US2849352A - Electroplating process - Google Patents

Description

United States Patent ELECTROPLATIN G PROCESS Alfred Kirstahler, Dusseldorf, and Wennemar Strauss and Wolf-Dieter Willmund, Dusseldorf-Holthausen, Germany, assignors to'Dehydag, Deutsche Hydrierwerke G. 111. b. IL, Dusseldorf, Germany, a corporation of Germany No Drawing. Application October 25, 1956 Serial No. 618,183

Claims priority, application Germany June 15, 1956 Claims. (Cl. 204--44) wherein R is a straight-chain or cyclic organic radical comprising at least two carbon atoms linked exclusively to oxygen, sulfur and/or nitrogen atoms, each of said carbon atoms being linked to a S-R SO H group,

R is a bivalent lower aliphatic radical, and n is an integer equal to the number of said carbon atoms in the radical R, or water-soluble salts of such compounds.

For example, triazine derivatives having the structural formula Lia-Sean wherein R, has the meaning above indicated, or their water-soluble salts, such as the alkali metal or ammonium salts, are suitable as brightening additives for electroplating baths in accordance with the present invention. The bivalent radical R may, for instance, be a methylene, ethylene, propylene, hydroxypropylene, chloropropylene or similarradical.

Such triazine compounds may, for example, be obtained by transforming tricyanogen chloride into trimercaptocyanuric acid, and thereafter reacting an alkali metal salt of the acid with an organic halogensulfonic acid, such as 2bromoethane-1'-sulfonic acid, 3-bromopropane-l-sulfonic acid, 3-chloro 2 hydroxypropane-l-sulfonic acid or their alkali metal salts, or with a sultonc, such as propanesultone or butanesult'one, to form the corresponding mercapto-alkanesulfonic acid triazine derivatives or their salts.

Other suitable compounds havingthe above general Formula I are those wherein the radical R is a 5- or 6- membered heterocyclic radical with at least two nitrogen atoms. Compounds of this type are, for example, 1,3,4- thiodiazole-2,5-bis(mercaptopropane-l-sulfonic acid) Patented Aug. 26, 1958 ice , 2 1,3,4-thiodiazole-2,5-bis(mercapto 2 hydroxypropanel-sulfonic acid) or 1,3,4 oxdiazole 2,5 bis(mercaptopropane-Lsulfoiric acid) and the like, or their water-soluble salts, such as alkali metal and ammonium salts.

As previously pointed out, however, the radical R in Formula I need not necessarily be a cyclic radical. Thus, similarly suitable for use as brightening agents in electroplating baths in accordance with the present invention are acyclic compounds, such as dithiobiuret-S,S'-dipropanesulfonic acid wherein R, has the meaning defined in Formula I and R is an aliphatic of aromatic radical, and their watersoluble salts. The dibas'ic S-alkanesulfonic acids may be obtained, for example, by reacting methylene, ethylene, hexamethyleneor phenylene-dithiourea with propanesultone, butanesultone or halogen-alkanesulfonic acids or alkali metal salts thereof,

Finally, also tribasic and higher polybasic S- alkanesulfonic acids and their water-soluble salts, such as those obtained by reacting polyurea compounds with halogenalkanesulfonic acids or sultones in accordance with the above method, are effective as brightening agent's according to the present invention.

The b'righteners disclosed herein may advantageously be employed in conjunction with all types of electroplating baths, and especially with electroplating solutions for the production of copper, nickel, silver, zinc, cadmium, bronze and brass electrodep'osits.

While the brightening additives in accordance with the present invention will produce bright and lustrous metal electrodeposits when used as the sole additives in electroplating baths, they may also be employed in combination with known brightening additives, smoothing agents, sequestering agents, inhibitors, anionic, cationic or electroneut'ral surface-active agents, salts which increase the conductivity of the bath and similar additives customarily used to improve the metal electrodeposits.

For example, suitable additional brightcners are those which are disclosed in copending application Serial No. 442,199, filed July 8, 1954. Examples of sequestering agents are compounds disclosed in copending applications Serial No. 458,984, filed September 28, 1954, and Serial No. 544,586, filed November 2, 1955, and in German Patent No. 934,508; in other words, the term sequestering agents is intended to designate those additives which prevent the mineral salts in hard water and impurities in the inorganic metal salt from interfering with the brightening effect of the brightening additive.

The quantity of the S-alkanesulfonic acid compounds added to electroplating baths according to the present invention may range from 0.01 to 20 gm. per liter of bath. The effective current density range of such electroplating baths lies between 0.5 and 12 amp./dm. and the temperature of the solution may reach as high as 60 C.

during the electroplating procedure. The current density range at which the optimum brightening effect is achieved will vary from one particular brightener to the other, but in general the range is of considerable breadth for the entire group of brighteners herein disclosed. The optimum current density range may, however, be broadened by employing a mixture of two or more members of the group.

Particularly noteworthy is the fact that the addition of the S-alkanesulfonic acid compounds described herein to electroplating baths makes it possible to produce fullbright electroplates within an exceptionally broad range of temperatures, namely between 15 and 60 C. At temperatures higher than room temperature the optimum current density range is shifted toward considerably higher values (about 15 amp./dm. Moreover, because of the ability of our brightening agents to produce fullbright electrodeposits at relatively high bath temperatures, it is possible to use the brighteners in copper-plating baths which because of high rates of current flow develop a considerable amount of heat and therefore operate at temperatures up to 40 C. and even 50' C.

Electroplating baths modified in accordance with our invention may be employed to deposit metal electrodeposits on any desired customary base metal, such as iron, steel, zinc and similar non-precious metals or alloys thereof. In the case of copper-plating baths, the base metal may first be provided with a thin copper coating in a separate cyanide bath in customary fashion, or the base metal may be provided directly with the final copper plate without a preliminary thin copper base coat in accordance with the process disclosed in copending application Serial No. 458,983, filed September 28, 1954.

In all cases, electroplating baths modified in accordance with the present invention produce full-bright electrodeposits of extraordinary high quality which do not require subsequent bufling or polishing.

The following examples will further illustrate the present invention and enable others skilled in the art to understand it more completely. It will be understood, however, that the invention is not limited'to these particular examples.

Example I were dissolved in an acid aqueous copper sulfate bath -composed of water, 220 gm. per liter crystalline copper sulfate and 60 gm. per liter sulfuric acid. Sheet metal objects copper-plated in this electroplating solution at room temperature and at elevated temperatures up to 60 C. with a current density from 0.5 to 8 amp./dm.

were provided with a full-bright copper clectrodeposit which did not require bufling or polishing.

I Example II The same full-bright copper electrodeposits were obtained when 0.2 to- 1.5 gm. per liter of the trisodium salt -(CHzh-BOaNB.

were added to the acid copper sulfate solution described in Example I instead of the trisodium salt of 1,3,5-triazine-2,4,6-tri-(mercaptopropane 1 sulfonic acid), and brass and iron objects were copper-plated therein under the conditions of temperature and current density described in Example I.

Example III 0.5 to 1.0 gm. per liter of the disodium salt of 1,8,4- thiodiazole-Z,S-bis-(mercaptopropane 1 sulfonic acid) having the structural formula was added to an acid copper sulfate solution composed of water, 200 gm. per liter crystalline copper sulfate and 60 gm. per liter sulfuric acid. Brass and iron objects electroplated in this solution at current densities from 2 to 10 amp./dm. and at temperatures between room temperature and C. were provided with a full-bright, high-quality copper plate which required no buifing or polishing subsequent to rinsing.

Example IV 0.2 to 1.0 gm. per liter of the dipotassium salt of N,N-methylene-di-(isothiourea-S-propane 1 sulfonic acid) having the structural formula was added to the acid copper sulfate solution of Example III instead of the disodium salt of l,3,4-thiodiazole-2,5-

bis-(mercaptopropane-l-sulfonic acid). Brass and iron objects electroplated in this modified copper sulfate bath at current densities from 1 to 11 amp./dm. and at temperatures between room temperature and about C. were provided with full-bright, high-quality copper plates which required no bufiing or polishing.

Example V 1.2 gm. per liter of the trisodium salt of 1,3,5-triazine- 2,4,6-tri-(mercaptopropane-Z-hydroxy 1 sulfonic acid) having the structural formula shown in Example II and 0.8 to 1.2 gm. per liter 1,3-bis-(dibutylamino)-propanol-2, described in said copending application Serial No. 458,984,

were added to an acid copper sulfate solution composed of water, 220 gm. per liter crystalline copper sulfate and gm. per liter sulfuric acid. Brass and iron objects electroplated in this solution at temperatures from room temperature to 60 C. and at current densities from slightly above 0 amp./dm. up to 15 amp./dm. were provided with full-bright copper electrodeposits of exceptionally high quality which required no additional bufl'ing or polishing. i

Example VI From 1 to gm. per liter of the ammonium salt of 1,3,5-triazine-2,4,6-tri-(mercaptopropane 2 hydroxy-lsulfonic acid) having the structural formula Example VII From 0.5 to 1.5 gm. per liter of the disodium salt of 1,3,4 thiodiazole-2,5-di-(mercaptopropane 1 sulfonic acid) having the structural formula were dissolved in a zinc cyanide bath composed of water, 57 gm. per liter zinc cyanide, 72 gm. per liter sodium hydroxide and 40 gm. per liter sodium cyanide. Sheet steel electroplated in this solution at current densities from 1 to amp./dm. and at temperatures between room temperature and about 40 C. were provided with full-brigl1t zinc electrodeposits of extremely high quality which re quired no additional bufling or polishing.

Example VIII From 1 to 2 gm. per liter of the disodium salt of N,N- methylene-di-(isothiourea S-propane 1 sulfonic acid) having the structural formula were dissolved in a cadmium cyanide bath composed of water, 125 gm. per liter cadmium sulfate, 140 gm. per liter sodium cyanide and 72 gm. per liter sodium hydroxide. Steel and iron objects electroplated in this solution at current densities from 3 to 8 amp./dm. and at temperatures between room temperature and about 35 C. were provided with full-bright cadmium electroplates of extremely high quality which required no further bufiing or polishing.

Example IX 1.0 gm. per liter of the trisodium salt of 1,3,5-triazine- 2,4,6-tri-(mercaptopropane 1 sulfonic acid) having the structural formula shown in Example II, 0.05 gm. per liter N,N-diethyl-dithiocarbamic acid-ethylester-w-sodium sulfonate and 1.2 gm. per liter 1,3-bis-(diethylamino)- propanol-2, as well as 0.5 gm. per liter of the sodium salt of an acid sulfuric acid ester mixture of ethoxylated fatty alcohols with alkyl radicals having from 12 to 18 carbon atoms, were dissolved in an acid copper sulfate bath composed of water, 220 gm. per liter crystalline copper sulfate and 60 gm. per liter sulfuric acid. Iron objects electroplated in this solution at 40 C. and at a current density "between 5 and 12 amp./dm. were provided with full bright copper electroplates of extremely high quality, even when the iron objects had not previously been provided with a preliminary copper plate in a copper cyanide solution.

Example X The disodium salt of the 1,3,4-thiazole-2,5-bis-mercapto-2'-oxypropane-1'-sulfonic acid was substituted for 6 the thiadiazole derivative in Example HI. A fullabright copper plate was obtained.

Example XI The disodium salt of the 1,3,4-triazole-2,5-bis-mercaptopropane-1-sulfonic acid was used instead of the triazin derivatives according to Example II. An excellent copper plate was obtained.

Example XII The dipotassium salt of N,N'-m'ethylene-di-(isothiourea-S-prop-ane-l-sulfonic acid) according to Examples IV and VIII is substituted by an equal amount of the salts of the corresponding ethylene, hexamethylene or phenylene derivatives. Full-bright copper electroplates were obtained.

Example XIV The disodium salt of the dithiobiuret-S,S'-dipropane sulfonic acid was substituted for the N,N'-methylene-di- (isothiourea-S-propane-l-sulfonic acid) in Example VIII. A good bright copper plate was formed.

While we have disclosed various specific embodiments of our invention, it will be apparent to persons skilled in the art that the present invention is not limited to these specific embodiments and that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. An electroplating bath for producing bright electrodeposits of metals selected from the group consisting of copper, zinc, cadmium, nickel, silver, bronze and brass, comprising an aqueous solution of an inorganic salt of the metal to be electrodeposited and, as a brightener, an organic sulfonic acid compound having the general formula wherein R is selected from the group consisting of straightchain and cyclic organic radicals comprising at least two carbon atoms linked exclusively to atoms selected from the group consisting of oxygen, nitrogen and sulfur, each of said carbon atoms being linked to an SR --SO X group, R is a bivalent lower aliphatic radical, X is selected from the group consisting of hydrogen, alkali metal and ammonium, and n is an integer equal to the number of said carbon atoms in the radical R, said brightening agent being present in suflicient amount to effect the brightening action.

2. An electroplating bath according to claim 1, wherein R is a 1,3,5-triazine radical.

3. An electroplating bath according to claim 1, wherein R is a 1,3,4-thiodiazole radical.

4. An electroplating bath according to claim 1, wherein R is a N,N-methylene-di-isothiourea radical.

5. The process of producing bright and lustrous deposits of metal selected from the group consisting of copper, zinc, cadmium, nickel, silver, bronze and brass, which comprises electrodepositing said metal from a bath containing said metal in the form of an aqueous solution of an inorganic salt of the metal in the presence of a brightening agent having the general formula wherein R is selected from the group consisting of straight chain and cyclic organic radicals comprising at least two carbon atoms linked exclusively to atoms selected from the group consisting of oxygen, nitrogen and sulfur, each of said carbon atoms being linked to an SR SO X group, R is a bivalent lower aliphatic radical, X is selected from the group consisting of hydro- 7 gen, alkali metal and ammonium, and n is an integer equal 9. The electroplating bath v.of claim 1 wherein the to the number of said carbon atoms in the radical R, said quantity of brightener in said bath is between about 0.01 brightening agent being present in sufficient amount to to20 gin/liter. efiect the brightening action. 10. The process of claim 5 wherein the quantity of 6. The process according to claim 5, wherein R is a 5 brightener used is between about 0.01 to 20 gm./liter. 1,3,5-triazine radical.

7. The process according to claim 5, wherein R is a s mn Cited in the file of this Patent 1, h 1 radical- UNITED STATES PATENTS 8. The process according to claim 5, wherein R is a N,N-methylene-di-isothiourea radical. 10 2647866 Brown 1953 UNITED STATES PATENT OFFICE U CERTIFICATE OF CORRECTION Patent No 2,849,352 August 26, 1958 Alfred Kirstahler et al,

of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, lines 3 to 5 for that portion of the formula reading OH OH Example I, for that portion of the formula reading "NaO S=" read NaO S== column '4, 'linevl4, Example II, for that portion of the formula'reading "NaO SN" read Na0 s= n,

Signed and sealed this 30th day of December 1958., Attest:

KARL AXLINE ROBERT C. WATSON Attcsting Officer Commissioner of Patents

Claims (1)

1. AN ELECTROPLATING BATH FOR PRODUCING BRIGHT ELECTRODEPOSITS OF METALS SELECTED FROM THE GROUP CONSISTING OF COPPER, ZINC, CADMIUM, NICKEL, SILVER, BRONZE AND BRASS, COMPRISING AN AQUEOUS SOLUTION OF AN INORGANIC SALT OF THE METAL TO BE ELECTRODEPOSITED AND, AS A BRIGHTENER, AN ORGANIC SULFONIC ACID COMPOUND HAVING THE GENERAL FORMULA