Use of carboxylic acid esters as lubricants

Abstract

The presently claimed invention is directed to the use of carboxylic acid esters which are obtained by reacting aliphatic dicarboxylic acids and a mixture of structurally different monoalcohols having 10 carbon atoms as lubricants and a process for their preparation.

Claims

1. A lubricant composition comprising one or more carboxylic acid esters that are obtainable by reacting a mixture comprising: a) at least one acid selected from the group consisting of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides, b1) a monoalcohol having 10 carbon atoms and a structure of the general formula I, ##STR00010## wherein R.sub.1 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.2 is H or methyl, R.sub.3 is selected from the group consisting of ethyl, propyl and iso-propyl, and b2) a monoalcohol having 10 carbon atoms and a structure of the general formula II, ##STR00011## wherein R.sub.4 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.5 is H or methyl, R.sub.6 is selected from the group consisting of ethyl, propyl and iso-propyl, with the proviso that the monoalcohol b1) and the monoalcohol b2) have a different structure and the monoalcohols b1) and b2) are present in a molar ratio in the range of 1.05:1 to 2.0:1 in relation to the acid a) and a weight ratio of monoalcohol b1) to monoalcohol b2) is in the range of 5:1 to 95:1.

2. The lubricant composition of claim 1, wherein the aliphatic dicarboxylic acid is selected from the group consisting of glutaric acid, diglycolic acid, succinic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, 2,6-decahydronaphthalenedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 2,5-norbornanedicarboxylic acid.

3. The lubricant composition of claim 1, wherein the aliphatic dicarboxylic acid is adipic acid.

4. The lubricant composition of claim 1, wherein R.sub.1 is pentyl, R.sub.2 is H, and R.sub.3 is propyl.

5. The lubricant composition of claim 1, wherein R.sub.4 is 2-methyl-butyl, R.sub.5 is H, and R.sub.6 is propyl.

6. The lubricant composition of claim 1, wherein the mixture further comprises a monoalcohol b3) having 10 carbon atoms and a structure of the general formula III, ##STR00012## wherein R.sub.7 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.8 is H or methyl, R.sub.9 is selected from the group consisting of ethyl, propyl and iso-propyl, with the proviso that monoalcohol b3) has a different structure from both the monoalcohol b1) and the monoalcohol b2).

7. The lubricant composition of claim 1 obtainable by reacting a mixture comprising adipic acid, 2-propyl-heptanol, 2-propyl-4-methyl-hexanol and 2-propyl-5-methyl-hexanol.

8. A method for improving the hydrolysis stability of lubricants comprising obtaining as lubricants one or more carboxylic acid esters obtainable by reacting a mixture comprising: a) at least one acid selected from the group consisting of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides, b1) a monoalcohol having 10 carbon atoms and a structure of the general formula I, ##STR00013## wherein R.sub.1 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.2 is H or methyl, R.sub.3 is selected from the group consisting of ethyl, propyl and iso-propyl, and b2) a monoalcohol having 10 carbon atoms and a structure of the general formula II, ##STR00014## wherein R.sub.4 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.5 is H or methyl, R.sub.6 is selected from the group consisting of ethyl, propyl and iso-propyl, with the proviso that the monoalcohol b1) and the monoalcohol b2) have a different structure and the monoalcohols b1) and b2) are present in a molar ratio in the range of 1.05:1 to 2.0:1 in relation to the acid a) and a weight ratio of monoalcohol b 1) to monoalcohol b2) is in the range of 5:1 to 95:1.

9. The lubricant composition of claim 1 further comprising one or more additives selected from the group consisting of polymer thickeners, viscosity index (VI) improvers, antioxidants, corrosion inhibitors, detergents, dispersants, demulsifiers, defoamers, dyes, wear protection additives, EP (extreme pressure) additives, AW (antiwear) additives, and friction modifiers.

10. The lubricant composition of claim 1 that is effective as an industrial oil.

11. The lubricant composition of claim 1, comprising a diester (1) of an acid selected from the group consisting of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides and b1) a monoalcohol having 10 carbon atoms and a structure of the general formula I, ##STR00015## wherein R.sub.1 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.2 is H or methyl, R.sub.3 is selected from the group consisting of ethyl, propyl and iso-propyl, and a diester (2) of an acid selected from the group consisting of aliphatic dicarboxylic acids and aliphatic dicarboxylic acid anhydrides and b2) a monoalcohol having 10 carbon atoms and a structure of the general formula II, ##STR00016## wherein R.sub.4 is selected from the group consisting of pentyl, iso-pentyl, 2-methyl-butyl, 3-methyl-butyl and 2,2-dimethyl-propyl, R.sub.5 is H or methyl, R.sub.6 is selected from the group consisting of ethyl, propyl and iso-propyl, as lubricants.

12. The method of claim 8 further comprising adding one or more additives selected from the group consisting of polymer thickeners, viscosity index (VI) improvers, antioxidants, corrosion inhibitors, detergents, dispersants, demulsifiers, defoamers, dyes, wear protection additives, EP (extreme pressure) additives, AW (antiwear) additives, and friction modifiers to the one or more carboxylic acid esters.

13. A metalworking fluid which comprises the lubricant composition of claim 1.

14. A transformer oil which comprises the lubricant composition of claim 1.

15. A coating composition which comprises the lubricant composition of claim 1.

16. A plasticizing agent which comprises the lubricant composition of claim 1.

17. The lubricant composition of claim 1, wherein the weight ratio of monoalcohol b1) to monoalcohol b2) is in the range of 6:1 to 50:1.

18. The lubricant composition of claim 1, wherein the weight ratio of monoalcohol b1) to monoalcohol b2) is in the range of 10:1 to 40:1.

19. The lubricant composition of claim 1, wherein the weight ratio of monoalcohol b1) to monoalcohol b2) is in the range of 20:1 to 35:1.

Description

EXAMPLES

(1) DIDA is commercially available for example as Synative ES DIDA from BASF SE, Ludwigshafen

(2) Propylheptanol is commercially available from BASF SE, Ludwigshafen [93.0% by weight 2-propyl-heptanol; 2.9% by weight 2-propyl-4-methyl-hexanol; 3.9% by weight 2-propyl-5-methyl-hexanol and 0.2% by weight 2-isopropylheptanol]

Example 1

Preparation of Di-(2-propylheptyl)-adipate (DPHA)

(3) A mixture of structural isomers of an alcohol with 10 carbon atoms which is available by BASF SE as propylheptanol (2.4 mol) and adipic acid (1.0 mol) is reacted in the present of iso-propyl-butyl-titanate (0.001 mol) in an autoclave under inert gas (N.sub.2) at a reaction temperature of 230 C. Water which is formed during the reaction is removed from the reaction mixture through an inert gas stream (N.sub.2-stream). After 180 minutes the excess alcohol is removed from the mixture by distillation at a pressure of 50 mbar. The thus obtained adipic acid ester is then neutralised with 0.5% NaOH at 80 C. Afterwards the organic phase and the aqueous phase are separated, followed by washing the organic phase two times with water. In a further step the organic phase is purified by treating the crude adipic acid ester with steam at 180 C. and 50 mbar. Then the ester is dried by subjecting it to a N.sub.2 stream at 150 C. and 50 mbar. Finally the ester is mixed with activated carbon and is filtered using as a rheological agent supra-theorit at 80 C. under reduced pressure. The adipic acid ester shows a density of 0.916 g/cm.sup.3 at 20 C., measured according to DIN 51757, respectively ASTM D 4052.

Example 2

(4) Viscosity Measurement

(5) The viscosity of the esters is determined in a standard test according to DIN 51562-1.

(6) Pour Point Measurement

(7) The pour point of the esters is determined in a standard test according to ASTM D97.

(8) Demulsification Measurement

(9) The viscosity of the esters is determined in a standard test according to DIN ISO 6614.

(10) TABLE-US-00001 TABLE 1 Method DIDA DPHA Unit Viscosity at 40 C. DIN 51562-1 13.9 11.49 mm.sup.2/s Viscosity at 100 C. DIN 51562-1 3.6 2.98 mm.sup.2/s Pour point ASTM D97 60 80 C. Demulsification DIN ISO 10/35/35 40/40/0 minutes 6614

Example 3

(11) Cloud Point Measurement

(12) The cloud point of the esters is determined in a standard test according to ASTM D5773.

(13) TABLE-US-00002 TABLE 2 Lubricant formulations A and B (all values in weight-%) Formulation A with Formulation B with DIDA DPHA PAO 6 (Nexbase 2006, 52.0% 52.0% polyalpha-olefin, obtainable from Neste Oil N.V, Belgium) DIDA 10.0% DPHA 10.0% Thickener (Lubrizol 8406, 13.0% 13.0% polyiso-butylene, available from Lubrizol) Thickener (Lubrizol 8407 from 13.0% 13.0% Lubrizol) Additives (Anglamol 6004, 12.0% 12.0% additive package available from Lubrizol) Viscosity at 40 C. 113.75 mm.sup.2/s 112.75 mm.sup.2/s Viscosity at 100 C. 16.71 mm.sup.2/s 16.56 mm.sup.2/s Viscosity index (VI) 160 159 Density at 15 C. 0.8660 g/ml 0.8648 g/ml Cloud Point 32.0 C. 47.0 C. Brookfield viscosity at 40 C. 101 000 mPa/s 99 000 mPa/s

(14) The lower cloud point is a result of the improved solubility of the additives in the formulations.

Example 4

(15) Hydrolysis Test

(16) The hydrolytic stability was determined by measuring the acid value during a 9-day reaction with water at 100 C. as described in Svensk Standard S-155181.

(17) TAN=total acid number in mg KOH/g

(18) TABLE-US-00003 TABLE 3 DPHA DIDA Day Value (TAN) Increase [%] Value (TAN) Increase [%] 0 0.22 0.27 1 0.09 0.13 0.44 0.17 2 0.13 0.09 0.17 0.10 3 0.17 0.05 0.17 0.10 6 0.25 0.03 0.78 0.51 8 0.26 0.04 1.09 0.82 9 0.28 0.06 1.29 1.02