WO2023042597A1 - Carbon fiber bundle and production method therefor - Google Patents
Carbon fiber bundle and production method therefor Download PDFInfo
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- WO2023042597A1 WO2023042597A1 PCT/JP2022/031179 JP2022031179W WO2023042597A1 WO 2023042597 A1 WO2023042597 A1 WO 2023042597A1 JP 2022031179 W JP2022031179 W JP 2022031179W WO 2023042597 A1 WO2023042597 A1 WO 2023042597A1
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- fiber bundle
- carbon fiber
- flameproofing
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Images
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F6/18—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
Definitions
- the present invention relates to a carbon fiber bundle that is suitable for fabrics that has excellent shapeability while having high properties for enhancing the energy absorption performance of carbon fiber composite materials, and a method for producing the same.
- CFRP carbon fiber reinforced plastics
- impact resistance high impact energy absorption performance
- the carbon fiber fabric uses carbon fiber bundles in which carbon fiber single fibers are bundled, the cross section of the carbon fiber bundles is elliptical in the woven state.
- the plain weave structure in which one warp and weft alternately rise and fall has the advantage that the number of interlacing yarns is large and the shape is easy to stabilize, but there is a problem that large crimps occur at the intersecting parts where the warp and weft yarn intersect. there is a point In particular, in fabrics using carbon fiber bundles having a large total fineness, this tendency becomes greater because carbon fiber bundles having a large thickness intersect.
- woven fabrics using carbon fiber bundles include unidirectional woven fabrics and multidirectional woven fabrics, and attempts have been made to reduce or avoid crimping by using a woven structure such as a twill weave structure, but none of these are available.
- strand strength the excellent resin-impregnated strand strength of carbon fiber bundles
- crimping of the current woven structure is unavoidable.
- improving carbon fiber bundles is more effective than improving them, the impact resistance of the entire CFRP was not satisfactory because of the low elongation of the carbon fiber bundles used in the fabric.
- Patent Document 1 uses a carbon fiber bundle having a thickness of 0.09 mm or less and a basis weight of 85 g/m 2 or less to obtain a thin, wide and flat carbon fiber bundle. reduces the crimp of the carbon fiber bundle, and obtains a high reinforcing effect in thin CFRP.
- Patent Document 2 As an attempt to increase the strand strength and elongation of the carbon fiber bundle itself, in Patent Document 2, by increasing the fracture toughness value, the maximum strand strength is 8.4 GPa, and the resin-impregnated strand elastic modulus (hereinafter abbreviated as strand elastic modulus ) and achieved 325 GPa (Example 3). Similarly, in Patent Document 3, a maximum strand strength of 7.9 GPa and a maximum strand elastic modulus of 350 GPa are obtained by increasing the fracture toughness of carbon fibers (Example 7). In terms of the cross-sectional shape of the carbon fiber bundle, Patent Document 4 attempts a method of twisting the carbon fiber bundle in the flameproofing step, and obtains a carbon fiber bundle having a flat cross section.
- strand elastic modulus resin-impregnated strand elastic modulus
- Patent Document 5 the strand strength of the carbon fiber bundle is increased to a certain level by increasing the distortion of the ratio of the major axis to the minor axis of the carbon fiber single fiber by the method of mixing carbon fibers with different cross-sectional shapes and twisting the carbon fiber bundle. We have succeeded in flattening the cross section of the carbon fiber bundle while keeping it level.
- Patent Document 1 a high reinforcing effect of the fabric is obtained by thinning the carbon fiber bundles.
- the elongation and openability of the carbon fiber bundle were not satisfactory values.
- Patent Documents 2 and 3 an attempt is made to improve the strand strength by improving the toughness, but since twisting is not performed at the stage of the flameproofing treatment, the single fiber cross-sectional shape is not controlled, and the carbon fiber There was a problem that the bundle was thick and thick. Even if the carbon fiber bundle were torn in half and used as a thin bundle, the single fiber cross-sectional shape was not sufficient to reduce the thickness of the bundle.
- Patent Document 4 although the flatness of the cross section of the carbon fiber bundle is increased by twisting in the flameproofing process, it does not pay attention to the elongation due to the strand strength or strand elastic modulus, so even at the maximum, the examples The strand strength was unsatisfactory at 5.6 GPa, and the elongation was also unsatisfactory.
- Patent Document 5 attempts to mix and twist carbon fibers with different cross-sectional shapes to increase the degree of distortion of the single fiber cross-sectional shape and increase the flatness of the cross-sectional shape of the carbon fiber bundle, but does not focus on the elongation.
- the maximum strand strength was 4.8 GPa (Example 7) and the strand elastic modulus was 317 GPa, so the elongation was not satisfactory.
- attempts to improve the strand strength and elongation of carbon fiber bundles and attempts to improve the flatness of carbon fiber bundles have been made separately until now, but the effects are completely different.
- the operation performed to improve the flatness reduces the strand strength, it is not easy to combine them, and the combination of the two has not been studied so far.
- the carbon fiber bundles are more suitable for textiles.
- Strand strength is high, elongation is high for impact resistance, total fineness is small for crimp reduction, and flatness of carbon fiber bundles is large.
- An object of the present invention is to provide a carbon fiber bundle having a large degree of distortion.
- the present invention provides a carbon fiber bundle having a plurality of single fibers, which has a strand elastic modulus of 260 to 350 GPa, a strength of 6.0 to 8.5 GPa, and an elongation of 1.8%.
- the number of filaments is 1,000 to 9,000, the total fineness is 0.15 to 0.35 g/m, and the average value of the ratio of the major axis to the minor axis of the cross section of the single fiber is 1.01 to 1.08.
- the carbon fiber bundle has a coefficient of variation of 1 to 4% and a degree of skew of 0.3 to 1.2.
- the carbon fiber bundle of the present invention has high strand strength and high elongation, and since the total fineness of the carbon fiber bundle is small and the strain of the carbon fiber single fiber is large, the cross section of the carbon fiber bundle can be made thin. As a result, the CFRP made from the woven fabric of this carbon fiber bundle has excellent energy absorption performance.
- the average value of the ratio of the major axis to the minor axis of the single fiber cross section is 1.01 to 1.08, preferably 1.01 to 1.05, more preferably 1.01 to 1.03. is.
- the ratio of major diameter to minor diameter refers to the ratio obtained by dividing the major diameter by the minor diameter in the cross section of a single fiber.
- the cross section of a single fiber refers to the cross section of a single fiber perpendicular to the fiber axis.
- the major diameter refers to the maximum value of the Feret diameter, which is the length of the longer side of a rectangle drawn so as to circumscribe the cross section of a single fiber.
- the major axis is the major axis, and the minor axis of the ellipse having the same cross-sectional area as the cross section of the single fiber.
- the average value is a simple average without weighting, and it means that the closer the average value of the ratio of major diameter to minor diameter is to 1.00, the more single fibers have a circular cross section. Since the elongation of the carbon fiber bundle tends to decrease as the average value of the ratio of major to minor diameters increases, the average value of the ratio of major to minor diameters should be 1.01 or more, and the average value of the ratio to major to minor diameters is 1.08. If it is below, the elongation of the carbon fiber bundle can be maintained without being greatly reduced.
- a commonly known method for controlling the average ratio of the major axis to the minor axis of the single fiber cross section within the above range is to change the conditions of the coagulation bath.
- the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.00 to 1.03 is preferably 30 to 90%, more preferably 40 to 85%, and even more preferably 50 to 80%.
- the greater the ratio of major to minor diameters the easier the spreadability becomes, but if the ratio of the number of single fibers having a ratio of major to minor diameters of 1.00 to 1.03 exceeds 90%, the strand strength may decrease.
- the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.00 to 1.03 is 30% or more, it is easy to achieve both of these properties at a high level.
- a monofilament having a ratio of the major axis to the minor axis of 1.00 to 1.03 can be obtained by adjusting the coagulation conditions or by adjusting the force for crushing the monofilament in the direction perpendicular to the fiber axis.
- the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.04 to 1.10 is preferably 10 to 40%, more preferably 15 to 25%.
- 10% or more of the single fibers having a ratio of major axis to minor axis of 1.04 to 1.10 are contained, it is easy to achieve both of these properties at a high level.
- a monofilament having a major/minor diameter ratio of 1.04 to 1.10 can be obtained by adjusting the coagulation conditions or by adjusting the force for crushing the monofilament in the direction orthogonal to the fiber axis.
- the coefficient of variation of the ratio of major diameter to minor diameter of the number of single fibers is 1 to 4%, preferably 1 to 3%, more preferably 1 to 2%.
- the coefficient of variation is calculated by dividing the standard deviation by the average value and multiplying by 100, as generally defined.
- a large coefficient of variation of the ratio of the major diameter to the minor diameter means that the ratio of the major diameter to the minor diameter is widely distributed.
- the coefficient of variation is 1% or more, the carbon fiber bundle is excellent in opening property, and when it is 4% or less, the elongation of the carbon fiber bundle is not significantly impaired.
- a method for controlling the coefficient of variation of the ratio of the major axis to the minor axis of the single fiber cross section within the above range will be described later.
- the distortion of the ratio of the major axis to the minor axis of the single fiber is 0.3 to 1.2, preferably 0.3 to 1.1, more preferably 0.4 to 1.0. , more preferably 0.6 to 1.0.
- Skewness is a parameter that represents the asymmetry of distribution and is defined by the following equation (1).
- Skewness n/((n ⁇ 1) ⁇ (n ⁇ 2)) ⁇ (xi ⁇ x>)/s ⁇ 3 (1)
- n is the number of single fibers (number)
- xi is the ratio of the major axis to the minor axis of the i-th single fiber (-)
- ⁇ x> is the average value of the ratio of the major axis to the minor axis (-)
- s is the ratio of the major axis to the minor axis.
- ⁇ means that the sum is taken for the number n of single fibers.
- a skewness value of 0 indicates that the distribution is bilaterally symmetrical
- a negative value indicates that the tail is on the small side
- a positive value indicates that the tail is on the large side.
- a state in which the ratio of the major axis to the minor axis is highly skewed means a state in which there is a certain amount of single fibers with a large ratio of the major axis to the minor axis, but the average value of the ratio of the major axis to the minor axis remains low.
- the flame resistant fiber is twisted to apply tension to generate a pressing force between the single fibers. Control by transforming. By observing the cross section of the obtained carbon fiber single fiber and making fine adjustments, the carbon fiber bundle of the present invention satisfies the numerical range.
- the carbon fiber bundle of the present invention has 1,000 to 9,000 filaments.
- the number of filaments is the number of single fibers contained in the carbon fiber bundle. If the number of filaments is 1,000 or more, sufficient elongation can be obtained, and if the number of filaments is 9,000 or less, the total fineness is reduced. It can be kept small to obtain a suitable crimp angle for textiles.
- the number of filaments can be arbitrarily determined in the process of manufacturing the polyacrylonitrile-based carbon fiber precursor fiber bundle.
- the carbon fiber bundle of the present invention has a total fineness of 0.15-0.35 g/m, more preferably 0.20-0.30 g/m.
- the total fineness is the mass per 1m of the carbon fiber bundle, and is related to the single fiber diameter and the number of filaments of the carbon fiber bundle. The smaller the total fineness, the smaller the crimp angle. If the total fineness is 0.15 g/m or more, CFRP with excellent impact resistance can be obtained, and if it is 0.35 g/m or less, a crimp angle suitable for woven fabric can be obtained.
- the total fineness can be obtained by measuring the length of the carbon fiber bundle and the mass for that length. The total fineness can be controlled by adjusting the number of filaments other than the single fiber diameter. Identical properties tend not to be obtained.
- the carbon fiber bundle of the present invention has a strand elastic modulus of 260 to 350 GPa, preferably 270 to 320 GPa, more preferably 270 to 300 GPa.
- the strand elastic modulus is an index that indicates how difficult it is to deform a carbon fiber bundle when a load is applied, in other words, it is an index that indicates the lightness of the material.
- the strand elastic modulus of the carbon fiber bundle can be evaluated according to the resin-impregnated strand tensile test described in JIS R7608:2004. Although the stress-strain curve of the carbon fiber bundle exhibits downwardly convex nonlinearity, the strain range is set to 0.1 to 0.6%, and the strand elastic modulus within that range is used.
- the strand elastic modulus is 260 GPa or more, the carbon fiber bundle is lightweight, and if the strand elastic modulus is 350 GPa or less, the elongation can be kept high relative to the strength obtained, so sufficient impact resistance can be obtained. can get.
- the strand elastic modulus can be controlled by the maximum temperature in the carbonization process, the heat treatment time at the maximum temperature, the heating rate, the stretching ratio, and the like.
- the carbon fiber bundle of the present invention has a strand strength of 6.0 to 8.5 GPa, preferably 6.5 to 8.0 GPa, more preferably 7.0 to 8.0 GPa.
- Strand strength is an index showing how difficult it is to break when a load is applied to a carbon fiber bundle.
- the strand strength of the carbon fiber bundle can be evaluated according to the resin-impregnated strand tensile test described in JIS R7608:2004. If the strand strength is 6.0 GPa or more, sufficient impact resistance can be obtained, and although there is no upper limit for the strand strength, if the strand strength is as high as 8.5 GPa, the impact resistance tends to reach a sufficiently satisfactory level.
- Strand strength can be enhanced by controlling various conditions such as flameproofing conditions and carbonization conditions, such as defect suppression and fracture toughness improvement.
- the carbon fiber bundle of the present invention has an elongation of 1.8% or more, preferably 2.0% or more, more preferably 2.2% or more, and still more preferably 2.4% or more. .
- the elongation of the carbon fiber bundle can be evaluated according to the resin-impregnated strand tensile test described in JIS R7608:2004. It is difficult to measure the elongation of carbon fiber bundles because the stress-strain curve exhibits nonlinearity, but in this tensile test, the elongation is calculated by dividing the above-mentioned strand strength by the above-mentioned strand elastic modulus. .
- the elongation of the carbon fiber bundle can be adjusted by controlling the balance between the strand strength and the strand elastic modulus.
- the area ratio obtained by dividing the area of the cross section of the carbon fiber bundle by the area of the rectangle defined later is preferably 0.50 to 0.70. , more preferably 0.60 to 0.70. If the area ratio is 0.78, it means that the cross section is elliptical with respect to the theoretically defined rectangle. This indicates that the single fibers forming the carbon fiber bundle are partially dented. If it is 0.70 or less, the carbon fiber bundle can be made flat because it partially has a single fiber having a depression as an effect of inserting a plurality of fiber bundles into one groove. It is possible to ensure the flatness of the carbon fiber bundle when it is made into a woven fabric.
- the cross-sectional shape of the carbon fiber bundle is affected by the flameproofing tension and twist angle, but partial depressions in the carbon fiber bundle are mainly caused by inserting multiple fiber bundles into one groove in the flameproofing process and making them contact each other. can be controlled by
- a polyacrylonitrile-based polymer is preferably used as a raw material for producing a polyacrylonitrile-based carbon fiber precursor fiber bundle (hereinafter sometimes abbreviated as a precursor fiber bundle).
- the polyacrylonitrile-based polymer preferably accounts for 90 to 100 mol % of at least acrylonitrile polymer.
- the polyacrylonitrile-based polymer preferably contains a copolymer component from the viewpoint of improving strand strength.
- a monomer that can be used as a copolymerization component a monomer containing one or more carboxylic acid groups or amide groups is preferably used from the viewpoint of promoting flame resistance.
- either a dry-wet spinning method or a wet spinning method may be used as the spinning method, but it is preferable to use the dry-wet spinning method, which is advantageous for the strand strength of the resulting carbon fiber bundle.
- the spinning process includes a spinning process in which a spinning solution is discharged from a spinneret into a coagulating bath by a dry-wet spinning method for spinning, a washing process in which the fiber bundle obtained in the spinning process is drawn while being washed in a water bath, and the It preferably comprises a dry heat treatment step of dry heat-treating the fiber bundle obtained in the water washing step, and optionally includes a steam drawing step of steam-drawing the fiber bundle obtained in the dry heat treatment step. In addition, it is also possible to change the order of each step as appropriate.
- the spinning solution is obtained by dissolving the polyacrylonitrile-based polymer described above in a solvent in which polyacrylonitrile is soluble, such as dimethylsulfoxide, dimethylformamide and dimethylacetamide.
- the coagulation bath preferably contains a solvent such as dimethylsulfoxide, dimethylformamide and dimethylacetamide used as a solvent for the spinning solution, and a so-called coagulation promoting component.
- a solvent such as dimethylsulfoxide, dimethylformamide and dimethylacetamide used as a solvent for the spinning solution
- a so-called coagulation promoting component a component that does not dissolve the polyacrylonitrile-based polymer and is compatible with the solvent used for the spinning solution can be used.
- water As the coagulation promoting component.
- the cross-sectional shape changes depending on the coagulation conditions, and the cross-section becomes circular when the concentration of the solvent in the coagulation bath is low (40% by mass or less) and when it is high (near 80% by mass). It becomes a ⁇ -shaped cross section when it is concentrated.
- the fibers are preferably provided with an oil such as silicone.
- silicone oils preferably contain amino-modified silicones.
- a known method for the dry heat treatment process can be used for the dry heat treatment process.
- the drying temperature is 100-200°C.
- a precursor fiber bundle suitable for obtaining the carbon fiber bundle of the present invention can be obtained by performing steam drawing as necessary. Steam drawing is preferably performed at a draw ratio of 2 to 6 times in pressurized steam.
- a carbon fiber bundle is obtained by subjecting a precursor fiber bundle to a flameproofing step, a preliminary carbonization step, and a carbonization step.
- the resulting flameproofed fiber bundle has a 1,370 cm -1 peak intensity in the infrared spectrum.
- the ratio of the peak intensity at 453 cm -1 is in the range of 0.70 to 0.75, and the ratio of the peak intensity at 1,254 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum is 0.50 to 0
- it is controlled to be in the 0.65 range.
- the peak at 1,453 cm ⁇ 1 in the infrared spectrum is derived from alkene, and decreases as flame resistance progresses.
- a peak at 1,370 cm ⁇ 1 and a peak at 1,254 cm ⁇ 1 are peaks derived from the flameproof structure, and increase as the flameproofing progresses.
- the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 is preferably about 0.63 to 0.69. .
- the peak intensity ratio decreases as the flameproofing progresses, and the decrease is particularly large in the initial stage.
- the amount of the copolymer component contained in the polyacrylonitrile-based polymer constituting the precursor fiber bundle is small, and the precursor fiber
- the conditions may be set mainly by paying attention to a high degree of crystal orientation of the bundle, a small single fiber fineness of the precursor fiber bundle, and a high flameproofing temperature in the latter half.
- the polyacrylonitrile-based carbon fiber precursor fiber bundle was heated until the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum was in the range of 0.98 to 1.10. Minute flameproofing (first flameproofing step), followed by a higher temperature than the first flameproofing step, where the ratio of the peak intensity at 1,453 cm to the peak intensity at 1,370 cm in the infrared spectrum is 0. .70 to 0.75 and for 5 to 20 minutes until the ratio of the 1,254 cm -1 peak intensity to the 1,370 cm -1 peak intensity in the infrared spectrum is in the range of 0.50 to 0.65. Flameproofing (second flameproofing step) is preferred.
- the flameproofing temperature should be adjusted to a high value, but an appropriate flameproofing temperature depends on the properties of the precursor fiber bundle.
- a flameproofing temperature of preferably 260-290° C. is preferred to control the range of the infrared spectrum described above.
- the flameproofing temperature need not be constant, and may be set in multiple stages.
- the flameproofing temperature is high and the flameproofing time is short.
- the flameproofing time is preferably 10 to 25 minutes, and the flameproofing is preferably performed at a flameproofing temperature within the above range.
- the flameproofing time mentioned here means the time during which the fibers stay in the flameproofing furnace
- the flameproof fiber bundle means the fiber bundle after the flameproofing process and before the preliminary carbonization process.
- the peak intensity described here refers to the absorbance at each wavelength after baseline correction of the spectrum obtained by measuring the infrared spectrum of a small amount of the flameproof fiber bundle sampled, especially the peak splitting. not performed.
- the concentration of the sample is diluted with KBr so as to be 0.67% by mass and measured. In this way, the infrared spectrum should be measured every time the setting of the flameproofing conditions is changed, and the conditions should be examined.
- the strand strength of the obtained carbon fiber bundle can be controlled.
- the flameproofing step means heat-treating the precursor fiber bundle at 200 to 300°C in an oxygen-containing atmosphere.
- the total processing time of the flameproofing step can be appropriately selected, preferably within the range of 15 to 40 minutes.
- the flameproofing treatment time is set so that the specific gravity of the obtained flameproofed fiber is preferably 1.28 to 1.32.
- a more preferable treatment time for the flameproofing step depends on the flameproofing temperature. Unless the specific gravity of the flameproof fiber bundle is 1.28 or more, the strand strength of the carbon fiber bundle may decrease. If the specific gravity of the flameproof fiber bundle is 1.32 or less, the strand strength can be increased.
- the specific gravity of the flameproofing fiber bundle is controlled by the treatment time of the flameproofing step and the flameproofing temperature.
- the timing of switching from the first flameproofing step to the second flameproofing step is such that the specific gravity of the fiber bundle is preferably in the range of 1.21 to 1.23. Also in this case, the conditions of the flameproofing step are controlled with priority given to satisfying the range of the infrared spectrum intensity ratio. Preferred ranges of the treatment time for flameproofing and the flameproofing temperature vary depending on the properties of the precursor fiber bundle and the copolymer composition of the polyacrylonitrile polymer.
- twisting treatment for adjusting the degree of distortion is performed in this second flameproofing step, and the twist angle of the fiber bundle during the flameproofing treatment is preferably 0.2° or more.
- the method of twisting the fibers during the flameproofing treatment can be selected from known methods. Specifically, there is a method in which the precursor fiber bundle is once wound on a bobbin and then, when the fiber bundle is unwound, the bobbin is rotated in a plane orthogonal to the unwinding direction, or a method in which the fiber bundle is running without being wound on the bobbin.
- the twist can be controlled by a method of bringing a rotating roller or belt into contact with the fiber bundle to impart a twist. The larger the twist angle, the more the effect of improving the flatness of the carbon fiber bundle can be obtained.
- the tension of the fiber bundle during the flameproofing treatment is preferably 0.7 to 1.5 mN/dtex.
- the tension in the flameproofing step was obtained by dividing the tension (mN) measured at the inlet side of the flameproofing furnace by the total fineness (dtex), which is the product of the single fiber fineness (dtex) of the precursor fiber bundle used and the number of filaments. shall be By controlling the tension within the above numerical range, it becomes easier to give the carbon fiber monofilament a dent.
- the second flameproofing step a plurality of fiber bundles are put into one groove of the roller for flameproofing.
- This keeps the tension on the individual flameproofed fiber bundles low while increasing the overall tension of the multiple fiber bundles per groove, so that on the roller some single fibers have A directional stress is applied, and the ratio of the major axis to the minor axis of the cross section of the single fiber tends to increase.
- the cross-sectional shape of some single fibers can be controlled while maintaining the overall cross-sectional shape.
- the plural is preferably 2 to 6, more preferably 3 to 5.
- the fiber bundles obtained in the first and second flameproofing steps are treated in an inert atmosphere at a maximum temperature of 500 to 1,200 ° C. to a specific gravity of preferably 1.5. Heat treat to ⁇ 1.8.
- the draw ratio in the preliminary carbonization step is preferably 1.00 to 1.20. If the draw ratio in the preliminary carbonization step is 1.00 or more, the strand elastic modulus tends to increase, and the strand strength tends to increase. When the draw ratio in the preliminary carbonization step is 1.20 or less, the strand elastic modulus is easily suppressed to 350 GPa or less.
- the pre-carbonized fiber bundle is carbonized in an inert atmosphere, preferably at a maximum temperature of 1,000-1,500°C, more preferably at a maximum temperature of 1,000-1,200°C.
- the maximum temperature of this carbonization step is preferably low from the viewpoint of increasing the elongation of the obtained carbon fiber bundle, and if it is too low, the strand strength may decrease, so it is preferable to set it in consideration of both. .
- the maximum temperature treatment time in the carbonization step is preferably 20 to 60 seconds.
- the temperature elevation rate in the carbonization step is preferably 0.40-1.10°C/sec, more preferably 0.40-0.60°C/sec.
- the rate of temperature rise in the carbonization step affects the desorption rate of cracked gas, and therefore affects the strand strength.
- the heating rate is defined as the average rate at which the fiber passes through the temperature range of 1,000 to 1,100°C per second.
- the temperature is often controlled by the set temperature of the heater, so the temperature rise rate is calculated from the temperature at the center of the installation position of each heater and the fiber passage timing. If the heating rate is 0.40° C./second or more, a stable strand elastic modulus can be easily obtained, and if it is 1.10° C./second or less, a decrease in strand strength can be easily suppressed.
- the carbon fiber bundles obtained as described above are preferably subjected to oxidation treatment to introduce oxygen-containing functional groups.
- the carbon fiber bundle is obtained by subjecting the fiber bundle obtained in the carbonization step to electrolytic surface treatment.
- electrolytic surface treatment gas-phase oxidation, liquid-phase oxidation and liquid-phase electrolytic oxidation are used, but liquid-phase electrolytic oxidation is preferably used from the viewpoint of high productivity and uniform treatment.
- the liquid-phase electrolytic oxidation method is not particularly limited, and a known method may be used.
- a sizing treatment can be applied to impart bundling properties to the obtained carbon fiber bundles.
- a sizing agent having good compatibility with the matrix resin can be appropriately selected according to the type of the matrix resin used in CFRP.
- the carbon fiber bundle of the present invention is preferably used mainly as yarn for crimped fabrics.
- a unidirectional woven fabric or a multidirectional woven fabric can be used. It is effective to use it for bidirectional fabrics.
- a plain weave structure in which one warp and one weft are alternately floating and interlaced is preferable because the number of crossing points of weaving yarns is large and the shape is easily stabilized.
- the reinforcing fabric can be manufactured by the following method.
- the flat and substantially untwisted carbon fiber bundles as described above are used as warp and/or weft yarns, and are transversely unwound so that the flatness of the carbon fiber bundles does not deteriorate and untwisting is not applied.
- each weaving yarn may be opened or widened during or after weaving.
- the reinforcing fabric as described above is used for forming preforms, prepregs, and CFRP, and exhibits excellent properties as a reinforcing base material. At least one sheet of any one of the reinforcing fabrics can be used for the preform.
- the reinforcing fabric thus obtained is preferably used for members requiring high mechanical properties. It is preferable to form this reinforcing fabric into CFRP as a fabric prepreg or vacuum forming using a fabric substrate.
- the carbon fiber bundle of the present invention satisfies all of the strand elastic modulus, strand strength, elongation, total fineness, the average value of the ratio of the major diameter to the minor diameter, the coefficient of variation, and the degree of distortion to enhance the impact resistance of CFRP. point is important.
- the methods for measuring various physical property values used in the present invention are as follows.
- Total fineness> A 10 m length sample of the carbon fiber bundle to be measured is dried at 120° C. for 2 hours, and the measured mass is divided by 10 to obtain the total fineness, which is the mass per 1 m.
- the carbon fiber bundle to be measured is dried at 120° C. for 2 hours before use.
- a dry automatic density meter is used, nitrogen is used as a measurement medium, a 10 cc type sample container is used, and the volume of the sample is adjusted to 3 to 6 cc. Measurement is performed 3 times and the average value is used.
- an Accupic 1330 type dry automatic density meter manufactured by Shimadzu Corporation was used.
- the strand strength, strand elastic modulus and elongation of the carbon fiber bundle are obtained according to the resin-impregnated strand test method of JIS R7608:2004, according to the following procedure.
- normal pressure, temperature of 125° C., and time of 30 minutes are used. Seven carbon fiber strands are measured, and the average values are taken as the strand strength, strand elastic modulus and elongation.
- the strain range for calculating the strand elastic modulus is 0.1 to 0.6%.
- twist angle in flameproof treatment is calculated by the following formula using the basis weight y (g/m), density d (g/cm 3 ), and twist number T (turn/m) of the precursor fiber bundle used. .
- Twist angle (°) arctan ⁇ (0.01 x y/( ⁇ x d)) 0.5 x 10 -6 x ⁇ x T ⁇ .
- the method for evaluating the ratio of the major axis to the minor axis, the coefficient of variation, and the degree of skewness is not particularly limited as long as the evaluation is performed according to the above definitions, but the evaluation can be performed, for example, as follows. First, the carbon fiber bundles are aligned and put together with a carbon tape so as to wrap them in a cylindrical shape. In this state, scissors are applied perpendicular to the fiber axis to cut, thereby exposing the cross section of the single fiber. Such single fiber cross-sections are observed using a scanning electron microscope and saved as images.
- the saved images are read into the open source image analysis software "ImageJ” (Version 1.53h) and the single fiber cross-section contours are traced using the “Polygon selections” tool. At this time, one contour is traced with 20 to 100 points. The contour trace is then converted to a smooth curve using the "Fit spline” tool. After conversion, the points are moved and fine-tuned to better match the profile of the monofilament cross-section and the traced curve. Subsequently, the “AR (aspect ratio)” is calculated using the “Analyze particles” tool. In addition, the aspect ratio refers to the ratio of major axis to minor axis in the present invention.
- the number of single fibers may be any number, but the number of single fibers is selected so that no statistical deviation appears. For example, the same operation is performed on 50 single fibers. At this time, single fibers are evenly selected from different portions of the carbon fiber bundle.
- the ratio of the number of single fibers having a specific ratio of major axis to minor axis is a value (%) obtained by dividing the number of single fibers having a specific ratio of major axis to minor axis by the total number of evaluated single fibers and multiplying by 100.
- the average value (-), coefficient of variation (%), and skewness (-) are calculated from all evaluated single fiber counts.
- the skewness of the ratio of major diameter to minor diameter is calculated according to the following formula (1).
- Skewness n/((n ⁇ 1) ⁇ (n ⁇ 2)) ⁇ (x i ⁇ x>)/s ⁇ 3 (1)
- n is the number of single fibers (pieces)
- x i is the ratio of the major diameter to the minor diameter of the i-th single fiber (-)
- ⁇ x> is the average value of the ratio of the major diameter to the minor diameter (-)
- s is the major diameter to the minor diameter.
- ⁇ means that the sum is taken for the number n of single fibers.
- SEM scanning electron microscope
- S-4800 manufactured by Hitachi High-Technologies Corporation was used as a scanning electron microscope, and observation was carried out at an accelerating voltage of 5 keV.
- Openability is evaluated in a state in which no sizing agent is adhered to the carbon fiber bundle. If the sizing agent is adhered, it is removed by burning off the sizing agent in an oven or by washing in a solvent before evaluation. A carbon fiber bundle of 2 cm is sampled, and is assumed to be untwisted. A carbon fiber bundle is placed on a 10 cm square glass plate, and a slide glass is placed on it. The carbon fiber bundle is moved 10 times alternately by 3 mm in the axial direction and the vertical direction. The yarn width change was measured before and after this operation, and the average value obtained by repeating this operation 10 times was used as an index of the openability. The greater the ratio of the yarn width expansion, the better the openability.
- the openability is judged from A to C by how many times the yarn width of the carbon fiber bundle is larger than the yarn width before measurement.
- the cross-sectional shape of the carbon fiber bundle is measured as follows.
- the carbon fiber bundle is allowed to hang under its own weight in a state where it is substantially untwisted and with almost no tension applied, and the entire carbon fiber bundle is fixed by applying an adhesive or the like. Cut so as not to destroy the shape of A cross section of the cut carbon fiber bundle is observed with a polarizing microscope to acquire an image.
- the acquired images are loaded into the open-source image analysis software "ImageJ" (Version 1.53h) and the single fiber cross-section contours are traced using the "Polygon selections" tool. At this time, one contour is traced with 20 to 100 points on the contour.
- the contour trace is then converted to a smooth curve using the "Fit spline” tool.
- the "Analyze particles” tool is used to obtain the length and position information of the Feret diameter and the area within the contour.
- the length of the line segment that intersects perpendicularly with the line segment that is the Feret diameter and has the longest distance to the contour is obtained.
- the cross-sectional shape of the carbon fiber bundle is determined by the area within the contour, the Feret diameter, and the length of the line segment perpendicular to the Feret diameter, and calculated according to the following formula (2).
- A is the Feret diameter
- B is the length of the aforementioned line segment perpendicular to the Feret diameter
- C is the area within the contour, which correspond to the letters in FIG.
- the cross-sectional shape is determined by determining the area ratio of the carbon fiber bundle cross-section from the rectangle (A ⁇ 2B) defined by two sides and the area (C) within the contour.
- Example 1 A polyacrylonitrile-based polymer was polymerized by a solution polymerization method using dimethylsulfoxide as a solvent to obtain a spinning solution.
- the resulting spinning solution was once discharged into the air from a spinneret and introduced into a coagulation bath consisting of an aqueous solution of 35% by mass of dimethyl sulfoxide maintained at 0°C to obtain a coagulated filament by a dry-wet spinning method.
- the coagulated yarn was washed with water by a conventional method, it was stretched 3.5 times in two hot water baths. Subsequently, an amino-modified silicone-based silicone oil agent was applied to the fiber bundle after the water-bath drawing, and a drying and densification treatment was performed using a heating roller at 160°C.
- the fiber was drawn 3.7 times in pressurized steam to make the total draw ratio 13 times, and then entangled to obtain a precursor fiber bundle having 6,000 single fibers.
- the single fiber fineness of the precursor fiber bundle was 0.7 dtex.
- the conditions for the first flameproofing step are a flameproofing temperature of 250°C and a flameproofing time of 11 minutes
- the second flameproofing step is carried out under the conditions of a flameproofing temperature of 280°C and a flameproofing time of 6 minutes (conditions 1) While maintaining a tension of 0.8 mN/dtex in an oven in an air atmosphere, two precursor fiber bundles are put into each groove of the rollers before and after the flameproofing furnace for flameproofing treatment, and the flameproof fiber bundles are got At this time, the flameproofing step was performed while twisting the precursor fiber bundle at 15 turns per meter.
- the obtained flame-resistant fiber bundle was subjected to a preliminary carbonization treatment at a draw ratio of 1.20 in a nitrogen atmosphere at a maximum temperature of 800°C to obtain a preliminary carbonized fiber bundle.
- the obtained pre-carbonized fiber bundle was carbonized in a nitrogen atmosphere at a maximum temperature of 1,400° C. and a draw ratio of 0.950.
- the rate of temperature increase in the carbonization step was 0.45° C./second, and the residence time at the maximum temperature was 60 seconds.
- Tables 1 and 2 show the physical properties of the final carbon fiber bundle obtained by subjecting the obtained carbon fiber bundle to surface treatment and coating treatment with a sizing agent.
- Example 2 By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 1.0 mN / dtex, and the carbon fiber precursor fiber bundle was twisted at 15 rotations per 1 m, and each groove of the roller before and after the flameproofing furnace A carbon fiber bundle was obtained in the same manner as in Example 1, except that three carbon fiber precursor fiber bundles were added to the . Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 3 A carbon fiber bundle was obtained in the same manner as in Example 2, except that the tension during flameproofing was changed to 1.2 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 4 A carbon fiber bundle was obtained in the same manner as in Example 2, except that the tension during flameproofing was changed to 1.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 5 A carbon fiber bundle was obtained in the same manner as in Example 2, except that two precursor fiber bundles were put into each groove of the rollers before and after the flameproofing furnace. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- the first flameproofing step was performed under the conditions of a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the second flameproofing step was carried out under the conditions of a flameproofing temperature of 288°C and a flameproofing time of 5 minutes (Condition 2).
- the tension at the time of flameproofing was set to 1.0 mN/dtex, and the precursor fiber bundle was twisted at 7 turns per 1 m, and 4 twists per groove of the rollers before and after the flameproofing furnace.
- a carbon fiber bundle was obtained in the same manner as in Example 1, except that one precursor fiber bundle was added. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 7 The conditions for the first flameproofing step were a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the conditions of the second flameproofing step were a flameproofing temperature of 283°C and a flameproofing time of 5 minutes (Condition 3). obtained a carbon fiber bundle in the same manner as in Example 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 8 The conditions for the first flameproofing step were a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the conditions of the second flameproofing step were a flameproofing temperature of 281°C and a flameproofing time of 7 minutes (Condition 4). obtained a carbon fiber bundle in the same manner as in Example 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 9 A carbon fiber bundle was obtained in the same manner as in Example 8, except that the number of filaments in the precursor fiber bundle was 8,000. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Example 10 The single fiber fineness of the precursor fiber bundle is 0.5 dtex, the first flameproofing step is performed at a flameproofing temperature of 250 ° C., and the flameproofing time is 11 minutes.
- a carbon fiber bundle was obtained in the same manner as in Example 8 except that the curing time was 6 minutes (Condition 5). Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Comparative Example 2 A carbon fiber bundle was obtained in the same manner as in Comparative Example 1 except that the tension during flameproofing was changed to 1.6 mN/dtex by changing the draw ratio during flameproofing, and the temperature conditions for flameproofing were changed to Condition 2. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Comparative Example 3 A carbon fiber bundle was obtained in the same manner as in Comparative Example 1, except that the tension during flameproofing was changed to 2.0 mN/dtex by changing the draw ratio during flameproofing, and the flameproofing temperature condition was changed to Condition 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Comparative Example 5 A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 2.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Comparative Example 6 A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 1.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- Comparative Example 7 A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 0.6 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
- the carbon fiber bundle of the present invention is a carbon fiber that is suitable for a textile reinforcing material that has both excellent mechanical properties peculiar to carbon fiber and flatness of the cross section of the carbon fiber bundle in a high balance.
- a high-performance fabric reinforcing material can be obtained with high productivity.
Abstract
According to the present invention, a carbon fiber composite material, which has excellent energy absorption and is composed of a carbon fiber having high strength and high elongation, is provided by a production method yielding an excellent production amount. This carbon fiber bundle having a plurality of single fibers has a strand elastic modulus of 260-350 GPa, a strength of 6.5-8.5 GPa, an elongation of at least 1.8%, a filament number of 1,000-9,000, and a total fineness of 0.15-0.35 g/m, wherein the average value of major axis/minor axis ratios in single fiber cross sections is 1.01-1.08, the coefficient of variation is 1-4%, and the skewness is 0.3-1.2.
Description
本発明は、炭素繊維複合材料のエネルギー吸収性能を高めるための高い特性を有しつつ、賦形性に優れる織物に適した炭素繊維束およびその製造方法に関する。
The present invention relates to a carbon fiber bundle that is suitable for fabrics that has excellent shapeability while having high properties for enhancing the energy absorption performance of carbon fiber composite materials, and a method for producing the same.
ポリアクリロニトリル系炭素繊維束（以下、本明細書では特筆しない限り、炭素繊維束はポリアクリロニトリル系炭素繊維束についての記載であるとする）は軽量かつ高強度・高弾性率の材料であり、部材の軽量化には重要な材料である。炭素繊維強化プラスチック（以下、ＣＦＲＰと略記することがある）の補強基材には、力学特性と賦形性を両立するために炭素繊維束を用いて織物の形態にした補強織物が多用されている。このような補強基材を用いたＣＦＲＰは、その優れた性能を活かして自動車・航空機等の構造材に使われており、高い引張強度や高い衝撃エネルギー吸収性能（以下、耐衝撃性と略記することがある）に優れることを満足することが求められている。
Polyacrylonitrile-based carbon fiber bundles (hereinafter, unless otherwise specified, carbon fiber bundles in this specification refer to polyacrylonitrile-based carbon fiber bundles) are lightweight, high-strength, and high-elastic-modulus materials. is an important material for weight reduction. As a reinforcing base material for carbon fiber reinforced plastics (hereinafter sometimes abbreviated as CFRP), reinforcing fabrics in the form of fabrics using carbon fiber bundles are often used in order to achieve both mechanical properties and formability. there is CFRP using such a reinforcing base material is used for structural materials such as automobiles and aircraft due to its excellent performance, and has high tensile strength and high impact energy absorption performance (hereinafter abbreviated as impact resistance). It is required to be satisfied with being excellent in
炭素繊維織物は、炭素繊維単繊維を集束させた炭素繊維束を用いているので、織り込まれた状態においては、炭素繊維束の断面が楕円形であるために、特に従来公知の二方向織物については、たて糸とよこ糸が１本交互に浮き沈みして交錯する平織構造が織糸の交錯点数が多く、形態が安定しやすい利点があるが、たて糸とよこ糸が交錯する交錯部で大きくクリンプするという問題点がある。特に、総繊度が大きい炭素繊維束を使用した織物では、厚みの大きい炭素繊維束が交錯しているのでこの傾向が大きくなる。クリンプが大きな織物は、そのＣＦＲＰに応力が作用した場合に、クリンプした交錯部に応力が集中するため炭素繊維束の性能が十分に発揮できない。すなわち、織物を用いたＣＦＲＰの伸度は十分とは言えなかった。
Since the carbon fiber fabric uses carbon fiber bundles in which carbon fiber single fibers are bundled, the cross section of the carbon fiber bundles is elliptical in the woven state. The plain weave structure in which one warp and weft alternately rise and fall has the advantage that the number of interlacing yarns is large and the shape is easy to stabilize, but there is a problem that large crimps occur at the intersecting parts where the warp and weft yarn intersect. there is a point In particular, in fabrics using carbon fiber bundles having a large total fineness, this tendency becomes greater because carbon fiber bundles having a large thickness intersect. In fabrics with large crimps, when stress is applied to the CFRP, the stress concentrates on the crimped intersecting portions, so the performance of the carbon fiber bundle cannot be fully exhibited. In other words, the elongation of CFRP using woven fabric was not sufficient.
炭素繊維束を用いた織物の形態としては他に一方向織物や、多方向織物があり、綾織組織等の織物構造にすることによりクリンプを低減もしくは避けるという試みもなされているが、そのどれもが炭素繊維束の有する優れた樹脂含浸ストランド強度（以下、ストランド強度と略記することがある）を良く発現できているとは言いがたく、現状織物構造のクリンプは避けがたいため、織物構造の改善よりも炭素繊維束を改善することの方が効果としては大きいものの、織物に用いられている炭素繊維束は伸度が低いために ＣＦＲＰ全体の耐衝撃性が満足できるものではなかった。
Other forms of woven fabrics using carbon fiber bundles include unidirectional woven fabrics and multidirectional woven fabrics, and attempts have been made to reduce or avoid crimping by using a woven structure such as a twill weave structure, but none of these are available. However, it is difficult to say that the excellent resin-impregnated strand strength of carbon fiber bundles (hereinafter sometimes abbreviated as strand strength) can be expressed well, and crimping of the current woven structure is unavoidable. Although improving carbon fiber bundles is more effective than improving them, the impact resistance of the entire CFRP was not satisfactory because of the low elongation of the carbon fiber bundles used in the fabric.
織物のクリンプ角を低減する試みとして特許文献１では厚みが０.０９ｍｍ以下で、目付が８５ｇ／ｍ２以下である炭素繊維束を用いて、薄くて幅の広い扁平な炭素繊維束を得ることで炭素繊維束のクリンプを低減させ、薄いＣＦＲＰにおいて高い補強効果を得ている。
As an attempt to reduce the crimp angle of the woven fabric, Patent Document 1 uses a carbon fiber bundle having a thickness of 0.09 mm or less and a basis weight of 85 g/m 2 or less to obtain a thin, wide and flat carbon fiber bundle. reduces the crimp of the carbon fiber bundle, and obtains a high reinforcing effect in thin CFRP.
炭素繊維束自身のストランド強度および伸度を高める試みとして、特許文献２では破壊靱性値を高めることによりストランド強度が最大で８．４ＧＰａ、樹脂含浸ストランド弾性率（以下、ストランド弾性率と略記することがある）で３２５ＧＰａを達成している（実施例３）。特許文献３でも同様に炭素繊維の破壊靱性値を高めることにより、ストランド強度が最大で７．９ＧＰａ、ストランド弾性率が３５０ＧＰａを得ている（実施例７）。また、炭素繊維束の断面形状という面では、特許文献４が耐炎化工程において炭素繊維束に撚りを入れるという方法を試みており、束の断面が扁平な炭素繊維束を得ている。特許文献５では断面形状の異なる炭素繊維の混合と炭素繊維束に撚りを入れるという手法により炭素繊維単繊維の長径短径比の歪度を大きくすることで、炭素繊維束のストランド強度を一定のレベルに保ちながら炭素繊維束の断面を扁平にするということに成功している。
As an attempt to increase the strand strength and elongation of the carbon fiber bundle itself, in Patent Document 2, by increasing the fracture toughness value, the maximum strand strength is 8.4 GPa, and the resin-impregnated strand elastic modulus (hereinafter abbreviated as strand elastic modulus ) and achieved 325 GPa (Example 3). Similarly, in Patent Document 3, a maximum strand strength of 7.9 GPa and a maximum strand elastic modulus of 350 GPa are obtained by increasing the fracture toughness of carbon fibers (Example 7). In terms of the cross-sectional shape of the carbon fiber bundle, Patent Document 4 attempts a method of twisting the carbon fiber bundle in the flameproofing step, and obtains a carbon fiber bundle having a flat cross section. In Patent Document 5, the strand strength of the carbon fiber bundle is increased to a certain level by increasing the distortion of the ratio of the major axis to the minor axis of the carbon fiber single fiber by the method of mixing carbon fibers with different cross-sectional shapes and twisting the carbon fiber bundle. We have succeeded in flattening the cross section of the carbon fiber bundle while keeping it level.
しかしながら、従来の技術には次のような課題がある。
However, conventional technologies have the following problems.
特許文献１では、炭素繊維束を薄くすることにより織物の高い補強効果を得ているが、炭素繊維束を流下する液流中に供給して開繊する方法の提案であって、炭素繊維束の特性には言及されていないために炭素繊維束の伸度においても開繊性においても満足できる値ではなかった。特許文献２、３では、靱性の向上によりストランド強度の改善を試みているが、耐炎化処理の段階で撚りをかけることは行っていないため、単繊維断面形状が制御されておらず、炭素繊維束として太く、かつ厚みが大きい問題があった。仮に、炭素繊維束を半分に引き裂いて細い束として用いたとしても束の厚みを薄くすることには十分な単繊維断面形状とはなっていなかった。特許文献４では、耐炎化工程において撚りをかけることで炭素繊維束断面の扁平度を高められているものの、ストランド強度やストランド弾性率による伸度には着目していないために最大でも実施例においてストランド強度が５．６ＧＰａと満足できるものでなく、伸度も満足できるものではなかった。特許文献５では、断面形状の異なる炭素繊維の混合及び有撚の試みにより単繊維断面形状の歪度を高め炭素繊維束断面の扁平度を高めているが、伸度には着目しておらず、実施例において最大でもストランド強度が４．８ＧＰａ（実施例７）であり、ストランド弾性率も３１７ＧＰａとなっていることから、伸度が満足できる結果とはなっていなかった。このように、炭素繊維束においてストランド強度及び伸度に関する改善の試みと炭素繊維束の扁平度を向上するための単繊維断面形状に関する試みは今まで別々に行われていたが、効果が全く異なるうえに扁平度向上のために行う操作はストランド強度を低下させるため、組み合わせることは容易ではなく、その両者の組み合わせはこれまで検討されてこなかった。
In Patent Document 1, a high reinforcing effect of the fabric is obtained by thinning the carbon fiber bundles. However, the elongation and openability of the carbon fiber bundle were not satisfactory values. In Patent Documents 2 and 3, an attempt is made to improve the strand strength by improving the toughness, but since twisting is not performed at the stage of the flameproofing treatment, the single fiber cross-sectional shape is not controlled, and the carbon fiber There was a problem that the bundle was thick and thick. Even if the carbon fiber bundle were torn in half and used as a thin bundle, the single fiber cross-sectional shape was not sufficient to reduce the thickness of the bundle. In Patent Document 4, although the flatness of the cross section of the carbon fiber bundle is increased by twisting in the flameproofing process, it does not pay attention to the elongation due to the strand strength or strand elastic modulus, so even at the maximum, the examples The strand strength was unsatisfactory at 5.6 GPa, and the elongation was also unsatisfactory. Patent Document 5 attempts to mix and twist carbon fibers with different cross-sectional shapes to increase the degree of distortion of the single fiber cross-sectional shape and increase the flatness of the cross-sectional shape of the carbon fiber bundle, but does not focus on the elongation. In the examples, the maximum strand strength was 4.8 GPa (Example 7) and the strand elastic modulus was 317 GPa, so the elongation was not satisfactory. In this way, attempts to improve the strand strength and elongation of carbon fiber bundles and attempts to improve the flatness of carbon fiber bundles have been made separately until now, but the effects are completely different. In addition, since the operation performed to improve the flatness reduces the strand strength, it is not easy to combine them, and the combination of the two has not been studied so far.
そこで、本発明では炭素繊維束をより織物に適しているストランド強度が高く、耐衝撃性のために伸度が高く、クリンプを小さくするために総繊度が小さく、炭素繊維束の扁平度が大きくかつ歪度が大きい炭素繊維束を提供することを目的とする。
Therefore, in the present invention, the carbon fiber bundles are more suitable for textiles. Strand strength is high, elongation is high for impact resistance, total fineness is small for crimp reduction, and flatness of carbon fiber bundles is large. An object of the present invention is to provide a carbon fiber bundle having a large degree of distortion.
上記の目的を達成するために、本発明は複数本の単繊維を有する炭素繊維束であってストランド弾性率が２６０～３５０ＧＰａ、強度が６．０～８．５ＧＰａ、伸度が１．８％以上、フィラメント数が１，０００～９，０００、総繊度が０．１５～０．３５ｇ／ｍであり、かつ単繊維横断面の長径短径比の平均値が１．０１～１．０８、変動係数が１～４％、歪度が０．３～１．２である炭素繊維束である。
In order to achieve the above objects, the present invention provides a carbon fiber bundle having a plurality of single fibers, which has a strand elastic modulus of 260 to 350 GPa, a strength of 6.0 to 8.5 GPa, and an elongation of 1.8%. The number of filaments is 1,000 to 9,000, the total fineness is 0.15 to 0.35 g/m, and the average value of the ratio of the major axis to the minor axis of the cross section of the single fiber is 1.01 to 1.08. The carbon fiber bundle has a coefficient of variation of 1 to 4% and a degree of skew of 0.3 to 1.2.
本発明の炭素繊維束は、高ストランド強度・高伸度であり、炭素繊維束の総繊度が小さいことと炭素繊維単繊維の歪度が大きいことから炭素繊維束の断面を薄くできる。その結果として、この炭素繊維束による織物で作製したＣＦＲＰはエネルギー吸収性能に優れる。
The carbon fiber bundle of the present invention has high strand strength and high elongation, and since the total fineness of the carbon fiber bundle is small and the strain of the carbon fiber single fiber is large, the cross section of the carbon fiber bundle can be made thin. As a result, the CFRP made from the woven fabric of this carbon fiber bundle has excellent energy absorption performance.
本発明において、その単繊維横断面の長径短径比の平均値は１．０１～１．０８であり、好ましくは１．０１～１．０５であり、より好ましくは１．０１～１．０３である。本発明において長径短径比とは、単繊維横断面における長径を短径で除した比のことを指す。また、本発明において単繊維横断面とは、繊維軸に垂直な単繊維の断面のことを指す。また、本発明において長径とは、単繊維横断面に外接するように長方形を描いた場合の辺のうち、長い方の長さであるフェレ径の最大値のことを指し、短径とは、かかる長径を長軸とし、単繊維横断面と断面積が等しい楕円の短軸のことを指す。平均値は重み付けなどをしない単純平均であり、長径短径比の平均値が１．００に近いほど、単繊維横断面が真円に近い単繊維が多いことを意味する。長径短径比の平均値が大きいほど炭素繊維束の伸度が低下しやすいために長径短径比の平均値は１．０１以上であれば良く、長径短径比の平均値が１．０８以下であれば炭素繊維束の伸度を大きく低下させずに保持することができる。単繊維横断面の長径短径比の平均値を上記範囲に制御する方法は、凝固浴条件の変更が一般的に知られている。
In the present invention, the average value of the ratio of the major axis to the minor axis of the single fiber cross section is 1.01 to 1.08, preferably 1.01 to 1.05, more preferably 1.01 to 1.03. is. In the present invention, the ratio of major diameter to minor diameter refers to the ratio obtained by dividing the major diameter by the minor diameter in the cross section of a single fiber. In the present invention, the cross section of a single fiber refers to the cross section of a single fiber perpendicular to the fiber axis. In the present invention, the major diameter refers to the maximum value of the Feret diameter, which is the length of the longer side of a rectangle drawn so as to circumscribe the cross section of a single fiber. The major axis is the major axis, and the minor axis of the ellipse having the same cross-sectional area as the cross section of the single fiber. The average value is a simple average without weighting, and it means that the closer the average value of the ratio of major diameter to minor diameter is to 1.00, the more single fibers have a circular cross section. Since the elongation of the carbon fiber bundle tends to decrease as the average value of the ratio of major to minor diameters increases, the average value of the ratio of major to minor diameters should be 1.01 or more, and the average value of the ratio to major to minor diameters is 1.08. If it is below, the elongation of the carbon fiber bundle can be maintained without being greatly reduced. A commonly known method for controlling the average ratio of the major axis to the minor axis of the single fiber cross section within the above range is to change the conditions of the coagulation bath.
本発明において、長径短径比が１．００～１．０３の単繊維本数割合が好ましくは３０～９０％、より好ましくは４０～８５％、さらに好ましくは５０～８０％である。長径短径比が大きいほど開繊性が高まりやすいが、長径短径比が１．００～１．０３の単繊維本数割合が９０％を超えるとストランド強度が低下することがある。長径短径比が１．００～１．０３の単繊維本数割合が３０％以上であると、これらの特性を高いレベルで両立しやすい。長径短径比が１．００～１．０３の単繊維は、凝固の条件を調整することや、単繊維を繊維軸に直交する方向に押しつぶす力を調整することなどにより得ることができる。
In the present invention, the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.00 to 1.03 is preferably 30 to 90%, more preferably 40 to 85%, and even more preferably 50 to 80%. The greater the ratio of major to minor diameters, the easier the spreadability becomes, but if the ratio of the number of single fibers having a ratio of major to minor diameters of 1.00 to 1.03 exceeds 90%, the strand strength may decrease. When the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.00 to 1.03 is 30% or more, it is easy to achieve both of these properties at a high level. A monofilament having a ratio of the major axis to the minor axis of 1.00 to 1.03 can be obtained by adjusting the coagulation conditions or by adjusting the force for crushing the monofilament in the direction perpendicular to the fiber axis.
本発明において、長径短径比が１．０４～１．１０の単繊維本数割合が好ましくは１０～４０％、より好ましくは１５～２５％である。長径短径比が大きいほど開繊性が高まりやすいが、長径短径比が１．０４～１．１０の単繊維本数割合が４０％を超えるとストランド強度が低下することがある。長径短径比が１．０４～１．１０の単繊維本数が１０％以上含まれると、これらの特性を高いレベルで両立しやすい。長径短径比が１．０４～１．１０の単繊維は、凝固の条件を調整することや、単繊維を繊維軸に直交する方向に押しつぶす力を調整することなどにより得ることができる。
In the present invention, the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.04 to 1.10 is preferably 10 to 40%, more preferably 15 to 25%. The greater the ratio of the major axis to the minor axis, the easier the openability becomes, but if the ratio of the number of single fibers having the ratio of the major axis to the minor axis of 1.04 to 1.10 exceeds 40%, the strand strength may decrease. When 10% or more of the single fibers having a ratio of major axis to minor axis of 1.04 to 1.10 are contained, it is easy to achieve both of these properties at a high level. A monofilament having a major/minor diameter ratio of 1.04 to 1.10 can be obtained by adjusting the coagulation conditions or by adjusting the force for crushing the monofilament in the direction orthogonal to the fiber axis.
本発明において、その単繊維本数の長径短径比の変動係数は１～４％であり、好ましくは１～３％であり、より好ましくは１～２％である。変動係数は一般的な定義のとおり標準偏差を平均値で割り、１００をかけることにより算出する。長径短径比の変動係数が大きいことは、長径短径比が幅広く分布していることを意味しており、炭素繊維束断面が扁平としやすいかの指標である炭素繊維束の開繊性に関連する。変動係数が１％以上であれば炭素繊維束の開繊性に優れ、４％以下であれば炭素繊維束の伸度を大きく損なわない。単繊維横断面の長径短径比の変動係数を上記範囲に制御する方法は、後述する。
In the present invention, the coefficient of variation of the ratio of major diameter to minor diameter of the number of single fibers is 1 to 4%, preferably 1 to 3%, more preferably 1 to 2%. The coefficient of variation is calculated by dividing the standard deviation by the average value and multiplying by 100, as generally defined. A large coefficient of variation of the ratio of the major diameter to the minor diameter means that the ratio of the major diameter to the minor diameter is widely distributed. Related. When the coefficient of variation is 1% or more, the carbon fiber bundle is excellent in opening property, and when it is 4% or less, the elongation of the carbon fiber bundle is not significantly impaired. A method for controlling the coefficient of variation of the ratio of the major axis to the minor axis of the single fiber cross section within the above range will be described later.
本発明において、その単繊維の長径短径比の歪度は０．３～１．２であり、好ましくは０．３～１．１であり、より好ましくは０．４～１．０であり、さらに好ましくは０．６～１．０である。歪度は、分布の非対称性を表すパラメータであり、以下の式（１）で定義される。
歪度＝ｎ／（（ｎ－１）×（ｎ－２））×Σ｛（ｘｉ－＜ｘ＞）／ｓ｝３ ・・・（１）
ここで、ｎは単繊維の本数（本）、ｘｉはｉ番目の単繊維の長径短径比（－）、＜ｘ＞は長径短径比の平均値（－）、ｓは長径短径比の標準偏差（－）を意味する。また、Σは単繊維の本数ｎの分だけ和をとることを意味する。注目する任意のパラメータの頻度分布において、 歪度の値が０では分布が左右対称、負の値は小さい側に裾野を引くこと、正の値は大きい側に裾野を引くことを、それぞれ表す。 In the present invention, the distortion of the ratio of the major axis to the minor axis of the single fiber is 0.3 to 1.2, preferably 0.3 to 1.1, more preferably 0.4 to 1.0. , more preferably 0.6 to 1.0. Skewness is a parameter that represents the asymmetry of distribution and is defined by the following equation (1).
Skewness = n/((n−1)×(n−2))×Σ{(xi−<x>)/s} 3 (1)
Here, n is the number of single fibers (number), xi is the ratio of the major axis to the minor axis of the i-th single fiber (-), <x> is the average value of the ratio of the major axis to the minor axis (-), and s is the ratio of the major axis to the minor axis. means the standard deviation (-) of Also, Σ means that the sum is taken for the number n of single fibers. In the frequency distribution of an arbitrary parameter of interest, a skewness value of 0 indicates that the distribution is bilaterally symmetrical, a negative value indicates that the tail is on the small side, and a positive value indicates that the tail is on the large side.
歪度＝ｎ／（（ｎ－１）×（ｎ－２））×Σ｛（ｘｉ－＜ｘ＞）／ｓ｝３ ・・・（１）
ここで、ｎは単繊維の本数（本）、ｘｉはｉ番目の単繊維の長径短径比（－）、＜ｘ＞は長径短径比の平均値（－）、ｓは長径短径比の標準偏差（－）を意味する。また、Σは単繊維の本数ｎの分だけ和をとることを意味する。注目する任意のパラメータの頻度分布において、 歪度の値が０では分布が左右対称、負の値は小さい側に裾野を引くこと、正の値は大きい側に裾野を引くことを、それぞれ表す。 In the present invention, the distortion of the ratio of the major axis to the minor axis of the single fiber is 0.3 to 1.2, preferably 0.3 to 1.1, more preferably 0.4 to 1.0. , more preferably 0.6 to 1.0. Skewness is a parameter that represents the asymmetry of distribution and is defined by the following equation (1).
Skewness = n/((n−1)×(n−2))×Σ{(xi−<x>)/s} 3 (1)
Here, n is the number of single fibers (number), xi is the ratio of the major axis to the minor axis of the i-th single fiber (-), <x> is the average value of the ratio of the major axis to the minor axis (-), and s is the ratio of the major axis to the minor axis. means the standard deviation (-) of Also, Σ means that the sum is taken for the number n of single fibers. In the frequency distribution of an arbitrary parameter of interest, a skewness value of 0 indicates that the distribution is bilaterally symmetrical, a negative value indicates that the tail is on the small side, and a positive value indicates that the tail is on the large side.
織物で必要なクリンプ角の低減を実現するためには炭素繊維束の断面を扁平にする必要があるが、そのために炭素繊維単繊維の長径短径比の平均値を大きくしたり、長径短径比の変動係数を制御したりするだけでは炭素繊維束の伸度が低下してしまう問題があり、歪度を上記範囲に制御することが炭素繊維束の伸度と開繊性を両立する上で重要であることがわかった。
In order to reduce the crimp angle required for woven fabrics, it is necessary to make the cross section of the carbon fiber bundle flat. There is a problem that the elongation of the carbon fiber bundle is reduced only by controlling the coefficient of variation of the ratio. was found to be important in
長径短径比の歪度が大きい状態とは、定義上、長径短径比の大きな単繊維がある一定量存在するものの、長径短径比の平均値は低めを維持した状態を意味する。長径短径比が小さいほど炭素繊維束の伸度が高く保たれ、長径短径比が大きいほど逆に炭素繊維束の開繊性が高くなる。炭素繊維束の開繊性のバランスは、長径短径比の異なる単繊維の存在割合に強く影響されると考えられるが、長径短径比が大きい単繊維による炭素繊維束の開繊性の向上効果の方が、長径短径比が小さい単繊維による炭素繊維束の伸度の低下効果と比較して相対的に大きく、長径短径比が大きい単繊維を僅かに加えることが、伸度を低下させず炭素繊維束の開繊性の向上効果を最大化するために重要であると考えられる。
By definition, a state in which the ratio of the major axis to the minor axis is highly skewed means a state in which there is a certain amount of single fibers with a large ratio of the major axis to the minor axis, but the average value of the ratio of the major axis to the minor axis remains low. The smaller the major/breadth ratio is, the higher the elongation of the carbon fiber bundle is maintained. It is thought that the balance of the spreadability of carbon fiber bundles is strongly affected by the ratio of single fibers with different ratios of major to minor diameters. The effect is relatively large compared to the effect of lowering the elongation of the carbon fiber bundle due to the single fiber having a small major axis to minor axis ratio. It is considered to be important for maximizing the effect of improving the openability of the carbon fiber bundle without reducing the carbon fiber bundle.
長径短径比の歪度が０．３以上のとき、両者を高いレベルで両立することができる。長径短径比の歪度が１．２以下のとき、伸度を満足できる範囲とできる。本発明において、長径短径比の変動係数、歪度を上記した範囲に制御する方法については、耐炎化繊維に撚りを加えて張力を作用させることにより単繊維間に押し付けの力を発生させて変形させて制御を行う。得られた炭素繊維単繊維の横断面を観察し、微調整することにより、本発明の炭素繊維束は数値範囲を満足する。
When the skewness of the major axis to minor axis ratio is 0.3 or more, both can be achieved at a high level. When the skewness of the ratio of the major diameter to the minor diameter is 1.2 or less, the elongation can be in a satisfactory range. In the present invention, regarding the method of controlling the coefficient of variation of the ratio of major diameter to minor diameter and the degree of distortion within the above range, the flame resistant fiber is twisted to apply tension to generate a pressing force between the single fibers. Control by transforming. By observing the cross section of the obtained carbon fiber single fiber and making fine adjustments, the carbon fiber bundle of the present invention satisfies the numerical range.
本発明の炭素繊維束は、フィラメント数が１,０００～９,０００本である。フィラメント数は炭素繊維束に含まれる単繊維の本数のことであり、フィラメント数が１,０００本以上であれば十分な伸度を得ることができ、９,０００本以下であれば総繊度を小さく保ち、織物に適したクリンプ角を得ることができる。フィラメント数はポリアクリロニトリル系炭素繊維前駆体繊維束の製造過程において任意に定めることができる。
The carbon fiber bundle of the present invention has 1,000 to 9,000 filaments. The number of filaments is the number of single fibers contained in the carbon fiber bundle. If the number of filaments is 1,000 or more, sufficient elongation can be obtained, and if the number of filaments is 9,000 or less, the total fineness is reduced. It can be kept small to obtain a suitable crimp angle for textiles. The number of filaments can be arbitrarily determined in the process of manufacturing the polyacrylonitrile-based carbon fiber precursor fiber bundle.
本発明の炭素繊維束は、総繊度が０．１５～０．３５ｇ／ｍであり、より好ましくは０．２０～０．３０ｇ／ｍである。総繊度は、炭素繊維束１ｍあたりの質量のことであり、炭素繊維束の単繊維直径とフィラメント数に関連し、総繊度が小さいほどクリンプ角が小さくなる。総繊度は０．１５ｇ／ｍ以上であれば、優れた耐衝撃性のＣＦＲＰを得ることができ、０．３５ｇ／ｍ以下であれば、織物に適したクリンプ角を得ることができる。総繊度は炭素繊維束の長さとその長さに対する質量を測定することにより得ることができる。総繊度は、単繊維直径以外ではフィラメント数を調整することで制御できるが、フィラメント数を少なくした場合には炭素繊維束の伸度が低下しやすくなって、単純にフィラメント数を変更しただけで同一の特性が得られない傾向がある。
The carbon fiber bundle of the present invention has a total fineness of 0.15-0.35 g/m, more preferably 0.20-0.30 g/m. The total fineness is the mass per 1m of the carbon fiber bundle, and is related to the single fiber diameter and the number of filaments of the carbon fiber bundle. The smaller the total fineness, the smaller the crimp angle. If the total fineness is 0.15 g/m or more, CFRP with excellent impact resistance can be obtained, and if it is 0.35 g/m or less, a crimp angle suitable for woven fabric can be obtained. The total fineness can be obtained by measuring the length of the carbon fiber bundle and the mass for that length. The total fineness can be controlled by adjusting the number of filaments other than the single fiber diameter. Identical properties tend not to be obtained.
本発明の炭素繊維束は、ストランド弾性率が２６０～３５０ＧＰａであり、好ましくは２７０～３２０ＧＰａであり、より好ましくは２７０～３００ＧＰａである。ストランド弾性率は、炭素繊維束に荷重がかかったときの変形のしにくさを示す指標であり、言い換えれば、材料の軽量性を表す指標となる。炭素繊維束のストランド弾性率は、ＪＩＳ Ｒ７６０８：２００４に記載の、樹脂含浸ストランドの引張試験に従って評価することができる。炭素繊維束の応力－歪み曲線は下に凸の非線形性を示すが、歪み範囲は０．１～０．６％として、その範囲でのストランド弾性率を用いる。ストランド弾性率が２６０ＧＰａ以上であれば炭素繊維束の軽量性が良く、ストランド弾性率が３５０ＧＰａ以下であれば、得られる強度に対して伸度を高く保つことができるため、十分な耐衝撃性を得られる。ストランド弾性率は、炭素化工程の最高温度、最高温度の熱処理時間、昇温速度、延伸比などにより制御できる。
The carbon fiber bundle of the present invention has a strand elastic modulus of 260 to 350 GPa, preferably 270 to 320 GPa, more preferably 270 to 300 GPa. The strand elastic modulus is an index that indicates how difficult it is to deform a carbon fiber bundle when a load is applied, in other words, it is an index that indicates the lightness of the material. The strand elastic modulus of the carbon fiber bundle can be evaluated according to the resin-impregnated strand tensile test described in JIS R7608:2004. Although the stress-strain curve of the carbon fiber bundle exhibits downwardly convex nonlinearity, the strain range is set to 0.1 to 0.6%, and the strand elastic modulus within that range is used. If the strand elastic modulus is 260 GPa or more, the carbon fiber bundle is lightweight, and if the strand elastic modulus is 350 GPa or less, the elongation can be kept high relative to the strength obtained, so sufficient impact resistance can be obtained. can get. The strand elastic modulus can be controlled by the maximum temperature in the carbonization process, the heat treatment time at the maximum temperature, the heating rate, the stretching ratio, and the like.
本発明の炭素繊維束は、ストランド強度が６．０～８．５ＧＰａであり、好ましくは６．５～８．０ＧＰａであり、より好ましくは７．０～８．０ＧＰａである。ストランド強度は、炭素繊維束に荷重がかかったときの破断しにくさを示す指標である。炭素繊維束のストランド強度は、ＪＩＳ Ｒ７６０８：２００４に記載の、樹脂含浸ストランドの引張試験に従って評価することができる。ストランド強度が６．０ＧＰａ以上であれば十分な耐衝撃性を得られ、ストランド強度に上限はないが８．５ＧＰａもあれば耐衝撃性が十分に満足できるレベルとなりやすい。ストランド強度は、欠陥抑制や破壊靭性値の改善など、耐炎化条件や炭化条件など種々の条件を制御することにより高めることができる。
The carbon fiber bundle of the present invention has a strand strength of 6.0 to 8.5 GPa, preferably 6.5 to 8.0 GPa, more preferably 7.0 to 8.0 GPa. Strand strength is an index showing how difficult it is to break when a load is applied to a carbon fiber bundle. The strand strength of the carbon fiber bundle can be evaluated according to the resin-impregnated strand tensile test described in JIS R7608:2004. If the strand strength is 6.0 GPa or more, sufficient impact resistance can be obtained, and although there is no upper limit for the strand strength, if the strand strength is as high as 8.5 GPa, the impact resistance tends to reach a sufficiently satisfactory level. Strand strength can be enhanced by controlling various conditions such as flameproofing conditions and carbonization conditions, such as defect suppression and fracture toughness improvement.
本発明の炭素繊維束は、伸度が１．８％以上であり、好ましくは２．０％以上であり、より好ましくは２．２％以上であり、さらに好ましくは２．４％以上である。炭素繊維束の伸度は、ＪＩＳ Ｒ７６０８：２００４に記載の、樹脂含浸ストランドの引張試験に従って評価することができる。炭素繊維束は、応力－歪み曲線が非線形性を示すために伸度の測定は難しいが、本引張試験では、上述のストランド強度を上述のストランド弾性率で除することで、伸度を算出する。伸度が１．８％以上であれば、十分な耐衝撃性を得られ、伸度に上限はないが、３．０％もあれば耐衝撃性が十分であることが多い。炭素繊維束の伸度は、ストランド強度とストランド弾性率のバランスをそれぞれ制御、両立することによって調整することができる。
The carbon fiber bundle of the present invention has an elongation of 1.8% or more, preferably 2.0% or more, more preferably 2.2% or more, and still more preferably 2.4% or more. . The elongation of the carbon fiber bundle can be evaluated according to the resin-impregnated strand tensile test described in JIS R7608:2004. It is difficult to measure the elongation of carbon fiber bundles because the stress-strain curve exhibits nonlinearity, but in this tensile test, the elongation is calculated by dividing the above-mentioned strand strength by the above-mentioned strand elastic modulus. . Sufficient impact resistance can be obtained if the elongation is 1.8% or more, and although there is no upper limit to the elongation, as much as 3.0% is often sufficient for impact resistance. The elongation of the carbon fiber bundle can be adjusted by controlling the balance between the strand strength and the strand elastic modulus.
炭素繊維束の断面形状は、炭素繊維束断面の面積を後述の定義された長方形の面積で除した面積比率（炭素繊維束断面の面積比率）が０．５０～０．７０であることが好ましく、より好ましくは０．６０～０．７０である。面積比率が０．７８であれば理論的には定義された長方形に対して断面が楕円であることを意味し、面積比率が０．７８よりも小さい場合、炭素繊維束断面に窪みが発生して、炭素繊維束を構成する単繊維において部分的に窪みが発生していることを示している。０．７０以下であれば、複数本の繊維束を１つの溝に入れた効果として窪みを持つ単繊維を部分的に有することになるため、炭素繊維束として扁平とすることができ、結果として織物にした際の炭素繊維束の扁平性を確保することができる。０．５０以上であれば炭素繊維束を構成する単繊維の過剰な変形を抑制することができるため、炭素繊維束のストランド強度を確保することができる。炭素繊維束の断面形状は耐炎化張力や撚り角などの影響を受けるが、炭素繊維束における部分的な窪みは主に耐炎化工程において１つの溝に複数本の繊維束を入れ、互いに接触させることによって制御することができる。
Regarding the cross-sectional shape of the carbon fiber bundle, the area ratio obtained by dividing the area of the cross section of the carbon fiber bundle by the area of the rectangle defined later (the area ratio of the cross section of the carbon fiber bundle) is preferably 0.50 to 0.70. , more preferably 0.60 to 0.70. If the area ratio is 0.78, it means that the cross section is elliptical with respect to the theoretically defined rectangle. This indicates that the single fibers forming the carbon fiber bundle are partially dented. If it is 0.70 or less, the carbon fiber bundle can be made flat because it partially has a single fiber having a depression as an effect of inserting a plurality of fiber bundles into one groove. It is possible to ensure the flatness of the carbon fiber bundle when it is made into a woven fabric. If it is 0.50 or more, excessive deformation of single fibers constituting the carbon fiber bundle can be suppressed, so that the strand strength of the carbon fiber bundle can be ensured. The cross-sectional shape of the carbon fiber bundle is affected by the flameproofing tension and twist angle, but partial depressions in the carbon fiber bundle are mainly caused by inserting multiple fiber bundles into one groove in the flameproofing process and making them contact each other. can be controlled by
以下、本発明の炭素繊維束の製造方法を説明する。
The method for producing the carbon fiber bundle of the present invention will be described below.
ポリアクリロニトリル系炭素繊維前駆体繊維束（以下、前駆体繊維束と略記することがある）の製造に供する原料としては好ましくはポリアクリロニトリル系重合体を用いる。なお、本発明においてポリアクリロニトリル系重合体とは、少なくともアクリロニトリルがかかる重合体の９０～１００モル％を占めることが好ましい。前駆体繊維束の製造において、ポリアクリロニトリル系重合体は、ストランド強度向上の観点から、好ましくは共重合成分を含む。共重合成分として使用可能な単量体としては、耐炎化を促進する観点から、カルボン酸基またはアミド基を１種以上含有する単量体が好ましく用いられる。
A polyacrylonitrile-based polymer is preferably used as a raw material for producing a polyacrylonitrile-based carbon fiber precursor fiber bundle (hereinafter sometimes abbreviated as a precursor fiber bundle). In the present invention, the polyacrylonitrile-based polymer preferably accounts for 90 to 100 mol % of at least acrylonitrile polymer. In the production of the precursor fiber bundle, the polyacrylonitrile-based polymer preferably contains a copolymer component from the viewpoint of improving strand strength. As a monomer that can be used as a copolymerization component, a monomer containing one or more carboxylic acid groups or amide groups is preferably used from the viewpoint of promoting flame resistance.
前駆体繊維束を製造するにあたり、製糸方法は乾湿式紡糸法および湿式紡糸法のいずれを用いてもよいが、得られる炭素繊維束のストランド強度に有利な乾湿式紡糸法を用いるのが好ましい。
In producing the precursor fiber bundle, either a dry-wet spinning method or a wet spinning method may be used as the spinning method, but it is preferable to use the dry-wet spinning method, which is advantageous for the strand strength of the resulting carbon fiber bundle.
製糸工程は、乾湿式紡糸法により紡糸口金から凝固浴に紡糸溶液を吐出させて紡糸する紡糸工程と、該紡糸工程で得られた繊維束を水浴中で洗浄しつつ延伸する水洗工程と、該水洗工程で得られた繊維束を乾燥熱処理する乾燥熱処理工程からなり、必要に応じて、該乾燥熱処理工程で得られた繊維束をスチーム延伸するスチーム延伸工程を含むことが好ましい。なお、各工程の順序を適宜入れ替えることも可能である。紡糸溶液は、前記したポリアクリロニトリル系重合体を、ジメチルスルホキシド、ジメチルホルムアミドおよびジメチルアセトアミドなどのポリアクリロニトリルが可溶な溶媒に溶解したものである。
The spinning process includes a spinning process in which a spinning solution is discharged from a spinneret into a coagulating bath by a dry-wet spinning method for spinning, a washing process in which the fiber bundle obtained in the spinning process is drawn while being washed in a water bath, and the It preferably comprises a dry heat treatment step of dry heat-treating the fiber bundle obtained in the water washing step, and optionally includes a steam drawing step of steam-drawing the fiber bundle obtained in the dry heat treatment step. In addition, it is also possible to change the order of each step as appropriate. The spinning solution is obtained by dissolving the polyacrylonitrile-based polymer described above in a solvent in which polyacrylonitrile is soluble, such as dimethylsulfoxide, dimethylformamide and dimethylacetamide.
前記凝固浴には、紡糸溶液の溶媒として用いたジメチルスルホキシド、ジメチルホルムアミドおよびジメチルアセトアミドなどの溶媒と、いわゆる凝固促進成分を含ませることが好ましい。凝固促進成分としては、前記ポリアクリロニトリル系重合体を溶解せず、かつ紡糸溶液に用いる溶媒と相溶性があるものを使用することができる。具体的には、凝固促進成分として水を使用することが好ましい。このとき、凝固の条件で断面形状が変化することが知られており、凝固浴における溶媒の濃度が４０質量％以下の薄い場合と８０質量％近辺の濃い場合に円形断面となり、その中間的な濃度のときにβ形断面となる。
The coagulation bath preferably contains a solvent such as dimethylsulfoxide, dimethylformamide and dimethylacetamide used as a solvent for the spinning solution, and a so-called coagulation promoting component. As the coagulation promoting component, a component that does not dissolve the polyacrylonitrile-based polymer and is compatible with the solvent used for the spinning solution can be used. Specifically, it is preferable to use water as the coagulation promoting component. At this time, it is known that the cross-sectional shape changes depending on the coagulation conditions, and the cross-section becomes circular when the concentration of the solvent in the coagulation bath is low (40% by mass or less) and when it is high (near 80% by mass). It becomes a β-shaped cross section when it is concentrated.
前記水洗工程における水洗浴としては、温度が３０～９８℃の複数段からなる水洗浴を用いることが好ましい。また、水洗工程における延伸倍率は、２～６倍であることが好ましい。その後、ストランド強度を向上する目的から、繊維にシリコーン等からなる油剤を好ましくは付与する。かかるシリコーン油剤は、好ましくはアミノ変性シリコーンを含有するものを用いる。
As the water washing bath in the water washing step, it is preferable to use a water washing bath having a temperature of 30 to 98°C and consisting of multiple stages. Further, the draw ratio in the washing step is preferably 2 to 6 times. After that, for the purpose of improving the strand strength, the fibers are preferably provided with an oil such as silicone. Such silicone oils preferably contain amino-modified silicones.
乾燥熱処理工程は、公知の方法を利用することができる。例えば、乾燥温度は１００～２００℃が例示される。
A known method can be used for the dry heat treatment process. For example, the drying temperature is 100-200°C.
前記した水洗工程、乾燥熱処理工程の後、必要に応じ、スチーム延伸を行うことにより、本発明の炭素繊維束を得るのに好適な前駆体繊維束が得られる。スチーム延伸は、加圧スチーム中において、延伸倍率は好ましくは２～６倍である。
After the water washing step and the drying heat treatment step, a precursor fiber bundle suitable for obtaining the carbon fiber bundle of the present invention can be obtained by performing steam drawing as necessary. Steam drawing is preferably performed at a draw ratio of 2 to 6 times in pressurized steam.
炭素繊維束を製造する方法において、前駆体繊維束を耐炎化工程、予備炭素化工程、および炭素化工程に供することにより、炭素繊維束を得る。炭素繊維束のストランド強度を高めるためには、特に前駆体繊維束を耐炎化工程に供する際に、得られた耐炎化繊維束が、赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，４５３ｃｍ－１のピーク強度の比が０．７０～０．７５の範囲、かつ、赤外スペクトルの１，３７０ｃｍ－１のピーク強度に対する１，２５４ｃｍ－１のピーク強度の比が０．５０～０．６５の範囲になるように制御するのが好ましい。赤外スペクトルにおける１，４５３ｃｍ－１のピークはアルケン由来であり、耐炎化の進行とともに減少していく。１，３７０ｃｍ－１のピークと１，２５４ｃｍ－１のピークは耐炎化構造に由来するピークであり、耐炎化の進行とともに増加していく。得られた耐炎化繊維の比重が１．３５の場合に、１，３７０ｃｍ－１のピーク強度に対する１，４５３ｃｍ－１のピーク強度の比が、０．６３～０．６９程度であることが好ましい。さらに、１，３７０ｃｍ－１のピーク強度に対する１，２５４ｃｍ－１のピーク強度の比が０．５０～０．６５となるように耐炎化条件を設定することが好ましい。かかるピーク強度比は耐炎化の進行とともに減少していき、特に初期の減少が大きいが、耐炎化条件次第では、時間を増やしてもかかるピーク強度比が０．６５以下とならないこともある。
In the method for producing a carbon fiber bundle, a carbon fiber bundle is obtained by subjecting a precursor fiber bundle to a flameproofing step, a preliminary carbonization step, and a carbonization step. In order to increase the strand strength of the carbon fiber bundle, especially when subjecting the precursor fiber bundle to the flameproofing process, the resulting flameproofed fiber bundle has a 1,370 cm -1 peak intensity in the infrared spectrum. The ratio of the peak intensity at 453 cm -1 is in the range of 0.70 to 0.75, and the ratio of the peak intensity at 1,254 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum is 0.50 to 0 Preferably, it is controlled to be in the 0.65 range. The peak at 1,453 cm −1 in the infrared spectrum is derived from alkene, and decreases as flame resistance progresses. A peak at 1,370 cm −1 and a peak at 1,254 cm −1 are peaks derived from the flameproof structure, and increase as the flameproofing progresses. When the specific gravity of the obtained flame-resistant fiber is 1.35, the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 is preferably about 0.63 to 0.69. . Furthermore, it is preferable to set the flameproofing conditions such that the ratio of the peak intensity at 1,254 cm −1 to the peak intensity at 1,370 cm −1 is 0.50 to 0.65. The peak intensity ratio decreases as the flameproofing progresses, and the decrease is particularly large in the initial stage.
この２つのピーク強度比を目的の範囲内で両立させるためには、基本的には、前駆体繊維束を構成するポリアクリロニトリル系重合体に含まれる共重合成分の量が少ないこと、前駆体繊維束の結晶配向度が高いこと、前駆体繊維束の単繊維繊度を小さくすること、および耐炎化温度を後半に高くすることに主に注目して条件設定すればよい。
In order to make these two peak intensity ratios compatible within the target range, basically, the amount of the copolymer component contained in the polyacrylonitrile-based polymer constituting the precursor fiber bundle is small, and the precursor fiber The conditions may be set mainly by paying attention to a high degree of crystal orientation of the bundle, a small single fiber fineness of the precursor fiber bundle, and a high flameproofing temperature in the latter half.
ポリアクリロニトリル系炭素繊維前駆体繊維束を、赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，４５３ｃｍ－１のピーク強度の比が０．９８～１．１０の範囲となるまで８～２５分間耐炎化し（第１耐炎化工程）、続いて、第１耐炎化工程よりも高い温度で、赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，４５３ｃｍ－１のピーク強度の比が０．７０～０．７５の範囲、かつ、赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，２５４ｃｍ－１ピーク強度の比が０．５０～０．６５の範囲となるまで５～２０分間耐炎化（第２耐炎化工程）することが好ましい。第２耐炎化工程の耐炎化時間を短くするためには耐炎化温度を高く調整すればよいが、適切な耐炎化温度は前駆体繊維束の特性に依存する。耐炎化温度を好ましくは２６０～２９０℃になるようにすることが、上述の赤外スペクトルの範囲に制御するために好ましい。耐炎化温度は一定である必要はなく、多段階の温度設定でも構わない。得られる炭素繊維束のストランド強度を高めるためには、耐炎化温度は高く、耐炎化時間を短くすることが好ましい。第１耐炎化工程は、耐炎化時間が好ましくは１０～２５分で、上述の範囲となるような耐炎化温度で耐炎化することが好ましい。
The polyacrylonitrile-based carbon fiber precursor fiber bundle was heated until the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum was in the range of 0.98 to 1.10. Minute flameproofing (first flameproofing step), followed by a higher temperature than the first flameproofing step, where the ratio of the peak intensity at 1,453 cm to the peak intensity at 1,370 cm in the infrared spectrum is 0. .70 to 0.75 and for 5 to 20 minutes until the ratio of the 1,254 cm -1 peak intensity to the 1,370 cm -1 peak intensity in the infrared spectrum is in the range of 0.50 to 0.65. Flameproofing (second flameproofing step) is preferred. In order to shorten the flameproofing time in the second flameproofing step, the flameproofing temperature should be adjusted to a high value, but an appropriate flameproofing temperature depends on the properties of the precursor fiber bundle. A flameproofing temperature of preferably 260-290° C. is preferred to control the range of the infrared spectrum described above. The flameproofing temperature need not be constant, and may be set in multiple stages. In order to increase the strand strength of the obtained carbon fiber bundle, it is preferable that the flameproofing temperature is high and the flameproofing time is short. In the first flameproofing step, the flameproofing time is preferably 10 to 25 minutes, and the flameproofing is preferably performed at a flameproofing temperature within the above range.
ここで述べる耐炎化時間とは耐炎化炉内に繊維が滞留している時間を意味し、耐炎化繊維束とは、耐炎化工程後、予備炭素化工程前の繊維束を意味する。また、ここで述べるピーク強度とは、耐炎化繊維束を少量サンプリングして赤外スペクトルを測定して得られたスペクトルをベースライン補正した後の各波長における吸光度のことであり、特にピーク分割などは行わない。また、試料の濃度は０．６７質量％となるようにＫＢｒで希釈して測定する。このように、耐炎化条件設定を変更するたびに赤外スペクトルを測定して、条件検討すればよい。耐炎化繊維束の赤外スペクトルピーク強度比を適切に制御することで、得られる炭素繊維束のストランド強度を制御することができる。
The flameproofing time mentioned here means the time during which the fibers stay in the flameproofing furnace, and the flameproof fiber bundle means the fiber bundle after the flameproofing process and before the preliminary carbonization process. In addition, the peak intensity described here refers to the absorbance at each wavelength after baseline correction of the spectrum obtained by measuring the infrared spectrum of a small amount of the flameproof fiber bundle sampled, especially the peak splitting. not performed. In addition, the concentration of the sample is diluted with KBr so as to be 0.67% by mass and measured. In this way, the infrared spectrum should be measured every time the setting of the flameproofing conditions is changed, and the conditions should be examined. By appropriately controlling the infrared spectrum peak intensity ratio of the flameproof fiber bundle, the strand strength of the obtained carbon fiber bundle can be controlled.
本発明において、耐炎化工程とは、前駆体繊維束を酸素含有雰囲気で２００～３００℃で熱処理することを言う。
In the present invention, the flameproofing step means heat-treating the precursor fiber bundle at 200 to 300°C in an oxygen-containing atmosphere.
耐炎化工程のトータルの処理時間は、好ましくは１５～４０分の範囲で適宜選択することができる。また、得られる炭素繊維束のストランド強度を向上させる目的から、得られる耐炎化繊維の比重が好ましくは１．２８～１．３２となるように耐炎化の処理時間を設定する。より好ましい耐炎化工程の処理時間は耐炎化温度に依存する。耐炎化繊維束の比重は１．２８以上なければ炭素繊維束のストランド強度が低下することがある。耐炎化繊維束の比重が１．３２以下であればストランド強度を高めることができる。耐炎化繊維束の比重は耐炎化工程の処理時間と耐炎化温度により制御する。また、第１耐炎化工程から第２耐炎化工程に切り替えるタイミングは、繊維束の比重を好ましくは１．２１～１．２３の範囲とする。この際も前記赤外スペクトル強度比の範囲を満たすことを優先して耐炎化工程の条件を制御する。これらの耐炎化の処理時間や耐炎化温度の好ましい範囲は前駆体繊維束の特性やポリアクリロニトリル系重合体の共重合組成によって変化する。
The total processing time of the flameproofing step can be appropriately selected, preferably within the range of 15 to 40 minutes. For the purpose of improving the strand strength of the obtained carbon fiber bundle, the flameproofing treatment time is set so that the specific gravity of the obtained flameproofed fiber is preferably 1.28 to 1.32. A more preferable treatment time for the flameproofing step depends on the flameproofing temperature. Unless the specific gravity of the flameproof fiber bundle is 1.28 or more, the strand strength of the carbon fiber bundle may decrease. If the specific gravity of the flameproof fiber bundle is 1.32 or less, the strand strength can be increased. The specific gravity of the flameproofing fiber bundle is controlled by the treatment time of the flameproofing step and the flameproofing temperature. Further, the timing of switching from the first flameproofing step to the second flameproofing step is such that the specific gravity of the fiber bundle is preferably in the range of 1.21 to 1.23. Also in this case, the conditions of the flameproofing step are controlled with priority given to satisfying the range of the infrared spectrum intensity ratio. Preferred ranges of the treatment time for flameproofing and the flameproofing temperature vary depending on the properties of the precursor fiber bundle and the copolymer composition of the polyacrylonitrile polymer.
歪度を調節するための撚りの処理はこの第２耐炎化工程で行い、耐炎化処理中の繊維束の撚り角は０．２°以上であることが好ましい。本発明において耐炎化処理中の撚り角は、用いた前駆体繊維束の目付ｙ（ｇ／ｍ）と密度ｄ（ｇ／ｃｍ３）、撚り数Ｔ（ターン／ｍ）を用いて、次の式により計算する。
撚り角（°）＝ａｒｃｔａｎ｛（０．０１×ｙ／（π×ｄ））０．５×１０－６×π×Ｔ｝。 The twisting treatment for adjusting the degree of distortion is performed in this second flameproofing step, and the twist angle of the fiber bundle during the flameproofing treatment is preferably 0.2° or more. In the present invention, the twist angle during the flameproofing treatment is calculated using the basis weight y (g/m), the density d (g/cm 3 ), and the number of twists T (turns/m) of the precursor fiber bundle used. Calculate by formula.
Twist angle (°) = arctan {(0.01 x y/(π x d)) 0.5 x 10 -6 x π x T}.
撚り角（°）＝ａｒｃｔａｎ｛（０．０１×ｙ／（π×ｄ））０．５×１０－６×π×Ｔ｝。 The twisting treatment for adjusting the degree of distortion is performed in this second flameproofing step, and the twist angle of the fiber bundle during the flameproofing treatment is preferably 0.2° or more. In the present invention, the twist angle during the flameproofing treatment is calculated using the basis weight y (g/m), the density d (g/cm 3 ), and the number of twists T (turns/m) of the precursor fiber bundle used. Calculate by formula.
Twist angle (°) = arctan {(0.01 x y/(π x d)) 0.5 x 10 -6 x π x T}.
耐炎化処理中の繊維に撚りを加える方法としては、公知のものから選ぶことができる。具体的には、前駆体繊維束を一旦ボビンに巻き取った後、該繊維束を巻き出す際にボビンを巻き出し方向に対して直交する面に旋回させる方法や、ボビンに巻き取らず走行中の繊維束に対して回転するローラーやベルトを接触させて撚りを付与する方法などにより制御することができる。撚り角は大きいほど炭素繊維束の扁平度向上効果をより得ることができるが、０．２°以上であればその効果を得ることができる。
The method of twisting the fibers during the flameproofing treatment can be selected from known methods. Specifically, there is a method in which the precursor fiber bundle is once wound on a bobbin and then, when the fiber bundle is unwound, the bobbin is rotated in a plane orthogonal to the unwinding direction, or a method in which the fiber bundle is running without being wound on the bobbin. The twist can be controlled by a method of bringing a rotating roller or belt into contact with the fiber bundle to impart a twist. The larger the twist angle, the more the effect of improving the flatness of the carbon fiber bundle can be obtained.
第２耐炎化工程で、撚りを加える場合、耐炎化処理中の繊維束の張力を好ましくは０．７～１．５ｍＮ／ｄｔｅｘとする。耐炎化工程における張力は、耐炎化炉入側で測定した張力（ｍＮ）を、用いた前駆体繊維束の単繊維繊度（ｄｔｅｘ）とフィラメント数との積である総繊度（ｄｔｅｘ）で除したものとする。該張力を上記の数値範囲に制御することで、炭素繊維単繊維に凹みを付与しやすくなる。
When twisting is applied in the second flameproofing step, the tension of the fiber bundle during the flameproofing treatment is preferably 0.7 to 1.5 mN/dtex. The tension in the flameproofing step was obtained by dividing the tension (mN) measured at the inlet side of the flameproofing furnace by the total fineness (dtex), which is the product of the single fiber fineness (dtex) of the precursor fiber bundle used and the number of filaments. shall be By controlling the tension within the above numerical range, it becomes easier to give the carbon fiber monofilament a dent.
さらに第２耐炎化工程で、複数の繊維束をローラーの１つの溝に投入して耐炎化する。これによって、個々の耐炎化繊維束への張力は低く維持しつつ、１つの溝あたりの複数の繊維束全体の張力を高くし、それによってローラー上ではいくつかの単繊維には横断面に垂直方向の応力が加えられ、単繊維横断面の長径短径比が大きくなりやすい。このような張力付与の方法によって全体の断面形状を維持したままに、一部の単繊維の断面形状を制御することができる。ここで、複数とは好ましくは２～６本であり、より好ましくは３～５本である。
Furthermore, in the second flameproofing step, a plurality of fiber bundles are put into one groove of the roller for flameproofing. This keeps the tension on the individual flameproofed fiber bundles low while increasing the overall tension of the multiple fiber bundles per groove, so that on the roller some single fibers have A directional stress is applied, and the ratio of the major axis to the minor axis of the cross section of the single fiber tends to increase. By such a method of applying tension, the cross-sectional shape of some single fibers can be controlled while maintaining the overall cross-sectional shape. Here, the plural is preferably 2 to 6, more preferably 3 to 5.
予備炭素化する予備炭素化工程においては、上記第１および第２耐炎化工程で得られた繊維束を、不活性雰囲気中、最高温度５００～１，２００℃において、比重が好ましくは１．５～１．８になるまで熱処理する。予備炭素化工程の延伸倍率は、好ましくは１．００～１．２０である。予備炭素化工程の延伸倍率が１．００以上であればストランド弾性率が高まりやすく、ストランド強度を高めやすい。予備炭素化工程の延伸倍率が１．２０以下であるとストランド弾性率を３５０ＧＰａ以下に抑制しやすい。
In the preliminary carbonization step of pre-carbonizing, the fiber bundles obtained in the first and second flameproofing steps are treated in an inert atmosphere at a maximum temperature of 500 to 1,200 ° C. to a specific gravity of preferably 1.5. Heat treat to ~1.8. The draw ratio in the preliminary carbonization step is preferably 1.00 to 1.20. If the draw ratio in the preliminary carbonization step is 1.00 or more, the strand elastic modulus tends to increase, and the strand strength tends to increase. When the draw ratio in the preliminary carbonization step is 1.20 or less, the strand elastic modulus is easily suppressed to 350 GPa or less.
予備炭素化された繊維束を不活性雰囲気中、好ましくは最高温度１，０００～１，５００℃において、より好ましくは最高温度１，０００～１，２００℃で炭素化する。この炭素化工程の最高温度は、得られる炭素繊維束の伸度を高める観点からは、低い方が好ましく、低すぎるとストランド強度が低下する場合があり、両者を勘案して設定することが好ましい。
The pre-carbonized fiber bundle is carbonized in an inert atmosphere, preferably at a maximum temperature of 1,000-1,500°C, more preferably at a maximum temperature of 1,000-1,200°C. The maximum temperature of this carbonization step is preferably low from the viewpoint of increasing the elongation of the obtained carbon fiber bundle, and if it is too low, the strand strength may decrease, so it is preferable to set it in consideration of both. .
また、炭素化工程の最高温度の処理時間は好ましくは２０～６０秒である。最高温度での処理時間が短いほどストランド弾性率を低く制御できるため、処理時間は６０秒以内が好ましく、処理時間が２０秒以上であれば安定したストランド弾性率が得られやすい。
Also, the maximum temperature treatment time in the carbonization step is preferably 20 to 60 seconds. The shorter the treatment time at the highest temperature, the lower the strand elastic modulus can be controlled. Therefore, the treatment time is preferably 60 seconds or less, and if the treatment time is 20 seconds or longer, a stable strand elastic modulus can be easily obtained.
炭素化工程での昇温速度は好ましくは０．４０～１．１０℃／秒であり、より好ましくは０．４０～０．６０℃／秒である。炭素化工程の昇温速度は、分解ガスの脱離速度に影響するためにストランド強度に影響する。本発明において、昇温速度は１，０００～１，１００℃領域を平均して１秒あたり何℃の速度で繊維が通過するかと定義する。炭素化工程ではヒーターでの設定温度で温度を制御することが多いため、それぞれのヒーターの設置位置中心の温度と繊維の通過タイミングから昇温速度を算出する。かかる昇温速度は０．４０℃／秒以上であればストランド弾性率が安定して得られやすく、１．１０℃／秒以内であればストランド強度の低下を抑制しやすい。
The temperature elevation rate in the carbonization step is preferably 0.40-1.10°C/sec, more preferably 0.40-0.60°C/sec. The rate of temperature rise in the carbonization step affects the desorption rate of cracked gas, and therefore affects the strand strength. In the present invention, the heating rate is defined as the average rate at which the fiber passes through the temperature range of 1,000 to 1,100°C per second. In the carbonization process, the temperature is often controlled by the set temperature of the heater, so the temperature rise rate is calculated from the temperature at the center of the installation position of each heater and the fiber passage timing. If the heating rate is 0.40° C./second or more, a stable strand elastic modulus can be easily obtained, and if it is 1.10° C./second or less, a decrease in strand strength can be easily suppressed.
以上のようにして得られた炭素繊維束は、好ましくは酸化処理が施され、酸素含有官能基が導入される。
The carbon fiber bundles obtained as described above are preferably subjected to oxidation treatment to introduce oxygen-containing functional groups.
本発明において、上記炭素化工程で得られた繊維束を電解表面処理して炭素繊維束を得る。電解表面処理は、気相酸化、液相酸化および液相電解酸化が用いられるが、生産性が高く、均一処理ができるという観点から、好ましくは液相電解酸化が用いられる。本発明において、液相電解酸化の方法については特に制約はなく、公知の方法で行えばよい。
In the present invention, the carbon fiber bundle is obtained by subjecting the fiber bundle obtained in the carbonization step to electrolytic surface treatment. As the electrolytic surface treatment, gas-phase oxidation, liquid-phase oxidation and liquid-phase electrolytic oxidation are used, but liquid-phase electrolytic oxidation is preferably used from the viewpoint of high productivity and uniform treatment. In the present invention, the liquid-phase electrolytic oxidation method is not particularly limited, and a known method may be used.
かかる電解表面処理の後、得られた炭素繊維束に集束性を付与するため、サイジング処理をすることもできる。サイジング剤には、ＣＦＲＰに使用されるマトリックス樹脂の種類に応じて、マトリックス樹脂との相溶性の良いサイジング剤を適宜選択することができる。
After such an electrolytic surface treatment, a sizing treatment can be applied to impart bundling properties to the obtained carbon fiber bundles. As the sizing agent, a sizing agent having good compatibility with the matrix resin can be appropriately selected according to the type of the matrix resin used in CFRP.
本発明の炭素繊維束は、好ましくは主にクリンプを有する織物の織糸として用いられる。その形態としては、一方向織物や、多方向織物を使用することができるが、本発明においては炭素繊維束断面の扁平性によるクリンプ低減の効果から、炭素繊維束をたて糸およびよこ糸とした従来公知の二方向織物に用いることが有効である。なかでもたて糸とよこ糸が１本交互に浮き沈みして交錯する平織構造が織糸の交錯点数が多く、形態が安定しやすいことから好ましい。
The carbon fiber bundle of the present invention is preferably used mainly as yarn for crimped fabrics. As its form, a unidirectional woven fabric or a multidirectional woven fabric can be used. It is effective to use it for bidirectional fabrics. Among them, a plain weave structure in which one warp and one weft are alternately floating and interlaced is preferable because the number of crossing points of weaving yarns is large and the shape is easily stabilized.
このような扁平状態の、実質的に撚りがない炭素繊維束からなる補強織物は、繊維密度を大きくしても、各炭素繊維束の交錯部におけるクリンプは極めて小さく抑えられ、ＣＦＲＰにした際に高い伸度特性が得られる。さらに、織物の形態で各炭素繊維束が扁平な状態に維持されているために、樹脂の含浸性が極めて良い。したがって、均一な特性のＣＦＲＰが得られ、目標とする伸度特性が容易に得られる。ここで「実質的に撚りがない」とは、炭素繊維束１ｍ当たりに１ターン以上の撚りがない状態をいう。炭素繊維束に撚りがあると、その撚りがある部分で凹凸が発生する。このため、製織された織物は、外力が作用した際にその撚り部分に応力が集中し、ＣＦＲＰに成形した場合に伸度特性が不均一となってしまう。本発明の炭素繊維束は撚りをほどいて用いることができる。
In such a reinforcing fabric made of carbon fiber bundles in a flat state and substantially untwisted, even if the fiber density is increased, the crimp at the intersecting portion of each carbon fiber bundle is suppressed to be extremely small, and when it is made into CFRP High elongation properties can be obtained. Furthermore, since each carbon fiber bundle is maintained in a flat state in the form of a woven fabric, the resin impregnation property is extremely good. Therefore, CFRP with uniform properties can be obtained, and target elongation properties can be easily obtained. Here, "substantially no twist" means a state in which there is no twist of 1 turn or more per 1 m of the carbon fiber bundle. If the carbon fiber bundle is twisted, unevenness occurs at the twisted portion. For this reason, when an external force acts on the woven fabric, stress is concentrated on the twisted portion, and when the fabric is molded into CFRP, the elongation characteristics become uneven. The carbon fiber bundle of the present invention can be used after being untwisted.
補強織物は、次のような方法により製造できる。前述のような扁平で実質的に撚りがない炭素繊維束をたて糸および／またはよこ糸とし、その炭素繊維束の扁平度がくずれないように、かつ解舒撚りがかからないように横取り解舒し、必要に応じて、製織中あるいは製織後に各織糸を開繊、拡幅するとよい。上記のような補強織物は、プリフォームやプリプレグ、さらにはＣＦＲＰの成形に供され、補強基材として優れた特性を発揮する。プリフォームは、前記いずれかの補強織物を少なくとも１枚用いることができる。凹凸が極めて小さいので、これを用いたプリフォームは型への賦形性が極めて良好であり、ＣＦＲＰに成形した際にも表面が平滑になる。このようにして得られた補強織物は、高い力学物性を要求する部材に好ましく用いられる。この補強織物を織物プリプレグとしてＣＦＲＰに成形することや織物基材を用いて真空成形することが好ましい。
The reinforcing fabric can be manufactured by the following method. The flat and substantially untwisted carbon fiber bundles as described above are used as warp and/or weft yarns, and are transversely unwound so that the flatness of the carbon fiber bundles does not deteriorate and untwisting is not applied. Depending on the requirements, each weaving yarn may be opened or widened during or after weaving. The reinforcing fabric as described above is used for forming preforms, prepregs, and CFRP, and exhibits excellent properties as a reinforcing base material. At least one sheet of any one of the reinforcing fabrics can be used for the preform. Since the unevenness is extremely small, a preform using this material has extremely good shapeability into a mold, and the surface becomes smooth even when molded into a CFRP. The reinforcing fabric thus obtained is preferably used for members requiring high mechanical properties. It is preferable to form this reinforcing fabric into CFRP as a fabric prepreg or vacuum forming using a fabric substrate.
本発明の炭素繊維束は、ストランド弾性率、ストランド強度、伸度、および、総繊度、長径短径比の平均値、変動係数、歪度の全てを満足することがＣＦＲＰの耐衝撃性を高める点で重要である。
The carbon fiber bundle of the present invention satisfies all of the strand elastic modulus, strand strength, elongation, total fineness, the average value of the ratio of the major diameter to the minor diameter, the coefficient of variation, and the degree of distortion to enhance the impact resistance of CFRP. point is important.
本発明において用いられる各種物性値の測定方法は、次のとおりである。
The methods for measuring various physical property values used in the present invention are as follows.
＜総繊度＞
測定する炭素繊維束について、長さ１０ｍ分をサンプリングし、１２０℃で２時間絶乾させた後に測定した質量を１０で除することにより、１ｍあたりの質量である総繊度を求める。 <Total fineness>
A 10 m length sample of the carbon fiber bundle to be measured is dried at 120° C. for 2 hours, and the measured mass is divided by 10 to obtain the total fineness, which is the mass per 1 m.
測定する炭素繊維束について、長さ１０ｍ分をサンプリングし、１２０℃で２時間絶乾させた後に測定した質量を１０で除することにより、１ｍあたりの質量である総繊度を求める。 <Total fineness>
A 10 m length sample of the carbon fiber bundle to be measured is dried at 120° C. for 2 hours, and the measured mass is divided by 10 to obtain the total fineness, which is the mass per 1 m.
＜密度＞
測定する炭素繊維束について、１２０℃で２時間絶乾させてから用いる。乾式自動密度計を用い、測定媒体として窒素、試料容器は１０ｃｃタイプ、試料量は体積で３～６ｃｃになるように調整する。測定は３回行い、その平均値を用いる。なお、本測定では、株式会社島津製作所製アキュピック１３３０形乾式自動密度計を用いた。 <Density>
The carbon fiber bundle to be measured is dried at 120° C. for 2 hours before use. A dry automatic density meter is used, nitrogen is used as a measurement medium, a 10 cc type sample container is used, and the volume of the sample is adjusted to 3 to 6 cc. Measurement is performed 3 times and the average value is used. In addition, in this measurement, an Accupic 1330 type dry automatic density meter manufactured by Shimadzu Corporation was used.
測定する炭素繊維束について、１２０℃で２時間絶乾させてから用いる。乾式自動密度計を用い、測定媒体として窒素、試料容器は１０ｃｃタイプ、試料量は体積で３～６ｃｃになるように調整する。測定は３回行い、その平均値を用いる。なお、本測定では、株式会社島津製作所製アキュピック１３３０形乾式自動密度計を用いた。 <Density>
The carbon fiber bundle to be measured is dried at 120° C. for 2 hours before use. A dry automatic density meter is used, nitrogen is used as a measurement medium, a 10 cc type sample container is used, and the volume of the sample is adjusted to 3 to 6 cc. Measurement is performed 3 times and the average value is used. In addition, in this measurement, an Accupic 1330 type dry automatic density meter manufactured by Shimadzu Corporation was used.
＜ストランド強度、ストランド弾性率、伸度＞
炭素繊維束のストランド強度、ストランド弾性率および伸度は、ＪＩＳ Ｒ７６０８：２００４の樹脂含浸ストランド試験法に従い、次の手順に従い求める。樹脂処方としては、“セロキサイド（登録商標）”２０２１Ｐ（ダイセル社製）／３フッ化ホウ素モノエチルアミン（東京化成工業（株）製）／アセトン＝１００／３／４（質量部）を用い、硬化条件としては、常圧、温度１２５℃、時間３０分を用いる。炭素繊維のストランド７本を測定し、その平均値をストランド強度、ストランド弾性率および伸度とする。なお、ストランド弾性率を算出する際の歪み範囲は０．１～０．６％とする。 <Strand strength, strand elastic modulus, elongation>
The strand strength, strand elastic modulus and elongation of the carbon fiber bundle are obtained according to the resin-impregnated strand test method of JIS R7608:2004, according to the following procedure. As the resin formulation, "Celoxide (registered trademark)" 2021P (manufactured by Daicel Corporation) / boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / acetone = 100/3/4 (parts by mass) was used and cured. As the conditions, normal pressure, temperature of 125° C., and time of 30 minutes are used. Seven carbon fiber strands are measured, and the average values are taken as the strand strength, strand elastic modulus and elongation. The strain range for calculating the strand elastic modulus is 0.1 to 0.6%.
炭素繊維束のストランド強度、ストランド弾性率および伸度は、ＪＩＳ Ｒ７６０８：２００４の樹脂含浸ストランド試験法に従い、次の手順に従い求める。樹脂処方としては、“セロキサイド（登録商標）”２０２１Ｐ（ダイセル社製）／３フッ化ホウ素モノエチルアミン（東京化成工業（株）製）／アセトン＝１００／３／４（質量部）を用い、硬化条件としては、常圧、温度１２５℃、時間３０分を用いる。炭素繊維のストランド７本を測定し、その平均値をストランド強度、ストランド弾性率および伸度とする。なお、ストランド弾性率を算出する際の歪み範囲は０．１～０．６％とする。 <Strand strength, strand elastic modulus, elongation>
The strand strength, strand elastic modulus and elongation of the carbon fiber bundle are obtained according to the resin-impregnated strand test method of JIS R7608:2004, according to the following procedure. As the resin formulation, "Celoxide (registered trademark)" 2021P (manufactured by Daicel Corporation) / boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / acetone = 100/3/4 (parts by mass) was used and cured. As the conditions, normal pressure, temperature of 125° C., and time of 30 minutes are used. Seven carbon fiber strands are measured, and the average values are taken as the strand strength, strand elastic modulus and elongation. The strain range for calculating the strand elastic modulus is 0.1 to 0.6%.
＜耐炎化処理における撚り角＞
耐炎化処理における撚り角は、用いた前駆体繊維束の目付ｙ（ｇ／ｍ）と密度ｄ（ｇ／ｃｍ３）、撚り数Ｔ（ターン／ｍ）を用いて、次の式により計算する。
撚り角（°）＝ａｒｃｔａｎ｛（０．０１×ｙ／（π×ｄ））０．５×１０－６×π×Ｔ｝。 <Twisting angle in flameproof treatment>
The twist angle in the flameproof treatment is calculated by the following formula using the basis weight y (g/m), density d (g/cm 3 ), and twist number T (turn/m) of the precursor fiber bundle used. .
Twist angle (°) = arctan {(0.01 x y/(π x d)) 0.5 x 10 -6 x π x T}.
耐炎化処理における撚り角は、用いた前駆体繊維束の目付ｙ（ｇ／ｍ）と密度ｄ（ｇ／ｃｍ３）、撚り数Ｔ（ターン／ｍ）を用いて、次の式により計算する。
撚り角（°）＝ａｒｃｔａｎ｛（０．０１×ｙ／（π×ｄ））０．５×１０－６×π×Ｔ｝。 <Twisting angle in flameproof treatment>
The twist angle in the flameproof treatment is calculated by the following formula using the basis weight y (g/m), density d (g/cm 3 ), and twist number T (turn/m) of the precursor fiber bundle used. .
Twist angle (°) = arctan {(0.01 x y/(π x d)) 0.5 x 10 -6 x π x T}.
＜長径短径比および変動係数、歪度の統計量＞
長径短径比、変動係数及び歪度の評価方法は、上記の定義に従って評価する限り特に限定されないが、例えば次のように評価することができる。
まず、炭素繊維束を引き揃え、円筒状に包み込むようにカーボンテープでまとめる。この状態で、繊維軸に垂直となるようにはさみをあてて、切断することにより、単繊維横断面を露出させる。かかる単繊維横断面を、走査電子顕微鏡を用いて観察し、画像として保存する。保存した画像を、オープンソースの画像解析ソフトウェア“ＩｍａｇｅＪ（イメージ・ジェイ）”（Vｅｒｓｉｏｎ１．５３ｈ）に読み込み、単繊維横断面の輪郭を“Ｐｏｌｙｇｏｎ ｓｅｌｅｃｔｉｏｎｓ（ポリゴン・セレクションズ）”ツールを用いてトレースする。このとき、ひとつの輪郭につき、２０～１００個の点で１周分をトレースする。つづいて、“Ｆｉｔ ｓｐｌｉｎｅ（フィット・スプライン）”ツールを用いて輪郭のトレースをなめらかな曲線に変換する。変換後、単繊維横断面の輪郭とトレースした曲線がよりよく一致するように点を移動させて微調整する。ひきつづいて、“Ａｎａｌｙｚｅ ｐａｒｔｉｃｌｅｓ（アナライズ・パーティクルズ）”ツールを用いて、“ＡＲ（アスペクト比）”を算出する。なお、アスペクト比は、本発明における長径短径比のことを指す。単繊維本数は何本であっても良いが統計的に偏りが現れない本数で行い、例えば単繊維５０個に対して同様の操作を行う。このとき、炭素繊維束の異なる部分から、満遍なく単繊維を選ぶようにする。特定の長径短径比の単繊維本数割合とは、特定の長径短径比の単繊維本数を評価した全ての単繊維本数で除し、１００をかけた値（％）である。評価した全ての単繊維本数から平均値（－）および変動係数（％）、歪度（－）を算出する。なお、長径短径比の歪度は以下の式（１）に従って計算する。
歪度＝ｎ／（（ｎ－１）×（ｎ－２））×Σ｛（ｘｉ－＜ｘ＞）／ｓ｝３ ・・・（１）
ここで、ｎは単繊維の本数（本）、ｘｉはｉ番目の単繊維の長径短径比（－）、＜ｘ＞は長径短径比の平均値（－）、ｓは長径短径比の標準偏差（－）を意味する。また、Σは単繊維の本数ｎの分だけ和をとることを意味する。なお、以下の実施例では、走査電子顕微鏡として日立ハイテクノロジーズ社製の走査電子顕微鏡（ＳＥＭ）“Ｓ－４８００”を用い、加速電圧は５ｋｅＶとして観察を行った。 <Ratio of major axis to minor axis, coefficient of variation, and statistics of skewness>
The method for evaluating the ratio of the major axis to the minor axis, the coefficient of variation, and the degree of skewness is not particularly limited as long as the evaluation is performed according to the above definitions, but the evaluation can be performed, for example, as follows.
First, the carbon fiber bundles are aligned and put together with a carbon tape so as to wrap them in a cylindrical shape. In this state, scissors are applied perpendicular to the fiber axis to cut, thereby exposing the cross section of the single fiber. Such single fiber cross-sections are observed using a scanning electron microscope and saved as images. The saved images are read into the open source image analysis software "ImageJ" (Version 1.53h) and the single fiber cross-section contours are traced using the "Polygon selections" tool. At this time, one contour is traced with 20 to 100 points. The contour trace is then converted to a smooth curve using the "Fit spline" tool. After conversion, the points are moved and fine-tuned to better match the profile of the monofilament cross-section and the traced curve. Subsequently, the "AR (aspect ratio)" is calculated using the "Analyze particles" tool. In addition, the aspect ratio refers to the ratio of major axis to minor axis in the present invention. The number of single fibers may be any number, but the number of single fibers is selected so that no statistical deviation appears. For example, the same operation is performed on 50 single fibers. At this time, single fibers are evenly selected from different portions of the carbon fiber bundle. The ratio of the number of single fibers having a specific ratio of major axis to minor axis is a value (%) obtained by dividing the number of single fibers having a specific ratio of major axis to minor axis by the total number of evaluated single fibers and multiplying by 100. The average value (-), coefficient of variation (%), and skewness (-) are calculated from all evaluated single fiber counts. In addition, the skewness of the ratio of major diameter to minor diameter is calculated according to the following formula (1).
Skewness = n/((n−1)×(n−2))×Σ{(x i −<x>)/s} 3 (1)
Here, n is the number of single fibers (pieces), x i is the ratio of the major diameter to the minor diameter of the i-th single fiber (-), <x> is the average value of the ratio of the major diameter to the minor diameter (-), and s is the major diameter to the minor diameter. Means the standard deviation (-) of the ratio. Also, Σ means that the sum is taken for the number n of single fibers. In the following examples, a scanning electron microscope (SEM) "S-4800" manufactured by Hitachi High-Technologies Corporation was used as a scanning electron microscope, and observation was carried out at an accelerating voltage of 5 keV.
長径短径比、変動係数及び歪度の評価方法は、上記の定義に従って評価する限り特に限定されないが、例えば次のように評価することができる。
まず、炭素繊維束を引き揃え、円筒状に包み込むようにカーボンテープでまとめる。この状態で、繊維軸に垂直となるようにはさみをあてて、切断することにより、単繊維横断面を露出させる。かかる単繊維横断面を、走査電子顕微鏡を用いて観察し、画像として保存する。保存した画像を、オープンソースの画像解析ソフトウェア“ＩｍａｇｅＪ（イメージ・ジェイ）”（Vｅｒｓｉｏｎ１．５３ｈ）に読み込み、単繊維横断面の輪郭を“Ｐｏｌｙｇｏｎ ｓｅｌｅｃｔｉｏｎｓ（ポリゴン・セレクションズ）”ツールを用いてトレースする。このとき、ひとつの輪郭につき、２０～１００個の点で１周分をトレースする。つづいて、“Ｆｉｔ ｓｐｌｉｎｅ（フィット・スプライン）”ツールを用いて輪郭のトレースをなめらかな曲線に変換する。変換後、単繊維横断面の輪郭とトレースした曲線がよりよく一致するように点を移動させて微調整する。ひきつづいて、“Ａｎａｌｙｚｅ ｐａｒｔｉｃｌｅｓ（アナライズ・パーティクルズ）”ツールを用いて、“ＡＲ（アスペクト比）”を算出する。なお、アスペクト比は、本発明における長径短径比のことを指す。単繊維本数は何本であっても良いが統計的に偏りが現れない本数で行い、例えば単繊維５０個に対して同様の操作を行う。このとき、炭素繊維束の異なる部分から、満遍なく単繊維を選ぶようにする。特定の長径短径比の単繊維本数割合とは、特定の長径短径比の単繊維本数を評価した全ての単繊維本数で除し、１００をかけた値（％）である。評価した全ての単繊維本数から平均値（－）および変動係数（％）、歪度（－）を算出する。なお、長径短径比の歪度は以下の式（１）に従って計算する。
歪度＝ｎ／（（ｎ－１）×（ｎ－２））×Σ｛（ｘｉ－＜ｘ＞）／ｓ｝３ ・・・（１）
ここで、ｎは単繊維の本数（本）、ｘｉはｉ番目の単繊維の長径短径比（－）、＜ｘ＞は長径短径比の平均値（－）、ｓは長径短径比の標準偏差（－）を意味する。また、Σは単繊維の本数ｎの分だけ和をとることを意味する。なお、以下の実施例では、走査電子顕微鏡として日立ハイテクノロジーズ社製の走査電子顕微鏡（ＳＥＭ）“Ｓ－４８００”を用い、加速電圧は５ｋｅＶとして観察を行った。 <Ratio of major axis to minor axis, coefficient of variation, and statistics of skewness>
The method for evaluating the ratio of the major axis to the minor axis, the coefficient of variation, and the degree of skewness is not particularly limited as long as the evaluation is performed according to the above definitions, but the evaluation can be performed, for example, as follows.
First, the carbon fiber bundles are aligned and put together with a carbon tape so as to wrap them in a cylindrical shape. In this state, scissors are applied perpendicular to the fiber axis to cut, thereby exposing the cross section of the single fiber. Such single fiber cross-sections are observed using a scanning electron microscope and saved as images. The saved images are read into the open source image analysis software "ImageJ" (Version 1.53h) and the single fiber cross-section contours are traced using the "Polygon selections" tool. At this time, one contour is traced with 20 to 100 points. The contour trace is then converted to a smooth curve using the "Fit spline" tool. After conversion, the points are moved and fine-tuned to better match the profile of the monofilament cross-section and the traced curve. Subsequently, the "AR (aspect ratio)" is calculated using the "Analyze particles" tool. In addition, the aspect ratio refers to the ratio of major axis to minor axis in the present invention. The number of single fibers may be any number, but the number of single fibers is selected so that no statistical deviation appears. For example, the same operation is performed on 50 single fibers. At this time, single fibers are evenly selected from different portions of the carbon fiber bundle. The ratio of the number of single fibers having a specific ratio of major axis to minor axis is a value (%) obtained by dividing the number of single fibers having a specific ratio of major axis to minor axis by the total number of evaluated single fibers and multiplying by 100. The average value (-), coefficient of variation (%), and skewness (-) are calculated from all evaluated single fiber counts. In addition, the skewness of the ratio of major diameter to minor diameter is calculated according to the following formula (1).
Skewness = n/((n−1)×(n−2))×Σ{(x i −<x>)/s} 3 (1)
Here, n is the number of single fibers (pieces), x i is the ratio of the major diameter to the minor diameter of the i-th single fiber (-), <x> is the average value of the ratio of the major diameter to the minor diameter (-), and s is the major diameter to the minor diameter. Means the standard deviation (-) of the ratio. Also, Σ means that the sum is taken for the number n of single fibers. In the following examples, a scanning electron microscope (SEM) "S-4800" manufactured by Hitachi High-Technologies Corporation was used as a scanning electron microscope, and observation was carried out at an accelerating voltage of 5 keV.
＜開繊性＞
開繊性は、炭素繊維束にサイジング剤を付着させない状態で評価する。サイジング剤が付着している場合は、オーブン中でサイジング剤を焼き飛ばすか、溶媒中で洗浄することによって除去してから評価する。炭素繊維束２ｃｍをサンプリングし、撚りがない状態とする。１０ｃｍ四方のガラス板の上に炭素繊維束を設置し、その上からスライドガラスをかぶせる。炭素繊維束の軸方向と垂直方向に左右３ｍｍずつ交互に１０回動かす。この操作の前後で糸条幅変化を測定し、１０回繰り返した平均値を開繊性の指標とする。糸条幅が拡がる比率が大きいほど、開繊性に優れる。なお、開繊性は炭素繊維束の糸条幅が測定を行う前の糸条幅に対しての何倍となっているかでＡ～Ｃから判断する。
Ａ：元糸条幅に対して測定後の幅が４倍以上である。
Ｂ：元糸条幅に対して測定後の幅が２倍以上４倍未満である。
Ｃ：元糸条幅に対して測定後の幅が２倍未満である。 <Openability>
Openability is evaluated in a state in which no sizing agent is adhered to the carbon fiber bundle. If the sizing agent is adhered, it is removed by burning off the sizing agent in an oven or by washing in a solvent before evaluation. A carbon fiber bundle of 2 cm is sampled, and is assumed to be untwisted. A carbon fiber bundle is placed on a 10 cm square glass plate, and a slide glass is placed on it. The carbon fiber bundle is moved 10 times alternately by 3 mm in the axial direction and the vertical direction. The yarn width change was measured before and after this operation, and the average value obtained by repeating this operation 10 times was used as an index of the openability. The greater the ratio of the yarn width expansion, the better the openability. The openability is judged from A to C by how many times the yarn width of the carbon fiber bundle is larger than the yarn width before measurement.
A: The measured width is 4 times or more the original yarn width.
B: The width after measurement is 2 times or more and less than 4 times the original yarn width.
C: The measured width is less than twice the original yarn width.
開繊性は、炭素繊維束にサイジング剤を付着させない状態で評価する。サイジング剤が付着している場合は、オーブン中でサイジング剤を焼き飛ばすか、溶媒中で洗浄することによって除去してから評価する。炭素繊維束２ｃｍをサンプリングし、撚りがない状態とする。１０ｃｍ四方のガラス板の上に炭素繊維束を設置し、その上からスライドガラスをかぶせる。炭素繊維束の軸方向と垂直方向に左右３ｍｍずつ交互に１０回動かす。この操作の前後で糸条幅変化を測定し、１０回繰り返した平均値を開繊性の指標とする。糸条幅が拡がる比率が大きいほど、開繊性に優れる。なお、開繊性は炭素繊維束の糸条幅が測定を行う前の糸条幅に対しての何倍となっているかでＡ～Ｃから判断する。
Ａ：元糸条幅に対して測定後の幅が４倍以上である。
Ｂ：元糸条幅に対して測定後の幅が２倍以上４倍未満である。
Ｃ：元糸条幅に対して測定後の幅が２倍未満である。 <Openability>
Openability is evaluated in a state in which no sizing agent is adhered to the carbon fiber bundle. If the sizing agent is adhered, it is removed by burning off the sizing agent in an oven or by washing in a solvent before evaluation. A carbon fiber bundle of 2 cm is sampled, and is assumed to be untwisted. A carbon fiber bundle is placed on a 10 cm square glass plate, and a slide glass is placed on it. The carbon fiber bundle is moved 10 times alternately by 3 mm in the axial direction and the vertical direction. The yarn width change was measured before and after this operation, and the average value obtained by repeating this operation 10 times was used as an index of the openability. The greater the ratio of the yarn width expansion, the better the openability. The openability is judged from A to C by how many times the yarn width of the carbon fiber bundle is larger than the yarn width before measurement.
A: The measured width is 4 times or more the original yarn width.
B: The width after measurement is 2 times or more and less than 4 times the original yarn width.
C: The measured width is less than twice the original yarn width.
＜炭素繊維束断面形状＞
炭素繊維束の断面形状は次の様に測定する。実質的に撚りがなくほとんど張力がかかっていない状態で炭素繊維束を自重で垂れ下がらせ、炭素繊維束全体に接着剤等を付与して固定し、接着剤が乾燥した後、炭素繊維束断面の形状を崩さない様に切断する。切り出した炭素繊維束断面を偏光顕微鏡で観察し、画像を取得する。取得した画像を、オープンソースの画像解析ソフトウェア“ＩｍａｇｅＪ（イメージ・ジェイ）”（Vｅｒｓｉｏｎ１．５３ｈ）に読み込み、単繊維横断面の輪郭を“Ｐｏｌｙｇｏｎ ｓｅｌｅｃｔｉｏｎｓ（ポリゴン・セレクションズ）”ツールを用いてトレースする。このとき、ひとつの輪郭につき、輪郭上に２０～１００個の点で１周分をトレースする。つづいて、“Ｆｉｔ ｓｐｌｉｎｅ（フィット・スプライン）”ツールを用いて輪郭のトレースをなめらかな曲線に変換する。ひきつづいて、“Ａｎａｌｙｚｅ ｐａｒｔｉｃｌｅｓ（アナライズ・パーティクルズ）”ツールを用いて、フェレ径の長さと位置の情報及び輪郭内の面積を取得する。続いてフェレ径となっている線分に垂直に交わり、輪郭への距離が最長の線分の長さを取得する。炭素繊維束の断面形状は輪郭内の面積、フェレ径、フェレ径に垂直に交わる前記の線分長さで判断し、以下の式（２）に従って計算する。
Ｃ／（Ａ×２Ｂ）・・・（２）
ここで、Ａはフェレ径、Ｂはフェレ径に垂直に交わる前述の線分長さ、Ｃは輪郭内の面積であり、図１のそれぞれの文字に対応している。これにより定義された二つの辺による長方形（Ａ×２Ｂ）と輪郭内の面積（Ｃ）により炭素繊維束断面の面積比率を求めることにより断面形状を判断する。 <Cross-sectional shape of carbon fiber bundle>
The cross-sectional shape of the carbon fiber bundle is measured as follows. The carbon fiber bundle is allowed to hang under its own weight in a state where it is substantially untwisted and with almost no tension applied, and the entire carbon fiber bundle is fixed by applying an adhesive or the like. Cut so as not to destroy the shape of A cross section of the cut carbon fiber bundle is observed with a polarizing microscope to acquire an image. The acquired images are loaded into the open-source image analysis software "ImageJ" (Version 1.53h) and the single fiber cross-section contours are traced using the "Polygon selections" tool. At this time, one contour is traced with 20 to 100 points on the contour. The contour trace is then converted to a smooth curve using the "Fit spline" tool. Subsequently, the "Analyze particles" tool is used to obtain the length and position information of the Feret diameter and the area within the contour. Next, the length of the line segment that intersects perpendicularly with the line segment that is the Feret diameter and has the longest distance to the contour is obtained. The cross-sectional shape of the carbon fiber bundle is determined by the area within the contour, the Feret diameter, and the length of the line segment perpendicular to the Feret diameter, and calculated according to the following formula (2).
C/(A×2B) (2)
Here, A is the Feret diameter, B is the length of the aforementioned line segment perpendicular to the Feret diameter, and C is the area within the contour, which correspond to the letters in FIG. The cross-sectional shape is determined by determining the area ratio of the carbon fiber bundle cross-section from the rectangle (A×2B) defined by two sides and the area (C) within the contour.
炭素繊維束の断面形状は次の様に測定する。実質的に撚りがなくほとんど張力がかかっていない状態で炭素繊維束を自重で垂れ下がらせ、炭素繊維束全体に接着剤等を付与して固定し、接着剤が乾燥した後、炭素繊維束断面の形状を崩さない様に切断する。切り出した炭素繊維束断面を偏光顕微鏡で観察し、画像を取得する。取得した画像を、オープンソースの画像解析ソフトウェア“ＩｍａｇｅＪ（イメージ・ジェイ）”（Vｅｒｓｉｏｎ１．５３ｈ）に読み込み、単繊維横断面の輪郭を“Ｐｏｌｙｇｏｎ ｓｅｌｅｃｔｉｏｎｓ（ポリゴン・セレクションズ）”ツールを用いてトレースする。このとき、ひとつの輪郭につき、輪郭上に２０～１００個の点で１周分をトレースする。つづいて、“Ｆｉｔ ｓｐｌｉｎｅ（フィット・スプライン）”ツールを用いて輪郭のトレースをなめらかな曲線に変換する。ひきつづいて、“Ａｎａｌｙｚｅ ｐａｒｔｉｃｌｅｓ（アナライズ・パーティクルズ）”ツールを用いて、フェレ径の長さと位置の情報及び輪郭内の面積を取得する。続いてフェレ径となっている線分に垂直に交わり、輪郭への距離が最長の線分の長さを取得する。炭素繊維束の断面形状は輪郭内の面積、フェレ径、フェレ径に垂直に交わる前記の線分長さで判断し、以下の式（２）に従って計算する。
Ｃ／（Ａ×２Ｂ）・・・（２）
ここで、Ａはフェレ径、Ｂはフェレ径に垂直に交わる前述の線分長さ、Ｃは輪郭内の面積であり、図１のそれぞれの文字に対応している。これにより定義された二つの辺による長方形（Ａ×２Ｂ）と輪郭内の面積（Ｃ）により炭素繊維束断面の面積比率を求めることにより断面形状を判断する。 <Cross-sectional shape of carbon fiber bundle>
The cross-sectional shape of the carbon fiber bundle is measured as follows. The carbon fiber bundle is allowed to hang under its own weight in a state where it is substantially untwisted and with almost no tension applied, and the entire carbon fiber bundle is fixed by applying an adhesive or the like. Cut so as not to destroy the shape of A cross section of the cut carbon fiber bundle is observed with a polarizing microscope to acquire an image. The acquired images are loaded into the open-source image analysis software "ImageJ" (Version 1.53h) and the single fiber cross-section contours are traced using the "Polygon selections" tool. At this time, one contour is traced with 20 to 100 points on the contour. The contour trace is then converted to a smooth curve using the "Fit spline" tool. Subsequently, the "Analyze particles" tool is used to obtain the length and position information of the Feret diameter and the area within the contour. Next, the length of the line segment that intersects perpendicularly with the line segment that is the Feret diameter and has the longest distance to the contour is obtained. The cross-sectional shape of the carbon fiber bundle is determined by the area within the contour, the Feret diameter, and the length of the line segment perpendicular to the Feret diameter, and calculated according to the following formula (2).
C/(A×2B) (2)
Here, A is the Feret diameter, B is the length of the aforementioned line segment perpendicular to the Feret diameter, and C is the area within the contour, which correspond to the letters in FIG. The cross-sectional shape is determined by determining the area ratio of the carbon fiber bundle cross-section from the rectangle (A×2B) defined by two sides and the area (C) within the contour.
［実施例１］
ポリアクリロニトリル系重合体を、ジメチルスルホキシドを溶媒として溶液重合法により重合させ、紡糸溶液を得た。得られた紡糸溶液を紡糸口金から一旦空気中に吐出し、０℃に保持されたジメチルスルホキシド３５質量％の水溶液からなる凝固浴に導入する乾湿式紡糸法により凝固糸条を得た。 [Example 1]
A polyacrylonitrile-based polymer was polymerized by a solution polymerization method using dimethylsulfoxide as a solvent to obtain a spinning solution. The resulting spinning solution was once discharged into the air from a spinneret and introduced into a coagulation bath consisting of an aqueous solution of 35% by mass of dimethyl sulfoxide maintained at 0°C to obtain a coagulated filament by a dry-wet spinning method.
ポリアクリロニトリル系重合体を、ジメチルスルホキシドを溶媒として溶液重合法により重合させ、紡糸溶液を得た。得られた紡糸溶液を紡糸口金から一旦空気中に吐出し、０℃に保持されたジメチルスルホキシド３５質量％の水溶液からなる凝固浴に導入する乾湿式紡糸法により凝固糸条を得た。 [Example 1]
A polyacrylonitrile-based polymer was polymerized by a solution polymerization method using dimethylsulfoxide as a solvent to obtain a spinning solution. The resulting spinning solution was once discharged into the air from a spinneret and introduced into a coagulation bath consisting of an aqueous solution of 35% by mass of dimethyl sulfoxide maintained at 0°C to obtain a coagulated filament by a dry-wet spinning method.
この凝固糸条を、常法により水洗した後、２槽の温水浴中で、３．５倍の延伸を行った。続いて、この水浴延伸後の繊維束に対して、アミノ変性シリコーン系シリコーン油剤を付与し、１６０℃の加熱ローラーを用いて、乾燥緻密化処理を行った。加圧スチーム中で３．７倍延伸することにより、製糸全延伸倍率を１３倍とし、その後、交絡処理を行って、単繊維本数６，０００本の前駆体繊維束を得た。前駆体繊維束の単繊維繊度は０．７ｄｔｅｘであった。
After the coagulated yarn was washed with water by a conventional method, it was stretched 3.5 times in two hot water baths. Subsequently, an amino-modified silicone-based silicone oil agent was applied to the fiber bundle after the water-bath drawing, and a drying and densification treatment was performed using a heating roller at 160°C. The fiber was drawn 3.7 times in pressurized steam to make the total draw ratio 13 times, and then entangled to obtain a precursor fiber bundle having 6,000 single fibers. The single fiber fineness of the precursor fiber bundle was 0.7 dtex.
次に、第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８０℃、耐炎化時間６分の条件を用いて（条件１）、空気雰囲気のオーブン中で張力０．８ｍＮ／ｄｔｅｘとしつつ、耐炎化炉前後のローラーの１つの溝あたりに２本の前駆体繊維束を投入して耐炎化処理し、耐炎化繊維束を得た。また、このとき前駆体繊維束に１ｍあたり１５回転の撚りを入れながら耐炎化工程を行った。
Next, the conditions for the first flameproofing step are a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the second flameproofing step is carried out under the conditions of a flameproofing temperature of 280°C and a flameproofing time of 6 minutes (conditions 1) While maintaining a tension of 0.8 mN/dtex in an oven in an air atmosphere, two precursor fiber bundles are put into each groove of the rollers before and after the flameproofing furnace for flameproofing treatment, and the flameproof fiber bundles are got At this time, the flameproofing step was performed while twisting the precursor fiber bundle at 15 turns per meter.
得られた耐炎化繊維束を、最高温度８００℃の窒素雰囲気中において、延伸比１．２０で予備炭素化処理を行い、予備炭素化繊維束を得た。得られた予備炭素化繊維束を、窒素雰囲気中において、最高温度１，４００℃、延伸比０．９５０で炭素化処理を行った。このとき炭素化工程の昇温速度は０．４５℃／秒、最高温度での滞留時間は６０秒であった。得られた炭素繊維束に表面処理およびサイジング剤塗布処理を行って最終的な炭素繊維束としたものの物性を表１および２に示す。
The obtained flame-resistant fiber bundle was subjected to a preliminary carbonization treatment at a draw ratio of 1.20 in a nitrogen atmosphere at a maximum temperature of 800°C to obtain a preliminary carbonized fiber bundle. The obtained pre-carbonized fiber bundle was carbonized in a nitrogen atmosphere at a maximum temperature of 1,400° C. and a draw ratio of 0.950. At this time, the rate of temperature increase in the carbonization step was 0.45° C./second, and the residence time at the maximum temperature was 60 seconds. Tables 1 and 2 show the physical properties of the final carbon fiber bundle obtained by subjecting the obtained carbon fiber bundle to surface treatment and coating treatment with a sizing agent.
［実施例２］
耐炎化時の延伸比を変更することで耐炎化時の張力１．０ｍＮ／ｄｔｅｘとし、炭素繊維前駆体繊維束に１ｍあたり１５回転の撚りを入れ、耐炎化炉前後のローラーの１つの溝あたりに３本の炭素繊維前駆体繊維束を投入した以外は、実施例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 2]
By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 1.0 mN / dtex, and the carbon fiber precursor fiber bundle was twisted at 15 rotations per 1 m, and each groove of the roller before and after the flameproofing furnace A carbon fiber bundle was obtained in the same manner as in Example 1, except that three carbon fiber precursor fiber bundles were added to the . Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力１．０ｍＮ／ｄｔｅｘとし、炭素繊維前駆体繊維束に１ｍあたり１５回転の撚りを入れ、耐炎化炉前後のローラーの１つの溝あたりに３本の炭素繊維前駆体繊維束を投入した以外は、実施例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 2]
By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 1.0 mN / dtex, and the carbon fiber precursor fiber bundle was twisted at 15 rotations per 1 m, and each groove of the roller before and after the flameproofing furnace A carbon fiber bundle was obtained in the same manner as in Example 1, except that three carbon fiber precursor fiber bundles were added to the . Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例３］
耐炎化時の延伸比を変更することで耐炎化時の張力１．２ｍＮ／ｄｔｅｘとした以外は、実施例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 3]
A carbon fiber bundle was obtained in the same manner as in Example 2, except that the tension during flameproofing was changed to 1.2 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力１．２ｍＮ／ｄｔｅｘとした以外は、実施例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 3]
A carbon fiber bundle was obtained in the same manner as in Example 2, except that the tension during flameproofing was changed to 1.2 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例４］
耐炎化時の延伸比を変更することで耐炎化時の張力１．５ｍＮ／ｄｔｅｘとした以外は、実施例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 4]
A carbon fiber bundle was obtained in the same manner as in Example 2, except that the tension during flameproofing was changed to 1.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力１．５ｍＮ／ｄｔｅｘとした以外は、実施例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 4]
A carbon fiber bundle was obtained in the same manner as in Example 2, except that the tension during flameproofing was changed to 1.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例５］
耐炎化炉前後のローラーの１つの溝あたりに２本の前駆体繊維束を投入した以外は、実施例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 5]
A carbon fiber bundle was obtained in the same manner as in Example 2, except that two precursor fiber bundles were put into each groove of the rollers before and after the flameproofing furnace. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化炉前後のローラーの１つの溝あたりに２本の前駆体繊維束を投入した以外は、実施例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 5]
A carbon fiber bundle was obtained in the same manner as in Example 2, except that two precursor fiber bundles were put into each groove of the rollers before and after the flameproofing furnace. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例６］
第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８８℃、耐炎化時間５分の条件を用いて（条件２）、耐炎化時の延伸比を変更することで耐炎化時の張力１．０ｍＮ／ｄｔｅｘとし、前駆体繊維束に１ｍあたり７回転の撚りを入れ、耐炎化炉前後のローラーの１つの溝あたりに４本の前駆体繊維束を投入した以外は、実施例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 6]
The first flameproofing step was performed under the conditions of a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the second flameproofing step was carried out under the conditions of a flameproofing temperature of 288°C and a flameproofing time of 5 minutes (Condition 2). By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 1.0 mN/dtex, and the precursor fiber bundle was twisted at 7 turns per 1 m, and 4 twists per groove of the rollers before and after the flameproofing furnace. A carbon fiber bundle was obtained in the same manner as in Example 1, except that one precursor fiber bundle was added. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８８℃、耐炎化時間５分の条件を用いて（条件２）、耐炎化時の延伸比を変更することで耐炎化時の張力１．０ｍＮ／ｄｔｅｘとし、前駆体繊維束に１ｍあたり７回転の撚りを入れ、耐炎化炉前後のローラーの１つの溝あたりに４本の前駆体繊維束を投入した以外は、実施例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 6]
The first flameproofing step was performed under the conditions of a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the second flameproofing step was carried out under the conditions of a flameproofing temperature of 288°C and a flameproofing time of 5 minutes (Condition 2). By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 1.0 mN/dtex, and the precursor fiber bundle was twisted at 7 turns per 1 m, and 4 twists per groove of the rollers before and after the flameproofing furnace. A carbon fiber bundle was obtained in the same manner as in Example 1, except that one precursor fiber bundle was added. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例７］
第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８３℃、耐炎化時間５分の条件を用いた（条件３）以外は、実施例６と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 7]
The conditions for the first flameproofing step were a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the conditions of the second flameproofing step were a flameproofing temperature of 283°C and a flameproofing time of 5 minutes (Condition 3). obtained a carbon fiber bundle in the same manner as in Example 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８３℃、耐炎化時間５分の条件を用いた（条件３）以外は、実施例６と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 7]
The conditions for the first flameproofing step were a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the conditions of the second flameproofing step were a flameproofing temperature of 283°C and a flameproofing time of 5 minutes (Condition 3). obtained a carbon fiber bundle in the same manner as in Example 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例８］
第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８１℃、耐炎化時間７分の条件を用いた（条件４）以外は、実施例６と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 8]
The conditions for the first flameproofing step were a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the conditions of the second flameproofing step were a flameproofing temperature of 281°C and a flameproofing time of 7 minutes (Condition 4). obtained a carbon fiber bundle in the same manner as in Example 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８１℃、耐炎化時間７分の条件を用いた（条件４）以外は、実施例６と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 8]
The conditions for the first flameproofing step were a flameproofing temperature of 250°C and a flameproofing time of 11 minutes, and the conditions of the second flameproofing step were a flameproofing temperature of 281°C and a flameproofing time of 7 minutes (Condition 4). obtained a carbon fiber bundle in the same manner as in Example 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例９］
前駆体繊維束のフィラメント数を８，０００本とした以外は、実施例８と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 9]
A carbon fiber bundle was obtained in the same manner as in Example 8, except that the number of filaments in the precursor fiber bundle was 8,000. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
前駆体繊維束のフィラメント数を８，０００本とした以外は、実施例８と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 9]
A carbon fiber bundle was obtained in the same manner as in Example 8, except that the number of filaments in the precursor fiber bundle was 8,000. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［実施例１０］
前駆体繊維束の単繊維繊度を０．５ｄｔｅｘとし、第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８２℃、耐炎化時間６分の条件を用いた（条件５）以外は、実施例８と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 10]
The single fiber fineness of the precursor fiber bundle is 0.5 dtex, the first flameproofing step is performed at a flameproofing temperature of 250 ° C., and the flameproofing time is 11 minutes. A carbon fiber bundle was obtained in the same manner as in Example 8 except that the curing time was 6 minutes (Condition 5). Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
前駆体繊維束の単繊維繊度を０．５ｄｔｅｘとし、第１耐炎化工程を耐炎化温度２５０℃、耐炎化時間１１分の条件を用いて、第２耐炎化工程を耐炎化温度２８２℃、耐炎化時間６分の条件を用いた（条件５）以外は、実施例８と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Example 10]
The single fiber fineness of the precursor fiber bundle is 0.5 dtex, the first flameproofing step is performed at a flameproofing temperature of 250 ° C., and the flameproofing time is 11 minutes. A carbon fiber bundle was obtained in the same manner as in Example 8 except that the curing time was 6 minutes (Condition 5). Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例１］
耐炎化時の延伸比を変更することで耐炎化時の張力０．６ｍＮ／ｄｔｅｘとし、前駆体繊維束を撚る前に合糸して１２，０００本にしてから撚りを入れた以外は、実施例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 1]
By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 0.6 mN/dtex, and before twisting the precursor fiber bundle, 12,000 yarns were combined and then twisted. A carbon fiber bundle was obtained in the same manner as in Example 1. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力０．６ｍＮ／ｄｔｅｘとし、前駆体繊維束を撚る前に合糸して１２，０００本にしてから撚りを入れた以外は、実施例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 1]
By changing the draw ratio at the time of flameproofing, the tension at the time of flameproofing was set to 0.6 mN/dtex, and before twisting the precursor fiber bundle, 12,000 yarns were combined and then twisted. A carbon fiber bundle was obtained in the same manner as in Example 1. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例２］
耐炎化時の延伸比を変更することで耐炎化時の張力１．６ｍＮ／ｄｔｅｘとし、耐炎化温度条件を条件２にした以外は、比較例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 2]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 1 except that the tension during flameproofing was changed to 1.6 mN/dtex by changing the draw ratio during flameproofing, and the temperature conditions for flameproofing were changed to Condition 2. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力１．６ｍＮ／ｄｔｅｘとし、耐炎化温度条件を条件２にした以外は、比較例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 2]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 1 except that the tension during flameproofing was changed to 1.6 mN/dtex by changing the draw ratio during flameproofing, and the temperature conditions for flameproofing were changed to Condition 2. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例３］
耐炎化時の延伸比を変更することで耐炎化時の張力２．０ｍＮ／ｄｔｅｘとし、耐炎化温度条件を条件６にした以外は、比較例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 3]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 1, except that the tension during flameproofing was changed to 2.0 mN/dtex by changing the draw ratio during flameproofing, and the flameproofing temperature condition was changed to Condition 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力２．０ｍＮ／ｄｔｅｘとし、耐炎化温度条件を条件６にした以外は、比較例１と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 3]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 1, except that the tension during flameproofing was changed to 2.0 mN/dtex by changing the draw ratio during flameproofing, and the flameproofing temperature condition was changed to Condition 6. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例４］
特開２０１５－６７９１０号公報の実施例１に倣って第１耐炎化工程を耐炎化温度２４０℃、耐炎化時間３０分の条件を用いて、第２耐炎化工程を耐炎化温度２８０℃、耐炎化時間３０分の条件を用い（条件７）、耐炎化での合糸をしなかったこと、炭素化処理の最高温度１，３５０℃、延伸比０．９６０、炭素化工程の昇温速度は１．５０℃／秒、最高温度での滞留時間は１８０秒でとした以外は、実施例７と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 4]
Following Example 1 of JP-A-2015-67910, the first flameproofing step was performed at a flameproofing temperature of 240°C and the flameproofing time was 30 minutes, and the second flameproofing step was performed at a flameproofing temperature of 280°C and a flameproofing time of 30 minutes. Using the conditions of 30 minutes of carbonization time (Condition 7), no doubling in flameproofing, maximum temperature of carbonization treatment 1,350 ° C., draw ratio 0.960, temperature increase rate in carbonization process A carbon fiber bundle was obtained in the same manner as in Example 7, except that the heating rate was 1.50° C./sec and the residence time at the maximum temperature was 180 sec. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
特開２０１５－６７９１０号公報の実施例１に倣って第１耐炎化工程を耐炎化温度２４０℃、耐炎化時間３０分の条件を用いて、第２耐炎化工程を耐炎化温度２８０℃、耐炎化時間３０分の条件を用い（条件７）、耐炎化での合糸をしなかったこと、炭素化処理の最高温度１，３５０℃、延伸比０．９６０、炭素化工程の昇温速度は１．５０℃／秒、最高温度での滞留時間は１８０秒でとした以外は、実施例７と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 4]
Following Example 1 of JP-A-2015-67910, the first flameproofing step was performed at a flameproofing temperature of 240°C and the flameproofing time was 30 minutes, and the second flameproofing step was performed at a flameproofing temperature of 280°C and a flameproofing time of 30 minutes. Using the conditions of 30 minutes of carbonization time (Condition 7), no doubling in flameproofing, maximum temperature of carbonization treatment 1,350 ° C., draw ratio 0.960, temperature increase rate in carbonization process A carbon fiber bundle was obtained in the same manner as in Example 7, except that the heating rate was 1.50° C./sec and the residence time at the maximum temperature was 180 sec. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例５］
耐炎化時の延伸比を変更することで耐炎化時の張力２．５ｍＮ／ｄｔｅｘとした以外は、比較例４と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 5]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 2.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力２．５ｍＮ／ｄｔｅｘとした以外は、比較例４と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 5]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 2.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例６］
耐炎化時の延伸比を変更することで耐炎化時の張力１．５ｍＮ／ｄｔｅｘとした以外は、比較例４と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 6]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 1.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力１．５ｍＮ／ｄｔｅｘとした以外は、比較例４と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 6]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 1.5 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例７］
耐炎化時の延伸比を変更することで耐炎化時の張力０．６ｍＮ／ｄｔｅｘとした以外は、比較例４と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 7]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 0.6 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
耐炎化時の延伸比を変更することで耐炎化時の張力０．６ｍＮ／ｄｔｅｘとした以外は、比較例４と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 7]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 4, except that the tension during flameproofing was changed to 0.6 mN/dtex by changing the draw ratio during flameproofing. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
［比較例８］
炭素化工程の昇温速度を０．９０℃／秒とした以外は比較例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 8]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 2, except that the rate of temperature increase in the carbonization step was set to 0.90°C/sec. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
炭素化工程の昇温速度を０．９０℃／秒とした以外は比較例２と同様にして炭素繊維束を得た。得られた炭素繊維束の評価結果を表１および２に記載する。 [Comparative Example 8]
A carbon fiber bundle was obtained in the same manner as in Comparative Example 2, except that the rate of temperature increase in the carbonization step was set to 0.90°C/sec. Tables 1 and 2 show the evaluation results of the obtained carbon fiber bundles.
Ａ フェレ径
Ｂ フェレ径に垂直に交わる線分長さ
Ｃ 輪郭内の面積 A Feret diameter B Length of line perpendicular to Feret diameter C Area within contour
Ｂ フェレ径に垂直に交わる線分長さ
Ｃ 輪郭内の面積 A Feret diameter B Length of line perpendicular to Feret diameter C Area within contour
本発明の炭素繊維束は、炭素繊維特有の優れた力学的特性と、炭素繊維束の断面の扁平性を高いバランスで兼ね備えた織物補強材に適した炭素繊維である。本発明の炭素繊維束を用いることにより、高性能な織物補強材を高い生産性で得ることができる。
The carbon fiber bundle of the present invention is a carbon fiber that is suitable for a textile reinforcing material that has both excellent mechanical properties peculiar to carbon fiber and flatness of the cross section of the carbon fiber bundle in a high balance. By using the carbon fiber bundle of the present invention, a high-performance fabric reinforcing material can be obtained with high productivity.
Claims (8)
- 複数本の単繊維を有する炭素繊維束であって、ストランド弾性率が２６０～３５０ＧＰａ、ストランド強度が６．０～８．５ＧＰａ、伸度が１．８％以上、フィラメント数が１，０００～９，０００本、総繊度が０．１５～０．３５ｇ／ｍであり、かつ単繊維横断面の長径短径比の平均値が１．０１～１．０８、変動係数が１～４％、歪度が０．３～１．２である、炭素繊維束。 A carbon fiber bundle having a plurality of single fibers, having a strand elastic modulus of 260 to 350 GPa, a strand strength of 6.0 to 8.5 GPa, an elongation of 1.8% or more, and a filament number of 1,000 to 9. ,000, the total fineness is 0.15 to 0.35 g / m, the average value of the ratio of the major axis to the minor axis of the single fiber cross section is 1.01 to 1.08, the coefficient of variation is 1 to 4%, the strain A carbon fiber bundle having a degree of 0.3 to 1.2.
- 炭素繊維束断面の面積比率が０.５０～０．７０である、請求項１に記載の炭素繊維束。 The carbon fiber bundle according to claim 1, wherein the area ratio of the cross section of the carbon fiber bundle is 0.50 to 0.70.
- 伸度が２．０％以上である、請求項１または２に記載の炭素繊維束。 The carbon fiber bundle according to claim 1 or 2, which has an elongation of 2.0% or more.
- 伸度が２．２％以上である、請求項１～３のいずれかに記載の炭素繊維束。 The carbon fiber bundle according to any one of claims 1 to 3, which has an elongation of 2.2% or more.
- 長径短径比が１．０４～１．１０の単繊維本数割合が１０～４０％である、請求項１～４のいずれかに記載の炭素繊維束。 The carbon fiber bundle according to any one of claims 1 to 4, wherein the ratio of the number of single fibers having a major to minor axis ratio of 1.04 to 1.10 is 10 to 40%.
- 長径短径比が１．００～１．０３の単繊維本数割合が３０～９０％である、請求項１～５のいずれかに記載の炭素繊維束。 The carbon fiber bundle according to any one of claims 1 to 5, wherein the ratio of the number of single fibers having a ratio of major axis to minor axis of 1.00 to 1.03 is 30 to 90%.
- ポリアクリロニトリル系炭素繊維前駆体繊維束を、赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，４５３ｃｍ－１のピーク強度の比が０．９８～１．１０の範囲となるまで８～２５分間耐炎化する第１耐炎化工程、
赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，４５３ｃｍ－１のピーク強度の比が０．７０～０．７５の範囲、かつ、赤外スペクトルにおける１，３７０ｃｍ－１のピーク強度に対する１，２５４ｃｍ－１のピーク強度の比が０．５０～０．６５の範囲となるまで５～２０分間耐炎化する工程において、耐炎化処理中の繊維束の撚り角を０．２°以上とし、耐炎化処理中の繊維束の張力を０．７～１．５ｍＮ／ｄｔｅｘとし、複数の繊維束をローラーの１つの溝に投入する第２耐炎化工程、
該第１および第２耐炎化工程で得られた繊維束を最高温度５００～１，２００℃の不活性雰囲気中で延伸倍率を１．００～１．２０として予備炭素化する予備炭素化工程、
該予備炭素化工程で得られた繊維束を最高温度１，０００～１，５００℃の不活性雰囲気中で炭素化する炭素化工程、
該炭素化工程で得られた繊維束を電解表面処理して炭素繊維束を得る、炭素繊維束の製造方法。 The polyacrylonitrile-based carbon fiber precursor fiber bundle was heated until the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum was in the range of 0.98 to 1.10. A first flameproofing step for minute flameproofing,
The ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum is in the range of 0.70 to 0.75, and the peak intensity at 1,370 cm -1 in the infrared spectrum is 1 , 254 cm −1 in the step of flameproofing for 5 to 20 minutes until the ratio of peak intensities at 254cm −1 is in the range of 0.50 to 0.65, the twist angle of the fiber bundle during the flameproofing treatment is set to 0.2° or more, A second flameproofing step of setting the tension of the fiber bundle during the flameproofing treatment to 0.7 to 1.5 mN/dtex and introducing a plurality of fiber bundles into one groove of the roller;
a preliminary carbonization step of pre-carbonizing the fiber bundles obtained in the first and second flameproofing steps in an inert atmosphere at a maximum temperature of 500 to 1,200° C. at a draw ratio of 1.00 to 1.20;
a carbonization step of carbonizing the fiber bundle obtained in the preliminary carbonization step in an inert atmosphere at a maximum temperature of 1,000 to 1,500° C.;
A method for producing a carbon fiber bundle, comprising subjecting the fiber bundle obtained in the carbonization step to an electrolytic surface treatment to obtain a carbon fiber bundle. - 前記炭素化工程において、最高温度の処理時間が２０～６０秒、昇温速度が０．４０～１．１０℃／秒で炭素化する、請求項７に記載の炭素繊維束の製造方法。 The method for producing a carbon fiber bundle according to claim 7, wherein in the carbonization step, carbonization is performed at a maximum temperature treatment time of 20 to 60 seconds and a temperature increase rate of 0.40 to 1.10°C/second.
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