JPH10266066A - Carbon fiber tow and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon fiber tow relatively uniform in adhesivity to matrix resin, thus capable of stabilizing the mechanical properties of the composite materials made by use thereof by subjecting a carbon fiber tow to such surface treatment as to periodically repeat anodization and cathodic reduction via an electrolyte solution. SOLUTION: A carbon fiber tow >=10,000 filaments of single fiber produced by baking acrylic fiber as precursor fiber is introduced into an electrolytic surface treatment unit where the tow is subjected to surface treatment in an electrolyte solution such as aqueous sulfuric acid solution by periodically repeating anodization and cathodic reduction through supplying electricity so that the reduction ratio defined by the relationship: reduction ratio = quantity of electricity for reduction/(quantity of electricity for oxidation + quantity of electricity for reduction) fall within the range 0.001 to 0.5, thus obtaining the objective carbon fiber tow 0.02-0.2 in the surface oxygen concentration: O/C determined by the X-Ray photoelectron spectroscopy and <=30% in the adhesive force variance among single fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a carbon fiber tow and a method for producing the same. More specifically, the present invention relates to a carbon fiber tow having a small variation in adhesive properties with a matrix resin, and furthermore, a stable and good adhesive property with a matrix resin, and a method for producing the same.

[0002]

2. Description of the Related Art Carbon fibers are used as a composite material composed of various matrix resins. In order to make use of the properties of the carbon fibers in the composite material, adhesion to the matrix resin is important. Generally, carbon fibers have been subjected to a surface treatment, and the peel strength and the shear strength of the composite material have been improved by improving the adhesiveness to a matrix resin.

In recent years, from the viewpoint of improving productivity, the number of monofilaments constituting the precursor fiber, that is, the number of filaments, has tended to increase. Also, the number of filaments of carbon fiber tow fired at the same time has increased, resulting in uniform surface treatment. Sex is required. In the case of carbon fiber tow with a large number of filaments, single fibers around the tow are easy to be treated during surface treatment, especially electrolytic surface treatment, so the treatment becomes uneven inside and outside the carbon fiber tow, and the properties of the composite material may deteriorate. There is. In other words, oxidation is difficult to progress in the single fiber located inside the tow,
Oxidation proceeds too much for single fibers located on the outer periphery of the tow. For this reason, the single fibers located inside the tow have insufficient surface treatment and have low adhesion to the matrix resin, while the single fibers located outside the tow have sufficient adhesion, but due to excessive oxidation. Causes a decrease in fiber strength. In particular, in a high modulus carbon fiber tow, the amount of electrolytic treatment must be increased because the graphite structure tends to develop, that is, the surface is more inactivated. As a result, the electrolytic surface treatment inside and outside the carbon fiber tow becomes more uneven, and the tendency of deteriorating the properties of the composite material becomes significant.

[0004] The non-uniformity of the surface treatment is considered to be due to the fact that the electrolytic solution does not sufficiently diffuse into the tow. There have been proposed methods for increasing the diffusion efficiency of the electrolyte into the electrolyte (JP-A-63-264967, JP-A-1-298275, JP-A-7-189113).
JP, JP-B-6-21420, JP-A-7-20
7573). In each case, the unevenness of processing inside and outside of the tow is suppressed by diffusion of the electrolyte into the inside of the carbon fiber tow. However, particularly when a strong electrolytic treatment is performed with a high modulus carbon fiber tow, the treatment unevenness in the single fiber is still insufficiently suppressed, and stable composite material properties have not yet been obtained.

In view of the present situation, the present inventors have studied in detail the electrolytic treatment method of carbon fiber tow, particularly reduction electrolysis, and have found that this can reduce the variation in the adhesiveness between the carbon fiber tow and the matrix. They have found and completed the present invention.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, that is, to reduce the variation in the adhesive force and to improve the adhesive force between the carbon fiber tow and the matrix resin. An object of the present invention is to provide a carbon fiber tow capable of stably improving the mechanical properties of the obtained composite material.

[0007]

Means for Solving the Problems To solve the above problems, the carbon fiber tow of the present invention has the following constitution. That is, the number of single fibers is a carbon fiber tow having 10,000 filaments or more, the surface oxygen concentration O / C measured by X-ray photoelectron spectroscopy is 0.02 to 0.2, and the adhesive force between the single fibers is A carbon fiber tow having a variation of 30% or less.

Further, in order to solve the above-mentioned problems, a method for producing a carbon fiber tow of the present invention has the following constitution.
That is, the precursor fibers are fired, and the number of single fibers is 100
A carbon fiber tow having a length of at least 00 filaments is obtained, and thereafter, anodization is performed such that a reduction rate defined by the following formula is 0.001 to 0.5 with respect to the carbon fiber tow by power supply through an electrolyte solution. A method for producing a carbon fiber tow, characterized in that a surface treatment is performed by periodically repeating cathodic reduction.

Reduction rate = reduction electricity amount / (oxidation electricity amount + reduction electricity amount)

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the carbon fiber tow of the present invention will be described in detail.

When the variation in the adhesive strength of the single fibers in the carbon fiber tow was examined in detail, the carbon fiber tow produced by the specific surface treatment showed a variation in the adhesive properties between the single fiber and the inside of the single fiber with the matrix resin. , And it was found that an unprecedentedly high adhesive strength could be obtained. This is considered as follows.

The variation in the adhesive force between the single fibers in the carbon fiber tow occurs because oxidation does not proceed inside the tow and oxidation proceeds too much outside. This is because the single fibers on the outer periphery of the tow are easily treated during the electrolytic surface treatment, so that the treatment of the carbon fiber tow may be uneven between the single fibers. In addition, single fibers having specific locations such as protrusions and edge portions that are susceptible to oxidation may be excessively oxidized, and oxidation may not proceed with single fibers that are not easily oxidized, and the treatment may be uneven between the single fibers. . For this reason,
As a result, the dispersion of the physical properties of the composite material increases, and stable mechanical physical properties cannot be obtained. As a result, the composite material has low durability.

When the carbon fiber tow is anodized, a functional group is first generated in a specific portion of the single fiber, such as a projection or an edge, which is easily oxidized. If the anodic oxidation is continued, either continuously or intermittently, the generation of the functional group further proceeds at the same location and in the vicinity. Therefore, in order to generate a functional group in a place where anodic oxidation is difficult, anodic oxidation more than necessary is necessary. Although the bond with the matrix resin is high at the location where the functional group is locally generated, excessive anodic oxidation causes structural destruction and lowers the substrate strength, and as a result, high adhesive strength cannot be obtained. From the above, a single fiber having many specific places such as a projection portion and an edge portion which are susceptible to oxidation has high adhesive strength, and a single fiber having few places susceptible to oxidation has low adhesive strength. As a result, the dispersion of the adhesive force between the single fibers in the carbon fiber tow increases.

On the other hand, in the cathodic reduction, a highly reactive functional group such as a generated hydroxyl group or a carboxyl group is eliminated, so that conversion to a carbonyl group or a structure without a functional group is obtained. As a result, the surface of the carbon fiber becomes inactive, and as a result, the adhesive force decreases due to the decrease in the number of functional groups. However, cathodic reduction occurs where oxidation has occurred, especially where oxidation is prone. This is presumably because the place that is susceptible to oxidation has been converted to a carbon structure containing oxygen having a high electric resistance value, that is, a structure that is relatively resistant to oxidation by cathodic reduction. If anodic oxidation is subsequently performed, it is considered that a portion that is hardly oxidized in the first electrolytic surface treatment is relatively easily oxidized, and the whole is uniformly treated. Therefore, by performing cathodic reduction at an appropriate reduction rate, places with excessively high adhesive strength are reduced,
It was found that the dispersion of the adhesive force in the single fiber was small, and high adhesive strength was obtained as a result. At the same time, by performing the appropriate reduction treatment, the degree of the oxidation treatment between the single fibers becomes uniform, and as a result, the variation in the adhesive force between the single fibers in the carbon fiber tow is reduced.

In order to make the surface treatment uniform between the single fibers inside and outside the carbon fiber tow, it is necessary for the electrolytic current to flow uniformly between the single fibers. In the pulse electrolysis, although the electrolytic solution enters the inside of the carbon fiber tow by diffusion, the diffusivity of the electrolytic solution greatly changes depending on the application method to the carbon fiber tow. When the carbon fiber tow comes into direct contact with the electrode without intervening in the electrolyte,
As the number of filaments increases, the single fibers that are in contact with the electrodes are more likely to flow, making it difficult to perform uniform treatment within the bundle. on the other hand,
Once the carbon fiber tow is opened via the electrolytic solution and applied indirectly, the current flow in the carbon fiber tow becomes uniform. However, if the voltage is applied continuously or intermittently, the adhesive strength in the single fiber varies, and as a result, the composite material adhesive strength varies. Therefore, only by periodically repeating the anodic oxidation and the appropriate amount of cathodic reduction, variations between both single fibers and within single fibers can be suppressed. Tow is obtained.

The carbon fiber tow of the present invention has a surface oxygen concentration O / C measured by X-ray photoelectron spectroscopy of 0.02-0.
2, preferably 0.04 to 0.15, more preferably 0.06 to 0.1. When O / C exceeds 0.2,
Although the chemical bond between the functional group of the resin and the outermost surface of the carbon fiber becomes strong, the oxide layer, which is considerably lower than the strength of the carbon fiber substrate itself, covers the carbon fiber surface layer, and the resulting composite The lateral properties of the material will be low. If the O / C is less than 0.02, a composite material using such a carbon fiber tow does not have a sufficiently satisfactory lateral characteristic.

Here, the surface oxygen concentration O / C refers to a value obtained by X-ray photoelectron spectroscopy according to the following procedure. First, a carbon fiber tow from which a sizing agent or the like has been removed with a solvent is cut and spread on a stainless steel sample support, and the photoelectron escape angle is set to 90 °.
Using α _1,2 , 1 × 10 ^-8 torr in the sample chamber
The degree of vacuum is maintained. As a correction of a peak due to charging at the time of measurement, first, the main peak binding energy value of C _1S is set to 284.6.
Adjust to eV. C _1S peak area is 282-296e
It is obtained by drawing a straight base line in the range of V,
The O _1S peak area was determined by drawing a linear baseline in the range of 528 to 540 eV. Surface oxygen concentration O
/ C is the ratio of the O _1S peak area to the C _1S peak area,
It was represented by the atomic ratio calculated by dividing by the sensitivity correction value specific to the device. In the examples described later, ESCA-750 manufactured by Shimadzu Corporation was used, and the sensitivity correction value unique to the above-described apparatus was 2.85.

In the carbon fiber tow of the present invention, the number of single fibers constituting the tow is 10,000 filaments or more.
It is preferably at least 15,000 filaments, more preferably at least 20,000 filaments. This is 100
If the number of filaments is less than 00 filaments, the variation in the adhesive strength of the single fibers in the carbon fiber tow can often be reduced without using a specific manufacturing method described later.

The carbon fiber tow of the present invention has a variation in the adhesive strength between the single fibers of 30% or less, preferably 25% or less, more preferably 20% or less. If the variation in the adhesive strength between the single fibers exceeds 30%, the inherent properties of the composite material such as the adhesive strength cannot be sufficiently exhibited, resulting in low composite material properties. As a result, the fatigue characteristics of the steel sheet continuously applied with the load may be lowered.

In the present invention, the adhesive strength of a single fiber refers to the interfacial shear strength determined according to the following procedure. First, Bakelite (registered trademark) ERL4 manufactured by Union Carbide Co., Ltd.
221 100 parts, boron trifluoride monoethylamine 3
Parts, and an epoxy resin prepared with 4 parts of acetone, and resin beads having a length of 100 to 120 μm are attached to a single fiber. The resin beads were cured at a rate of 5 ° C./min at 130 ° C. for 30 minutes. Subsequently, the single fiber with the resin beads attached is passed through a slit, and the beads are pulled out at a constant speed. The slit width is
The drawing speed is set at 0.5 mm / min according to the carbon fiber diameter plus 0.1 μm. The interface shear strength (τ) is determined from the obtained load (P) by the following equation.

Τ = P / 2πrl where r is a single fiber radius and 1 is a bead length.

The interfacial shear strength is measured five times by changing the position of each single fiber in the longitudinal direction of 50 single fibers randomly collected from the inside of the carbon fiber tow. Here, the variation in the adhesive strength between the single fibers is a variation rate (%) over 50 single fibers after averaging five measured values of each single fiber. Indicates the rate of change of 5 points for each single fiber
Averaged over 0 tubes. The average value of the measured values at all 250 points is called the average interfacial shear strength.

Next, a preferred production method for obtaining the carbon fiber tow of the present invention will be described.

First, the precursor fiber is fired to obtain a carbon fiber tow having a single fiber count of 10,000 filaments or more to be subjected to a surface treatment described later. Known precursor fibers such as polyacrylonitrile-based, pitch-based, and rayon-based precursor fibers can be used as the precursor fibers. Preferably, polyacrylonitrile-based fibers from which a high-strength carbon fiber tow is easily obtained are preferred. Hereinafter, the case where the acrylic fiber is used as the precursor fiber will be described in detail by way of example.

As the spinning solution, a solution or suspension of a polyacrylonitrile homopolymer or copolymer component can be used. However, it is necessary to enhance the filtration to remove impurities from the polymer to obtain high-performance carbon fibers. Important for. As a spinning method, a wet method, a dry method, a dry-wet method, and the like can be adopted, but a wet method or a dry-wet method, which easily provides high strength, is preferable, and a dry-wet method is particularly preferable.

The spinning stock solution is coagulated, washed, stretched, and applied with an oil agent to form a precursor fiber, and further subjected to so-called calcination such as flame resistance, carbonization, and, if necessary, graphitization, to obtain a carbon fiber tow. Throughout the spinning and baking processes, minimizing impurities such as dust and foreign matter from the utility or atmosphere, preventing the introduction of defects into the fibers, and increasing the orientation by applying tension are important to obtain high-performance carbon fibers. It is. As the conditions for carbonization or graphitization, the maximum heat treatment temperature is set to 1100 ° C. or higher, preferably 1300 ° C. or higher.

From the viewpoint of increasing the strength and the elastic modulus, suppressing the breakage of the single fibers during the production of carbon fibers, and suppressing the variation in the strength between the single fibers, the diameter of the single fibers is from 3 μm to 7.5 μm.
m or less, preferably 4 μm or more and 6 μm or less. The single fiber diameter of the carbon fiber tow can be calculated from the fineness and specific gravity of the carbon fiber tow assuming that the fiber cross section is circular. In general, the diameter of the single fiber of the carbon fiber does not substantially change before and after the surface treatment.

The number of single fibers constituting the carbon fiber tow to be subjected to the surface treatment is 10,000 filaments or more, preferably 15,000 filaments or more, more preferably 200 filaments or more.
00 filament or more. 100 filaments
When the number of filaments is less than 00 filaments, the variation in the adhesive force between the single fiber inside the carbon fiber tow and the single fiber on the outer periphery becomes relatively small, and the effect of the present invention is reduced.

In an electrolytic surface treatment apparatus having a plurality of electrolytic cells, such a carbon fiber tow is supplied with an electrolytic solution through an electrolytic solution, that is, indirectly supplied with electricity. Reduction rate of
Electrolytic surface treatment by periodically repeating anodic oxidation and cathodic reduction so as to be 0.001 or more and 0.5 or less, preferably 0.01 or more and 0.4 or less, and more preferably 0.1 or more and 0.3 or less. I do.

Reduction ratio = reduction electricity amount / (oxidation electricity amount + reduction electricity amount) When the reduction ratio is less than 0.001, local anodic oxidation proceeds, so that the dispersion of the adhesive force of the single fibers becomes large. In addition, because of excessive anodization, the strength of the substrate is reduced, and as a result, stable composite properties cannot be obtained. Further, if the reduction ratio exceeds 0.5, the entire fiber surface becomes inactive, and finally the amount of generated functional groups decreases,
As a result, sufficient adhesive strength cannot be obtained.

The number of electrolysis tanks is not limited as long as the reduction rate of the final electrolyzer is within the above range, but is not more than 10 tanks, preferably not more than 6 tanks, and furthermore, the surface inertness due to the reduction electrolysis treatment. In the case of two tanks which are not subjected to surface treatment, the surface treatment effect of the present invention is extremely preferable. In addition, the residence time of the carbon fiber tow is reduced to reduce the effect of the reduction treatment in the electrolytic cell immediately before the final electrolytic cell, and the ratio of the tank length of the final electrolytic cell to the cell length of the electrolytic cell immediately before is set to 1 or more. Below, it is good to be 10 or more and 50 or less.

The shape of the carbon fiber tow during the surface treatment is such that the number of filaments per unit width is 5,000 filaments / mm or less, preferably 2,000 filaments / m2.
m or less is good. If it exceeds 5,000 filaments / mm, the diffusion of the electrolyte becomes insufficient, and the dispersion of the adhesive force between the single fibers may increase.

There are no particular restrictions on the electrolyte used in the surface treatment, but acids such as sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, ammonium nitrate, ammonium hydrogen nitrate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium hydroxide and water Potassium oxide, hydroxides such as barium hydroxide, inorganic salts such as sodium carbonate, sodium hydrogen carbonate, sodium phosphate and potassium phosphate, organic salts such as sodium maleate, sodium acetate, potassium acetate and sodium benzoate, or , Ammonia, ammonium carbonate, ammonium bicarbonate and the like can be used alone or as a mixture of two or more.

The amount of electricity oxidized in the final electrolytic cell is preferably optimized according to the degree of carbonization of the surface-treated carbon fiber tow, and the total amount of electricity is 5 to 1000 coulombs / g (the number of coulombs per gram of carbon fiber tow). ), And more preferably in the range of 10 to 500 coulomb / g. If it exceeds 1,000 coulombs / g, the substrate strength of the carbon fiber itself may decrease.

The waveform of the periodic current supplied to the carbon fiber tow is not particularly limited as long as the condition is such that the reduction ratio is in the above-mentioned range. Normally, a square wave, a triangle wave, and a sine wave can be used.
When the degree of carbonization is high, it is particularly preferable that instantaneous flow of an oxidizing overcurrent causes breakage of the graphite structure and the fiber surface is easily activated.

The cycle of the current waveform supplied to the carbon fiber tow is 10 kHz or more and 5 Hz or less, preferably 500 H
It is preferably from z to 10 Hz. If the period is less than 10 kHz, anodic oxidation and cathodic reduction do not proceed, and a high adhesive strength may not be obtained. If the period exceeds 5 Hz, the electrolyte does not enter the carbon fiber tow due to diffusion,
Electrolytic surface treatment inside and outside the carbon fiber tow may be uneven.

The time required for one anodic oxidation, so-called anodic oxidation time, is 2 μsec or more and 2 sec or less, preferably 50 μsec or more and 0.1 sec or less, more preferably 1 msec or more and 50 sec or less.
A millisecond or less is good. If the anodic oxidation time is shorter than 2 μs, 1
Since the reduction is performed without sufficient oxidation in a single pass, the amount of the generated functional groups is small and a high adhesive strength may not be obtained in some cases. In addition, if the anodic oxidation time exceeds 2 seconds, the anodic oxidation locally progresses excessively, causing a decrease in strength, and a variation in the adhesive strength of the single fiber increases, and as a result, stable composite material characteristics cannot be obtained. There is.

The time required for one cathodic reduction, that is, the so-called cathodic reduction time is 2 μsec or more and 2 sec or less, preferably 5 μsec or less.
The time is preferably from 0 μsec to 0.1 sec, more preferably from 1 ms to 50 ms. If the cathodic reduction time is shorter than 2 μs, sufficient anodic oxidation proceeds without sufficient reduction, and the dispersion of the adhesive strength of the carbon fiber tow tends to increase. On the other hand, if the cathodic oxidation time exceeds 5 seconds, the entire fiber surface becomes inactive and the total amount of functional groups becomes low, so that sufficient adhesive strength may not be obtained.

In the present invention, an apparatus used for surface treatment,
The so-called electrolytic treatment apparatus is not particularly limited as long as the apparatus is applied through the electrolytic solution. However, it is preferable to apply the electrolytic solution by ejecting the electrolytic solution from below the carbon fiber tow. It is preferably 10 tanks or less from the viewpoint of equipment cost. The ejection amount of the electrolyte is 1 mm /
It is preferably at least 20 seconds / second. If it is less than 1 mm / sec, the flow of the electrolytic solution into the carbon fiber tow by the ejection is insufficient, and the surface treatment between the single fibers may be uneven during pulse electrolysis. If it exceeds 20 mm / sec, the alignment may be disturbed in the case of low strength of the carbon fiber tow, and a single fiber may be broken to lower the strength.

A sizing agent is applied to the carbon fiber tow subjected to the surface treatment as required. As the sizing agent, it is preferable to select according to the matrix resin used for the composite material, for example, epoxy resin, polyurethane resin, polyester resin, polyimide resin,
An isocyanate compound, a surfactant and the like can be used alone or as a mixture of two or more thereof. In applying the sizing agent to the carbon fiber tow, it is general that the sizing agent is immersed in a solution in which the sizing agent is dissolved in the solvent or a dispersion liquid in which the sizing agent is dispersed, that is, a so-called sizing solution, and then dried. In order to suppress unevenness in the amount of sizing agent attached between the single fibers in the carbon fiber tow, the carbon fiber tow in a widened state, for example, in a state widened to a shape at the time of the surface treatment as described above, is immersed in a sizing liquid. Is preferred.

[0041]

The present invention will be described more specifically with reference to the following examples.

First, a method for measuring individual characteristic values used in the present invention will be described.

The strand strength and elastic modulus were determined by the following procedures. It was measured according to the resin impregnated strand test method of JIS-R-7601. Bakelite (registered trademark) ERL42221 / 3 manufactured by Union Carbide Co., Ltd.
Boron fluoride monoethylamine / acetone = 100/3
/ 4 (parts by weight), and cured at 130 ° C. for 30 minutes under normal pressure. Ten strands were measured, and the average value was used.

The composite material properties were measured as follows.
First, a resin for evaluating composite material properties was prepared by using Japanese Patent Publication No. Hei 4-8005.
The adjustment was performed as follows according to Example 1 disclosed in Japanese Unexamined Patent Publication No. 4 (Kokai) No.
That is, Epicoat 1001 manufactured by Yuka Shell Epoxy Co., Ltd.
3.5 kg (35 parts by weight), 2.5 kg (25 parts by weight) of Epicoat 828 manufactured by Yuka Shell Epoxy, and 3.0 kg of Epicron N740 manufactured by Dainippon Ink and Chemicals, Inc.
(30 parts by weight), Yuko Shell Epoxy Epicoat 1
52, 1.5 kg (15 parts by weight), 0.8 kg (8 parts by weight) of Denka Formal # 20 manufactured by Denki Kagaku Kogyo Co., Ltd. and 0.5 kg (5 parts by weight) of dichlorophenyldimethylurea were added, followed by stirring for 30 minutes. A resin composition was obtained. The minimum viscosity of the resin was 20 cps. This was coated on release paper to form a resin film.

The composite test piece was prepared as follows. First, a resin film coated with a resin to be combined with carbon fiber on a silicon-coated paper is wound around a steel drum having a circumference of about 2.7 m, and then the carbon fiber pulled out of the creel is wound on the resin film via a traverse. After taking and arranging, the resin film is covered again on the fiber, and then the resin is impregnated into the fiber by rotating and pressing with a pressure roll, and the width is 300 mm and the length is 2.7 m.
To prepare a unidirectional prepreg.

At this time, the drum is heated to 60 to 70 ° C. in order to improve the resin impregnation between the fibers, and the fiber weight of the prepreg is adjusted by adjusting the rotation speed of the drum and the feed speed of the traverse. A prepreg having 200 g / m ² and a resin amount of about 35% by weight was prepared.

The prepreg prepared as described above was cut, the interlaminar shear strength (hereinafter, referred to as ILSS), and the ILSS after fatigue loading, the prepregs were laminated in one direction, and applied with an autoclave at 3 kgf / cm ² · G. Reduction 135
The resultant was cured by heating under a curing condition of 2 ° C. for 2 hours to produce a unidirectional laminate having a thickness of about 2 mm.

The test piece for ILSS is 6.5 mm in width and 1 in length.
The measurement was performed at a crosshead speed of 1.0 mm / min with a support span set to four times the thickness of the test piece using an ordinary three-point bending test jig. Eight measurements were made and the average was determined.

The test piece for fatigue load was 6.5 mm in width and 2 in length.
A GFRP tab having a thickness of about 1.2 mm and a length of 50 mm was adhered to both ends of the test piece, and a load of 80% to 8% of the maximum breaking stress was applied at a frequency of 5 Hz in a sinusoidal waveform.
Added in. IL after loading 10 6 times, after fatigue loading
Cut out the test piece width 6.5mm and length 14mm for SS,
The measurement was performed using a normal three-point bending test jig, setting the support span to four times the thickness of the test piece, and setting the crosshead speed to 1.0 mm.
/ Min. Eight measurements were made and the average was determined.

Example 1 Acrylonitrile (AN) 9
Using a copolymer consisting of 9.4 mol% and 0.6 mol% of methacrylic acid, a single yarn denier of 0.1% was obtained by a dry-wet spinning method.
7d, an acrylic fiber having 18,000 filaments was obtained. After the obtained fiber bundle is subjected to a flame-proof treatment, the maximum temperature is 2400.
The carbon fiber tow was obtained by firing in a carbonization furnace at ℃. This carbon fiber tow has a strand strength of 5.0 GPa and an elastic modulus of 430 G
Pa. This carbon fiber tow is subjected to surface treatment continuously under the following conditions using the electrolytic treatment apparatus (the length ratio of the second tank and the first tank is 20) shown in FIG. 1 to obtain a surface-treated carbon fiber tow. Was. The ejection amount of the electrolytic solution was 10 mm / sec, and the width of the fiber bundle in the electrolytic tank was increased to 1,000 filaments / mm. Using a pulse power supply (BWS60-5 manufactured by Takasago Seisakusho),
As a current waveform of the second tank, a rectangular wave shown in FIG.
0 Hz was generated. The electrolyte solution is a sulfuric acid aqueous solution (0.
1 mol / liter), and the oxidation treatment amount is 100 coulombs / liter.
g, reduction amount: 20 coulomb / g, reduction ratio = 0.17
Processed. The anodic oxidation time was set to 10 ms, the cathodic reduction time was set to 10 ms, and the immersion time in the electrolyte was set to 1 second. No oxide desorption was observed.

The obtained surface-treated carbon fiber tow is made of O / C
= 0.05, average interfacial shear strength 55 MPa, variation in adhesive strength between single fibers 24%, variation in adhesive strength within single fibers 15%, strand strength 5.0 GPa, strand elastic modulus 430 GPa. The composite material using was ILSS84GPa (CV value 0.7%) and interlayer shear strength after fatigue loading of 80 MPa (CV value 1.2%).

Example 2 A surface-treated carbon fiber tow was obtained in the same manner as in Example 1 except that the current waveform in the second tank was changed to the waveform shown in FIG. The resulting surface-treated carbon fiber tow has an O / C = 0.08, an average interfacial shear strength of 56 MPa,
The variation in the adhesive strength between the single fibers was 24%, the variation in the adhesive strength within the single fibers was 16%, and the strand strength was 5.0 GPa. The composite material using this carbon fiber tow was ILSS8.
It was 6 GPa (CV value 0.6%).

(Example 3) The oxidation treatment amount was 50 coulombs /
g, the amount of reduction treatment was 5 coulombs / g, and a surface-treated carbon fiber tow was obtained in the same manner as in Example 1 except that the treatment was performed at a reduction ratio of 0.09. The resulting surface-treated carbon fiber tow is O / C
= 0.07, average interfacial shear strength 52 MPa, variation in adhesive strength between single fibers 27%, variation in adhesive strength within single fibers 18%, strand strength 5.1 GPa, composite material using this carbon fiber tow Is ILSS81GPa (C
(V value: 1.2%).

Example 4 A surface-treated carbon fiber tow was obtained in the same manner as in Example 1 except that the reduction amount was 1 coulomb / g and the reduction ratio was 0.01. The resulting surface-treated carbon fiber tow has an O / C = 0.08 and an average interfacial shear strength of 51MP.
a, the dispersion of the adhesion between the single fibers was 29%, the dispersion of the adhesion within the single fiber was 20%, and the strand strength was 4.8 GPa. The composite material using the carbon fiber tow was ILSS
It was 80 GPa (CV value 1.2%).

Comparative Example 1 A surface-treated carbon fiber tow was obtained in the same manner as in Example 1 except that the electrolytic apparatus shown in FIG. 2 was used. The obtained surface-treated carbon fiber tow has O / C = 0.1
0, average interfacial shear strength 49 MPa, variation in adhesive strength between single fibers 36%, variation in adhesive strength within single fibers 24%,
The strand strength is 4.5 GPa, and the composite material using this carbon fiber tow is ILSS77 GPa (CV value 1.
8%).

Comparative Example 2 A surface-treated carbon fiber tow was obtained in the same manner as in Example 1 except that the amount of reduction was 0 coulomb / g. The resulting surface-treated carbon fiber tow has an O / C =
0.08, average interfacial shear strength 51 MPa, variation in adhesion between single fibers 32%, variation in adhesion within single fibers 2
0% and a strand strength of 4.9 GPa. The composite material using this carbon fiber tow is ILSS79 GPa (CV
Value 1.6%).

Example 5 Acrylonitrile (AN) 9
Using a copolymer consisting of 9.4 mol% and 0.6 mol% of methacrylic acid, single yarn denier 1.
An acrylic fiber having 0d and a filament number of 24,000 was obtained. After the obtained fiber bundle is subjected to the flame-proof treatment, the maximum temperature is 1300.
The carbon fiber tow was obtained by firing in a carbonization furnace at ℃. This carbon fiber tow has a strand strength of 5.1 GPa and an elastic modulus of 230 G
Pa. This carbon fiber tow was continuously subjected to surface treatment using the electrolytic treatment apparatus shown in FIG. 1 under the following conditions to obtain a surface-treated carbon fiber tow. The width of the fiber bundle in the electrolytic cell is
The width was increased to 2000 filaments / mm. As a current waveform, a rectangular wave shown in FIG. 3 and a frequency of 50 Hz were generated. The electrolyte solution is a sulfuric acid aqueous solution (0.1 mol / L),
The oxidation treatment amount was 10 coulombs / g, the reduction treatment amount was 2 coulombs / g, and the reduction rate was 0.17. The anodic oxidation time was 20 ms and the cathodic reduction time was 20 ms. The immersion time in the electrolyte was 1 second.

The obtained surface-treated carbon fiber tow is made of O / C
= 0.10, average interfacial shear strength of 62 MPa, variation in adhesive strength between single fibers of 24%, variation in adhesive strength within single fibers of 17%, strand strength of 5.2 GPa and strand elastic modulus of 230 GPa. The composite material using was ILSS90GPa (CV value 0.5%) and ILSS84MPa (CV value 1.3%) after fatigue loading.

(Example 6) The ejection amount of the electrolyte was 0.8 mm
/ Sec, the width of the fiber bundle in the electrolytic cell is 6000 filaments /
A surface-treated carbon fiber tow was obtained in the same manner as in Example 5, except that the thickness was changed to mm. The resulting surface-treated carbon fiber tow has an O / C = 0.08, an average interfacial shear strength of 60 MPa,
The adhesive strength between single fibers was 29%, the adhesive strength within single fibers was 21%, and the strand strength was 5.1 GPa. The composite material using this carbon fiber tow was ILSS8.
It was 9 GPa (CV value 1.0%).

Example 7 A carbon fiber tow was obtained in the same manner as in Example 1 except that the current waveform in the second tank was changed to that shown in FIG. The resulting surface-treated carbon fiber tow is O /
C = 0.07, average interfacial shear strength 58 MPa, variation in adhesive strength between single fibers 23%, variation in adhesive strength within single fibers 15%, strand strength 5.1 GPa. Composite using this carbon fiber tow The material is ILSS82GPa
(CV value: 1.0%).

[0061]

According to the present invention, it is possible to obtain a carbon fiber tow having a small variation in the adhesive force of a single fiber composed of a single fiber having 10,000 filaments or more, and by using such a carbon fiber tow, a high reliability can be obtained. A composite material is obtained.

[Brief description of the drawings]

FIG. 1 is a side view of an electrolytic processing apparatus used in an example.

FIG. 2 is a side view of the electrolytic processing apparatus used in the comparative example.

FIG. 3 is an example of a pulse-feeding current waveform suitably used in the present invention.

FIG. 4 is an example of a pulse-feed current waveform suitably used in the present invention.

FIG. 5 is an example of a pulse-feeding current waveform suitably used in the present invention.

[Explanation of symbols]

 1: carbon fiber tow 2: pulse power generator 3: electrode plate 4: electrolyte 5: electrode roll

Claims (2)

[Claims] 1. A carbon fiber tow having a single fiber count of 10,000 filaments or more, wherein the surface oxygen concentration O / C measured by X-ray photoelectron spectroscopy is 0.02 to 0.2,
A carbon fiber tow wherein the variation in the adhesive strength between the single fibers is 30% or less. 2. The precursor fiber is fired, and the number of single fibers is 10
A carbon fiber tow of 2,000 filaments or more is obtained, and thereafter, anodization is performed such that a reduction rate defined by the following formula is 0.001 to 0.5 with respect to the carbon fiber tow by power supply through an electrolyte solution. A method for producing a carbon fiber tow, wherein a surface treatment is performed by periodically repeating cathodic reduction. Reduction rate = reduction electricity amount / (oxidation electricity amount + reduction electricity amount)