EP0566956B1 - Corrosion inhibitor - Google Patents

Abstract

The present invention relates to corrosion inhibitors which are characterised by a content of amine-free salt of a half-ester of an alkylsuccinic or alkenylsuccinic acid, the alkyl or alkenyl substituents thereof containing 8 to 30 carbon atoms, preferably 9 to 15 carbon atoms.

Description

Corrosion protection agents are used in many areas of metalworking when it comes to protecting the metal parts used from rust. The previously used corrosion protection agents contain constituents such as petroleum sulfonates, salts of alkylsulfonamidocarboxylic acids and amine salts of a partial ester of an alkyl or alkenyl succinic acid.
DE-A-26 40 854 discloses lubricant compositions with antirust properties based on amine salts of a partial ester of an alkyl or alkenyl succinic acid.
Corrosion protection agents based on alkylarylsulfonic acids, alkanolamine and partial esters of an alkyl or alkenylsuccinic acid are known from EP-A-336 467.

It has been shown that sulfur-containing compounds, such as alkylarylsulfonic acids, petroleum sulfonates, salts of alkylsulfonamidocarboxylic acids, can easily be broken down by microorganisms, such as sulfur-reducing bacteria. Nitrogen-containing corrosion inhibitors, especially secondary amines, can e.g. are chemically converted into health-endangering nitrosamines.

Especially with regard to the use of health-friendly anti-corrosion agents, it is important to get nitrogen-free, especially amine-free agents, the use of which does not endanger health.

The object of the invention is to provide anti-corrosion agents which are free of amines and which, when used, preclude the formation of substances which are hazardous to health, such as nitrosamines.

Surprisingly, it has been found that salts, in particular alkali and alkaline earth salts of alkyl or alkenylsuccinic acid semiesters, can be used as corrosion inhibitors, and a hazard from nitrosamines can thus be excluded.

The invention relates to corrosion inhibitors, characterized by a content of amine-free salt of a half ester of an alkyl or alkenyl succinic acid, the alkyl or alkenyl substituents of which contain 8 to 30 carbon atoms, preferably 9 to 15 carbon atoms.

The amine-free salts, especially alkali and alkaline earth salts, are obtained by esterification of alkyl or alkenyl succinic anhydride with alcohol, preferably in equimolar amounts, optionally with the addition of a catalyst, such as alcoholate solution, at temperatures up to the boiling point of the solution, preferably 20 ° C. to boiling point, particularly preferably 40-80 ° C. The reaction is preferably carried out with nitrogen gas. After the alcohol has been added, the solution is advantageously stirred at a temperature up to the boiling point of the solution, preferably from 60 ° C. to the boiling point of the solution. The half-esters obtained are mixed with dilute alkali to a pH above 7, preferably up to a pH in the range of 9.

The half ester is derived from an alkyl or alkenyl succinic acid in which the alkenyl or alkyl substituent contains 8 to 30 carbon atoms, preferably 9 to 15 carbon atoms. Examples of such succinic acids are octenyl, dodecenyl, hexadecenyl, isooctadecenyl or triacontenyl succinic acid. The substituent group can also consist of a polyolefinic group, such as a tri, tetra or pentapropenyl group.

The alcohol used to form the half ester preferably has 1 to 15 carbon atoms and preferably contains an alkyl alcohol (alkanol) such as methanol, ethanol, propanol or butanol.
The lye, which is reacted with the half ester of substituted succinic acid, is preferably aqueous hydroxide solution, such as sodium hydroxide solution or potassium hydroxide solution.
Aqueous solutions of polyvalent metal hydroxides, such as alkaline earth metal hydroxides, are also suitable.

The aqueous solution of the amine-free salts thus obtained can be used directly as an anti-corrosion agent without further purification of the alkyl or alkenylsuccinic acid.
These amine-free salts can be used in the case of aqueous corrosion protection agents, and are preferably used in a concentration of 0.5 to 65% by weight, particularly preferably 1-10% by weight, based on the aqueous solution. The pH of the aqueous anticorrosive agent is above pH 7, preferably at a pH of approximately 9.

40 - 80 Gew.-%

eines Salzes eines Halbesters einer Alkyl- oder Alkenylbernsteinsäure,

30 - 1 Gew.-%

eines Oxethylats der Formel R¹ - O -(CH₂CH₂O)_nH,
wobei R¹ gleich C₁₀-C₂₂-Alkyl, C₁₀-C₂₂-Alkenyl oder Alkaryl ist
und n gleich 1 bis 10, bevorzugt 1 bis 5 ist,

30 - 1 Gew.-%

Fettsäure der Formel R² - COOH
wobei R² gleich C₁₀-C₂₀-Alkyl oder C₁₀-C₃₀-Alkenyl ist und

30 - 0 Gew.-%

Ethercarbonsäure der Formel R³ - O - (CH₂CH₂O)_n - CH₂ - COOH,
wobei R³ gleich C₁₀-C₂₂-Alkyl, C₁₀-C₂₂-Alkenyl oder Alkaryl ist
und n gleich 1 bis 10, bevorzugt 1 bis 5 ist.

The amine-free salts can also be used in a mixture with other compounds as anti-corrosion agents.
Such an anti-corrosion agent consists of, for example

40-80% by weight

a salt of a half ester of an alkyl or alkenyl succinic acid,

30-1% by weight

an oxyethylate of the formula R ¹ - O - (CH ₂ CH ₂ O) _n H,
where R ¹ is C ₁₀ -C ₂₂ alkyl, C ₁₀ -C ₂₂ alkenyl or alkaryl
and n is 1 to 10, preferably 1 to 5,

30-1% by weight

Fatty acid of the formula R ² - COOH
wherein R ² is C ₁₀ -C ₂₀ alkyl or C ₁₀ -C ₃₀ alkenyl and

30-0% by weight

Ether carboxylic acid of the formula R ³ - O - (CH ₂ CH ₂ O) _n - CH ₂ - COOH,
wherein R ³ is C ₁₀ -C ₂₂ alkyl, C ₁₀ -C ₂₂ alkenyl or alkaryl
and n is 1 to 10, preferably 1 to 5.

Such anti-corrosion agents are characterized by complete "solubility" in combination with water. When mixed with water, they form finely divided emulsions that can be clear (transparent) opal or milky.

Mixtures of the above-mentioned amine-free salts of the half esters of alkyl or alkenylsuccinic acid with oxethylates, fatty acids and optionally ether carboxylic acids are preferably used with mineral oils, in an amount of up to 70% by weight of mineral oil, based on the total weight, and show good properties as corrosion inhibitors.

Suitable mineral oils are mineral oils which consist of paraffins, naphthenes and partly of aromatics and usually have viscosities of 25 to 30 mm ² / s, measured at 20 ° C.

The above-mentioned mixtures of amine-free salts, oxyethylates, fatty acids and optionally ether carboxylic acids have an emulsifying and corrosion-inhibiting effect in aqueous metalworking aids containing mineral oil.
Metalworking aids are also to be understood as cooling lubricants.

The 0.1-10% by weight, preferably 1-5% by weight aqueous solutions of the amine-free salts of the half esters of alkyl or alkenylsuccinic acid, with oxethylates, fatty acids and optionally ether carboxylic acids and mineral oil are preferably used as corrosion inhibitors, where they show good results especially with regard to good hard water stability.

The test results listed below show that the amine-free salts according to the invention are effective as anti-corrosion agents.

Table 1 shows the corrosion-inhibiting effect of an aqueous alkaline solution of the amine-free salt.
Table 2 shows the corrosion-inhibiting effect of a mixture.

The corrosion-inhibiting effect was determined using the Herbert test (DIN 51360/1) and the filter paper test (DIN 51360/2).

example 1 Tripropenylsuccinic acid monomethyl Na salt

224.0 g (1.0 mol) of tripropenyl succinic anhydride and 0.5 g (30% by weight) of Na-methanolate solution are introduced. At 45-55 ° C., 35.2 g (1.1 mol) of methanol (technical) are added dropwise under an N ₂ atmosphere over the course of about 15 minutes. Then allowed to stir at 65 ° C for 5 hours. At approx. 40 mm Hg, the excess methanol is distilled off at an internal temperature of up to 100 ° C (distillate: 3.3 g). 250.0 g of an orange-colored liquid product are obtained, which is converted to the Na salt (about pH 9) by adding 33% aqueous NaOH.

Example 2 Tripropenyl succinic acid monoisobutyl ester sodium salt

224.0 g (1.0 mol) of tripropenylsuccinic anhydride are initially introduced and preheated to 80.degree. 74.1 g (1.0 mol) of isobutanol are added dropwise at 80 ° C. in the course of 30 minutes under an N ₂ atmosphere. Then allowed to stir at 105 ° C for 5 hours. 297.4 g of an orange-colored clear liquid are obtained, which is converted to the Na salt (about pH 9) by adding 33% aqueous NaOH.

Example 3 Mono-i-propyl ester sodium tetrapropenyl succinate

266 g (1.0 mol) of tetrapropenylsuccinic anhydride are introduced and on Preheated to 80 ° C. 60.1 g (1.0 mol) of i-propanol are added dropwise at 80 ° C. in the course of 30 minutes under an N ₂ atmosphere. Then allowed to stir at 80 ° C for 12 hours. 299.2 g of a clear oil are obtained, which is converted to the Na salt (about pH 9) by adding 33% aqueous NaOH.

Example 4 Monoisobutyl tetrapropenyl succinate sodium salt

266.0 g (1.0 mol) of tetrapropenyl succinic anhydride are introduced and preheated to 80 ° C. 74.1 g (1.0 mol) of isobutanol are added dropwise at 80 ° C. in the course of 30 minutes under an N ₂ atmosphere. Then allowed to stir at 105 ° C for 5 hours. 338.4 g of clear oil are obtained, which is converted to the Na salt by adding 33% aqueous NaOH (approx. PH 9).

Example 5 Pentapropenylsuccinic acid monomethyl Na salt

348 g (1.0 mol) of pentapropenyl succinic anhydride and 0.5 g (30% by weight) of Na-methanolate solution as catalyst are introduced. At 50 ° C., 26.9 g (0.84 mol) of methanol (technically) are added dropwise under an N ₂ atmosphere over the course of about 30 minutes (slightly exothermic reaction). Then allowed to stir at 65 ° C for 4 hours. This gives 372.4 g of a brown, clear oil which is converted to the Na salt (about pH 9) by adding 33% aqueous NaOH.

Example 6 Pentapropenyl succinic acid mono-i-propyl ester Na salt

348 g (1.0 mol) of pentapropenylsuccinic anhydride are introduced. At 80 ° C under an N ₂ atmosphere 50.5 g (0.84 mol) of i-propanol within about 40 Dripped minutes. Then allowed to stir at 80 ° C for 12 hours. 394.6 g of a brown, clear oil are obtained, which is converted to the Na salt (about pH 9) by adding 33% aqueous NaOH.

Example 7 C _12/14 alkenylsuccinic acid monomethyl Na salt

138 g (0.5 mol) of C _12/14 alkenylsuccinic anhydride and 0.25 g (30% by weight) of Na-methanolate solution are initially introduced and heated to 50.degree. 16.1 g (0.5 mol) of methanol are added dropwise over a period of 15 minutes at 50 ° C. under an N ₂ atmosphere. Then allowed to stir at 65 ° C for 5 hours. 148.2 g of a yellowish, clear liquid are obtained, which is converted to the Na salt by adding 33% aqueous NaOH (approx. PH 9).

Example 8 C _12/14 alkenyl succinic acid monoisopropyl ester Na salt

414 g (1.5 mol) of C _12/14 alkenyl succinic anhydride are introduced and heated to 80 ° C. 90.2 g (1.5 mol) of isopropanol are added dropwise at 80 ° C. in the course of 30 minutes under an N ₂ atmosphere. Then allowed to stir at 80 ° C for 12 hours. This gives 503 g of a yellow clear product which is converted to the Na salt by adding 33% aqueous NaOH (approx. PH 9).

Claims (10)

1. An anticorrosive comprising an amine-free salt of a monoester of an alkyl- or alkenylsuccinic acid whose alkyl or alkenyl substituents contain 8 to 30 carbon atoms, preferably 9 to 15 carbon atoms.
2. An anticorrosive as claimed in claim 1, wherein the salt is an alkali metal or alkaline earth metal salt.
3. An anticorrosive as claimed in claim 1 or 2, wherein the monoester is the monoester of alkyl- or alkenylsuccinic acid and an alcohol having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms.
4. An anticorrosive as claimed in one of claims 1 to 3, wherein the succinic monoester comprises the monoester of a polyolefinic succinic acid, preferably tri-, tetra- or pentapropenylsuccinic acid.
5. An anticorrosive as claimed in one of claims 1 to 4, which includes 0.5 to 65% by weight, preferably 1 to 10% by weight, of an amine-free salt of a monoester of an alkyl- or alkenylsuccinic acid, relative to an aqueous solution.
6. An anticorrosive as claimed in claim 1, which includes

   40-80% by weight   of a salt of a monoester of an alkyl- or alkenylsuccinic acid as mentioned in claim 1,

   30-1% by weight   of an ethoxylate of the formula R¹-O-(CH₂CH₂O)_nH,
   in which R¹ is C₁₀-C₂₂-alkyl,
   C₁₀-C₂₂-alkenyl or alkaryl and n is 1 to 10, preferably 1 to 5,

   30-1% by weight   of a fatty acid of the formula R²-COOH,
   in which R² is C₁₀-C₃₀-alkyl or C₁₀-C₃₀-alkenyl, and

   30-0% by weight   of an ethercarboxylic acid of the formula R³-O-(CH₂CH₂O)_n-CH₂-COOH,
   in which R³ is C₁₀-C₂₂-alkyl,
   C₁₀-C₂₂-alkenyl or alkaryl, and n is 1 to 10, preferably 1 to 5.
7. An anticorrosive as claimed in claim 6, which includes up to 70% by weight of mineral oil, relative to the total weight.
8. An anticorrosive as claimed in claim 6 or 7, which includes 0.1-10% by weight, preferably 1-5% by weight, of a mixture of amine-free salt, ethoxylate, fatty acid, and, if desired, ethercarboxylic acid and mineral oil, relative to an aqueous solution.
9. Use of an amine-free salt of a monoester of an alkyl- or alkenylsuccinic acid whose alkyl or alkenyl substituents contain 8 to 30 carbon atoms as cooling lubricant or metal-working auxiliary.
10. Use of an anticorrosive as claimed in claim 6 to 8 as cooling lubricant or metal-working auxiliary.