Bath for the galvanic deposition of gold and gold alloys, and uses thereof

Abstract

The invention relates to a bath for the electrodeposition of gold and gold alloys and to its use for producing dental moldings. In this bath, the gold is in the form of a gold sulfite complex. The bath according to the invention and/or the use according to the invention is distinguished by the fact that in addition to the optional presence of further metals and standard additives for gold sulfite baths of this type, there is at least one bismuth compound. This bismuth compound is preferably a complex compound, in particular with the complex-forming agents NTA, HEDTA, TEPA, DTPA, EDNTA or EDTA. The invention has a whole range of advantages associated with it. One advantage which should be particularly emphasized is that the addition of bismuth can be added to the bath as early as during its preparation. This means that the user is provided with a bath which is able to function for a prolonged period of time and to which it is not imperative to add further additives prior to the electrodeposition.

1 . Bath, preferably aqueous bath for the electrodeposition of gold and gold alloys, in which the gold is in the form of a gold sulfite complex, characterized in that the bath contains at least one bismuth compound, preferably at least one water-soluble bismuth compound, and if appropriate at least one compound of at least one further metal and standard additives for gold sulfite baths of this type.  
     
     
         2 . Bath according to  claim 1 , characterized in that the gold sulfite complex is an ammonium-gold sulfite complex.  
     
     
         3 . Bath according to  claim 1  or  claim 2 , characterized in that it has a pH of >7, preferably from 7 to 9.  
     
     
         4 . Bath according to one of the preceding claims, characterized in that it contains copper as a further metal.  
     
     
         5 . Bath according to one of the preceding claims, characterized in that it contains iron as a further metal.  
     
     
         6 . Bath according to one of the preceding claims, characterized in that it contains at least one precious metal, preferably at least one precious metal from the platinum group, as a further metal.  
     
     
         7 . Bath according to one of  claims 4  to  6 , characterized in that it contains at least one water-soluble bismuth compound and at least one water-soluble copper compound.  
     
     
         8 . Bath according to  claim 5  or  claim 6 , characterized in that it contains at least one water-soluble bismuth compound and at least one water-soluble iron compound.  
     
     
         9 . Bath according to one of  claims 4  to  8 , characterized in that it contains at least one water-soluble bismuth compound, at least one water-soluble copper compound and at least one water-soluble iron compound.  
     
     
         10 . Bath according to one of the preceding claims, characterized in that the bismuth compounds and preferably also the compounds of the further metals are complex compounds, preferably chelate compounds.  
     
     
         11 . Bath according to  claim 10 , characterized in that the complex compounds contain organic complex-forming agents, preferably organic chelate-forming agents.  
     
     
         12 . Bath according to  claim 11 , characterized in that the complex-forming agents or chelate-forming agents are NTA, HEDTA, TEPA, DTPA, EDNTA or in particular EDTA.  
     
     
         13 . Bath according to one of the preceding claims, characterized in that the bismuth compounds are present in the bath in a concentration of between 0.05 mg/l and their saturation concentration.  
     
     
         14 . Bath according to  claim 13 , characterized in that the bismuth compounds are present in the bath in a concentration of between 0.05 mg/l and 1 g/l in particular between 0.1 mg/l and 10 mg/l.  
     
     
         15 . Bath according to one of the preceding claims, in particular according to one of  claims 1  to  14 , characterized in that the compounds of the further metals are present in the bath in a concentration of between 0.1 mg/l and 200 g/l, preferably between 0.1 mg/l and 500 mg/l.  
     
     
         16 . Bath according to  claim 15 , characterized in that the compounds of the further metals are present in the bath in a concentration of between 1 mg/l and 20 mg/l, preferably between 2 mg/l and 10 mg/l.  
     
     
         17 . Bath according to one of the preceding claims, characterized in that it is substantially free of physiologically harmful additives, preferably is free of arsenic, antimony and thallium compounds.  
     
     
         18 . Bath according to one of the preceding claims, characterized in that the gold is present in the bath in a concentration of between 5 and 150 g/l.  
     
     
         19 . Bath according to  claim 18 , characterized in that the gold is present in the bath in a concentration of between 10 and 100 g/l, preferably between 10 and 50 g/l, in particular between 30 and 48 g/l.  
     
     
         20 . Use of a bath according to one of the preceding claims for the production of prosthetic moldings for the dental sector by means of electrodeposition, in particular for the production of dental frames, such as crowns, bridges, superstructures and the like.  
     
     
         21 . Use of at least one bismuth compound, preferably of at least one water-soluble bismuth compound, for the production of prosthetic moldings for the dental sector by means of electrodeposition, in particular as a constituent of a bath according to one of  claims 1  to  19 .  
     
     
         22 . Use according to  claim 21 , characterized in that the bismuth compound is a complex compound, in particular chelate compound, which preferably contains an organic complex-forming agent or chelate-forming agent.  
     
     
         23 . Use according to  claim 22 , characterized in that the complex-forming agent or chelate-forming agent is NTA, HEDTA, TEPA, DTPA, EDNTA or in particular EDTA.  
     
     
         24 . Use according to one of  claims 21  to  23 , characterized in that the bismuth compound is added directly during preparation of the bath.  
     
     
         25 . Use according to one of  claims 21  to  23 , characterized in that the bismuth compound is added to the bath immediately before or during the electrodeposition.  
     
     
         26 . Use according to one of  claims 21  to  25 , characterized in that the bismuth compound is added to the bath after an electrodeposition step for top-up purposes.  
     
     
         27 . Use according to one of  claims 20  to  26 , characterized in that the prosthetic molding is deposited in a layer thickness of more than 10 μm, preferably in a layer thickness of between 100 and 300 μm, in particular in a layer thickness of approx. 200 μm.  
     
     
         28 . Process for producing prosthetic moldings for the dental sector from gold and gold alloys by electrodeposition, in particular for the production of dental frames, such as crowns, bridges, superstructures and the like, characterized in that a gold or gold alloy layer is deposited from a bath according to one of  claims 1  to  19  on a suitable substrate, e.g. on a cast which has been molded from a tooth stump, and is then separated from the substrate.  
     
     
         29 . Process according to  claim 28 , characterized in that the substrate is composed of an electrically nonconductive material, in particular plaster or plastic, the surface of which has been made conductive, in particular with the aid of conductive silver.  
     
     
         30 . Process according to  claim 28 , characterized in that the substrate is composed of at least one metal.  
     
     
         31 . Use or process according to one of  claims 20  to  30 , characterized in that the deposition takes place at high current densities, preferably at current densities of up to 10 A/dm 2 .  
     
     
         32 . Use or process according to one of  claims 20  to  31 , characterized in that the deposition takes place using what is known as the pulse-plating process.  
     
     
         33 . Use or process according to one of  claims 20  to  32 , characterized in that the prosthetic molding is veneered with ceramic and/or plastic.  
     
     
         34 . Use or process according to  claim 33 , characterized in that a molding veneered with ceramic is fired.  
     
     
         35 . Use or process according to  claim 33 , characterized in that a molding veneered with plastic is cured using light, in particular using visible light.