DE1144864B - Lubricants for aircraft gas turbines - Google Patents

Description

The invention relates to lubricants for aircraft gas turbines, consisting of ester mixtures, which have been produced by one-step or multi-step esterification of the following compounds:

a) aliphatic monohydric alcohols or a mixture of such alcohols,

b) aliphatic dicarboxylic acids or a mixture of such acids and

c) a certain mixture of diols.

When such components are implemented in one or more stages, a mixture of the various ester products. The individual chain molecules present in the mixture do not show only a different chain length determined by statistical laws, but also a constitution, which can vary from molecule to molecule. Also this different constitution is subject to statistical principles, with a particularly large number of options if used as reaction component a), b) and / or c) mixtures of corresponding starting compounds will.

Certain ester blends made in this manner are well known as materials having lubricating and plasticizing properties. They are usually made by one of the following three methods: ~

1. One-step process in which all reactants together in the presence of a drag * be heated by means of water under the reflux condenser.

2. Two-step process in which the diol and the dicarboxylic acid together in the presence of a Entrainer for water are heated under the reflux condenser and then the product ßend is heated with alcohol under the reflux condenser.

3. Two-step process in which the alcohol and dicarboxylic acid are first put together in the presence of a Entrainer for water can be heated under the reflux condenser and then the product is heated with dicarboxylic acid under the reflux condenser.

However, the response of the three components can be broken down into any number of stages. These Production is not protected in the context of the present invention.

Regardless of the manufacturing process or the materials used, the product is a mixture obtained from different ester molecules.

It has now been found that by using certain diols in such ester mixtures of the above type Lubricants for aircraft gas turbines

Applicant:

The British Petroleum Company Limited,
London

Representative: Dr.-Ing. A. v. Kreisler, patent attorney,
Kohl, Deichmannhaus

Claimed priority: Great Britain of July 2, 1959 (No. 22 713)

Ronald Alfred Dean and Patrick Gould,

Sunbury-on-Thames, Middlesex (Great Britain),

have been named as inventors

the ester mixtures are given certain desirable properties so that they are particularly good for lubrication of aircraft gas turbines are suitable.

The invention therefore provides ester mixtures of the type described above for use as a lubricant for aircraft gas turbines, in which a mixture of tert-pentyl glycol is used as component c) and polyethylene glycol 200 is used. (Polyethylene glycol 200 is a commercially available mixture of polyethylene glycols with an average molecular weight of 200, consisting essentially of polyethylene glycols up to hexaethylene glycol, with tetraethylene glycol being the main component.)

The esters are preferably formed by a single or multi-stage esterification of the following compounds:

a) A monohydric aliphatic alcohol with 8 to 13 carbon atoms or a mixture such alcohols,

b) one or more of the following acids: azelaic acid, Sebacic acid and adipic acid,

c) a mixture of tert-pentyl glycol and polyethylene glycol 200

The most suitable monohydric alcohols are 3,5,5-trimethylhexanol, 2-ethylhexanol, isooctanol (as formed in the oxo process) or isotridecanol (as in the Oxo process formed).

The mixture of diols used in the preparation suitably contains not more than 90%, preferably not more than 75% ^(a uf a molar basis) of the individual components.

309 538/380

The molar ratio of monohydric alcohol to dicarboxylic acid to diol is expediently 2 to 10: 2: 0.5 to 5, preferably 2.2 to 10: 2: 1 to 2.

The type and amounts of the reactants are preferably to be chosen so that the ester formed is one Has a viscosity in the range from 3 to 15, in particular from 5 to 10 cSt at 99 ° C.

Below are some examples of the composition of the starting materials of the esters according to the invention given:

Raw materials

Ester A

Isooctanol 6.0 moles

Sebacic acid 3.0 moles

Polyethylene glycol 200 0.75 moles

tert-pentyl glycol 0.75 mol

Catalyst: NaHSO ₄ 6 g

Entrainer for water: benzene .. 120 cm ³

The starting materials are heated to 120 ° C. until a steady reflux of benzene is established. the The reaction is continued at 120 ° C until the acid number of the product has fallen to 0.4 mg KOH per gram. This occurs after 24 hours. The product is then distilled, initially at 20 mm Hg for removal the low boiling fractions, and then at 0.2 mm Hg up to the temperature at which the diester begin to transition. The end product has the following properties:

Kinematic toughness

at 99 ° C.
at 38 ° C.
at -40 ° C

7.79 cSt
38.00 cSt
1135OcSt

Ester A

specification
DERD 2487

0.596
0.623 (max.)

0.644
0.648 (max.)

Thermal stability

Percentage change in viscosity at 38 ° C after heating to 280 ° C for 6,12,18 and 24 hours after Test method according to specification DERD 2487, edition No. 3:

First rehearsal Second rehearsal 6 hours -3.6
-3.3
-4.6
-3.0 -1.2
-2.3
-3.1
-7.5 12 hours ........ 18 hours 24 hours

. Again, the counts are well within the specification DERD 2487 set limits.

The ester met, the conditions of the homogeneity test specification DERD 2487. The specification requires that the oil (50 cm ³⁾ was heated 1.5 hours to 28O ⁰ C, 18 hours - 54 ° C and then cooled for 7 days at room temperature is left standing. The oil must remain homogeneous throughout the entire time.

Ester B

Raw materials

Isooctanol 10.5 moles

Sebacic acid 3.0 moles

Polyethylene glycol 200 0.75 mol

ίο tert-pentyl glycol 0.75 mol

Catalyst: NaHSO ₄ 6 g

Entrainer for water: benzene .. 120 cm ³

The preparation is carried out in the same way as for ester A, with acidity after 24 hours of 0.7 mg KOH per gram is achieved. The product has the following properties:

Kinematic toughness

at 99 ° C 5.25 cSt

at 38 ° C 23.14 cSt

at -40 ° C 519OcSt

Raw materials

Ester C

Isooctanol

Sebacic acid

tert-pentyl glycol

Polyethylene glycol 200

Catalyst: NaHSO ₄

Entrainer for water: benzene

4MoI 2MoI 0.5 mol 0.5 mol 6g 120 cm ³

35

These viscosity values are well within the limits set out in the specification DERD 2487, edition No. 3, set out by the British Ministry of Supply for lubricants for aircraft gas turbines.

The production is carried out in the same way as for Ester A. After 7 hours an acidity of 0.3 mg KOH per gram is reached. The product has the following Characteristics:

viscosity

at 99 ° C ..
at 38 ⁰ C ..
at -40 ° C

7.53 cSt 36.16 cSt 10 54OcSt

ASTM vessels
99 to 38 ° CI 38 to -40 ° CI 99 to -40 ° C

45

0.626
0.639 (max.) The ester C fulfills the conditions of the homogeneity test according to specification DERD 2487. Its ASTM gradients are as follows:

99 to 38 ° C ..
38 to -4O ⁰ C
99 to -40 ° C

Raw materials

0.598 0.648 0.629

Ester D

55

60

Isooctanol 12 moles

Sebacic acid 6 moles

Polyethylene glycol 200 1.5 mol

tert-pentyl glycol 1.5 moles

Catalyst: NaHSO ₄ 12 g

Entrainer for water: benzene .. 200 cm ³

The preparation is carried out in the same way as for ester A. After 6 hours, the acidity is 0.5 mg KOH per gram reached. The product has the following viscosities:

99 ° C 7.33 cSt

38 ⁰ C 35.02 cSt

-4O ⁰ C 983 OcSt

To the advantage of using a mixture of tert-pentyl glycol and polyethylene glycol 200 as opposed to To illustrate the use of either diols alone, esters E and F are made as follows:

Ester E.
Raw materials

Isooctanol 2.8 moles

Sebacic acid 2.0 moles

tert-pentyl glycol 1.0 mole

Catalyst: NaHSO ₄ 2.4 g

Entrainer for water: benzene .. 125 cm ⁸

The production is carried out in the same way as for Ester A. After 13.5 hours an acidity of 0.9 mg KOH per gram is reached. The product has the following viscosities:

99 ° C 7.79 cSt

38 ° C 41.04cSt

-40 ⁰ C 1412OcSt

The product therefore does not meet the conditions of the homogeneity test.

Diol Kinematic -40 ° C Ester Tenacity in
Centistokes at 14120 tert-pentyl glycol 99 ° C E. Polyethylene glycol 200 7.79 11350 A. + tert-pentyl glycol Polyethylene glycol 200 7.79 9 830 D. + tert-pentyl glycol 10 900 Polyethylene glycol 200 7.33 F. Polyethylene glycol 200 6.97 10 540 C. + tert-pentyl glycol 7.53

15 The same was used in all of the above examples common practice is to use benzene as an entrainer for water during the esterification reaction. However, if the monohydric alcohol is used in excess in the reaction (as in the above Examples), it is not important that an additional entrainer is used for water, as that formed water can be taken away by the excess alcohol.

Ester F
Starting materials _go

Isooctanol 3.5 moles

Sebacic acid 2 moles

Polyethylene glycol 200 1 mole

Catalyst: NaHSO ₄ 1.2 g

Entrainer for water: benzene .. 75 cm ³

The production is carried out in the same way as for Ester A. After 13 hours an acidity of 0.6 mg KOH per gram is reached. The product has the following Viscosities:

99 ⁰ C 6.97 cSt

38 ⁰ C 33.09 cSt

-4O ⁰ C 10 90OcSt

45

A comparison of ester E, the tert.-pentyl glycol containing alone, resulting ester A that although both have a viscosity of 7.79 cSt at 99 ° C, however, that the ester diol mixture containing a significantly lower the viscosity at -40 ⁰ C has. Similarly, a comparison of ester D having an ester F, the polyethylene glycol 200 comprises only that of the glycol mixture containing esters at -40 ⁰ C has a lower viscosity, although the viscosity is significantly higher at 99 ⁰ C. In the same way, the ester C, which contains the diol mixture, at -40 ⁰ C a lower viscosity than the ester F, although its viscosity is substantially higher at 99 ⁰ C. These values are compiled in the following table.

Claims (6)

PATENT CLAIMS: 1. Lubricant for aircraft gas turbines, consisting of an ester mixture that is or multi-stage implementation of a) monohydric aliphatic alcohols, b) aliphatic dicarboxylic acids, c) diols, e.g. B. tert-pentyl glycol or its mixtures with other diols, has been obtained, characterized in that the reaction component (c) is a mixture of tert-pentyl glycol and polyethylene glycol 200. 2. Lubricant according to claim 1, characterized in that the molar ratio of the components (a): (b): (c) 2 to 10: 2: 0.5 to 5, preferably 2.2 to 10: 2: 1 to 2. 3. Lubricant according to claim 1 and 2, characterized in that the amount of tert-pentyl glycol or polyethylene glycol 200 not more than 90 mol percent, in particular not more than 75 mol percent, of the diol mixture and the two components in particular in equimolecular Relationship exist. 4. Lubricant according to claim 1 to 3, characterized in that it is monovalent as component (a) aliphatic alcohols with 8 to 13 carbon atoms and in particular 3,5,5-trimethylhexanol, 2-ethylhexanol, Contains isooctanol and / or isotridecanol. 5. Lubricant according to claim 1 to 4, characterized in that it is azelaic acid as component (b) Contains sebacic acid and / or adipic acid. 6. Lubricant according to claim 1 to 5, characterized in that it has a viscosity at 99 ⁰ C in the range from 3 to 15, in particular 5 to 10 cSt. © 309 538/380 2.63