DE3416857A1 - Phenoxyalkanecarboxylic acid alkanolamine salts as water-soluble corrosion inhibitors - Google Patents

Abstract

The invention relates to the use of water-soluble alkanolamine salts of phenoxyalkanecarboxylic acids as low-foam water-soluble corrosion inhibitors in aqueous systems and anti-corrosion agents for aqueous systems which contain them.

Description

Phenoxvalkanecarboxylic acid alkanolamine salts as water-soluble

Corrosion Inhibitors The invention relates to the use of alkanolamine salts of phenoxyalkanecarboxylic acids as low-foam, water-soluble corrosion inhibitors in aqueous systems and corrosion inhibitors for aqueous systems, the phenoxyalkanecarboxylic acid alkanolamine salts contain.

In technical cleaning and cooling processes that take place in the present play of water, the problem of corrosion protection always arises, if metals at risk of corrosion, especially iron or ferrous alloys, directly affected by these processes, for example in cleaning processes, through cooling water or cooling lubricants for metalworking.

Another problem, especially with cooling water and cooling lubricants, is excessive foaming that occurs when the water is organic Corrosion protection agents, which often show surfactant properties, are added. So far, therefore, have mostly been used together with the organic corrosion protection agent foam suppressors can still be used.

It is known, for example, that according to US Pat. No. 3,775,320 long chain Alkylphenoxyacetic acids, for example nonylphenoxyacetic acid, in the form of imidazoline or diamine salts are used as corrosion inhibitors in lubricating greases and lubricating oils can be. However, these products are not soluble in water. Also in the DE-AS 1,224,584 are oil emulsions containing p-nonylphenoxyacetic acid as a corrosion inhibitor is added, is described. DE-OS 2 137 783 teaches that water-soluble salts halophenoxyalkanecarboxylic acids such as 2,4-dichlorophenoxyacetic acid alone develop little or no corrosion-inhibiting effect. However the addition of boric acid provides corrosion protection for ferrous metals in aqueous media, the additional chelating agents, which are sometimes even corrosive act like citric acid, tartaric acid, nitrilotriacetic acid or ethylenediaminetetraacetic acid included, achieved. The use of such mixtures as water-soluble corrosion inhibitors is also due to the strong herbicidal effect of the halophenoxyalkanecarboxylic acids against possible contamination of the wastewater. In addition, anti-corrosion agents are increasingly being used desired that do not contain boric acid.

Furthermore, the use of p-tert-butylbenzoic acid and its Salts as corrosion protection agents in aqueous systems from FR-A 2 268 791 known. Their use is increasing in recent times due to toxicological concerns restricted.

The object of the invention was to find corrosion inhibitors for aqueous systems that are 1. water-soluble, 2. good corrosion protection show, 3. if possible do not tend to foam and 4. are insensitive to water hardness.

The object is achieved, surprisingly, in the use of phenoxyalkanecarboxylic acids of the formula I. in which R1 and R2 denote a hydrogen atom or an alkyl radical with 1 to 4 carbon atoms and n denotes a number from 2 to 4, whereby R2 as an alkyl radical can only occur once, in the form of its water-soluble alkanolamine salts as a corrosion protection agent.

In formula I, R1 and R² are hydrogen and methyl, and n is 2 and 3, where R2 can only be methyl once, particularly preferred.

The invention accordingly also provides anti-corrosion agents for aqueous systems containing the alkanolamine salts to be used according to the invention Formula I contain in addition to the usual additives.

Usual additives are, for example, surfactants (wetting agents), such as alkylphenol ethoxylates, Dispersants, such as salts of polymeric carboxylic acids, emulsifiers, such as alkyl or alkylarylsulfonates, solubilizers such as glycols, especially propylene glycol, lower aliphatic alcohols or cumene sulfonic acid sodium salt, polyglycols, such as Polyethylene or polypropylene glycol or polyethylene / polypropylene block polymers, Defoamers, e.g. polypropylene glycol, thickeners such as polyacrylamides, org. Liquid holder, such as polyethylene glycol, oils such as mineral oils and vegetable lead, lubricants, e.g. Phosphorus and sulfur compounds, and complexing agents such as EDTA sodium salt.

These anti-corrosion agents contain the water-soluble salts of the Formula I in a concentration of 1 to 50, preferably from 2 to 20th % By weight, based on the total weight. Provide the usual means or formulations usually concentrates, which are further diluted in practical use can be.

The compounds to be used according to the invention have a very high good corrosion-inhibiting effect, are readily soluble in water, do not develop any Foam and do not form deposits in hard water. They are excellent for rust-protecting cleaners and test liquids, for cooling lubricants, cooling water additives, Hydraulic fluids, coolants or generally as an anti-corrosion additive.

For practical use, it is often advantageous to use the To use anti-corrosive agents together with already known ones. Such connections with corrosion-inhibiting effects are, for example, alkanolamines themselves, ethylenediamine, Phosphates and phosphoric acid alkanolamine salts, aliphatic carboxylic acids such as 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid or octanoic acid, aromatic carboxylic acids such as benzoic acid or para-tertiary-butylbenzoic acid> aliphatic dicarboxylic acids, such as azelaic and sebacic acid, substituted succinic and glutaric acids, amidocarboxylic acids, Sulfonamidocarboxylic acids, phosphonates, acidic phosphoric acid esters, copper corrosion protection agents, such as toluene triazole or mercaptobenzothiazole, fatty acids, nitrites, nitrates, silicates, Boric acid, borates and boric acid esters, ammonia, caustic soda and potassium hydroxide, sarcosides and Polycarboxylates. A mutual increase is often advantageous here to observe the corrosion protection effect.

The phenoxyalkanecarboxylic acids of the formula I are known or can be prepared by methods known from the literature.

For the case n - 2, the phenoxy acids are obtained, for example, by Addition of appropriately substituted phenols to acrylonitrile followed by acidic Saponification of the nitriles according to Ann. Chip. (Rome) 1968, 455ff.

Typical examples are: 3-phenoxypropionic acid 3- (4-methylphenoxy) propionic acid 3- (2-methylphenoxy) propionic acid 3- (3-methylphenoxy) propionic acid 3- (4-n-propylphenoxy) propionic acid 3- (4-sec-Butylphenoxy) propionic acid 3- (4-tert-Butylphenoxy) propionic acid Phenoxy acids of the formula I, in which n is a number of 3 or 4, can by reaction appropriately substituted phenols with lactones, such as butyrolactone or valerolactone, according to DRP 741 687. Typical examples are: 4-phenoxybutyric acid 4- (2-methylphenoxy) butyric acid 4- (3-methylphenoxy) butyric acid 4- (4-methylphenoxy) butyric acid 4- (4-tert-butylphenoxy) butyric acid 4- (4-ethylphenoxy) butyric acid 5-phenoxyvaleric acid 5- <2-methylphenoxy) valeric acid 5- (3-methylphenoxy) valeric acid 5- (4-methylphenoxy) valeric acid 5- (4-Ethylphenoxy) valeric acid The following are also mentioned, for example: 3-Phenoxybutyric acid 3- (2-methylphenoxy) butyric acid 3- (3-methylphenoxy) butyric acid 3- (4-methylphenoxy) butyric acid 3- (4-Ethylphenoxy) butyric acid, 4-phenoxyvaleric acid, 4- (2-methylphenoxy) valeric acid 4- (3-methylphenoxy) valeric acid 4- (4-methylphenoxy) valeric acid 4- <4-tert .butylphenoxy) valeric acid 5-phenoxycaproic acid 5 - (2-methylphenoxy) caproic acid 5- (3-methylphenoxy) caproic acid 5- (4-methylphenoxy) caproic acid Particularly preferred to be emphasized are the 3- (methylphenoxy) propionic acids and 4- (methylphenoxy) butyric acids as well as 4-phenoxybutyric acid.

The phenoxyalkanecarboxylic acids are used in a manner known per se Alkanolamines neutralized. To achieve a liquid consistency, you can Mix up to 30% by weight of water with the salts.

For the purposes of the invention, all the alkanolamines come into consideration Form water-soluble salts, especially alkanolamines with 1 to 3 alkanol radicals each with 2 to 4 carbon atoms or alkanolamines with 1 to 2 alkanol radicals with 2 to 4 carbon atoms and an alkyl radical with 1 to 4 carbon atoms.

Examples include mono-, di- or triethanol or isopropanolamine, N-methyl-mono- or -diethanolamine and N-methyl-mono- or -diisopropanolamine. Finally, alkanolamines derived from ethylenediamine can also be considered such as quadruple ethoxylated or propoxylated ethylenediamine. In addition, mixtures of different alkanolamine salts can also be used.

Have as particularly effective corrosion inhibitors for aqueous systems the diethanol and triethanolamine salts of 3- (methylphenyloxy) propionic acids, 4- (methylphenoxy) butyric acids and 4-phenoxybutyric acid.

Only in the relatively narrow range according to the invention with regard to this on the meanings of R1, R2 and n in formula I is the desired goal, namely good corrosion protection, good water solubility, low foaming tendency and to combine insensitivity to water hardness.

This is surprising. With regard to p-nonylphenoxyacetic acid it was to be expected that with short residues R1 the anti-corrosion effect would be lost.

The results of Table 1 show that the optimum of the four most important Properties can actually only be achieved in this narrow range. if n means 1 (Comparative Examples 1 to 4 and 5), is the anti-corrosion effect too low. This applies regardless of whether R1 is a hydrogen atom (comparative examples 1 and 3) or an alkyl group (Comparative Examples 2, 4 and 5). If n is larger than 4 (Comparative Examples 6 and 9), the water solubility and water hardness resistance are no longer given. This applies when R1 denotes a hydrogen atom (comparative example 6) or a longer alkyl chain (Comparative Example 9).

If R1 is an alkyl chain with more than 4 carbon atoms (comparative examples 7 to 9) means, the water hardness resistance and water solubility is not (Comparative Examples 8 and 9) and there is a significantly higher foaming tendency on (Comparative Example 7). This applies both to n = 2 (comparative example 7), for n s 3 (comparative example 8) as well as for n greater than 4 (comparative example 9).

It was therefore surprising that the invention to be used Alkanolamine salts of the phenoxyalkanecarboxylic acids of the formula I and containing them Preparations all application properties required at the outset are optimal meet, as can be seen from the test table.

Example 1 22.4 parts by weight 3-phenoxypropionic acid 73.0 parts by weight triethanolamine and 4.6 parts by weight of water are mixed at 65 ° C until a clear liquid is formed.

Example 2 16.2 parts by weight of 3- (2-methylphenoxy) propionic acid 72.9 parts by weight Triethanolamine and 10.9 parts by weight of water are mixed until a clear liquid arises.

Example 3 19.8 parts by weight of 3- (4-methylphenoxy) propionic acid 70.5 parts by weight Triethanolamine and 9.7 parts by weight of water are mixed until a clear liquid arises.

Example 4 20.0 parts by weight of 3- (3-methylphenoxy) propionic acid 70.9 parts by weight Triethanolamine and 9.1 parts by weight of water are stirred at 60 ° C until a homogeneous liquid results.

Example 5 23.8 parts by weight of 3- (4-tert-3utylphenoxy) propionic acid 71.4 Parts by weight of triethanolamine and 4.8 parts by weight of water are mixed at 65 ° C. there is a clear liquid.

Example 6 25 parts by weight of 4-phenoxybutyric acid and 75 parts by weight of triethanolamine are mixed at 65 OC until a homogeneous liquid is obtained.

Example 7 25 parts by weight of 4- (2-methylphenoxy) butyric acid and 75 parts by weight Triethanolamine are mixed at 65 OC until a homogeneous liquid is obtained.

Comparative Example 1 17.6 parts by weight of phenoxyacetic acid 64.7 parts by weight Triethanolamine and 17.6 parts by weight of water are stirred at 50.degree.

The result is a brown, clear oil.

Comparative Example 2 20 parts by weight of 2- (2-methylphenoxy) acetic acid 60 parts by weight of triethanolamine and 20 parts by weight of water are stirred at 50.degree.

Comparative Example 3 18.8 parts by weight of 2-phenoxypropionic acid 62.5 parts by weight Triethanolamine and 18.8 parts by weight of water are stirred at 50.degree. It arises a yellow, clear Ö1.

Comparative Example 4 20 parts by weight of 2- (2-methylphenoxy) propionic acid 60 parts by weight of triethanolamine and 20 parts by weight of water are stirred at 50 ° C. a clear liquid is present.

Comparative Example 5 20 parts by weight of 2- (4-methylphenoxy) propionic acid 60 parts by weight of triethanolamine and 20 parts by weight of water are stirred at 50 ° C. a clear liquid is present.

Comparative Example 6 25 parts by weight of 6-phenoxycaproic acid 75 parts by weight Triethanolamine are mixed at 50 ° C until a clear liquid is present.

Comparative Example 7 50 parts by weight of 3- (4-nonylphenoxy) propionic acid 50 parts by weight of triethanolamine are stirred at 50 ° C. until a clear liquid is present.

Comparative Example 8 70 parts by weight of 4- (4-nonylphenoxy) butyric acid 30 parts by weight of triethanolamine are stirred at 50.degree. A brown liquid is created.

Comparative Example 9 50 parts by weight of 6- (4-nonylphenoxy) caproic acid 50 parts by weight of triethanolamine are mixed at 50.degree.

Application testing of the products according to the invention and of Comparison substances In addition to the products according to the invention mentioned in the examples For comparison, a number of other phenoxyalkanecarboxylic acid alkanolamine salts are shown in the table used, which is the extremely narrow area of the optimal coincidence of the different application properties is demonstrated that the goal of the invention.

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

The rating scale is as follows: 4 P very severe corrosion 3 P strong corrosion 2 = moderate corrosion 1 P low corrosion O = no corrosion Foaming behavior: The impact method was used based on DIN 53 902. The simple test procedure, in which the stamp with the Perforated plate by hand 30 times in 30 s evenly up and down and then carefully is pulled out. The foam volume is measured on the graduated foam cylinder Read off in ml for 1 min., 5 min. And 10 min.

Information about temperature and concentration are also important and water hardness.

Table of concentration and foaming behavior, gray cast iron filter paper, pH value Appearance of the 3% solution of the (impact method, test (1% in in dist. In 20 ° d hard salt in 3% in dist. 2% 3% dist. Water water water water, space in 20 ° d hard water) wt.% Temperature) water * DIN 51 360 foam volume in ml according to 1 min 5 min 10 min Example 1 95.4 0 0 0 3 2 8.2 clear clear Example 2 89.1 30 15 0 2 0 8.5 clear clear example 3 90.3 20 20 20 2 0 8.3 clear clear example 4 90.9 20 10 10 2 0 8.4 clear almost clear Example 5 95.2 300 90 70 3 1 8.4 almost clear almost clear Example 6 100.0 50 30 20 1 0 8.3 clear clear Example 7 100.0 250 80 30 1 0 8.4 clear clear comparison 1 82.4 lane 0 0 4 4 8.3 clear clear comparison 2 80.0 lane 0 0 4 4 8.3 opaque opaque comparison 3 81.2 trace 0 0 4 4 8.3 clear clear comparison 4 80.0 60 20 10 4 3 8.3 clear clear comparison 5 80.0 30 20 10 4 3 8.4 clear clear comparison 6 100.0 - - - 3 1 8.9 cloudy cloudy, precipitation comparison 7 100.0 800 800 750 2-3 1 8.2 cloudy cloudy, precipitation comparison 8 100.0 - - - - - - cloudy, deposition cloudy, precipitation Comparison 9 100.0 - - - - - - cloudy, deposition cloudy, precipitation Formulation examples for anti-corrosive agents (parts are always parts by weight) 1. Anti-rust cleaner a) The following cleaner with corrosion protection is a typical formulation for indoor storage: 65 parts water 12.5 parts product according to Example 1 10 Parts of triethanolamine 5 parts of monoethanolamine and 7.5 parts of surfactant mixture (based on of ethoxylated alkylphenol) b) Composition for a cleaner as a top degreaser with rust protection for indoor storage: 78 parts water 5 parts product according to the example 2 14.5 parts of monoethanolamine, 0.5 parts of alkoxylated oxo alcohol and 2 parts of copolymer based on maleic acid / alkyl vinyl ether in the form of the sodium salt c) Composition for a cleaning bath with rust protection for temporary storage: 65 parts water 15 parts Diethanolamine 8 parts of product according to Example 6 6 parts of fatty acid condensation product 3 parts of polymeric polycarboxylic acid sodium salt and 3 parts of phosphoric acid approx. 85% strength In practice, around 3% solutions of these formulations are used.

2. Rust-protecting test liquids As a crack detection agent, impression liquid or passivating agents with an anti-corrosive effect can be diluted with the the following formulation can be used: 50 parts of water 15 parts Product according to Example 3 23 parts of diethanolamine 2 parts of phosphoric acid approx. 85% 8 parts of aliphatic carboxylic acid (3,5,5-trimethylhexanoic acid) 2 parts of polymeric polycarboxylic acid sodium salt 3. Cooling lubricants for metalworking formulation for a water-soluble Cooling lubricant, which is used in a 3% solution: 10 parts drinking water 14 parts of triethanolamine, 2 parts of boric acid, 36 parts of the product according to Example 4, 21 parts phosphated polyether 13 parts polyethylene glycol 4 parts polymeric polycarboxylic acid sodium salt 4. Cooling water treatment agent Composition of a cooling water treatment agent without chromate, phosphate and zinc, which is used in an amount of about 30 to 100 mg / l becomes: a) 30 parts of polymeric polycarboxylic acid, 10 parts of phosphonobutane tricarboxylic acid (50 parts in water), 20 parts of product according to Example 1, 40 parts of water b) 45 parts Water, 21 parts of product according to Example 7, 5 parts of ethylenediaminetetraacetic acid Na salt> 10 parts of hydroxy-ethylidene-1,1-diphosphonic acid (60% in water), 7 parts of triethanolamine, 1 part phosphoric acid (85%), 1.5 parts methylbenzotriazole and 9.5 parts polymer Polycarboxylic acid sodium salt 5. Hydraulic fluids concentrate for a flame retardant and oil-free hydraulic fluid: a) 50 parts water, 10 parts product according to the example 2, 10 parts of phosphated polyether, 2 parts of mercaptobenzothiazole, 10 parts of polymeric Polycarboxylic acid sodium salt, 5 parts of triethanolamine salt of a nitrogen-containing Carboxylic acid, 13 parts morpholine.

b) Hydraulic fluid with the addition of an alkanolamine soap to dampen foam in hard water. The composition represents a concentrate for dilution with hard water: 50 parts of water, 10 parts of the product according to Example 1, 10 parts phosphated polyether, 2 parts methylbenzotriazole, 4 parts oleic acid, 16 parts Diethanolamine, 8 parts of polymeric polycarboxylic acid sodium salt.

6. Radiator rust and antifreeze composition for one Rust and antifreeze as an additive to automobile cooling water: a) 90 parts propanediol, 1 part phosphoric acid, 5 parts triethanolamine, 1 part sodium nitrite, 1 part borax, 0.5 parts of mercaptobenzothiazole, 1.5 parts of the product according to Example 1.

b) 90 parts of ethylene glycol, 2 parts of potassium hydrogen phosphate, 2 parts Product according to Example 1, 2 parts of sodium nitrate, 1 part of tolyltriazole (methylbenzotriazole), 1 part sodium benzoate, 2 parts sodium metasilicate.

7. Extremely low-foaming, highly effective corrosion protection additive 30 parts Product according to Example 1, 20 parts of azelaic acid, 20 parts of boric acid diethanolamine ester, 30 parts of monoethanolamine.

Such a mixture can be added to formulations in which In addition to their actual purpose, corrosion protection is to be achieved.

Claims (6)

Claims 1. Use of alkanolamine salts of phenoxyalkanecarboxylic acids of the formula I. in which R1 and R2 denote a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms and n denotes a number from 2 to 4, whereby R2 as an alkyl radical can only occur once, as low-foam corrosion inhibitors in aqueous systems. 2. Use of alkanolamine salts of acids of the formula I according to claim 1, in which R1 and R2 denote a hydrogen atom or methyl, n denotes the number 2 or 3 and where the radical R2 can only be methyl once, as corrosion inhibitors. 3. Use of diethanol and triethanolamine salts of 3- (methylphenoxy) propionic acids, 4- (methylphenoxy) butyric acids or 4-phenoxybutyric acid according to claim 1. 4. Use of alkanolamine salts of acids of formula 1 according to claim 1 in anti-corrosion agents for aqueous systems in an amount of 1 to 50% by weight, based on the total weight. 5. Corrosion inhibitors for aqueous systems, the alkanolamine salts of formula I according to claim 1 in addition to conventional additives. 6. Corrosion protection agent according to claim 5, which is a water-soluble Salt of an acid of the formula I in an amount of 1 to 50% by weight, based on the Total weight, included.