KR101340140B1 - Acrylonitrile swollen yarn for carbon fiber, precursor fiber bundle, flame-proof fiber bundle, carbon fiber bundle, and production methods thereof - Google Patents

Abstract

Provided are carbon fiber bundles for obtaining fiber reinforced resins having high mechanical properties. An acrylonitrile swelling yarn for non-emulsified carbon fibers having a perforated part having a width of 10 nm or more in the circumferential direction of the fiber on the surface of the single fiber in the range of 0.3 / μm ² or more and 2 μm ² or less. The precursor fiber obtained by treating this swelling yarn with a silicone type oil agent has silicon content of 1700 ppm or more and 5000 ppm or less, and the silicon content after 8-hour oil wash with methyl ethyl ketone using a Soxhlet extractor is 50 ppm or more and 300 ppm or less. As for a fiber, the acrylonitrile copolymer of 96.0 mass% or more and 99.7 mass% or less of an acrylonitrile and 0.3 mass% or more and 4.0 mass% or less of unsaturated hydrocarbon which has at least one carboxyl group or an ester group is preferable.

Description

ACRYLONITRILE SWOLLEN YARN FOR CARBON FIBER, PRECURSOR FIBER BUNDLE, FLAME-PROOF FIBER BUNDLE, CARBON FIBER BUNDLE, AND PRODUCTION METHODS THEREOF}

The present invention is a carbon fiber bundle for obtaining a high quality, high performance fiber-reinforced resin having excellent mechanical properties, in particular, such as aircraft applications, industrial applications, and swelling yarns, precursor fiber bundles and abrasions used in the production thereof. Relates to chlorinated fiber bundles.

In order to improve the mechanical properties of a resin molded article, it is generally practiced to composite a fiber with a resin as a reinforcing material. In particular, molding materials in which carbon fibers excellent in specific strength and inelasticity are composited with high-performance resins exhibit very excellent mechanical properties, and therefore, they are being actively used as structural materials such as aircraft and high-speed moving bodies. In addition, there is a demand for higher strength and higher rigidity, and additionally, a material having excellent specific strength and non-rigidity, and the performance of carbon fibers is also required to achieve higher strength and higher elastic modulus.

In order to manufacture such a high performance carbon fiber, it is necessary to obtain the acrylonitrile precursor fiber bundle for carbon fiber which is excellent in intensity expression property, and to bake these precursor fiber bundles on optimal conditions. In particular, densification of the structure of the precursor fiber bundles, thorough elimination of the starting point of defect point formation, and setting of firing conditions that are difficult to form the defect point have been studied. For example, Patent Document 1 proposes a method of improving the uniformity of structure and orientation by stretching a coagulated yarn with a solvent in a solvent-containing stretching bath when the precursor fiber bundle is obtained by a wet-and-dry spinning method. . Stretching the coagulated yarn in a bath containing a solvent is a method generally known as a solvent stretching technique, and is a method of enabling stable stretching treatment by solvent plasticization. Therefore, it is considered to be very excellent as a method of obtaining a fiber with high uniformity of structure and orientation. However, by stretching the bundle of fibers in the swollen state by containing the solvent, the resulting filaments are easily squeezed out of the filament together with the stretching, so that the resulting filaments are easy to form a coarse structure, and the desired dense It cannot be said to have a structure. As a result, it was difficult to obtain a carbon fiber bundle having high strength.

In addition, Patent Literature 2 proposes a technique of focusing on the pore distribution of the coagulated yarn and drying and densifying the coagulated yarn having a high densified structure to obtain precursor fibers having excellent strength expression. The pore distribution obtained by the mercury porosimetry reflects the properties of the bulk including the interior from the surface layer of the filament, and is a very good method for evaluating the compactness of the overall structure of the fiber. From precursor fiber bundles that are at or above the level of overall density, high-strength carbon fibers in which defect point formation is suppressed are obtained. However, when the fracture state of the carbon fiber is observed, it is present at a very high rate to make the fracture starting point near the surface layer. This means that a defect point exists near the surface layer. That is, this technique is insufficient in order to manufacture the precursor fiber bundle excellent in the compactness of the surface layer vicinity.

Patent Document 3 proposes a method for producing an acrylonitrile-based precursor fiber bundle having high density as a whole fiber and very high density of the surface layer portion. Moreover, in patent document 4, since the oil agent penetrates into a fiber surface layer part and inhibits densification, the technique which pays attention to the micro void of the surface layer part and suppresses penetration of an oil agent is proposed. However, since the technique which suppresses oil penetration and the technique which suppresses defect point formation require a very complicated process, it is difficult to put into practical use. For this reason, in the technique under consideration, the effect of stably suppressing the penetration of an oil agent into the surface layer portion is insufficient, and the strength of the carbon fiber is still not sufficient.

Japanese Patent Laid-Open No. 5-5224 Japanese Patent Laid-Open No. 4-91230 Japanese Patent Publication No. 6-15722 Japanese Patent Laid-Open No. 11-124744

An object of the present invention is to provide a carbon fiber bundle for obtaining a fiber reinforced resin having high mechanical properties.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors revealed the appropriate form and property of the acrylonitrile swelling yarn and precursor fiber bundle for carbon fiber, and it has a dense internal structure by optimizing the solidification conditions and extending | stretching conditions of a spinning fiber. In addition, swelling yarns were found near the surface that could inhibit emulsion penetration.

The said subject is solved by the following group of this invention.

The 1st invention is not oil-processed which has the opening part which has a width of 10 nm or more in the circumferential direction of a fiber in the surface of short fiber in the range of 0.3 piece / micrometer <^2> or more and 2 piece / micrometer <^2> or less. Acrylonitrile swelling yarn for carbon fiber.

[2] The second invention is an acrylonitrile system obtained by copolymerizing 96.0% by mass or more and 99.7% by mass or less of acrylonitrile and 0.3% by mass or more and 4.0% by mass or less of unsaturated hydrocarbon having at least one carboxyl group or ester group as essential components. Dissolving a copolymer in an organic solvent in a concentration range of 20% by mass or more and 25% by mass or less to prepare a spinning stock solution having a temperature of 50 ° C or more and 70 ° C or less,

[2] A coagulation bath consisting of an aqueous solution having a temperature of −5 ° C. or more and 20 ° C. or less and an organic solvent concentration of 78.0% by mass or more and 82.0% by mass or less after discharging this spinning stock solution into the air once from a discharge hole by using a dry-wet spinning method. (B) solidifying in (c) to obtain a coagulated yarn bundle containing the organic solvent,

[3] A step of stretching the coagulated yarn bundle in a range of 1.0 to 1.25 times in air and further stretching in a warm water solution containing an organic solvent, wherein the total draw ratio by both stretching is 2.6 to 4.0 times. Process to extend as follows,

[4] Subsequently, it is a manufacturing method of a swelling company which has the process of desolvating with hot water, and extending | stretching by 0.98 times or more and 2.0 times or less in hot water further.

3rd invention is the acrylonitrile copolymer which copolymerized 96.0 mass% or more and 99.7 mass% or less of acrylonitrile and 0.3 mass% or more and 4.0 mass% or less of unsaturated hydrocarbon which has one or more carboxyl group or ester group as an essential component. A precursor fiber bundle for carbon fibers having a silicon content of 1700 ppm or more and 5000 ppm or less, wherein the silicon content after emulsion cleaning for 8 hours by methyl ethyl ketone using a soxhlet extractor is 50 ppm. It is more than 300 ppm or less of precursor fiber bundles for carbon fibers.

According to a fourth aspect of the present invention, an oil agent containing a silicone compound as a main component is attached to a bundle of the swelling yarns, followed by drying with an oil agent component of 0.8% by mass or more and 1.6% by mass or less with respect to 100% by mass of the swelling yarn, followed by thermal stretching or steam stretching. It is a manufacturing method of the precursor fiber bundle for carbon fiber which extends | stretches by 1.8 to 6.0 times of range by the method.

5th invention by passing the said bundle of precursor fibers through the flame retardant furnace of the hot air circulation type of 220-260 degreeC for 30 minutes or more and 100 minutes or less, and heat-processing in an oxidizing atmosphere with elongation rate 0% or more and 10% or less, It is a manufacturing method of the flame resistant fiber bundle which satisfy | fills the following four conditions.

(1) Intensity ratio (B / A) of peak A (2θ = 25 °) and peak B (2θ = 17 °) in the equatorial direction by fiber bundle wide-angle X-ray measurement 1.3 or more, (2) Peak B The orientation degree of (80) or more, (3) The orientation degree of the peak A is 79% or more, (4) Density 1.335 g / cm <^3> or more 1.360 g / cm <^3> or less.

In the sixth invention, the resin-impregnated strand strength is 6000 MPa or more, the strand elastic modulus measured by ASTM method is 250 to 380 GPa, and the ratio between the long diameter and the short diameter of the cross section perpendicular to the fiber axis direction of the short fibers (long diameter / short diameter) Is 1.00 to 1.01 and the diameter of the short fibers is 4.0 µm to 6.0 µm, and at least one or more pores having a diameter of 2 nm or more and 15 nm or less exist in a cross section perpendicular to the fiber axis direction of the short fiber.

The seventh invention, the precursor fiber bundle, 1.335 g / cm density by heat treatment under an oxidizing atmosphere ³ or 1.355 g / cm ³ or less in chloride fibers and then into a bundle, an inert atmosphere of a temperature of less than 300 ℃ 700 ℃ of One or more carbonization furnaces having a temperature gradient from 1000 ° C. to firing temperature in an inert atmosphere, followed by heating from 1.0 ° C. to 3.0% with an elongation of 2% or more and 7% or less with a first carbonization furnace having a gradient. It is a manufacturing method of the carbon fiber bundle which heat-processes 1.0 minutes or more and 5.0 minutes or less, applying the elongation of -6.0% or more and 2.0% or less with a furnace.

The swelling yarn of this invention can suppress that the silicone oil which is a main component of an oil agent penetrates into the surface layer part of precursor fiber. Carbon fiber bundles obtained by flameproofing and carbonizing the precursor fiber bundles can provide a fiber-reinforced resin having excellent mechanical performance and high mechanical properties.

In the present invention, the coagulated yarn is a eutectic yarn taken out from the coagulating solution and not provided for the stretching treatment. A swelling yarn is a process yarn which performed the extending | stretching process and the washing process to the coagulated yarn, and is a process yarn before giving an oil agent adhesion and a drying process.

[Swelling company]

The acrylonitrile swelling yarn (hereinafter referred to as "swelling yarn" as appropriate) for the carbon fiber of the present invention has 0.3 openings having a width of 10 nm or more in the circumferential direction of the fiber in a state before performing an emulsion treatment. ㎛ ² or more to have the surface of the monofilament in two / ㎛ ² within the following range. This swelling yarn is provided in a process of attaching, drying and further stretching an oil agent having a silicone compound to form a precursor fiber bundle, but the swelling yarn having such a surface greatly suppresses the penetration of the oil component into the swelling yarn surface layer portion. It becomes possible.

As a polymer which comprises a swelling yarn, Acrylonitrile which makes 96.0 mass% or more and 99.7 mass% or less of acrylonitrile units and 0.3 mass% or more and 4.0 mass% or less of unsaturated hydrocarbon units which have at least one carboxyl group or ester group as an essential component. It is preferable that it is a reel copolymer. By setting the content of acrylonitrile to 96.0 mass% or more and 99.7 mass% or less, the structural irregularity of the ladder polymer formed in the flameproofing reaction can be reduced, and the decomposition reaction during the subsequent high temperature treatment can be carried out. It can suppress, and it can be set as the dense carbon fiber with few defect points which cause a strength fall. Moreover, it is known that the unsaturated hydrocarbon component which has a carboxyl group or an ester group becomes a starting point of the flameproof reaction in a flameproofing process, The graphene which has few structural irregularities and defects by making the content into 0.3 mass% or more and 4.0 mass% or less It is possible to obtain a flame resistant yarn suitable for obtaining carbon fibers having a (graphene) laminated structure in high yield.

The swelling yarn can suppress the penetration of the oil component by quantifying the residual silicone compound after 8 hours of oil extraction and washing in methyl ethyl ketone after the predetermined amount of the oil agent containing the specific silicone compound is adhered and subjected to dry densification. It is possible to evaluate whether it has a surface layer part.

[Evaluation of emulsion permeability of swelling yarn]

The emulsion permeability of swelling yarn can be evaluated as follows.

First, the following (1) amino modified silicone oil and (2) emulsifier are mixed, and an aqueous dispersion (aqueous fiber emulsion) is prepared by the phase-phase emulsification method. This aqueous fiber emulsion is attached to the swelling yarn.

(1) amino modified silicone: KF-865 (manufactured by Shin-Etsu Chemical Co., Ltd., first-class side chain type, kinematic viscosity 110 cst (25 ° C), amino equivalent 5,000 g / mol), 85 mass%,

(2) Emulsifier: NIKKOL BL-9EX (manufactured by Nikko Chemicals Co., Ltd., POE (9) lauryl ether), 15% by mass.

Subsequently, it is dried with a drying roll to completely evaporate water, and then drawn twice between the heat rolls. In this way, the fiber bundle whose silicon content obtained by a fluorescent X-ray apparatus is 1700 ppm or more and 5000 ppm or less is obtained. Subsequently, the silicon content of the fiber bundle after performing emulsion extraction cleaning for 8 hours with methyl ethyl ketone in a Soxhlet extractor is measured by the fluorescent X-ray apparatus.

It is preferable that silicon content (remaining amount) of oil extraction extraction washing | cleaning is 50 ppm or more and 300 ppm or less of swelling sand of this invention. More preferably, this value is 50 ppm or more and 200 ppm or less.

The fact that the silicon content of the fiber bundle after oil extraction extraction cleaning exceeds 300 ppm means that the density of the surface layer portion that suppresses the penetration of the oil component into the surface layer portion is insufficient, and the carbon fibers obtained after the firing process have a large number of portions in the surface layer portion. It becomes to include a space | gap. As a result, the target high strength carbon fiber cannot be obtained. On the other hand, the fact that this value does not reach 50 ppm means that the amount of oil permeation into the surface layer portion of the swelling yarn is very small, which is considered to be due to the formation of a very dense outer skin layer in the surface layer portion of the fiber in the coagulation bath.

In addition, the swelling yarn of this invention [2. It is more preferable that the swelling degree measured by the swelling degree measuring method of swelling yarn] is 80 mass% or less. The fact that the swelling degree exceeds 80 mass% indicates that the density of the inner layer structure of the swelling yarn is slightly lowered. In this case, even if defect point formation can be suppressed in the surface layer part, the possibility of defect point formation in an inner layer part becomes high, and as a result, carbon fiber which has high mechanical performance cannot be obtained. More preferable swelling degree is 75 mass% or less.

In addition, the compactness of swelling yarn can also be evaluated by measuring the pore distribution inside a fiber. The average pore size of the swelling yarn of the present invention is 55 nm or less, and the total pore volume is preferably 0.55 ml / g or less. As for an average pore size, it is more preferable that it is 50 nm or less, and it is still more preferable that it is 45 nm or less. Moreover, it is more preferable that the total pore volume is 0.50 ml / g or less, and it is still more preferable that it is 0.45 ml / g or less. These swelling yarns are dense because there are no large pores inside the fiber, and the proportion of the pores is further low. If a dense skin layer is formed on the surface of the fiber in the coagulation bath, the pore size and the pore volume inside the fiber tend to increase. In order to obtain the target high-strength carbon fiber, it is desirable to satisfy both of the densification of the surface layer of the swelling yarn to suppress the penetration of the oil agent and of having a dense structure with few voids inside the fiber as described above. On the other hand, the pore distribution of the swelling yarn is described in [4. Pore distribution measuring method of swollen yarn].

[Manufacturing Method of Swelling Yarn]

The swelling yarn of this invention can be manufactured by wet spinning or wet-wetting spinning the spinning stock solution which consists of an acrylonitrile-type copolymer and an organic solvent.

As an acrylonitrile type copolymer, what copolymerized acrylonitrile and the unsaturated hydrocarbon which has one or more carboxyl groups or an ester group as an essential component is mentioned. Examples of the unsaturated hydrocarbon having at least one carboxyl group or ester group include acrylic acid, methacrylic acid, itaconic acid, methyl acrylate, methyl methacrylate, and ethyl acrylate. Any of these, or the acrylonitrile copolymer which copolymerized 2 or more types from 0.3 mass% or more and 4.0 mass% or less and 96.0 mass% or more and 99.7 mass% or less of acrylonitrile is used preferably. More preferable acrylonitrile content is 98 mass% or more.

It is known that the unsaturated hydrocarbon component having a carboxyl group or an ester group serves as a starting point for the flameproof reaction in the flameproofing step. If the content is too small, the flameproof reaction does not sufficiently occur, and there is a problem in forming the structure of the flameproof fiber. Will result. On the other hand, when there are too many, a rapid reaction will arise by the presence of many reaction origins, and as a result, a deteriorated structural form will be formed, and carbon fiber which has high performance cannot be obtained. When the content is 0.3% by mass or more and 4.0% by mass or less, the balance between the starting point of the flameproof reaction and the reaction rate becomes good, the structure is dense, and the formation of a structural misalignment portion that appears to be a defect point in the carbonization step is suppressed. It is possible. Moreover, since it has appropriate reactivity, it can produce a flameproof reaction in a comparatively low temperature range, and can flameproof on both sides of an economic side and a safety side. Therefore, it is possible to obtain a flame resistant yarn suitable for obtaining a carbon fiber having a high yield of a graphene laminated structure with few structural irregularities and defects.

As the third component, acrylamide derivatives such as acrylamide, methacrylamide, N-methylol acrylamide and N N-dimethylacrylamide, vinyl acetate and the like can be used. The suitable method of copolymerizing the mixture of monomers may be, for example, redox polymerization in aqueous solution or emulsion polymerization using a suspension polymerization in a heterogeneous system, and any other polymerization method, and the present invention is limited by these polymerization methods. It doesn't happen.

In the spinning step, first, a spinning stock solution having a temperature of 50 to 70 ° C. in which an acrylonitrile copolymer is dissolved in an organic solvent at a concentration of 20 to 25% by mass is prepared. 20 mass% or more is preferable, and, as for solid content concentration of a spinning dope, More preferably, it is 21 mass% or more. By setting the solid content concentration to 20% or more, the amount of solvent moving from the inside of the filament in the solidification process can be reduced, and a coagulated sand having the required density can be obtained. Moreover, by setting it as 25 mass% or less, since it can set it as a suitable undiluted | stock solution viscosity, stock solution discharge from a nozzle becomes stable and it is easy to manufacture. That is, by making solid content concentration into 20-25 mass%, the coagulated yarn which has high density and a homogeneous structure can be manufactured stably.

In addition, by setting the temperature of the spinning stock solution to 50 ° C or higher, it is possible to obtain a suitable stock solution viscosity without lowering the solid content concentration, and by setting it to 70 ° C or lower, the temperature difference with the coagulating solution can be reduced. . That is, when the temperature of the spinning stock solution is 50 to 70 ° C, the coagulated yarn having a high density and a homogeneous structure can be stably produced.

The organic solvent is not particularly limited, but dimethylformamide, dimethylacetamide or dimethyl sulfoxide is more preferably used. More preferably, it is dimethylformamide which is excellent in the dissolving ability of an acrylonitrile type copolymer.

The spinning method may be either wet spinning or wet and dry spinning. More preferably, it is wet and dry spinning. This is because it is easy to form a dense coagulated yarn, and in particular, the density of the surface layer portion can be enhanced. The wet and dry spinning discharges the prepared spinning stock solution into the air once from the spinneret in which the nozzle holes are arranged, and then discharges it into the coagulating liquid filled with the mixed solution of the heated organic solvent and water. To coagulate and take the coagulated yarn. It is preferable that a coagulating liquid sets temperature -5-20 degreeC and the organic solvent concentration 78-82 mass%. It is because it is easy to form a dense coagulated yarn in this range, and especially the density of a surface layer part can be improved. The more preferable temperature range is -5 degreeC-10 degreeC, and the more preferable organic solvent concentration range is the aqueous solution which made 78.5 mass% or more and 81.0 mass% or less. By making the organic solvent concentration of a coagulating liquid into 81.0 mass% or less, the compactness of a surface layer part can be maintained and penetration of an oil agent into a fiber surface layer part can be suppressed. In addition, by setting the concentration of the organic solvent to 78.5% by mass or more, rapid solidification of the surface layer in the solidification process is suppressed, formation of the outer skin layer is suppressed, and the internal density is lowered since the solidification rate is relatively gentle. I never do that. That is, by making the organic solvent concentration of the coagulating liquid into 78.5-81.0 mass%, the coagulated yarn with a dense surface and inside of a fiber can be obtained together.

The coagulated yarn performs stretching and washing treatment. There is no restriction | limiting in particular in the order of extending | stretching and a washing process, You may wash | clean after extending | stretching, You may perform extending | stretching and washing simultaneously. The washing method may be any method as long as it can be removed. Especially preferable extending | stretching and washing | cleaning process of a coagulation company are extending | stretching in the pre-stretching tank whose solvent concentration is lower than the coagulation liquid and whose temperature is high before washing. As a result, a uniform fibril structure can be formed in the coagulated yarn.

Stretching coagulated yarn in a bath containing a solvent has conventionally been known as a solvent stretching technique, which enables stable stretching treatment by solvent plasticization, and as a result, it is possible to obtain a uniformity in both structure and orientation. have. However, by stretching the fiber bundle containing the solvent in the swelled state, the formation of the fibril structure and the orientation of the structure by stretching are insufficient, and further, the filament obtained from rapidly squeezing an oil agent from the inside of the filament has a coarse structure. It was easy to form, and it was not possible to have the compact structure made into the objective. In the present invention, after setting the temperature and the concentration of the spinning stock solution and the coagulating solution optimally, a dense fibril structure can be formed by performing a solvent stretching treatment under an optimum combination of the conditions of the solvent stretching tank and the stretching ratio.

A bundle of coagulated yarns containing an organic solvent is first drawn in air, and then stretched in a drawing bath in which a warm water solution containing an organic solvent is put. The temperature of the warm water solution is preferably in the range of 40 ° C. or higher and 80 ° C. or lower. By making temperature 40 degreeC or more, favorable elongation can be ensured and formation of a uniform fibril structure becomes easy. Moreover, since it does not produce an excessive plasticization effect by setting it as 80 degrees C or less, the desolvent on the surface of thread yarns advances suitably, and since extending | stretching becomes uniform, it is quality as a swelling yarn. This becomes good. More preferable temperature is 55 degreeC or more and 75 degrees C or less.

Moreover, as for the organic solvent density | concentration in the warm water solution containing an organic solvent, 30 mass% or more and 60 mass% or less are preferable. This density | concentration is the range which can provide a stable extending | stretching process, and can form a dense uniform fibril structure in an inside and surface layer. More preferable concentration is 40 mass% or more and 50 mass% or less.

A preferred method of stretching the coagulated yarn is to make the stretching in the air 1.0 to 1.25 times, and the draw ratio of the sum in the air and the hot water solution to be 2.6 to 4.0 times. The coagulated yarn contains a large amount of solvent and has a swollen fibril structure. Coarse fibrillated structure formation of such a structure can be avoided by making elongation in air 1.0 to 1.25 times the coagulation | solidification yarn which consists of such a structure. Moreover, by making it 1.0 times or more, nonuniform shrinkage is suppressed.

Moreover, sufficient stretching can be performed by making the draw ratio of the sum total in air and hot water solution 2.6 times or more, and the fibril structure orientated in the desired fiber axis direction can be formed. Moreover, by making the total draw ratio into 4.0 times or less, the precursor fiber bundle which consists of a dense structure form can be made without breaking the fibril structure itself. That is, in the range of 2.6 times or more and 4.0 times or less, the dense fibril structure oriented in the axial direction of the fiber can be formed. More preferably, the total draw ratio is from 2.7 to 3.5 times.

Moreover, as a more preferable extending | stretching method, extending | stretching magnification in the organic solvent hot water solution is made 2.5 times or more. This is because the stretching in the organic solvent hot water solution is performed at a relatively high temperature, so that stretching can be performed without causing structural destruction. Therefore, as for extending | stretching distribution in air and the organic solvent hot water solution, it is preferable to set distribution of extending | stretching in the organic solvent hot water solution high. More preferably, extending | stretching in air is 1.0 times or more and 1.15 times or less.

In this way, although the surface part can obtain a dense swelling yarn, in order to obtain a more preferable dense swelling yarn, the swelling yarn is manufactured by the extending | stretching method mentioned above using the coagulation yarn bundle containing the organic solvent whose swelling degree is 160 mass% or less. . This is because the inner layer structure of the coagulated yarn is dense.

After the stretching treatment, the fiber bundle is washed with warm water of 50 ° C or more and 95 ° C or less to remove the organic solvent. Furthermore, after washing, the fiber bundle in the swollen state without solvent powder can be stretched in hot water to further increase the orientation of the fiber, and it is also possible to modify the stretching by adding a slight relaxation. Preferably, 0.98 times or more and 2.0 times or less of extending | stretching is performed in hot water of the temperature of 70-95 degreeC. When a draw ratio is 0.98 times or more and less than 1.0 times, it becomes a process to relax. In the previous step, in the fiber bundle provided at a high draw ratio, the stretching strain is taken, which is effective for stable stretching in the subsequent stretching step. In the range whose stretching ratio is 1.0 times or more and 2.0 times or less, the orientation degree of a fibril structure can be improved and the density of a surface layer can be raised. More preferably, drawing is 0.99 times or more and 1.5 times or less.

In this way, a swelling yarn is obtained by extending | stretching and washing | cleaning process to a coagulated yarn.

[Dry heat drawing]

A predetermined amount of oil is adhered to the swelling yarn to densify dry matter. Dry densification is good to dry and densify by a well-known drying method, and there is no restriction | limiting in particular. A method of passing a plurality of heating rolls is preferably used. The fiber bundle after dry densification is stretched in a hot-heated fruit at 100 to 200 ° C or between a heating roll at 150 to 220 ° C or on a heating plate in a pressurized steam at 130 to 200 ° C to improve further orientation. After densification, it is wound up to obtain a precursor fiber bundle.

[Bulb fiber bundle]

The precursor fiber bundle for carbon fiber of the present invention (hereinafter, appropriately referred to as "precursor fiber bundle") is not less than 96.0 mass% and not more than 99.7 mass% of acrylonitrile and 0.3 mass% of unsaturated hydrocarbon having at least one carboxyl group or ester group. It is composed of an acrylonitrile copolymer copolymerized with at least 4.0% by mass or less as an essential component, and has a silicon content of 1700 ppm or more and 5000 ppm or less after treatment with an oil containing a silicone-based compound as a main component, to methyl ethyl ketone using a Soxhlet extractor. The silicon content after emulsion cleaning for 8 hours is 50 ppm or more and 300 ppm or less. Silicon content is measured with a fluorescent X-ray apparatus. In addition, the silicon content after oil agent washing | cleaning is a measured value based on the evaluation by the oil agent adhesion | attachment or oil agent washing in the said [Evaluation of the oil permeability of swelling company].

If the silicon content of the precursor fiber bundle after being treated with an oil agent is 1700 ppm or more and 5000 ppm or less, fusion between the filaments does not occur in the flameproofing process, while oxygen diffusion into the filament inside of the surface layer with the excess silicon compound is inhibited, and Insufficient place of the chlorine reaction can be prevented, and the occurrence of thread breakage can be suppressed in a higher temperature carbonization step. As a result, stable process passability can be maintained.

The precursor fiber bundle of this invention is 300 ppm or less of silicon content of the fiber bundle after oil extraction extraction washing. Here, the silicon content exceeding 300 ppm indicates that the silicon compound oil penetrates into the surface layer portion, and the amount thereof is increasing. As a result, in the flameproofing and the electrocarbonization process (800 ° C. or lower) of the firing step, the silicone oil remaining in the surface layer portion does not scatter and remains in the late carbonation step (above 800 ° C.), resulting in the final carbon fiber. It is to form a plurality of voids in the surface layer portion of the. Therefore, the target high strength carbon fiber cannot be obtained. On the other hand, the silicon content of the fiber bundle after the oil extraction extraction cleaning is 300 ppm or less means that the silicon compound adhering to the precursor fiber penetrates into the surface layer portion and exists in the vicinity of the surface layer, but the ratio of the existence state that is hard to be extracted is small and the outermost layer portion It means that it exists. In such a state, the silicon compound is scattered without forming a defect point from the outermost layer portion in the flameproofing step or carbonization step of the firing step. The silicon content after more preferable oil agent extraction washing is 200 mass ppm or less.

The precursor fiber bundle has a fine fiber of 0.5 dtex or more and 1.0 dtex or less, and the ratio (long diameter / short diameter) of the long cross-section of the fiber cross section of the short fiber (long diameter / short diameter) is 1.00 or more and 1.01 or less and the fiber axis of the short fiber. It is preferable that there is no surface uneven | corrugated structure extended in a direction, the height difference (Rp-v) of a top part and a minimum part is 30 nm or more and 100 nm or less, and center line average roughness Ra is 3 nm or more and 10 nm or less. If the (Rp-v) value is 30 nm or more, or the (Ra) value is 3 nm or more, the smoothness of the surface of the precursor fiber filament is not excessive. This is due to the low elongation in the spinning step derived from the outer skin layer formed in the solidification step, so that small breakage of the surface fibrils does not occur, and formation of minute defect points can be avoided. Furthermore, by the excessive bundle as a fiber bundle which is an aggregate of filaments, uneven flameproof treatment by the inhibition of the oxygen diffusion into the filament inside a flameproofing process can also be avoided. On the other hand, it is thought that the density of the structure near the surface layer can be made to a sufficient level by setting the (Rp-v) value to 100 nm or less or the (Ra) value to 10 nm or less. That is, when a (Rp-v) value has a surface which seems to be 30 nm or more and 100 nm or less, and (Ra) value is 3 nm or more and 10 nm or less, it is set as the structure which has the density of the structure of the surface vicinity vicinity enough, and also has sufficient elongation. It is possible to reduce the chance of defect point formation near the surface layer in the firing step from spinning. As a result, a high strength carbon fiber bundle can be obtained.

Here, the surface uneven | corrugated structure extended in a fiber axis direction means the wrinkle structure of 0.6 micrometers or more in length which exists substantially parallel to a fiber axis direction. The acrylonitrile fiber bundle usually has a volume shrinkage due to solidification and subsequent stretching treatment, and a wrinkled structure extending in the fiber axis direction is formed on the surface. Formation of its corrugated structure is suppressed by suppressing formation of a firm outer skin layer in the solidification step and smoothly realizing volume shrinkage. In addition, it is known that formation of its wrinkled structure is greatly suppressed by wet and dry spinning. It is preferable that precursor fiber bundle does not have a wrinkle structure of 0.6 micrometers or more in length.

A fiber having a ratio of the long diameter to the short diameter (long diameter / short diameter) of 1.00 to 1.01 of the short fiber cross section is a short fiber having a perfect circle or a cross section close to a perfect circle, and has excellent structural uniformity near the fiber surface. . More preferable ratio of the long diameter to the short diameter (long diameter / short diameter) is 1.00 to 1.005.

Fibers with a fineness range of 0.5 to 1.0 dtex of short fibers have a small fiber diameter, so that the structural nonuniformity in the cross-sectional direction generated in the firing step can be reduced. A more preferable range is 0.5 to 0.8 dtex.

[Method for Producing Precursor Fiber Bundle]

The said precursor fiber bundle of silicon content of the said predetermined amount can be manufactured by sticking and drying the oil agent which has a silicone compound as a main component to the swelling yarn of this invention, and performing an extending | stretching process by heat drawing or steam drawing. .

Although the silicone compound which is a main component of an oil agent is not restrict | limited, An amino modified polydimethylsiloxane or an epoxy modified polydimethylsiloxane is used preferably from a viewpoint of interaction with an acrylonitrile-type copolymer. In particular, amino-modified polydimethylsiloxane is preferable from the viewpoint that the swelling yarn of the present invention has a high density of the surface layer portion and is easy to coat the surface layer and is difficult to detach from the surface layer.

Moreover, it is excellent from a heat resistant viewpoint that one part of the methyl group of polydimethylsiloxane skeleton is substituted by the phenyl group. Most suitable amino modified polydimethylsiloxanes are those having a kinematic viscosity at 25 ° C. of 50 to 5,000 cst and an amino equivalent of 1,700 to 15,000 g / mol.

Although the amino modification type is not particularly limited, the primary side chain type, the primary and secondary side chain types, and the sock end modified type are suitable. It is also possible to mix these types or mix and use them. If the kinematic viscosity at 25 ° C is 50 cst or more, it has a sufficient molecular weight that does not volatilize, scattering from the fiber is suppressed throughout the flameproofing process, expresses the function as an original process oil, and the production of stable carbon fibers is possible. Become. Further, by setting the kinematic viscosity at 25 ° C. to 5000 cst or less, a part of the oil agent is transferred from the fiber bundle to the roll or the like in the flameproofing step, and the viscosity is increased by being subjected to a heat treatment for a relatively long time, resulting in adhesiveness, The problem is that some of the fiber bundles are wound around the rolls. In addition, by setting the amino equivalent to 1,700 g / mol or more, the thermal reactivity of the silicone is suppressed, and a part of the oil agent is transferred from the fiber bundle to the roll and the like, thereby avoiding the problem that a part of the fiber bundle is wound on the roll. Can be. By setting the amino equivalent to 15,000 g / mol or less, since the affinity between the precursor fiber and the silicone is sufficient, scattering from the fiber can be suppressed throughout the flameproofing step. That is, when the kinematic viscosity at 25 ° C. of the oil is in the range of 50 to 5,000 cst and the amino equivalent is in the range of 1,700 to 15,000 g / mol, the problem of entanglement of fibers caused by the transition of the oil to a roll or the like or in the flameproofing process There is no sudden scattering of an oily agent, and it can carry out stably continuously for a long time from spinning to flameproof processing.

As amino-modified polydimethylsiloxane of a primary side chain type, KF-864, KF-865, KF-868, KF-8003 (all are the Shin-Etsu Chemical Co., Ltd. product) etc. are mentioned. Examples of the class 1 and 2 side chain types include KF-859, KF-860, KF-869, and KF-8005 (all manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of the sock end modified type include Ciraplane FM-3311, FM-3221, FM-3325 (all manufactured by Chisso Corporation), KF-8012 (manufactured by Shin-Etsu Chemical Co., Ltd.), and the like.

An oil agent is comprised from the compound called surfactant, the softening agent which gives the outstanding process permeability, and the smoothing agent to make an aqueous emulsion. As the surfactant, nonionics are mainly used, and EO / PO adducts of pluronic or higher alcohols are used. In particular, Newpole PE-78, PE-108, and PE-128 (all manufactured by Sanyo Chemical Co., Ltd.), which are polyoxyethylene / polyoxypropylene block polymers, are suitable.

A softening agent and a smoothing agent use an ester compound, a urethane compound, etc. Content of the silicone compound in an oil agent is 30 mass%-90 mass%. If it is 30 mass% or more, fusion suppression in a flameproofing process is enough. Moreover, if it is 90 mass% or less, the stability of the emulsion of an oil agent can be easily made sufficient level, and stable precursor fiber can be manufactured. That is, when content of the silicone type compound in an oil agent is 30 mass%-90 mass%, also in the precursor fiber with a dense surface like this invention, the fusion inhibitory effect in a flameproofing process can fully be exhibited, and stability in an oil-adhesion process Furthermore, since the uniformity of an adhesion state is implement | achieved, the performance expression stabilization of the carbon fiber obtained can be aimed at.

The adhesion amount of the oil agent which has a silicone compound as a main component is 0.8 mass%-1.6 mass%. After tanning, it is provided for dry densification. Dry densification is good to dry and densify by a well-known drying method, and there is no restriction | limiting in particular. Preferably, it is a method of letting a some heating roll pass. By setting the adhesion amount of the oil agent to 0.8 to 1.6% by mass, it is possible to reduce the irregularity of the flame-resistant structure due to lack of diffusion of oxygen due to fusion between fibers due to the lack of coating of the oil agent and excessive adhesion. Carbon fibers having strength can be produced.

The fiber bundle after dry densification is stretched 1.8 to 6.0 times in a pressurized steam or dry heat fruit at 130 to 200 ° C or between heating rolls or on a heating plate, if necessary, to further improve orientation and densification to obtain precursor fiber bundles. . More preferably, the draw ratio is 2.4 to 6.0 times, more preferably 2.6 to 6.0 times.

[Method of producing flame retardant fiber bundle]

The precursor fiber bundle is passed through a flame resistant flame furnace of 220 to 260 ° C. for 30 minutes or more and 100 minutes or less and heat-treated under an oxidizing atmosphere at an elongation rate of 0% or more and 10% or less, thereby giving a density of 1.335 g / cm ³ or more and 1.360 Up to g / cm ³ flame resistant fiber bundles can be obtained. In the flameproofing reaction, there are cyclization reactions by heat and oxidation reactions by oxygen, and it is important to balance these two reactions. In order to balance these two reactions, the flameproofing treatment time is suitable for 30 minutes or more and 100 minutes or less. In the case of less than 30 minutes, the part in which oxidation reaction has not fully produced exists in the inside of short fiber, and large structural stain is produced in the cross-sectional direction of short fiber. As a result, the carbon fiber obtained will have a nonuniform structure, and high mechanical performance will not be expressed. On the other hand, when it exceeds 100 minutes, much oxygen exists by the part near the surface of short fiber, and the reaction which an excess oxygen loses by the heat processing at the high temperature after that generate | occur | produces a defect point, High strength carbon fiber is not obtained.

More preferable salt-resistant treatment time is 40 minutes or more and 80 minutes or less. When the density of the flame resistant yarns is less than 1.335 g / cm ^{3, the} flame resistance becomes inadequate, a decomposition reaction occurs by heat treatment at a high temperature thereafter, and thus a defect point is formed, so that a high strength carbon fiber is not obtained. When the yarn-resistant density exceeds 1.360 g / cm ³ , since the oxygen content of the fiber increases, a reaction at which excess oxygen is lost due to the heat treatment at a high temperature thereafter occurs, and a defect point is formed, so that a high strength carbon No fiber is obtained. The more preferable range of the saline chloride density is 1.340 g / cm ³ or more and 1.350 g / cm ³ or less.

Proper elongation in the flame resistant brazier is necessary to maintain and improve the orientation of the fibril structure forming the fibers. At elongation of less than 0%, the orientation of the fibril structure cannot be maintained, the orientation in the fiber axis in the formation of the structure of carbon fibers is not sufficient, and excellent mechanical performance does not develop. On the other hand, when the elongation exceeds 10%, the fibrillated structure itself breaks, and the subsequent formation of the structure of the carbon fiber is impaired, and the break point becomes a defect point, so that high strength carbon fiber cannot be obtained. More preferable elongation is 3% or more and 8% or less.

Preferred methods for producing the flame resistant fiber bundles include peak A (2θ = 25 °) and peak B (2θ = 17 °) in the equator direction by fiber bundle wide-angle X-ray measurement by heat-treating the precursor fiber bundle under the above-described oxidizing atmosphere. The intensity ratio (B / A) of 1.3 or more, the orientation of the peak A is 79% or more, the orientation of the peak B is 80% or more, and the density is from 1.335 g / cm ³ to 1.360 g / cm ³ or less will be.

The crystal structure derived from the polyacrylonitrile 100 reflection at the peak B (2θ = 17 °) is closely related to the formation of the structure of the carbon fiber. And once this crystal orientation degree and crystallinity are made low in the manufacturing process of a carbon fiber, it will become difficult to return to it, and there exists a tendency for the performance expression property of a carbon fiber to fall. Here, (100) represents the crystal direction. In particular, in the flameproofing step, the structure of the precursor fiber is greatly changed, and in addition, it is a step of forming a group of graphite crystals, which is a basic structure of carbon fiber. The crystal structure derived from the reflection of the polyacrylonitrile 100 at the peak B (2θ = 17 °) has a large change due to the flameproofing process, and the degree of change is remarkably different depending on the condition setting of the flameproofing process. In order to obtain a highly oriented flame resistant fiber, it is necessary to perform appropriate treatment, and the degree of orientation is closely related to crystallinity, and the crystallinity is remarkably lowered as the degree of orientation decreases. On the contrary, if high orientation can be maintained, a highly crystalline one according to it is obtained. For this reason, a flame resistant fiber bundle having a crystal structure having an intensity ratio (B / A) of 1.3 or more, an orientation degree of peak A of 79% or more, and an orientation degree of peak B of 80% or more is preferable.

Such flameproof fiber bundles can be obtained relatively easily by using the precursor fiber bundle of the present invention. In the step of heat-treating the precursor fiber bundle under an oxidizing atmosphere, the elongation treatment conditions are divided into at least three blocks, and 3.0% or more and 8.0% or less in a range of fiber density of 1.200 g / cm ³ or more and 1.260 g / cm ³ or less. Elongation is performed, and elongation is 0.0% or more and 3.0% or less in a density of 1.240 g / cm ³ or more and 1.310 g / cm ³ or less, and -1.0 in a range of 1.300 g / cm ³ or more and 1.360 g / cm ³ or less. It is preferable to set flame resistance conditions, such as extending | stretching% or more and 2.0% or less.

[Carbon fiber]

Next, the flame resistant fiber bundle is heat-treated for 1.0 minute to 3.0 minutes with an elongation of 2% or more and 7% or less with a first carbonization furnace having a temperature gradient of 300 ° C or higher and 800 ° C or lower in an inert atmosphere such as nitrogen. Suitable treatment temperatures are treated with a linear temperature gradient from 300 ° C to 800 ° C. Considering the temperature of the flameproofing of the previous process, the initiation temperature is preferably 300 ° C or more. When the maximum temperature exceeds 800 ° C., the fibers become very brittle, making transition to the next step difficult. More preferable temperature range is 300-750 degreeC. More preferable temperature range is 300-700 degreeC.

There is no restriction | limiting in particular regarding a temperature gradient, It is preferable to set a linear gradient. At less than 2% elongation, the orientation of the fibril structure cannot be maintained, the orientation in the fiber axis in the formation of the carbon fiber structure is not sufficient, and excellent mechanical performance cannot be exhibited. On the other hand, in the elongation exceeding 7%, the breakage of the fibril structure itself occurs, which impairs the subsequent formation of the structure of the carbon fiber, and the breakage point becomes a defect point, and a high strength carbon fiber cannot be obtained. More preferable elongation is 3% or more and 5% or less. Suitable treatment times are 1.0 minutes to 3.0 minutes. In the treatment of less than 1.0 minute, a severe decomposition reaction due to a rapid temperature rise occurs, and a high strength carbon fiber cannot be obtained. If it exceeds 3.0 minutes, the influence of plasticization of process electricity will arise, the tendency for the orientation of a crystal | crystallization will fall, and the mechanical performance of the carbon fiber obtained as a result will be impaired. More preferable treatment time is 1.2 minutes to 2.5 minutes.

Next, carbon fiber is obtained by performing heat treatment under tension with a second carbonization furnace which can set a temperature gradient in an inert atmosphere such as nitrogen in a range of 1000 to 1600 ° C. Furthermore, if necessary, heat treatment is performed under tension in an inert atmosphere with a third carbonization furnace having a desired temperature gradient. The setting of temperature depends on the desired elastic modulus of carbon fiber. In order to obtain a carbon fiber having high mechanical performance, the maximum temperature of the carbonization treatment is preferably lower, and the elastic modulus can be increased by lengthening the treatment time, so that the maximum temperature can be lowered as a result. In addition, by lengthening the processing time, the temperature gradient can be set gently, which is effective in suppressing defect point formation.

Although it depends also on the temperature setting of a 1st carbonization furnace, a 2nd carbonization furnace may be 1000 degreeC or more. Preferably it is 1050 degreeC or more. There is no restriction | limiting in particular regarding a temperature gradient, It is preferable to set a linear gradient. 1.0 minute-5.0 minutes are suitable for processing time. More preferably, they are 1.5 minutes-4.2 minutes. In this heat treatment, since the fiber bundle is accompanied by a large shrinkage, it is important to heat-treat under tension. Elongation is suitably -6.0% to 2.0%. If it is less than -6.0%, the orientation of the crystal in the fiber axis direction is bad, and sufficient performance is not obtained. On the other hand, in the case of exceeding 2.0%, breakage of the structure itself formed up to now occurs, defect point formation becomes remarkable, and a significant drop in strength occurs. More preferable elongation is in the range of -5.0% to 0.5%.

The carbon fiber bundles thus obtained are provided to the surface oxidation treatment. As a surface treatment method, well-known methods, ie, oxidation treatment by electrolytic oxidation, chemical oxidation, air oxidation, etc. are mentioned, Any may be sufficient. The electrolytic oxidation treatment which is widely practiced industrially is the most suitable method from the viewpoint that stable surface oxidation treatment is possible and control of the surface treatment state can be performed by changing an electric quantity. Here, even if the amount of electricity is the same, the surface state varies greatly depending on the electrolyte used and the concentration thereof, but it is preferable to carry out oxidation treatment by flowing an electric quantity of 10 to 200 coulombs / g of carbon fiber as an anode in an alkaline aqueous solution having a pH greater than 7. . As electrolyte, it is suitable to use ammonium carbonate, ammonium bicarbonate, calcium hydroxide, sodium hydroxide, potassium hydroxide and the like.

Next, the carbon fiber bundles are provided for sizing treatment. A sizing agent can be performed by dissolving the thing dissolve | dissolved in the organic solvent, the emulsion liquid disperse | distributed to water with an emulsifier, etc. to a carbon fiber bundle by the roller dipping method, the roller contact method, etc., and drying this. In addition, adjustment of the adhesion amount of the sizing agent to the surface of a carbon fiber can be performed by adjustment of the density | concentration of a sizing agent liquid, and adjustment of the amount of squeeze. Moreover, drying can be performed using a hot air, a hotplate, a heating roller, various infrared heaters, etc. Subsequently, after sizing agent is attached and dried, it is wound up to bobbin to obtain a carbon fiber bundle.

By using the precursor fiber bundle or the flame resistant fiber bundle of the present invention, a carbon fiber bundle excellent in mechanical performance can be obtained by applying the above-described firing method.

The carbon fiber bundle of the present invention has a resin-impregnated strand strength of 6000 MPa or more, a strand elastic modulus of 250 to 380 GPa measured by the ASTM method, and a ratio of the long diameter and short diameter of the cross section perpendicular to the fiber axis direction of the short fibers (long diameter). / Short diameter) is 1.00 to 1.01, the diameter of the short fibers is 4.0 to 6.0 탆, and at least one or more pores having a diameter of 2 nm or more and 15 nm or less exist in the cross section perpendicular to the fiber axis direction. Since there are few voids or less, it can be set as having a very high strand strength. In particular, even in a carbon fiber bundle with high elastic modulus, high strand strength can be expressed. More suitably, the said void is 50 or less.

Further suitable carbon fiber bundles are those in which the average diameter of the voids in the range of 2 to 15 nm in diameter observed in the cross section perpendicular to the fiber axis direction of the short fibers is 6 nm or less. An average diameter of 6 nm or less indicates that the oil agent uniformly existed in the precursor fiber bundle without being frequently infiltrated locally. By securing this 6 nm or less, the strength expression property of stable carbon fiber can be implement | achieved.

In the carbon fiber bundle of the present invention, the total A (nm ² ) of the area of the voids present in the cross section perpendicular to the fiber axis direction of the short fibers is preferably 2,000 nm ² or less. Also, it is preferable that the voids corresponding to more than 95% of total A ⁽² nm), present between the position of depth 150nm from the surface of the fiber. The short fibers have such a structure, indicating that the oil agent was present only in the polar surface portion near the surface layer in the precursor fiber bundle.

In the present invention, it is preferable that the nodule strength obtained by dividing the tensile fracture stress of the carbon fiber bundles by the cross-sectional area (mass and density of the bundles per unit length) of the fiber bundles is 900 N / mm ² or more. More preferably, it is 1000 N / mm <^2> or more, More preferably, it is 1100 N / mm <^2> or more. The nodule strength can be an index reflecting the mechanical performance of the fiber bundle in a direction other than the fiber axis, and in particular, the performance in the vertical direction can be seen simply with the fiber axis. In a composite material, the material is often formed by pseudo isotropic lamination and forms a complex stress field. At that time, in addition to the tensile and compressive stresses in the fiber axis direction, stresses in directions other than the fiber axis are also generated. In addition, when a relatively high speed distortion such as an impact test is applied, the generated stress state inside the material is quite complicated, and strength in a direction different from the fiber axis direction becomes important. Therefore, when the nodule strength is less than 900 N / mm ² , sufficient mechanical performance does not develop in the pseudoisotropic material.

Example

Hereinafter, the present invention will be described in detail by way of examples. In addition, the measurement and evaluation of the performance of the various fiber in a present Example depend on the following method.

〔One. Swelling degree of coagulated yarn]

The fiber bundles running in the spinning process are taken out, placed in a sealable polyethylene bag and immediately stored in a refrigerator at or below 5 ° C. The time from the start of storage until the swelling degree measurement is completed is within 8 hours.

After weighing the weighing bottle previously dried by direct balance, a sample of about 3 g is taken from the fiber bundle, and put into a weighing bottle. The sample is placed in a cylinder for dehydration of a tabletop centrifuge and set in a centrifuge. After centrifugal treatment (crude dehydration) for 10 minutes at a rotation speed of 3000 revolutions per minute, the sample after dehydration is transferred to a weighing bottle and weighed. This mass is referred to as wet mass A.

If the sample after the crude dehydration still contains a solvent, dehydration is performed after sufficient washing with water. The sample after crude dehydration or washing and dehydration is transferred to a weighing bottle, and dried in a dryer at 105 ° C. for 3 hours while the lid is removed. The sample after drying is transferred to a desiccator while it is put in a weighing bottle, and after being cooled slowly for 20 to 30 minutes, the mass of the weighing bottle is measured. Let this mass be the dry mass B.

The swelling degree is calculated from the following formula.

Swelling degree (%) = (A-B) / B × 100%

〔2. Swelling degree measuring method of swelling yarn]

The swelling sand collected in the spinning process is used as a sample. It is performed by the same method as the measurement of swelling degree of coagulated yarn.

[3. Surface Form Observation of Swelling Yarn]

The swelling sand collected in the spinning process is used as a sample. The solvent contained in the swelling yarn is replaced with t-butanol, the swelling yarn is rapidly frozen with liquid nitrogen, and the fiber sample is kept at a temperature of -30 to -25 ° C and freeze-dried for 24 hours under a reduced pressure of about 3 Pa. . After fixing the dry fiber sample to the SEM observation sample stage with carbon paste, platinum was sputtered to a thickness of about 3 nm with a sputtering device and accelerated by a scanning electron microscope (Nihon Electronics Co., Ltd., product name: JSM-7400F). The surface morphology is observed under a voltage of 3 kV and an observation magnification of 50,000 times.

The width of the circumferential direction is measured with respect to the space | gap which opened on the fiber surface, and the number of the spaces whose width exceeds 10 nm is counted. The same measurement is performed about 50 or more swelling yarns, the total pore number and observation area are measured, and the average value (average pore number) of the number of voids per unit area (1 micrometer ² ) is calculated | required.

〔4. Measurement method of pore distribution of swelling yarn]

The swelling sand collected in the spinning process is dried by the following method. That is, the swelling yarn is fixed to a fixed length so as not to shrink and deform in the drying process, and the mixing ratio of water / t-butanol is sequentially immersed in a mixture of 80/20, 50/50, 20/80, 0/100 by 30 minutes The solvent contained in the swelling yarn is replaced with t-butanol. Subsequently, this swelling yarn sample is placed in a flask and rapidly frozen in liquid nitrogen, followed by freeze drying for 24 to 72 hours under a reduced pressure of 100 Pa or less while maintaining the sample temperature at -30 to -20 ° C.

Samples of freeze-dried swelling yarn bundles were cut to a length of about 10 mm with a razor and weighed about 0.15 g, and were subjected to mercury poloshimetha (manufactured by Shimadzu Corporation, product name: Autopore IV) under atmospheric pressure to a maximum pressure of 30,000 psia. Measure pore distribution. The average pore size (nm) is obtained as the weighted volume average pore size of the pore volume to the pore size. The total pore volume V (ml / g) is the mercury intrusion amount V1 (ml / g) when the pore size is at a pressure corresponding to 500 nm and the mercury intrusion amount V2 when the pore size is at a pressure corresponding to 10 nm ( ml / g) to obtain the following formula.

V = V2-V1

[5. Silicon content measurement of precursor fiber bundles]

[Measurement device]

Fluorescence X-ray analyzer: Rigaku Electric Industries, Ltd., product name: ZSX100e,

Target: Rh (end window type) 4.0 kW,

Spectral crystal: RX4,

Detector: PC (proportional counter),

Slit: Std.,

Diaphragm: 10mmφ,

2θ: 144.681 °,

Measuring line: Si-Kα,

Excitation voltage: 50kV,

Excitation current: 70 mA.

〔How to measure〕

A measurement sample is prepared by uniformly winding a bundle of precursor fibers in an acrylic resin plate having a length of 20 mm, a width of 40 mm, and a width of 5 mm so that there is no gap. Fluorescence X-ray intensity of silicon is measured by a normal fluorescence X-ray analysis method. From the fluorescent X-ray intensity of the silicon of the obtained precursor fiber bundles, the silicon content of the fiber bundles is determined using a calibration curve. The measurement number is n = 10, and those average values are calculated | required and used as a measurement value.

[6. Measurement of Surface Concave-Convex Structure of Precursor Fiber]

Both ends of the short fibers of the precursor fiber bundle are fixed with carbon paste on a metal sample holder plate attached to the scanning probe microscope device, and measured under the following conditions with a scanning probe microscope. First, the shape of a short fiber is measured by a scanning probe microscope. The measurement image is measured by measuring the cross-sectional profile in the vertical direction in the fiber axis by image analysis, and the height difference (Rp-v) and the center line average roughness Ra of the highest part and the lowest part of the contour curve are obtained. Ten short fibers are measured and an average value is obtained.

〔Measuring conditions〕

Devices: SII Nanotechnology's SPI4000 Probe Station, SPA400 (Unit),

Scan Mode: Dynamic Force Mode (DFM) (Shape Measurement),

Probe: SI-DF-20, manufactured by SII Nano Technologies, Inc.

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

Scanning speed: 1.0 Hz,

Pixels: 512 × 512,

Measurement environment: room temperature, air.

For one single fiber, one image is obtained under the above conditions, and the image is analyzed under the following conditions with image analysis software (SPIWin).

(Image analysis condition)

On the obtained shape, [Flat processing], [Median 8 processing], and [3rd order tilt correction] are performed, and the image which fit-corrected the curved surface to the plane is obtained. From the surface roughness analysis of the plane-corrected image, the cross-sectional profile in the vertical direction is measured by the fiber axis, and the height difference (Rp-v) and the center line average roughness Ra of the highest and lowest points of the contour curve are obtained.

[Flat processing]

It is a process for removing the deformation and undulation in the Z-axis direction shown in the image data due to lift, vibration, creep of the scanner, and the like, and a process for removing the deformation of the data by the device on the SPM measurement.

[Median 8 processing]

In the 3x3 window (matrix) centering on the data point S to be processed, an operation is performed between S and D1 to D8, and the Z data of S is substituted to effect the filter of smoothing or removing noise. To get.

Median 8 treatment is obtained by substituting S for the median value of S data and 9 points of Z data of D1 to D8.

(3rd order tilt correction)

The inclination correction calculates and fits a curved surface by least square approximation from the entire data of the processing target image, and corrects the inclination. (1st) (2nd) (3rd) shows the next number of the curved surfaces to fit, and fits a 3rd curved surface in 3rd order. By the 3rd degree correction process, the curvature of the fiber of data is removed and it is set as a flat image.

[7. Measurement of X-ray Diffraction Intensity and Crystal Orientation of Flame Resistant Fiber Bundle]

The flame resistant fiber bundles are cut to any length at 5 cm of fiber length, and 12 mg of the fibers are collected, and the sample fiber axes are aligned so that they are exactly parallel to each other. The width in the direction perpendicular to the longitudinal direction of the fiber is 2 mm, and the fiber bundle is trimmed with a uniform thickness in both the width direction and the longitudinal direction of the fiber. The end of this fiber bundle is impregnated with a vinyl acetate / methanol solution and fixed so as not to collapse.

This is fixed to a wide-angle X-ray diffraction sample stage, and the diffraction intensity in the equator direction is measured by a transmission method to obtain a diffraction intensity profile (vertical axis: diffraction intensity, horizontal axis: 2θ (unit: °)). From the obtained profile, the value of the diffraction intensity peak tower near 2θ = 17 ° corresponding to the polyacrylonitrile 100 reflection and 2θ = 25 ° corresponding to the graphite (002) reflection was detected, and the value was determined as the peak intensity. Shall be.

In addition, crystal orientation degree calculates the half value width W (unit: degree) of a peak by measuring the diffraction profile of an azimuth direction at the peak position of each reflection, and calculates it by following Formula.

Crystal orientation degree (%) = {(180-W) / 180} × 100

The measurement of crystal orientation degree takes three sample fiber bundles in the longitudinal direction of the fiber bundle of a measurement object, measures crystal orientation degree, respectively, and calculate | requires an average value.

On the other hand, X-ray diffraction measurement, using a CuKα ray (using a Ni filter) X-ray generator (trade name: TTR-III, a rotating vs. cathode-type X-ray generator) manufactured by Rigaku Corporation as an X-ray source, the diffraction intensity profile was It is detected by a scintillation counter made by Rigaku Corporation. The output is 50kV-300mA.

〔8. Evaluation of Cross-sectional Shape of Precursor Fiber and Carbon Fiber]

The ratio of the long diameter and short diameter (long diameter / short diameter) of the fiber cross section of the short fiber which comprises a fiber bundle is determined as follows.

After passing a fiber bundle for measurement through a tube of vinyl chloride resin having an internal diameter of 1 mm, the sample is cut in a round shape with a knife. Subsequently, this sample was adhered to the SEM sample table with the fiber cross section facing upwards, and further sputtered Au to a thickness of about 10 nm, and then accelerated by an electron microscope (Philips company, product name: XL20 scanning type). The fiber cross section was observed under the conditions of a voltage of 7.00 kV and an operating distance of 31 mm, and the long and short diameters of the fiber cross section of the short fibers were measured.

[9. Evaluation of Strand Properties of Carbon Fiber Bundles]

The preparation of the strand test body of the resin-impregnated carbon fiber bundle and the measurement of strength are performed in accordance with JIS R7608. However, calculation of elastic modulus is performed using the deformation range according to ASTM.

[10. Evaluation of Porosity in Carbon Fiber Bundle Cross Sections]

The short fibers are removed from the bundle of carbon fibers, and the platinum is sputtered to a thickness of 2 to 5 nm by a sputter apparatus, and then the carbon is coated to a thickness of 100 to 150 nm by a carbon coater apparatus. Thereafter, a tungsten protective film was deposited to a thickness of about 500 nm using a focused ion beam processing apparatus (manufactured by Hitachi High Technologies, Inc., product name: FB-2000A), and then etched with a convergent ion beam having an acceleration voltage of 30 kV. The flakes (thickness 100 to 150 nm) of the cross section of the fiber are obtained.

This thin piece is observed by the transmission electron microscope (The Hitachi High Technologies Co., Ltd. product, product name: H-7600), and the cross section of a single fiber is observed by the magnification of 150,000 times-200,000 times on the conditions of 100 kV of acceleration voltages.

In addition, by using image analysis software (product of Nihon Ropa Co., Ltd., product name: Image-Pro Plus), the part of the void which appears to be bright in a TEM image is extracted, and the number of voids N is counted throughout the cross section. The area of the voids is measured to calculate the circle equivalent diameter d (nm). In addition, the total A (nm ² ) and the average pore diameter D (nm) of the area of the voids are obtained.

In addition, the depth T (nm) of the void is obtained. T is a distance between the position where the cumulative value reaches 95% of the area A and the distance between the fiber surface when the area value is accumulated sequentially from the gap close to the fiber surface. That is, when all the voids appearing in the cross section of short fibers are covered, the radius at which the void of area 0.95 A draws a circle existing on the outer circumference side is r, and the radius of the short fiber is R. , T is requested by

T = R-r.

Said measurement is performed about five fibers, and an average value is calculated | required.

[11. Measurement of nodule strength of carbon fiber bundles]

25 mm long gripping parts are attached to both ends of a 150 mm long bundle of carbon fiber to make a test specimen. When preparing a test body, the carbon fiber bundle is pulled under the load of 0.1 * 10 <^-3> N / denier. A knot is formed almost at the center part of this test body, and the crosshead speed | rate at the time of tension is performed at 100 mm / min. The nominal strength is obtained by dividing the tensile fracture stress by the cross-sectional area of the fiber bundle (mass and density of the bundle per unit length). The number of tests shall be 12 and the minimum and maximum values shall be removed and 10 average values shall be displayed.

(Example 1 and Comparative Examples 1 to 3)

[Preparation of Swelling Yarn and Precursor Fiber]

Acrylonitrile and methacrylic acid were polymerized by aqueous suspension polymerization to obtain an acrylonitrile copolymer comprising acrylonitrile units / methacrylic acid units = 98/2 mass%. The obtained polymer was dissolved in dimethylformamide to prepare a spinning stock solution having a concentration of 23.5% by mass.

This spinning stock solution was once discharged into the air from a spinneret having a diameter of 0.13 mm and a discharge hole having a hole number of 2000, and then passed through a space of about 4 mm, and then heated to 15 ° C., 79.5 mass% dimethyl foam. The aqueous solution containing the amide was discharged into the coagulated liquid filled to solidify, and the coagulated yarn was taken out. Subsequently, after extending | stretching 1.1 to 1.3 times in air, it extended | stretched 1.1 to 2.9 times with the drawing tank which filled the aqueous solution containing 30 mass% dimethylformamide heated at 60 degreeC. After extending | stretching, the fiber bundle containing a solvent was wash | cleaned with clean water, and then extending | stretching 1.2 to 2.2 times was performed in 95 degreeC hot water.

Subsequently, the fiber bundle was made to have 1.1 mass% of the oil agent which has amino modified silicone as a main component, and it dried and densified. The fiber bundle after dry densification was stretched 2.2 times to 3.0 times between heating rolls at 180 ° C., and further wound up after winding to improve orientation and densification to obtain precursor fiber bundles. The fineness of the precursor fiber was 0.77 dtex. In addition, the ratio (long diameter / short diameter) of the long diameter and short diameter of the fiber cross section of a short fiber was 1.005.

Here, the oil agent which has amino modified silicone as a main component used the following.

Amino modified silicone; KF-865 (made by Shin-Etsu Chemical Co., Ltd., first-class side chain type, viscosity 110 cst (25 ° C.), amino equivalent 5,000 g / mol, 85 mass%,

Emulsifiers; NIKKOL BL-9EX (product of Nikko Chemicals, POE (9) lauryl ether), 15 mass%.

[Salt, carbonization]

Subsequently, the precursor fiber bundles were flameproofed by introducing a plurality of precursor fiber bundles into parallel to the flameproofing furnace and blowing air heated to 220 to 280 ° C into the precursor fiber bundles, thereby densifying the precursor fiber bundles to a density of 1.342 g / A bundle of flame resistant fibers of cm ³ was obtained. Where density 1.200 g / cm ³ To about 1.250 g / in the range of cm ³ subjected to a 5.0% elongation, and a density 1.250 g / cm ³ to perform a 1.5% elongation in the range of 1.300 g / cm ^3, and 1.300 g / cm ³ to 1.340 g / cm Elongation was -0.5% in the range of ³ . The elongation rate of the total was 6%, and the flameproofing treatment time was 70 minutes.

The flame resistant fiber bundles were then passed through an elongation of 4.5% with a first carbonization furnace having a temperature gradient of 300 to 700 ° C. in nitrogen. The temperature gradient was set to be linear. The processing time was 1.9 minutes.

Further, heat treatment was performed at an elongation rate of -3.8% using a second carbonization furnace in which a temperature gradient of 1000 to 1250 ° C was set in a nitrogen atmosphere. Subsequently, elongation rate -0.1% heat treatment was performed using the 3rd carbonization furnace which set the temperature gradient of 1250-1500 degreeC in nitrogen atmosphere, and the carbon fiber bundle was obtained. The elongation rate combined the 2nd carbonization furnace and the 3rd carbonization furnace was -3.9%, and the processing time was 3.7 minutes.

[Surface treatment of carbon fiber]

Subsequently, the solution was run in an aqueous solution of 10% by mass of ammonium bicarbonate, and the carbon fiber bundle was used as an anode to conduct electricity through the counter electrode so as to have an electric quantity of 40 coulombs per 1 g of the carbon fiber to be treated. did. Next, 0.5 mass% of hydrane (LAN) N320 (made by DIC Corporation) was stuck, it wound up in the bobbin, and the carbon fiber bundle was obtained. In Example 1 and Comparative Examples 1-3, the ratio (long diameter / short diameter) of the long diameter and short diameter of the fiber cross section of the short fiber of carbon fiber was 1.005, and the diameter was 4.9 micrometer.

[Production of one-way prepreg]

) 프리프레그(이하, 「UD 프리프레그」라고 함)를 제작했다.156 carbon fiber bundles which began to wind from bobbin were put together on the release paper which apply | coated B stage epoxy resin # 410 (180 degreeC hardening type), and the epoxy resin was impregnated through the heat-compression roller. A protective film was laminated thereon, and the unidirectional shearing of resin content of about 33% by mass, carbon fiber density 125 g / m ² , and width of 500 mm (

) Prepreg (hereinafter referred to as "UD prepreg").

[Formation of Laminated Plates and Mechanical Performance Evaluation]

 The laminated board was shape | molded using the said UD prepreg, and the 0 degree tensile strength of the laminated board was measured by the evaluation method based on ASTMD3039.

The stretching conditions in the spinning process are shown in Table 1.

[Evaluation of fiber]

Swelling degree of coagulated and swelled yarn obtained, measurement of surface pore width of swelled yarn, wide-angle X-ray measurement of precursor fiber bundle, TMA evaluation, and wide-angle X-ray measurement of flame resistant yarn, observation of strand strength, elastic modulus and cross-sectional void of carbon fiber, nodule strength The measurement was performed. The results are shown in Table 2. It was confirmed that Example 1 was made of carbon fiber with high mechanical performance.

(Examples 2 to 16 and Comparative Examples 4 to 9)

In the same manner as in Example 1, the conditions of the spinning process were partially changed to obtain swelling yarns and precursor fiber bundles. The fineness of the precursor fiber was 0.77 dtex, and the ratio (long diameter / short diameter) of the long diameter and the short diameter of the fiber cross section of the short fiber was 1.005. Subsequently, carbon fiber bundles were produced under the same firing conditions. The ratio (long diameter / short diameter) of the long diameter and short diameter of the fiber cross section of the short fiber of carbon fiber was 1.005, and the diameter was 4.9 micrometer.

In Table 1, the conditions of a spinning process and the evaluation result of various fiber bundles are put together in Table 2, and are shown.

(Examples 17 to 20)

Using the precursor fiber bundle obtained in Example 14, only the heat treatment conditions were changed to the second and third carbonization furnaces, and the other conditions were the same as those in Example 14, to produce a carbon fiber bundle. Table 3 shows the heat treatment conditions and the properties of the carbon fiber bundles.

(Examples 21 to 25 and Reference Examples 1 and 2)

Using the precursor fiber bundle obtained by changing only the fineness of the short fibers under the same spinning conditions as in Example 14, except that only the heat treatment conditions were changed to the second and third carbonization furnaces in the firing conditions of Example 15. Carbon fiber bundles were produced under the same firing conditions as in Example 15. The properties of the precursor fibers, heat treatment conditions, and carbon fiber bundles are shown in Table 4.

(Examples 26 to 28 and Reference Examples 3 and 4)

The precursor fiber bundle and the carbon fiber bundle were produced on the conditions similar to Example 14 except having changed the kind of amino modified silicone of an oil agent.

The properties of the amino modified silicone species, precursor fibers and carbon fiber bundles used are shown in Table 5.

(Examples 29 to 31)

In the same manner as in Example 1, the conditions of the spinning process were partially changed to obtain swelling yarns and precursor fiber bundles. The fineness of the precursor fiber was 0.77 dtex, and the ratio (long diameter / short diameter) of the long diameter and the short diameter of the fiber cross section of the short fiber was 1.005. Then, the carbon fiber bundle was manufactured on the same baking conditions. The ratio (long diameter / short diameter) of the long diameter and short diameter of the fiber cross section of the short fiber of carbon fiber was 1.005, and the diameter was 4.9 micrometer.

Table 1 shows the conditions of the spinning process and Table 2 shows the evaluation results of the various fiber bundles.

 The carbon fiber bundle of the present invention can be used as a structural material such as an aircraft or a high-speed moving object.

Claims (26)

It consists of the acrylonitrile copolymer which copolymerized 96.0 mass% or more of acrylonitrile 99.7 mass% or less and 0.3 mass% or more and 4.0 mass% or less of unsaturated hydrocarbon which has one or more carboxyl group or ester group as an essential component, Acrylonitrile for non-emulsified carbon fibers having a pore having a width of 10 nm or more in the circumferential direction on the surface of the short fibers in the range of 0.3 / μm ² or more and 2 μm ² or less. Swelling yarn. The method of claim 1,
The pore distribution measured by a mercury intrusion method WHEREIN: The average pore size is 55 nm or less, and the total pore volume is 0.55 ml / g or less. delete delete The manufacturing method of the acrylonitrile swelling yarn for carbon fiber which has the opening part which has a width 10 nm or more in the circumferential direction of a fiber in the range of 0.3 / micrometer <^2> or 2 / micrometer <^2> or less on the surface of short fiber. As
[1] An acrylonitrile-based copolymer obtained by copolymerizing 96.0 mass% or more and 99.7 mass% or less of acrylonitrile and 0.3 mass% or more and 4.0 mass% or less of unsaturated hydrocarbon having at least one carboxyl group or ester group as essential components, 20 Dissolving in an organic solvent in a concentration range of not less than 25% by mass to prepare a spinning stock solution having a temperature of 50 ° C or more and 70 ° C or less,
[2] A coagulation bath consisting of an aqueous solution having a temperature of −5 ° C. or more and 20 ° C. or less and an organic solvent concentration of 78.0% by mass or more and 82.0% by mass or less after discharging this spinning stock solution into the air once from a discharge hole by using a dry-wet spinning method. Coagulating in a step of obtaining a coagulated yarn bundle containing the organic solvent,
[3] After stretching the coagulated yarn bundle in a range of 1.0 to 1.25 times in air, a hot water solution of 40 ° C. or higher and 80 ° C. or lower further containing an organic solvent having a concentration of 30% by mass or more and 60% by mass or less. As a process of extending | stretching in the process, The process of extending | stretching making the total draw ratio by two draw into 2.6 times or more and 4.0 times or less, And
[4] A process for producing a swelling yarn having a step of subsequently desolvating with hot water of 50 ° C. or higher and 95 ° C. or lower and further stretching the water from 0.98 to 2.0 times in hot water of 70 ° C. or higher and 95 ° C. or lower. The method of claim 5, wherein
The organic solvent is either dimethylformamide or dimethylacetoamide. The method of claim 5, wherein
The manufacturing method which makes draw ratio 2.5 times or more and 4.0 times or less in the said hot water solution. The method according to claim 6,
The manufacturing method which makes draw ratio 2.5 times or more and 4.0 times or less in the said hot water solution. Silicone compound which consists of 96.0 mass% or more and 99.7 mass% or less of acrylonitrile and the acrylonitrile copolymer which copolymerized 0.3 mass% or more and 4.0 mass% or less of unsaturated hydrocarbon which has one or more carboxyl group or ester group as an essential component, A precursor fiber bundle for carbon fibers having a silicon content of 1700 ppm or more and 5000 ppm or less, wherein the silicon content is greater than or equal to 50 ppm and 300 ppm or less after 8 hours emulsion washing with methyl ethyl ketone using a soxhlet extractor. Precursor fiber bundles. The method of claim 9,
The fineness of the short fibers is 0.5 dtex or more and 1.0 dtex or less, and the ratio of the long diameter and the short diameter (long diameter / short diameter) of the fiber cross section of the short fibers is 1.00 or more and 1.01 or less and exists in parallel in the fiber axis direction of the short fibers. There is no surface concave-convex structure, which is a corrugated structure having a length of 0.6 μm or more, and the height difference (Rp-v) of the highest part and the lowest part of the image in which the shape of the single fiber is measured by a scanning probe microscope is 30 nm or more and 100 nm. It is below and a precursor fiber bundle whose center line average roughness (Ra) is 3 nm or more and 10 nm or less. As a manufacturing method of the precursor fiber bundle for carbon fiber of Claim 9 or 10,
The oil agent containing a silicone compound is stuck to the bundle of the swelling yarn obtained by the manufacturing method of any one of Claims 5-8, and it adhere | attaches 0.8 mass% or more and 1.6 mass% or less of an oil agent component with respect to 100 mass% of swelling yarns, and is dried. Then, the method of producing a precursor fiber bundle for carbon fibers is drawn in a range of 1.8 to 6.0 times by thermal stretching or steam stretching. The method of claim 11,
The manufacturing method which uses an amino modified silicone compound which satisfy | fills the following conditions (1) and (2) as a silicone compound.
(1) kinematic viscosity at 25 ° C. or more and 50 cst or more and 5000 cst or less,
(2) 1,700 g / mol or more and 15,000 g / mol or less in amino equivalent weight. The manufacturing method of the precursor fiber bundle for carbon fibers which makes an oil agent containing a silicone compound adhere to the bundle of swelling yarns of Claim 1 or 2. The precursor fiber bundle obtained by the manufacturing method according to claim 13 is passed through a flame resistant flame furnace of 220 to 260 ° C. for 30 minutes or more and 100 minutes or less, and the elongation rate is 0% or more and 10% or less, under an oxidizing atmosphere. The manufacturing method of the flame-resistant fiber bundle which satisfy | fills the following conditions by heat processing.
(1) the intensity ratio (B / A) of peak A (2θ = 25 °) and peak B (2θ = 17 °) in the equatorial direction by fiber bundle wide-angle X-ray measurement, 1.3 or more;
(2) the orientation of peak B is 80% or more,
(3) the orientation of peak A is 79% or more,
(4) Density 1.335 g / cm ³ or more and 1.360 g / cm ³ or less. The precursor fiber bundle according to claim 9 or 10 is passed through a hot air circulation flameproofing furnace at 220 to 260 ° C. for 30 minutes to 100 minutes, and the heat treatment is performed under an oxidizing atmosphere at an elongation of 0% to 10%. The manufacturing method of the flameproof fiber bundle which satisfy | fills the following conditions by doing.
(1) the intensity ratio (B / A) of peak A (2θ = 25 °) and peak B (2θ = 17 °) in the equatorial direction by fiber bundle wide-angle X-ray measurement, 1.3 or more;
(2) the orientation of peak B is 80% or more,
(3) the orientation of peak A is 79% or more,
(4) Density 1.335 g / cm ³ or more and 1.360 g / cm ³ or less. 15. The method of claim 14,
Dividing the decompression processing condition into at least three decompression processing blocks,
In the first stretch treatment block, the fiber has a density of 3.0% or more and 8.0% or less in a range of 1.200 g / cm ³ or more and 1.260 g / cm ³ or less,
In the second stretching block, fibers having a density of at least 0.0% and at most 3.0% in a range of at least 1.240 g / cm ³ and at most 1.310 g / cm ³ , and
In the third stretch treatment block, the fiber has a density of -1.0% or more and 2.0% or less in a range of 1.300 g / cm ³ or more and 1.360 g / cm ³ or less
A method for producing a flame retardant fiber bundle, which comprises: a second stretch treatment of fibers having a fiber density of 1.240 g / cm ³ or more and 1.260 g / cm ³ or less in the stretch treatment block including the first stretch treatment block; A flame retardant fiber bundle that provides to the third stretch treatment block a fiber having a fiber density of 1.300 g / cm ³ or more and 1.310 g / cm ³ or less in the stretch treatment block including the second stretch treatment block. Method of preparation. The method of claim 15,
Dividing the decompression processing condition into at least three decompression processing blocks,
In the first stretch treatment block, the fiber has a density of 3.0% or more and 8.0% or less in a range of 1.200 g / cm ³ or more and 1.260 g / cm ³ or less,
In the second stretching block, fibers having a density of at least 0.0% and at most 3.0% in a range of at least 1.240 g / cm ³ and at most 1.310 g / cm ³ , and
In the third stretch treatment block, the fiber has a density of -1.0% or more and 2.0% or less in a range of 1.300 g / cm ³ or more and 1.360 g / cm ³ or less
A method for producing a flame retardant fiber bundle, which comprises: a second stretch treatment of fibers having a fiber density of 1.240 g / cm ³ or more and 1.260 g / cm ³ or less in the stretch treatment block including the first stretch treatment block; A flame retardant fiber bundle that provides to the third stretch treatment block a fiber having a fiber density of 1.300 g / cm ³ or more and 1.310 g / cm ³ or less in the stretch treatment block including the second stretch treatment block. Method of preparation. Resin impregnated strand strength is 6000MPa or more, the strand elastic modulus measured by ASTM method is 250-380GPa, and ratio of the long diameter and short diameter (long diameter / short diameter) of the cross section perpendicular | vertical to the fiber axis direction of short fiber is 1.00-1.01 The carbon fiber bundle whose diameter of a short fiber is 4.0 micrometers-6.0 micrometers, and 1 or more and 100 or less space | gap whose diameter is 2 nm or more and 15 nm or less exists in the cross section perpendicular | vertical to the fiber axis direction of a short fiber. The method of claim 18,
A carbon fiber bundle having an average diameter of the voids of 6 nm or less. The method of claim 18,
A carbon fiber bundle having a total A (nm ² ) of the area of the voids of 2,000 nm ² or less. The method of claim 19,
A carbon fiber bundle having a total A (nm ² ) of the area of the voids of 2,000 nm ² or less. The method according to any one of claims 18 to 21,
A bundle of carbon fibers in which pores corresponding to 95% or more of the sum A (nm ² ) of the total area of the pores present in the cross section perpendicular to the fiber axis direction of the short fibers are located at a depth of 150 nm from the surface of the fiber. 22. The method according to any one of claims 18 to 21,
Carbon fiber bundles that are carbon fibers with a nominal strength of 900 N / mm ² or greater. 23. The method of claim 22,
Carbon fiber bundles that are carbon fibers with a nominal strength of 900 N / mm ² or greater. As a manufacturing method of the carbon fiber bundle of Claim 18,
Claim 9 or after the precursor fiber bundle according to claim 10, in my chloride fiber bundle density of 1.335 g / cm ³ at least 1.355 g / cm ³ or less by the heat treatment under an oxidizing atmosphere, more than 300 ℃ in an inert atmosphere 700 ℃ One having a temperature gradient from 1000 ° C. to firing temperature in an inert atmosphere, followed by heating from 1.0 ° C. to 3.0% with an elongation of 2% or more and 7% or less with a first carbonization furnace having the following temperature gradient. A method of producing a carbon fiber bundle, wherein the carbonization furnace is subjected to a heat treatment of 1.0 minutes to 5.0 minutes while applying an elongation of -6.0% to 2.0%. As a manufacturing method of the carbon fiber bundle of Claim 18,
By the precursor fiber bundle obtained by the method as defined in claim 11, wherein the heat treatment under the oxidizing atmosphere, 1.335 g / cm ³ at least 1.355 g / cm ³ after my chloride fiber bundle or less, more than 300 ℃ in an inert atmosphere 700 As long as the first carbonization furnace having a temperature gradient of not more than 0 ° C. is heated at least 1.0% and not more than 3.0 minutes while applying 2% or more and 7% or less elongation, and subsequently has a temperature gradient from 1000 ° C. to firing temperature in an inert atmosphere. A method for producing a carbon fiber bundle, wherein the carbon fiber furnace is subjected to a heat treatment of 1.0 minute to 5.0 minutes with an elongation of -6.0% to 2.0%.