WO2017005284A1 - Copper-patinated gemstone setting - Google Patents

Abstract

The invention relates to a method for producing artificial copper patina on a gemstone setting. The patina is characterized by an appearance that corresponds to a natural aging progression. The invention also relates to products produced by the method.

Description

 Gemstone setting with copper patina

Field of the invention

The invention relates to a method for producing an artificial copper patina on a gemstone socket, which has a copper-containing layer and a protective layer. The method is characterized in particular by the fact that a protective layer is applied to a thermally treated copper layer.

State of the art

For the design of gemstone settings, it is often desirable that the metallic jewelry parts assume a characteristic appearance created by weathering and aging. Specifically, copper is known for its characteristic blue-green appearance due to weathering and aging. The layer that forms is called patina. For the processing of jewelry, the natural aging process takes far too long. Therefore, there is great interest in producing this effect artificially. The gemstone setting itself is not completely made of copper, as copper is too soft for jewelry processing. In jewelery production, a jewelery base is often made of, for example, brass, a copper-zinc alloy or pure zinc. These materials are easy to coat. By wearing on the skin, as is usually the case with jewelery, the desired "Vi ntage effect" would become very unsightly as a result of the reaction with sweat after a short time, it is therefore desirable to develop a metal-containing layer sequence, which in particular in the jewelry sector the decorative requirements of a "Vi ntage- effect" and the wearing requirements, in particular a protection against sweat, is sufficient.

US Pat. No. 7,018,677 B2 and US Pat. No. 8,007,866 B2 already disclose the artificial production of an appearance which is similar to that of the patina. In it, the effect is realized only with dyes or colors. To artificially produce as natural a copper patina as possible, it is desirable to use copper itself. In US 8,956,510 B2 the coating of jewelry is described. Although the production of coatings is known for jewelry, but the generation of the most natural copper patina is not mentioned.

Object of the present invention is to realize an artificial copper patina on a gemstone setting, which is also friendly to the skin, does not react with sweat, has good adhesion and protects against mechanical erosion, such as scratches. Description of the invention

Surprisingly, it has been found that the natural copper patina can be produced artificially by the process of the invention and the patina of the gemstone socket by the use of a protective varnish does not react with sweat and is protected from scratching. For jewelry, this is of great importance, since the gemstone settings meet the wear requirements by the protective coating.

The subject matter of the present application is therefore a process for coating a gemstone socket, characterized by the following steps: a) optional cleaning of the surface of the gemstone socket,

 b) applying a copper layer to the gemstone socket,

 c) treating the copper-plated gemstone version with

 d) an acidic or basic copper salt solution or

 c2) with an acid or a base and subsequently with a copper salt solution, d) thermal aftertreatment of the copper-plated parts,

 e) optional post-treatment with a copper salt solution and thermal aftertreatment in any repetition of both steps,

 f) applying a protective varnish.

Step a):

The gemstone socket is optionally cleaned or degreased in step a) before the copper plating. Degreasing is the removal of adhering fats, oils or other contaminants with degreasing agents. This improves the adhesion of the copper layer.

The cleaning can be done mechanically, for example by grinding and polishing, with solvents, for example ethyl acetate, or else with ultrasound, for example with the Evolution WP-K device from German Sonic. Another option for pretreatment is electrolytic degreasing. During the electrolytic degreasing, the gemstone socket is in a solution and is then cleaned by applying a current. In electrolytic degreasing, a distinction is made between cathodic and anodic degreasing. The cathodic degreasing proceeds under hydrogen evolution and the anodic degreasing under evolution of oxygen. The cathodic degreasing is preferably used because it can be achieved with jewelry bodies such as brass very good cleaning.

In addition, to further improve the adhesion of the metal layer, the surface of the gemstone socket may be treated with acids to remove oxide layers. Sulfuric acid has proven to be advantageous for the cleaning of brass jewel casings. Step b):

In general, there are many processes for coating metal parts, for example electroless processes in solution or electrolytic processes, or also processes such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). In this case, a thin metal layer is deposited on the surface of a material to be coated. All of these methods are suitable in principle according to the invention. The electrolytic processes are electrochemical depositions of metal layers on surfaces to be coated. Conductive materials, such as conductive metals, conductive metal alloys or conductive plastics, are suitable for this type of surface coating. In the electrolytic processes, the material to be coated is placed in a solution of the coating material. By applying an external current, the coating material deposits on the material to be coated.

Electroless coating processes in solution, such as reductive, occur without the use of an external power source. Such a metal deposition with the addition of reducing agents to the electrolyte is based on the oxidation of the reducing agent with release of electrons, which lead to a reduction of the metal ions.

The inventive method allows for jewelry in terms of aesthetics and design very many design options. The copper patina can be applied electrolytically in principle to any conductive material, for example on brass or on electrically conductive plastics. Preference according to the invention gemstone frames are used, which are made of brass or a brass-containing alloy, since brass is particularly suitable for processing technical reasons. Brass is easy to coat and is easy to machine. Brass and all other metals listed here are used in the purity known to those skilled in the art.

If a gemstone mount is made of zinc die-cast, it is advantageous to pre-clad first with a cyanide copper electrolyte. The resulting, usually thin copper layer is then reinforced with an acidic copper electrolyte. Pre-coppering is necessary because it is not possible to directly coat zinc die-cast parts due to the low pH of an acidic copper electrolyte. The zinc would dissolve. In contrast, brass jewel casings can be directly coated with an acidic copper electrolyte.

In step b) of the process according to the invention, the copper layer is preferably deposited electrolytically. With electrolytic processes, the copper layer can be selectively deposited. The Thickness of the deposited copper layer is preferably 5 to 200 μιτι, in particular 5 to 100 μιτι and particularly preferably 10 to 50 μιτι. A minimum layer thickness of 5 μιτι is necessary because material is removed by further process steps. A layer thickness of more than 200 μιτι is not very advantageous because no additional advantages are associated with it.

Step c):

The copper-plated parts are treated in process step c) with a mixture of acid and copper salt solution or base and copper salt solution. Nitric acid or acetic acid is preferably used according to the invention as the acid. As the copper salt, copper nitrate is preferably used. When using nitric acid and copper nitrate gives the best adhesion, which is why this combination is particularly preferred. Alternatively, the copper-plated gemstone socket can be treated first with the acid or base and then with the copper salt solution. The use of the mixture of acid or base and copper salt solution has the advantage that two process steps can be handled in one. As an alternative to nitric acid, it is also possible to use a base, preferably ammonia. According to the invention, the combination of ammonia and copper sulfate is preferred. The copper-plated gemstone setting discolors bluish with a solution of ammonia and copper sulfate and a solution of acetic acid and copper acetate greenish.

Step d):

In step d) of the process, the gemstone socket is thermally treated. According to the invention, the thermal aftertreatment is preferably carried out at temperatures in the range of 50Ό-190Ό. The thermal post-treatment has proven to be advantageous for the desired color change. At temperatures above 190 °, the gemstone setting discolors towards black, which is undesirable for aesthetic reasons.

Steps):

The cooled gemstone setting is optionally treated again with a copper salt solution. As the copper salt according to the invention is copper nitrate, Cu (II) acetate or copper sulfate. Thereafter, the gemstone setting in the temperature range of 50Ό - 190Ό thermally treated. The process step e) can be carried out in any repetition and serves to reinforce the copper patina effect.

Step f):

In step f) of the method, a protective varnish is applied to the gemstone socket. The protective varnish prevents the metal parts from reacting and improving with the sweat of the skin also the resistance of the metal layers. According to the invention, varnish is understood as meaning a liquid or pulverulent coating material which is applied thinly to objects and is built up by chemical or physical processes, for example evaporation of the solvent, to form a continuous, solid layer. Paints often contain binders, fillers, pigments, solvents, resins and / or acrylates and additives, such as biocides. For example, acrylic lacquers, epoxy lacquers or polyurethane lacquers are suitable according to the invention.

Acrylic paints are manufactured on the basis of acrylic resins. Acrylic resins are synthetic resins and are considered particularly durable. Acrylic resins are based on polymers or copolymers of acrylic acid or methacrylic acid and their esters. They are often copolymerized with other unsaturated monomers, such as styrene or acrylonitrile. Acrylic paints are either dissolved in solvents or dispersed in water and applied to the coated gemstone mount. Acrylic coatings have a high weather resistance and are UV-resistant and are therefore particularly well suited according to the invention.

Epoxy paints often contain the two components epoxy resin and hardener. Epoxy resins are polyadducts of epichlorohydrin with bisphenol derivatives, for example A, F or S. These are crosslinked with a hardener. Usually, the two components epoxy resin and hardener are mixed shortly before processing. Epoxy coatings are characterized by high chemical and mechanical resistance, but are not optimal in terms of UV resistance.

For polyurethane coatings, the urethane group is characteristic. They are commercially available as single-component and multicomponent coatings, for example the hardener is already mixed with the master varnish in the case of one-component varnish, and the two-component varnish contains hardener and stock varnish. Polyurethane coatings are particularly hard, abrasion resistant and resistant to water, oils and chemicals.

According to the invention, a polyurethane varnish is preferably used as the protective varnish. Polyurethane paints have good adhesion properties and are resistant. Two-component polyurethane acrylic resin coatings have proved to be advantageous according to the invention, in particular the products DE 4259x the company Hesse and Lignal, since they are saliva and sweat resistant according to DIN 53160. They can be applied without thermal aftertreatment and are lightfast.

Another object of the application are gemstone versions, which are obtainable by the method according to the invention. The preferred embodiments of the method lead to inventively preferred products. General process description

In process step a), the gemstone socket is optionally cleaned or degreased. For degreasing of brass parts is especially the cathodic, alkaline electrolytic degreasing. In this degreasing, the electrolytic solution contains, for example, caustic soda and surfactants. The degreasing is carried out for a period of at least 1 minute, a temperature of 35Ό - 55Ό and a current density of at least 3 A / dm ^2, for example with the 1018 agent IWG-Plating Vienna. In order to remove oxide layers from the brass surface, treatment of the gemstone casing with 5-15% sulfuric acid (% by weight) has proved to be advantageous. The gemstone socket is immersed in the sulfuric acid according to the invention for about 1 minute. Thereafter, the gemstone socket is cleaned with deionized water. Inadequate cleaning can damage both the electrolytes and the quality of the copper layer.

In process step b) the gemstone socket is coated electrolytically with copper. The electrolyte used can be, for example, Cupracid® 210 from Atotech. When coppering the metal parts is particularly preferably a copper layer thickness of 10 - 50 μιτι deposited. The gemstone socket is treated in step c) of the process with an aqueous solution of acid or base and copper salt, for example by immersing it in the aqueous solution of acid or base and copper salt. For the treatment of brass has proven due to good adhesion properties nitric acid (about 0.1 to 1 mol / l) and copper nitrate (about 3 - 7 mol / l). The gemstone socket is usually treated for about 30 seconds with the aqueous solution of nitric acid and copper nitrate or with the aqueous solution of acetic acid (about 3 - 5 wt .-%) and Cu (II) acetate (about 0.5 - 1 mol / l). Another alternative is an aqueous solution of Cu (II) SO ₄ (about 0.1-0.3 mol / l) and ammonia (about 0.02-0.04 mol / l).

Acid or base and copper salt do not have to be used in a solution. The gemstone socket can also be treated first with the acid or base and then in a further step with the copper salt. The use of the acid or base and copper salt in a solution has the advantage that two process steps can be handled in one.

After the action of the acid or base and the copper salt, the gemstone casing is dried at about 20 ° to 30 ° C. and, in process step d), thermally treated with a hot air blower in the range of 50 ^° C.-190 ^° C.

The cooled gemstone socket is optionally cleaned with deionized water and then treated again in process step e) with an aqueous copper salt solution by immersing the socket. As copper salt according to the invention copper nitrate, Cu (II) acetate or Copper sulphate. An aqueous copper nitrate solution having a concentration of 1 to 7 mol / l, preferably 1 to 3.5 mol / l, has proven to be advantageous for the adhesion. Thereafter, the gemstone version is again at about 20Ό - 30Ό ge dried and thermally treated. For the thermal aftertreatment, the gemstone socket is again dried with a hot air blower in the range of 50Ό - 190Ό. The process step e) can be repeated as often as desired.

On the cooled gemstone setting a protective lacquer is applied in step f), for example, to prevent the reaction of skin sweat with the gemstone setting. As a protective varnish, acrylic varnish, epoxy varnish, for example Duralit® 1516-754 S from Rohm and Haas or also polyurethane varnish can be used. A two-component polyurethane-acrylic resin paint, for example DE 42597-0040 from Hesse & Lignal, has proved to be advantageous.

Inventive Example (FIG. 1)

A gemstone setting made of brass was coated in the following manner with a copper patina. The gemstone frame made of the FRMSBR alloy from AGS Alpha Guss Metals and Alloys GmbH Pforzheim was degreased electrolytically with the agent 1018 from IWG-Plating Wien for 5 minutes at a temperature of 45 ° and a current density of 5 A / dm ² . Thereafter, the degreased brass parts were washed with deionized water. For removal of oxide layers, the brass jewelry frame was immersed for about 1 minute in a 10% sulfuric acid (wt .-%). Thereafter, the gemstone socket was washed again with deionized water.

Subsequently, the brass jewel case was dipped wet in a copper bath and coated in the bright copper bath Cupracid® 210 from Atotech at 25 ° and a current density of 3 A / dm ^{2 for} about 20 minutes.

The copper-plated gemstone socket was immersed for about 20 seconds in an aqueous solution of nitric acid (1 mol / l) and copper nitrate (7 mol / l) and then dried for about 20 minutes at about 25. Thereafter, the frame was thermally treated with a hot air blower and a temperature of about 180 °.

The cooled gemstone socket was again washed with deionized water and then immersed for about 20 seconds in an aqueous copper nitrate solution (3 mol / l). Then the gemstone setting was dried for about 20 minutes at about 25Ό and then with a hot air blower at about 180Ό thermally aftertreated It.

The cooled gem stone mount was coated with the protective varnish by immersing it in the two-component polyurethane acrylic resin paint DE 42597-0040 the company Hesse & Lignal and dried at about 25Ό for a period of about 14 hours.

Claims

Claims Gemstone setting with copper patina 1 . A method of coating a gemstone socket characterized by the steps of: a) optionally cleaning the surface of the gemstone socket;  b) applying a copper layer to the gemstone socket,  c) treating the copper-plated gemstone version with  c1) an acidic or basic copper salt solution or  c2) with an acid or a base and subsequently with a copper salt solution, d) thermal aftertreatment of the copper-plated parts,  e) optional post-treatment with a copper salt solution and thermal aftertreatment in any repetition of both steps,  f) applying a protective varnish. 2. The method according to claim 1, characterized in that the gemstone mount is made of brass or a brass-containing alloy. 3. The method according to at least one of the preceding claims, characterized in that the copper layer is deposited electrolytically. 4. The method according to at least one of the preceding claims, characterized in that the layer thickness of the copper layer is 5 - 200 μιτι, preferably 5 - 100 μιτι and particularly preferably 10 - 50 μιτι. 5. The method according to at least one of the preceding claims, characterized in that is used as the acid nitric acid. 6. The method according to at least one of the preceding claims, characterized in that is used as the acid acetic acid. Process according to at least one of the preceding claims, characterized in that ammonia is used as the base. Method according to at least one of the preceding claims, characterized in that copper nitrate is used as the copper salt. Method according to at least one of the preceding claims, characterized in that the thermal aftertreatment is carried out at temperatures in the range of 50Ό - 190 ^S C. 0. Method according to at least one of the preceding claims, characterized in that the protective lacquer is a polyurethane lacquer. 1 . Gemstone socket obtainable by a method according to at least one of the preceding claims.