US 3432509 A
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United States Patent 574,843 U.S. Cl. 260-295 7 Claims Int. Cl. C0711 31/34, 31/44; C23b /08 ABSTRACT OF THE DISCLOSURE In accordance with certain of its aspects, this invention relates to novel pyridinium compounds having a cation of the structure iLoHz-oEcH wherein A and B may each be selected from the group consisting of hydrogen, carboxamido-CoNH- acetyl- COCH and carbomethoxy-COOCH and at least one of A and B is other than hydrogen, and to the use of pyridinium compounds as primary brighteners in the electrodeposition of nickel.
This application is a divisional application of application Ser. No. 347,046 filed Feb. 24, 1964 which has matured into U.S. Patent 3,296,103 granted J an. 3, 1967.
This invention relates to electroplating nickel and more particularly to the electrodeposition of bright nickel.
Nickel electrodeposits as plated from Watts, high chloride, fluoborate, etc. type baths are not bright when plated in thicknesses substantially greater than those of very thin strike" or flash coatings. Such deposits do not increase in luster with increasing thickness but rather decrease in brightness until dull matte deposits are obtained. To obtain thick bright deposits from such baths, it is necessary to add certain additives, commonly of organic nature, which assist in producing highly lustrous deposits with good rate of brightening. It is a common characteristic of such so-called bright nickel plating baths that the deposits tend to increase in luster with increasing thickness. A particular advantage of these bright nickel baths is that bright deposits can be obtained on basis metals which have not been polished or which do not have a high starting luster, within reasonable specification thicknesses of nickel. Other concomitant advantages such as leveling or the ability of the deposits to fill in pores, scratches, or other superficial defects of the basis metal, may also be obtained.
Addition agents useful as brighteners in nickel plating baths are generally divided into two classes on the basis of their predominant function. Primary brighteners are materials used in very low or relatively low concentration, typically 0.002-0.2 g./l., which by themselves may or may not produce visible brightening action. Those primary brighteners which may exhibit some brightening eiiects when used alone generally also produce deleterious side effects such as reduced cathode efficiency, poor deposit color, deposit brittleness and exfoliation, very narrow bright plate range, or failure to plate at all on low current density areas. Secondary brighteners are materials which are ordinarily used in combination with primary brighteners but in appreciably higher concentration than that of the primary brighteners, typically 1 g./l. to 30 g./l. These materials, by themselves, may produce some brightening or grain-refining eifects, but the deposits are not usually mirror bright and the rate of brightening is usually inadequate.
Ideally, when primary and secondary brighteners of properly chosen and compatible nature are combined it is possible to obtain, over a wide current density range, ductile, leveled deposits which exhibit a good rate of brightening. The rate of brightening and leveling may vary in degree depending on the particular cooperating additives chosen and their actual and relative concentrations. A high degree of rate of brightening and leveling is generally desirable, particularly where maximum luster is desired with minimum nickel thicknesses. The concentrations of the secondary brighteners may usually vary within fairly wide limits. The concentrations of the primary brighteners must usually be maintained within fairly narrow limits in order to maintain desirable properties including good ductility, adequate coverage over low current density areas, etc. Any bright nickel system which can be rendered more tolerant to fluctuations in primary brightener concentrations will have obvious advantages, particularly since the low concentration of primary brighteners and the intrinsic chemical nature of some make strict control by chemical analysis difiicult. A primary brightener which can be used over a wide range of concentration is of great value in bright nickel plating.
It is an object of this invention to provide improved nickel plate by use of a new class of superior primary brighteners. It is a further object of this invention to provide an efiicient process for electrodepositing bright and smooth nickel deposits. Another object of this invention is to provide bath compositions for nickel plating from which bright nickel electrodeposits are obtained. Other objects of this invention may be apparent to those skilled in the art on inspection of the following description.
In accordance with certain of its aspects, the process of this invention comprises electrodepositing nickel from an aqueous nickel electroplating bath containing a secondary brightener and, as a primary brightener, a compound having a cation of the structure ILOHZ-CECH wherein A and B may each be selected from the group consisting of hydrogen, carboxamido-CONH acetyl- COCH and carbomethoxy-COOCH and at least one of A and B is other than hydrogen.
Typical compounds of this class which may be effective as primary brighteners are the following:
TABLE I (A) 3-carboxamido N-propargyl pyridinium bromide (B) 3-acetyl N-propargyl pyridinium bromide (C) 3-carbomethoxy N-propargyl pyridinium bromide (D) 4-carboxamido N-propargyl pyridinium bromide (E) 4-acetyl N-propargyl pyridinium bromide (F) 4-carbomethoxy Npropargyl pyridinium bromide The novel class of primary brighteners of this invention when used in combination with (a) suitable secondary brighteners or (b) secondary and secondary auxiliary brighteners, may give brilliant, nickel deposits which have excellent ductility, good low current density coverage and luster, good rate of brightening, and good leveling characteristics. It is a particular feature of this invention that the preferred novel primary brighteners may be used over a wide range of concentation with attainment of good low current density coverage and ductility of the deposits.
Another outstanding advantage is that these novel primary brighteners can withstand long electrolysis without build-up in the nickel plating bath of harmful decomposition products. Prior art nickel plating techniques may include the use of a number of acetylenically quaternized nitrogen heterocyclic compounds as primary brighteners; but they either produce inadequately lustrous deposits or are difficult to synthesize in high purity and yield; they have limited compatibility with the more commonly used additives. The compounds of this invention, including the 3- and 4-substituted propargyl pyridinium quaternaries, do not have these defects and in addition exhibit low rates of consumption. The 3- and 4-substituent groups of this invention are specifically chosen. Other groups in these positions either may be the quaternaries difficult or impossible to synthesize or result in compounds ineffective as primary brighteners.
The primary brighteners of this invention may be used in concentrations of 0.005 g./l. to 0.10 g./ 1., the particular concentration chosen depending on the particular t pes and concentration of secondary and secondary auxiliary brighteners used, and also on such factors as the concentrations of nickel sulfate, nickel chloride, and boric acid; operating conditions with respect to temperature and degree of agitation; degree of luster, rate of brightening and leveling desired; and the finish of the basis metal. It is preferred to use between 0.01 g./l. and 0.05 g./l.
Secondary brighteners (typically present in amount of 1 g./l. to 75 g./l., and preferably 1 g./l. to 20 g./l.) which are useful in combination with the primary brighteners, are generally aromatic sulfonates, sulfonamides or sulfimides which may include such substituted aromatic compounds as 1,3,6-naphthalene trisulfonate, sodium or potassium salts of saccharin, sodium or potassium salts of orthosulfo-benzaldehyde, benzene sulfonamide, benzene monosulfonate, etc. For use in high chloride type nickel plating baths, a preferred secondary brightener may be a sodium or potassium salt of sulfonated dibenzothiophene dioxide, prepared by sulfonating diphenyl with fuming sulfuric acid (20% oleum) for about 2 hours, isolating the reaction product, and neutralizing. The predominant reaction product is believed to be the compound containing three sulfonic acid groups, together with some monoand disubstituted components. The secondary brighteners are generally characterized by having at least one sulfone or sulfonic acid group attached to a nuclear carbon of a homocyclic aromatic ring.
Auxiliary secondary brighteners such as sodium-2- propene-l-sulfonate; sodium-3-ch1oro-2-butene-1 sulfonate; mixed isomer of sodium-Z-butene-2-hydroxy-l-sulfomate and sodium-2-butene-1-hydroxy-2-sulfonate, prepared by reacting butadiene monoxide with sodium sulfite; or phenyl propiolamide may be used in conjunction with the secondary brightener or brighteners.
Conventional baths and processes for electroplating bright nickel are described in Principles of Electroplating and Electroforming, Blum and Hogaboom, pages 362-381, revised third edition, 1949, McGraw-Hill Book Co., Inc., New York; and in Modern Electroplating, edited by A. G. Gray, The Electrochemical Society, 1953, pages 299-355. The control and operating conditions, including the concentration of the bath ingredients, pH, temperature, cathode current density, etc., of these conventional baths are generally applicable to the present invention. Practically all baths for electroplating bright nickel contain nickel sulfate; a chloride, usually nickel chloride; a buffering agent, usually boric acid; and a wetting agent, e.g. sodium lauryl sulfate, sodium lauryl ether sulfate, or sodium 7-ethyl-2-methyl-4-undecanol sulfate. Such baths include the Well-known Watts bath and the high chloride bath. Other baths may contain, as the source of the nickel, a combination of nickel fluoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride. Typical Watts-type baths and high chloride baths are noted in Tables II and III.
TABLE II.WATTS-TYPE BATHS Nickel sulfate 200 g./l. to 400 g./l. Nickel chloride 30 -g./l. to 75 g./l. Boric acid 30 g./l. to 50 g./l. Temperature 38 C. to 65 C. Agitation Mechanical and/or air or solution pumping, etc. pH 2.5 to 4.5 electrometric. TABLE III-HIGH CHLORIDE BATHS Nickel chloride g./l. to 300 g./l. Nickel sulfate 40 g./l. to 150 g./l. Boric acid 30 g./l. to 50 g./l. Temperature 38 C. to 65 C. Agitation Mechanical and/or air or solution pumping, etc. pH 2.5 to 4.5 electrometric.
Best plating results are usually achieved in the electrodeposition process when there is used a method of preventing the thin film immediately adjacent to the cathode from becoming depleted in cation content. This is desirably accomplished by agitation, such as by air agitation, solution pumping, moving cathode rod, etc.
For the purpose of giving those skilled in the art a better understanding of the invention, illustrative examples are given. In each of the examples, an aqueous acidic nickel-containing bath was made up with the specified components. Electrodeposition of nickel was carried out by passing electric current through an electric circuit comprising a nickel anode an a sheet metal cathode, both immersed in the bath. The baths were agitated, usually by a moving cathode. Bright electrodeposits were obtained in all the tests included herein as examples.
In examples 1 through 14 inclusive, the following standard bath was used as a base solution:
G./l. Nickel sulfate 300 Nickel chloride 60 Boric acid 45 Sodium lauryl sulfate 0.25
The primary brighteners are identified from Table I, supra. The secondary brighteners which are used in the following examples as noted in Table IV infra, include:
TABLE IV.SECONDARY BRIGHTENERS The auxiliary secondary brighteners which are used in the following examples as noted in Table V infra include:
TABLE V.-AUXILIARY SECONDARY BRIGHTENERS (K) sodium-3-chloro-2-butene-l-sulfonate (L) sodium allyl sulfonate In the following examples a.s.d. signifies amperes per square decimeter.
TABLE VI Example No. Additive Amount, g./l. CD a.s.d. Temp, 0.
G 2. 0 K 3. 0 3 C 0.020 4 60 G 2. 0 K 3.0 4 D 0. 030 4 60 G 4. 0 K 4.0 5 E 0.020 4 60 G 2. 0 K 3. 0 6 F 0. 020 5 50 G 2. 0 K 3. 0 7 A 0.030 5 60 H 4. 0 K 4. 0 8 B 0. 030 4 60 H 4. 0 K 3. 0 9 B 0. 030 6 55 H 2. 0 K 4. 0 10 E 0.020 4 60 G 4. 0 L 2. 0 11 E 0. 030 5 60 I 2. 0 L 2.0 12 A 0.020 4 50 J 4. 0 K 3. 0 13 E 0.020 5 60 G 2. 0 K 3. 0 14 A 0. 020 4 55 In Examples 15-18 inclusive, the following standard The foregoing examples illustrate specific baths and processes. It is understood that the compositions and conditions may be varied. Although the potassium and sodium salts were most often used and are preferred, they may be partially or completely replaced by such other salts as nickel, magnesium, etc. salts.
The nickel electrodeposits obtained from baths utilizing the novel brightener combination are advantageous in that mirror-bright lustrous electrodeposits having a high degree of ductility are obtained over a wide range of cathode current densities. The bright nickel electrodeposits are preferably plated on a copper or copper alloy basis metal. However, they may be electrodeposited directly on such metals as iron, steel, etc.
The novel primary brighteners of this invention may be prepared by the following reaction:
Typical reactants which may be employed in the process of this invention may include:
3-carboxamido pyridine (nicotinamide) 3-carbomethoxy pyridine (methyl nicotiuate) 3-acetyl pyridine Typical reactants which may be employed in the process of this invention may include:
4-carboxamido pyridine (isonicotinamide) 4-carbomethoxy pyridine (methyl isonicotinate) 4-acetyl pyridine Typical reactants HCEC--CH2X which may be employed include those wherein X may be halogen. Most preferred because of ease of reaction and availability may be propargyl bromide, HCEC-CHzBl'.
It will be apparent to those skilled in the art that inertly substituted reactants may be employed.
The reaction of the heterocyclic compound and the acetylenic halide may typically be effected under mild conditions, preferably in the presence of solvent. The reaction may occur readily in high yield typically at room temperature with slight warming usually occurring at the beginning of the reaction. The product generally may be a well-defined crystalline solid which may be recovered from the reaction system as by filtration followed by washing with appropriate solvent such as acetone. Recrystallization is generally unnecessary and the product may be easily air-dried.
The reaction may be carried out in the presence of inert solvents including preferably acetone, dimethylformamide, or mixtures thereof.
Carrying out the reaction may include dissolving one mole of the heterocyclic compound in an excess of solvent sufficient to dissolve the compound. Typically the solvent may be present in amount of 3-4 times the weight of the compound. To this mixture there may be added at least one mole and preferably 1-1.5 moles of acetylenic halide, preferably propargyl bromide. The mixture may be allowed to stand at room temperature for two hours to several days depending on the particular product being prepared.
Conversion of the novel compounds to other novel compounds in practice of this invention may be effected by the reaction thereof with e.g. soluble silver salts of desired anions such as acetate, sulfate, perchlorate, methosulfate, etc. Typically this reaction may be elfected in aqueous medium by mixing equivalent amounts of the reactants and filtering 011 the insoluble silver halide, e.g.
AgOOOCHa them-c5011 CONH;
occur Preparation of the novel compounds of this invention may be further illustrated by the following illustrative specific Examples 19-21:
Example 19.-Synthesis of 3-carboxamido N-propargyl pyridinium bromide 35 g. nicotinamide, 100 ml. dimethylformamide, and 25 ml. propargyl bromide were allowed to stand at room temperature for 68 hours. The crystalline product was filtered 01f, washed with acetone and air-dried. Yield 68 g. (94% )M.P. 187190 C. (by melting point as determined in the Fisher-Johns apparatus).
Example ZO-Synthesis of 3-carbomethoxy N-propargyl pyridinium bromide g. of methylnicotinate, 25 ml. dimethylformamide, and ml. propargyl bromide were allowed to stand at room temperature for 3 hours. The crystalline product was filtered off, washed with acetone and air-dried. Yield 15.55 g. (83%)-M.P. 135-136 C. (Fisher-Johns).
Example 21-Synthesis of 4-acetyl N-propargyl pyridinium bromide 10.8 g. 4-acetylpyridine, 25 ml. dimethylformamide, and 10 ml. propargyl bromide were allowed to stand at room temperature for 25.5 hours. To the reaction mixture m1. acetone were added and the crystalline product was filtered oif, washed with acetone and dried in a desiccator. Yield 18.1 g. (85%)-M.P. (darkens C. melts with decomposition about 280 C.) (Fisher-Johns).
Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.
1. A compound of the formula References Cited UNITED STATES PATENTS 9/1962 Heilling 204-49 FOREIGN PATENTS 1,066,068 5/1961 Germany.
HENRY R. JILES, Primary Examiner.
40 ALAN L. ROTMAN, Assistant Examiner.
US. Cl. X.R.