EP0341536B1 - Mixtures of alkenylsuccinic acids, arylsulfonylanthranilic acids and alkanol amines and their use as corrosion inhibitors in aqueous systems - Google Patents

Abstract

The invention relates to a corrosion inhibitor containing synergistic mixtures of arylsulphonylanthranilic acids, alkenylsuccinic acids and alkanolamines, and to the use thereof as highly effective, low-foaming corrosion inhibitors, insensitive to water hardness, in aqueous systems.

Description

The invention relates to synergistic mixtures of alkenyl succinic acids, arylsulfonylanthranilic acids and alkanolamines and their use as highly effective, low-foaming and water hardness-insensitive corrosion inhibitors in aqueous systems.

In technical processes that take place in the presence of water, the problem of corrosion protection always arises when metals at risk of corrosion, such as iron, aluminum, zinc, copper or their alloys, for example through cleaning processes, cooling water, cooling lubricants, hydraulic fluids and other functional solutions and Emulsions are affected.

Frequently, the problem of excessive foaming occurs in such processes and the use of anti-corrosion agents, for example in the case of emulsions due to the emulsifiers used and in solutions using anti-corrosion agents with surfactant properties. Additional foam dampers are often necessary, which create new problems: they often disrupt the technical processes and in many cases impair the corrosion protection effect. Water-insoluble foam dampers are often filtered out in circulation systems.

In addition, the requirements for occupational safety and environmental compatibility continue to be in contrast to those for the high corrosion protection effect with small amounts, i.e. that it is desirable to get by with the smallest possible amounts. As a rule, attempts are currently being made to meet these requirements with anti-corrosion agents based on nitrite, boric acid and their esters, borates, p-tert-butylbenzoic acid and, in some cases, zinc salts.

However, nitrite is toxic, water-polluting and can form carcinogenic nitrosamines with the amines that are often used for corrosion protection. Boron compounds are only moderately toxic, but under certain conditions are poisonous to plants, pollute water and can adversely affect steel surfaces. p-tert-Butylbenzoic acid has been recognized as chronically toxic in animal experiments. Zinc salts pollute water, sewage sludge and sediments.

With the corrosion inhibitors used in practice, the desired low application amounts can often not be achieved.

Sulfonamidocarboxylic acids according to DE-C2-1298672 and EP-B1-029529 are known as water hardness-stable, low-foam corrosion inhibitors. However, they only work optimally in mixtures with boron compounds, e.g. emerges from DE-C2-2840112. The disadvantages of the boron compounds have already been discussed above.

The alkenylsuccinic acid derivatives according to DE-A-2943963, for example, achieve good corrosion protection values without the addition of boron, nitrite or zinc with largely no foam. However, these are sensitive to water hardness, i.e. they form precipitates in hard water, which makes them unusable for many applications and can cause major problems.

EP-B1-029529 describes the use of alkanolamine salts, of arylsulfonamide carboxylic acids, preferably of arylsulfonylanthranilic acid, as corrosion inhibitors. Such substances have little foam and are not sensitive to water hardness. However, they do not quite achieve the effectiveness of the above. Succinic acid derivatives.

The object of the invention is to provide an aqueous anticorrosive agent in which the properties of good water solubility, high anticorrosive action, insensitivity to the hardness of the water and very good low-foaming properties are achieved in the best possible way.

The solution to the problem consists in the use of mixtures of C₈- to C₉-alkenylsuccinic acids according to DE-A-2 943 963 and arylsulfonylantranilic acids according to EP-B1-29 529 in the presence of alkanolamines or aqueous solutions of these mixtures as corrosion inhibitors. There are unexpected synergistic advantages for these mixtures or solutions.

A)

einer C₈- bis C₉-Alkenylbernsteinsäure,

B)

einer Arylsulfonylanthranilsäure der Formel I

 

in der R¹ und R² Wasserstoff, Fluor, Chlor, Brom, einen Allyl- oder Alkoxy-Rest mit 1 bis 4 Kohlenstoffaotmen, wobei die Summe der Kohlenstoffatome der Reste R¹ und R² die Zahl 7, vorzugsweise 3, nicht übersteigen soll, A einen Benzol- oder Naphthalinrest und R³ Wasserstoff oder einen Alkylrest mit 1- bis 4-C-Atomen bedeuten, und

C)

Mono-, Di- und/oder Tri-(C₂- bis C₄-alkanol)-aminen, wobei das Gewichtsverhältnis A: B 1: 7 bis 4: 1, bevorzugt 1: 4 bis 3: 1, beträgt und das Gewichtsverhältnis (A + B): C 3: 1 bis 1: 4, bevorzugt 2: 1 bis 1: 3, beträgt. Weiterhin sind Gegenstand der vorliegenden Erfindung wäßrige Lösungen der genannten Mischungen, die diese Mischungen in einer Konzentration, bezogen auf das Gesamtgewicht, von 0,5 bis 40 Gew.%, bevorzugt 1 bis 10 Gew.%, enthalten. Schließlich ist Gegenstand der Erfindung die Verwendung der genannten Mischungen und ihrer wäßrigen Lösungen als Korrosionsschutzmittel in wäßrigen Systemen.

The present invention relates to mixtures of

A)

a C₈ to C₉ alkenyl succinic acid,

B)

an arylsulfonylanthranilic acid of the formula I.

in which R¹ and R² are hydrogen, fluorine, chlorine, bromine, an allyl or alkoxy radical having 1 to 4 carbon atoms, the sum of the carbon atoms of the radicals R¹ and R² not exceeding 7, preferably 3, A being a benzene - Or naphthalene radical and R³ is hydrogen or an alkyl radical having 1 to 4 carbon atoms, and

C)

Mono-, di- and / or tri- (C₂- to C₄-alkanol) amines, the weight ratio A: B being 1: 7 to 4: 1, preferably 1: 4 to 3: 1, and the weight ratio (A + B): C 3: 1 to 1: 4, preferably 2: 1 to 1: 3. The present invention furthermore relates to aqueous solutions of the mixtures mentioned which contain these mixtures in a concentration, based on the total weight, of 0.5 to 40% by weight, preferably 1 to 10% by weight. Finally, the invention relates to the use of the mixtures mentioned and their aqueous solutions as corrosion inhibitors in aqueous systems.

The mixtures to be used according to the invention provide corrosion protection which synergistically exceeds that of the individual compounds described. The aqueous solutions of these mixtures have a low foam level and, moreover, surprisingly also have a reduced sensitivity to water hardness compared to the alkanolamine salts of the individual components A and B. There is an unforeseeable synergism. The mixtures according to the invention are thus able to achieve the above object in an outstanding manner.

Of the C₈ to C₉ alkenylsuccinic acids, the di-isobutenylsuccinic acid as described in Example 1 of DE-A1-2943963 is preferred.

Preferred arylsulfonylanthranilic acids, as described in the above-mentioned European patent, are those in which R 1 and R 2 are hydrogen or methyl, A is a benzene radical and R 3 is hydrogen. Accordingly, the particularly preferred arylsulfonylanthranilic acids are N-phenylsulfonyl- and N- (o-tolylsulfonyl) -anthranilic acid.

Mono-, di- and / or tri- (C₂- to C₄-alkanol) amines include, in particular, mono-, di- and triethanolamine and mono-, di- and tri-iso-propanolamine. Diethanolamine, trichloramine and mixtures thereof are preferred. In practice, in addition to the pure amines, these are expediently mixtures of mono-, di- and triethanolamine, preferably of diethanol and triethanolamine, as are obtained in the industrial production processes. A mixture of about 5% by weight mono-, about 55% by weight di- and 40% by weight triethanolamine or, for example, 85% by weight tri- and 15% by weight diethanolamine is particularly preferred.

As mentioned above, the concentration of the mixture (A + B + C), based on the pure substance and on the total weight of the aqueous solution, is 0.5 to 40, preferably 1 to 10% by weight. The most particularly preferred range is 1 to 4% by weight.

The mixtures according to the invention or their aqueous solutions can be used in all aqueous systems which come into contact with iron, its alloys (steels), aluminum, its alloys, zinc or copper or their alloy. Examples include Hydraulic fluids, cooling lubricants, neutral to alkaline technical cleaners or mine water, which are particularly hard and salt-rich, and which are used directly in mining as mixing water, e.g. for hydraulic processes, are used and have a particularly strong corrosive effect.

The application concentrations fluctuate depending on the area of application and the type of aqueous medium and the metals to be protected. In general, based on the industrially used aqueous system, 0.01 to 5% by weight, based on the mixture of substances (A + B + C), is used. The concentration should preferably be 0.1 to 5% by weight.

The optimal quantitative ratio of components A and B to each other depends on the application. It is expedient to proceed in such a way that a quantitative ratio of 1: 1 is assumed, which generally gives results which are close to the optimum. The most favorable quantitative ratio (A + B): C can be determined very simply by adding such an amount of C that the pH of the aqueous solution is between 7 and 9. This pH range is usually met when the proportion of C in the mixture (A + B + C) is 33 to 75, preferably 50 to 70% by weight.

Depending on requirements, additional auxiliaries can be added to the mixtures according to the invention or their aqueous solutions which increase their performance properties. This can be used, for example, for wetting improved, the growth of microorganisms suppressed or the loss of precipitation by substances which are dissolved in the aqueous systems can be prevented.

Typical additives are, for example, surfactants as wetting agents, such as alkylphenol ethoxylates, dispersants, such as salts of polymeric carboxylic acids, emulsifiers, such as alkyl or alkylarylsulfonates, solubilizers, such as glycols, in particular propylene glycol, lower aliphatic alcohols or sodium cumene sulfonic acid salt, polyglycols, such as polyethylene or polyols or polyethylene / polypropylene block polymers and others

The corrosion protection agents according to the invention are tested using the methods described below:

The corrosion protection effect was determined by the "gray cast iron filter paper test", DIN 51 360, part 2.

The rating scale is as follows:

4 =

very strong corrosion

3 =

severe corrosion

2 =

moderate corrosion

1 =

low corrosion

0 =

no corrosion

Water hardness sensitivity:

According to DIN 51360, part 2, point 8, hard water was prepared by mixing fully deionized water with 3.04 mmol / l CaCl₂ · 6H₂O and 0.54 mmol / l MgSO₄ · 7H₂O. Using this water, solutions of the mixtures according to the invention were prepared in a concentration of 2% by weight, based on the pure substance content. After standing overnight, the following was assessed:

Solution clear / almost clear / opaque / cloudy. no precipitation / low precipitation / sediment.

Foam behavior:

The impact method was used based on DIN 53 902. 200 ml of a 1% by weight solution of the mixture according to the invention in deionized water were filled in a graduated glass cylinder of 60 cm in length with an inside diameter of 6 cm. Then the cylinder went vertical and a perforated plate with a diameter of 5.9 cm and 24 holes with a diameter of 4 mm is drawn up and down evenly on a rod 30 times in 30 seconds and then carefully pulled out. The volume of the foam in ml was read after 1.5 and 10 min.

Examples

A:

Di-isobutylenbernsteinsäure

B:

Phenylsulfonyulanthranilsaure

DEA-TEA:

Mischung aus 5 Gew.% Monoethanolamin, 55 Gew.% Diethanolamin und 40 Gew.% Triethanolamin

TEA:

Triethanolamin.

The following examples and the results obtained in the table illustrate the invention. In the table mean:

A:

Di-isobutylene succinic acid

B:

Phenylsulfonyulanthranilic acid

DEA-TEA:

Mixture of 5% by weight monoethanolamine, 55% by weight diethanolamine and 40% by weight triethanolamine

TEA:

Triethanolamine.

Claims (7)

1. A mixture of

A)   a C₈-C₉-alkenylsuccinic acid,

B)   an arylsulfonylanthranilic acid of the formula I

    where R¹ and R² are each hydrogen, fluorine, chlorine, bromine, allyl or alkoxy of 1 to 4 carbon atoms, where the total of carbon atoms in R¹ and R² must not exceed 7, A is a benzene or naphthalene radical and R³ is hydrogen or alkyl of 1 to 4 carbon atoms, and

C)   mono-, di- and/or tri-(C₂-C₄-alkanol)amines, where the ratio A: B is from 1: 7 to 4: 1 by weight, and the ratio (A + B): C is from 3: 1 to 1: 4 by weight.

2. A mixture as clamed in clair 1, where the ratio A: B is from 1: 4 to 3: 1 by weight and the ratio (A + B): C is from 2: 1 to 1: 3 by weight.

3. A mixture as clamed in claim 1 or 2, wherein the component C is di- and/or triethanolamine, where appropriate in the form of technical mixtures thereof.

4. A mixture as clamed in any of claims 1 to 3, wherein the component A is di-isobutenylsuccinic acid and the component B is phenyl- or toluenesulfonylanthranilic acid.

5. An aqueous solution of a mixture as clamed in any of claims 1 to 4 in water, where the concentration of the mixture is from 0.5 to 40 % by weight based on the total weight of the aqueous solution.

6. An aqueous solution as clamed in claim 5, wherein the concentration of the mixture in the aqueous solution is from 1 to 10 % by weight based on the total weight.

7. The use of a mixture as clamed in any of claims 1 to 4 or an aqueous solution as clamed in claims 5 or 6 as anticorrosion agent in aqueous systems.