LUBRICANT COMPRISING A DIESTER OF ADIPIC ACID WITH A TRIDECANOL

Abstract

The invention relates to a lubricant comprising a diester of adipic acid with a tridecanol mixture which comprises 20 to 60% of at least triply branched tridecanols, 10 to 50% doubly branched tridecanols, and 5 to 30% singly branched and/or linear tridecanols, and where the percentages are determined by gas chromatography.

Claims

1.-15. (canceled)

16. A lubricant comprising a diester of adipic acid with a tridecanol mixture which comprises 20 to 60% of at least triply branched tridecanols, 10 to 50% doubly branched tridecanols, and 5 to 30% singly branched and/or linear tridecanols, and where the percentages are determined by gas chromatography.

17. The lubricant according to claim 16 where the tridecanol mixture is obtained by hydroformylation and hydrogenation of a mixture of isomeric dodecenes.

18. The lubricant according to claim 17 where the mixture of isomeric dodecenes is obtained by reacting a hydrocarbon mixture comprising butenes on a heterogeneous catalyst.

19. The lubricant according to claim 16 where the tridecanol mixture comprises 25 to 50% of at least triply branched tridecanols.

20. The lubricant according to claim 16 where the tridecanol mixture comprises 20 to 45% doubly branched tridecanols.

21. The lubricant according to claim 16 where the tridecanol mixture comprises 10 to 25% singly branched and/or linear tridecanols.

22. The lubricant according to claim 16 where the tridecanol mixture comprises at least 85 wt % of linear or branched tridecanols.

23. The lubricant according to claim 22 where the tridecanol mixture comprises at least 98 wt % of linear or branched tridecanols.

24. The lubricant according to claim 16 where the tridecanol mixture comprises less than 15 wt % dodecanol.

25. The lubricant according to claim 24 where the tridecanol mixture comprises less than 2 wt % dodecanol.

26. The lubricant according to claim 16 where the tridecanol mixture comprises less than 5 wt % tetradecanol.

27. The lubricant according to claim 26 where the tridecanol mixture comprises less than 1 wt % tetradecanol.

28. The lubricant according to claim 22, wherein the tridecanol mixture comprises at least 98 wt % of linear or branched tridecanols, the tridecanol mixture comprises less than 2 wt % dodecanol and the tridecanol mixture comprises less than 1 wt % tetradecanol.

29. The lubricant according to claim 16 where the tridecanol mixture has a degree of branching in the range from 1.1 to 3.5 as determined by H-NMR.

30. The lubricant according to claim 28 where the tridecanol mixture has a degree of branching in the range from 1.9 to 2.4 as determined by H-NMR.

31. The lubricant according to claim 16 further comprising a base oil selected from the group consisting of mineral oils, polyalphaolefins, polymerized and interpolymerized olefins, alkyl naphthalenes, alkylene oxide polymers, silicone oils, phosphate ester and carboxylic acid ester; and a lubricant additive.

32. A method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant as defined in claim 16.

Description

EXAMPLES

Example 1: Tridecanol Mixture

[0099] A technical mixture of tridecanol was prepared as described in US 2003/0187114 starting from a technical Ca-raffinate. A technical mixture of butane and butenes isomers was subjected to dimerization on a heterogeneous catalyst to produce a mixture of octene isomers and dodecene isomers. The dodecene isomers were separated by distillation. The isomeric dodecenes were hydroformylated with synthesis gas comprising hydrogen and carbon monooxide, and subsequently hydrogenated with hydrogen. The resulting tridecanol mixture was isolated by fractional distillation.

[0100] The density of the isotridecanol mix was 0.843 g/cm.sup.3, the refractive index n.sub.D.sup.20 was 1.448, the viscosity was 34.8 mPas, and the boiling range was from 251 to 267° C. (according to DIN 51751).

[0101] The fraction of the tridecanol isomers was at least 99.0% by area as determined by gas chromatography according to DIN 55685. The content of dodecanol and of tetradecanol was each below 1% by area as determined by gas chromatography.

Example 2: GC Analysis

[0102] The tridecanol mixture from Example 1 was analyzed by gas chromatography as described in US 2003/0187114 using the Kovacs method:

[0103] A specimen of the isotridecanol was trimethylsilylated using 1 ml of N-methyl-N-trimethylsilyl-trifluoroacetamide per 100 μl of specimen for 60 minutes at 80° C. For separation by gas chromatography use was made of a Hewlett Packard Ultra 1 separating column of 50 m in length, based on 100%-methylated silicone rubber, with an internal diameter of 0.32 mm. Injector temperature and detector temperature were 250° C. and the oven temperature was 160° C. (isothermal). The split was 80 ml/min. The carrier gas was nitrogen. The inlet pressure was set to 2 bar. 1 μl of the specimen was injected into the gas chromatograph, and the separated constituents were detected by means of FID (flame ionization detector).

[0104] The reference substances used here were

[0105] n-undecanol: Retention index (“RI”) 1100

[0106] n-dodecanol: Retention index 1200

[0107] n-tridecanol Retention index 1300.

[0108] For evaluation purposes the gas chromatogram was subdivided into the following regions:

[0109] Region 1: Retention index less than 1180

[0110] Region 2: Retention index from 1180 to 1217

[0111] Region 3: Retention index greater than 1217

[0112] The areas of the tridecanol peaks were set to 100 percent by area. The results are summarized in Table 1.

[0113] For comparison, a commercial mixture of tridecanols (Exxal® 13 from Exxon Mobil, USA) was analyzed and the results are summarized in Table 1 “Comparative”. The density was 0.843-0847 g/cm3, hyroxyl number 275-295 mg KOH/g, boiling range 250-270° C., the fraction of C9 and C10 alcohol was about 2 wt %, and of C14 and higher alcohols about 5 wt %. The amount of C12 alcohols is about 30% according to Table 1 in WO 2010/057847.

TABLE-US-00001 TABLE 1 Retention index Branching Ex. 1 Comparative less than 1180 at least triply branched 46% 85% 1180 to 1217 doubly branched 35% 13% greater than 1217 singly branched and/or linear 19%  2%

Example 3: Synthesis of Diester of Adipic Acid

[0114] The tridecanol mixture of Example 1 (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 about 180 minutes the excess alcohol is removed from the mixture by distillation at a pressure of 50 mbar. The thus obtained diester of adipic acid 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 diester of adipic acid is dried by subjecting it to a N.sub.2 stream at 150° C. and 50 mbar. Finally the diester of adipic acid is mixed with activated carbon and is filtered using as a rheological agent supra-theorit at 80° C. under reduced pressure.

[0115] The colourless to yellowish liquid had a boiling range of 321-324° C. (ASTM D1120) and a density of 0.907 at 20° C.

Example 4: Performance Test of Diester

[0116] Various performance test of the diester of Example 3 were made and summarized in Table 2. For comparison, a diester of adipic acid and Exxal® 13 (as analyzed in Example 2) is prepared as described in Example 3 (“Comparative Diester”) and tested.

[0117] The thermal oxidative stability “RPVOT” was tested according to ASTM D2272. This standard test utilizes an oxygen-pressured vessel to evaluate the oxidation stability oils in the presence of water and a copper catalyst coil at 150° C. The time (minutes) was measured until the pressure decreases for 175 kPa below the maximum. The longer it takes, the more resistant the oil is against oxidation. All samples contained 0.5 wt % of the antioxidant Irganox® L06, an octylated phenyl-alpha-naphthylamine commercially available from BASF SE.

[0118] The data demonstrated that the viscosity index, the pour point, the flash point, and the thermal oxidative stability improved.

TABLE-US-00002 TABLE 2 Ex. 3 Comparative Diester Viscosity at 40° C. (ASTM D445)  23 mm.sup.2/s  26 mm.sup.2/s Viscosity at 100° C. (ASTM D445) 5.1 mm.sup.2/s 5.2 mm.sup.2/s Viscosity Index (ASTM D2270) 150 135 Pour Point (ASTM D97) −66° C. −60° C. Flash Point COC (ASTM D92) 247° C. 236° C. RPVOT 1216 min 758 min

Example 5: Traction Test

[0119] The diester of Example and and the Comparative Diester were tested in the MTM (Mini-Traction Machine) instrument using the so-called traction test mode. In this mode, the friction coefficient is measured at a constant mean speed of over a range of slide roll ratios (SRR) to give the traction curve. The disc is held in a bath containing a test lubricant so that the contact between the ball and flat is fully immersed. The ball shaft is aligned with respect to the disk so as to prevent spin in the contact and the slide-roll ratio is con-trolled independently by driving both the ball and the disk with separate motors. The disc and ball used for the experiments were made of steel (AISI 52100), with a hardness of 750 HV and Ra<0.02 μm. The diameter was 45.0 mm and 19.0 mm for the disc and the ball respectively. The tractions curves were run 38 Newton, 200 mm/s speed and 70° C. temperature.

[0120] The slide-roll ratio (“SRR”) was varied from 0 to 50 percent and the traction coefficient (“T.C.”) measured. The resulting diagram is shown in FIG. 1. The square line represents the data for the inventive diester of Example 2, and the triangular line the data for the Comparative Diester. This demonstrated the improved friction properties of the inventive diester.