ANTIOXIDANT MIXTURE FOR HIGH VISCOUS POLYALKYLENE GLYCOL BASESTOCK

Abstract

The invention relates to a lubricant comprising a polyalkylene glycol basestock, a phenol selected from an ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with a C.sub.1-18 aliphatic alcohol, and an aromatic amine of the formula (I) as defined hereinafter. The invention further relates to a method for preparing the lubricant comprising the step of contacting the polyalkylene glycol basestock, the phenol, and the aromatic amine of the formula (I); and to a method for reducing the oxidative degradation of the polyalkylene glycol basestock comprising the step of contacting the polyalkylene glycol basestock, the phenol, and the aromatic amine of the formula (I).

Claims

1.-15. (canceled)

16. A lubricant comprising a polyalkylene glycol basestock, a phenol selected from an ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with a C.sub.1-18 aliphatic alcohol, and an aromatic amine of the formula (I) ##STR00006## wherein R1 and R2 are H or together represent the group A ##STR00007## and R3 and R4 are independently H or C.sub.2-C.sub.30 alkyl.

17. The lubricant according to claim 16, where the phenol is an ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with methanol, ethanol, n-octanol, isooctanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, pentaerythritol, trimethylhexanediol, trimethylolpropane.

18. The lubricant according to claim 16, where the phenol is an ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with isooctanol or 1,6-hexanediol.

19. The lubricant according to claim 16, where the polyalkylene glycol basestock has a kinematic viscosity at 40° C. in the range from 500-3000 mm.sup.2/s.

20. The lubricant according to claim 16, 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.

21. The lubricant according to claim 16, where the polyalkylene glycol basestock is an ethoxylated and propoxylated C.sub.2-C.sub.8 alkandiol.

22. The lubricant according to claim 16, where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 500 to 50 000 Da.

23. The lubricant according to claim 22, where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 1000 to 20000 Da.

24. The lubricant according to claim 23, where the polyalkylene glycol basestock is an alkoxylated alcohol with a number average molecular weight Mn in the range from 3000 to 10000 Da.

25. The lubricant according to claim 16, where R1 and R2 together represent the group A, R3 is H, and R4 is C.sub.2-C.sub.30 alkyl.

26. The lubricant according to claim 25, where the phenol is an ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with 1,6-hexanediol or with isooctanol.

27. The lubricant according to claim 16, where R1 and R2 are H, and R3 and R4 are independently C.sub.2-C.sub.30 alkyl.

28. The lubricant according to claim 27, where the phenol is an ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with octadecanol.

29. The lubricant according to claim 16, where R3 and R4 are indepen-dently H or n-propyl, isopropyl, n-, iso-, or tert.-butyl, n-pentyl, isoamyl, neopentyl, 2-ethyl-butyl, n-hexyl, 1-methylpentyl, 1,3-dimethylbutyl, n-heptyl, isoheptyl, n-octyl, 1,4,4-trime-thyl-2-pentyl, 3,4-, 3,5- or 4,5-dimethyl-1-hexyl, 3- or 5-methyl-1-heptyl, 1,1,3,3-tetra-methylbutyl, 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.

30. The lubricant according to claim 16, where the weight ratio between the phenol and the aromatic amine is from 1.5:1 to 1:1.5.

31. The lubricant according to claim 16, where the weight ratio between the phenol and the aromatic amine is from 2:1 to 1:2.

32. The lubricant according to claim 16, where the weight ratio between the phenol and the aromatic amine is from 5:1 to 1:5.

33. A method for preparing the lubricant as defined in claim 16 comprising the step of contacting the polyalkylene glycol basestock, the phenol, and the aromatic amine of the formula (I).

34. A method for reducing the oxidative degradation of the polyalkylene glycol basestock as defined in claim 16 comprising the step of contacting the polyalkylene glycol basestock, the phenol, and the aromatic amine of the formula (I).

Description

EXAMPLES

[0079] PAG Basestock: random ethoxylated and propoxylated 1,4-butandiol, 60 wt.-% ethylene oxide units, Mn about 6500 g/mol (based on OH number), KV40 about 1100 mm.sup.2/s, KV100 about 200 mm.sup.2/s. [0080] 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]. [0081] Phenol Antioxidant A: ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with isooctanol. [0082] Phenol Antioxidant C: ester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with 1,6-hexanediol.

Example 1

[0083] The lubricants samples (each 30 g) contained the PAG basestock and 0.75 wt % of the Phenol 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 B 0.75  0.75 Phenol Antioxidant A 98.75 — Phenol Antioxidant C — 98.75

Example 2

[0084] The lubricants 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 0 100 100 2 97 96 4 93 94 8 86 88 10 81 81

[0085] The data showed, that there was no increase and only a low decrease in viscosity due to decomposition of the polyalkylene glycol basestock.