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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/64—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of silver
• • 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
  • C25D3/46—Electroplating: Baths therefor from solutions of silver
• • 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

• Mixture usable as a brightener in an electroplating bath of silver, gold or one of their alloys is a brightener in an electroplating bath of silver, gold or one of their alloys.
• the present invention relates to a mixture in solid form, in particular usable as a brightener in an electrolytic deposition bath for silver, gold or one of their alloys, as well as its preparation process and its uses.
• the inventor of the present invention sought a process different from those described in the literature, for preparing product A, avoiding, in particular, resorting to the use of carbon sulfide known for its toxic effects and moreover, for its polluting nature of the final product and realized, quite surprisingly, that, by reacting on thiosemicarbazide an excess of xanthate of an alkali metal or ammonium, it was possible to prepare a mixture of products in solid form, more precisely a mixture of product A and of ammonium xanthate or of alkali metal which exhibited a much improved glossiness compared to product A alone.
• the invention relates, according to a first object, as a new industrial product, a new mixture of solids.
• the invention relates to a process for manufacturing such a mixture of solid products.
• the invention relates to aqueous compositions containing this mixture in solution.
• the invention relates to uses of these solid mixtures as well as the above aqueous compositions as a brightening agent as well as electrolytic baths containing these new brighteners. More specifically, according to an essential characteristic, the invention relates to a mixture in solid form, in particular usable as a brightener in an electroplating bath of silver, gold or one of their alloys containing:
• M + denotes an alkali cation or an ammonium
• the xanthate (II) is an alkyl xanthate of sodium, potassium or ammonium in which the alkyl group R is a saturated, linear alkyl or branched.
• the proportions of the compounds of formula (I) and (II), constituting the mixture of the invention can vary very widely.
• the amount of xanthate (II) contained in the mixture of the invention will advantageously be chosen so that this compound (II) is present in said mixture in an amount effective to improve the brightening power of the dithiocarbamoyldiothiocarbazate (I) in an electrolytic silver deposition cyanide bath.
• the mixture of the invention will advantageously comprise from 0.0003 to 80% and, preferably from 0.0003 to 40% by mass of xanthate of formula (II), preferably of sodium alkyl, potassium or ammonium in which the alkyl group is a linear or branched C 6 -C 6 saturated alkyl.
• xanthate of formula (II) preferably of sodium alkyl, potassium or ammonium in which the alkyl group is a linear or branched C 6 -C 6 saturated alkyl.
• the mixtures according to the invention can be obtained by reaction of the thiosemicarbazide with an xanthate of formula (II) in excess, in the presence of a solvent brought to a temperature advantageously between 35 and 100 ° C., the solvent being chosen so that the operation is advantageously carried out at the reflux temperature of said solvent.
• This reaction will preferably take place by reacting at least 1.05 mole of xanthate of formula (II) per mole of thiosemicarbazide.
• the invention also relates to a process for preparing the above solid mixtures.
• Such a process comprises a step of reacting thiosemicarbazide with a xanthate of formula (II) as defined above, in excess, the reaction taking place in a solvent brought to a temperature between 35 and 100 ° C and being followed by a recovery step by filtration of a solid mixture.
• solvents which can be used to carry out the above reaction are relatively wide. They may be different solvents or mixtures of solvents chosen from the group consisting of C, C 6 alcohols, such as in particular, methanol, ethanol, propanol-1, isopropanol, butanol , pentanol or hexanol, ethers, in particular ethyl ether, triethylamine, acetonitrile, dioxane and water and their mixtures.
• C C 6 alcohols
• ethers in particular ethyl ether, triethylamine, acetonitrile, dioxane and water and their mixtures.
• reaction step between the thiosemicarbazide and the xanthate of formula (II) is advantageously followed by at least one step of spinning, filtration, rinsing with a solvent, in particular a rinsing step with absolute ethanol, or drying, these stages preceding the stage of recovery of the solid proper.
• a solvent preferably in an alcohol, for example in methanol, ethanol or propanol-2
• thiosemicarbazide and an alkylxanthate of an alkali metal or d ammonium for example potassium ethyl xanthate.
• This reaction takes place preferably by bringing the solvent to reflux, in general at a temperature between 40 and 80 ° in the case of an alcoholic solvent.
• reaction takes place.
• the reaction mixture is then cooled to ambient temperature or, preferably to a temperature less than or equal to 10 ° C. This cooling causes the precipitation of a yellow solid salt which is isolated by vacuum filtration. It is then preferably carried out with a rinsing with a small amount of alcohol and the recovered solid product is dried, preferably at a temperature between 35 and 65 ° C to obtain a yellow solid product.
• This yellow solid product shows by analysis, in particular by analysis by infrared spectroscopy, that it contains the two solid products of the mixtures I and II of the invention.
• the invention relates, according to another of its essential characteristics, to an alkaline aqueous composition resulting from the dissolution of a solid mixture according to the invention, as defined above, in water, in the presence of a base capable of bringing the pH of this aqueous composition to a value between 10 and 14.
• any base or mixture of bases capable of bringing the pH of said composition to a value between 10 and 14.
• bases are preferably chosen from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate and ammonium carbonate as well as sodium, potassium or ammonium phosphate, triethylamine and their mixtures.
• the invention relates to the use, as a brightener, in a bath of electrolytic deposition of silver, gold or one of their alloys, mixtures as defined above. as well as aqueous compositions obtained by dissolving these mixtures in the presence of a base making it possible to bring the pH of this aqueous composition to a value between 10 and 14.
• the alcohol chosen for the preparation of these image enhancers is preferably methanol, ethanol or isopropanol.
• the invention relates to electrolytic baths intended for the electrolytic deposition of silver, gold or one of their alloys containing, as brightening agent, a solid mixture as defined above or an aqueous basic solution containing this mixture obtained by dissolving this solid mixture, said brightening agent being, if necessary, used in the presence of a solution acting as a gloss enhancer as defined above.
• the electrolytic baths of the invention advantageously contain from 0.3 to 150 g / l of silver, preferably from 3 to 150 g / l of silver, and / or 0.1 to 75g / l of gold, these two metals presenting preferably in the form of a cyanide, preferably in the form of a double alkaline cyanide.
• the solid mixture content is generally at least 0.05 mg / l of solid mixture and preferably from 0.05 to 1,500 mg / l. This concentration can also be obtained by using the appropriate amount of an aqueous composition as defined above.
• the electrolytic baths of the invention in particular cyanide baths, can contain all the constituents conventionally used in electrolytic baths, in particular cyanide baths intended for the deposition of silver, gold, gold alloys / silver or alloys containing silver and / or gold as the main metal.
• These baths advantageously contain from 0.1 to 200 g / l of free potassium cyanide.
• the baths of the invention also advantageously contain a wetting agent, generally in proportions of between 0.0001 and 25 g / l.
• wetting agent use is advantageously made of a wetting agent chosen from the group consisting of Turkish red oil, sodium 1, 3, 6-naphthalene sulfonate, sodium 2-naphthalene sulfonate, products of condensation of sodium naphthalene sulfonate and formaldehyde, polyglycolesters, dimethoxytetraglycol, sulfonated fatty acid amides and polyoxyethylated alkylamine.
• a wetting agent chosen from the group consisting of Turkish red oil, sodium 1, 3, 6-naphthalene sulfonate, sodium 2-naphthalene sulfonate, products of condensation of sodium naphthalene sulfonate and formaldehyde, polyglycolesters, dimethoxytetraglycol, sulfonated fatty acid amides and polyoxyethylated alkylamine.
• the electrolytic baths of the invention advantageously additionally contain at least one compound chosen from the group consisting of arsenic, antimony, selenium, tellurium, lead in solution, EDTA and its alkali salts, alkali carbonates, alkali hydroxides, ammonia, alkaline phosphates, naphthalene sulfonic acid, thiourea, thioacetamide, thiosulfates, alkali sulfites, alkaline succinates, alkali tartrates, alkaline citrates, alkaline gluconates, mercaptobenzothiazole, glycerol, ethylene glycol and its alkaline salts. All these products have, in the case of the present invention, the advantages already known in the prior art.
• sodium thiosulfate helps provide additional shine in the case of silver deposition baths.
• the gold baths will advantageously contain alkaline phosphates and / or an alkali thiosulfate, additives known in the prior art, acting respectively as buffer salt and conductive salt, or brightener. They may also advantageously contain nickel in cyanide form as an alloy metal.
• EDTA in the form of a sodium salt acts by strongly complexing certain metallic impurities, which makes it possible to avoid defects in the appearance of the metallic deposit linked to metallic pollution.
• an antimony complex in particular a complex in the form of glycerol
• the electrolytic bath of the invention may comprise, in solution, in a conventional manner, different alloy metals, in sufficient quantities for the bath to deposit a silver and / or gold alloy containing such a metal. It will be possible, in particular, to include in the bath, alloying metals chosen from the group consisting of palladium, tin, copper, nickel, cobalt, zinc, cadmium, antimony, indium and germanium, these metals being in sufficient quantities for the bath, when in use, to deposit an alloy of silver and / or gold containing between 0 and 40% by weight of this alloy metal .
• alloying metals chosen from the group consisting of palladium, tin, copper, nickel, cobalt, zinc, cadmium, antimony, indium and germanium, these metals being in sufficient quantities for the bath, when in use, to deposit an alloy of silver and / or gold containing between 0 and 40% by weight of this alloy metal .
• Example 2 Preparation of a brightening solution a.
• the solid obtained in Example 1 is dissolved at a concentration of 25 g / l, in a solution of potassium hydroxide, the pH of which is adjusted to 12.
• the three baths obtained in a, b and c are introduced into a HULL cell operating under 1A for a period of 10 min with a rotation speed of 250 rpm.
• Example 4 Electrolytic bath intended for depositing silver A solution is prepared containing:
• the three electrolytes prepared above are introduced into a HULL cell which is operated for a period of 10 min at 1 A, with a rotation speed of 250 rpm.
• Example 5 Electrolytic bath intended for depositing silver A solution is prepared containing:
• the solution prepared above is introduced into a HULL cell which is operated for 10 min at a current intensity of 1 A with a rotation speed of 250 rpm.
• a glossy deposit is obtained for current densities of between 0.001 and 5A / dm 2 .
• This deposit contains a nickel content of between 0.01 and 3%.
• Example 1 the effect of a solid mixture obtained according to Example 1 consisting of potassium ethylxanthate and potassium dithiocarbamoyldithiocarbazate is compared with the effect obtained with each of its constituents alone.
• the brightening mixture may be introduced, with comparable results, in the form of an alkaline solution of the solid mixture.
• a bath is prepared containing:
• This electrolytic bath makes it possible to obtain shiny gold deposits which can be used in decorative applications.

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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)

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• 2001
  • 2001-06-12 FR FR0107646A patent/FR2825721B1/fr not_active Expired - Fee Related
• 2002
  • 2002-06-12 EP EP02745515A patent/EP1397532A1/de not_active Withdrawn
  • 2002-06-12 CN CNA028118626A patent/CN1516754A/zh active Pending
  • 2002-06-12 WO PCT/FR2002/002003 patent/WO2002101119A1/fr not_active Ceased

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