DE2951542A1 - USE OF ALKANOLAMINE SALTS OF CYCLIC AMIDIC ACIDS AS A CORROSION PROTECTANT IN AQUEOUS SYSTEMS - Google Patents

Description

BASF Aktiengesellschaft -,?. O.Z. 0050/034205

Use of alkanolamine salts of cyclic amic acids as a corrosion protection agent in aqueous systems

The invention relates to the use of alkanolamine salts of cyclic amic acids as 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 are at risk of corrosion, such as iron, aluminum, zinc, copper or their alloys are affected by these processes, e.g. in cleaning processes, in cooling water or cooling lubricants as well as in hydraulic fluids.

In the case of such process media, the problem of excessive foam formation also arises, in particular when substances with surfactant properties are used as corrosion protection agents are present. This problem could

20 can only be solved by additionally present foam suppressors, but the processes mentioned if did not bother, at least made them less economical.

From DE-OS 27 58 123 alkanolamine salts of maleic-N- (Cg- to C ₁₂ ) -alkylamide acids are known with which these problems can be solved, provided that these salts are present in the process medium in low concentration.

Certain forms of application, e.g. if contact corrosion occurs between different metals should be prevented, e.g. in metal cutting higher concentrations of inhibitors so that adequate corrosion protection can be achieved.

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^r In machining of metals such as when ^Ί drilling, tapping, milling, sawing or grinding of workpieces, is the foaming of the process fluid is particularly important. For such higher concentrations, however, the maleamic acid salts to be used according to the abovementioned literature reference are not yet sufficient with regard to the lack of foam.

The aim of the invention were those substances that were also in higher concentration - with otherwise at least equally good Corrosion protection effect - do not foam.

The aim of the invention was surprisingly achieved with alkanolamine salts of cyclic amic acids as defined of the claims achieved.

From US-PS 23 78 ^ 42 are 'calcium salts of N-alkylated Phthalamic acids are known as rust preventive lubricating oil additives, and so is U.S. Patent 3,095 cyclic amic acids as corrosion inhibitors. However, these compounds are in accordance with the literature references mentioned Oil but not water soluble - they are only used as lubricating oil or fuel additives -.

According to the invention it has now been found that cyclic amic acids of the definition given in claim 1 simultaneously are low-foaming and offer very good corrosion protection if they are in the form of alkanolamine salts. At first glance, the measure may appear to be such amic acids as alkanolamine salts and thus in water-soluble form seem obvious to use, but it has been found that, depending on the chains, the length and structure of the am Amide nitrogen-bound longer alkyl radical either (if the chain is too long) too strong foamer, which almost

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are insoluble in water, or if the chain is too short or an n-alkyl chain without branches the corrosion protection effect at least declines sharply.

The narrow range of the chain length and des The degree of isomerization thus enables the desired goal to be achieved; at the same time also decreases the electrolyte sensitivity.

In detail it was found that with amic acids of the formula I - as alkanolamine salts - the anticorrosive Effect decreases sharply when R is an n-octyl or

means lower n-alkyl radical. When R is isoalkyl, this reduction in effectiveness occurs with residues with fewer than 8 carbon atoms.

If the carbon number "in the longest chain of the isoalkyl radical (> 8) is too high, the foam development will already be too great.
20th

The amic acid salts to be used according to the invention lead differ from the defined cyclic amic acids and alkanolamines.

The amic acids in which carboxylic acid and carbonamide group are adjacent, and in which the carbon atoms carrying these groups are not olefinic, one obtains e.g. by reacting the corresponding cyclic acid anhydrides of the formula II

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.CO

> II,

"CO

in which the circle according to formula I is defined, with Amines of formula III

HN III 10

in which R and R are also defined according to formula I.

The ring can be mononuclear aromatic, for example a penzene ring, which can optionally be substituted by C ₁ to C ^ - -alkyl groups, fluorine, chlorine, bromine atoms, nitro groups or carboxyl groups.

It can also be aliphatic, namely mono- or bicyclic, with 5 or 6 carbon atoms being present per ring. The ring system here are the cyclopentane, cyclopentene, cyclohexane, cyclohexene, the bicyclo {2.2.Ij heptane, -heptene radical or the bicyclo-2.2.2J octane or octene radical. The abovementioned substituents are also possible here.

The preferred anhydrides are, for example, phthalic acid, TetrahydroDhthalic acid, hexahydrophthalic acid or bicyclo - [2.2.Ij-hept-2-en-5,6-dicarboxylic acid anhydride as Output connections.

Amines that react with such anhydrides are, for example, primary amines such as isooctylamines, isononylamines, Isodecylamine, Isoundecylamine and Isododecylamine, preferably the isooctyl and isononylamines or secondary amines, such as N-methyl-N-isooctylamine, N-ethyl-N-isooctyl-

L.

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amines, N-Propyl-N-isooctylamine, N- (n-Butyl) -N-isooctylamine, N- (iso-butyl) -N-isooctylamine, N-methyl-N-isononylaraine, N-Ethyl-N-isononylamine, N- (n-Butyl) -N-isononylamine, N- (iso-butyl) -N-isononylamine, N-methyl-N-isodecylamine, N-ethyl-N-isodecylamine, M-methyl-N-isoundecylamine, N-methyl-N-isododecylamine, with 6 to 8 carbon atoms in the longest alkyl chain.

Particularly preferred here are N-methyl-N-isooctyl and
-isononylamine.

These amines can be mixed with appropriate
n-Cg-C ₁₂ -alkyl- or C ₁ - to C ^ -alkyl-n-Cg-C ^ -alkylamines are used, in an amount that the
later end products up to 90 wt. - based on the alkanolamine salt - contained in the corresponding n-alkylamic acid salts. These mixtures originate, for example, from the oxo synthesis.

The anhydrides can be reacted with the amines by customary methods that do not have any specific explanation need.

The amic acids obtained are then neutralized with the alkanolamines in a manner known per se.

In order to achieve a liquid consistency, the salts obtained can be added up to 25% by weight. Mix in water.

"Alkanolamines" within the meaning of the invention can be all representatives that come into consideration, provided they are capable of forming water-soluble salts, that is to say primarily
C ₂ - to C ₁₁ alkanolamines or NC ₁ - to C ^ -alkyl-Cp- to C ^ -alkanolamines.

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* "Individual special representatives are, for example, mono-, Di- or triethanol- or -isopropanolamine or N-methyl- -mono- or -di-ethanol- or -isopropanolamine. In the end Alkanolamines derived from ethylenediamine can also be considered, for example Multiply ethoxylated or propoxylated ethylenediamine.

The N-2-ethylhexyl-, N-methyl-N- (2-ethylhexyl) -, the N-isonyl- and the N-methyl-N-isononyl half-amides of phthalic acid and tetrahydrophthalic acid, which have been neutralized with triethanolamine or diethanolamine.

With these agents, anti-corrosion agents have been found that are extremely effective in aqueous systems and practically do not foam even in higher concentrations.

Depending on the intended use, the agents are added to the process media at 0.01 to 5 wt. - based on the medium added, Exceeding and falling below are possible, but do not bring any additional advantages.

The following examples illustrate the invention. example 1

129 g (1.0 mol) of 2-ethylhexylamine are added dropwise with stirring to a suspension of 1 ^ 8 g (1.0 mol) of phthalic anhydride in 500 ml of toluene, the temperature being kept ^{at 50 ° C. by gentle cooling.} The resulting clear solution is stirred for a further 2 hours. White crystals precipitate. Dilute with 250 ml of n-heptane 35

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• "and sucks at + 1O ⁰ C from. The crystals are dried in a water jet vacuum.

Melting point 82 - 83 ⁰ C 5 acid number 197 (theoretical 202)

38 parts by weight of this phthalamic acid, 60 parts by weight of triethanolamine with one portion

Diethanolamine and

1Q 15 parts by weight water are mixed at 3O ⁰ C until a clear liquid is obtained.

Example 2

Each to a suspension of 148 g of phthalic anhydride in

500 ml of toluene are added dropwise with stirring, 171 g of C ₀ ZC ₁₁ -AIkVl-

3 0 amine mixture (originating from the oxo synthesis; bp ^J '60 to

30 ⁰ C). The temperature is kept ^{below 50 ° C. by cooling.} A clear solution is created. Toluene is used at 2Q. 50 ⁰ C evaporated in a water jet vacuum. The last residues of the solvent are removed by azeotropic distillation three times with 20 ml of water each time at 50 ^° C. in a water-jet vacuum. What remains is a light yellow oil with a water content of 3 - 5 % '

Acid number 160 (theoretical 176 for C ₁₁ ).

36 parts by weight of this Phthalamidsäuregemisches and 3 * 1.7 parts by weight of triethanolamine (as in Example 1) are mixed at 30 ⁰ C until a clear liquid is he *.

Example 3

71.6 g are added dropwise with stirring to a suspension of 1k g (0.5 mol) of phthalic anhydride in 250 ml of toluene

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** (0.5 mol) of isononyl, wherein the reaction temperature is maintained by cooling below 5O ⁰ C. The resulting clear solution is subsequently stirred for 2 hours. The crystals which have precipitated out are filtered off with suction after dilution with 250 ml of n-heptane and dried. Melting point 79 ° C
Acid number 186 (theor. 192.5)

36 parts by weight of the resulting phthalamic acid, 47.1 parts by weight of triethanolamine (as in Example 1) and 10 parts by weight of water are stirred at 3O ⁰ C until a clear liquid.

Example 4

129 g (1.0 mol) of 2-ethylhexylamine are added dropwise with stirring to a suspension of 152 g (1.0 mol) of tetrahydrophthalic anhydride in 500 ml of toluene. The reaction temperature is kept ^{below 50 ° C. by cooling.} The mixture is then stirred for a further 2 hours and the clear reaction solution is concentrated in a water-jet vacuum. The residue solidifies to a yellow, waxy mass.

Acid number 194 (theor. 199.6)

36 parts by weight of this tetrahydrophthalamic acid and 49.7 parts by weight of triethanolamine (as in Example 1) are mixed at 30 ° C until a clear liquid results.

Example 5 30

To a suspension of 2 4.8 g (0.17 mol) of phthalic anhydride in 85 ml of toluene, 24 g (0.17 mol) of N-methyl-N- (2-ethylhexyl) amine was added dropwise. After removing the solvent, an oil remains, 35

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* "Acid number 187 (theor. 193).

52 parts by weight of this phthalamic acid and 5 ^, 4 parts by weight of triethanolamine (as in Example 1) are stirred at 30 ⁰ C until a clear liquid.

Example 6

36.7 g (0.28 Mol) 2-ethylhexylamine, the temperature rising to about 45 ° C and a clear solution. The reaction mixture is stirred for 2 hours. The crystals which have precipitated in the meantime are filtered off with suction and ^{dried at 50 °} C. in a water jet vacuum.
Melting point 128 ° C
Acid number 188 (theoretical 191.5)

Ho 20 parts by weight of the above amic acid, 56 parts by weight of triethanolamine (as in Example 1) and 20 parts by weight of water

are stirred at 50 ⁰ C until a clear liquid is formed.

Example 7

12.2 g (0.095 mol) of 2 are added dropwise to a suspension of 17.8 g (0.1 mol) of bicyclo- [i.2.2 ~ I- -oct-2-en-5,6-dicarboxylic anhydride in 60 ml of toluene -Ethylhexylamine. The temperature rises to approx. HO ⁰ C , a clear solution is formed. When stirring, crystals precipitate, which are filtered off with suction, washed with toluene and then

35 be dried in a jet vacuum.

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washed with toluene and then at 50 ⁰ C in the water

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Melting point 125 ° C

Acid number 177 (theoretical 183)

23.5 parts by weight of the above amic acid,

33.0 parts by weight of triethanolamine (as in Example 1) and 15 parts by weight of water

are mixed at 5O ⁰ C until a clear liquid is formed.
TO

Example 8

To a suspension of 49.3 g (0.3 mol) of bicyclo- [j.2.ll- -hept-2-en-5,6-dicarboxylic anhydride in 500 ml of toluene, UO, 7 g (0.28 mol) N-methyl-N- (2-ethylhexyl) amine added dropwise. The temperature rises to about 35 ^0C. After everything goes into solution at first, crystals precipitate when the mixture is stirred. The mixture is concentrated, the crystals filtered off, washed with n-heptane and dried at 50 ⁰ C in water

20 jet vacuum.
Melting point 79 ° C
Acid number ISO (theoretical I83)

k0 parts by weight of the above amic acid,

60.8 parts by weight of triethanolamine (as in Example 1) and 15 parts by weight of water

are stirred at 5O ⁰ C until a clear liquid results.

30 Example 9

Preparation of the phthalamic acid as in Example 1. 30 parts by weight of this phthalamic acid and

70 parts by weight of N, N ₁ N ', N'-tetrakis- (2-hydroxypropyl) -ethyl-35

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Lendiamine are mixed until a clear liquid is found results.

Example 10 5

Production of the phthalamic acid as in example 30 parts by weight of this phthalamic acid and 70 parts by weight of N, N, N ', N'-tetrakis- (2-hydroxyethyl) -ethylenediamine are mixed until a clear liquid results. 10

Comparison 1:

Phthalic acid mono-isoamyl amide as triethanolamine salt

Comparison 2: Phthalic acid mono-n-octyl amide as triethanolamine salt

Comparison 3: Phthalic acid mono-o-toluidide as triethanolamine salt

20 Comparison 4:

Phthalic acid mono-di (2-ethylhexyl) amide as triethanolamine salt

Comparison 5 '25 phthalic acid mono-tridecyl as triethanolamine

Comparison 6:

Maleic acid mono-2-ethylhexyl amide as a triethanolamine salt according to DE-OS 27 58 30th

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^ Application testing of the products according to the invention and comparison substances

In addition to those according to the invention mentioned in the examples Products, a number of other amic acids are used as a comparison in the table, which makes the extremely narrow area of the coincidence of the various application properties is demonstrated, which constitute the aim of the invention. Comparison 6 represents the most advanced state of the art compared to the-K), here especially in low-foaming (3 / Sige solution) is exceeded. Particular attention should be paid to the foam resistance, i.e. the foam volume after 10 minutes.

The corrosion tests were carried out as follows:

a) Herbert corrosion test

The anti-corrosion effect is effective in one and two-strength aqueous solution and with different Water hardness demonstrated on the Herbert-Test-System introduced at the metal processing sector. This consists of a standardized gray cast iron plate and standardized steel chips 5 mm long, which are supplied by Alfred Herbert, Coventry / England. the square plate with dimensions 100 χ 100

χ 5 mm is determined using a belt grinder before the test Carefully sanded with corundum-emery belt of grain size 120, with white spirit and Ethanol washed and dried with a clean cloth.

Then the steel chips supplied with the test system are made under standardized conditions 0.40? Carbon steel can be obtained by means of

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* "with a suitable metal or plastic spoon the fit of a normal teaspoon in four piles on the prepared cast steel plate set that they are equidistant from each other and from the edges of the plate. The shavings should lie in a single layer in the narrowest possible position.

The solutions or emulsions to be tested for their corrosion behavior are added to the piles of chips by means of a measuring pipette in such an amount that the liquid reaching the cast steel plate is held together by the chips. After standing for 24 hours in an atmosphere of 70 % relative humidity, the chips are shaken off the plate by tilting. Behind it. what remains is the clearly visible outline of the dried-on aqueous medium. At the points of contact between the chips and the plate, rust marks of smaller or larger size have formed, depending on the corrosiveness of the liquid, which can also have grown together to form a closed layer of rust. The assessment can be made by visually estimating the percentage of rust.

25 b) Gray cast iron filter paper test

Another corrosion test consists of the gray cast iron filter paper sample. A Petri dish with an inner diameter of approx. 10 cm with a matching lid dish is used. Place in the Petri dish Black band round filter. Use a suitable spoon to place 5 to 10 g of coarse gray cast iron on the filter GG-20 chips distributed so that an even pile in the middle, which is approx. 1.5 cm from the edge all around. The chips are approx. 5 to 8 mm Length and must be made of clean gray carbon GO-20 material

L

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»· Without the use of drilling oil or other cooling" * Lubricants be obtained. All fine components must be sieved off. From the on corrosiveness To be tested solution or emulsion c each 5 ml evenly with a graduated pipette on the Given shavings. The pH value of the test liquid is registered as it is essential for the assessment Meaning is. It can be set to a certain standard value, e.g. 8.5. After

wj 'moistening, the lid shell is placed and left to stand for ^{2 hours under normal laboratory conditions at 23 to 25 0} C and about 70 % relative humidity. Then the lid is removed and the filter briefly reversed and onto the surface of

«E tap water placed, removing it from the shavings is released. Immediately afterwards, the filter paper freed in this way is followed by an indicator solution Sprayed and soaked composition:

2Q Ig potassium hexacyanoferrate (III) 30 g table salt 1 1 water.

The indicator is then allowed to act in air for 17 seconds. Finally, it is carefully in flowing Rinsed drinking water and air-dried in a moderately warm place. Result on the filter paper After this procedure, depending on the corrosiveness of the medium, brown-yellow, yellow and / or blue-green Spots of different intensity, the brown-yellow or yellow color to be assessed less favorably is. Impeccable behavior is indicated by the absence of any brown or yellow coloration, and at most traces of blue-green pale spots. The filters are completely colourfast

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bil and can therefore be used for documentation. A rating scale can be as follows: (-) very bad: intensive large predominantly

yellow-brown spots

(-) bad:

intense large spots with roughly the same yellow-brown and blue-green proportion of

(+ -) mediocre:

(+) good:

(++) very good:

pale medium-sized spots with roughly equal yellow and blue-green parts;

severely pale, small (pinhead-sized) spots or medium-sized ones Spots predominantly blue-green;

No spots or at most very few, very small pale blue-green Stains.

c) Foaming behavior

Based on DIN 53 902, the impact

25 method used. The simple test procedure in which the stamp with the perforated plate was sufficient for testing by hand 30 times in 30 s evenly up and down and then carefully pulled out (IG impact method). The foam volume is on the

Read off 30 graduated foam cylinders in ml after 1.5 and 10 minutes. Information is also important about temperature, concentration and water hardness.

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Ul

ro ο

^r table

(Concentrations
in % of the concentrate)

Concentrate foaming behavior (concentration (Schlap method, of the salt in 3 Jt deet. Water, water) skin temperature)

Volume of foam in ml after 1 m1η η. 5 min Herbert test (plate Ϊ rust)

15t in 10 ° d 2% in 23 ° d 2% in 20 ° d

after 10 min (drinking water)

according to DIM 51160

-η

example 1 Example 2 Example 3 example 1 Example 5 Example 6

Example] 7

Example 8

At spie] 9

Example 10

Comparison 1
Comparison 2
Comparison 3
Comparison l |
Comparison 5
Comparison 6

fl6.7 %

100 %

«9.3 t

100 %

100 *

82.8 *

79 *

87 %

100 Jt

100 %

90.2 mill

85.0 %

92, p

100 %

100 Jt

100 Jt

20th

10

200

20th

20th

10

30th

0
0
0
0
0

20th
2
0

0 0 350 190 0 0 1300 1300 550 550 "170 390

100
5

90
5

10
0

O 2 0 5 0

10

5 0

50 10 «10 10 30 0

0 1 5

5 5 5

100

15th

100

25th

15th

ρ TK) M. CO
cn O cn O UI O O
CO O
UI

κ>

cn

Nl

cn

CD>

CO

-ti

Tabel

O N) OO

Qraitflufo filter paper test

l J! in 10 ° d 2% in 23 d 2t in 20 ° d

pH value Appearance of the ltipen (1 % in water) solution in dist. water

(Drinking water)

(Drinking water) according to DIN 513 ^ 0

example 1 ++ to + ♦ ♦ ♦ + to + 8.5 transparent example 2 ++ to + 8.3 cloudy example 3 + ♦ ++ to + 8.5 cloudy example Ί ♦ + ♦ 8, H. transparent example '3 + + to f ♦♦ ++ to + R ₁ H transparent example 6th + ++ to + 8th,". transparent example 7th ⁺ ♦ 8, i) transparent example 8th f + 8.3 clear example 9 ♦ ♦♦ ♦♦ 8.7 transparent example 10 ++ to + 8.9 transparent

Comparison 1 VerKletoh 2 Comparison 3 Comparison ¹ I Comparison 5 I oil 6

+ to + -

♦♦ to t

++ to +

+ to + ·

to + -

8.5 8, i »

8.5 8.5 8.5

almost clear cloudy

almost clear drifts almost clear

O CO O cn UI O O cn CO J> ro O
vji

Claims (1)

Claims (1.1 Use of alkanolamine salts of amic acids \ y of the formula I.
5 in which the circle is a mononuclear aromatic K) ring or a mono- or bicyclic aliphatic Ring system with in each case 5 or 6 carbon atoms per ring, R is an isoalkyl radical with a longest chain of 6 to 8 carbon atoms and a total gas number of 8 to 12 carbon atoms and R is an alkyl radical with 1 to M denotes carbon atoms or hydrogen, the carboxyl and carbonamide groups being non-olefinic C atoms are bound and arranged in "adjacent position, as corrosion inhibitors in aqueous systems. To claim 1, characterized 2, use of salts according to 'that additionally up to 90 wt.? - based on the total of all alkanolamine salts - Used on alkanolamine salts of compounds of the formula I in which R is an n-alkyl radical with 8 to 12 carbon atoms and R ² denote an alkyl radical with 1 to 4 carbon atoms or hydrogen. 536/79 Ze / Rei December 20, 1979 L. 130027/0281 ORlGJNAL INSPECTED