JP6522971B2 - Method of manufacturing fiber bundle - Google Patents

Description

  The present invention relates to a method for producing a fiber bundle, which comprises the step of surface-treating a treated fiber bundle.

  Reinforcing fibers such as carbon fiber and glass fiber have excellent specific strength and specific elastic modulus, and are excellent in lightness. Therefore, they can be used only for conventional sports and general industrial applications as reinforcing fibers for thermosetting and thermoplastic resins. It is widely used for aerospace and space applications, automotive applications and so on. As applications for use are expanded, fiber-reinforced resin composites (hereinafter referred to as composites) are required to have higher performance.

The performance of the composite depends not only on the difference in mechanical properties between the reinforcing fiber and the matrix resin used, but also on the difference in interface properties such as the adhesion between the reinforcing fiber and the resin. However, due to the difference in surface energy with the matrix resin, the reinforcing fiber, in particular, the carbon fiber, has low wettability to the resin and low adhesiveness to the resin. Therefore, the surface oxidation treatment introduces functional groups such as hydroxyl groups and carboxyl groups on the surface of the fiber bundle to improve the adhesion to the resin.

  As a method of surface oxidation treatment of the fiber bundle, liquid phase oxidation treatment such as electrolytic oxidation treatment or chemical solution oxidation treatment, or vapor phase oxidation treatment is known, but electrolytic oxidation treatment is industrial because it is easy to be treated. Widely implemented. However, in the method of surface treatment of the fiber bundle by liquid phase oxidation treatment such as electrolytic oxidation treatment or chemical solution oxidation treatment, it is necessary to wash the chemical solution such as electrolyte adhering to the fiber bundle after the surface treatment. And manufacturing costs may increase. In addition, there is a concern that the physical properties of the composite may be adversely affected by the chemical solution remaining as an impurity in the fiber bundle after the treatment.

On the other hand, in the gas phase oxidation process using an oxidizing gas, no chemical solution remains in the treated fiber and no disposal of the chemical solution or waste liquid is required, so the environmental load is small and the cost is also advantageous. It is.
As a surface treatment method using an oxidizing gas, heating in a gas containing an oxidizing gas, a method using plasma or an electromagnetic wave, etc. are known. For example, Patent Document 1 proposes a method of performing heat treatment at 600 to 800 ° C. in an oxidizing atmosphere having a carbon concentration of 15 to 30% by mass, but under such conditions the oxidizing action on carbon fibers is insufficient .

Patent Document 2 proposes a surface treatment method by gas phase oxidation using ozone which is an oxidizing gas. However, ozone is very easily decomposed, and particularly at high temperatures, decomposition is severe, so ozone is treated at a low temperature, but in such treatment, the oxidation reaction becomes extremely slow and the oxidation action is insufficient. Further, Patent Document 3 proposes a surface treatment method using a solution in which ozone is dissolved. However, even in the processing method disclosed in Patent Document 3, the oxidation action is still not satisfactory.
Therefore, there is a need for a method for producing a surface-treated fiber bundle that can perform surface oxidation treatment efficiently without leaving a chemical solution in the treated fiber bundle.

Japanese Patent Application Publication No. 2009-544863 JP 2000-154460 A JP 2009-099344 A

  An object of the present invention is to provide a method for producing a fiber bundle, which can efficiently treat the surface of the treated fiber bundle without leaving the chemical solution in the treated fiber bundle.

The method for producing a fiber bundle of the present invention is a method for producing a fiber bundle in which a fiber bundle is treated by immersing a treated fiber bundle in a solution tank filled with a treatment solution, and the treatment solution has a particle diameter of 1000 nm. It is a manufacturing method of the fiber bundle which is a processing solution which has the following air bubbles. The bubble is preferably a bubble containing a reactive gas, and ozone is preferred as the reactive gas. Further, the number of bubbles contained in the treatment solution is preferably 0.1 × 10 ⁷ cells / mL or more.
In the present invention, it is preferable to include the step of rupturing the air bubbles in the solution tank, and it is also preferable that the treatment solution is a reactive solution in which a reactive gas is dissolved at a concentration of 0.1 to 120 ppm. A carbon fiber bundle is preferably used as the treated fiber bundle used in the present invention.

  The carbon fiber bundle of the present invention has an oxygen atom / carbon atom abundance ratio (O / C) of 20% or more as determined by X-ray photoelectron spectroscopy, and has a binding energy value of 0 by X-ray photoelectron spectroscopy. It is a carbon fiber bundle in which the ratio of the abundance of atoms other than carbon atoms and oxygen atoms measured in the region of ̃1100 eV to the abundance of carbon atoms is 0 to 3%.

By using the method for producing a fiber bundle of the present invention, it is possible to efficiently obtain a surface-treated fiber bundle without leaving a chemical solution in the treated fiber bundle.
Since the carbon fiber bundle of the present invention has a high oxygen concentration on the fiber surface and is low in different elements, when the carbon fiber bundle of the present invention is used as a reinforcing fiber, the interface adhesion between fiber and resin is excellent and has high performance. You can get a composite.

The method for producing a fiber bundle of the present invention is a method for producing a fiber bundle, wherein the treated fiber bundle is immersed in a solution tank filled with a treatment solution to treat the treated fiber bundle, and the treatment solution has a particle diameter Is a method for producing a fiber bundle, which is a treatment solution having air bubbles of 1000 nm or less.
Since the treatment solution having air bubbles with a particle diameter of 1000 nm or less has high treatment activity, it is possible to oxidize the fiber bundle surface with high treatment efficiency, and to obtain a surface-treated fiber bundle efficiently. . In the present invention, the average particle size (number average particle size) of air bubbles having a particle size of 1000 nm or less is preferably 10 to 500 nm, more preferably 50 to 300 nm.

In the present invention, the number of bubbles having a particle diameter of 1000 nm or less per unit volume contained in the treatment solution is preferably 0.1 × 10 ⁷ cells / mL or more, and 1 × 10 ⁷ cells / mL or more More preferably, it is 5 × 10 ⁷ to 1 × 10 ¹⁰ cells / mL.
The processing solution containing air bubbles having a particle size of 1000 nm or less can be prepared using a known micro air bubble generator. As a well-known micro-bubble generator, for example, an ultra-fine micro-bubble generator ASK3 type manufactured by Asp, a micro-bubble nano-bubble generator "YJ nozzle" manufactured by Enviro-Vision, etc. may be mentioned.

  In the present invention, the gas contained in the air bubble of 1000 nm or less is not particularly limited, and, for example, reactive gas such as oxidizing gas and reducing gas, and inert gas can be used. By using a reactive gas as the gas contained in the bubbles, it is possible to obtain a surface treatment effect according to the nature of the gas. For example, the surface of the fiber bundle can be oxidized by using an oxidizing gas as the reactive gas, and the surface of the fiber bundle can be reduced by using a reducing gas as the reactive gas. On the other hand, even when an inert gas is used as the gas contained in the bubbles, a surface treatment effect such as removal of foreign matter on the surface of the fiber bundle can be obtained. The method for producing a fiber bundle of the present invention is more effective when a reactive gas, in particular an oxidizing gas, is used as the gas contained in the air bubbles.

  Examples of oxidizing gases include ozone, nitrogen monoxide, nitrogen dioxide, nitrous oxide, nitrous oxide, nitrous oxide, nitrous oxide, nitrous oxide, sulfur monoxide, sulfur dioxide, sulfur trioxide, oxygen, etc. It can be mentioned. Preferably, it is ozone which has high reaction activity and does not contain any element other than oxygen. As a reducing gas, hydrogen, carbon monoxide, hydrogen sulfide etc. are mentioned, for example. Examples of the inert gas include rare gases such as argon, helium and neon, and nitrogen. Among them, it is preferable to use argon or nitrogen.

  The reactive gas used in the present invention may contain an inert gas to control the surface treatment reaction. In the present invention, the inert gas is preferably 0 to 80 vol%, more preferably 0 to 30 vol%, and still more preferably 0.1 to 20 vol% based on the volume of the total gas.

  In the present invention, the treatment solution is preferably a treatment solution in which a reactive gas is dissolved at a mass concentration of 0.1 to 120 ppm separately from the bubbles. Surface treatment can be performed more efficiently by setting the concentration of the reactive gas dissolved in the treatment solution to 0.1 to 120 ppm. When the concentration of the reactive gas is too low, the surface treatment effect tends to be low. On the other hand, the higher the concentration of the reactive gas, the higher the surface treatment effect. However, if the concentration is too high, there is a tendency that no sufficient increase in the treatment effect can be seen with respect to the increase of the reactive gas supply amount. is there. Examples of the solvent for the reactive solution include water and solutions for liquid phase oxidation such as electrolyte solution and oxidizing solution. Among them, water is preferable, and distilled water, deionized water, and pure water with few impurities are particularly preferable. preferable.

In the present invention, the treatment time is not particularly limited, but is preferably 0.1 to 60 minutes from the viewpoint of uniformity of reaction and productivity.
Further, the treatment temperature at the time of surface treatment of the fiber bundle is not particularly limited, but the temperature of the treatment solution is preferably -30 to 30 ° C, and more preferably -25 to 20 ° C. If the treatment temperature becomes too high, bubbles or reactive gases dissolved in the solution are likely to be decomposed or released from the solution into the open air, and the efficiency of surface treatment tends to decrease.

  In the present invention, it is preferable to have the step of rupturing the air bubbles in the solution tank. By bursting the air bubbles in the solution tank, the surface treatment effect of the fiber bundle is further enhanced. The method of rupturing the air bubble in the solution tank is not particularly limited. For example, ultrasonic irradiation, application of vibration, application of electric current, directly or indirectly to the fiber bundle or the solution tank may be used. The method of conducting the treatment, the stirring treatment of the treatment solution, etc. may be mentioned, and the method of performing ultrasonic irradiation, vibration application and energization treatment to the fiber bundle directly or indirectly makes the air bubbles around the fiber bundle It is preferable because it can be selectively repelled. Moreover, ultrasonic irradiation is preferable from the viewpoint of the quality of the fiber bundle to be obtained.

In the present invention, it is preferable to dry the fiber bundle at 100 to 250 ° C. after the surface treatment. The drying process can remove the gas attached to the surface of the fiber bundle.
The production method of the present invention can surface-treat known fiber bundles such as carbon fibers, glass fibers, aramid fibers, polyester fibers without limitation. Among them, it can be preferably used for surface treatment of carbon fibers. In the present invention, known carbon fibers such as PAN-based and pitch-based can be surface-treated without limitation. As a carbon fiber used by this invention, it is preferable to use a PAN-type carbon fiber from the surface of the composite physical property obtained.

  The fineness of the fiber bundle used in the present invention is not particularly limited, but the single fiber fineness is preferably 0.1 to 50 dtex, more preferably 0.5 to 2.0 dtex, and the total fineness of the fiber bundle is It is preferably 10 to 500,000 tex, more preferably 150 to 10,000 tex. The number of filaments of the fiber bundle used in the present invention is preferably 1,000 to 100,000, more preferably 3,000 to 50,000. Further, from the viewpoint of production efficiency, 12000 or more is more preferable, and 24000 or more is even more preferable.

In the present invention, the treated fiber bundle may be subjected to pretreatment such as widening treatment or preliminary oxidation treatment using a known technique.
The method for producing a fiber bundle of the present invention as described above does not require a chemical solution such as an electrolytic solution, so that the chemical solution does not remain in the treated fiber, and no disposal of the chemical solution or waste liquid is required. Therefore, the load on the environment is low, and the surface treatment of the fiber bundle can be performed efficiently.

The production method of the present invention can surface-treat known carbon fibers such as PAN-based and pitch-based without limitation, but as carbon fibers used in the present invention, PAN-based carbon can be obtained from the viewpoint of the composite physical properties to be obtained. It is preferred to use fibers. The PAN-based carbon fiber can be produced, for example, by the following method.
After spinning a spinning solution obtained by polymerizing a monomer containing 90 mass% or more, preferably 95 mass% or more of acrylonitrile, PAN fiber obtained by washing with water, drying and drawing is used as a precursor fiber . The number of filaments of the precursor fiber is preferably 1000 filaments or more, and more preferably 12000 filaments or more in terms of production efficiency.

The precursor fiber is subjected to a flameproofing treatment in heated air at 200 to 300 ° C. for 10 to 100 minutes to obtain a flameproofed fiber. In the flameproofing process, it is preferable to draw the precursor fiber in the range of a draw ratio of 0.90 to 1.20.
Furthermore, after carbonizing the obtained flame resistant fiber at low temperature from 300 ° C. to 1000 ° C., carbon fiber having a dense internal structure can be obtained through a two-step carbonization process of carbonizing at high temperature from 1000 to 2000 ° C. . When a higher elastic modulus is required, graphitization may be further performed at a high temperature of 2000 to 3000 ° C.

  By using the carbon fiber bundle thus obtained as the treated fiber bundle and the gas contained in the air bubbles as the oxidizing gas, the use of the method for producing a fiber bundle of the present invention as described above results in little residual chemical solution. It is possible to obtain the carbon fiber bundle of the present invention having high surface oxygen concentration which is efficiently surface-treated. The degree of oxidation treatment of the carbon fiber bundle is evaluated by the oxygen concentration on the fiber surface, and specifically, the abundance ratio (O / C) of oxygen atom to carbon atom on the fiber surface determined by X-ray photoelectron spectroscopy is It is preferable that it is 20% or more. The larger the value of O / C, the higher the adhesion between the carbon fiber and the resin, and the higher the strength of the composite material obtained using the carbon fiber. In addition, if different elements other than carbon atom and oxygen atom exist on the carbon fiber surface, the adhesion between the carbon fiber and the resin tends to decrease, so the different elements other than carbon atom and oxygen atom on the carbon fiber surface are It is preferable that the amount be small. Specifically, the ratio of the amount of carbon atoms to the amount of atoms other than oxygen atoms to the amount of carbon atoms measured in the region of binding energy value 0 to 1100 eV by X-ray photoelectron spectroscopy is 0 to 3% Is preferred. When the method for producing a fiber bundle of the present invention is used, the remaining chemical solution can be reduced, and therefore, carbon fibers containing a small amount of different elements can be obtained.

  The carbon fiber bundle of the present invention has a high oxygen concentration on the surface of the fiber and a small amount of different elements, so the wettability to the resin is high and the adhesiveness to the resin is excellent. Therefore, when the carbon fiber bundle of the present invention is used as a reinforcing fiber, a composite having high interfacial adhesion and high performance can be obtained.

  In the present invention, it is preferable that the fiber bundle is subjected to a surface treatment according to the above-mentioned production method of the present invention and then subjected to a sizing treatment as required. The sizing method can be performed by a conventionally known method, and the sizing agent is preferably used after changing the composition appropriately in accordance with the application, adhering to a fiber bundle, and then drying. The adhesion amount of the sizing agent is preferably 0.1 to 3.0%, more preferably 0.1 to 1.5%. If the adhesion amount of the sizing agent is too large, the openability of the fiber bundle may be reduced, and the matrix resin may tend to cause poor impregnation into the fiber bundle.

In general, when the amount of the attached sizing agent is small, there is a problem that a portion to which the sizing agent is not attached is formed, and it is difficult to maintain uniformity. However, the fiber bundle produced according to the present invention has uniformly formed surface functional groups, and the wettability of the fiber surface is uniformly improved. Therefore, even with a small amount of adhesion, the sizing agent is uniformly uniform. Can be attached.
The surface-treated fiber bundle thus obtained, in particular a carbon fiber bundle, is used as a reinforcing fiber for thermoplastic resin, thermosetting resin, etc., in sports applications, leisure applications, general industrial applications, aerospace applications, automotive applications It can be widely used.

Using the fiber bundle obtained by the production method of the present invention, a composite material can be obtained by a known means or method such as autoclave molding, press molding, resin transfer molding, filament winding molding, etc. in combination with a matrix resin.
As the matrix resin, a thermosetting resin or a thermoplastic resin is used. Specific examples of the thermosetting matrix resin include epoxy resin, unsaturated polyester resin, phenol resin, vinyl ester resin, cyanate ester resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin and cyanate ester resin And a polyimide resin having a bismaleimide resin, a polyimide resin having an acetylene end, a polyisoimide resin, a polyimide resin having a nadic acid end, and the like. These can also be used as 1 type, or 2 or more types of mixtures. Among them, epoxy resins and vinyl ester resins excellent in heat resistance, elastic modulus and chemical resistance are particularly preferable. These thermosetting resins may contain, in addition to the curing agent and the curing accelerator, commonly used coloring agents, various additives, and the like.

As a thermoplastic resin, for example, polypropylene, polysulfone, polyether sulfone, polyether ketone, polyether ether ketone, aromatic polyamide, aromatic polyester, aromatic polycarbonate, polyether imide, polyarylene oxide, thermoplastic polyimide, polyamide And polyamide imide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyacrylonitrile, polyaramid, polybenzimidazole and the like.
The content of the resin composition in the composite material is 10 to 90% by weight, preferably 20 to 60% by weight, and more preferably 25 to 45% by weight.

  Hereinafter, the present invention will be specifically described by way of examples. The evaluation method of the physical property of each fiber in each example and comparative example was based on the following method.

<Air bubble generator>
As a bubble generation device, a super fine bubble generation device ASK3 type manufactured by Alp Co., Ltd. was used.

<Particle size of air bubble>
The particle diameter of bubbles (nano bubbles) having a particle diameter of 1000 nm or less and the number of bubbles per unit volume (number / mL) were measured by a nano particle analysis apparatus manufactured by Nanosite. The average particle size of the nanobubbles was determined as the number average particle size in the measurement range of the particle size of 40 to 1000 nm.
Particle size of the bubble (microbubble) exceeding 1000nm is used Sysmex Corp. laser particle measuring instrument to determine the D ₅₀ average particle size.

<Atom abundance ratio of carbon fiber surface>
The abundance ratio of atoms on the surface of the carbon fiber was measured by X-ray photoelectron spectroscopy according to the following procedure using an X-ray photoelectron spectrometer (ESCA JPS-9000MX manufactured by Nippon Denshi Co., Ltd.). After carbon fibers were cut out and spread and arranged on a stainless steel sample support stand, the photoelectron escape angle was set to 90 degrees. MgK _α was used as an X-ray source, and the inside of the sample chamber was kept at a vacuum of 1 × 10 ⁻⁶ Pa. First, measurement (wide scan) was performed in a binding energy value of 0 to 1100 eV, peak positions of observed spectra were confirmed, and atoms present on the surface of carbon fiber were identified. Next, precise measurement (narrow scan) was performed for each detected peak, and the abundance ratio of each atom was calculated using the peak area ratio and the sensitivity correction value unique to the device. The correction of the peaks associated with charging during measurement is the binding energy value _B.1 of the main peak of C _1s . E. Was set to 284.6 eV. The peak area derived from each of the detected elements was obtained by drawing a straight baseline in the following range.
O atom: 528 to 540 eV (O _1s )
C atom: 282-292 eV (C _1s )
N atom: 394 to 406 eV (N _1s )
Si atom: 96 to 108 eV (Si 2 _p )

<Size agent adhesion amount (combustion method)>
Remove the carbon fiber bundle 5 m, to measure the weight _{W 1.} After burning at 450 ° C. for 60 minutes in a nitrogen atmosphere and returning to room temperature, the weight W ₂ was measured again, and the amount of attached size was determined by the following equation.
Size adhesion amount% = ((W ₁ −W ₂ ) / W ₁ ) × 100

<Strand strength measurement>
The tensile strength and the tensile elastic modulus of the epoxy resin impregnated strand were measured according to JIS R 7608.

Example 1
Precursor fiber PAN fiber strands (single fiber fineness 0.7 dtex, filament number 24000) are flameproofed to a fiber specific gravity of 1.35 in air, then in nitrogen gas atmosphere at a maximum temperature of 650 ° C. Low temperature carbonized. Thereafter, high temperature carbonization was performed at 1300 ° C. under a nitrogen atmosphere to produce a carbon fiber. When the atomic abundance ratio of the surface of the obtained carbon fiber not subjected to the surface treatment is measured using an X-ray photoelectron spectrometer, C atoms, O atoms, N atoms, Si atoms are detected, and O atoms relative to C atoms are detected. The amount of atoms (surface oxygen concentration (O / C)) is 2.6%, and the amounts of N atoms and Si atoms which are different elements other than C and O with respect to C atoms (different elements exist) The ratio was 3.9% (N / C: 2.4%, Si / C: 1.5%).
Subsequently, the non-surface-treated carbon fiber was immersed in a solution bath filled with a treatment solution in which ozone was dissolved, and surface treatment was performed for 5 minutes. The ozone concentration (mass concentration) of the treatment solution is 8 ppm, the amount of bubbles with a particle diameter of 1000 nm or less containing 400 ppm of ozone gas is 26 × 10 ⁷ cells / mL, and the average particle diameter of the bubbles with a particle diameter of 1000 nm or less is It was 190 nm.

The treatment solution in which ozone is dissolved causes 400 ppm (volume concentration) of ozone gas generated from an ozone generator (Oscar manufactured by Aquoa) to be detonated in pure water to dissolve ozone in pure water, and then bubbles are generated. Using a generator, air bubbles having a particle diameter of 1000 nm or less were blown and prepared. The ozone concentration was measured using an ozone concentration sensor (dissolved ozone measurement type).
When the atomic abundance ratio of the surface of the obtained carbon fiber is measured using an X-ray photoelectron spectrometer, C atoms, O atoms, N atoms, and Si atoms are detected, and O / C is 27%, The surface treatment improved the O / C of the fiber surface, confirming that the carbon fiber surface was oxidized. On the other hand, the different element existence ratio was 2.3% (N / C: 1.3%, Si / C: 1.0%).
The treated carbon fiber is sized using a sizing agent based on bisphenol A epoxy resin as the main component, and the sizing agent bath concentration is adjusted to 1.0 wt% to obtain a carbon fiber bundle. When the strand tensile strength was measured, it showed a good strength of 4980 MPa.

Example 2
The unsurface-treated carbon fiber obtained in the same manner as in Example 1 was immersed in a solution bath filled with the treatment solution, and surface treatment was performed for 5 minutes. The average particle size of bubbles of 1000 nm or less in the treatment solution was 170 nm, and the amount of bubbles of 1000 nm or less in the treatment solution was 24 × 10 ⁷ cells / mL. In Example 2, while immersing the treated fiber bundle in the solution tank, the carbon fiber bundle was irradiated with ultrasonic waves of 45 Hz for 10 seconds at 1 minute intervals to rupture bubbles in the solution.
When O / C of the obtained carbon fiber was measured, it was 40% and the improvement of O / C of the fiber surface was further recognized rather than Example 1 which has not performed ultrasonic irradiation. On the other hand, the different element existence ratio was 1.7% (N / C: 0.9%, Si / C: 0.8%).
The carbon fiber after the treatment was subjected to sizing treatment in the same manner as in Example 1, and the strand tensile strength of the carbon fiber bundle was measured, and as a result, it showed a good strength of 5200 MPa.

Example 3
A surface-treated carbon fiber bundle was obtained in the same manner as in Example 2 except that the surface treatment time was changed to 2 minutes.
When O / C of the obtained carbon fiber was measured, it was 22% and the improvement of O / C of the fiber surface was recognized. On the other hand, the dissimilar element existence ratio was 1.8% (N / C: 0.8%, Si / C: 1.0%).
The carbon fiber after the treatment was subjected to sizing treatment in the same manner as in Example 1, and the strand tensile strength of the carbon fiber bundle was measured, and as a result, it showed a good strength of 5220 MPa.

Example 4
The surface treatment was performed in the same manner as in Example 2 except that irradiation was continued without interruption of ultrasonic waves, to obtain O / C carbon fibers.
When O / C of the obtained carbon fiber was measured, it was 43% and the improvement of O / C of the fiber surface was further recognized rather than Example 2. On the other hand, the different element existence ratio was 1.7% (N / C: 0.8%, Si / C: 0.9%).
The carbon fiber after the treatment was subjected to sizing treatment in the same manner as in Example 1, and the strand tensile strength of the carbon fiber bundle was measured and found to be 4880 MPa.

Comparative Example 1
In the same manner as in Example 1, PAN fiber strands (single fiber fineness 0.7 dtex, number of filaments 24000), which are precursor fibers, are flameproofed in air to a fiber specific gravity of 1.35, and then a nitrogen gas atmosphere Medium, low temperature carbonized at a maximum temperature of 650 ° C. Thereafter, high temperature carbonization was performed at 1300 ° C. under a nitrogen atmosphere to produce a carbon fiber. When the atomic abundance ratio of the surface of the obtained carbon fiber not subjected to the surface treatment is measured using an X-ray photoelectron spectrometer, C atoms, O atoms, N atoms, Si atoms are detected, The abundance of O atoms (surface oxygen concentration (O / C)) is 2.6%, and the abundance of N atoms and Si atoms which are different elements other than C and O with respect to C atoms (different elements The abundance ratio) was 3.9%.
Sizing is performed by adjusting the concentration of the sizing agent bath so that the sizing agent adhesion amount is 1.0 wt% with a sizing agent whose main component is bisphenol A epoxy resin without performing surface treatment on unsurface-treated carbon fibers. I did the processing. The strand tensile strength of the obtained carbon fiber bundle was 4520 MPa, which was lower than those of Examples 1 to 4.

Comparative Example 2
When preparing the treatment solution, carbon fibers were prepared in the same manner as in Example 1, except that an ozone dissolved solution having an ozone concentration of 8 ppm containing no bubbles having a particle diameter of 1000 nm or less was used as the surface treatment solution without blowing air bubbles. Surface oxidation treatment was performed. The O / C of the obtained carbon fiber was measured to be 13%, and the fiber surface was hardly oxidized. On the other hand, the dissimilar element existence ratio was 3.4% (N / C: 2.1%, Si / C: 1.3%).
The carbon fiber after the treatment was subjected to sizing treatment in the same manner as in Example 1, and the strand tensile strength of the carbon fiber bundle was measured to be 4610 MPa, which was lower than in Examples 1 to 4.

Comparative Example 3
When preparing the treatment solution, instead of air bubbles having a particle diameter of 1000 nm or less, microbubbles having a particle diameter of 1000 nm were blown, and an ozone dissolved solution having an ozone concentration of 8 ppm containing no air bubbles having a particle diameter of 1000 nm or less was used as a treatment solution. The surface oxidation treatment of the carbon fiber was performed in the same manner as in Example 1 except for the above. The average particle size of air bubbles in the oxidizing solution used in Comparative Example 3 was 5000 nm. The O / C of the obtained carbon fiber was measured to be 15%, and the fiber surface was hardly oxidized. On the other hand, the dissimilar element existence ratio was 3.2% (N / C: 1.9%, Si / C: 1.3%).
The carbon fiber after the treatment was subjected to sizing treatment in the same manner as in Example 1, and the strand tensile strength of the carbon fiber bundle was measured, and it was 4640 MPa, which was lower than Examples 1-4.

Comparative Example 4
The unsurface-treated carbon fiber obtained in the same manner as in Example 1 was subjected to an electrolytic treatment using a 6.3 mass% nitric acid aqueous solution as an electrolyte solution under the condition of an electric charge of 50 coulomb / g. The O / C of the obtained carbon fiber is 23%. On the other hand, the foreign element abundance ratio is high as compared to Examples 1 to 4 with 5.7% (N / C: 4.3%, Si / C: 1.4%), particularly nitrogen derived from the treatment solution Many atoms were detected.

Claims (7)

  A method for producing a fiber bundle, comprising immersing a to-be-treated fiber bundle in a solution tank filled with a treatment solution, and surface treating the fiber bundle, wherein the treatment solution is a treatment solution having bubbles with a particle diameter of 1000 nm or less. A method for producing a fiber bundle, characterized in that The method for producing a fiber bundle according to claim 1, wherein the number of the bubbles contained in the treatment solution is 0.1 × 10 ⁷ cells / mL or more.   The manufacturing method of the fiber bundle of Claim 1 or 2 which has the process of bursting the said bubble in the said solution tank.   The method for producing a fiber bundle according to any one of claims 1 to 3, wherein the air bubble of 1000 nm or less is an air bubble containing a reactive gas.   The method for producing a fiber bundle according to any one of claims 1 to 4, wherein the treatment solution is a treatment solution in which a reactive gas is dissolved at a concentration of 0.1 to 120 ppm.   The method for producing a fiber bundle according to claim 4 or 5, wherein the reactive gas is ozone.   The method for producing a fiber bundle according to any one of claims 1 to 6, wherein the fiber bundle to be treated is a carbon fiber bundle.