JP2002371438A - Graphitized fiber and composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-modulus graphitized fiber and a composite material having high performance and slight scattering of quality. SOLUTION: This graphitized fiber has a surface in which average value of the intensity ratio I1360/I1580 measured by Raman spectrometry is 0.20 to 0.75 and <=5% coefficient of variation of the parameter in longitudinal direction. This composite material is constituted by using the graphitized fiber as a reinforcing material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphitized fiber and a composite material which are suitable for use in aerospace and the like where high performance and small variation in quality are required and high quality and high precision are required.

[0002]

2. Description of the Related Art Since carbon fibers have higher specific strength and specific elastic modulus than other reinforcing fibers, carbon fibers are industrially widely used as reinforcing fibers for composite materials by utilizing their excellent mechanical properties. I have. Above all, so-called graphitized fibers with an elastic modulus of 350 GPa or more are being widely used in general industrial applications such as machine tools, taking advantage of their high rigidity, in addition to conventional sports and aerospace applications. Rather, it is becoming more demanding to achieve higher performance at a lower cost.

[0003] The most widely used polyacrylonitrile-based graphitized fibers are acrylic precursors of 200 to
Through a flame-proofing step of converting into a flame-resistant fiber under an oxidizing atmosphere of 400 ° C., a carbonizing step of carbonizing under an inert atmosphere of at least 1000 ° C. and a graphitizing step of graphitizing under an inert atmosphere of 2000 ° C. or more , Manufactured industrially.

In these firing steps, fusion of single fibers occurs, and the quality of carbon fibers and graphitized fibers obtained is reduced.
There was a problem of degrading the quality. To solve this problem, many techniques for applying a silicone oil agent having high heat resistance to an acrylic precursor have been proposed, and are widely applied industrially as an indispensable technique. For example, 3-4
No. 0152 discloses that an oil agent in which a specific amino-modified silicone, epoxy-modified silicone, or alkylene oxide-modified silicone is mixed has a small weight loss upon heating in air and nitrogen and has a high anti-fusing effect. I have. However, the inventors of the present invention have studied that such a conventionally known silicone oil has a sufficient effect of preventing fusion of single fibers,
It became clear that intervening between the single fibers hindered the supply of oxygen which is essential for the flame-proofing reaction, and as a result, unevenness in the progress of the flame-proofing reaction, that is, so-called firing unevenness was induced. Such non-uniformity in firing is considered to be a major factor in quality variation even after graphitization of the fiber through the subsequent carbonization step. In order to produce high-performance graphitized fibers with high productivity, it is advantageous to fire a precursor having a smoother surface at a high yarn density and a high tension. At present, it is necessary to lower the yarn density, tension and processing speed in order to maintain the quality.

As a technique for suppressing unevenness in firing, the present inventors have applied a technique using an acrylic precursor having a specific surface roughness (Japanese Patent Laid-Open No. 11-217734).
However, in an acrylic precursor having a smoother surface, which is advantageous for improving the strength of the obtained graphitized fiber, the effect of suppressing the effect is not necessarily sufficient.
In fact, it has become apparent through subsequent studies, and there is a need for more effective means for suppressing uneven firing.

[0006]

SUMMARY OF THE INVENTION In view of the background of the prior art, an object of the present invention is to provide a graphitized fiber and a composite material having high performance and small variation in quality.

[0007]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the graphitized fiber of the present invention has an average intensity ratio I1360 / I1580 measured by Raman spectroscopy of 0.1.
It has a surface of 20 to 0.75, and the variation rate of the parameter in the longitudinal direction is 5% or less. Further, the composite material of the present invention is characterized in that the graphitized fiber is configured as a reinforcing material.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made to solve the above-mentioned problems, that is, to produce graphitized fibers having high performance and small variation in quality, by suppressing uneven sintering in a flame-proofing step and without reducing productivity. By controlling the variation in crystallinity to a small value, it was determined that such a problem could be solved at once.

That is, the present invention is based on the fact that there is a correlation between uneven sintering in flame resistance and the hardening behavior of the silicone oil applied in the spinning process at the time of heat treatment. It has been found that unevenness in firing due to flame resistance can be effectively suppressed. As a result, the variation in crystallinity of the surface of the obtained graphitized fiber can be controlled, and the graphitized fiber with small variation in quality can be obtained.

The graphitized fiber of the present invention has an intensity ratio I13 of the fiber surface measured by Raman spectroscopy according to a method described later.
The average value of 60 / I1580 is 0.20 to 0.75, preferably 0.25 to 0.70, and more preferably 0.30.
It is important that it is ~ 0.65. That is, the average value corresponds to the crystallinity of the graphitized fiber surface, and the larger the value, the lower the crystallinity. In order to obtain a graphitized fiber having a high elastic modulus, the average value is preferably in the above-mentioned range. If the average value is out of the range, a high-performance graphitized fiber aimed at by the present invention cannot be obtained.

At the same time, the rate of change of the parameter in the longitudinal direction is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less. The lower limit of the fluctuation rate is about 0.01% from the measurement accuracy. Such a variation rate corresponds to a variation in crystallinity of a minute region on the surface of the graphitized fiber, and the lower the variation rate, the more effective in reducing the variation in quality. If the rate of change exceeds 5.0%, the high quality graphitized fiber aimed at by the present invention cannot be obtained.

Intensity ratio I1 measured by Raman spectroscopy
The measurement of 360 / I1580 is performed by the following method. An arbitrary single yarn is taken out from the graphitized fiber bundle and fixed to a sample stage. A laser beam focused to a beam diameter of 1 μm is irradiated, and Raman spectra at 20 points are measured at 10 μm intervals in the longitudinal direction of the fiber. At each measurement point, among the obtained spectrum is read intensity ratio of 1360 cm ^-1 and 1580 cm ^-1, respectively and I1480, I1580, to calculate the intensity ratio I1360 / I1580. The strength ratio of 20
The average of the points is taken as the average value, and the variation rate is calculated by the following equation.

Fluctuation rate (%) = (measured standard deviation of 20 points) / (average value) × 100 The graphitized fiber of the present invention is obtained by the method described below from the viewpoint of obtaining a high-strength graphitized fiber. The surface area ratio measured by an atomic force microscope is 1.0 to
It is preferably 1.05, more preferably 1.0 to 1.02, and even more preferably 1.0 to 1.01. If the ratio is out of the above range, the effects of the present invention may not be easily obtained.

Further, the graphitized fiber of the present invention has a strand strength of 3.5 to 6.5 GPa and a strand elastic modulus of 35.
It is preferably from 0 to 650 GPa, more preferably from 4.0 GPa to 6.0 GPa in strand strength and from 380 to 600 GPa in strand elastic modulus from the viewpoint of the aerospace composite material.

Although the composite material of the present invention is constituted by using such a graphitized fiber as a reinforcing material, it is particularly suitable as an aerospace composite material because of its high performance and small variation in quality. Used for

Next, a method for producing the graphitized fiber of the present invention will be described.

In order to produce the graphitized fiber of the present invention,
It is indispensable to highly suppress unevenness in firing generated in the flame-proofing step, and it is preferable to use the following silicone oil.

The silicone oil agent comprises an amino-modified silicone and a polyoxyethylene compound as essential components, and has a molar ratio of a polyoxyethylene portion of the polyoxyethylene compound to a terminal amino group contained in the amino-modified silicone. It is preferable to use the one in which (M) satisfies the following formula. That is, the molar ratio (M) is preferably from 12 to 35, more preferably 1 to 35.
It is good to be 5 to 33, particularly preferably 18 to 30.

12 ≦ M ≦ 35 M = Mp / Ma Ma: mole number of terminal amino group of amino-modified silicone contained in 100 g of silicone oil agent Mp: mole number of polyoxyethylene portion contained in 100 g of silicone oil agent An oxyethylene-based compound is a compound composed entirely or partially of polyoxyethylene. Further, the number of moles of amino groups, is that the number of moles of -NH ₂ in the amino-modified base terminal of an amino modified silicone.

Further, the number of moles of the polyoxyethylene moiety means the total number of --CH ₂ C contained in the silicone oil agent.
Is that the H ₂ O-molar number. That is, it means that it also includes the number of moles of —CH ₂ CH ₂ O— contained in the emulsifier, preservative, stabilizer and the like. Particularly in the present invention has a feature in place of using a particular emulsifier containing -CH ₂ CH ₂ O-.

By controlling the composition to the specific composition described above, the crosslinking of the silicone oil during the heat treatment is promoted, and this effectively acts on the suppression of uneven sintering in the flameproofing step which is the object of the present invention. When the molar ratio M is less than 12 or exceeds 35, crosslinking is hardly generated, and as a result, the graphitized fiber of the present invention is hardly obtained.

The reason why unevenness in firing in the flame-proofing step can be suppressed by crosslinking the silicone oil agent is not necessarily clear, but is presumed as follows. Burning unevenness of flame resistance
This is due to the fact that the permeation of oxygen into the yarn bundle is hindered and a portion that is not sufficiently supplied is generated, and the silicone oil present between the single fibers is considered as one of the hindrance factors. That is, the silicone oil penetrates between the single fibers and acts like a sealing agent. Generally, the silicone oil agent is applied just before the drying step in the spinning process and is subjected to a heat treatment. If the oil state having fluidity is maintained without cross-linking during the drying heat treatment, then it can be freely deformed in accordance with the space between the single fibers, so that there is a high possibility of thick deposit between the single fibers, and as a result, the sealing effect is improved. It is thought to increase. On the other hand, if the polymer is crosslinked quickly and the fluidity is suppressed to a low level, it is considered that deposition between the single fibers is prevented, the constraint between the single fibers is reduced, and firing unevenness is unlikely to occur.

As the amino-modified silicone used in the silicone oil agent of the present invention, those having a basic structure of polydimethylsiloxane and having a part of methyl groups in side chains modified with amino groups are preferably used. Those to which another modifying group is added in addition to the amino group can also be used. The amino group as a modifying group may be a monoamine type or a polyamine type, but from the viewpoint of accelerating crosslinking, a polyamine type is preferable, and among them, a diamine type is more preferably used.

The amino group is considered to be a starting point of the crosslinking reaction. The higher the amount of modification, the more the crosslinking reaction is promoted, but the amount of sediment deposited on the roller, that is, the so-called gum-up amount may increase. , a modified amount, in terms of the terminal amino group amount on the weight of -NH _2, 0.05 to 10 wt%, and more preferably from 0.1 to 5 wt%. The lower the viscosity of the amino-modified silicone at 25 ° C., the higher the reactivity and the crosslinking reaction is accelerated. However, from the viewpoint of heat resistance, the higher the viscosity, the more preferable.
10,000 cSt is preferable, and 700 to 7000 cSt
Is more preferable, and 1000 to 4000 cSt is further preferable.

The ratio of the amino-modified silicone to all the silicones contained in the silicone oil is preferably at least 20% by weight, more preferably at least 30% by weight, particularly preferably at least 40% by weight. 2
If the amount is less than 0% by weight, crosslinking of the silicone oil agent becomes insufficient, and a sufficient effect of suppressing unevenness in firing may not be obtained.

The structure and composition of the polyoxyethylene compound used in the silicone oil agent are not particularly limited as long as the molar ratio (M) can be within the above-mentioned specific range, but a uniform crosslinking reaction can be realized. In view of the above, it is preferable that the compatibility with the silicone is high.

As specific examples of the polyoxyethylene compound, polyoxyethylene ether and polyoxyethylene-modified silicone are preferably used.
It is not limited to these. Conventionally, polyoxyethylene ethers and polyoxyethylene-modified silicones have been used as emulsifiers for dispersing silicone oils in water and for the purpose of improving emulsion stability. However, the graphitized fiber of the present invention can be obtained only when the above specific composition is combined with the amino-modified silicone.

The polyoxyethylene ether is preferably represented by the following chemical formula 1.

[0029]

Embedded image

R ₁ : an organic group having 1 to 100 carbon atoms containing an alkyl group or a phenyl group n ₁ : an integer of _{1 to} 100 More preferably, polyoxyethylene alkyl ether, polyoxyethylene alkylamino ether, polyoxyethylene alkyl Phenyl ether is used.

The number of moles of addition of such polyoxyethylene n
₁ is more preferably 2 to 50, particularly preferably 3 to 20.

As the polyoxyethylene-modified silicone, those having a basic structure of polydimethylsiloxane and a part of methyl groups in side chains modified with polyoxyethylene are preferably used. At that time, the modification amount of the polyoxyethylene-modified silicone is preferably 10 to 80% by weight,
More preferably 20 to 70% by weight, even more preferably 3 to 70% by weight.
0-60 weight% is good. The viscosity at 25 ° C.
20-1000 cSt is preferred, and 50-800 cSt
Is more preferable, and 100 to 500 cSt is particularly preferable.

The silicone oil contains an amino-modified silicone and a polyoxyethylene compound as essential components, and is used in an amount of 150 parts by weight based on a total of 100 parts by weight of the amino-modified silicone and the polyoxyethylene compound.
A compound other than the amino-modified silicone and the polyoxyethylene-based compound can be added in an amount not exceeding the weight part. More preferably, the total amount of such compounds does not exceed 100 parts by weight, even more preferably does not exceed 50 parts by weight. If the amount of the compound other than the amino-modified silicone and the polyoxyethylene compound exceeds 150 parts by weight, crosslinking of the silicone oil may not be sufficiently promoted. The compounds other than the amino-modified silicone and the polyoxyethylene-based compound referred to herein do not include a solvent for diluting the silicone compound and a dispersion medium for dispersing the silicone compound. The dispersion medium referred to here is a medium in which the silicone compound is dispersed. For example, in the case of a water emulsion, it refers to water.

The silicone oil preferably contains an epoxy-modified silicone from the viewpoint of improving heat resistance. In that case, those having a basic structure of polydimethylsiloxane and a part of methyl groups in side chains are modified are preferably used. The epoxy-modified group may be alicyclic or glycidyl, but is preferably an alicyclic compound from the viewpoint of long-term stability. The modification amount of the epoxy-modified silicone is preferably 0.05 to 10% by weight, and 0.1 to 5% by weight.
% By weight is more preferred. Further, the viscosity of the epoxy-modified silicone at 25 ° C. is preferably higher from the viewpoint of heat resistance, and is preferably from 1,000 to 30,000 cSt.
00 to 20000 cSt is more preferable, and 8000 to 1
5000 cSt is more preferred. Further, when the content of the epoxy-modified silicone is too large, the effect of suppressing uneven baking may be reduced, and when the content is small, the effect of improving heat resistance may be reduced. Is preferably 10 to 300 parts by weight, more preferably 20 to 200 parts by weight, and 3
0-100 parts by weight is more preferred.

It is preferable that an antioxidant is not added to such a silicone oil because of the possibility of delaying the crosslinking of the silicone oil.

The silicone oil agent may be in the form of an oil, a solution diluted with an organic solvent or the like, or may be in the form of an emulsion. From the viewpoint of simplicity of application, it is preferable to use an aqueous emulsion. When forming an aqueous emulsion, an appropriate emulsifier can be added to the silicone compound, but the emulsifier is preferably not more than 40 parts by weight based on 100 parts by weight of the silicone compound. The type of emulsifier is not particularly limited, but nonionic and anionic emulsifiers are preferably used. Above all, a nonionic emulsifier is more preferable from the viewpoint of emulsification stability, and as a specific example, the above-described polyoxyethylene ether is preferably used.

By using polyoxyethylene ether as an emulsifier and forming a water emulsion, the mixed state of the amino-modified silicone and the polyoxyethylene portion in the silicone oil becomes more uniform and fine,
It is preferable to obtain the graphitized fiber of the present invention.

Further, such a silicone oil agent preferably has high heat resistance from the viewpoint of preventing fusion in the firing step. As an index of heat resistance, a heating residual ratio (R) measured by a method described later is preferably 40 to 90%, more preferably 50 to 85%, and more preferably 60 to 80%.
% Is particularly preferred. If it is less than 40%, the effect of the present invention is not easily obtained, and the strength of the graphitized fiber finally obtained by fusion may be reduced. If it exceeds 90%, the adhesive strength between the graphitized fibers and the matrix when used as a composite material may decrease.

As the matrix material used for the composite material of the present invention, any material such as plastic, metal, ceramics, and carbon can be used. A plastic having good adhesive properties with the resin is preferred. Among them, a thermosetting resin excellent in heat resistance represented by an epoxy resin is more preferably used.

The volume ratio of carbon fibers in the composite material of the present invention is preferably 30 to 90 vol%, and 40 to 80 vol%.
ol% is more preferable, and 50 to 70 vol% is still more preferable. When the volume ratio is low, the performance of the composite material with the carbon fiber of the present invention may not be sufficiently improved.
If the volume ratio is high, a portion where the matrix material does not exist between the carbon fibers may occur, and a sufficient composite effect may not be obtained.

The structure of the composite material of the present invention may be such that the carbon fibers are arranged in one direction as continuous fibers, may be arranged in a plurality of directions, and may be included as a woven fabric or a short fiber. The configuration can be selected according to the purpose. When used for aerospace applications, continuous fibers are preferably arranged isotropically.

Next, a method for producing the graphitized fiber of the present invention will be described. As the precursor used in the present invention,
Acrylic, pitch, rayon and the like can be preferably exemplified, but acrylic is more preferable from the viewpoint of obtaining high-performance graphitized fibers. Hereinafter, the precursor fiber for the graphitized fiber of the present invention will be described by typifying an acrylic precursor. As components of such an acrylic precursor, at least 95% by mole or more, more preferably 98% by mole or more of acrylonitrile and 5% by mole or less, more preferably 2% by mole or less, of promoting flame resistance and containing acrylonitrile together with Those obtained by copolymerizing a polymerizable flame retardant component can be suitably used.

A copolymer comprising a vinyl group-containing compound (hereinafter, referred to as a vinyl monomer) is preferably used as the flame retardant component. Specific examples of the vinyl monomer include acrylic acid, methacrylic acid, and itaconic acid, but are not limited thereto. In addition, a copolymer composed of an ammonium salt of acrylic acid, methacrylic acid, or itaconic acid partially or wholly neutralized with ammonia is more preferably used as a component for promoting flame resistance.

As the stock solution for spinning, a conventionally known solution polymerization method, suspension polymerization method, emulsion polymerization method and the like can be adopted. As the solvent used for the spinning solution, organic and inorganic conventionally known solvents can be used. It is particularly preferable to use an organic solvent, and specifically, dimethylsulfoxide, dimethylformamide, dimethylacetamide and the like are used, and dimethylsulfoxide is particularly preferably used.

As the spinning method, a dry-wet spinning method or a wet spinning method is preferably employed, but the former is more preferably used because a raw yarn having a smoother surface can be produced with high productivity.

The raw spinning solution is discharged directly or indirectly from a die into a coagulation bath to obtain a coagulated yarn. The coagulation bath solution is preferably composed of a solvent used for the spinning solution and a coagulation accelerating component from the viewpoint of simplicity, and more preferably water is used as the coagulation accelerating component. The ratio of the spinning solvent and the coagulation accelerating component in the coagulation bath and the temperature of the coagulation bath liquid are appropriately selected and used in consideration of the denseness, surface smoothness, spinnability and the like of the obtained coagulated yarn.

The obtained coagulated yarn is preferably washed and stretched in one or more water baths controlled at a temperature of 20 to 98 ° C. The draw ratio can be appropriately set as long as yarn breakage and adhesion between the single fibers do not occur. However, in order to obtain an acrylic precursor having a smoother surface, it is preferably 5 times or less, more preferably 4 times or less. It is preferably 3 times or less. Further, from the viewpoint of improving the denseness of the obtained acrylic precursor, the maximum temperature of the stretching bath is preferably 50 ° C. or higher, more preferably 70 ° C. or higher.

It is preferable to apply the above-mentioned silicone oil agent to the water-swollen yarn after washing and stretching.
The application method may be appropriately selected and used in consideration of uniform application to the inside of the yarn. Specifically, the yarn is immersed in an oil bath, sprayed and dripped on the traveling yarn. Such means are adopted.

The amount of the silicone oil applied is preferably 0.1 to 5% by weight, more preferably 0.3 to 3% by weight, more preferably 0.5 to 2% by weight, based on the dry weight of the fiber.
% By weight is more preferred. If the amount is less than 0.1% by weight, fusion between the single fibers may occur, and the tensile strength of the obtained graphitized fibers may decrease. If it exceeds 5% by weight, the graphitized fiber of the present invention may be difficult to obtain.

It is preferable that the yarn to which the oil agent is applied is dried quickly. The method of drying is not particularly limited, but a method of directly contacting a plurality of heated rollers is preferably used. The higher the drying temperature, the faster the cross-linking reaction of the silicone oil agent is promoted, and it is preferable from the viewpoint of productivity. Therefore, the drying temperature can be set high within a range where fusion between the single fibers does not occur. Specifically, the temperature is preferably 150 ° C. or higher, more preferably 180 ° C. or higher. Usually, the upper limit of the drying temperature is about 200 ° C. The drying time is preferably a time sufficient for the swollen yarn to dry. Further, it is preferable that the yarn is brought into contact with the roller in a state where the yarn is widened as much as possible so that the heating state of the yarn is uniform.

It is preferable that the dried yarn is further drawn in steam under pressure or under dry heat from the viewpoint of the density and productivity of the obtained acrylic precursor. The steam pressure or temperature during the post-stretching and the post-stretching ratio may be appropriately selected and used within a range in which yarn breakage and fluff do not occur.

The acrylic precursor used in the present invention is:
The surface is preferably smooth from the viewpoint of obtaining high-performance graphitized fibers. The smoothness is preferably determined by using a surface area ratio measured by an AFM (atomic force microscope) by a method described later as an index, and the surface area ratio is preferably 1.00 to 1.05,
1.00 to 1.02, more preferably 1.0 to 1.02.
0 to 1.01 is more preferable. The smoother the effect of applying the silicone oil agent of the present invention, the more easily the effect is significantly expressed,
If it exceeds 1.05, it may be difficult to obtain the graphitized fiber of the present invention.

The single fiber fineness of the acrylic precursor used in the present invention is preferably 0.1 to 2.0 dTex, more preferably 0.3 to 1.5 dTex, and more preferably 0.5 to 1.0 dTex. 2dTex is more preferred. The smaller the fineness is, the more advantageous in terms of tensile strength and elastic modulus of the obtained graphitized fiber, but the productivity is reduced. Therefore, it is preferable to select it in consideration of the balance between performance and cost.

Further, the method for producing the graphitized fiber of the present invention will be described.

An acrylic precursor is produced by the preferred method as described above, and the graphitized fiber of the present invention can be produced by firing the acrylic precursor by the method described below.

The oxidization temperature is preferably 200 to 300 ° C.
It is preferable from the viewpoint of reducing the cost and improving the performance of the obtained graphitized fiber that the yarn be flame-resistant at a temperature lower by 10 to 20 ° C. than the temperature at which the yarn breaks due to the heat storage of the reaction heat. The degree of progress of oxidization is preferably in the range of 70 to 90%, more preferably 74 to 86%, and the flame shrinkage retention of the oxidized yarn measured by the method described later is used as an index.
~ 84% is more preferred. The oxidization time is from 10 to 10 from the viewpoint of improving the productivity and the performance of the obtained graphitized fiber.
100 minutes is preferable, and 30 to 60 minutes is more preferable. This oxidization time refers to the total time during which the yarn stays in the oxidization furnace. If this time is less than 30 minutes, the double structure of each single fiber becomes remarkable as a whole, and the effect of the present invention may not be obtained. The draw ratio of the flameproofing process is 0.8
5 to 1.05 is good, 0.87 to 1.02 is more preferable, and 0.90 to 1.00 is still more preferable.

The temperature in the preliminary carbonization step is preferably 300 to 800 ° C. Further, the stretching ratio is preferably 0.98 to 1.10, more preferably 0.99 to 1.05.
More preferably, it is 00 to 1.02.

The temperature in the carbonization step is preferably from 800 to 2000 ° C. The maximum temperature is appropriately selected and used according to the required characteristics of the desired graphitized fiber.
When the temperature is lower than 00 ° C., the tensile strength and the elastic modulus of the obtained graphitized fiber may decrease. The draw ratio in the carbonization step may be appropriately selected in accordance with the required characteristics of the desired graphitized fiber within a range that does not cause deterioration in quality such as fluff.

The temperature of the graphitization step is from 2000 to 2800 ° C.
It is good. The maximum temperature is appropriately selected and used depending on the required characteristics of the desired graphitized fiber. The drawing ratio in the graphitization step may be appropriately selected according to the required characteristics of the desired graphitized fibers within a range in which the quality is not deteriorated such as generation of fluff.

The adhesion strength of the obtained graphitized fiber to a matrix when a composite material is formed by surface treatment can be further increased. As the surface treatment method, gas phase and liquid phase treatments can be adopted, but in consideration of productivity and quality variation, electrolytic treatment in liquid phase treatment is preferably applied.

As the electrolytic solution used for the electrolytic treatment, acids such as sulfuric acid, nitric acid and hydrochloric acid, alkalis such as sodium hydroxide, potassium hydroxide and tetraethylammonium hydroxide and salts thereof can be used. An aqueous solution containing ions is preferred. For example, ammonium nitrate, ammonium sulfate, ammonium persulfate, ammonium chloride, ammonium bromide, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium hydrogen carbonate, ammonium carbonate, or a mixture thereof can be used.

The quantity of electricity in the electrolytic treatment varies depending on the graphitized fiber used.
A high amount of electricity is required. The surface treatment amount is X
The surface oxygen concentration O / C and surface nitrogen concentration N / C of the graphitized fiber measured by X-ray photoelectron spectroscopy (ESCA) are as follows:
0.05 or more and 0.40 or less, respectively, and 0.02
It is preferable to be in the range of not less than 0.30 and not more than 0.30.

By satisfying these conditions, the adhesion between the graphitized fiber and the matrix is at an appropriate level, and the adhesion is too strong, resulting in a very brittle destruction and a reduction in strength. Or
Although the strength is strong, the adhesive strength is too low, and the disadvantage that the non-longitudinal mechanical properties do not appear can be prevented,
Features having composite properties balanced in the vertical and horizontal directions are exhibited.

The obtained graphitized fiber is further subjected to a sizing treatment as required. Sizing agents include
A sizing agent having good compatibility with the matrix is preferable, and is selected and used in accordance with the matrix.

The measured values described above and the measured values in Examples described later were measured by the following methods. <Raman spectroscopy of graphitized fiber> The measurement apparatus and measurement conditions were as follows.

Measuring device: Ramaonor T-64000 microprobe manufactured by JobinYvon Beam splitter: right Objective lens: 100 times Beam diameter: 1 μm Cross slit: 400 μm Light source Laser type: Ar + (NEC 5145A) Laser power: 80 mW Spectrometer ・ Configuration: 640mm Triple Monochromator ・ Diffraction grating: 600gr / mm (manufactured by Spectrograph) ・ Dispersion: Single, 21A / mm ・ Slit: 100μm Detector: CCD (1024 × 256 manufactured by JobinYvon) <Acrylic precursor and graphitized fiber Surface area ratio by AFM> Acrylic precursor or graphitized fiber to be used for measurement is fixed on a sample table, and the surface is measured by an atomic force microscope.
Nano Instruments NanoS
Using Cope III, an image of a three-dimensional surface shape is obtained under the following conditions.

Probe: SiN cantilever (Olympus Kogyo Kogyo Co., Ltd., spring constant 0.7 N / m) Measurement environment: At room temperature in the air Observation mode: Contact mode (constant force) Scanning speed: 0.2 to 0.5 Hz Scanning range : 2.4 μm × 2.4 μm About the obtained image, the software (Na
noScopeIII version 4.22r2, primary Fl
atten filter, lowpass filter, 3rd order P
data processing by using a lane fit filter)
Calculate the actual surface area and projected area. As for the projected area, the projected area on a secondary curved surface or the like approximated in consideration of the curvature of the fiber cross section is calculated and used. The surface area ratio is defined by the following equation.

Surface area ratio = actual surface area / projected area <Remaining rate of heating of silicone oil R> The remaining rate of heating was determined by heat-treating silicone oil in air at 240 ° C. for 60 minutes, and subsequently in nitrogen at 450 ° C. for 30 seconds. It refers to the residual rate after doing so. The measurement is performed according to the following procedure. When the silicone to be applied is an oil or emulsion or solution,
About 1 g of the emulsion or solution is collected in an aluminum container having a diameter of about 60 mm and a height of about 20 mm, and dried in an oven at 105 ° C. for 5 hours. The heat-resistant residual ratio is measured by a balance (TG).

Sample pan: aluminum diameter 5 m
m, height 5 mm Sample amount: 15 to 20 mg Heat treatment in air: air flow rate 30 ml / min, heating rate 1
0 ° C / min, 240 ° C Heat treatment time: 60 minutes Atmosphere change: Change from air to nitrogen at 240 ° C and 5
Hold for 1 minute Heat treatment in nitrogen: Nitrogen flow rate 30 ml / min, temperature rise rate 10 ° C./min, 450 ° C. Heat treatment time: 30 seconds The total weight retention rate in this heat treatment is defined as a heating residual rate R. <Vibration Cycle of Silicone Oil by Rigid Pendulum Free Damping Vibration Method> Based on Rigid Pendulum Free Damping Vibration Method, R & D Co., Ltd.
The vibration cycle is measured using -3000. When the silicone oil to be measured is an emulsion or solution,
About 1 g of the emulsion or solution is collected in an aluminum container having a diameter of about 60 mm and a height of about 20 mm, and the solvent is removed by drying at 50 ° C. and / or vacuum drying. The water emulsion is dried at 50 ° C. for 10 hours. Next, a coated substrate made of a galvanized steel plate having a length of 5 cm, a width of 2 cm and a thickness of 0.5 mm (ST manufactured by A & D Corporation)
On P-012), a silicone oil to be measured is applied to the entire surface in the substrate width direction so as to have a thickness of 20 to 30 μm. Immediately after application, set the tester and start measurement. The temperature of the tester is adjusted to 30 ° C. in advance, and after setting the coating plate and the pendulum, the temperature is raised to 180 ° C. at a rate of 50 ° C./min and held at 180 ° C. for 10 minutes. in the meantime,
The cycle is measured continuously at 7 second intervals. The following pendulum is used.

Edge used: Knife-shaped edge (RBE-160 manufactured by A & D Corporation) Pendulum weight / inertia ratio: 15 g / 640 g · cm (FRB-100 manufactured by A & D Corporation) It is obtained by the formula.

T = T30-T180 T30: Vibration cycle at 30 ° C. (second) T180: Vibration cycle after heat treatment at 180 ° C. for 10 minutes (second) The principle of the free damping vibration method of the rigid pendulum is, for example,
51 (1978), 403p, etc.
The vibration cycle measured by the measuring method corresponds to the degree of crosslinking of the silicone oil agent, and a smaller value indicates a higher degree of crosslinking. Therefore, the vibration cycle difference T corresponds to the curing behavior at the time of heating, and indicates that the larger the difference, the easier the crosslinking. <Strength and Elastic Modulus of Graphitized Fiber> The strength of the graphitized fiber is determined by a method described in Japanese Industrial Standards (JIS) -R-7601 “Resin-impregnated strand test method”. However, the resin-impregnated strand of the graphitized fiber to be measured was “BAKELITE” ERL4221 (100 parts by weight) / boron trifluoride monoethylamine (3 parts by weight) /
Acetone (4 parts by weight) is impregnated into the graphitized fiber, and 13
It is formed by curing at 0 ° C. for 30 minutes. In addition, the number of strands to be measured is set to ten, and the average value of each measurement result is defined as the strength and elastic modulus of the graphitized fiber. <Flame shrinkage retention rate of flameproofed yarn> A flameproofed yarn bundle is sampled about 40 cm, and marked with a non-combustible material such as a clip so as to have a test length of 20 cm. Next, fix one end and 3
A tension of 10 g per 300 dTex is applied, and the marked sample length is heated by a Bunsen burner flame. At this time, the height of the flame of the Bunsen burner was set to about 15 cm, the upper third of the flame was used, and the interval between marks was set to about 15 seconds / 2.
Heat while moving one and a half times at a speed of 0 cm. Thereafter, the length between marks is measured, and this is defined as Wb (mm). The flame shrinkage retention (%) is defined by the following equation.

Flame shrinkage retention (%) = (Wb / 200) × 100 <Stretchability in Preliminary Carbonization Step>
Under a condition in which the temperature is raised to a maximum temperature of 650 ° C. at 0 ° C./min, a preliminary carbonization step is continuously passed to measure a critical draw ratio at which a yarn break occurs.

[0073]

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

In the examples and comparative examples,
Amino-modified silicone, polyoxyethylene (POE)
Lauryl ether, polyoxyethylene (POE) -modified silicone, and epoxy-modified silicone used were as shown below.

Amino-modified silicone: A dimethyl silicone having a methyl group at a terminal, in which a part of a side chain is substituted with an amino group represented by the following chemical formula 2, was used. The modification amount of the amino group is 40 equivalents in terms of the amino equivalent of the terminal amino group.
00. The viscosity at 25 ° C. is 3000 cS
t.

[0076]

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POE lauryl ether: The one represented by the following chemical formula 3 was used.

[0078]

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POE-modified silicone: A dimethyl silicone having a methyl group at a terminal, in which a part of the side chain was substituted with a polyoxyethylene group represented by the following chemical formula 4, was used. The amount of modification of the polyoxyethylene group was 50% by weight in terms of the ratio of the weight of the polyoxyethylene group to the weight of the POE-modified silicone. The viscosity at 25 ° C. was 500 cSt.

[0080]

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Epoxy-modified silicone: A dimethyl silicone having a methyl group at a terminal, in which a part of the side chain was substituted with an epoxy group represented by the following chemical formula 5, was used. The modification amount of the epoxy group was 4000 in terms of epoxy equivalent. The viscosity at 25 ° C. was 15000 cSt.

[0082]

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Example 1 Water was added to amino-modified silicone, POE-modified silicone, POE lauryl ether, and epoxy-modified silicone having the composition ratios shown in Tables A to E, and emulsified using a homomixer and homogenizer. To obtain a silicone oil agent having a pure content of 30% by weight.

Using the silicone oil, a vibration cycle difference T by a free damping vibration method of a rigid pendulum was measured as an index of the degree of crosslinking of the oil during heat treatment.

Further, an acrylic precursor was prepared by the following method.

A copolymer consisting of 99.5 mol% of acrylonitrile and 0.5 mol% of itaconic acid was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent to obtain a spinning dope having a concentration of 22% by weight. After polymerization, the ammonia gas is
By blowing to 8.5 to neutralize itaconic acid and introducing an ammonium group into the polymer component, the hydrophilicity of the spinning dope was improved. The obtained spinning dope was used for 40
Using a spinneret having a diameter of 0.15 mm and a number of holes of 4,000, once discharged into the air and allowed to pass through a space of about 4 mm, a coagulation bath composed of a 35% dimethyl sulfoxide aqueous solution controlled at 3 ° C. It was coagulated by dry-wet spinning. The obtained coagulated yarn is washed with water and then at 70 ° C.
The resulting silicone oil was applied by stretching it three times in hot water and passing through an oil bath. The concentration in the oil bath was adjusted by diluting with water so as to have a pure content of 2.0%. Further, using a heating roller at 180 ° C., a drying treatment for a contact time of 40 seconds was performed. The dried yarn obtained is
By drawing in 0.4 MPa-G pressure steam, the total drawing ratio of the yarn is set to 14 times, and the single yarn fineness is 0.8 dT.
ex, an acrylic precursor having 12000 single fibers was obtained. In addition, the silicone oil agent adhesion amount of the obtained acrylic precursor was 1.0% in pure content, and the surface area ratio of the acrylic precursor was 1.01.

The obtained acrylic precursor was converted to 240
In air at ２280 ° C., it was converted to a flame resistant yarn having a flame shrinkage retention of 80%. The flame resistance time was 40 minutes, and the draw ratio in the flame resistance step was 0.90. With respect to the obtained flame-resistant yarn, the stretchability in the preliminary carbonization step as an index of uneven firing was measured.

Table 1 shows the measurement results.

Comparative Example 1 A silicone oil was prepared in the same manner as in Example 1 except that the composition ratio of the silicone oil was F and G in Table 1, and the vibration cycle difference T and the preliminary carbonization of the oxidized yarn were performed. The stretchability in the process was measured.

Table 1 shows the measurement results.

[0091]

[Table 1]

As is clear from Table 1, Comparative Example 1 has a lower degree of cross-linking during heat treatment of the silicone oil agent than that of Example 1, and the obtained oxidized yarn is subjected to a preliminary carbonization step. It can be seen that the extensibility is low, that is, firing unevenness is remarkable.

Example 2 The flame-resistant yarn produced in Example 1 was pre-carbonized in an inert atmosphere at 300 to 800 ° C., then carbonized at a maximum temperature of 1900 ° C., and further graphitized at a maximum temperature of 2600 ° C. did. The stretching ratio in the preliminary carbonization step is
0.98. Further, the obtained graphitized fiber was subjected to anodizing treatment at 250 coulomb / g-CF in a sulfuric acid aqueous solution to produce a graphitized fiber. The intensity ratio I360 / I1580, strength, elastic modulus, and surface area ratio by AFM of the obtained graphitized fiber were measured by Raman spectroscopy. The surface area ratios were all 1.00.

The other measurement results are shown in Table 2.

Comparative Example 2 Graphitized fibers were produced in the same manner as in Example 2 except that the oxidized yarn produced in Comparative Example 1 was used. The intensity ratio I1360 / I1580, strength, elastic modulus, and surface area ratio by AFM of the obtained graphitized fiber were measured by Raman spectroscopy. The surface area ratio was 1.00.

Table 2 shows the other measurement results.

[0097]

[Table 2]

As is clear from Table 2, Comparative Example 2 has a greater variation in crystallinity of the surface of the graphitized fiber obtained and a greater variation in strength and elastic modulus than that of Example 2. You can see that.

Example 3 Using the oil agent C shown in Table 1,
Example 2 was repeated except that the flame-resistant yarn prepared in Example 1 was used and the maximum temperature in the graphitization step was 2300 ° C.
A graphitized fiber was produced in the same manner as described above. The intensity ratio I1360 / I1580, intensity, elastic modulus, and surface area ratio by AFM of the obtained graphitized fiber were measured by Raman spectroscopy. The surface area ratio was 1.00.

Table 3 shows other measurement results.

[Comparative Example 3] Using the oil agent F shown in Table 1,
A graphitized fiber was produced in the same manner as in Example 3, except that the flame-resistant yarn produced in Comparative Example 1 was used. Intensity ratio of the obtained graphitized fiber by Raman spectroscopy I1360 / I158
0, strength, elastic modulus, and surface area ratio by AFM were measured.
The surface area ratio was 1.00.

Table 3 shows other measurement results.

Example 4 The maximum temperature in the graphitization step was set to 28.
A graphitized fiber was produced in the same manner as in Example 3 except that the temperature was set to 00 ° C. Intensity ratio I1360 / I1580, strength, elastic modulus, AFM of the obtained graphitized fiber by Raman spectroscopy
Was measured. The surface area ratio was 1.00.

Table 3 shows other measurement results.

[Comparative Example 4] The maximum temperature of the graphitization step was 28
A graphitized fiber was produced in the same manner as in Comparative Example 3 except that the temperature was changed to 00 ° C. Intensity ratio I1360 / I1580, strength, elastic modulus, AFM of the obtained graphitized fiber by Raman spectroscopy
Was measured. The surface area ratio was 1.00.

Table 3 shows other measurement results.

[0107]

[Table 3]

As is evident from Table 3, the graphitized fibers obtained in Comparative Examples 3 and 4 have a greater variation in crystallinity on the surface of the graphitized fiber obtained, and the strength and elastic modulus are higher than those in Examples 3 and 4. It can be seen that the variation of

Example 5 A composite material was produced using the oil agent C shown in Table 1 and the carbon fiber produced in Example 2 and an epoxy resin as a matrix material. The composite material was produced by isotropically laminating continuous fiber unidirectional prepregs having a volume content of 60 vol% of the carbon fibers, followed by autoclave molding.

The obtained composite material was excellent in mechanical properties such as tensile strength and compressive strength, and had little variation.

[0111]

According to the present invention, graphitized fibers and composite materials having high performance and high elastic modulus with little quality variation can be provided with high productivity.

Continued on front page F term (reference) 4F072 AA04 AA07 AB10 AD23 4G046 EA02 EA03 EB02 EB13 EC01 4L037 AT02 CS04 FA01 FA07 FA08 FA09 FA10 FA12 PA55 PC11 PF12 PF19 PF45 PG04 PS02 PS12 UA12 UA20

Claims (5)

[Claims] 1. Intensity ratio I136 measured by Raman spectroscopy
A graphitized fiber having a surface having an average value of 0 / I1580 of 0.20 to 0.75, and a rate of change in the strength ratio in a longitudinal direction of 5% or less. 2. The method according to claim 1, wherein the surface area ratio measured by AFM is 1.00 to
The graphitized fiber according to claim 1, wherein the ratio is 1.05. 3. The graphitized fiber has a strand strength of 3.5 to 3.5.
6.5 GPa and a strand elasticity of 350 to 6
The graphitized fiber according to claim 1, wherein the fiber is 50 GPa. 4. A composite material comprising the graphitized fiber according to claim 1 as a reinforcing material. 5. The composite material according to claim 4, wherein the composite material is for aerospace.