DE2223390A1 - Corrosion-inhibiting compounds - Google Patents

Description

DR. E. WiEGAND DIFL-ING, W. NiEMANN

DR.M. KCHLCR DJPL-ING. C. GCRNHARDT 2223390

MÖNCHEN HAMBURG

TELEPHONE: 555 476 8000 MDN CH EN 15,

TELEGRAMMEiKARPATENT NUSSBAUMSTRASSE 10

May 12, 1972 W. 41028/72

Mobil Oil Corporation New York, N.Y. (V.St.A.)

Corrosion-inhibiting compounds

The invention is concerned with the inhibition of corrosion by masses which come into contact with hydrocarbon liquids with metals included. In particular, the invention relates to the inhibition of this corrosion by the addition of a Additive to the mass that gives it the desired properties.

Most hydrocarbon liquids or compounds containing them will corrode on contact with metals. The extent of this corrosion depends to a large extent on the system with which or wherein the hydrocarbon liquid is used or the ambient conditions in such use. For example, metalworking systems can be very difficult to corrode, even at low temperatures be in case the hydrocarbon liquid aqueous emulsions contain no inhibitor.

In other systems, such as automotive engines, which require hydrocarbon fluids of shear viscosity the problem of corrosion becomes even worse

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sharper due to the high operating temperatures. If If the corrosion is not controlled, sludge and stains can form on the lubricated parts. These deposits can drastically reduce the efficiency of the engine and it actually does will be destroyed if the material is left on the engine for long periods of operation.

The use of certain acids and oil soluble acids in lubricants is known. For example, US Pat. No. 2,223,129 describes a hydrocarbon oil lubricant containing compounds such as phenyl mercaptostearic acid as extreme pressure agents. Moreover, in the US Patent 2,281,676 turbine oils are given mainly treated solvent from a leichten.mäßig refined petroleum distillate with a viscosity of 150-160 at 38 ^C C (1OO ° F) and fatty acids having 10 to 20 carbon atoms, for example Lauric acid, myristic acid, palmitic acid and stearic acid are composed. These acids are believed to be corrosive agents.

U.S. Patent 2,474,604 describes the application certain alkyl thiocarboxylic acids, including cetylthioacetic acid, as a rust inhibitor for mineral oils. U.S. Patent 2,477,356 states that alkylthioacetic acids, for example octadecylthioacetic acid, can be used as an anti-corrosion agent.

According to the invention, however, there is an organic mass, a hydrocarbon liquid and a corrosion-inhibiting amount of an acid of the formula

RSR ¹ - COOH

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where R is an alkyl group having 2 to 16 carbon atoms, R ^{1 is} a straight-chain or branched-chain divalent hydrocarbon group, such as an alkylene, arylene or aryl-substituted alkylene group, each containing 4 to 22 carbon atoms, or a group of the formula '

-If-SR ¹ - COOH

wherein R "represents an alkylene group having 4 to about 32 carbon atoms, or contains an amine salt of such an acid. In the above formulas, since PJ can be branched, R ^{1 can mean}

-CH (CH ₂ ) _n
R ""

so that the entire unit has the specified number of carbon atoms, i.e. 4 to about 22 carbon atoms can own.

It follows from this that the thioacids which can be used in the context of the present compositions are practically composed of two Classes, namely monocarboxylic acids of the formula

R - S - R ¹ - COOH and dicarboxylic acids of the formula

HOOC - R '- S - R "- S - R ¹ - COOH.

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The structure of the dicarboxylic acids can also be in the dimeric Form, viz

[- rhi -sR ¹ - COOH] ₂

where R "'is an alkylene group with 2 to 16 carbon atoms. In this case the group R ^fM bonded to the sulfur atoms is analogous to the same group in the monocarboxylic acids (R), ie a hydrocarbon group with 2 to 16 carbon atoms.

As can be seen from the above formulas, the sulfur-bridged hydrocarbon or divalent Hydrocarbon radical be an alkyl or alkylene group and according to the invention this group must be at least Contain 2 carbon atoms and a maximum of about 16 carbon atoms. The other divalent hydrocarbon group (R 'and R "' in the formula) can be an alkylene or be an arylene group. This follows from the fourth given below.

The alkylthiocarboxylic acids (monocarboxylic acids) according to the invention can be prepared in good yields using methods known per se. Quite In general, derivatives of acetic acid and propionic acids can be prepared by reacting the corresponding thiol salt with the corresponding chloric acid, thus:

RSM + Cl R '- COOH> RSR ¹ - COOH + MCl

This procedure is described in detail in J. Am. Chern. Soc. Volume 69, page 693 (194-7). In the German Patent 840,966 is a method of making Butyric acid derivatives by reacting with a thiol salt

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γ-butyrolactone indicated.

The dimer acid (dicarboxylic acid) can by reaction of a dithiol with a lactone in the presence of an alkali alkoxide. In the following example 3 this procedure is explained in detail.

If the additives according to the invention are used with hydrocarbon liquids, they are preferred used as a free acid, but can also be in the form. their liquid-soluble amine salts to achieve of anti-corrosion properties. The amines may consist of primary, secondary or tertiary and include alkylamines wherein the alkyl group is about 14 to contains about 40 carbon atoms or they can arylamines, such as aniline and the like, or they can be of the type where the nitrogen atom is part of a ring system, is for example pyridine. These salts can be prepared by mixing one mole of the diamine with one mole of the Making acid.

The hydrocarbon liquids which can be used in the invention include mineral oils, both light oils and oils of lubricating viscosity, including naphthenic, paraffinic and aromatic oils. Also included are liquid Kohlenwaseerstoffbrennstoffe including gasoline, jet fuel and the like with a boiling range of about 15 to about 315 G ^n, and synthetic hydrocarbon oils, can have the Schinierstoffviskosität or not. These synthetic hydrocarbon oils include those obtained by polymerizing an olefin with about 3 bir. about 10 carbon atoms were obtained. A preferred example of a synthetic hydrocarbon is one which is produced by polymerizing

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BATHROOM 0RK3JNAL

Decene-1 to which trimers or tetramers was made. However, any such liquid polymer containing from about 6 to about 60 carbon atoms can be used will.

The oils listed above can be employed in a variety of ways. The closest of these is that as a lubricant, either for applications employing relatively mild conditions, as in Switching contacts or for applications involving high temperatures. This latter case involves lubrication of automobile engines. Other areas of use include hydraulic fluids, turbine oils, Gear oils and cutting or grinding oils.

Another important area is metalworking. The oils used in the machining of metals may or may not be of lubricating viscosity, which of dor specific application. A metal pre-coat that is applied prior to storage or the salting operation requires a fairly viscous oil by its nature. However, the oils in coolants generally need that are of the oil-in-water type, not lubricating viscosities own.

Of the areas listed above, one of the most important is hydraulic fluids. In this particular field, particularly in its application to the aviation field, a requirement is that. Superplasticizer retains its properties even at low temperatures. A disadvantage of the said known additives is that they are completely union at the required low temperatures, or if they are are soluble to any substantial extent, these Löf>

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liclikeit does not result in an effective concentration of the additive. The additives of the invention showed themselves soluble in a Decentriraeröl to an extent of 1% and more at -12 ⁰ C, while on the other hand, the additives the US Patents 2,747,604 and 2,477,356 are insoluble according to this in the same oil. For example, the 4- (ethylthio) -dodecanoic acid was more than 1 % soluble in the decene trimer oil at -12 ^C C, while the n- (dodecylthio) acetic acid was not even 0.05 % soluble therein at the same temperature.

It has been found that a mass, regardless of whether it contains the hydrocarbon as the main liquid or a large amount of ¥ water, about 0.01 % to about 5% by weight, preferably about 0.01 to about 0.2 % of the Alkylthiohydrocarboxylic acid or its salt must contain in order to give effective anti-corrosion properties therefor.

When used as an aqueous mass, the water makes up about 50 % to about 99 % of the total mass. If it is convenient or necessary to use an emulsion, any of the known emulsifiers can be used.

Having generally described the invention above, the following examples are specific Explanation of the practical implementation. It goes without saying that these examples are only illustrative and limit the invention not.

example 1

A 1 1 flask was fitted with a stirrer, thermometer, dropping funnel and nitrogen inlet pipe. - 400 ml of benzene, 63.7 g of ethanethiol (1.043 KoI) were added to the flask. and then 53.5 g of sodium methoxide (0.991 mole) with stirring

2 0 9 8 A 97 1 0 6 8

added under nitrogen. The mixture was heated and stirred, and methanol and benzene were distilled off. After the dry salt had cooled to room temperature, 152 g (0.770 mol) of yn-octyl-y-butyrolactone were added. The mixture was heated under nitrogen for 16 hours at 15O ⁹ C and stirred. 400 ml of a 6N hydrochloric acid were then added with stirring and heating. The aqueous layer was separated from the crude product and extracted through two 200 ml portions of benzene. This extract was combined with the crude product. The benzene was distilled off at atmospheric pressure. In vacuum distillation, 126 g of purified 4- $ methylthio) were dodecanoic acid having a boiling point 146-151 ⁰ C at 0.2 mm mercury obtained.

Analvse calculated found C. 65.17 % 64.90 % H 10.84 % 10.66 % S. 12.3 % 12.2 % Example 2

Following the procedure of Example 1, the product was prepared by reacting 10.0 g of sodium methoxide with 34.0 g of 1-decanethiol in 200 ml of benzene and then 60 g of γ-phenyl-ybutyrolactone The crude sulfidic acid (59 g) was obtained by dissolving in a solution of 50 g of sodium carbonate Purified in 1500 ml of water and extraction of this material with two 250 ml portions of η-hexane. The product was out of the aqueous solution by adding 6 η-hydrochloric acid.

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sets and collected in ethyl ether. After evaporation of the ether, 50 g of 4- (n-decylthio) -4-phenylbutyric acid remained.

analysis calculated found C. 71.38 % 71,59 ° / o H 9.59 % 9.48 % S. 9.5 % 9.3 % Example 3

A dimer acid of the formula

[H00C (CH _{2) 2} CH (nC ₈ H ₁₇₎ -S-CH ₂ CH ₂ J ₂

• was manufactured in the following way:

10.0 parts of 1,4-butanedithiol became 100 cm * benzene
was added and, with vigorous stirring and passing in N ₂ , 8.86 parts of sodium methoxide were added. Benzene and methanol were stripped off and, after cooling the residue, 40.0 parts of yn-octyl-y-butyrolactone were added
and the reactants are ^{heated to 150 °} C. overnight.

250 parts of water were then added, the total amount of water Transfer to a separatory funnel and add ethyl ether. All of the materials were placed in a beaker

• 7.

and acidified with concentrated hydrochloric acid in 100 cnr benzene. The organic layers were combined and evaporated _{on a hot plate under N 2.}

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Example 4

The 4- (n-dodecylthio) butyric acid was made in the same way prepared as in Example 1 from n-dodecyl mercaptan, sodium methoxide and γ-butyrolactone.

Evaluation of the products

The above products have been used as rust preventive agents in the presence of synthetic sea water accordingly according to ASTM D665-60, Method B, evaluated.

The products gave the following results when examined according to the above procedure. The oil used was a 150 SUS (100 ^° F) citronelle turbine base oil.

Ge \ i .-% Compound 0.06 0.05

Example 1 exists

Example 2 exists

Example 3 fails (severe rust)

Example 4 fails (medium grate)

These results show that there is good inhibition with the sulfur atom in various positions in the acid chain can be obtained. They also show that aryl groups can be present in the molecule.

It has surprisingly been found that (1) if R is the required number of alkyl carbon atoms when R 'is an alkyl group of fewer than 4 carbon atoms, or (2) when R is an aromatic hydrocarbon group, the product fails as a rust inhibitor. This also results from the following values,

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those under the same conditions and the same oil as obtained above.

Weight-tf compound 0.06 % 0.03 %

(n-Butylthio) acetic acid - fails (n-Octadecylthio) acetic acid - fails 3- (Phenylthio) propionic acid fails

4- (n-octadecylthio) butyric acid - failed

4- (Phenylthio) -butyric acid fails 4- (Phenylthio) -dodecanoic acid fails

(heavy rust)

Another consideration due to the second set of values is the fact that if the chain length is from R exceeds about 16 or 17 carbon atoms, the additive fails as an anti-rust agent. It follows from this. Value, therefore, that R must be an alkyl chain and the prescribed one Must have length for acceptable activity. It also turns out that, albeit an aromatic Group can be connected to R *, the radical R is not aromatic may be.

In the foregoing, the invention has been described on the basis of preferred embodiments, although they are neither based on them is limited, nor are modifications excluded.

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Claims (7)

- 12 claims 1. Organic mass based on a liquid hydrocarbon and a carboxylic acid as a corrosion inhibitor, characterized in that the corrosion inhibitor .from an acid of the form, el RSR ¹ - COOH, wherein R is an alkyl group having 2 to 16 carbon atoms, R ^! a straight or branched chain divalent hydrocarbon group having 4 to 22 carbon atoms or one group - R "- S - R • - COOH denote where R "is an alkylene group having 4 to 32 carbon atoms represents, or an amine salt of such an acid. 2. Composition according to claim 1, characterized in that it contains 0.01 to 5 wt .-% of the acid or the salt. 3. Composition according to claim 1 or 2, characterized in that the amine contains 4 to 40 carbon atoms. 4. Composition according to claim 1 to 3 »characterized in that the acid consists of ethylthiododecanoic acid. 5. Composition according to claim 1 to 3 »characterized in that the acid is bestdt from n-decylthiopheny! Butyric acid. 6. Composition according to claim 1 to 3> characterized in that that the acid consists of dodecylbutyric acid. 7. Composition according to claim 1 to 3, characterized in that the acid has the formula [HOOC- (CHp) p-CH • (C _n H ₁₇ ) -S-CH _p CH ₉ ] ρ. 209849/1068