US1959376A - Process for producing metal powders - Google Patents

Description

May 22, 1934. r J. H. LucAs PROCESS FOR PRODUCING METAL POWDERS Filed Sept. 26, 1930 INVENTCR Jam 8 a HLucd Patented May 212, 11934 PATENT OFFICE,

raocsss FOR PRODUCING METAL POWDERS James 11. Lucas, Elmhurst, N. Y., assignor Nichols Copper Company, New York, N. 'Y., a corporation of New York Application September 26, 1930, Serial No. 484,540

' 13 Claims. (Cl. 204-1) This invention relates to a process and apparatus for producing metal powders.

A method and apparatus used heretofore for this purpose included spaced cathode rods and anodes dipping into an electrolyte bath adjacent said rods. The bath was an electrolyte of copper sulphate and sulphuric acid. Current passing through the electrolyte from the anodes to the cathode rods deposited copper on these rods in a fluffy mass or slime. The deposit on the rods was allowed to build up ,for about minutes and at 15 minute intervals the rods where given a jarring by hand which caused at least some of the deposit to fall oil and into the bottom of the 15 electroylte bath from which it was ultimately removed, and after washing andv drying was screened to secure a copper powder of the desired particle size.

This old systempresented disadvantages which may be briefly summarized as follows:The

building up of the copper deposit on the rods caused the rods to increase in size, thus changing the density of the current'at the cathode. The density 01' current determines the particle size of the copper deposit on the rods and if the density changes as is the case where thedeposit on the rods is constantly changing, the size of these particles varies. When the particles, therefore, were jarred oi oi the rods, particles of varied size where recovered from the bottom of the electrolyte bath. The variation in density of the current caused some large crystals to form along with thoseiof a smaller size, thus necessitating sieving to remove the large crystals. According to the old system where it was desired to obtain crystals which would pass through a 200 mesh or better, with the jarring of the rods every 15 therefore, necessary to start oil! with anodes of relatively high purity in order to avoid the presence of these impurities in the resulting copper powder, such as iron, silver, tin, lead and zinc. In addition in the old system the rods required replacing about once a week due to the fact that at the point where the rods enteredthe electrolyte, oxidation by the old system occurred with eating away of the rods at that point until they were finally eaten through and dropped to the bottom of the tank.

An object of the present invention accordingly is to do away with these dimculties and to pro- '60 vide a simple eflicient apparatus and process for producing metal powders such as copper; powder which shall be simple, relatively inexpensive to operate, requiring little supervision, doing away with the necessity for renewal of'parts as in 05 the old system. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the novel apparatus and combinations thereof, as

well as the novel processes and stepsof processes which may be carried out in such apparatus, specific embodiments of which are described.

'herein by way of example only and in accordance with the manner in which I now prefer to practice the invention.

In the accompanying drawing wherein I have shown a preferred embodiment of my apparatus, Fig. 1 shows a somewhat diagrammatic side ele vation, partly in section,.of an apparatus embodying my invention. Fig. 2 is a plan view corresponding to Fig. l and showing the relative positions of anodes and cathodes. Fig. 3 is a detailed view of the spray used for washing away the copper powder scraped ofi the cathodes, and Fig. 4 is a somewhat enlarged detailed view of a device for controlling the overflow of electrolyte from the electrolyte bath.

Referring now to this drawing, I shall describe the apparatus as applied to the production o1 copper powder of a desired degree of purity and containing a copper content which may be as high as 99.75%. It is to be understood, however, that the invention herein is not restricted to apparatus or method of producing copper powder but is applicable generally to production of other 95 metallic powders which are susceptible to electro-deposition in powder form.

The numeral 1 designates a series of spaced copper supports. supporting in turn copper anode plates 2 here shown as in the form of ap'prox'im mately segments. The plates 2 may be made of relatively impure copper. It is not necessary that these plates be made up of copper of a high degree of purity as was the case with the anode plates used in the prior operation described above. 5 Of course if desired such pure copper plates may be used, but their employment is not important.

Thus a considerable saving in anode. expense may be effected. 4 These anode plates are, suit ably supported on. the bars 1 by means of wires 3 1 are in turn supported by the sides of a lead-lined wooden tank 4 provided with a dished bottom leading to a valved exit which will be described a er.

The tank 4 contains an electrolyte bath of copper sulphate and sulphuric acid.

The cathodes consist of a series of rotating copper disks alternating with the anodes 5 and submerged edgewise in the electrolyte bath.

In order to provide the proper current density passing between the anodes and cathodes, a device which will be described later'is provided to control the overflow of the electrolyte and hence its depth. The depth of immersion of the electrodes in the electrolyte determines the current density. For producing a commercial copper powder with this apparatus, I prefer to submerge the cathodes to about one-quarter their depth.

The cathodes are mounted on a shaft 6 supported in bearings 7 at either end of the tank 4, the bearings being suitably insulated from said tank. Mounted on this shaft is a steel sprocket 8 driven by a chain 9 from a smaller sprocket 10 mounted on its shaft 11 supported on said tank. The sprocket 8 is suitably insulated from the shaft 6 by means of an insulated bushing.

A source of current supply, not shown, has its positive pole connected to the anodes through wiring 12 attached to a conducting strip 13 with which the anode bars lare in contact. The negative pole is connected by means of wires'14 connected to the bearing block 7.

When current passes the anodes to the rotating cathodes, a thin fiuffy deposit or slime of copper is deposited on that portion of the cathode disk 5 which is submerged. The rotation of these disks is preferably continuous and therefore there is a continuous deposition of copper made on both faces thereof. It will be noted that the disks 5 are rotating in clockwise direction as shown in Fig. 1 and. therefore the copper is being depositedfrom the moment that the disk enters the electrolyte on the right side of the tank until it emerges from the left side, then from the left side the copper remains on the disk until it comes to a position just in advance of where it enters the tank. At this point a scraping device is provided shown more clearly in Figs. 1 and 3. The scraping device consists of :two troughs 15, the inner edges of which are sharpened to form scrapers 16 and contact each with the near face of one of the cathode disks.

These pairs of scrapers are provided for each of the cathode disks in the series. Immediately above each of the troughs 15 are positioned sprays 1'7 which are connected in a system to be later described for spraying electrolyte on to the copper as it is scraped ofi. The stream of electrolyte thus carries along the particles of copper with it and the troughs being inclined towards a series of exit pipes 18. The electrolyte with the copper passes through these pipes and into a settling tank 19.

The sprays as noted are part of a circulating system. This circulating system supplies electrolyte for washing and conveying away the cop- 1,959,376 passing through holes in the plate. The bars 1 22. The electrolyte bath, the tanks 19, 20, 21 and pump 22 are all connected by piping, so as to permit a continuous flow of electrolyte heated to 120 F. or a selected temperature as desired.

The tank 4 is connected by means of an L shaped pipe 22a with a pipe 23 leading to an overflow box 24'for the tank 19 which communicates by pipe 25 with receiving'tank 20. Situated in the L pipe is a short length of pipe 26 so designed that it projects into the upright portion of the L to give an exit for electrolyte from the tank 4 at the desired height to give a proper current density between the anodes 2 and cathodes 5. If the pipe 26 reaches nearly to the top of the tank 4, the exit through this pipe 26 will insure that the electrolyte bath in tank 4 will rise until it overflows 26 and the depth of liquid then in the tank 4 will be equal to the distance between the bottom of the tank and the top of the pipe 26. By substituting a medium length of pipe somewhat shorter than the one just mentioned, a slightly lower depth of liquid may be maintained and this depth may be varied as desired within the limits of the height of the upright member in the L, by changing the lengths of the pipe 26. Of course the L may have the height of the upright member varied as required.

The receiving tank 19 receives the electrolyte with copper particles suspended therein and when conveyed to this receiving tank, the particles settle out therein, the electrolyte passing off through a pipe 27 into the overflow be 24 and then through the pipe 25 to the receiving tank 20. The pump 22 is connected directly to the receiving tank. It is preferably a motor driven centrifugal pump and is connected by means of piping 28 to deliver into the upper portion of heating tank 21. In this heating tank is a series of steam coils 29 connected with a source of steam and tea discharge not shown. The electrolyte in this tank is heated indirectly by the steam and when heated to approximately 120 F. or other desired temperature passes out through the valved pipe 30 into a pipe 31 which is branched, one branch supplying electrolyte to the sprays 17 and the other branch 32 delivering the heated electrolyte to the tank 4.

The settling tank 19 is provided with a valve 33 at an exit in the bottom thereof, the valve being manually operable by a valve stem 34. When the valve 33 is pulled up, the copper particles with electrolyte pass through a pipe 35 into a delivery pipe 36 from whence it passes into a wheeled filtering car 3'7 where it is received on a filter tray 38, the electrolyte beirig sucked oil through the suction filter of the car and being later As noted above the anode plates may be of impure copper and where this is the case it will be obvious that impurities therein, whichare not deposited by electro-deposition, will fall to the bottom of tank 4 collecting on the dished surface thereof. In the center of the bottom is a valve 39 seated in an L projection of the pipe 36 provided with a valve stem 40 which may be operated from below to unseat the valve upwardly to allow the impurities in the tank 4 to run out In carrying out the process of my invention,v

I prefer to proceed as follows in producing a copper powder. Current is passed from the anodes 2 to the rotating cathode copper disks. Under preferred circumstances the current density at the anodes will average approximately 85 amperes per square foot while the current density at the cathodes will average approximately 250. amperage per square foot. I rotate the copper disks at the rate of about one or less revolutions per minute, the cathodes being submerged to about one-quarter of their depth in the electrolyte to give the desired current density. The anode is immersed substantially entirely. the current density to the preferred amount for the size of copper particles desired by selecting a pipe 26 of the proper height so that the level of the electrolyte in the tank 4 is sufficient to give the current density desired. The preferred elec-' trolyte contains from about 2.3% to 2.45% of copper, as copper sulphate, and from about 11.3% foo-11.4% sulphuric acid. .The copper deposited, as the rotating cathodes pass through the tank 4, then passes around through an angle of somewhat less than 180 until it reaches the'trough 15 with its scraper where the deposit is scraped off and washed away by electrolyte flowing through the spray 17, from the tank 21. I prefer to maintain the electrolyte at 120 F. and for this purpose a circulating, and heating system is provided. The electrolyte flowing from the tank 4 passes downwardly through the overflow box 24 of the settling tank and thence it passes into the receiving tank. The copper particles washed away by the spray 17 flow into the pipes 18 and thence into the settling tank where the copper settles out and may be removed when collected in sufiicient quantity from the settling tank 19. The excess electrolyte passes into the settling tank .overfiow box and then into the receivingtank 20. From the latter the pump 22 pumps the electrolyte up to the heating tanks 21 where it is heated and then allowed to flow by gravity to supply electrolyte to the tank 4 and spray 17. The settling tank is dumped periodically into thefilter 37, the copper powder being washed on the filter, the washing being preferably done with boiled water at a temperature somewhat below 120 F. in order to prevent oxidation. It is then transferred to the vacuum dryer and dried, preferably in accordance with the application of Fitzpatrick et a1. mentioned above.

The impurities settling out from the anodes are collected by dumping the electrolytic cell tank and allowing the impurities to run into car 37 where they are washed and then dried in a vacuum dryer.

All of the copper powder produced ,as above in accordance with my invention, was removed from the vacuum dryer and found to pass through, a 200 mesh screen. The resultant product averaged 99.6% purity. In some instances it was as high as 99.73% pure. The theoretical amount of finely divided copper in pounds that can be produced by 90 hours using a current of about 890 amperes, is equal to 210 pounds. The ampere I regulate Y efiiciency secured by operation of my invention, I have found to be pounds=about 85% The apparatus is of simple construction. The current density maintained by it varieslittle, if any, during the operation of the apparatus and consequently the particle size of the resultant copper or other metal is substantially uniform. Since the cathodes are continuously rotating and are being sprayed over their whole surface by the electrolyte, the difliculty of having oxidation at the liquid level of the electrolytetending to eat away the cathode as in the case of rods used in the old practice, is eliminated. The apparatus and process operate with high efiioiency. Furthermore impure anodes may be used thus saving in the expense of these electrodes.

As pointed out above other metals than copper which are susceptible to'electro-deposition in the manner indicated, may be employed in the apparatus and process described. In addition varying current densities may be employed as required or preferred. It will, of course, be understood that I do not restrict myself to anodes of any particular impurity, but I find it desirable to use a commercial copper as anodes containing approximately a total of .3% of solid impurities as gold, silver, lead, nickel, cobalt, antimony and arsenic.

Having thus described my invention with particularly with reference to the preferred method of. carrying out the same, it will be obvious to those skilled in-the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit and scope of my invention, and I aim in the appended claims to cover such changes and modifications as are within the scope of the invention.

What is claimed as new and desired to secure by Letters Patent is:-

1. A process for making copper powder or the like which comprises, passing a current through an electrolyte bath-from an anode to a cathode 3. A process for making copper powder or the like which comprises passing a current through an electrolyte bath from an anode to a-cathode while moving the latter, dissolving the anode in the bath, depositing spongy metal on the cathode, scraping off the cathode the metal deposit formed thereon without passing it through the bath,.and conveying the deposit away in a non-oxidizing medium.

4. A process for making copper powder or the like which comprises passinga current through an electrolyte bath from an anode to a cathode, dissolving the anode in the bath, depositing spongy metal on the cathode, moving the cathode, scraping off the metal deposited thereon without passing it through the bath, and conveying the deposit away in a non-oxidizing medium.

5. A process for making copper powder or the like which comprises, passing a current through an electrolyte bath from an impure anode soluble in said electrolyte bath to a movingcathode, and removing the metal deposit formed on said cathode while allowing impurities to settle out in said bath, supplying electrolyte to said bath and Withdrawing it therefrom.

6. A process for making copper powder or the like which comprises, passing a current through a heated electrolyte bath from an impure anode soluble in said electrolyte "bath to a moving cathode, removing the metal deposit formed on said cathode allowing impurities to settle out in said bath, and continuously supplying heated electrolyte to said bath and withdrawing it therefrom.

'7. A process for making copper powder or the like which comprises, passing 'a current in an electrolyte bath from an anode to -a moving cathode, regulating the current density to secure small particles of metal nearly uniform in size on the cathode and scraping off the metal deposit formed on said cathode while protecting the deposit from oxidation by the air, conveying said deposit away to a settling tank, and drying it' while substantially preventing oxidation thereof.

8. A process for making copper powder or the like which comprises, passing a current through an electrolyte bath from a relatively impure anode to a cathode, and scraping the deposit from the cathode without passing it through said bath,

conveying the deposit away in a stream of electrolyte for protecting the deposit from oxidation by the air and collecting impurities from said anode as said impurities are deposited in said bath and recovering them.

9. A process for making copper powder or the like which comprises, passing a current from spaced relatively impure anode plates to interposed cathodes while rotating the latter in a heated electrolyte bath, regulating the current density to obtain a deposit on the cathodes of nearly uniformly sized particles by adjusting the depth of submersion of said cathodes, scraping off the deposit, and conveying it to a settling tank while protecting it from oxidation by air.

10. A process for making copper powder or the like which comprises, passing a current from spaced relatively impure anode plates to interposed cathode plates while rotating the latter while partially submerged in an electrolyte bath heated to approximately 120 F., regulating the current density to obtain a deposit on the cathodes of nearly uniformly sized particles by adjusting the depth of submersion of said cathodes, scraping off the deposit and conveying it to a settling tank in a non-oxidizing medium, circulating the electrolyte through the bath while maintaining it at approximately 120 F., and dumping the said cathodes in said-bath, scraping off the copper therefor, and past heating coils to keep the liquid settling tank periodically into a filter and washing the copper powder thereon.

11. A process for making copper powder which comprises, passing a current from spaced relatively impure copper anode plates to interposed cathode copper discs partially submerged in an electrolyte bath of copper sulphate and sulphuric acid heated to about 120 F. while rotating the cathode discs, regulating the current density to secure small particles of copper of nearly uniform size on the cathodes by adjusting the depth of submersion of the latter in said bath, scraping off the copper deposit and conveying it to a settling tank while protecting it from oxidation by air, circulating the electrolyte through the bath and a receiving tank therefor while maintaining the electrolyte at about 120 F., and dumping the settling tank periodically into a filter and washing the copper powder thereon.

12. A process for making copper powder which comprises, passing a current from spaced relatively impure copper anode plates to rotating cathode copper disks placed between said anodes and submerged edgewise to about one-quarter their depth in an electrolyte bath of copper sulphate and sulphuric acid heated to about 120 F., regulating the current density to secure small particles of copper nearly uniformly sized on the cathodes by adjusting the depth of submersion of deposit and washing it into a trough and then into a settling tank and protecting it from oxidation by the air, circulating the electrolyte through the bath, settling tank, and a receiving tank 11 0 in the bath at about F., dumping the settling tank periodically into a filter and washing the copper powder thereon, keeping the said powder submerged in water, then transferring to a dryer and drying, collecting impurities from the anodes as said impurities drop to the bottom of said bath and throwing said impurities on the filter separate from the copper powder and washing and drying the impurities.

13. A process for making copper powder which 120 comprises immersing an impure copper anode in a circulating electrolyte capable of dissolving the anode, rotating a cathode partially immersed in said electrolyte near said anode, passing a current from anode to cathode adapted to deposit spongy copper, depositing copper on said cathode while dissolving the anode, but without depositing impurities on said cathode, scraping off the copper deposit on the cathode and washing it away with a stream of electrolyte to a settling tank, allowing the copper powder to settle and drawing off the electrolyte and returning it to the circulating electrolyte.

' JAMES H. LUCAS.

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