BE1027163B1 - Corrosion inhibitors, improved paint and anti-corrosive coating - Google Patents

Abstract

The present invention is concerned with corrosion inhibitor preparations and anti-corrosion paints and anti-corrosion primers. Corrosion-protecting paints that contain anion-exchanging polymers in the form of basic anions as well as in nitrite form or nitrate form as well as an alkaline earth and alkali phosphate guarantee effective corrosion protection of iron alloys through passivation. Polymers with imidazolium groups or phosphonium groups are preferred. In addition, an anti-corrosive preparation or paint also contains alkaline earth phosphate particles in order to create a system for the slow release of anti-corrosive ions even in low-ion water, so that the metal to be protected is constantly in a passive state and in an optimal alkaline pH range is held.

Description

M BE2014 / 0805 1 Corrosion inhibitors, improved paint and anti-corrosive coating Technical area

This patent application deals with corrosion inhibitors and anti-corrosion coatings such as anti-corrosion paints. This invention is particularly concerned with corrosion inhibitors and anti-corrosion coatings and anti-corrosion paints for articles made of iron, steel and other iron alloys. This invention is also concerned with the manufacture of anti-corrosion additives for primers.

Background of the invention

In our patent application 10 2014 207 517.3 of April 21. In 2014, a combination of anion-exchanging polymers or copolymers with quaternary alkylammonium groups (or quaternary arylalkylammonium groups) in hydroxide form and in nitrite form with a poorly soluble, non-corrosive salt such as an alkaline earth phosphate such as Caz (PO4) 2 was used as an inexpensive corrosion inhibitor for Iron alloys presented. These anion-exchanging polymers with quaternary ammonium groups were, in addition to commercial, strongly basic anion exchangers in hydroxide form or nitrite form, in particular water-insoluble, solvent-soluble copolymers which are obtainable by copolymerization of vinylbenzyltrialkylammonium chloride or diallyldimethylammonium chloride with styro] and / or styro] Butadiene and the subsequent exchange of clay in the hydroxide form or nitrite form.

However, there is a compatibility problem with these corrosion inhibitors and primers containing these corrosion inhibitors with numerous polymers of conventional topcoats and with light metals, which can lead to peeling off of the paint layers or to etching of the base metal. The primers in question can release alkaline solutions in such a way that, for example, an acrylate-based topcoat would be subject to alkaline hydrolysis of the ester groups.

Brief description of the invention

The present invention deals with corrosion inhibitors and anti-corrosion paints that solve these compatibility problems.

It was found that corrosion inhibitors, the anion-exchanging polymers (or copolymers) with quaternary alkylammonium groups or quaternary arylalkylammonium groups in nitrite form or other quaternary alkylammonium nitrites or quaternary arylalkylammonium nitrites and sparingly soluble salts such as alkaline earth phosphates such as Caz (PO4) »contain, Iron, steel and other iron alloys also protect if, instead of anion-exchanging polymers in hydroxide form, other polymers (or copolymers) with alkylammonium groups (or quaternary arylalkylammonium groups) in the form of a weaker basic anion such as a carboxylic acid anion such as acetate form or benzoate form can be added.

Brief description of the drawing figures

These and the other features, aspects and advantages of the present invention will be better understood with reference to the following description, appended claims, and accompanying drawings, wherein:

Fig. 1 shows the structure of a further class of copolymers with quaternary alkylammonium groups in the acetate form (or hydroxide form) and nitrite form as part of a preparation of corrosion inhibitors according to an embodiment of the present invention;

Fig. 2 shows the structure of copolymers with imidazolium groups in the acetate form (or hydroxide form) and nitrite form and t-butyl acrylate (or t-butyl methacrylate) according to a further embodiment of the present invention;

Fig. 3 shows the structure of copolymers with pyridinium groups in the acetate form (X '= acetate or hydroxide form, X' = OH) and nitrite form (X- = NO; 7) and t-butyl acrylate (or t-butyl methacrylate) according to a further embodiment of the present invention;

Fig. 4 shows the structure of copolymers with triphenylphosphonium groups

(for example in the acetate form (or hydroxide form) and nitrite form) and t-butyl acrylate (or t-butyl methacrylate) according to a further embodiment of the present invention;

Fig. 5 shows the structure of copolymers with julolidinium groups (for example in the acetate form (or hydroxide form) and nitrite form) and t-butyl acrylate (or t-butyl methacrylate) according to a further embodiment of the present Invention; and

6 shows the change in the pH of a preparation according to the invention of anion-exchanging polymers with quaternary ammonium groups and strontum phosphate in the purest water according to a further embodiment of the present invention through the slow release of hydroxide ions; and

These and the other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. Description of the types of execution

In our patent application DE10 2014 207 517.3 from April 21. In 2014, a combination of anion-exchanging polymers or copolymers with quaternary alkylammonium groups in hydroxide form and nitrite form with a sparingly soluble, non-corrosive salt such as an alkaline earth phosphate such as Ca: (PO.): As a corrosion inhibitor for iron alloys was presented.

Without being bound to a theory, it is assumed that the anti-corrosive effect of these polymers is based on the fact that

1. Corrosion-promoting anions such as chloride ions are captured by the polymer layer,

2. Corrosion-promoting anions are exchanged for corrosion-protecting anions such as nitrite clays and alkaline hydroxide anions, which prevent corrosion by passivating iron alloys,

3. the quaternary ammonium compounds also show a corrosion-protective effect and an effect as a biocide.

4. by adding a sparingly water-soluble salt such as an alkaline earth phosphate

System for the very slow release of alkaline hydroxide anions (and nitrite ions) in the presence of low-ion water (such as rainwater) is created by the anion exchanger from small traces of phosphate ions, which are dissolved in an inventive anti-corrosion paint when water comes into contact with alkaline earth phosphate particles removed from the solution equilibrium and exchanged for alkaline hydroxide ions (and nitrite ions). As a result, the metal part to be protected is kept permanently in an alkaline pH range that is favorable for passivating iron in the presence of water (see Fig. 6) and thus passivated and extremely effective preventive even within a considerable radius around a paint layer according to the invention, even on bare, uncoated Places protected from rust. If the coating according to the invention in question is coated with hydrophobic lacquers as a primer, this system for protection against corrosion is only effective where there is a threat of corrosion due to the ingress of moisture.

At the same time, the preparation according to the invention is environmentally friendly, since the polymers according to the invention are not water-soluble and cannot be washed out and thus do not get into the environment.

The inventive polymers and preparations are only partially compatible with conventional acrylate-based paints, for example, since the strongly alkaline solutions which can be released from them by water can hydrolytically attack conventional paints and, for example, polymers made from methacrylic acid esters or acrylic acid esters can saponify.

It was found, however, that instead of anion-exchanging polymers in hydroxide form in such a corrosion-protecting preparation, anion-exchanging polymers in the form of a weaker basic anion can also be used in order to obtain a satisfactory effect as a corrosion inhibitor.

As such weaker basic counter anions in copolymers with quaternary alkylammonium groups (or quaternary arylalkylammonium groups), anions of organic carboxylic acids are particularly preferred.

Preference is given to all carboxylic acid anions which form readily soluble salts with the cation of the sparingly soluble salt (in many examples calcium and strontium ions or zinc clays with double positive charges).

More preferred are anions of weak carboxylic acids with the largest possible pKa (i.e. the lowest possible acid constant K i), which should be above a value of 4.0, optimally above a value of 4.7.

Also preferred are anions of aliphatic and aromatic dicarboxylic acids such as azelaic acid and phthalate anions, although other anions of dicarboxylic acids may also be suitable. The dicarboxylic acids can be branched or unbranched, contain double or triple bonds or carry substituents such as hydroxyl groups, nitro groups or cyano groups.

More preferred are anions of the weakest possible dicarboxylic acids (pKa> 4.0 for the second stage), which -depending on the cation of the sparingly soluble salt in the anti-corrosive preparation- form easily soluble lithium salts, alkaline earth salts or zinc salts such as tartrate anions, Anions of maleic acid, fumarate anions or phthalate anions.

The use of anions of tricarboxylic acids, which form readily soluble salts with alkaline earth or zinc ions, is also preferred, provided they can be eluted from the anion-exchanging polymer with anions of the poorly soluble salt.

Anions with> 4 carboxylic acid groups are generally difficult to elute and are less suitable, even if individual anions could be suitable.

Anions of monocarboxylic acids are preferred because of their easy elution, their easily soluble alkaline earth metal salts and (apart from formic acid) the favorable pKs value of the carboxylic acids.

Short-chain aliphatic monocarboxylic acid anions of C, -Cs-carboxylic acids (formate to valerate anions) such as acetate ions or propionate anions and anions of aromatic monocarboxylic acids such as benzoate ions are highly preferred, although longer-chain carboxylic acids are also suitable could be. The carboxylic acids in question can be branched or unbranched and carry substituents such as, for example, hydroxyl groups or halogens. The carboxylic acid anions in question can also contain double bonds or triple bonds, such as, for example, cinnamic acid anions.

It is optimal to use copolymers with quaternary alkylammonium groups (or arylalkylammonium groups) in acetate form.

Polymers in the form of other basic anions such as hydrogen carbonate ions, hydrogen phosphate ions, phosphate ions, tetraborate anions, borate anions, hydrogen borate anions, carbonate ions, alkyl carbonate anions or silicate ions are also preferred. Also preferred are polymers in the form of molybdate ions, tungstate ions or vanadate ions, although other anions such as chromate ions can also be suitable.

Polymers in the form of hydrogen carbonate ions, hydrogen phosphate ions, hydrogen borate anions and silicate ions such as Si30% are more preferred.

According to a further preferred embodiment of the present invention, polymers in nitrite form can be completely or partially replaced by polymers in nitrate form, which are more stable. Polymers in the form of other oxidizing anions such as permanganate and manganate ions can also be suitable.

Preferred corrosion protection preparations according to the invention contain a molar ratio of polymers with quaternary ammonium groups in nitrite form or nitrate form to polymers with quaternary ammonium groups in the form of such basic anions or hydroxide form based on the functional groups between 20: 1 to 1:20. A molar ratio of 10: 1 to 1:10 is preferred, a molar ratio of 5: 1 to 1: 5 is more preferred, an optimal molar ratio of 1: 1 to 3: 1 with a small excess of polymers in nitrite Shape. Preparations with a substance ratio of more than 20: 1 may show a short-term protective effect, while preparations with a substance ratio below 1:20 do not guarantee satisfactory corrosion protection, although ratios above 100: 1 or below 1: 100 still provide a certain short-term Can show protective effect.

Basic anions (e.g. hydroxide ions, acetate ions) and nitrite ions can, according to a further preferred embodiment of the present invention, be bound to a single anion exchange polymer resin instead of two resins.

Preferred corrosion protection preparations according to the invention also contain at least one sparingly soluble salt such as alkaline earth phosphates such as calcium phosphate in a molar ratio to the functional groups of the above polymers between 0.1 and 2.0. A molar ratio between 0.1 and 0.9 is preferred, a molar ratio between 0.3 and 0.8 is more preferred for alkaline earth phosphates, a molar ratio between 0.4 and 0.7 is most preferred and a molar ratio of m / z is used for anions Y ”of a salt Me, Y n, , ie 0.67 for calcium phosphate is optimal. Mole ratios below 0.01 do not provide satisfactory protection against corrosion against rainwater, while mole ratios above 1.0 offer no significant advantage.

Instead of alkaline earth phosphates such as calcium phosphate (Ca: (PO4) 2), strontium phosphate, barium phosphate, magnesium phosphate, lithium phosphate and other poorly soluble alkaline earth salts such as carbonates, chromates, molybdates or oxalates with a charge> 2 can be used. However, alkaline earth phosphates are preferred.

Preferred copolymers with anion exchange action are copolymers (or terpolymers) of vinylbenzyltrimethylammonium chloride and methacrylates, acrylates and styrene, as well as copolymers of diallyldimethylammonium chloride with acrylates, methacrylates or styrene, whose glass transition temperature is preferably between 30 ° C and 100 ° C , is most preferably between 40 ° C and 80 ° C. Also preferred are copolymers (or terpolymers) of acrylamidopropyltrimethylammonium chloride (and analogous esters bound to quaternary ammonium groups, see FIG. 1), which have a quaternary ammonium group bound via a molecular bridge (BR in FIG. 1), with acrylates, methacrylates or styrene.

According to one embodiment of the present invention, the tert-butyl esters of acrylic acid (t-butyl acrylate, ie Rs = t-butyl, R3 = H) or methacrylic acid (t-butyl methacrylate, ie Rs = t-butyl, R3 = CHz) and styrene are highly preferred as monomers for alkali-resistant copolymers, because they also provide homopolymers that are resistant to relatively strong alkalis (pH <12). Such copolymers offer good resistance to alkaline solutions but also to alkaline oxidation products of base metals, so that the paint cannot be decomposed by alkaline solutions. Also preferred as further monomers are methyl methacrylate (MMA).

According to a further embodiment of the present invention, anion exchange polymers (or copolymers or terpolymers) are preferred which instead of quaternary ammonium groups contain imidazolium groups, pyridinium groups, pyrrolium groups or quaternary phosphonium groups, although others contain positively charged quaternary groups Groups of heterocyclic compounds and of trimethylenediamine (DABCO) or quinuclidine or sulfonium groups, benzimidazolium groups or triazolium groups can likewise be suitable.

A mole fraction of monomers with positively charged functional groups such as quaternary ammonium groups, imidazolium groups or phosphonium groups in all monomers (including monomers without charged groups) for the production of the anion-exchanging polymers according to the invention between 0.01 mol% and 30 mol% is preferred. A mole fraction between 1 mol% and 20 mol% is more preferred. Most preferred is a mole fraction of the functionalized monomers between 5 mol% and 10 mol%. Polymers with a mole fraction below 0.01 mol% do not offer reliable corrosion protection, while polymers with a mole fraction above 30 mol% are soluble in water and would therefore be washed off the object to be protected by water and rain.

In a further embodiment of the present invention, inert polymers such as polystyrene or poly (t-butyl acrylate) can also be added to a preparation according to the invention.

Although the formation of nitrosamines from quaternary ammonium ions and nitrite in a sufficiently alkaline solution is practically impossible even in ppt traces, N-alkyl imidazolium groups, pyridinium groups, pyrrolium groups or quaternary phosphonium groups have the advantage to form no nitrosamines even after oxidative cleavage of one or more N-alkyl groups (or P-alkyl groups) in acidic solution. Alkali-resistant 1-alkyl-2-alkyl-3-alkyl-imidazolium groups such as, for example, 1-alkyl-2-isopropyl-3-alkylimidazolium groups or 1-alkyl-2-methyl-3-alkyl-imidazolium groups are particularly preferred , Tris (2,4,6-trialkoxyphenyl) benzylphosphonium groups such as, for example, tris (2,4,6-trimethoxyphenyl) benzylphosphonium groups (see FIG. 4, R = CH3O-) or tetrabenzylphosphonium groups, for which no Nitrosamines can be formed, although other alkali-resistant quaternary phosphonium groups with oxidation-resistant substituents may also be suitable.

Imidazolium derivatives which carry alkyl groups or benzyl groups on both nitrogen atoms are also particularly preferred (see FIG. 2), although other substituents may also be suitable. Even after oxidative cleavage of the N-alkyl groups, these do not form any nitrosamines with suitable substituents and the starting materials are economically available on an industrial scale.

Most preferred are the more base-resistant imidazolium groups that can be prepared from 2-alkylimidazole, for example 2-isopropyl-1-methyl-3-benzylimidazolium groups, with isopropyl groups and methyl groups being preferred as alkyl substituents, although also other alkyl groups such as t-butyl groups or trifluoromethyl groups come into consideration. Phenyl, benzyl and cyclohexyl substituents in this 2-position of imidazole are less preferred, since the imidazoles in question thus substituted can form nitrosamines with nitrite in acidic solution. The imidazoles in question can be bonded to the polymer chain by reaction with copolymers of vinylbenzyl chloride (obtained for example by emulsion polymerization) and converted into imidazolium salts. Alternatively, comparable copolymers can also be obtained by direct copolymerization of vinylimidazoles, allylimidazoles or imidazolyl derivatives (e.g. 2- (1H-imidazol-1-yl) ethyl ester) of acrylic acid or methacrylic acid such as 2- (1H-imidazol-1-yl) ethyl methacrylate with other monomers are produced.

According to a further embodiment of the present invention, the groups concerned can be bound to the main polymer chain by means of oxidation-resistant bridges. Such difluoromethyl bridges can be generated by chlorodifluoromethylation of aromatics using chlorodifluoroacetic anhydride. This has the advantage that any nitrosamines formed remain bound to the polymer until they break down (e.g. due to UV radiation).

To prevent the oxidative splitting off of N-alkyl groups, which can lead to the formation of undesired tertiary or even secondary amines, according to a further embodiment of the present invention, oxidation-resistant substituents can be introduced on the nitrogen. Oxidation-resistant perfluoroalkyl groups such as, for example, N-trifluoromethyl groups, which can be introduced by electrophilic trifluoromethylation, are particularly suitable as oxidation-resistant substituents on nitrogen atoms. Oxidation-resistant perfluoroalkyl groups can also be used as substituents in the 2-position on the imidazole ring in order to improve the alkali resistance of the imidazolium ring. Such copolymers can alternatively also be prepared by copolymerizing vinyl imidazoles with other monomers.

Polymers with pyridinium groups are also preferred (see FIG. 3). Since, according to the literature, pyridine does not form nitrosamines either, such polymers should not show any nitrosamine formation upon oxidative cleavage of the pyridine ring. Such polymers can also alternatively be produced by copolymerizing vinyl pyridines with other monomers.

According to a further embodiment of the present invention, polymers with positively charged quaternary ammonium groups in which the nitrogen atoms are contained in bicyclic systems, such as, for example, N-alkylated 1,2,4,5-tetrahydropyrrolo [3,2,1- hi] indole or more preferably N-alkylated julolidine (2,3,6,7-tetrahydro-1H, 5H-pyrido [3,2,1-ij] quinoline), which is connected to the polymer main chain via a suitable bridge via one of the carbon atoms are bound (see Fig. 5). In the case of an oxidative cleavage of two alkyl groups on the nitrogen atom, amines can be formed here thanks to the three bridges to the main polymer chain, which remain firmly attached to the polymer even if nitrosamines are subsequently formed, so that no nitrosamines can be released. Alternatively, alkylated quinuclidine can be linked to a polymer chain in an analogous manner to achieve this benefit. A binding of the quaternary nitrogen atom via two bridges would be similarly advantageous.

Most preferred are copolymers obtained by copolymerizing t-butyl acrylate or t-butyl methacrylate or alkyl methacrylates such as methyl methacrylate or styrene with the synthons vinylbenzyltrimethylammonium hydroxide or a vinylbenzyltrimethylammonium carboxylate, in particular vinylbenzyltrimethylammonium, as well as copolymers of vinylbenzyltrimethylammonium acetate and vinylbenzylammonium acetate and copolymers obtained by Butyl acrylate or t-butyl methacrylate or alkyl methacrylates such as methyl methacrylate or styrene with 1-vinylbenzyl-2-alkyl-3-alkylimidazolium hydroxide (ie 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H-imidazole-3-ium hydroxide ) or 1-vinylbenzyl-2-alkyl-3-alkylimidazolium carboxylate, in particular 1-vinylbenzyl-2-alkyl-3-alkylimidazolium acetate, and at least one monomer from the group 1- vinylbenzyl-2-alkyl-3-alkylimidazolium nitrate or 1-vinylbenzyl 2-alkyl-3-

alkylimidazolium nitrite would be available.

Instead of polymers with such functional groups, it is also possible to add ionic liquids to the anti-corrosion lacquers according to the invention, which are soluble in the lacquer. Preferred ionic liquids are those based on imidazolium ions such as 1-butyl-3-methylimidazolium acetate (bmim acetate) and 1-butyl-3-methylimidazolium nitrite (bmim nitrite), more preferably ionic liquids with organic cations with longer-chain alkyl groups such as for example 1-hexyl-3-methylimidazolium acetate (or nitrite) or 1-methyl-3-octylimidazolium acetate (or nitrite). The relevant alkyl groups in the 2-position or 3-position of the imidazole ring can be C 1 -C 2 -alkyl groups.

Ionic liquids based on pyridinium salts are also preferred. Ionic liquids which contain trimethoxysilyl groups in the cation, depending on the carrier material, are likewise preferred. Tonic liquids can also be used in combination with the functional polymers according to the invention.

According to a further embodiment of the present invention, ionic liquids bound to carriers such as silicon dioxide, glass or silicate particles or cyclodextrins are used as corrosion inhibitors. For this purpose, ionic liquids with cations with trimethoxysilyl groups or with anions such as bis (trifluoromethane) sulfonimide are preferred.

Ionic liquids with basic anions such as hydroxide, acetate, benzoate and other carboxylic acid anions and nitrite anions or, for example, molybdate anions, tungstate anions or vanadate anions are preferred, although other anions such as chromate anions are also suitable can.

More preferred are polymers with anion exchange properties which are supplied in the form of a basic anion (e.g. in hydroxide form or acetate form) and which are partially converted into the nitrite form.

As sparingly soluble salts in the inventive anti-corrosive preparations of functional polymers with basic anions and nitrite anions (or corresponding ionic liquids) with sparingly soluble salts, sparingly soluble alkaline earth phosphates, lithium phosphate and phosphates of transition metals such as zinc phosphate are preferred, albeit also other salts which do not contain any corrosive anions may be suitable. Calcium phosphate and

Strontium phosphate is more preferred. Most preferred is a mixture of phosphates with different solubility products.

According to one embodiment of the present invention soluble in an organic solvent long-chain copolymers (or terpolymers) with positively charged anion-exchanging groups in the relevant anion form (for example in acetate form and nitrite form) in a solvent as conventional, physically drying film formers with an anti-corrosive effect in the presence of sparingly soluble salts with anti-corrosive anions such as alkaline earth phosphates are preferred.

According to a further embodiment for environmentally friendly paints with a high solids content and a low solvent content, short-chain copolymers are dissolved in higher concentrations in solvents.

According to a further embodiment of the present invention, anti-corrosive preparations according to the invention are suitable for use in water-based paints. By adding small amounts of a hydrophobic solvent such as ethers, it can be achieved that the reaction to release corrosion-protecting anions does not start or starts with a delay despite the presence of water.

Corrosion-protecting anion exchange polymer salt preparations according to the present invention are compatible with polymers with epoxy groups and the anion exchange copolymers according to the invention can themselves carry epoxy groups and be cured by epoxy crosslinking reactions.

Aromatic carboxylic anhydrides such as pyromellitic anhydride or phthalic anhydride are preferred as reactants for these epoxy resins. In one embodiment of the present invention, tertiary amines, such as, for example, triethylenediamine (DABCO) and imidazoles, are preferred as catalysts for curing the epoxy resins.

In a further embodiment of the present invention, anti-corrosive preparations according to the invention are used in powder coatings for powder coating of metal objects. The above resins with additional epoxy groups are suitable for this purpose.

In a further embodiment of the present invention, corrosion protection systems according to the invention are used as a component of electro-dip paints

(KTL lacquers) are used. This requires additional functional groups such as tertiary amines in protonated form (preferably with the carboxylic acid anion of the anion exchanger groups) to make these polymers water-soluble, and additional reactive groups such as epoxy groups for later crosslinking of the cathodically deposited dip lacquers.

The polymers according to the invention are preferably prepared by polymerizing unsaturated compounds with aromatic or aliphatic radicals, which can enter into a subsequent alkylation reaction with amines or nitrogen-containing heterocycles such as imidazole, such as vinylbenzyl chloride with acrylates, methacrylates or styrene and subsequent reaction with a tertiary amine such as trimethylamine, triethylamine or other trialkylamines or nitrogen-containing heterocycles such as imidazole, more preferably 2,3-dimethylimidazole, 2-isopropyl-3-methylimidazole, 2-methyl-3-butylimidazole, 2-isopropyl-3-butylimidazole, although other substituted imidazoles or benzimidazoles may also be suitable.

In a preferred process, 1-vinylimidazole, more preferably 1-vinyl-2-methylimidazole, 1-vinyl-2-isopropylimidazole is polymerized with acrylates such as t-butyl methacrylate, methacrylates such as t-butyl methacrylate or methyl methacrylate, and the product is then polymerized with alkylating agents such as methyl iodide or 1-bromobutane converted into polymers with imidazolium groups. In a particularly preferred embodiment of this process, an alkyl carbonate is used as the alkylating agent.

Instead of the subsequent functionalization, vinylbenzyltrimethylammonium halides or 1-vinylimidazolium salts can also be polymerized directly with the methacrylates or acrylates or styrene in a suitable solvent.

The resulting polymers in the halide form can be converted into the hydroxide form by means of an alkali hydroxide solution for several hours, by means of a sodium acetate solution and this by means of sodium nitrite solution completely or preferably partially into the nitrite form by means of ion exchange, for example will.

A partial conversion of the polymers with anion-exchanging groups in hydroxide form or acetate form into the nitrite form is more preferred in order to always keep the polymer in a basic medium.

The resulting in the case of an alkylation with alkyl carbonates products in carbonate form can be converted directly into the acetate form by reaction with Bronsted acids such as acetic acid, the products formed advantageously being free of troublesome, corrosive halide ions such as chloride ions.

Although a free radical polymerization reaction is the most preferred production method for the production of the functional polymers according to the invention, anionic or cationic polymerisation reactions can also be suitable for production. Instead of polymers obtained by polymerization, polymers obtained by polycondensation or polyaddition can also be used for the anti-corrosive preparations according to the invention, if these are compatible with alkaline media and nitrite or nitrate ions. Functional polymers that are produced by graft copolymerization (“graft polymerization”) are also suitable.

According to a further embodiment of the present invention, the polymers according to the invention with anion-exchanging groups in nitrite form are also suitable for protecting other metals, such as light metals such as aluminum alloys. The preparations in question also expediently contain a sparingly water-soluble salt such as an alkaline earth phosphate. The preparations can also contain further corrosion inhibitors such as benzothiazoles or benzotriazole.

BEST WAY TO CARRY OUT THE INVENTION

The following examples illustrate the best mode for carrying out embodiments of the invention. Examples 1-5 demonstrate the production of copolymers according to the invention for use as corrosion inhibitors with imidazolium groups, Example 6 the production of a copolymer with ammonium groups.

EXAMPLES

Example 1 Copolymerization of t-butyl acrylate with vinylbenzyl chloride

23.44 g of t-butyl acrylate (98%, Sigma-Aldrich, Taufkirchen) and 3.45 g of vinylbenzyl chloride (97%, mixture of 3- and 4-isomers, Sigma-Aldrich, Taufkirchen) are each in by shaking with 0.5% sodium hydroxide solution freed from the stabilizers in a separating funnel. 23.10 g of t-butyl acrylate and 2.86 g of vinylbenzyl chloride are placed in a round bottom flask with 25.26 g of distilled water and 153.7 mg of sodium lauryl sulfate (Sigma-Aldrich, Taufkirchen) in 1.2613 g of distilled water. Water added. After adding a solution of 145.5 mg sodium hydrogen carbonate in 3.4148 g distilled water and 0.45 g ammonium peroxodisulfate (p.a., Fluka AG, Buchs, Switzerland) and

0.37 g of sodium peroxodisulfate (Bayer AG, Leverkusen) is flushed through the flask with argon for 20 minutes. The suspension is then polymerized by heating under reflux cooling and vigorous stirring with a magnetic stirrer at 70 ° C. for 3 hours. After cooling, the batch provides 13.6 g of an agglomerate cake of solid polymer and 49.7 g of a solution of a polymer latex. Example 2 Reaction of the copolymer with 1,2-dimethylimidazole

0.4 g of the polymer agglomerate from Example 1 are stirred with 7.0 g of 1,2-dimethylimidazole (Sigma-Aldrich, Taufkirchen) for 28 hours at room temperature with a magnetic stirrer. A slightly foaming dispersion of the desired polymer with imidazolium groups forms in chloride form. Example 3 Drying of the imidazolium copolymer

1 ml of the dispersion of the copolymer with imidazolium groups from Example 2 are applied to a glass plate and dried at 80 ° C. for at least 3 hours on the hot plate of a magnetic stirrer. The rest of the dispersion becomes through

The excess dimethylimidazole was removed by vacuum distillation at 80 ° C. Example 4 Conversion of the polymer into the hydroxide form or acetate form 1 The glass plate with the dried film of copolymers in the chloride form from Example 3 is made up for 24 hours in 80 ml of 1 M potassium hydroxide solution (from KOH purissimum pa, Fluka, Taufkirchen) dipped. The result is a film of the copolymer with imidazolium in hydroxide form, which by ion exchange with 1M acetic acid, sodium acetate solution (or sodium nitrite solution or potassium nitrate solution or nitric acid) for a period of 24 hours in the acetate form (or nitrite form and nitrate) Shape) is converted. Example 5 Preparation of a dispersion of the copolymer in acetate form in a solvent

The copolymers in acetate form prepared by the method from Example 4 is dissolved in 20 ml of tetrahydrofuran (dried over molecular sieves, Fluka, Taufkirchen) with heating to 63 ° C. under reflux. Example 6 Preparation of a copolymer with quaternary ammonium groups

13.8 g of the latex from Example 1 are filled with 5.8 g of triethylamine (Fluka AG, Buchs) in a round-bottom flask with a stir bar and heated at 40 ° C. for 5 days with stirring. The resulting dispersion of a polymer with quaternary ammonium groups is worked up as in Examples 3-5.

The present invention is industrially applicable for the corrosion protection of iron alloys.

Although the present invention has been described in considerable detail with reference to certain preferred embodiments, other embodiments are possible. For example, it is possible to use a copolymer in the form of dicyanamide form. Therefore, the scope of the appended claims should not be limited to the description of the preferred embodiments herein.

The reader's attention is drawn to all articles and documents filed at the same time as or prior to this description in connection with this application and which are available for public inspection with this description, and the contents of all such articles and documents are herein included by reference.

All features disclosed in this description (including all the appended claims, the abstract and the drawings) and / or all steps of any method or process thus published can be replaced by alternative features serving the same, equivalent or similar purpose, unless otherwise expressly stated. Thus, unless expressly stated otherwise, each feature disclosed is only an example of only a generic sequence of equivalent or similar features.

Claims (10)

Patent claims: 1. Lacquer preparation for use as an anti-corrosive paint, which contains a system for the delayed release of anti-corrosive anions when exposed to pure water or rainwater, containing: (a) at least one first polymer with anion exchange groups in the form of basic anions of a conjugate acid with a logarithmic acid constant pK,> 4; and (b) at least one second polymer with anion exchange groups in nitrate or nitrite form; and (c) at least one pigment made from a sparingly soluble salt Me, Y, n with anions Y ”with a charge z> 2 which do not promote corrosion, which are selected from the group consisting of alkaline earth phosphates, lithium phosphate, alkaline earth carbonates, alkaline earth molybdates, alkaline earth oxalates. 2. Paint preparation according to claim 1, wherein at least one alkaline earth phosphate is selected from the group of tristrontium phosphate, tricalcium phosphate and tribium phosphate as the sparingly soluble alkaline earth metal salt pigment. 3. Paint preparation according to claim 1 to 2, wherein the basic anions are anions from the group of hydroxide anions, carboxylic acid anions, hydrogen carbonate anions, borate anions, hydrogen phosphate anions, silicate anions, carbonate anions, alkyl carbonate anions and Dicyanamide anions are used. 4. A lacquer preparation according to claim 1 to 3, which contains anion-exchanging polymers which are wholly or partly in acetate form, in benzoate form, in propionate form or in phthalate form. 5. Lacquer preparation according to claim 1 to 4, wherein the anion-exchanging polymers contain polymers with imidazolium groups or pyridinium groups. 6. A lacquer preparation according to claim 1 to 4, wherein the anion-exchanging polymers contain polymers with phosphonium groups. 7. A lacquer preparation according to claim 1 to 6, wherein the anion-exchanging copolymers contained are copolymers or terpolymers of monomers with functional groups suitable for the production of anion-exchange groups with t-butyl acrylate or t-butyl methacrylate. 8. Polymers for one of the coating preparations according to claims 1 to 7, which are obtainable by radical copolymerization of: a) 0.1 mol% to 30 mol% of at least one monomer from the group of vinylbenzyltrimethylammonium acetate, vinylbenzyltrimethylammonium nitrate, 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H-imidazolium acetate, 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H-imidazolium nitrate, 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H -imidazolium nitrite, 1- vinyl-2-alkyl-3-alkyl-imidazolium acetate, 1-vinyl-2-alkyl-3-alkyl-imidazolium nitrate and 1-vinyl-2-alkyl-3-alkyl-imidazolium nitrite, vinylbenzyltrimethylphosphonium acetate, vinylbenzyltrimethyltrimethylphosphonium acetate , 2- (1H-imidazol-1-yl) ethyl methacrylate and 2- (1H-imidazol-1-yl) ethyl acrylate, said alkyl radicals on said imidazolium monomers being C 1 -Cn alkyl groups; b) 30 mol% to 99.9 mol% of at least one monomer from the group of t-butyl acrylate, t-butyl methacrylate, methyl methacrylate and other methacrylic acid esters and acrylic acid or methacrylic acid and other monomers. 9. Polymers for one of the lacquer preparations according to claim 1 to 8, which are obtainable by radical copolymerization of: a) 0.1 mol% to 20 mol% of at least one monomer from the group of vinylbenzyltrimethylammonium acetate, vinylbenzyltrimethylammonium nitrate, 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H-imidazolium acetate, 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H-imidazolium nitrate, 3- (4-ethenylbenzyl) -1-alkyl-2-alkyl-1H -imidazolium nitrite, 1- vinyl-2-methyl-3-methyl-imidazolium acetate, 1-vinyl-2-methyl-3-methyl-imidazolium nitrate, 1-vinyl-2-methyl-3-methyl-imidazolium nitrite, 1-vinyl-3 methyl imidazolium acetate, 1-vinyl-3-methyl-imidazolium nitrate, 1-vinyl-3-methyl-imidazolium nitrite, 1-vinyl-2-methyl-3-butyl-imidazolium acetate, 1-vinyl-2-methyl-3-butyl imidazolium nitrate, 1-vinyl-2-methyl-3-butyl-imidazolium nitrite, 1-vinyl-3-butyl-imidazolium acetate, 1-vinyl-3-butyl-imidazolium nitrate and 1-vinyl-3-butyl-imidazolium nitrite; b) 80 mol% to 99.9 mol% of at least one monomer from the group of t-butyl acrylate, t-butyl methacrylate, methyl methacrylate and other methacrylic acid esters and acrylic acid or methacrylic acid and other monomers. 10. prepolymer for a polymer for a lacquer preparation according to claim 1 to 6, wherein said prepolymer contains, in addition to said anion exchange groups, a reactive group for crosslinking which is selected from the group of epoxy groups and carboxylic acid anhydrides.