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
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
  • C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/002—Cell separation, e.g. membranes, diaphragms
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
• • 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
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
  • C25D3/10—Electroplating: Baths therefor from solutions of chromium characterised by the organic bath constituents used
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/04—Electroplating with moving electrodes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/08—Electroplating with moving electrolyte e.g. jet electroplating
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated

Definitions

• the invention relates to the use of an electrolyte for the electrolytic deposition of chromium as metal on gravure cylinders, in particular as a hard chrome layer or wear protection layer, a process for producing chromium layers, in particular hard chrome layers, on gravure cylinders, a gravure cylinder with a chromium layer obtainable by this process and a Electrolysis cell, which is designed to coat a gravure cylinder containing the electrolyte.
• the base cylinder is generally a steel tube core which is first coated with copper in an electrolytic bath and then with chromium after application of the image data. This process takes place by means of a galvanic coating of the gravure cylinder with chromium.
• Galvanic processes for surface coating on objects have long been known.
• articles can be given specific functional and / or decorative surface properties, for example hardness, corrosion resistance, metallic appearance, gloss, etc.
• this metal is deposited by means of direct current on the cathode connected object.
• the object to be coated is usually a metallic material. If this object is not electrically conductive, a metallization of the surface is carried out beforehand.
• Galvanic baths containing chromium are used in technical applications usually for the production of particularly hard mechanically resistant layers.
• chromium to objects is of particular technical relevance, with the resulting chromium layer serving either for decorative applications or as a hardcoat on objects for technical applications.
• decorative applications in particular a bright and highly reflective chromium layer is desired.
• the applied chromium layers are to be wear-resistant, abrasion-resistant and heat-resistant and corrosion resistant.
• Such items to be chromed are, for example, pistons, cylinders, liners or axle bearings.
• Galvanic plating is usually carried out in plating baths containing chromium (VI) salts and sulfuric acid using insoluble lead / antimony or lead / tin anodes.
• chromium (VI) salt in particular Cr0 3 is used.
• a chromic acid mist is entrained, which is severely detrimental to health and requires intensive extraction of the surface of the galvanic bath.
• chromium plating baths which reduce the surface tension to form a foam blanket.
• surfactants are also referred to as wetting agents.
• the chromium (VI) electrolytes also have the disadvantage that highly toxic and carcinogenic Cr0 3 is used.
• WO 2008/014987 A2 discloses an electrolyte for the electrodeposition of chromium layers as hard chrome layers for protection against wear and corrosion and / or as decorative chrome layers comprising a catholyte having at least one chromium (III) salt and at least one chromium (II) ion-stabilizing compound, and an anolyte comprising a Bronsted acid, wherein the catholyte and the anolyte by an anion-selective membrane Q
• the object of the present invention is to make it possible to provide chromium layers which do not have the disadvantages known from the prior art and which satisfy the requirements which have been made especially for chromium coatings on gravure printing cylinders.
• an electrolyte for the electrolytic deposition of chromium as metal on a gravure cylinder wherein the electrolyte comprises:
• the formic acid present in the electrolyte serves, in particular, to remove the oxygen formed from the chromium (III) salt by the reaction being carried out to CO 2 and H 2 O.
• the amount of formic acid in the electrolyte is favorably 1, 0 mol / 1 to 3.0 mol / 1, based on the electrolyte. With this amount of formic acid in the electrolyte is a particularly favorable removal of oxygen.
• This quantity refers to the electrolyte before the chromium deposition.
• the pH of the electrolyte changes.
• the compound of formula (I) is glycine, glycolic acid, sulfoacetic acid or a mixture of these. Further, it is preferable that in the electrolyte, the amount of the compound of the formula (I) is 0.5 mol / 1 to 1.5 mol / l based on the electrolyte.
• the compound of formula (I) is used to adjust the pH of the electrolyte, wherein the pH can be adjusted in a particularly favorable manner with the indicated amounts.
• the chromium (III) salt comprises an inorganic and / or an organic chromium (III) salt.
• chromium (III) salt means any chromium (III) salt with which chromium can be deposited as a metal layer on articles.
• the inorganic chromium (III) salt is potassium chrome alum, ammonium chrome alum, chromium sulfate, chromium nitrate, chromium chloride and mixtures of two or more thereof.
• the organic chromium (III) salt may preferably be chromium citrate, chromium formate, chromium oxalate and mixtures of two or more thereof.
• the amount of the chromium (III) salt is 0.25 mol / 1 to 2.0 mol / 1, based on the electrolyte. With these amounts, chromium layers can be produced on metallic objects by electrolytic deposition in a particularly favorable manner.
• an additive in the electrolyte is present as component (d) an additive.
• it comprises a complexing agent and / or a wetting agent.
• wetting agents wetting agents used in the production of chromium layers by electrodeposition can usually be present in the electrolyte. These wetting agents cause the lowering of the surface tension, thus allowing H 2 bubbles to detach from the cathode. As a result, pore formation can be avoided in a simple and favorable manner and thus uniform chromium layers can be produced.
• the complexing agents are preferably compounds with short-chain alkyl chains (1 - 4 C-atoms) with 1 or 2 carboxyl groups or their Derivatives and having 1 or 2 thio and / or sulfone groups or the following compound
• n is an integer from 1 to 5, in particular 3,
• Ri is a C 1 -C 5 -alkyl radical, in particular CH 3 CH 2 -, and
• X is a metal ion to balance the negative charge, in particular Na + , K + , Ca 2+ , Mg 2+ .
• Particularly preferred complexing agent is the compound N, N-dimethyl-dithiocarbamylpropylsulfonic acid sodium salt (DPS).
• DPS N, N-dimethyl-dithiocarbamylpropylsulfonic acid sodium salt
• the amount of the additive present in the electrolyte may be 0.01 g / 1 to 2.0 g / l, based on the electrolyte.
• the amount of the complexing agent may be 0, 5 mol / 1 to 4, 0 mol / 1.
• the amount of wetting agent may be 0 mol / 1 to 0, 5 mol / 1.
• the subject of the application is also a method for producing a chromium layer on a gravure cylinder.
• the electrolyte can be used in the process according to the invention.
• the chromium layer has proven to be particularly favorable for gravure cylinder, since it meets the high demands on chrome layers on such gravure cylinders.
• the electrolytic deposition of chromium layers can be carried out in an electrolysis cell which is filled with the electrolyte. This is the electrolyte described above. In the electrolyte anode and cathode are immersed. When a DC voltage is applied to these two electrodes, ie anode and cathode, the chromium is deposited on the gravure cylinder. In this case, this is connected as a cathode, that is, in the object to be coated is the cathode. If it is not metallically conductive, it can be made electrically conductive by a pretreatment. In some cases, this structure is varied so that an electrolysis cell is ready. - G -
• the electrolyte is separated by a semipermeable membrane into a cathode (electrolyte in the cathode space) and an anolyte (electrolyte in the anode space).
• the substrate i.
• a voltage is applied, a current flows through the membrane through the membrane into the catholyte.
• the anode used in the electrolytic cell may be an insoluble anode, e.g. be a Mischoxidanode.
• the anode may have a pocket, e.g. is designed as an anode basket.
• the pocket may be open at the top and serves to receive metallic chrome elements, e.g. Chrome pellets.
• the preparation of the chromium layer can be carried out at a pH of 2.0 to 4.5.
• the adjustment of the pH can be carried out by the above compound of the formula (I).
• the preparation of the chromium layer can be carried out at a temperature of 20 ° C to 60 ° C. This can be achieved, for example, by setting the temperature of the electrolyte to a value within this range by means of corresponding heating and cooling devices.
• the chromium layer can be produced at a current density of 5 to 60 A / dm 2 .
• the electrolyte can be moved, for example so that a circulation of five bath volumes, ie volume of the electrolyte, takes place per hour. Since devices known per se for depositing chromium layers on articles can be used for the method according to the invention, the volumes of the electrolyte baths of these devices known per se serve as a basis for determining the bath volumes in the method according to the invention.
• the gravure cylinder can be moved at a speed of 1 to 20 cm / s.
• chromium coatings of particularly outstanding quality are obtained, which surprisingly satisfy the requirements imposed on gravure cylinders.
• smooth, uniform surfaces are obtained which have substantially no pores, smallpox or craters.
• the layer thickness of the chromium layers obtained can be thicker than previously available layers.
• layer thicknesses of 100 ⁇ and more can be obtained.
• chromium layers of high hardness can be produced, in particular of more than 900 HV.
• the chromium layers obtainable using the electrolyte or using the method according to the invention are corrosion-resistant, wear-resistant, have favorable frictional properties and are thermally and chemically resistant.
• the available chrome layers are bright and well reflective, so they are also suitable for decorative purposes.
• the chromium coating can be applied using the electrolyte according to the invention or with the method according to the invention in a simpler, faster and more cost-effective manner.
• the chromium layer which was prepared using the electrolyte or using the method according to the invention, a greater thickness than previously available layers, a smooth, uniform surface, which is in particular free of pores, smallpox and Kra- ter , as well as a very high hardness.
• the chromium layers obtained with the electrolyte or the method according to the invention have a lattice constant of 2.92 angstroms or more and can thus be termed amorphous layers.
• the chromium layers obtainable with the electrolyte or with the method according to the invention differ from chromium layers, which can be produced with other electrolytes and / or other processes according to the prior art.
• FIG. 1 shows the diffractogram of the chromed brass sample.
• the chromium layer thickness (18 ⁇ ) is so large that no signals appear from the ground (brass).
• the crystallite size was calculated to be 2-3 nm, ie the chromium is X-ray amorphous.
• the lattice constant was calculated from the interplanar spacing: 292.32 pm (JCPDF database: 288.39 pm). The lattice constant of 292.32 pm corresponds to 2, 9232 ⁇ as stated above.
• the invention furthermore relates to a chromium layer obtainable by the process according to the invention, as described in detail above.
• an electrolytic cell containing an anode, a cathode and an electrolyte, as described in detail above, the subject of the invention, wherein the electrolytic cell according to the invention is designed so that gravure cylinder can be coated, in particular gravure cylinder or gravure rolls, such as They are used for example in printing processes.
• FIG. 2 shows a bath apparatus in a schematic illustration during a cylinder change phase
• FIG. 3 shows the bath apparatus according to FIG. 2 during a galvanization phase.
• FIGS. 2 and 3 show a bath apparatus in different process states, namely firstly at the time of a cylinder change (FIG. 2), when a gravure cylinder 21 has just been inserted into the bath apparatus by means of a crane (not shown) and through storage facilities belonging to a storage facility. bridge 22 is held and in a Galvanmaschinesphase (Fig. 3), in which the lateral surface of the gravure cylinder 21 is to be coated with chromium. Since the components in FIGS. 2 and 3 are substantially identical, they are identified by the same reference numerals.
• the bath apparatus has an upper tub 23 and a lower tub 24 arranged underneath.
• a liquid electrolyte 25 which is pumped by means of a pump 26 from the lower trough 24 in the upper trough 23 and via a vertically movable in at least two positions overflow 27 back into the lower trough 24 flows.
• a vertically movable anode device is further arranged, which essentially consists of an anode rail 28 and an anode basket 29, which is electrically and mechanically coupled to the anode rail 28 and serves as a metal holding device.
• the anode basket 29 may also consist of a plurality of assembled anode baskets or grids or be designed as an anode pocket.
• the anode basket 29 is made of titanium and filled with chromium pellets as metal elements 29a.
• the chromium decomposes, so that chromium ions migrate via the electrolyte 25 to the surface of the gravure cylinder 21 connected as cathode and settle there in the form of a chromium coating.
• the anode basket 29 may also be part of an insoluble anode.
• the metallic chromium available at the anode is dissolved in the electrolyte 25 and thus enriches the electrolyte 25.
• Of the bearing bridges 22 is shown in Figs. 2 and 3, only one.
• the two bearing bridges 22 are movable on rails 30a, 30b in the axial direction of the gravure cylinder 21 by means of spindles or other suitable adjusting mechanisms, so that they clamp the rotogravure cylinder 21 between them and keep them rotatable.
• Fig. 3 shows the bathing apparatus in the plating phase in which the gravure cylinder 21 is almost completely submerged.
• immersion depths can be greater than 65% for large cylinders (1500 mm in circumference) and up to 80% for smaller cylinders (800 mm in circumference).
• the anode basket 29 is pulled up laterally, so that it forms an approximately 50% larger Korbober Structure compared to the known semi-submersible bath.
• the anode rail 28 is moved with the anode basket 29 down into the upper trough 23, as shown in Fig. 2.
• the overflow 27 is lowered, so that the electrolyte 25 flows down to the height level 31 into the lower sump 24.
• the upper tub 23 is tapered in the lower region.
• the rejuvenation can z. B. with the help of additionally inserted sheets 33 or by appropriate adaptation of the walls of the upper tub.
• blocks or boxes it is possible to use blocks or boxes to displace volume.
• the limitation or reduction of the volume of the upper trough 23 has the advantage that not too much electrolyte 25 has to be pumped up from the lower trough 24. Accordingly, there is no risk that the sub-tub 24 is completely emptied and the pump 26 runs dry.
• the latter has a catholyte and an anolyte, the electrolyte according to the invention being present in the catholyte.
• the electrolysis cell according to the present invention is expressly understood as an electrolytic cell containing the electrolyte as detailed above is described contains.
• a container that can be used as an electrolytic cell any suitable for the skilled person in question vessel can be used, as it is in particular commonly used in electroplating.
• the cathode used is usually the object to be coated, on which the chromium layer is to be deposited, ie the gravure cylinder.
• Anodes which are known to the person skilled in the art can be used as the anode.
• the anode may be a sheet, plate material, sintered material or expanded material.
• insoluble anodes are those made from a material selected from the group consisting of platinized titanium, graphite, stainless steel, titanium coated with iridium-transition metal mixed oxide, tantalum or niobium or special carbon material and combinations of these anodes. It is possible if the anode material used is a titanium, niobium or tantalum sheet coated with mixed metal oxides. Furthermore, mixed metal oxide anodes, in particular of iridium-ruthenium mixed oxide, iridium-ruthenium-titanium mixed oxide or iridium-tantalum mixed oxide can be used.
• the anode may be a mixed oxide anode in which titanium as the anode base material is coated with platinum, iridium or palladium oxide.
• the shape of the anode can be adapted by the skilled person according to the respective purpose.
• the anode system may, for example, be one in which the anode is in direct contact with a membrane, ie the anode is coated with a membrane. It is a so-called direct contact membrane anode, as it is known from DE 10 2010 055 143 AI.
• polymers can be used in a favorable manner as polymer membrane: polypyrene membranes, olefin polymer membranes, sulfonated polystyrene membranes, fluorinated / perfluorinated sulfonated polymer membranes (PFSA membranes), S-PEEK-S-PSU, PSU-CI, ICVT membranes, aryl polymer membranes, polyether ketone membranes, polybenzimidazole membranes, thermoplastic polymer membranes, perfluorosulfonic acid polymer membranes, perfluoro carboxylate ionomers, polyamides, polyamines, poly (vinyl alcohol) membranes and perfluorophosphonate membranes.
• PFSA membranes fluorinated / perfluorinated sulfonated polymer membranes
• PFSA membranes fluorinated / perfluorinated sulfonated polymer membranes
• PFSA membranes fluorinated / perfluor
• the electrolyte can be used in a particularly favorable manner or the process according to the invention can be carried out in a particularly favorable manner, so that chromium layers with above-mentioned intrinsic properties can be obtained. Shafts on gravure cylinders can be obtained in a particularly favorable manner.
• additives (brightener and wetting agents) indicated in the table were added to the electrolyte in the amounts shown in the table.
• the Verchromungsstrom had a container in which the gravure cylinder to be coated could be hung vertically so that they can be moved at different rotational speed.
• Three anodes (direct contact anodes) were mounted in a ring around the cylinder so that the distance between anode and cylinder could be varied.
• Direct contact anodes are anodes in which an ion-permeable membrane is applied directly to the anode sheet.
• polymers can be used in a favorable manner as polymer membrane: polypyrole membranes, olefin polymer membranes, sulfonated polystyrene membranes, fluorinated / perfluorinated sulfonated polymer membranes (PFSA membranes), S-PEEK-S-PSU, PSU-CI, ICVT membranes, aryl polymer membranes, polyether ketone membranes, polybenzimidazole membranes, thermoplastic polymer membranes, perfluorosulfonic acid polymer membranes, perfluoro carboxylate ionomers, polyamides, polyamines, poly (vinyl alcohol) membranes, and perfluorophosphonate membranes.
• PFSA membranes fluorinated / perfluorinated sulfonated polymer membranes
• PFSA membranes fluorinated / perfluorinated sulfonated polymer membranes
• PFSA membranes fluorinated / perflu
• permeable membranes can be used for cations.
• a circulation pump for the electrolyte was installed in the system, whose pumping capacity could also be varied.
• a filter is installed in the electrolyte circuit.
• a heating and cooling device is used to keep the temperature constant.
• a pH sensor permanently measures the pH, which is kept within the desired range by the addition of formic acid. The actual temperature and pH are given in the table.
• DPS N, N-dimethyl-dithiocarbamyl-propyl-sulfonic acid sodium salt
• the layer thickness was always about 10 ⁇ deposited.
• the anodes used were coated with a special ion-selective membrane (Navion ®). This prevented the oxidation of Cr (III) to Cr (VI), which arrests the chromium deposition.
• Navion ® ion-selective membrane
• the above examples show that the chromium layers obtained are particularly well suited for coating gravure cylinders.

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• Organic Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
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• 2014
  • 2014-11-14 DE DE102014116717.1A patent/DE102014116717A1/de not_active Withdrawn
• 2015
  • 2015-11-13 WO PCT/EP2015/076551 patent/WO2016075287A1/de active Application Filing
  • 2015-11-13 PL PL15794193T patent/PL3250733T3/pl unknown
  • 2015-11-13 ES ES15794193T patent/ES2893649T3/es active Active
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