Corrosion Inhibitors

In U.S. Pat. No. 3,703,587, there is described and claimed:

"1. The process of inhibiting corrosion of metals and alloys in contact with corrosive media which comprises contacting said metals and alloys with a poly-ester-amide-acid composition formed by reacting (1) an alkyl or an alkenyl succinic acid or the anhydride thereof with (2) a polyol, the product of which is reacted with an alkanol amine to form an ester-amide and then reacting said so formed ester-amide with an alkyl or an alkenyl succinic acid or the anhydride thereof."

The present invention relates to a composition comprising:

(1) an alkenyl succinic acid or anhydride (ASAA), and

(2) the reaction product of ASAA and a trialkanol amine amine such as triethanolamine (TEA) where ASAA (3 moles) is reacted with TEA (1 mole) to yield the Triester; and to the use thereof in corrosion inhibition.

Thus, this invention relates to a mixture of (1) alkenyl succinic acid or the anhydride thereof and (2) the reaction product of about 3 moles of an alkenyl succinic acid or an anhydride thereof (also referred to as "ASAA") with one mole of a trialkanol amine or substituted trialkanol amine (the triester); and to the process of preparing this product. More particularly, the triester is prepared from the above reactants having 3 ester groups per molecule. Still more particularly, the triester has the idealized formula: ##STR1## wherein Z is an alkylene or substituted alkylene radical for example, from 2 to 12 or more carbon atoms, but preferably 2 to 8 carbon atoms; wherein one of the R's on each succinic moiety is an alkenyl radical having at least 2 carbons, for example 2 to 32 or more carbons, but preferably 8 to 18 carbons and the other R' on each succinic moiety is hydrogen. The R's may also be the corresponding alkyl group, i.e., alkyl succinic acids or anhydrides.

This invention also relates to the use of the mixture of compositions for various uses, particularly as corrosion or rust inhibitors, such as for oil wells, oil refineries, in slushing oils, refined mineral oil such as gasoline, jet fuel, etc.

The trialkanol amines employed in preparing the triester contain alkylene or substituted alkylene radicals and 3 aminohydroxy radicals, i.e., alkanol amines expressed by the formula:

wherein Z is an alkylene or substituted alkylene radical, for example 2 to 12 or more, but preferably 3 to 8 carbons.

Thus, Z is an alkylene radical which can be straight-chained or branched-chain, for example ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, etc., and isomers thereof, for example-isopropylene, isobutylene, isopentylene, isohexylene, isoheptylene, isooctylene, isononylene, isodecylene, etc. The alkylene radical can be straight-chained, singly-branched, for example ##STR2##

The weight ratio of (1) ASAA to (2) triester can vary widely depending on the particular reactants, the particular systems in which it is employed, etc.

In general, the weight ratio of (1) to (2) is about 60 to 40, such as from about 40 to 60, for example from about 80 to 20, but preferably from about 20 to 80, with an optimum of about 50 to 50.

Any alkenyl succinic acid anhydride or the corresponding acid is utilizable in the present invention. The general structural formulae of these compounds are: ##STR3## wherein R is an alkenyl radical. The alkenyl radical can be straight-chain or branched-chain; and it can be saturated at the point of unsaturation by the addition of a substance which adds to olefinic double bonds, such as hydrogen, sulfur, bromine, chlorine, or iodine. It is obvious, of course, that there must be at least two carbon atoms in the alkenyl radical, but there is no real upper limit to the number of carbon atoms therein. However, it is preferred to use an alkenyl succinic acid anhydride reactant having between about 8 and about 18 carbon atoms per alkenyl radical. In order to produce the reaction products of this invention, however, an alkenyl succinic acid anhydride or the corresponding acid must be used. Succinic acid anhydride and succinic acid are not utilizable herein. For example, the reaction product produced by reacting with succinic acid anhydride is unsatisfactory. Although their use is less desirable, the alkenyl succinic acids also react, in accordance with this invention, to produce satisfactory reaction products. It has been found, however, that their use necessitates the removal of water formed during the reaction and also often causes undesirable side reactions to occur to some extent. Nevertheless, the alkenyl succinic acid anhydrides and the alkenyl succinic acids are interchangeable for the purposes of the present invention. Accordingly, when the term "alkenyl succinic acid anhydride" is used herein, it must be clearly understood that it embraces the alkenyl succinic acids as well as their anhydrides, and the derivatives thereof in which the olefinic double bond has been saturated as set forth hereinbefore. Non-limiting examples of the alkenyl succinic acid anhydride reactant are ethenyl succinic acid anhydrides; ethenyl succinic acid; ethyl succinic acid anhydride; propenyl succinic acid anhydride; sulfurized propenyl succinic acid anhydride; butenyl succinic acid; 2-methyl-butenyl succinic acid anhydride; 1,2-dichloropentyl succinic acid anhydride; hexenyl succinic acid anhydride; hexyl succinic acid; sulfurized 3-methylpentenyl succinic acid anhydride; 2,3-dimethylbutenyl succinic acid anhydride; 3,3-dimethylbutenyl succinic acid; 1,2-dibromo-2-ethylbutyl succinic acid; heptenyl succinic acid anhydride; 1,2-diodooctyl succinic acid; octenyl succinic acid anhydride; 2-methylheptenyl succinic acid anhydride; 4-ethylhexenyl succinic acid; 2-isopropylpentyl succinic acid anhydride; nonenyl succicinic acid anhydride; 2-propylhexenyl succinic acid anhydride; decenyl succinic acid; decenyl succinic acid anhydride; 5-methyl-2-isopropylhexenyl succinic acid anhydride; 1,2-dibromo-2-ethyloctenyl succinic acid anhydride; decyl succinic acid anhydride; undecenyl succinic acid anhydride; 1,2-dichloro-undecyl succinic acid; 3-ethyl-2-t-butylpentenyl succinic acid anhydride; dodecenyl succinic acid anhydride; dodecenyl succinic acid; 2-propylnonenyl succinic acid anhydride; 3-butyloctenyl succinic acid anhydride; tridecenyl succinic acid anhydride; tetradecenyl succinic acid anhydride; hexadecenyl succinic acid anhydride; sulfurized octadecenyl succinic acid; octadecyl succinic acid anhydride; 1,2-dibromo-2-methylpentadecenyl succinic acid anhydride; 8-propylpentadecyl succinic acid anhydride; eicosenyl succinic acid anhydride; 1,2-dichloro-2-methylnona decenyl succinic acid anhydride; 2-octyldodecenyl succinic acid; 1,2-diiodotetracosenyl succinic acid anhydride; hexacosenyl succinic acid, hexacosenyl succinic acid anhydride; and hentriacontenyl succinic acid anhydride.

The methods of preparing the alkenyl succinic acid anhydrides are well known to those familiar with the art. The most feasible method is by the reaction of an olefin with maleic acid anhydride. Since relatively pure olefins are difficult to obtain, and when thus obtainable, are often too expensive for commercial use, alkenyl succinic acid anhydrides are usually prepared as mixtures by reacting mixtures of olefins with maleic acid anhydride. Such mixtures, as well as relating pure anhydrides, are utilizable herein. Corresponding alkyl succinic anhydrides can also be employed, i.e., where the alkenyl group is saturated in any of the above instances, the preparation of alkyl succinic acids and anhydrides thereof is well known to the art.

A typical procedure for the preparation of the triester is the following which is illustrative only as a non-limiting procedure. The desired substituted succinic anhydride and trialkanol amine charges are weighed into a suitable jacketed acid-resisting vessel equipped with agitation temperature recording means and a reflux condenser. The charge is heated to about 95.degree.-100.degree. C. while agitating and held thereat and the progress of the reaction observed from time to time by withdrawing a sample and determining the neutralization number thereof. Heating is continued until the desired neutralization number is obtained or until it remains substantially constant. The reaction occurring is represented as follows: ##STR4##

The compositions of this invention which are soluble or dispersible therein are particularly useful as rust or corrosion inhibitors such as in refined petroleum products such as in gasoline, aviation, gasoline, jet fuels, turbine oils, fuel oils, etc.

They may be employed in any amount capable of inhibiting rust or corrosion, such as in minor amounts of at least 1 p.p.m., such as at least 5 p.p.m., for example 15 to 200 p.p.m., or more, but preferable 25-50 p.p.m. They are particularly effective in inhibition of rust and corrosion in refined petroleum products, such as petroleum distillates in contact with metals such as ferrous or other metal surfaces.

In certain instances, it may be desirable to add larger amounts of the compositions of the invention, such as up to about 100,000 p.p.m. or greater, for example from about 20 to 1,000 p.p.m. For example with lubricating oils about 500 to 1,000 p.p.m. or greater amounts are added. With heavy duty lube oil sometimes about 60,000 to 10,000 p.p.m. (i.e., about 6-10%) is sometimes added.

The following is a suitable test of evaluation for such compositions as rust inhibitors.

Use clean equipment for the test as specified in the ASTM method D665-60. Pour 300 ml. of the oil to be tested into the beaker and place the beaker in the testing apparatus. Cover the beaker with the beaker cover with the stirrer in position in the proper opening. Adjust the stirrer so that the shaft is 6 mm. off center in the beaker containing the oil sample and the blade is within 2 mm. of the bottom of the beaker.

Insert the test specimen assembly through the specimen in the bottom of the beaker.

After the test specimen assembly has been suspended in the oil to be tested for 10 minutes of static wetting time, start the stirrer and continue to stir for twenty minutes to insure complete wetting of the steel specimen. With the stirrer in motion, add 30 ml. of distilled water through the thermometer hole, discharging the water on the bottom of the beaker. (The thermometer is omitted.) Continue stirring for 24 hours at a speed of 1000 + or -50 r.p.m. from the time the water was added. Stop stirring at the end of the 24-hour period, remove the specimen, wash with isopropyl alcohol, then ASTM precipitation naphtha or isooctane. The specimen is air dried and graded immediately. After grading the specimen may be preserved by coating with a clear lacquer or plastic.

The procedure for rust-preventing characteristics of steam turbine oils in the presence of synthetic sea water shall be identical with that described earlier, except that synthetic sea water shall be used in place of distilled water in that portion of the procedure described earlier. The synthetic sea water shall have the following composition:

The solution can be conveniently prepared as follows. The methods avoids any precipitation in concentrated solutions with subsequent uncertainty of complete resolution. Using CP chemicals and distilled water, prepare the following stock solutions:

Visual inspection of the exposed steel specimen shall be as specified in ASTM method D665-60.

The appearance of the specimens are rated according to the following tables:

The following examples are presented for purposes of illustration and not of limitation.

In the examples in the Tables, the following compositions were compared:

A. Tetrapropenyl succinic acid (TPSA)

B. Triester of triethanol (TEA) amine and TPSA TPSA (3 moles) reacted with TEA (1 mole)

AB Equal amounts of weight of A and B.