WO2008031781A2

WO2008031781A2 - Method for using polymers comprising quaternary ammonium groups and urea groups as corrosion inhibitors for copper surfaces

Info

Publication number: WO2008031781A2
Application number: PCT/EP2007/059438
Authority: WO
Inventors: Frank Dietsche; Ralf Friedrich; Thomas Heidenfelder; Helmut Witteler
Original assignee: Basf Se
Priority date: 2006-09-15
Filing date: 2007-09-10
Publication date: 2008-03-20
Also published as: WO2008031781A3

Abstract

The invention relates to a method for protecting the surfaces of copper or copper alloys from corrosion. According to said method, the metallic surface is brought into contact with an aqueous medium which contains, as a corrosion inhibitor, a quaternary polymer comprising ammonium groups and urea groups, thiourea groups and/or iminourea groups in a numerical ratio of between 1.5 : 1 and 2.5 : 1.

Description

Use of polymers comprising quaternary ammonium groups and urea groups as a corrosion inhibitor for copper surfaces

description

The present invention relates to a method for protecting the surfaces of copper or copper alloys from corrosion, in which the metallic surface is brought into contact with an aqueous medium containing as corrosion inhibitor a quaternary ammonium groups and urea groups, thiourea groups and / or imino urea groups in the numerical ratio Containing 1, 5: 1 to 2.5: 1 comprising polymer.

Articles and workpieces of copper and copper alloys often tend to tarnish under conditions of use, i. for the formation of colored corrosion layers, such as, for example, oxide, hydroxide and / or carbonate layers on the surface. Even if such layers do not necessarily result in the destruction of the workpiece, they are often undesirable for aesthetic reasons. Even very thin corrosion layers u.U. significantly reduce the electrical conductivity, which can be very disadvantageous for applications of copper in the field of electrical engineering and in particular electronics.

Corrosion inhibitors for preventing or at least containing corrosion are known in principle. They often act specifically only for one kind of metals, i. Good corrosion inhibitors for ferrous metals need not necessarily be good corrosion inhibitors for copper or copper alloys.

It is known to use benzotriazoles as corrosion inhibitor for copper surfaces. For example, see US Pat. No. 5,746,947. This class of corrosion inhibitors finds application, inter alia, in liquid media in contact with copper surfaces, e.g. Cleaners, stains or Entlackern for copper surfaces or cooling or heating media, which flow through copper pipes or copper equipment.

Benzotriazoles have limited solubility in water. Thus, the solubility of 1-H-benzotriazole in water at room temperature and pH 7 is only about 20 g / l. As the pH increases, the solubility due to salt formation increases. Tolyltriazole has a solubility of less than 10 g / l at RT in water.

Furthermore, benzotriazoles have only limited effectiveness in some media. Thus, they have a pronounced tendency to precipitate in strongly saline media. Furthermore, they can even promote corrosion in environments containing sulfides (Electrochem. Solid-State Lett., Vol. 9 (3), B19-B23 (2006)). EP 243 780 A2 discloses polymers comprising urea groups and quaternary ammonium groups, a process for preparing such polymers and their use in detergents, hair shampoos and for the treatment of textiles. Such polymers are commercially available.

US 3,982,894 discloses a method for corrosion protection of metals, in particular iron, in which polymers with quaternary ammonium groups are used. The polymers are polycondensation products of mono- and / or polyamines with various organic dichlorides or epichlorohydrins. The polymers have no urea groups.

US Pat. No. 6,448,211 B1 discloses a method for passivating iron over surfaces, in which a composition is used which comprises gluconic acid and the urea group-comprising cationic polymer poly (oxy-1,2-ethanediyl (dimethylimino) -1,3-propanediyliminocarbonylimino 1, 3-propanediyl (dimethylimino) -1, 2-ethanediyl dichloride).

EP 1 069 21 1 A2 discloses a copper plating bath comprising at least one acid, a copper salt, a sulfur-containing organic brightener and an organic compound intended to ensure a uniform surface. The latter compound may also be polymers comprising quaternary ammonium groups and urea groups.

EP 1 201 789 A2 discloses a plating bath for depositing Sn-Zn alloys using polymers which have quaternary ammonium groups and also urea groups, thiourea groups or imino urea groups.

None of the cited documents discloses the use of quaternary ammonium groups and polymers containing urea groups for the corrosion protection of copper or copper alloys.

The object of the invention was to provide a method for protecting copper from corrosion, in particular when in contact with aqueous media, in which very good water-soluble, salt-stable and readily biodegradable polymers are used.

Accordingly, a method has been found for protecting the surfaces of copper or copper alloys from corrosion in which the metallic surface is contacted with an aqueous medium comprising at least one water-soluble corrosion inhibitor, the water-soluble corrosion inhibitor being a polymer P which quaternary ammonium groups and urea groups, thiourea groups and / or imino urea groups in the numerical ratio from 1, 5: 1 to 2.5: 1, provided that the solubility of the polymer P in water is at least 50 g / l.

In a preferred embodiment of the invention, the polymer comprises P structural units of the following formula (I)

where the abbreviations R ¹ , R ² and X have the following meaning:

R ¹ : independently of one another an aliphatic, straight-chain, branched or cyclic hydrocarbon group having 1 to 30 C atoms, wherein the hydrocarbon groups may also have substituents and / or non-terminal non-terminal carbon atoms in the hydrocarbon groups by N- and / or O atoms can be substituted;

R ² : independently of one another an aliphatic and / or aromatic, straight-chain, branched or cyclic hydrocarbon group having 1 to 30 carbon atoms, wherein the hydrocarbon radicals may also have substituents and / or non-adjacent non-terminal carbon atoms in the hydrocarbon groups N and / or O atoms may be substituted;

X ^" : monovalent anions or polyvalent anions 1 / p YP-, where Y represents a p-valent anion.

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

With the method according to the invention, the surfaces of copper or copper alloys can be protected from corrosion. Other metals in copper alloys may be, for example, one or more of Zn, Sn, Pb, Al, Si, Mn, Ni, Fe or Cr. Examples of typical alloys include brass or bronze. The invention is not limited to alloys with certain copper levels. For example, Al-Cu alloys with a copper content of less than 10% by weight can also be protected by means of the method according to the invention. Such alloys are used, for example, in dishwashers. They can be the surfaces of arbitrary bodies of copper or copper alloys, for example sheets, foils or pipes. These do not have to be surfaces that consist exclusively of copper, but they can also be surfaces in which only parts made of copper or copper alloys exist. As an example, be called circuit boards.

To carry out the method, the copper surface is brought into contact with an aqueous formulation or an aqueous medium which comprises at least one polymer P. Of course, several different polymers P can be used.

The polymer P to be used is a cationic polymer which comprises quaternary ammonium groups and urea groups which are linked to one another by means of suitable groups. The urea groups may also be thioan groups and / or imino urea groups. The numerical ratio of quaternary ammonium groups to urea groups in the polymer is preferably from 1.5: 1 to 2.5: 1, preferably from 1.8: 1 to 2.2: 1 and more preferably about 2: 1. The linking groups are preferably groups which contain alkylene groups, oxyalkylene groups and / or OH groups. Such polymers and their preparation are in principle known to the person skilled in the art, e.g. from EP 243 780 A2.

In a preferred embodiment, polymer P is a polymer which comprises structural units of the following formula (I):

Here, the radicals R ¹ independently of one another are aliphatic, straight-chain, branched or cyclic hydrocarbon groups having 1 to 30 C atoms, preferably 2 to 20 C atoms and particularly preferably 2 to 10 C atoms. The radicals R ¹ may be different or preferably the same. The hydrocarbon radicals can also have substituents, in particular those which have N and / or O atoms, and furthermore non-adjacent non-terminal C atoms in the hydrocarbon radicals can also be substituted by N and / or O atoms. It is preferably unsubstituted hydrocarbon radicals. The hydrocarbon radicals are preferably linear 1, ω-alkylene groups of the general formula - (CH ₂ ) _n -, where n is a natural number of 2 to 10, preferably 2 to 6. Particularly preferred is a 1, 3-propylene radical -CH ₂ -CH ₂ -CH ₂ -.

The radicals R ² are, independently of one another, aliphatic and / or aromatic, straight-chain, branched or cyclic hydrocarbon groups having 1 to 30 C atoms, preferably 2 to 20 C atoms and particularly preferably 2 to 10 C atoms. The radicals R ² may be different or preferably the same. The hydrocarbon radicals may also have substituents, in particular those which have N and / or O atoms, preference is given to OH groups as substituents. Furthermore, non-adjacent non-terminal C atoms in the hydrocarbon radicals can also be substituted by N and / or O atoms, preferably by O atoms. Preferred radicals include linear 1, ω-alkylene groups of the general formula - (CH ₂ ) _n -, where n is a natural number of 2 to 10, preferably 2 to 6, 1, ω-Alkylenethergruppen such as - (CH ₂ ) _m -O- (CH ₂ ) _m - or - (CH ₂ ) _m -O- (CH ₂ ) _m -O- (CH ₂ ) _m -, where m is 2, 3 or 4, simply OH-substituted alkylene groups such as -CH ₂ -CH (OH) -CH ₂ -, -CH (CH ₂ OH) -CH ₂ - or double OH-substituted alkylene groups such as -CH ₂ -CH (OH) -R ³ -CH (OH) -CH ₂ -, wherein R ^{3 is} an aliphatic see and / or aromatic hydrocarbon radical having 1 to 20 C-atoms or an alkoxy radical of the general formula - (- CH ₂ -CH R ⁴ -O-) ι-, and wherein I is for 1 to 10, preferably 1 to 5 and R ^{4 is} H or CH ₃ .

In addition to the structural units (I), the polymer P may optionally also comprise further structural units. As a rule, however, at least 45%, preferably 60% and particularly preferably at least 80% of the molar mass M _{n of} a given polymer (A) should consist of the structural units (I).

The anions X "can be any monovalent anions, such as, for example, Ch, Br, -, CH 3 SO 3" or OH. "Monovalent anions can also be replaced by a corresponding number 1 / p of p-polyvalent ions YP-. , where p is the charge number of the anion.

In a preferred embodiment of the invention, the polymers P are obtainable by condensation of

• at least one amine (A), prepared by reaction of

at least one mono (N, N-dialkylaminoalkyl) amine (A1) with

at least one bifunctional compound (A2) selected from the group urea, thiourea, iminourea or dialkyl carbonates, wherein the molar ratio of the sum (A1) to (A2) is 1, 5: 1 to 2.1: 1,

Optionally further aliphatic and / or aromatic amines (B) each having two secondary and / or tertiary amino groups, in an amount of not more than 60 mol% with respect to the sum of (A) and (B),

With

At least one bifunctional compound (C) selected from the group of halomethyloxiranes, bisepoxides, alkylene dihalides and dihaloalkyl ethers,

wherein the molar ratio of (C) / [(A) + (B)] is 0.6: 1 to 1.4: 1.

Such polymers include structural units (I).

As mono (N, N-dialkylaminoalkyl) amines (A1), which are used for the preparation of the amine (A), are in principle all known in the art mono (N, N-dialkylaminoalkyl) amines, wherein the individual alkyl fragments of these compounds optionally may carry further substituents. Of course, mixtures of several, different mono (N, N-dialkylaminoalkyl) amine (A1) can be used.

(A1) is preferably mono (N, N-dialkylaminoalkyl) amines of the general formula (II)

R ⁵ R ⁵ N- (CH ₂ ) H -NH ₂ (II),

in which the variables have the following meaning:

R ⁵ , R ^{5 '} independently of one another are C 1 -C 6 -alkyl, preferably C 1 -C ₄ -alkyl, which may also be substituted by OH; particularly preferably methyl; n is a natural number of 2 to 10, preferably 2 to 6.

Particular preference is given to N, N-dialkylaminoalkylamines of the formula (II) which carry the same alkyl radicals on the nitrogen atom. Among these, the dimethylaminoalkylamines, especially N, N-dimethylaminopropylamine, are again very particularly preferred. In a first reaction stage, the amines (A1) are condensed with bifunctional compounds (A2) selected from the group consisting of urea, thiourea, imino urea or dialkyl carbonates. Preferred as the bifunctional compound (A2) is urea.

The condensation can be carried out, for example, by reacting the components (A1) and (A2) in bulk at a temperature of 120 to 180 ^° C. In the reaction of urea or urea derivatives with the amine (A1) produces ammonia, in the reaction of dialkyl carbonates of the corresponding alcohol. The expulsion of ammonia or alcohols from the reaction mixture can be facilitated, for example, by passing nitrogen through the reaction mixture.

The molar ratio of the dialkylaminoalkylamine (A1) to the bifunctional compound (A2) is from 1.5: 1 to 2.1: 1, preferably from 1.7: 1 to 2.1: 1 and more preferably from 1.8: 1 to 2: 1 ,

During condensation, the amines (A) or, as a rule, a mixture of different amines (A) are formed. Depending on the molar ratio (A1) / (A2), these are essentially diamines which have two terminal tertiary amino groups as well as condensation products which have a terminal tertiary amino group and a terminal urea group. Depending on the ratio of the two amines, the structure of the polymer P can be controlled. A slight excess of urea has proven to be useful.

In a second reaction stage, the amines formed (A) are reacted with at least one bifunctional compound (C) selected from the group of halomethyloxiranes, bisepoxides, alkylene dihalides and dihaloalkyl ethers.

In this second reaction stage, in addition to the amines (A), it is optionally also possible to react further, at least secondary diamines (B) other than (A). This allows the properties of the polycondensation product formed, i. Influence polymer P

However, the amount of such further amines (B) should not exceed 55 mol%, preferably 40 mol%, particularly preferably 25 mol% and very particularly preferably 10 mol%, relative to the amount of all amines (A) and (B) used together.

The at least secondary diamines (B) may be aliphatic and / or aromatic diamines. They are preferably cyclic, aromatic or aliphatic diamines. Of course, mixtures of different diamines (B) can be used. Examples of aliphatic amines (B) include amines of the general formula R ⁵ R ⁵ N-R ⁶ -NR ⁵ R ^{5 "} where R ⁵ and R ^{5 'are} as defined above and R ^{6 is} any linking group, preferably a hydrocarbon group Suitable diamine (B) can also be prepared by linking in each case two of the above-described mono (N, N-dialkylaminoalkyl) amines (A1) via the primary amino groups in a suitable manner , For example, by reaction with Dicarbonäsuren or diisocyanates.

Examples of suitable cyclic diamines (B) include in particular imidazole and its alkyl derivatives, piperazine and its alkyl derivatives, pyrazine and pyrimidine. The term "alkyl derivatives" should also be understood as meaning derivatives whose alkyl substituents are functionalized by further substituents, such as, for example, amino or hydroxyl groups. Specific examples of piperazine and imidazole derivatives are: 1-, 2- and 4- (C 1 -C 25 -alkyl) imidazoles, especially 1-, 2- and 4- (C 1 -C 6 -alkyl) imidazoles, such as 1-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 4-methylimidazole and 1- (3-aminopropyl) imidazole; 2,4-di (C 1 -C 25 -alkyl) imidazoles, especially 2,4-di (C 1 -C 6 -alkyl) imidazoles, such as 2-ethyl-4-methylimidazole; 1- (C 1 -C 25 -alkyl) -piperazines, especially 1- (C 1 -C 6 -alkyl) -piperazines, such as 1-methyl-piperazine; 1, 4-di (C 1 -C 25 -alkyl) piperazines, especially 1,4-di (C 1 -C 6 -alkyl) piperazines, such as 1, 4-dimethylpiperazine, 1, 4-bis (3-aminopropyl) -piperazine, 1- (2-Aminomethyl) piperazine and 1- (2-hydroxyethyl) piperazine.

Preferred diamines (B) are unsubstituted imidazole and with Ci-Cβ-alkyl in the 1-, 2- or 4-position at least monosubstituted imidazole, with unsubstituted imidazole is particularly preferred.

For the reaction with the amines (A) and optionally (B), bifunctional compound (C) selected from the group of alkylene dihalides (C1), dihaloalkyl ethers (C2), halomethyloxiranes (C3) or bisepoxides (C4) are used. Here u.a. the quaternary ammonium groups.

Particularly suitable alkylenedihalides (C1) are the .omega.,. Omega.'-dichlorides, dibromides and diiodides of unbranched alkanes having 2 to 8 carbon atoms, the bromides being preferred and the chlorides being particularly preferred.

Particularly suitable alkylene dihalides (C1) include, for example, 1,2-dichloroethane, 1,2-dibromoethane, 1,3-dichloropropane, 1,4-dichlorobutane, 1,5-dichloropentane and 1,6-dichlorohexane, where 1 , 2-dichloroethane, 1, 4-dichlorobutane and 1, 6-dichlorohexane are preferred.

Particularly suitable dihaloalkyl ethers (C2) are di (ω, ω'-halo-C 2 -C 6 -alkyl) ethers and (ω-halo-C 2 -C 6 -alkoxy-C 2 -C 6 -alkyl) (ω-halogen-C 2 -C 6 -alkyl) C 6 -alkyl) ether, where halogen may again denote chlorine, bromine or iodine, bromine being preferred and chlorine being is particularly preferred. Examples include di (2-chloroethyl) ether and (2-chloro-ethoxyethyl) (2-chloroethyl) ether.

Suitable Halomethyloxirane (C3) preferably have 3 to 7 carbon atoms, whereby also the chlorine compounds are preferred here. Particularly preferred halomethyloxirane (C3) is epichlorohydrin.

Particularly suitable bisepoxides (C4) are bisepoxialkanes having 4 to 7 carbon atoms and bisepoxides based on oligomeric and polymeric alkylene glycols, in particular C 2 -C 3 -alkylene glycols, such as oligo- and polyethylene glycol bis-epoxides, oligo- and polypropyleneglycol bisepoxides and bisepoxides of EO / PO copolymers. Preferred bisepoxides (C4) are bisepoxibutane and oligo- and polyethylene glycol bis-epoxides.

The molar ratio of bifunctional compound (C) to the amine components (A) and optional (B) is 0.6: 1 to 1.3: 1, preferably 0.8: 1 to 1, 1: 1 and more preferably about 1: 1.

The choice of the molar ratio (C) / [(A) + (B)] represents a further possibility to specifically control the molecular weight of the cationic polycondensation products.

The reaction of (C) with (A) and (B) is usually carried out with heating. Temperatures of 80 to 120 ^° C., for example temperatures of about 100 ^° C., have proven to be suitable in particular. The reaction can be carried out in bulk or preferably in a suitable solvent, preferably water. In general, the reaction times are 2 to 20 h.

If the resulting polymers P still contain tertiary amino groups, they may additionally be treated with alkylating agents, e.g. Dimethyl sulfate, Ci-C22-alkyl halides or benzyl chloride, are reacted, whereby the tertiary amino groups are quaternized. The reaction with the alkylating agent can be carried out directly in the reaction mixture obtained in the reaction according to generally known methods.

Excess amounts of the bifunctional compound (C) and optionally the alkylating agent can be removed after the reaction by means of methods known to those skilled in the art, for example by means of steam distillation.

The polymers used by the process described are readily water-soluble or at least water-dispersible. They can be separated from the aqueous reaction mixture by methods known to those skilled in the art. However, the aqueous solutions without isolation of the polymer P are preferably used for the used according to the invention, of course, the concentration can be adjusted appropriately.

According to the invention, polymers P are used which have a solubility of at least 50 g / l. The solubility of the polymers is preferably at least 100 g / l.

The respectively desired solubility can be influenced by the person skilled in the art in a manner known in principle by the choice of the substituents R ¹ and R ² . Is each have more carbon atoms, the radicals R ¹ and R ^2, the lower, in general, the solubility of the polymer. Of course, the hydrophilicity of the radicals R ¹ and R ^{2 can} also be increased by hydrophilic substituents and / or substitution of C atoms by N and / or O atoms. Particularly high solubilities of more than 200 g / l can be achieved if R ^{1 is} a linear 1, ω-alkylene group of the general formula - (CHb) _n - and n is a natural number of 2 to 10 and R ² for the said 1, ω-alkylene group, a 1, ω-Alkylenethergruppe or an OH-substituted alkylene group having 2 to 10 carbon atoms.

The average molecular weight M _{w of} the polymers P can be set by the person skilled in the art, depending on the desired application, by the choice of the reaction conditions and the amount of the starting materials. Depending on the conditions, M _w of 500 to 1,000,000 g / mol can be obtained. For the present application, in particular average molecular weights M _w of 1000 to 100,000 g / mol are suitable, preferably 2000 to 80,000 g / mol and more preferably from 4000 to 50,000 g / mol.

In the method according to the invention for protecting the surfaces of copper or copper alloys from corrosion, the copper surface is brought into contact with an aqueous formulation or with an aqueous medium comprising at least one polymer P.

Corrosion should be understood in a manner known in principle to be the disadvantageous and quality-reducing change of a material emanating from the surface and caused by inadvertent chemical or electrochemical attack. The nature of the corrosive media that are in contact with the surface does not matter. It may be, for example, gaseous, liquid or solid constituents corrosive media.

In the method according to the invention essentially two different embodiments are to be distinguished.

In a first advantageous embodiment, the aqueous medium is an aqueous formulation for coating, which comprises at least one polymer. Mer P and optionally comprises further constituents, with which the surface is coated and then dried. In this case, a thin layer of the polymer P and optionally further constituents of the formulation remains on the surface. The surface is thus subjected to a protective treatment in order to protect it against corrosive effects, which act on the surface only after the coating.

The coating may be carried out by conventional techniques known to those skilled in the art, for example by dipping, spraying, brushing, rolling or pouring. Corresponding apparatuses are known to the person skilled in the art. Drying can be done by simply drying in air at room temperature. However, it can of course also be supported by heating and / or passing gas streams, for example by heating in a drying oven or drying channel or by appropriate IR emitters.

The formulation used for coating preferably comprises only water as the solvent. Optionally, water-miscible organic solvents can also be added. Examples include especially water-miscible alcohols such as methanol, ethanol, n-propanol or i-propanol. However, an aqueous mixture generally comprises at least 50% by weight of water, preferably at least 75% by weight, more preferably at least 85% by weight and most preferably at least 95% by weight, based in each case on the amount of all solvents together.

The aqueous formulation may optionally comprise further components besides the at least one polymer P. Examples include in particular acids, bases or buffer systems for adjusting the pH. The polymer P according to the invention can in principle be used at all pH values, in particular pH values from 0.5 to 13, preferably 0.5 to 9.5. An application in a neutral or acidic medium having a pH of 0.5 to 7, preferably 1 to 6 and particularly preferably 1 to 5 to 5 is particularly advantageous. Examples of suitable acids include hydrochloric acid, methanesulfonic acid, citric acid, amidosulfonic acid or Phosphoric acid. Examples of bases include in particular NaOH, KOH, sodium carbonate or ammonia.

In addition to the polymers P, the formulation may also comprise other water-soluble or water-dispersible polymers or prepolymers and / or crosslinking components. Furthermore, metal ions, fillers, dyes, defoamers, metal deactivators or other typical paint constituents may also be present.

The amount of polymers P in the aqueous formulation will be determined by those skilled in the art according to the desired properties. An amount of from 0.01% by weight to 10% by weight, preferably from 0.02 to 5% by weight and particularly preferably from 0.025% by weight to 3% by weight, based in each case on the amount of all components of the formulation, has proven useful. To prepare the aqueous formulation for coating, the aqueous solution of the polymer resulting from the preparation may preferably be used without further purification.

In a second advantageous embodiment of the method, the surface is protected from the corrosive influence of the aqueous medium itself, which is in contact with the surface of the copper or copper alloy. The corresponding medium can be permanently or even temporarily in contact with the surface.

Examples of such aqueous media include aqueous cooling or heating fluids circulating in heating or cooling circuits comprising copper pipes and / or other components of copper. Also to be mentioned are in particular cleaners, stains or Entlacker for surfaces of copper or copper alloys. Although such cleaners should dissolve impurities on the surface, such as oxide layers, carbonate layers or fatty layers, they should not attack the copper surface itself. The addition of the polymers P can effectively prevent the dissolution of copper or copper alloys.

The at least one polymer P may preferably be added to the aqueous medium before it is first contacted, or only while the medium is already in contact with the surface.

The aqueous media to be protected contain as further constituents, the components customary for the particular application. In particular, it may be further constituents selected from the group of acids, bases or surfactants. According to the invention, the polymers P can be combined particularly advantageously with cationic surfactants having quaternary ammonium groups.

Examples of corresponding cationic surfactants include N, N-dimethyl-N- (C 2 -C 4 -hydroxyalkyl) (C 7 -C 25 -alkyl) ammonium salts, mono- and di- (C 7 -C 25 -alkyl) dimethylammo quaternized with alkylating agents. ammonium compounds, in particular quaternary esterified mono-, di- and trialkanolamines esterified with Cs-C22-carboxylic acids or lauryl / myristyltrimethylammonium methosulphate.

The polymers P used according to the invention can be used both in acidic and in alkaline media, for example at a pH of 0.5 to 13. Use is particularly advantageous at a pH of 0.5 to 9.5, preferably in a neutral or acidic medium having a pH of 0.5 to 7, particularly preferably 1 to 6 and very particularly preferably 1, 5 to 5. The amount of polymers P in the medium is determined by the person skilled in the art, depending on the nature of the medium, in particular on its corrosivity. An amount of from 0.01% by weight to 10% by weight, preferably from 0.1 to 5% by weight, in each case based also on the amount of all components of the particular medium, has proven useful. In the case of only moderately corrosive media, it will be more appropriate to orientate at the lower limit; in the case of strongly corrosive media such as, for example, strongly acidic, strongly alkaline or strongly saline media, amounts of from 0.5 to 5% by weight, for example from 1 to 4% by weight , % especially proven.

The use according to the invention of the polymers P has a number of advantages:

The polymers P can be used in particular in strongly saline media. They are also soluble in the presence of high salt concentrations or do not precipitate. They can be used advantageously in media having a salt content of at least 5% by weight of salts with respect to the amount of all components of the medium. The salt content may preferably be at least 10% by weight and more preferably at least 20% by weight. Particularly advantageously, the polymers P can also be used in sulfide-containing media.

Formulations of the polymers P can also be formulated without precipitation in the pH range of 0.5 and 13, even at elevated temperatures. For example, remains a solution of the polymer at pH 1 even when heated to 80 ⁰ C clear. They are particularly suitable for acidic formulations.

The media which are in contact with the copper surface may be at room temperature. The process of the invention can be advantageously carried out especially at elevated temperatures, for example at a temperature> 30 ⁰ C, preferably> 40 ⁰ C and particularly preferably> 50 ⁰ C.

The polymers are not hazardous to water and have good bioeliminability. They are degradable with hypochlorite.

The invention will be illustrated in the following examples.

A) Preparation of the polymers used P:

1st stage: Preparation of the amine (A) by reacting N, N-dimethylaminopropylamine with urea

A mixture of 916.6 g (9.0 mol) of N, N-dimethylaminopropylamine (compound (Ala)) and 300.5 g (5.0 mol) of urea (compound (Al b)) is dissolved under nitrogen inlet. initially in 35 min at 122 ° C and then heated to 155 ° C in 4 h and then stirred for a further 12 h at this temperature.

The amine (A) is obtained in the form of a yellowish, clear liquid.

2nd stage: preparation of the polymers P No. 1-7

An aqueous solution (about 38% by weight) of the amine (A) prepared as above and, if appropriate, of the amine (B) was heated to 80 ^° C. and the bifunctional compound (C) was added dropwise thereto in the course of about 8 minutes. The mixture is stirred at 100 ⁰ C th and then subjected to a two-hour steam distillation.

The amounts of (A), (C) and optionally (B) used, the solids content and pH of the resulting aqueous polymer solutions and the K value of the polymers are summarized in Table 1

The determination of the indicated K values is carried out according to H. Fikentscher, Cellulose Chemistry, Volume 13, pages 58-64 and 761-774 (1932) as 1 wt .-% solution in 3 wt .-% saline solution at 25 ° C. The K values provide an indication of the molecular weight and the viscosity.

Table 1

B) Use of the polymers P for the protection of copper surfaces

B1) Determination of the inhibition efficiency of polymer P in acidic media

The test shows to what extent the dissolution of copper by a solution which is in contact with a copper surface for a long time is prevented by the addition of a corrosion inhibitor.

Experimental method:

1. For the tests, a sheet of fine copper of size 50 mm x 20 mm x 1 mm is used. It is cleaned up for the tests as follows:

The oxide layer is first sanded with a fine emery paper (particle size P 120). Thereafter, the copper sheet is immersed in an acid bath (32% HCl) and the residual oxide layer removed at RT while stirring.

After 2-3 minutes, the copper sheet is removed and rinsed for five seconds under running demineralized water.

The pre-treated in the acid bath copper sheet is at 10 volts in a degreasing from

20 g NaOH

22 g of Na ₂ CO ₃

16 g of Na ₃ PO ₄ x 12 H ₂ O.

1 g of EDTA tetrasodium salt, powder 0.5 g of a nonionic surfactant (ethoxylated nonylphenol, about 10 EO)

Units) immersed between the electrodes and connected as a cathode. The voltage is adjusted so that the current is 1 A. After 30 seconds, the copper sheet is removed and rinsed for five seconds under running demineralised water, blown off with air and used immediately for test purposes. The sheets will be used directly in the corrosion test without further storage, because otherwise the re-forming oxide layer falsifies the result of the corrosion test.

2. The test electrolyte used is a citrate buffer (pH 2) of the following composition:

6.3042 g citric acid 0.299 g NaOH 3.5648 g NaCl to 1000 ml demineralized water 3. The corrosion inhibitor to be tested is dissolved in the test electrolyte in the amount indicated in Table 1. The pH is measured.

4. Before the test, the mass is determined with the analytical balance. The copper sheet is used immediately after weighing. The prepared copper sheet is hung in a 250 ml beaker filled with test electrolyte so that it is completely covered by the electrolyte.

5. The beaker is stored for 24 hours at room temperature. After 24 hours, the pH is measured again.

6. The copper sheet is removed from the solution, rinsed with demineralized water and blown dry with air. Then the mass is determined. The efficiency is set by the mass loss Δmp _r0 be in relation to the mass loss in a corresponding control experiments without inhibitor Δmo. The following applies: E = (Δmo-Δmp _r0 be) / Δmo A double determination is carried out for each measured value. The results are summarized in Table 2.

Table 2: Results of the gravimetric corrosion tests

The experiments show that the inhibition efficiency of polymer 1 is better at higher levels. B2) Treatment of copper surfaces

The test shows to what extent the atmospheric corrosion of a copper surface under severe conditions (salt spray chamber) is inhibited by the previous treatment of the surface with a corrosion inhibitor.

Execution:

A purified copper sheet was used as described under B1).

The cleaned copper sheet was immersed at RT for 1 to 2 seconds in a 0.8% strength aqueous solution of polymer 1, blown off with nitrogen and dried at RT for 30 min.

Thereafter, the copper sheet was stored for 4 h in a Salzsprühkammer (DIN 510021) with 5% NaCl mist.

For comparison, an untreated sample was used, and a copper sheet was similarly immersed in a 0.8% aqueous solution of 1H-benzotriazole.

Result:

B3) Storage stability in the presence of high salt concentrations

Purified copper sheet was used as described under B1).

Two solutions of salts in water were used. The first solution contained 6.4% ZnBr ₂ , 41, 1% CaBr ₂ and 17% CaCl ₂ (each wt%), the second 45.4% ZnBr ₂ , 25.7% CaBr ₂ and 2.8% CaCl ₂ . The pH of the solutions was in each case 1 to 2. In each case 3% by weight of polymer 1 were added to the solutions.

The copper sheets were stored for 1 week at about 100 ⁰ C in the solutions. The polymer used did not precipitate, nor did the copper sheets show any discoloration.

Claims

claims

A method of protecting the surfaces of copper or copper alloys from corrosion by contacting the metallic surface with an aqueous medium comprising at least one water-soluble corrosion inhibitor, characterized in that the water-soluble corrosion inhibitor is a polymer P which is quaternary Ammonium groups and urea groups, thiourea groups and / or imino urea groups in the numerical ratio of 1, 5: 1 to 2.5: 1, with the proviso that the solubility of the polymer P in water is at least 50 g / l.

Process according to claim 1, characterized in that the polymer P is structural units (I)

in which the abbreviations R ¹ , R ² and X have the following meaning:

R ² : independently of one another an aliphatic and / or aromatic, straight-chain, branched or cyclic hydrocarbon group having 1 to 30 C atoms, where the hydrocarbon radicals may also have substituents and / or non-adjacent non-terminal C atoms in the hydrocarbon groups N and / or O atoms may be substituted;

X-: monovalent anions or polyvalent anions1 / p YP-, where Y represents a p-valent anion.

3. Process according to claim 2, wherein R ^{1 is} a linear 1, ω-alkylene group of the general formula - (CHb) _n - and n is a natural number from 2 to 10 and R ^{2 is} the said 1, ω-alkylene group, a 1, ω-Alkylenethergruppe or an OH-substituted alkylene group having 2 to 10 carbon atoms.

4. The method according to claim 1, characterized in that the polymer P is obtainable by reaction of

• at least one amine (A), prepared by condensation of

at least one mono (N, N-dialkylaminoalkyl) amine (A1) with

at least one bifunctional compound (A2) selected from the group consisting of urea, thiourea, iminourea or dialkyl carbonates,

wherein the molar ratio of the sum (A1) to (A2) is 1, 5: 1 to 2.1: 1,

With

At least one bifunctional compound (C) selected from the group of halomethyloxiranes, bisepoxides, alkylene dihalides and dihalogenoalkyl ethers,

wherein the molar ratio of (C) / [(A) + (B)] is 0.6: 1 to 1.4: 1.

5. The method according to any one of claims 1 to 4, characterized in that it is the aqueous medium is a formulation for coating, and the surface is coated with the aqueous formulation and then dried.

6. The method according to any one of claims 1 to 4, characterized in that it is the same medium in the aqueous medium, which acts corrosively on the surface.

7. The method according to claim 6, characterized in that the aqueous medium has a pH of 0.5 to 7.

8. The method according to claim 6, characterized in that the aqueous medium has at least one further constituent selected from the group of acid, bases or surfactants.

9. The method according to claim 6, characterized in that the aqueous medium comprises salts in a concentration of at least 5 wt.%.

10. The method according to claim 6, characterized in that the temperature of the medium is> 30 ⁰ C.

1 1. A method according to claim 6, characterized in that it is a sulfide-containing medium.

12. The method according to claim 6, characterized in that it is the medium is a cleaner for copper surfaces.