Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/48—Electroplating: Baths therefor from solutions of gold
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/62—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of gold

Definitions

• Minimum demands also have to be satisfied with regard to further properties, such as wear resistance, porosity, corrosion resistance, inter alia.
• the layers deposited, in particular in the dental sector have to comply with particular aesthetic requirements, for example relating to the color, the shine or the surface condition.
• certain further demands may be imposed on the composition of the deposited layers, for example with regard to biocompatibility. Biocompatibility of the materials may be particularly important especially in the dental sector, since gold or gold alloy layers with the maximum possible purity are required for example for patients suffering from allergies.
• a further problem is that the additives not only have to be metered in at a later stage, but also that the correct metering, i.e. the required quantity of additive, is dependent on the other bath and process parameters. Factors of influence in this context are, for example, the proportions of the other constituents in the bath, the concentration of the electroactive ions, the geometry of the deposition vessel (cell geometry) the temperature and the current density. In most cases, the user attempts to solve these problems by, on account of his lack of specialist chemical engineering knowledge, working according to what is known as a metering table provided by the manufacturer of the bath and measuring the quantity of additive as a function of the number of objects to be electroplated.
• DE-C2 2 723 910 (corresponds to FR-A 2353656) claims a multiplicity of additive mixtures for baths for the electrolytic deposition of gold or gold alloys. These additional mixtures are intended to improve the properties of the deposits formed.
• Compulsory constituents of these additive mixtures are at least one organic water-soluble nitro compound of a certain general formula and at least one water-soluble metal compound of an element selected from the group consisting of arsenic, antimony, bismuth, thallium and selenium.
• Additive mixtures which, in addition to the nitro compound, also contain a water-soluble bismuth compound are in this case too restricted to use in cyanide-based baths.
• U.S. Pat. No. 5,277,790 has disclosed an additive for a bath based on a gold sulfite complex which likewise has to contain both an organic polyamine or a mixture of polyamines and an aromatic organic nitro compound.
• DE-A1 3 400 670 describes a bath based on gold sulfite complex which contains an additive comprising water-soluble thallium salt and a carboxylic acid which is free of hydroxyl and amino groups.
• the invention is based on the object of providing a bath for the electrodeposition of gold and gold alloys which at least partially avoids the drawbacks outlined above.
• it is intended to make the production of prosthetic dental moldings by electrodeposition even more reliable and safer and to further simplify handling of the baths used for this purpose.
• it is intended to create the option of providing the user with a bath which has already been provided with all the required constituents and additives and is therefore able to function.
• the intention is for it to be possible for the baths in question to be operated substantially with biocompatible, i.e. physiologically harmless compounds without the quality of the layers deposited being adversely affected.
• complex-forming agents or chelate-forming agents in this context are in particular NTA (nitrilotriacetic acid), HEDTA (N-(2-hydroxyethyl)ethylenediaminetriacetic acid), TEPA (tetraethylene pentamine), DTPA (diethylenetriaminepentaacetic acid), EDNTA (ethylenedinitrilotetraacetic acid) and the preferred complex-forming agent/chelate-forming agent EDTA (ethylenediaminetetraacetic acid).
• water-soluble bismuth salts e.g. sulfates, nitrates, sulfamates, phosphates, pyrophosphates, acetates, citrates, phosphonates, carbonates, oxides, hydroxides, inter alia.
• organic complex-forming agents include: organic phosphonic acids, carboxylic acids, dicarboxylic acids, polyoxycarboxylic acids, hydroxycarboxylic acids, diketones, diphenols, salicylaldehydes, polyamines, polyaminocarboxylates, diols, polyols, dipolyamines, aminoalcohols, aminocarboxylic acids, aminophenols.
• the bismuth compound (or if appropriate a plurality of such compounds) is(are) present in the bath in a concentration of between 0.05 mg/l and the saturation concentration of this(these) bismuth compound(s) in the bath.
• concentrations of between 0.05 mg/l and 1 g/l in the bath are preferred.
• Low concentrations are generally preferred, with concentrations between 0.1 mg/l and 10 mg/l being particularly useful within the latter range.
• the concentration of gold in the bath according to the invention is not fundamentally critical. It is preferable for the gold to be present in the bath in a concentration of between 5 and 150 g/l. In particular, gold concentrations of between 10 and 100 g/l, preferably between 10 and 50 g/l, in the bath are selected. A particular advantage of the invention is that it is possible to select gold concentrations in the bath of between 30 and 48 g/l. These relatively high concentrations make the bath according to the invention particularly suitable for the rapid deposition of thick layers, as is fundamentally desirable in the field of production of prosthetic moldings in dental technology.
• the concentration of the further metal in the bath can also be varied within wide limits as a function of the alloy which it is desired to deposit.
• the metals can be added in the form of their preferably water-soluble compounds, in particular salts, or in the form of preferably water-soluble complex compounds.
• the concentrations of the metal compounds may preferably be selected to be between 0.1 mg/l and 200 g/l. Within this range, the concentration may be between 0.1 and 500 mg/l and in particular between 1 and 20 mg/l. In this case too, low concentrations are preferred. Concentrations of between 2 mg/l and 10 mg/l are further preferred within the latter range.
• the gold sulfite complex in the bath according to the invention may in principle be any complex which is known from the prior art. It is preferably what is known as ammonium-gold sulfite complex, in which, therefore, the gold ion has been complexed by the sulfite ions and at least one ammonium ion is present at “counterion”.
• the preferred ammonium-gold sulfite complex has a range of advantages over other gold sulfite complexes. For example, compared to sodium/potassium-gold sulfite complexes, a significantly increased stability of the complex in the gold bath is responsible for a range of advantageous properties. These are, for example, a longer shelf life, reduced sensitivity to impurities and a lower light sensitivity. Moreover, baths comprising ammonium-gold sulfite complexes can be operated at a significantly lower pH of approximately 7-9. This makes baths of this type easier and safer for users with a lack of specialist chemical knowledge to handle compared to the Na/Ka-gold sulfite complex baths with pHs of approximately 10.
• the targeted incorporation of low copper contents in the gold layer while at the same time avoiding incorporation of bismuth, in addition to the high level of purity also enables the functional properties of the gold layer to be accurately controlled, such as for example the hardness, shine, surface properties, color, etc.
• iron as a further metal in the gold bath
• Iron does not cause any problems in use and is even required by the body as an essential trace element.
• the quantitative iron-bismuth ratio in the gold bath and on the other hand by selection of the type of iron compound/iron complex compound, it allows the composition and properties of the gold layer deposited to be controlled even more accurately.
• the bath according to the invention includes the bismuth compound and the interaction between the above-described additions of compounds of further metals in the gold bath), the reduction or prevention of the incorporation of physiologically harmful additives in the layer formed by electroplating, as described in the introduction, is nevertheless retained. Therefore, even when various metals, such as for example copper and/or iron, are present, the bath according to the invention is also able to selectively prevent the incorporation of, for example, antimony.
• the bath according to the invention may contain further standard additives which are customarily present in baths of this type based on a gold sulfite complex.
• Additives of this type are known to the person skilled in the art and can be varied in the standard ranges within the scope of his specialist knowledge. For example, conductive electrolytes with their conductive salts, buffer systems/buffer mixtures, what are known as stabilizers and wetting agents are present. If appropriate, brighteners and/or fine-grain additives which are known from the prior art may also be present in the bath according to the invention.
• the invention also comprises the use of the bath according to the invention as described above for the production of prosthetic moldings for the dental sector by means of electrodeposition.
• a use of this type is intended in particular for the production of what are known as dental frames, such as crowns, bridges, superstructures and the like.
• the prosthetic moldings are in this case electrodeposited on a substrate.
• a substrate In this context, one also refers to the process known as galvanoforming.
• the self-supporting, stable molding is separated from the substrate and processed further.
• the substrate may, for example, be a cast molded from a tooth stump or an implant build-up part (prefabricated or individually prepared).
• the invention also encompasses the 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.
• the bismuth compound is used as a constituent of a bath according to the invention as described above.
• Bismuth compounds which can preferably be used have already been explained extensively above, and consequently reference can be made to the corresponding parts of the description.
• the use in accordance with the invention is intended for the production of prosthetic moldings which have sufficient stability in the galvanoforming process. Accordingly, it is customary to provide molding layer thicknesses of more than 10 ⁇ m.
• the layer thicknesses of the molding are preferably between 100 and 300 ⁇ m, with in particular layer thicknesses of approx. 200 ⁇ m being deposited.
• the provision of layer thicknesses of this type means that the invention is suitable not just for the production of crowns but also of bridges and other superstructures.
• the invention also comprises a process for producing prosthetic moldings for the dental sector from gold and gold alloys by electrodeposition.
• This process is intended in particular for the production of dental frames, such as crowns, bridges, superstructures and the like.
• a gold or gold alloy layer is deposited on a suitable substrate from a bath in accordance with the invention, and the layer obtained is separated (demolded) from the substrate.
• the substrate may, for example, be a cast which has been molded from a tooth stump or an industrially prefabricated or individually treated implant build-up part.
• the substrate is preferably composed of an electrically nonconductive material, in particular plaster or plastic. This normally relates to situations in which a cast has been molded from the tooth stump.
• the surface of the nonconductive substrate is then made conductive prior to the electrodeposition, in particular with the aid of conductive silver.
• the substrate is composed of at least one metal which is itself already conductive.
• suitable substrates which may be mentioned are inner telescopes (usually made from a cast and milled dental alloy) or implant build-up parts, such as implant build-up posts. Parts of this type usually consist of titanium or titanium alloys.
• the process according to the invention and also the uses according to the invention are preferably characterized in that the deposition takes place at high current densities, which usually results in short electrodeposition times. It is preferable to select current densities of up to 10 A/dm 2 , in particular current densities of up to 8 A/dm 2 .
• the bath according to the invention can still be used very successfully at such high current densities.
• the use according to the invention or the process according to the invention can preferably be carried out in such a way that the deposition takes place using what is known as the pulse-plating process.
• This type of electrodeposition of metal likewise uses direct current.
• this direct current is applied as a pulsed current, i.e. in the form of current pulses which are interrupted by pauses.
• the use of the pulse-plating process in dental technology is shown in DE-A1 198 45 506 in the name of the present Applicant, the content of which is in this respect incorporated by reference in the content of the present description.
• the use of the pulse-plating process in the present invention has the advantage that the deposits can be formed in the desired thickness, for example of approx. 200 ⁇ m, within relatively short times.
• the use according to the invention and the process according to the invention are preferably characterized in that the prosthetic molding deposited is veneered with ceramic and/or plastic during its further processing.
• the desired tooth replacement is produced in this way.
• a molding which has been veneered with ceramic is fired in the usual way after the ceramic has been applied, for example at temperatures of up to approximately 950° C.
• a molding which has been veneered with plastic, after the plastic has been applied, is irradiated with light, in particular with visible light, in order for it to be cured, after the surface of the molding has previously been conditioned using suitable processes which are known to the person skilled in the art.
• the bath according to the invention is eminently suitable for the production of prosthetic moldings (dental prostheses).
• the properties of the deposits are at least as good as those achieved with deposits formed from gold sulfite baths which operate, for example, with antimony compounds being metered in.
• the quality of the deposits in the bath according to the invention tends to match the specific requirements of dental technology even more successfully.
• the pure gold layers obtained with the bath according to the invention are a golden yellow color and are extremely shiny, and therefore satisfy particularly high aesthetic demands. Of course, it is optionally also possible to produce matt and/or rough surfaces.
• the firing stability of these layers, which is imperative if they are to be veneered with ceramic, is provided with a reproducible reliability despite the fact that it is possible to dispense with an antimony compound in the gold bath. As far as the Applicant is aware, this has not hitherto been the case in any bath which is able to operate without an antimony compound.
• a further advantage of the bath according to the invention is that it is clearly insensitive to plastics which have been introduced into the bath and are provided, for example, as tooth stump materials or to cover metallic parts which are not to be coated by electrodeposition.
• plastics of this type cast molding plastics
• enamels covering enamels
• the bath is insensitive to such disruptive influences, it is possible to operate at relative high current densities (cf. above, up to 8 A/dm 2 or 10 A/dm 2 ).
• a further advantage of the bath according to the invention is found to be that a bath of this type with bismuth additive functions without problems, and in particular with above-average results, in various devices (including from a number of different manufacturers) which are in commercial use in the dental sector for electrodeposition.
• the result of this has been that each manufacturer has normally offered a specific gold bath for a very specific device whose process parameters have been matched to this gold bath.
• the baths used also contain standard additives for gold sulfite baths.
• additives are known to the person skilled in the art.
• they are conductive salts (sulfites, sulfates and phosphates), wetting agents or stabilizers, such as for example nitro acids.
• the bath according to the invention differs from the known baths in particular through the addition of the bismuth compound, and on account of this addition it is if appropriate possible (although not necessary) to dispense with additives which are present in conventional baths, such as for example antimony compounds or nitro compounds.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Dental Preparations (AREA)
• Electroplating Methods And Accessories (AREA)

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• 2002
  • 2002-02-28 BR BR0207724-8A patent/BR0207724A/pt not_active Application Discontinuation
  • 2002-02-28 JP JP2002568818A patent/JP4183240B2/ja not_active Expired - Fee Related
  • 2002-02-28 US US10/469,146 patent/US20040065225A1/en not_active Abandoned
  • 2002-02-28 EP EP02744906.5A patent/EP1366219B1/de not_active Expired - Lifetime
  • 2002-02-28 AU AU2002308221A patent/AU2002308221A1/en not_active Abandoned
  • 2002-02-28 WO PCT/EP2002/002128 patent/WO2002068728A1/de active Application Filing
  • 2002-02-28 CA CA002438207A patent/CA2438207A1/en not_active Abandoned
  • 2002-02-28 CN CNB028056736A patent/CN100392155C/zh not_active Expired - Lifetime

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