US3523873A

US3523873A - Electrodeposition of strippable metal coatings and compositions and artiticles useful therefor

Info

Publication number: US3523873A
Application number: US513854A
Authority: US
Inventors: Eugene Mitchell Elkin
Original assignee: Canadian Copper Refiners Ltd
Current assignee: Canadian Copper Refiners Ltd
Priority date: 1965-12-14
Filing date: 1965-12-14
Publication date: 1970-08-11
Anticipated expiration: 1987-08-11
Also published as: DE1533443A1; DE1533443B2; SE319946B; BE691208A

Description

United States Patent 01 fice 3,523,873 Patented Aug. 11, 1970 3,523,873 ELECTRODEPOSITION F STRIPPABLE METAL COATINGS AND COMPOSITIONS AND ARTI- TICLES USEFUL THEREFOR Eugene Mitchell Elkin, Montreal, Quebec, Canada, as-

signor to Canadian Copper Refiners Limited, Toronto, Ontario, Canada, a corporation of Canada No Drawing. Filed Dec. 14, 1965, Ser. No. 513,854 Int. Cl. C23b 7/ 00, 7/02 US. Cl. 204-3 10 Claims ABSTRACT OF THE DISCLOSURE It has been found that a dressing or parting agent composition comprising an aqueous emulsion containing minor amounts by way of a polar, saturated, substantially waterinsoluble aliphatic organic compound or a sulfur-containing material is useful and yields improved results when employed in an operation for the preparation of metal cathode starting sheets, such as copper cathode starting sheets.

This invention relates to the electrodeposition of metals. More particularly, this invention relates to the electrodeposition of metals onto a substrate, such as a metal or electrically conductive substrate, under conditions such that the electrodepositioned metal is readily separable or stripable from the substrate.

In accordance with one embodiment this invention is directed to a method of making a metal cathode starting sheet, such as a continuous, coherent, essentially holefree copper cathode starting sheet, useful in the electrorefining of metals. In accordance with another embodiment this invention is directed to an electrically conductive substrate coated with a parting agent, which permits the ready separation of electrodeposited metal from the coated substrate. In accordance with yet another embodiment, this invention is directed to a parting agent composition useful in the manufacture of metal cathode starting sheets, such as copper cathode starting sheets, employed in the electrorefining of metals. In accordance with still another embodiment, this invention is directed to a parting agent composition useful in electroforming operations.

Although emphasis is placed in the disclosure of this invention on the applicability of the invention to the electrorefining of copper and to the manufacture of copper cathode starting sheets, the practices and the various embodiments of this invention also appear to be applicable in the electrorefining of other metals including nickel and the like, particularly in electrorefining operations wherein substantially pure metal is electrodeposited upon a smooth metal substrate and the resulting electrodeposited metal stripped or otherwise removed from the metal substrate in the form of a thin, smooth, coherent, substantially holefree sheet.

In the preparation of copper cathode starting sheets useful in the electrorefining of copper, copper is electrodeposited upon a smooth metal sheet or blank, such as a smooth plate of rolled copper, which has been coated with a parting agent. The essential functions of the parting agent are to provide a suitable surface for the electrodeposition of copper, to prevent adherence of the electrodeposited copper to the copper plate and to facilitate the removal or stripping of the electrodeposited copper from the copper plate in the form of a continuous, coherent, subsubstantially hole-free sheet.

It has been a practice heretofore to coat the surface of the blank used in the electrodeposition of metal with a film of a petroleum derived parting agent or dressing usually comprising a lubricating oil, transformer oil, diesel oil or fuel oil or mixtures thereof, including lubricating greases and gasoline. Such dressings or parting agents are usually applied by hand swabs or rollers or by dipping in a tank containing such dressings and by other means.

It has also been suggested to employ as a dressing 9. waterabase soluble oil emulsion, see Cadwell-U.S. 3,046,- 203 issued July 24, 1962. Also, it is not uncommon to include in parting agent compositions various additives, such as anti-oxidants, anti-foam agents, germicides, wetting agents and the like. However, it has been experienced in actual commercial operations for the preparation of copper cathode starting sheets that when dressings or parting agents containing a petroleum-derived material or a petroleum composition are employed, non-uniform results are often obtained. It appears that petroleum-derived or petroleum products vary, depending upon the manufacturer, the source of the crude petroleum and the type and/ or severity of refining to which the petroleum product has been subjected. These variations in the origin and the processing of such petroleum products influence the performance of such petroleum products when employed as a dressing or parting agent in the manufacture of starting sheets, such as copper cathode starting sheets.

For example, petroleum products when employed as dressings in the preparation of copper cathode starting sheets sometimes appear to cause holes in the sheets, presumably caused by excess amounts of petroleum product as well as by unknown causes. Also, roughness of the electrodeposited copper sheet accompanied by sharp protuberances is often observed. Further, a rash of smooth, rounded-01f pimples irregularly covering the surface of the electrodeposited copper, difficulty in initiating the parting or separation of the electrodeposited copper from the copper blank, difficulty in stripping or parting the electrodeposited copper from the copper blank, difficulty in separating and pullling off the electrodeposited copper from around the side edges of the copper blank and formation of finely divided electrodeposited dust on the surface of the copper blank have also been observed and experienced when parting agents containing petroleum de rived materials or compositions are employed. Ihe aforementioned dust tends to become firmly attached to the copper blank and to roughen its surface with eventual detrimental affect upon the stripping operation.

Because of these difficulties observed when petroleumcontaining dressings are employed in the production of copper cathode starting sheets, it has been experienced that about 5-l0% of the copper cathode starting sheets are defective. It has also been experienced that upon those occasions when the petroleum supplier and/or manufacturer changes sources or refining techniques the percentage of defective copper cathode starting sheets may increase up to 25% and even higher of the total number of sheets produced.

Accordingly, it is an object of this invention to provide a dressing or parting agent of controlled composition.

It is another object of this invention to provide an improved electroforming operation involving the production of strippable electroformed metal products.

It is yet another object of this invention to provide an improved process for the manufacture of cathode starting sheets useful in the electrorefining of metals.

It is still another object of this invention to provide a coated, electrically conductive substrate useful in electroforming operations and the like.

It is a specific object of this invention to provide an improved process for the manufacture of copper cathode starting sheets.

Yet another specific object of this invention is to provide a coated metal substrate particularly useful in the electrorefining of metal.

How these and other objects of this invention are achieved will become apparent in the light of the accompanying disclosure. In at least one embodiment of this invention at least one of the foregoing objects will be achieved.

In accordance with this invention it has been discovered that a dressing or parting agent composition comprising an aqueous emulsion containing minor amounts by weight of a polar, saturated, substantially water-insoluble, aliphatic organic compound and a sulfur-containing material is useful and yields improved results when employed in an operation for the preparation of metal cathode starting sheets, such as copper cathode starting sheets. Further, it has been discovered that an electrically conductive substrate, such as a metal substrate, coated with a parting agent in accordance with this invention and comprising an aqueous emulsion containing a polar, saturated, substantially water-insoluble, aliphatic, organic compound and a sulfur-containing material, permits the ready separation of electrodeposited metal from the coated substrate or surface.

The polar, saurated, substantially water-insoluble, aliphatic, organic compound which may be of commercial grade or reagent grade quality comprising one of the components of the parting agent composition in accordance with this invention is selected from the group comprising fatty acids, fatty alcohols and derivatives thereof, such as esters and glycerides. The polar, saturated, organic compound may be liquid or solid at a temperature in the range from about 60 F. to about 100 F., more or less. It is required, however, that the polar, saturated, organic compound be substantially water-insoluble at such temperatures. Specifically, the polar, saturated, organic compound should have a water-solubility not in excess of about 5% by weight at about 150 F. based on the resulting solution. The purpose of the polar, saturated, organic compound in the parting agent composition of this invention is to form a film or barrier on the substrate or surface to which it is applied such that after electrodeposition of metal thereon the electrodeposited metal can be stripped therefrom with little difficulty and substantially in the shape or outline of the substrate surface itself.

Polar, saturated, organic compounds which have been found to be useful in compositions in accordance with this invention include the fatty acids, such as stearic acid, the fatty alcohols, such as decyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, cetyl alcohol, i.e. a C straight chain alcohol, hexadecyl alcohol, i.e. a C branched chain alcohol, stearyl alcohol, arachidyl alcohol, the aliphatic esters, such as butyl stearate, isopropyl palmitate, isopropyl stearate, glycerol monostearate, ethylene glycol monostearate, diethylene glycol stearate, propylene glycol stearate, sorbitan monostearate and sorbitan tristearate.

Other polar, saturated, aliphatic, organic compounds useful in the preparation of compositions in accordance with this invention include decanoic acid, palmitic acid, ntridecanoic acid and their higher molecular weight homologues. Polar, saturated, fatty, substantially water-insoluble, aliphatic, organic compounds containing at least carbon atoms per molecule, such as 12-60 carbon atoms per molecule, and having a solubility in water not greater 4 than about 5% by weight in the resulting solution at a temperature of about F. yield satisfactory results. Mixtures of such organic compounds are also usefully employed in the compositions of this invention.

The other component of the dressing or parting agent compositions of this invention is a sulfur-containing material. This other component may be prepared by dissolving sulfur in a polar, saturated, fatty, organic compound such as the aforementioned polar, saturated, substantially water-insoluble, aliphatic, organic compound in compositions of this invention. A solution prepared by dissolving sulfur in n-hexadecyl alcohol has been found to yield satisfactory results.

Sulfur-containing compounds which have been found to be useful include mercaptopropionic acid, n-butyl-sulfide, n-octyl mercaptan and lauryl mercaptan. In general, sulfur-containing organic compounds, such as alkyl sulfides and alkyl mercaptans containing at least four carbon atoms per molecule, such as alkyl sulfides and alkyl mercaptans containing from four to twenty-four carbon atoms per molecule, are useful in the practice of this invention.

The amount of sulfur-containing material in compositions in accordance with this invention is small, less than about 1% by weight of the composition. For example, it has been observed that in the manufacture of copper cathode starting sheets employing a dressing or parting agent composition in accordance with this invention if the sulfur-containing material content of the dressing is too high the resulting electrodeposited copper will be lacy i.e. have the appearance of lace.

Any suitable emulsifying agent may be employed in the preparation of aqueous emulsions containing the polar, saturated, aliphatic, organic compound and the sulfurcontaining material in accordance with this invention. Satisfactory results have been obtained in the manufacture of copper cathode starting sheets when the emulsifying agent employed in the preparation of the parting agent compositions comprises a sodium dodecylbenzene sulfonate. Other useful emulsifying agents include linear alkyl aryl sulfonates and the corresponding water-soluble salts and linear alcohol sulfates and the corresponding watersoluble salts.

In the dressing or parting agent compositions in accordance with this invention the polar, saturated, aliphatic, organic compound is usually present in an amount in the range 220% by weight based on the aqueous emulsion and the sulfur-containing material is usually present in the emulsion in an amount in the range 0.05 to 0.15% by weight. The emulsifying agent is present in an amount effective to emulsify the polar, saturated, substantially water-insoluble, aliphatic, organic compound and is usually present in an amount in the range 0.4-4% by weight.

The dressing or parting agent composition may be applied by any suitable means to the substrate upon which the metal is to be electrodeposited, such as swabs or rollers, or by spraying or by dipping or immersing the substrate, e.g. the copper starting blank, into the emulsion and then raising the blank and permitting the excess emulsion to drain. Usually when dipping the blank in the emulsion it is not necessary to hold the blank therein for more than one or two seconds. Holding the raised blank, after dipping, above the dipping tank to drain excess emulsion into the dipping tank is useful to decrease consumption of the emulsion.

Copper starting blanks coated with a composition in accordance with this invention were employed in electrolytic cells under commercial copper refining conditions for the preparation of copper cathode starting sheets. The resulting electrodeposited copper cathode starting sheets were smooth and without defect and were readily stripped from the blanks without diificulty.

The following are descriptions of compositions and methods for the preparation of compositions in accordance with this invention. Water at a temperature of about -175 F. was introduced to within about 18" from the top into a tank measuring 48" high, 48" long and 18" wide. The tank was also provided with a A horsepower Lightnin mixer which had a shaft about 3 feet long to which were fixed two propellers, each about 3" in diameter. Seventy pounds hexadecyl alcohol and fourteen pounds Sulframin 85 flakes, a sodium n-dodecylbenzene sulfonate were added to the hot water in the tank. More hot water was then added to within 4" from the top of the tank, and the resulting admixture was agitated for at least eight hours by means of the Lightnin mixer. The order and the rate of addition of the components are not critical. It is preferable, however, to first add the polar, saturated, aliphatic, organic compound, such as the fatty alcohol, and then to add the emulsifying a ent.

The following day, when the resulting emulsion had cooled to about ambient temperature, agitation was again commenced and about 1.4 pounds mercaptopropionic acid was added. Agitation of the admixture was continued for at least about 2 hours.

The resulting emulsion now contained hexadecyl alcoholabut 5 by weight Sulfrarnin *85-about 1% by weight mercaptopropionic acidabout 0.1% by welght.

The sulfur-containing material, such as the thiolactic acid, is usually added last since sulfur-containing materials, particularly the organic sulfur-containing compounds, have an unpleasant odor, especially when warmed. Cooling of the emulsion before the addition of the sulfur-containing material is a matter of convenience and preference so as to decrease the odor. Upon the addition of the mercaptopropionic acid the emulsion is ready for use by immersing therein the copper blanks.

After immersion, the copper blanks are placed in commercial copper electrolytic cells and substantially pure copper electrodeposited thereon. When the desired thickness, about of electrodeposited copper has been reached, the blanks containing the electrodeposited copper are removed from the cells and the resulting formed electrodeposited copper starting sheets are pulled or stripped therefrom as smooth, continuous, coherent, essentially hole-free sheets.

Other aqueous emulsions found to be useful and to yield satisfactory results in accordance with the practices of this invention include aqueous emulsions having the compositions:

In the preparation of aqueous emulsion compositions in accordance with this invention, as the sulfur-containing material component of the emulsion a sulfur solution prepared by the addition of 4 grams of elemental sulfur per 1000 cc. of hexadecyl alcohol followed by heating to a temperature in the range about 180-l90 F. to dissolve the sulfur, thereby yielding a sulfur solution containing 0.4% by weight sulfur, has been found to be useful, particularly in combination with hexadecyl alcohol as the polar, saturated, substantially water-insoluble, aliphatic, organic compound.

Other sulfur-containing materials found to be useful include n-lauryl mercaptan and n-octyl mercaptan. These may be added directly to the agitated emulsion.

As indicated hereinabove the practice of this invention is not only applicable to the manufacture of copper cathode starting sheets but would also appear to be applicable to the manufacture of nickel cathode starting sheets and the like. Also, as indicated herein, the practice of this invention is applicable to electroforming operations to improve and aid in the release of the electrodeposited metal from the substrate material.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many modifications, alterations and substitutions are possible in the practice of this invention without departing from the spirit or scope thereof.

I claim:

1. A material comprising an electrically conductive substrate coated with a film or layer of a composition comprising 220% by weight of a polar, saturated, substantially water-insoluble, aliphatic, organic compound selected from the group consisting of fatty acids, fatty alcohols and ester and glyceride derivatives thereof and a minor amount in the range 0.054% by weight of a sulfur-containing material.

2. A material in accordance with claim 1 wherein said electrically conductive substrate is a smooth plate of rolled copper.

3. In an operation wherein a parting agent is applied to an electrically conductive substrate, the parting agent serving as an aid for the stripping and removal of metal subsequently electrodeposited on said substrate, the improvement which comprises employing as said parting agent a composition comprising an aqueous emulsion containing 2-20% by weight of a polar, saturated, substantially water-insoluble, aliphatic, organic compound selected from the group consisting of fatty acids, fatty alcohols and ester and glyceride derivatives thereof and about 0.05-1% by weight of a sulfur-containing material.

4. A method in accordance with claim 3 wherein said electrodeposited metal is a metal selected from the group consisting of copper, nickel and the like.

5. A method in accordance with claim 3 wherein said electrodeposited metal is copper.

6. A method in accordance with claim 3 wherein said sulfur-containing material is selected from the group consisting of sulfur solutions, mercaptopropionic acid, nbutyl sulfide, n-octyl mercaptan and lauryl mercaptan.

7. A method of making copper cathode starting sheets which comprises applying to the surface of a smooth copper plate an aqueous emulsion comprising a minor amount in the range 220% by weight of a polar, saturated, substantially Water-insoluble, aliphtaic, organic compound selected from the group consisting of fatty acids, fatty alcohols and ester and glyceride derivatives thereof and a minor amount in the range of 0.05-1% by weight of a sulfur-containing material and a minor amount of an emulsifying agent for said polar, organic compound, electrodepositing substantially pure copper on the surface of the thus-coated copper plate and stripping the resulting electrodeposited copper from said copper plate su'bsantially in the form of a smooth, coherent, essentially holefree, copper sheet.

8. A method in accordance with claim 7 wherein said sulfur-containing material is selected from the group consisting of alkyl sulfides and alkyl mercaptans containing from 4 to 24 carbon atoms per molecule.

9. A method in accordance with claim 7 wherein said sulfur-containing material is mercaptopropionic acid.

10. A method in accordance with claim 7 wherein said sulfur-containing material is prepared by the addition of elemental sulfur to hexadecyl alcohol in the proportion 7 8 of about 4 grams of elemental sulfur per 1000 cc. of FOREIGN PATENTS hexadecyl alcohol.

341,246 1/1931 Great Britain. References Cited OTHER REFERENCES UNITED STATES PATENTS 5 JOHN H. MACK, Primary Examlner 2,555,321 6/1951 Dalton 204-2 0,046,203 7/1962 Caldwell 204 12 T. TUFARIELLO, Asslstant Exarnmer 3,271,190 9/1966 Nadeau 106-2 U.S. C1. X.R. 3,231,339 10/1966 Edgar 204-12 10 204-12 630,796 8/1899 Becker 2044 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,523,873 Da ed August 11, 1970 In ent EUGENE MITCHELL ELKIN It is certified that error appears in the above-identified patent and that: said Letters Patent are hereby corrected as shown below:

In Column 7, under "References Cited UNITED STATES PATENTS", the second reference is incorrect. This line should read 3,0 6,203 7/1962 Cadwell 20 +--12 slim ocfzv 1970 (SEAL) Attest:

Edward M. Fletcher, 11;

Attcsting ()ffim WHIIIIAH E. JR.

Commissioner of Patents FORM POWSO USCOMM-DC 6OS7B-P6O U s GOVERNHENY PRINTING OFFICE I OS66 334