JPH10298772A - Copper-coated carbon powder, its production, and production of conductive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a loss due to non-plating, and to prevent the coarsening of particles by flocculation of the particles. SOLUTION: At the time of producing the copper-coated carbon powder by forming coating layers of metal copper on the surfaces of carbonaceous powder by electroless plating, mechanical motions, such as agitation, vibration and fluidization, are applied to the carbonaceous powder during the progression of a deposition reaction of the metal copper and the carbonaceous powder is previously subjected to a substrate plating treatment by a plating path contg. copper sulfate of the amt. to attain >=0.8 to <3.0% in terms of the metal copper as a copper component and thereafter, the carbonaceous powder is subjected to the plating reaction to deposit the metal copper in correspondence to the amts. of the injection while prescribed chemicals for plating, for example, respective solns. of copper sulfate, caustic soda and formalin, are successively injected to the soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous powder provided with a metallic copper coating and a method for producing the same, and further relates to the production of a conductive member made from the carbon powder provided with the metallic copper coating. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, graphite or metallic graphite has been used as a suitable material for a brush which is a component for supplying, rectifying, or collecting power to a motor, a rectifier, or a generator. The natural graphite brush has a problem that it has a small frictional resistance but is easily worn due to its softness. Artificial graphite has low frictional resistance and a certain degree of hardness, but has a somewhat high electrical resistivity and 1600 graphite raw material.
It is manufactured at a high temperature of 2000 ° C. or higher by current heating and then graphitized by sintering at a temperature of 2,000 ° C., which is extremely expensive and difficult to reduce cost. There was a problem.

[0003] The metallic graphite used for the brush material is manufactured by mixing copper powder and graphite and sintering them. By changing the mixing ratio, the electrical resistivity, the coefficient of friction, and the like are changed. However, copper powder and graphite have a problem that when they are fine powders, it is difficult to obtain a homogeneous mixed molded product due to a large difference in specific gravity. Was.

[0004] It is also considered that by plating copper on the carbonaceous powder, the carbonaceous powder and the copper powder can be mixed substantially homogeneously. As a method of electroplating copper on the carbonaceous powder, an electroplating method and an electroless plating method can be considered, but the present inventors have conducted intensive research on the latter electroless plating method, which has a relatively simple equipment cost. Was done. In the process, the following points were found to be important issues to be solved in the electroless plating method.

First, when an electroless copper plating bath having a composition and temperature introduced in technical literature is reacted with carbonaceous powder, carbonaceous powder on which metallic copper is plated and carbonaceous powder on which no copper is plated Once this occurs, the carbonaceous powder that is not plated does not change as it is even after a considerable amount of plating time, so it must ultimately be eliminated as a loss, and the copper-coated carbonaceous powder must be removed. There was a problem that the yield was extremely reduced. This loss rate may reach 50% or more, which has been a major obstacle to commercializing the electroless plating method.

Second, even when metallic carbon is plated on the carbonaceous powder for a time, the precipitated metallic copper tends to bond with each other. There has been a problem that the secondary particles are aggregated into a granular state, and finally into a large solidified dumpling state. As described above, it has been difficult to obtain a copper-coated carbonaceous powder in a powder state in which carbonaceous powder in a primary particle state is coated with metallic copper. In addition, it has been attempted to return the particle size of the coagulated coarse or lump copper-coated carbonaceous material to the state of primary particles using a pulverizer, but in this case, the carbonaceous part having low strength is broken. As a result, the coated metal copper layer was destroyed and the carbonaceous material was exposed, and as a result, only a heterogeneous material was obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. First, it is necessary to mix copper metal and carbonaceous powder substantially uniformly. In order to provide a copper-coated carbonaceous powder that can be used, secondly, when depositing and coating metallic copper on the surface of the carbonaceous powder, the yield is good and the particles are agglomerated due to aggregation. And a method for producing a copper-coated carbonaceous powder capable of maintaining the state of the primary particles at the beginning.
Thirdly, the present invention provides a method for producing a conductive member using the copper-coated carbonaceous powder as a material and having both conductivity and sliding lubrication.

[0008]

SUMMARY OF THE INVENTION The above-mentioned problem is caused by the fact that the inside is made of carbonaceous powder of primary particles, and the surface thereof is provided with a coating layer of metallic copper obtained by electroless plating. This can be solved by using a powdery material. And
In the invention of the copper-coated carbonaceous powder, a form in which the coating amount of metallic copper to the carbonaceous powder is 25% by weight to 40% by weight,
Alternatively, it can be embodied in a form in which the coating amount of metallic copper on the carbonaceous powder is 32% by weight to 38% by weight.

The second problem is that, when depositing a coating layer of metallic copper on the surface of the carbonaceous powder in the bath solution by electroless plating, the carbonaceous powder is prevented from aggregating due to the deposition of metallic copper. And a base plating treatment is performed in advance by a plating bath in which a copper salt containing a copper component of 0.8% to 3.0% in terms of metallic copper is mixed with the carbonaceous powder. The problem can be solved by a method for producing a copper-coated carbonaceous powder.

In this method of producing a copper-coated carbonaceous powder, a predetermined plating agent is sequentially injected into a bath solution after the base plating treatment is performed, and metallic copper is deposited in accordance with the injection amount. The present invention can be preferably embodied in a form in which a plating reaction to be performed is controlled and a predetermined amount of a metal copper coating layer is deposited.

In the method of producing a copper-coated carbonaceous powder, a first step of mixing the carbonaceous powder with an aqueous solution of potassium sodium tartrate for depositing a coating layer of metallic copper on the surface of the carbonaceous powder by electroless plating, While stirring the bath solution, 0.8% in terms of metallic copper was added to the carbonaceous powder.
Copper sulfate containing about 3.0% of a copper component, caustic soda in a ratio of 0.5 to 1.2 grams per gram of the copper sulfate;
Also, formalin in a concentration of 37% in a ratio of 3 to 8 cc is injected and mixed, and a precipitation reaction of metallic copper is performed until the carbonaceous powder changes from floating to sedimentable.
Step, and further, while stirring the bath, an aqueous solution of copper sulfate containing a copper component of 25% to 40% in terms of metallic copper with respect to the carbonaceous powder.
An aqueous solution containing 5 to 1.2 grams of caustic soda and a 37% equivalent of formalin, also at a rate of 0.5 to 2.0 cc, were continuously fed by a metering pump.
A third step of completing the metal copper precipitation reaction, wherein at least the second step and the third step are performed at a bath temperature of 40.
It can also be embodied in a form characterized in that it is performed within the range of -60 ° C.

A third problem is that a coating layer of metallic copper obtained by electroless plating on the surface of carbonaceous powder is provided in an amount of 25 to 40% by weight, more preferably 32 to 38% by weight, In addition, the present invention can solve the above problem by a method for producing a conductive member, which is characterized in that copper-coated carbonaceous powder having an average particle diameter in the range of 0.2 to 5.0 μm is molded by pressure and sintered.

[0013]

Next, an embodiment of the present invention will be described based on a method for producing a copper-coated carbonaceous powder.
The feature of the method for producing a copper-coated carbonaceous powder of the present invention is that, first, in forming a metal copper coating layer on the surface of the carbonaceous powder by electroless plating, during the progress of the metal copper precipitation reaction, The bath liquid containing the carbonaceous powder is sufficiently agitated, vibrated, and subjected to mechanical movement such as flow so as to prevent the formation of bridges due to metallic copper precipitated between the carbonaceous powders. It is to prevent granulation.

[0014] Secondly, as a step prior to plating a predetermined amount, a copper salt containing 0.8% to 3.0% in terms of metallic copper as a copper component with respect to the carbonaceous powder in advance, for example, It is characterized in that the base plating treatment is performed by a plating bath containing copper sulfate. By performing the base plating process, it is possible to effectively prevent a loss that a carbonaceous powder to which plating does not adhere is generated in a considerable proportion of the carbonaceous powder to be plated, as described above. is there. The reason for this is not clear, but it is considered that when the above-mentioned predetermined amount of copper salt is used, the concentration does not become such that the growth of the metallic copper coating layer is rapidly promoted.

The predetermined amount of the copper salt suitable for this purpose is as follows:
3.0% in terms of metallic copper as a copper component with respect to the carbonaceous powder
Although it is below, it is particularly preferable to further reduce this to 2.0% or less from the viewpoint of preventing loss, but at this stage, it is necessary to set it to 0.8% or more in order to exert at least the effect as a base plating. .

Further, after performing the above-described underplating treatment, while continuously injecting each of the electroless copper plating agents such as copper sulfate, caustic soda and formalin solutions into the bath solution, In a preferred embodiment, the plating reaction for depositing copper is performed continuously and continuously in accordance with the amount of the injected copper. By doing so, it is possible to obtain the advantage of suppressing abrupt reaction and preventing coarsening so that the deposited copper does not form a bridge while performing a plating reaction at an appropriate speed.

Further, a method for producing such a copper-coated carbonaceous powder will be described more specifically. First, the operation of the first step is to mix a raw material carbonaceous powder with an aqueous solution of potassium sodium tartrate as a pretreatment step for performing electroless plating. The purpose of this operation is to carry out the plating treatment intensively on the carbonaceous powder in the second and subsequent steps. For 1 kg of the carbonaceous powder, 4 liters of an aqueous solution of about 20% by weight of caustic tartrate is used. And the optimum temperature of the bath is 40 ° C to 50 ° C.

Next, as a second step, a base plating process is performed. In this case, copper sulfate containing a copper component of 0.8% to 3.0% in terms of metal copper is added to the carbonaceous powder, and at the same time, 0.1 g of copper sulfate is added to 1 gram of the copper sulfate.
5 to 1.2 grams of caustic soda and 3 to 8 cc of formalin in a concentration of 37% are put into the bath solution prepared in the first step and mixed to cause a precipitation reaction of a very small amount of metallic copper. is there. In this case, the addition amount of copper sulfate is preferably 0.8% to 3.0% in terms of metallic copper, but as described above, it is further 2.0% or less in order to more reliably reduce poor plating. Good to do.

In the second step, the bath temperature is 40 to 50 ° C., preferably 45 to 50 ° C.
While maintaining the temperature within the range of ° C., the carbonaceous powder is sufficiently stirred to maintain a fluid state in which the carbonaceous powder is always inwardly rolled in without a floating state with little movement. This operation is performed until the carbonaceous powder changes from floating to sedimentable. In this case, the initial pH was 8 to 8.5, but gradually increased to 10 as the plating reaction progressed. Will be exceeded. The time required for the reaction during this period is approximately 10 to 15 minutes.

As a third step, a finish plating process is performed. Here, first, each solution of copper sulfate, caustic soda and formalin is prepared in advance. Here, the amount of copper sulfate is based on the target value of metallic copper to be plated on the carbonaceous powder, but it is not preferable to set the amount to more than 50%. The amount of caustic soda and formalin used simultaneously is 0.5 g to 1.2 g of an aqueous solution containing caustic soda per 1 g of the copper sulfate.
0.5% to 2.0cc formalin and 37% concentration
Copper sulphate, caustic soda and formalin prepared in such a ratio were continuously added to the bath solution after the completion of the second step by a metering pump while maintaining the ratio.
It is fed over 0 to 60 minutes to gradually advance the precipitation reaction of metallic copper. In this case, of the copper sulfate, caustic soda, and formalin, plating treatment is possible even if only the formalin is initially added in its entirety at once, but copper sulfate and caustic soda need to be gradually fed in this way. .

In this case, the feeding speed of the chemical may be adjusted in accordance with the state of deposition of metallic copper, and the speed at which metallic copper does not bridge between carbonaceous powders may be determined in advance. The total feed amount is determined in accordance with the target value of copper metal plating. However, the amount of copper sulfate to be fed should be 50% by weight or less in terms of metal copper based on carbonaceous powder. From the viewpoint of suppressing aggregation and coarsening of porous powder particles. Further, as described later, 25 to 40% by weight is appropriate for the use of the raw material for the power supply member.
A quantity corresponding to ~ 38% by weight is preferred

In the third step, the plating reaction is carried out by sequentially feeding the reaction solution into the reaction bath solution for a predetermined time, instead of simultaneously supplying a predetermined amount of the plating reaction agent to the reaction solution. This is where the important features of the present invention reside. Also in this step, it is possible to keep the carbonaceous powder in a constantly flowing state without keeping the bath temperature in the range of 40 to 60 ° C., preferably 45 to 55 ° C. by the cooling means. is necessary.

After the above plating operation is completed, a dewatering process is performed. Here, the copper-coated carbonaceous powder on which the plating reaction has been completed is settled, the supernatant is removed, and then washing and dehydration are repeated a few times to remove the plating agent. Next, after immersion and mixing in a discoloration inhibitor, for example, an aqueous sodium phosphate solution, dewatering, washing and dehydration are performed in the same manner as described above. Finally, after moistening with acetone, if a sufficient amount of water is removed by a dehydrator and sufficiently dried by a dryer with weak warm air, a copper-coated carbonaceous powder of a copper metal color can be obtained.

According to the embodiment of the present invention described above,
In forming a coating layer of metallic copper on the surface of the carbonaceous powder in the bath solution by electroless plating, a weak plating process is first performed on the raw carbonaceous powder by a base plating process, which is the second step, and thereafter, The loss that metal copper does not adhere in the finish plating process can be prevented.

Then, as a third step, the plating reaction is carried out slowly and continuously in accordance with the injection amount of the plating agent, so that a violent reaction such as rapid precipitation of metallic copper does not occur. Further, during the plating operation, the bath liquid is sufficiently stirred to keep the carbonaceous powder in a fluidized state at all times without causing the carbonaceous powder to settle, so that there is enough room for the precipitated metallic copper to bind the carbonaceous powder to each other. Therefore, the carbonaceous powder does not agglomerate and the primary particles are not aggregated into a granular state. Therefore, it is possible to obtain a copper-coated carbonaceous powder in which individual carbonaceous powder particles in a primary particle state are coated with metallic copper.

The amount of metallic copper coated on the copper-coated carbonaceous powder thus obtained can be appropriately increased or decreased by, for example, adjusting the weight of the copper salt to be subjected to the reaction. In order to suppress the coarsening of the particles, it is appropriate that the content is not more than 50% by weight, and the powder for producing the conductive member for supplying electric power of the electric motor by the sintering method is an electric power of a sintered body. From the viewpoint of balancing conductivity and lubricity, a preferable range is 25 to 40% by weight in weight ratio, and a particularly preferable coating amount is 32 to 38% by weight in weight ratio.

[0027] Further, such a metal copper coating layer is provided,
An appropriate binder is added to the copper-coated carbonaceous powder having an average particle size in the range of 0.2 to 5.0 μm, and the resultant is filled in a mold having a predetermined shape, and is subjected to pressure molding. Is heated in a reducing atmosphere furnace at a maximum temperature of 750 ° C. to 850 ° C. to obtain a conductive member having sufficient strength. In addition, if necessary, a cutting process or the like may be further performed so that a desired shape can be formed. The carbonaceous material used as the carbonaceous powder in the present invention may be any of amorphous carbon such as coke, natural graphite such as graphite, and crystalline carbon such as artificial graphite. is there.

[0028]

Next, examples of the present invention will be described with reference to comparative examples outside the scope of the present invention. Table 1 summarizes the plating conditions in this example. Conditions other than those shown here were performed according to the contents of the embodiment described above. Table 2 shows the difference between the conditions of this example and the comparative example.
Are shown together. Comparative Examples 1 and 2 are methods each of which lacks the base plating treatment of the present invention. Particularly, Comparative Example 2 is a method in which the plating agent of Example is continuously injected into the bath solution for a predetermined time. That is, the same amount of plating agent is injected into the bath solution at a time to perform plating.

[0029]

[Table 1]

[0030]

[Table 2]

According to this example, almost no loss of the carbonaceous powder floating in the bath solution without plating was observed in the finish plating process, whereas the loss rate in the comparative example 1 was small. Remarkably reached about 35%, and about 55% in Comparative Example 2.

When the state of the copper-coated carbon powder after the finish plating treatment is compared, microscopic observation shows that, in the case of the embodiment, no agglomerated portion was observed in the granular secondary particles, and the carbon surface No imperfect coating layer, such as exposed parts, was observed. On the other hand, in the case of Comparative Example 1, about 80% or more of the particles were in a form of agglomerated into granular secondary particles. In the case of Comparative Example 3, a situation in which the carbon powder solidified in a lump was observed with the naked eye during the plating process. At the end of the plating process, the whole became a single lump-like mass, and it was impossible to separate the individual particles. Met.

In the above embodiment, by adjusting the weight of copper sulfate used for the finish plating,
The coating amount of the metallic copper on the carbonaceous powder raw material, that is, the metallization ratio could be controlled with an accuracy within ± 2% by weight.
Then, three types of copper-coated carbonaceous powders having a coating layer having a metallization ratio of 35 ± 2% by weight and having an average particle size of 0.5, 1.5, and 3.5 μm were prepared according to this example. This was press-formed into a predetermined shape, and sintered at a maximum temperature of 800 ° C. in a reducing atmosphere to produce a power supply brush of an electric motor. All of these do not have the high manufacturing costs of artificial graphite, have sufficient wear strength, have low electrical resistivity, and have sufficiently low frictional resistance, so as conductive members such as power supply brushes, It has been found that the graphite material has favorable physical properties to compensate for the disadvantages.

[0034]

The copper-coated carbon powder, the method for producing the same, and the method for producing a conductive member according to the present invention are constructed as described above. Secondly, it is possible to provide a copper-coated carbonaceous powder capable of being mixed in a homogeneous state, and secondly, when depositing and coating metallic copper on the surface of the carbonaceous powder to minimize the loss of plating failure, Provided is a method for producing a copper-coated carbonaceous powder capable of preventing the particles from agglomerating and coarsening, thereby maintaining the initial state of the primary particles. Third, it is possible to provide a method for manufacturing a conductive member having both conductivity and sliding lubrication. Therefore, the present invention is a novel invention which has solved the conventional problems, and has a very large industrial value.

Claims (7)

[Claims] Claims (1) The inside is made of carbonaceous powder of primary particles,
A copper-coated carbonaceous powder comprising a metal copper coating layer obtained by electroless plating on its surface. 2. The coating amount of metallic copper on carbonaceous powder is as follows:
The copper-coated carbonaceous powder according to claim 1, wherein the amount is 25% by weight to 40% by weight. 3. The coating amount of metallic copper on carbonaceous powder is as follows:
The copper-coated carbonaceous powder according to claim 1, wherein the weight ratio is 32% by weight to 38% by weight. 4. When depositing a coating layer of metallic copper on the surface of the carbonaceous powder in the bath solution by electroless plating, the carbonaceous powder is mechanically moved so as not to aggregate due to the deposition of metallic copper, Producing a copper-coated carbonaceous powder, wherein a base plating treatment is performed in advance by a plating bath in which a copper salt containing a copper component of 0.8% to 3.0% in terms of metallic copper is added to the carbonaceous powder. Method. 5. After performing the base plating treatment, a predetermined plating agent is sequentially injected into the bath solution, and a plating reaction for depositing metallic copper is controlled in accordance with the injection amount, and
The method for producing a copper-coated carbonaceous powder according to claim 4, wherein a predetermined amount of a metallic copper coating layer is deposited. 6. A first step of mixing a carbonaceous powder with an aqueous solution of potassium sodium tartrate to deposit a metallic copper coating layer on the surface of the carbonaceous powder by electroless plating. Copper sulfate containing a copper component of 0.8% to 3.0% in terms of metallic copper with respect to powder, 0.5 to 1.2 grams of caustic soda per 1 gram of copper sulfate, and 3 37% concentration of ~ 8cc
A second step of injecting and mixing the converted formalin and performing a precipitation reaction of metallic copper until the carbonaceous powder changes from floating to sedimentable, and further, while stirring the bath solution, 25% to 40 in metal copper equivalent
% Aqueous copper sulfate solution containing 0.5% to 1.2 grams of caustic soda per gram of copper sulfate, and 37% concentration of 0.5% to 2.0 cc. The method further includes a third step of continuously feeding the converted formalin with a constant-rate pump to complete the precipitation reaction of metallic copper, wherein at least the second step and the third step are performed at a bath temperature of 40 to 60 ° C. Producing a copper-coated carbonaceous powder. 7. A coating layer of metallic copper deposited by electroless plating on the surface of a carbonaceous powder in an amount of 25% by weight to 40% by weight, and has an average particle diameter in a range of 0.2 to 5.0 μm. A method for producing a conductive member, comprising press-forming and sintering copper-coated carbonaceous powder.