JP2010037669A - Method for producing carbon fiber base material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber base material having excellent dispersibility of carbon fiber during base formation and excellent mechanical characteristics when made into a molded product. <P>SOLUTION: The carbon fiber base material is produced by a production step having at least four steps of a step (I) for feeding a carbon fiber bundle to which 0.1-10 mass% of a water-soluble polyurethane and/or a water-soluble polyamide is attached, into a dispersion medium; a step (II) for preparing a slurry in which a carbon fiber constituting the carbon fiber bundle is dispersed into the dispersion medium; a step (III) for transporting the slurry to a step (IV); and a step (IV) for removing the dispersion medium from the slurry and forming a carbon fiber base material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a carbon fiber substrate.

  Fiber reinforced molded base materials made of reinforced fibers such as carbon fiber and glass fiber and thermoplastic resins are excellent in specific strength and specific rigidity, so they can be used in electrical / electronic applications, civil engineering / architecture applications, automotive applications, aircraft applications, etc. Widely used. In particular, a molded article using a base material in which reinforcing fibers are uniformly dispersed has isotropic mechanical properties, and if it exhibits high strength, the applicable applications are very many. Therefore, various studies have been made so far regarding the production conditions of the fiber-reinforced molded base material in which the reinforcing fibers are uniformly dispersed.

  Patent Document 1 (International Publication No. 2007/97436 pamphlet) describes a monofilament carbon fiber having a mass average fiber length of 0.5 to 10 mm as a reinforcing fiber of a fiber-reinforced thermoplastic resin molded body. Moreover, it is described that when a carbon fiber having an orientation parameter of −0.25 to 0.25 is used, a molded article having excellent mechanical properties and isotropic mechanical properties can be obtained. This fiber-reinforced thermoplastic resin molded article is obtained by (I) a step of heating and melting a thermoplastic resin contained in a molding material, (II) a step of placing the molding material in a mold, and (III) adding a molding material in the mold. And (IV) a step of solidifying the molding material in the mold, and (V) a step of opening the mold and demolding the fiber reinforced thermoplastic resin molded body.

  Various studies have been made on carbon fibers used for such fiber-reinforced molded substrates.

  Patent Document 2 (International Publication No. 2006/018139 pamphlet) is a carbon fiber in which a plurality of single fibers are converged, and a sizing agent mainly composed of a surfactant is attached to the single fibers. Further, it is described that carbon fibers for water-based process having a surface oxygen index and a contact angle with water within a predetermined range can be suitably used for producing a carbon fiber papermaking substrate, an intermediate substrate for molding, and the like.

  In Patent Document 3 (Japanese Patent Laid-Open No. 1-207499), in a wet papermaking method using an aqueous slurry containing carbon fibers, the slurry is selected from a water-soluble salt of humic acid and a water-soluble salt of humic acid-oxidized product. It is described that a uniform and good carbon fiber sheet can be obtained by adding a formation improver consisting of at least one member.

International Publication No. 2007/97436 Pamphlet International Publication No. 2006/018139 Pamphlet JP-A-1-207499

However, when a carbon fiber web useful as an intermediate of a fiber reinforced molding base material is produced using the carbon fiber bundle of Patent Document 2, the fiber dispersibility of the carbon fiber at the time of papermaking is relatively good. Further improvements have been demanded in order to make the mechanical properties and the like higher performance. Moreover, the carbon fiber web manufacturing process is not particularly mentioned, and development including a process for improving productivity has been desired. Furthermore, with only a sizing agent mainly composed of a surfactant, the sizing agent may easily fall off in the paper making process, and further improvement is desired in order to further improve the fiber dispersion state. It was.
Further, in Patent Document 3, since the humic compound is put in the slurry, the active ingredient is diffused in the slurry, and it is not sufficient to disperse the carbon fiber effectively, and further, the effect of the dispersion itself is insufficient. Met.

  An object of this invention is to provide the manufacturing method which can obtain the carbon fiber base material which is excellent in the dispersibility of the carbon fiber at the time of papermaking, and is excellent in a mechanical characteristic when it is set as a molded article.

  As a result of repeated studies, the present inventors have found that the above problem can be solved by producing a carbon fiber web using a carbon fiber bundle having water-soluble polyurethane or water-soluble polyamide adhered thereto. Reached.

That is, the present invention provides the following [1] to [20].
[1] A method for producing a carbon fiber substrate, the step (I) of charging a dispersion medium with a carbon fiber bundle to which 0.1 to 10% by mass of water-soluble polyurethane and / or water-soluble polyamide is adhered, the carbon fiber A step (II) of preparing a slurry in which the carbon fibers constituting the bundle are dispersed in the dispersion medium, a step (III) of transporting the slurry, and removing the dispersion medium from the slurry to produce a carbon fiber substrate. The manufacturing method of the carbon fiber base material which has at least 4 process of process (IV).
[2] The method for producing a carbon fiber substrate according to [1], wherein the water-soluble polyurethane and the water-soluble polyamide have a dissolution rate in water of 5 minutes or less.
[3] The method for producing a carbon fiber substrate according to [1] or [2], wherein the water-soluble polyurethane and / or water-soluble polyamide is a linear polymer containing a polyalkylene glycol unit in the molecular chain.
[4] The method for producing a carbon fiber substrate according to any one of [1] to [3], wherein the steps (I) to (IV) are performed online.
[5] The method for producing a carbon fiber substrate according to any one of [1] to [4], wherein a required time from the start of the step (I) to the start of the step (IV) is within 10 minutes.
[6] The carbon fiber substrate according to [5], wherein the height H1 of the liquid level of the slurry in the step (II) is higher than the height H2 of the liquid level of the slurry in the step (IV). Production method.
[7] The difference H1-H2 between the height H1 of the slurry level in the step (II) and the height H2 of the slurry level in the step (IV) is 0.1 to 5 m [6]. The manufacturing method of the carbon fiber base material of description.
[8] The mass content of carbon fibers in the dispersion medium in the slurry prepared in the step (II) is C1, and the mass content of carbon fibers in the dispersion medium in the slurry at the start of the step (IV) is C2. The carbon fiber substrate production method according to any one of [1] to [7], wherein C1 / C2 is in the range of 0.8 to 1.2.
[9] In the step (I), the dispersion medium and the carbon fiber bundle are continuously added, and the steps (I) to (IV) are continuously performed. The manufacturing method of the carbon fiber base material in any one.
[10] The step (I) is a step of supplying the dispersion medium and the carbon fiber to a dispersion tank, and the step (II) is a step of preparing the slurry in the dispersion tank. The manufacturing method of the carbon fiber base material in any one of 1]-[9].
[11] The method for producing a carbon fiber substrate according to [10], wherein a ratio W1 / W2 between the width W1 of the transport portion and the width W2 of the carbon fiber substrate is 0.5 to 1.0. .
[12] The method for producing a carbon fiber substrate according to any one of [1] to [11], which is performed while maintaining the liquid surface height H1 of the slurry in the step (II) substantially the same.
[13] The method for producing a carbon fiber substrate according to any one of [1] to [12], wherein the step (III) is performed by an overflow method.
[14] The method for producing a carbon fiber substrate according to any one of [1] to [13], wherein in the step (IV), the obtained carbon fiber substrate is drawn at a take-up speed of 10 m / min or more.
[15] The method for producing a carbon fiber substrate according to any one of [1] to [14], wherein the basis weight of the carbon fiber substrate is 10 to 500 g / m ² .
[16] The method for producing a carbon fiber substrate according to any one of [1] to [15], wherein the carbon fiber bundle has a length of 1 to 50 mm.
[17] The method for producing a carbon fiber substrate according to any one of [1] to [16], wherein the mass content of the carbon fiber in the slurry in the step (II) is 0.01 to 1% by mass.
[18] The carbon fiber group according to any one of [1] to [17], wherein a surface oxygen concentration ratio O / C measured by X-ray photoelectron spectroscopy of the carbon fiber is 0.05 to 0.50. A method of manufacturing the material.
[19] The method for producing a carbon fiber substrate according to any one of [1] to [18], wherein the slurry is aqueous.
[20] Electrical / electronic equipment parts, civil engineering / architectural parts, structural parts for automobiles / motorcycles, or aircraft using the carbon fiber substrate produced by the production method according to any one of [1] to [19] Parts.

  According to the present invention, it is possible to obtain a carbon fiber base material having excellent fiber dispersibility of carbon fibers at the time of paper making and excellent mechanical properties when formed into a molded product, and high mass productivity is expected.

  The method for producing a carbon fiber substrate of the present invention comprises a step (I) of charging a dispersion medium with a carbon fiber bundle having 0.1 to 10% by weight of water-soluble polyurethane and / or water-soluble polyamide attached thereto, Step (II) for preparing a slurry in which carbon fibers constituting the dispersion are dispersed in the dispersion medium, Step (III) for transporting the slurry, and Step (IV) for obtaining a carbon fiber substrate by removing the dispersion medium from the slurry At least.

  In the step (I), a carbon fiber bundle to which 0.1 to 10% by mass of water-soluble polyurethane and / or water-soluble polyamide is attached is put into a dispersion medium.

  Water-soluble polyurethane and water-soluble polyamide mean water-soluble polyurethane and polyamide, respectively. Polyurethane means a molecule having a urethane bond (—NH—COO—) in the molecule. Polyamide means a molecule having an amide bond (—NH—CO—) in the molecule, and various nylons are exemplified. Water-soluble means a property that is soluble in water. Preferable examples of the water-soluble polyurethane and the water-soluble polyamide are preferably those having a water dissolution rate of 5 minutes or less. The dissolution rate in water is measured by, for example, bringing a sample into contact with water of a film-like material having a constant thickness and area and stirring (stirring condition: 400 ml of water is prepared in a cylindrical 1000 ml beaker having a diameter of 100 mm and a thickness of 0. 05 mm, 30 mm long × 30 mm wide film-like material is added and stirred at a speed of 200 revolutions / minute), and the time until the film-like material disappears can be obtained.

  The water-soluble polyurethane and water-soluble polyamide preferably contain a polyalkylene glycol unit in the molecular chain. In addition, when using water-soluble polyurethane and water-soluble polyamide together, it is preferable that at least one contains a polyalkylene glycol unit in the molecular chain, and it is more preferable that both have this unit.

  The polyalkylene glycol unit means a repeating unit of alkylene glycol including ethylene glycol. The content of the polyalkylene glycol unit in the molecular chain constituting the water-soluble polyurethane and water-soluble polyamide is preferably 30 to 95% by mass. The content of the polyalkylene glycol unit is determined using an existing polymer analysis technique such as NMR or IR.

  The water-soluble polyurethane and the water-soluble polyamide are preferably linear polymers. The straight chain means a state having substantially no branched chain. The polymer means a high molecular weight molecule, preferably a molecular weight of 5000 to 500,000, more preferably a molecular weight of 10,000 to 300,000.

  One type of water-soluble polyurethane and water-soluble polyamide may be used alone, or two or more types may be used in combination.

  Examples of carbon fibers include PAN-based carbon fibers, pitch-based carbon fibers, cellulose-based carbon fibers, vapor-grown carbon fibers, and graphitized fibers thereof. PAN-based carbon fibers are carbon fibers made from polyacrylonitrile fibers. Pitch-based carbon fiber is carbon fiber made from petroleum tar or petroleum pitch. Cellulosic carbon fibers are carbon fibers made from viscose rayon, cellulose acetate, or the like. Vapor-grown carbon fibers are carbon fibers made from hydrocarbons or the like. Of these, PAN-based carbon fibers are preferable because they are excellent in balance between strength and elastic modulus.

  One type of carbon fiber constituting the carbon fiber web may be used, or two or more types may be used.

  The carbon fiber preferably has a surface oxygen concentration ratio O / C measured by X-ray photoelectron spectroscopy of 0.05 to 0.50, more preferably 0.06 to 0.3. Even more preferable is a value of 0.07 to 0.2. When the surface oxygen concentration ratio is 0.05 or more, the amount of polar functional groups on the surface of the carbon fiber is ensured and the affinity with the thermoplastic resin composition is increased, so that stronger adhesion can be obtained. Moreover, when the surface oxygen concentration ratio is 0.5 or less, it is possible to reduce a decrease in strength of the carbon fiber itself due to surface oxidation.

The surface oxygen concentration ratio means the ratio of the number of oxygen (O) and carbon (C) atoms on the fiber surface. The procedure for obtaining the surface oxygen concentration ratio by X-ray photoelectron spectroscopy will be described below with an example. First, carbon fibers from which the sizing agent and the like adhering to the carbon fiber surface were removed with a solvent were cut to 20 mm, spread on a copper sample support base, and then arranged using an A1Kα1,2 as an X-ray source. The chamber is maintained at 1 × 10 ⁸ Torr. The kinetic energy value (KE) of the main peak of C _1s is set to 1202 cV as a peak correction value associated with charging during measurement. C _1s peak area E. Is obtained by drawing a straight base line in the range of 1191 to 1205 eV. O _1s peak area E. Is obtained by drawing a straight base line in the range of 947 to 959 eV.

The surface oxygen concentration is calculated as an atomic ratio by using a sensitivity correction value unique to the apparatus from the ratio between the O _1s peak area and the C _1s peak area. As an X-ray photoelectron spectroscopy apparatus, a model ES-200 manufactured by Kokusai Electric Inc. can be used, and the sensitivity correction value can be calculated as 1.74.

  The means for controlling the surface oxygen concentration O / C of the carbon fiber to 0.05 to 0.5 is not particularly limited, and examples include techniques such as electric field oxidation treatment, chemical solution oxidation treatment, and gas phase oxidation treatment. Is done. Of these, electric field oxidation treatment is preferred because it is easy to handle.

  As the electrolytic solution used for the electric field oxidation treatment, aqueous solutions of the following compounds are preferably used. Inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, inorganic hydroxides such as sodium hydroxide, potassium hydroxide and barium hydroxide, inorganic metal salts such as ammonia, sodium carbonate, sodium hydrogen carbonate, sodium acetate, sodium benzoate, etc. Organic salts, and in addition to these sodium salts, potassium salts, barium salts and other metal salts, ammonium salts, and other organic compounds such as hydrazine. Among these, an inorganic acid is preferable as the electrolytic solution, and sulfuric acid and nitric acid are particularly preferably used. The degree of the electric field treatment can control O / C on the surface of the carbon fiber by setting the amount of electricity flowing in the electric field treatment.

The carbon fiber bundle may be composed of continuous reinforcing fibers or discontinuous carbon fibers, but in order to achieve a better dispersion state, the discontinuous carbon fiber bundles Preferably, chopped carbon fiber is more preferable.
Further, the number of single fibers constituting the carbon fiber bundle is not particularly limited, but is preferably 24,000 or more, and more preferably 48,000 or more from the viewpoint of productivity. The upper limit of the number of single fibers is not particularly limited, but considering the balance between dispersibility and handleability, productivity, dispersibility, and handleability can be kept good if there are about 300,000. .

  The length of the carbon fiber bundle is preferably 1 to 50 mm, and more preferably 3 to 30 mm. If it is less than 3 mm, it may be difficult to efficiently exhibit the reinforcing effect of the reinforcing fiber, and if it exceeds 30 mm, it may be difficult to maintain good dispersion. The length of the carbon fiber bundle means the length of the single fiber constituting the carbon fiber bundle. The length of the reinforcing fiber bundle in the fiber axis direction is measured with a caliper, or the single fiber is taken out from the reinforcing fiber bundle and observed with a microscope. Can be measured.

  The dispersion medium (dispersion liquid) means a medium capable of dispersing the carbon fiber bundle. Examples of the dispersion medium include so-called solvents such as water and alcohol, with water being preferred. As water, in addition to normal tap water, water such as distilled water and purified water can be used. A surfactant may be mixed in the water as necessary. Surfactants are classified into a cation type, an anion type, a nonionic type, and an amphoteric type. Of these, nonionic surfactants are preferably used, and polyoxyethylene lauryl ether is more preferably used. . The concentration of the surfactant when mixing the surfactant with water is usually 0.0001% by mass or more and 0.1% by mass or less, preferably 0.0005% by mass or more and 0.05% by mass or less.

  The input amount of the carbon fiber bundle can be adjusted in the range of usually 0.1 g or more and 10 g or less, preferably 0.3 g or more and 5 g or less as the amount of water (dispersion) 1 l. By setting it as the said range, a carbon fiber bundle can disperse | distribute efficiently to a dispersion medium and the slurry disperse | distributed uniformly can be obtained in a short time. When the carbon fiber bundle is dispersed in water (dispersion), stirring is performed as necessary.

  In step (II), a slurry is prepared in which carbon fibers constituting a carbon fiber bundle are dispersed in a dispersion medium.

The slurry refers to a suspension in which solid particles are dispersed. In the present invention, an aqueous slurry is preferable.

  The mass content of carbon fibers in the slurry (solid content concentration in the slurry) is preferably 0.01% by mass or more and 1% by mass or less, and preferably 0.03% by mass or more and 0.5% by mass or less. More preferred. Papermaking can be performed efficiently by being in the above range.

  Step (II) is usually carried out in a dispersion tank. The dispersion tank is a tank (container) that can contain slurry. When using a dispersion tank, it is preferable that the dispersion medium and the carbon fiber bundle in the step (I) are directly performed on the dispersion tank. Of course, it goes without saying that the dispersion medium and the carbon fiber bundle may be first introduced into a tank other than the dispersion tank, and the contents of the tank may be transferred to the dispersion tank to perform the step (II). A dispersion tank may be equipped with a stirring apparatus as needed.

  In step (III), the slurry obtained in step (II) is transported.

  Step (III) is usually performed in a transport section that connects a dispersion tank in which step (II) is performed and a papermaking tank in which step (IV) is performed.

  The width of the transport portion is not particularly defined, but the ratio W1 / W2 between the width W1 of the transport portion and the width W2 of the carbon fiber substrate is preferably 0.5 to 1.0, and 0.7 to 1. More preferably 0. If W1 / W2 is less than 0.5, it may take a long time for transportation in the step (III). If W1 / W2 exceeds 1.0, the dispersion state of the slurry in step (IV) may be insufficient, and the width of the slurry fluidizing portion increases when the slurry flows from the transport portion to step (IV). In addition, the slurry is loaded and the dispersion state may be insufficient. Here, the “width of the transport part” means the major axis of the cross section of the transport part. For example, when the cross section of the transport part is rectangular, it means the longer diameter. The “width of the carbon fiber substrate” means the width (one shorter than the length) of the length, width, and thickness of the carbon fiber substrate obtained in the step (IV). In addition, when each width changes with parts, it shall mean the average value.

  The width of the transport section is usually in the range of 0.1 to 2 m. The width | variety of a carbon fiber base material is 0.2-2 m normally.

  The shape of the transport part is not particularly limited as long as it can transport the slurry, and is usually tubular. If necessary, a liquid feed pump is provided in the middle of the transport section. The liquid feed pump is preferably a low shear pump such as a diaphragm pump or a snake pump.

  Step (III) may be performed by an overflow method. Thereby, it is possible to prevent the carbon fibers in the slurry to be transported from being sheared and settle and aggregate, and maintain the dispersibility in the slurry. Moreover, economical transportation is possible without using power such as a pump.

  The overflow method means a method of feeding liquid overflowing from a container (tank) to the next container (tank) using gravity. In other words, this is a system for feeding liquid without substantially using power such as a liquid feed pump.

  In the case of the overflow method, the transport section is preferably inclined. That is, when the transport section is viewed from the horizontal direction, it is preferable that the connection point between the dispersion tank and the transport section is higher than the connection point between the papermaking tank and the transport section. The inclination angle is more preferably 30 to 60 ° and 40 to 55 °. If the inclination angle is less than 30 °, it may take a long time for transportation in the step (III). When the tilt angle exceeds 60 °, when the overflow method is used, the flow rate during transportation of the slurry increases, so that excessive shear is applied to the slurry when reaching the step (IV), and the slurry in the step (IV) There is a possibility that the dispersion state becomes insufficient.

  Here, the inclination angle means the angle on the vertically lower side of the portion where the center line of the pipe of the transport section and the line parallel to the direction of gravity intersect.

  In addition, when performing process (III) by an overflow system, it is preferable that the connection part with the dispersion tank of a transport part is located in the wall surface of a dispersion tank, especially upper direction.

  In the case of the overflow method, it is preferable that the transport portion is linear, that is, a shape having no direction change point such as a curved portion or a bent portion.

  In the case of the overflow method, the height of the transport part is 60 mm or more, preferably 100 mm or more. By being 60 mm or more, the contact area between the wall surface of the transport section and the slurry can be made relatively small with respect to the amount of slurry to be transported, and re-aggregation of the dispersed fibers due to the generation of shearing force on the slurry when contacting the wall surface. Can be reduced. Here, the height of the transport section means the diameter of the transport section when the transport section is viewed from the horizontal direction. When the transport portion is rectangular (the long side is the base material width direction and the short side is the base material thickness direction), the length of the short side corresponds to the “height of the transport portion”. Although the upper limit of the height of a transport part is not specifically limited, Usually, it is 500 mm or less. If there is a difference in the height of the transport section depending on the part, the average value is meant.

  The shape of the transport section will be described with reference to FIGS. 1-8, the process (I) and the process (II) are performed in a dispersion tank, the process (IV) is performed in a papermaking tank, and the process (III) is connected to the dispersion tank and the papermaking tank. It is a figure which shows typically the positioning seen from the horizontal direction of a dispersion | distribution tank, a papermaking tank, and a transport part in the case of performing in a transport part. The transport part 13 in FIGS. 1 to 6 and FIG. 8 has a linear shape.

  The inclination angle of the transport portion means an angle r formed by the center line q of the transport portion 13 and the line P extending in the direction of gravity in the vertical direction in each figure. The transport section 13 in FIGS. 1, 5, and 6 is inclined from the dispersion tank 11 toward the papermaking tank 12, and the inclination angle is 30 to 60 °. The transport unit 13 in FIG. 2 connects the dispersion tank 11 and the papermaking tank 12 horizontally, and the inclination angle is approximately 90 °. The transport section 13 in FIG. 3 is inclined from the dispersion tank 11 toward the papermaking tank 12, and the inclination angle is 30 to 60 °. The transport section 13 in FIG. 4 connects the dispersion tank 11 and the papermaking tank 12 in the direction of gravity, and the inclination angle is approximately 0 °. The transport section 13 in FIG. 8 also has an inclination angle of approximately 0 ° as in FIG. 4 and includes a pump 25 in the middle of the transport section 13.

  In FIG. 1, FIG. 5 and FIG. 6, the connection portion 14 of the transport portion 13 with the dispersion tank 11 is located above the wall surface of the dispersion tank 11. Therefore, if the dispersion tank, papermaking tank, and transport section are positioned as shown in FIG. 1, step (III) can be performed by the overflow method.

  In step (IV), the dispersion medium is removed from the slurry to obtain a carbon fiber substrate.

  Step (IV) is usually carried out in a papermaking tank. The papermaking tank is a tank (container) that can contain slurry and has a papermaking surface capable of sucking moisture. The papermaking surface is generally provided near the bottom surface, and the material is exemplified by a mesh sheet.

  In this invention, the carbon fiber base material obtained in process (IV) can be taken up. The carbon fiber substrate can be taken up by being wound on a roll. The take-up speed is preferably 10 m / min or more. The upper limit of the take-up speed is usually 100 m / min or less.

  When the mass content of carbon fiber in the slurry prepared in step (II) is C1, and the mass content of carbon fiber in the slurry at the start of step (IV) is C2, C1 / C2 is 0.00. The range is preferably 8 to 1.2, more preferably 0.9 to 1.1. When C1 / C2 is less than 0.8, in order to increase C2, it is necessary to remove only the dispersion medium or to introduce only reinforcing fibers, which complicates the process and that the dispersion state of the slurry is insufficient. There is a risk. If C1 / C2 exceeds 1.2, the dispersed state of the slurry in step (IV) may be insufficient.

  Step (I) to step (IV) are preferably performed online. Online is a system in which each process is continuously performed, and is an antonym of offline. That is, online means a process in which each process is performed as a series of flows, and is different from a process in which each process is independent. A carbon fiber base material can be obtained in a short time by carrying out steps (I) to (IV) on-line.

  The level H1 of the slurry liquid level in the step (II) is preferably higher than the height H2 of the slurry liquid level in the step (IV). “The height of the liquid level of the slurry” means the position of the liquid level when the slurry is viewed from the horizontal direction. “At a high position” means that when the height of two liquid levels is expressed as a measured value as a distance from a reference located vertically below the height, one height is higher than the other. That is, it means that one of the two liquid surface heights is located vertically below the other.

  Among them, the difference H1-H2 between the height H1 of the slurry level in the step (II) and the height H2 of the slurry level in the step (IV) is preferably 0.1 to 5 m. More preferably, it is 0.5-2m. If it is less than 0.1 m, it may take a long time for transportation in the step (III). On the other hand, if it exceeds 5 m, the dispersion state of the slurry in step (IV) may be insufficient.

  The height H1 of the liquid level of the slurry in the step (II) and the height H2 of the liquid level of the slurry in the step (IV) will be described with reference to FIGS. The liquid surface height H1 of the slurry (shaded portion) in the dispersion tank 11 is represented by a distance H1 of the liquid surface position B with respect to the reference A positioned vertically below H1 and H2. The liquid surface height H2 of the slurry (shaded portion) in the papermaking tank 12 is represented by a distance H2 of the liquid surface position C with respect to the liquid surface reference A. In order to maintain the difference between the heights H1 and H2 of the liquid level of the slurry, as shown in FIGS. 1, 3, 4 and 7, the dispersion tank 11 and the papermaking tank 12 are shifted with respect to the direction of gravity. 2, 5 and 6, as shown in FIG. 2, FIG. 5 and FIG. 6, if the height of the liquid level of the slurry in each tank is adjusted according to the amount of slurry and the size of the tank, the dispersion The positions in the gravity direction of the tank 11 and the papermaking tank 12 may be horizontal.

  In order to maintain the height H1 of the liquid level of the slurry in the step (II) at a position higher than the height H2 of the liquid level of the slurry in the step (IV), for example, the step (II) is a dispersion tank and the step (IV ) In a papermaking tank, it is preferable to install these two tanks so that the position of the bottom surface of the dispersion tank is located vertically above the position of the top surface of the papermaking tank.

  The time required from step (I) to the start of step (IV) is preferably within 10 minutes. If it exceeds 10 minutes, depending on the type of carbon fiber, the carbon fiber dispersed in the slurry may be re-agglomerated. The lower limit of the time required from the step (I) to the start of the step (IV) is not particularly limited, but is usually 1 minute or more.

In the step (I), it is preferable that the dispersion medium and the carbon fiber bundle are continuously charged and the steps (I) to (IV) are continuously performed. Thereby, a carbon fiber base material can be obtained in a shorter time. In addition, if a large amount of slurry is added at once, a part of the slurry may take a long time to be paper-made, and the dispersion state may be deteriorated. Can be made in small amounts efficiently while maintaining the dispersed state. “Continuously input” and “Continuously execute” means continuous input, and sequentially or continuously execute steps (II) to (IV) for the raw materials to be administered in step (I). Means that. In other words, in a series of steps, it means a state in which the supply of the raw material of the dispersed slurry and the supply of the slurry are continued, and it means a process that considers mass production rather than the process of producing a certain amount of slurry first. Examples of the method of continuously charging and executing include a method other than the batch method, a method of charging at a constant speed, and a method of charging a substantially constant amount at a predetermined interval. Examples of the conditions for feeding at a constant rate include conditions for feeding the dispersion medium at 1 × 10 ³ to 1 × 10 ⁷ g / min and the carbon fiber bundle at 0.1 to 1 × 10 ⁵ g / min. As conditions for introducing a substantially constant amount at a predetermined interval, 1 × 10 ³ to 1 × 10 ⁷ g of the dispersion medium and 0.1 to 1 × 10 ⁵ g of the carbon fiber bundle are added every 1 to 5 minutes. The conditions to do are illustrated.

  It is preferable that the height H1 of the liquid level of the slurry in the step (II) is maintained at substantially the same height throughout the step (II). Particularly when the steps (I) to (IV) are continuously performed, the level H1 of the liquid level of the slurry in the step (II) is kept substantially the same throughout the step (II). It is preferable.

  “Maintains substantially the same height throughout the step (II)” means that the height variation is within 100 mm, preferably within 50 mm, more preferably the variation during the step (II). It means not (0 mm). In order to keep the height H1 of the liquid level of the slurry in the step (II) substantially the same throughout the step (II), it is preferable to continuously perform the step (I). For example, when the step (II) is performed in a dispersion tank, it is preferable that the dispersion medium and the carbon fiber are continuously supplied to the dispersion tank, and the steps (I) to (IV) are continuously performed. .

Basis weight of the carbon fiber base material is preferably 10 to 500 g / m ^2, and more preferably 50 to 300 g / m ^2. If it is less than 10 g / m ^2, it may cause problems in handling such as tearing of the substrate, and if it exceeds 500 g / m ² , it may take a long time to dry the substrate, resulting in problems in subsequent processes. is there.

  The carbon fiber substrate obtained in the present invention can be used as a fiber reinforced molded substrate containing a thermoplastic resin or a thermosetting resin. The fiber reinforced molding base material can be used for various applications such as electrical / electronic equipment parts, civil engineering / architectural parts, automobile / motorcycle parts, aircraft parts, etc., and is preferably used for electronic equipment parts, automotive structural parts. It is done.

Production Example 1 (A1: PAN-based carbon fiber)
Using a copolymer composed of 99.4 mol% of acrylonitrile (AN) and 0.6 mol% of methacrylic acid, an acrylic fiber bundle having a single fiber denier 1d and a filament number of 12,000 was obtained by a dry and wet spinning method. The obtained acrylic fiber bundle was heated at a draw ratio of 1.05 in air at a temperature of 240 to 280 ° C., converted to flame-resistant fiber, and then heated in a temperature range of 300 to 900 ° C. in a nitrogen atmosphere. After 10% stretching at a rate of 200 ° C./min, the temperature was raised to a temperature of 1,300 ° C. and baked. This carbon fiber bundle is an aqueous solution containing sulfuric acid as an electrolyte, and is subjected to an electrolytic surface treatment of 3 coulombs per gram of carbon fiber, further provided with a sizing agent by an immersion method, and dried in heated air at a temperature of 120 ° C. Fiber was obtained.
Total number of filaments 12,000 Single fiber diameter 7μm
Mass per unit length 0.8g / m
Specific gravity 1.8g / cm ³
Tensile strength (Note 1) 4.2 GPa
Tensile modulus (Note 2) 230 GPa
Sizing type Water-soluble polyurethane resin ("Texanol" PE-10F, manufactured by Yoshimura Oil Chemical Co., Ltd.)
Polyethylene glycol unit (molecular weight 4000)
Sizing adhesion amount (Note 3) 1.5% by mass
O / C (Note 4) 0.10

Production Example 2 (A2: PAN-based carbon fiber)
Using a copolymer composed of 99.4 mol% of acrylonitrile (AN) and 0.6 mol% of methacrylic acid, an acrylic fiber bundle having a single fiber denier 1d and a filament number of 12,000 was obtained by a dry and wet spinning method. The obtained acrylic fiber bundle was heated at a draw ratio of 1.05 in air at a temperature of 240 to 280 ° C., converted to flame-resistant fiber, and then heated in a temperature range of 300 to 900 ° C. in a nitrogen atmosphere. After 10% stretching at a rate of 200 ° C./min, the temperature was raised to a temperature of 1,300 ° C. and baked. Further, a sizing agent was applied by an immersion method and dried in heated air at a temperature of 120 ° C. to obtain a PAN-based carbon fiber.
Total number of filaments 12,000 Single fiber diameter 7μm
Mass per unit length 0.8g / m
Specific gravity 1.8g / cm ³
Tensile strength (Note 1) 4.2 GPa
Tensile modulus (Note 2) 230 GPa
Sizing type Water-soluble polyurethane resin ("Texanol" PE-10F, manufactured by Yoshimura Oil Chemical Co., Ltd.)
Polyethylene glycol unit (molecular weight 4000)
Sizing adhesion amount (Note 3) 1.5% by mass
O / C (Note 4) 0.05

Production Example 3 (A3: PAN-based carbon fiber)
Using a copolymer composed of 99.4 mol% of acrylonitrile (AN) and 0.6 mol% of methacrylic acid, an acrylic fiber bundle having a single fiber denier 1d and a filament number of 12,000 was obtained by a dry and wet spinning method. The obtained acrylic fiber bundle was heated at a draw ratio of 1.05 in air at a temperature of 240 to 280 ° C., converted to flame-resistant fiber, and then heated in a temperature range of 300 to 900 ° C. in a nitrogen atmosphere. After 10% stretching at a rate of 200 ° C./min, the temperature was raised to a temperature of 1,300 ° C. and baked. This carbon fiber bundle is an aqueous solution containing sulfuric acid as an electrolyte, and is subjected to an electrolytic surface treatment of 3 coulombs per gram of carbon fiber, further provided with a sizing agent by an immersion method, and dried in heated air at a temperature of 120 ° C. Fiber was obtained.
Total number of filaments 12,000 Single fiber diameter 7μm
Mass per unit length 0.8g / m
Specific gravity 1.8g / cm ³
Tensile strength (Note 1) 4.2 GPa
Tensile modulus (Note 2) 230 GPa
Sizing type Water-soluble polyurethane resin ("Melpol" F-220 manufactured by Sanyo Chemical Co., Ltd.)
Polyethylene glycol unit (molecular weight 20,000)
Sizing adhesion amount (Note 3) 1.5% by mass
O / C (Note 4) 0.10

Production Example 4 (A4: PAN-based carbon fiber)
Using a copolymer composed of 99.4 mol% of acrylonitrile (AN) and 0.6 mol% of methacrylic acid, an acrylic fiber bundle having a single fiber denier 1d and a filament number of 12,000 was obtained by a dry and wet spinning method. The obtained acrylic fiber bundle was heated at a draw ratio of 1.05 in air at a temperature of 240 to 280 ° C., converted to flame-resistant fiber, and then heated in a temperature range of 300 to 900 ° C. in a nitrogen atmosphere. After 10% stretching at a rate of 200 ° C./min, the temperature was raised to a temperature of 1,300 ° C. and baked. This carbon fiber bundle is an aqueous solution containing sulfuric acid as an electrolyte, and is subjected to an electrolytic surface treatment of 3 coulombs per gram of carbon fiber, further provided with a sizing agent by an immersion method, and dried in heated air at a temperature of 120 ° C. Fiber was obtained.
Total number of filaments 12,000 Single fiber diameter 7μm
Mass per unit length 0.8g / m
Specific gravity 1.8g / cm ³
Tensile strength (Note 1) 4.2 GPa
Tensile modulus (Note 2) 230 GPa
Sizing type polyurethane resin (Daiichi Kogyo Seiyaku "Superflex" 840)
Sizing adhesion amount (Note 3) 1.5% by mass
O / C (Note 4) 0.10

Production Example 5 (A5: PAN-based carbon fiber)
Using a copolymer composed of 99.4 mol% of acrylonitrile (AN) and 0.6 mol% of methacrylic acid, an acrylic fiber bundle having a single fiber denier 1d and a filament number of 12,000 was obtained by a dry and wet spinning method. The obtained acrylic fiber bundle was heated at a draw ratio of 1.05 in air at a temperature of 240 to 280 ° C., converted to flame-resistant fiber, and then heated in a temperature range of 300 to 900 ° C. in a nitrogen atmosphere. After 10% stretching at a rate of 200 ° C./min, the temperature was raised to a temperature of 1,300 ° C. and baked. This carbon fiber bundle is an aqueous solution containing sulfuric acid as an electrolyte, and is subjected to an electrolytic surface treatment of 3 coulombs per gram of carbon fiber, further provided with a sizing agent by an immersion method, and dried in heated air at a temperature of 120 ° C. Fiber was obtained.
Total number of filaments 12,000 Single fiber diameter 7μm
Mass per unit length 0.8g / m
Specific gravity 1.8g / cm ³
Tensile strength (Note 1) 4.2 GPa
Tensile modulus (Note 2) 230 GPa
Sizing type Water-soluble polyurethane resin ("Texanol" PE-10F, manufactured by Yoshimura Oil Chemical Co., Ltd.)
Polyethylene glycol unit (molecular weight 4000)
Sizing adhesion amount (Note 3) 15% by mass
O / C (Note 4) 0.10

Production Example 6 (A6: PAN-based carbon fiber)
Using a copolymer composed of 99.4 mol% of acrylonitrile (AN) and 0.6 mol% of methacrylic acid, an acrylic fiber bundle having a single fiber denier 1d and a filament number of 12,000 was obtained by a dry and wet spinning method. The obtained acrylic fiber bundle was heated at a draw ratio of 1.05 in air at a temperature of 240 to 280 ° C., converted to flame-resistant fiber, and then heated in a temperature range of 300 to 900 ° C. in a nitrogen atmosphere. After 10% stretching at a rate of 200 ° C./min, the temperature was raised to a temperature of 1,300 ° C. and baked. This carbon fiber bundle is an aqueous solution containing sulfuric acid as an electrolyte, and is subjected to an electrolytic surface treatment of 3 coulombs per gram of carbon fiber, further provided with a sizing agent by an immersion method, and dried in heated air at a temperature of 120 ° C. Fiber was obtained.
Total number of filaments 12,000 Single fiber diameter 7μm
Mass per unit length 0.8g / m
Specific gravity 1.8g / cm ³
Tensile strength (Note 1) 4.2 GPa
Tensile modulus (Note 2) 230 GPa
Sizing type Water-soluble polyamide resin (A-774 manufactured by Matsumoto Yushi Co., Ltd.)
Polyethylene glycol unit (molecular weight 4000)
Sizing adhesion amount (Note 3) 1.5% by mass
O / C (Note 4) 0.10

Production Example 3 (F: acid-modified polypropylene resin film)
“Admer” (registered trademark) QE510 (specific gravity 0.91, melting point 160 ° C.) manufactured by Mitsui Chemicals, Inc. is press-molded at a temperature of 200 ° C. and a pressure of 20 Mpa for 1 minute to produce an acid-modified polypropylene resin film F having a thickness of 50 μm. did.

(Note 3) Measurement conditions for the amount of sizing agent attached As a sample, about 5 g of carbon fiber to which the sizing agent was attached was collected and put into a heat-resistant container. The container was then dried at 120 ° C. for 3 hours. After being cooled to room temperature while taking care in a desiccator so as not to absorb moisture, the weighed mass was defined as W ₁ (g). Subsequently, the whole container was heated in a nitrogen atmosphere at 450 ° C. for 15 minutes, and then cooled to room temperature while taking care not to absorb moisture in a desiccator, and the weighed mass was defined as W ₂ (g). Through the above treatment, the amount of the sizing agent attached to the carbon fiber was determined by the following equation.
(Formula) Adhering amount (% by mass) = 100 × {(W ₁ −W ₂ ) / W ₂ }
In addition, the measurement was performed 3 times and the average value was employ | adopted as adhesion amount.

(Note 4) O / C measurement It was determined by X-ray photoelectron spectroscopy according to the following procedure. First, carbon fibers from which deposits and the like were removed from the carbon fiber surface with a solvent were cut into 20 mm, and spread on a copper sample support table. A1Kα1 and 2 were used as the X-ray source, and the inside of the sample chamber was kept at 1 × 10 ⁸ Torr. The kinetic energy value (KE) of the main peak of C _1s was adjusted to 1202 cV as a peak correction value associated with charging during measurement. C _1s peak area E. It was obtained by drawing a straight base line in the range of 1191 to 1205 eV. O _1s peak area, E. As a linear base line in the range of 947 to 959 eV.

The surface oxygen concentration was calculated as an atomic number ratio from the ratio of the O _1s peak area to the C _1s peak area using a sensitivity correction value unique to the apparatus. As an X-ray photoelectron spectroscopy apparatus, Kokusai Denki Co., Ltd. model ES-200 was used, and the sensitivity correction value was set to 1.74.

-Evaluation of dispersed state of reinforcing fiber The web was cut into a square shape of 50 mm x 50 mm from an arbitrary part of the carbon fiber web obtained by papermaking and observed with a microscope. A state where 10 or more carbon fibers were bundled, that is, the number of carbon fiber bundles with insufficient dispersion was measured. This procedure is performed 20 times, and with the average value, less than 1 carbon fiber bundle with insufficient dispersion is double-round, and 1 to less than 5 carbon fiber bundles with insufficient dispersion. ◯, 5 to less than 10 carbon fiber bundles with insufficient dispersion were evaluated as Δ, and 10 or more carbon fiber bundles with insufficient dispersion were evaluated as x.

-Evaluation of molded product mechanical properties A carbon fiber web obtained by papermaking was cut into 200 mm x 200 mm and dried at 120 ° C for 1 hour. Three layers of the carbon fiber web after drying and the acid-modified polypropylene resin film F were laminated so as to be resin film F / carbon fiber web / resin film F. This laminate was press-molded at a temperature of 200 ° C. and a pressure of 30 MPa for 5 minutes, and cooled to 50 ° C. while maintaining the pressure to produce a carbon fiber reinforced resin sheet having a thickness of 0.12 mm. Eight of these resin sheets were laminated, press-molded at a temperature of 200 ° C. and a pressure of 30 MPa for 5 minutes, and cooled to 50 ° C. while maintaining the pressure to obtain a carbon fiber reinforced resin molded product having a thickness of 1.0 mm. Using the obtained molded product, the bending strength was evaluated by n = 10 according to ISO 178 method (1993). In addition, the evaluation result of bending strength was described as a relative value with Example 1 as 100.

-Dissolution rate in water A film sample having a length of 30 mm x a width of 30 mm and a thickness of 0.05 mm was used as an evaluation sample. The film-like sample was formed into a film having the above shape by heating and pressing each component. 400 ml of water was prepared in a cylindrical 1000 ml beaker having a diameter of 100 mm, a film sample was added, and the mixture was stirred at a speed of 200 revolutions / minute. The time until the film-like sample disappeared was visually confirmed, and the time required for the disappearance of the film-like sample was taken as the dissolution rate.

Example 1
Carbon fiber A1 was cut into 6.4 mm with a cartridge cutter to obtain chopped carbon fiber (A1-1).

  1.5 mass% of water-soluble polyurethane was made to adhere to chopped carbon fiber A1-1. A carbon fiber substrate was produced from the carbon fiber bundle to which such water-soluble polyurethane was adhered.

  For production, an apparatus 03 shown in FIG. 9 was used. The production apparatus 03 includes a cylindrical container having a diameter of 300 mm as the dispersion tank 11, a papermaking tank 12 having a mesh conveyor 21 having a papermaking surface 19 having a width of 200 mm at the bottom, and a straight line connecting the dispersion tank 11 and the papermaking tank 12. The conveyor 22 (inclination angle 45 degrees) 13 and the mesh conveyor 21 are connected, and the conveyor 22 carbon fiber web which can convey the carbon fiber web (carbon fiber base material) 20 is provided. The dispersion tank 11 has a concave shape with two openings (a wide-mouth opening 23 and a narrow-mouth opening 24) on the upper surface, and the stirrer 16 is installed on the wide-mouth opening 23 side. From 24, the carbon fiber bundle 17 and the dispersion liquid (dispersion medium) 18 can be charged.

A dispersion liquid having a concentration of 0.1% by mass composed of water and a surfactant (manufactured by Nacalai Tex Corporation, polyoxyethylene lauryl ether (trade name)) was prepared. The introduction of the dispersion and the fiber bundle into the dispersion tank was started (step (I)). While manufacturing, continuously adjusting the input amount so that the carbon fiber concentration in the slurry in the dispersion tank becomes a constant concentration and the height H1 of the liquid level of the slurry in the dispersion tank becomes constant. The above dispersion and chopped carbon fiber were continuously charged. Stirring was started simultaneously with the start of charging of the raw material into the container to prepare a slurry (step (II)). When 40 liters of slurry was collected, the opening cock at the bottom of the container was adjusted to open and poured into the papermaking tank via the transport section (step (III)). At this time, the height H1 of the slurry liquid level in the dispersion tank was 50 cm higher than the slurry liquid level H2 in the papermaking tank. Water was sucked from the slurry and taken up at a speed of 10 m / min to continuously obtain a carbon fiber web having a width of 200 mm (step (IV)). The basis weight of the carbon fiber web was 20 g / m ² .

  The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

(Example 2)
Carbon fiber A3 was cut into 6.4 mm with a cartridge cutter to obtain chopped carbon fiber (A3-1).

The same procedure as in Example 1 was performed except that chopped carbon fiber A3-1 was used instead of chopped carbon fiber A1-1. The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.
(Example 3)

  Carbon fiber A6 was cut into 6.4 mm with a cartridge cutter to obtain chopped carbon fiber (A6-1).

  The same procedure as in Example 1 was performed except that chopped carbon fiber A6-1 was used instead of chopped carbon fiber A1-1 and water-soluble polyamide was used instead of water-soluble polyurethane. The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

Example 4
The same material as in Example 1 was used for overflow. The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

(Example 5)
Carbon fiber A2 was cut to 6.4 mm with a cartridge cutter to obtain chopped carbon fiber (A2-1).
The same procedure as in Example 1 was performed except that chopped carbon fiber A2-1 was used instead of chopped carbon fiber A1-1. The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

(Comparative Example 1)
In Example 1, it carried out like Example 1 except having used chopped carbon fiber A-1 as it was (no water-soluble polyurethane was made to adhere). The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

(Comparative Example 2)
In Example 1, it carried out like Example 1 except having used polyurethane (insoluble in water) instead of water-soluble polyurethane. The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

(Comparative Example 3)
In Example 1, it carried out like Example 1 except the adhesion amount of water-soluble polyurethane having been 15 mass%. The execution conditions and the evaluation results of the obtained carbon fiber web are shown in Table 1.

  As is clear from Table 1, by using a carbon fiber bundle to which water-soluble polyurethane or water-soluble polyamide was attached in an amount of 0.1 to 10% by mass, a carbon fiber web excellent in dispersion state could be obtained. .

  It has been clarified that the use of fibers having a high O / C makes it possible to further improve the mechanical properties of the molded article of the carbon fiber web (see Examples 1, 2, and 5).

It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a figure which shows typically an example of the positioning seen from the horizontal direction of a dispersion tank, a papermaking tank, and a transport part. It is a horizontal sectional view which shows an example of the manufacturing apparatus of a carbon fiber base material.

Explanation of symbols

03 Carbon fiber substrate manufacturing apparatus 11 Dispersion tank 12 Papermaking tank 13 Transport part 14 Connection part 16 of transport part and dispersion tank Stirrer 17 Chopped carbon fiber (carbon fiber bundle)
18 Dispersion (dispersion medium)
19 Paper surface 20 Carbon fiber web (carbon fiber substrate)
21 Mesh conveyor 22 Conveyor 23 Wide opening 24 Narrow opening 25 Pump H1 Slurry level H2 in step (II) Slurry level A in step (IV) Standard B In step (II) Slurry level C Slurry level p in step (IV) Line q parallel to the direction of gravity Angle formed by the center line rp and q of the transport section on the vertically lower side

Claims (20)

  A method for producing a carbon fiber substrate, wherein a carbon fiber bundle having 0.1 to 10% by mass of water-soluble polyurethane and / or water-soluble polyamide is introduced into a dispersion medium (I), and the carbon fiber bundle is constituted A step (II) of preparing a slurry in which carbon fibers to be dispersed are dispersed in the dispersion medium, a step (III) of transporting the slurry, and a step of removing the dispersion medium from the slurry to produce a carbon fiber substrate (IV) The manufacturing method of the carbon fiber base material which has at least 4 process of 4).   The method for producing a carbon fiber substrate according to claim 1, wherein the water-soluble polyurethane and the water-soluble polyamide have a dissolution rate in water of 5 minutes or less.   The method for producing a carbon fiber substrate according to claim 1 or 2, wherein the water-soluble polyurethane and / or water-soluble polyamide is a linear polymer containing a polyalkylene glycol unit in a molecular chain.   The manufacturing method of the carbon fiber base material in any one of Claims 1-3 which implements from the said process (I) to the said process (IV) online.   The manufacturing method of the carbon fiber base material in any one of Claims 1-4 which makes the required time from the start of the said process (I) to the start of the said process (IV) within 10 minutes.   The manufacturing method of the carbon fiber base material of Claim 5 which exists in the position where the height H1 of the liquid level of the slurry in the said process (II) is higher than the height H2 of the liquid level of the slurry in the process (IV).   The difference H1-H2 between the height H1 of the liquid level of the slurry in the step (II) and the height H2 of the liquid level of the slurry in the step (IV) is 0.1 to 5 m. A method for producing a carbon fiber substrate.   When the mass content of carbon fibers in the dispersion medium in the slurry prepared in the step (II) is C1, and the mass content of carbon fibers in the dispersion medium in the slurry at the start of the step (IV) is C2. Furthermore, the manufacturing method of the carbon fiber base material in any one of Claims 1-7 which makes C1 / C2 into the range of 0.8-1.2.   The dispersion medium and the carbon fiber bundle are continuously charged in the step (I), and the steps (I) to (IV) are continuously performed. A method for producing a carbon fiber substrate.   The step (I) is a step of supplying the dispersion medium and the carbon fiber to a dispersion vessel, and the step (II) is a step of preparing the slurry in the dispersion vessel. The method for producing a carbon fiber substrate according to any one of 9.   The manufacturing method of the carbon fiber base material of Claim 10 whose ratio W1 / W2 of the width W1 of the said transport part and the width W2 of the said carbon fiber base material is 0.5-1.0.   The manufacturing method of the carbon fiber base material in any one of Claims 1-11 performed while maintaining the height H1 of the liquid level of the slurry in the said process (II) substantially the same height.   The manufacturing method of the carbon fiber base material in any one of Claims 1-12 which performs the said process (III) by an overflow system.   The method for producing a carbon fiber substrate according to any one of claims 1 to 13, wherein in the step (IV), the obtained carbon fiber substrate is drawn at a take-up speed of 10 m / min or more. The manufacturing method of the carbon fiber base material in any one of Claims 1-14 whose fabric weights of the said carbon fiber base material are 10-500 g / m < ² >.   The manufacturing method of the carbon fiber base material in any one of Claims 1-15 whose length of the said carbon fiber bundle is 1-50 mm.   The manufacturing method of the carbon fiber base material in any one of Claims 1-16 whose mass content of the carbon fiber in the slurry in the said process (II) is 0.01-1 mass%.   The manufacturing method of the carbon fiber base material in any one of Claims 1-17 whose surface oxygen concentration ratio O / C measured by the X ray photoelectron spectroscopy of the said carbon fiber is 0.05-0.50.   The method for producing a carbon fiber substrate according to any one of claims 1 to 18, wherein the slurry is aqueous.   An electrical / electronic device part, a civil / architectural part, a structural part for an automobile / motorcycle, or an aircraft part using the carbon fiber base material produced by the production method according to claim 1.

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