Use of Complex Polyesteramines And Polyester Polyquaternary Ammonium Compounds As Corrosion Inhibitors

Abstract

Use of complex polyester amines and polyester quaternary ammonium compounds as corrosion inhibitors for metal surfaces, and a method for protecting a metal surface from corrosion by contacting the metal surface with said corrosion inhibitor.

Claims

1.-30. (canceled)

31. A method for protecting a metal surface from corrosion, the method comprising a step of bringing the metal into contact with an effective amount of a branched polyester selected from the group consisting of i) a branched polyester polyamine formed by reaction of A) a polycarboxylic acid having 3 or 4 carboxylic acid groups, or a reactive derivative thereof, with B) a monocarboxylic acid having the formula (I)
R.sup.1COOH  (I) wherein R.sup.1 is an acyl group having from 6 to 28 carbon atoms, or a reactive derivative thereof, and C) an alkanolamine having the formula (II) ##STR00008## wherein R2 is a straight or branched chain alkyl residue having from 1 to 24 carbon atoms, an alkenyl residue having from 2 to 24 carbon atoms or a polyoxyalkylene residue of the formula —(D-0)r-R.sup.3; R3 is hydrogen, an alkyl group having 1 to 18 carbon atoms or an acyl group having 2 to 18 carbon atoms; A, B, D independently from each other are a C.sub.2- to C4-alkylene group or a mixture of those; x, y, z independently from each other are integers from 1 to 2; ii) a branched polyester quaternary ammonium compound obtainable by quatemization of the branched polyester polyamine i); and iii) a mixture of branched polyester polyamine (i) and branched polyester quaternary ammonium compound (ii).

32. The method according to claim 31, wherein the branched polyester (i) and/or (ii) is added to a fluid getting into contact with the metal surface.

33. The method according to claim 31, wherein the polycarboxylic acid having 3 or 4 carboxylic acid groups has the formula (III) ##STR00009## wherein Y is an optionally substituted aliphatic group having from 2 to 15 carbon atoms, an aliphatic aminoalkylene group having from 3 to 12 carbon atoms and from 1 to 3 nitrogen atoms, or an optionally substituted aromatic group having from 6 to 18 carbon atoms; and X is hydrogen, a C.sub.1- to C.sub.20-alkyl group, a carboxylic acid group or a carboxylic acid derivative, a keto group, —OH or -OR4, wherein R4 is a C.sub.1-C.sub.4 alkyl group.

34. The method according to claim 31, wherein Y is an alkylene or alkenylene radical having from 2 to 10 carbon atoms.

35. The method according to claim 33, wherein Y is an alkylene or alkenylene radical having 2, 3 or 4 carbon atoms.

36. The method according to claim 33, wherein Y is substituted by one or two hydroxyl groups.

37. The method according to claim 33, wherein Y is an alkylene radical containing one or more nitrogen atoms.

38. The method according to claim 37, wherein the nitrogen atom is part of an amino group, and preferably of a tertiary amino group.

39. The method according to claim 31, wherein the reactive derivative of the polycarboxylic acid (A) is an acid anhydride, an acid chloride and/or an ester, preferably an ester with an alcohol having from 1 to 6 carbon atoms.

40. The method according to claim 31, wherein R.sup.1 is unsaturated.

41. The method according to claim 31, wherein the monocarboxylic acid (B) is a mixture of fatty acids with different degrees of unsaturation wherein the mixture has an iodine value, determined according to the method of Wijs, of at least 50 g I.sub.2/100 g.

42. The method according to claim 31, wherein the monocarboxylic acid (B) is an essentially saturated fatty acid wherein the mixture has an iodine value, determined according to the method of Wijs, of less than 50 g 12/100 g.

43. The method according to claim 31, wherein the reactive derivative of the monocarboxylic acid (B) is an acid anhydride, an acid chloride and/or an ester, preferably an ester with an alcohol having from 1 to 6 carbon atoms.

44. The method according to claim 31, wherein the molar ratio between the polycarboxylic acid (A) and the monocarboxylic acid (B) is from 1:50 to 2:1, preferably from 1:10 to 1:1, and especially preferred from 1:7 to 1:1.5.

45. The method according to claim 31, wherein R.sup.2 is an alkyl residue having 1 to 18 carbon atoms or an alkenyl residue having from 2 to 18 carbon atoms.

46. The method according to claim 31, wherein R.sup.2 is an alkyl residue having from 1 to 12 carbon atoms and preferably having from 1 to 6 carbon atoms.

47. The method according to claim 31, wherein the molar ratio between the alkanolamine (C) and the total molar amount of the acids (polycarboxylic acid (A) plus monocarboxylic acid (B)) is from 10:1 to 1:5 and preferably from 5:1 to 1:2.

48. The method according to claim 31, wherein the polyester polyamine (i) and/or the polyester quaternary ammonium compound (ii) further contains a minor amount of a structural element derived from a dicarboxylic acid (D) or a derivative thereof.

49. The method according to claim 48, wherein the dicarboxylic acid (D) has formula (IVa) or (IVb) ##STR00010## wherein Z is an optionally substituted aliphatic group having from 2 to 15 carbon atoms, an aliphatic aminoalkyl group having 3 to 12 carbon atoms and 1 to 3 nitrogen atoms, or an optionally substituted aromatic group having from 6 to 18 carbon atoms.

50. The method according to claim 31, wherein the branched polyester polyamine (i) formed by reaction of (A), (B), (C) and optionally (D) has been reacted with a quaternizing agent.

51. The method according to claim 50, wherein the quatemizing agent is an alkylating agent.

52. The method according to claim 31, wherein from 1 to 99% of the nitrogen atoms present in the branched polyester quaternary ammonium compound (ii) are quaternized.

53. The method according to claim 31, wherein a metal surface is protected from corrosion.

54. The method according to claim 53, wherein the metal surface is of a metal or alloy comprising iron.

55. The method according to claim 31, wherein a pipeline, a pump, a tank and other equipment used for example in oil- and gas fields or in refineries is protected from corrosion.

56. The method according to claim 31, wherein (i) and/or (ii) is dosed into a fluid comprising water getting into contact with the metal surface.

57. The method according to claim 56, wherein the concentration of (i) and/or (ii) in the fluid is from 1 to 2,000 ppm (by weight).

58. The method according to claim 31, wherein the polyester polyamine (i) and/or the polyester quaternary ammonium compound (ii) is part of a formulation comprising a diluent.

59. The method according to claim 58, wherein the diluent is water or a water miscible organic solvent, preferably selected from water, monohydric alkyl alcohols having 1 to 8 carbon atoms, di- and trihydric alcohols having 2 to 6 carbon atoms and C.sub.1 to C.sub.4 alkyl ethers of said alcohols.

60. The method according to claim 31, wherein the polyester polyamine (i) and/or the polyester quaternary ammonium compound (ii) is part of a formulation comprising one or more further ingredients selected from further corrosion inhibitors being different from (i) and (ii), dispersing or cleaning surfactants, defoamer additives, neutralizing amines, sulfide inhibitors, H.sub.2S scavengers, paraffin inhibitors, asphaltene inhibitors, hydrate inhibitors, and/or biocides

61. The method according to claim 60, wherein the further corrosion inhibitor being different from (i) and (ii) is selected from the group consisting of organic sulfur compounds, organic phosphate esters, organic acids, inorganic acids, amines, imidazolines, pyridines, quinolines, fatty acids and their derivatives.

Description

EXAMPLES

[0112] In order to clearly and demonstrably illustrate the current invention, several examples are presented below, these are however, non-limiting and have been specifically chosen to show those skilled in the art, the logic taken to arrive at the final formulations.

[0113] All reagents used were of commercial grade. If not stated otherwise, references to percent values and ppm refer to percent by weight respectively ppm by weight.

[0114] The molecular weight averages and molecular weight distributions were determined by SEC (Size Exclusion Chromatography) against poly(vinyl pyrrolidone) standards on a hydrophilic static phase (PSS Novema) in 80% 0,1 M NaCl+0,3% trifluoroacetic acid/20% acetonitrile at 25° C. For detection, the refractive index of the effluent was monitored.

[0115] Acid numbers were determined upon dilution of the sample with methanol/2-propanol=1/1 (v/v) solvent by potentiometric titration with tetrabutylammonium hydroxide (TBAH) dissolved in methanol/2-propanol, c=0.1 mol/l up to the equivalence point.

[0116] Basic nitrogen content was determined by potentiometric titration in acetic acid with perchloric acid solution in acetic acid, c=0,1 moVl up to the equivalence point.

[0117] Hydroxyl values were determined by acetylation of the sample in pyridine/acetic anhydride=25/1 (v/v) for 1 hour. The excess acetic anhydride was hydrolyzed with water and the resulting acetic acid was titrated with ethanolic potassium hydroxide solution, c=0,5 moVl up to the equivalence point.

[0118] Iodine values were determined according to the method of Wijs (EN 14111).

[0119] The dry matter content of the reaction products was determined by drying the polymer solutions on an infrared balance until constant weight, whereby the dry matter content is the part of the tested solution in percent per weight which remains in the drying dish.

Example 1

[0120] 590 g (2.1 mol) distilled mixed fatty acid comprising as main components 12 wt.-% Cis, and 80 wt.-% Cie fatty acids and having an iodine value of 105 g 12/100 g and 230 g (1.2 mol) citric acid were charged into a round-bottom flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a stirrer. The mixture was heated to 120° C. under stirring. 447 g (3.0 mol) triethanolamine were added continuously with the temperature not exceeding 130° C. Subsequently the batch was slowly heated to 180° C. while distilling off the water formed during the reaction. After 10 hours the acid number had decreased to 5 mg KOH/g and the reaction was stopped. The obtained solvent-free polyester reaction product (sample 1A) was a viscous liquid and had a hydroxyl value of 168 mg KOH/g, a mean weight average molecular weight Mw of 72,280 g/mol and a polydispersity of 2.8.

[0121] For subsequent quatemization the above polyester was dissolved in 610 g 2-butoxyethanol. Within 1 hour 357 g (2.83 mol) dimethyl sulfate was added with the temperature not exceeding 65° C. After all dimethyl sulfate was added the batch was stirred at 65° C. for another 2.5 h. The reaction was stopped after the content of basic nitrogen remained constant for more than 20 minutes and no residual dimethyl sulfate was analyzed. The reaction product (sample 1B) had a dry matter content of 68.6 wt.-%.

Example 2

[0122] 67.7 g (0.33 mol) distilled mixed fatty acid comprising 72 wt.-% C12 and 24 wt.-% C14 fatty acids as main components and having an iodine value of 0.2 g 1.sub.2/100g and 30 g (0.15 mol) citric acid were charged into a round-bottom flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a stirrer. The mixture was heated to 120° C. under stirring. 70.1 g (0.47 mol) triethanolamine were added continuously with the temperature not exceeding 130° C. Subsequently the batch was slowly heated to 180° C. while distilling off the water formed during the reaction. After 6 hours the acid number had decreased to 5 mg KOH/g and the reaction was stopped. The obtained solvent-free polyester reaction product (sample 2A) was a viscous liquid.

[0123] For subsequent quatemization 101,85 g of the above polyester was dissolved in 36 g 2-butoxyethanol. Within 1 hour 29.5 mL (0.31 mol) dimethyl sulfate was added with the temperature not exceeding 65° C. After all dimethyl sulfate was added the batch was stirred at 75° C. for another 3.5 h. The reaction was stopped after the content of basic nitrogen remained constant for more than 20 minutes and no residual dimethyl sulfate was analyzed. The reaction product (sample 2B) had a dry matter content of 79.5 wt.-%.

Example 3

[0124] 164.8 g (0.59 mol) of the distilled mixed C.sub.16/18 fatty acids described in example 1 and 49.5 g (0.21 mol) butane tetracarboxylic acid were charged into a round-bottom flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a stirrer. The mixture was heated to 120° C. under stirring. 153.4 g (1.26 mol) N-methyldiethanolamine were added continuously with the temperature not exceeding 130° C. Subsequently the batch was slowly heated to 180° C. while distilling off the water formed during the reaction. After 6 hours methane sulfonic acid (0.002 mol) was added and the reaction mixture was stirred for additional 18 hours at 180° C. The acid number had decreased to 4 mg KOH/g and the reaction was stopped. The obtained solvent-free polyester reaction product (sample 3A) was a viscous liquid.

[0125] For subsequent quatemization 95.6 g of the above polyester was dissolved in 33 g iso-propanol. Within 1 hour 28.1 mL (0.3 mol) dimethyl sulfate was added with the temperature not exceeding 65° C. After all dimethyl sulfate was added the batch was stirred at 75° C. for another 5 h. The reaction was stopped after the content of basic nitrogen remained constant for more than 20 minutes and no residual dimethyl sulfate was analyzed. The reaction product (sample 3B) had a dry matter content of 79.1 wt.-%.

Example 4

[0126] 148.3 g (0.53 mol) distilled mixed fatty acid comprising mainly C.sub.1e-C.sub.20 fatty acids including unsaturated components and 48.5 g (0.25 mol) nitrilotriacetic acid were charged into a round-bottom flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a stirrer. The mixture was heated to 120° C. under stirring. 138.2 g (1.14 mol)N-methyldiethanolamine were added continuously with the temperature not exceeding 130° C. Subsequently the batch was slowly heated to 180° C. while distilling off the water formed during the reaction. After 9 hours methane sulfonic acid (0.002 mol) was added and the reaction mixture was stirred for additional 19.5 hours at 180° C. The acid number had decreased to 25 mg KOH/g and the reaction was stopped. The obtained solvent-free polyester reaction product (sample 4A) was a viscous liquid.

[0127] For subsequent quatemization 96,5 g of the above polyester was dissolved in 34 g 2-butoxyethanol. Within 1 hour 29.9 mL (0.32 mol) dimethyl sulfate was added with the temperature not exceeding 65° C. After all dimethyl sulfate was added the batch was stirred at 75° C. for another 7.5 h. The reaction was stopped after the content of basic nitrogen remained constant for more than 20 minutes and no residual dimethyl sulfate was analyzed. The reaction product (sample 4B) had a dry matter content of 78.8 wt.-%.

[0128] Example 5 (comparative according to WO 2012/028542)

[0129] 230 g tallow fatty acid (0.82 mol), 195 g methyl diethanolamine (1.64 mol) and 180 g adipic acid (1.23 mol) were added to a round-bottomed flask fitted with a condenser, a thermometer, a heating mantle, a nitrogen inlet, and a mechanical stirrer. The reaction mixture was slowly heated to 170° C. Commencing at 150° C., the water produced during the reaction started to distil off. After 3.5 h, vacuum was applied gradually in order to more completely remove the water. After 4h, the endpoint vacuum of 16 mbar was reached. The progress of the reaction was monitored by titration for acid value. After 7h at 174° C. under vacuum the reaction was stopped. The acid value of the obtained solvent-free product (comparative sample 5A) was 10.3 mg KOH/g.

[0130] For quatemization, 240.2 g polyester from example 5 were dissolved in 43.5 g 2-butoxyethanol and heated to 57° C. in a stirred autoclave. Methylchloride (36.6 g) was added over 90 minutes. Post-reaction was then carried out for 10 hours at 93±3° C. 252 g of the final product (comparative sample 5B) were obtained as a paste containing 13.6% (w/w) of 2-butoxyethanol. .sup.1H-NMR spectroscopy showed that no non-quatemised amine was left.

[0131] For comparison purposes, N-tallow alkyl hexahydropyrimidinium ethoxylate methosulfate (sample 6) was tested as well. This monomeric quat is a corrosion inhibitor which has proven to be especially efficient for corrosion inhibition in sour environments.

[0132] Corrosion Testing

[0133] In order to evaluate the corrosion inhibition efficacy of the polyesters according to the invention, 4 different test methods were employed: Linear Polarizing Resistance (LPR), Rotating Cylinder Electrode Test (RCE), Shell wheel test and High Pressure/High Temperature Rotating Cage Autoclave Test (RCA). For all testing 3.5% NaCl brine was used. For the application tests the materials to be tested (inventive as well as comparative) were diluted with butyl glycol to an active content of 25 wt.-% prior to testing. The dosage rates given in the tables refer to these 25 wt.-% active formulations.

[0134] Linear polarization resistance (LPR) measurements were made with a Gamry electrochemical measurement system. The working electrode was made of a 1018 carbon steel (CS) cylinder with a surface area of 3.16 cm.sup.2. A Hastelloy C276 electrode was used as a pseudoreference, and a titanium rod was used as the counter electrode. The corrosion inhibitors were added based on the brine volume after the baseline corrosion rate was monitored for approximately 1.5 hours. From the polarization resistance measured in certain time intervals, the corrosion rate was determined according to the Stern-Geary equation. The % protection was calculated from the following equation:

% protection=(1-(x/y))*100

wherein [0135] x=corrosion rate in the presence of corrosion inhibitor (mm/year); and [0136] y=corrosion rate in the absence of corrosion inhibitor (mm/year).

[0137] The test results are given in Table 1.

TABLE-US-00001 TABLE 1 Results of LPR testing Test Corrosion Protection [%] No. Sample ppm 0.5 h 1 h 3 h 5 h 7 h 9 h 1 1A 50 66 81 3 94 95 93 2 1B 50 77 84 90 88 91 95 3 2A 50 60 66 78 84 91 92 4 2B 50 74 79 85 87 92 92 5 3A 50 73 78 86 90 92 93 6 3B 50 62 77 94 95 96 97 7 4A 50 70 74 89 94 94 95 8 4B 50 72 76 91 93 94 96 9 5A 50 53 55 58 60 62 65 10 5B (comp.) 50 62 61 61 67 70 73 11 99 wt.-% 3B + 1 wt.-% 50 95 97 99 99 99 99 2-mercaptoethanol

[0138] Corrosion Testing in the Rotating Cylinder Electrode Test (RCE)

[0139] RCE tests were conducted in Pyrex glass reaction kettles. In the sweet system evaluations they were continuously purged with CO.sub.2 at 65° C. and for the sour system testing they were continuously purged at 65° C. with a 200 ppm H.sub.2S, 20% CO.sub.2 blend with the balance made up of N.sub.2. The corrosion inhibitor evaluation testing solution consitsted of 900 mL of 3.5% NaCl brine for the sweet systems and a 90/10 percent brine/petroleum mixture for sour systems. The brine was deaerated for three hours, with respect to the system gases, in the reaction kettles prior to inserting the working electrodes to achieve an anaerobic condition. A magnetic stir bar and hot plate combination was used to agitate the solution during the initial deaeration period. The electrode rotation rate was set at 4,000 RPM, which generated a wall shear stress of 22 Pa. Flow meters were used to ensure the gas flow rates were identical between the reaction kettles.

[0140] Corrosion rates were determined by LPR methodology as described above. The test was allowed to run for sixteen hours. Test results are given in tables 2 and 3.

TABLE-US-00002 TABLE 2 Results of sweet RCE testing Corrosion Protection [%] Test No. Sample ppm after 2 h after 16 h 12 1B 15 95.9 98.4 13 5B (comp.) 15 94.1 97.2

[0141] Corrosion testing in the Shell Wheel Test

TABLE-US-00003 TABLE 3 Results of sour RCE testing Corrosion Protection [%] Test No. Sample ppm after 2 h after 16 h 14 1B 15 97.7 97.7 15 5B (comp.) 15 97.1 97.3

[0142] In the Shell wheel test, carbon steel coupons (DIN 1.1203 with surface area 15 cm.sup.2) were immersed into a saltwater/petroleum mixture (9:1) previously degassed with CO.sub.2 for one hour with the saltwater being a 5% NaCl solution adjusted to pH 3.5 with acetic acid) and exposed to this medium at a peripheral speed of 40 rpm at 600 C for 24 hours. The mass loss in presence of 50 ppm of the formulated corrosion inhibitors was compared to the loss in absence of the inhibitor (blank). Test results are given in table 4.

TABLE-US-00004 TABLE 4 Results of wheel testing Inhibitor mass loss [mg] Protection Test No. Sample blank inhibited [%] 16 1A 34.5 4.8 86 17 1B 33.3 7.2 78 18 2A 34.5 3.6 90 19 2B 34.8 7.9 77 20 3A 34.5 8.2 76 21 3B 37.0 4.4 88 22 4A 34.5 4.4 87 23 4B 37.0 7.3 80 24 (comp.) 5A 33.3 13.7 59 25 (comp.) 5B 34.8 16.8 52

[0143] Above test results demonstrate that the polymeric inhibitor samples 1A, 1B, 2A, 2B, 3A, 3B, 4A and 4B according to different embodiments of the invention give an excellent corrosion protection under representative test conditions also at quite low dose levels. The corrosion protection is well improved over the comparative linear polymers based on a dicarboxylic acid (samples 5A, 5B). Presumably, this is due to an improved transfer of the polymers to the aqueous phase.

[0144] Corrosion Testing in the Rotating Cage Autoclave Test (RCA)

[0145] Autoclaves equipped with rotating cages (RCA) were used to simulate high shear conditions for the purpose of evaluating system corrosivity and inhibitor performance. The testing solution consisted of 720 mL 3.5% NaCl brine and 80 mL LVT-200 oil. The synthetic brine had three cycles of vacuum/CO.sub.2 charge to the vessel prior to initiating the test to remove dissolved oxygen and to achieve an anaerobic system. Two weight loss corrosion coupons fixed on the rotating cage were used in each autoclave. General corrosion rates were calculated by weight loss measurement. A blank was run for comparison. Test conditions have been summarized below in Table 5. Test results obtained with polyesters as single active component are shown in tables 6 and 8.

[0146] Table 7 gives a comparison of the performance of polyester 1B according to the invention with polyester 5B according to the state of the art in a formulated corrosion inhibitor package.

TABLE-US-00005 TABLE 5 Conditions for RCA Corrosion Testing: Temperature 65° C. Gas Composition, sweet 15% CO.sub.2; balance N.sub.2 Gas Composition, sour 200 ppm H.sub.2S, 15% CO.sub.2; balance N.sub.2 Pressure 70 bar Brine Composition Synthetic brine (3.5% NaCl) Test Duration 72 hours Stir Rate 1700 rpm

TABLE-US-00006 TABLE 6 Results of sweet RCA testing Average corrosion Percent Test No. Sample ppm rate [mpy] protection 26 blank — 193.8 — 27 1B 150 105.7 45.5 28 5B (comp.) 150 125.7 38.9

TABLE-US-00007 TABLE 7 Results of sweet RCA testing of samples 1B and 5B in combination with further corrosion inhibitors Average corrosion Percent Test No. Sample ppm* rate [mpy] protection 29 blank — 60.1 — 30 1B 150  6.4 89.6 31 5B (comp.) 150 18.0 70.0 *The additives used in tests 30 and 31 contained, besides the polymeric corrosion inhibitor 1B respectively 5B, a mixture comprising a mixture of oligomeric fatty acids, ethoxylated alkyl imidazoline, phosphoric acid ester, and thioglycolic acid. The tests were conducted by replacing 5B in the formulation with 1B to compare the performance of the two chemicals in an otherwise identical formulation.

TABLE-US-00008 TABLE 8 Results of sour RCA testing Average corrosion Percent Test No. Sample ppm rate [mpy] protection 32 blank — 124.4 — 33 1B 150 4.1 96.7 34 6 (comp.) 150 8.99 92.8

[0147] Biodegradability and acute toxicity of a branched polyester polyamine have been compared with a comparative linear polyester polyamine. Biodegradability was tested in seawater using the OECD 306 closed bottle test at a test concentration of 2.00 mg/I. The acute toxicity was tested according to the OECD 203 Fish Acute Toxicity Test (992) over a 96-hour exposure period. The test specimens were Sheepshead Minnow (Cyprinodon variegatus).

TABLE-US-00009 TABLE 9 Biodegradability according to OECD 306 Test inhibitor biodegradability 35 sample 1B 75% (28 days) 36 (comp.) sample 5B 62% (28 days)

TABLE-US-00010 TABLE 4 Fish Acute Toxicity according to OECD 203 Test Test inhibitor LC.sub.50 value 37 sample 1B   <10 ppm (96 hours) 38 (comp.) sample 5B >14.6 ppm (96 hours)