CN113348271A

CN113348271A - Surface treatment of anodized aluminum

Info

Publication number: CN113348271A
Application number: CN202080010289.9A
Authority: CN
Inventors: P·沃尔克; S·埃舍尔
Original assignee: Freudenberg SAS
Current assignee: Freudenberg SAS
Priority date: 2019-01-21
Filing date: 2020-01-17
Publication date: 2021-09-03
Also published as: EP3914755A1; WO2020152047A1; DE102019101449A1

Abstract

The present invention relates to a method for surface treatment of anodized aluminum, anodized aluminum treated according to the method, a treating agent for surface treatment of anodized aluminum, and use of the treating agent.

Description

Surface treatment of anodized aluminum

Technical Field

Background

Corrosion is a problem in the manufacture, processing and use of articles containing aluminum.

In order to protect and mechanically stabilize the aluminum surface, it is electrochemically treated by anodization, in which the naturally occurring oxide layer on the aluminum metal is artificially enhanced or replaced (anodization). The aluminium parts may be pretreated, i.e. degreased and pickled, before the actual anodizing. In this case, only a thin native oxide layer is also removed. Different types of anodized layers are known depending on the manufacturing conditions and the aluminum alloy.

The industrial anodic oxidation layer is at room temperature and about 1 to 2A/dm²Is prepared in a sulfuric acid, oxalic acid, phosphoric acid, acetic acid or boric acid electrolyte, for example. Anodized surfaces are generally colorless and protect aluminum from corrosion and scratching to some extent compared to untreated surfaces.

The current density for preparing the hard anodized layer is higher than that of the conventional anodic oxidation, for example, about 2-5A/dm². Due to the high amperage required, the electrolyte must be cooled to prevent overheating of the components. Suitable electrolytes are sulfuric acid and sulfuric acid-containing acid mixtures. Compared to industrial anodization, hard anodized layers are characterized by particularly improved wear and scratch resistance.

The third method is bright anodizing. In this method, the metal surface is given a high gloss by treatment in a special chemical or electrochemical polishing bath before anodizing. For example, in the case of chemical polishing, the aluminum surface is pickled on an acidic basis, wherein the aluminum is removed.

The anodized layer has a porous structure with pore sizes that depend on the electrolyte and process parameters selected. Dyes or other substances may optionally be embedded in these pores. The openings of the holes may be closed by compaction in an aqueous solution (hot or cold compaction) in order to constrain the embedded dye and/or prevent the embedding of corrosion-promoting substances. Hot compaction is performed by treatment with water at temperatures of 95-100 ℃, and is therefore associated with high energy consumption. In this case, alumina hydrate (diaspore) is formed in the pores. In the case of cold compaction, the closing of the pores can be carried out at a lower temperature of about 30 ℃ and thus shows improved energy efficiency with respect to hot compaction. In this case, the treatment is usually carried out with nickel, cobalt or chromium compounds. For example, in cold pressing with nickel and fluoride salts, nickel hydroxide is embedded in the pores and fluoride reacts with the anodized aluminum oxide to produce aluminum fluoride. The disadvantage of cold compaction is the use of toxic compounds, such as nickel salts, which are furthermore carcinogenic and allergenic.

The anodization and subsequent compaction do improve the corrosion resistance relative to bare aluminum. However, this method still remains to be improved in various aspects. In conventional hot compaction, the energy consumption is very high due to the high processing temperature. Furthermore, conventional hot compaction may lead to dye out-diffusion in the case of dyed aluminum oxide layers. As mentioned above, known methods for cold compaction require the use of heavy metal salts, such as nickel salts. Furthermore, it is not known from the prior art that the sealing of the surface of the anodized layer of aluminum is subsequently carried out by compacting in an immersion bath, in order to carry out the surface treatment of the aluminum efficiently with less equipment and energy.

Various solutions for optimizing the corrosion resistance of metal surfaces are known from the prior art.

US 2005/0126427 describes a composition for treating metal surfaces and a method for depositing a metal or metal alloy on a plastic surface. The composition comprises an amino-containing polymer, water and other surface active compounds. The composition of US 2005/0126427 is particularly useful for passivating aluminium surfaces. As passivation method, only phosphatization is mentioned, i.e. the application of a phosphate layer on the metal to be treated. There is no mention of passivating the aluminum surface by a hot compaction process.

EP 0490231 describes the use of polyethyleneimine derivatives and polyvinylamine derivatives as coatings for aluminum-based support materials. The support material is used for producing offset printing plates. The polyethyleneimine derivatives and polyvinylamine derivatives are located in intermediate layers between the support material and the positive, negative or electrophotographically working photosensitive layer. The photosensitive layer must then be removed from the carrier without residues.

The aluminium oxide layer may be coloured to obtain a decorative effect. Generally, a distinction is made between adsorption dyeing, electrolytic dyeing and mass dyeing (anodic oxidation dyeing).

In organic dye adsorption dyeing, the anodized aluminum surface is immersed in a dye solution. Here, the dye molecules accumulate mainly in the upper region of the pores of the anodized layer and interact with the oxidized layer. The higher the concentration of dye in the solution, the more pronounced the intercalation of the dye in the pores of the oxide layer.

Electrolytic dyeing is carried out using an alternating voltage. The electrolyte comprises a non-ferrous metal salt, such as tin (II) sulfate. The duration of the treatment depends on the desired color depth. The metal ions penetrate deep into the pores of the layer. The partially metal-filled pores now produce a fast color through absorption and scattering effects. Many different hues may be achieved.

Unlike the above dyeing method, in the interference dyeing method, the color of the alumina surface is not generated by the embedded foreign ions but by the interference inside the alumina layer. Depending on the layer thickness of the oxide layer and the associated extinction, different colors (e.g. blue, green, grey or red) can be reproducibly displayed.

There remains a need for improved immobilization and stabilization of the colored aluminum oxide layer produced by the anode. Thus, for example, it is known that in adsorption dyeing, adsorbed dyes are electrostatically bound to the oxide surface. The dye can be easily removed from the uncompacted layer with water (dye bleed). Therefore, after the coloring of the anodized layer, it is hot-compacted with water at a temperature of 95 to 100 ℃. However, there is also the problem here that the dye insufficiently fixed on the oxide surface may diffuse out of the anodized layer.

The object of the present invention is to provide a surface treatment method which fixes a dye in an anodized layer in the case of coloring the anodized aluminum layer, thereby preventing the dye from bleeding out (out-diffusion) during compaction.

Another object of the present invention is to provide a further improved method for surface treatment, i.e. a method that can be performed in only one bath and/or that requires less energy to hot compact the anodized surface.

It has surprisingly been found that this object is achieved by the process for the surface treatment of anodized aluminum with a specific treatment agent, the treatment agent and the use thereof according to the invention.

The method according to the invention and the treatment agent used therein have the following advantages:

the treatment agent is free of heavy metals, such as nickel,

-the treatment agent is fluoride-free,

the method is well suited for fixing dyes on the surface of anodized aluminum,

one-pot methods (one bath, less cost and effort) can be used,

said method is suitable for warm compaction at temperatures significantly below 100 ℃ (energy saving).

Disclosure of Invention

A first object of the present invention is a method for surface-treating anodized aluminum oxide with a treating agent comprising an amino group-containing compound having at least two amino groups, the method comprising the steps of:

i) contacting the surface of the anodized aluminum with the treatment agent, and

ii) compacting the surface of the anodized aluminum treated in step i).

The invention also provides a treated anodised aluminium prepared by a process according to the invention.

The invention also provides anodized aluminum treated with the treating agent used according to the invention.

The invention also provides a treating agent for use in the surface treatment of the anodized aluminum according to the invention.

The method according to the invention is advantageously used for fixing dyes on the surface of anodized aluminum. Furthermore, with the method according to the invention, the treatment step and the compacting step can be carried out in only one immersion bath (one-pot process), or the compacting temperature in the compacting step can be reduced.

Within the scope of the present invention, a "treatment step" is understood to mean bringing the surface of the anodized aluminum into contact with a treatment agent.

The term "anodic oxidation" (Eloxal) stands for the electrolytic oxidation of aluminum. Within the scope of the present invention, "anodized aluminum" is understood to mean aluminum whose surface has been electrochemically treated and forms an oxide layer. In other words, an electrochemically generated oxide layer has built up on the surface. Anodization using direct current, wherein the aluminum is switched to the anode, is also known as "anodizing" (anodising). The anodization is carried out according to methods known to those skilled in the art.

The aluminum may be surface pretreated prior to anodization. Suitable surface pretreatment methods are selected from degreasing, pickling, polishing and combinations thereof. Methods for surface pretreatment are known to those skilled in the art.

The anodization is usually carried out by means of direct current (anodizing), an alternating current method also being known. Sulfuric acid or sulfuric acid-containing acid mixtures or acids different therefrom, for example oxalic acid, phosphoric acid, tartaric acid or boric acid, are generally used as electrolytes. The anodic oxidation is preferably carried out at a temperature of about 0 to 50 c, particularly preferably 15 to 45 c. For example, a DC voltage of 5 to 50V, preferably 10 to 30V, is suitable. The anodization time was about 3min/μm layer structure. The oxide layer obtained generally has a layer thickness in the range from about 2 μm to 50 μm, preferably from 3 μm to 20 μm.

Within the scope of the present invention, "anodized aluminum", "anodized layer of aluminum", "aluminum oxide layer" are used synonymously.

The anodized aluminum may be colored after anodizing and before the surface treatment method according to the present invention. Alternatively, unpigmented anodized aluminum may be used for the surface treatment according to the invention.

Within the scope of the present invention, "compacting" is understood to mean treating the electrochemically generated oxide layer to close the openings of the pores. A distinction is made between hot compaction (which is usually carried out in hot water at 96-100 ℃) and medium-temperature compaction (which is likewise carried out in hot water at temperatures of usually 70- <95 ℃).

Compaction methods are known from US 3,257,244, US6,447,665 and US6,059,897. Reference is made to these documents in their entirety.

Step i)

In step i) of the method according to the invention, the surface of the anodized aluminum is contacted with a treatment agent comprising an amino-containing compound.

The amino group-containing compound preferably has at least two amino groups. The amino groups are selected from primary and secondary amine groups. Low molecular weight amino-containing polymer compounds and mixtures thereof are suitable.

Preferably, the low molecular weight amino group-containing compound has a molecular weight of 100 to 300g/mol, preferably 100 to 200 g/mol.

Preferably, the molecular weight of the polymeric amino compound is from 301 to 10000g/mol, preferably from 350 to 4000 g/mol.

Suitable compounds are in principle amino-containing linear, branched or cyclic compounds having at least two primary amino groups. Preference is given to compounds having at least two primary amino groups and one secondary amino group. Furthermore, these amino group-containing compounds may have a tertiary amino group and/or a quaternary amino group.

Amino group-containing compounds having at least three amino groups, preferably 3 to 100 amino groups, are preferably used. The weight-average molecular weight of the amino-containing compounds used according to the invention is generally from 100 to 10000g/mol, preferably from 100 to 4000g/mol, in particular from 100 to 3000 g/mol. The amino-containing polymer compounds may also be crosslinked so that in some cases no molecular weight can be specified, although the polymers can be dispersed, emulsified or suspended in solvents which are common in industry. The determination of the weight average molecular weight is familiar to the person skilled in the art and is carried out, for example, by size exclusion chromatography or gel permeation chromatography (SEC/GPC) with the aid of customary detectors, for example concentration detectors (conventional calibration) or detectors (universal calibration and triple detection). For example, it is suitable to use light scattering detectors, such as differential refractometer Agilent 1100 with UV photometer Agilent 1100 VWD and light scattering detector Wyatt Dawn EOS.

In a preferred embodiment, the amino-containing compound is present in the treating agent completely or partially protonated. Protonation is understood to mean that at least a portion of the groups of the amino-containing polymer compound are protonated, preferably at least 20 mol%, preferably more than 50 mol%, particularly preferably more than 70 mol%, most preferably more than 90 mol%, so that the total cationic charge of the amino-containing polymer compound is obtained.

Examples of suitable protonations are mineral acids, monocarboxylic acids, dicarboxylic acids and polyfunctional carboxylic acids and all other proton-releasing compounds and substances which are capable of protonating the corresponding nitrogen atom. In particular, water-soluble acids are suitable for protonation. Suitable inorganic acids are, for example, hydrochloric acid, sulfuric acid, phosphoric acid, phosphorous acid and sulfurous acid, boric acid. Suitable monocarboxylic acids are, for example, formic acid and acetic acid. Suitable dicarboxylic acids are, for example, oxalic acid, citric acid, lactic acid, tartaric acid.

Preferably, the amino-containing polymer compound has a charge density of at least 1meq/g (pH 2), preferably in the range of 1.5meq/g to 35meq/g (pH 2), preferably in the range of 5 to 30(pH 2).

Preferably, the amino-containing compound has a charge density of at least 1meq/g (pH 2), preferably in the range of 1.5meq/g to 35meq/g (pH 2), preferably in the range of 5 to 30(pH 2).

The charge density can be determined by titration with an oppositely charged compound, by measuring electrophoretic mobility and by determining the zeta potential by dynamic light scattering.

Preferably, the amino-containing compound is selected from the group consisting of low molecular weight polyamines, polyalkyleneimines, polyvinylamines, amino-modified polycarboxylic acids, polylysines, amine-terminated polyether polyols, end-group modified polyamines and copolymers, derivatives and mixtures thereof.

A preferred polyalkyleneimine is poly (C)₁-C₄Alkylene) imines, particularly preferably polyethyleneimines. It preferably has at least two alkyl units and three amino groups.

Suitable polyalkyleneimines are polymers having a main chain containing N atoms, which has primary amino groups at the ends of the chain and secondary and/or tertiary amino groups inside the polymer chain. A suitable embodiment is a linear polyalkyleneimine having only secondary amino groups within the polymer chain. Another suitable embodiment is a branched polyalkyleneimine having secondary and tertiary amino groups within the polymer.

The ratio of primary to secondary amino groups in the polyalkyleneimines is preferably at most 2.

Low molecular weight polyamines and polyethyleneimines are preferred.

Particularly preferably, the amino group-containing compound is selected from the group consisting of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, ethylenepropylenetriamine, triaminopropylamine, and higher polyethyleneimines.

In a particular embodiment, the amino-containing compound is selected from diethylenetriamine, triethylenetetramine, tetraethylenepentamine.

In another specific embodiment, the amino-containing compound is selected from polyethyleneimines.

The polyethyleneimine preferably has the following recurring units (I.1), (I.2) and (I.3)

Wherein,

x is from 1 to 250, preferably from 1 to 100, in particular from 1 to 70,

y is from 0 to 250, preferably from 0 to 100, in particular from 0 to 70;

z is from 2 to 300, preferably from 2 to 200, in particular from 2 to 100.

Suitable polyethyleneimines can be prepared by ring-opening polymerization of 2-alkyl-2-oxazolines and subsequent hydrolysis or by cationic initiated polymerization of ethyleneimine (aziridine). Preference is given to using polyethyleneimines which are prepared by cationically initiated polymerization of ethyleneimines. These have in particular a branched structure in which the proportion of primary and tertiary amino groups is about 30% each and the proportion of secondary amino groups is about 40%.

Preferred amino group-containing compounds are linear polyethyleneimines or low molecular weight polyamines. Preferred are linear polyethyleneimines or low molecular polyamines having the abovementioned recurring units (i.1), (i.2) and (i.3), where x is from 1 to 250, y is 0 and z is 2.

Preferred polyethyleneimines are obtainable, for example, from BASF SE under the name

G35 is commercially available.

Suitable polyvinylamines (polyaminoethylene) are the known products obtained by homo-or copolymerization of N-vinylformamide with subsequent partial or complete hydrolysis. Suitable processes for preparing polyvinylamines are disclosed, for example, in EP-A216387, DE-A3842820, DE-A19526626, DE-A19515943. In the poly (vinylformamide-co-vinylamine) polymer, the proportion of vinylamine repeating units (degree of hydrolysis) is generally from 0.5 to 100%, preferably from 50 to 100%.

Furthermore, derivatives of polyalkyleneimines and polyvinylamines having amino groups are also suitable, for example reaction products with carboxylic acids, sulfonic acids or carboxymethylation products.

Other suitable amino-containing compounds are amino-modified polycarboxylic acids. Preference is given to reaction products of diamines and polymers comprising, in copolymerized form, at least one acid-group-containing monomer. The monomers containing acid groups are selected, for example, from maleic acid, maleic anhydride, acrylic acid, methacrylic acid, ethacrylic acid, a-chloroacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid

Aconitic acid, fumaric acid and mixtures thereof. The acid group-containing monomer is preferably selected from the group consisting of maleic acid, maleic anhydride, acrylic acid, methacrylic acid and mixtures thereof. Preferred amino-modified polycarboxylic acids are the reaction products of styrene-maleic anhydride copolymers and diamines.

Other suitable amino-containing compounds are lysine, polylysine and polylysine derivatives. In the context of the present invention, the term "polylysine" refers to both crosslinked and uncrosslinked polymers (or oligomers) of lysine.

It contains the copolymerized amino acid lysine, which contains two amino groups, one on the a-carbon atom and one on the e-carbon atom. Polylysine preferably has a weight-average molar mass of 146 to 10000 g/mol. Preference is given to using polylysine having an average molar mass of from 146 to 5000g/mol, more preferably from 146 to 3000 g/mol. The amino units of lysine may be linked through the alpha and/or epsilon positions. The polymer chains can be cross-linked by lysine by reaction of two amino groups of a lysine unit, with the second amino group being condensed with another polylysine chain.

Depending on the reaction conditions, this type of crosslinking can occur during the preparation of polylysine. The preparation of polylysine is known and can be carried out, for example, by the methods described in JP 97-33122 or EP-A256423. In one embodiment of the invention, polylysine is used which is not crosslinked.

The term "polylysine derivative" denotes crosslinked and uncrosslinked copolymers or cooligomers of lysine with further monomers which are capable of reacting with lysine. The other monomers are preferably selected from the group consisting of monoamines, diamines and polyamines, monocarboxylic acids, dicarboxylic and polycarboxylic acids, monocarboxylic acids, esters of dicarboxylic and polycarboxylic acids, amides, halides and anhydrides, monoisocyanates, diisocyanates and polyisocyanates, alkyldiketones, lactones, lactams, amino acids and mixtures thereof. Such derivatives are described, for example, in US6111057 and US 6034204. Preferably, the polylysine derivative has a weight-average molar mass of 146 to 10000 g/mol. Preference is given to using polylysine derivatives having an average molar mass of from 146 to 5000g/mol, more preferably from 146 to 3000 g/mol. In the case of polylysine derivatives, the lysine units present may be linked via the amino groups in the alpha and/or epsilon positions. In particular in the case of higher molecular weight polylysine derivatives, the polymer chains can be crosslinked by lysine and/or by additionally present monomers, wherein in the case of crosslinking by lysine units the two amino groups of lysine react and/or in the case of crosslinking by additionally present monomer units the second functional group of the monomer reacts with another chain of the polylysine derivative. Depending on the reaction conditions, this type of crosslinking can take place during the preparation of the polylysine derivative. In one embodiment of the invention, non-crosslinked polylysine derivatives are used.

Suitable polylysines and polylysine derivatives may also be alkoxylated (see WO00/71601)

And optionally crosslinked (see WO 00/71600).

Suitable amine-terminated polyether polyols are at least one polyol with at least one C₂-C₁₈Alkylene oxide to form the reaction product of an alkoxylated polyol and an aminated alkoxylated polyol.

Suitable end-group-modified polyamines are polyether-terminated polyamines, with C₁-C₁₈-alkyl-modified polyamines or polyethylene-modified polyamines.

In a preferred embodiment, the treating agent used in the method of the present invention comprises as amino group-containing compound a low molecular weight polyamine, a polyethyleneimine, a polyvinylamine, and mixtures thereof. Particularly preferably, the treating agent comprises only polyethyleneimine as the amino group-containing compound, a low molecular weight polyamine, a polyvinylamine, and a mixture thereof. In particular, the treating agent comprises only low molecular weight polyamines or polyethyleneimines as amino-containing compounds and mixtures thereof.

In a preferred embodiment, the pH of the treatment agent is in the range of 5.5 to 8.0, preferably in the range of 5.8 to 7.0.

If the pH of the treatment agent is less than 5.5, the pH can be adjusted to the preferred pH range with the aid of a suitable base.

If the pH of the treatment agent is greater than 8.0, the pH can be adjusted to the preferred pH range with the aid of a suitable acid.

Suitable acids and bases are known to those skilled in the art.

In a preferred embodiment, the treating agent comprises an amino-containing compound at a concentration of 0.022 to 2.5g/L, preferably 0.05 to 1.0 g/L.

In a preferred embodiment, the treatment agent comprises

a)0.001 to 0.5% by weight, preferably 0.002 to 0.1% by weight, of an amino-containing compound

b)0.1 to 10% by weight, preferably 0.5 to 2% by weight, of a buffer,

c)0 to 2% by weight, preferably 0.5 to 1.5% by weight, of additives.

d) Water was added to 100 deg.f.

Suitable buffers are ammonium acetate or alkali and alkaline earth metal acetates. Common buffer systems are known to those skilled in the art.

Suitable additives are selected from the group consisting of biocides (Bioziden), coating inhibitors (BelagsVerhidender), corrosion inhibitors, wetting agents, solubility promoters, organic solvents, electrolytes, pH adjusters, antistatic agents, complexing agents, UV absorbers and mixtures thereof.

The biocide used is preferably formaldehyde-free.

Suitable coating inhibitors are, for example, low molecular weight and polymeric phosphonates or carboxylates.

The contacting of the surface of the anodized aluminum with the treating agent in step i) of the process according to the invention is preferably carried out by completely wetting the entire surface with the treating agent. Preferably, the surface of the anodized aluminum is contacted with the treating agent by immersing the anodized aluminum in an immersion bath containing the treating agent as defined above.

The contact time (bath time) is at least 0.2min, preferably 1 to 5 min. The maximum contact time is generally not critical and preferably does not exceed 60 min.

The temperature of the treating agent in step i) is preferably in the range of 15 ℃ to 50 ℃, preferably 20 ℃ to 35 ℃.

In a preferred embodiment, the anodized aluminum used in step i) is uncolored.

In a further preferred embodiment, the anodized aluminum is colored prior to the surface treatment in step i). Preferably, the anodized aluminum oxide is subjected to adsorption, electrolysis or interference coloration. In a particular embodiment, in step i), the surface of the adsorbed coloured anodized aluminium is contacted with a treatment agent.

The coloration of the anodized aluminum is carried out by methods known to those skilled in the art.

In adsorption coloration, for example, an organic dye is introduced into the openings of the pores of the oxide layer, wherein the organic dye remains adsorbed in the surface region of the surface. By means of the method, a broad spectrum with great homogeneity and reproducibility can be obtained.

The coloring may also be performed by so-called color anodization (whole color anodizing treatment). In mass-colored anodized aluminum, finely distributed inorganic pigment particles are not present in the pores of the oxide layer, but remain in the aluminum oxide layer as an alloy component. In this case, the anodic oxidation and the coloration of special aluminum alloys are usually carried out in only one process step using a direct voltage of up to 150V, using suitable organic acids, such as maleic acid, oxalic acid, sulfosalicylic acid or sulfophthalic acid, as electrolyte. However, for cost reasons (high energy consumption, complex cooling devices), the overall method is used less and less in practice.

In contrast, in the case of electrolytic coloring with the aid of metal salt solutions, the coloring of the colorless transparent oxide layer is carried out in a first step by anodic oxidation using direct current in an aqueous sulfuric acid solution and/or other electrolyte solutions, and subsequently in a second step (unlike adsorption dyeing) by depositing metal particles in the metal salt solution on the bottom of the pores of the oxide layer by alternating current. The colors range from light bronze to dark bronze to black. By deposition at the bottom of the pores, a fully lightfast color can be obtained.

The coloration of the anodized aluminum is preferably carried out by electrolytic or adsorptive coloration or a combination of these methods.

In the absorption dyeing process, the anodized aluminum is immersed, together with the not yet compacted anodized layer, in an aqueous dye bath containing dissolved organic dyes.

Preferably, in step i) of the process according to the invention, previously adsorbed coloured anodized aluminium is used.

In a specific embodiment, the anodized aluminum oxide is dyed with an organic anionic dye.

Suitable organic anionic dyes are selected from the group consisting of monoazo dyes, disazo dyes, polyazo dyes, metal complex azo dyes, phthalocyanine dyes, quinophthalone dyes, azine dyes, xanthene dyes, nitro dyes, nitroso dyes, diphenylmethane dyes, triphenylmethane dyes, indigo dyes, methine dyes, anthraquinone dyes, alkaline earth metal salts thereof and mixtures thereof. Suitable dyes are commercially available, for example from Okuno or Omya.

Step ii)

In step ii), the surface of the aluminium treated in step i) is compacted.

The compaction may be performed according to methods known in the art, for example: as described in US 3,257,244, US6,447,665 and US6,059,897.

The compaction in step ii) is preferably carried out at a temperature of 70 to 100 ℃, preferably 75 to 96 ℃.

In a preferred embodiment, in step ii), the surface of the aluminum treated in step i) is subjected to a hot press. The hot compaction is carried out at a temperature of preferably 70 to 100 ℃ and particularly preferably 96 to 100 ℃.

In another preferred embodiment, in step ii), the surface of the aluminium treated in step i) is subjected to warm compaction. The warm compaction is carried out at a temperature of preferably 70 to 100 ℃ and particularly preferably 75 to 96 ℃.

The compaction time is at least 1 min/. mu.m, preferably 3 min/. mu.m. The maximum compaction time is generally not critical and is preferably at most 5 min/. mu.m.

The compaction in step ii) is preferably carried out in an aqueous solution.

In addition to water, suitable aqueous solutions may contain at least one additive that is soluble under the treatment conditions.

Suitable additives are buffers such as acetates, aluminum hydroxide, polyacids, stabilizers, urea and optionally others.

Steps i) and ii) are carried out in at least one immersion bath.

In a preferred embodiment a, steps i) and ii) are carried out in two baths which are separate from one another. In bath 1, step i) was performed as described above. In bath 2, step ii) is carried out as described above. Preferably, the temperature in the dipping bath 1 is in the range of 15 to 40 ℃, particularly preferably 20 to 35 ℃. Preferably, the temperature in the dipping bath 2 is in the range of 70 to 100 ℃, particularly preferably 96 to 100 ℃.

Preferably, the anodized aluminum oxide is colored by adsorption, electrolytic or interference prior to surface treatment in step i) of embodiment a. Specifically, aluminum is adsorption colored as described above.

In a further preferred embodiment B, steps i) and ii) are carried out in a single immersion bath, the temperature preferably being from 70 to 100 ℃, particularly preferably from 75 to 96 ℃.

In another preferred embodiment C, steps i) and ii) are carried out in two baths which are separate from one another. In this embodiment, both baths comprise at least one amino group containing compound as defined previously. Preferably, the temperature in the dipping bath 1 is in the range of 15 to 45 ℃, particularly preferably 20 to 35 ℃. Preferably, the temperature in the dipping bath 2 is in the range of 70 to 100 ℃, particularly preferably 75 to 96 ℃.

The invention also provides an anodised aluminium treated by a method according to the invention.

The invention also provides anodized aluminum treated with the treating agent as described above.

The invention also provides the use of a treating agent as described above for the surface treatment of anodized aluminium.

The following examples are intended to illustrate the invention without limiting it in any way.

Drawings

FIG. 1: a graphical representation of Δ Ε values for different subsequent treatments; l1 a1 b1 is the direct value after staining, L2 a2 b2 is the value at the end of the subsequent treatment

FIG. 2: the effect of polyethyleneimine concentration on Δ Ε value; l1 a1 b1 is the direct value after staining, L2 a2 b2 is the value at the end of the subsequent treatment; 1.0 equivalent corresponds to 1g/L of starting material (50% by weight of polymer in starting material) in the dipping bath 2

FIG. 3: removal value of the established hot compaction process (with polyethylene as additive)Ethylenimine (PEI) is related to the compaction temperature during hot compaction. 30mg/dm required by Qualanod²The mark is black.

Detailed Description

Immersion bath 1 for surface treatment

Surface treatment of anodized aluminum was performed in the dipping bath 1 (composition in table 1) to fix the dye (step i).

Table 1 (3 min at 30 ℃, pH 6.0-6.2):

raw materials	Concentrate (kg/kg)	50mL/L bath lotion (g/L)
			Deionized water (VE Wasser)	0.521	-
Ammonium acetate (Ammoniumacetat)	0.319	17.5
			Urea (Harnstoff)	0.140	7.7
Phenoxyethanol (Phenoxythane)	0.010	0.6
			Polyethyleneimine (Polyethylenimin)	0.010	0.5

Bath for compaction 2:

the compaction of the anodized layer (step ii) was performed in bath 2 (composition in table 2).

TABLE 2 (bath solution: 2mL/L concentrate; 3 min/. mu.m anodic oxide layer, temperature ≥ 96 deg.C, pH 6.0-6.2)

Experiment 1: performing step i) and step ii) in separate baths:

the compaction of the anodized layer is carried out in a separate bath. For this purpose, the aluminum treated in the dipping bath 1 is subsequently immersed in the dipping bath 2. Baths 1 and 2 are applied here directly after the coloring of the anodized layer.

Experiment 2: carrying out steps i) and ii) in a bath

The surface of the anodized aluminum is compacted in a bath 2 containing 1G/L of Lupasol G20 at a temperature <96 ℃ (polyethyleneimine with a molar mass of 1300G/mol, 50% in water). The treatment time was 3min/μm of anodized layer.

Evaluation:

the quality of the surface treatment of the present invention is evaluated here in terms of the colour change before and after the treatment for sealing the anodized aluminium. In this case, known values of la b are used to define the color unambiguously. The direct colour after colouring of the anodized layer was compared as the basic value (L1 a1 b1) with the colour after compacting (bath 2, L2 a2 b2) and is shown as Δ E (fig. 1). As can be seen from fig. 1, in the case of using the hot compaction in the aqueous solution (bath 2) alone, and in the case of using the commercially available nickel-based product, the color change caused by the surface treatment process is very large (large Δ E value). If the dipping bath 1 (dipping bath 2) comprising the polyethyleneimine derivative is now used before the compaction, the Δ Ε value decreases significantly and therefore the color is stable during the surface treatment according to the invention.

FIG. 2 shows the effect of increasing polyethyleneimine concentration (1300 g/mol derivative in this example) on the Δ E value. The Δ E values which decrease with increasing polymer concentration indicate the fixing action of the polyethyleneimine.

The anodized test panels a and B were compared to each other. The value of test panel a is determined directly after staining. The test panels B were treated with a polyethyleneimine-based impregnation solution according to the invention (dip bath 1) and then subjected to process compaction (dip bath 2). The stabilizing effect of the polymer on the hue can already be seen with the naked eye. The plates were color point tested to check the quality of the compaction.

Test panel A after dyeing (before compaction), it is almost impossible to remove the dye drops directly, which results in the worst rating for this panel, with a Δ E value of 0.

Test board B the board evaluated very well, since the dye drops could be removed without leaving any residue, with a Δ E value of 8.93.

Figure 3 shows the use of polyethyleneimine in a hot compaction process (bath 2 with polyethyleneimine addition). At compaction temperatures below 90 ℃, the established hot compaction method (diamonds) showed significant deterioration in the removal test (this is shown by higher removal values on the Y-axis with decreasing temperature). If polyethyleneimine is added as an additive during compaction, lower removal values (circularity) are achieved at lower temperatures than in established processes. 30mg/dm required by Qualanod quality label (specification of Qualanod quality label for sulfuric acid-based aluminum anodization; version 1/2017; updated 11/21/2017; effective from 1/2018), even at 80 ℃²The level (determined according to ISO 3210) is also significantly lower, which was not possible in the established process before.

Claims

1. A method for surface treating anodized aluminum oxide with a treating agent comprising an amino group-containing compound having at least two amino groups, comprising the steps of:

ii) compacting the surface of the anodized aluminum treated in step i).

2. The method according to claim 1, wherein the anodized aluminum is colored with an adsorption, electrolysis or interference stain before the surface treatment in step i), or the anodized aluminum used in step i) is uncolored.

3. The method according to any one of the preceding claims, wherein the pH value of the treatment agent is in the range of 5.5 to 8.0, preferably in the range of 5.8 to 7.0.

4. The process according to any one of the preceding claims, wherein the temperature in step ii) is in the range of from 70 ℃ to 100 ℃, preferably from 75 ℃ to 96 ℃.

5. The method according to any one of the preceding claims, wherein the treatment agent comprises an amino-containing compound in a concentration ranging from 0.02 to 2.5g/L, preferably from 0.05 to 1.0 g/L.

6. The method according to any one of the preceding claims, wherein the amino group containing compound is selected from the group consisting of low molecular weight polyamines, polyalkyleneimines, polyvinylamines, amino modified polycarboxylic acids, polylysines, amine terminated polyether polyols, end group modified polyamines and copolymers, derivatives and mixtures thereof, preferably polyethyleneimines, polyvinylamines, low molecular weight polyamines and mixtures thereof, in particular polyethyleneimines and low molecular weight polyamines.

7. The method according to any one of the preceding claims, wherein the amino-containing compound has a charge density of at least 1meq/g (pH 2), preferably from 1.5meq/g to 35meq/g (pH 2), preferably from 5 to 30(pH 2).

8. The process according to any one of the preceding claims, wherein the molar mass of the amino group containing compound is in the range of from 100 to 10000g/mol, preferably in the range of from 100 to 4000, in particular in the range of from 100 to 3000 g/mol.

9. The method of any one of claims 1 to 8, wherein the steps i) and ii) are performed in a single immersion bath.

10. The method according to any one of claims 1 to 8, wherein the steps i) and ii) are carried out in two baths.

11. A treated anodized aluminum prepared according to the method of any one of claims 1-10.

12. Anodized aluminum treated with the treating agent as defined in any one of claims 1, 3, 5 to 8, 11 and 12.

13. Use of a treating agent as defined in any one of claims 1, 3, 5 to 8, 11 and 12 in a surface treatment for anodized aluminum.