JPS6250495A - Surface electrolytic treatment device for carbon fiber - Google Patents

Abstract

PURPOSE:To make tthe uniform electrolytic oxidation treatment of all carbon fibers in the stage of subjecting the surface of the carbon fibers for a carbon fiber-reinforced composite material to the electrolytic oxidation treatment by disposing anodes and cathodes into electrolytic cells at both ends of plural electrolytic cells and passing the group of the carbon fibers through the two electrolytic cells respectively, thereby constituting a series type power feed system. CONSTITUTION:The surface of the carbon fibers are subjected to the electrolytic oxidation treatment to improve the adhesiveness of a matrix material and the carbon fibers in the stage of producing the carbon fiber-refinforced composite material. The anode is disposed in the 1st cell of n-pieces of the electrolytic cells and the cathode is disposed in the final cell. Partition plates through which an electrolyte can flow freely are provided in the respective electrolytic cells. The tow of N-1 pieces of the carbon fibers is passed through the n-th cell and the (n-1)th cell. Electric current is passed in a series type in each cell by the type in which the tow in each cell is the cathode in the 1st cell, the anode in the 2nd cell and the 2nd tow in the 2nd cell is the cathode and the anode in the 3rd cell. Then the currents which flow in each piece of the tow have the same value and the thickness of the anodic oxidation treat ment layers is made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for electrolytically treating the surface of carbon fibers by electrolytic oxidation in order to improve adhesion to a matrix material in the production of carbon fiber reinforced composite materials. .

The present invention is effective for carbon fibers whose precursors are not only PAN-based and pitch-based but also other raw materials.

(Prior Art) In the electrolytic oxidation of carbon fibers, two known methods of supplying power to carbon fibers include a contact method using roll power supply and a non-contact method in which power is supplied non-contactly through an electrolytic solution.

In roll feeding, the carbon fiber and roll come into contact.

Fluffing and wrapping around rolls occur. On the other hand, these problems are solved by the non-contact method disclosed in, for example, Japanese Patent Publication No. 47-29942 (an example is shown in FIG. 2). However, the disadvantage of the non-contact method in the prior art is that it is difficult to uniformly supply power to each tow, and the degree of surface treatment is uniform. In other words, as shown in Figure 2, since power is supplied to many tows at the same time in the same power supply tank, the current flowing to each tow is constant depending on factors such as the degree of opening of the tows, the inclination of the power supply plate, and slight disturbances in the liquid flow. Therefore, non-uniformity occurs in the degree of surface treatment between the tows. In addition, since power is supplied to many tows in parallel from the same electrode, the anode current value in the power supply tank increases, resulting in significant electrolytic corrosion thinning of the power supply electrode, which is the anode! A: Frequent electrode replacement is required, and contamination of the electrolyte by substances dissolved by electrolytic corrosion adversely affects the physical properties of the carbon fibers, increasing the frequency of electrolyte replacement. On the other hand, parallel power supply has the advantage of simplifying the device configuration. In other words, the two-tank configuration of a power supply tank and an electrolytic tank is quite simple and has sufficient industrial significance.

(Problems to be Solved by the Invention) The drawbacks of the conventional non-contact electrolytic treatment are that the power supply between the tows becomes uneven due to parallel power supply from the same electrode to a large number of tows, and that the power supply of the power supply electrode becomes uneven. This results in excessive erosion. Therefore, the technical problem of the present invention is to keep the current flowing for each tow constant even in the non-contact method, to treat all tows uniformly, and to minimize galvanic corrosion of the power supply electrode.

(Means for Solving the Problems) As described above, uneven power feeding between tows and excessive thinning due to electrolytic corrosion of the power feeding electrodes are caused by power feeding to a large number of tows in parallel from the same electrode at once. Focusing on this point, the present invention solves the problem by performing a series type power supply.

Figure 1 is a typical example, and Figure 3 is a variation thereof. This will be explained using Figure 1 as an example. There are 5 tanks in total.

The first tank is used as a power supply tank, and the second to fifth tanks are used as electrolytic cells.

Two groups of carbon fibers pass through each electrolytic cell, but the two groups must not touch each other. In the following, for convenience of explanation, we will consider a virtual partition plate that divides each type into two rooms.

This partition plate is partially open, so that the electrolyte can move freely between the two chambers. The purpose of the divider plate is to ensure that the two groups of tows passing through each type do not touch each other. Now, an anode plate is arranged in one chamber of the first M tank, and a cathode plate is arranged in one chamber of the fifth tank. When an appropriate number of tows (two in Figure 1) are divided into one group, one group passes through one chamber in each of two adjacent tanks. In one tank 2, for example the first tank, a current flows from the electrolyte into the carbon fibers, and in the other tank 1, for example the second tank, a current flows out from the carbon fibers into the electrolyte. That is, in the first tank, the carbon fiber acts as a cathode, and in the second tank, the carbon fiber acts as an anode, and the carbon fiber is oxidized by the nascent oxygen generated at the anode. Looking at the flow of current in the entire device, the current is first supplied to the anode plate of the first tank, and then discharged from the cathode plate of the fifth tank while flowing in series through the tows and electrolyte running in each type. Number of tows per group is 1
An appropriate number of books or more may be used. As the number of tows per group increases, the influence of parallel power supply, which is a drawback of the prior art, becomes more pronounced, and the non-uniformity of current between tows becomes more pronounced. On the other hand, the number of required electrolytic cells decreases in inverse proportion to the number of tows. In an extreme case, when each group consists of one tow, a constant current flows through all the tows, so that the surface treatment progresses completely uniformly. However, since the number of required electrolytic cells is maximum, it is uneconomical in terms of equipment cost. In reality, an appropriate number should be selected in consideration of the allowable variation in the degree of surface treatment and the construction cost of the electrolytic cell.

In order to prevent the running tow from coming into contact with the tank wall when moving in and out of the electrolytic cell, a certain amount of electrolyte is circulated by a pump as shown in Figure 3, and overflows from the weir to increase the required height of the clay. Maintain the liquid level.

By running the tow across the width, the running tow can be immersed in the electrolyte. Next, regarding electrolysis of electrode plates, the current value can be lowered by connecting them in series, so thinning can be greatly improved and the frequency of electrode replacement can be reduced. It also reduces electrolyte contamination and reduces electrolyte consumption.

Example 1 The electrolytic oxidation experimental apparatus shown in Figure 3 was used. This neck brace is an embodiment of the present invention disclosed in FIG. 1, and is a series feeding type including a parallel type as part of the configuration.

The carbon fiber used in the experiment was a commercially available PAN-based carbon fiber with a thread diameter of 7 μm and a strand strength of 320 kg/
-1 elastic modulus: 22.5Tc+n/- and ILSS
; It was 5.1 kg/- (Note 1). Other experimental conditions are shown below.

Fermentation electrode plate Copper plate electrolyte 5wt% N2LOH aqueous electrolyte amount 501 Total number of tows 10 Number of filaments per tow 6,000 Current per tow 0.3A residence time
60 seconds continuous processing time 5 hours (from new solution to end of experiment) The results of an experiment under the above conditions are shown together with the results of a comparative example.

Here, in order to know the degree of uniform treatment, ILSS and strand strength were measured at 5 fish juice points for each tow, and the average value, maximum value, minimum value, and standard deviation were calculated. Furthermore, in order to check the electrode consumption and the degree of solution contamination, we measured the weight of the electrode plate and the Cu''+ concentration in the electrolyte before and after the test.For comparison with the conventional technology, all partition plates were removed from the experimental apparatus shown in Figure 3. This was then connected to a parallel power supply type experimental device (Figure 4).
). On the other hand, a test was conducted under exactly the same conditions as the above-mentioned series power supply experiment, and this was used as a comparative example.

ILSS average value (kg/-2) 8.5
8.0 Maximum value (kg/mm2) 8.7
8.7 Minimum value (kg/mm2) 8.3
7.0 drift standard deviation (kg/mm2)
0.13 0.58 Strand strength average value (kg/wn2) 322 308 Most dog value (kg/lll1n2) 330 32
7 Minimum value (kg/mm2) 310 282
Standard deviation (kg/m2) 6,3
16.3 Weight of electrode plate (before test) (g)
218.53 351.8311 (
(after test) (g) 218.51
351.65 weight loss (g) 0.02
0.18 Cu2+ concentration in electrolyte (mg#ri)
0.6 4.1 Based on the above results, it can be determined that the variations in ILSS and strand strength between tows are small, and the average value is stable at a high value, and that uniform processing has been achieved.

The weight of the electrode plate has also been significantly reduced. This corresponds well with the fact that the increase in Cu2+ concentration in the electrolyte is small.

(Note 1) As Mastrisk powder, epoxy resin (Evicron 850 manufactured by Dainippon Ink Chemical Co., Ltd.), curing agent (0N-5500 manufactured by Hitachi Chemical Co., Ltd.), and curing accelerator (ethyl methyl imidazole manufactured by Shikoku Kasei Co., Ltd.) are mixed in a ratio of 100 to 84 parts by weight. A carbon fiber-reinforced composite material test piece for ILSS measurement was prepared by using the mixture in step 1 and setting the volume content of carbon fiber to 60%. The ILSS measurement was performed using the short beam method.

Example 2 Thread diameter: 7 μm, strand strength: 324 kg/mo1
．． Elastic modulus: 21.5Ton/- and ILSS; 4.9k
The same experiment was conducted using the same equipment as in Example 1 using commercially available rayon-based carbon fiber having a weight of 1.5 g/-. The experimental conditions and experimental results are shown below.

Graphite plate electrolyte
5wt% NaOH aqueous electrolyte amount 504 Number of tows Number of filaments per 10 tows 6,000 Current per tow
Regarding 0.3AILSS and strand strength, the average value, maximum value, minimum value, and standard deviation were calculated from the measurement data of 100 points of 1° fish juice for each tow.

ILSS average value (kg/mm2) 8.6
8.2 Maximum value (kg/a2) 8.7
8.8 Minimum value (kg/+nm2) 8.3
7.5 standard deviation (kg/mm'),
0.11 0.35 Strand strength average value
(kg/mm2) 327 305 maximum value (kg/mm2) 335 331 minimum value (
kg/m+n2) 313 294 standard deviation (
kg/mm2) 5.8 13.5 Electrode plate weight (before test) (g) 281.08
452.54 (after test) (g)
280.86 450.22 weight loss (g)
0.22 2.32 It is clear that the degree of contamination of the solution due to oxidative dissolution of graphite is higher in the comparative example than in the present invention because it was colored dark brown.

Example 3 The same experiment was carried out using the same equipment as in Example 1 using carbon fiber obtained by melt spinning, infusibility, and carbonization firing mesophase pitch prepared from cracked oil residue from a fluid catalytic cracker. did. Carbon fiber thread diameter: 10 μm, strand strength:
268 kg/wA, elastic modulus: 31.8 Ton/-, and ILSS: 3.2 kg/nJ. The experimental conditions and experimental results are shown below.

Experimental conditions Electrode plate Graphite slope electrolyte
5wt%N a OH aqueous electrolyte amount 50β Number of tows Number of filaments per 10 tows 6,000 Current per tow 0.42A residence time
Continuous processing time of 60 seconds 10 hours (new solution - until the end of the experiment) The number of experimental results measured is 10 points for each tow, and the weight is 00 points.

ILSS average value (kg/mm2) 8.2
7.8 Maximum value (kg/rom”) 8.5
8.6 Minimum value (kg/mm2) 8.0
6.7 standard deviation (kg/mm2)
0.13 0.45 Strand strength average value
(kg/rran2) 266 23
5 Maximum value (kg/mm2) 275 271 Minimum value (kB/mm2) 259 201 Standard deviation (kg/++m”) 6.4 20
．． 5 Electrode plate weight (before testing) (g)
279.74 431.72 (after test) (g)
279.33 428.32
Weight reduction) 0.41 3.40 Although the degree of solution contamination was not quantified as in Example 2, visual inspection revealed that the comparative example was more brownish in color and had a higher degree of contamination.

(Effects of the Invention) As is clear from the above description, by employing the electrolytic oxidation using series power supply according to the present invention, the unevenness of the current between the tows is reduced, and uniform processing becomes possible. Furthermore, the power supply rf and the current passing through the pole are reduced, so the electrode consumption is reduced.

Electrode replacement frequency is reduced. Furthermore, the power supply electrode is 1t at the end
1"1, by independently recycling only the overflow liquid of the power supply electrode, contamination of the electrolyte is limited to a small part. In principle, the method can be applied not only to PAN-based, pitch-based, and rayon-based carbon fibers, but also to carbon fibers using other thick materials as precursors.

[Brief explanation of the drawing]

FIG. 1 shows an example of a non-contact series power feeding device disclosed in the present invention. FIG. 2 is an example of a conventional non-contact parallel power feeding device. Figures 3 and 4 are schematic diagrams of the experimental equipment used in the embodiments of the present invention, and the latter is a series-feed type and the latter is a parallel-fed type.

Claims (4)

[Claims] (1) When subjecting carbon fibers to surface electrolytic treatment by immersing them in an electrolytic solution, N tanks are provided for an integer N of 2 or more, an anode plate is placed in the first tank solution, and the anode plate is In a surface electrolytic treatment device that supplies power to the tank, disposes a cathode plate in the N-th tank liquid, and discharges from the cathode plate, the tow is composed of an appropriate number of tows for an integer n of 2 or more and N or less (N-1). There are groups of carbon fibers, and the (n-1)th group of carbon fibers is the (n-1)th group of carbon fibers.
n-1) An apparatus for surface electrolytic treatment of carbon fibers, characterized by passing through a bath liquid and then passing through an n-th bath liquid. (2) Except for the first tank and the Nth tank, the nth tank has the (n-1th tank)
2. The carbon fiber surface electrolytic treatment apparatus according to claim 1, wherein the carbon fibers of the group ) and the n-th group pass through and the groups do not come into contact with each other. (3) A patent claim in which the carbon fibers of the first group pass through the first tank without contacting the anode plate, and the carbon fibers of the (N-1) group pass through the Nth tank without contacting the cathode plate. The carbon fiber surface electrolytic treatment device according to item 1, (4) For the (n-1)th group of carbon fibers,
-1) Power supply from the electrolyte to the carbon fiber in the tank and the nth
2. The surface electrolytic treatment apparatus for carbon fibers according to claim 1, wherein the discharge from the carbon fibers to the electrolyte in the tank is performed in a non-contact manner via the electrolyte.