JPH0321672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of electroplating carbon fiber bundles. More specifically, when electroplating a carbon fiber bundle continuously, a plurality of cathodes are provided and the entire current is distributed to each cathode, and the electroplating is performed in multiple stages to eliminate the bond between the single fibers inside the fiber bundle. The present invention relates to a method for obtaining bond-free carbon fiber bundles.

In recent years, there has been remarkable progress in carbon fiber-reinforced composite materials that use carbon fiber as a reinforcing material. In particular, when metal-coated carbon fibers are used as reinforcing materials for non-conductive base materials such as thermosetting resins, thermoplastic resins, and rubber, the conductivity of these composite materials is significantly improved. With the recent development and spread of electronic equipment, electromagnetic interference and high frequency interference have become major problems, and composite materials with metal-coated carbon fiber fillers have been developed as shielding materials with excellent mechanical properties and formability. Become.

Further, a carbon fiber-reinforced metal-based composite material using the coated metal of metal-coated carbon fiber as a base material is excellent as a lightweight structural material, a conductive material, and a sliding material.

Electroplating is a method for coating carbon fiber bundles with metal, but conventional electroplating on carbon fiber bundles has had the problem of slow plating speed and lack of productivity.

In other words, the specific resistance of carbon fiber is 10 ^-6 Ω− of ordinary metal.
It is difficult to increase the plating speed because it has a large value of 10 ^-3 to 10 ^-4 Ω-cm per cm, has poor conductivity, and cannot increase the current density. When the current density is increased, the carbon fiber bundle generates heat and the film formed on the surface of the carbon fiber bundle is crosslinked, making it difficult to plate the inside of the carbon fiber bundle, and the thickness of the film on the surface and inside of the carbon fiber bundle decreases. There are problems such as not being able to obtain uniform products. Therefore, in order to obtain a film with a uniform thickness, the current density has to be reduced, which inevitably lowers productivity.

Therefore, the present invention proposes a method for electroplating carbon fiber bundles that solves the above-mentioned drawbacks and has excellent productivity.

That is, when electroplating a carbon fiber bundle continuously, a plurality of cathodes are provided in the running direction of the fiber bundle, and the total current is controlled so that the amount of current at each cathode is In _-1 ≧In≧In ₊₁ (In This is a method of electroplating carbon fiber bundles, characterized in that the electroplating is performed in multiple stages by distributing the current in the range of (the amount of current at the n-th cathode).

Here, the carbon fiber bundle refers to carbon fibers and graphite fibers consisting of about 100 or more continuous single fibers. It is necessary to distribute the total current to the carbon fiber bundle so that the amount of current at each cathode falls within the range of In _-1 ≧In≧In ₊₁ (In is the amount of current at the n-th cathode). That is, the current of the cathode near the plating bath side should be larger than or the same as the current of the next cathode. By distributing the total current in this way, the closer the carbon fiber bundle is to the plating bath exit side, the thicker the coating is, the lower the resistance, and the more conductive it is. If the values are small or the same, the coating formed on the surface of the carbon fiber bundle will not be crosslinked, and the thickness of the coating on the surface and inside of the carbon fiber bundle will be uniform, which will further improve productivity.

On the other hand, contrary to the present invention, if the total current is distributed so that the amount of current at each cathode is in the range In _-1 < In < In ₊₁ (In: the amount of current at the nth cathode), the plating bath The film thickness of the carbon fiber bundle coating near the side is thicker, the resistance is lower, and the conductivity is improved. In addition, because the current amount of the next cathode is large, the coating is applied to the carbon fiber bundle surface due to the synergistic effect. The uniformity of the film thickness on the surface and inside of the carbon fiber bundle is significantly impaired.

When electroplating a carbon fiber bundle, a method is known in Japanese Patent Publication No. 52-43770, in which the carbon fiber bundle is energized from two or more points and the voltage supplied from the first energized point is higher than that from the second energized point. It is being

The method described in this publication applies a high voltage (3 to 20 volts) at the first energized point to generate hydrogen gas and spread the fiber bundle into individual fibers, and then from the second energized point onwards. This provides a voltage within the range used for ordinary electroplating (2 to 6 volts).

The present invention attempts to achieve the intended purpose by adjusting the electroplating speed by adjusting the amount of supplied current. Simply changing the supply voltage does not allow the electroplating speed to be adjusted without adjusting the supply current, and thus the object of the present invention cannot be achieved.

When electroplating carbon fiber as in the present invention,
Regarding a method for preventing the occurrence of crosslinks between fibers due to the metal coating formed on the fiber surface by providing multiple cathodes and distributing the total current to each cathode in a specific relationship, and performing electroplating in multiple stages. is not known.

The electroplating method according to the present invention is applicable to Cu, Ni, Cr, Zn, Cd, Pb, Sn, which can be electroplated normally.
Can be used for plating Au, Ag and their alloys.

The present invention will be explained below using the drawings.

1, 2 and 3 are schematic diagrams showing an embodiment of an apparatus for carrying out the method of the invention.

In Fig. 1, the carbon fiber bundle 4 is connected to the entry side nip roller 5.
Then, electroplating is performed in the plating zone in the plating bath 9 by applying current from the first cathode 1, and then electroplating is performed in the plating zone via the first cathode 1 and then at the second cathode. While repeating this process, the carbon fiber bundle 4 is electroplated, passed through the output nip roller 6, washed with water, dried, and then wound up.
The first cathode 1 may be provided in common with the inlet nip roller 5' of the plating bath 9 as shown in FIG. 2, or independently as shown in FIG. 1, or a plurality of plating baths 9 may be provided and each A cathode may be placed at Metsuki bath 9
When there is one cathode and a plurality of cathodes, the number of anode metals 8 may be one as shown in FIG. 1 or the same number as the cathodes as shown in FIG.

The amount of current distributed to each cathode is determined by plating the carbon fiber bundle closer to the outlet side of the plating bath, which improves conductivity and reduces resistance. Adjust the current so that it is smaller than or equal to the amount of current given from the cathode. The carbon fiber bundle 4 energized from the first cathode 1 is electroplated in the plating zone in the plating bath 9, and is once taken out of the plating solution 7 and placed at the second electrode 2.
The power is turned on again. Since the carbon fiber bundle 4 at this time has improved conductivity and lower resistance than the carbon fiber bundle 4 in the previous zone, it is easier to perform electroplating in the plating zone than in the plating zone, and the amount of current is the same. It needs to be made smaller.

The total current is then distributed in the same manner.

In this way, by distributing the total current so that the amount of current at each cathode is in the range of In _-1 ≧In ≧ In ₊₁ (In is the amount of current at the nth cathode), there is no crosslinking phenomenon and carbon A uniform film thickness can be obtained on the surface and inside of the fiber bundle, and productivity can be dramatically improved.

The present invention will be described below with reference to Examples and Comparative Examples.

Example A carbon fiber bundle consisting of 12,000 single fibers each having a diameter of 7 μm was nickel-plated continuously in two stages. The plating bath composition was a normal bath containing 150 g of nickel sulfate, 15 g of ammonium chloride, and 15 g of boric acid, and the plating solution had a pH of 6.0 and a temperature of 25°C. The total current was distributed at 5 A to the first cathode and 4 A to the second cathode.
The traveling speed of the carbon fiber bundle was 25 cm/min, and the residence time in the plating bath was 4 minutes.

When the nickel-coated carbon fiber bundle thus obtained was observed using a scanning electron microscope, it was found that each single fiber on the surface and inside of the carbon fiber bundle was uniformly coated with nickel, and the nickel film thickness was 0.27 to 0.32μ.
It was hot.

Comparative Example A carbon fiber bundle was continuously nickel-plated under the same conditions as in the example except that the total current was distributed to the first cathode at 4A and the second cathode at 5A. In this case, the thickness of the nickel film inside and on the surface of the carbon fiber bundle varied greatly, ranging from 0.12 to 0.45μ, and a so-called crosslinking phenomenon was observed in which several to several dozen fibers were plated all at once.

In addition, in order to obtain a carbon fiber bundle in which each single fiber is uniformly coated with nickel both inside and on the surface of the carbon fiber bundle, which is the same as that obtained in the example using the one-step plating method, the total current is 5A, and the carbon fiber Set the traveling speed of the bundle to 12
It had to be less than half that, cm/min.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are schematic diagrams showing an embodiment of an apparatus for carrying out the method of the present invention. 1: first cathode, 2: second cathode, 3: third cathode,
4: Carbon fiber bundle, 5: Entry side nip roller,
5': Inlet side nip roller and first cathode, 6: Output side nip roller, 7: Plating liquid, 8: Anode metal,
9: Plating bath, , indicates the plating zone.

Claims (1)

[Claims] 1. When continuously electroplating a carbon fiber bundle, a plurality of cathodes are provided in the running direction of the fiber bundle, and the total current is set such that the amount of current at each cathode is In _-1 ≧ In ≧ A method for electroplating carbon fiber bundles, characterized in that the electroplating is performed in multiple stages by distributing the current in a range of In ₊₁ (In represents the amount of current at the n-th cathode).