the thickness of the fiber bundle in the width direction of the fiber bundle of 30% or less.
The carbon fiber bundle according to claim 1, wherein the number of single fibers is 20000 or more.
The carbon fiber bundle according to claim 1 or 2, wherein the average thickness of the fiber bundle is 0.18-0.28 mm.
The carbon fiber bundle according to any one of claims 1 to 3, wherein the width variation rate of the fiber bundle in the length direction of the fiber bundle is 13% or less.
The carbon fiber bundle according to any one of claims 1 to 4, wherein the width of the fiber bundle is 13 to 18 mm
The carbon fiber bundle according to any one of claims 1 to 5, wherein the flatness (width/average thickness) of the fiber bundle is 60-70.
The carbon fiber bundle according to any one of claims 1 to 6, which has a cantilever value of 210 to 250 mm and a sticking property of 0.18 m or less.
The carbon fiber bundle according to any one of claims 1 to 7, wherein the amount of sizing agent attached is 0 to 20% by mass.
The carbon fiber bundle according to any one of claims 1 to 8, which has an interfiber dynamic friction coefficient of 0.2 or less.
The carbon fiber bundle according to any one of claims 1 to 9, which has a fiber-to-metal dynamic friction coefficient of 0.18 or less.
In an averaging member having two or more parallel bars arranged between a sizing agent dryer and a winder or a transfer device, the surface A of the carbonized fiber bundle and the surface B opposite to the surface A are respectively A method of producing a carbon fiber bundle, comprising passing the carbonized fiber bundle through the averaging member in contact with the rod one or more times.
The method for producing a carbon fiber bundle according to claim 11, wherein the distance between adjacent bars of the parallel bars is 15 to 50 mm.
In the passing, the carbonized fiber bundle is brought into contact with the parallel rod in a state where the surface direction of the carbon fiber bundle in contact with the roller one ahead from the parallel rod is twisted by 90 °. 13. The method for producing a carbon fiber bundle according to claim 11 or 12, wherein the carbon fiber bundle is passed through.
In the passing, the maximum width of the carbonized fiber bundles in contact with the parallel bars is 5 to 20% wider than the width of the carbon fiber bundles in contact with the roller immediately before the parallel bars. The method for producing a carbon fiber bundle according to any one of claims 11 to 13, wherein the carbon fiber bundle is passed through as
3. The roller is positioned upstream of the parallel rods in the running direction of the carbonized fiber bundles, and the length direction of the rollers and the length direction of the parallel rods are substantially perpendicular to each other. 15. The production method according to 13 or 14.
Any one of claims 13 to 15, wherein the distance from the center of the roller to the center of the parallel bars is preferably 200 to 1500 mm, more preferably 500 to 1000 mm at the shortest position. Method of manufacture as described.
In the passing, the carbonized fiber bundle is flat, and one surface A of the carbonized fiber bundle is brought into contact with the parallel rod located upstream in the traveling direction of the carbonized fiber bundle, The carbonized fiber bundle is caused to pass through the averaging member by bringing the other surface B of the carbonized fiber bundle into contact with the parallel rod located downstream in the traveling direction of the carbonized fiber bundle. 17. A method for producing a carbon fiber bundle according to any one of 11 to 16.
The carbon fiber bundle according to any one of claims 11 to 17, comprising changing the orientation of the surface of the carbonized fiber bundle about the length direction of the carbonized fiber bundle before the passing. manufacturing method.
In changing the direction of the surface, it is preferable to tilt the surface of the carbonized fiber bundle in the width direction within a range of 30° to 150° with the length direction of the carbonized fiber bundle as an axis; It is more preferable to tilt the surface of the carbonized fiber bundle in the width direction within the range of 45° to 135° with the length direction of the fiber bundle as the axis; It is more preferable to tilt the surface of the carbonized fiber bundle in the width direction within the range of 60° to 120°; 19. Manufacturing method according to claim 18, wherein a tilting of 90[deg.] is particularly preferred.
Changing the direction of the surface includes a roller positioned upstream of the two or more parallel rods in the running direction of the carbonized fiber bundle, and a parallel roller positioned most upstream of the two or more parallel rods in the running direction of the carbonized fiber bundle. 20. The manufacturing method according to claim 18 or 19, wherein the manufacturing method is carried out between a strong bar.
The manufacturing method according to any one of claims 11 to 20, which is a method for manufacturing the carbon fiber bundle according to any one of claims 1 to 10.