CORROSION INHIBITORS FOR FUELS AND LUBRICANTS

Abstract

The present invention relates to novel uses of corrosion inhibitors in fuels and lubricants.

Claims

1. A corrosion inhibitor, comprising a reaction product of polyisobutene that contains free acid groups, wherein the reaction product is obtained by reacting: (A) a polyisobutene having a number-average molecular weight Mn of 200 to 10 000 with, (B) at least one ,-unsaturated mono- or dicarboxylic acid or derivative thereof selected from the group consisting of a monoalkyl ester, a dialkyl ester and an anhydride, in a stoichiometric ratio of more than one equivalent of the ,-unsaturated mono- or dicarboxylic acid or derivative thereof (B) per reactive double bond in the polyisobutene (A), wherein at least one of the following conditions is satisfied: when compound (B) includes a monoalkyl ester, a dialkyl ester, or a mixture thereof, at least 10% of the ester groups present in the reaction product are in hydrolyzed form, and when compound (B) includes an anhydride, at least 10% of the anhydride groups present in the reaction product are in hydrolyzed form.

2. The corrosion inhibitor according to claim 1, wherein the polyisobutene (A) has a number-average molecular weight M.sub.n of 500 to 2500.

3. The corrosion inhibitor according to claim 1, wherein the compound (B) is selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, ethylacrylic acid and derivatives thereof.

4. The corrosion inhibitor according to claim 1, wherein the compound (B) is selected from the group consisting of maleic acid, fumaric acid, itaconic acid (2-methylenebutanedioic acid), citraconic acid (2-methylmaleic acid), glutaconic acid (pent-2-ene-1,5-dicarboxylic acid), 2,3-dimethylmaleic acid, 2-methylfumaric acid, 2,3-dimethylfumaric acid, methylenemalonic acid, tetrahydrophthalic acid and derivatives thereof.

5. The corrosion inhibitor according to claim 1, wherein the compound (B) is maleic anhydride.

6. The corrosion inhibitor according to claim 1, wherein the reaction product has a bismaleation level of 10% to 40%.

7. The corrosion inhibitor according to claim 1, wherein a proportion of unconverted polyisobutene in the reaction product is not more than 30% by weight.

8. A process, comprising reducing corrosion on a nonferrous metal surface with the corrosion inhibitor of claim 1.

9. The process of claim 8, wherein the corrosion inhibitor is contained in a gasoline fuel having a sodium content, a potassium content, or both, of at least 0.1 ppm by weight.

10. The process of claim 8, wherein the corrosion inhibitor is contained in a gasoline fuel having a magnesium content, a calcium content, or both, of at least 0.1 ppm by weight.

11. The process of claim 8, wherein the corrosion inhibitor is contained in a gasoline fuel having a zinc content of at least 0.1 ppm by weight.

12. The process of claim 8, wherein the reducing of corrosion involves preventing and reducing deposits in a fuel system.

Description

EXAMPLES

GPC Analysis

[0194] Unless stated otherwise, the mass-average molecular weight Mw and number-average molecular weight Mn of the polymers was measured by means of gel permeation chromatography (GPC). GPC separation was effected by means of two PLge Mixed B columns (Agilent) in tetrahydrofuran at 35 C. Calibration was effected by means of a narrow-distribution polystyrene standard (from PSS, Germany) having a molecular weight of 162-50 400 Da. Hexylbenzene was used as a marker for low molecular weight.

Synthesis Example 1

[0195] 524 g (0.54 mol) of a polyisobutene having a number-average molar mass Mn of 1000 g/mol and a content of -double bonds of 87% were initially charged together with 87 g (0.89 mol) of maleic anhydride in a 1 L autoclave equipped with a stirrer and thermometer. The mixture was converted under nitrogen at 210 C. over the course of 8 hours, in the course of which the pressure rose to 3 bar. The reaction mixture was cooled down to room temperature, transferred to a round-bottom flask with the aid of 1 L of toluene and filtered. Solvent and maleic anhydride were removed on a rotary evaporator at 190 C. at 1 mbar. 580 g of a dark brown, oily and viscous product were obtained.

[0196] In order to ascertain the hydrolysis number, the product was dissolved in toluene to give a 50% solution. The hydrolysis number of the product was measured by reaction of 10 mL of the solution obtained with excess potassium hydroxide, followed by back-titration of the potassium hydroxide residue with hydrochloric acid. The hydrolysis number was found to be 120 mg KOH/g.

[0197] 10 mL of the solution were then eluted through a silica gel column in order to determine the content of unfunctionalized polyisobutene. All the polyisobutene that had reacted with maleic anhydride was retained on the column, and polyisobutene was eluted with hexane. According to this, the reaction mixture comprised 13.4% by weight of unfunctionalized polyisobutene.

[0198] According to the above measurements, the reaction mixture comprised, as well as 13.4% by weight of unfunctionalized polyisobutene, monofunctionalized and difunctionalized polyisobutenesuccinic anhydride, which, assuming that no other by-products were present, gives a bismaleation level of 40.3%.

Synthesis Example 2: Hydrolysis of the Polyisobutenesuccinic Anhydride from Synthesis Example 1

[0199] 101 g of the polyisobutenesuccinic anhydride from synthesis example 1 were dissolved in 100 ml of ethyl methyl ketone in a 500 ml four-neck flask with reflux condenser and thermometer. The orange solution was heated to 50 C. and 50 ml of water were added dropwise over the course of 6 minutes, with the temperature of the mixture being held between 48 and 53 C. The mixture was subsequently heated under reflux at 75-76 C. for 5 hours under reflux. 150 ml of toluene were added to the solution and a water separator with 30 ml of toluene was mounted onto the flask. The mixture was stirred under reflux at 80 to 85 C. for 2 hours, and 48 ml of aqueous phase were removed continuously via the water separator. As soon as further formation of water came to a stop, the mixture was cooled to room temperature and filtered and the solution was concentrated on a rotary evaporator at 80 C. and 1 mbar. This gave 99.9 g of an orange, turbid product with an oily viscosity.

[0200] In an analogous manner to synthesis example 1 and 2, by altering the maleic anhydride:polyisobutene stoichiometry, reaction mixtures with a bismaleation level of 10% or 16.9% (17.6% by weight of unfunctionalized polyisobutene) were obtained in synthesis examples 3 and 4, respectively.

Use Examples

1) Calcium Compatibility Test:

[0201] 100 mL of motor oil (Shell Helix, FIG. 1, left-hand beaker, with a Ca content of 1500 ppm, Mg content of 1100 ppm and Zn content of 1300 ppm) were heated to 70 C. in the beaker and then 1 mL of corrosion inhibitor was added. Should the solution still be clear, a further 1 mL of inhibitor is added. If the solution turns cloudy, the test is considered to have been failed (e.g. FIG. 1, right-hand beaker). FIG. 1 shows, in the right-hand beaker, 1 mL of dimer fatty acid (dimeric oleic acid; CAS: 61788-89-4, 40% in Solvent Naphtha) was used. Distinctly visible turbidity is apparent.

[0202] FIG. 2 shows, from left to right, the pure Shell Helix, oil admixed with product from synthesis example 4, oil admixed with product from synthesis example 2, and oil admixed with product from synthesis example 3. It is seen that all of the products do not result in any turbidity.

2) Steel Corrosion Test to ASTM D 665 B (Gasoline)

[0203] The fuel used was conventional E0 CEC RF-12-09 gasoline fuel from Haltermann (batch number 1878), which was additized with 490 mg/kg of an additive package composed of polyisobuteneamine and carrier oil (polyether). The corrosion inhibitors specified in the table which follows were added to the formulation in the amounts specified (based on active component) and subjected to a corrosion test to ASTM D 665 B in saltwater.

[0204] Dimer fatty acid as corrosion inhibitor (dimeric oleic acid; CAS: 61788-89-4, 40% in Solvent Naphtha) was used as a comparison.

TABLE-US-00001 Dosage Assessment Corrosion Bismaleation [mg/kg] according Formulation inhibitor level active to NACE E0 base fuel E Formulation 1** Dimer fatty 5 B++ acid Formulation 2** Synthesis 40.3% 5 A example 2 Formulation 3** Synthesis .sup.10% 10 B+ example 3 Formulation 4** Synthesis 16.9% 5 B+ example 4 **Polyisobuteneamine-containing base package with polyether carrier oil at 490 mg/kg

[0205] The assessment was made as follows:

A 100% rust-free
B++0.1% or less of the total surface area rusted
B+0.1% to 5% of the total surface area rusted
B 5% to 25% of the total surface area rusted
C 25% to 50% of the total surface area rusted
D 50% to 75% of the total surface area rusted
E 75% to 100% of the total surface area rusted