JP2008248411A - Surface-treating apparatus for carbon fiber strand - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treating apparatus for a carbon fiber strand, which is capable of obtaining a carbon fiber having a uniformly electrolytically oxidized surface. <P>SOLUTION: This surface-treating apparatus for a carbon fiber strand has an inner vessel circulating an electrolyte from lower direction to upper direction, and overflowing the electrolyte liquid from its upper end; an electrolysis vessel equipped with a plurality of the inner vessels in series at a prescribed interval in its inside and also consisting of an outer vessel for receiving the electrolyte liquid overflown from each of the inner vessels; electrodes inserted into each of the inner vessels; rectifying plates inserted horizontally into each of the inner vessels above the electrode and formed with many penetrated holes in thickness direction; a liquid electrolyte tank receiving and storing by the liquid electrolyte in the outer vessel; and a pump for sending out the liquid electrolyte in the tank to the inner vessel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface treatment apparatus for carbon fiber strands that performs electrolytic oxidation treatment on the surface of carbon fibers by immersing the carbon fiber strands in an electrolytic solution of an electrolytic cell equipped with electrodes.

  Carbon fiber composite materials reinforced with carbon fiber made of thermosetting resin or thermoplastic resin have features such as high tensile strength and tensile modulus, and excellent heat resistance and fatigue properties. -Widely used in fields such as space.

  The carbon fiber is manufactured by heating a raw material fiber such as an acrylic fiber to 200 to 300 ° C. in the air to form a flame resistant fiber, and then firing at 1000 ° C. or higher in an inert gas atmosphere.

  Mechanical properties such as strength and elastic modulus of the carbon fiber composite material are greatly influenced by the affinity and adhesion between the carbon fiber and the matrix resin. Therefore, after passing through the flameproofing step and the carbonization step, an oxidation treatment for introducing oxygen-containing functional groups into the surface of the carbon fiber is generally performed for the purpose of increasing the affinity with the matrix resin.

  As the oxidation treatment of the carbon fiber surface, it is known to treat by a method such as chemical liquid oxidation / electrolytic oxidation or gas phase oxidation in a liquid phase. Among these surface treatments, electrolytic oxidation treatment in a liquid phase has been widely adopted because of high productivity and uniform treatment. The liquid phase electrolytic oxidation treatment is a treatment method in which carbon fiber is electrolytically oxidized by applying a voltage between the carbon fiber and an electrode in an aqueous electrolyte solution.

  Carbon fibers are manufactured in a bundle shape of about 1,000 to 80,000 in the manufacturing process. The surface treatment of the carbon fiber is performed by immersing a number of strands running in parallel in the electrolyte. Various types of electrolytic cells have been developed in the past. For example, the electrolytic solution overflows from the electrolytic cell, and the carbon fiber is allowed to pass where the liquid level is slightly higher than the side wall of the electrolytic cell. Therefore, an overflow type electrolytic cell for surface treatment has been conventionally used (for example, see Patent Document 1). In this electrolytic cell, there is no need to use a guide roller for immersing the carbon fiber in the electrolytic solution or pulling it up from the electrolytic solution. ing. On the other hand, since it is necessary to always supply the electrolytic solution to the electrolytic cell to overflow, the surface oxidation treatment state is easily affected by the flow rate of the electrolytic solution. In the case where a large number of strands are subjected to surface treatment at the same time, there is a problem that unevenness occurs in the surface oxidation state between the strands.

When carbon fiber with non-uniform surface oxidation treatment is blended with the matrix resin, the adhesion between the part of the carbon fiber surface with few functional groups and the matrix resin is insufficient, and a composite material with high composite properties can be obtained. Absent.
JP 58-115123 A (FIG. 1)

  An object of the present invention is to provide a surface treatment apparatus for carbon fiber strands, in which carbon fiber surfaces are uniformly oxidized between a large number of carbon fiber strands, and carbon fibers exhibiting high composite properties when obtained in a matrix resin are obtained. There is.

  As a result of intensive studies, the inventor has inserted a rectifying plate in the electrolytic cell, so that the flow rate of the electrolyte supplied to the strands is constant between the strands, and variations in the surface treatment state between the strands are suppressed. I found out. Furthermore, the present inventors have found that a carbon fiber strand having a more uniform surface treatment state can be obtained by dividing the current plate into a plurality of sections and changing the aperture ratio for each section, thereby completing the present invention.

  That is, the present invention that solves the above problems is described below.

  [1] An inner tank for flowing an electrolyte solution from below to above and overflowing the electrolyte solution from the upper end, and a plurality of the inner tanks arranged in series with a predetermined interval therebetween, and each inner tank An electrolytic tank composed of an outer tank that receives the electrolytic solution overflowed from the electrolyte, an electrolytic solution tank that receives and stores the electrolytic solution in the outer tank, and the electrolytic solution in the electrolytic solution tank in the inner tank. A carbon having a pump to be sent out, an electrode inserted in the lower side of the inner tank, and a current plate horizontally inserted in the inner tank above the electrode and having a plurality of through holes formed in the thickness direction. Surface treatment equipment for fiber strands.

  [2] The shape of the inner tank is a rectangular tube shape whose upper end is opened and whose lower end is closed by the lower wall, and an inflow port for receiving an electrolyte is formed at the center of the lower wall [1] The surface treatment apparatus for carbon fiber strands as described in 2.

  [3] The carbon fiber according to [2], wherein a diameter of the inlet in a direction perpendicular to the row direction of the inner tank is 15 to 80% of an inner tank inner width in a direction perpendicular to the row direction of the inner tank. Surface treatment equipment for strands.

  [4] The current plate is divided into three sections of first to third sections having different opening ratios from the center of the inner tank to the outside in a direction perpendicular to the row direction of the inner tank, and the opening of the section The surface treatment apparatus for carbon fiber strands according to [1], wherein the rates are in the order of 0.3% to less than 9%, 9% to less than 15%, and 15% to 60%.

  [5] The surface treatment apparatus for carbon fiber strands according to [4], wherein the areas of the first to third sections in the horizontal plane of the current plate are 5 to 10%, 0 to 20%, and 70 to 90%, respectively.

  In the surface treatment apparatus of the present invention, a rectifying plate is inserted in an electrolytic cell inner tank in which an electrolytic solution flows from below to above. For this reason, the electrolyte rises from the rectifying plate installation location to the upper end side of the inner tank at a uniform flow rate, and overflows from the upper end of the inner tank to the outer tank. According to the processing apparatus of the present invention, since the overflow height can be made uniform in the machine width direction of the apparatus, the surface oxidation treatment state of the carbon fiber strands is suppressed from variation among the strands. According to the present invention, since a large number of carbon fiber strands can be uniformly surface-treated at the same time, a carbon fiber composite material having high mechanical strength can be obtained by blending this carbon fiber with a thermosetting resin or a thermosetting resin. Can be obtained.

  A schematic configuration diagram of an example of a surface treatment apparatus used in the present invention is shown in FIG.

  In FIG. 1, 100 is a surface treatment apparatus and 1 is an electrolytic cell. The electrolytic cell 1 includes a plurality of inner tanks 3 and an outer tank 13.

  FIG. 2 is a plan view of the inner tank 3, FIG. 3 is a side sectional view, and FIG. 4 is a front sectional view.

  3 and 4, the upper end 3a of the inner tank 3 formed in a rectangular tube shape is opened, and the lower end is closed by the lower wall 3b. An inflow port 9 is formed at the center of the lower wall 3b. An inflow pipe 10 penetrating the lower wall of the outer tub 13 is connected to the inflow port 9.

  An electrode 5 formed in a flat plate shape is inserted into the inner tank 3. One end of the electrode 5 is bent along the inner wall of the inner tank 3, supported by a holding member (not shown) outside the electrolytic cell, and connected to an external power source.

2 to 4, the arrow A indicates the traveling direction of the carbon fiber strand 11, and the arrow B (that is, the direction perpendicular to the arrow A) indicates the machine width direction of the apparatus. An electrode 5 is disposed in the vicinity of the lower wall 3 b in the inner tank 3. The length of the electrode 5 in the A direction and the length in the B direction are shorter than the inner length L ₂ and the inner width L _{1 of the} inner tank 3, respectively. A rectifying plate 7 is horizontally inserted above the electrode 5. The rectifying plate 7 has a large number of through-holes 7a penetrating in the thickness direction.

As shown in FIG. 1, a large number of inner tanks 3 are arranged in series in the outer tank 13 along the traveling direction of the carbon fiber strands 11. Center distance between the inner adjacent tank 3, to the inner length _{L 2} of the inner tank is about 115 to 250%. A voltage is applied to the electrodes 5 provided in the large number of inner tanks 3 so as to alternately act as anodes and cathodes between adjacent inner tanks.

  The inner tank 3 is disposed so that the upper end 3a thereof is the same height as the upper end 13a of the outer tank or higher than the upper end 13a of the outer tank. A discharge port 15 is formed in the side wall 13 b of the outer tub 13.

  In FIG. 1, 17 is an electrolyte tank, and 19 is a pump. The discharge port 15 and the electrolyte tank 17 are connected by a discharge rod 21, and the electrolyte tank 17 and the pump 19 are connected by a pipe 23.

  A pipe 25 is connected to the outlet of the pump 19. The pipe 25 and the inflow pipe 10 connected to the lower wall of each inner tank 3 are connected by a branch pipe 29 in which a valve 27 is interposed.

  An electrolytic solution such as sulfuric acid stored in the electrolytic solution tank 17 is introduced into the inner tank 3 from the inlet 9 by the pump 19. Then, after passing between the electrode 5 and the inner tank side wall, it passes the through-hole 7a formed in the baffle plate, becomes a uniform flow, and distribute | circulates the inside of the inner tank 3 from the downward direction upwards. The electrolytic solution overflowing from the inner tank 3 at the upper end of the inner tank 3 is received by the outer tank 13. Thereafter, it flows out from the discharge port 15 formed in the outer tub 13 to the discharge tank 21 and is stored again in the electrolyte tank 17.

  The carbon fiber strand 11 is immersed in the electrolytic solution by passing through the electrolytic solution overflowing from the inner tub to the outer tub 13 on the inner tub 3. Since the carbon fiber has high conductivity, the surface of the carbon fiber is electrolytically oxidized in the electrolytic solution by applying a voltage to the electrodes 5 acting as anodes or cathodes alternately between the adjacent inner tanks 3, and carboxyl groups, Oxygen-containing functional groups such as carbonyl groups are introduced on the carbon fiber surface. The carbon fiber strands 11 are repeatedly immersed in an electrolytic solution that overflows from the inner tank to the outer tank by passing over the electrolytic tank 1, and the surface is repeatedly electrolytically oxidized. The carbon fiber strand 11 is subjected to the electrolytic oxidation treatment when the passage through the electrolytic cell is completed, and is sent to subsequent processes such as water washing, sizing application, and drying. Then, it is wound up by a winder to become a final product.

  In addition, in the said description, although the case where one inflow port 9 was formed in the center of the lower wall 3a of the inner tank 3 was demonstrated, two or more may be formed. When a plurality of inflow ports are formed, it is preferable to form them in the machine width direction so that the electrolyte flows uniformly in the inner tank.

Machine width direction of the diameter of the inlet 9, preferably 10 to 60% with respect to the inner tank width _{L 1,} and more preferably from 15 to 50%.

  It is preferable that the processing amount X of the carbon fiber processed with the processing apparatus of this invention shall be 1.0-250 kg / hr. If it is less than 1.0 kg / hr, the treatment state of the carbon fiber is less likely to be uneven, so there is little need to insert a current plate. If it exceeds 250 kg / hr, the machine width of the apparatus becomes too large, and it becomes difficult to make the flow rate of the electrolyte uniform.

The flow rate Y of the electrolyte flowing from the inlet 9 into the inner tank 3 varies depending on the conditions such as the volume of the inner tank, but it is a general purpose for processing several tens to several hundreds of carbon fiber strands in parallel and processing them at a time. In the case of a simple electrolytic cell, it is 0.3 to 120 m ³ / hr. If it is less than 0.3 m ³ / hr, it is difficult to make the overflow height sufficient, and if it exceeds 120 m ³ / hr, a portion where the overflow height becomes too high is generated to maintain a uniform liquid level. It becomes difficult.

The carbon fiber throughput X (kg / hr) and the electrolyte flow rate Y (m ³ / hr) preferably satisfy the relationship of 0.1 <Y / X <25. If the value of Y / X is less than 0.1, it is difficult to perform a sufficient surface treatment on the carbon fiber strand. If the value of Y / X exceeds 25, a part where the overflow height becomes too high is generated. It becomes difficult to maintain a uniform liquid level.

  The average flow rate of the electrolyte solution on the inner tank outlet side is preferably 4 to 30 mm / sec. If it is less than 4 mm / sec, the overflow height of the electrolyte is insufficient, and if it exceeds 30 mm / sec, it is difficult to make the flow rate uniform, and it is difficult to keep the overflow height uniform. The average flow velocity on the inner tank outlet side can be within the above range by adjusting the flow rate of the electrolyte supplied to the inner tank 3.

  The diameter of the through hole formed in the rectifying plate 7 is preferably 2 to 25 mm. If it is less than 2 mm, it is difficult to produce and clogging may occur. If it exceeds 25 mm, the flow rate extremely increases at the hole portion, and it is difficult to make the flow rate distribution uniform by the current plate.

  The pitch of the through holes is preferably 2.5 to 100 mm. When the pitch is less than 2.5 mm, in addition to difficulty in manufacturing, there is a possibility that the resistance is reduced and the effect of inserting the current plate is lost. If it exceeds 100 mm, the flow rate extremely increases at the hole portion, and it is difficult to make the flow rate distribution uniform.

  The opening ratio of the current plate is preferably 0.3 to 60% in terms of the average value of the whole. If it is less than 0.3%, the resistance increases extremely, and the burden on the device increases. If it exceeds 60%, the effect of inserting the current plate is insufficient.

The opening ratio of the rectifying plate 7 is preferably changed according to the distance from the inlet 9, the shape of the electrode, and the like so that the surface treatment is uniformly performed between the carbon fiber strands 11. A preferred example of the current plate 7 is shown in FIG. The current plate is divided into three sections S _{1 to} S ₃ from the center toward the outside in the longitudinal direction. The aperture ratio of each segment is less than 0.3% to 9% by _{S 1} in order, less than 9% to 15%, and 60% or less than 15%. Moreover, it is preferable that the areas of S _{1 to} S ₃ are 5 to 10%, 0 to 20%, and 70 to 90% of the area of the current plate, respectively.

  The number of the inner tanks 3 disposed in the outer tank 13 is preferably 2 to 32, and more preferably 4 to 24.

  In the above description, the electrode 5 has been described in the case where only one end is bent along the inner wall of the inner tank 3 and is supported by a holding member (not shown) outside the electrolytic cell. And may be supported at both ends by a holding member (not shown) that is bent along the outer periphery.

The thickness of the electrode 5 is preferably 2 to 20 mm. The length of the electrode 5 in the machine width direction is preferably 0.2 to 0.9 times the inner width L ₁ of the inner tank 3, and the length of the carbon fiber strand in the running direction is the inner length of the inner tank 3. it is is preferably a 0.6 to 1.0 times the _{L 2.}

  As a material of the electrode 5, for example, platinum, SUS316L, titanium, or a metal surface such as copper plated with platinum can be used.

  The treatment time per inner tank of the carbon fiber strand 11 is preferably 1.0 to 5.0 seconds, and more preferably 1.5 to 3.0 seconds. The running speed of the carbon fiber is usually about 50 to 600 m / h.

  Electrolytic solutions used for electrolytic oxidation treatment of carbon fiber include inorganic acids such as sulfuric acid, nitric acid and hydrochloric acid, inorganic hydroxides such as sodium hydroxide and potassium hydroxide, inorganic salts such as ammonium sulfate, sodium carbonate and sodium hydrogen carbonate. An electrolyte aqueous solution such as

  As the carbon fiber to be subjected to electrolytic oxidation treatment in the present invention, any carbon fiber such as petroleum / coal pitch-based, rayon-based, lignin-based, etc. can be used in addition to polyacrylonitrile (PAN) -based carbon fiber.

  The carbon fiber strand 11 is usually manufactured in a bundle shape in which about 1000 to 80000 filaments having a diameter of 4 to 12 μm are gathered. In the processing apparatus of this invention, it is not limited to the said fiber diameter and the number of filaments, What kind of fiber diameter and the number of filaments can be processed.

The amount of electricity applied to the carbon fiber strand 11 may be appropriately determined according to conditions such as the type of electrolyte used for the electrolyte solution 7 and the elastic modulus of the carbon fiber strand 11. For example, when an electrolytic oxidation treatment of carbon fiber having an elastic modulus of 24 tonf / mm ² is performed using an ammonium sulfate aqueous solution as the electrolytic solution, the amount of electricity applied to the carbon fiber is preferably 3 to 40 C / g. More preferably, it is 30 C / g.

  The electrolytic oxidation treatment temperature of the carbon fiber strand 11 is in the range of 10 to 80 ° C, but preferably 20 to 50 ° C.

  As an index for performing the surface treatment of the carbon fiber strand 11, it is preferable to manage the surface oxygen concentration ratio (O / C) of the carbon fiber that can be measured using X-ray photoelectron spectroscopy (ESCA). When a carbon fiber is mixed with a thermosetting resin to form a composite material, it is preferable to perform electrolytic oxidation treatment so that O / C is 0.05 to 0.4.

Example 1
Using the surface treatment apparatus shown in FIG. 1, electrolytic treatment of carbon fiber strands was performed under the following conditions.
Inner tank dimensions: machine width direction 2600mm, depth 250mm, height 120mm
Inner tank volume: 0.078 m ³
Carbon fiber treatment amount: 90kg / hr
Electrolyte: Nitric acid (6%) aqueous solution Electrolyte flow rate: 240 L / min
Inner tank outlet side flow velocity: 6.15 mm / s
Inlet: One location in the center of the bottom of the inner tank (50mm diameter)
Electrode: Machine width direction 2500mm, depth 100mm, thickness 5mm
Distance between electrode and inner tank lower wall: 95mm
Distance between current plate and inner tank lower wall: 105mm
Current plate: The one having a thickness of 5 mm described in Table 1 was used.

Example 2
Using the surface treatment apparatus shown in FIG. 1, electrolytic treatment of carbon fiber strands was performed under the following conditions.
Inner tank dimensions: machine width direction 2600mm, depth 500mm, height 120mm
Inner tank volume: 0.156 m ³
Carbon fiber treatment amount: 90kg / hr
Electrolyte: ammonium sulfate (10%) aqueous solution Electrolyte flow rate: 600 L / min
Inner tank outlet side flow velocity: 7.69 mm / s
Inlet: One in the center of the bottom of the inner tank (80mm diameter)
Electrode: Machine width direction 2500mm, depth 200mm, thickness 5mm
Distance between electrode and inner tank lower wall: 95mm
Distance between current plate and inner tank lower wall: 105mm
Current plate: The one having a thickness of 5 mm described in Table 2 was used.

Example 3
Using the surface treatment apparatus shown in FIG. 1, electrolytic treatment of carbon fiber strands was performed under the following conditions.
Inner tank dimensions: machine width direction 900mm, depth 50mm, height 40mm
Inner tank volume: 0.0018 m ³
Carbon fiber throughput: 3.3 kg / hr
Electrolyte: Nitric acid (6%) aqueous solution Electrolyte flow rate: 25 L / min
Inner tank outlet side flow velocity: 9.26 mm / s
Inlet: One in the center of the bottom of the inner tank (20mm diameter)
Electrode: Machine width direction 900mm, depth 30mm, thickness 5mm
Distance between electrode and inner tank lower wall: 5mm
Distance between current plate and inner wall lower wall: 27mm
Current plate: The one having a thickness of 3 mm described in Table 3 was used.

  In the apparatuses of Examples 1 to 3, when the overflow height of the inner tank was measured on a scale at five points in the machine width direction, all were in the range of 3 to 4 mm.

Comparative Example 1
Surface treatment of the carbon fiber strand was performed in the same manner as in Example 3 except that the current plate was not used. When the overflow height of the inner tank was measured at five points in the machine width direction, a variation of 0 to 6 mm was observed.

It is a schematic block diagram which shows an example of the surface treatment apparatus of this invention. It is a schematic plan view of the electrolytic cell used with the surface treatment apparatus of this invention. It is a schematic side sectional view of the electrolytic cell shown in FIG. FIG. 3 is a schematic front sectional view of the electrolytic cell shown in FIG. 2. It is a top view which shows an example of the baffle plate used with the surface treatment apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolysis tank 3 Inner tank 5 Electrode 7 Current plate 7a Through-hole 9 Inflow port 10 Inflow tube 11 Carbon fiber strand 13 Outer tank 15 Outlet 17 Electrolyte tank 19 Pump 21 Discharge rod 23, 25 Pipe 27 Valve 29 Branch pipe 100 Surface Processing equipment

Claims (5)

An inner tank that allows the electrolyte to flow from the bottom to the top and overflows the electrolyte from the upper end and a plurality of the inner tanks arranged in series at a predetermined interval are provided inside, and overflowed from each inner tank. An electrolytic tank comprising an outer tank for receiving the electrolytic solution, an electrolytic solution tank for receiving and storing the electrolytic solution in the outer tank, and a pump for sending the electrolytic solution in the electrolytic tank into the inner tank A carbon fiber strand comprising: an electrode inserted on the lower side of the inner tank; and a current plate horizontally inserted above the electrode into the inner tank and having a plurality of through holes formed in the thickness direction. Surface treatment equipment. The shape of the inner tank is a rectangular tube shape having an upper end opened and a lower end closed by a lower wall, and an inflow port for receiving an electrolytic solution is formed at the center of the lower wall. Surface treatment equipment for carbon fiber strands. The surface for carbon fiber strands according to claim 2, wherein the diameter of the inlet in the direction perpendicular to the row direction of the inner tank is 15 to 80% of the inner tank inner width in the direction perpendicular to the row direction of the inner tank. Processing equipment. The rectifying plate is divided into three sections of first to third sections having different opening ratios in the direction perpendicular to the row direction of the inner tank from the center of the inner tank toward the outside, and the opening ratios of the sections are in order. The surface treatment apparatus for carbon fiber strands according to claim 1, which is 0.3% or more and less than 9%, 9% or more and less than 15%, or 15% or more and 60% or less. The surface treatment apparatus for carbon fiber strands according to claim 4, wherein the areas of the first to third sections on the horizontal plane of the current plate are 5 to 10%, 0 to 20%, and 70 to 90%, respectively.

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