JP5540676B2 - Carbon fiber precursor fiber, method for producing the same, and method for producing carbon fiber - Google Patents

Description

  The present invention relates to a method for producing a carbon fiber precursor fiber and a method for producing a carbon fiber for efficiently obtaining a large amount of high-performance and high-quality carbon fibers.

  Since carbon fiber has higher specific strength and specific modulus than other fibers, it can be used as a reinforcing fiber for composite materials in addition to conventional sports applications, aerospace applications, automobiles, civil engineering / architecture, pressure vessels and Widely used in general industrial applications such as windmill blades, there is a strong demand for further improvements in productivity and higher performance.

  Among the carbon fibers, the most widely used polyacrylonitrile (hereinafter sometimes abbreviated as PAN) carbon fiber is a wet spinning, dry spinning or spinning solution composed of a PAN polymer as its precursor. After carbon fiber precursor fiber (hereinafter may be abbreviated as precursor fiber) is obtained by dry and wet spinning, it is heated in an oxidizing atmosphere at a temperature of 200 to 400 ° C. to convert it into flame resistant fiber. However, it is produced industrially by heating and carbonizing in an inert atmosphere at a temperature of at least 1000 ° C.

  The improvement in the productivity of PAN-based carbon fibers has been performed from the viewpoints of spinning, flame resistance or carbonization of carbon fiber precursor fibers. Above all, with respect to the improvement of the productivity of the carbon fiber precursor fiber, the prior art has the following problems. That is, in spinning to obtain a carbon fiber precursor fiber, the number of spinneret holes and the critical speed (hereinafter also referred to as “spinnability”) for pulling the coagulated yarn associated with the characteristics of the PAN-based polymer solution. The productivity is limited by the limit draw ratio accompanying the solidified structure. That is, in obtaining a multifilament carbon fiber precursor fiber, the productivity is limited by how much the final spinning speed determined by the take-up speed and the draw ratio is increased. Increasing the spinning speed to improve productivity results in a decrease in stretchability, and the production process tends to become unstable.If the spinning speed is lowered, the production process stabilizes, but the productivity decreases. There was a problem that it was difficult to achieve both stabilization of the production process.

  There is a spinning method as a factor that greatly affects the spinnability. In the dry-wet spinning method, the spinning solution is once discharged into the air (air gap) and then introduced into the coagulation bath, so that the substantial spinning draft rate is absorbed by the raw liquid flow in the air gap and spinnable. Therefore, it is an excellent method for improving productivity. However, as the speed increased, it was impossible to withstand the coagulation tension generated by the liquid resistance caused by the yarn running in the coagulation bath at a high speed, and there was a limit to improving the spinning speed.

  Furthermore, not only the productivity improvement of a precursor fiber but the manufacturing energy reduction of a precursor fiber is required. Under the coagulation bath conditions with less coagulation accelerating component, the amount of coagulation accelerating component used in the whole spinning process is reduced, and energy for separating and recovering the coagulation accelerating component from the mixture of the solvent and the coagulation accelerating component can be reduced. However, if the concentration of the coagulation bath is high, the viscosity of the coagulation bath liquid increases. The higher the viscosity, the faster the liquid flow to the center of the base and just below the base when the yarn travels in the coagulation bath, resulting in unstable discharge. It was.

  Several proposals have been made so far for high-speed yarn production in PAN-based fibers. In order to reduce the production cost of carbon fibers, the present inventors have proposed a technique that can increase the spinning speed and the spinning draft rate by using a PAN-based polymer having a specific molecular weight distribution. (See Patent Document 1). However, when the yarn is taken up at high speed in the high viscosity coagulation bath liquid, the flow of the coagulation bath liquid becomes large, and fluff may be generated during the yarn making process, and the effect of improving productivity is limited. there were. In addition, a technique has been proposed in which a spinning draft ratio is set to 5 to 50 by using a high-viscosity spinning solution and providing a specific air gap (see Patent Document 2). In order to maintain wet heat characteristics without deteriorating the texture and mechanical performance, the hole diameter of the spinneret is 0.3 mm, the number of holes is 36, and the conditions of the low viscosity coagulation bath liquid are Therefore, in order to improve productivity, when spinning was performed under the conditions of the number of pores and the high viscosity coagulation bath, stable spinning could not be achieved. In addition, a technique has been proposed in which a uniform performance acrylic fiber is obtained by rectifying the coagulation bath liquid directly under the base by using a base having a non-perforated portion and perforated in an annular array (patent) Experiments were conducted with a low-viscosity coagulation bath solution, and even when this technique was used, stable spinning could not be achieved when high-speed spinning was performed with a high-viscosity coagulation bath solution.

  That is, productivity improvement is insufficient with any of the conventionally known methods, and a method capable of spinning at high speed even under the conditions of increasing the number of pores and high concentration coagulation bath is required.

  On the other hand, in the flameproofing process, if the flameproofing temperature is increased so as to accelerate the progress of flameproofing, the higher the temperature, the lower the fiber strength, and the furnace atmosphere by heat storage in the fiber bundle due to exothermic reaction. The temperature in the fiber bundle was higher than the temperature, causing yarn breakage. Therefore, in the flameproofing process, it is difficult to increase the flameproofing temperature, and it is difficult to increase the flameproofing speed. In the technique proposed by the present inventors, the precursor fiber surface is too smooth and the fiber bundle is highly converging, so heat accumulation in the fiber bundle of the flameproofing reaction is likely to occur (see Patent Documents 1, 4, and 5). ).

JP 2008-248219 A JP-A-11-107034 Japanese Patent Laid-Open No. 62-125209 JP 2009-270248 A International Publication No. 2009/057332

  The present invention solves the above-mentioned problems of the prior art, that is, even if an attempt is made to spin in a high viscosity coagulation bath liquid at a high speed using a spinneret having a porous number, the carbon fiber precursor fiber is stably produced. An object of the present invention is to propose a method for producing carbon fiber stably with less generation of fluff even in a short period of flame resistance.

In order to achieve the above object, the method for producing a precursor fiber for carbon fiber of the present invention has the following configuration.
(1) The Z-average molecular weight Mz (F) of the polyacrylonitrile polymer constituting the fiber is 600,000 to 2,000,000, and the polydispersity Mz (F) / Mw (F) (Mw (F) The weight average molecular weight of the polyacrylonitrile-based polymer is 2 to 5, the root mean square roughness Rms measured in the range of 3 μm with an atomic force microscope is 17 to 40 nm, and the single fiber fineness is 0. A carbon fiber precursor fiber having a coefficient of variation of a single fiber cross-sectional diameter of 0 to 5%, which is 3 to 1.5 dtex and measured according to the method of (I) below .
(I) Cutting the precursor fiber bundle by adjusting the height perpendicular to the fiber axis, and observing the cross-sectional shape of the single fiber using an optical microscope, the single fiber having the thinnest measurement magnification is about 1 mm. The magnification is about 200 to 400 times, and the obtained image is subjected to image analysis for six sheets to determine the cross-sectional area of the single fiber of the precursor fiber, and the cross-sectional area (fiber diameter) of the single fiber from the cross-sectional area, The variation coefficient of the diameter (variation coefficient of the single fiber cross-sectional diameter) is obtained.
(2) R value determined by RAMAN spectroscopy and specified in the specification is 2.7 to 3.0, single fiber strength is 6 to 9 cN / dtex, and raw yarn crystal orientation is 91 to 94%. The carbon fiber precursor fiber according to (1) above.
(3) The carbon fiber precursor fiber according to (1) or (2), wherein the roundness is 0.85 to 1.
(4) Using a spinneret having a minor axis of 75 to 200 mm and a number of holes of 3000 to 30000, the coagulation bath solution is coagulated in a coagulation temperature at a coagulation temperature of 7 to 15 mPa · s under spinning conditions. A method for producing a carbon fiber precursor fiber that is dry and wet-spun so that the yarn travels at a speed of 35 to 200 m / min, wherein the Z average molecular weight (Mz (P)) is 800,000 to 6 million, and the polydispersity (Mz (P) / Mw (P)) (Mw (P) represents a weight average molecular weight) A spinning solution containing a polyacrylonitrile polymer having a weight average molecular weight of 2.7 to 10 is used. 50, and the angle of the spinning solution discharged from the outermost hole of the spinneret to the spinneret surface vertical direction is 5 to 15 °.
(5) The method for producing a carbon fiber precursor fiber according to (4), wherein the spinning solution is discharged into a coagulation bath under coagulation bath conditions having a coagulation value of 23 to 40 g.
(6) The carbon fiber according to (4) or (5), wherein the total draw ratio of the coagulated yarn from the take-up roller is 10 to 20 times, and the winding speed of the precursor fiber bundle is 600 to 2000 m / min. A method for producing precursor fibers.
(7) The method for producing a carbon fiber precursor fiber according to any one of (4) to (6), wherein a take-up speed of the coagulated yarn is 50 to 200 m / min.
(8) The distance between the coagulation bath liquid level before sinking and the spinneret is set to 5 to 10 mm, and the depth at which the coagulation bath liquid level sinks by spinning is controlled to 5 to 20 mm. The manufacturing method of the carbon fiber precursor fiber in any one of 7).
(9) The carbon fiber precursor fiber according to any one of (1) to (3) or the carbon fiber precursor fiber obtained by the production method according to any one of (4) to (8). A flameproofing step for flameproofing in air at a temperature of 200 to 300 ° C, a precarbonization step for precarbonizing the fiber obtained in the flameproofing step in an inert atmosphere at a temperature of 300 to 800 ° C, A method for producing carbon fibers, wherein carbon fibers are sequentially obtained through carbonization steps in which the fibers obtained in the preliminary carbonization step are carbonized in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.

  According to the present invention, a PAN-based polymer solution having a large specific molecular weight distribution is used, and by adjusting the discharge and spinning conditions of the precursor fiber, a spinneret having a high number of pores is used to form a high viscosity coagulation bath liquid. High-quality carbon fiber precursor fibers can be stably discharged even when the coagulation bath has a large fluctuation in the liquid level of the coagulation bath. Can be manufactured.

  In addition, by using a high-quality carbon fiber precursor fiber, it is possible to stably produce a high-strength carbon fiber with less yarn breakage and less fluff even in the firing step.

  In addition, the use of precursor fibers with moderate bundling, small single fiber cross-sectional diameter, and high crystallinity results in very little fluff even when flame resistant at high temperatures, and a large amount of carbon fiber at high speed. Can be manufactured.

  The present invention adopts a spinning solution containing a polyacrylonitrile-based polymer having a specific molecular weight distribution, and a severe condition in which the accompanying flow is large and the coagulation bath liquid level fluctuation is severe by adopting discharge conditions specialized for the spinning solution. A process for producing a carbon fiber precursor fiber that can be stably produced without lowering the processability even under the above can be obtained.

  In the present invention, the weight average molecular weight is abbreviated as Mw, the Z average molecular weight is abbreviated as Mz, the number average molecular weight is abbreviated as Mn, and when referring to all the PAN-based polymers constituting the fiber, the subscript (F) When referring to a PAN-based polymer, the subscript (P) is added, and in the description of the measurement method common to both, the subscript ((F) or (P)) is omitted. And In the present invention, various molecular weights are measured by a gel permeation chromatograph method (hereinafter sometimes abbreviated as GPC method), and are expressed in terms of polystyrene.

  In the spinning solution used in the present invention, a PAN-based polymer having a ratio of Z average molecular weight Mz (P) to weight average molecular weight Mw (P) of Mz (P) / Mw (P) of 2.7 or more is a solvent. It is dissolved in. Since the PAN-based polymer having such a molecular weight distribution contains a polymer component having a large molecular weight, the effects of the present invention are remarkably exhibited.

  First, the PAN polymer that can be suitably used in the present invention will be described. In the present invention, the Z average molecular weight (hereinafter abbreviated as Mz (P)) measured by the gel permeation chromatograph (hereinafter abbreviated as GPC) method (the details of the measurement method will be described later) is 80. The polydispersity (Mz (P) / Mw (P)) (Mw (P) represents a weight average molecular weight, hereinafter abbreviated as Mw (P)) is 2.7 to 6,000,000. 10. Mz (P) is preferably 2 million to 6 million, more preferably 2.5 million to 4 million, and further preferably 2.5 million to 3.2 million. The polydispersity (Mz (P) / Mw (P)) is preferably 5 to 8, and more preferably 5.5 to 7.

  The index regarding the average molecular weight and molecular weight distribution measured by the GPC method will be described below.

The average molecular weight measured by the GPC method includes number average molecular weight (hereinafter abbreviated as Mn), weight average molecular weight (Mw (P)), z average molecular weight (Mz (P)), Z + 1 average molecular weight (M _{Z + 1} ( P)). Mn is sensitively influenced by the low molecular weight substances contained in the polymer compound. In contrast, Mw (P) is more sensitive to the contribution of high molecular weight than Mn. Mz (P) is more sensitive to the contribution of high molecular weight than Mw (P), and Z + 1 average molecular weight (hereinafter abbreviated as M _{Z + 1} (P)) is more sensitive to the contribution of high molecular weight than Mz (P). To receive.

The molecular weight distribution obtained using the average molecular weight measured by the GPC method includes molecular weight distribution (Mw (P) / Mn), polydispersity (Mz (P) / Mw (P) and M _{Z + 1} (P ) / Mw (P)), and the use of these can indicate the distribution of molecular weight. When the molecular weight distribution (Mw (P) / Mn) is 1, it is monodisperse, and as the molecular weight distribution (Mw (P) / Mn) becomes larger than 1, the molecular weight distribution becomes broader around the low molecular weight side. In contrast, as the polydispersity (Mz (P) / Mw (P)) becomes larger than 1, the molecular weight distribution becomes broader around the high molecular weight side. Further, as the polydispersity (M _{Z + 1} (P) / Mw (P)) becomes larger than 1, the molecular weight distribution becomes broader around the high molecular weight side. In particular, the polydispersity (M _{Z + 1} (P) / Mw (P)) is remarkably increased when two types of polymers having significantly different Mw (P) are mixed. Here, the molecular weight measured by GPC method shows the molecular weight of polystyrene conversion.

  By using the PAN-based polymer of the present invention, it is possible to achieve both improvement in productivity and stabilization when a carbon fiber precursor fiber is obtained by wet spinning, dry spinning or dry-wet spinning of a spinning solution containing such a polymer. A mechanism that can produce a high-quality carbon fiber precursor fiber with less fuzzing is not necessarily clear, but is considered as follows. In dry spinning or dry-wet spinning, when the PAN polymer is stretched and deformed immediately after the mouthpiece hole is solidified, the ultra high molecular weight product and the high molecular weight product of the PAN polymer are entangled in the spinning solution, When the molecular chain between the entangled molecules is tensioned around an ultrahigh molecular weight substance, a rapid increase in elongational viscosity, that is, strain hardening occurs. As the PAN-based polymer solution is thinned immediately after the die hole is solidified, the elongational viscosity of the thinned portion is increased, the spinning speed is increased to stabilize the flow, and the spinning draft rate is increased. Can be increased. In the spinning solution state, even if it does not coagulate, it can be wound up and wound at several tens of meters / minute, and a particularly remarkable effect is obtained that a spinnability that is unthinkable in solution spinning can be obtained. Similarly, in the fibers after spinning or dry-wet spinning and coagulating, the elongational viscosity is increased and the stretchability is improved, so that the generation of fluff is suppressed.

  Therefore, it is preferable that the polydispersity (Mz (P) / Mw (P)) is large. If Mz (P) is in the range of 800,000 to 6 million, the polydispersity (Mz (P) / Mw (P)) ) Of 2.7 or more, sufficient strain hardening occurs, and the degree of improvement in the discharge stability of the spinning solution containing the PAN polymer is sufficient. Further, when the polydispersity (Mz (P) / Mw (P)) is too large, strain hardening is too strong, and the discharge stability improvement effect of the spinning solution containing the PAN-based polymer may be reduced. When the Mz (P) is in the range of 800,000 to 6 million and the polydispersity (Mz (P) / Mw (P)) is 10 or less, the ejection stability of the spinning solution containing the PAN polymer is improved. The degree is sufficient. Further, when the polydispersity (Mz (P) / Mw (P)) is in the range of 2.7 to 10, if the Mz (P) is less than 800,000, the strength of the precursor fiber may be insufficient, and Mz (P If P) is larger than 6 million, it may be difficult to discharge.

  Further, the smaller Mw (P) / Mn (P) is, the smaller the content of low molecular components that are likely to be structural defects of the carbon fiber. Therefore, the smaller the Mw (P) / Mn (P), the more preferable Mw (P) / Mw (P). ) / Mn (P) is preferably small. That is, even if the molecular weight side is broad and the low molecular weight side is broad, the drop in ejection stability is small, but the low molecular weight side is preferably as sharp as possible, and Mz (P) / Mw (P) is Mw. It is preferably 1.5 times or more, and more preferably 1.8 times or more with respect to (P) / Mn (P). According to the study by the present inventors, in radical polymerization such as aqueous suspension or solution method, which is usually performed in the polymerization of acrylonitrile (hereinafter abbreviated as AN), the molecular weight distribution has a lower molecular weight side. Therefore, Mw (P) / Mn becomes larger than Mz (P) / Mw (P). Therefore, when performing polymerization under special conditions such as the type and ratio of the polymerization initiator and sequential addition, or when using general radical polymerization, there is a method of mixing two or more PAN-based polymers. The method of mixing is simple. The smaller the number of types to be mixed, the easier and the two types are often sufficient from the viewpoint of ejection stability.

  The Mw (P) of the polymer to be mixed is a PAN-based polymer having a large Mw (P) as the A component, and a PAN-based polymer having a small Mw (P) as the B component, and the Mw (P) of the A component is It is preferably 1 million to 15 million, more preferably 1 million to 5 million, and Mw (P) of the B component is preferably 50,000 to 900,000. This is a preferred embodiment because the larger the difference between the Mw (P) of the A component and the B component, the greater the Mz (P) / Mw (P) of the mixed polymer. ) Is greater than 15 million, the productivity of the A component may decrease, and when the Mw (P) of the B component is less than 150,000, the strength of the precursor fiber may be insufficient, and Mz (P) It is realistic that / Mw (P) is 10 or less.

  Specifically, the ratio of the weight average molecular weight of the A component and the B component is preferably 4 to 45, and more preferably 20 to 45.

  The weight ratio of the A component and the B component is preferably 0.003 to 0.3, more preferably 0.005 to 0.2, and 0.01 to 0.1. Further preferred. When the weight ratio of the A component to the B component is less than 0.003, strain hardening may be insufficient, and when it is greater than 0.3, the discharge viscosity of the polymer solution may increase so that the discharge may become difficult.

  When mixing the polymer of component A and component B, a method of mixing both polymers and then diluting with a solvent, a method of mixing each of the polymers diluted in a solvent, and a high molecular weight material that is difficult to dissolve A method in which the B component is mixed and dissolved after diluting the A component in the solvent, and a solution in which the monomer constituting the B component is mixed with a solution obtained by diluting the high molecular weight A component in the solvent. It is possible to employ a mixing method. For mixing, a method of stirring in a mixing tank, a method of quantifying with a gear pump or the like and mixing with a static mixer, a method of using a twin screw extruder, or the like can be preferably employed. From the viewpoint of uniformly dissolving the high molecular weight product, a method of first dissolving the component A which is a high molecular weight product is preferable. In particular, in the case of producing a carbon fiber precursor, the dissolved state of the high molecular weight component A is extremely important, and even if a slight amount of undissolved material exists, it is recognized as a foreign substance. Voids may be formed inside the carbon fiber.

  Specifically, the polymer concentration of the component A with respect to the solvent, that is, when assuming a solution consisting only of the component A and the solvent, the polymer concentration of the component A in the solution is preferably 0.1 to 5% by weight. Then, the B component is mixed, or the monomers constituting the B component are mixed and polymerized. The polymer concentration of the component A is more preferably 0.3 to 3% by weight, and further preferably 0.5 to 2% by weight. More specifically, the polymer concentration of the component A is preferably a quasi-dilute solution in which the polymers are slightly overlapped as an aggregate state of the polymer, and the component B is mixed or the component B is mixed. When the constituent monomers are mixed and polymerized, the mixed state is likely to be uniform, so that a dilute solution that is in an isolated chain state is a more preferable embodiment. The concentration of the dilute solution is considered to be determined by the intramolecular exclusion volume determined by the polymer molecular weight and the solubility of the polymer in the solvent. Less likely to agglomerate and become foreign matter. When the polymer concentration exceeds 5% by weight, an undissolved product of component A may be present. When the polymer concentration is less than 0.1% by weight, it is effective because it is a dilute solution depending on the molecular weight. Is often saturated.

  As described above, the polymer concentration with respect to the solvent of the component A is preferably 0.1 to 5% by weight, and then the method of mixing and dissolving the component B may be used. It is preferable to employ a method of mixing a product obtained by diluting a product with a solvent and a monomer constituting the component B and mixing the monomers by solution polymerization.

  The method for adjusting the polymer concentration of the component A to the solvent to 0.1 to 5% by weight may be a method using dilution or a method using polymerization. When diluting, it is important to stir until it can be diluted uniformly, and the dilution temperature is preferably 50 to 120 ° C. The dilution time varies depending on the dilution temperature and the concentration before dilution, and may be appropriately set. When the dilution temperature is less than 50 ° C, it may take time to dilute, and when it exceeds 120 ° C, the component A may be altered. In addition, from the viewpoint of reducing the process of diluting the overlapping of the polymers and mixing them uniformly, from the production of the A component to the start of mixing of the B component, or the polymerization of the monomer constituting the B component. Meanwhile, the polymer concentration with respect to the solvent of the component A is preferably controlled in the range of 0.1 to 5% by weight. Specifically, when the component A is produced by solution polymerization, the polymerization is stopped when the polymer concentration is 5% by weight or less, and the component B is mixed therewith, or the monomer constituting the component B is mixed. This is a method of polymerizing the monomer. Usually, when the ratio of the charged monomer to the solvent is small, it is often difficult to produce a high molecular weight product by solution polymerization, so the ratio of the charged monomer is increased. At the stage of 5% by weight or less, the polymerization rate is low and a large amount of unreacted monomer remains. The B component may be mixed after removing the unreacted monomer by volatilization, but from the viewpoint of omitting the process, it is preferable to solution polymerize the B component using the unreacted monomer.

  The component A preferably used in the present invention desirably has compatibility with PAN, and is preferably a PAN-based polymer from the viewpoint of compatibility. As the composition, AN is preferably 93 to 100 mol%, and copolymerization may be carried out if the monomer copolymerizable with AN is 7 mol% or less, but the chain transfer constant of the copolymerization component is smaller than AN. When it is difficult to obtain the required Mw (P), it is preferable to reduce the amount of the copolymer component as much as possible.

  Examples of monomers copolymerizable with AN include acrylic acid, methacrylic acid, itaconic acid and their alkali metal salts, ammonium salts and lower alkyl esters, acrylamide and its derivatives, allyl sulfonic acid, methallyl sulfonic acid and Those salts or alkyl esters can be used. Moreover, it is preferable that A component is substantially linear PAN, and it is preferable not to use the monomer etc. which have a polyfunctional vinyl group. The branching and cross-linking structure is simply determined by whether the relationship between the molecular weight and the radius of rotation obtained by the gel permeation chromatography method-multi-angle light scattering photometry (GPC-MALLS) method is the same as that of linear PAN. I can judge. Those having a crosslinked structure by a covalent bond, a hydrogen bond, or an ionic bond tend to have a smaller radius of rotation than the molecular weight, and are not included in the linear PAN in the present invention.

  The polymerization method for producing the PAN-based polymer as component A can be selected from a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, etc., and the purpose of uniformly polymerizing AN and copolymer components It is preferable to use a solution polymerization method. In the case of polymerizing using the solution polymerization method, as the solvent, for example, a solvent in which PAN is soluble, such as an aqueous zinc chloride solution, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, is preferably used. When it is difficult to obtain the required Mw (P), a solvent having a large chain transfer constant, that is, a solution polymerization method using a zinc chloride aqueous solution or a suspension polymerization method using water is also preferably used.

  As the composition of the PAN-based polymer, which is the B component suitably used in the present invention, AN is preferably 93 to 100 mol%, and a monomer copolymerizable with AN is copolymerized if it is 7 mol% or less. However, as the amount of the copolymerization component increases, molecular breakage due to thermal decomposition at the copolymerization portion becomes more prominent in the flameproofing step, and the tensile strength of the resulting carbon fiber decreases.

  Examples of the monomer copolymerizable with AN include, for example, acrylic acid, methacrylic acid, itaconic acid and alkali metal salts thereof, ammonium salts and lower alkyl esters, acrylamide and derivatives thereof, allyl, from the viewpoint of promoting flame resistance. Sulfonic acid, methallylsulfonic acid and their salts or alkyl esters can be used.

  The polymerization method for producing the B component PAN-based polymer can be selected from a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, and the like. It is preferable to use a solution polymerization method. In the case of polymerizing using the solution polymerization method, as the solvent, for example, a solvent in which PAN is soluble, such as an aqueous zinc chloride solution, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, is preferably used. Among these, dimethyl sulfoxide is preferably used from the viewpoint of PAN solubility. The raw materials used for these polymerizations are preferably used after passing through a filter medium having a filtration accuracy of 1 μm or less.

  The aforementioned PAN-based polymer is dissolved in a solvent in which the PAN-based polymer is soluble, such as dimethyl sulfoxide, dimethylformamide, and dimethylacetamide, to obtain a spinning solution. In the case of using solution polymerization, if the solvent used for polymerization and the spinning solvent are the same, a step of separating the obtained PAN-based polymer and re-dissolving in the spinning solvent becomes unnecessary.

  The polymer concentration in the spinning solution is preferably in the range of 5 to 30% by weight, more preferably 14 to 25% by weight, and most preferably 18 to 23% by weight. If the polymer concentration is less than 5% by weight, the amount of solvent used increases, and the amount of spinning solution discharged from the single die hole increases, which may make it difficult to increase the spinning draft in setting spinning conditions. On the other hand, when the polymer concentration exceeds 30% by weight, the entanglement increases, the molecular weight between the entanglements decreases, and the spinnability may decrease. The polymer concentration of the spinning solution can be adjusted according to the amount of solvent used.

  In the present invention, the polymer concentration is the weight percent of the PAN polymer contained in the PAN polymer solution. Specifically, after weighing the PAN-based polymer solution, the measured PAN-based polymer solution is removed to a solvent that does not dissolve the PAN-based polymer and is compatible with the solvent used for the PAN-based polymer solution. After solvent, the PAN polymer is weighed. The polymer concentration is calculated by dividing the weight of the PAN polymer after desolvation by the weight of the PAN polymer solution before desolvation.

  Further, the viscosity of the spinning solution at a temperature of 45 ° C. is preferably in the range of 15 to 200 Pa · s, more preferably in the range of 20 to 150 Pa · s, and more preferably in the range of 30 to 100 Pa · s. Most preferably. When the solution viscosity is less than 15 Pa · s, since the formability of the spun yarn is lowered, the speed at which the yarn taken out from the die is taken, that is, the spinnability tends to be lowered. Further, when the solution viscosity exceeds 200 Pa · s, the entanglement increases and the molecular weight tends to decrease. The viscosity of the spinning solution can be controlled by the weight average molecular weight, the polymer concentration, and the type of solvent.

  The viscosity of the PAN polymer solution at a temperature of 45 ° C. can be measured with a B-type viscometer. Specifically, the PAN-based polymer solution placed in a beaker is immersed in a hot water bath adjusted to a temperature of 45 ° C. to adjust the temperature, and as a B-type viscometer, for example, B8L manufactured by Tokyo Keiki Co., Ltd. Using a viscometer, rotor No. 4 is used, and the viscosity of the PAN polymer solution is in the range of 0 to 100 Pa · s. p. m. The viscosity of the PAN-based polymer solution is in the range of 100 to 1000 Pa · s. p. m. Measure with

  Furthermore, it is preferable to use this polymer solution after filtration using a filter having a filtration accuracy of 0.5 to 10 μm.

  In the present invention, a carbon fiber precursor fiber is produced by spinning the spinning solution obtained as described above by a dry and wet spinning method.

  The present inventors have found the discharge conditions for running the coagulated yarn at a high speed when the shape and the number of holes of the spinneret necessary for improving the productivity and the coagulation bath conditions have been reached.

  In the present invention, the number of holes in the die is 3000 to 30000. When the number of holes is less than 3000, productivity is lowered, and in such a state, it is difficult to obtain the effect of the present invention. On the other hand, when the number of holes exceeds 30000, the die becomes too large, and it may be difficult to rectify the coagulation bath liquid of the present invention.

  The base hole may be arranged in any of a circular shape, a rectangular shape, and an annular shape. However, the rectangular shape has a major axis and a minor axis, and the smaller the minor axis, the smaller the discharge angle, which is preferably 75 to 200 mm, and preferably 75 to 200 mm. 175 mm. Here, the diameter of the base indicates the length of the part having the base hole, and the short diameter indicates the diameter of the circumscribed circle of the outermost hole in the case of a circular base, and indicates the width of the ring in the case of an annular shape. . It is proportional to the distance required to supply the coagulation bath liquid to the part farthest from the outer peripheral part of the die. When the short diameter of the die exceeds 200 mm, the coagulation bath liquid is fed to the center of the die even if the discharge conditions are adjusted. If the flow is too large and the discharge angle becomes large and the short axis of the die is less than 75 mm, the die shape needs to be too long, and the productivity is lowered.

  In the present invention, the die hole is preferably circular so that the hole shape does not increase the discharge speed relative to the cross-sectional area. When the hole shape is circular, the minimum hole diameter of the die hole is 0. It is preferably 18 mm to 0.35 mm, and more preferably 0.25 to 0.3 mm. When the hole diameter is less than 0.18 mm, the discharge linear velocity is high, and it is often difficult to increase the spinning draft. When the hole diameter exceeds 0.35 mm, it is necessary to increase the spinning draft too much, and the discharge is not effective. May be stable. Since the discharge linear velocity changes depending on the diameter of the die hole, it is effective for controlling the spinning draft. Moreover, although an appropriate hole diameter changes also with the single hole discharge amount of a polymer solution, it is preferable to make it into the said range in general.

  In the present invention, the hole diameter of the nozzle hole can be measured by observing the spinneret surface with a microscope.

  Moreover, it is preferable that the maximum value of L / D which is a ratio of the average hole diameter (D) and average hole length (L) of a spinneret is 1-3. When L / D is less than 1, ejection may not be stable, but as L / D is larger, the shear application time becomes longer and molecular weight is more likely to decrease, so L / D is preferably 3 or less. The influence of L / D is small on the hole diameter, and means such as increasing the hole length at the outer peripheral portion can be used. Since the average value determines the overall characteristics rather than the minimum value, the average value is used.

  In order to suppress the swelling of the spinning solution immediately after discharge, that is, the so-called ballast effect, it is also preferable to perform reverse taper processing to gradually widen the hole after passing through the minimum hole diameter. When the spinning solution is introduced into the spinneret hole, it is possible to taper processing, to perform it stepwise, or to eliminate the corners in order to reduce the elongation strain in the elongation flow, and the elongation viscosity distortion used in the present invention. Effective in combination with a hardened spinning solution. That is, it is effective for strain hardening in the extension region immediately after discharge from the die and increasing the extension viscosity before discharge to increase the coagulation tension.

  The angle of the spinning solution discharged from the outermost hole of the spinneret with the spinneret surface vertical direction (hereinafter also referred to as a discharge angle) is 5 to 15 °. The yarn discharged from the spinneret is folded back by a spinning guide, properly converged, and taken up by a driving roller. Since the yarn travels with the coagulation bath liquid in the peripheral portion, the coagulation bath liquid tends to be insufficient immediately below the base. Therefore, the coagulation bath liquid flows from the periphery of the base directly below the base, particularly toward the center. Due to the flow of the coagulation bath liquid, the yarns may be rapidly focused and the discharge angle may be increased. When the discharge angle increases, the pitch between the single fibers at the liquid level immediately below the mouthpiece is narrower than the hole pitch, and adhesion between the single fibers is likely to occur. If the discharge angle exceeds 15 °, adhesion between the single fibers occurs, process passability decreases, and if the discharge angle is less than 5 °, the yarn cannot be converged and the running of the yarn becomes unstable.

  What is important in the present invention is that the spinning draft of the spinning solution is in the range of 5-50. Here, the spinning draft is obtained by dividing the surface speed of the roller (the winding speed of the coagulated yarn) having a driving source with which the spun yarn (filament) first comes out of contact with the base by the discharge linear speed from the base. Value. The spinning draft is proportional to the elongation strain, and it is possible to suppress an increase in the discharge angle of the spinning solution from the nozzle hole due to the flow of the coagulating bath liquid by applying a strong strain and increasing the elongation viscosity. The conventional polymer solution has the property that the elongational viscosity decreases or is almost constant when strain is applied, but the polymer solution of the present invention exhibits the property that the elongational viscosity improves when strained. Therefore, a preferable result is given in reducing the discharge angle. If the spinning draft is less than 5, the diameter of the die hole may have to be reduced in order to obtain the desired fineness of the precursor fiber, and a spinning draft of 50 or less is sufficient from the viewpoint of reducing the shear rate. Since the spinning draft can be easily changed by changing the discharge amount and changing the discharge linear velocity, change the discharge linear velocity and check the discharge angle to adjust it to the discharge angle of the present invention. That's fine. Since the discharge amount is related to the production amount, the set spinning draft may be obtained by finally fixing the discharge amount and changing the diameter of the spinneret so that the required production amount is obtained.

  The distance between the coagulation bath liquid surface before sinking and the spinneret (hereinafter sometimes referred to as air gap height (Ha)) is preferably 5 to 10 mm. When Ha is less than 5 mm, the deformation of the spinning solution may become too rapid and the spinning solution may break easily. When Ha exceeds 10 mm, the strain rate becomes too small and the spinning solution tends to break. There is.

  It is preferable to control the depth at which the coagulation bath liquid level just below the die sinks as the yarn travels to 5 to 20 mm. In general, sinking the coagulation bath liquid level often leads to instability of discharge and is rarely performed, but the discharge is stable in the spinning solution used in the present invention. By increasing the accompanying flow depending on the conditions and reducing the solidification tension, the sinking depth increases, but the spinning process can be stabilized. The difference in height between the peripheral part of the base and the liquid level just below the base stabilizes the flow of the coagulation bath liquid and stabilizes the discharge. If the submerged depth is less than 5 mm, the process stability is insufficient, and if it exceeds 20 mm, the spinning solution may be easily broken before reaching the liquid level. The sinking depth can be controlled by the viscosity of the coagulating bath liquid, the running speed of the yarn, and the hole pitch of the die.

  From the viewpoint of improving the productivity and obtaining a precursor fiber suitable for flame resistance in a short time, the take-up speed of the coagulated yarn is 35 to 200 m / min, preferably 50 to 200 m / min, more preferably 85 to 150 m / min. When the take-up speed of the coagulated yarn is less than 35 m / min, the surface unevenness of the precursor fiber becomes small, and when the take-up speed of the coagulated yarn exceeds 200 m / min, the variation coefficient of the single fiber cross-sectional diameter of the precursor fiber is increased. growing. When the discharge linear velocity is low, the target productivity can be achieved by increasing the spinning draft.

  The coagulation bath used in the present invention includes a PAN polymer solvent such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, zinc chloride aqueous solution, and sodium thiosulfate aqueous solution used as a solvent in the PAN polymer solution, and so-called coagulation. A mixture of facilitating ingredients is used. As the coagulation accelerating component, those which do not dissolve the PAN-based polymer and are compatible with the solvent used in the PAN-based polymer solution are preferable. Specific examples of the coagulation accelerating component include water, methanol, ethanol, and acetone. However, water does not need to be recovered, and in terms of safety, the amount of coagulation accelerating component necessary for coagulation is small. Most preferably, is used.

  In the present invention, the coagulation value of the coagulation bath liquid is preferably 23 to 40 g, more preferably 29 to 40 g, and more preferably 30 to 35 g. In the present invention, the coagulation value means that a coagulation bath solution is gradually added dropwise to a solution in which 1% by weight of a polymer used for spinning is dissolved in 50 cc of a solvent used for spinning to start precipitation, and the solution turns from transparent to cloudy. It is defined as the amount of coagulation bath solution (g) that changes. In the test, the temperature is adjusted to 25 ° C. If the coagulation bath liquid itself is added dropwise, it may be too diluted and white turbidity may be difficult, and it may be difficult to determine the starting point of the white turbidity. It can be set as the coagulation value in terms of the amount of coagulation bath liquid containing the amount of coagulation promoting component. If the two values are different, the latter is regarded as the coagulation value.

  The coagulation value varies depending on the molecular weight and copolymer composition of the polymer, the concentration of the polymer solution, the type of solvent, the type of coagulation-promoting component, and the solvent concentration, and must be measured according to the spinning conditions. It is preferable to control by the kind and solvent concentration of the solvent. As the solvent concentration increases, the coagulation promoting component decreases, so the coagulation value increases. Even if the coagulation value is less than 23 g or exceeds 40 g, the surface of the precursor fiber becomes too smooth.

  Here, the kind of solvent is considered. Although it is related to the copolymerization component and the coagulation accelerating component, when PAN not containing the copolymerization component is dissolved in various solvents and water is examined as the coagulation accelerating component, dimethylacetamide <dimethylformamide <dimethylsulfoxide < The amount of coagulation accelerating component is increased in the order of zinc chloride aqueous solution <sodium thiosulfate aqueous solution. The value varies depending on the copolymerization component, etc., but when using PAN of 100% Mw 320,000 and dissolved in various solvents to make water a coagulation promoting component, the coagulation values are 4 g of dimethylacetamide and 5 g of dimethylsulfoxide, respectively. 10 g of an aqueous zinc chloride solution and 20 g of an aqueous sodium thiosulfate solution.

  The concentration of the solvent in the coagulation bath can be slowly solidified as much as possible to obtain a coagulated yarn in a uniform and dense coagulation state, and the amount of coagulation-promoting components can be reduced to separate and recover the solvent and coagulation-promoting components. Energy can be reduced. When dimethyl sulfoxide is taken as an example, the solvent concentration of the coagulation bath is preferably 69% by weight or more, more preferably 72% by weight or more, and further preferably 75% by weight or more. When the solvent concentration is increased, there is a critical concentration, and there is a solvent concentration at which the formation of the yarn becomes impossible. However, it is generally difficult to homogenize the solidified state at this solvent concentration, and the solvent concentration is critical. It is preferable that it is below the concentration.

  Moreover, when a solvent is an organic solvent, when it mixes with water, coagulation bath liquid viscosity becomes high and has a peak. If the viscosity of the coagulation bath liquid is high, there is an effect of reducing yarn fluctuation in the coagulation bath, but on the other hand, resistance of the coagulation bath liquid is increased, and disturbance of the coagulation bath liquid occurs directly under the base, Spinnability is reduced. In the present invention, even if the viscosity of the coagulation bath liquid is high, the spinnability is hardly lowered for the same reason as described above. The viscosity of the coagulation bath liquid is 7 to 15 mPa · s with the set coagulation bath temperature as the measurement temperature. It is preferable that When the viscosity of the coagulation bath liquid is 7 mPa · s or more, the yarn swaying in the coagulation bath is suppressed and the accompanying flow of the coagulation bath liquid is increased, so that the coagulation tension can be reduced. Is 15 mPa · s or less, the accompanying flow of the coagulation bath liquid becomes too large, the sinking depth becomes too large, and the discharge angle tends to be too large, so that the spinnability tends to decrease. Moreover, it becomes easy to control the root mean square surface roughness of the precursor fiber within the range of the present invention by setting the viscosity of the coagulation bath solution within the above range. The viscosity of the coagulation bath liquid can be controlled by the type of solvent used in the coagulation bath, the concentration of the solvent and the coagulant, and the temperature.

  In the present invention, the viscosity of the coagulation bath liquid can be measured with a B-type viscometer. As conditions, rotor No. 1 was used, and the rotor rotational speed was 60 r. p. m. Measure with

  In the present invention, the coagulation bath temperature is preferably 0 to 30 ° C. The coagulation bath temperature affects the diffusion rate of the solvent into the coagulation bath and the diffusion rate of the coagulation accelerating component into the spinning solution. As a result, the lower the coagulation bath temperature, the denser the coagulated yarn, and the higher the strength of the carbon fiber. Is obtained. In the present invention, the measurement of the coagulation value itself is a constant temperature. However, if the measurement is performed with a change, the coagulation value increases as the temperature increases. The coagulation bath temperature is more preferably 5 to 20 ° C, still more preferably 10 to 15 ° C.

  In the present invention, after a PAN polymer solution is introduced into a coagulation bath and coagulated to form a coagulated yarn, a carbon fiber precursor fiber is obtained through a water washing step, an in-bath drawing step, an oil agent application step, and a drying step. It is done. Moreover, you may add a dry heat extending process and a steam extending process to said process. The solidified yarn may be directly stretched in the bath without the water washing step, or may be stretched in the bath after removing the solvent by the water washing step. Usually, the stretching in the bath is preferably performed in a single or a plurality of stretching baths adjusted to a temperature of 30 to 98 ° C. The draw ratio at that time is preferably 1 to 5 times, and more preferably 1 to 3 times.

  After the stretching step in the bath, it is preferable to apply an oil agent made of silicone or the like to the stretched fiber yarn for the purpose of preventing adhesion between single fibers. As the silicone oil, it is preferable to use a silicone oil containing a modified silicone such as amino-modified silicone having high heat resistance.

  As the drying step, for example, a drying condition in which a drying temperature is 70 to 200 ° C. and a drying time is 10 seconds to 200 seconds gives preferable results. As an improvement in productivity and an improvement in the degree of crystal orientation, it is preferable to stretch in a heating heat medium after the drying step. As the heating heat medium, for example, pressurized steam or superheated steam is suitably used in terms of operational stability and cost, and the draw ratio is usually 1.5 to 10 times.

  The total draw ratio of the coagulated yarn from the take-off roller is preferably 10 to 20 times in order to enhance the orientation of the precursor fibers and the degree of crystal orientation and increase the strength. When the total draw ratio is less than 10 times, the overall orientation degree and the crystal orientation degree of the precursor fiber are insufficient. On the other hand, when the total draw ratio exceeds 20 times, the strength of the precursor fiber may be reduced. .

  The precursor fiber winding speed (final spinning speed), which is the product of the coagulated yarn take-up speed and the total draw ratio from the coagulated yarn take-up roller, is preferably 600 to 2000 m / min, more preferably 700 to 2000 m / min. Minutes, 1000 to 2000 m / min. When the winding speed of the precursor fiber is less than 600 m / min, the overall orientation degree of the precursor fiber is difficult to increase, and when the winding speed of the precursor fiber exceeds 2000 m / min, the single fiber of the precursor fiber The coefficient of variation of the cross-sectional diameter may become large.

  The precursor fiber of the present invention thus obtained has a weight average molecular weight Mz (F) of 600,000 to 2,000,000, preferably 700,000 to 2,000,000, more preferably 900,000 to 2,000,000. Composed of coalescence. When it consists of a low molecular weight PAN-based polymer having an Mz (F) of less than 600,000, the strength of the precursor fiber is lowered and fluff is likely to occur in the flameproofing step. Further, in the case of a PAN polymer having a high molecular weight such that Mz (F) exceeds 2 million, it is necessary to set the weight average molecular weight Mz (P) of the polymer in the spinning solution to exceed 6 million. In that case, in order to increase the entanglement between the molecular chains and increase the extended chain length, the polymer concentration can be lowered and the entanglement can be lowered with a quasi-dilute solution, but for another purpose of the present invention. Deviation from high productivity.

  In the precursor fiber of the present invention, the polydispersity Mz (F) / Mw (F) (Mz represents the Z average molecular weight of the fiber) of the PAN polymer constituting the precursor fiber is 2 to 5. Preferably, it is 2.2-4, More preferably, it is 3-4. When Mz (F) / Mw (F) is less than 2, the effect of suppressing the generation of fluff in the flameproofing step, particularly when flameproofing at high temperatures is insufficient. Moreover, since the effect which suppresses the fluff generation | occurrence | production of a flame-proofing process increases as Mz (F) / Mw (F) is high, on the other hand, a fiber whose Mz (F) / Mw (F) exceeds 5, Since the entanglement of the polymer in the spinning solution for obtaining it becomes too large and the discharge becomes difficult, it is difficult to obtain. Since Mz (F) / Mw (F) is the same as or lower than Mz (P) / Mw (P), spinning containing a PAN-based polymer in which Mz (P) / Mw (P) is within the scope of the present invention Mz (F) / Mw (F) is controlled by adjusting the conditions of the spinning process using the solution.

The root-mean-square surface roughness Rms of the atomic force microscope of a single fiber of the precursor fiber of the present invention is measured in the range of 3 [mu] m, i.e. smoothness is 1 7 to 40 nm, good Mashiku is a 19~30nm . When Rms is less than 17 nm, that is, when the surface of the precursor fiber is excessively smooth, the precursor fiber is too focused, and heat may be accumulated in the flameproofing process to cause fluffing. When it exceeds 40 nm, that is, when the surface unevenness is large, the convergence as a precursor fiber bundle is lowered in the flameproofing process, and fluff is generated. Rms can be controlled by adjusting the viscosity of the coagulation bath solution within the range of the present invention, and can also be appropriately adjusted by controlling the coagulation number and the coagulation take-up speed within the range of the present invention.

  The crystal orientation degree of the precursor fiber of the present invention is preferably 91 to 94%, more preferably 92 to 94%. When the degree of crystal orientation is less than 91%, the tension is hardly increased in the flameproofing step, and fluff may be generated. On the other hand, if the degree of crystal orientation exceeds 94%, the stretch ratio may not be set high in the flameproofing process, and fluff may occur. The degree of crystal orientation can be controlled by adjusting the total draw ratio from the take-up roller of the coagulated yarn and the draw tension in each step.

The precursor fiber of the present invention has a RAMAN dichroic ratio R value obtained by RAMAN spectroscopy of 2.7 to 3.0, preferably 2.8 to 3.0. Unlike the degree of crystal orientation, the total degree of orientation reflecting the degree of amorphous orientation and the degree of crystallinity can be measured by the RAMAN dichroic ratio. In RAMAN spectroscopy, RAMAN scattering corresponding to the vibration of a specific molecular chain is observed by laser light. In the case of PAN, a CN stretching mode appears in the vicinity of 2240 cm ⁻¹ , with other peaks such as C—H. The degree of overall orientation can be measured by normalizing and examining the peak ratio in the fiber axis direction and the direction perpendicular to the fiber axis. That is, the laser excitation wavelength is set to 785 nm, and the measurement is performed by condensing the laser beam on the precursor fiber surface and measuring the polarization plane with the fiber axis at 0 °, rotating the stage by 90 °, Is set to 90 ° on the fiber axis as 90 ° measurement. After the baseline is drawn, the ratio of the peak intensity in the vicinity of 2240 cm ^-1 and the peak intensity in the vicinity of 1480 cm ⁻¹ of each measurement is R ′. R ′ (0 °) / R ′ (90 °) is defined as the RAMAN dichroic ratio R. Measurements of n = 6 were performed using different single fibers for each sample. Spectral comparison and analysis use those averages. When the stretching is performed, the R value increases with an increase in the degree of crystal orientation, but it has been found that the R value is likely to increase relative to the degree of crystal orientation when the spinning speed is greatly increased. The higher the R value, the less fluffing occurs in the flameproofing process. When the R value is less than 2.7, the fluff cannot be suppressed without lowering the flameproofing temperature, and the R value is 3.0. It was difficult to produce precursor fibers without generation of fluff.

  In the present invention, the single fiber strength of the precursor fiber measured in a bundle state is preferably 6 to 9 cN / dtex. When the single fiber strength is lower than 6 cN / dtex, fluff may be generated in the flameproofing process. On the other hand, if the single fiber strength exceeds 9 cN / dtex, the draw ratio may not be set high in the flameproofing process. In addition, fluff may occur. The single fiber strength can be controlled by adjusting the total draw ratio from the take-up roller of the coagulated yarn and the draw tension in each step.

  The single fiber fineness of the carbon fiber precursor fiber thus obtained is 0.3 to 1.5 dtex, preferably 0.3 to 1.1 dtex, more preferably 0.6 to 1.1 dtex. It is. If the single fiber fineness is too small, not only the productivity is lowered, but also the process stability of the yarn making process and the carbon fiber firing process may be lowered due to the occurrence of yarn breakage due to contact with a roller or a guide. On the other hand, if the single fiber fineness is too large, the heat storage in the flameproofing process is large and the yarn tends to break, and the difference in internal and external structures in each single fiber after flameproofing becomes large, and the processability decline in the subsequent carbonization process, Cost performance may be lowered by lowering the tensile strength and tensile modulus of the carbon fiber obtained.

  The variation coefficient of the single fiber cross-sectional diameter of the precursor fiber of the present invention is 0 to 5%, preferably 1 to 2%. If the fiber diameter fluctuates in the longitudinal direction of the fiber, fluff is generated when passing through the process with a long furnace length. Therefore, the variation coefficient of the cross-sectional diameter is 5% or less, and this coefficient of variation is 1 when spinning with multifilaments. It is often more than%. In order to control the coefficient of variation within the range of the present invention under the high coagulation bath liquid viscosity condition and the high speed coagulation take-up speed condition, the precursor fiber production method of the present invention may be followed.

  In the present invention, the roundness of the precursor fiber is preferably 0.85 (ellipse close to a perfect circle) to 1 (perfect circle), more preferably 0.91 to 1. When the roundness of the precursor fiber is less than 0.85, the bundle property of the fiber bundle in the flameproofing process may be lowered. The roundness can be controlled by adjusting the coagulation bath concentration and temperature during the production of the precursor fiber.

  A method for measuring the coefficient of variation and the roundness of the single fiber cross-sectional diameter of the precursor fiber will be described below. The precursor fiber bundle is aligned with the height perpendicular to the fiber axis and cut with a razor, and the cross-sectional shape of the single fiber is observed using an optical microscope. The measurement magnification is about 200 to 400 times the magnification so that the thinnest single fiber is about 1 mm, and the cross-sectional area and circumference of the single fiber of the precursor fiber are obtained by image analysis of the obtained images. From the cross-sectional area, the diameter of the cross section of the single fiber (fiber diameter) is obtained, and the roundness of the single fiber is obtained using the following formula.

Roundness = 4πS / L ²
(In the formula, S represents the cross-sectional area of the single fiber, and L represents the circumference of the single fiber.)
The diameter variation coefficient is the variation coefficient of the diameter obtained above.

  The obtained carbon fiber precursor fiber is usually in the form of a continuous fiber (filament). The number of filaments per one yarn (multifilament) is preferably 3000 to 60000. Since the obtained carbon fiber precursor fiber is homogeneous, the number of filaments per yarn is preferably larger for the purpose of improving the productivity in the firing process, and can be stably fired. is there. If the number of filaments exceeds 60000, the flameproofing treatment may not be performed uniformly throughout the bundle. The effect of the present invention becomes more remarkable as the number of filaments increases. The number of filaments can be controlled by the number of spinneret holes and the number of yarns obtained from a plurality of weights. The more the number of nozzle holes, the higher the cost performance, but it is better to increase the number of combined yarns in terms of discharge stability. The yarns may be combined after leaving the coagulation bath until flame resistance, but it is preferable from the viewpoint of equipment productivity that the yarns are combined after leaving the coagulation bath.

Next, the manufacturing method of the carbon fiber of this invention is demonstrated.
In the present invention, the carbon fiber precursor fiber obtained as described above is flame-proofed in which the carbon fiber precursor fiber is flame-resistant while being stretched in air at a temperature of 200 to 300 ° C. while stretching a stretch ratio of 0.8 to 1.2; A pre-carbonization step of pre-carbonizing the fiber obtained in the step while drawing at a draw ratio of 0.95-1.2 in an inert atmosphere at a temperature of 300 to 800 ° C., and a fiber obtained in the pre-carbonization step. Carbon fibers can be obtained through a carbonization step in which carbonization is performed while stretching at a stretch ratio of 0.96 to 1.05 in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.

  In the present invention, flame resistance refers to a step of heat treatment at 200 to 300 ° C. in an atmosphere containing 4 to 25 mol% or more of air. Usually, the spinning process and the flameproofing process are discontinuous, but part or all of the spinning process and the flameproofing process may be performed continuously. Moreover, it is preferable to set the maximum atmospheric temperature in the flameproofing process to 270 to 300 ° C. in order to improve the productivity of the flameproofing process. If the maximum atmospheric temperature in the flameproofing process is too high, the physical properties of the carbon fiber may be lowered.

  The stretch ratio when making flame resistant is 0.8 to 1.2, preferably 0.9 to 1.1. If the draw ratio at the time of flame resistance is less than 0.8, the tension in the flame resistance process is lowered, and scratching may occur in the flame resistance furnace slits, etc., and the single fiber strength distribution of the resulting carbon fiber is expanded. On the other hand, if the stretch ratio at the time of flame resistance exceeds 1.2, the stretch tension is too high and is pressed by a roller or the like so that an indentation remains or a defect may be enlarged.

  The flameproofing treatment time can be appropriately selected within a range of 10 to 100 minutes. However, for the purpose of improving the production stability of the subsequent preliminary carbonization and the mechanical properties of the resulting carbon fiber, It is preferable to set the specific gravity within a range of 1.3 to 1.38.

  Pre-carbonization and carbonization are performed in an inert atmosphere, and as the inert gas used, for example, nitrogen, argon, xenon, or the like is used. Nitrogen is preferably used from an economical viewpoint.

  The temperature of preliminary carbonization shall be 300-800 degreeC. In addition, it is preferable that the temperature increase rate in preliminary carbonization is set to 500 degrees C / min or less.

  The stretch ratio when performing preliminary carbonization is 0.95 to 1.2, preferably 1.0 to 1.1. When the draw ratio at the time of preliminary carbonization is less than 0.95, the degree of orientation of the resulting preliminary carbonized fiber becomes insufficient, and the strand tensile elastic modulus of the carbon fiber decreases. On the other hand, if the draw ratio during preliminary carbonization exceeds 1.2, the draw tension may be too high and may be pressed by a roller or the like to leave indentations or enlarge defects.

  The carbonization temperature is preferably 1,000 to 2,000 ° C, more preferably 1,200 to 1800 ° C, and still more preferably 1,300 to 1,600 ° C. Generally, the higher the maximum temperature of carbonization, the higher the tensile tensile modulus of the strand, but the tensile strength becomes a maximum at around 1,500 ° C. Therefore, the carbonization temperature is set in consideration of the balance between the two.

  The stretch ratio when carbonizing is 0.96 to 1.05, preferably 0.97 to 1.05, and more preferably 0.98 to 1.03. When the draw ratio at the time of carbonization is less than 0.96, the orientation degree and denseness of the obtained carbon fiber become insufficient, and the strand tensile elastic modulus is lowered. On the other hand, if the drawing ratio during carbonization exceeds 1.05, the drawing tension may be too high and may be pressed by a roller or the like to leave indentations or enlarge defects.

  When a carbon fiber having a higher elastic modulus is desired, graphitization can be performed following the carbonization step. The temperature of the graphitization step is preferably 2000 to 2800 ° C. The maximum temperature is appropriately selected and used according to the required characteristics of the desired carbon fiber. The drawing ratio in the graphitization step is preferably selected as appropriate within a range where no deterioration in quality such as generation of fluff occurs according to the required characteristics of the desired carbon fiber.

  The obtained carbon fiber can be subjected to electrolytic treatment for its surface modification. The electrolytic solution used for the electrolytic treatment includes an acidic solution such as sulfuric acid, nitric acid and hydrochloric acid, an alkali solution such as sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, ammonium carbonate and ammonium bicarbonate, or a salt thereof as an aqueous solution. Can be used as Here, the amount of electricity required for the electrolytic treatment can be appropriately selected according to the carbonization degree of the carbon fiber to be applied.

  Electrolytic treatment can optimize the adhesion to the carbon fiber matrix in the resulting fiber reinforced composite material, causing brittle fracture of the composite material due to too strong adhesion and lowering the tensile strength in the fiber direction In addition, although the tensile strength in the fiber direction is high, the adhesive property with the resin is poor, and the problem that the strength characteristics in the non-fiber direction are not expressed is solved, and in the obtained fiber reinforced composite material, in both the fiber direction and the non-fiber direction A balanced strength characteristic is developed.

  After the electrolytic treatment, a sizing treatment can also be applied to give the carbon fiber a bundling property. As the sizing agent, a sizing agent having good compatibility with the matrix resin or the like can be appropriately selected according to the type of resin used.

  The carbon fiber obtained by the present invention can be produced by various molding methods such as autoclave molding as a prepreg, resin transfer molding as a preform of a woven fabric, and filament winding. And it is suitably used as a sports member such as a golf shaft.

Hereinafter, the present invention will be described more specifically with reference to examples. The measurement method used in this example will be described next.
<Various molecular weights: Mz, Mw>
In the case of measuring a polymer, a sample solution in which the polymer to be measured is dissolved in dimethylformamide (added with 0.01 N lithium bromide) at a concentration of 0.1% by weight is prepared. When measuring the precursor fiber, a sample solution is prepared by dissolving the sample to be measured in dimethyl sulfoxide at a concentration of 0.1 w / v%. For the prepared sample solution, a molecular weight distribution curve is obtained from a GPC curve measured under the following conditions using a GPC apparatus, and Mz (P) and Mw (P) or Mz (F) and Mw (F) are calculated. To do. The measurement is performed three times, and the average values of Mz (P) and Mw (P) are used.
-Column: Column for polar organic solvent GPC-Solvent: Dimethylformamide (0.01N-lithium bromide added)
・ Flow rate: 0.5ml / min ・ Temperature: 75 ℃
・ Sample filtration: Membrane filter (0.45μm cut)
・ Injection volume: 200 μl
・ Detector: Differential refractive index detector Mw uses at least six types of monodispersed polystyrenes with different molecular weights and known molecular weights to create an elution time-molecular weight calibration curve, and corresponds to the corresponding elution time on the calibration curve. It is obtained by reading the molecular weight in terms of polystyrene.

  In this example, CLASS-LC2010 manufactured by Shimadzu Corporation as a GPC device, and TSK-GEL-α-M (× 2) manufactured by Tosoh Corporation as a column and TSK-guard Column α manufactured by Tosoh Corporation, Calibration curves were manufactured by Wako Pure Chemical Industries, Ltd. as dimethylformamide and lithium bromide, 0.45 μm-FHLP FILTER manufactured by Millipore Corporation as a membrane filter, and RID-10AV manufactured by Shimadzu Corporation as a differential refractive index detector. As the monodisperse polystyrene for production, those having molecular weights of 184000, 427000, 791000 and 1300000, 1810000, 420000 were used.

<Viscosity bath viscosity>
Measurement was performed using a B-type viscometer. As conditions, rotor No. 1 was used, and the rotor rotational speed was 60 r. p. m. Measured with

<Coagulation value>
A solution in which 1% by weight of the polymer used for spinning is dissolved in 50 cc of the solvent used for spinning is adjusted to a temperature of 5 ° C. The coagulation accelerating component is gradually added dropwise to the stirred solution, and the addition is continued after confirming that the temperature is stabilized at 25 ° C. and sufficiently stirred. Precipitation formation was started and it was visually confirmed that the solution changed from transparent to cloudy, and the amount of the coagulation-promoting component dropped was measured. From the solidification promoting component concentration (%) of the coagulation bath to be set, the solidification value (g) = the amount of solidification promoting component dropped (g) / coagulation promoting component concentration × 100 was obtained. The measurement was performed 3 times and the average value was adopted.

<Discharge angle>
A photograph was taken between the discharge surface and the liquid surface of the base from the direction perpendicular to the short diameter of the base, and the discharge state of the outermost hole of the base was measured. The angle from the direction perpendicular to the die surface was taken as the discharge angle.

<Subduction depth>
A coagulation bath with a transparent base on the side of the coagulation bath. Take a picture of the gap between the discharge surface of the base and the liquid surface from the direction perpendicular to the short axis of the base. The level difference of the liquid level was measured and set as the subduction depth.

<RAMAN dichroic ratio of precursor fiber>
The measurement apparatus and measurement conditions were as follows.
Measuring device: JobonYvon RamaonorT-64000 microprobe (microscopic mode)
Objective lens: 100 times beam diameter: 1 μm
Laser excitation wavelength: 785 nm
Laser power: 33mW
Diffraction grating: 600 gr / mm (manufactured by Spectrograph)
Slit: φ50μm
Detector: CCD (1024 × 256 made by JobinYvon)
In the measurement, the laser beam was condensed on the surface of the precursor fiber, the measurement was performed at 0 ° when the polarization plane was aligned with the fiber axis, the stage was rotated 90 °, and the polarization plane was set at 90 ° about the fiber axis. The time was measured at 90 °. The ratio of the peak intensity in the vicinity of the peak intensity and 1480 cm ^-1 in the vicinity of 2240 cm ^-1 of each measurement and R 'on minus the baseline. R ′ (0 °) / R ′ (90 °) was used as the RAMAN dichroic ratio R value. Measurements of n = 6 were performed using different single fibers for each sample. Spectral comparison and analysis used those averages.

<Crystal orientation degree of precursor fiber>
The degree of orientation in the fiber axis direction was measured as follows. The fiber bundle is cut to a length of 40 mm, and 20 mg is precisely weighed and sampled so that the sample fiber axes are exactly parallel, and then a thickness of 1 mm is uniform using a sample adjusting jig. Sample fiber bundles were arranged. After impregnating with a thin collodion solution and fixing it so as not to lose its shape, it was fixed to a sample table for wide-angle X-ray diffraction measurement. From the half width (H °) of the spread of the profile in the meridian direction including the highest intensity of diffraction observed near 2θ = 17 °, using Cu Kα ray monochromated with a Ni filter as the X-ray source. The degree of crystal orientation (%) was determined using the following formula. The n number was 3.

Crystal orientation degree (%) = [(180−H) / 180] × 100
In addition, Shimadzu Corporation XRD-6100 was used as said wide angle X-ray diffraction apparatus.

<Single fiber fineness of precursor fiber>
The dried fiber having a filament number of 6,000 was wound 10 times on a 1 m metal frame, and then its weight was measured to calculate the weight per 10,000 m.

<Precursor fiber square average surface roughness Rms>
A sample of a single precursor fiber to be evaluated placed on a sample stage and fixed at both ends with an adhesive solution (for example, a stationery correction solution) is used as a sample, and an image of a three-dimensional surface shape is obtained using an atomic force microscope. obtain. In the present example, an SPI 3800N / SPA-400 manufactured by Seiko Instruments Inc. was used as an atomic force microscope, and a three-dimensional surface shape image was obtained under the following conditions.
Probe: Silicon cantilever (Seiko Instruments, DF-20)
Measurement mode: Dynamic force mode (DFM)
Scanning speed: 1.5Hz
Scanning range: 3μm × 3μm
Resolution: 256 pixels × 256 pixels The obtained image of the three-dimensional surface shape is obtained by fitting the primary plane by the least square method from the entire data of the image, taking into account the curvature of the fiber cross section, First-order inclination correction to correct the in-plane inclination, followed by second-order inclination correction to correct the quadratic curve in the same way, then surface roughness analysis by the attached software, the root mean square surface roughness Rms was calculated. The measurement was performed by sampling 10 different single fibers at random, and performing each measurement once for each single fiber for a total of 10 times.

<Strength of precursor fiber>
The precursor fiber bundle was tested at a test length of 50 mm and a tensile speed of 100 mm / min, and an average of n = 10 values was used.

<Cross-sectional shape and diameter variation coefficient of precursor fiber monofilament>
The precursor fiber bundle was aligned with the height perpendicular to the fiber axis and cut with a razor, and the cross-sectional shape of the single fiber was observed using an optical microscope. The measurement magnification is about 200 to 400 times the magnification so that the thinnest single fiber is about 1 mm, and the cross-sectional area and circumference of the single fiber of the precursor fiber are obtained by image analysis of the obtained images. The cross-sectional diameter (fiber diameter) of the single fiber was determined from the cross-sectional area, and the roundness of the single fiber was determined using the following formula.

Roundness = 4πS / L ²
(In the formula, S represents the cross-sectional area of the single fiber, and L represents the circumference of the single fiber.)
The diameter variation coefficient was the variation coefficient of the diameter obtained above.

<Adhesion evaluation>
50 cm of fiber bundles after coagulation take-up were collected when yarn was produced under the conditions of the following examples and comparative examples, and the fiber bundles were swimmed in a vat with black bottom and 2 cm of water, and observed for the condition of the looseness. Then, the adhesion state was evaluated. The evaluation criteria are as follows.
1: Dispersed into a single fiber.
2: When tapping the fiber bundle in water with tweezers, it breaks into single fibers.
3: Including a fiber bundle that does not disperse in units of several.
4: Including a fiber bundle that does not disperse in units of several tens.
5: Contains a plurality of fiber bundles that cannot be separated in units of several tens.

<Process stability during precursor fiber production>
The process stability was evaluated by counting the number of fluff of the precursor fiber for 1000 m before winding up the precursor fiber when the yarn was produced under the conditions of the following examples and comparative examples. The evaluation criteria are as follows.
1: (number of fuzz / one fiber bundle / 1000 m) ≦ 1
2: 1 <(number of fuzz / 1 fiber bundle / 1000 m) ≦ 2
3: 2 <(number of fuzz / 1 fiber bundle · 1000 m) ≦ 5
4: 5 <(number of fuzz / 1 fiber bundle / 1000 m) <60
5: (number of fuzz / 1 fiber bundle / 1000 m) ≧ 60
<Process stability during flame resistance>
After the precursor fibers of the following examples and comparative examples were combined so as to be 12,000 filaments, the atmosphere temperature was kept constant at 270 ° C., and the yarn was placed in a horizontal hot air circulation furnace having a furnace length of 7.5 m. While introducing at a speed of 2.5 m / min and stretching at a draw ratio of 1.0, the number of fluff was counted for 40 minutes on the exit side of the furnace to evaluate the process stability. The evaluation criteria are as follows.
1: (number of fluff / one fiber bundle / 100 m) ≦ 1
2: 1 <(number of fuzz / 1 fiber bundle / 100 m) ≦ 2
3: 2 <(number of fuzz / 1 fiber bundle / 100 m) ≦ 40
4:40 <(number of fuzz / 1 fiber bundle / 100 m) <400
5: (number of fuzz / 1 fiber bundle / 100 m) ≧ 400
[Example 1]
100 parts by weight of AN, 1 part by weight of itaconic acid, and 130 parts by weight of dimethyl sulfoxide were mixed and placed in a reaction vessel equipped with a reflux tube and a stirring blade. After replacing the space in the reaction vessel with nitrogen to an oxygen concentration of 100 ppm, as a radical initiator, 0.002 part by weight of 2,2′-azobisisobutyronitrile (AIBN) was added, and the following conditions were added while stirring: The heat treatment (referred to as polymerization condition B) was performed.

-Hold at 65 ° C for 2 hours-Decrease in temperature from 65 ° C to 30 ° C (Temperature drop rate: 120 ° C / hour)
Next, 240 parts by weight of dimethyl sulfoxide, 0.4 part by weight of AIBN as a radical initiator, and 0.1 part by weight of octyl mercaptan as a chain transfer agent were weighed and introduced into the reaction vessel, and the following stirring was performed. A heat treatment (referred to as polymerization conditions A) of (1) to (4) was performed and polymerized by a solution polymerization method to obtain a PAN polymer solution.
(1) Temperature increase from 30 ° C to 60 ° C (temperature increase rate 10 ° C / hour)
(2) Hold for 4 hours at a temperature of 60 ° C. (3) Increase the temperature from 60 ° C. to 80 ° C. (Temperature increase rate: 10 ° C./hour)
(4) Hold for 6 hours at a temperature of 80 ° C. Use the obtained PAN-based polymer solution to prepare a polymer concentration of 20% by weight, and then blow ammonia gas until the pH reaches 8.5. Thus, an ammonium group was introduced into the PAN polymer while neutralizing itaconic acid to obtain a spinning solution. The PAN-based polymer in the obtained spinning solution had Mw (P) of 480,000, Mz (P) / Mw (P) of 5.7, M _{Z + 1} (P) / Mw (P) of 14, The viscosity of the solution was 45 Pa · s.

  The obtained spinning solution was run at a temperature of 40 ° C. at a temperature of 5 ° C. by running a 5 mm air gap once from a spinneret having a hole number of 3000, a spinneret hole diameter of 0.3 mm, and a short diameter of the base of 175 mm. Spinning was performed by a dry-wet spinning method introduced into a coagulation bath composed of an aqueous solution of% dimethyl sulfoxide to obtain a coagulated yarn. Under this condition, a coagulated yarn was obtained under the conditions of a discharge linear velocity of 3 m / min, a spinning draft rate of 12, and a coagulation take-up speed of 40 m / min, and the adhesion was evaluated. At this time, the discharge angle from the die was 14 °, and the sinking depth was 8 mm. After washing the obtained coagulated yarn with water, it is stretched in hot water at a temperature of 70 ° C. at a stretch ratio of 2 times in a bath, further provided with an amino-modified silicone oil, and dried using a hot drum at a temperature of 190 ° C. Thereafter, the carbon fiber precursor fiber having a single fiber fineness of 1.1 dtex was obtained by post-stretching 6 times in pressurized water vapor of 0.4 MPa. The quality of the obtained carbon fiber precursor fiber was excellent, and the yarn passing through the spinning process observed before winding the precursor fiber was also stable.

[Example 2]
Except that the first AIBN charge was changed to 0.001 part by weight, the space in the reaction vessel was replaced with nitrogen to an oxygen concentration of 1000 ppm, and the polymerization condition A was changed to the following polymerization condition C A spinning solution was obtained in the same manner as in Example 1.
(1) Hold for 4 hours at a temperature of 70 ° C. (2) Decrease in temperature from 70 ° C. to 30 ° C. (Cooling rate 120 ° C./hour)
The PAN polymer in the obtained spinning solution has Mw (P) of 340,000, Mz (P) / Mw (P) of 2.7, and M _{Z + 1} (P) / Mw (P) of 7.2. The viscosity of the spinning solution was 40 Pa · s. Spinning was carried out in the same manner as in Example 1 except that the spinning solution was changed to the spinning solution obtained as described above. The quality of the obtained carbon fiber precursor fiber was excellent, and the yarn passing through the spinning process observed before winding the precursor fiber was also stable.

[Example 3]
A spinning solution was obtained in the same manner as in Example 2 except that the first AIBN charge was changed to 0.002 parts by weight and that the holding time was 1.5 hours under the polymerization condition C. The PAN polymer in the obtained spinning solution had Mw (P) of 320,000, Mz (P) / Mw (P) of 3.4, and M _{Z + 1} (P) / Mw (P) of 12, The viscosity of the solution was 35 Pa · s. Spinning was carried out in the same manner as in Example 1 except that the spinning solution was changed to the spinning solution obtained as described above. The quality of the obtained carbon fiber precursor fiber was excellent, and the yarn passing through the spinning process observed before winding the precursor fiber was also stable.

[Comparative Example 1]
100 parts by weight of AN, 1 part by weight of itaconic acid, 0.4 parts by weight of 2,2′-azobis (2-methylpropionitrile) (hereinafter abbreviated as AIBN) as a radical initiator, and octyl mercaptan as a chain transfer agent 1 part by weight was uniformly dissolved in 370 parts by weight of dimethyl sulfoxide, and it was put into a reaction vessel equipped with a reflux tube and a stirring blade. After replacing the space in the reaction vessel with nitrogen until the oxygen concentration becomes 1000 ppm, heat treatment is performed under the polymerization condition A in Example 1, and the remaining unreacted monomer is polymerized by a solution polymerization method to obtain a PAN-based polymer. A solution was obtained.
The polymer concentration with respect to the solvent of the obtained PAN-based polymer solution was a little less than 20% by weight.
The obtained PAN-based polymer solution was prepared so that the polymer concentration was 20% by weight, and then ammonia gas was blown until the pH reached 8.5 to neutralize itaconic acid, while the ammonium group was neutralized. Was introduced into the polymer to obtain a spinning solution. Except for changing the spinning solution to the spinning solution obtained as described above, spinning was attempted in the same manner as in Example 1. However, when the yarn was placed on the coagulation take-up roller, the yarn was broken just below the base and could be sampled. There wasn't.

[Comparative Example 2]
(Method similar to Example 1 of Japanese Patent Application Laid-Open No. 2008-248219) Using the spinning solution used in Example 1, air was once discharged from a spinneret having a hole number of 6000, a spinneret hole diameter of 0.15 mm, and a shorter diameter of 175 mm. The gap was run and spun by a dry-wet spinning method introduced into a coagulation bath composed of an aqueous solution of 20% by weight dimethyl sulfoxide controlled at a temperature of 3 ° C. to obtain a coagulated yarn. Under this condition, a coagulated yarn was obtained under the conditions of a discharge linear velocity of 7 m / min, a spinning draft rate of 4, and a coagulation take-up speed of 28 m / min, and adhesion evaluation was performed. Since the viscosity of the coagulation bath liquid was low and the coagulation take-up speed was slow, the discharge angle from the die was 14 °, the sinking depth was 0 mm, and the adhesion was small. Thereafter, a precursor fiber of 0.7 dtex was obtained in the same manner as in Example 1 except that the coagulation / discharge conditions were changed as described above, but the process passability was slightly deteriorated as compared with Example 1.

[Comparative Example 3]
Spinning in the same manner as in Comparative Example 2 except that a precursor single fiber of 1.1 dtex was obtained under the conditions of a coagulation bath concentration and temperature, a discharge linear velocity of 13 m / min, a spinning draft rate of 3, and a coagulation take-up speed of 40 m / min. Went. When it became a high-viscosity coagulation bath solution and taken up at high speed, the accompanying flow to the central part of the die became large, the discharge angle was large, and the sinking depth was large. Since the discharge angle was increased, adhesion increased, and process passability was greatly reduced.

[Comparative Example 4]
Spinning was performed in the same manner as in Comparative Example 3 except that the same spinning solution as in Comparative Example 1 was used. The discharge angle was larger than that of Comparative Example 3, and the process passability was further deteriorated.

[Comparative Example 5]
Spinning was performed in the same manner as in Example 3 except that a spinneret having a short diameter of 220 mm was used. Since the discharge angle was larger than in Example 3 and the adhesion increased, the process passability decreased.

[Example 4]
Spinning was performed in the same manner as in Example 3 except that a spinneret having a short diameter of 75 mm was used. The discharge angle was smaller than in Example 3, and the process passability was good.

[Example 5]
Spinning was carried out in the same manner as in Example 3 except that a spinneret was used in which the long diameter of the base was lengthened and the number of holes in the base was 16,000 while the short diameter was maintained.

[Example 6]
Spinning was carried out in the same manner as in Example 3 except that the spinneret with the longer diameter of the base and the base diameter maintained to 24,000 while the short diameter was maintained, the process passability was good.

[Example 7]
Spinning was carried out in the same manner as in Example 3 except that the solvent concentration of the coagulation bath was 79%, the bath solution temperature was 10 ° C., and the coagulation bath solution viscosity was 8 mPa · s. The skin layer was thinned due to the high coagulation bath temperature, and the process passability was slightly deteriorated. However, the discharge angle was reduced and the adhesion was reduced because the coagulation bath viscosity was lowered.

[Example 8]
Spinning was carried out in the same manner as in Example 7 except that the bath temperature of the coagulation bath was 15 ° C. and the viscosity of the coagulation bath solution was 7 mPa · s. The skin layer was thinned due to the high coagulation bath temperature, and the process passability was slightly deteriorated. However, the discharge angle was reduced and the adhesion was reduced because the coagulation bath viscosity was lowered.

[Comparative Example 6]
Spinning was performed in the same manner as in Example 7 except that the bath temperature of the coagulation bath was 25 ° C. and the viscosity of the coagulation bath solution was 5 mPa · s. Since the coagulation bath temperature was high, the skin layer became thinner, and the process passability was greatly deteriorated.

[Examples 9 to 11]
Spinning was carried out in the same manner as in Example 3 except that the amount of spinning solution discharged from the die was increased according to the coagulation take-up speed and the coagulation take-up speed was changed as shown in Table 1. Although the sinking depth of the coagulation bath liquid level increased, there was no significant decrease in process passability and stable spinning was possible.

[Comparative Examples 7 to 9]
Spinning was performed in the same manner as in Comparative Example 4, except that the amount of spinning solution discharged from the die was increased according to the coagulation take-up speed and the coagulation take-up speed was changed as shown in Table 1. The submergence depth of the coagulation bath liquid level was increased, and as in Comparative Example 4, since the discharge angle was large, the process passability was greatly deteriorated.

[Example 12]
Spinning was carried out in the same manner as in Example 4 except that the diameter of the nozzle hole was changed and the spinning draft 8 was changed. Since the discharge angle was increased, the process passability was slightly deteriorated, but spinning was possible without problems.

[Example 13]
Spinning was carried out in the same manner as in Example 4 except that the diameter of the die hole was changed and the spinning draft 5 was changed. Since the discharge angle was increased, the process passability was slightly deteriorated, but spinning was possible without problems.

[Example 14]
Spinning was carried out in the same manner as in Example 3 except that the coagulation take-up speed was increased and the spinning draft was changed. Although the spinning draft increased, the discharge angle became smaller and the coagulation take-up speed increased, but the spinning was stable.

[Comparative Example 10]
Polymerization was carried out in the same manner as in Comparative Example 1 except that 0.2 part by weight of octyl mercaptan was changed to 240 parts by weight of dimethyl sulfoxide to obtain a polymer having Mw (P) of 200,000. The polymer concentration of this polymer solution was adjusted to 27% by weight to obtain a spinning solution. The obtained spinning solution is spun by a wet-wet spinning method from a spinning nozzle having a hole number of 36, a spinning nozzle hole diameter of 0.3 mm, and a short nozzle diameter of 10 mm at a temperature of 40 ° C. It was a thread. At this time, the coagulation bath conditions were made of an aqueous solution of 70% by weight dimethyl sulfoxide controlled at a temperature of 40 ° C. so that the viscosity of the coagulation bath solution was the same as in the example of Patent Document 2. Spinning was performed under the conditions of a discharge linear speed of 5 m / min, a spinning draft rate of 13.6, and a coagulation take-up speed of 65 m / min. The coagulation bath liquid viscosity is low, the number of nozzle holes is small, and the distance between the center part and the outer peripheral part is short, so the flow of the coagulation bath liquid directly under the center part of the base is small and relatively stable spinning is possible. It was not satisfactory from the viewpoint of sex.

[Comparative Example 11]
Spinning was carried out in the same manner as in Comparative Example 10 except that the conditions of the spinneret and the coagulation bath were the same as in Example 1. However, since the discharge angle was large and the coagulated yarns were bonded together, stable spinning was possible. There wasn't.

[Comparative Example 12]
Polymerization was carried out in the same manner as in Comparative Example 1 except that 0.3 parts by weight of AIBN and octyl mercaptan were not added to obtain a polymer having Mw (P) 900,000. A spinning solution was obtained by adjusting the polymer concentration to 20% by weight. The obtained spinning solution was spun by a dry and wet spinning method from a spinning nozzle having a hole number of 16000, a spinning nozzle hole diameter of 0.19 mm, and a short nozzle diameter of 67 mm at a temperature of 40 ° C. It was a thread. At this time, it was set as the coagulation bath condition which consists of the aqueous solution of 20 weight% dimethylsulfoxide controlled to the temperature of 3 degreeC so that only the Example of patent document 3 and the coagulation bath liquid viscosity might become the same. Spinning was performed under the conditions of a discharge linear speed of 0.5 m / min, a spinning draft rate of 8, and a coagulation take-up speed of 4 m / min. Since the viscosity of the coagulation bath solution was low and the coagulation take-up speed was slow, the flow of the coagulation bath solution just below the center of the die was small and a relatively stable spinning could be performed, but this was not satisfactory from the viewpoint of productivity.

[Comparative Example 13]
Spinning was carried out in the same manner as in Comparative Example 12 except that the coagulation bath conditions, the discharge amount, and the coagulation take-up speed were the same as in Example 1. However, since the discharge angle was large and the coagulated yarns were bonded together, the spinning was stable. Could not be spun.

[Comparative Example 14]
Spinning was performed in the same manner as in Example 14 except that the spinning draft was changed by lowering the discharge linear velocity. Since the spinning draft was increased too much, the yarn breakage occurred just below the die, and the process passability was greatly deteriorated.

[Examples 15 to 18]
A spinning solution was obtained in the same manner as in Example 1 except that the heat treatment (65 ° C.) holding time under the polymerization condition B was changed from 2 hours to 1.5 hours. Spinning was carried out in the same manner as in Example 1 except that the precursor fiber production conditions were changed as shown in Table 2 to obtain precursor fibers. The total draw ratio was set by adjusting the post-draw ratio.

[Example 19]
Spinning was carried out in the same manner as in Example 1 except that the precursor fiber production conditions were changed as shown in Table 2 to obtain precursor fibers.

[Examples 20 and 21]
Spinning was carried out in the same manner as in Example 1 except that dimethyl sulfoxide was added so that the polymer concentration of the spinning solution was 15% by weight, and the precursor fiber production conditions were changed as shown in Table 2. Body fibers were obtained.

[Comparative Example 15]
A spinning solution was obtained in the same manner as in Example 5 of Japanese Patent Application No. 2009-09704, and spinning was performed by setting the conditions as shown in Table 1 with reference to the same conditions to obtain precursor fibers.

[Comparative Example 16]
A spinning solution was obtained in the same manner as in Example 1 of JP-A-2008-248219, and spinning was performed with the conditions set as shown in Table 1 with reference to the same conditions. That is, using the obtained spinning solution, coagulating with an aqueous solution of 20% by weight dimethyl sulfoxide having a pore number of 12,000, spinning under the spinneret and discharge conditions shown in Table 2, and controlling at a temperature of 3 ° C. Spinning was performed by a dry and wet spinning method introduced into a bath to obtain a coagulated yarn. The spinning draft at this time was adjusted to 2.5 times to obtain a coagulated yarn. The single fiber fineness of the dried coagulated yarn was 10.5 dtex. The coagulated yarn thus obtained was washed with water and then stretched at 90 ° C. in warm water at a stretch ratio of 3 times in a bath, and an amino-modified silicone-based silicone oil was further added to obtain a stretched yarn in the bath. The drawn yarn in the bath thus obtained was dried for 30 seconds using a roller heated to a temperature of 165 ° C., steam drawn at a steam drawing ratio of 5 times, and a precursor fiber having a single fiber fineness of 1 dtex was obtained. Obtained.

[Comparative Example 17]
Spinning was performed in the same manner as in Comparative Example 16 except that the coagulation bath conditions were changed as shown in Table 2 to obtain precursor fibers.

[Comparative Example 18]
A spinning solution was obtained in the same manner as in Example 1 of Japanese Patent Application No. 2008-287520, and spinning was performed with the conditions set as shown in Table 1 with reference to the same conditions. That is, the obtained spinning solution was run at a temperature of 40 ° C. from a spinneret having a hole number of 100 and a spinneret hole diameter of 0.2 mm, and once moved through a 15 mm air gap, and controlled to a temperature of 5 ° C. Spinning was performed by a dry-wet spinning method introduced into a coagulation bath made of an aqueous solution to obtain a coagulated yarn. At this time, the spin rate at which yarn breakage occurs is measured by adjusting the amount of liquid fed to the spinneret so that the discharge linear velocity is 8 m / min and changing the winding speed of the coagulated yarn. It was. Moreover, after obtaining a coagulated yarn under conditions of a discharge linear velocity of 1 m / min and a spinning draft rate of 14, and after washing with water, the coagulated yarn is stretched in a bath at a temperature of 70 ° C. at a stretch ratio of 2 times in a bath, and further amino-modified silicone silicone Oil is applied, dried using a hot drum at a temperature of 130 ° C., and then stretched at a double magnification while drying in a non-contact manner using a heating furnace at a temperature of 165 ° C. to obtain a single fiber fineness of 1.3 dtex. Carbon fiber precursor fiber was obtained.

[Comparative Examples 19 and 20]
Spinning was performed in the same manner as in Comparative Example 1 except that the precursor fiber production conditions were changed as shown in Table 2 to obtain precursor fibers.

  Tables 1 and 2 show the results of the precursor fiber production conditions and the evaluation thereof in the above Examples and Comparative Examples, and Table 3 shows the properties of the precursor fibers.

  In the present invention, by stably discharging a PAN-based polymer capable of performing high-speed spinning, a high-quality precursor fiber is produced without impairing productivity and reducing production costs. By using the obtained precursor fiber, it is useful because it can stably produce a high-quality and high-strength carbon fiber even in the firing step.

Claims (9)

The polyacrylonitrile polymer constituting the fiber has a Z average molecular weight Mz (F) of 600,000 to 2,000,000, and the polydispersity Mz (F) / Mw (F) (Mw (F) is the poly The weight average molecular weight of the acrylonitrile polymer) is 2 to 5, the root mean square surface roughness Rms measured in the range of 3 μm with an atomic force microscope is 17 to 40 nm, and the single fiber fineness is 0.3 to A carbon fiber precursor fiber having a variation coefficient of a single fiber cross-sectional diameter of 0 to 5%, which is 1.5 dtex and measured according to the method of (I) below .
(I) Cutting the precursor fiber bundle by adjusting the height perpendicular to the fiber axis, and observing the cross-sectional shape of the single fiber using an optical microscope, the single fiber having the thinnest measurement magnification is about 1 mm. The magnification is about 200 to 400 times, and the obtained image is subjected to image analysis for six sheets to determine the cross-sectional area of the single fiber of the precursor fiber, and the cross-sectional area (fiber diameter) of the single fiber from the cross-sectional area, The variation coefficient of the diameter (variation coefficient of the single fiber cross-sectional diameter) is obtained. The R value determined by RAMAN spectroscopy and specified in the specification is 2.7 to 3.0, the single fiber strength is 6 to 9 cN / dtex, and the raw yarn crystal orientation is 91 to 94%. The carbon fiber precursor fiber according to claim 1. The carbon fiber precursor fiber according to claim 1 or 2, wherein the roundness is 0.85 to 1. Using a spinneret having a minor axis of 75 to 200 mm and a number of holes of 3000 to 30000, the coagulated yarn is 35 in the coagulation bath liquid under the condition that the viscosity at the coagulation temperature of the coagulation bath liquid is 7 to 15 mPa · s. A method for producing a carbon fiber precursor fiber that is dry and wet-spun so as to run at a speed of ˜200 m / min, the Z average molecular weight (Mz (P)) is 800,000 to 6,000,000, and the polydispersity (Mz ( P) / Mw (P)) (Mw (P) represents a weight average molecular weight) is a spinning solution containing a polyacrylonitrile polymer having a weight average molecular weight of 2.7 to 10, and a spinning draft is 5 to 50, A method for producing a carbon fiber precursor fiber, characterized in that the angle of the spinning solution discharged from the outermost hole of the spinneret and the spinneret surface vertical direction is 5 to 15 °. The manufacturing method of the carbon fiber precursor fiber of Claim 4 which discharges the said spinning solution in the coagulation bath of coagulation bath conditions whose coagulation number is 23-40g. The method for producing a carbon fiber precursor fiber according to claim 4 or 5, wherein a total draw ratio of the coagulated yarn from a take-up roller is 10 to 20 times, and a winding speed of the precursor fiber bundle is 600 to 2000 m / min. . The manufacturing method of the carbon fiber precursor fiber in any one of Claims 4-6 whose take-up speed of the said coagulated yarn is 50-200 m / min. The distance between the coagulation bath liquid level before sinking and the spinneret is set to 5 to 10 mm, and the depth at which the coagulation bath liquid level sinks by spinning is controlled to 5 to 20 mm. The manufacturing method of the carbon fiber precursor fiber of description. The carbon fiber precursor fiber according to any one of claims 1 to 3, or the carbon fiber precursor fiber obtained by the production method according to any one of claims 4 to 8, at a temperature of 200 to 300 ° C. A flameproofing step for flameproofing in the air, a precarbonization step for precarbonizing the fiber obtained in the flameproofing step in an inert atmosphere at a temperature of 300 to 800 ° C., and a fiber obtained in the preliminary carbonization step A method for producing carbon fiber, wherein carbon fibers are sequentially obtained through a carbonization step of carbonizing in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.