HK1137785B - Copper-tin electrolyte and method for depositing bronze layers - Google Patents

Description

Copper-tin electrolyte and method for depositing bronze layers

Technical Field

The invention relates to copper-tin electrolytes which are free of toxic components such as cyanides or sulfur compounds (Thiovertandung). The invention also relates to a method for depositing decorative bronze layers on consumer goods and industrial goods using the electrolyte according to the invention.

Background

The articles of daily use or daily use articles, such as those defined in the daily use article specification, are finished (veredelt) with a thin, oxidation-stable metal layer for decorative reasons and to prevent corrosion. These layers must be mechanically stable and should not exhibit the phenomenon of tempering or abrasion in the case of longer-term use. Since 2001, the sale of commodities coated with nickel-containing refined alloys was no longer permitted in europe under eu directive 94/27/EC or was only possible under severe conditions, since nickel and nickel-containing metal layers are involved in contact allergens. It has now been established, inter alia, that bronze alloys are used as a substitute for nickel-containing refined layers, with which such articles of everyday use, which represent mass products, can be inexpensively refined in the electroplating wheel or rack plating process to form allergen-free, aesthetically pleasing articles.

For the production of bronze layers, in addition to the conventional methods using cyanide-containing and thus highly toxic alkaline plating baths, different electroplating methods are known which, depending on their composition of the electrolyte, can be largely classified as belonging to one of two main classes of the prior art: a method using an organic sulfonic acid-based electrolyte or a method using a pyrophosphate-based plating bath.

For example, EP 1111097a2 describes an electrolyte which, in addition to organic sulfonic acids and tin and copper ions, also contains dispersants and brighteners and optionally antioxidants. EP 1408141a1 describes a method for the galvanic deposition 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. DE 10046600a1 describes a plating bath containing alkyl or alkanol sulfonic acids which, in addition to soluble tin and copper salts, contain organic sulphur compounds, and a method for using such a plating bath.

A serious disadvantage of the above-mentioned electrolytes prepared on the basis of organic sulfonic acids is their high corrosiveness. For example, a plating bath based on methanesulfonic acid typically has a pH of less than 1. The high corrosiveness of these baths limits their range of application, allowing for substrate materials to be refined, and requires the use of particularly corrosion-resistant working tools in order to carry out the process.

EP 1146148A2 describes cyanide-free copper-tin pyrophosphate-based electrolytes which, in addition to a 1: 1 molar ratio of the reaction product of an amine and an epihalohydrin, contain cationic surfactants. WO 2004/005528 describes cyanide-free pyrophosphate-copper-tin electrolytes which contain additives composed of amine derivatives, epihalohydrins and glycidyl ether compounds.

Electrolyte based on pyrophosphoric acid generally has a very limited long-term stability and must be renewed frequently.

Methods for producing solderable copper-tin layers as a substitute for tin-lead solder are also known from the electronics industry, wherein a large selection of acidic supporting electrolytes can be used. For example, EP 1001054a2 describes a tin-copper electrolyte comprising a water-soluble tin salt, a water-soluble copper salt, one of an inorganic or organic acid or a water-soluble salt thereof, and one or more compounds selected from the group consisting of the generally toxic thiourea or thiol derivatives. The plating bath according to the invention described there may also comprise one or more compounds selected from carboxylic acids, lactones, phosphoric acid-condensates, phosphonic acid derivatives or water-soluble salts thereof or combinations thereof.

In the case of the production of bronze layers for the electronics industry, the solderability of the resulting layer and optionally its mechanical adhesion strength are important properties of the layer to be produced. The appearance of the layer is generally less meaningful than its functionality for applications in the field. In contrast, for the production of bronze layers on consumer goods, the decorative effect of the resulting layer is an important target parameter in addition to the long-term durability of the layer, with as little change in appearance as possible.

Disclosure of Invention

It is therefore the object of the present invention to provide a long-term stable electrolyte which is suitable for depositing mechanically stable decorative bronze layers on consumer and industrial goods and which is free from toxic constituents. It is also an object of the present invention to provide a method for applying decorative bronze layers to everyday and industrial goods using an electrolyte which is free from toxic components.

These objects are achieved by an electrolyte which, in addition to the metal to be deposited in the form of a water-soluble salt, also contains one or more phosphonic acid derivatives as complexing agents. Toxic components, such as cyanides and sulfur compounds, such as thiourea derivatives and thiol derivatives, are not included in the electrolyte according to the present invention. A method is also provided by which decorative bronze alloy layers can be applied to everyday and industrial goods using the non-toxic electrolyte according to the invention.

"non-toxic" is understood here to mean that the electrolyte according to the invention thus identified is free of any substances classified as "toxic" (T) or "very toxic" (T) according to the regulations in force in Europe relating to dangerous goods and substances⁺) The substance of (1).

The metals copper and tin or copper, tin and zinc to be deposited are present in the electrolyte according to the invention. They are introduced in the form of water-soluble salts, which are preferably selected from the group consisting of sulfites, sulfates, phosphates, pyrophosphates, nitrites, nitrates, halides, hydroxides, oxide-hydroxides and oxides or combinations thereof. What salts are introduced into the electrolyte in what amount determines the color of the resulting decorative bronze layer and can be adjusted to the customer's requirements. The electrolyte according to the invention preferably contains 0.2 to 5g/l of copper, 0.5 to 20g/l of tin and 0 to 5g/l of zinc, each based on the volume of the electrolyte, for the application of decorative bronze layers to consumer goods and industrial goods. For the refining of the commodity it is particularly preferred to introduce the metal to be deposited as a sulfate, phosphate, pyrophosphate or chloride in such a way that the resulting ion concentrations are 0.3 to 3g of copper, 2 to 10g of tin and 0 to 3g of zinc, each based on per liter of electrolyte.

The process of applying decorative bronze layers to everyday and industrial goods with the electrolyte according to the invention is carried out in an electroplating process. It is important here that the metal to be deposited remains in solution at all times during the treatment, whether the galvanic coating is carried out in a continuous or discontinuous process.

To ensure this, the electrolyte according to the invention contains a phosphonic acid derivative as complexing agent.

Preference is given to using these compounds: aminophosphonic acid AP, 1-amino-methylphosphonic acid AMP, amino-tris (methylenephosphonic acid) ATMP, 1-amino-ethylphosphonic 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-dichloro-vinyl) -phosphonic acid, (4-chlorophenyl-hydroxymethyl) -phosphonic acid, diethylenetriaminepenta (methylenephosphonic acid) DTPMP, ethylenediamine-tetrakis (methylenephosphonic acid) EDTMP, 1-hydroxyethane- (1, 1-di-phosphonic acid) HEDP, hydroxy-ethyl-amino-bis (methylenephosphonic acid) HEMPA, hexamethylenediamine-tetrakis (methyl-phosphonic 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 from the following group: amino-tris (methylenephosphonic acid) ATMP, diethylene-triamine-penta (methylenephosphonic acid) DTPMP, ethylenediamine-tetrakis (methylenephosphonic acid) EDTMP, 1-hydroxyethane- (1, 1-di-phosphonic acid) HEDP, hydroxy-ethyl-amino-bis (methylenephosphonic acid) HEMPA, hexamethylenediamine-tetrakis (methyl-phosphonic acid) HDTMP, salts derived therefrom or condensates derived therefrom, or combinations thereof. Preference is given to using from 50 to 200 g of phosphonic acid derivative per liter of electrolyte, particularly preferably from 75 to 125 g per liter of electrolyte.

The pH of the electrolyte according to the invention, which is strongly influenced by the type and amount of phosphonic acid derivative used and is an important influence of the long-term stability of the electrolyte, is adjusted to 6 to 14, preferably 8 to 12.

The electrolyte may contain, in addition to the metal to be deposited and the phosphonic acid derivative used as complexing agent, organic additives which act as brighteners, wetting agents or stabilizers. The addition of brighteners and wetting agents is only preferred if special requirements are made on the appearance of the decorative bronze layer to be deposited. With their help, the layer gloss can be adjusted to the full scale of silk matt to high gloss, except for the bronze layer color which is decisively dependent on the proportion of metal to be deposited.

Preferably one or more compounds selected from the group consisting of: monocarboxylic and dicarboxylic acids, alkanesulfonic acids and aromatic nitro compounds. These compounds act as electrolyte plating bath stabilizers. Particular preference is given to using oxalic acid, alkanesulfonic acids or nitrobenzotriazoles or mixtures thereof.

The electrolyte according to the invention is characterized in that it does not contain a substance classified as toxic (T) or very toxic (T)⁺) Of (4) a toxic substance. I.e. without cyanide, thiourea derivatives and thiol derivatives. In particular, the addition of the above-mentioned sulfur compounds has a detrimental effect on the plating result. Bronze layers, which are deposited galvanically from a bath with the addition of sulphur compounds, have a mottled or matt-hazy appearance and are therefore unsuitable for decorative coatings for everyday articles.

The non-toxic electrolyte according to the invention is particularly suitable for the galvanic application of decorative bronze layers to everyday and industrial goods. It can be used in wheel plating, rack plating, Band (Band-) plating or continuous (Durchlauf-) plating equipment.

In a corresponding method, for the galvanic application of decorative bronze alloy layers, the daily goods and industrial goods to be coated (hereinafter collectively referred to as substrates) are immersed in a non-toxic electrolyte according to the invention to form a cathode. The electrolyte is preferably tempered in the range of 20-70 ℃. The current density is preferably adjusted to be in the range of 0.01 to 100 amperes per square decimeter [ A/dm ]²]Depending on the kind of plating equipment. For example, a current density of 0.05 to 0.50A/dm is particularly preferable in the wheel plating method². In the rack plating method, the current density is preferably 0.2-10A/dm²Particularly preferably 0.2-5A/dm²。

Different anodes can be used in case a non-toxic electrolyte according to the invention is applied. Soluble or insoluble anodes are equally suitable, for example a combination of soluble and insoluble anodes.

As the soluble anode, such a material selected from the group consisting of: electrolytic copper, phosphorus-containing copper, tin-copper alloys, zinc-copper alloys and zinc-tin-copper alloys. Combinations of different soluble anodes of these materials are particularly preferred, as well as combinations of soluble tin-anodes with insoluble anodes.

As the insoluble anode, such a material selected from the group consisting of: platinized titanium (platiniertem Titan), graphite, iridium-transition metal-mixed oxides and special carbon material ("diamond-like carbon" DLC) or combinations of these anodes. Mixed oxide anodes made of iridium-ruthenium mixed oxide, iridium-ruthenium-titanium mixed oxide or iridium-tantalum mixed oxide are particularly preferred.

If insoluble anodes are used, this is a particularly preferred variant of the process when the substrate, which is the cathode and is to be provided with a decorative bronze layer, is separated from the insoluble anodes by means of ion-exchange membranes in such a way that a cathode chamber and an anode chamber are formed. In such a case the cathode compartment is only filled with the non-toxic electrolyte according to the invention. An aqueous solution containing only the conductive salt is preferably present in the anode compartment. Tin (II) -ion Sn prevention by such an arrangement²⁺To tin (IV) -ion Sn⁴⁺Can be detrimental to the plating process.

In the membrane process with insoluble anode and non-toxic electrolyte according to the invention, the current density is preferably adjusted to 0.05-2A/dm². The temperature-adjusting treatment of the electrolyte is preferably carried out at 20 to 70 ℃. Cation-or anion-exchange membranes can be used as ion-exchange membranes. Preference is given to using Nafion membranes which have a thickness of from 50 to 200. mu.m.

Examples

The examples and comparative examples described below will further illustrate the present invention.

Insoluble platinum-titanium anodes were used in all the described experiments.

Example 1:

for the deposition of a yellowish bronze layer by means of round plating, a non-toxic electrolyte according to the invention is used, which comprises 120g/L hydroxyethyl-amino-bis (methylene-phosphonic acid) HEMPA, 2g/L copper sulfate, 6g/L tin sulfate and 0.1g/L low-molecular polyethyleneimine in water. The pH of the electrolyte was 11.

The electrolyte was temperature conditioned at 60 ℃ during the entire deposition process. At 0.1-0.2A/dm²A bronze layer with a yellow tint typical of bronze with a uniform gloss is obtained in a wheel plating apparatus at the adjusted current density of (a).

Example 2:

in order to produce a layer of bronze yellow in a device in which the substrate constituting the cathode is fixed on a support, a non-toxic electrolyte according to the invention is used, which comprises 100g/L ethylenediamine-tetrakis (methylenephosphonic acid) EDTMP, 4g/L copper pyrophosphate, 5g/L tin pyrophosphate and 3g/L zinc pyrophosphate dissolved in water. The plating bath also contained 15g/L methanesulfonic acid as a stabilizer. The pH of the bath was 8.

At 0.5-1A/dm²The adjusted current density and the temperature-controlled treatment of the electrolyte at 50 ℃ give a bright, flawless bronze layer with a yellow shade.

Example 3:

for the deposition of the white bronze layer an electrolyte was used which contained 50g/L ethylenediamine-tetra (methylenephosphonic acid) EDTMP and 50 g/L1-hydroxyethane- (1, 1-di-phosphonic acid) HEDP in aqueous solution. As metals to be deposited, there are copper in copper sulfate 0.5g/L, tin in tin sulfate 4.0g/L and zinc in zinc sulfate 2 g/L. The pH of the non-toxic electrolyte according to the invention is 10. At a plating bath temperature of 50 ℃ and a concentration of 0.1-0.2A/dm²The mechanically stable and beautiful white bronze layer is obtained by the wheel plating method and the rack plating method under the current density of (1).

Example 4:

for the wheel plating deposition of white bronze, an electrolyte according to the invention is used which contains 100g/L ethylenediamine-tetra (methylenephosphonic acid) EDTMP, copper from 0.5g/L copper pyrophosphate, tin from 5g/L tin pyrophosphate, zinc from 2g/L zinc pyrophosphate and 15g/L methanesulfonic acid for stabilization in water. The pH of the electrolyte was 10. The temperature conditioning treatment is carried out at 50 ℃ during the deposition process.

Using 0.05-0.2A/dm²The adjusted current density of (a) results in a plated layer having a white metallic luster typical for cupronickel, which is glossy even and exhibits good mechanical adhesion strength.

Example 5:

when an electrolyte containing 90g/L of 1-hydroxyethane- (1, 1-di-phosphonic acid) HEDP was used in the rack plating process, a clear white bronze layer was also obtained. The concentration of the metal to be deposited was 0.5g/L copper in copper chloride, 5g/L tin in tin chloride and 1g/L zinc in zinc chloride. 0.05g/L of the sodium salt of propargyl sulfonic acid was contained as a stabilizer. The pH of the plating bath was 9, the temperature of the plating bath during the entire plating process was 55 ℃ and the adjusted current density was 0.2A/dm²。

Example 6:

an electrolyte according to the invention is used which, in addition to copper in 0.5g/L copper chloride, tin in 5g/L tin chloride and vanillin (Vanilin) 1.5g/L, contains the sodium salt of DTPMP diethylenetriamine-penta (methylenephosphonic acid) in a concentration of 80g/L, which has a pH of 8 and is treated at a reduced temperature of 50 ℃ in the range from 0.1 to 0.2A/dm²The regulated current density of the copper alloy can also produce a white bronze layer with no defects in gloss by a rack plating method and a wheel plating method.

Example 7:

the electrolyte of the present invention was used, which contained ethylenediamine-tetra (methylenephosphonic acid) EDTMP at a concentration of 80g/L and amino-tri (methylenephosphonic acid) ATMP at 10g/L in addition to copper in 0.5g/L copper pyrophosphate, tin in 5g/L tin pyrophosphate, zinc in 2g/L zinc pyrophosphate and methanesulfonic acid at 20g/L, had a pH of 10 and was temperature-adjusted at 50 ℃ and was treated at 0.1A/dm²Can also produce a gloss with no flaws at the adjusted current densityHave a grey to black-coloured bronze layer and which have good mechanical properties.

All of the electrolytes described in the examples are suitable for excellent application of decorative bronze layers to everyday and industrial goods while maintaining the given process parameters.

Comparative example:

three additional plating tests were conducted while maintaining the test framework described in example 2, wherein three different electrolytes were used. All electrolytes are based on the formulation according to the invention chosen in example 2 and comprise 100g/L ethylenediamine-tetrakis (methylene-phosphonic acid) EDTMP, 4g/L copper pyrophosphate of copper, 5g/L tin pyrophosphate and 3g/L zinc pyrophosphate in water. The bath contains, in addition to 15g/L of methanesulfonic acid, a small amount of sulfur compounds, namely:

a.) thioglycolic acid in the plating bath of the first comparative test;

b.) thiolactic acid in the plating bath of the second comparative test;

c.) thiourea, in the plating bath of the third comparative test.

The process parameters selected correspond to the conditions adjusted in example 2.

Poor plating results were obtained using all three comparative baths. The bronze layer obtained, although mechanically stable, had an unaesthetic gloss, i.e. mottled, matt and with a haze (Schleier). None of these baths are suitable for applying decorative bronze layers to everyday and industrial goods.

Claims (12)

1. A non-toxic electrolyte for the deposition of decorative copper-tin bronze alloy layers on consumer and industrial goods, comprising the metal to be deposited in the form of a water-soluble salt, characterized in that the electrolyte comprises one or more phosphonic acid derivatives as complexing agent and is free from cyanides, thiourea derivatives and thiol derivatives, and that it comprises only copper and tin or copper, tin and zinc as the metal to be deposited; it comprises as phosphonic acid derivative one or more compounds selected from the group consisting of: 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, diethylene-triamine penta (methylenephosphonic acid) DTPMP, ethylenediamine-tetrakis (methylenephosphonic acid) EDTMP, 1-hydroxyethane- (1, 1-di-phosphonic acid) HEDP, N-bis (methylenephosphonic acid) HEDP, N-methyl-ethyl-phosphonic acid, N-methyl-ethyl-phosphonic acid, N-, Hydroxyethyl-amino-bis (methylenephosphonic acid) HEMPA, hexamethylenediamine-tetrakis (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.

2. The electrolyte of claim 1, wherein the electrolyte has a pH of 6 to 14.

3. The electrolyte as claimed in claim 1, characterized in that it comprises one or more stabilizing compounds selected from the group consisting of monocarboxylic and dicarboxylic acids, alkanesulfonic acids and aromatic nitro compounds.

4. The electrolyte according to any one of claims 1 to 3, characterized in that the water-soluble salt of the metal to be deposited is selected from the group consisting of sulfite, sulfate, phosphate, pyrophosphate, nitrite, nitrate, halide or combinations thereof.

5. The electrolyte as claimed in claim 4, characterized in that the metal to be deposited is present in ionically dissolved form, with the ionic concentration of copper being 0.2 to 5g/l of electrolyte, the ionic concentration of tin being 0.5 to 20g/l of electrolyte and the ionic concentration of zinc being 0 to 5g/l of electrolyte.

6. Process for the galvanic application of decorative copper-tin bronze alloy layers to everyday objects and industrial objects, in which the substrate to be coated is immersed in an electrolyte which contains the metal to be deposited in the form of a water-soluble salt, using a non-toxic electrolyte, characterized in that the electrolyte contains one or more phosphonic acid derivatives as complexing agent and is free from cyanides, thiourea derivatives and thiol derivatives, and it contains only copper and tin or copper, tin and zinc as the metal to be deposited; it comprises as phosphonic acid derivative one or more compounds selected from the group consisting of: 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, diethylene-triamine penta (methylenephosphonic acid) DTPMP, ethylenediamine-tetrakis (methylenephosphonic acid) EDTMP, 1-hydroxyethane- (1, 1-di-phosphonic acid) HEDP, N-bis (methylenephosphonic acid) HEDP, N-methyl-ethyl-phosphonic acid, N-methyl-ethyl-phosphonic acid, N-, Hydroxyethyl-amino-bis (methylenephosphonic acid) HEMPA, hexamethylenediamine-tetrakis (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.

7. A method according to claim 6, characterized in that the electrolyte is tempered at 20-70 ℃.

8. A method according to claim 7, characterized in that the current density is adjusted to be in the range of 0.01-100 amperes per square decimeter.

9. The method according to claim 8, characterized in that a soluble anode is used, which is composed of a material selected from the group consisting of: electrolytic copper, phosphorus-containing copper, tin-copper alloys, zinc-copper alloys and zinc-tin-copper alloys or combinations of these anodes.

10. The method according to claim 8, characterized in that an insoluble anode is used, which is composed of a material selected from the group consisting of: platinized titanium, graphite, iridium-transition metal-mixed oxides and special carbon materials or combinations of these anodes.

11. The method according to claim 9, characterized in that an insoluble anode is used, which is composed of a material selected from the group consisting of: platinized titanium, graphite, iridium-transition metal-mixed oxides and special carbon materials or combinations of these anodes.

12. Method according to claim 10 or 11, characterized in that the cathode and the insoluble anode are separated from each other by an ion exchange membrane in the formation of a cathode compartment and an anode compartment and only the cathode compartment contains a non-toxic electrolyte, such that Sn is present²⁺To Sn⁴⁺Is inhibited.