CH645409A5 - METHOD FOR COLORING OXIDE LAYERS OF ALUMINUM OR ALUMINUM ALLOYS WITH ORGANIC COMPOUNDS. - Google Patents

Description

The present invention relates to a method for coloring oxide layers of aluminum or aluminum alloys with organic compounds.

Aluminum or aluminum alloys are often used for signs, scales, front panels, etc. As a rule, the homogeneity and porosity of the artificially created oxide layers are used. Dyes can be stored in the pores and the homogeneity guarantees a clean, uniform appearance of the colored oxide layer. The pore openings can be closed by a simple post-treatment (sealing). The oxide layer is treated with boiling water, for example. In this treatment, the aluminum oxide usually absorbs water molecules in its crystal lattice and increases in volume, which closes the pores. Since this process is generally irreversible, any dye stored in the pores is excellently protected.

In order to color an oxide layer, it is generally brought into contact with the solution of the desired suitable dye and allowed to soak up. Other methods use e.g. colored metal oxides, which are generated either during the oxidation of the aluminum or afterwards in the layer. However, processes are also known, for example, for evaporating dyes into the layer.

There are many ways to create patterns in the layer that are generally required for signs. On the whole, one can distinguish two groups: the direct and the indirect method.

In the direct method, the color, usually thickened with a colloid, is applied directly to the oxide layer, e.g. in offset or screen printing.

With the indirect method, a template is usually applied to the oxide layer, which covers the areas not to be treated. You can basically use the positive and negative method, i.e. either cover the areas not to be colored and then apply the paint, or first color the entire layer and cover the areas that are to remain colored and decolorize the rest, for example by etching or destroying the dye. The template can also be applied e.g. done in offset or screen printing.

By repeating the workflow, both methods - both direct and indirect - can usually also achieve multicolored effects. Combinations of both methods are generally possible.

The ink or stencil is generally applied using mechanical printing aids. But since the latter usually require a printing form, e.g. Screen, offset printing plate, stamp, etc., the production of which is quite complex, photographic printing methods are generally preferred for smaller series.

For the indirect method one uses e.g. a photoresist whose solubility is changed by the influence of light in certain solvents. E.g. If an anodized aluminum plate coated with it is exposed under a negative or positive and then washed with a suitable solvent, the washed-out areas are exposed and can be colored. For the direct method one uses e.g. the property of silver salts to be reduced after exposure to light from certain chemicals and thus to produce a silver picture. Methods with other light-sensitive metal salts are also known, for example.

For example, it is also known that various azo dyes are suitable for coloring artificial oxide layers of aluminum. Azo dyes are generally formed when diazo compounds are reacted with suitable organic compounds, known as couplers.

In contrast, the idea according to the invention of producing these dyes is new.

It has now been found a process for dyeing oxide layers of aluminum or aluminum alloys with organic compounds, which is characterized in that at least one diazo compound is introduced into pores of the oxide layer and with formation of a dye by external influences or with at least one further organic compound, which before or is introduced into pores after the diazo compound is reacted. The oxide layers are preferably produced artificially in the process according to the invention. The oxide layers treated in this way can then be rinsed and / or compacted again.

Before the dye is formed, the ability of at least one diazo compound in the oxide layer to form dyes can be changed by irradiation with electromagnetic waves, the wavelengths of which correspond to or are shorter than the infrared range. The radiation is preferably carried out with waves from the UV range.

The irradiation usually takes place after the introduction of at least one diazo compound, but before the initiation of the reaction.

The preferred artificial oxide layers of aluminum or aluminum alloys can be produced using known methods. The direct current sulfuric acid process is preferred; that is, the so-called GS process. In general, however, it is also possible to produce these oxide layers in other ways, e.g. with the sulfuric acid alternating current process, the chromic acid process, the Ematal process or also an electroless process, etc.

Commercial aluminum alloys or commercial aluminum can be used in the process according to the invention.

However, the quality suitable for anodic oxidation is preferably used.

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645 409

An example of diazo compounds which are used in the process according to the invention and with themselves, i.e. can be reacted by external influences such as temperature increase, radiation, change in pH, exposure to a gas, etc., and thereby form a dye, the diazo compound of l-amino-8-naphthol-3,6-disulfonic acid, the so-called H-acid.

However, diazo compounds which change during application to the oxide layer and form a dye can also be used in the process according to the invention.

However, the present invention also includes the possibility that at least one diazo compound introduced into the oxide layer is reacted with a so-called coupler, a dye being formed. Examples of suitable diazo compounds are the products A, C, HC-1, Y etc. from Kalle, Wiesbaden.

Examples of suitable couplers are the products 1, 5, 13, 38 etc. from Kalle, Wiesbaden.

Any diazo compound and any so-called coupler can be used in the process according to the invention.

Commercially available diazo salts, such as those e.g. used in the diazo type, implemented with the appropriate commercially available couplers.

The concentrations of the diazo compounds and the couplers, e.g. in the form of aqueous solutions, there are no limits. Usually the concentration chosen depends on the solubility of the diazo compound or the coupler, the desired color intensity of the resulting dye, the cost factor, etc.

With photosensitive diazo compounds, it is generally advantageous to work in dim light so that the diazo compounds are not changed.

In general, the diazo compound and then the coupler are placed in the oxide layer; however, the reverse order is usually also possible.

One of the two components mentioned above can therefore be introduced into the oxide layer and the other component, e.g. allow it to act as a solution or gas from the outside, in which case the azo dye is formed in the oxide layer.

Since the coupling of the two components often only takes place in certain pH ranges, you can also incorporate both components into the layer if you make sure that their pH is outside the coupling ranges.

In this case, the dye is formed as soon as the pH value is caused by external influences, e.g. Ammonia or hydrogen chloride atmosphere, etc., moves into the coupling area. The coupling usually takes place in the alkaline range. The reaction in the pores is usually instantaneous; however, in some cases it can extend over a longer period of time.

The components can be applied, for example, as follows; Application with a cotton ball, immersion in solutions, spraying with a spray gun, pouring on with a pouring machine, rolling on with a rolling machine, etc.

The method according to the invention is normally carried out at atmospheric pressure and ambient temperature. Depending on the circumstances, higher or lower temperatures can also be used.

As explained above, the treated oxide layer can also be rinsed. This generally has the advantage that the soluble constituents, which do not form the dye, are washed out and a subsequent reaction, such as darkening or decomposition of the dye, etc., can be avoided.

As explained above, the treated oxide layer can also be further compacted. The advantage of post-compaction is generally that the surface is insensitive to dirt and protected from washing out the paint or paints because the pores are closed. The densification can be achieved, for example, by waxing in, painting, i.e. through paint protection, impregnation with a water-repellent agent, e.g. Silicone, treatment with boiling water, treatment with at least one aqueous solution of suitable chemical compounds, e.g. Nickel acetate, cobalt acetate, etc. The densification is preferably carried out by treatment with boiling water.

An advantage of the present invention is

that one can coat the oxide layers with one component and by choosing the second one it is in the hand to produce different colors.

Another advantage is the possibility of producing insoluble azo dyes (pigments) in the oxide layer, which can prove to be a great advantage in further processing, e.g. Weather fastness, bleeding in sealing, etc.

Many diazo salts are generally light sensitive, i.e. they lose their ability to form azo dyes with couplers when exposed to light. This principle has long been used in the diazo type, for example:

A paper coated with a photosensitive diazo salt is usually exposed under a positive and then reacted with a coupler.

As mentioned above, exposure to electromagnetic waves can alter the ability of at least one diazo compound in the oxide layer to form dyes.

If, according to the present invention, a suitable diazo salt is introduced into the oxide layer, fully or partially exposed under a positive and reacted with a coupler, a colored image of the positive generally arises because the diazo salt and its are destroyed in the exposed areas Loses ability to form azo dyes with couplers.

UV light is preferably used for the irradiation. Actinic tubes, quartz lamps, arc lamps, xenon lamps or daylight are preferably used as light sources for the radiation.

There are usually no limits to the possible combinations between the diazo compounds, the couplers and the radiation; for example, it is possible first to store the diazo compound in the oxide layer, to change it in the desired manner with the irradiation, and then to allow the compound thus obtained to react with the coupler. However, it is also possible to introduce both components into the oxide layer and then to carry out the irradiation. As mentioned above, many other possible combinations for color formation can be used in the method according to the invention.

By irradiating the diazo compounds embedded in the oxide layer, e.g. Patterns, characters or images can be generated. The products thus produced can be used as signs, front panels, scales, circuit diagrams, traffic signs, identity cards, etc.

The shelf life of these products manufactured with the method according to the invention corresponds at least to a normal anodized sign quality, but as a rule exceeds this by far.

The present invention can be further explained using the following examples:

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example 1

A previously chemically matted sheet of aluminum or an aluminum alloy, which is suitable for decorative anodic oxidation, was anodized in the usual direct current sulfuric acid process under the following conditions:

Electrolyte sulfuric acid 180 g / 1 electrolyte

Aluminum 5-15 g / 1 electrolyte

Temperature 19-22 ° C

Current density 1.5 A / dm2

Duration 30 min.

After the oxidation, the sheet was post-treated in 15 to 20 percent nitric acid for 5 minutes, rinsed and dried.

A solution of real blue salt BB (diazotized 4-amino-2,5-diethoxy-anilide zinc double salt) 10 g was carried with a cotton ball

Acetic acid about 90% to 100 ml for 1 min on the oxide layer. Afterwards one dried and dried with a warm air device. A positive was placed on the sheet and exposed from a distance of 60 cm with a quartz lamp for 30 seconds.

The exposed sheet was in a solution of phloroglucin 5 g dist. Water to 100 ml

Ammonia solution 25% to pH 10

submerged. The picture immediately appeared black-brown on a light background. The sheet was then rinsed thoroughly with water and subjected to the usual post-compression (“sealing”) with warm water at 96 to 100 ° C. for 30 minutes.

Example 2

A sheet was treated in accordance with Example 1, but after exposure was immersed in the following solution: 2,3-naphthoic acid-morpholinopropyl-amide (Kalle, Wiesbaden:

Coupler 38) 3 g

Distilled water to 100 ml

Ammonia solution 25% to pH 10

A violet picture immediately appeared, which after the subsequent watering and sealing lost its red cast in favor of blue.

Example 3

A sheet anodized according to example 1 was coated with the following solution:

4-diazo-dimethylanaline zinc chloride (Kalle, Wiesbaden: Diazo A) 5 g hexylresorcinol 5 g

Acetic acid about 90% 30 g

Methyl alcohol to approx. 100 ml

After 30 seconds the sheet was rubbed dry with a dry cotton ball. The exposure was carried out under a positive as described in Example 1. The exposed sheet was covered with a flow paper, which was impregnated with subsequent solution and then dried well. Ammonium bicarbonate 10 g

Polyvinyl alcohol (M4 / 88 Hoechst) as a 10% solution in ethanol 1 ml

Ammonia solution 25% 20 ml dist. Water to 100 ml

The whole was pressed together for 20 seconds with a heating plate heated to about 120 ° C (e.g. iron). The image developed dark brown, but took on a khaki brown color during the subsequent rinsing, which it retained even after sealing.

Example 4

A sheet pretreated and anodized according to Example 1 was poured with the following solution: 2,4,2 ', 4'-tetraoxy-diphenyl sulfide 5 (Kalle, Wiesbaden: Coupler 2) 4 g of 4-diazo-2-methylphenyl pyrrolidine ZnCh

(Kalle, Wiesbaden: Diazo Y) 6 g thiourea 4 g

10 acetic acid approx. 90% 5 ml

NaHS03 solution in methanol saturated 5 ml butyl glycol 15 ml

Methanol to 100 ml

After drying, exposure was carried out as in Example 1, but the exposure time was 1 minute instead of 30 seconds. The exposed sheet was then subjected to a one-minute heat treatment at 140 ° C. The result was a dark brown image, which was not changed by the subsequent rinsing and sealing.

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Example 5

An anodized, unsealed sheet with an oxide layer thickness of at least 18 µm was sprayed with the following solution:

25 4-Diazo-2,5-diethoxy-phenylmorpholine Zi ZnCh

(Kalle, Wiesbaden: Diazo HC) 10 g dist. Water to 100 ml

After drying, an acetate film was placed on it, which was poured over the following solution on the sheet side and then dried:

β-naphthylamine 5 g

Urea 10 g

Ethyl cellulose solution 10% in 35 ethanol 15 ml

Butyglycol 15 ml

Methanol to 100 ml

By squeezing with a heating plate (e.g. iron) heated to 120 ° C for 20 seconds, an orange color developed in the layer, which remained unchanged even after subsequent rinsing and washing.

Example 6

An anodized, unsealed sheet with a 45 oxide layer of at least 15 (the following solution was applied for 1 min (cotton ball): 4-diazo-diethylaniline ZnCh (Kalle, Wiesbaden: Diazo C) 10 g urea 5 g

50 least Water to 100 ml

Then it was stripped with a sharpened rubber squeegee and dried. After the exposure, the sheet was covered with an acetate film, the side of which facing the sheet was prepared as follows: Over-55 pour with the following solution:

1,8-naphthylenediamine 5 g

Ethyl cellulose solution 10% in ethanol 15 ml

Butyl glycol 10 ml

60 methanol to 100 ml and let dry well. A hot plate (e.g. iron) at 130 ° C was pressed onto the film for 20 seconds. The image developed red in the unexposed areas. This fatbe remained unchanged during the subsequent rinsing with 65 water and the sealing.

Example 7

A sheet was treated as in Example 6, but on

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Instead of the film from Example 6, a piece of film from Example 5 was used, which had not yet been subjected to the heat treatment. The result was an orange picture that survived all post-treatments without damage.

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Example 8

A sheet pretreated and anodized according to Example 1 was coated with a solution of the following composition for 1 minute:

4-diazo-diethylaniline ZnCh 10 g 10

2,5-dimethyl-4-dimethylaminomethyl

phenol HCl

(Kalle, Wiesbaden: Coupler 13) 6 g dist. Water to 100 ml and then rubbed dry '5 with a dry cotton ball. After exposure under the positive (according to Example 1), the Bl.ech was placed in a closed container in which 25 percent ammonia solution evaporated in an open dish. The evaporated ammonia gas shifted the pH of the diazo coupler mixture towards the 20 coupling area (from acidic to alkaline). A yellow image of the positive emerged in a short time. After 5 minutes the sheet was removed from the container, rinsed and sealed.

Example 9

An anodized, unsealed sheet with an oxide layer thickness of at least 15 μm was coated with the following solution for at least one minute: 4-diazo-dimethylaniline zinc double salt (Kalle, Wiesbaden: Diazo A)

Sodium salt of 2 g

2,7-dioxynaphtalin-3,6-disulfonic acid (Kalle, Wiesbaden: Coupler 5) 4 g of dist. Water to 100 ml and then stripped with a sharp rubber squeegee and dried. Exposure and development was carried out in accordance with Example 8.

After development in the ammonia atmosphere, the image of the positive was blue; purple after sealing.

Example 10

A sheet was treated according to Example 8, but in the end instead of the sealing according to Example 9, it was coated and processed again. The sign was then 3 colors. After the sealing, the colors were yellow (solution from Example 8), violet (Example 9) and light brown (at the points where the two colors overlapped).

Claims (6)

645 409 1. A method for coloring oxide layers of aluminum or aluminum alloys with organic compounds, characterized in that at least one diazo compound is introduced into pores of the oxide layer and with formation of a dye by external influences or with at least one further organic compound which is in before or after the diazo compound Pores is introduced, is reacted. 2. The method according to claim 1, characterized in that artificially produced oxide layers are used. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that the oxide layer treated in this way is then rinsed and / or post-compressed. 4. The method according to claim 1, characterized in that before the formation of the dye by irradiation with electromagnetic waves whose wavelengths correspond to the infrared range or are shorter, the ability of at least one diazo compound in the oxide layer to form dyes is changed. 5. The method according to claim 4, characterized in that the radiation takes place in the UV range. 6. The method according to claim 4, characterized in that the radiation after the introduction of at least one diazo compound but before the initiation of the reaction.