EP3142800A1

EP3142800A1 - Method for coating metal surfaces of substrates and objects coated in accordance with said method

Info

Publication number: EP3142800A1
Application number: EP15722190.4A
Authority: EP
Inventors: Wolfgang Bremser; Martin Droll; Oliver Seewald; Evgenija Niesen-Warkentin; Lars Schachtsiek; Manuel Traut; Michael Schwamb; Daniel Wasserfallen; Vera Sotke; Aliaksandr FRENKEL; Ron Eilinghoff; Stephanie Gerold
Original assignee: Chemetall GmbH
Current assignee: Chemetall GmbH
Priority date: 2014-05-14
Filing date: 2015-05-12
Publication date: 2017-03-22
Also published as: WO2015173232A1; MX2016014764A; KR20170007779A; JP2020164999A; DE102015208764A1; US20170081542A1; AU2015261015B2; CA2947464A1; SG11201609525VA; JP2017523300A; CN106661369B; AU2015261015A1; CN106661369A

Abstract

The invention relates to a method for coating surfaces, to a corresponding coating, and to the use of the objects coated in accordance with said method. In accordance with the invention the object is achieved by a method for coating metallic surfaces of substrates that comprises or consists of the following steps: I) providing a substrate having a cleaned metallic surface, II) contacting and coating metallic surfaces with an aqueous composition in dispersion and/or suspension form, III) optionally rinsing the organic coating, and IV) drying and/or baking the organic coating or V) optionally drying the organic coating and coating it with a similar or further coating composition prior to drying and/or baking, characterized in that the coating in step II is carried out with an aqueous composition in dispersion and/or suspension form that comprises a complex fluoride, and at least one anionic polyelectrolyte is added to a nonionically or anionically/nonionically stabilized dispersion of film-forming polymers and/or to a suspension of film-forming inorganic particles and a coating forms that is based on an ionogenic gel comprising cations dissolved out of the metallic surface.

Description

Process for coating metallic surfaces of substrates and objects coated by this process

The invention relates to a method for the coating of surfaces, a corresponding coating and the use of coated articles by this method. There are numerous methods to produce homogeneous coatings on particular metallic surfaces by means of dipping. Here, for the production of, in particular, anticorrosion coatings predominantly consisting of an organic matrix and / or organic and / or inorganic additional components, preferably in the techniques described below.

The classical methods are based on the use of the Theological properties of the formulations used to achieve a complete coating of a joined workpiece. Although, by continuously rotating the subject workpiece after the dipping operation, accumulation of coating material at critical locations can be reduced, it is not possible with this method to achieve a completely homogeneous coating. In addition, at locations with higher coating levels during the drying and / or crosslinking process, voids such as blistering and cookers can occur which affect the quality of the overall coating.

The electrophoretic methods avoid this problem by using electric current to deposit a uniform coating in the dipping. With this method, it is possible to produce homogeneous coatings on metallic workpieces. The deposited coatings show a very good adhesion in the wet state to the metallic substrate. Without detachment of the coating, it is possible to treat the workpiece in a subsequent rinsing step. As a result, the previously inaccessible areas on the workpiece are freed from excess coating solution and thus no defects can occur during the drying process. This technique has the disadvantage that in addition to the amount of electrical energy and in addition to the necessary plunge pool, the too An increase in costs, so-called edge alignment occur because electric fields are built inhomogeneous on macroscopic edges and the edges are coated unevenly and possibly incomplete. In the construction of the workpieces also cavities must be avoided, since at these points, an effect comparable to the phenomenon of Faraday cage occurs. Due to the reduction of the electric field strengths necessary for depositing, no or only a greatly reduced coating can be applied to the workpiece on such areas (throwing problem), which leads to an impairment of the coating quality. In addition, this technique has the following disadvantages in an electric immersion coating (ETL), such as in cathodic dip painting (KTL): A corresponding immersion bath, together with all electrical and mechanical equipment from the temperature control, power supply and electrical insulation, circulation device and feed device to the Disposal of the anolyte acid, which is formed in the electrolytic coating, and constructed very expensive with an ultrafiltration for Lackrezyklierung and control devices. The process management requires a very high technical effort also due to the large currents and energy quantities as well as the equalization of the electrical parameters on the bath volume and the precise adjustment of all process parameters and in the maintenance and cleaning of the system.

The known autophoretic methods are based on an electroless concept consisting of a pickling attack of the substrate surface used in which metal ions are dissolved out of the surface and coagulated due to the concentration of metallic ions at the resulting interface an emulsion. Although these methods do not have the above-mentioned limitation of the electrolytic processes with respect to the Faraday cage effect, the coatings produced during the process must be fixed after the first activation step in a complex multistage dipping process. Furthermore, the pickling attack leads to unavoidable contamination of the active zone by metal ions which must be removed from the zones. Moreover, the method relies on a chemical deposition process that is not is self-regulating and can not be stopped if necessary, such. B. by switching off the electric current in the electrolytic process. Thus, with a longer residence time of the metallic substrates in the active zones, the formation of too high a layer thickness is unavoidable.

It is a long-felt desire, efficient and cost-effective to form homogeneous coatings in a dipping process in order to produce as much as possible closed and substantially flat coatings in greater thickness.

It is therefore the object of proposing a method by means of which a coating formulation can be deposited homogeneously over a liquid system and, if necessary, also rinsing-resistant on metallic surfaces in a simple way. It was also the task of proposing a simple procedure for this purpose.

The object is achieved with a method for coating metallic surfaces of substrates comprising the steps or consisting of the steps:

I. providing a substrate having a cleaned, metallic surface,

II. Contacting and coating metallic surfaces with an aqueous composition in the form of dispersion and / or suspension,

III. optionally rinsing the organic coating and

IV. Drying and / or baking of the organic coating or

V. optionally drying the organic coating and coating with a similar or further coating composition before drying and / or baking,

wherein in step II the coating is carried out with an aqueous composition in the form of dispersion and / or suspension comprising a complex fluorides selected from the group consisting of hexa- or tetrafluorides of the elements titanium, zirconium, hafnium, silicon, aluminum and / or boron in one Amount of 1, 1 10 ^"6 mol / l to 0.30 mol / l based on the cations containing a nonionic or anionic nonionic stabilized dispersion of film-forming polymers and / or a Suspension of film-forming inorganic particles having a solids content of 2 to 40 wt .-% and an average particle size of 10 to 1000 nm, which is stable in the pH range of 0.5 to 7.0, at least one polyelectrolyte in an amount of 0 0.01 to 5.0% by weight, based on the total mass of the resulting mixture, the aqueous composition having a pH in the range 0.5 to 7.0 and forming a coating based on an ionic gel, which binds the cations dissolved out of the metallic surface, these cations originating from a pretreatment stage and / or from the contacting in step II. For the purposes of the present invention, the term "anionically nonionically stabilized dispersion" is also used interchangeably with "electrosterically stabilized dispersion". The inventive addition of complex fluorides leads to substantially homogeneous coatings with dry film thicknesses in the range of 20 μιτι to 100 μιτι on galvanized sheet steel and dry film thicknesses> 1 μιτι on cold-rolled steel or aluminum. Surprisingly, for the nonionic dispersion, corrosion protection up to a factor of 10 was found to be higher than that of the coating processes based on ionic coatings known from the prior art. Preferably, the complex fluoride in an amount of 1, 1 10 ^"5 mol / l to 0.15 mol / l preferably 1, 1 10 ^{" 4} mol / l used to 0.05 mol / l based on the cations, wherein the aqueous Composition has a pH in the range of 1, 0 to 6.0, more preferably 1, 5 to 5.0. The coating according to the invention exhibits a single-layer structure, wherein either a more or less homogeneous coating or a coating is or can be formed, in which the particles accumulate somewhat more closely near the metallic surface. According to the invention, the substrates to be coated having a metallic surface are metals, metallically coated surfaces or metal surfaces pretreated with primers, from which metal cations can still be dissolved out. In particular, the term "to be coated Surface (s) "in the context of this application surfaces of metallic objects and / or metallic particles, optionally with eg a metallic coating such as based on zinc or zinc alloy and / or with at least one coating of a pretreatment or treatment composition such as based on chromate, Cr ³⁺ , Ti compound, Zr compound, silane / silanol / siloxane / polysiloxane, and / or organic polymer.

In principle, all types of metallic materials are possible among the metallic materials, in particular those of aluminum, iron, copper, titanium, zinc, magnesium, tin and / or alloys containing aluminum, iron, calcium, copper, magnesium, nickel, chromium , Molybdenum, titanium, zinc and / or tin, wherein their use can also be adjacent and / or in succession. If appropriate, the material surfaces can also be precoated and / or be, for example, with zinc or an alloy containing aluminum and / or zinc.

As objects to be coated, it is possible in principle to use all types of objects which consist of a metallic material or are provided with at least one metallic coating, in particular metal-coated polymeric or fiber-reinforced, polymeric materials. Particularly preferred articles are in particular tapes (coils), sheets, parts such as e.g. Small parts, joined components, intricately shaped components, profiles, rods and / or wires.

The term "electroless plating" in the context of this application means that when coating with the solution and / or dispersion (= suspension and / or emulsion) containing composition in contrast to the known electrolytic processes for the preparation of the subsequent coating from the outside, an electrical voltage less than 100 V is created.

Preferably, the invention relates to a process in which at least one polyelectrolyte is selected from the groups a) polysaccharides based on Glycogen, amylose, amylopectin, callose, agar, algins, alginates, pectins, carrageenans, celluloses, chitins, chitosans, curdlanes, dextrans, fructans, collagens, gellan gum, gum arabic, starches, xanthans, tragacanth, karayans, tara gums and glucomannans; b) of natural origin based on polyamino acids, collagens, polypeptides, lignins and / or c) a synthetic anionic polyelectrolyte based on polyamino acids, polyacrylic acids, polyacrylic acid copolymers, acrylamide copolymers, lignins, polyvinylsulfonic acid, polycarboxylic acids, polyphosphoric acids or polystyrenes or contains thereof consists.

Preferably, the process according to the invention is one in which the aqueous composition and / or the organic coating produced therefrom contain at least one type of cation selected from those based on cationic salts selected from the group consisting of melamine salts, nitrososalts, oxonium salts, ammonium salts, Salts with quaternary nitrogen cations, salts of ammonium derivatives and metal salts of Al, B, Ba, Ca, Cr, Co, Cu, Fe, Hf, In, K, Li, Mg, Mn, Mo, Na, Nb, Ni, Pb, Sn, Ta, Ti, V, W, Zn and / or Zr. For the purposes of this application, the term "copolymers" describes polymers which are composed of two or more different monomer units, in which case copolymers can be subdivided into five classes, as illustrated by a binary copolymer composed of two different comonomers A and B. :

1 . Statistical copolymers in which the distribution of the two monomers in the chain is random (AABABBBABAABBBABBABAB ....);

2. Gradient copolymers, similar in principle to the random copolymers, but with a variable proportion of a monomer in the course of the chain (AAAAAABAABBAABABBBAABBBBBB);

3. Alternating or alternating copolymers with a regular arrangement of the monomers along the chain (ABABABABABABABABABAB ....); 4. block copolymers consisting of longer sequences or blocks of each monomer (AAAAAAAAABBBBBBBBBBBB ...), wherein, depending on the number of blocks, one also speaks of diblock, triblock, multiblock copolymers;

5. Graft copolymers in which blocks of one monomer are grafted onto the backbone of another monomer.

For the purposes of this application, the term "derivatives" denotes a derived substance of similar structure to a corresponding basic substance Derivatives are substances whose molecules have a different atom or a different atomic group instead of an H atom or a functional group, or in which one or more several atoms / atomic groups were removed.

The term "polymer (s)" in the context of this application means monomer (s), oligomer (e), polymer (s), copolymer (s), block copolymer (e), graft copolymer (e), their mixtures and their compounding to organic and / or essentially organic base. [0102] Usually, the "polymer (s)" in the context of this application are predominantly or wholly present as polymer (s) and / or copolymer (s). The process according to the invention is particularly preferably one in which the aqueous composition and / or the organic coating produced therefrom has a content of organic particles based on polyacrylates, polyurethanes, polyepoxides and / or their hybrids.

So-called polyacrylate-polyurethane hybrid resins can be differentiated into hybrid systems, which are produced by pure mixing of the various dispersions (blends or formulations), into those which have a chemical bond between the different polymer types and into those in which the different polymer classes interpenetrating Train networks (IPN).

Usually, such polyurethane-polyacrylate hybrid dispersions are prepared by emulsion polymerisation of a vinyl polymer ("polyacrylate") in an aqueous polyurethane dispersion, but it is also possible to prepare the polyurethane-polyacrylate hybrid dispersion as a secondary dispersion. Aqueous polyacrylate-polyepoxide hybrid dispersions are usually prepared by addition reactions of a bifunctional epoxide with bifunctional amine monomer building blocks and subsequent reaction with a polyacrylate having sufficient carboxyl functions. As in the case of the polyurethane secondary dispersions, the water dispersibility can be achieved, for example, by carboxylate groups which have been converted into anionic groups with amines and subsequent dispersion in water.

Hybrid dispersions for forming a layer on the substrate may, in addition to polyurethane and polyepoxide constituents, preferably also contain organic polymers and / or copolymers based on polyvinyl alcohols, polyvinyl acetates, polybutyl acrylates and / or other acrylic acid esters. Acrylic esters are esters which are derived from the acrylic acid (CH ₂ = CH-COOH) and thus carry the functional group (CH ₂ = CH-COOR). Acrylic methyl ester, ethyl acrylate, butyl acrylate and ethylhexyl acrylate are produced in large quantities. The main application of acrylic acid esters is in homo- and copolymers, the z. For example, acrylic acid, acrylamides, methacrylates, acrylonitrile, fumaric acids, itaconic acid, maleates, vinyl acetate, vinyl chloride, styrene, butadiene and unsaturated polyesters, polyepoxide esters, polyacrylamides, polyacrylic acids, polycarbonates, polyesters, polyethers, polystyrene butadienes, poly (meth) acrylic acid esters, polyvinyl acetate copolymers with acrylic acid esters and / or copolymers with dibutyl maleate and / or with vinyl esters of at least one Koch acid, polyethylenes, polyvinyl chlorides, polyacrylonitriles, polyepoxides, polyurethanes, polyacrylates, polymethacrylates, polyesters, polyamides, polytetrafluoroethylenes, polyisobutadienes, polyisoprenes, silicones, silicone rubbers and / or derivatives thereof contain. These are in particular at least 50 wt .-% of the solids and active ingredients in the aqueous composition.

The term "pretreatment" means a treatment (= contacting the surfaces to be coated with a usually liquid composition), in which subsequently, optionally after a subsequent coating, a further coating for protecting the layer sequence and the article such as at least one lacquer is applied. In a prior pretreatment prior to activating a surface with an activating agent to help electrostatically charge the surface, the surfaces to be treated may be first alkaline cleaned, if necessary, and contacted with a pre-treatment composition, particularly to form a conversion layer. Then, the surfaces treated and / or coated in this way may optionally be coated with a primer and / or with an optionally deformable protective layer, in particular with a corrosion protection primer, and / or optionally oiled. The BÖlung serves in particular the temporary protection of the treated and / or coated in particular metallic surfaces.

In principle, any type of pretreatment is possible as pretreatment: For example, aqueous pretreatment compositions based on phosphate, phosphonate, silane / silanol / siloxane / polysiloxane, lanthanide compound, titanium compound, hafnium compound, zirconium compound, acid, metal salt and / or organic polymer can be used.

In the further treatment of these coated substrates can be carried out, if necessary, regardless of whether or not before oil has been applied, in particular alkaline cleaning.

A coating with a corrosion protection primer such as a welding primer can allow additional protection against corrosion, especially in cavities and poorly accessible areas of a substrate, formability and / or availability eg when folding, gluing and / or welding. In industrial practice, a corrosion protection primer could be used in particular if the substrate coated therewith, such as, for example, a metal sheet, is shaped after the coating with the anticorrosive primer and / or is added with a further component and if further coatings are only then applied. If, in addition, an anticorrosive primer is applied under the activation layer and under the particle coating in this process, a significantly improved corrosion protection is usually produced. The term "substantially rinsing-resistant" in the sense of this application means that under the conditions of the respective plant and process sequence the respective last coating is not completely removed by a rinsing process (= rinsing), so that a coating can be produced, preferably a closed coating ,

In the method according to the invention, the most diverse types of particles, particle sizes and particle shapes can be used as particles.

Oxides, hydroxides, carbonates, phosphates, phosphosilicates, silicates, sulfates, organic polymers including copolymers and derivatives thereof, waxes and / or compounded particles, in particular those based on anticorrosive pigments, organic polymers, may preferably be used as particles in the aqueous composition for forming the layer , Waxes and / or compounded particles, and / or mixtures thereof. They preferably have particle sizes in the range from 5 nm to 15 μm, preferably from 20 nm to 1 μm, particularly preferably from 50 nm to 500 nm. They are preferably water-insoluble particles.

Compounded particles have in a particle a mixture of at least two different substances. Compounded particles can often have other substances with very different properties. You may, for example, partially or wholly contain the composition for a paint, possibly even containing non-particulate substances such as surfactant, defoamers, dispersants, paint auxiliaries, other types of additives, dye, corrosion inhibitor, low water-soluble anticorrosion pigment and / or other substances that customary and / or known for corresponding mixtures. Such paint components may be suitable and / or frequently used, for example, for organic coatings for forming, for anticorrosive primers and other primers, for colored coatings, fillers and / or clearcoats. A corrosion protection primer usually has electrically conductive particles and is electrically weldable. In general, it is often preferred that a) a mixture of chemically and / or physically dissimilar particles, b) particles, aggregates and / or agglomerates of chemically and / or physically dissimilar particles and / or c) compounded particles in the composition and / or be used in the particle layer formed therefrom.

It is often preferred that the particle-containing composition and / or the particle layer formed therefrom contain at least one nonparticulate substance in addition to at least one type of particle, in particular additives, dyes, corrosion inhibitors and / or slightly water-soluble anticorrosive pigments. In particular, colored and / or optionally also a limited proportion of electrically conductive particles, in particular based on fullerenes and other carbon compounds with graphite-like structures and / or carbon black, optionally also nanocontainers, can be used as particles in the composition and / or in the particle layer formed therefrom and / or nanotubes. On the other hand, coated particles, chemically and / or physically modified particles, core-shell particles, compounded particles of various substances, encapsulated particles and / or nanocontainers can be used in particular as particles in the composition and / or in the coating formed therefrom.

In the method according to the invention, it is preferable for the particle-containing composition, the particle layer formed therefrom and / or the coating formed therefrom, for example by filming and / or crosslinking, to comprise, in addition to at least one type of particle, at least one dye, one color pigment, one anticorrosive pigment, a corrosion inhibitor, a conductive pigment, another type of particles, a silane / silanol / siloxane / polysiloxane / silazane / polysilazane, a coating additive and / or an additive such as in each case at least one surfactant, a defoamer and / or a dispersant contains / contain , In the method according to the invention, it is preferred that the composition and / or the coating formed therefrom in addition to at least one type of particles and optionally next to at least one non-particulate substance partially or completely a chemical composition for a primer, a paint such as a filler , Topcoat and / or clearcoat.

As additives to the organic polymers of the particles, pigments and / or additives, as are frequently used in paints and / or primers, are recommended in many embodiments.

Film formation can be improved by the use of thermoplastic polymers and / or by the addition of substances which serve as temporary plasticizers. Film-forming aids act as specific solvents that soften the surface of the polymer particles and allow their fusion. It is advantageous if, on the one hand, these plasticizers remain in the aqueous composition for a sufficiently long time in order to have a long effect on the polymer particles, and then evaporate and thus escape from the film. Furthermore, it is advantageous if a residual water content is present for a sufficiently long time during the drying process.

Particularly advantageous as film-forming aids are so-called long-chain alcohols, in particular those having 4 to 20 C atoms, such as a butanediol,

a butyl glycol,

a butyl diglycol,

an ethylene glycol ether such as

ethylene glycol,

ethylene glycol monomethyl ether,

Ethylglykolpropylether,

ethylene glycol hexyl ether, Diethylenglykolmethy-Jether,

diethylene,

diethylene glycol butyl ether,

Diethylene glycol hexyl ether or a

Polypropylene glycol ethers as

propylene glycol monomethyl ether,

dipropylene glycol monomethyl ether,

tripropylene,

propylene glycol,

dipropylene,

Tripropylenglykolmonobutylether,

propylene glycol monopropyl,

dipropylene glycol monopropyl ether,

Tripropylenglykolmonopropylether,

propylene glycol phenyl ether,

trimethyl pentanediol,

a polytetrahydrofuran,

a polyether polyol and / or a polyester polyol.

For example, crosslinking can be performed with certain reactive groups, e.g. Isocyanate, isocyanurate and / or melamine groups take place.

The subsequent coating is preferably dried in such a way that, in particular, existing organic polymer particles can film, so that a largely or completely homogeneous coating is formed. The drying temperatures can be chosen so high in some embodiments that the organic polymeric components can crosslink.

In the method according to the invention, in some embodiments it is preferred that a particle layer containing substantially organic particles is formed and, for example, filmed and / or crosslinked during drying. The filming takes place in some embodiments, even without the presence of film-forming aids. Here, the particles of the Coating, especially if they are present predominantly or wholly as organic polymers, preferably filmed to a substantially closed or to a closed coating, in particular during drying. In this case, it is often preferred that the drying temperature of a coating, which consist predominantly or entirely of organic polymers, be chosen so that a substantially closed or a closed coating is formed. If necessary, at least one film-forming auxiliary can be added to the filming, in particular based on at least one long-chain alcohol. In embodiments with a plurality of particle layers on top of each other, it is preferable to first apply all the particle layers and then film them together and / or crosslink them.

The content of at least one film-forming assistant in the aqueous composition - in particular in the bath - 0.01 to 50 g / L based on solids including active ingredients, preferably 0.08 to 35 g / L, particularly preferably 0.2 to 25 g / L be. The weight ratio of organic film former levels to film forming aid levels in the aqueous composition.

In this case, it is often preferred that the drying, filming and / or crosslinking in the temperature range of 5 to 350 ° C, preferably 80 to 200 ° C, more preferably in the temperature range of 150 to 190 ° C based on the furnace temperature and / or based on Peak metal temperature (PMT) occurs. The selected temperature range is largely dependent on the nature and amount of the organic and optionally also the inorganic constituents and optionally also on their film-forming temperatures and / or crosslinking temperatures.

Preferably, the invention relates to a method in which the aqueous composition and / or the organic coating produced therefrom has a content of at least one complexing agent for metal cations or a polymer which has been complexing modified metal cations.

The process according to the invention is particularly preferably one in which the aqueous composition and / or the organic Coating has a content of at least one complexing agent selected from those based on maleic acid, alendronic acid, itaconic acid, citraconic acid or mesaconic acid or the anhydrides or half esters of these carboxylic acids.

Advantageously, the aqueous composition and / or the organic coating produced therefrom has a content of at least one emulsifier.

It is particularly preferred that the aqueous composition and / or the organic coating produced therefrom has a content of at least one emulsifier. Preferably, the aqueous composition and / or the organic coating produced therefrom contains a mixture of at least two different polyelectrolytes.

Particularly preferably, the aqueous composition and / or the organic coating produced therefrom contains a mixture of two pectins. Further preferably, the aqueous composition and / or the organic coating produced therefrom contains at least one polysaccharide selected from those having a degree of esterification of the carboxy function in the range from 5 to 75% based on the total number of alcohol and carboxy groups.

Most preferably, the aqueous composition and / or the organic coating produced therefrom comprises at least one polysaccharide and / or at least one further polyelectrolyte selected from those having a molecular weight in the range from 500 to 1 000 000 g / mol ^-1 .

Preferably, the aqueous composition and / or the organic coating produced therefrom contains at least one polysaccharide and / or at least one further polyelectrolyte selected from those having a degree of amidation of the carboxy functions in the range of 1 to 50%, a degree of epoxidation of the carboxy functions of up to 80%. Particularly preferred in the process according to the invention is that the polyelectrolytes are modified or modified with adhesion-promoting adhesive groups selected from the group consisting of chemical groups of multifunctional epoxides, isocyanates, primary amines, secondary amines, tertiary amines, quaternary amines, amides, imides, Imidazoles, formamides, Michael reaction products, carbodiimides, carbenes, cyclic carbenes, cyclocarbonates, multifunctional carboxylic acids, amino acids, nucleic acids, methacrylamides, polyacrylic acids, polyacrylic acid derivatives, polyvinyl alcohols, polyphenols, polyols having at least one alkyl and / or aryl radical, caprolactam, phosphoric acids, phosphoric acid esters , Epoxide esters, sulfonic acids, sulfonic acid esters, vinylsulfonic acids, vinylphosphonic acids, catechol, silanes and the silanols and / or siloxanes, triazines, thiazoles, thiazines, dithiazines, acetals, hemiacetals, quinones, saturated alcohols formed therefrom These include fatty acids, unsaturated fatty acids, alkyds, esters, polyesters, ethers, glycols, cyclic ethers, crown ethers, anhydrides, as well as acetylacetones and beta-diketo groups, carbonyl groups and hydroxy groups.

Advantageously, as cations leached from the metallic surface and / or added to the aqueous composition, Al, Cu, Fe, Mg, Ca and / or Zn are selected. The aqueous composition and / or the organic coating produced therefrom particularly preferably contains at least one additive selected from additives consisting of the group of biocides, dispersing aids, film-forming auxiliaries, acidic and / or basic pH adjusters, thickeners and leveling agents. Most preferably, before contacting and coating the metallic surfaces with an aqueous composition in process stage II, the metallic surfaces are cleaned, pickled and / or pretreated.

Advantageously, the aqueous composition forms a coating based on an ionic gel, in which the dry film formed thereby or later has a thickness of at least 1 μm. Particularly preferably, the organic coating is formed in 0.05 to 20 minutes in an immersion bath and has after drying to a dry film thickness in the range of 5 to 100 μιτι on.

The invention further relates to an aqueous composition comprising in a dispersion of film-forming polymers and / or a suspension of film-forming inorganic particles having a solids content of 2 to 40% by weight and an average particle size of 10 to 1000 nm at least one polyelectrolyte in an amount from 0.01 to 5.0 wt .-% based on the total mass of the resulting mixture, wherein the aqueous composition has a pH in the range of 4 to 1 1.

Preferably, the aqueous composition is one which contains in the dispersion of film-forming polymers a content of organic particles based on polyacrylates, polyurethanes, polyepoxides and / or their hybrids, a content of at least one complexing agent selected from those based on maleic acid, alendronic acid, itaconic acid , Citraconic acid or mesaconic acid or anhydrides or half-esters of these carboxylic acids and at least one polyelectrolyte based on pectins or gellan gum.

It has been found that substantially closed or closed coatings with a layer thickness in the range from 5 nm to 50 μm can be produced from the surfaces coated according to the invention, in particular in the range from 10 nm to 40 μm, preferably from 15 nm to 1 μm , Corresponding layer thicknesses can have the individual coatings before and / or after their film formation and / or prior to their crosslinking. It has been found that the surfaces coated according to the invention, from which substantially closed or closed coatings were subsequently produced, could be produced in a significantly simpler and significantly less expensive manner than, for example, electrocoating, autophoretic dip coating or powder coating coatings. Furthermore, it has been shown that such coatings produced according to the invention can be equivalent in their properties to electrocoating, autophoretic dip coating or powder coating coatings of today's industrial practice.

It has surprisingly been found that the method according to the invention, which is not or substantially no electrolytic process, even in the case that it is slightly assisted with electrical voltage, and therefore usually requires no application of an external electrical voltage, in a simple manner and can be operated without complicated control. This method can be used in a wide temperature range and also at room temperature, if the subsequent drying is dispensed with.

It has further been found that in the method according to the invention for the application of the activating agent no costly control measures are required to achieve a uniform and homogeneous coating, and that high-quality protective subsequent coatings are formed with low chemical consumption, the thickness in the range of 500 nm 30 μιτι reach.

It is surprising that the process according to the invention with regard to the deposition, in particular of the subsequent coating, is a self-regulating process in which no costly control measures are required and high-quality protective coatings are formed with low consumption of chemicals.

Furthermore, it was found that the sequential deposited according to the invention formed a homogeneous layer with a uniform dry film thickness on a complex shaped workpiece, comparable to the quality of a conventional electrophoretically or autophoretically deposited paint layer. The coating of the invention can be preferably used for coated substrates as wire, wire mesh, tape, sheet metal, profile, trim, part of a vehicle or missile, element for a household appliance, element in construction, frame, guard rail, radiator or fence element, molding more complicated Geometry or small parts such as screw, nut, flange or spring. It is particularly preferably used in the automotive industry, in construction, for the appliance industry, for household appliances or in heating. The use of the method according to the invention is particularly preferred for coating substrates which have caused problems in the coating with an electrodeposition paint.

The invention will be explained in more detail with reference to 4 exemplary embodiments and 10 comparative examples. They were used as substrates in

Step I used:

1: electrolytically galvanized steel sheet with a zinc layer coating of 5 μm, sheet thickness 0.81 mm;

2: Cold-rolled steel, sheet thickness approx. 0.8 mm:

3: Aluminum alloy grade AC 170, sheet thickness approx. 1, 0 mm

and the following general treatment steps are carried out: II. Alkaline purification:

industrial alkaline cleaner e.g. 30 g / L Gardoclean® S 5176 and 4 g / L Gardobond® Additive H 7406 from Chemetall GmbH in water, preferably in tap or drinking water quality. The plates were spray-cleaned for 180 seconds at 60 ° C and then rinsed for 120 s with city water and 120 s with deionized water in the dipping.

III. Coating the surfaces with dispersions according to the invention for the formation of the organic coating: Composition of the dispersion A

List of abbreviations:

NH ₃ ammonia solution (25%)

AS: acrylic acid

DPE: diphenylethylene

MMA: methyl methacrylate

APS: ammonium peroxodisulfate

BMA: butyl methacrylate

HEMA: hydroxyethyl methacrylate

MS: maleic acid

VTES: vinyltriethoxysilane

nfA: non-volatile content (corresponds to solids content)

Dispersion B

Anionically stabilized dispersion having a film-forming temperature of 25 ° C, a solids content of 49-51%, a pH of 7.0-8.0, a viscosity of 20-200 mPas, a density of 1.04 g / cm3, a particle size from about 160 nm and -14 to -18 mV. The dispersion is adjusted to a solids content of 10% for the further treatment with demineralized water. Dispersion C

Nonionically stabilized dispersion having a solids content of 50-54%, a pH of 5.0-6.0, a viscosity of 1500-3000 mPas and a density of 1.799 g / cm3. The table data refer to the amount of solution per liter of formulation and the resulting solids content based on the formulation. The dispersion is adjusted to a solids content of 10% for the further treatment with demineralized water. For Comparative Examples 1 to 3, only the dispersion A without addition of the polyelectrolytes suitable for use according to the invention was used. If necessary, the mixture was adjusted to a pH of 4 with acid, preferably nitric and / or phosphoric acid, before use. For the comparative examples 4 to 6, only the polyelectrolytes in question for use according to the invention were used. In Comparative Example 7, all the components of the aqueous solution according to the invention were used except for the complex fluorides.

IV: Rinse the organic coating:

Rinsing after the organic coating serves to remove non-adherent components of the formulation and clusters of the formulation and to make the process as close to reality as usual in the automotive industry. For in the automotive industry, rinsing with water is usually done either by a dip rinse or a splash rinse.

V: drying and / or crosslinking of the coating:

Drying or drying with filming, in particular of the organic polymeric constituents: 175 ° C for 15 minutes.

Parallel investigations with eddy current measuring device and

Scanning electron microscopy (SEM) made it clear that according to the invention coatings were formed from which largely closed or closed coatings could be formed by contacting the surfaces with dispersions and / or formulations. example 1

Substrate 1 was coated with a mixture of 0.25% by weight based on the total amount of the resulting mixture with a pectin having a molecular weight of about 70,000 g / mol, a degree of amidation of 0%, a degree of esterification of 52%, an epoxidation degree of 0%, a galacturonic acid content of 87% and 0.25% by weight based on the total amount of the resulting mixture, a pectin having a molecular weight of about 70,000 g / mol, a degree of amidation of 0%, a degree of esterification of 10%, a Epoxidation degree of 0%, a galacturonic acid content of 85% mixed with 99.5 wt .-% of the above-described dispersion C. To the mixture was added 10.0 g / l of 20% hexafluorozirconic acid. It was a dry film thickness of 20 μιτι to 25 μιτι measured with an eddy current measuring device and REM determined.

Example 2

Experiment 1 was repeated with substrate 2 and determined a dry film thickness of 20 μιτι to 25 μιτι with REM.

Example 3

Experiment 1 was repeated with substrate 3 and determined a dry film thickness of 5 μιτι to 10 μιτι with REM.

Example 4

Substrate 3, with a mixture of 0.25% by weight, based on the total amount of the resulting mixture, was a pectin having a molecular weight of about 70Ό00 g / mol, a degree of amidation of 0%, a degree of esterification of 52%, an epoxidation degree of 0%, a galacturonic acid content of 87% and 0.25% by weight based on the total amount of the resulting mixture, a pectin having a molecular weight of about 70Ό00 g / mol, a degree of amidation of 0%, a degree of esterification of 10%, a Epoxidation degree of 0%, a galacturonic acid content of 85% with 99.5 wt. % of the dispersion C mixed. To the mixture was added 10.0 g / L of 20% hexafluorotitanic acid. It was a dry film thickness of 8 μιτι to 10 μιτι measured with an eddy current meter and REM determined. Comparative Example 1

Substrate 1 was coated with Dispersion A. No dry film thickness was determined with SEM. Comparative Example 2

Substrate 2 was coated with Dispersion A. No dry film thickness was determined with SEM. Comparative Example 3

Substrate 3 was coated with Dispersion A. No dry film thickness was determined with SEM. Comparative Example 4

The coating of substrate 1 with the polyelectrolytes mentioned in the description of the invention without mixing with dispersion A gave a dry film thickness of 300 nm to 500 nm.

Comparative Example 5

The coating of substrate 2 with the polyelectrolytes mentioned in the description of the invention without mixing with dispersion A gave a dry film thickness of 300 nm to 500 nm.

Comparative Example 6 The coating of substrate 3 with the polyelectrolytes mentioned in the description of the invention without mixing with dispersion A gave a dry film thickness of 300 nm to 500 nm. Comparative Example 7

Substrate 3 was coated with a mixture of 0.25% by weight based on the total amount of the resulting mixture with a pectin having a molecular weight of about 70,000 g / mol, a degree of amidation of 0%, a degree of esterification of 52%, an epoxidation degree of 0%, a galacturonic acid content of 87% and 0.25% by weight based on the total amount of the resulting mixture, a pectin having a molecular weight of about 70,000 g / mol, a degree of amidation of 0%, a degree of esterification of 10%, a Epoxidation degree of 0%, a galacturonic acid content of 85% coated with 99.5 wt .-% of the above-described dispersion A in the dipping. No dry film thickness could be determined.

Comparative Example 8 Substrate 1 was coated with a mixture of 0.25% by weight based on the total amount of the resulting mixture having a pectin having a molecular weight of about 70,000 g / mol, a degree of amidation of 0%, a degree of esterification of 52% Epoxidation degree of 0%, a galacturonic acid content of 87% and 0.25% by weight based on the total amount of the resulting mixture, a pectin having a molecular weight of about 70,000 g / mol, a degree of amidation of 0%, a degree of esterification of 10% , an epoxidation degree of 0%, a galacturonic acid content of 85% with 99.5 wt .-% of the dispersion B described above mixed. To the mixture was added 2.0 g / L of 20% hexafluorozirconic acid. It was a dry film thickness of 55 μιτι to 65 μιτι measured with an eddy current meter and REM determined. Comparative Example 9

Comparative Example 8 was repeated with substrate 2 and determined a dry film thickness of 15 μιτι to 25 μιτι with REM.

Comparative Example 10

Comparative Example 8 was repeated with substrate 3 and determined a dry film thickness of 3 μιτι to 4 μιτι with REM.

The microscopic images show a homogeneous layer formation throughout, indicating a reliable, self-regulating and easily controllable coating process.

Claims

claims

1 . Method for coating metallic surfaces of substrates comprising the steps or consisting of the steps:

I. providing a substrate having a cleaned, metallic surface,

III. optionally rinsing the organic coating and

IV. Drying and / or baking of the organic coating or

characterized,

in step II, the coating is carried out with an aqueous composition in the form of dispersion and / or suspension which comprises a complex fluoride selected from the group consisting of hexa- or tetrafluorides of the elements titanium, zirconium, hafnium, silicon, aluminum and / or boron in one Amount of 1, 1 10 ^"6 mol / l to 0.30 mol / l based on the cations, wherein a nonionic or anionic nonionic stabilized dispersion of film-forming polymers and / or a suspension of film-forming inorganic particles having a solids content of 2 to 40% by weight and an average particle size of 10 to 1000 nm, which is stable in the pH range of 0.5 to 7.0, at least one nonionic or anionic nonionic polyelectrolyte in an amount of 0.01 to 5, 0 wt .-% based on the total mass of the resulting mixture is added, wherein the aqueous composition has a pH in the range of 0.5 to 7.0 and a coating au f forms a base of an ionic gel, which binds cations dissolved out of the metallic surface and these cations come from a pretreatment stage and / or from the contacting in step II. A method according to claim 1, characterized in that a complex fluorides in an amount of 1, 1 10 ^"5 mol / l to 0.15 mol / l preferably 1, 1 10 ^{" 4} mol / l to 0.05 mol / l based to the cations, the aqueous composition having a pH in the range of 1.0 to 6.0, preferably 1.5 to 5.0.

A method according to claim 1 or 2, characterized in that at least one anionic polyelectrolyte is selected from the groups a) polysaccharides based on glycogen, amyloses, amylopectins, calloses, agar, algins, alginates, pectins, carrageenans, celluloses, chitins, chitosans, Curdlanes, dextranes, fructans, collagens, gellan gum, gum arabic, starches, xanthans, tragacanths, karayans, tara gums and glucomannans; b) anionic polyelectrolytes of natural origin based on polyamino acids, collagens, polypeptides, lignins and / or c) synthetic anionic polyelectrolytes based on polyamino acids, polyacrylic acids, polyacrylic acid copolymers, acrylamide copolymers, lignins,

Contains or consists of polyvinylsulfonic acid, polycarboxylic acids, polyphosphoric acids or polystyrenes.

A method according to claim 1 to 3, characterized in that the anionic polyelectrolyte contains or consists of at least one polysaccharide based on pectins or gellan gum.

A method according to claim 1 to 3, characterized in that the aqueous composition and / or the organic coating produced therefrom contains a mixture of at least two different nonionic or anionic-nonionic polyelectrolytes.

A method according to claim 5, characterized in that the aqueous composition and / or the organic coating produced therefrom contains a mixture of two pectins. Method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom at least one anionic polysaccharide selected from those having a degree of esterification of the carboxy function in the range of 5 to 75% based on the total number of alcohol and carboxy groups.

Method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom at least one polysaccharide and / or at least one further polyelectrolyte selected from those having a molecular weight in the range of 500 to 1 000 000 g / mol ^"1 .

Method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom comprises at least one polysaccharide and / or at least one further polyelectrolyte selected from those having a degree of amidation of the carboxy functions in the range from 1 to 50%, a degree of epoxidation of carboxy functions of up to 80%.

Method according to one or more of the preceding claims, characterized in that the polyelectrolytes are modified or modified with adhesion-promoting adhesive groups selected from the group consisting of chemical groups of multifunctional epoxides, isocyanates, primary amines, secondary amines, tertiary amines, quaternary amines, amides, imides, imidazoles, formamides, Michael reaction products, carbodiimides, carbenes, cyclic carbenes, cyclocarbonates, multifunctional carboxylic acids, amino acids, nucleic acids, methacrylamides, polyacrylic acids, polyacrylic acid derivatives, polyvinyl alcohols, polyphenols, polyols having at least one alkyl and / or Aryl radical, caprolactam, phosphoric acids, phosphoric acid esters, epoxide esters, sulfonic acids, sulfonic acid esters, vinylsulfonic acids, vinylphosphonic acids, catechol, silanes and the silanols and / or siloxanes, triazines, thiazoles, thiazines formed therefrom, Dithiazines, acetals, hemiacetals, quinones, saturated fatty acids, unsaturated fatty acids, alkyds, esters, polyesters, ethers, glycols, cyclic ethers, crown ethers, anhydrides, as well as acetylacetones and of beta-diketo groups, carbonyl groups and hydroxy groups. 1 1. Method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom has a content of at least one complexing agent for metal cations or a polymer which has been complexing modified metal cations. 12. The method of claim 1 1, characterized in that the aqueous composition and / or the organic coating produced therefrom selected a content of at least one complexing agent selected from those based on maleic acid, alendronic acid, itaconic acid, citraconic acid or mesaconic acid or the anhydrides or half esters thereof Has carboxylic acids.

13. The method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom contains at least one type of cations selected from those based on cationic salts selected from the group consisting of melamine salts, Nitrososalzen,

Oxonium salts, ammonium salts, salts with quaternary nitrogen cations, salts of ammonium derivatives and metal salts of Al, B, Ba, Ca, Cr, Co, Cu, Fe, Hf, In, K, Li, Mg, Mn, Mo, Na, Nb, Ni, Pb, Sn, Ta, Ti, V, W, Zn and / or Zr. 14. Process according to claim 13, characterized in that as cations dissolved out from the metallic surface and / or added to the aqueous composition, Al, Cu, Fe, Mg and / or Zn are selected.

15. The method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the thereof produced organic coating has a content of organic particles based on polyacrylates, polyurethanes, polyepoxides and / or their hybrids.

16. The method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom has a content of at least one emulsifier.

17. The method according to claim 16, characterized in that the aqueous composition and / or the organic coating produced therefrom has a content of at least one emulsifier.

18. The method according to one or more of the preceding claims, characterized in that the aqueous composition and / or the organic coating produced therefrom at least one additive selected from additives consisting of the group of biocides, dispersants, film-forming aids, acidic and / or basic auxiliaries for Adjusting the pH, thickener and leveling agent contains.

19. The method according to one or more of the preceding claims, characterized in that the aqueous composition forms a coating based on an ionic gel, and that the case or later formed dry film has a thickness of at least 1 μιτι.

20. The method according to one or more of the preceding claims, characterized in that the organic coating is formed in 0.05 to 20 minutes in an immersion bath and after drying has a dry film thickness in the range of 5 to 100 μιτι. 21. Aqueous composition obtained in an anionically stabilized dispersion of film-forming polymers and / or a suspension of film-forming inorganic particles having a solids content of 2 to 40% by weight and an average particle size of 10 to 1000 nm, which is in the pH range of 0, 5 to 7.0 is stable, at least one polyelectrolyte in an amount of 0.01 to 5.0 wt .-% based on the total mass of the resulting mixture and a complex fluorides selected from the group consisting of hexa- or tetrafluorides of the elements titanium, zirconium, hafnium, silicon, aluminum and / or boron in one Amount of 1, 1 10 ^"6 mol / l to 0.30 mol / l based on the cations, wherein the aqueous composition has a pH in the range of 4 to 1 1.

Aqueous composition according to claim 21, characterized in that in a dispersion of film-forming polymers, a content of organic particles based on polyacrylates, polyurethanes, polyepoxides and / or their hybrids, a content of at least one complexing agent selected from those based on maleic acid, alendronic acid , Itaconic acid, citraconic acid or mesaconic acid or anhydrides or half-esters of these carboxylic acids and at least one anionic polyelectrolyte based on pectins or gellan gum.

23. Use of the method according to any one of claims 1 to 22 for coating substrates which have caused problems in the coating with an electrodeposition paint.