JPH02153076A - Production of copper-silver two-layer coated powder - Google Patents

Abstract

PURPOSE:To efficiently and industrially produce Cu-Ag two-layer coated powder having superior uniformity and adhesion by chemically plating powder with Cu in a Cu plating soln., adding Ag ions to the plating soln. and chemically plating the Cu coated powder with Ag. CONSTITUTION:Powder with a noble metal such as Pt captured on the surface by a known method is chemically plated with Cu by immersion in a chemical Cu plating soln. contg. inorg. salts such as copper sulfate as a Cu ion source, an alkali such as NaOH, a complexing agent such as EDTA and a reducing agent such as formaldehyde. Ag ions or Ag complex ions are then added to the plating soln. in the form of an aq. silver nitrate soln., etc., and the Cu coated powder is chemically plated with Ag. Cu-Ag two-layer coated powder having superior uniformity and adhesion is industrially produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a copper-silver double-layer coated powder, and more specifically, injects silver ions or! into a used chemical copper plating solution. The present invention relates to an industrially applicable method for producing copper-silver double-layer coated powder with reduced plating waste liquid, which involves adding Ijf ions and subsequently subjecting the copper coated powder to chemical silver plating.

The present invention is suitable as a method for producing a copper-silver double-layer coated powder used for conductive fillers, conductive fibers, fillers for powder metallurgy, conductive auxiliary molding powders, contact materials, and the like.

[Conventional technology] A chemical plating method in which metal ions in a plating bath are reduced to metal using a reducing agent and deposited on the substrate surface is a chemical plating method that uses copper, nickel,
It is widely used for plating cobalt and these alloys, and is considered to be a suitable method for metal plating on powder as it can also be plated on non-metallic substrates (Jitsugyo Surface Technology, September issue).

(1980), pp. 8-12).

As the copper-silver double-layer plating method for powder, a method has been adopted in which the copper plating powder is plated using a conventional method, filtered, washed with water, and then dried, and then plated again using a chemical silver plating method, an electric plating method, etc. has been done.

As a chemical copper plating method for inorganic powder, the inorganic powder is catalyzed and then immersed in a chemical copper plating solution such as a Rochelle salt bath or an EDTA bath for copper plating (Japanese Patent Publication No. 58-017825). (Refer to publications, etc.), inorganic powder whose surface has been treated with a precious metal-capturing surface treatment agent is treated with a solution containing a precious metal to trap the precious metal on the surface, and then immersed in a chemical copper plating solution to perform cave plating. (Unexamined Japanese Patent Publication No. 6)
0-181294 etc.) is disclosed.

In addition, as a chemical silver plating method, nitric acid, ammonia?
There are methods using Rochelle salt and glucose as reducing agents in the 8-liquid, and immersion plating methods such as silver cyanide bath method and silver nitrate bath method (Metal Surface Technology, Vol. 36° No. 5.
(See P2-10.1985), silver cyanide bath method as an electroplating method (Electrochemistry Handbook, 4th edition, P377-37
8, 1986.1.25) is known.

[Problem that the invention seeks to solve]

As a method for producing a two-layer coating powder, a simple combination of the general chemical copper plating method and chemical silver plating method cited above produces two layers with uniform and even coating on both copper and silver. It is extremely difficult to obtain a coating.

Therefore, an industrially applicable method for producing a double-layered silver-coated powder has not yet been established.

SUMMARY OF THE INVENTION An object of the present invention is to provide an industrially applicable method for producing a copper-limited two-layer coated powder that is uniform, has no uneven adhesion, and has excellent adhesion.

[Means for solving problems]

In order to achieve the above object (as a result of intensive research, t5), the present inventors applied chemical copper plating to the body, and then added silver ions or silver complex ions to the chemical copper plating solution used therein,
The inventors discovered that by subsequently performing chemical silver plating, a copper-silver double-layer plating could be formed on the powder with high efficiency, and the present invention was completed.

The present invention uses a powder that captures precious metals on its surface to produce copper ions,
After applying chemical copper plating to the powder by immersing it in a chemical copper plating solution containing an alkali, a complexing agent, and a reducing agent, silver ions or silver complex ions are added to this plating solution, and then the copper-coated powder is coated with silver ions or silver complex ions. This is a method for producing copper-silver double-layer coated powder, which is characterized by applying chemical silver plating.

In the present invention, the powder to be subjected to chemical copper-silver double-layer plating is a powder, granule, plate, or fibrous substance that is stable against a chemical copper plating solution, such as muscovite mica, fluoride, etc. Logovite mica 5 Synthetic mica 5 Platy powder such as sericite, potassium titanate whiskers, acicular inorganic powder such as wollastonite, ashest, sepiolite, silica, alumina, talc, shirasu balloon, graphite, glass flakes, Crystalline or amorphous inorganic powders such as silicon nitride and silicon carbide, inorganic fibers such as glass fiber, carbon fiber, and silicon fiber, natural fibers such as wood pulp, bast fiber, type 1 hair fiber, nylon,
Examples include synthetic fibers such as vinylon, polyester, polyethylene, and polypropylene, and synthetic resin powders.

Powder with noble metal captured on its surface is powder in which fine particles of noble metal such as palladium, platinum, rhodium, etc. are attached or a film is formed on the surface of the powder to be plated with steel. There is no particular limit to the amount of precious metal captured, but in the case of inorganic powder, 3X1 per 100 parts by weight of powder.
0-3~3×10-! A range of ffi parts is preferred.

There is no particular restriction on the method of trapping the noble metal on the surface of the powder, and various known methods can be employed.

For example, a method in which the powder is immersed in an acidic solution of stannous chloride and then in an acidic solution of a noble metal, and a method in which the powder is immersed in a mixed acidic solution of stannous chloride and a noble metal and then treated with hydrochloric acid. Alternatively, a method may be adopted in which the powder is surface treated with a noble metal-capturing surface treatment agent and then treated with a solution containing a noble metal.

Copper ions are a copper source for forming a copper coating on the surface of powder by reduction, and inorganic salts such as copper sulfate, copper chloride, copper nitrate, and copper acetate are used as copper ion sources. Ru.

Alkali is used to neutralize the acid generated by ion dissociation of copper salts and liberate copper ions, and usually
Sodium hydroxide, sodium carbonate, ammonium hydroxide, etc. are used.

The complexing agent is used to form a chelate ring with copper ions so that the copper ions stably exist in the chemical steel plating solution. Complexing agents preferably used in chemical copper plating are used.

The reducing agent is a component for reducing copper ions to metallic copper, and for example, formaldehyde (formalin), rose formaldehyde, etc. are used.

Silver ions or silver complex ions are used to form a silver coating on the W4 coating of powder steel plated powder by reduction! source, for example, silver nitrate aqueous solution, EDTA-1111
T ion, ethylenediamine-silver complex ion, ammonium-silver complex ion, etc. are used.

In the present invention, copper plating and silver plating are performed continuously using the same plating bath.

The quality of the copper-silver double layer coated powder depends on the quality of the copper coating.

In copper plating, by controlling the PTI of the plating bath and controlling the rate of copper precipitation onto the powder surface, a uniform copper coating with excellent adhesion can be formed on the powder surface.

Particularly in copper plating by batch operation, the initial pH is maintained low and the copper precipitation rate is reduced to 0.
Keep it below 5mg/cd・11r.

After completion of copper plating, the plating is carried out by adding silver ions or silver complex ions all at once or continuously to the plating bath containing the copper coating powder and the used copper plating solution. At the end of copper plating, the reducing agent remaining in the plating solution reduces the negative ions, or the coated copper replaces silver ions or silver complex ions, and silver precipitates on the copper coating to form a silver coating, A powder coated with two layers of copper and silver is obtained.

In the above operation, after the copper-silver double-layer plating of the powder is completed through a series of operations, the copper-silver double-layer coated powder is separated and the plating waste liquid contains the spent copper ions, alkali and reducing agent, and the copper-silver double-layer coated powder. By adding the complexing agent that has adhered to the body and taken out of the system, it can be used repeatedly as a chemical copper plating solution.

With the repeated use of plating waste liquid, by-product salts such as sodium sulfate and sodium formate accumulate in the plating bath, but even if these salts are saturated, the plating bath remains stable, and if they precipitate, , it can be used repeatedly by taking it out of the system together with the copper-silver double-layer coated powder.

[For production]

The present invention is characterized in that after chemical copper plating is completed, ions or silver complex ions are added to the plating bath without changing the plating bath, and then chemical silver plating is performed on the copper-coated powder.

In the present invention, the plating solution after chemical copper plating is
Copper complexing agents, reducing agents, by-product salts, etc. remain, and silver ions or 11j! remain in the plating solution after chemical copper plating. By adding ions and subsequently performing chemical silver plating of the copper-coated powder obtained by chemical copper plating, the silver ions or silver complex ions are reduced by the residual reducing agent and the coated copper, and the copper-coated powder is reduced. Silver deposits uniformly on the surface of the copper plate, forming a silver coating with uniform and excellent adhesion.
A powder coated with two layers of silver is obtained. In particular, by performing silver plating without taking the copper-coated powder out of the system after copper plating is completed, the copper is not oxidized and frees from ions and roots.
Since f ions are replaced and precipitated, a good silver coating can be obtained.

In addition, in the present invention, since no silver ions remain in the plating solution after silver plating, by preparing the copper ions and reducing agent in the plating solution after finishing the grudge,
Can be used repeatedly as a chemical copper plating solution.

〔Example〕

The present invention will be explained in more detail by Examples and Comparative Examples.

However, the scope of the present invention is not limited in any way by the following examples.

(1) Preparation of copper-silver double-layer coated powder (a) Sample 1 Cu-Ag double-layer coated glass fiber - treated with aminosilane, average particle size 11 μm, average length 0.
100 g of 5 mm short glass fibers was immersed in 1.500 mj2 of an acidic aqueous solution of hydrochloric acid with a tin chloride concentration of 0.2 g/l at 50°C for 30 minutes, filtered and washed with water, and then soaked in an acidic aqueous solution of hydrochloric acid with a palladium chloride concentration of 17 mg/l at room temperature. The fibers were immersed in water for 30 minutes, filtered and washed with water to obtain short glass fibers with palladium captured on their surfaces.

The short glass fibers subjected to the above surface activation treatment were added to a 2N chemical steel plating solution with the following composition, and the plating reaction was started at a reaction temperature of 70°C, pH 0.5, and water was added after about 5 minutes. Add sodium oxide to adjust the pH to 9°2,
The plating reaction was continued for a period of time to obtain copper-coated short glass fibers.

[Chemical copper plating solution composition] CuSOa ・5HtO60g / 1[! DTA・4
Na・2HxO120g/It11cIIO (35%)
74 mm! / j! Next, a nitrate #jff aqueous solution (AgNOs: 31 g
100 rrl was added and kept under stirring for 10 minutes to obtain a copper-silver double-layer coated short glass fiber: Sample 1.

The resulting copper-silver double-layer coated short glass fibers had a copper content of 20
．． The silver content was 1.45% by weight, and the color tone was bright printing color.

Further, the volume resistivity at a volume filling factor (vf) of 10.0% was 8×10−′Ω·Cl11.

Furthermore, as a result of observation using a scanning electron microscope and an X-ray microanalyzer, it was observed that a uniform copper-silver two-layer coating was formed on the surface of the short glass fibers.

(b) Sample 2 Copper-silver double layer coated polyester fiber average diameter 15 μm 1 average length 0.8 mm Polyester shortening! 150g, tin chloride concentration 1.0g/j! After being immersed in an acidic solution of hydrochloric acid at room temperature for 30 minutes, filtered and washed with water, the palladium chloride concentration was 10 mg/j! The fibers were immersed in an acidic aqueous solution of hydrochloric acid at room temperature for 30 minutes, filtered, and washed with water to obtain short polyester fibers with palladium trapped on their surfaces.

The polyester short fibers obtained by the above surface activation treatment were added to a chemical copper plating solution 21 having the following composition, and the reaction temperature was 70° C., the initial pH was 1. The plating reaction was started under the conditions of 0. After about 5 minutes, sodium hydroxide was added to adjust the pH to 9.
．． 3, and the reaction was continued for an additional 700 minutes to obtain copper-coated polyester short fibers.

[Chemical copper plating solution composition]

Cu5On ・511t0 80 g
/ IEDTA・4Na・2HxO160g/e+1
CIIO (35%) 125m1/j! Next, the pH of the reaction solution after chemical copper plating was adjusted to 9.0, and a silver nitrate-ethylenediamine solution (AgNO324
3g/E, ethylenediamine: 25 g/β) 100
mρ was added continuously over a period of 15 minutes, a copper plating reaction was followed by a plating reaction, and a copper-silver double-layer coated polyester staple fiber: Sample 2 was obtained.

The obtained copper-silver double-layer coated polyester short fiber had a copper content of 44.0% by weight and a silver content of 3.0% by weight, and the color tone was a bright copper color with a slight beige tinge.

Further, the volume resistivity at a volume filling factor (vf) of 8.0% was 1.0×10 −2 Ω·1.

Further, as a result of observation using a scanning electron microscope and an X-ray microanalyzer, it was observed that a uniform copper-silver two-layer coating was formed on the surface of the polyester short fibers.

(C) Sample 3 Copper-root double-layer coated polyester fiber Copper sulfate and formalin with a copper ion ratio of 1.2 equivalents were added to the reaction solution after completion of limited plating in Example 2 to form a chemical copper plating solution with the following composition. was prepared.

[Chemical copper plating solution composition]

Cu5On ・511g0 80 g
/ IEDTA・4Na・2HzOf
60 g/IHIIJIO (35%)
120m1! ,/j! NatSOa
120g/I! HCOONa
100 g/1 Polyester short fibers subjected to surface activation treatment in the same manner as in Example 2 were added to this chemical copper plating solution, and the reaction temperature was 70°C.
The reaction was started under the conditions of 10.7, and after about 5 minutes, sodium hydroxide was added to adjust the pH to 9.2, and then the pH was adjusted to 75.
The reaction was continued for a minute to obtain copper-coated polyester short fibers.

A silver nitrate-EDTA solution (8 g NOs: 23.6 g/j!, EDTA; 60
g/f) 100mj! was added, and following the copper plating reaction, a grudge reaction was performed to obtain a copper-silver double-layer coated polyester short fiber: Sample 3.

The resulting copper-silver double-layer coated polyester staple fiber had a copper content of 43.5% by weight, a silver content of 1.6% by weight, and had a bright copper color tone.

Further, the volume resistivity at a volume filling factor (vf) of 8.0% was 1.5×10 −′Ω·1.

Further, as a result of observation using a scanning electron microscope and an X-ray microanalyzer, it was observed that a uniform copper-silver two-layer coating was formed on the surface of the polyester short fibers.

(d) Sample 4 Copper-gold double-layer coated carbon fiber average diameter 1
50 g of pitch-based short carbon fibers having a diameter of 3 μm and an average length of 0.8 mm were mixed with an aqueous sodium hydroxide solution (NaOll:
After degreasing using 100 g/12) and washing with water, it was soaked in an acidic solution of hydrochloric acid with a tin chloride concentration of 1.0 g/l at room temperature for 30 min.
Soaked for a minute, filtered, washed with water, then palladium chloride concentration 10mg/j! Hydrochloric acid acid water? 11'm.

The fibers were soaked in water for 30 minutes at room temperature, filtered, and washed with water to obtain pitch-based short carbon fibers with palladium captured on their surfaces.

The pitch-based short carbon fibers obtained by the above surface activation treatment were added to a chemical copper plating solution 2j2 having the following composition, and a plating reaction was started at a reaction temperature of 70°C and an initial pH of 10.5 for about 5 minutes. Afterward, sodium hydroxide was added to adjust the pH to 9.0, and the reaction was continued for an additional 70 minutes to obtain copper-coated pitch-based short carbon fibers.

[Chemical copper plating solution composition]

Cu5Oa ・514g0 40 g
/ IEDT^・4Na・2To0 80 g
/IIC) 10 (35%) 60 m
l/j! Next, 100mj of silver nitrate aqueous solution (AgNOs: 23g/f) was added to the reaction solution after chemical copper plating was completed.
was added, followed by a copper plating reaction and then a silver plating reaction to obtain sample 4: pitch-based short carbon fiber coated with two layers of copper and silver.

The obtained pitch-based short carbon fiber coated with two layers of copper and roots had a copper content of 47.0% by weight, a silver content of 1.5% by weight, and a bright copper color tone.

Further, the volume resistivity at a volume filling factor (vf) of 7.5% was 1.5XIO-''Ω·cm.

Furthermore, as a result of observation using a scanning electron microscope and an X-ray microanalyzer, it was observed that a uniform copper-silver two-layer coating was formed on the surface of the pitch-based short carbon fibers.

(2) Composite material for electromagnetic shielding (Application example 1) Glass short fiber coated with two layers of copper and silver obtained in Example 1; Sample I or short carbon fiber coated with two layers of copper and silver obtained in Example 4: Sample 4 was mixed with ABS resin (QF type, made by Denki Kagaku ■) as a conductive filler, and heated at 260°C using a Ni-Goo.
A test piece of a composite material for electromagnetic shielding was prepared by kneading and compression molding at a temperature of .

Volume resistivity value and ASTM using the prepared test piece
0 whose frequency characteristics were measured in accordance with ES-7-83
To measure frequency characteristics, we used a near-field measurement jig (NFC-10
00, manufactured by Electrontric Co., Ltd.) was used.

Table 1 shows the volumetric filling rate of the conductive filler in the composite material and the properties of the composite material.

Table 1 Characteristics of ABS resin composite material molded product As shown in Table 1, the resin molded product containing the copper-silver double-layer coated fiber of the present invention as a conductive filler has a volume filling rate of the conductive filler of 10. % or less, the volume resistivity is small and exhibits excellent electromagnetic shielding properties in a wide frequency range of 0-10-1000.

(3) Conductive paper for electromagnetic shielding (Application example 2) Copper-silver double-layer coated polyester staple fiber obtained in Example 2 or Example 3: Sample 2 or Sample 3, polyethylene synthetic pulp (SW
P-E620. Made by Mitsui Petrochemical Co., Ltd.) and Canadian Freeness Test 4a3'70m1 softwood bleached kraft pulp (NBKP) as paper stock components, using a hand paper machine in accordance with JISP-8209, containing copper-silver double-layer coated polyester short fibers. Rate 30% by weight and 40ffi amount%, SW
P/NBKP-2/1 (weight ratio), Tsubo 180g/rd
After paper making and drying under the following conditions, 1
Heat fusion treatment was performed at a temperature of 40°C to produce a sheet-like conductive paper.

Surface resistance value of the prepared conductive paper and ASTMES7-8
The frequency characteristics were measured in accordance with 3.

The measuring device used in Application Example 1 was used to measure the frequency characteristics.

The measurement results are shown in Table 2.

Table 2 Characteristics of conductive paper Basis weight -80 g/nf As shown in Table 2, this conductive paper has a small surface resistance value and exhibits electromagnetic shielding characteristics of 50 dB or more in all frequency regions.

(4) Moisture resistance of conductive paper (Application example 3 and reference example) Copper-silver diN coated polyester short fiber of Example 2: Sample 2,
Copper-coated polyethylene short fibers obtained in the process of manufacturing the double-layer coated polyester short fibers of Example 2: Reference sample 1 and the copper-nickel double-layer coated fibers obtained by chemically nickel plating the copper-coated polyethylene short fibers. Polyester staple fiber (copper content: 40.2% by weight, nickel content: 10
．． 1% by weight): using reference sample 2, conductive polyester staple fiber content 30% by weight, SWP/NBKP=47/2
A sheet-like conductive paper was produced by processing in the same manner as in Application Example 2 under the conditions of 3 (Iffi ratio) and basis weight F: JOg/po.

The obtained conductive paper was subjected to a humidity test in which it was exposed to conditions of a temperature of 48''C and a relative humidity of 85% for 48 hours, and the surface resistance value and electromagnetic shielding properties before and after the humidity test were measured.

The measurement results are shown in Table 3.

Table 3 Moisture resistance properties of conductive paper Tsubo! -80g/I As shown in Table 3, the moisture resistance of the conductive paper using the copper-silver double layer coated polyester staple fiber of the present invention is as follows. Even better than conductive paper using fibers.

That is, this result shows that the silver coating of the copper-silver double-layer coated polyester short fiber is formed by uniformly M-adhering on the copper coating.

〔Effect of the invention〕

In the present invention, as shown in the above example, a uniform silver coating can be formed on the copper coating with high efficiency by a simple operation of adding root ions or silver complex ions to the reaction solution after chemical copper plating is completed. be done.

In addition, the reaction solution after silver plating is used as a copper plating solution.
One ring can be used (see Example 3), so that
Since the expensive complexing agent used in chemical plating is not discarded as plating waste and is used repeatedly, powder can be coated with two layers of copper and silver at extremely low cost.

The present invention provides a manufacturing method that can produce industrially applicable copper-silver double-layer coated powder with excellent uniformity, adhesion, and adhesive properties, and its industrial significance is extremely high. big.

Claims (1)

[Claims] (1) Powder with precious metals captured on its surface is immersed in a chemical copper plating solution containing copper ions, an alkali, a complexing agent, and a reducing agent to perform chemical copper plating. A method for producing a copper-silver double-layer coated powder, which comprises adding silver ions or silver complex ions and subsequently subjecting the copper coated powder to chemical silver plating.