Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
  • C25D11/243—Chemical after-treatment using organic dyestuffs
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/20—Electrolytic after-treatment
  • C25D11/22—Electrolytic after-treatment for colouring layers

Definitions

• the invention relates to a process for the adsorptive coloring of anodically produced surfaces of aluminum and / or aluminum alloys with organic, anionic dyes in aqueous solution.
• the surface of aluminum and / or aluminum alloys is usually provided with an anodic oxidation with an approximately 20 ⁇ m thick porous oxide layer, which can be colored in various ways to achieve decorative effects.
• Adsorptive dyeing processes usually include dyeing techniques in which organic dyes or inorganic pigments penetrate into the pores of the anodically produced oxide layer by single or multiple dipping into aqueous or non-aqueous dyeing solutions, or are formed therein by chemical reaction.
• the previous anodization i.e. the anodic oxide layer is generally built up according to the so-called GS method.
• an aluminum workpiece is anodized in a solution containing 150-200 g / l sulfuric acid at a temperature of 18 - 20 ° C and a DC voltage of about 15 to 18 V.
• the anodizing times are about 3 min / ⁇ m layer build-up.
• Air is usually used during the anodization in an amount of 8 m3 / m2h for circulation and cooling.
• the actual coloring is then carried out by immersing the anodized workpiece in an appropriate dye solution at mostly elevated temperatures.
• the anodically produced oxide layers are usually compacted in aqueous solution at temperatures in the range from 95 to 100.degree.
• organic-chemical adsorption dyeing with dyes is known, among other things.
• Anionic dyes are predominantly used for dyeing.
• the adsorption of anionic dyes is mainly based on the exchange of the bisulfates of the aluminum oxide surface for dye anions. The author therefore describes that especially acidic dyes, preferably those containing sulfonic acid groups, are suitable for coloring aluminum oxide.
• the object of the present invention is to provide an improved process for the adsorptive coloring of anodically produced surfaces of aluminum and aluminum alloys with organic anioinic dyes in aqueous solution, it being possible in particular to dispense with an intermediate step between the adsorptive coloring and the compression process .
• Another object of the present invention is to extend the service life of the dye baths used for adsorptive dyeing.
• the alkaline earth metal sulfates formed in the inventive adsorptive coloring do not adversely affect the adsorptive coloring. Even a high concentration of water-soluble alkaline earth metal salt or alkaline earth metal sulfate in the dye bath in no way disturbs the uniformity of the adsorptive dyeing.
• the concentration of free sulfate ion is of course also significantly less than 0.1 g / l.
• the dye bath is usually re-sharpened with water-soluble alkaline earth metal salts when free alkaline earth metal ions can no longer be detected in the dye bath.
• the process according to the invention also gains particular importance in continuous spray processes for adsorptive coloring with organic, anionic dyes in aqueous solution, since the dye baths are continuously recycled and new sulfate is always introduced.
• a particular embodiment of the invention consists in the use of the alkaline earth metal salts of the organic, anionic dyes.
• the exclusive use of alkaline earth metal salts of the organic, anionic dyes is not sufficient to set the concentration of sulfate ions to less than or equal to 0.1 g / l. In many cases, however, to re-sharpen the dyebaths, it is sufficient to use the barium salts of the dyes directly without the need for further addition of water-soluble alkaline earth metal salts.
• the process is characterized in that mono, bis, polyazo dyes, metal-complex azo dyes, phthalocyanine dyes, quinophthalone dyes, azine dyes, xanthene dyes, nitro, nitroso dyes, di- as organic anionic dyes and / or their alkaline earth metal salts. , Triphenylmethane dyes, indigoid dyes, methine dyes, anthraquinone dyes or mixtures thereof.
• xanthene dyes show a strong sensitivity to the presence of sulfate ions in the dyebath.
• the limit values for the sulfate sensitivity in the dyes are of the order of 0.1 g / l. According to the invention, this means that at concentrations of more than 0.1 g / l there is insufficient coloring of the anodically produced surface for industrial use. It is believed that this sulfate sensitivity has hitherto hindered the widespread use of adsorptive staining with xanthene dyes.
• xanthene dyes are selected from fluorescein, eosin, 2,7-dichlorofluorescein, eosin scarlet, 4,5,6,7-tetrachlorofluorescein, cyanosine, calcein, 4-aminofluorescein, 4,5-diiodofluorescein , 4,5-dibromofluorescein, 5-aminofluorescein, methyleosin and / or erythrosin or their alkaline earth metal salts.
• alkaline earth metal salts of the above-mentioned dyes can be used, it is usually necessary to use additional alkaline earth metal salts which have a particularly low solubility product in the formation of alkaline earth metal sulfates.
• the process for adsorptive dyeing is characterized in that water-soluble calcium, strontium and / or barium salts are added to the dye bath or the dyes in the form of their calcium, strontium and / or barium salts together with other water-soluble alkaline earth metal salts starts.
• the use of the corresponding calcium salts is less preferred if the dyes to be used have been found to be extremely sensitive to sulfate.
• the use of water-soluble barium salts is particularly preferred due to the solubility product of barium sulfate.
• a further embodiment of the present invention is characterized in that calcium salts are added to the dyebath. These are used in particular for less sulfate-sensitive dyes.
• the amount of barium salts to be used can be set extremely low if necessary. However, the minimum amount should be set so that the concentration of free sulfate ions in the dyebath is less than 0.1 g / l.
• the upper limit of the alkaline earth metal salts to be used is practically determined by the solubility of these salts in the dyebath.
• the alkaline earth metal salts in concentrations are used in which the alkaline earth metal salts do not dissolve. Rather, it is entirely possible within the scope of the present invention to blend the alkaline earth metal salts of the organic, anionic dyes with the corresponding organic anion dyes themselves in such a way that the object according to the invention is achieved.
• a depot effect is achieved by an excess of free alkaline earth metal ions in the dyebath. Larger amounts of free alkaline earth metal ions do not interfere with the dyeing process any more than the failed alkaline earth metal sulfates.
• alkaline earth metal salts Practically all water-soluble alkaline earth metal salts can be used as the alkaline earth metal salts to be added.
• the corresponding alkaline earth metal halides, nitrates, nitrites and / or acetates can be used here, inter alia, for the purposes of the present invention.
• the alkaline earth metal nitrates and / or acetates are preferably used.
• the organic anionic dye and / or their alkaline earth metal salts are used in an amount of 0.05 to 20 g / l in the dyebath.
• a preferred embodiment of the present invention consists in that the organic anionic dyes and / or their alkaline earth metal salts in an amount of 0.5 to 5 g / l.
• the pH of the adsorptive coloring is not critical. However, in order to keep the dyes in solution as salts, it is preferred according to a preferred embodiment of the present invention to adjust the pH in the range from 1 to 8. In a preferred embodiment of the present invention, a pH in the range from 3 to 8 is set.
• the temperature during the coloring in the range from room temperature to the boiling point, preferably in the range from 40 to 70 ° C.
• the oxide layers are subjected to generally known compression processes. During this compression, anhydrous Al2O3 turns into hydrate, which takes up a larger volume and thereby closes the pores. The subsequent compression essentially prevents leaching out of the paint, at the same time improves the light fastness and also generally increases the corrosion resistance of the layer.
• a preferred embodiment of the present invention consists in compacting the colored surfaces of aluminum and / or aluminum alloys.
• the oxide layer is usually first electrolytically pre-colored in a light to dark bronze tone and then directly over-colored with the organic, anionic dyes and / or their alkaline earth metal salts in a second bath.
• Two different, coloring, real substances - deposited metal and dye molecule lie on top of each other in the layer and do not interfere with each other.
• the layers are as hard as in the case of electrolytic coloring.
• the dyeings are carried out by methods known per se, for example by dipping or spraying.
• the name of the aluminum alloy is given in accordance with DIN 3315, material no. 3; AlMg 1 was used.
• the sheets are degreased in an aqueous solution consisting of 5% P3-Almeco R 18 (alkaline cleaner containing borates, carbonates, phosphates and nonionic surfactants) at a temperature of 70 ° C. It was then pickled in a long-term pickle using 112 g / l of dissolved aluminum and 80 g / l of NaOH using P3-Almeco R 46 (pickling agent containing alkali, alcohols and salts of inorganic acids). P3-Almeco R 46 was dosed in a ratio of 1: 6 to NaOH. At 65 ° C was about 15 min. stained.
• P3-Almeco R 18 alkaline cleaner containing borates, carbonates, phosphates and nonionic surfactants
• Bath composition 200 g / l sulfuric acid, 10 g / l aluminum; Air injection 8 m3 / m2h; Temperature: 20 ° C DC voltage: 15 V.
• the anodizing time was about 3 min per ⁇ m layer build-up; i.e. the total anodizing times for the oxide layers of approximately 20 ⁇ m given in the examples below were approximately 45 to 70 minutes.
• the colored surfaces were compacted in a water bath at temperatures of about 96 to 98 ° C.
• Example 1 shows the influence of the sulfate sensitivity when using fluorescein sodium.
• 0.1 g / l sulfate ions no disturbing influence is noticeable.
• a significantly lighter color is obtained.
• Example 2 The comparison of Example 2 with Comparative Examples 2a, 2b and 2c confirms the sulfate sensitivity when stained with eosin yellowish; a concentration of less than 0.1 g / l is regarded as the limit for the maximum amount of sulfate ions in the dyebath. It was also proven that barium ions do not negatively influence the color.
• Example 3 The comparison of Example 3 with Comparative Examples 3a, 3b and 3c gives a limit value for the maximum sulfate ion concentration of less than 0.1 g / l of sulfate ions.
• barium salts do not negatively influence the color.
• the anodized aluminum sheet was not colored at a pH of 7.2 over a period of 15 minutes at a temperature of 60 ° C. .
• Examples 4, 4a and 4b as well as comparative example 4 show in particular the depot effect of a large alkaline earth metal ion concentration. It can also be seen that a Large amounts of free alkaline earth metal ions or alkaline earth metal salt deposits in the dyebath have no disruptive influence.
• a red coloration of an anodized aluminum sheet was produced using the dyebath according to Example 5 with the further use of 5.0 g / l ammonium sulfate under the above-mentioned conditions.
• Examples and comparative examples 5 show in an impressive manner the dependence of the quality of the color coating on the sulfate ion concentration. While in Example 5c the sulfate ion concentration is sufficient to influence the competitive adsorption of sulfate ions and dye molecule accordingly, an excellent color can be observed again by adding alkaline earth metal salt as in Example 5d.

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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)
• General Chemical & Material Sciences (AREA)
• Coloring (AREA)

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• 1988
  • 1988-07-25 DE DE3825213A patent/DE3825213A1/de not_active Withdrawn
• 1989
  • 1989-07-17 EP EP89113100A patent/EP0355390A1/fr not_active Withdrawn
  • 1989-07-17 KR KR1019900700624A patent/KR900702086A/ko not_active Application Discontinuation
  • 1989-07-17 AU AU39763/89A patent/AU3976389A/en not_active Abandoned
  • 1989-07-17 WO PCT/EP1989/000835 patent/WO1990001079A1/fr unknown

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