US3313732A - Cyclic keto esters and lubricants containing them - Google Patents

Description

United States Patent 3,313,732 CYCLIC KETO ESTERS AND LUBRICANTS CONTAINTNG THEM Keith Coupland and John Pennington, Hull, and Sidney John Branch, Horusea, England, assignors to The DllS- tillers Company Limited, Edinburgh, Scotland, :1 British company No Drawing. Filed Nov. 12, 1954, Ser. No. 410,772 Claims priority, application Great Britain, Nov. 28, 1963, 46,968/63; Apr. 1, 1964, 13,512/64 1 Claim. (Cl. 252-57) This invention relates to synthetic lubricants and in particular to synthetic lubricant bases.

Synthetic lubricant bases may comprise, for example, esters such as dioctyl and dinonyl sebacates. In order to fulfill completely the requirements of a practical lubricant composition, various additives are customarily added to the base, which normally constitutes at least 60% and more, usually at least 90% by weight of the lubricant composition. Such additives include antioxidants (for instance phenothiazine or dioctyl phenothiazine); viscosity index improvers (for instance polymethacrylates or polyglycolethers); load carrying additives (for instance tritolyl phosphate or trixylyl phosphate), metal de-activators and anti-corrosion agents. The nature and quantity of such additives are varied as required for any particular lubricant composition to fulfill specific desiderata.

The present invention provides a synthetic lubricant base containing at least one keto-ester of formula:

CH2. CH2.C ozR CCH2. CH2. C 02R wherein R R R and R are the same or different alkyl groups, each of preferably from 4 to 16 carbon atoms, and R is an alkyl group such as the methyl group.

These compounds may, with advantage, be used as synthetic lubricant bases in admixture with a compound having at least two ester groupings in the molecule, such as the alkyl esters of organic dicarboxylic acids and monocarboxylic acid esters of polyalcohols. It is contemplated that halogen-substituted esters are also useful as compounds having at least two ester groupings in the molecule.

3,313,732 Patented Apr. 11, 1967 Accordingly the present invention further provides a synthetic lubricant base composition comprising at least one keto-ester of formula ice H2CCH2 wherein R R R R and R are as hereinbefore defined, in admixture with a compound having at least two ester groupings in the molecule.

Suitable compounds having at least two ester groupings in the molecule include dioctyl sebacate, dinonyl sebacate, esters of trimethylol propane such as trimethylol propane tricaprylate and esters of pentaerythritol.

The proportions of keto-ester and compound having at least tWo ester groupings in the molecule in the synthetic lubricant bases of the invention will, naturally, vary within wide limits according to the requirements for the particular base to be formulated. Suitable proportions are Within the range to 10%, especially 70% to 25%, particularly 30-35% of keto-ester by weight of the total base.

The keto-esters employed in the synthetic lubricant bases of the invention can be prepared for example by cyanoethylation of the appropriate cycloalkanone or alkylsubstituted cycloalkanone, followed by hydrolysis of the resulting tetraor tri-nitrile, to give the corresponding acid. Such a reaction is described for specific compounds in J. Amer. Chem. Soc., 64, 2850-2858. The acid is then esterified with a small excess of the appropriate alcohol together with entrainer and an esterification catalyst. The reaction conditions are selected to give esterification temperatures within the range of C. to 180 C., preferably between C. and C. High temperatures Within the quoted ranges do not significantly affect ester yield or quality, but are useful in promoting satisfactory reaction rates. The entrainer may be for example benzene, toluene, cyelohexane or any other hydrocarbon capable of forming a binary azeotrope with Water. The alcohol used may be any saturated aliphatic or cycloaliphatic alcohol having from 1 to 16, preferably 4 to 16 carbon atoms. The excess of alcohol employed in the esterification is suitably at least 2% and preferably 313% based on the Weight of acid. Any of the known esterification catalysts may be used, but sulphuric acid is preferred. The amount of catalyst used depends on the purity of the acid to be esterified, but generally 0.05 to 1.0% W./ W. sulphuric acid based on the total esterification charge is satisfactory.

The crude ester is generally dark brown in colour and can be decolourized by ozone, potassium permanganate, bromine or sodium hypochlorite, but it is preferred to wash the crude ester with 2 X A volumes of aqueous 10% w./v. sodium hydroxide solution, l x A volume of aqueous 10% w./v. sodium chloride solution and l X A volume of distilled water. Sodium hydroxide solutions of less than 5% w./v. are less effective decolourants and significant improvements are not obtained by the use of odium hydroxide solutions of greater concentration than w./v.

Some of the keto-esters of which the preparation has been described above are new compounds. Accordingly the present invention still further provides keto-esters of wherein R R R and R have the meanings ascribed It may be seen from the table that keto-esters of this invention have very good oxidative stability and thermal volatility and possess adequate viscosity at 210 F., and adequate low temperature fluidity.

Example 7 A mixture of 70% of the keto-ester of Example 3 With 30% of dioctyl sebacate was evaluated according to the above procedure. It had the following properties:

Oxidative stability, percent W./W. loss 26 Thermal volatility, percent w./w. loss 3 Viscosity increase Nil Viscosity at 210 F., centistokes 8.6 Pour point, F. -65

Example 8 A mixture of 55% of the keto-ester of Example 3 with 45% of dinonyl sebacate was evaluated according to the procedure described in Example 1 in respect of oxidative stability, viscosity and pour point. The results were as follows:

Oxidative stability, percent weight loss Viscosity at 210 F., centistokes 7.8 Viscosity at 100 F., centistokes 52.1 Pour point, F. Below 60 The normal volatility of this material was assessed in similar manner to that used in Example 1 but under more severe conditions, since the temperature of the ester was maintained at 340 C. The thermal properties of this material at this temperature are shown in Table 2, together with the properties of dinonyl sebacate.

TABLE 2 Thermal volatility (340 C.) After test Ester Weight Acid N 0.,

loss, Viscosity increase Mg. KoH/g. Appearance percent Dinonyl sebacate 36 Material solidified, 238 Solid. 55% Ester 4, dinonyl sebacate. 27 Small 36 Slight darkening.

The invention is illustrated by the following examples in which oxidative stability was assessed by the method of the American Standard for the Testing of Materials No. D972-56, except that for Examples 4 to 6 the test temperature used was 500 F. Viscosities and pour points were determined by conventional methods, and the measurement of thermal volatility was made by passing nitrogen through the sample at two litres per hour for 6 /2 hours (6 hours in the cases of Examples 4-6) at a temperature of 300 C.; the loss in weight, the appearance and the increase in viscosity of the samples were noted at the end of the test.

Examples 1-6 A comparison of the properties of keto-esters in ac- Example 9 A mixture of 45% of the keto-ester of Example 4 with of dioctyl sebacate, with the addition of 3% of a polymeric methacrylate viscosity index improver had the following properties:

Oxidative stability, percent weight loss 51 Viscosity at 210 F., centistokes 7.6 Viscosity at 100 F., centistokes 39.6 Pour point, F. Below Example 10 A mixture of of the keto-ester of Example 4 with 35% of trimethylol propane tricaprylate had the following properties:

cordance with the invention having a structural formula Oxidative Stability, P Weight 1055 26 containing a cyclohexanone ring with th of di l Viscosity at 210 F., centistokes 8.0 sebacate and those of another keto-ester of th i ve ti 60 Viscosity at F., centistokes 52.2 are Shown in the following Table 1. Pour point, F. -60

TABLE 1 Oxidative Thermal volatility Examplc/ Stability Viscosity at Pour COIHIJHI'ISOII Ester Weight loss 210 F. Cenpoint, Number (percent) Weight loss Viscosity tistokes F.

(percent) increase A Dinonyl seh'ira tP 79 12 7 4. 6 8O Esters of this invention:

R R R R =n-Butyl 15 15 Nil 10. G -35 R ,R ,R and R mixed C 0 a 15 6 Nil 17. 0 -15 R R R R =2-etliyllicxy1 l6 6 Nil 14. 4 20 R ,R ,R and R mixed C3, C nlkyL. l4 6 Nil 12. 0 30 R ,R ',R =ri-butyl, R =1uetlryl 28 -10 1,l,3,3 tetra(n-butyl-fl-propionnte) cyclopeutan-2-one 6 Example 11 A mixture of 33% of the keto-ester of Example 1 with 66% of trimethylol propane tricaprylate had the following properties:

Oxidative stability (500 F.), percent weight loss 20 Viscosity at 210 F., centistokes 5.3

Viscosity at 100 F., centistokes 30.6

Pour point, F. 65

We claim:

A synthetic lubricant composition wherein the lubricant base comprises at least one keto-ester of formula selected from the group consisting of CCH2. CH2. 0 02R References Cited by the Examiner UNITED STATES PATENTS 2,386,736 10/1945 Bruson 260465.4 X 2,403,570 7/1946 Weist et a1. 260464 2,460,536 2/ 1949 Rogers 260465.4 X 3,057,815 10/1962 Bartlett et a1. 252-57 X FOREIGN PATENTS 63 8,161 3/1962 Canada.

OTHER REFERENCES Barnes et aL: Lubricating Engineering, August 1957, pages 454-458.

DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner.