WO2006021309A1

WO2006021309A1 - Method for passivating metallic surfaces by using itaconic acid homopolymers or copolymers

Info

Publication number: WO2006021309A1
Application number: PCT/EP2005/008445
Authority: WO
Inventors: Frank Klippel; Matthias KLÜGLEIN; Gunnar Schornick; Alexander Göthlich; Frank Dietsche; Helmut Witteler
Original assignee: Basf Aktiengesellschaft
Priority date: 2004-08-24
Filing date: 2005-08-04
Publication date: 2006-03-02
Also published as: EP1786953A1; CA2575008A1; US20090007990A1; CN100554509C; JP2008510603A; CN101006201A; DE102004041142A1; JP4514794B2

Abstract

The invention relates to a method for passivating metallic surfaces by treating the surface with an acidic, aqueous solution which comprises at least one homopolymer or copolymer of itaconic acid. The invention also relates to passivation layers and metallic surfaces that can be obtained by the inventive method.

Description

Process for passivating metallic surfaces using itaconic acid homo- or copolymers

The present invention relates to a method for passivating metallic surfaces by treating the surface with an acidic, aqueous preparation which comprises at least one homo- or copolymer of itaconic acid. The invention further relates to passivation layers and metallic surfaces obtainable by the method.

The corrosion protection treatment of modern metallic materials is usually carried out in multi-stage processes, and the surface of treated metals has meh¬ rere different layers.

The protection of metallic components from corrosion has great economic importance. At the same time, the requirements for corrosion protection are becoming ever higher. By way of example, it should be noted that with newer car types nowadays up to 12 years warranty against rust through are granted.

The corrosion protection treatment of aluminum surfaces and the surfaces of galvanized metals, in particular of galvanized or hot-dip galvanized iron or steel, is of particular importance technically and economically. The corrosion protection of zinc is based on the fact that it is less noble than the metallic material itself and therefore first itself corroded. The metallic material itself remains intact as long as it is still covered with zinc throughout.

In the presence of atmospheric oxygen, Zn or Zn forms on the surface.

Alloys, Al or Al alloys first a thin oxide layer, which slows down the corro¬ sive attack on the underlying metal more or less depending on the external conditions.

In order to enhance the protective effect of such an oxide layer, Al and Zn surfaces are usually subjected to an additional passivation treatment. In the course of such a treatment, a part of the metal to be protected dissolves, and is then immediately re-incorporated into an oxide film on the metal surface. This film is similar to the already existing oxide film, but offers a stronger protection. It is commonly referred to as a passivation layer. It often also improves the adhesion of paint coatings applied to the metal. Instead of the term "passivation layer", the term "conversion layer" is therefore often used interchangeably, sometimes also the term "pretreatment layer" or "aftertreatment layer", depending on where in the manufacturing process the treatment takes place. Passivation layers are comparatively thin and usually have a thickness of not more than 3 μm. To enhance the corrosion protection, additional (paint) layers are applied to the passivation layer in the case of a rule. It is usually a combination of several layers of lacquer, each serving different purposes. They serve to protect the passivation layer and the metal from corrosive gases and / or liquids but also from mechanical damage, such as stone impact and of course also aesthetic purposes. Coating layers are usually significantly thicker than passivation layers. Typical thicknesses range from 5 μm to 400 μm.

The passivation can be used for permanent corrosion protection or even for temporary corrosion protection. A temporary protection is used only for storing or transporting a metal sheet or other metallic workpiece and is removed before the final processing.

Heretofore, passivation layers on zinc or aluminum surfaces were usually obtained by treating the workpiece to be protected with aqueous, acidic solutions of CrO ₃ . The mechanism of such a passivation is complex. Among other things, metallic Zn or Al is released from the surface and precipitates again in the form of amorphous zinc chromium oxides or aluminum chromium oxides. However, the layers may also contain foreign ions and / or further components from the treatment solution. In particular, in the treatment with chromic acid, it can not be avoided that a certain proportion of Cr (VI) is also incorporated into the passivation layer.

In order to avoid treatment with carcinogenic Cr (VI) solutions, the treatment of the metallic surfaces with acidic, aqueous Cr (III) solutions has been proposed. For example, see US 4,384,902 or WO / 40208. However, there are increasing numbers of customers on the market who want completely passivating chromium-free processes. To avoid the use of Cr (VI) such as Cr (III), therefore, the use of polymers is becoming increasingly important.

DE-A 195 16 765 discloses a chromium and fluoride-free process for producing conversion coatings on metallic surfaces of Zn or Al. The acidic solution used for passivating comprises a water-soluble polymer, phosphoric acid and Al chelate complexes. Optionally, it is also possible to use polymers and copolymers of (meth) acrylic acid.

DE-A 197 54 108 discloses a chromium-free aqueous corrosion inhibitor which comprises hexafluoro anions of Ti (IV) and / or Zr (IV), vanadium ions, cobalt ions and phosphoric acid. Optionally, still further different film-forming polymers can be added, including carboxyl-containing copolymers such as acrylic acid / maleic acid copolymers. JP-A 2001-164377 discloses the production of black steel sheets, beispiels¬ example for the production of black cases for consumer electronics. The sheet is coated with a paint of metal ions, a water-soluble polymer, an aqueous polymer dispersion and an acid. In one example, a water-soluble polymer of 70% acrylic acid and 30% itaconic acid is mentioned. The passivation of metals by means of an itaconic acid copolymer is not disclosed by the document.

JP-A 2001-158969 discloses a final coating for metallic surfaces, in particular the black housing, with 50 to 98% by weight of an aqueous polymer dispersion, metal ions, a water-soluble polymer and an acid. In one example, a water-soluble polymer of 70% acrylic acid and 30% itaconic acid is mentioned. The passivation of metals by means of an itaconic acid copolymer is not disclosed by the document.

JP-A 2003-027202 discloses a process for treating a galvanized Stahlble¬ Ches with a composition of a metallic compound, a water-soluble organic resin and an acid. The polymer may also be a copolymer of a carboxyl-containing monomer and further carboxyl-containing monomers or OH-containing monomers. In the examples, a copolymer of 70% acrylic acid and 30% itaconic acid is mentioned. The font contains no information on how the polymer is made.

Our unpublished, unpublished application DE 103 53 845 discloses a process for passivating metal surfaces using copolymers of from 50 to 99.9% by weight of (meth) acrylic acid, from 0.1 to 50% by weight of acidic como - Nomerer, including ethylenically unsaturated dicarboxylic acids and optionally 0 to 30 wt.% Of other comonomers. The dicarboxylic acid may be, for example, itaconic acid. However, the document contains no information on special production methods for itaconic acid-containing polymers.

In addition to achieving very good corrosion protection, a passivation process, in particular a chromium-free process, must also meet a number of procedural requirements.

The passivation can be carried out by immersing the workpieces to be passivated in a passivating solution. For this purpose, loose workpieces (eg screws) can be filled into a drum and the drum immersed. Larger workpieces can also be mounted on a suitable frame and the frame can be immersed. In the dipping method, the contact time between the passivating solution and the workpiece can be determined comparatively freely by the person skilled in the art, and thus quite thick passivation layers can also be obtained. The contact time can be in the range of minutes. More complex workpieces are usually joined together in this technique, for example, welded together from steel parts and then galvanized and passivated as a whole.

For the production of flat metal workpieces such as Automobil¬ parts, body panels, equipment panels, facade cladding, Deckenverklei¬ applications or window profiles metal sheets are formed by means of suitable techniques such as punching, drilling, folding, profiling and / or deep drawing. Larger components, such as, for example, automobile bodies, are optionally joined together by welding a plurality of individual parts. The raw material for this purpose are usually long metal strips, which are produced by rolling the metal and wound into rolls ("coils") for storage and transport.

The galvanizing and passivation of such metal strips is carried out on an industrial scale in continuous plants. The metal strip is first galvanized by a galvanizing device, e.g. a tray with molten zinc, and then by another device for passivation, for example e- benfalls a pan or a rinsing device. As a rule, further process steps are carried out continuously, for example cleaning or rinsing steps or else the application of a first coat of varnish to the passivation layer. Typical speeds at which metal strips are driven through the continuous systems are 50 to 100 m / min. This means that the contact time between the metallic surface and the preparation used for passivating is only short. Usually only a few seconds are available for treatment. A process which is suitable industrially must therefore nevertheless have sufficient results with only short contact times.

The object of the invention was therefore to provide an improved, preferably chromium-free, method for passivating metallic surfaces of Zn, Zn alloys, Al or Al alloys, which offers improved corrosion protection over the prior art and in which Nevertheless, only a short contact time between the metallic surface and the preparation used for passivating is required for a satisfactory result. In particular, the method should also be able to be carried out continuously.

Accordingly, a process has been found for passivating metallic surfaces, in which the surface is treated with an acidic, aqueous preparation comprising at least one water-soluble itaconic acid homo- or copolymer, the polymer being composed of the following monomeric units:

(A) 0.1 to 100% by weight of itaconic acid, (B) 0 to 99.9% by weight of at least one monoethylenically unsaturated monocarboxylic acid, and

(C) 0 to 40% by weight of at least one further ethylenically unsaturated monomer which has acidic groups and is different from (A) and (B)

(D) 0 to 30% by weight of at least one further ethylenically unsaturated monomer other than (A), (B) and (C), the amount in each case being based on the total amount of all monomers copolymerized in the copolymer, and the copolymer is obtainable by radical polymerization in aqueous solution at a temperature of less than 120 ⁰ C.

In a preferred embodiment of the invention, the metallic surface is the surface of a band metal and furthermore passivation is preferably carried out by means of a continuous process.

The invention further relates to a passivation layer on a metallic surface, which is obtainable by the method, as well as metallic surfaces comprising such a passivation layer.

Surprisingly, it has been found that the metal surfaces obtained by means of the process according to the invention using itaconic acid-containing polymers are significantly more resistant to corrosion than when known polymers, such as, for example, acrylic acid / maleic acid copolymers, are used. Particularly surprisingly, the itaconic acid copolymers synthesized according to the invention at less than 12O ⁰ C have a significantly better corrosion protection effect than itaconic acid copolymers, which were synthesized at higher temperatures.

The acrylic acid-itaconic acid copolymers prepared according to the invention have a markedly improved passivation compared with acrylic acid-maleic acid copolymers. The itaconic acid copolymers contain lower residual monomer contents in comparison to corresponding maleic acid copolymers. By substitution of maleic acid for itaconic acid, it is possible to obtain a higher proportion of dicarboxylic acid in the polymers according to the invention, which likewise has a positive effect on the passivation properties.

More specifically, the following is to be accomplished for the invention:

The metallic surfaces which can be passivated by means of the method according to the invention are, in particular, the surfaces of non-precious metals. metals. It may be, for example, the surface of iron, steel, Zn, Zn alloys, Al or Al alloys.

The inventive method is particularly suitable for passivation of metallic surfaces of Zn, Zn alloys, Al or Al alloys. These may be the surfaces of bodies or workpieces made entirely of the said metals or alloys. However, they may also be the surfaces of bodies coated with Zn, Zn alloys, Al or Al alloys, wherein the bodies may consist of other materials, for example of other metals, alloys, polymers or composite materials. In particular, it may be the surface of galvanized iron or steel. In a particular embodiment of the method is the surface of a band metal, in particular electrolytically galvanized or hot galvanized steel.

Zn or Al alloys are known to the person skilled in the art. Depending on the desired application, the skilled person will select the type and amount of alloying components. Typical components of zinc alloys for hot dip processes include in particular Al, Pb, Si, Mg, Sn, Cu or Cd. Zinc alloys that are electrodeposited typically include Fe, Co, Ni or Mn. METHODS Typical constituents of aluminum alloys include in particular Mg, Mn, Si, Zn, Cr, Zr, Cu or Ti. These may also be Al / Zn alloys in which Al and Zn are present in approximately the same amount , Steel coated with such alloys is commercially available.

The preparation used for passivation comprises one or more homopolymers and / or copolymers comprising itaconic acid units and optionally monoethylenically unsaturated monocarboxylic acids and optionally further monomers as structural units.

The polymers used are water-soluble or at least water-dispersible. The term water-soluble in the context of this invention is intended to mean that the copolymer or copolymers used should be homogeneously soluble in water. The term "water-dispersible" means that the solution is not very clear, but the polymer is homogeneously distributed therein and also does not settle out.Preferably, they are polymers which are water-soluble.

Preferably, the copolymers used should be completely miscible with water, although this is not absolutely necessary in every case. However, they must be water-soluble at least to such an extent that passivation by means of the process according to the invention is possible. As a rule, the copolymers used should have a solubility of at least 50 g / l, preferably 100 g / l and more preferably at least 200 g / l. It is known to the person skilled in the art of water-soluble polymers that the solubility of COOH-group-containing polymers in water can be dependent on the pH. As a reference point, therefore, in each case the desired ge for the particular application pH should be selected. A copolymer which, at a certain pH, has insufficient solubility for its intended use may have sufficient solubility at a different pH.

The monomer (A) for the preparation of the homo- or copolymer used according to the invention is itaconic acid:

/ CH ₂ -COOH H ₂ C = C

^X COOH

The itaconic acid can also be used in the form of its salts, for example as the alkali or ammonium salt. It is also possible to use derivatives of itaconic acid which readily hydrolyse to itaconic acid in aqueous solution, for example the corresponding anhydride, mono- or diesters or acid amides. Of course, mixtures of such derivatives can be used.

The polymer used according to the invention may be a homopolymer or preferably a copolymer of itaconic acid.

The amount of itaconic acid in the polymers is 0.1 to 100% by weight, preferably 10 to 50% by weight, more preferably 15 to 45% by weight, very preferably 20 to 40% by weight and for example 25 to 35% by weight. %, which is based on the sum of all monomers in the polymer.

The polymer used according to the invention can furthermore comprise up to 99.9% by weight of one or more monomers (B). These are monoethylenically unsaturated monocarboxylic acids.

Examples of suitable monoethylenically unsaturated monocarboxylic acids (B) include acrylic acid, methacrylic acid, crotonic acid, vinylacetic acid or else C ₁ -C ₄ -halloesters of monoethylenically unsaturated dicarboxylic acids. Preferred monomers are acrylic acid and methacrylic acid, particularly preferred is acrylic acid.

Of course, mixtures of several different, monoethylenically unsaturated monocarboxylic acids can be used. The amount of all monomers (B) together is preferably from 50 to 90% by weight, more preferably from 55 to 85% by weight, very preferably from 60 to 80% by weight and, for example, from 65 to 75% by weight.

Optionally, the copolymer according to the invention may further comprise from 0 to 40% by weight of at least one further ethylenically unsaturated monomer (C) other than (A) and (B). The monomers (C) each have at least one acidic group. Particularly preferred are each monoethylenic monomers. The monomers (C) are free-radically polymerizable.

The monomers (C) may be, for example, carboxyl monomers (C1), monomers containing phosphoric acid groups and / or monomers (C2) comprising phosphonic acid groups, or monomers (C3) comprising sulfonic acid groups.

The monomers (C) can also be used in the form of their salts, for example as alkali metal or ammonium salts. Furthermore, it is also possible to use those derivatives of monomers (C) which hydrolyze readily to the free acids in aqueous solution, for example anhydrides, mono- or diesters or acid amides. Of course, mixtures of such derivatives can be used.

Examples of carboxyl group-containing monomers (C1) include, in particular, ethylenically unsaturated dicarboxylic acids, such as e.g. Maleic acid, mesaconic acid, citraconic acid, fumaric acid, or methylenemalonic acid. Preferred monomer (C1) is maleic acid or maleic anhydride.

Examples of suitable monomers (C2) include vinylphosphonic acid, monovinyl phosphonate, allylphosphonic acid, monoesters of phosphoric acid, 3-butenylphosphonic acid, mono (3-butenyl) phosphorates, mono- (4-vinyloxybutyl) phosphates, (phosphonoxyethyl) acrylate, methacrylic acid (phosphonoxyethyl ) esters, mono (- 2-hydroxy-3-vinyloxypropyl) phosphoric acid, phosphoric mono (1-phosphonoxymethyl-2-vinyloxy-ethyl) ester, phosphoric mono (3-allyloxy-2-hydroxy-propyl ) esters, phosphoric acid mono-2- (allylox-1-phosphonoxymethyl-ethyl) ester, 2-hydroxy-4-vinyloxymethyl-1, 3,2-dioxaphosphole, 2-hydroxy-4-allyloxymethyl-1,3,2 -dioxaphosphol. It is also possible to use salts and / or esters, in particular C ₁ to C ₈ mono-, di- and optionally trialkyl esters of the monomers comprising phosphoric acid and / or phosphonic acid groups.

A preferred monomer (C2) is vinylphosphonic acid or hydrolyzable esters or salts thereof.

Examples of sulfonic acid group-containing monomers (C3) include allylsulfonic acid, methallylsulfonic acid, styrenesulfonate, vinylsulfonic acid, allyloxybenzenesulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid, 2- (methacryloyl) ethylsulfonic acid and their alkali metal salts.

Of course, mixtures of several different monomers (C) can be used. Preference is given to monomers (C1) comprising carboxyl groups and to monomers (C2) comprising phosphoric acid groups and / or phosphonic acid groups.

If monomers (C) are present, their amount together is preferably 0.1 to 20% by weight, more preferably 0.2 to 15% by weight and most preferably 0.5 to 10% by weight.

If monomer (C) comprises monomers comprising phosphoric acid groups and / or phosphonic acid groups, in particular vinylphosphonic acid, amounts of from 5 to 40% by weight, preferably from 10 to 30% by weight, are particularly preferred 12 to 28% by weight and very particularly preferably 20 to 25% by weight proven.

Furthermore, the copolymer may optionally contain from 0 to 30% by weight of at least one further free-radically polymerizable, ethylenically unsaturated monomer (D) other than (A), (B) and (C). In addition, no other monomers are used.

The monomers (D) serve to fine-tune the properties of the copolymer. They are chosen by the skilled person depending on the desired properties of the copolymer aus¬. The monomers (D) are also free-radically polymerizable.

Preferably, these are also monoethylenically unsaturated monomers. In special cases, however, small amounts of monomers with several polymerizable groups can be used. As a result, the copolymer can be crosslinked to a small extent.

Examples of monomers (D) include C ₁ to C ₈ alkyl esters or C ₁ to C ₄ hydroxyalkyl esters of (meth) acrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate or butanediol-1, 4-monoacrylate. The alcohol components in the (meth) acrylic esters can also be alkoxylated alcohols. ₁₈ alcohols containing 2 to 80 moles of ethylene oxide, propylene oxide, butylene oxide or to C comprise mixtures thereof - may be mentioned here in particular alkoxylated C. ₁ Examples of such alkoxylated products include methylpolyglycol (meth) acrylate or (meth) acrylic acid esters of C ₁₃ / C ₁₅ -oxo alcohol reacted with 3, 5, 7, 10 or 30 mol of ethylene oxide or mixtures thereof, (Methyl) styrene, maleimide, maleic acid N-alkylimide, Maleinsäurehalbamide or Maleinsäurehalbester.

Also suitable are vinyl or allyl ethers, e.g. Methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, vinyl cyclohexyl ether, vinyl 4-hydroxybutyl ether, decyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, 2- (diethylamino) ethyl vinyl ether, 2- (di-n-butyl-amino) ethyl vinyl ether or methyl diglycol vinyl ether or the corresponding allyl compounds. Also used may be vinyl esters such as vinyl acetate or vinyl propionate.

Examples of basic monomers include acrylamides and alkyl-substituted acrylamides, e.g. Acrylamide, methacrylamide, N-tert-butylacrylamide or N-methyl (meth) acrylamide. Furthermore, basic monomers such as 1-vinylimidazole and N-vinylpyrrolidone can be used.

Examples of crosslinking monomers include molecules having a plurality of ethylenically unsaturated groups, for example di (meth) acrylates, such as ethylene glycol di (meth) acrylate or butanediol-1,4-di (meth) acrylate or poly (meth) acrylates, such as trimethylolpropane tri (meth) acrylate or di (meth) acrylates of oligo- or polyalkylene glycols such as di-, tri- or tetraethylene glycol di (meth) acrylate. Other examples include vinyl (meth) acrylate or butanediol divinyl ether.

Of course, a mixture of different monomers (D) can be used. The amount of all monomers (D) used together is 0 to 30% by weight, based on the total amount of all monomers used for the process.

Preferably, the amount is 0 to 20 wt.%, Particularly preferably 0 to 15 and most preferably 0 to 10 wt.%. If crosslinking monomers (D) are present, their amount should generally not exceed 5%, preferably 2% by weight, based on the total amount of all monomers used for the process. It may be, for example, 10 ppm to 1 wt.%.

The person skilled in the art selects the type and amount of monomers used, depending on the desired passivation. He will take into account that the polymer should be water-soluble or water-dispersible. Monomers which could worsen the water solubility of the polymer are therefore used by the person skilled in the art only in amounts such that no negative effects can occur.

Particularly preferred are copolymers of about 25 to 30% by weight of itaconic acid and about 70 to 75% by weight of acrylic acid, in particular about 26 to 28% by weight of itaconic acid and about 72 to 74% by weight of acrylic acid. Particular preference is given to terpolymers of about 23 to 30% by weight of itaconic acid, about 67 to 75% by weight of acrylic acid and about 0.1 to 10% by weight of vinylphosphonic acid, in particular about 25 to 27% by weight of itaconic acid from about 68 to 70% by weight of acrylic acid and about 3 to 5% by weight of vinylphosphonic acid.

In a further embodiment of the invention, terpolymers of about 10 to 30% by weight of itaconic acid, about 50 to 70% by weight of acrylic acid and about 10 to 30% by weight of vinylphosphonic acid, in particular about 15 to 25% by weight have also Itaconic acid, about 55 to 65% by weight of acrylic acid and about 15 to 25% by weight of vinylphosphonic acid.

The monomers used are radically polymerized in aqueous solution.

The term "aqueous" means that the solvent or diluent used comprises water as the main constituent, but also shares of water-miscible organic solvents may be present, which may be necessary, for example, in order to increase the solubility of certain monomers, in particular To improve monomers (D) in the reaction medium.

The solvent or diluent used accordingly has at least 50% by weight of water with respect to the total amount of the solvent. In addition, one or more water-miscible solvents can be used. Particular mention should be made here of alcohols, for example monoalcohols such as ethanol, propanol or isopropanol, dialcohols such as glycol, diethylene glycol or polyalkylene glycols or derivatives thereof. Preferred alcohols are propanol and isopropanol. The proportion of water is preferably at least 70% by weight, more preferably at least 80% by weight, particularly preferably at least 90% by weight. Most preferably, only water is used.

The carrying out of the free-radical polymerization is known in principle to a person skilled in the art.

The free-radical polymerization is preferably started by the use of suitable polymerization initiators. Alternatively, however, it can also be triggered by suitable radiation, for example. The free-radical initiators should be soluble in the solvent of the reaction, preferably water-soluble.

Among the thermally activatable polymerization initiators are initiators having a decomposition temperature in the range of 30 to 150 ⁰ C, in particular from 50 to 120 ⁰ C, is preferred. This temperature refers as usual to 10h half-life. As initiators it is possible to use all compounds which decompose into free radicals under the polymerization conditions, for example inorganic peroxo compounds, such as peroxodisulfates, in particular ammonium, potassium and preferably sodium peroxodisulfate, peroxosulfates, hydroperoxides, percarbonates and hydrogen peroxide and the so-called redox initiators , Preference is given to the use of water-soluble initiators. In some cases it is advantageous to use mixtures of different initiators, for example mixtures of hydrogen peroxide and sodium or potassium peroxodisulfate. Mixtures of hydrogen peroxide and sodium peroxodisulfate can be used in any proportion.

Suitable organic peroxy compounds are diacetyl peroxide, di-tert-butyl peroxide, diamyl peroxide, dioctanoyl peroxide, didecanoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, bis (o-toloyl) peroxide, succinyl peroxide, tert-butyl peracetate, tert-butyl permaleinate, tert-butyl perisobutyrate, tert-butyl perpivalate, tert-butyl peroctoate, tert-butyl perodecanoate, tert-butyl perbenzoate, tert-butyl peroxide, tert-butyl hydroperoxide (water-soluble), cumene hydroperoxide, tert-butyl peroxy-2-ethylhexanoate and diisopropyl peroxydicarbamate ,

Preferred initiators are also azo compounds. These may be soluble in organic solvents, such as 2,2'-azobis (4-methoxy-2,4-dimethyl valeronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 1, 1'-azobis (cyclohexane 1-carbonitrile), 1 - [(cyano-1-methylethyl) azo] formamide, 2,2'-azobis (N-cyclohexyl-2-methylpropionamide), 2,2'-azobis (2,4-dimethyl valeronitrile) , 2,2'-Azobis (2-methylbutyronitrile), 2,2'-azobis [N- (2-propenyl) -2-methyl-propionamide], 2,2'-azobis (N-butyl-2-methyl-propionamide). Preferably, however, they are water-soluble, such as. 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propanediol dihydrate, 2, 2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2 , 2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamide) dihydrochloride, 2,2'-azobis [2- (3,4,5, 6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane], 2,2'-azobis {2-methyl-N- [2- (2- 1-hydroxybuthyl)] propionamide}.

Further preferred initiators are also redox initiators. The redox initiators contain as oxidizing component at least one of the abovementioned peroxo compounds and as reducing component, for example, ascorbic acid, glucose, sorbose, ammonium or alkali metal hydrogen sulfite, sulfite, thiosulfate, hyposulfite, pyrosulfite, sulfide or sodium hydroxymethyl sulfoxylate. As reducing component of the redox catalyst it is preferable to use ascorbic acid or sodium pyrosulfite. Based on the amount of polymer used in the polymerization For example, 1 × 10 -5 to ^5- mole% of the reducing component of the redox catalyst is used as a monomer.

In combination with the initiators or the redox initiator systems, transition metal catalysts may additionally be used, e.g. Salts of iron, cobalt, nickel, copper, vanadium and manganese. Suitable salts are e.g. Iron (II) sulfate, cobalt (II) chloride, nickel (II) sulfate, copper (I) chloride. The reducing transition metal salt is usually used in an amount of from 0.1 to 1000 ppm, based on the sum of the monomers. For example, combinations of hydrogen peroxide and iron (II) salts, such as a combination of 0.5 to 30, are particularly advantageous

Wt .-% hydrogen peroxide and 0.1 to 500 ppm FeSO ₄ x 7 H ₂ O, in each case based on the sum of the monomers.

Examples of suitable photoinitiators are acetophenone, benzoin ethers, Benzyldialkyl- ketones and their derivatives. They are not or hardly soluble in water, but they bring in alcohol, so that dispersion can be achieved.

Preferably, thermal initiators are used, with water-soluble azo compounds and water-soluble peroxo compounds being preferred. Particularly preferred are inorganic peroxo compounds, in particular hydrogen peroxide and especially sodium peroxodisulfate or mixtures thereof, optionally in combination with 0.1 to 500 ppm FeSO ₄ .7H ₂ O. Very particular preference is given to hydrogen peroxide.

Of course, it is also possible to use mixtures of different initiators, provided that they do not adversely affect one another. The amount is determined by the skilled person depending on the desired copolymer. As a rule, 0.05% by weight to 20% by weight, preferably 0.1 to 15% by weight and particularly preferably 0.2 to 8% by weight, of the initiator are used with respect to the total amount of all monomers.

In addition, suitable regulators, such as, for example, mercaptoethanol, can also be used in a manner known in principle. Preferably, no controllers are used.

The polymerization can also be carried out in the presence of a base. This completely or partially neutralizes the acidic groups, in particular the carboxyl groups of the monomers.

As bases, for example, NaOH, KOH or NH ₃ can be used. Also suitable are amines.

Examples of suitable amines include linear, cyclic and / or branched C ₁ - C ₈ - mono-, di- and trialkylamines, linear or branched C ₁ - C ₈ mono-, di- or Trialka- nolamines, in particular mono-, di- or trialkanolamines, linear or branched C ₁ -C ₈ -alkyl ethers of linear or branched C ₁ -C ₈ -mono-, di- or trialkanolamines, oligo- and polyamines such as, for example, diethylenetriamine or polyethyleneimines, heterocyclic amines such as morpholine, piperazine, imidazole, piperidine or certain aromatic amines such as benzotriazole or tolyltriazole. The amines can also be alkoxylated, in particular ethoxylated. As a result, the water solubility of amines with longer alkyl chains can be advantageously increased.

The person skilled in the art will make a suitable choice among the amines.

Preferred are linear or branched C ₁ -C ₈ -mono-, di- or trialkanolamines, be¬ particularly preferred are mono-, di- and triethanolamine and / or the corresponding ethoxylated products.

If bases are used, the degree of neutralization should generally not exceed 30 mol% based on the total amount of all acidic groups of the monomers. The degree of neutralization is preferably not more than 20 mol%, particularly preferably not more than 10 mol%.

Most preferably, no base is used.

The bases may be added before or during the polymerization. It is preferably added already before or at the latest at the beginning of the polymerization. The base can be added either at once or in a time interval which corresponds at most to the entire reaction time. The base can in this case be added to the monomer feed. The base is preferably added to the original before the beginning of the polymerization.

According to the invention, the polymerization is carried out at a temperature of less than 120 ⁰ C. Apart from this, the temperature can be varied by the person skilled in the art within wide limits depending on the type of monomers used, the initiator and the desired result. Has been proven in this case a minimum temperature of et¬ wa 6O ⁰ C. The temperature can be kept constant during the polymerization or it can be driven even temperature profiles. Preferably, the polyethylene is merisationstemperatur 75-115 ⁰ C, more preferably 80 to 110 ⁰ C and more preferably 90-108 ⁰ C and most preferably 95 to 105 ° C.

The polymerization can be taken vor¬ in conventional apparatus for free-radical polymerization. If one works above the boiling point of the water or the mixture of water and other solvents, working in a suitable pressure vessel, otherwise it can be operated without pressure. Preferably, the Polymerization made without pressure. For example, it can be polymerized under reflux.

In the polymerization, it has proven itself regularly to provide itaconic acid or its derivatives in aqueous solution. Thereafter, the monocarboxylic acid and the initiator, expediently also be metered in aqueous solution. Inlet times of 0.5 h to 24 h, preferably 1 h to 12 h, have proven useful.

In this way, the concentration of the more reactive monocarboxylic acids in the aqueous solution is kept relatively low. This reduces the tendency to react the monocarboxylic acid with itself, and a more uniform incorporation of the itaconic acid units into the copolymer is achieved. If optionally used monomers (C) and / or (D) are inert to react, it is also advisable to submit them together with the itaconic acid. Of course, they can also be added drop by drop later. After the feed of all monomers may also follow a post-reaction time, for example, from 0.5 to 3 hours. This ensures that the polymerization reaction proceeds as completely as possible.

Of course, the skilled person can also carry out the polymerization in other ways.

The synthesized polymers can be isolated from the aqueous solution by conventional methods known to those skilled in the art, for example by evaporation of the solution, spray-drying, freeze-drying or precipitation.

However, the polymers are particularly preferably not isolated at all from the aqueous solution after the polymerization but the resulting solutions of the polymer solutions are used as such.

In order to facilitate such direct further use, the amount of the aqueous solvent should be from the beginning so dimensioned that the concentration of the polymer in the solvent is suitable for the application. A concentration of from 15 to 70% by weight, based on the sum of all components, preferably from 20 to 65% by weight, more preferably from 25 to 60% by weight and, for example, from 45 to 55% by weight, has proven particularly useful.

The polymers according to the invention are soluble or at least dispersible in water or at least 50% by weight of water-containing aqueous solvent mixtures, it being known to the person skilled in the art that the solubility of COOH-rich polymers can be strongly pH-dependent. It therefore refers here to the pH values at which the polymers are used for passivation, ie to an acidic solution, in particular The term "water-dispersible" means that the solution is not very clear, but that the polymer is homogeneously distributed in it and does not settle out, preferably polymers which are water-soluble are.

The pH of the polymer solution is generally less than 5, preferably less than 4 and more preferably less than 3.

The molecular weight M _w (weight average) of the copolymers is 5,000 to 2,000,000 g / mol, preferably at least 10,000 g / mol, more preferably at least 15,000 g / mol. As a rule, M _{w is} 20,000 g / mol to 1,000,000 g / mol, preferably 30,000 g / mol to 900,000 g / mol, more preferably 40,000 g / mol to 800,000 g / mol and most preferably 50,000 g / mol to 700,000 g / mol. It is determined by the person skilled in the art according to the intended use.

The preparation of the polymer or polymers used according to the invention is an aqueous, acidic formulation.

The polymers according to the invention can be used in particular for the treatment of metallic surfaces. For this purpose, the polymers according to the invention can be used in particular as components of corresponding formulations, for example as components of cleaners, pickling solutions, corrosion inhibitors and / or formulations for passivating.

The copolymers according to the invention can be used particularly advantageously for the passivation of metallic surfaces or for the formation of passivation layers on metals. Instead of the term "passivation layer", the term "conversion layer" is often used interchangeably, sometimes also the term "pretreatment layer." They are particularly suitable for chromium-free passivation.

Any desired metallic surfaces can be treated, in particular passivated, by means of the polymers according to the invention. However, they are preferably surfaces of low or high-alloy steel or surfaces of Zn, Zn alloys, Al or Al alloys. These may be the surfaces of bodies or bodies which completely consist of the said metals or alloys. However, they may also be the surfaces of Zn ₁ Zn alloy, Al or Al alloy coated bodies, which bodies may be made of other materials such as other metals, alloys, polymers or composites. In particular, it may be the surface of galvanized iron or steel. In a particular embodiment of the method, it is the surface of a band metal, in particular special for electrolytically galvanized or hot-dip galvanized steel. In a further preferred embodiment, it may be an automobile body.

Zn or Al alloys are known to the person skilled in the art. Depending on the desired application, the skilled person will select the type and amount of alloying components. Typical constituents of zinc alloys for hot dip processes include in particular Al ₁ Pb, Si, Mg, Sn ₁ Cu or Cd. Typical alloy components in Zn alloys which are electrodeposited are Ni, Fe, Co and Mn. Typical components of aluminum alloys include in particular Mg, Mn, Si, Zn, Cr, Zr, Cu or Ti.

It may also be Al / Zn alloys in which Al and Zn are present in approximately the same amount. Steel coated with such alloys is commercially available.

The solvent or diluent used for the copolymers is water or an aqueous solvent mixture containing at least 50% by weight of water. If an aqueous mixture is used, the mixture preferably comprises at least 65% by weight, more preferably at least 80% by weight and most preferably at least 95% by weight of water. The data relate in each case to the total amount of all solvents. Further components of a mixture may be water-miscible solvents. Examples include monoalcohols such as methanol, ethanol or propanol, higher alcohols such as ethylene glycol or polyether polyols and ether alcohols such as butyl glycol or methoxy propanol.

Preferably, only water is used as solvent.

The concentration of the copolymers in the formulation will be determined by one skilled in the art according to the desired application. For example, the thickness of the passivation layer depends on the chosen process technology, but it can also depend on the viscosity of the composition used for passivation. In general, a concentration of 0.01 g / l to 500 g / l, preferably 0.1 g / l to 200 g / l, and particularly preferably 0.5 g / l to 5 g / l has proven. The indicated concentrations relate to the ready-to-use preparation. As a rule, it is possible first to prepare a concentrate which is first diluted to the desired concentration with water or optionally other solvent mixtures on site.

The preparation used according to the invention is acidic. It generally has a pH of from 0.5 to 6, wherein, depending on the substrate and the mode of application and the duration of action of the preparation on the surface, narrower pH ranges can be selected. For example, the pH is adjusted to treat aluminum surfaces. preferably in the range of 2 to 4 and in the case of treatment of zinc or galvanized steel, preferably in the range of 1 to 5.

The pH of the preparation can be controlled on the one hand by the nature and concentration of the COOH-containing polymers or copolymers and er¬ is thus automatically. It should be noted in this connection that the COOH groups in the polymer are possibly u.U. can also be completely or partially neutralized.

However, the preparation may optionally also comprise at least one inorganic or organic acid or mixtures thereof. Examples of suitable acids include phosphoric, sulfuric or nitrogen-containing acids such as phosphoric acid, phosphonic acid, sulfuric acid, sulfonic acids such as methanesulfonic acid, sulfamic acid, p-toluenesulfonic acid, m-nitrobenzenesulfonic acid and derivatives thereof, nitric acid, hydrofluoric acid, hydrochloric acid, formic acid or Acetic acid. The acid is preferably selected from the group consisting of HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ , formic acid or acetic acid. Particularly preferred are H ₃ PO ₄ and / or HNO ₃ . Of course, mixtures of different acids can be used.

Conversely, bases may also be used to increase the pH.

Examples of phosphonic acids include 1-hydroxyethane-1, 1-diphosphonic acid (HEDP), 2-phosphonobutane-1, 2,4-tricarboxylic acid (PBTC), aminotri (methylenephosphonic acid) (ATMP), ethylenediaminetetra (methylenephosphonic acid) (EDTMP) or Diethylenetriaminepenta (methylenephosphonic acid) (DTPMP).

The type and concentration of the acid in the preparation will be determined by one skilled in the art according to the desired application and pH. In general, a concentration of 0.01 g / l to 30 g / l, preferably 0.05 g / l to 3 g / l, and more preferably 0.1 g / l to 5 g / l has proven.

The preparation may also optionally comprise further components via the components mentioned.

The optionally present components can be, for example, transition metal ions and compounds, for example Ce, Ni, Co, V, Fe, Zn, Zr, Ca, Mn, Mo, W, Ti, Zr, Hf, Bi, Cr and / or the lanthanides act. They may also be compounds of main group elements, such as Si and / or Al. The compounds can be used, for example, in the form of the respective aqua complexes. However, they can also be complexes with other ligands, such as fluoride complexes of Ti (IV), Zr (IV) or Si (IV) or oxometallates such as MoO ₄ ^{2 "} or WO ₄ ^2" . You can also continue Complexes with typical chelating ligands such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA) or methylglycinediacetic acid (MGDA).

Further optional components include surface-active compounds, corrosion inhibitors or typical electroplating aids. The person skilled in the art will make an appropriate selection of the optionally possible optional components as well as their quantities depending on the desired application. Examples of particularly preferred corrosion inhibitors which can be used in combination with the itaconic acid polymers include benzotriazole and / or tolyltriazole.

The preparation may also comprise other water-soluble polymers as additional components for the fine control of the properties. Examples of such polymers include, in particular, polymers comprising carboxylate groups, which merely do not correspond to the above definition of the composition. Examples which may be mentioned are poly (meth) acrylic acids and also copolymers of (meth) acrylic acid with monomers having acid groups, for example maleic acid, fumaric acid, crotonic acid or vinylacetic acid. The amount of such additional (co) polymers is determined by the person skilled in the art, depending on the desired properties of the passivation layer. However, it should as a rule not exceed 30% by weight, preferably 20% by weight and particularly preferably 10% by weight, relative to the amount of all the polymers used.

The passivation is preferably a passivation that is essentially free of chromium. This should mean that at most small amounts of chromium compounds could be added for fine control of the properties of the passivation layer. The amount should not exceed 2% by weight, preferably 1% by weight, and more preferably 0.5% by weight, of chromium with respect to all constituents of the composition. If chromium compounds are to be used; should preferably Cr (III) compounds are used. In any case, the Cr (VI) content should be kept so low that the Cr (VI) content on the passivated metal does not exceed 1 mg / m ² .

Particularly preferred is a chromium-free passivation, ie the einge¬ set preparation contains no Cr compounds. However, the term "chromium-free" does not exclude the indirect and intrinsic inadvertent introduction of small amounts of chromium into the process, namely if passivates are made by means of the process according to the invention which comprise chromium as an alloy constituent, for example Cr-containing steel , it is always within the scope of the possible that small amounts of chromium in the metal to be treated are dissolved by the preparation used for the process and, accordingly, inadvertently into the Preparation can get. Even when using such metals and the resulting consequences, the process should be regarded as "chromium-free".

In the method according to the invention for passivating metallic surfaces, the surface of the metal is treated with the preparation, for example by spraying, dipping or rolling. After a dipping process, you can drain the workpiece to remove excess treatment solution; In the case of sheets, metal foils or the like, however, excess treatment solution can also be squeezed or doctored off, for example. In the treatment, at least parts of the polymer used as well as other components of the preparation are chemisorbed by the surface of the metal, so that a firm bond between the surface and the component comes about. The treatment with the preparation is usually carried out at room temperature or temperatures above room temperature without that lower temperatures should be excluded in principle. In Re- gel trap, the treatment at 20 to 90 ⁰ C, preferably 25 to 80 ⁰ C and particularly preferably 30 to 60 ⁰ C. For this purpose, the bath can be heated with the formulation, but an elevated temperature may also adjust itself automatically by one dips warm metal into the bath.

It is possible to rinse the surface after the treatment with a cleaning liquid, in particular with water, in order to remove residues of the preparation used according to the invention from the surface.

However, the treatment may also be a so-called "no-rinse" process, in which the treatment solution is dried directly in a drying oven immediately after application without rinsing off.

The treatment of the metal surface with the preparation and the crosslinker may be carried out batchwise or preferably continuously. A continuous process is particularly suitable for treating strip metals. The metal strip is driven, in this case by a trough or a spraying device with the preparation and optionally a trough or spraying device and optionally by further pre- or post-treatment stations.

The duration of treatment is determined by the person skilled in the art according to the desired properties of the layer, the composition used for the treatment and the technical conditions. It can be significantly less than a second or several minutes. In the continuous process, it has proven particularly useful to contact the surface with the preparation for a period of 1 to 60 seconds. After treatment, the solvent used is removed. The removal can be carried out at room temperature by simple evaporation in air at room temperature.

However, the removal of the solvent can also be assisted by suitable auxiliaries, for example by heating and / or by passing gas streams, in particular air streams. The evaporation of the solvent can be assisted for example by IR emitters, or also, for example, by drying in a drying channel. Has proven useful for drying temperature of 3O ⁰ C a to 16O ⁰ C, preferably from 40 ° C to 100 ° C and particularly preferably 50 ° C to 80 ° C. This refers to the temperature on the metal surface, the dryer temperature may need to be set higher and is selected by the expert.

The process according to the invention may optionally comprise one or more pretreatment steps. For example, the metallic surface can be cleaned prior to passivation with the preparation used according to the invention, e.g. to remove fats or oils. Furthermore, it can also be pickled prior to passivation to remove oxide scale, scale, temporary corrosion protection and the like. Furthermore, the surface must also be optionally rinsed with water after and between such pretreatment steps, and the residues of rinsing solutions or pickling solutions removed.

The passivation layer can additionally be crosslinked. For this purpose, for example, a crosslinker may be added to the preparation used, provided that it does not already react in the preparation. However, it is also initially possible to treat the metal with the preparation and then treat the layer with a suitable crosslinker, for example by spraying it with the solution of a crosslinking agent.

Suitable crosslinkers should be water-soluble or at least soluble in the said aqueous solvent mixture. Examples of suitable crosslinkers include, in particular, those which have at least 2 crosslinking groups selected from the group of aziran, oxirane or thiirane groups. Further details of suitable crosslinkers are disclosed in our application WO 2005/042801, to which we expressly refer at this point.

By means of the method according to the invention, a passivation layer on a metallic surface is obtainable. The exact structure and composition of the passivation layer is not known to us. However, in addition to the usual amorphous oxides of aluminum or zinc and, if appropriate, further metals, it also comprises the reaction products of the polymer and optionally of the crosslinker and / or further components of the formulation. The composition of the passivation layer is in Generally not homogeneous, but the components appear to have concentration gradients.

The thickness of the passivation layer is adjusted by the person skilled in the art according to the desired properties of the layer. As a rule, the thickness is 0.01 to 3 μm, preferably 0.1 to 2.5 μm, particularly preferably 0.2 to 2 μm, very particularly preferably 0.3 to 1.5 μm and, for example, 1 to 2 μm , The thickness can be influenced, for example, by the type and amount of the components applied and the contact time. Furthermore, it can be influenced by process parameters, for example by doctoring off or rolling off too much applied treatment solution.

The thickness of the layer is determined by differential weighing before and after the action of the composition used according to the invention on the metal surface, assuming that the layer has a specific density of 1 kg / l. In the following, "layer thickness" is always understood to mean a size determined independently of the specific density that the layer actually has.These thin layers are sufficient to achieve outstanding corrosion protection ,

A further subject of the present application is a metallic surface which comprises the passivation layer according to the invention. The passivation layer is applied directly to the actual metal surface. In a preferred embodiment, it is a strip metal made of steel, which comprises a coating of Zn or a Zn alloy, and on which a passivation layer according to the invention is applied. It can also be an automobile body, which is coated with the passivation layer according to the invention.

The metallic surface with passivation layer can be overlaid in a manner known in principle with one or more color or effect paint layers. Typical paints, their composition and typical as Schicht¬ follow in several paint layers are known in the art in principle.

The passivation according to the invention can be used at various processing stages. It can be made for example by a steel manufacturer. Here, a steel strip can be galvanized in a continuous process and passivated directly after galvanizing by treatment with the formulation used according to the invention. Passivation at this stage is often referred to by the expert as "after-treatment". This can only be a temporary passivation, which serves for protection against corrosion during storage and during transport and / or during further process steps, but is removed again before application of the permanent corrosion protection. The acidic copolymers can be removed from the surface again by cleaning with aqueous alkaline solutions.

But it may also be a permanent corrosion protection treatment, which remains on the belt or the finished molded workpiece and is provided with zusätzli¬ Chen lacquer layers. Passivation at this stage is often referred to by the skilled person as "pretreatment".

The passivated and possibly lacquered sheets, strips or other metallic semifinished products can be further processed into metallic workpieces, for example an automobile body. As a rule, at least one separating step and one forming step are required. Larger components can then be assembled from individual parts. During forming, the shape of the material is usually changed in contact with a tool. They may, for example, be pressure transformations, such as rolling or embossing, tensile compressive forming, such as drawing, deep drawing, collar drawing or pressing, tensile forming, such as lengths or widths, bending, such as bending, round rolling or folding, and shear forming, such as twisting or sliding act.

By means of the method according to the invention for passivation a significantly better corrosion protection is achieved than when using itaconic acid copolymers, which were obtained at higher temperatures.

The following examples are intended to illustrate the invention in more detail:

Measurement methods: The K values were measured according to H. Fikentscher, Cellulose-Chemie, Vol. 13, pp. 58-64 and 71-74 (1932) in 1% strength by weight aqueous solution at 25 ° C. M _w values were determined by gel permeation chromatography.

Preparation of the polymers

Comparative Example 1

Copolymer of 75% by weight of acrylic acid and 25% by weight of maleic acid

480 g of maleic anhydride and 22.5 mg of iron sulfate in one liter of deionized water are introduced into a 6 l pressure reactor with anchor stirrer, temperature control and introduction of nitrogen. Under nitrogen atmosphere is heated to 115 to 120 ⁰ C. After reaching this temperature, 1670 g of acrylic acid in 1, 21 deionized water, and within 5 h, 115 g of 30% hydrogen peroxide solution and 300 ml of deionized water are uniformly added within 4h. During the polymerization, the pressure is maintained at 3 to 4 bar by gentle decompression.

After cooling, a yellowish, clear polymer solution having a solids content of 45.6% and a K value (1% in deionized water) of 26.0 is obtained.

Comparative Example 2:

Copolymer of acrylic acid / itaconic acid (73/27) at 120 ⁰ C polymerization actuator in Druckre-

In a 6I pressure reactor equipped with anchor stirrer, temperature control, nitrogen inlet and 2 feed points, 444 g of itaconic acid, 15.5 mg of ferrous sulfate heptahydrate, and 889 g eήtionisiertes water are presented.

Under nitrogen atmosphere is heated to 120 ⁰ C. After reaching this temperature, feed 1, consisting of 1188.0 g of acrylic acid and 926 g of deionized water, and within 6 hours feed 2, consisting of 81.6 g of hydrogen peroxide (30% strength), and within 5 h 177 g of deionized water are added evenly. After the end of feed 1, an additional 133 g of deionized water are added. Tion mix the Reak¬ further 2 hours at 120 ⁰ C is stirred. During the polymerization, the pressure is maintained at 3 to 4 bar by gentle decompression. The batch is diluted with water.

After cooling, a yellowish, clear polymer solution having a solids content of 17.9% and a K value (1% in deionized water) of 83.5 is obtained. By means of ¹ H-NMR spectrum, no free itaconic acid could be detected.

example 1

Copolymer of acrylic acid and itaconic acid (73/27), pressure-free polymerization at 100 ° C

In a stirred pot with paddle stirrer and internal thermometer, 111.0 g of itaconic acid are dissolved in 250 g of deionized water and heated with 3.875 mg of iron (II) sulfate heptahydrate to gentle reflux (internal temperature 98 ° C.). Then be within 5 h feed 1, consisting of 297.0 g of acrylic acid and 398.0 g of deionized water, and within 6 h feed 2, consisting of 6.12 g of sodium peroxodisulfate in 180 g of water was added. After the end of feed 1, a further 2 is stirred at 98 ^° C. This gives a light yellow, clear polymer solution having a solids content of 36.4% and a K value (1% in deionized water) of 59.6. By means of ¹ H-NMR spectrum, no free itaconic acid could be detected.

Example 2

Copolymer of acrylic acid and itaconic acid (73/27); Pressure-free polymerization at 100 ^° C.

111.0 g of itaconic acid are dissolved in 250 g of deionized water in a stirred pot with paddle stirrer and internal thermometer and heated to a gentle reflux with 3.875 mg of iron (II) sulfate heptahydrate (internal temperature 98.degree. C.). Then within 5 h feed 1, consisting of 297.0 g of acrylic acid and 398.0 g of deionized water, and within 6 h feed 2, consisting of 20.4 g of hydrogen peroxide (30%) in 180 g of water was added. After the end of feed 1, another 2 is stirred at 98.degree. The batch is diluted in several portions with a total of 750 g of water. A light yellow, clear polymer solution having a solids content of 15.0% and a K value (1% in deionized water) of 115.2 is obtained. It was not possible to detect any free itaconic acid by means of ¹ H-NMR spectra.

Example 3

Terpolymer of acrylic acid, itaconic acid and vinylphosphonic acid (69/26/5); Pressure-free polymerization at 100 ° C

In a stirred pot with paddle stirrer and internal thermometer, 111.0 g of itaconic acid are dissolved in 250 g of deionized water and heated with 3.875 mg of iron (II) sulfate heptahydrate to gentle reflux (internal temperature 98 ° C.). Then within 5 h feed 1, consisting of 297.0 g of acrylic acid, 22.7 g of vinylphosphonic acid and 346.0 g of deionized water, and within 6 h feed 2, consisting of 42.8 g of hydrogen peroxide in 180 g of water. After the end of feed 1, another 2 is stirred at 98.degree. The batch is diluted in several portions with a total of 700 g of water. This gives a light yellow, clear polymer solution having a solids content of 21, 2% and a K value (1% in deionized water) of 37.8. Example 4

Acrylic acid-acetylic acid-vinylphosphonic acid copolymer

In a stirred pot with paddle stirrer and internal thermometer, 161.3 g of itaconic acid and 152 g of vinylphosphonic acid (95%) are dissolved in 200 g of deionized water and mixed with 703 mg of iron (II) sulphate heptahydrate to give slight reflux (internal temperature 98.degree C). Then, feed 1, consisting of 430.0 g of acrylic acid and 455 g of deionized water, and within 6 h feed 2, consisting of 42.5 g of sodium peroxodisulfate in 160 g of water are added within 5 h. After the end of feed 1, the mixture is stirred at 98 ^° C. for a further 2 h. This gives a light yellow, clear Polymerlö¬ solution with a solids content of 48.8% and a K value (1% in deionized water) of 28.2.

Passivation of metallic surfaces

Metallic surface and its pretreatment:

For the tests, alkaline galvanized or hot-galvanized steel sheets (approx. 100x190x0.7 mm, 20 μm zinc coating) were used.

The alkaline zinc-coated steel sheets (AV) can be sec in a cleaning solution (0.5% HCl + 0.1% Lutensol ^® AP 10, BASF AG) for about 5. Immersed and instantly rinsed with deionized water and dried by blowing.

The hot-dip galvanized steel sheets (HV) are immersed in an alkaline degreasing for 120 sec. At 50 ⁰ C and immediately rinsed with deionized water and dried by blowing.

Preparation of the preparation used according to the invention

The synthesized polymers were dissolved in water (solids content 5% by weight), homogenized and filled into an immersion bath. The cleaned sheets are immersed directly for 30 s in the 5O ⁰ C tempered polymer solution and dried at RT. The edges of the passivated sheet are taped.

Differential weighing

The thickness of the layer is determined by differential weighing before and after the composition has had an effect on the metal surface and assuming that

Layer has a specific density of 1 kg / l, determined. The following will be under "Layer thickness" always understood such a determined size, regardless of what specific density the layer actually has.

The determined by Differenzwäg ung layer thicknesses are between 1.5 and 3 microns. The service life is determined in the salt spray test.

Test method

salt spray test

The result of a salt spray test according to DIN 50021 serves as a measure of the corrosion-inhibiting effect. Depending on the type of corrosion damage observed, the service life in the corrosion test is defined differently.

- Form white spots of generally more than 1 mm in diameter

(Zn or Al oxide, so-called white rust), the service life is given as the time after which the damage pattern corresponds to the evaluation level 8 in DIN EN ISO 10289 of April 2001, Appendix B, page 19.

If black spots of generally less than 1 mm diameter (in particular zinc provided with a passivation layer) form before white rust spots form, the service life is given as the time after which the damage pattern corresponds to the evaluation level 8 in DIN EN ISO 10289 April 2001, Appendix A, page 9.

Test chamber volume: 400I

Spray mist throughput measured according to DIN: 2.2 ml / h

The results of the tests are summarized in Table 1.

Table 1: Results of Examples and Comparative Examples

(O

nb not determined

The examples and comparative examples show that by the inventive Ver¬ drive for passivation using Itaconsäurepolymeren with a Poly merisationstemperatur of less than 120 ⁰ C a significantly better corrosion protection is achieved, than when using Itaconsäurepolymeren which sation by polymerisation at higher Temperatures were produced. The effectiveness is also higher than that of acrylic acid-maleic acid copolymers.

Claims

claims

1. A method for passivating metallic surfaces by treating the surface with an acidic, aqueous preparation comprising at least one itaconic acid homo- or copolymer, wherein the polymer is composed of the following monomeric units:

(A) 0.1 to 100% by weight of itaconic acid,

(B) 0 to 99.9 wt.% Of at least one monoethylenically unsaturated monocarboxylic acid, and

(D) 0 to 30% by weight of at least one further ethylenically unsaturated monomer other than (A), (B) and (C), the amount in each case being based on the total amount of all the monomers copolymerized in the copolymer is characterized in that the copolymer by free-radical polyvinyl lymerisation in aqueous solution at a temperature of less than 12O ⁰ C available.

2. Process according to Claim 1, characterized in that the amount of itaconic acid is 10 to 50% by weight and the amount of monoethylenically unsaturated monocarboxylic acids is 50 to 90% by weight.

3. Process according to claim 2, characterized in that the amount of itaconic acid is 20 to 45% by weight.

4. The method according to any one of claims 1 to 3, characterized in that the amount of monomer (C) 0.1 to 40 wt.% Is.

5. The method according to any one of claims 1 to 4, characterized in that it is in the acidic group in monomer (C) at least one group aus¬ selected from the group of carboxyl groups, phosphoric acid groups and phosphonic acid groups.

6. The method according to any one of claims 1 to 5, characterized in that monomer (C) is vinylphosphonic acid.

A process according to claim 1, characterized in that the polymer is a terpolymer of 55 to 65% by weight of acrylic acid, 15 to 25% by weight of itaconic acid and 15 to 25% by weight of vinylphosphonic acid.

8. The method according to any one of claims 1 to 7, characterized in that one carries out the polymerization at a temperature of 90 to 105 ° C.

9. The method according to any one of claims 1 to 8, characterized in that it is a metallic surface of Zn, Al or alloys thereof.

10. The method according to any one of claims 1 to 9, characterized in that it is a substantially chromium-free process.

11. The method according to any one of claims 1 to 10, characterized in that the treatment is carried out by means of rolling, spraying or dipping method.

12. The method according to any one of claims 1 to 11, characterized in that it is the surface of a metal band at the metal surface.

13. The method according to claim 12, characterized in that it is the strip metal to electrolytically galvanized or hot-dip galvanized steel.

14. The method according to claim 12 or 13, characterized in that one carries out the treatment by means of a continuous process.

15. The method according to any one of claims 12 to 14, characterized in that the surface is brought into contact with the preparation for a period of 1 to 60 s.

16. The method according to any one of claims 1 to 15, characterized in that the formulation additionally comprises benzyl and / or tolyltriazole.

17. passivation layer on a metallic surface obtainable by a Ver¬ drive according to one of claims 1 to 16.

18. Passivierungsschicht according to claim 17, characterized in that the thickness is 0.01 to 3 microns.

19. A metallic surface comprising a passivation layer according to claim 17 or 18.

20. Metallic surface according to claim 19, characterized in that on the passivation layer are still one or more superposed lacquer layers.

21. A metallic surface according to claim 20, characterized in that it is the surface of an automobile body.

22 steel strip metal comprising a coating of Zn or a Zn alloy having a surface according to claim 19 or 20.