DE1151084B - Lubricating oil for aircraft gas turbines - Google Patents

Description

Aircraft Gas Turbine Lubricating Oil The invention relates to synthetic ones Lubricants, in particular for lubricating aircraft gas turbines.

The subject of patent 1126 054 is a lubricating oil for aircraft gas turbines based on a mixture of diesters of aliphatic dicarboxylic acids and complex esters of the general formula R-OOC-R, - COO- (R2 OOC-R, -COO) nR (I) and / or HO - (R2 - OOC - R1 - COO) n - Ra - OH (II) where in these formulas R is an alkyl radical, R1 is the hydrocarbon radical of an aliphatic or aromatic diacid, R2 is the radical of a diol and n is a number up to 15. These lubricating oils according to the main patent are characterized in that at least one radical R2 in the complex esters is the radical of a 2,2-dimethylpropanediol-1,3 and that the total mixture also has a viscosity of 4 to 30 c5t at 99.degree. These complex esters require a sufficiently high viscosity over a wide temperature range and a relatively low pour point of the lubricating oil mixture. The mixtures show other important properties, e.g. B. good thermal stability.

The invention relates to a lubricating oil mixture, which is a further development is the subject of the main patent and further shows improved properties. According to the invention, this is the further development of the lubricating oil mixture described in that in the complex ester of the general formula R-OOC --- R1 --- COO --- (R2 - OOC - R1 - COO) n ---- R in which R, R1 and R2 have the general meanings given have at least one radical R2 instead of a 2,2-dimethyl-propanediol-1,3 radical is a 2-methyl-2-ethylpropanediol-1,3 radical.

Otherwise, the details of the main patent apply. In the complex star of the general formula I, R therefore in particular denotes alkyl radicals with 4 up to 18 carbon atoms and R1 is the hydrocarbon radical of an aliphatic or aromatic dicarboxylic acid, especially alkylene radicals having 4 to 14 carbon atoms. In the lubricating oil mixture, the complex esters are mixed with liquid aliphatic ones Diesters of saturated aliphatic dicarboxylic acids in which the specified Complex esters are soluble. The components of the mixture are used in such quantities used that the viscosity of the mixtures at 99 ° C in the range of 4 to 30 cSt lies. The viscosity at this temperature is preferably in the range of 4 up to 10 and especially at 6 to 10 cSt. The lubricant mixture according to the invention preferably contains 5 to 60, in particular 10 to 35 percent by weight of the complex ester.

The preferred diesters for use in the lubricant mixture according to the invention correspond to the general formula R400CR.COOR4 in which R, an alkylene radical with 4 up to 14 carbon atoms and R4 saturated aliphatic alkyl radicals with 4 to 18 Are carbon atoms and preferably with branched chains. The residues R4 can be the same or different.

Examples of suitable diesters are: di- (2-ethylhexyl) sebacate (dioctyl sebacate); Di- (3,5,5-trimethylhexyl sebacate) (dinonyl sebacate); 2-Ethylhexyl- (3,5,5-trimethylhexyl sebacate) (octyhaonyl sebacate) According to the invention, polyesters of the general formula 1 with a viscosity at 25 ° C. of at least 50, preferably at most 50,000, in particular at least 500, preferably at most 25,000 cSt preferred, especially those polyesters in which the radicals R 1 have 6 to 10, preferably 6 to 8 carbon atoms and are in particular the octamethylene radical.

Different R and Ri residues can be present in the respective polyester molecule different R4 residues in the respective diester molecule and mixtures of the different Polyester molecules and / or diester molecules can be in the same lubricant mixture be used.

Those suitable for use in the lubricant mixture according to the invention Polyesters of the general formula I can be carried out by processes known per se Implementation of the following components can be made in one or more stages: a) an acid or acids of the formula HOOCR1COOH or the anhydrides of such acids (as far as they exist, b) aliphatic monohydric alcohols of the formula ROH and c) 2-methyl-2-ethyl-propanediol-1,3. This diol is a commercially available product. In the given formulas R and R1 have the meaning given above. In general, the molar parts should of diol are at least half the molar parts of alcohol and all of them Molar parts of alcohols and diols must be greater than the molar part of acids.

As already mentioned, mixtures of different polyesters of the general formula I can be used in the lubricant mixture to produce the lubricant mixture, ie polyesters with different values of n and with different alcohol and acid residues can be present in the molecule. In such a mixture, of course, the average value of n need not necessarily be an integer. In the production of the polyester mixture, the constituents to be converted do not necessarily have to Table 1 Molar ratios of viscosity at 25 ° C Polyester 2-ethyl-2-methyl sebacic acid propane-1: 3-diol I propylene glycol 2-ethylhel cst P 10 ...... ..... 0.67 (0.67 - 0.07 17.500 P52 ........... 3.00 j - 2.85 0.90 3.060 The polyesters P 10 and P 52 both correspond the given general formula, but with the difference that in the polyester P 52 (which is given for comparison purposes), R2 the remainder of the are present in proportions of whole numbers.

Polyesters or their mixtures are preferred for the invention, in which n values up to 15, in particular. Has values up to 10.

Examples of acids and alcohols used in the manufacture of the polyester can be used are aliphatic dicarboxylic acids, such as adipic acid, pimelic acid, Suberic acid, azelaic acid and brassylic acid, and / or aromatic dicarboxylic acid, e.g. B. phthalic acid. Sebacic acid has proven to be particularly suitable. As alcohols are for example 2-ethylhexyl alcohol, 2-ethylbutyl alcohol, cetyl alcohol, tertiary Pentyl alcohol and trimethyl nonyl alcohol are suitable. 2-Ethylhexyl alcohol is particularly preferred.

If desired, any suitable antioxidant for the lubricant, for example phenothiazine, can be added to the mixture. Example The polyesters P 10 and P 52 are produced from the components specified in Table 1 in the following way: The reaction components are introduced into a three-necked flask which is provided with a stirrer, a feed pipe for nitrogen and a vertical condenser heated with steam, to which a downward-facing water cooler is connected. Nitrogen is blown in at a rate of about 51 per hour and heated as follows (internal temperatures): The contents of the flask are quickly brought to 130 ° C. and held there for 4 hours. After the reaction has been continued at temperatures of 150, 180 and 200 ° C. for 2 hours each, the distillate is collected and the upper layer of 2-ethylhexyl alcohol is returned to the flask. The diol content of the lower layer is calculated from a refractive index determination, and after a corresponding amount has been added to the flask, the mixture is heated to 240 ° C. until the acid number has fallen below 5 mg KOH / g. At this point the pressure is reduced to 17 mm Hg and the reaction is continued at 240 ° C. until the acid number has fallen below 1 mg KOH / g.

The composition and properties of the polyesters are given in Table 1: Propylene glycol, ie the remainder. These polyesters are blended with octyl nonyl sebacate (ONS) and phenothiazine to form Blends B 10 and B 52, which have the composition and properties described in the table below. Table 2 Mixture components Thermal stability at 300 ° C Weight percent low temperature Mixture 1 behave anti-increase in viscosity change ONS polyester oxidation- the neutralization value at 37.8 ° C I medium mg KOt-Lg ° / o I. B 10 87.16 11.84 j 1.0 6.4 after 2 hours -5.19 after 2 hours Viscosity 9500 cSt (P 10) 16.3 after 5 hours -8.42 after 5 hours at -40 ° C B52 82.2 16.8 1.0 27.3 after 2 hours -21.0 after 2 hours immobile (P 52) 30.1 after 23/4 hours at -40 ° C y After pre-cooling to -55 ° C for 12 hours. It can be seen from the table that the mixture (B 10) according to the invention shows a greatly improved thermal stability in comparison with the mixture B 52 which contains the polyester P 52 using propylene glycol. (The thermal stability is indicated by a slight increase in the neutralization value and a slight change in viscosity after a high-temperature treatment). In addition, mixture B 10 shows excellent low-temperature behavior, while mixture B 52 is practically unusable at these low temperatures. The viscosity of mixture B 10 is 7.80 cSt at 98.9 ° C and 36.44 cSt at 37.8 ° C.

The low-temperature behavior of the mixtures according to the invention can can be further improved by the addition of anti-crystallization agents. Can be used e.g. B. polymerized alkyl esters of acrylic or methacrylic acid, however, it is advantageous if it has good low-temperature behavior without the addition Such means can be achieved as this has an adverse effect on both the thermal stability as well as the shear stability of the mixtures.

It is true that there is only one way of producing those used according to the invention Polyester described, but these can of course also be replaced by other customary Methods, e.g. B. by the glycol half ester method, in which acids and glycol first under suitable conditions to a compound of the general formula HOOCR1C00 (R. "OOCR1C00) nH and subsequent conversion of the terminal acid groups with monofunctional ones Alcohols are produced.

Claims (1)

PATENT CLAIM: Lubricant for aircraft gas turbines based on a mixture of diesters of aliphatic dicarboxylic acids and complex esters of the general formula R-OOC-Rl-COO - (R2 OOC-Rl -COO) nR in which R is an alkyl radical, R1 the hydrocarbon radical of an aliphatic or aromatic Dicarboxylic acid, R, the remainder of a diol mixture which contains at least one remainder of a 2,2-dimethylpropanediol-1,3 and n is a number up to 15 and the viscosity of the mixture is 4 to 30 cSt at 99 ° C, according to patent 1126 054, characterized in that at least one radical R2 in the complex ester is the radical of a 2-methyl-2-ethylpropanediol-1,3 instead of the 2,2 dimethylpropanediol radical.