CH709580B1 - Corrosion-protective paint preparation. - Google Patents

Abstract

The present invention relates to corrosion-protective paint preparations. Corrosion-protective paint preparations, which contain anion-exchanging polymers in the form of basic anions as well as in nitrite or nitrate form as well as an alkaline earth and alkali phosphate, ensure effective protection against corrosion of iron alloys by passivation. Polymers with imidazolium groups or phosphonium groups are preferred. According to a preferred embodiment, a corrosion-protecting preparation or paint also contains alkaline earth metal phosphate particles in order to create a system for the slow release of corrosion-protecting ions even in ion-poor water, so that the metal to be protected is constantly in a passive state and in an optimally alkaline pH -Interval is held.

Description

Description Technical Field This patent application deals with anti-corrosion paint preparations 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 dated April 21, 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- Corrosion-promoting salt such as an alkaline earth metal phosphate such as Ca ₃ (PO ₄ ) _{2 presented} as inexpensive corrosion inhibitors for iron alloys. In addition to commercial, strongly basic anion exchangers in hydroxide or nitrite form, these anion-exchange polymers with quaternary ammonium groups were, in particular, water-insoluble, solvent-soluble copolymers which can be obtained by copolymerizing vinylbenzyltrialkylammonium chloride or diallyldimethylammonium chloride with styrene and / or butadiene in addition to the subsequent ion exchange into the hydroxide form or nitrite form.

However, there is a compatibility problem of these corrosion inhibitors and primers, which contain these corrosion inhibitors, with numerous polymers of conventional topcoats and with light metals, which can lead to peeling off of the lacquer layers or an etching of the base metal. This is because the primers in question can release alkaline solutions such that e.g. an acrylic-based topcoat would be subject to alkaline hydrolysis of the ester groups.

Brief Description of the Invention The present invention addresses anti-corrosion paint preparations that solve these compatibility problems.

Corrosion-protecting paint preparations according to the invention contain functionalized film formers with anion-exchanging groups in the form of basic anions and anion-exchanging groups in nitrite or nitrate form, as described in claim 1 and explained in detail below in order to achieve a far more effective corrosion protection than this can be achieved with environmentally friendly corrosion inhibitors according to the state of the art, such as zinc phosphate, the effectiveness of which - insofar as this exists at all - is extremely low.

It has been 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 poorly soluble salts such as alkaline earth metal phosphates ₂ such as Ca ₃ (PO ₃ ) Contain, protect iron, steel and other iron alloys 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, for example in the form of a carboxylic acid anion such as in acetate Form or benzoate form can be added.

It has also been found that paints based on epoxy resin, their epoxy resins, hardeners or other reactive additives such as reactive thinners carry appropriate functional groups such as imidazolium, ammonium or phosphonium groups, and a salt such as an alkaline earth metal phosphate (e.g. Calcium phosphate) contain the desired corrosion protection. However, no large-scale radical copolymerization of special monomers is required to produce these colors.

According to a further embodiment of the present invention, the anti-corrosion paints according to the invention based on epoxy (see claim 10) can be used in a primer.

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, in which:

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;

CH 709 580 B1

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 ₂ ) and t-butyl acrylate (or t-butyl methacrylate) according to a further embodiment of the present invention;

Figure 4 shows the structure of copolymers with triphenylphosphonium groups (e.g. in the acetate form (or hydroxide form) and nitrite form) and t-butyl acrylate (or t-butyl methacrylate) according to another embodiment of the present invention;

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;

Fig. 6 shows the change in pH of a preparation according to the invention of anion-exchange polymers with quaternary ammonium groups and strontium phosphate in the purest water according to a further embodiment of the present invention by slow release of hydroxide ions;

7A and 7B an epoxy resin with a functional imidazolium group according to the invention (see claims 8 to 10) in nitrate (X '= NO ₃ ) or in the form of basic anions X' such as in acetate form (X = CH ₃ COO);

8 shows a hardener with a functional imidazolium group according to the invention (see claims 8 to 10) in nitrate (X = NO ₃ ) or in the form of basic anions X ', such as in acetate form (X = CH ₃ COO) ; and

9 shows a reactive component with a functional imidazolium group according to the invention in

Nitrate (X = NO ₃ ) or in the form of basic anions X 'such as in acetate form (X = CH ₃ COO) shows.

[0010] These and the other features, aspects and advantages of the present invention will be better understood with reference to the following description and appended claims.

Description of the embodiments [0011] 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 poorly soluble, non-corrosive salt such as an alkaline earth metal phosphate such as Ca ₃ (PO ₄ ) _{2 was presented} as a corrosion inhibitor for iron alloys.

Without being bound by theory, it is believed that the corrosion-protecting effect of these polymers is based on the fact that

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

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

3. the quaternary ammonium compounds also show a corrosion-protecting effect and effect as a biocide,

4. by adding a sparingly water-soluble salt such as an alkaline earth metal phosphate, a system for the very slow release of alkaline hydroxide anions (and nitrite ions) in the presence of low-ion water (such as rainwater) is formed by the anion exchanger having slight traces of phosphate ions, which are caused by contact Water to alkaline earth phosphate particles are dissolved in an anti-corrosive paint according to the claims 6 and 7, 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 the presence of water in an alkaline pH interval which is favorable for the passivation of iron (see FIG. 6) and is thus passivated and extremely effectively preventively even in a considerable area around an inventive color layer

Claims (1)

Claim 1 protected even against bare, uncoated areas from rust. If the coating according to the invention is coated as a primer with hydrophobic lacquers, this system for corrosion protection is only effective where corrosion threatens through the entry 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 therefore do not get into the environment. CH 709 580 B1 The polymers and preparations according to the invention are, however, only partially compatible with conventional lacquers, for example based on acrylate, since the strongly alkaline solutions which can be released from them by water can hydrolytically attack conventional lacquers and, for example, polymers from Can saponify methacrylic acid esters or acrylic acid esters. However, it was found that instead of anion-exchanging polymers in hydroxide form in such a corrosion-protecting preparation, also anion-exchanging polymers in the form of a weakly basic anion can 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. Preferred are 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 ions charged twice). Anions of weak carboxylic acids with a pK _s as large as possible (ie an acid constant K _s as low as possible), which should be above a value of 4.0, optimally above a value of 4.7, are more preferred. Anions of aliphatic and aromatic dicarboxylic acids such as, for example, azelaic acid and phthalate anions are also preferred, 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 weakest possible dicarboxylic acids (pK _s > 4.0 for the second stage) which - depending on the cation of the sparingly soluble salt in the anti-corrosion preparation - form easily soluble lithium salts, alkaline earth metal 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 metal or zinc ions is also preferred, provided that they can be eluted from the anion-exchanging polymers with anions of the sparingly soluble salt. Anions with> 4 carboxylic acid groups are generally difficult to elute and are less suitable, even if individual anions could be suitable. [0023] Preference is given to anions of monocarboxylic acids for their ease of elution, alkaline earth metal salts and their easily soluble (except for formic acid) of low pK _s -value of the carboxylic acids. Short-chain aliphatic monocarboxylic acid anions of C - to C ₅ -carboxylic acids (formate to valerate anions) such as, for example, acetate ions or propionate anions and anions of aromatic monocarboxylic acids such as, for example, benzoate ions are preferred, although longer-chain carboxylic acids are also preferred could be suitable. The carboxylic acids in question can be branched or unbranched and carry substituents such as hydroxyl groups or halogens. The carboxylic acid anions in question may also contain double bonds or triple bonds, such as cinnamic acid anions. The use of copolymers with quaternary alkylammonium groups (or arylalkylammonium groups) in acetate form is optimal. Also preferred are 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. Polymers in the form of molybdate ions, tungstate ions or vanadate ions are also preferred, although other anions such as chromate ions may also be suitable. Polymers in the form of hydrogen carbonate ions, hydrogen phosphate ions, hydrogen borate anions and silicate ions such as Si ₃ O ₇ ^2. Are more preferred. According to a further preferred embodiment of the present invention, polymers in nitrite form according to claim 1 can be replaced in whole or in part by polymers in nitrate form which are more stable. Polymers in the form of other oxidizing anions such as permanganate and manganate ions may 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, a molar ratio of 1: 1 to 3: 1 with a slight excess of polymers in nitrite is optimal. Shape. Preparations with a substance quantity ratio above 20: 1 may show a protective effect that is too short-term, while preparations with a substance quantity 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 protection Can show protective effect. CH 709 580 B1 Basic anions (e.g. hydroxide ions, acetate ions) and nitrite ions can, according to a further preferred embodiment of the present invention as claimed in claim 1, be bonded 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, for example, alkaline earth metal 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 0.1 and 0.5 is more preferred for alkaline earth phosphates, a molar ratio between 0.1 and 0.25 is most preferred and a molar ratio of 1 / (mz) is used for anions Y ^z 'of a salt Me _n Y _m , ie 0.167 for calcium phosphate is optimal. Mole ratios below 0.01 do not provide satisfactory corrosion protection against rainwater, while mole ratios above 0.5 do not offer any significant advantage. Instead of alkaline earth phosphates such as calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), strontium phosphate, barium phosphate, magnesium phosphate, lithium phosphate and other poorly soluble alkaline earth metal 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 activity are copolymers (or terpolymers) of vinylbenzyltrimethylammonium chloride and methacrylates, acrylates and styrene are also suitable, as are copolymers of diallyldimethylammonium chloride with acrylates, methacrylates or styrene, the glass transition temperature of which is preferably between 30 ° C. and 100 ° C, most preferably between 40 ° C and 80 ° C. Also preferred are copolymers (or terpolymers) of acrylamidopropyltrimethylammonium chloride (as well as analog esters that are bound to quaternary ammonium groups, see FIG. 1) that carry 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 R ₅ = t-butyl, R ₃ = H) or methacrylic acid (t-butyl methacrylate, ie R ₅ = t-Butyl, R ₃ = CH ₃ ) and styrene as monomers for alkali-resistant copolymers are highly preferred, because they also provide homopolymers against 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 lacquer cannot be decomposed by alkaline solutions. Methyl methacrylate (MMA) are also preferred as further monomers. According to a further embodiment of the present invention, according to claim 9, anion exchange polymers (or copolymers or terpolymers) are preferred which contain imidazolium groups, pyridinium groups, pyrrolium groups or quaternary phosphonium groups instead of quaternary ammonium groups, although other positively charged quaternaries Groups of, for example, heterocyclic compounds and trimethylene diamine (DABCO) or quinuclidine or sulfonium groups, benzimidazolium groups or triazolium groups may also be suitable. A mole fraction of monomers with positively charged functional groups such as quaternary ammonium groups, imidazolium groups or phosphonium groups on all monomers (including monomers without charged groups) for the preparation 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 proportion of less than 0.01 mol% do not offer reliable corrosion protection, while polymers with a proportion of more than 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, for example, 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, even after oxidative cleavage of one or more N-alkyl groups (or P-alkyl groups) in acidic solution to form no nitrosamines. Alkali-resistant 1-alkyl-2-alkyl-3-alkylimidazolium groups such as, for example, 1-alkyl-2-isopropyl-3-alkylimidazolium groups or 1-alkyl-2-methyl-3-alkylimidazolium 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 = CH ₃ O-) or tetrabenzylphosphonium groups in which none from the outset Nitrosamines can form, 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 with suitable substituents, these do not form any nitrosamines and the starting materials are inexpensively available on an industrial scale. Most preferred are the more base-resistant imidazolium groups which can be prepared from 2-alkylimidazole, for example 2-isopropyl-1-methyl-3-benzylimidazolium groups, where as alkyl substituents CH 709 580 B1 Isopropyl groups and methyl groups are preferred, although other alkyl groups such as t-butyl groups or trifluoromethyl groups are also suitable. Phenyl, benzyl and cyclohexyl substituents in this 2-position of imidazole are less preferred since the imidazoles in question, which are substituted in this way, can form nitrosamines with nitrite in acidic solution.