US2872406A - Anode frame - Google Patents

Description

Feb. 3, 1959 D. M. BUCHANAN ANODE FRAME Filed Sept. 23. 1954 N A m H. C N U B N m V A D 1 JT H U i e S s tefl ANODE FRAME David M. Buchanan, Woodside, N. Y., assignor to Union Carbide Corporation, a corporation of New York Application September 23, 1954, Serial No. 457,933

1 Claim. (Cl. 204-295) The present invention relates to an improved anode frame for use in the electrowinning of metal values from an electrolytic solution.

Prior to the present invention, in compartment type cells employed in the electrolytic production of chromium, manganese, and other similar metals, wood was extensively used as an anode frame material to maintain the anode plate terminals mechanically spaced and electrically insulated from one another, while providing low resistance to the passage of electrolyte between and around the anode frames. Difliculty was encountered in the electrolytic operation because electrolyte absorbed by the wooden anode frame material caused to frame to warp, and in many instances, reacted chemically with it. As a consequence, critical dimensions and clearances could not be maintained for any sustained length of time, and steady, eflicient operation of the compartment cell could not be assured.

Attempts were made in the past to solve this problem by using as anode frame materials, resinous materials having chemical resistance to electrolytic solutions. But none of these had any signal success. For instance, polyethylene and related resins proved to be too elastic, and did not possess sufiicient structural rigidity. Other resins such as melamines and ureas showed evidences of chemical attack by the electrolyte. Still other resins like fluorothene were impractical because of high cost.

It is, therefore, an object of the present invention to provide an anode frame made from resinous materials having good dimensional stability at higher temperatures normally encountered in electrolytic plating operations, and resistance to chemical attack by solutions used in the electrowinning of metals.

Another object of the invention is to provide an anode frame that can be made by injection molding in one piece from a resinous material having high dielectric properties and chemical resistance to electrolyte solutions used for the electrowinning of metals.

In the drawings:

Fig. 1 is a front elevational view with parts broken away, and partly in section, illustrating an anode frame constructed in accordance with the present invention;

Fig. 2 is a side elevational view of the anode frame shown in Fig. 1;

Fig. 3 is a plan view of the anode frame shown in i Fig. 1;

Fig. 4 is an enlarged vertical section taken along the line 4-4 in Fig. 1;

Fig. 5 is a cross-sectional view of the anode frame taken along .the line 5-5 in Fig. 1;

Fig. 6 is a cross-sectional view of the anode frame taken along the line 6-6 in Fig. 1; and

Fig. 7 is an anode frame similar to Fig. 1, but showing modification thereof.

The present invention is an improvement upon prior an anode frame materials. It has been found that a very suitable anode frame to be used in electrolytic having a styrene-acrylonitrile copolymer base.

2,872,406 Patented Feb. 3, 1959 processes can be produced from an organic compound Preferably those organic compounds are employed which contain between percent and percent of acrylonitrile. At the temperatures employed in normal electrolytic plating operations these materials are unaffected by dilute acids and alkalies. They possess excellent electrical insulation properties, outstanding surface finish, and good moldability properties. In addition, anode frames made 0 of styrene acrylonitrile copolymer material are particu- July well suited to be mass produced by injection molding, and may be cured tack-free in the presence of air in the range to be encountered in the practice of the invention.

The preferred class of compounds within the practice 'of the present invention are copolymers made by reacting together approximately 28 parts of acrylonitrile and 72 parts styrene monomer. They are copolymerized to form a thermoplastic copolymer which can be molded under heat and pressure. It is characterized by having a higher heat distortion temperature and greater toughness than polystyrene, and greater resistance to reagents, such as electrolytes, than polystyrene and other thermoplastics.

One of the advantages arising from the use of anode frames made of compounds of the type mentioned above overthe the use of wooden anode frames is the fact that in the temperature range normally employed in electrolytic plating operations, clearance dimensions can be more easily controlled. In the practice of the present invention the composition of the organic compound to be used as the anode frame material can be easily and carefully controlled in exactly the correct proportions to achieve the optimum value for any specific type of electrolyte which is to be used in conjunction therewith.

In forming the anode frame material, several variables will affect the quality of the product. One of the more important variables is the temperature. While electrolytic plating will usually occur at relatively low temperatures, in practice the temperature employed will normally be on the order of F. to 180 F., and

preferably about F. However, it is to be understood that temperatures -up to about 200 F. may be safely employed in plating operations. Above temperatures of about 200 F., distortion is quite rapid, making subsequent use of the anode frame impractical.

The anode frame of the present invention may be constructed to comply with the specifications of most elec trolytic processes, and is particularly well suited for use in the electrowinning of metals such as chromium and manganese, which are adapted to deposit out of aqueous electrolytic solutions. The electrode frame of the present invention is not affected by electrolytes having a chloride or a sulfate radical at temperatures below 200 F. Further, such frame may be efliciently and effectively operated at a pH of between 1.8 and 2.6.

In accordance with the present invention, an anode frame 10 is preferably made from an acrylonitrile copolymer material of the type described hereinabove. This frame may comprise a top wall 12, a bottom wall 13 and side walls 14 and 15, which may be suitably molded in one piece, as by injection molding. In order to impart structural rigidity to the anode frame. 10, each of these anode frame walls may be channel shaped, the top Wall 12 being preferably U-shaped and having a web 17 and upwardly projecting flanges 18 and 19.

For the purpose of receivably carrying an anode plate terminal 20, the web 17 is provided with an elongated slot 21, the slot 21 extending from juncture of web 17 with the web of side wall 14 to juncture of web 17 with web of side wall 15. In the modification shown in Fig.

7, two anode plate receiving slots 22 and 23 are illustrated in order that the anode frame assembly may be operated at full or one-half rated capacity or to facilitate handling of the anode plates.

The bottom anode frame wall 13' is also of channel form, preferably having an inverted U-shaped cross secare of U-shaped channel form, each having respectively a web 29 and opposed and outwardly extending flanges 3t). Vertically spaced ribs 32 in each of the side walls 14 and serve to impart strength and rigidity to the anode frame.

To confine the anolyte solution within the immediate vicinity of the anode plate, a gas permeable, liquid semipermeable, flexible cloth or membrane covering 33, preferably of Dynel woven fabric, is cemented to both sides of the anode frame 10. This construction permits escape of the gases evolved at the positive plates, and at the same time restricts flow of anolyte solution outside the confines of the anode frame.

Where a series of anode frames are used in an electrolytic process, both faces of each of the anode frames are covered with a membrane covering 33 in the manner illustrated in Fig. 1. However, where the anode frame is disposed at the extreme end of the frame series, only one face thereof need be covered with said membrane covering. in such case the endmost face is usually sealed with a liquid and gas-impermeable sheet of material, preferably of the same composition as the anode frame.

In the embodiment of the invention shown in Fig. 1, the anolyte is introduced into an opening 34 in the top of the anode frame 10 by means of an anode frame feed tube 35, preferably made of an electrolyte-resistant material similar to that of the anode frame 10. Circulation of the anolyte solution in the frame 10 is effected by a piping arrangement (not shown) which communicates with the inside of the frame 10 through inlet and outlet openings 36 and 37 in the side wall 29.

Bafiles may be provided if necessary inside the anode frame to prevent the anolyte from being discharged directly through the discharge opening 37.

It will be noted that because of the flexibility of the membrane 33, it may contact the anode plate and disrupt the uniformity of the plating operation. -To the end that contact between the membrane 33 and the anode plate 20 may be avoided, there is provided therebetween a series of anode frame rods 38. In assembly, these rods are held in position at their upper and lower ends respectively by means of openings 39 in the upper web 17 (see Fig. 4), which straddle the slot 21, and vertically 6 aligned blind end sockets 40 in the lower web 24 positioned on opposite sides of the guide slot 27.

The thickness of the side webs 29, as well as the flanges of the anode frames, may be suitably tapered to facilitate ejection of the anode frame from the mold.

From the above it will be seen that an improved anode frame may be made in one piece as by injection molding from a styrene acrylonitrile copolymer organic compound. The anode frame is admirably suited for use in most electrolytic plating processes, being not only resistant to chemical attack, but also exhibiting remarkable dimensional stability at temperatures up to 200 F.

it will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

What is claimed is:

An anodic electrolytic cell adapted to be removably inserted in a frame unit of a cell tank with other like cells without swelling comprising a monolithic, hollow, rectangular frame of a styrene acrylonitrile copolymer base having chemical resistance to electrolytic solutions and high structural rigidity and dimensional stability at temperatures up to approximately 200 C., said frame comprising a pair of spaced vertical side walls, a lower wall integral with the lower ends of said side walls, and an upper wall integral with the upper ends of said side walls, said frame walls forming a pair of flat rectangular surfaces in parallel planes, a pair of liquid semi-permeable diaphragm coverings attached respectively to said surfaces and forming an enclosed compartment in the interior of said frame, an elongated slot in said upper wall adapted to loosely receive a fiat rectangular electrode, a pair of openings in one of said side walls for circulating liquid electrolyte in said compartment, each of said frame walls comprising a central web and a pair of outwardly projecting end flanges, the inner surface of said web forming a part of the inside wall surface of said enclosed compartment, and the outer opposed surfaces of said projecting flanges forming a part of said flat rectangular surfaces, and a plurality of spaced rigid rods secured in said frame and disposed on opposite sides of said compartment for preventing contact between said diaphragm coverings and said electrode, whereby warpage and de terioration of said cell in an electrolyte solution is substantially avoided.

References Cited in the file of this patent UNITED STATES PATENTS 1,368,227 Sperry Feb. 8, 1921 1,861,796 Hodges June 7, 1932 2,512,973 Schumacher June 27, 1950 2,543,059 Rawles Feb. 27, 1951 2,739,116 Carosella Mar. 20, 1956 FOREIGN PATENTS 543,294 Great Britain Feb. 18, 1942 OTHER REFERENCES Bureau of Mines Bulletin #463, 1946, pages to 66 including Figs. 30, 31 and 33.

Schildknecht, Vinyl and Related Polymers, 1952, pages 48 to 54.

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