JPS60181294A - Production of inorganic powder having metallic film on surface - Google Patents

Abstract

PURPOSE:To obtain inorg. powder having a metallic film of a desired thickness by subjecting the inorg. powder to a surface treatment with a soln. contg. noble metal ions then forming a desired chemical plating layer and subjecting further the powder to electroplating. CONSTITUTION:Inorg. powder of mica, etc. is subjected to a surface treatment using a surface treating agent such as gamma-chloropropyl trimethoxysilane or the like having a property to capture noble metals and the surface thereof is prepd. by immersing the powder into a soln. contg. noble metal ion of palladium chloride, etc. The powder is then treated by a plating liquid contg. required metallic ions of Ni, Zn, etc. to form a plating layer to the extent of covering the powder surface. The powder is subjected to electroplating of Ni, etc. by using a required plating soln. in succession thereto to form a plating layer to a desired thickness. The metal-coated inorg. powder which has good conductivity and is suitable as a packing material for an electromagnetic shielding material is obtd. by the above- mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing inorganic powder having a metal coating on its surface. By applying electroplating to the plastic, it has a strongly adhered metal film with a sufficient thickness on the surface that can impart electromagnetic shielding properties, antistatic properties, mechanical strength, etc. to the plastic when mixed with the plastic. The present invention relates to a method for producing inorganic powder.

Recently, with the spread of various electronic devices, electromagnetic noise caused by these devices is becoming a serious social problem. For this reason, there has been an increasing need for electromagnetic shielding materials to prevent disturbances caused by such noise. Until now, this electromagnetic shielding material has been produced by metal spraying on a suitable base material.
However, these are expensive and have poor durability, so they are not necessarily satisfactory in practical terms.

Incidentally, inorganic powders are widely used as fillers in various fields, such as the field of plastics.
Since it is not conductive, if it gets mixed into plastic,
Plastics cannot have antistatic or electromagnetic shielding properties.

On the other hand, conductive fillers include powders of various metals or alloys, but these are generally used as pigments for printing paints, and although they can be used as colorants for plastics, they have a low elastic modulus. Therefore, it cannot be used as a reinforcing agent. Furthermore, metal powder is treated as a dangerous substance, and its management is extremely difficult.

On the other hand, a method is known in which an inorganic powder having a metal film obtained by subjecting the surface of the inorganic powder to a sensitization and activation treatment and then chemical plating is used as a filler. However, with ordinary chemical plating methods, it is difficult to form a complete plating layer that completely covers the surface of the inorganic powder, and the bonding strength between the inorganic powder and the plating layer is insufficient. .

Therefore, although it may be effective to some extent when used in places where the adhesion of the plating film is not required, under harsh conditions such as when kneading into plastic, the plating film will peel off and provide good electromagnetic shielding properties. As a product, the conductivity is insufficient, and it is almost impossible to put it to practical use.

For this reason, the present inventors conducted research to improve the shortcomings of conventional chemical plating methods and to develop a technology that can apply a plating layer that can be sufficiently used as a filler for electromagnetic shielding materials. Inorganic powder, which has been previously surface-treated using a noble metal-capturing surface treatment agent, is surface-treated with a solution containing noble metal ions to form a noble metal layer on the surface of the inorganic powder, and then the required metal ions are added to the surface of the inorganic powder. When the metal is deposited in the form of a film on the surface of the precious metal layer, a strong and uniform metal film is formed on the surface of the inorganic powder, and the inorganic powder has conductivity. We discovered that this can be obtained and proposed an electromagnetic shielding material using this material.

By the way, among plating methods, chemical plating is generally expensive due to its slow deposition rate and the use of expensive reducing agents12, whereas electroplating has these drawbacks. This method is considered to be more preferable as an industrially implemented method because the required plating layer can be formed efficiently without any problems.

However, since inorganic powder itself does not have conductivity, electroplating cannot be applied, and as mentioned above, chemical plating has to be relied upon.

Therefore, the present inventors conducted further research.

After forming a plating layer to the extent that it covers at least substantially the entire surface of the inorganic powder by the chemical plating method described above and imparting conductivity, the required layer thickness is obtained by a normal electroplating method. By forming a plating layer up to 5-1, it was discovered that the material was suitable as a filler for electromagnetic shielding material, and based on this knowledge, the present invention was accomplished.

That is, in the present invention, an inorganic powder surface-treated using a noble metal-capturing surface treatment agent is surface-treated using a solution containing noble metal ions, and then treated with a chemical plating solution containing the desired metal ions. Coat the entire surface of the powder7
The present invention provides a method for producing an inorganic powder having a metal film on its surface, which is characterized by forming a plating layer to the extent that the powder is wet, and then further electroplating to obtain a plating layer with a desired thickness. .

The inorganic powder having a metal film on the surface obtained by the method of the present invention is chemically stable because, unlike metal fibers and metal powder, the inside is a stable inorganic substance and metal is present only on the surface. Moreover, when blended into plastics, high conductivity can be imparted with a small metal content without any loss in moldability, and a high reinforcing effect can be obtained by using a plate-shaped photoresist such as mica. It has the advantage of being able to

As the inorganic powder used in the method of the present invention, inorganic substances conventionally used as extenders, colorants, and reinforcing agents for plastics, rubber, etc. can be used. These include, for example, platy mica minerals such as muscovite mica, phlogopite mica, and synthetic fluorinated mica, acicular minerals such as potassium titanate whiskers, wollastonite, asbestos, and sepiolite, as well as silicic minerals. Examples of the material include alumina, talc, shirasu balloon, g≠phite, glass flakes, glass fiber, carbon fiber, and silicon fiber, but plate-like mica minerals are particularly preferred from the viewpoint of reinforcing effect. In the method of the present invention, a metal film is formed on the surface of the inorganic powder by a chemical plating method and an electroplating method. It needs to be good. There are no particular restrictions on the shape of the trench inorganic powder, and various shapes such as plate, needle or fiber, and granule can be used.

In order to produce inorganic powder having a υ metal film on its surface by the method of the present invention, such inorganic powder is first subjected to surface treatment using a noble metal-capturing surface treatment agent. A film of the surface treatment agent is formed on the body surface. In this case, the noble metal-capturing surface treatment agent is one that can increase the adsorption ability of the inorganic powder to noble metals when it is adsorbed to the inorganic powder. An organic compound having at least one functional group having an affinity for precious metals and at least one functional group having a scavenging property (affinity) for noble metals is used.

Examples of functional groups that have an affinity for inorganic powders include carboxyl groups, ester groups, amino groups, amide groups, imino groups, hydroxyl groups, nitrile groups, halogen groups (chloro groups, bromine groups, etc.), and isocyanate groups. , glycidoxy groups, alkoxy groups bonded to silane and titanium, unsaturated groups such as vinyl groups, etc. Groups that exhibit capture properties for noble metals include the various functional groups mentioned above,
Examples include unsaturated groups such as a pyridine ring and a vinyl group.

The two or more functional groups possessed by this noble metal-capturing surface treatment agent may be of the same type or different types, and the bonding positions may be either at both ends of the molecule or at the side chain. Further, the molecular weight range of the surface treatment agent having these functional groups may be from a low molecular weight compound to an oligomer or a polymer, and is not particularly limited.

The bonding strength of the surface treatment agent to the inorganic powder differs depending on whether the functional group of the surface treatment agent is chemically or physically bonded to the surface of the inorganic powder. When bonding to the surface treatment agent, the bonding force of the surface treatment agent is strong, and as a result, the adhesion of the resulting metal film is also high. For example, in the case of silane coupling agents and titanium coupling agents, alkoxy groups are chemically bonded to the powder surface, while in the case of surface treatment agents that are soluble in water or alcohol, they are When dissolved in a solvent, the surface of the powder is treated using this solution, and the powder is dried, the surface treatment agent adheres to the surface of the powder by physicochemical adsorption force. Since adhesion due to such physicochemical adsorption power is not very strong,
It is best to make the carbon chain (methylene bond) in the treating agent molecule hydrophobic enough to prevent water from entering the adhesion interface and prevent the surface treating agent from detaching from the powder surface, or to increase its molecular weight. For example, when the surface treatment agent is an aliphatic compound, preferably an aliphatic compound having three or more methylene groups is used.

Examples of the noble metal scavenging surface treatment agent having two or more functional groups as described above include γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and γ-methacryloxypropyltriethoxysilane. , N-β-aminoethyl-T~
silane compounds such as ruaminopropyltrimethoxysilane N-β-aminoethyl-r-aminopropylmethyldimethoxysilane; amine compounds such as hexamethylenediamine, trimethylenediamine, and diaminododecane; Dicarboxylic acids; glycol compounds such as triethylene glycol and polyethylene glyconopediglycolamine; nitrile compounds such as malonitrile and polyacrylonitrile;
Isopropyltri(dioctylpyrophosphinate)
In addition to titanate compounds such as titanate, titanium di(dioctyl pyrophosphate) oxyacetate, isopropyl (N-ethylamino-ethylamine) titanate, and isopropyl triisostearoyl titanate, maleated polybutadiene, terminally carboxylated polybutadiene, terminally glycolized polybutadiene, Butadiene polymers such as acrylonitrile/butadiene copolymers and polybutadiene, butadiene copolymers and their graft compounds; unsaturated fatty acids such as linoleic acid and lylunic acid; chlorinated products such as chlorinated paraffin and chlorinated polyethylene; and melamine resins and melamine-urea. Examples include condensation resins such as cocondensation resins, urea resins, and phenol resins, and epoxy resins. As mentioned above, there are various noble metal-capturing surface treatment agents used in the present invention, and surface treatment agents suitable for the purpose of the invention can be confirmed through experiments.

In order to treat inorganic powder with a surface treatment agent capable of trapping metals as described above, the surface treatment agent is mixed with a suitable solvent, for example,
A wet method involves dissolving the inorganic powder in water, ethyl alcohol, acetone, toluene, dimethylformamide, dimethyl sulfoxide, dioxane, etc. to form a solution, immersing the inorganic powder in the solution, and then evaporating the solvent. , a dry method in which the solution is mechanically coated using a Henschel mixer or the like is used. In this case, the concentration of the surface treatment agent in the solution varies depending on the surface area of the powder, but preferably the maximum coverage area (i
/SJ), the specific surface area of the powder (m'/f), and the amount of powder to be treated (2). For example, when the specific surface area is about 5 doors/2, the weight factor is 0.5 to 2.

Further, after the surface treatment, the evaporation temperature of the solvent used is sufficient to volatilize the solvent from the powder. Furthermore, when using a silane-based surface treatment agent that undergoes a dehydration condensation reaction with the powder surface or between surface treatment agents, melamine resin, epoxy resin that undergoes a polymerization reaction, etc., after solvent volatilization, the
It is preferable to heat the reaction at a temperature of 0° C. for about 1 to 3 hours.

The inorganic powder surface-treated as described above has a modified surface so that a functional group capable of trapping noble metals is exposed on the surface. By contacting the powder with a solution, the functional groups capture the noble metal, and the noble metal is completely formed on the surface of the powder. In addition, noble metals are dispersed in advance in the surface treatment agent.1. ? It is also possible to fix the noble metal on the surface of the inorganic powder at the same time as the solvent is volatilized. This noble metal layer exhibits a catalytic effect when the metal ions contained therein are deposited on the powder surface from the subsequent chemical plating solution. As the noble metal in this case, palladium, platinum, gold, etc. are used, but palladium is preferable.

This solution containing noble metal ions can be prepared according to conventionally known methods, for example, by dissolving a soluble salt of a noble metal such as a halide in water in the presence of a solubilizing agent such as hydrochloric acid. . The amount of precious metal deposited is 3 x 10 parts by weight per 100 parts by weight of inorganic powder.
-5 to 3X10' parts by weight, preferably 3X]O-' to
3 x 10-'' parts by weight. The powder surface-treated with the solution containing noble metal ions is washed with water and subjected to the next chemical plating treatment.

As the chemical plating solution used in the present invention, various conventionally known ones can be employed. In addition, various metals can be mentioned as metals added to the plating solution to form a surface film on the inorganic powder. For example, N
i + Co + W + Fe + QuAg, A
u, Pd, Pt, Rh, Ru, Z
Examples include n. 'Also, the metal film formed on the surface of the inorganic powder may be made of a single metal or an alloy such as Ni.
-Co.

N1-W, Ni-Fe, Co-W, (!o
-re, Ni-0u, etc., but when forming an alloy film, the plating solution contains:
A plurality of metal salts may be added as desired. Chemical plating treatment on the surface-treated inorganic powder can be performed according to conventionally known methods, and generally, a plating solution containing metal salts, reducing agents, complexing agents, buffers, stabilizers, etc. is used. Adopted. In this case, the reducing agent used is sodium hypophosphite, sodium borohydride, aminoborane, formalin, etc., and the complexing agent or buffer used is formic acid, acetic acid, succinic acid, citric acid, tartaric acid, malic acid, etc. , glycine, ethylenediamine, E! DTA, triethanolamine, etc. are used.

A typical composition of the chemical plating solution is, for example, metal salt 10
~200 f//l, hypophosphite 0.3-50? /l
, a pH buffering agent of 5 to 3001/l, and preferably glycine 5 to 2009/l as an auxiliary additive to such a plating solution.
At can be added.

In addition, as other plating liquid, metal salt 10~2002/l
, carboxylate or EDTA salt 10-100 l/l, alkali hydroxide 10-609/l, alkali carbonate 5-50
Copper and silver are representative metals that can be plated.

Chemical plating treatment is usually performed at a temperature of 20 to 95°C, with stirring and force so that a uniform film is formed on the powder surface.
It is preferable to carry out from In this way, plating is continued until a metallization rate of 5% by weight or more is finally obtained, although it varies depending on the particle size and surface area of the powder.

In the present invention, as described above, since the surface properties of the inorganic powder have been modified to be suitable for chemical plating, it is extremely easy to form a metal film on the surface by chemical plating.

In the case of the present invention, not only fresh chemical plating solution but also used chemical plating waste solution can be used as the chemical plating solution. times) after
It can be used as a chemical plating solution in the present invention by adding a complexing agent and a reducing agent.

In the present invention, it is necessary to apply the chemical plating over the entire surface of the inorganic powder, and the inorganic powder that has been chemically plated in this way is further subjected to an electroplating process. In this electroplating process, it is necessary to use a specially shaped cathode so that the metal is deposited uniformly on the powder, and to use a method that periodically separates the powder from the cathode. It is. In addition, since the plating solution is stirred, the anode must be wrapped in a plastic net or a diaphragm may be used to prevent the metal deposited on the powder from coming into contact with the anode and causing dissolution. preferable.

As such electroplating treatment, for example, a nickel plating method, a copper plating method, a zinc plating method, etc. are used. In the nickel plating method, for example, the plating solution may contain 20 to 1,000 nickel salts. /l, boric acid 4~s ot7
t, 1,4-butynediol 0.1-0.5 f/l and saccharin 0.1-5 f/l, and pH 12
, adjusted to 0 to 5.0, and the liquid temperature is 30 to 70°C.
Electroplating is carried out under plating conditions of cathode current density of 1 to 20 A/di, with air stirring or circulating plating solution, until the metallization rate reaches 10% by weight or more. In the copper plating method, for example, 20~20~2oot7t of copper salt is used as the plating solution.
, 100-500 t/l of potassium pyrophosphate and 0.1-5-/l of ammonia, and a pH of 8-5.
9, liquid temperature 15-70°C, cathode current density 1-]OA/drr? Under plating conditions, the metallization rate is 10% by weight while air stirring or circulating the plating solution.
Electroplating is carried out until the top is reached. On the other hand, in the zinc plating method, for example, 10 to 500% of zinc salt is used as the plating solution.
and chloride 5 to 50 (1/l) and pH
adjusted to 2-6, or zinc salt 10-5002/
1, the pH of which was adjusted to 6.0 to 8.0 with ammonia, was used at a liquid temperature of 20 to 50°C and a cathode current density of 0.
Electroplating is performed under plating conditions of 1 to 60 A/am' while air stirring or circulating the plating solution until the gold ovalization rate reaches 10% by weight or higher.

18- The thus obtained inorganic powder having a metal coating on its surface can be added to plastics at a ratio of 10 to 70% by weight to provide excellent electromagnetic shielding properties to the plastics. Provides antistatic properties, mechanical strength, etc.

The plastics used here are thermoplastics,
Any thermosetting plastic may be used, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyacetal resin, polyurethane resin, nylon 6, ethylene-vinyl acetate copolymer. Polyester resins, ethylene-acrylic acid copolymers, ABS resins, epoxy resins, unsaturated polyester resins, phenolic resins, and the like are used.

Such a plastic composition can be applied in a conventionally used shape, and the manufacturing method of the product is appropriately carried out depending on the type, purpose, shape, etc. of the resin to be applied.
For example, in order to form molded objects in the form of plates, cylinders, boxes, pellets, etc., a mixture of plastic and filler can be processed by vacuum forming, extrusion molding, injection molding, calendar molding, compression molding, etc. In addition, in order to make a coating composition for forming a film, it is sufficient to add and mix a plastic emulsion or a plastic solvent solution RFC filler, and further,
When used as a rubber composition, the filler may be added to the usual rubber composition.

The above plastic composition has excellent electromagnetic shielding properties and high strength, and is particularly useful as equipment for various electronic devices, communication devices, medical devices, measuring instruments, and the like.

Next, the present invention will be explained in more detail with reference to Examples. The metallization rate of the filler in each example was defined as follows.

Example 1 Using mica and glass flakes with an average particle size of 60 mesh, 100 f of each was treated with a noble metal-capturing surface treatment agent,
γ-Aminopropyltriethoxysilane in 1 part ethanol
After being immersed in a solution dissolved in 20 CC at a concentration of 1.0 weight percent at room temperature for 2 hours, it was dried at a temperature of 110° C. for 2 hours to volatilize the solvent. Next, 20 grams each of the surface-treated mica flakes and glass flakes thus obtained were dissolved in an acidic aqueous solution of palladium chloride in hydrochloric acid (pacz2
Concentration 5×1O-6S'/7ri50 mI! at room temperature to 30
After soaking for a minute, it was filtered and washed twice with 20 cc of deionized water for surface treatment. Next, each of the surface-treated mica flakes and glass flakes is put into a nickel plating waste solution having the following composition, and treated with stirring at a temperature of 60 to 90°C for 2 to 5 minutes to chemically plate the surface. I gave 17.

-21 = Nickel plating waste liquid composition Nickel sulfate 30 f// Sodium hypophosphite 109/L Sodium succinate 16 g/L Sodium malate a o t7 Then, using a nickel plating solution with the following composition, The surface was electrolytically plated with nickel while the plating solution was being circulated at a temperature of 40° C. and a cathode current density of IA/d.

Nickel sulfate 3809/L nickel chloride 309/L Boric acid 409/L pH 3 The product obtained in this way has a nickel film on the surface, and when the conductivity of this product was examined using a tester, it was found to have good conductivity. It was confirmed that the

Example 2 22- Phlogopite mica powder 100 r'i with average particle size 120-140 mesh, epoxy resin C epoxy sail 57
, polyamide 0.51 i') was immersed in a mixed solution of ethanol and acetone (l) for 30 minutes, then the filtered solvent was evaporated, and the mixture was cured at 110°C for 1 hour. The mica powder 202 surface-treated in this way was dissolved in an acidic aqueous solution of palladium chloride in hydrochloric acid'/(1(
Pa, c72 concentration] X 10 fl/me) 50
ml for 1 hour at room temperature [7, then filtered to perform surface treatment. Next, the surface-treated mica powder was poured into a copper electroless plating solution having the following composition, stirred and treated at 50° C. for 30 minutes to coat the surface with copper.

CuSO4.5 H2O40f//l E'DTA-4Na 20 i/1 HCHO (35%) 148 me pH 11 Next, using a nickel plating solution having the composition shown in Example 1, the temperature was 45°C and the cathode current density IA/d. , tyi'' condition with a diaphragm inside (100 + nnyf
Electroplating was carried out in 150i+A). In this electroplating, in order to increase the contact between the mica powder and the cathode, a 100-mesh cylindrical stainless steel is placed in the center of the interior, and the pole rotates with the rotation of the barrel. Mica powder was removed from the electrode surface using a plastic brush.

The internal electroless plated copper film obtained in this way,
To determine the electrical resistance of mica powder whose surface has an electroplated nickel film, fill a cylinder with the powder at a volume filling rate of 20% by volume, and use the 4-terminal method (current values from both ends and the middle 2 The results are shown in Table 1.

Table 1 In addition, when the volume resistivity of mica powder having a film of only electroless plated copper was measured in the same manner as above, it was found that A
1. Door 2 and A3 are each 2.38 x 10. 4.5 X 10 and 1. I x 10
It was Ω・m.

Example 3 The types of metal compounds in the inorganic powder and plating solution were changed,
In the same manner as in Example 1, inorganic powders having metal coating 1 [surfaces] having the combinations shown in Table 2 were obtained.

Table 2 Application Example 1 Using 70 gobite-based powder with a particle size of 120 to 140 mesh, the surface was treated in the same manner as in Example 1, and then
A Ni film was formed on the powder surface by electroless chemical plating with a metallization rate of 26.2% by weight, and then a Ni film was further formed thereon by electroplating.

The final total gold fill rate of the obtained product was 48.84% by weight, and Ni by electroless plating and N by electroplating
The proportions within 1 were 18.16% by weight and 30.68% by weight, respectively.

The volume resistivity of the mica powder having a metal film on the surface thus obtained is determined by filling a cylinder with C so that the volume filling ratio becomes 20% by volume, and using the four-terminal method (current value is applied from both ends,
Measure by taking the voltage from two points in between (if 7, then 8
×10 Ω・(7).

Note that in the case of only electroless chemical plating treatment, this volume resistivity was 2.2×10 Ω·m.

The mica powder with this metal film on the surface is
The electromagnetic wave transmission loss at 4000 MHz using a detube was kneaded using a kneader so that the volume filling rate was 20% by weight per unit, and was obtained by compression molding. there were.

vinegar.

Table 3 Application example 2 Using phlogomite-based mica powder with various particle sizes,
After the base treatment was performed in the same manner as in Example 1, electroless chemical plating treatment and electroplating treatment were performed with different metallization rates to obtain mica powders having N1 coatings on the surface.

These powders were treated in the same manner as in Application Example 1.

These results are shown in Table 4.

Application Example 3 Using phlogovite-based mica powder with a particle size of 120 to 140 mesh, the surface was treated in the same manner as in Example 3, and then the surface of the powder was subjected to electroless chemical plating to achieve a metallization rate of 35.
A 0% by weight Ou film was formed, and then a N] film was further formed by electroplating. The final total metallization rate of the obtained product was 50.5% by weight, and the percentage of O by electroless plating and N1 by electroplating was 26%.
．． 6% by weight and 23.9% by weight.

The volume resistivity of the mica powder having the metal film on the surface thus obtained was measured using the method shown in Application Example 1, and it was found that the volume resistivity was 5×100.
It was the mouth. In addition, in the case of only electroless chemical copper plating, the filling rate was 1.7×10 Ω·min at the same filling rate.

This mica powder, which has a copper coating inside and a nickel coating on the surface, is added to low viscosity ABS at a volume filling rate of 20% by weight.
The electromagnetic wave transmission loss of the obtained composite material was determined by the same method as in Application Example 1 to 400.
As a result of measurement at 0 MHz, an electromagnetic interference effect of 25 dB was obtained.

Example 4 After applying chemical nickel plating in the same manner as in Example 1, using a zinc plating solution with the composition shown below, a cathode box containing flakes was placed in the plating solution, and the cathode box was rotated or semi-rotated. Galvanized.

The plating conditions were a temperature of 38°C and a cathode current density of -! #, A/d
m′.

Composition of zinc plating solution Metallic zinc 7.5t/l Sodium cyanide 11.3 ? / Sodium hydroxide 67.5g/1 NaON/zn ratio 1.5 The product thus obtained has a zinc film on its surface, and when the conductivity of this product was examined using a tester, it was found to be good. It was confirmed that the material has excellent conductivity.

Example 5 Water-soluble melamine resin 2f and its curing agent 0. ．． A solution of palladium chloride in hydrochloric acid (concentration 2.5
20-W was added, and then phlogovite mica (80~
120 mesh) After adding 100 r and stirring,
Leave it for 2 hours. Subsequently, after filtration, it was dried in a dryer at 110°C for 2
After time curing and drying, electroless nickel plating was performed in the same manner as in Example 1. At this time, the metallization rate was adjusted to 19.8% by weight. The volume resistivity of this mica powder that has a full nickel coating is 1.2X10 when the filling rate is 20 cm.
In the case of 25% of ohms, it was 1.0 ohms.

This powder is 40? 3 using a copper plating bath with the composition shown below.
It was placed in the barrel shown in Example 2 and electroplated for 3 hours under the conditions of 0° C. and cathode current density aA/di.

C! uso4-5H20250t/1 H2So4 5ot/l Allylthiourea o, 3t/l pH 0.8 The amount of copper plating is 8051, and the weight proportions of nickel and copper in the total weight are 16.5% and 16.8%, respectively.
It became. The volume resistivity after copper plating is a filling rate of 20q.
For 6, 9X10'Ω・saw, for 25chi, 3.4X
It became 10 Ω・sub.

Example 6 Using the method shown in Example 2, phlogopite-based mica powder (8
0 to 120 mesh) was subjected to electroless copper plating to obtain one with a metallization ratio of 32 inches. The volume resistivity of this powder was 2.0×10”Ω·− at a volumetric optical density of 20.

Furthermore, mica powder 4 with this electroless plated copper film
01 was subjected to electrolytic copper plating by the method shown in Example 5 for 1 hour 30 minutes.
4.0 Of electrolytic copper was deposited. therefore,
The percentages of electroless plated copper and electroplated copper on mica in the total weight were 29.1% and 9.1%, respectively. The volume resistivity of this powder was 1.8 x 10 Ω·m at a volumetric optical density of 20 cm.

Claims (1)

[Scope of Claims] 1. Inorganic powder that has been surface treated using a precious metal trapping surface treatment agent is surface treated using a solution containing noble metal ions, and then treated with a chemical plating solution containing the required metal ions. A metal coating characterized in that a plating layer is formed to cover substantially the entire surface of the powder, and then electroplating is applied to form a plating layer of a required thickness. A method for producing an inorganic powder having on the surface. 2. The manufacturing method according to claim 1, wherein the inorganic powder is mica. 3. The manufacturing method according to claim 1 or 2, wherein the chemical plating solution is a chemical plating waste solution or a metal gotting waste solution. 4. The manufacturing method according to claim 1, 2, or 3, wherein the metal coating is made of nickel, zinc, copper, cobalt, chromium, silver, or gold alone or an alloy thereof.