EP1961840B1 - Copper-tin electrolyte and method for depositing bronze layers - Google Patents

Abstract

Non-toxic electrolyte for electroplating consumer goods and technical equipment with bronze contains copper, tin and optionally zinc, all as water-soluble salts, and one or more phosphonic acid derivatives as complex formers. It is free from cyanides, thiourea derivatives and thiol derivatives. An independent claim is included for a method for electroplating consumer goods and technical equipment with bronze in which they are immersed in an electrolyte as described.

Description

The invention relates to a copper-tin electrolyte which is free of toxic ingredients such as cyanides or thio compounds. Furthermore, the invention relates to a method for depositing decorative bronze layers on consumer goods and technical objects using the electrolyte according to the invention.

Commodities or articles of daily use, as defined in the Ordinance on Commodities, are refined for decorative reasons and to prevent corrosion with thin, oxidation-stable metal layers. These layers must be mechanically stable and should not show tarnish or signs of wear even after prolonged use. Since 2001, the sale of consumer goods coated with nickel-containing refining alloys is no longer permitted in Europe under EU Directive 94/27 / EC or only under strict conditions, as it is nickel and nickel-containing metal layers about contact allergens. In particular, bronze alloys have become established as a substitute for nickel-containing finishing layers, with which commodity-representing consumer goods in galvanic drum or frame coating processes can be inexpensively refined into allergen-free, handsome products.

For the production of bronze layers - in addition to conventional methods using cyanide-containing and thus highly toxic, alkaline baths - various galvanic methods are known, which can be assigned according to the composition of their electrolytes usually one of two observed in the prior art main groups: Process using organosulfonic acid based electrolytes or processes using diphosphoric acid based baths.

For example, this describes EP 1 111 097 A2 an electrolyte which contains, in addition to an organosulfonic acid and ions of tin and copper dispersants and brighteners, and optionally antioxidants. EP 1408 141 A1 describes a process for the electrodeposition of bronzes in which an acidic electrolyte is used which, in addition to tin and copper ions, contains an alkylsulfonic acid and an aromatic nonionic wetting agent. The DE 100 46 600 A1 describes a bath containing alkyl or alkanolsulfonic acid, which in addition to soluble tin and copper salts contains organic sulfur compounds, and a method using this bath.

A major disadvantage of such produced on the basis of organosulfonic electrolytes is their high corrosivity. For example, baths based on methanesulfonic acids often have pH values below one. The high degree of corrosivity of these baths limits their field of application with regard to the substrate materials to be refined and requires the use of particularly corrosion-resistant working materials for carrying out the process.

EP 1 146 148 A2 describes a cyanide-free copper-tin electrolyte based on diphosphoric acid, which contains a cationic surfactant in addition to the reaction product of an amine and an epihalohydrin in a molar ratio of 1: 1. WO 2004/005528 describes a cyanide-free diphosphoric acid copper-tin electrolyte containing an additive composed of an amine derivative, an epihalohydrin and a glycidyl ether compound.

Electrolytes based on diphosphoric acid generally have very limited long-term stability and must be renewed frequently.

From the electronics industry are also known processes for the production of solderable copper-tin layers, which are used as a replacement of tin-lead solders, known, in which usually a wider range of acidic base electrolytes can be used. So describes EP 1 001 054 A2 a tin-copper electrolyte which contains a water-soluble tin salt, a water-soluble copper salt, an inorganic or organic acid or one of its water-soluble salts, and one or more compounds from the group of the - usually toxic - thiourea or thiol derivatives. The bath according to the invention described therein may also contain one or more compounds selected from the group consisting of carboxylic acids, lactones, phosphoric acid condensates, phosphonic acid derivatives or water-soluble salts thereof or combinations thereof.

When producing bronze layers for the electronics industry, the solderability of the resulting layer and optionally its mechanical adhesive strength are the decisive properties of the layer to be produced. The appearance of the layers is generally less significant than their functionality for use in this area. For the production of bronze layers on consumer goods, however, the decorative effect of the resulting layer in addition to the long shelf life the layer with as unchanged as possible the essential target parameters.

It is therefore an object of the present invention to provide a long-term stable electrolyte, which is suitable for the deposition of mechanically stable and decorative copper-tin bronze layers on consumer goods and technical objects, and which is free of toxic ingredients. It is another object of the present invention to provide a method for applying decorative copper-tin bronze layers to consumer goods and technical articles using an electrolyte free of toxic ingredients.

This object is achieved by an electrolyte which, in addition to the metals to be deposited copper and tin or copper, tin and zinc, which are present in the form of water-soluble salts, contains one or more phosphonic acid derivatives as complexing agents. Toxic ingredients such as cyanides and thio compounds such as thiourea derivatives and thiol derivatives are not included in the electrolyte of the invention. In addition, a method is provided by means of which decorative bronze alloy layers can be applied to consumer goods and technical articles using the non-toxic electrolyte according to the invention.

"Non-toxic" in the sense of this document is understood to mean that in the so-called electrolyte according to the invention no substances are contained, which according to the regulations in force in Europe for handling dangerous goods and hazardous substances as "toxic" (T) or "very toxic "(T ⁺ ) are to be classified.

The metals are incorporated in the form of water-soluble salts, which are preferably selected from the group of sulfites, sulfates, phosphates, diphosphates, nitrites, nitrates, halides, hydroxides, oxide hydroxides and oxides, or combinations thereof. Which salts in which amount are introduced into the electrolyte, determines the color of the resulting decorative bronze layers and can be adjusted according to customer requirements. Preferably, the electrolyte according to the invention for applying decorative bronze layers to consumer goods and technical articles contains between 0.2 and 5 grams per liter of copper, between 0.5 and 20 grams per liter of tin and between 0 and 5 grams per liter of zinc, based in each case Volume of the electrolyte. Particularly preferred for the processing of consumer goods is the introduction of the metals to be deposited as sulfates, phosphates, diphosphates, or chlorides in the In such a way that the resulting ion concentration ranges from 0.3 to 3 grams of copper, 2 to 10 grams of tin and 0 to 3 grams of zinc, each per liter of electrolyte.

The application of decorative bronze layers on durable goods and technical items with the electrolyte according to the invention is carried out in a galvanic process. It is important that the metals to be deposited are kept permanently in solution during the process, regardless of whether the galvanic coating takes place in a continuous or in a discontinuous process.

To ensure this, the electrolyte according to the invention contains phosphonic acid derivatives as complexing agents.

Preference is given to using the compounds aminophosphonic acid AP, 1-aminomethylphosphonic acid AMP, amino-tris (methylenephosphonic acid) ATMP, 1-aminoethylphosphonic acid AEP, 1-aminopropylphosphonic acid APP, (1-acetylamino-2,2,2-trichloroethyl) -phosphonic acid, (1 Amino-1-phosphono-octyl) -phosphonic acid, (1-benzoylamino-2,2,2-trichloroethyl) -phosphonic acid, (1-benzoylamino-2,2-dichlorovinyl) -phosphonic acid, (4-chlorophenyl-hydroxymethyl) -phosphonic acid , Diethylenetriaminepenta (methylenephosphonic acid) DTPMP, ethylenediamine-tetra (methylenephosphonic acid) EDTMP, 1-hydroxyethane- (1,1-di-phosphonic acid) HEDP, hydroxyethylamino-di (methylenephosphonic acid) HEMPA, hexamethylenediamine-tetra (methylphosphonic acid) HDTMP, (( Hydroxymethyl-phosphonomethyl-amino) -methyl) -phosphonic acid, nitrilo-tris (methylenephosphonic acid) NTMP, 2,2,2-trichloro-1- (furan-2-carbonyl) -amino-ethylphosphonic acid, salts derived therefrom or condensates derived therefrom, or combinations thereof.

Particular preference is given to using one or more compounds selected from the group consisting of amino-tris (methylenephosphonic acid) ATMP, diethylenetriamine-penta (methylenephosphonic acid) DTPMP, ethylenediamine-tetra (methylenephosphonic acid) EDTMP, 1-hydroxyethane- (1,1-di-phosphonic acid ) HEDP, hydroxyethylamino-di (methylenephosphonic acid) HEMPA, hexamethylenediamine tetra (methylphosphonic acid) HDTMP, salts derived therefrom or condensates derived therefrom, or combinations thereof. Preference is given to using 50 to 200 grams of phosphonic acid derivatives in liters of electrolyte, more preferably 75 to 125 grams per liter of electrolyte.

The pH of the electrolyte according to the invention, which is greatly influenced by the type and amount of phosphonic acid derivatives used and an important predictor for the long-term stability of the electrolyte is set between 6 and 14, preferably between 8 and 12.

In addition to the metals to be deposited and the phosphonic acid derivatives used as complexing agents, the electrolyte may contain organic additives which perform functions as brighteners, wetting agents or stabilizers. The addition of brightener and wetting agent is preferred only for special requirements on the appearance of the decorative bronze layers to be deposited. With their help - in addition to the color of the bronze layers, which largely depends on the ratio of the metals to be deposited - the layer gloss can be adjusted in all gradations between semi-gloss and high gloss.

Preferably, the addition of one or more compounds is selected from the group of mono- and dicarboxylic acids, the alkanesulfonic acids and the aromatic nitro compounds. These compounds act as Elektrolytbadstabilisatoren. Particularly preferred is the use of oxalic acid, of alkanesulfonic acids or of nitrobenzotriazoles or of mixtures thereof.

The electrolyte according to the invention is characterized by the fact that it is free of hazardous substances classified as toxic (T) or very toxic (T ⁺ ). There are no cyanides, no thiourea derivatives and no thiol derivatives. In particular, the addition of said thio compounds adversely affects the coating result. Bronze plating that has been electrodeposited from thio-compounded baths has a mottled or dull-fogged appearance and is therefore unsuitable for the decorative coating of consumer goods.

The non-toxic electrolyte according to the invention is particularly suitable for the electroplating of decorative bronze layers on consumer goods and technical articles. It can be used in drum, rack, belt or continuous galvanic systems.

In a corresponding process for the electroplating of decorative bronze alloy layers, the consumer goods and technical articles to be coated (hereinafter referred to collectively as substrates) dip into the non-toxic electrolyte according to the invention and form the cathode. The electrolyte is preferably tempered in a range of 20 to 70 ° C. Preferably, a current density is set in the range 0.01 to 100 amperes per square decimeter [A / dm ² ] and which depends on the type of coating system. Thus, in drum coating processes, current densities between 0.05 and 0.50 A / dm ^{2 are} particularly preferred. In rack coating processes, preference is given to choosing current densities between 0.2 and 10 A / dm ² , particularly preferably 0.2 to 5 A / dm ² .

When using the non-toxic electrolyte according to the invention, various anodes can be used. Soluble or insoluble anodes are also suitable, as is the combination of soluble and insoluble anodes.

As soluble anodes, those made of a material selected from the group consisting of electrolytic copper, phosphorus-containing copper, tin, tin-copper alloy, zinc-copper alloy and zinc-tin-copper alloy are preferably used. Particularly preferred are combinations of different soluble anodes from these materials, as well as the combinations of soluble tin anodes with insoluble anodes.

Preferred insoluble anodes are those made of a material selected from the group consisting of platinized titanium, graphite, iridium-transition metal mixed oxide and special carbon material ("Diamond Like Carbon" DLC) or combinations of these anodes. Especially preferred are mixed oxide anodes of iridium-ruthenium mixed oxide, iridium-ruthenium-titanium mixed oxide or iridium-tantalum mixed oxide.

If insoluble anodes are used, this is a particularly preferred embodiment of the method if the substrates to be provided with decorative bronze layers, which constitute the cathode, are separated from the insoluble anode by an ion exchange membrane in such a way that a cathode space and form an anode space. In such a case, only the cathode compartment is filled with the non-toxic electrolyte according to the invention. In the anode compartment, there is preferably an aqueous solution which contains only one conductive salt. By such an arrangement, the anodic oxidation of tin (II) ions Sn ²⁺ to tin (IV) ions Sn ⁴⁺ , which would adversely affect the coating process, is prevented.

In membrane processes which are operated with insoluble anodes and the non-toxic electrolyte according to the invention, current densities in the range from 0.05 to 2 A / dm ² are preferably set. The temperature of the electrolyte is preferably carried out at 20 to 70 ° C. As ion exchange membranes, cationic or anionic Exchange membranes are used. Preferably, Nafion membranes having a thickness of 50 to 200 μm are used.

The examples described below and the comparative example are intended to explain the invention in more detail.

In all the experiments described, an insoluble platinum-titanium anode was used.

Example 1:

For drum deposition of yellow bronze layers, a non-toxic electrolyte according to the invention was used which contained 120 g / L of hydroxyethylamino-di (methylene phosphonic acid) HEMPA, 2 g / L copper in copper sulfate, 6 g / L tin in tin sulfate and 0.1 g / L low molecular weight polyethyleneimine in water. The pH of the electrolyte was 11.

During the entire deposition process, the electrolyte was heated at 60 ° C. At a set current density of 0.1 to 0.2 A / dm ² , in an apparatus for drum coatings, optically uniform bronze layers having the yellowish coloration typical for bronze were obtained.

Example 2:

To produce yellow bronze layers in an apparatus in which the substrates forming the cathode are mounted on a rack, a non-toxic electrolyte according to the invention was used, containing 100 g / L of ethylenediamine tetra (methylenephosphonic acid) EDTMP, 4 g / L of copper in copper diphosphate , 5 g / L of tin in tin diphosphate and 3 g / L of zinc in zinc diphosphate dissolved in water. The bath also contained 15 g / L of methanesulfonic acid as a stabilizer. The pH of the bath was 8.

At a set current density of 0.5 to 1 A / dm ² and a temperature of the electrolyte at 50 ° C was obtained optically flawless bronze layers with yellow color.

Example 3:

For the deposition of white bronze layers, an electrolyte was used which in aqueous solution contained 50 g / L ethylenediamine tetra (methylenephosphonic acid) EDTMP and 50 g / L 1-hydroxyethane- (1,1-di-phosphonic acid) HEDP. As metals to be deposited 0.5 g / L copper in copper sulfate, 4.0 g / L tin in tin sulfate and 2 g / L zinc in zinc sulfate. The non-toxic electrolyte according to the invention had a pH of 10. At a bath temperature of 50 ° C. and a current density of 0.1 to 0.2 A / dm ² , mechanically stable and considerable white bronze layers were obtained in drum and frame coating processes.

Example 4:

For drum deposition of white bronze, an electrolyte according to the invention was used which contains 100 g / L ethylenediamine tetra (methylenephosphonic acid) EDTMP, 0.5 g / L copper in copper diphosphate, 5 g / L tin in tin diphosphate, 2 g / L zinc in zinc diphosphate and 15 g / L of the stabilizing methanesulfonic acid in water. The pH of the electrolyte was 10. During the deposition process, a temperature of 50 ° C was carried out.

With a set current density of 0.05 to 0.2 A / dm ² layers were obtained with the white-metallic whitish-metallic gloss, which were optically uniform and showed good mechanical adhesion.

Example 5:

Also, proper white bronze layers were obtained when an electrolyte containing 90 g / L of 1-hydroxyethane- (1,1-di-phosphonic acid) HEDP was used in a rack coating process. The concentrations of the metals to be deposited were 0.5 g / L copper in copper chloride, 5 g / L tin in tin chloride and 1 g / L zinc in zinc chloride. The stabilizer contained 0.05 g / L of the sodium salt of propargyl sulfonic acid. The pH of the bath was 9, the bath temperature during the entire coating process 55 ° C and the set current density 0.2 A / dm ^second

Example 6:

With an electrolyte according to the invention which, in addition to 0.5 g / L of copper in copper chloride, 5 g / L of tin in tin chloride and 1.5 g / L of vaniline, contained the sodium salt of diethylenetriaminepenta (methylenephosphonic acid) DTPMP in a concentration of 80 g / L, had a pH of 8 and was tempered at 50 ° C, could also be at a set current density of 0.1 to 0.2 A / dm ² produce optically flawless white bronze layers in rack and drum coating process.

Example 7:

With an electrolyte according to the invention, in addition to 0.5 g / L copper in copper diphosphate, 5 g / L tin in tin diphosphate, 2 g / L zinc in zinc diphosphate and 20 g / L methanesulfonic acid ethylenediaminetetra (methylenephosphonic) EDTMP in a concentration of 80 g / L and 10 g / L of amino-tris (methylenephosphonic acid) ATMP contained, had a pH of 10 and was heated at 50 ° C, allowed at a set current density of 0.1 A / dm ² optically flawless bronze layers produce an anthracite gray to black color, which had good mechanical properties.

All of the electrolytes described in the examples are ideally suited for the application of decorative bronze layers to consumer goods and technical articles while maintaining the specified process parameters.

Comparative Example:

1. a.) Thioglycolsäure im ersten vergleichsweise getesteten Bad;
2. b.) Thiomilchsäure im zweiten vergleichsweise getesteten Bad;
3. c.) Thioharnstoff im dritten vergleichsweise getesteten Bad.

While maintaining the experimental setup shown in Example 2, three further coating experiments were carried out using three different electrolytes. All electrolytes were based on the formula of the invention chosen in Example 2 and contained 100 g / L ethylenediamine tetra (methylenephosphonic acid) EDTMP, 4 g / L copper in copper diphosphate, 5 g / L tin in tin diphosphate and 3 g / L zinc in zinc diphosphate in water , In addition to 15 g / L of the stabilizing methanesulfonic acid, the baths additionally contained small amounts of a thio compound, namely:

1. a.) Thioglycolic acid in the first comparatively tested bath;
2. b.) thiolactic acid in the second comparatively tested bath;
3. c.) Thiourea in the third comparatively tested bath.

The selected process parameters corresponded to the conditions set in Example 2.

With all three comparison baths, a poor coating result was obtained. The resulting bronze layers were mechanically stable, but visually unsightly, so stained, dull and covered with veils.

None of these baths are suitable for applying decorative bronze layers to consumer goods and technical items.

Claims (13)

1. Non-toxic electrolyte for the deposition of decorative copper-tin bronze alloy layers on consumer goods and industrial articles which contains the metals to be deposited in the form of water-soluble salts, characterized in that the electrolyte contains one or more phosphonic acid derivatives as complexing agents and is free of cyanides, thiourea derivatives and thiol derivatives and it contains copper and tin or copper, tin and zinc as metals to be deposited.
2. Electrolyte according to Claim 1, characterized in that it contains one or more compounds selected from the group consisting of aminophosphonic acid AP, 1-aminomethylphosphonic acid AMP, aminotris-(methylenephosphonic acid) ATMP, 1-aminoethyl-phosphonic acid AEP, 1-aminopropylphosphonic acid APP, (1-acetylamino-2,2,2-trichloroethyl)-phosphonic acid, (1-amino-1-phosphonooctyl)-phosphonic acid, (1-benzoylamino-2,2,2-trichloroethyl)phosphonic acid, (1-benzoylamino-2,2-dichlorovinyl)phosphonic acid, (4-chlorophenyl-hydroxymethyl)phosphonic acid, diethylenetriaminepenta(methylenephosphonic acid) DTPMP, ethylenediaminetetra(methylenephosphonic acid) EDTMP, 1-hydroxyethane(1,1-diphosphonic acid) HEDP, hydroxyethylaminodi(methylenephosphonic acid) HEMPA, hexamethylenediaminetetra(methylphosphonic acid) HDTMP, ((hydroxymethylphosphonomethylamino)methyl)phosphonic acid, nitrilotris-(methylenephosphonic acid) NTMP, 2,2,2-trichloro-1-(furan-2-carbonyl)aminoethylphosphonic acid, salts derived therefrom and condensates derived therefrom and combinations thereof as phosphonic acid derivatives.
3. Electrolyte according to Claim 1, characterized in that the pH of the electrolyte is in the range from 6 to 14.
4. Electrolyte according to Claim 1, characterized in that one or more stabilizing compounds selected from the group consisting of monocarboxylic and dicarboxylic acids, alkanesulphonic acids and aromatic nitro compounds are present.
5. Electrolyte according to any of Claims 1 to 4, characterized in that the water-soluble salts of the metals to be deposited are selected from the group consisting of sulphites, sulphates, phosphates, diphosphates, nitrites, nitrates, halides, hydroxides, oxide-hydroxides, oxides and combinations thereof.
6. Electrolyte according to Claim 5, characterized in that the metals to be deposited are present in ionically dissolved form and the ionic concentration of copper is in the range from 0.2 to 5 gram per litre of electrolyte, the ionic concentration of tin is in the range from 0.5 to 20 gram per litre of electrolyte and the ionic concentration of zinc is in the range from 0 to 5 gram per litre of electrolyte.
7. Process for the electrolytic application of decorative copper-tin bronze alloy layers to consumer goods and industrial articles, in which the substrates to be coated are dipped into an electrolyte containing the metals to be deposited in the form of water-soluble salts, characterized in that a non-toxic electrolyte which contains one or more phosphonic acid derivatives as complexing agents and is free of cyanides, thiourea derivatives and thiol derivatives is used.
8. Process according to Claim 7, characterized in that the electrolyte is maintained at a temperature in the range from 20 to 70°C.
9. Process according to Claim 8, characterized in that a current density in the range from 0.01 to 100 ampere per square decimetre is set.
10. Process according to Claim 9, characterized in that soluble anodes made of a material selected from the group consisting of electrolytic copper, phosphorus-containing copper, tin, tin-copper alloys, zinc-copper alloys and zinc-tin-copper alloys or combinations of these anodes are used.
11. Process according to Claim 9, characterized in that insoluble anodes made of a material selected from the group consisting of platinized titanium, graphite, iridium-transition metal mixed oxides and special carbon material ("diamond-like carbon", DLC) or combinations of these anodes are used.
12. Process according to Claim 10, characterized in that insoluble anodes made of a material selected from the group consisting of platinized titanium, graphite, iridium-transition metal mixed oxides and special carbon material ("diamond-like carbon", DLC) or combinations of these anodes are used.
13. Process according to Claim 11 or 12, characterized in that cathode and insoluble anode are separated from one another by an ion-exchange membrane to form a cathode space and an anode space and only the cathode space contains the non-toxic electrolyte so that the anodic oxidation of Sn²⁺ to Sn⁴⁺ is prevented.