KR20010023902A - Pretreatment before painting of composite metal structures containing aluminum portions - Google Patents

Abstract

In a chemical pretreatment method of a composite metal structure comprising a steel, galvanized steel surface and / or alloy-zinc plated steel surface portion together with an aluminum or aluminum alloy portion, the first step is a metal structure and a zinc phosphate layer on the aluminum portion. Without forming, the steel and galvanized and / or alloy-zinc plated steel sheets were treated with a zinc phosphate treatment solution to form a surface-coated crystalline zinc phosphate layer, followed by a second step to produce a conversion layer over the aluminum portion. On uncoated steel, galvanized and / or alloy-zinc plated steel sheets, the crystalline zinc phosphate layer is contacted with a solution which does not dissolve excessively.

Description

Pretreatment pre-painting of composite metal structures containing aluminum parts {PRETREATMENT BEFORE PAINTING OF COMPOSITE METAL STRUCTURES CONTAINING ALUMINUM PORTIONS}

For many reasons, such as weight, strength or recyclability, aluminum is increasingly used in vehicle construction. The expression "aluminum" in the present invention includes not only pure aluminum but also an aluminum alloy in which aluminum is a main component. Examples of mainly used alloying elements include silicon, magnesium, copper, manganese, chromium and nickel and the like, and the total weight ratio of such alloying elements in the alloy generally does not exceed 10%. Engine and gear parts, wheels, seat frames, etc. already contain large quantities of aluminum, while the use of aluminum in bodywork is currently not only used for hoods, rear truck lids, interior door parts and many small parts. It is confined to parts such as truck cabins, side walls of transports or attachments of minivans. In total, less than 5% of the metal surface of automobile bodies worldwide is made of aluminum. The increasing use of aluminum in this sector is being intensively studied by the aluminum and automotive industries.

The present invention relates to a method for pre-corrosion corrosion pretreatment of a composite metal structure comprising aluminum and / or aluminum alloy portions in addition to steel and / or galvanized steel portions. The method is particularly for use in automobile manufacturing. In automobile manufacturing, bodywork or bodywork components comprising structural parts of aluminum and / or aluminum alloys, in addition to structural parts of steel and / or galvanized steel, undergo conversion chemical pretreatment prior to painting. In this regard, cathode electron immersion coating is commonly used as the first painting step. The process according to the invention is particularly suitable as a pretreatment step for this step.

The process of the present invention differs from previous conventional pretreatment methods in automobile manufacturing in that the surface-coated zinc phosphate layer is deposited on the steel and / or galvanized steel surface without coating the aluminum surface to a significant extent in the first step. The second step involves treating the already formed zinc phosphate layer with an excessive attack and, in fact, preferably with a solution which forms a surface layer on the aluminum surface while at the same time enhancing the anticorrosion action.

Thus, a two step process is involved, the first step involving conventional zinc phosphate treatment. Of course, it is necessary to use a zinc phosphate treatment solution without a layer formed on aluminum. Such zinc phosphate treating solutions are known in the art and are recited hereafter as examples. In the second step a solution is used which has an effective component for forming a protective layer on aluminum. In this regard, the nature and concentration of this solution should be chosen so that on the one hand it forms a layer on the aluminum surface and on the other hand the crystalline zinc phosphate layer formed on the iron and / or zinc surface is not excessively damaged.

The purpose of phosphating metals is metals that are already firmly adhered to the metal surface which already improves corrosion resistance and contributes to substantial improvement of coating adhesion and resistance to creepage under corrosion stress with paints or other organic coatings. To prepare a phosphate layer. Such phosphate treatment processes have long been known. For pretreatment prior to coating, in particular before electroimmersion coating, the phosphate treatment solution is for example low zinc phosphate containing a relatively low concentration of zinc ions, for example 0.5 to 2 g per liter (hereinafter generally abbreviated as "g / l"). Treatment processes are particularly suitable. The basic parameter in this low zinc phosphate treatment bath is the weight ratio of phosphate ions to zinc ions, the weight ratio being generally above 8 and may be up to 30.

It has been found that phosphate layers with substantially improved corrosion protection and paint adhesion can be formed by using other polyvalent cations together in zinc phosphate treatment baths. For example, a low phosphate process in which 0.5 to 1.5 g / l manganese ions and 0.3 to 2.0 g / l nickel ions are added to produce a metal surface for painting, for example, so-called for cathodic electron immersion coating of a vehicle body. Widely used in "tri-cation" processes.

Nickel and alternative cobalt are also classified as dangerous from the point of view of toxicological and effluent treatment, but are currently as effective as tri-cation processes, but use nickel and / or cobalt in significantly lower concentrations, preferably using both metals at all. Efforts are being made to find phosphate treatment processes.

EP-A-459 541 contains phosphate which does not contain killing nickel and contains, in addition to zinc and phosphate, 0.2 to 4 g / l manganese and 1 to 30 mg per liter (usually abbreviated to mg / l). Solutions are described. In addition to zinc and phosphate from DE-A 42 10 513, nickel-free phosphate treatment solutions containing hydroxylamine as promoter as well as 0.5 to 25 mg / l copper ions are known. This phosphate solution also optionally contains 0.15 to 5 g / l manganese.

German patent application DE 196 06 017.6 discloses a phosphate treatment solution with reduced concentrations of heavy metals containing 0.2 to 3 g / l zinc ions, 1 to 150 mg / l manganese ions and 1 to 30 mg / l copper ions. This is described. This phosphate treatment solution may optionally contain 50 mg / l nickel ions and 100 mg / l cobalt ions. Further optional components are 0.2 to 1.5 g / l lithium cation.

DE 195 38 778 describes the adjustment of the coating weight of the phosphate layer by the use of hydroxylamine as accelerator. The use of hydroxylamine and / or its compounds to influence the formation of phosphate crystals is known in many publications. EP-A-315 059 is a special effect that results from the use of hydroxylamine in phosphate baths, although zinc concentrations in phosphate baths exceed the typical range for low zinc processes, but phosphate crystals on steel are desired. Or in the form of nodes. In this way it is possible to operate a phosphate treatment bath with a zinc concentration of 2 g / l or less and a weight ratio of phosphate to zinc as low as 3.7. The required hydroxylamine concentration is given as 0.5 to 50 g / l, preferably 1 to 10 g / l.

WO 93/03198 discloses a tri-cationic phosphate treatment bath in which a zinc content of 0.5 to 2 g / l, a nickel and manganese content of 0.2 to 1.5 g / l in each case and a specific weight ratio of zinc to other divalent cations is maintained. A method of using hydroxylamine is described. The bath also contains 1 to 2.5 g / l of "hydroxylamine promoter", which represents a hydroxylamine salt, preferably hydroxylamine ammonium sulfate.

This technique is commonly used to improve the so-called passivating post-rinsing, and the corrosion protection achieved by the phosphate layer, also called post-passivating. Treatment baths containing chromic acid are still widely used for this purpose. However, due to operational safety and environmental protection, there is a tendency to replace this chromium containing passivating bath with a chromium free treatment bath. Organic reactive solutions containing complex substituted poly (vinylphenol) are known for this purpose. Examples of such compounds are described in DE-C-31 46 265. Particularly effective polymers of this type contain amine substituents and will be obtainable by the Mannich reaction between poly (vinylphenol) and aldehydes and organic amines. Such polymers are described, for example, in EP-BP-91 166, EP-B-319 016 and EP-B-319 017. Polymers of this type are also used within the scope of the present invention and the contents of the four documents cited immediately above are hereby incorporated by reference, except to the extent that they do not conform to the teachings apparent herein. The use of polyvinyl phenol derivatives for the surface treatment of aluminum is known, for example, from EP-B-319 016 mentioned above.

WO 90/12902 describes a chromium-free coating for aluminum, having an aluminum surface having a pH in the range of about 2.5 to 5.0 and containing not only phosphate ions but also fluoric acid of zirconium, titanium, hafnium and silicon elements in addition to polyvinyl phenol derivatives. Contact with the treatment solution.

In US-A-5 129 967

(a) 10 to 16 g / l polyacrylic acid or a copolymer of acrylic acid,

(b) 12 to 19 g / l hexafluorozirconic acid,

(c) 0.17 to 0.3 g / l hydrofluoric acid and

(d) A treatment bath for no-cleaning treatment of aluminum containing hexafluorotitanic acid of 0.6 g / l or less (called "dried in place conversion coating" in US-A-5 129 967) is described.

EP-B-8 942

(a) 0.5 to 10 g / l polyacrylic acid or polyacrylic acid ester,

(b) not only a treatment solution for aluminum cans, preferably containing one or more of 0.2 to 8 g / l compound H ₂ ZrF ₆ , H ₂ TiF ₆ and H ₂ SiF ₆ , wherein the pH of the solution is less than 3.5;

(a) 25 to 100 g / l polyacrylic acid or polyacrylic acid ester,

(b) 25 to 100 g / l of one or more of compounds H ₂ ZrF ₆ , H ₂ TiF ₆ and H ₂ SiF ₆ and

(c) An aqueous concentrate for supplying a treatment solution containing a free fluoride ion source that produces 17 to 120 g / l of free fluoride is described.

DE-C-19 33 013 describes a treatment bath exceeding pH 3.5, which suitably measures the amount of boron, titanium or zirconium in an amount of 0.1 to 15 g / l, measured as a stoichiometric equivalent as boron, titanium or zirconium. In addition to complex fluorides it further contains 0.5 to 30 g / l of oxidizing agent, in particular sodium meta-nitrobenzenesulfonate. DE-C-24 33 704 describes, in particular, a treatment bath to improve paint adhesion and permanent corrosion protection in aluminum acids, which treatments range from 0.1 to 5 g / l polyacrylic acid, polyacrylic acid or polyacrylic acid. It may contain not only esters but also 0.1 to 3.5 g / l ammonium fluoride zirconate calculated by ZrO ₂ . The pH of this bath may vary over a wide range. In general, best results are obtained when the pH is between 6 and 8. US-A-4 992 116 describes a treatment bath for the conversion treatment of aluminum having a pH value of about 2.5 to 5, which contains at least the following three components.

(a) phosphate ions in a concentration range of 1.1 × 10 ⁻⁵ to 1.3 × 10 ⁻³ mole / liter, corresponding to 1 to 500 mg / l,

(b) zirconium, titanium, hafnium, and silicon (from 1.1 × 10 ⁻⁵ to 5.3 × 10 ⁻³ mole / liter (typically abbreviated to “mole / l”), corresponding to 1.6-380 mg / l of each element); Fluoric acid of the element and

(c) 0.26 to 20 g / l polyphenol compound obtained by reacting poly (vinylphenol) with aldehyde and organic amine.

The molar ratio of fluoric acid to phosphate should be maintained at about 2.5: 1 to 1:10.

DE-A-27 15 292 describes a treatment bath for chromium-free pretreatment of aluminum cans, which contains at least 10 ppm titanium and / or zirconium, 10 to form complex fluorides of titanium and / or zirconium present. To 1000 ppm phosphate and a sufficient amount of fluoride of 13 ppm or more and a pH value of 1.5-4.

WO 92/07973 describes a chromium-free treatment method for aluminum, which is 0.01 to about 18 weight percent H ₂ ZrF ₆ and 0.01 to about 10 weight percent 3- (NC _1-4 alkyl- in acidic aqueous solution). N-2-hydroxyethyl-aminomethyl) -4-hydroxystyrene polymer is used as an essential component. Optional components include from 0.05 to 10 weight percent dispersed SiO ₂ , 0.06 to 0.6 weight percent polymer solubilizer as well as surfactants. Among the "reaction products of poly (vinylphenol) and amines containing aldehydes and organic hydroxyl groups" described below include the polymers mentioned above and can be used within the scope of the present invention.

In fact, in joint phosphating the surface of aluminum and the surface of steel and / or galvanized steel, technical compromises have to be taken in the composition of the phosphating bath. The aluminum ions released from the aluminum surface by etching and picking act as poisons to the phosphate treatment solution and prevent the formation of zinc phosphate crystals on the iron surface. The molten aluminum must therefore be precipitated or blocked in a suitable way. For this purpose free fluoride ions or complex bound fluoride ions are generally added to the phosphate bath.

If the solubility products of the corresponding salts are excessive, the fluoride ions block the aluminum ions by complex formation and / or precipitate the aluminum ions as hexa-fluoraluminates of sodium and / or potassium. In addition, free fluoride ions typically increase the corrosion attack on the aluminum surface so that a somewhat sealed and sealed zinc phosphate layer can be formed on the aluminum surface.

Joint phosphating of aluminum structural parts together with steel and / or galvanized steel surfaces thus has the technical disadvantage that the phosphating bath must be monitored very accurately in terms of fluoride content. This will increase the related control and monitoring work and require storage and metering of the fluoride containing solution as a separate supplemental feed solution. In addition, the precipitated hexafluoroaluminate will increase the amount of phosphate treated sludge, thereby increasing its removal and treatment costs.

There is therefore a need for a pretreatment process for complex structural parts, for example vehicle bodies, which include steel and / or galvanized steel parts in addition to aluminum parts. The formulation range for phosphate baths should be extended to reduce the associated conditioning and monitoring work. The result of the overall pretreatment will in particular be the formation of a conversion layer on all exposed metal surfaces suitable as anticorrosion paint support prior to cathodic electron immersion coating.

The present invention relates to a method for pre-corrosion corrosion pretreatment of a composite metal structure comprising aluminum and / or aluminum alloy portions in addition to steel and / or galvanized steel portions.

Summary of the Invention

The object of the present invention is achieved by a method of chemical pretreatment of a composite metal structure comprising steel, galvanized steel surfaces and / or alloy-zinc plated steel portions together with aluminum or aluminum alloy portions before organic coating,

(I) Composite metal structures are formed on steel and galvanized and / or alloy-zinc plated steel sheets to form a surface-coated crystalline zinc phosphate layer having a coating weight in the range of 0.5 to 5 g / m ^2, but with a zinc phosphate layer on the aluminum portion. Following a first step of treatment with a zinc phosphate treatment solution that does not form, with or without intermediate washing with water,

(II) The crystalline zinc phosphate layer formed on the steel, galvanized and / or alloy-zinc plated steel sheet in the step (I) of not forming a conversion layer on the aluminum portion of the composite metal structure 60, 50, 40, 30 , A second step of contact with a treatment solution that does not dissolve in excess of 20, 15, 10, 8 or 6% (lower values are preferred).

The condition that no zinc phosphate layer is formed on the aluminum portion in the treatment step (a) means that no sealed and sealed crystalline layer is formed at all, and the mass per unit area of deposited zinc phosphate is 0.5 g per square meter (generally " abbreviated to g / m ² "). To meet this condition, the phosphate bath may optionally be formulated as long as specific conditions for fluoride concentration are observed. Such conditions may be found in EP-B-452 638. This document summarizes the conditions under which a sealed zinc phosphate layer is formed on an aluminum surface. According to this, for example, the concentration of free fluoride ions, measured in g / l, must satisfy a condition exceeding 8 / T at a particular temperature T (° C.). However, within the scope of the present invention, no zinc phosphate layer should be formed on aluminum in the phosphating step (I), in contrast to the teaching of EP-B-452 638 in the phosphate solution at a specific temperature T (° C.). The concentration (g / l) of free fluoride ions present should be less than 8 / T.

Thus, preferably in the phosphate treatment step (I), it has a pH in the range of about 2.5 to 3.6 and a temperature in the range of about 20 to 65 ° C. and is specified by the formula 8 / T (“T” represents the bath temperature (° C.)). Preference is given to using zinc phosphate treating solutions which do not contain more g / l of free fluoride. Regardless of the respective components described, preferably the zinc phosphate treatment solution is also

0.3-3 g / l zinc (II),

5 to 40 g / l phosphate ions,

And one or more of the following accelerators.

0.3-4, or more preferably 1-4 g / l chlorate ions,

0.01 to 0.2 g / l nitrite ions,

0.05 to 2, or more preferably 0.2 to 2 g / l of m-nitrobenzenesulfonate ions,

0.05 to 2 g / l m-nitrobenzoate ion,

0.05 to 2 g / l of p-nitrophenol,

0.001 to 0.15, or more preferably 0.001 to 0.070 g / l of hydrogen peroxide in free or bonded form,

0.1 to 10 g / l of hydroxylamine in free or bound form, and

0.1 to 10 g / l of reducing sugar.

The experiment shows that if the zinc phosphate treated solution in step (I) additionally contains one or more cations in the following amounts, the corrosion protection and paint adhesion of the crystalline zinc phosphate layer formed in this phosphate treated bath is improved.

0.001-4 g / l manganese (II),

0.001 to 4 g / l nickel (II),

0.002 to 0.2 g / l copper (II),

0.2 to 2.5 g / l magnesium (II),

0.2 to 2.5 g / l calcium (II),

0.01 to 0.5 g / l iron (II),

0.2-1.5 g / l lithium (I) and

0.02 to 0.8 g / l tungsten (IV).

More preferably, the zinc concentration ranges from about 0.8 to 1.6 g / l. Zinc concentrations of, for example, 2 to 3 g / l, exceeding 1.6 g / l, may result in a slight advantage for the process while increasing the incidence of sludge in the phosphate treatment bath. During the phosphate treatment of the galvanized surface, additional zinc is introduced into the phosphate bath via etching to adjust this zinc concentration in the working phosphate bath. From about 1 to 50 mg / l of nickel and about with as low a nitrate content as possible, which does not contain nickel or cobalt or exceed 0.5 g / l as compared to a phosphate bath having a nitrate component of greater than 0.5 g / l Nickel and / or cobalt ions in the concentration range of 5 to 100 mg / l cobalt improve corrosion protection and paint adhesion. This approach leads to a desirable compromise between the performance of the phosphate bath on the one hand and the requirements of the effluent technology treatment on the other hand.

Manganese content in phosphate treatment baths with reduced amounts of heavy metals may range from about 0.001 to 0.2 g / l. In other baths a manganese content of about 0.5 to 1.5 g / l is common.

It is known from DE-A-195 00 927 that lithium ions in amounts of about 0.2 to 1.5 g / l improve the corrosion protection achievable with zinc phosphate treatment baths. Lithium concentrations in the range from about 0.2 to 1.5, in particular from about 0.4 to 1 g / l, also have a beneficial effect on corrosion protection and subsequent workup in the phosphate treatment process according to the invention.

Apart from the already mentioned cations incorporated into the phosphate layer or at least positively affecting the crystal growth of the phosphate layer, the phosphate bath also generally contains sodium, potassium and / or ammonium ions to adjust the free acid. The term "free acid" is well known to those skilled in the art of phosphate treatment. The method chosen for determining the free acid and total acid at this stage is specified in the example. Free acid and total acid are important control parameters for phosphate baths because they have a significant effect on coating weight. The free acid value of 0 to 1.5 points in the part phosphate treatment or less than 2.5 points in the coil phosphate treatment and the total acid value of about 10 to 30 points or preferably in the case of immersion phosphate treatment is preferably in the technical standard range. And are suitable within the scope of the present invention.

For the phosphate treatment of the zinc surface, it is not absolutely necessary for the phosphate treatment bath to contain a so-called accelerator. However, in phosphating steel surfaces, it is essential that the phosphate solution contains more than one accelerator. Such promoters are commonly used in the prior art as components of zinc phosphate treatment baths. The term accelerator refers to a substance that chemically reacts with hydrogen produced on a metal surface by the etching action of an acid in a self-reducing manner. In addition, the oxidation promoter has the effect of iron oxide (II) ions released by the etching action on the steel surface in the trivalent oxidation state so as to precipitate as iron (III) phosphate.

In step (II), a solution according to the prior art for producing a conversion layer on aluminum may be used. However, this solution should not dissolve the crystalline zinc phosphate layer formed in step (I) excessively. The pH of this solution should therefore be in the range of 2.5 to 10, preferably 3.3 to 10. Preferably, in step (II) a solution containing a component which further surface stabilizes the crystalline zinc phosphate layer is selected. Such solutions are hereinafter referred to by way of example. In the scope of the process sequence according to the invention, in step (II), the metal structure is generally brought into contact with the treatment solution by spraying or dipping. The temperature of the treatment solution for step (II) is preferably selected in the range of 20 to 70 ° C.

By way of example, a treatment solution may be used in step (II) having a pH in the range from about 5 to 5.5 and containing from about 0.3 to 1.5 g / l hexafluorotitanate and / or hexafluoro zirconate ions as a whole. . If this treatment solution further contains 0.01 to 0.1 g / l of copper ions for step (II), it may be advantageous to prevent corrosion of the crystalline zinc phosphate layer produced in step (I).

In addition, a treatment solution having a pH of 3.5 to 5.8 and containing 10 to 500 mg / l of organic polymer selected from poly-4-vinylphenol compounds of formula (I) may be used in step (II),

(I)

In the above formula,

n is an integer from 5 to 100,

X and Y each independently represent a hydrogen or CRR ¹ OH moiety,

R and R ¹ are each independently hydrogen or an aliphatic or aromatic moiety having 1 to 12 carbon atoms.

In step (II), treatment solutions containing polyvinylphenol derivatives which in particular follow the teachings of EP-B-319 016 are preferred. This document also describes a process for preparing such polyvinylphenol derivatives. Thus, in step (II), 10 to 5000 mg / l selected from amino group-containing homopolymers or copolymer compounds having a pH of 3.3 to 5.8 and comprising at least one polymer selected from the group consisting of substances (α) and (β) It is preferable that a treatment solution containing an organic polymer of is used, wherein (α) is each composed of polymer molecules, and the polymer molecules have one or more units according to the following formula (II), and (β) are each It consists of a polymer molecule which does not contain units according to formula (II) but which comprises at least one unit according to formula (III)

(II)

In the above formula,

R ² to R ⁴ are each independently of one another, independently of each other in one molecule of the component and in one polymer molecule, if there is at least one polymer molecular unit following the above formula, each of these units is independently of the hydrogen moiety, It is selected from the group consisting of an alkyl moiety having 1 to 5 carbon atoms and an aryl moiety having 6 to 18 carbon atoms,

Y ¹ to Y ⁴ are each independently of one another, except as noted below, provided that there is at least one polymer molecular unit in accordance with the above formula in one polymer molecule independently of each other and in one molecule of the component, Independently of each other in each unit is a hydrogen moiety, a -CH ₂ Cl moiety, an alkyl moiety having 1 to 18 carbon atoms, an aryl moiety having 6 to 18 carbon atoms, a moiety according to formula -CR ¹² R ¹³ 0R ¹⁴ , wherein R ¹² to R ¹⁴ is each selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl and a phosphoalkyl moiety) and a moiety Z according to one of the following two formulas: Selected from

Wherein R ⁵ to R ⁸ are each independently of each other, independently of each other in one molecule of the component, and in one polymer molecule, if there is at least one polymer molecular unit following the above formula, each of these units is independent of each other Is selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety and a phosphoalkyl moiety, R ⁹ is a hydrogen moiety, an alkyl moiety, an aryl moiety, hydroxy or polyhydroxy alkyl moiety, an amino or polyamino alkyl moiety, a mercapto or a polymer mercapto alkyl moiety, phosphonate or poly phosphonate alkyl moiety, -O ^- moiety and is selected from the group consisting of -OH part),

In at least one unit of each selected polymer molecule, at least one of Y ¹ to Y ⁴ is a previously defined partial Z,

W ¹ is independent of each other in each molecule of the component of the substance, and in the unitary polymer molecule, if there is at least one unit of the polymer according to the above formula, independently of each other in the unit, hydrogen moiety, acyl moiety, acetyl moiety , Benzoyl moiety; 3-aryloxy-2-hydroxypropyl moiety; 3-benzyloxy-2-hydroxypropyl moiety; 3-butoxy-2-hydroxypropyl moiety; 3-alkyloxy-2-hydroxypropyl moiety; 2-hydroxyoctyl moiety; 2-hydroxyalkyl moiety; 2-hydroxy-2-phenylethyl moiety; 2-hydroxy-2-alkylphenylethyl moiety; Benzyl, methyl, ethyl, propyl, unsubstituted alkyl, unsubstituted aryl, unsubstituted alkylbenzyl; Halo or polyhalo alkyl, or halo or poly haloalkenyl moieties; Moieties derived from condensation polymerization products of ethylene oxide, propylene oxide or mixtures thereof by removing one hydrogen atom; Sodium, potassium, lithium, ammonium or substituted ammonium, phosphonium or substituted phosphonium cation moieties,

(III)

In the above formula,

R ¹⁰ to R ¹¹ are each independently of one another, independently of one another in each of the molecules of the component and in one polymer molecule, if there is at least one polymer molecular unit following the above formula, independently of one another in each of these units, the hydrogen moiety; , An alkyl moiety having 1 to 5 carbon atoms and an aryl moiety having 6 to 18 carbon atoms,

Y ⁴ to Y ⁶ are each independently of one another, except as specified below, provided that there is at least one polymer molecular unit in accordance with the above formula in one polymer molecule independently of one another and in each of the molecules of the component, Independently of each other in each of the units, a hydrogen moiety, —CH ₂ Cl moiety, an alkyl moiety having 1 to 18 carbon atoms, an aryl moiety having 6 to 18 carbon atoms, and the formula —CR ¹² R ¹³ 0R ¹⁴ , wherein R ¹² to R ¹⁴ are Moieties each selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety and a phosphoalkyl moiety), and a moiety defined for said material α. Z is selected from the group consisting of Z and at least one of Y ¹ to Y ⁴ in at least one unit of each selected polymer molecule is a previously defined partial Z,

W ² is independent of each other in each molecule of the component of the substance, and independently of one another in the unit of a single polymer molecule if there is at least one unit of the polymer according to the above formula, a hydrogen moiety, an acyl moiety, an acetyl moiety. , Benzoyl moiety; 3-aryloxy-2-hydroxypropyl moiety; 3-benzyloxy-2-hydroxypropyl moiety; 3-butoxy-2-hydroxypropyl moiety; 3-alkyloxy-2-hydroxypropyl moiety; 2-hydroxyoctyl moiety; 2-hydroxyalkyl moiety; 2-hydroxy-2-phenylethyl moiety; 2-hydroxy-2-alkylphenylethyl moiety; Benzyl, methyl, ethyl, propyl, unsubstituted alkyl, unsubstituted aryl, unsubstituted alkylbenzyl; Halo or polyhalo alkyl, halo or poly haloalkenyl moieties; Moieties derived from condensation polymerization products of ethylene oxide, propylene oxide or mixtures thereof by removing one hydrogen atom; Is selected from the group consisting of sodium, potassium, lithium, ammonium or substituted ammonium, phosphonium or substituted phosphonium cation moieties, and the term "polymer molecule" used in the definitions of materials (α) and (β) is not less than 300 daltons. It includes a molecule that is neutral.

Usually, mainly for economic reasons, the use of molecules consisting mainly of units according to one of the formulas (I) and (II) described above exclusively with the exception of relatively short terminal groups as substances (α) and / or (β) It is preferable. Again, for economic reasons, formaldehyde and secondary amines grafted with partial Z on some activated benzene rings in the reacted material are reacted with homopolymers of p-vinyl phenol in the case of material (α) or material (β) Is prepared by reacting with a phenol-aldehyde condensation product.

In some particular cases, however, it may be more useful to use chemically more complex forms of materials (α) and / or (β). For example, the above components (α) or (β) that do not need to initially meet the requirements for (α) or (β), ie the requirement that each molecule contains at least one portion Z. Condensation reaction products by reacting molecules of the condensable form to which one or more distinct forms of molecules selected from the group consisting of phenols, tannins, novolak resins, lignin compounds, aldehydes, ketones and mixtures thereof To produce molecules, and if necessary condensation reaction products are optionally reacted with (1) aldehydes or ketones and (2) secondary amines to introduce at least one above defined portion Z into the molecule, ) Or (β).

Another example of a more complex material that can be used as material (α) is a material in which the polymer chain is at least primarily a copolymer of simple 4-vinyl phenol or substituted 4-vinyl phenol and another vinyl monomer, examples of which are acrylic Ronitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone, isopropenyl methyl ketone, acrylic acid, methacrylic acid, acrylamide, methacrylamide, n-amyl methacrylate, Styrene, m-bromostyrene, p-bromostyrene, pyridine, diaryldimethylammonium salt, 1,3-butadiene, n-butyl acrylate, t-butylamino-ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-butyl vinyl ether, t-butyl vinyl ether, m-chlorostyrene, o-chlorostyrene, p-chlorostyrene, n-substituted methacrylate, N, N-diarylmelamine, N , N-di-n-butylacrylamide, di-n-butyl itacorate, di-n-butyl maleate, diethylaminoethyl methacrylate, diethylene glycol monovinyl ether, diethyl fmarate, diethyl Itacorate, diethylvinyl phosphate, vinylphosphonic acid, diisobutyl maleate, diisopropyl itacorarate, diisopropyl malate, dimethyl fmarate, dimethyl itacorate, dimethyl malate, di-n -Nonyl fmaleate, di-n-nonyl malate, dioctyl fmaleate, di-n-octyl itacrate, di-n-propyl itachorate, N-heterovinyl vinyl ether, acidic ethyl fmarate, acidic ethyl Maleate, ethyl acrylate, ethyl cinnamate, N-ethyl methacrylamide, ethyl methacrylate, ethyl vinyl ether, 5-ethyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine-1-oxide, gly Cydyl acrylate, glycidyl methacryl Yate, n-hexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isobutyl methacrylate, isobutyl vinyl ether, isophen pen, isopropyl methacrylate, isopropyl vinyl Ether, itaconic acid, lauryl methacrylate, methacrylamide, methacrylic acid, methacrylonitrile, N-methanol acrylamide, N-methylol-methacrylamide, N-isobutoxymethylacrylamide, N-isobu Methoxy-methylmethacrylamide, N-alkyloxymethylacrylamide, N-alkyl-oxymethylmethacrylamide, N-vinylcaprolactam, methyl acrylate, N-methylmethacrylamide, α-methylstyrene, m-methyl Styrene, o-methylstyrene, p-methylstyrene, 2-methyl-5-vinylpyridine, n-propyl methacrylate, sodium p-styrenesulfonate, stearyl methacrylate, styrene, p-styrenesulphone, p- Styrenesulfonamide, Vinyl bromide, 9-vinyl carmazole, vinyl chloride, vinylidenechloride, 1-vinylnaphthalene, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyridine N-oxide, 4-vinylpyridine and N Vinylpyrrolidone, and the like.

For primarily economic reasons, the following preferred embodiments, which have improved corrosion resistance and / or increased solubility, are applied to the molecules of substances (α) and (β) independently for each preferred embodiment:

R²To R⁶, R¹⁰, R¹¹, W^OneAnd W²Are each independently of one another and independently of each other in the same or in different units preferably a hydrogen moiety,

Y ¹ to Y ⁶ are each independently of one another and independently from each unit in the same or different molecules preferably a hydrogen moiety or a part Z,

Each polymer molecule as defined above does not exceed at least 2, 3, 4, 5, 6, 7 or 8, preferably preferably 100, 75, 50, 40, 30 or 20 (preferably higher in number). Comprising a plurality of units corresponding to one of formulas (II) and (III),

In the composition used in step (II) according to the present invention, the ratio of the number of aromatic Zs to the number of aromatic nuclei in the whole part (α) and (β) in total is at least 0.01: 1.0, 0.03: 10, 0.05: 1.0, 0.10: 1.0, 0.20: 1.0, 0.40: 1.0, 0.50: 1.0, 0.60: 1.0, 0.70: 1.0, 0.80: 1.0, 0.90: 1.0 or 0.95: 1.0, independently preferably 2.0: 1.0, 1.6: 1.0, 1.50: 1.0, Not exceeding 1.40: 1.0, 1.30: 1.0, 1.20: 1.0, 1.10: 1.0 or 1.00: 1.0 (preferably higher in value),

In the composition used in step (II) according to the invention the carbon number in the entirety of the materials (α) and (β) is (i) 3 to 8, or preferably 4 to 6 and (ii) at the R ⁵ to R ⁸ residues. In the formula given above, at least one of R ⁵ to R ⁸ in the formula given above for the portion Z defined by the portion Z having one hydroxyl group less than the number of carbon atoms of which are each bonded to a carbon atom of “polyhydroxy portion Z” The ratio of the total number of portions Z of the composition to the water of at least 0.10: 1.0, 0.20: 1.0, 0.30: 1.0, 0.40: 1.0, 0.50: 1.0, 0.60: 1.0, 0.70: 1.0, 0.80: 1.0, 0.90: 1.0 or 0.98: 1.0 (The earlier the value is preferred) (the preparation of such materials is described in the references mentioned above).

Poly (5-vinyl-2-hydroxy-N-benzyl) -N-methylglucamine is the most preferred form of a special polymer, which is at least partially present as an ammonium salt in the acidic pH range to be set.

Regardless of the polyvinyl phenol derivative and the acid (preferably phosphate) for pH adjustment, solutions containing no more active ingredient may be used. However, further addition of active ingredients, in particular hexafluorotitanate ions and hexafluorozirconate ions, may improve layering on aluminum. For example, the pH is preferably in the range of about 3.3 to 5.8 and contains about 100 to 5000 mg / l in the form of methylethanolamine derivatives or N-methylglucamine derivatives of polyvinyl phenol as organic polymers and is 10 to 2000 mg / l. Solutions with the addition of l phosphate ions, 10 to 2500 mg / l hexafluorotitanate ions or hexafluorozirconate ions and 10 to 1000 mg / l manganese ions may be used.

Because of the specific costs involved in the preparation, solutions or dispersions of organic polymers selected from homopolymers and / or copolymers of acrylic acid and methacrylic acid as well as their esters may be used in step (II) instead of polyvinyl phenol derivatives. will be. Preferably, these organic polymer solutions or dispersions have a pH value in the range of about 3.3 to 4.8 and contain about 250 to 1500 mg / l of organic polymer. In accordance with the teachings of EP-B-0 08 942, this polymer solution or dispersion may additionally contain hexaflourotitanate, hexaflourozirconate and / or hexaflorosilicate.

Of cold-rolled steel (hereinafter generally abbreviated to "CRS"), electrically galvanized steel (hereinafter abbreviated generally to "ZE"), electrically galvanized-iron plated steel (generally abbreviated to "ZFE") The process procedure according to the invention was tested on a metal plate sample and on aluminum 6111. This metal plate was first wiped off with alkali and activated with an activation solution containing titanium phosphate, as is common in the automotive manufacturing art. The plate was then immersed for 3 minutes in a 48 ° C. phosphate bath having the same composition.

Zn = 1.2g / l

Mn = 0.8 g / l

Ni = 0.8 g / l

PO ₄ ^3- = 18 g / l

NO ₂ ^- = 110ppm

Residual cation = Na ⁺

Free acid 1.1

Sealed phosphate layers having a coating weight in the range of ² g / m ² were deposited on cold rolled steel, electrically galvanized steel and electrically zinc-iron plated steel by a phosphate treatment procedure. Scanning electron micrographs showed that only widely dispersed zinc phosphate crystals formed on the aluminum plate.

As step (II), the sample plate was treated with a solution of one of the following compositions (a), (b) and (c) as well as complete deionized water (control test). This solution having a temperature of 25 ° C. was sprayed on the sample plate for 30 seconds. The plate was then sprayed with complete deionized water for 15 seconds and dried by blowing compressed air at room temperature. For the corrosion protection test, the plates were coated with three layers of paint structure (E-coat = PPG ED 5000, base coat = Dupont white 542 AB 839, Clear coat = Dupont RK 8010). Corrosion resistance tests were performed according to GM9540P-B process cycle from General Motors, which consists of the following steps:

1. (1.1) Spray each panel with sufficient salt spray solution (0.9 wt% salt, 0.1 wt% calcium chloride, 0.25 wt% sodium hydrogen carbonate and water as the remainder) to fully wet the panel. (1.2) Within 30 minutes after spraying the panel, the panel is placed in a controlled atmosphere to maintain a relative humidity of 25 ° C. and 30-50%. (1.3) removing the panel from the controlled atmosphere maintained during step (1.2) within 90 minutes after starting step (1.2), then repeating steps (1.1) and (1.2) three times each. In total, Step 1 consumes eight hours.

2. Test 8 hours condensate at 49 ° C. and 95-100% relative humidity.

3. Dry storage for 8 hours at 60 ° C. and a relative humidity of less than 30%.

4. Only dry storage at 25 ° C. and 30-50% relative humidity on weekends.

Each of the steps 1 to 3 just above formed a repeating cycle from Monday to Friday. Step 4 did not count for this cycle. The test lasted for 40 cycles (5 weeks per week for 8 weeks).

Table 1 below shows the composition of the three post-cleaning solutions, and Tables 2 and 3 show the zinc phosphate coating etch amount and average paint creepage, respectively, in the scribe (complete scribe width).

Table 1: Post-Cleaning Compositions

ingredient Quantity of ingredients Solution after cleaning (a), pH 2.7 Solution after washing (b), pH 3.5 Solution after washing (c), pH 2.9 polymer* 0.453 g / l 0.451 g / l 0.113 g / l phosphate 0.957 g / l 0.955 g / l 0.239 g / l Hexafluorotitanate 1 g / l 1 g / l 0.25g / l Mn (Ⅱ) 0.39 g / l 0.39 g / l 0.1g / l

Poly (5-vinyl-2-hydroxy-N-benzyl) -N-methylglucamine

Table 2: Zinc Phosphate Coating Etch Loss Values

Exam number Support Post-cleaning solution Coating reduction,% Example 1 CRS (a) 69 Example 2 CRS (b) 5 Example 3 CRS (c) 27 Example 4 ZE (a) 50 Example 5 ZE (b) 5 Example 6 ZE (c) 31 Example 7 ZFE (a) 50 Example 8 ZFE (b) One Example 9 ZFE (c) 25

Table 3: Corrosion Test Results

Exam number Support Post-cleaning solution Paint Creepage, mm Comparative Example 1 CRS Deionized water 9.6 Example 1 CRS (a) 8.8 Example 2 CRS (b) 3.1 Example 3 CRS (c) 4.2 Comparative Example 2 ZE Deionized water 2.2 Example 4 ZE (a) 1.6 Example 5 ZE (b) 1.8 Example 6 ZE (c) 1.8 Comparative Example 3 ZEF Deionized water 2.2 Example 7 ZEF (a) 1.3 Example 8 ZEF (b) 1.6 Example 9 ZEF (c) 1.1 Comparative Example 4 A16111 Deionized water 1.7 Example 10 A16111 (a) 0.9 Example 11 A16111 (b) 1.2 Example 12 A16111 (c) (c) 1.2

Claims (13)

A method of chemical pretreatment of a composite metal structure comprising at least one steel, galvanized steel surface or alloy-zinc plated steel portion together with at least one aluminum or aluminum alloy portion prior to organic coating, (I) The composite metal structure forms a surface-coated crystalline zinc phosphate layer having a coating weight in the range of 0.5 to 5 g / m ² on steel, galvanized and alloy-zinc plated steel sheets, but no zinc phosphate layer on the aluminum portion. Followed by the first step of treating with a zinc phosphate treatment solution, with or without intermediate cleaning with water, (II) a second step of contacting the composite metal structure with a treatment solution that does not dissolve more than 60% of the crystalline zinc phosphate layer over steel, galvanized and alloy-zinc plated steel but produces a conversion layer over the aluminum portion. How to. The amount of g according to claim 1, wherein in step (I), the zinc phosphate treated solution has a pH in the range of about 2.5 to 3.6 and a temperature in the range of about 20 to 65 ° C. and has a quotient of 8 or less divided by the solution temperature (° C.). / l) free fluoride, wherein the treatment solution in step (II) does not dissolve more than 25% of the crystalline zinc phosphate layer deposited in step (I). The zinc phosphate treating solution used in step (I) is 0.3-3 g / l zinc (II); 5 to 40 g / l of phosphate ions; And 0.3-4 g / l chlorate ions, 0.01 to 0.2 g / l nitrite ions, 0.05 to 2 g / l m-nitrobenzenesulfonate ions, 0.05 to 2 g / l m-nitrobenzoate ion, 0.05 to 2 g / l of p-nitrophenol, 0.001 to 0.15 g / l of hydrogen peroxide in free or bonded form, 0.1 to 10 g / l of hydroxylamine in free or bound form, and 0.1 to 10 g / l of reducing sugars, wherein the treatment solution in step (II) does not dissolve more than 10% of the crystalline zinc phosphate layer deposited in step (I). 4. The process according to claim 3, wherein the zinc phosphate treating solution used in step (I) further comprises at least one cation in the following amount. 0.001-4 g / l manganese (II), 0.001 to 4 g / l nickel (II), 0.002 to 0.2 g / l copper (II), 0.2 to 2.5 g / l magnesium (II), 0.2 to 2.5 g / l calcium (II), 0.01 to 0.5 g / l iron (II), 0.2-1.5 g / l lithium (I) and 0.02 to 0.8 g / l tungsten (IV). The process solution according to any one of claims 1 to 4, wherein the treatment solution used in step (II) has a pH of 3.5 to 5.5 and is 0.3 to 1.5 g / l hexafluororotate ions, hexafluorozirconate And ions or both ions. A process according to claim 5, wherein the treatment solution used in step (II) additionally contains 0.01 to 0.1 g / l of copper ions. 5. The process according to any one of claims 1 to 4, wherein the treatment solution used in step (II) has a pH of 3.5 to 5.5 and is selected from poly-4-vinylphenol molecules according to formula (I) a mg / l organic polymer. (Ⅰ) In the above formula, n is an integer from 5 to 100, X and Y each independently represent a hydrogen or CRR ¹ OH moiety, R and R ¹ are each independently hydrogen or an aliphatic or aromatic moiety having 1 to 12 carbon atoms. The process according to any one of claims 1 to 4, wherein the treatment solution used in step (II) has a pH of 3.3 to 5.8 and comprises 10 to 5000 mg / l organic polymer selected from the materials (α) and (β). (Α) is composed of a polymer molecule having at least one unit according to formula (II), and (β) does not include a unit according to formula (II) A process consisting of polymer molecules comprising at least one unit according to III). (II) In the above formula, R ² to R ⁴ are each independently of one another, independently of each other in one molecule of the component and in one polymer molecule, if there is at least one polymer molecular unit following the above formula, each of these units is independently of the hydrogen moiety, It is selected from the group consisting of an alkyl moiety having 1 to 5 carbon atoms and an aryl moiety having 6 to 18 carbon atoms, Y ¹ to Y ⁴ are each independently of one another, except as noted below, provided that there is at least one polymer molecular unit in accordance with the above formula in one polymer molecule independently of each other and in one molecule of the component, Independently of each other in each unit is a hydrogen moiety, a -CH ₂ Cl moiety, an alkyl moiety having 1 to 18 carbon atoms, an aryl moiety having 6 to 18 carbon atoms, a moiety according to formula -CR ¹² R ¹³ 0R ¹⁴ , wherein R ¹² to R ¹⁴ is each selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl and a phosphoalkyl moiety) and a moiety Z according to one of the following two formulas: Selected from Wherein R ⁵ to R ⁸ are each independently of each other, independently of each other in one molecule of the component, and in one polymer molecule, if there is at least one polymer molecular unit following the above formula, each of these units is independent of each other Is selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety and a phosphoalkyl moiety, R ⁹ is a hydrogen moiety, an alkyl moiety, an aryl moiety, hydroxy or polyhydroxy alkyl moiety, an amino or polyamino alkyl moiety, a mercapto or a polymer mercapto alkyl moiety, phosphonate or poly phosphonate alkyl moiety, -O ^- moiety and is selected from the group consisting of -OH part), In at least one unit of each selected polymer molecule, at least one of Y ¹ to Y ⁴ is a previously defined partial Z, W ¹ is independent of each other in each molecule of the component of the substance, and in the unitary polymer molecule, if there is at least one unit of the polymer according to the above formula, independently of each other in the unit, hydrogen moiety, acyl moiety, acetyl moiety , Benzoyl moiety; 3-aryloxy-2-hydroxypropyl moiety; 3-benzyloxy-2-hydroxypropyl moiety; 3-butoxy-2-hydroxypropyl moiety; 3-alkyloxy-2-hydroxypropyl moiety; 2-hydroxyoctyl moiety; 2-hydroxyalkyl moiety; 2-hydroxy-2-phenylethyl moiety; 2-hydroxy-2-alkylphenylethyl moiety; Benzyl, methyl, ethyl, propyl, unsubstituted alkyl, unsubstituted aryl, unsubstituted alkylbenzyl; Halo or polyhalo alkyl, or halo or poly haloalkenyl moieties; Moieties derived from condensation polymerization products of ethylene oxide, propylene oxide or mixtures thereof by removing one hydrogen atom; Sodium, potassium, lithium, ammonium or substituted ammonium, phosphonium or substituted phosphonium cation moieties, (III) In the above formula, R ¹⁰ to R ¹¹ are each independently of one another, independently of one another in each of the molecules of the component and in one polymer molecule, if there is at least one polymer molecular unit following the above formula, independently of one another in each of these units, the hydrogen moiety; , An alkyl moiety having 1 to 5 carbon atoms and an aryl moiety having 6 to 18 carbon atoms, Y ⁴ to Y ⁶ are each independently of one another, except as specified below, provided that there is at least one polymer molecular unit in accordance with the above formula in one polymer molecule independently of one another and in each of the molecules of the component, Independently of each other in each of the units, a hydrogen moiety, —CH ₂ Cl moiety, an alkyl moiety having 1 to 18 carbon atoms, an aryl moiety having 6 to 18 carbon atoms, and the formula —CR ¹² R ¹³ 0R ¹⁴ , wherein R ¹² to R ¹⁴ are Moieties each selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety and a phosphoalkyl moiety), and a moiety defined for said material α. Z is selected from the group consisting of Z and at least one of Y ¹ to Y ⁴ in at least one unit of each selected polymer molecule is a previously defined partial Z, W ² is independent of each other in each molecule of the component of the substance, and independently of one another in the unit of a single polymer molecule if there is at least one unit of the polymer according to the above formula, a hydrogen moiety, an acyl moiety, an acetyl moiety. , Benzoyl moiety; 3-aryloxy-2-hydroxypropyl moiety; 3-benzyloxy-2-hydroxypropyl moiety; 3-butoxy-2-hydroxypropyl moiety; 3-alkyloxy-2-hydroxypropyl moiety; 2-hydroxyoctyl moiety; 2-hydroxyalkyl moiety; 2-hydroxy-2-phenylethyl moiety; 2-hydroxy-2-alkylphenylethyl moiety; Benzyl, methyl, ethyl, propyl, unsubstituted alkyl, unsubstituted aryl, unsubstituted alkylbenzyl; Halo or polyhalo alkyl, halo or poly haloalkenyl moieties; Moieties derived from condensation polymerization products of ethylene oxide, propylene oxide or mixtures thereof by removing one hydrogen atom; "Polymer molecule", which is selected from the group consisting of sodium, potassium, lithium, ammonium or substituted ammonium, phosphonium or substituted phosphonium cation moieties and is used in the definition of materials (α) and (β), is at least 300 daltons electrically It includes molecules that are neutral. 9. The process according to claim 8, wherein at least 20% of the portion Z in the materials (α) and (β) of the treatment solution used in step (II) of the method is a polyhydroxyl portion Z. 9. The process according to claim 8, wherein the treatment solution used in step (II) of the process is (i) polyvinyl phenol having an average molecular weight in the range from 1000 to 10,000, (ii) formaldehyde or paraformaldehyde. And (iii) at least one secondary amine. The method of claim 10 wherein the secondary organic amine is selected from the group consisting of methylethanolamine, N-methylglucamine and mixtures thereof. The process of claim 11 wherein the treatment solution has a pH in the range of about 3.3 to 4.8 and contains between 100 and 5000 mg / l condensation reaction product and between 10 and 2000 mg / l phosphate ions and between 10 and 2500 mg / l hexafluorotitanate ion Or hexafluoro zirconate ions or all of these ions and from 10 to 1000 mg / l of ground ions. The process of claim 1, wherein the treatment solution used in step (II) has a pH value in the range of 3.3 to 5.8 and comprises homopolymers of acrylic acid, methacrylic acid, acrylic acid esters and methacrylic acid esters; 250 to 1500 mg / l organic polymer selected from the group consisting of copolymers.