DE1135605B - Lubricants and hydraulic fluids for high operating temperatures - Google Patents

Description

GERMAN

PATENT OFFICE

S67357IVc / 23c

REGISTRATION DATE: 29th F E B RU AR 1960

NOTICE
THE REGISTRATION
ANDOUTPUTE
EDITORIAL: AUGUST 30, 1962

The usual hydrocarbon lubricants do not correspond to the harsh working conditions of modern machines, engines and equipment, which work at temperatures above 200 ^° C. As a result, many new, non-hydrocarbon, high temperature lubricants have been produced. These include silicone fluids, esters of polycarboxylic acids and aliphatic alcohols, as well as polyalkylene glycols and their ether derivatives. Because of their resistance to oxidation and thermal decomposition under severe working conditions, fluorocarbons have also been proposed as high temperature lubricants. However, because of their high temperature coefficients for viscosity and because of the high freezing points, they are of minor importance in practice.

Another class of organic fluorine compounds which have good viscosity and freezing properties and which are also quite resistant to oxidation, pyrolysis and hydrolysis, include those compounds that are formed by the esterification of fluoroalcohols and only recently Time have become accessible.

However, in spite of the production of a large number of such fluoroesters, none of them combined the lubricity, thermal resistance and those required for high temperature lubricants Viscosity properties.

It has now been found that a specific group of fluoroesters or mixtures thereof Esters have exceptional physical and chemical resistance and good lubricating properties even at low temperatures and is particularly suitable for use as a lubricant and oxidation-resistant hydraulic fluid at high operating temperatures.

According to the invention, an ester of a benzene polycarboxylic acid of the general formula is used for this purpose

(ROOC) ₁₁ -:

- [COOR '(CF ₂ ) ^ X] ₆

in which R is an alkyl radical, R 'is a saturated divalent organic radical and X is hydrogen or fluorine and η is an integer from 1 to 24, while both α and b are integers from 1 to 3 and the sum {a + b ) has the value 3 or 4, or mixtures of such esters are used.

Preference is given to using esters in which R in the structural formula above is a methyl group and / or R 'represents a methylene group.

Esters in which η in the structural formula is a number from 2 to 10 are particularly suitable.

Lubricants and hydraulic fluids for high operating temperatures

Applicant:

Shell

International Research Maatschappij N.V., The Hague

Representative: Dr. K. Schwarzhans

and Dr. E. Jung, patent attorneys,

Munich 19, Romanplatz 10

Claimed priority:
V. St. v. America, March 2, 1959 (No. 796 254)

William Walter Reynolds, East Alton, IU. (V. St. A.), has been named as the inventor

In the context of the invention, preference is given to using those esters in which b in the structural formula given has the value 1 or 2.

The reason why compounds with R 'as the methylene group are preferred is because of the improved Heat and oxidation resistance of the -hydrogen atoms in an ester substituent in comparison to the chain hydrocarbons, which are further removed from the oxygen bond. For the same reason methoxycarbonyl groups are preferred to other alkoxycarbonyl groups.

There are three isomeric forms of benzenetricarboxylic acid: Trimellitic acid (benzene-1,2,4-tricarboxylic acid), hemimellitic acid (benzene-1,2,3-tricarboxylic acid) and trimesic acid (benzene-1,3,5-tricarboxylic acid). The benzene tetracarboxylic acid also exists in three isomers Forms, namely pyromellitic acid (benzene-1,2,4,5-tetracarboxylic acid), mellophanic acid (benzene-1,2,3,5-tetracarboxylic acid) and prehnitic acid (benzene-1,2,3,4-tetracarboxylic acid).

Although all six acids are equally suitable for making the new esters, will but the tricarboxylic acids are preferred because their fluoroesters have slightly lower pour points. For this Trimellitic acid is again very particularly preferred from the series of the compounds mentioned.

209 63S / 358

3 4

The new esters can be derived from being distilled by being carried out at atmospheric pressure

the formula H (CF ₂₎ »ROH fluorine labeled methanol at about 65 ⁰ C from. It is convenient that

alcohols that can be produced by being in reaction at temperatures between the boiling point

the USA.-Patent 2,559,628 described type of methanol and the boiling point of the relevant prove. You can perform generally described 5 fluoroalcohols. For the preferred

are called α, α, ω-Trihydroperfluoroalkotiole. Examples class of fluoroalcohols, namely the α, α, ω-trihydro-

for these alcohols are: perfluoroalcohols, this highest temperature is at

2,2-difluoroethanol; «,«, W-trihydrotetrafluoropropane atmospheric pressure in the order of 100 to

nol; ",", Cu-trihydrooctafluoropentanol; «,«, Co-Trihy- 200 ° C. If the reaction takes place at above atmospheric pressure droperfluoroheptyl alcohol; «,«, Ta-Trihydroperfluorno- io is carried out, serves as the upper temperature limit

nyl alcohol and ",", co-trihydroperfluorundecyl alcohol. the decomposition temperature of the reaction components.

The fluoroalcohols with the formula F (CF ₂ ) MROH The fluoroalcohols and the benzoyl carboxylic acid esters

are also for the ^; Preparation of the new esters are expedient in the presence of a catalytic

suitable. They can be described as «, α-Di amount of a strong acid converted under the hydroperfluoro alcohols. A typical example of a 15 reaction condition is non-volatile, such as hydrochloric acid,

Such a-dihydroperfluoro alcohol is trifluoroetha-phosphoric acid and sulfuric acid. Of these are

nol, CF ₃ CH ₂ OH. According to the literature, this is already amounts of only 0.1 percent by weight (calculated

Alcohol 10 ⁴ times more acidic than ethanol. Other Aiko- on the total amount of the reaction components)

hole of this type are z. B. α, α-Dihydroperfluorpro- effective, while 0.5 to 5 percent by weight preferred panol; α, α-dihydroperfluorobutanol; α, α-dihydroper-20 can be used.

fluoropentanol; «,« - dihydroperfluoroheptanol. During the implementation, inert diluents

Preferred representatives of both groups are: α, α, ω- medium can be used, in soft preferably

Trihydro- and «, a-dihydroperfluoroalkanols of which both the reaction components and the

Polyhydroperfluoropropanols are soluble up to the polyhydro-settlement products, for. B. Benzene and the perfhiorundecanols. Such alcohols with relative paraffins, especially those that have a little over

moderately low molecular weight results in fluorinated esters, the boiling point of the reaction components

which have the favorable combination of viscosity and boiling point.

Volatility, Lubricity and Heat Resistance The polyfluoroester formed can after completion

exhibit. the reaction can be isolated by the The new esters can be 30 reaction mixture with water or aqueous alkali according to a known method

are made by reacting polyalkyl mixed to remove the acidic catalyst,

esters of benzene polycarboxylic acids with the concerned then dries and removes the water

fenden polyhydroperfluoroalcohol in the presence of the mixture finally distilled to the remaining

catalytic amount of a strong acid. To separate the reaction components from the fluoroester.

Alkanol formed in the reaction is continuously converted from 35 Of course, other cleaning agents can also be used.

removed from the reaction mixture. methods are applied.

As a reaction participant in the transesterification campaign The new esters are light-colored, non-volatile, the methyl esters of the acids described are thin to fairly viscous at room temperature preferred because the resulting methanol is easily made up of substances. Benzene tridem are preferred Reaction mixture can be removed and dimethylpolyhydroperfluorallem derived from 40 carboxylic acids also because of the exceptionally cheap alkyl esters, which are obtained by reacting with, α, ω-trihydric the methyl fluoroalkyl polycarboxylate. perfluoroalkanols or with α, α-dihydroperfluoro-die Methyl esters themselves can be made by alkanols, e.g., trimellite Reacting the benzene polycarboxylic acid with dimethyl l, l, 3-trihydroperfluoropropyl ester; Trithanol in the usual way or by reacting the 45 mellitic acid dimethyl-lJjS-trihydroperfluoropentyl ester, Methanol with an anhydride of acid. Example- dimethyl trimesic acid 1,1,7-trihydroperfluoroheptyl manner the dimethyl monofluoroester can be a benzene ester; Trimesic acid dimethyl-1,1,9-trihydroperfluorotricarboxylic acid are made by applying nonylester; Mellitic acid dimetnyi-Ul ^ -trihydroperabout one mole of the fluoroalcohol and about one fluorobutyl ester; and mellitic acid dimethyl-l, l, 6-tri-MoIs of the benzenetricarboxylic acid ester in the case of the hydroperfluorohexyl ester and the corresponding diesterification reaction. Similarly, the hydro links. "Because of their asymmetry and the Monomethyl difluoro ester of benzene tricarboxylic acid- related low pour points are made by reacting about 2 moles of the dimethyl esters of polyhydroperfluoroalkyl fluoroalcohols with one mole of trimethylbenzene trimellitic acid particularly preferred, tricarboxylate. The trimethyl monofluoroester of a 55 case derived from benzene tetracarboxylic acids Benzene tetracarboxylic acid can be easily prepared from esters, preferably at least 2 of the esters Represent 1 mole of the fluoroalcohol and 1 mole of tetra-substituted methoxycarbonyl radicals. In methyl tetracarboxylate. ' this group of compounds can be the polyhydro- The reaction can be the same or different at atmospheric, over-perfluorocarbonyl groups, atmospheric or sub-atmospheric pressure 60 Examples of suitable compounds are: be performed. Because of the simplicity of the pyromellitic acid dimethyl-di- (l, l, 3-trihydroperfluoro process are just common devices and propyl) esters; Pyromellitic acid dimethyl-di- (l, l, 4-tri-working measures necessary. hydroperfluorobutyl) ester; Dimethyl pyromellitic acid - The methyl esters of benzene polycarboxylic acids are di- (l, l, 5-trihydroperfluoropentyl) esters; Pyromelliths with the fluoroalcohols at such temperatures 65 acid dimethyl - di - (1,1,6 - trihydroperfluorohexyl) - ester; implemented that the resulting methyl alcohol during pyromellitic acid dimethyl -1,1,5- trihydroperfluoropendent The course of the reaction continuously from the tyl-l, l, 7-trihydroperfluoroheptyl ester; Mellophanic acid reaction mixture is separated. If the reaction is dimethyl-di- (l, l, 9-trihydroperfluorononyl) ester; Preh-

5 6

nitsäuredimethyl-di- (l, l, ll-trihydroperfluoro) -ester and trimethylester, which after percolation by a

the corresponding esters of the α, α-dihydroperfluor column with active clay have a boiling range of 144 to

alkanols. 145 ° C at 0.4 mm.

Not only individual esters from the groups described can be used as lubricants, hydraulic fluids or as other force-transmitting fluids

can be used, but mixtures can also be used. A flask of 200 ecm capacity is filled with 50.4 g

such esters can be used. In combination with the (0.2 mol) trimethyl mellitic acid, prepared according to

Fluoroesters according to the invention can also include such Example 1, 66.4 g (0.2 mol) of 1,1,7-trihydroperfluorhep additives be used as charged to the verio tanol and 8 drops of concentrated hydrochloric acid,

improve the resistance to oxidation and The flask is about 38 cm high, with

Corrosion are known. Examples of such additional asbestos-clad column connected in which

substances are diarylamines, including phenyl-a-naph- a slow reflux is maintained for 24 hours-

thylamine and diphenylamine; Thiodiarylamines, is obtained. The methanol formed is then final Phenylthio - «- (methylnaphthyl) amine and 15 distilled and in a pre-cooled with rock ice

Thio-diethylphenyl) amine; Aminophenols inclusion layer. A total of 6.3 ecm or

borrowed N-n-valeryl-4-amino-3-pentadecylphenol and obtained 79% of the theoretical yield.

N-palmitoyl-p-aminophenol; Dialkyl selenides and the reaction mixture is cooled, in diethyl

Tellurides, such as didecyl selenide, dilauryl diselenide, diether were added, and this ethereal solution was added 3 times cetyltelluride and dilauryl selenium oxide; basic suif onate, 20 with 160 cc of a 4 ° / ₀ IgERI aqueous potassium hydroxide solution and

like calcium petroleum sulfonates and indium carboxylates, then 3 times with 150 ecm of distilled water each time

including indium-2-ethylhexanoate, indium-p-octyl- washed. The ether is then reduced under

benzoate and indium caprylate. The additives are stripped off pressure and 8 g fluoral alcohol at 32 ° C /

expediently distilled off in amounts of not more than 5.0 gm 0.4 mm. The product, a colorless oil,

weight percent, calculated on the ester, is used. 25 is then isolated, it is distilled at a maximum

Because of their excellent high temperature resistance - temperature of 209 ° C / 0.5 mm above. In this way

62.5 g of dimethyl-1,1,7-trihydroperfluoroheptyl-

compared to ion radiation, those according to the invention are trimellitated (corresponding to a 56.6% yield)

fluoroester used can also be used as a lubricating oil.

phase of lubricating greases, optionally in a mixture 30 By using 0.4 mol of the fluoroalcohol

with other, usual lubricating substances. in the above reaction can be similar

Suitable gelling agents are the usual soaps, the monomethyl-di- (l, l, 7-trihydroperfluorhep-

how alkali (sodium, lithium), alkaline earth (calcium) - tyl) trimellitate are obtained, soaps and soaps of polyvalent metals (aluminum)

and other soaps of fatty acids or oxy fatty acids, 35 Example 3 especially if the temperatures do not exceed 149 ° C

lie. For higher temperatures it is advisable to use 135 g (0.5 mol) of tetramethylpypromellitate,

Use grease-forming colloids, such as makes from methanol and pyromellitic acid after a

Silica aerogels, clays e.g. B. Trimethylstearyl similar procedure as in Example 1, is

ammonium bentonites, and in particular high temperature 40 set with 232 g (1 mol) 1,1,5-trihydroperfluorpene

tur-gelling agents, such as indanthrene dyes and tanol in the presence of 2 g of concentrated sulfur

Indogenous. acid. The mixture is refluxed for 24 hours

Graphite can be heated used for this purpose as well. After this time, the resulting will. The amount of gelling agent used is methanol and unreacted fluoroalcohol below depends on the desired consistency of the lubricating 45 reduced pressure removed and the reaction grease and on the temperature, which the lubricating product, which fluoroester, which is the lubricating product, is mixed in ether should be subjected. Normally and in the same way as with evidence if the amount is between 2 and 40 game 2 washed.

weight percentage of the total grease mixture. After this purification, the desired working method falls 50 methyl-di (1,1,5-trihydroperfluoropentyl) -pyromels are for the production of such lubricating greases known in the relevant art. lithate in high yield in the form of an oily, weakly

The following examples explain the working methods, yellow liquid.

according to which the new fluoroesters prepared and when the fluoroalcohol can be used in amounts of 1 mole per. The proportions of moles of pyromellitic acid in the above-described reaction in these examples - unless otherwise stated reaction is used, are obtained as reactants - expressed in parts by weight. For this tion product the trimethyl-LLS-trihydroperfluor production process is used, however, in the context of the pentylpyromellithat. Similarly, the invention cannot be protected. Talking monomethyltri- (fluoropentyl) pyromellitate. .j can be obtained if 3 moles of the 1,1,5-trihydroper example 1 _{6o fluorinated} tanol per mole of the pyromellitic acid is added.

A mixture of 70 g trimellitic acid and 2.5 g are used,

concentrated sulfuric acid is about 250 ecm.

Methanol heated under reflux for 24 hours. Example 4

finally, the unreacted methanol in 54 g (0.2 mol) of pyromellitic acid, 86 g (0.2 mol)

Distilled off at atmospheric pressure and the acidic catalyst 65 1,1,9-trihydroperfluorononanol and 106 g (0.2 mol)

by washing the reaction mixture with 1,1,11-trihydroperfluorundecanol and 7 ecm of

3 times 200 ecm of distilled water removed. This trated sulfuric acid takes a total of 36 hours

Is thus obtained in 70% yield mellitic to 14O ⁰ C heated. After this reaction time

the mixture cooled and the resulting methanol and unreacted fluoroalcohols under stripped under reduced pressure. The reaction product is taken up in ether, washed and placed in the in the manner described in Example 2 isolated.

The oily liquid obtained is a mixture of pyromellitic acid esters, the most important of which Representative, which is present in an amount of more than 50% of the mixture, pyromellitic acid dimethyl- (1,1,9-trihydroperfluorononyl) - (1,1,11-trihydroperfluorunde- xo cyl) ester. The remainder of the mix consists of about equimolecular amounts of pyromellitic acid dimethyl-di- (l, l, 9-trihydroperfluorononyl) - and di- (l, l, 11-trihydroperfluorundecyl) ester.

Example 5

A large number of ester lubricants are subjected to a test in which their behavior is tested under practical conditions. In the Oxydationsbeständigkeitstest which is given in the last column, samples of 5 g each of the lubricant into contact with copper wire to about 204,4 ⁰ C heated while air is passed at a rate of 4.3 liters per hour.

sample ° / o Evap
loss of performance
at 204.4 ⁰ C. Pour point
° C Hours to
adsorption
of 1 millimole O ₂ / g
at 204.4 ° C 1) methyl phenyl phthalate
2) phthalic acid - (1,1,3 - triliydroperfluorpropyl) - (1,1,
5-trihydroperfluoropentyl) ester
3) phthalic acid - (1,1,5 - trihydroperfluoropentyl) - (1,1,
7-trihydroperfluoroheptyl) ester
4) Trimellitic acid trimethyl ester
5) mixture of the camphor acid esters of (1,1,5-tri-
hydroperfluoropentane) - (1,1,7 - trihydroperfluorhep-
tan) - (l, l, 9-trihydroperfluorononane)
6) pentaerythritol tetracaproate
7) Trimellitic acid dimethyl-1,1,7-trihydroperfluorhep-
tylester 74
99.1
100
100
90.2
5.4
43.7 -178
- 45.6
- 42.8
- 6.7
- 31.7
- 53.90
- 20.6 141
220
19th
170

These comparative tests confirm that Sample 7 according to the invention is compatible with all known ester lubricants is superior through the combination of desirable properties: the evaporation loss at high temperatures is relatively low, the pour point is sufficiently low and the resistance to oxidation is excellent.

Claims (8)

PATENT CLAIMS: 1. Use of an ester of a benzene polycarboxylic acid of the general formula 40 (ROOCV-; [COO R '(CF ₂ ) ^ X] ₀ in which R is an alkyl radical, R 'is a saturated divalent organic radical and X is hydrogen or fluorine and η is an integer from 1 to 24, while both α and b are integers from 1 to 3 and the sum (a + b ) is 3 or 4, or mixtures of such esters as lubricants or hydraulic fluids for high operating temperatures. 2. Embodiment according to claim 1, characterized in that R is a methyl group and / or R 'represents a methylene group. 3. Embodiment according to claim 2, characterized in that η is a number from 2 to 10. 4. Embodiment according to claim 1 to 3, characterized in that esters are used in the molecule of which there are various polyhydroperfluorocarboxycarbonyl groups. 5. Embodiment according to claim 1 to 4, characterized in that esters are used in which b is 1 or 2. 6. Embodiment according to claim 1 to 5, characterized in that esters are used in which the sum {a + b) has the value 3. 7. Embodiment according to claim 1 to 5, characterized in that esters are used derived from pyromellitic acid. 8. Embodiment according to claim 1 to 6, characterized in that esters are used derived from trimellitic acid. © 20? 638/358 8.62