DE924489C - Bath for the galvanic deposition of metals - Google Patents

Description

The invention relates to a bath for depositing gloss of metals such as zinc, cadmium, tin, silver, nickel and especially copper and Copper alloys that contain a urea condensation product as a brightening additive.

For the purpose of the deposition of metals in shiny form by electroplating baths of various types have already become known which contain additives to achieve a gloss. A large number of inorganic or organic substances can be used as such additives, which, however, are often only effective with certain metals or have certain disadvantages, through their use, especially in continuous operation or when working at elevated levels Temperatures, is excluded or leads to difficulties.

According to the invention, the baths for the luster deposition of metals such as copper, zinc, Cadmium, tin, silver, soluble condensation products added as they are in the implementation of Acrolein or its a-substitution products, optionally in a mixture with other aldehydes, on the one hand and urea and substituted ureas on the other. For the urea component nitrogen or carbon substitution compounds of urea come from the general formula

NH ₂

into consideration, wherein R _{1 is} oxygen, sulfur or imine, R ₂ and / or R _{3 is} hydrogen, alkyl, alkenyl,

Aryl, aralkyl, or acyls, more saturated or unsaturated Acids mean. Condensation products particularly suitable for the purposes of the invention of this type are described in the German patent specifications 554552, 745422, 748842 and in the French patents 879 957, 884091 and 895 231. Such products in their manufacture the condensation was carried out in the presence of compounds containing hydroxyl groups, have proven themselves excellently here.

Particularly good results with regard to the surface formation of the metal deposits are achieved with the brightening additive according to the invention when the deposition from alkaline, before mainly from cyanide baths. In contrast to the majority of the known brighteners however, the urea condensation products can also be used in acidic baths. The amount of the addition of the condensation products described should in the case of the invention Baths are at least 0.5 g / l and can also be used within relatively wide limits vary. In general, smaller quantities are required for acidic baths than for alkaline, in which it is advantageous to work with additives between 3.5 to 35 g / l bath liquid. very good gloss effects can be achieved if the amount of condensation products is between 6 and 15 g / l, e.g. B. at 10 g / l. For alkaline For baths with less than 3.5 g / l addition of condensation products, it may be advisable to add one more other known brighteners, such as. B. potassium rhodanide to use.

In addition to urea condensation products, the baths according to the invention can also contain polyglycol esters, preferably those of fatty acids having 4 to 15 carbon atoms, expediently in amounts between 2 and 20 g / l. The amount of the additive is advantageously measured at about 5 to 10 g / l. The PoIyglycolester used must be resistant to soluble in water and at temperatures up to 70 ⁰ in alkalis to p _H values of from about. 13

Also an appropriately small proportion of alkali metal oxanthates, e.g. B. an addition of 0.01 to 1 g, preferably one of 0.05 to 0.2 g / l bath liquid, has proven to be beneficial for working the bath, since the gloss range can be broadened if necessary.
For the selection of the working conditions in the baths according to the invention, it must be taken into account that the gloss range widens with the amount of gloss added and the maximum gloss in the current density range between 1 and 10 Amp./dm ² shifts with increasing amounts to higher current densities. Although the selection of the most favorable current density also depends on the nature of the metal to be deposited, on the bath temperature and the amount of brightener, it is advisable to use current densities of ι to 2 Amp./dm ² and for alkaline ones of 4 to 5 amp./dm ² must be observed. Especially for the latter baths, it is appropriate in some cases to choose the operating temperature at 50 ⁰ and above, as a barrier anode film can form at lower temperatures approaches. The gloss formation can be promoted by a bath movement, for which a simple quiet movement of the cathode is generally sufficient.

While baths with organic brighteners do not normally switch to the switching process or do not respond appreciably, it has surprisingly been shown that you are with the invention Baths can use the periodic polarity reversal with success especially when heavy precipitation is to be generated. For example, the deposition period can be set to about 25 seconds and the plating time measured at 5 seconds.

The composition of the baths according to the invention is based on the examples below further explained.

To prepare the urea-acrolein condensation product used as a brightener, 60 parts by weight of urea are mixed with 60 parts of water, 140 parts of hexamethylenetetramine and 11 parts of acrolein, the mixture is gradually brought to 60 ° and held there for about 20 minutes. The mixture was then heated ^{to 150 ° C. for 1} hour with 150 parts of triethylene glycol. After cooling, an orange colored resin solution which was readily soluble in water was obtained.

95 Example 1

Cyanide copper bath

Composition: Cu (as K ₃ Cu [CN] ₄ ) = 6og / I, KCN = 15 g / l, KOH = 30 g / l, urea condensation product = 10.5 g / l, polyglycol ester from 20 mol ethylene oxide and fatty acids with 4 to 9 carbon atoms = 6 g / l.

At a bath temperature of 70 ⁰ and a current density 4-5 Amp./dm ² is perfectly shiny copper deposits, which can be nickel without further pretreatment in one of the customary nickel baths obtained.

Similar, if not quite as good, results are obtained if you take the added amount of the condensation product is reduced to about 1 g / l and the bath as a further brightener 15 g / l Adding potassium rhodanide;

115 Example 2

Cyanide zinc bath

Composition: Zn (CN) ₂ = 60 g / l, NaCN = 40 g / l, NaOH = 74 g / l, urea condensation product = 8 g / l, polyglycol ester (as in example 1) = 5 g / l

At a temperature of 30 to 40 ⁰ and a current density of 2 amps / dm ^{2, the} bath produces smooth, shiny deposits.

Even with a normal, commercially available zinc bath with the abovementioned additions of condensation product and polyglycol ester, the same gloss effect was achieved if the current density was increased to 3 to 4 amps / dm ² .

Example 3
Acid nickel bath

NiCl ₁ urea condensate

= 120 g / l, XN ₁ V ^ l ₂

Composition: Ni SO ₄
= 30 g / l, boric acid = 30 g / l,
cation product = 1 g / l.

The _pH value of the bath solution is 3. At a temperature of 40 ⁰ and current densities between ι and 2 Amp./dm ² are obtained bright deposits.

Example 4
Acid copper bath

Composition: CuSO ₄ = 125 g / l, H ₂ SO ₄ = 30 g / lj urea condensation product = 7 g / l.

The bath is operated with a moving cathode at about 20 ° and a current density of 7 Amp./dm ² and produces high-gloss, hard deposits.

Claims (8)

PATENT CLAIMS: i. Galvanic, especially cyanide bath for electrolytic gloss deposition of metals such as nickel, zinc, cadmium, tin, silver and their alloys, in particular Copper and copper alloys, characterized by a content of a preferably in The presence of compounds containing hydroxyl groups generated condensation product Acrolein and / or its α-substitution compounds or their mixtures with others Aldehydes on the one hand and urea and / or its N- and / or C-substitution compounds on the other hand from the general. formula C ^ - R ₁ R ₃
NH ₂ where R _{1 is} oxygen, sulfur or imine, R ₂ and / or R _{3 is} hydrogen, alkyl, alkenyl, aryl, aralkyl or acyls of saturated or unsaturated acids. 2. Galvanic bath according to claim 1, characterized by a content of at least 0.5 g urea acrolein condensation products per 11 bath liquid. 3. Bath according to claims 1 and 2, characterized in that that it contains the urea-acrolein condensation product in amounts between 3.5 and 35 g / l, preferably from 6 to 15 g / l. 4. Bath according to Claims 1 and 2, characterized by an additional content of polyglycol ester with fatty acids of one chain length to C ₁ ; expediently in amounts of such of in from C ₄ to C _{15 is} appropriate
2 to 20 g / l, preferably
5 to 10 g / l. 5. Bath according to claims 1 to 4, characterized by a suitably low content of Alkalixanthate from e.g. B. 0.01 to 1 g / l, preferably 0.05 to 0.2 g / l. 6. Bath according to claims 1 to 5, characterized in that that there is still one or more brighteners known per se, e.g. B. Potassium Rhodanide, contains. 7. Bath according to claims 1 to 6, characterized in that that the metals are deposited at temperatures of at least 50 ° will. 8. Bath according to claims 1 to 7, characterized in that that the deposition of the metals is carried out with periodic polarity reversal. 2.55