JPS5989788A - Method for electroplating staple fiber having electric conductivity - Google Patents

Abstract

PURPOSE:To manufacture electrically conductive staple fibers having favorable electric condutivity and physical properties by forming a cathode on the inside of the bottom of a plating vessel and by electroplating electrically conductive staple fibers while practically depositing the fibers on the botton of the vessel under stirring. CONSTITUTION:Electrically conductive staple fibers 5 to be plated are settled and deposited on the cathode forming inside 1a of the bottom of a plating vessel 1, an anode 7 is placed over the fibers 5, and the fibers 5 are electroplated with a prescribed electroplating soln. 8. At this time, the top blade part 9a of an impeller type stirrer 9 is buried in the fibers 5, and the fibers 5 are gently stirred so as to prevent violent scattering to an upper part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electroplating short fibers having electrical conductivity.

Traditionally, short metal fibers have been used in large quantities as conductive plastic fillers, friction materials, etc., and are considered to be a promising material in the future. As such short metal fibers, aluminum =
, aluminum alloy, copper, copper alloy, steel, stainless steel, cast iron, etc. Diameter 10-600μ, length 0.5
~6wILe products are currently on the market, but these short metal fibers are used as various fillers by utilizing the material of the base material itself. No surface treatment has been applied to it. Therefore, in the case of copper, copper alloy, steel, cast iron, etc., these short metal fibers have problems such as oxidation in air atmosphere, rust and corrosion in acid atmosphere5. Coating the surface with a stable metal of a different type is an effective method for preventing acid abrasion, rust, and corrosion of short metal fibers, and coating the surface of these short fibers with a highly conductive metal such as silver is an effective method. The present inventors thought that it was possible to obtain inexpensive highly conductive short fibers by doing so, and conducted various studies on applying metal coating to the surface of conductive short fibers such as short metal fibers.

Electroplating is generally considered to be a method of applying metal coating to such short fibers having conductivity, but in practice there are many very difficult problems. For example, for small parts such as screws and nuts used in precision parts, a small barrel may be used, a rope attachment may be used, or the object to be plated may be brought into close contact with the inner wall of the plating tank using centrifugal force. It is possible to perform electroplating using various methods, such as using a method of electroplating, but with these methods, it is difficult to apply electroplating uniformly to the surface of the short fibers. It is not possible to achieve homogeneous plating due to the unevenness.

In addition, conductive short fibers are mixed into the electroplating solution by blowing gas into the electroplating solution to create a slurry with the short fibers and the electroplating solution, and this slurry is brought into contact with the cathode to perform electroplating. There is also a method to do this, but this method has problems such as being complicated in terms of equipment and operation.
There is also a problem in terms of uniformity of plating.

Furthermore, chemical plating can be considered as a metal coating method for conductive short fibers, but this method is 5 to 10 times more expensive than electroplating, and is not suitable as a surface treatment method when used in large quantities as a filler. Not only does it have no economic advantage, but depending on the purpose of use, it may not necessarily show satisfactory performance in terms of film strength, adhesion, quality stability, etc. In particular, it is added to plastics etc. as conductive short fibers.
When mixing to obtain a conductive material that can be used for various purposes, it is necessary to coat the short fibers that serve as the base material with a metal plating film of the required thickness, uniformly, and with good adhesion. Low cost is also required, but if the plating method is used, it takes a considerable amount of time to form a thick plating layer, and the plating solution itself is relatively expensive, so it is difficult to manufacture. The cost becomes expensive. In addition, in the chemical plating method, metal coating using nickel plating is practical, but chemical nickel plating film has inferior conductivity and stability compared to silver, and it is necessary to use a conductive material instead of silver powder. The purpose cannot be fully satisfied.

In view of the above circumstances, the present inventors conducted extensive research into a method for reliably and effectively electroplating conductive short fibers using a simple device, and as a result, formed a cathode on the bottom of the plating tank, In addition to depositing conductive short fibers on the inner bottom surface of the By electroplating while maintaining short fibers deposited on the bottom of the plating tank,
It has been found that the above objectives are achieved.

That is, the present inventors first used an open-type inclined barrel, used the barrel body itself as a cathode, put short fibers inside, and inserted an anode through the open opening of the barrel body to reduce the rotational sound of the barrel. Electroplating was carried out with various ripples in the range of ~10 rpm, but uniform electroplating was not achieved, and a vibrating barrel was used instead of this type of rotating barrel, and electroplating was carried out under the full vibration of the short fibers. However, similarly good electroplating was not achieved, and only non-uniform electrodeposits were obtained in either case. Therefore, as a result of further consideration,
The inner bottom surface of the plating tank is used as a cathode, and all the short fibers are precipitated and deposited on this inner bottom surface, and the short fibers are stirred, preferably mechanically stirred by an impeller type stirrer, etc., and the short fibers are stirred. Uniform electroplating can only be achieved by performing plating under conditions where the short fibers are not substantially dispersed in the plating solution, and the short fibers remain completely settled and deposited, and do not scatter from the bottom of the plating tank. It was discovered that a uniform electrodeposited material could be obtained, and this led to the present invention.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

1 to 4 each show an example of a plating apparatus used for carrying out the method of the present invention. In the figure, 1 is a plating tank, and in the present invention, a cathode is provided on the inner bottom surface 1a of the plating tank 1. Form. As shown in Fig. 1.2.4, the method of forming a cathode mold bottom on the inner bottom surface 1a of the plating tank 1 is to form the plating tank 1 with metal, preferably stainless steel, and to A υ insulating layer 2 is formed on the side surface by a plastic coating, and only the inner bottom surface of the plating tank 1 is exposed to metal, and the cathode lead wire 3 is connected to the plating tank 1. As shown in , the plating tank l is formed of glass, and cathode sand 4 made of a metal temporary plate, preferably a stainless steel plate, is disposed on the inner bottom surface Ja of the plating tank l, and
A method such as connecting the cathode lead wire 3 to the cathode plate 4 may be adopted.

In the present invention, conductive short fibers 5 to be plated are precipitated and deposited on the inner bottom surface la forming the cathode of the plating tank 1, and connected to the anode lead wire 6 above the short fibers 5. Electroplating is carried out using a predetermined electroplating solution 8. In this case, the short fibers 5 are thoroughly stirred, preferably mechanically stirred with the short fibers. This is for stirring. , short fiber 5
'ff: As a method of mechanical stirring, an impeller set agitator 9 as shown on the mouth side is preferably used, and its tip blade part 9ai is disposed so as to be buried in the short fibers 5 to agitate the short fibers 5. This method is effective.

The rotational speed of the stirrer 9 is not necessarily limited, but it is preferably a slow speed that does not cause the short fibers 5 to be violently scattered upward from the inner bottom surface 1a of the plating tank 1. If the number of sweetfish is around 6 or more, the fibers may become entangled with each other due to stirring, making it impossible to obtain uniform plating, so it is particularly preferable to stir at a low speed.

1. Incorporate high-speed stirring in short intervals along with low-speed stirring,
A method in which short fibers are deposited and electrodeposited intermittently may also be suitably employed. In any case, it should be stirred so that the short fibers 5 can be maintained substantially precipitated and deposited on the inner bottom surface la of the plating tank 1, and the material, specific gravity, diameter, and length of the short fibers should be maintained. Although it varies depending on the speed, 5 usually 1 to 180 rpm,
In particular, rotational speeds of 2 to 100 rpm'm may be employed. Further, the stirrer 5 may be rotated continuously or intermittently.

Furthermore, in the present invention, as shown in FIG.

A power supply 1 is installed on the bottom of the hot water tank 12 filled with hot water 11 inside.
3 and an ultrasonic oscillator] 4 connected to the ultrasonic oscillator.

Furthermore, it is also possible to suitably adopt a method in which a plating slide 1 is disposed on the ultrasonic oscillator 14 and the short fibers 5 are subjected to low-speed agitation by the inbaler set agitator 9 and ultrasonic imaging by the ultrasonic oscillator 14. This makes it possible to favorably change the deposition state of the short fibers 5 and obtain a uniform electrodeposit.

If necessary, if the short fibers 5 have a small specific gravity or a small shape and are likely to scatter or float, a diaphragm 1 may be placed directly above the short fibers 5 as shown in FIG.
0 can be provided, thereby preventing the short fibers 5 from scattering and substantially maintaining the deposited state of the short fibers 5 on the inner bottom surface 1a of the plating tank 1. In this case, the diaphragm 10 is a non-conductive one with a bore diameter of 0.1 to 10 μm.

For example, polysalt fhipinylidene and the like are preferably used.

In the present invention, the diameter and length of the electrically conductive short fibers to be plated are not particularly limited, but according to the present invention, they are usually about 10 to 600 μ in diameter and 0.5 to 6 mA in length. can be suitably electroplated.

The material of the short fibers may be any material as long as it has conductivity and can be electroplated.For example, short metal fibers such as steel short fibers, iron short fibers, aluminum short fibers, brass short fibers, carbon short fibers, etc. Electrically conductive inorganic short fibers such as fibers, or non-conductive inorganic short fibers or organic short fibers (r) that have been made conductive using an appropriate conductive treatment method such as the heating method or vacuum evaporation method. Examples include.

These short fibers? When performing electroplating using a material, pretreatment depending on the material can be performed as necessary. For example, short steel fibers, short iron fibers, etc. are subjected to degreasing and pickling treatment, and short aluminum fibers, etc., are subjected to pretreatment such as full known zinc replacement treatment, followed by copper bronze strike plating. This allows for good electrical targeting. In addition, in the case of non-conductive short fibers, known chemical plating methods such as chemical nickel plating, r. The non-conductive short fibers thus made conductive can be electroplated in the same manner as the metal short fibers.

In the present invention, the type of electroplating solution is not limited, and known plating solutions such as copper, nickel, chromium, tin, zinc, silver, platinum, gold, rhodium, and palladium can be used. In this case, either an acidic solution or an alkaline solution can be suitably used as the plating solution, and multilayer plating can also be performed, such as by performing pot plating after nickel plating. Further, as the plating conditions, various conditions are adopted depending on the type of electroplating solution. For example, although the amount of current is not particularly limited, it is generally selected appropriately within the range of 1X10A/7 to IA/y, and if a normal nickel plating solution is used, the current amount is 1X10A/F to 2
It can be plated with a current of IOA/7, and if a blue f silver plating solution is used, 2 x 1 plating can be performed at room temperature.
It can be plated with a current of 0-8X10-3 A/P.

In the present invention, plating can be performed by circulating the plating solution using a pump as necessary and constantly replacing the plating solution with a new one.

The electroplating method for conductive short fibers of the present invention includes:
As described above, a cathode is formed on the inner bottom surface of the plating tank, and the short fibers to be plated are deposited on this inner bottom surface, and the short fibers are substantially deposited on the inner bottom surface of the plating tank while being stirred. This method is characterized by electroplating while maintaining a state in which the short fibers are kept in contact with each other under stirring.

Therefore, plating is performed while being in contact with the cathode formed on the bottom surface of the plating tank (t), and according to the present invention, the diameter is 10 to 60 mm.
Electroplating can be carried out uniformly and reliably even on minute short fibers such as 0 μm and 0.5 to 6 mm in length using simple and inexpensive equipment, with good adhesion, uniformity, and stable electroplating. You can get a kimono.

The electroplated film-coated short fibers obtained in this way are resistant to acid arsenic, rust, and corrosion, and have excellent heat resistance, chemical resistance, and abrasion resistance, and can be used as friction materials, conductive inks, paint,
It can be suitably used as a material for adhesives, plastics, plastic composites, concrete reinforcing materials, electromagnetic shielding materials, contacts, etc. In particular, silver-coated short fibers obtained by electro-silver plating have almost the same performance as silver powder, and can also be produced at a lower cost than silver powder.
It is extremely effective as a substitute for silver powder.

Among these, silver-plated short iron fibers, copper and copper alloy short fibers overcome the shortcomings of composite materials, such as being susceptible to acids, rust, and corrosion, and have excellent electrical conductivity! This is extremely useful in engineering and Qin.

The present invention will be specifically explained below with reference to all examples, but the present invention is not limited to the following examples.

(Example) Short iron fibers (diameter 30μ, length 3wa) were nickel-plated and silver-plated by the following method.

Degrease the sweet and short iron fibers 201, then wash with water.

Acid washing and water washing were performed to remove dirt and acid film on the surface of the short iron fibers.

The degreaser is Asahi Cleaner C-40 manufactured by Uezai Kogyo ■.
00 Zen 50971 was used, and degreasing was carried out by immersing it in this at a temperature of 50 to 600 for about 10 minutes and stirring.

Next, the pretreated short iron fibers were processed using an apparatus as shown in Figure 1. Electrolytic nickel plating was performed using the following conditions.

Nickel plating conditions Plating solution composition Nickel sulfate hexahydrate 280 P/1 salt r Ni hexahydrate 45 Boric acid
40 1 pi-14,2 Short iron fiber 50 y Plating tank (cathode) 3 (IOl stainless steel made (inner part is glass-coated, only the inner bottom surface is exposed entirely of stainless steel. Inner bottom surface 73mφ0
) Anode Nickel plate plating solution volume 200ml 1V cathode current volume 1
．． 4X10 A/, f plating temperature 5
5 C plating time 60 minutes Stirring Using an impeller set stirrer (
(Rotation speed: 6 rpm) Nickel plating was performed by completely precipitating and depositing short iron fibers on the bottom surface (cathode) of the plating tank.

After nickel plating, remove the plating solution, wash thoroughly with water, and prepare the nickel-plated film-coated iron fiber (N) under the following conditions.
i-Fe short fibers) were silver-plated.

The plating tank used was the same as above, and the anode was made of stainless steel.

Plating solution composition Blue 1 Silver 36 Li/J Back ratio Potassium
60 〃 Potassium carbonate 45 N PH12.0 Short iron fiber coated with nickel plating film Approximately 50y plating solution volume
200m/ Cathode current Fl, 0X10 1V'9 Plating temperature 25 C Plating time 15 minutes Stirring Using an impeller set stirrer (rotation speed 60 rprn) The short iron fiber coated with nickel plating film becomes grayish white in its entirety in about 5 minutes, and it is heated for 15 minutes. Later, it took on a silvery white color.

After silver plating, remove the plating solution, wash thoroughly with water, filter, and dry to coat the iron short fibers with a nickel plating film, and then produce the short fibers (Ag-Ni-Fe short fibers) coated with a silver plating film. Obtained.

Regarding Ni-Fe short fibers obtained by the method described above.

As a result of the SEM photograph and the nickel distribution image obtained using an X-ray microanalyzer, it was confirmed that nickel was uniformly electrodeposited on the short iron fibers. Furthermore, Ag-Ni-Fe short fibers, which are made by coating 5Ni-Fe short fibers with a silver plating film, were also found to be uniformly coated with silver. It was found that it can be obtained.

In addition, dinickel plating and silver plating were performed using short steel fibers in the same manner as described above. Obtained Ni-Cu
Short fibers and heter Ni--Cu short fibers were examined in the same manner as above, and both were found to be uniformly covered with electrodeposit.

Next, each of the short fibers obtained by the above electroplating and the untreated short iron and steel fibers as comparative products were pressure-molded to a diameter of 10 threads and a thickness of 31I @ at a pressure of 20 Kr/d using stearic acid as a binder. The conductivity of the molded product was then examined using a tester. In this case, various amounts of stearic acid were used to perform pressure molding, and the maximum amount of stearic acid at which each molded product exhibited electrical conductivity was determined.

The results are shown in the table. The results show the content of stearic acid in the entire molded product (all percentages indicate weight %, the same applies hereinafter), and the higher the content of stearic acid, the better the conductivity of the fibers.

From the results in the table, untreated short iron fibers and short copper fibers do not show conductivity unless the amount of binder used is below 13.3% and 13.5%, respectively, whereas these short fibers do not contain nickel. Those with plating are 23.5% and 27, respectively.
．． 1%, and those with further silver plating are 33.3% each.
%, 33.8% of the total binder mixture showed conductivity, and it was recognized that the conductivity was clearly improved.

That is, according to the method of the present invention, it is possible to easily and inexpensively electroplat metal fibers to obtain a highly conductive filler, and as described above, this filler can be used as an untreated short metal fiber. By using about twice as much binder as compared to the conventional method, it is recognized that the plated short fiber is a filler that has excellent properties that do not completely eliminate the properties of binders such as rubber and resin. Ta.

70% each of the chopped Ag-Ni-Cu short fibers and commercially available electrolytic silver powder were mixed with 30% Cemedine C (Cemedine Co., Ltd.)
Prepare a pastera mixed with and apply these onto a plastic substrate to a width of about 3WIL each.

A line section with a length of 20 mm was formed. After the adhesive had dried, the conductivity of each line was compared using a tester.
- Cu short fibers and commercially available electrolytic silver powder exhibit exactly the same degree of conductivity, and therefore Ag-Ni-Cu short fibers have substantially the same conductivity and performance vi- as commercially available ρ silver powder, and conductive filler and electromagnetic shielding. This Ag-Ni-
Since the base material of Cu short fibers is copper, the cost is reduced by 1
It can be reduced to about /2 to 1/3.

It has been recognized that it can be provided for a variety of purposes at a much lower cost than silver powder. In this way, by coating inexpensive short steel fibers with a nickel plating film and furthermore with a silver plating film, the shortcomings of short steel fibers, such as acid famine and corrosion, can be prevented by coating them with a nickel plating film and furthermore, a silver plating film. Because it is possible to obtain a conductive material that has the same electrical properties as silver powder, it has great industrial utility.

[Example 2] Plating was performed using 50P'e short glass fibers having a diameter of 50μ and a length of 3wIb by the following method.

First, short glass fibers were degreased, then washed with water, pickled, and washed with water, followed by chemical nickel plating according to the following steps.

Sensitizing: Stannous chloride bath solution 50t ILl water washing↓ Actipation: Salt f Hibaradium solution 50d↓ Water washing↓ fHigaku nickel plating: Kamizai Kogyo BEL nickel↓
1°51°C Reducing agent dimethylborazane) Washing with water The chemical nickel plating was carried out so that the weight of the nickel film was approximately 5 to 10% of the total weight.

Next, this short glass fiber was subjected to dielectric nickel plating, first electrolytic silver plating, and then electrolytic silver plating according to Example 1 using an apparatus as shown in FIG. 1 under the following conditions.

Plating solution composition Same chemical plating film coated short glass fiber as in Example 1 Approximately 50y7 plating tank (cathode)
Made of 800A stainless steel (inner part is coated with plastic and only the inner bottom surface is exposed stainless steel. Inner bottom surface has a diameter of 100 mm.) Anode Nickel number plating solution amount 400Kg Cathode current amount 1.4X10; to/no plating temperature 55C Plating time 120 minutes Stirring Using an impeller set stirrer (
Rotation speed 6 rpm) Plating @ Liquid composition Same plating bath (cathode) as in Example 1, Same anode as above Stainless steel temporary plating @ Liquid volume 400 m1, Cathode current amount 6.0 x 10 A/7 Plating temperature 25°C Plating time Stirring for 120 minutes Using a stirrer with an impeller set (rotation speed 1 Orpm) Ni-glass short fibers obtained by the above method ((electrolytic nickel plating film coated on Ni-glass short fibers coated with a nickel film) and Ag-Ni - All short glass fibers (further coated with a silver-plated film) have an electroplated film uniformly deposited on them, and it was discovered that a uniform electrodeposited product can be obtained by the method of the present invention. .

Also, if the short fibers are non-conductive, can they be removed before electroplating? However, in the present invention, when chemical plating is applied to short fibers, the thickness of the film may be such that electroplating is possible. The thickness of the film can be made thinner than that of the conventional method, and the cost can be significantly reduced.

In addition, when comparing the properties of the chemical nickel-plated non-conductive short fibers and the electro-nickel-plated non-conductive short fibers obtained by the method described above, it was found that the electrolytic nickel-plated short fibers obtained by the method of the present invention were nickel-plated. It was found that the plated film was less susceptible to acid abrasion and had very good stability.

That is, for 50 pieces of short glass fiber, 1) nickel plating @ film coated glass staple fiber obtained according to the above-mentioned 1) nickel plating method, and 5) electrolytic nickel plating as described above on the following page of 1) nickel plating. Electrolytic nickel membranes with similar nickel thicknesses were obtained by syllables with membrane-coated glass ffl# fibers (Ni-glass fibers), respectively with a diameter of 0 and a thickness of 3 When pressure molded to about maI and the conductivity of the molded product was measured with a tester, the short glass fiber coated with nickel plating film was 50 Kr/i.
In contrast, the Ni-glass short fiber according to the method of the present invention became conductive at a pressing force of 20 to 91,511 mm. Therefore, from this, it was recognized that by the method of the present invention, it is possible to obtain conductive short fibers that are conductive even at low pressure and have good physical properties, and furthermore, it is possible to significantly reduce the manufacturing cost.

Furthermore, the electrical conductivity was compared using the same method as shown in Example 1 using the Ag-Ni-glass short fibers obtained by the method described above and commercially available electrolytic silver powder. Iron powder was found to exhibit the same degree of conductivity.

[Brief explanation of the drawing]

1 to 4 are schematic sectional views each showing an example of a plating apparatus used in the present invention. 1゛...Metsukifu, 1a...Inner bottom surface, 3...Cathode lead wire, 4...Cathode plate, 5...Short fiber, 6...Yutou lead wire. 7. Anode. Applicant Uemura Kogyo Co., Ltd. Agent Masaru Takashi Kojima

Claims (1)

[Claims] 1. A cathode was formed on the inner bottom surface of the plating tank, and conductive short fibers to be plated were deposited on this inner bottom surface, and the short fibers were substantially deposited on the inner bottom surface of the plating tank under stirring. 1. A method for electroplating short fibers having conductivity, characterized by performing electroplating while maintaining a state.