DE1159581B - Ester-based lubricating oils - Google Patents

Description

It is known to add free dicarboxylic acids to mineral-based lubricating oils in order to increase their pressure absorption capacity and to improve resilience in harsh working conditions. Such an addition of free dicarboxylic acids is also used for synthetic lubricating oils on the basis of Esters of dibasic carboxylic acids have been recommended.

In contrast, the invention relates to lubricating oils, which essentially consist of another Basis, namely from liquid neutral esters of polyhydric alcohols and aliphatic monocarboxylic acids exist or contain a larger proportion of these esters. The word "neutral" is in that Meaning to understand that all hydroxyl groups of the polyhydric alcohol with the monocarboxylic acid are esterified. Esters of this type are known as substances with lubricating properties.

Certain esters of the type mentioned have lubricating properties that they use in almost every way Make lubrication of aircraft gas turbines suitable. However, they are quite corrosive to cadmium. This is a disadvantage since aircraft gas turbine lubricants usually contain cadmium in use Come into contact.

It has been found that the corrosion of cadmium can be reduced by esters of the type mentioned by adding small amounts of certain additives to them.

The invention therefore relates to ester-based lubricating oils with a low dissolved content free carboxylic acids, which are characterized in that the base is a for use as a synthetic Lubricating oil known neutral ester of polyhydric alcohols and aliphatic monocarboxylic acids and the free carboxylic acid is an aliphatic 3S di- or tricarboxylic acid with 4 to 12 carbon atoms, these in an amount of 0.001 to 0.15 percent by weight, based on the total lubricating oil, is present.

Here, the range mentioned for the added amounts of carboxylic acid includes in its upper range Limit the amounts of carboxylic acid that can normally be found in the lubricant base according to the invention to solve.

It should be noted that the neutral ester, which makes up the greater proportion by weight of the lubricant, can consist of a mixture of different ester molecules of the type described and that any given ester molecule can contain the residues of various monocarboxylic acids. With others In other words, the neutral ester can consist of the product obtained by esterifying one or more

Applicant:

The British Petroleum Company Limited,
London

Representative: Dr.-Ing. A. v. Kreisler,

Dr.-Ing. K. Schönwald, Dr.-Ing. Th. Meyer

and Dipl.-Chem. Dr. rer. nat. J. F. Fues,

Patent attorneys, Cologne 1, Deichmannhaus

Claimed priority:
Great Britain May 4, 1960 (No. 15 726)

Patrick Gould and Joyce Margery Hunt,

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

have been named as inventors

polyhydric alcohols with one or more aliphatic monocarboxylic acids.

It is particularly advantageous to use neutral esters of the above type in the lubricant, which are made from the following raw materials:

Polyhydric alcohols: ethylene glycol, propylene glycol, tert-pentyl glycol, 2-methyl-2-propyl-1,3-propanediol, Polyethylene glycol 200, trimethylolethane, trimethylpropane, pentaerythritol, dipentaerythritol, tripentaerythritol. Polyethylene glycol 200 is a commercially available mixture of polyethylene glycols with a average molecular weight of 200, consisting essentially of polyethylene glycols to hexaethylene glycol consist, with tetraethylene glycol being the main component. Polyhydric alcohols that are no Have hydrogen atom on any carbon atom in / 3-position to any hydroxyl group, proved to be particularly suitable for the production of esters, which are used as lubricants for aircraft gas turbines or components of these lubricants are suitable.

Monocarboxylic acids: aliphatic C ₂ -C ₁₀ acids, e.g. B. pelargonic acid, 2-ethylhexanoic acid, n-heptanoic acid, n-octanoic acid, isooctanoic acid, n-decanoic acid and propionic acid.

Most suitable neutral esters, in whose preparation the components are selected such that a product is obtained having a viscosity at 99 ⁰ C in

309 769/407

Range from 1 to 7, especially from 2 to 5 cSt. Certain esters of this type are suitable raw materials for aircraft gas turbine lubricants of the type used for U.S. Military Specifications MIL-L-7808C and MIL-L-9236 is required. These specifications call for a relatively thin oil. Thicker oils, such as, for example, according to the specifications DERD 2487 and DERD 2497 of the British Ministry of Aviation required can be obtained by thickening said neutral esters with more complex esters or polyesters consisting of a polyhydric alcohol and a dicarboxylic acid or from a polyhydric alcohol, a dicarboxylic acid and either a monohydric alcohol or a Monocarboxylic acid. The aforementioned polyhydric alcohols and monocarboxylic acids are also suitable for the production of these polyesters. Suitable dicarboxylic acids are aliphatic dicarboxylic acids with 6 to 10 carbon atoms, in particular sebacic acid, azelaic acid, Adipic acid and technical isosebacic acid. Suitable monohydric alcohols are monohydric aliphatic alcohols with 8 to 13 carbon atoms, in particular 2-ethylhexanol, isooctanol (as is the case, for example, with the Oxo process is obtained), 2,2,4-trimethylpentanol, 3,5,5-trimethylhexanol and isotridecanol (as in Oxo process occurs). A mixture of different polyesters can also be used as a thickening agent mentioned type can be used.

The free carboxylic acids used in the lubricant according to the invention can be straight-chain, branched or alicyclic, but preferably no other than the carboxylic acid groups contain functional groups. Succinic acid, sebacic acid, Butane-1,2,4-tricarboxylic acid and cyclohexane ~ 2,3-dicarboxylic acid.

The preparation of the esters given below is carried out by customary processes and is not here placed under protection.

example 1

A neutral triester is made from the following raw materials:

1,1,1-trimethylolpropane (2 moles) 268 g

n-octanoic acid (6.6 moles) 950.4 g

Toluene (water carrier) 100 cm ³

Catalyst 2 g

The catalyst used is a crystalline sodium aluminum silicate which has been heated to remove the water of hydration. It has a pH of up to 10.5 and a pore size of 4 Å. The catalyst is activated before use by heating it in an oven for 3 hours at 25O ⁰ C.

The feedstocks are refluxed with stirring for about hours. The water that forms during the reaction is removed. The highest temperature reached during this time is about 260 ⁰ C. The product is filtered off on a water jet pump to a bath temperature of 200 ° C to remove toluene and excess acid to. The Rohester is washed by at 6O ⁰ C for 45 minutes with 500 cm ³ of a 10% sodium carbonate solution and 500 cm ³ of isopropanol is stirred; it is then filtered and the aqueous layer is separated off. The Esterschicht is washed five times with 500 cm ³ of distilled water for 15 minutes at 6O ⁰ C. To facilitate the separation, 300 cm ^{3 of} n-heptane are added to the last wash. Finally, the ester is again stripped with a water jet pump up to a bath temperature of 200 ° C and then with an oil pump up to the boiling point of Trieste (206 ° C / 0.6 mm).

Part of the Trieste is subjected to the British Ministry of Aviation's cadmium corrosion test. Various free carboxylic acids were added to other parts that were also used in the cadmium corrosion test be subjected. The results of the test as well as the information about the used Additives are listed in Table 1.

Table 1 Added carboxylic acid Weight r \ U SoCl ICl 1 in percent by weight ver modification iridescent spots, in mg / cm ^s low black -1.0 Covering only slightly fogged up 0.01 sebacic acid only slightly fogged up 0.01 succinic acid + 0.03 + 0.03

In either case, the lubricant contains 1 percent by weight phenthiazine as an antioxidant.

Example 2

The base oil used is neopentyl glycol dipelargonate, which is mixed with one of azelaic acid and neopentyl glycol produced polyester had been thickened. The mixture contains 70 percent by weight neopentyl glycol dipelargonate and 30 percent by weight of the polyester. The mixture is 1 weight percent phenthiazine added. The results of the cadmium corrosion test are shown in Table 2.

Table 2

45

Added as an additive
Carboxylic acid in percent by weight Weight
modification
inmg / cm ² Appearance 0.01 butane-1,2,4-tricarbon
acid -15.2 etched
fog up

50

Example 3

1,1,1-trimethylolpropane triisooctanoate is used as the base oil, which is thickened with the same polyester as in Example 2 to a mixture that is 90.7 percent by weight 1,1,1-trimethylolpropane triisooctanoate and contains 9.3 percent by weight of the polyester. 1 percent by weight phenthiazine is added to the mixture. The results of the cadmium corrosion test are shown in Table 3.

65

Table 3

Carboxylic acid additive
in percent by weight Weight
modification
inmg / cm ² Appearance 0.01 cyclohexane-1,3-di-
carboxylic acid -6.80 etched
fog up

Claims (1)

5 6 The results given in Tables 1, 2 and 3 were tested. The sample will be taken while she is clearly illustrate the effectiveness of being open at the top in an oil bath for 22 hours Inhibitors of the corrosion of cadmium added 140 ± I ⁰ C heated while it is stirred. Of the Carboxylic acids. Strip is weighed before and after the test. the The surface described in Examples 2 and 3 is after the test for staining, The polyester used in experiments is tested for corrosion and erosion as follows. The acidity and posed: the viscosity of the sample will be before and after Test measured. The change is noted. By Starting materials used: _{Addition of free} carboxylic acids to prevent the Neopentyl glycol 2.8 mol i ° corrosion of cadmium will not reduce the acidity Azelaic acid 2 0 moles changed significantly and the viscosity usually slightly lowered. Alcohol and acid are heated together under nitrogen at 200 ⁰ C under stirring, wherein the located CLAIMS: water formed is removed. At the end of the reac- 15 tion, a small amount of benzene is added to 1. Ester-based lubricating oils with a small amount of the last traces of water as an azeotropic mixture containing dissolved free carboxylic acids, thereby removing benzene. The product is identified by the fact that the base is a water jet pump up to a maximum bath known per se neutral ester from polyvalent temperature of 200 ⁰ C and then 6 hours at a 20 alcohols and aliphatic monocarboxylic acids pressure of 0.5 mm and a bath temperature of and the free carboxylic acid an aliphatic di-200 ° C sucked off. The stripped material is or tricarboxylic acid having 4 to 12 carbon atoms is three times with 300 cm ³ of water at 6O ⁰ C and in an amount of 0.001 to 0.15 wt washed for 30 minutes and then 3 ¹ J ₂ hours at 25 to 40 ⁰ C. at percent, based on the total lubricating oil, before a pressure of 0.5 mm and finally 1 hour 25. stripped at 190 ^° C. and 0.5 mm. The product has 2. Lubricating oils according to claim 1, characterized in that the free carboxylic acid amber kinematic ^{viscosity acid} f 'glutaric acid, sebacic acid, butane-l, 2,4-tri-,. _QQO . .... "carboxylic acid and / or cyclohexane ^ -dicarbon- ^{D (Myy} _o ^C H4, ucs> t ₃₀ acid is. at 38 ⁰ C 1 927 cSt 3. Lubricating oils according to claim 1 and 2, characterized ASTM gradient 0.516 marked that it was additionally a lower one Acid number 1.1 mg KOH / g amount of a complex ester or a polyester, made from a polyhydric alcohol and The Ministry of Avi-35 cadmium corrosion test of a dicarboxylic acid or a polyvalent one ation requires that the weight change in mg / cm ² alcohol, a dicarboxylic acid and either one must not be more than ± 0.2 and that no monohydric alcohol or a monocarboxylic acid, visible corrosion or severe staining or contain. Blackening may be present. The test will be like Carried out as follows: A cadmium-plated steel 4 ° Considered publications: strip in 400 cm ^{3 of} the German Auslegeschriften Nos. 1 063 311, 1 084 411 in a beaker. © 309 769/407 12.63