ANTIOXIDANT MIXTURE FOR LOW VISCOUS POLYALKYLENE GLYCOL BASESTOCK

Abstract

The invention relates to a lubricant comprising a polyalkylene glycol basestock, an aromatic amine of the formula (I) as defined hereinafter, and a thioether of the formula (II) as defined hereinafter. The invention further relates to a method for preparing the lubricant comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II); and to a method for reducing the oxidative degradation of the lubricant comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II).

##STR00001##

Claims

1.-14. (canceled)

15. A lubricant comprising a polyalkylene glycol basestock, an aromatic amine of the formula (I) ##STR00008## wherein R1 and R2 are H or together represent the group A ##STR00009## and R3 and R4 are independently H or C.sub.2-C.sub.30 alkyl, and a thioether of the formula (II) ##STR00010##

16. The lubricant according to claim 15, comprising 0.05-5 wt % of the aromatic amine.

17. The lubricant according to claim 16, comprising 0.5-1.0 wt % of the aromatic amine.

18. The lubricant according to claim 15, comprising 0.05-5 wt % of the thioether.

19. The lubricant according to claim 18, comprising 0.5-1.0 wt % of thioether.

20. The lubricant according to claim 15, where the weight ratio between the thioether and the aromatic amine is from 1.5:1 to 1:1.5.

21. The lubricant according to claim 20, where the weight ratio between the thioether and the aromatic amine is from 5:1 to 1:5.

22. The lubricant according to claim 15, where the polyalkylene glycol basestock has a kinematic viscosity at 40° C. in the range from 10-300 mm.sup.2/s.

23. The lubricant according to claim 15, where the polyalkylene glycol basestock is an ethoxylated and propoxylated C.sub.1-C.sub.20 alkanol or C.sub.2-C.sub.20 alkandiol.

24. The lubricant according to claim 15, where the polyalkylene glycol basestock is an ethoxylated and propoxylated C.sub.1-C.sub.8 alkanol.

25. The lubricant according to claim 15, where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 400 to 10 000 Da.

26. The lubricant according to claim 15, where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 1000 to 1500 Da.

27. The lubricant according to claim 23, where the alkoxylated alcohol contains 30 to 70 wt-% ethylene oxide units, and 70 to 30 wt-% of propylene oxide units.

28. The lubricant according to claim 15, where R1 and R2 together represent the group A, R3 is H, and R4 is C.sub.2-C.sub.30 alkyl.

29. The lubricant according to claim 15, where R1 and R2 are H, and R3 and R4 are independently C.sub.2-C.sub.30 alkyl.

30. The lubricant according to claim 15, where R3 and R4 are independently H or n-propyl, isopropyl, n-, iso-, or tert-butyl, n-pentyl, isoamyl, neopentyl, 2-ethylbutyl, n-hexyl, 1-methylpentyl, 1,3-dimethylbutyl, n-heptyl, isoheptyl, n-octyl, 1,4,4-trimethyl-2-pentyl, 3,4-, 3,5- or 4,5-dimethyl-1-hexyl, 3- or 5-methyl-1-heptyl, 1,1,3,3-tetramethylbutyl, 2-ethylhexyl, branched octyl, branched octyl as obtained from a dimer of isobutylene, n-nonyl, 1,1,3-trimethylhexyl, branched nonyl as obtained from a trimer of tripropylene, 1-methylundecyl, 2-n-butyl-n-octyl, branched dodecyl obtained from a trimer of isobutylene or a tetramer of propylene, branched pentadecyl obtained from a pentamer of propylene, 2-n-hexyl-n-decyl or 2-n-octyl-n-dodecyl.

31. A method for preparing the lubricant as defined in claim 15 comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II).

32. A method for reducing the oxidative degradation of the polyalkylene glycol basestock as defined in claim 15 comprising the step of contacting the polyalkylene glycol basestock, the aromatic amine of the formula (I), and the thioether of the formula (II).

Description

EXAMPLES

[0076] PAG Basestock: random ethoxylated and propoxylated butanol, 50 wt-% ethylene oxide units, Mn about 1200 g/mol (based on OH number), KV40 about 50 mm.sup.2/s, KV100 about 10 mm.sup.2/s. [0077] Amine Antioxidant A: aromatic amine of the formula (I), where R1 and R2 are H, and R3 and R4 comprise independently branched octyl, included in CAS [68411-46-1]. [0078] Amine Antioxidant B: aromatic amine of the formula (I), where R1 and R2 together represent the group A, R3 is H, and R4 is branched octyl, CAS [51772-35-1]. [0079] Thioether Antioxidant: thioether of the formula (II).

Example 1

[0080] The lubricants samples (each 30 g) contained the PAG basestock and 0.75 wt % of the Thioether Antioxidant and the 0.75 wt % of the Amine Antioxidant as described in Table 1.

TABLE-US-00001 TABLE 1 Composition of lubricant (data in wt %) Lubricant A Lubricant B PAG Basestock 98.75  98.75  Amine Antioxidant A 0.75 — Amine Antioxidant B — 0.75 Thioether Antioxidant 0.75 0.75

Example 2

[0081] The lubricant samples (each 30 g) from example 1 were stored for several weeks at 150° C. in an open flask without stirring in the presence of a round copper blank (1 mm thick, 16 mm diameter, about 2 g). The KV40 was determined and the results summarized in Table 2. The KV40 before heating was set as 100%.

TABLE-US-00002 TABLE 2 Evaluation of the KV40 [%] on storage at 150° C. Weeks Lubricant A Lubricant B 0 101 101 2 105 103 4 103 98 8 106 104 10 102 102

[0082] The data showed, that there was only minor increase or decrease in viscosity due to 5 decomposition of the polyalkylene glycol basestock.