JPH0696771B2 - Electroless plating powder, conductive filler and method for producing the same - Google Patents

Description

The present invention relates to an electroless plating powder and a method for producing the same. More specifically, the present invention relates to an electroless plating powder formed by forming a dense and substantially continuous electroless plating film on an organic or inorganic powdery core material, and a method for producing the same, which is further developed to the electroless plating powder. Is provided as a conductive filler capable of imparting conductivity to a synthetic resin or an inorganic material.

[Conventional technology]

In general, electroless plating is applied irrespective of its shape or size, not to mention organic or inorganic materials, due to the progress of its technology and the development of its applications.
However, in many cases, the base material is often a plate or molded body,
With respect to powdered or granular core materials, the development of their uses is new, and there is no established manufacturing method. In reality, the core materials are treated in accordance with the conventional general method.

That is, in the case of electroless plating, a method of immersing a base material to be plated in a preliminarily prepared plating solution, causing the reaction for a predetermined time determined in advance, and then stopping the reaction is taken. .

Even if the substrate to be plated is a powder or powder, the same method as above is adopted, but in this case, the plating solution is rapidly added to perform plating, and after the reaction, the plating solution is filtered,
Stops such as quenching or dilution must be performed.

When the base material is a granular material (powder or powder), the plating reaction rate is abnormally fast because the specific surface area is remarkably large as compared with other base materials.

Therefore, since the pH of the plating solution and the fluctuation of each component are severe, it is extremely difficult to keep the plating solution stable by adjusting the pH and replenishing each component, and the plating rate becomes unstable each time.

On the other hand, there is no problem if the powder and granules can be thrown well into the plating solution all at once. However, if the powder and granules are thrown in over a long period of time, there will be a difference in the film thickness of the plating film at the beginning and at the end, resulting in non-uniformity.

In particular, when plating a powder or granular material, when a plating film is applied to agglomerated secondary particles, the secondary particles are broken during use and defects in the film due to exposure of the uncoated surface appear.

Therefore, when plating powder or granular material, it is most important to apply a plating film to a material in which secondary particles are well dispersed in a state where it is as small as possible, but it cannot be expected by conventional methods. It was

In view of the above facts that occur when plating fine particles of such a granular material, the present inventor has made the core material an aqueous suspension as a method of electroless plating the powdery core material,
A method of applying a plating film by adding an electroless plating solution to this has been developed, and several patent applications have already been filed (JP-A-60-59070, JP-A-60-16779,
JP-A-60-177182, JP-A-60-177183).

In addition to this, in the method of electroless plating on an organic core material, a metal film having excellent resistance under friction is formed by carrying out electroless plating after supporting precious metal ions with a precious metal-trapping surface treating agent as a pretreatment. Technology was also developed (Japanese Patent Laid-Open No. 61-64882).

[Problems to be Solved by the Invention]

The above-mentioned development technology is significantly improved compared to the conventional electroless plating method in which the powder that is the material to be plated is put into a plating bath that has been constructed in advance, and an improvement in quality was recognized,
In addition, there is a room for improvement, and it has not been possible to obtain a metal film that sufficiently satisfies the required performance.

That is, as is well known, to perform electroless plating, as a pretreatment, it is necessary to treat the surface of the material to be plated with palladium chloride to support metallic palladium as a catalyst nucleus. A method is employed in which a solution of stannous and palladium chloride is sequentially or simultaneously treated and then a plating treatment is performed. However, the coating of plated metal powder by this method is extremely inhomogeneous,
It has been experimentally confirmed that a continuous film is not formed and a considerable film thickness is required to form such a film. In addition, the coating has low resistance to friction, and the plated metal particles are coarse and often form a bumpy surface.

The reason for this is considered to be that the catalytic nucleus of palladium, which is the building speed of the plating reaction, is heterogeneously formed on the surface of the powder, and the plated metal is grown on the basis of this nucleus to form an island.

Although such a coated state has been considerably improved by the method described in JP-A-61-64882, basically the same tendency appears.

Next, when the metal-coated powder is used as a conductive filler, the first advantage is that it has a low specific gravity. However, assuming that the film thickness of the metal must be 1000 Å or more, the particle size of the powder that can be used is 1 μm or more. For easy understanding, Table 1 shows the relationship between the metal ratio (metal / product weight ratio) and the specific gravity when the powder having the specific gravity of 1.2 and each particle size is coated with 1000Å of the metal having the specific gravity of 9.0.

As is apparent from Table 1, it is practically and economically required to make the plated metal film as thin as possible, but for this purpose, a homogeneous and strong film cannot be solved.

The present invention has been succeeded in the development as a result of intensive studies for the purpose of improving a non-uniform plating film which is a conventional defect and producing a metal plating powder having a more uniform and strong covering power. is there.

[Means for Solving the Problems]

That is, the electroless plating powder provided by the present invention is an electroless plating powder obtained by subjecting a surface of an organic or inorganic core material to metal coating by an electroless plating method, and magnifying magnification by an electron microscope (SEM). The structural feature is that the fine metal particles form a dense and substantially continuous film when observed at a magnification of 5000 to 10,000 times, and are deposited and formed at a film thickness of at least 50Å.

Further, the conductive filler of the present invention is composed of the above electroless plating powder, and is a use application product for imparting conductivity to a base material such as a synthetic resin.

Furthermore, the method of the present invention for producing the electroless plating powder and the conductive filler described above has a capturing ability of noble metal ions, or a noble metal ion in an organic or inorganic core material powder to which a noble metal ion is added by surface treatment. Of the core material powder treated in the first step (catalyzing treatment) in which the metal is captured and then reduced to be supported on the surface of the metal core material, and the core material powder treated in the previous step is used to form an electroless plating solution. Second step of preparing an aqueous suspension by dispersing it in an aqueous medium containing various chemicals and adding at least two electroless plating constituent solutions individually and simultaneously to carry out an electroless plating reaction (Electroless plating treatment).

Hereinafter, the present invention will be described in detail.

First, the electroless plating powder according to the present invention is characterized in that the surface of the core material powder is deposited and coated as a dense and substantially continuous film on the surface of the core material powder as described above.

Here, “dense” means that homogeneous and fine metal particles are in a dense state, and almost no free metal particles that do not contribute to film formation or metal particles are formed in a bump shape. Say that.

The term "substantially continuous film" refers to a state in which the surface of the core material is uniformly covered in a dense state and the surface of the core material is barely exposed.

The above-mentioned deposited state of a substantially continuous film in which the metal particles are dense and substantially continuous is evaluated by the surface state visually observed when observed with an electron microscope (SEM) at a magnification of 5000 to 10000 times. For example, each of the photographs in the drawings is an electron micrograph showing the surface particle structure of the nickel-plated powder. Of these, FIGS.
a and FIG. 1-b are the plated products of the present invention, FIGS. 2 to 5 are conventional plated products, and FIGS. 6 to 8 are the nickel plated powders containing the methylmethacrylate resin sphere powder as the core material. The figure shows the plated product of the present invention, and FIGS. 7 to 8 show the conventional plated product).

Whereas the plating powder according to the present invention is coated as a dense and substantially continuous film, the plating powder according to the conventional method has coarse and inhomogeneous metal particles, and only bump particles are present. However, the exposed surface of the core material is recognized, and it is understood that it is not a dense and substantially continuous film.

As described above, since the electroless plating powder according to the present invention has a strong covering power, the resistance under friction during use is significantly larger than that of the conventional plating powder product. Although this is not uniform depending on the type of core material or plated metal or the purpose of use, the plated film may be as thin as possible, but at least for forming a homogeneous and substantially continuous film.
Must have a film thickness of 50Å. The plating film thickness referred to here is a calculated value obtained from the metal amount of the plating solution used for plating based on the surface area of the core material, but in the method of the present invention, a plating film is formed in a theoretically close amount. Therefore, it is almost the same as the case where this is obtained from the actual measurement of the plating amount.

The electroless plating powder according to the present invention is usually a single-layer plated product of the same type of metal, but may be a multi-layer plated product of two or more different metals if desired. The fine plated metal particles may be either crystalline or amorphous depending on the type and plating method. Further, for the same reason, the plated metal particles may be magnetic or non-magnetic.

The applicable plating metals are Fe, Cu, Co, Ag, Pd.
Or Au can be mentioned, but Ni is the most representative substance from the economical aspect. Zn and Mn cannot be applied alone, but can be applied as an alloy.

The core material as the material to be plated is not particularly limited, and an organic or inorganic water-dispersible powder described later can be applied.

The electroless plating powder of the present invention is particularly useful as a conductive filler such as a synthetic resin, but can also be used as a catalyst, a pigment and other decorative articles. When used as a pigment or a decorative article, when the electroless plating powder according to the present invention is heat-treated at a desired temperature, a powder having a beautiful colored metallic luster of green, blue, navy blue, or purple can be obtained. The adaptability can be further expanded.

Next, a method for producing the electroless plating powder according to the present invention will be described.

First, the nickel-plated base material (hereinafter, simply referred to as “core material”) will be described. The first feature thereof is that the core material is dispersible in water.

The core material dispersible in water means a core material that can be substantially dispersed in water to the extent that a plating film can be formed on the core material by a normal dispersion means such as stirring.

Since it can be suspended in water, it is substantially insoluble in water, preferably, it is insoluble or denatured in acid or alkali.

Therefore, if the core material is substantially water-insoluble and dispersible, its shape and size basically do not matter,
In many cases, the core material is powdery or granular. However, it may have a specific or unspecified particle shape such as a spherical shape, a fibrous shape, a hollow shape, a plate shape, or a needle shape, which is caused by the physical properties of the core material.

Therefore, it is not strictly meant that the core material is a powder, and for example, a plate-shaped, needle-shaped or fibrous core material having a large aspect ratio can be dispersed even if it has a size of several cm. It can be applied as a material.

The material of the core material includes all materials which can be electroless plated regardless of whether they are organic or inorganic. These may be natural products or synthetic products. Further, it is needless to say that the core material does not have to have a chemically uniform structure, but it may be either crystalline or amorphous.

As an example of the core material, as the inorganic core material,
Metals (including alloys), glass, ceramics, metal or non-metal oxides (including hydrates), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metals Phosphates, metal sulfides, metal salts, metal halides, carbon, etc., as the organic core material, natural fiber, natural resin, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene,
Thermosetting resin such as polyamide, polyacrylic ester, polyacrylonitrile, polyacetal, ionomer, polyester, alkyd resin, phenol resin, urea resin, melamine resin, xylene resin, silicone resin, epoxy resin or diallyl phthalate resin And the like. These may be one kind or a mixture of two or more kinds.

Next, the second feature of the core material is that the core material has the ability to capture noble metal ions, or its surface treatment is modified so that at least the surface has the ability to capture the metal ions. It means that there is.

Having the ability to capture noble metal ions means being able to capture noble metal ions as a chelate or a salt, an amino group,
It has one or more kinds of imino group, amide group, imide group, cyano group, hydroxyl group, nitrile group or carboxyl group on the surface of the core material. Examples of the substance having the capturing ability of the core material itself include organic substances such as amino resins, nitrile resins, and epoxy resins cured with an amino curing agent, and are preferably used. Examples of amino resins include urea, thiourea, melamine, benzoguanamine,
It is obtained by a condensation reaction of an amino compound such as acetoguanamine, dicyandiamide and aniline with an aldehyde such as formaldehyde, paraformaldehyde, acetaldehyde and glyoxal.

Therefore, in the present invention, when the core material itself does not have the capturing ability of the noble metal ion, it is necessary to modify any of the core materials to have the capturing ability by surface treatment. This modification can be performed according to the method described in JP-A-61-64882. Particularly in the present invention, it is preferable to apply a core material surface-treated with an epoxy resin that is cured with an amino group-substituted organosilane coupling agent or an amine curing agent.

Further, in the above description, the noble metal ion is particularly preferably a palladium or silver ion.

First step (catalyzing treatment) When the core material itself has the above-mentioned functional group, it may be directly subjected to the catalyzing treatment, but the core material other than that requires a surface modification treatment operation. That is, the core material is thoroughly stirred and dispersed in water or an organic solvent in which the surface treatment agent is dissolved, and then separated and dried. The surface treatment agent used is not uniform depending on the physical properties of the core material and its type, but in most cases, 0.3 to 100 mg is appropriate per 1 m ² / g of the specific surface area of the core material. The reason for this is
This is because if it is 0.3 mg or less, it is insufficient to give a uniform surface modifying effect, while if it is about 100 mg or more, there is a modifying effect but it is not economical.

Next, the core material having the ability to capture the precious metal ions is dispersed in a dilute acidic aqueous solution of a precious metal salt such as palladium chloride or silver nitrate to capture the precious metal ions. In this case, the solution concentration of 0.05 g / -1 g / is sufficient.

Such a pretreatment is known for a palladium salt, and usually an electroless plating treatment is then performed. In the present invention, the noble metal captured on the core material surface is reduced by the reducing agent used in the plating chemical solution to reduce the core material surface. It is an important operation. This reducing treatment may be carried out by adding a reducing agent after the capturing treatment of the noble metal ions, but preferably after separation after the capturing treatment and washing with water, an aqueous suspension prepared for shifting to the next plating step is obtained. The reducing agent is added as a solution or itself to complete the catalyzed treatment. The amount of the reducing agent added is not uniform because it depends on the specific surface area of the core material, but 0.01 to 10 g / is suitable for the suspension. In this case, it is preferable that a complexing agent is present, but it is not absolutely necessary. The temperature may be either normal temperature or heating and is not particularly limited.

As described above, according to the present invention, unlike the conventional case in which the catalyst nucleus is formed by the stannous chloride-palladium chloride treatment or the simple palladium chloride chelate capturing treatment, a uniform and complete catalyst nucleus is formed. A strong continuous plated metal film can be formed in combination with the action of the electroless plating process.

Second step (electroless plating treatment) What is important in this step is to prepare an aqueous suspension of the core material as much as possible during the electroless plating. The plating film applied to the agglomerated core material may expose the untreated surface during use under friction, so it is desirable to sufficiently disperse the core material in order to avoid this. For the same reason, it is preferable that sufficient dispersion treatment is performed in the previous step as well.

Since the dispersibility of the aqueous suspension depends on the physical properties of the core material,
Dispersion method is appropriately desired means, for example, from normal stirring to high-speed stirring, or using a shearing dispersion device such as a colloid mill or a homogenizer, to prepare a suspension in a dispersed state close to primary particles in which the agglomerates of the core material are removed as much as possible. It is desirable to do. When dispersing the core material,
For example, a dispersant such as a surfactant can be used as necessary as described above. The concentration of the suspension is not particularly limited, but if the concentration of the slurry is low, the plating concentration will be low and the processing capacity will be large, so it is not economical. Conversely, if the concentration is high, the concentration of the core material Since the dispersibility deteriorates, the desired slurry concentration may be appropriately set according to the physical properties of the core material. Often 1g / ~ 500g /, preferably 5g /
It is in the range of ~ 300g /. In addition, when plating the core material in this suspension, the temperature of the suspension should be adjusted in advance to a plateable temperature, in many cases 55 ° C or higher, so that plating can be carried out effectively. desirable.

Next, one of the features of the preparation of the aqueous suspension of the core material is that the dispersion medium is an aqueous medium containing at least one chemical agent constituting the electroless plating solution, especially an aqueous solution of a complexing agent. There is. Therefore, since the separation operation is not particularly required after the reduction treatment in the first step, it is sufficient to continuously shift to the operation in the second step as it is after the generation of hydrogen gas is completed.

In the above, at least one of the components constituting the electroless plating solution mainly refers to a complexing agent, an acid or alkali agent, or a surfactant, and a plating aging solution can be used if necessary.

Further, the complexing agent is a compound having a complexing action with respect to plating metal ions, and examples thereof include carboxylic acids such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or their alkali metal salts or ammonium salts. (salt),
Examples thereof include amino acids such as glycine, amines such as ethylenediamine and alkylamine, and ammonium, EDTA, and pyrophosphate (salt), which may be used alone or in combination of two or more. The content of the complexing agent in the suspension is
The range is 1 to 100 g /, preferably 5 to 50 g /.

The pH of the suspension is in the range of 4 to 14, but the setting of this range varies depending on the plating metal and the type of reducing agent used. Table 2 shows an example.

Table 2 Coated metal reducing agent Proper range (pH) Nickel Sodium hypophosphite 4-10 Nickel hydrazine 9-13 Nickel borohydride compound 7-14 Copper formalin 8-12 Gold borohydride compound 8-14 Silver 〃 8-14 This The plating solution prepared in advance for causing the electroless plating reaction is gradually added to the aqueous suspension of the core material thus prepared. In this case, it is necessary to make at least two electroless plating constituent liquids in the suspension and individually and simultaneously add them to carry out the plating reaction.

Examples of applicable metal salts include nickel salts such as nickel sulfate and nickel chloride, copper salts such as copper sulfate and copper nitrate, iron salts such as cobalt sulfate, iron chloride and iron sulfate, and iron salts such as silver nitrate and silver cyanide. Salts, gold cyanides, gold salts such as chloroauric acid, palladium salts such as palladium chloride, and, if necessary, soluble salts such as zinc and manganese can also be used as alloy components, and one or two of these may be used. It may be more than one species.

Next, as the reducing agent, for example, sodium hypophosphite, sodium borohydride, potassium borohydride, dimethylamine borane, hydrazine or formalin are used.

As the other agents, the above-mentioned complexing agent, pH adjusting agent, or gloss imparting agent which can be added if necessary is used.

The compounding ratios of the metal salt and the reducing agent to be added vary depending on their combination, and therefore are not uniform, but in many cases, it is desirable that the combination and the appropriate compounding ratio have a relationship as shown in Table 3.

Table 3 Metal salt Reducing agent Mixing ratio (molar ratio) Nickel Sodium hypophosphite 1: 2 to 3 Nickel Boron borohydride 1: 1.5 to 2.5 Nickel hydrazine 1: 3 to 5 Copper formalin 1: 3 to 5 Gold Hydrogen Alkali boride 1: 1.1 to 1.5 Silver 〃 1: 1.1 to 1.5 The drug concentration is not particularly limited as long as it is a saturated concentration of each drug, but when it is thin, it is not economical and the lower limit is naturally limited. The addition rate of the chemical solution directly affects the plating reaction and is significantly related to the surface area, physical properties, etc. of the core material.Therefore, in consideration of these, control is performed to form a uniform and strong film so that unevenness of the plating film does not occur. It is necessary to add in a quantitative manner in many cases.

As a matter of course, it is desirable that stirring, ultrasonic dispersion treatment, and the like be given as necessary, and that the temperature be set so that it can be controlled. Since the electroless plating solution is added to the aqueous suspension and diluted according to its volume, the plating operation is performed by immersing the base material to be plated in a bath having a normal plating solution concentration. Unlike
It can be used in a state where the concentration of the plating solution is higher than usual.

The plating reaction starts immediately by adding the plating solution, but if each chemical is added in an appropriate ratio, all the added metal salts will be reduced and deposited on the surface of the core material. The film thickness of can be adjusted arbitrarily.

The metal-coated powder thus obtained can be further coated with different layers in different layers.

In this case, after completion of the above plating reaction, the dissimilar metal plating solution is added by the same operation, or the reaction solution is once separated, a new suspension is prepared, and the dissimilar metal plating solution is added again. To be done.

After the addition of the plating solution is completed, hydrogen gas is not completely generated, and stirring is continued for a while for aging to complete the plating reaction operation. Then, after separation, washing and drying by a conventional method, the product is crushed as necessary and collected as a product.

[Action]

In the electroless plating powder according to the present invention, fine metal particles are formed as a dense and substantially continuous film which is extremely uniformly and strongly deposited. Therefore, even if it is kneaded with a synthetic resin or synthetic rubber, a phenomenon such as peeling of the film does not occur, and good conductive performance can be imparted, so that it can be useful as a conductive filler as it is.

Further, according to the production method of the present invention, the noble metal chelate captured on the surface of the core material powder is reduced to form a catalyst nucleus, which is combined with the action of the electroless plating reaction as described above. It is possible to produce a good quality electroless plating powder with good reproducibility.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

Examples 1 to 10 100 g of a liquid phenolic resin powder having a true specific gravity of 1.26, an average particle size of 20 μm and a specific surface area of 0.5 m ² / g [Bellbar R-800 manufactured by Kanebo Co., Ltd. under the trade name of Chisso ( Co., Ltd., trade name S-330] 0.1 g / aqueous solution 1 and thoroughly dispersed by stirring for about 15 minutes, then superseparated and then dried at a temperature of 105 ° C. to have a chelating ability. A surface-treated phenol resin powder was obtained.

Next, the powder is put into a catalyzed liquid 1 consisting of 0.1 g / palladium chloride and 0.1 ml / hydrochloric acid, dispersed in the same manner, stirred for 5 minutes, and then treated with excess pulp, repulp and excess palladium ion. went.

Then, each of the resin powders was put into each complexing agent aqueous solution shown in Table 4 and sufficiently dispersed to prepare an aqueous suspension kept at a temperature of 80 ° C., and then sodium hypophosphite powder was prepared. 2 g was added to each suspension and dissolved with stirring. Shortly after addition, foaming started to occur with hydrogen gas generation due to reduction of palladium ions, but when the foaming was completed, the catalyzation treatment was completed.

Next, the electroless plating solution shown in Table 5 was divided into solution a and solution b, and 86 ml of each was simultaneously added to each suspension while stirring at an addition rate of 10 ml / min.

After adding the total amount of plating solution, until the generation of hydrogen stops 80
The stirring was continued for a while while maintaining the temperature at 0 ° C.

Then, excess, hydrogen, excess, and drying were performed to obtain resin powder of each nickel plating coating. Since all the solutions after the plating reaction were colorless and transparent, it was found that the provided plating solution was completely consumed by the deposition on the resin surface due to the plating reaction and could be treated very effectively. .

When the surface of the obtained plated resin powder was observed with an electron microscope, they all had a uniform and smooth surface due to fine metal particles, and from this fact, a dense and substantially continuous film was deposited and deposited. It was confirmed that

Examples 11 to 20 100 g of each core material of Examples 11 to 17 shown in Table 6 was added to an epoxy resin [Cemedine Co., Ltd., trade name Cemedine 1500] and 1 g of each amino-based curing agent dissolved in 500 ml of ethanol. The mixture was charged, stirred and dispersed for 30 minutes, separated, ethanol was dispersed, and the mixture was further heated to 60 ° C. and subjected to surface treatment by coating an epoxy resin on the surface of each core material powder.

Thus, the powder of Examples 11 to 17 and the powder of Examples 18 to 20 in which the core material powder was surface-modified with an epoxy resin (used as it is without surface modification) was 0.1 g / a silver nitrate aqueous solution 1
After being stirred and dispersed for 30 minutes with a stirrer, silver core scavenging treatment was carried out for each core material in excess, repulp and excess.

Then, each core material powder was poured into 20 g of EDTA-3Na / aqueous solution 1 to sufficiently disperse, and the temperature was raised to 60 ° C. to prepare aqueous suspensions, and then sodium borohydride powder 0.5 g was added to each aqueous suspension and dissolved by stirring.
Shortly after the addition, foaming begins with the generation of hydrogen gas due to the reduction of silver ions. After a while, when the foaming was completed, the catalytic treatment was completed.

Next, 196.5 g / copper sulfate solution, 202.5 g / formalin solution and 157.4 g / sodium hydroxide solution were separately added to the respective solutions in the amounts shown in Table 6 at an addition rate of 3 ml / min at 60 ° C. under stirring. To each of the above suspensions in.

After the total amount of the plating solution was added, stirring was continued while maintaining the same temperature for about 15 minutes until the reaction was completed.

The copper plating powder formed on the surface of each core material was obtained by the same method as the above-mentioned example by the conventional method.

In addition, it was confirmed that all the excess liquid after the plating reaction was colorless and transparent, and that all the plating powders were plated products deposited as a dense and substantially continuous film of fine copper metal particles. .

Examples 21 to 26, Comparative Examples 1 and ² 30 g of mica powder having a true specific gravity of 2.89, an average particle size of 4.9 μm and a specific surface of 7.0 m ² / g was subjected to a trapping treatment of palladium ions in the same manner as in Example 1. Next, 5 g / sodium tartrate aqueous solution 1 was added to disperse the mixture and the temperature was raised to 70 ° C.

Then, 3 g of sodium hypophosphite powder was added and dissolved, and when the foaming phenomenon accompanying the generation of hydrogen gas due to the reduction of palladium ions was completed, the catalyzation treatment was completed.

Then, 224 g / nickel sulfate solution (liquid a) and 226 g /
Set each liquid of the mixed solution (solution b) of sodium hypophosphite solution and 85 g / sodium hydroxide solution to the amount shown in Table 7 for each solution.
It was added with stirring to an aqueous suspension prepared by sufficient dispersion at an addition rate of 10 ml / min.

After the total amount was added, stirring was continued while maintaining the temperature at 70 ° C. until the generation of hydrogen stopped.

Then, nickel-coated plated mica having different addition amounts shown in Table 7, respectively, which were subjected to recovery operation by a conventional method, were obtained.

Each of the obtained plated mica was a plated product deposited as a dense and substantially continuous film of fine nickel metal particles.

The metallization rate in Table 7 is a calculated value obtained from the added amount of the plating solution. However, since all the solutions after the plating reaction are colorless and transparent, the plating reaction is performed theoretically. I knew that.

Example 27 30 g of methylmethacrylate resin powder having an average particle size of 7 μm, a true specific gravity of 1.42 and a specific surface area of 6.03 m ² / g was subjected to a palladium ion scavenging treatment in the same manner as in Example 1.

This resin powder was added to 5 g / sodium tartrate aqueous solution 1 to maintain a temperature of 80 ° C. to prepare a sufficiently dispersed aqueous suspension, and 2 g of sodium hypophosphite powder was added and mixed to reduce palladium ions. The catalytic treatment was completed. 224g /
Nickel sulfate aqueous solution and mixed solution of 226 g / sodium hypophosphite aqueous solution and 119 g / sodium hydroxide aqueous solution 612 each
Each ml was added to the above suspension under stirring at an addition rate of 20 ml /. After adding the total amount, 80 until the generation of hydrogen stops
While maintaining the temperature of ° C, stirring was continued to perform a nickel plating primary coating treatment. Then, after overwashing, washing with water, and passing, the overcake was put into 50 g / EDTA-4Na aqueous solution and well dispersed under stirring, and the temperature was heated to 80 ° C. to prepare an aqueous suspension again.

Then, 14.63 g / potassium cyanide aqueous solution and 2.30 g /
Each 604 ml of a mixed solution of an aqueous sodium borohydride solution and an aqueous 12.18 g / sodium hydroxide solution was added to the above suspension under stirring at an addition rate of 1 θ ml / min. After the total amount was added, stirring was continued while maintaining the temperature at 80 ° C for 15 minutes. Then, after passing through a conventional method, washing with water, passing, and drying, a plating powder was obtained. The resulting plating powder was a nickel-gold double layer plating resin powder that was deposited and coated as a dense, substantially continuous film.

Comparative Example 3 30 g of mica powder having a true specific gravity of 2.89, an average particle size of 4.9 μm and a specific surface area of 7.0 m ² / g was put into an aqueous solution 2 containing 10 g of stannous chloride / and 1 ml / of hydrochloric acid, and well dispersed under stirring 15 Sensitizing treatment was performed for a minute. Next, this treated product was washed with water, then put into a solution 2 consisting of 1 g / palladium chloride and 1 ml / hydrochloric acid, well dispersed under stirring, and activated for 5 minutes to form a catalyst nucleus on the surface of the mica powder. .

Next, nickel sulfate 30g /, sodium hypophosphite 25
g /, sodium citrate 20g /, sodium acetate 10g /
And a plating solution of pH 5 consisting of 0.001 g of lead acetate / 20
A bath was prepared by heating to 60 ° C., and the mica powder which had been subjected to the above-mentioned catalytic treatment was added to the bath and dispersed by stirring. The pH of the solution during the reaction
Using an automatic controller, the initial pH was maintained by adding 160 g / sodium hydroxide aqueous solution. Further, when the reaction was stopped on the way, 200 g / sodium hypophosphite aqueous solution was added little by little to continue the reaction. When no foaming occurred even after adding the sodium hypophosphite aqueous solution, all the additions were stopped, the product was washed with water and overdried to obtain nickel-coated mica powder.

Comparative Example 4 30 g of mica powder having a true specific gravity of 2.89, an average particle size of 4.9 μm and a specific surface area of 7.0 m ² / g was subjected to a catalytic treatment in the same manner as in Comparative Example 3. Then, 20 g / sodium tartrate aqueous solution 1 was added to disperse the mixture and the temperature was raised to 70 ° C. to prepare an aqueous suspension.

Next, 3 g of sodium hypophosphite powder was added and dissolved by stirring. Shortly after addition, hydrogen gas is generated by reduction of palladium ions. 224g / after foaming subsides
Nickel sulfate aqueous solution (a liquid) and mixed aqueous solution of 226 g / sodium hypophosphite and 119 g / sodium hydroxide (b
Liquid) 10.72 of each was added individually and simultaneously to the above suspension under stirring at a rate of 10 ml / min. After the addition of the entire amount, stirring was continued while maintaining the temperature at 70 ° C until the generation of hydrogen stopped. Then, after washing with excess water, passing and drying, nickel-coated mica powder was obtained.

Comparative Example 5 30 g of mica powder having a true specific gravity of 2.89, an average particle size of 4.9 μm and a specific surface area of 7.0 m ² / g was subjected to a catalytic treatment in the same manner as in Example 1. Next, electroless nickel plating was performed using a plating solution prepared under the same conditions as in Comparative Example 3 to obtain nickel-coated mica powder.

Comparative Example 6 30 g of mica powder having a true specific gravity of 2.89, an average particle size of 4.9 μm and a specific surface area of 7.0 m ² / g was subjected to a catalytic treatment by capturing palladium ions under the same conditions as in Example 1.

Next, 5 g / sodium tartrate aqueous solution 1 was added and dispersed, and the temperature was raised to 70 ° C. to prepare an aqueous suspension. Next, 244 g / nickel sulfate aqueous solution (liquid a) and 226
After 20 ml each of a mixed aqueous solution (b solution) of g / sodium hypophosphite and 119 g / sodium hydroxide was added individually and simultaneously to the above suspension under stirring to start the plating reaction,
Immediately, liquids a and b were similarly added at a rate of 10 ml / min for each liquid volume of 2.4. After the addition of the entire amount, stirring was continued while maintaining the temperature at 70 ° C until the generation of hydrogen stopped. Then
After filtering, washing with water, filtering and drying, nickel-coated mica powder was obtained.

Analysis of Nickel Coating The nickel-coated powders obtained in Examples and Comparative Examples were put into nitric acid to dissolve the coating, and this was analyzed to measure nickel and phosphorus in the coating.

The results are shown in Table 8.

Conductivity measurement Polypropylene 35.7ml (32.13g) [Mitsubishi Yuka Co., Ltd. MA
-4, PP homopolymer] and nickel-plated mica sample powder 6.3m
1 using BRABENDER PLASTOGRAPH, temperature 220 ℃, 30R.
The mixture was kneaded for 5 minutes under PM conditions, taken out, and then rolled into a plate shape with a hot roll, and a plate with a thickness of 1 mm was formed with a hot press. The electrical resistance value of a test piece obtained by cutting the molded plate into 30 × 60 mm was measured to obtain a specific resistance value, and the electrical conductivity of the example product and the comparative example product was evaluated. The results are shown in Table 9.

As is clear from Table 9, the comparative example products had a remarkably larger amount of nickel plating than the example products, and despite the large film thickness, peeling of the plating film occurred during kneading with the resin, resulting in An effective conductive resin cannot be obtained because the specific resistance of the resin increases. On the other hand, each of the example products effectively imparts conductivity to the resin.

From this, it was found that the plating powder according to the present invention had a plating film firmly formed on the core material and could be applied as an excellent conductive filler.

Example 28 Example 1 per 30 g of spherical methyl methacrylate resin powder having an average particle size of 7 μm, a true specific gravity of 1.42 and a specific surface area of 6.03 m ² / g.
Similarly to the above, a trapping treatment of palladium ions was performed. Add this resin powder to 20g / sodium tartrate aqueous solution 1 and add
After maintaining at 65 ° C. to prepare an adequately dispersed aqueous suspension, 2 g of sodium hypophosphite was added and dissolved to reduce the palladium ions captured on the powder surface for catalytic treatment.

224 g / nickel sulfate aqueous solution and 226 g / sodium hypophosphite mixed solution of 119 g / sodium hydroxide 15.6 m each
l Each was added to the above suspension under stirring at an addition rate of 5 ml / min. After the total amount was added, stirring was continued while maintaining the temperature of 65 ° C. until the generation of hydrogen stopped. Then, the procedure of filtration, washing with water, and filtration was repeated three times and then dried to obtain a powder having a nickel plating film thickness of 50 Å. FIG. 6 is an electron microscope enlarged photograph (10000 times) of the obtained nickel-plated powder.

Comparative Example 7 A powder having a nickel plating film thickness of 50 Å was obtained under the same conditions as in Example 28 except that the step of carrying out a catalytic treatment for reducing the palladium ions captured on the surface of the resin powder was not performed. FIG. 7 is an electron microscope enlarged photograph (5000 times) of the obtained nickel plating powder.

Comparative Example 8 By the same method as in Example 28, palladium ions captured on the surface of the resin powder were reduced and then filtered to obtain a powder having catalytic activity. Next, the plating solution 2 of pH 5 consisting of nickel sulfate 30 g /, sodium hypophosphite 25 g /, sodium malate 50 g /, sodium acetate 15 g / and lead acetate 0.001 g / is heated to 70 ° C. and a bath is constructed. The powder having the above-mentioned catalytic activity was put into the bath and dispersed by stirring. During the reaction, the pH of the solution was adjusted and maintained at the initial pH by the addition of 160 g / sodium hydroxide aqueous solution using an automatic controller. When the reaction stopped halfway, 200 g / sodium hypophosphite aqueous solution was added little by little to continue the reaction. When foaming stopped even after adding the sodium hypophosphite aqueous solution, all the additions were stopped, and the operations of filtration, washing with water and filtration were repeated 3 times, and then dried to obtain a powder with a nickel plating film thickness of 500Å. FIG. 8 is an electron microscope enlarged photograph (5000 times) of the obtained nickel plating powder.

〔The invention's effect〕

The plating powder according to the present invention has a significantly uniform and strong plating film as compared with the conventional plating powder. In other words, it is an electroless plating powder with a large binding force, which is deposited and coated as a dense and substantially continuous film of fine metal particles without bump-shaped particles or uneven plating, which is widely used in various conductive fillers. It can be expected to be applied to various uses.

Furthermore, according to the method of the present invention, the noble metal chelate captured on the surface to be plated is reduced to form a catalyst nucleus unlike the conventional catalyst nucleus with colloidal or simple chelate palladium. In addition, in combination with the plating reaction based on the addition method, the plating powder as described above can be produced with good reproducibility and industrially advantageous.

Therefore, according to the present invention, the metallization rate can be made as small as possible, in other words, a strong submicron-class plating film can be provided, so that a plating powder having a low specific gravity can be obtained.

This, combined with the applicability of various core materials, enables the production of a homogeneous conductive material without causing separation when kneading paints, synthetic resins, synthetic rubbers, etc. as conductive fillers. It guarantees that it can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings are electron micrographs showing the particle structures of the surfaces of electroless nickel plating films obtained in Examples and Comparative Examples, and FIG. 1-a shows Example 26 (magnification of 500 times). ), 1st
Fig. b shows Example 26 (magnification of 5000 times), Fig. 2 shows Comparative Example 3
(Enlargement magnification 10,000 times), FIG. 3 shows Comparative Example 4 (Enlargement magnification 100
00 times), FIG. 4 shows comparative example 5 (enlargement magnification of 10,000 times),
-A (magnification of 500) and Fig. 5-b (magnification of 5)
(000 times) corresponds to Comparative Example 6 corresponding to FIGS. 1-a and 1-b, FIG. 6 shows Example 28 (magnification of 10,000 times), and FIG. 7 shows Comparative Example 7 (magnification of 5000 times). FIG. 8 shows each plating film of Comparative Example 8 (magnification of 5000 times).

Continuation of the front page (56) Reference JP-A-60-181294 (JP, A) JP-A-59-182961 (JP, A) JP-A-62-30885 (JP, A) JP-B-47-44975 (JP , B1) JP-B 57-6481 (JP, B2) JP-B 57-31533 (JP, B2)

Claims (8)

[Claims] 1. An electroless plating powder in which a surface of an organic or inorganic core material is coated with a metal by an electroless plating method, and the magnification is 5000 to 10000 by an electron microscope (SEM).
An electroless plating powder in which fine metal particles form a dense and substantially continuous film when observed under a double magnification, and are deposited and formed in a film thickness of at least 50Å. 2. The electroless plating powder according to claim 1, wherein the continuous film is a multi-layered plating film of different metals. 3. A conductive filler made of the electroless plating powder according to claim 1. 4. A noble metal ion is trapped in an organic or inorganic core material powder having a noble metal ion-trapping ability or a surface treatment to give a noble metal ion-trapping ability, and then the noble metal ion is reduced to obtain the metal. The first step (catalyzing step) of supporting the core material on the surface of the core material, and the core material powder treated in the previous step are dispersed in an aqueous medium containing at least one chemical agent constituting the electroless plating solution to form an aqueous solution. Second, a suspension is prepared, and at least two electroless plating constituent liquids are added to the suspension individually and simultaneously to carry out an electroless plating reaction.
A method for producing an electroless plating powder and a conductive filler, which comprises a step (electroless plating treatment). 5. The electroless plating powder and the electroconductivity according to claim 4, wherein the core material powder has a specific shape such as a substantially spherical shape, a fibrous shape, a hollow shape, a plate shape, or a needle shape, or an unspecified particle shape. Filler manufacturing method. 6. The core powder having at least the ability to capture precious metal ions on its surface is one or more resin powders of an epoxy resin, an acrylonitrile resin or an amino resin. Method for producing electroless plating powder and conductive filler. 7. A core material powder, which has been given a capturing ability of noble metal ions by surface treatment, is a substance surface-treated with an epoxy resin which is cured by an amino group-substituted organosilane coupling agent and / or an amine curing agent. Claim 4
A method for producing the described electroless plating powder and a conductive filler. 8. The method for producing an electroless plating powder and a conductive filler according to claim 4, wherein the catalytic treatment in the first step is performed by applying one of the reducing agents used in the electroless plating reaction.