|Publication number||US3058913 A|
|Publication date||Oct 16, 1962|
|Filing date||Nov 12, 1958|
|Priority date||Nov 13, 1957|
|Publication number||US 3058913 A, US 3058913A, US-A-3058913, US3058913 A, US3058913A|
|Inventors||Koch Ernst, Kollinsky Fritz, Ludwig Walter|
|Original Assignee||Roehm & Haas Gmbh|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (3), Classifications (31)|
|External Links: USPTO, USPTO Assignment, Espacenet|
TRIALKYL ESTERS OF A TRICARBQXYLIC AQE) HAVING THE COXYL GROUPS N NGN- ADJACENT CARBON ATOMS AND USE THERE- OF AS A LUBRICANT Ernst Koch, Traisa, Darmstadt, Fritz Kollinsky, Dar-mstadt-Eberstadt, and Walter Ludwig, Bensheim-Auerbash, Germany, assignors to Riihm & Haas G.m.b.H., Darmstadt, Germany No Drawing. Filed Nov. 12, 1958, Ser. No. 773,195 Claims priority, application Germany Nov. 13, 1957 Ciaims. (Cl. 252-56) This invention relates to synthetic lubricating oils capable of providing effective lubrication over a wide temperature range, including both sub-normal and elevated temperatures. More particularly, it relates to lubricating oils having a trialkyl ester of a limited class of tricarboxylic acids as an essential component.
The advent of jet aircraft, the attainment of supersonic speeds and penetration to increasingly higher altitudes has created an urgent need for lubricants endowed with special properties not possessed by conventional petroleum base lubricants or synthetic lubricants. let engines, aircraft instruments and hydraulic transmissions, for example, require fluids that will function effectively at very low and at very high temperatures. To be suitable a lubricant or hydraulic fluid should have a pour point below about 50 C., a flash point of about 230 C. or higher to avoid fire and loss by evaporation at elevated temperatures, and a high viscosity index in order to provide adequate lubrication within this wide operational temperature range.
We have found that tri-primary alkyl esters of tricarboxylic acids in which the alkoxycarbonyl groups are attached to non-adjacent and diiferent carbon atoms and in which at least two of the alkyl ester groups, and preferably all three, have predominantly straight chains containing from six to fourteen carbon atoms, possess a surprisingly desirable combination of properties that makes them of superior value as lubricants and lubricant components. They have high viscosity indexes, unusually low pour points in spite of high viscosities, and remarkably high flash points, a combination of tremendous industrial significance for the lubrication of engines, transmissions, instruments and the like in which the lubricant must perform its intended lubricating functions properly under the most severe extremes of temperature, as well as in hydraulic fluid applications.
This discovery is even more surprising when considered against the background of the art relating to synthetic diester lubricants. Developments in this art have led to the conclusion that the viscosity characteristics of diesters are rather definitely related to the ratio of length to cross section of the diester molecule. Thus, for example, it has been established that di-n-octyl sebacate, nC H OOC(CH --COOnC H1'z, has a considerably higher viscosity index than its less linear isomer, di- Z-ethyhexyl sebacate,
C2115 02135 it was to be expected, therefore, that because of their inherently lower length to cross section ratios, triesters would have poor viscosity indexes and hence little or no value as lubricants or lubricant components.
It is perhaps even more surprising that triesters, in contradistinction to diesters, possess higher viscosity indexes with lower length to cross section ratios. This is demonstrated by the fact that a tn'ester having two alkyl ester groups each containing from six to fourteen carbon atoms and one methyl ester group has a lower viscosity index than the corresponding triester in which 3,fl58,9l3 Patented Oct. 16, 1962 all three of the alkyl ester groups each contains six to fourteen carbon atoms, although the pour point is essentially the same.
The triesters can readily be prepared by esterification of tricarboxylic acids with predominantly straight chain, primary rnonohydric alcohols containing six to fourteen carbon atoms. The term predominantly straight chain alcohols is intended to include primary alcohols having a limited number of methyl and ethyl substituents on the primary carbon chain, as well as alcohols contalning hetero atoms, e.g., nitrogen, sulfur or oxygen in the chain.
The tricarboxylic acids useful in the preparation of the triesters are limited to those in which each of the carboxyl groups is separated from the adjacent carboxyl group by at least three carbon atoms. Representative tribasic acids include 1,3,6-hexane tricarboxylic acid HOOOCHzCHrCH--CHz-CH2CHzCOOH Iso-cam-phoronic acid a HOOCG--OHCHz-COOH H3 CHr-COOH 3-methyl-l,3,5-pentane tricarboxylic acid r HOOO'"CHT 'OHZC-CHTCHTOOOH oooH 2,4,6-heptane tricarboxylic acid OH3 CH OHZCH-CH2CHOH3 OOOH OOOH OOH 4-methyl-2,4,7-octane tricarboxylic acid (3H3 CH CHCHzC-CHzCH2-CH-CH9 OOH GOOH OOH For example, the tri-n-octylester of the above mentioned 3-methyl-l,3,5-pentane tricarboxylic acid has the following properties:
Viscosity (centistokes Pour Flash V.I. Point, Point,
Synthetic triesters which are useful for the purposes of the invention, can also be prepared by hydrogenating trimeric methyl methacrylate by the methods described in German Patents 855,554 and 903,932 and then subjecting the hydrogenated trimeric methyl methacrylate to alcoholysis with a predominantly straight-chain alcohol of six to fourteen carbon atoms. Although it is generally advisable to carry the alcoholysis to completion, it may be sufficient in individual cases to replace only two of the methyl groups by higher alkyl groups derived from higher alcohols. It is not always necesary to remove completely the oligomeric by-products produced during trimerization of monomeric methacrylate, for instance the dimerio, tetrameric or pentameric esters, before further treatment. The alcoholysis of the crude triester or the triester purified by distillation can be carried out with a suitable alcohol or a mixture of several suitable alcohols having between six and fourteen carbon atoms.
It is apparent also that the products employed in this invention can be prepared by esterification of a free tribasic acid with one or more of the alcohols discussed above, or by oligomerization of a monomeric methacrylic acid ester of a predominantly straight-chain alcohol having from six to fourteen carbon atoms. The ,esterification is eflfected in the presence of one of the usual esteri-' fication catalysts, such as concentrated sulfuric acid, hydrogen chloride or para-toluene sulfonic acid. Preferably a volatile organic diluent such as benzene or xylene is employed so that the water formed in the esterification can be removed by azeotropic distillation.
It is Within the scope of the invention to vary the lubrieating properties of the synthetic triesters by additions of anti-oxidants, high pressure additives, detergents, viscosity index improvers 'and the like. The useful tn'esters can also be converted, by techniques known in the diester art, into complex estersand then used as lubricant modifiers. In certain instances it is desirable to mix the useful triesters with other synthetic lubricants or lubricants having a base of mineral oil in order to obtain desired properties.
The favorable combination of properties of various triesters of a representative tricarboxylic acid is illustrated by way of example in the following table of data. The triesters are those of 4-methyl 2,4,7-octane tricar boxylic acid and have the general formula groups of which are derived from a straight-chain, primary alcohol having from six to fourteen carbon atoms and the carboxyl groups of which are positioned on nonadjacent and different carbon atoms.
4. The method of lubricating which comprises applying to surfaces. to be lubricated a lubricant comprising a trialkyl ester of an alkanetricarboxylic acid having at least seven carbon atoms wherein the carboxyl groups are positioned on non-adjacent and different'carbon atoms and at least two of the alkyl ester groups are derived from a primary alcohol having from six to fourteen carbon atoms, said alcohol being selected from the group consisting of straight chain alcohols and branched chain alcohols having substituents no higher than ethyl on a primary carbon chain. 7'
5. The method of lubricating which comprises applying to surfaces to be lubricated a lubricant comprising (3H3 CH3OH OHgOH-OOH -CH-CH O R1 0 0 R2 0 O 0 R3 Viscosity (Centistokes) Pour Flash R1,R2,Rs V.I. Point, Point,
OHzOH (CzHs): 21. 73 4. 07 92 -60 230 CHz?H (CH2)3CH3.-- 28. 49 4. 86 101 -58 234 02115 CH2CH:(|3H OHz- C (CHQL. 50. 7 6. 97 103 48 254 1 CH3 (OH9)5CH3 17. 2 3. 7 64 229 (CHz)sOH3. 21. 43 4. 31 63 238 (CH2)7CH3 23. 78 4. 78 138 -66 253 R1= (CH2)7CH3 28. 32 5. 48 140 -61 260 R2=R3=(CHz)9CHa (CH2) GH3 30. 6 5. 92 143. 5 5 6 The above data indicate the surprisingly low pour points and high flash points possessed by representative triesters of the invention and their suitability, as shown by their viscosity index values, as lubricants, hydraulic fluids and components thereof.
It is to be expected that numerous modifications and I other applications will readily become apparent to those skilled in the art upon reading this description. All such modifications and applications are intended to be included Within the scope of the inventionas defined in the appended claims. a
l. A lubricant having as an essential ingredient a trialkyl ester of an alkanetricarboxylic acid having at least seven carbon atoms wherein the carboxyl groups are positioned on non-adjacent and diiferent carbon atoms and at least two of the alkyl ester groups are derived from a primary alcohol having from six to fourteen carbon atoms, said alcohol being selected from the group consisting of straight chain alcohols and branched chain alcohols having substituents no higher than ethyl on a primary carbon chain. 7
2. A lubricant having as an essential ingredient a trialkyl ester of an alkanetricarboxylic acid having atleast 7 a uialkyl ester of an alkanetricarboxylic acid having at least seven carbon atoms wherein the carboxyl groups are positioned on non-adjacent and 'difierent carbon 59 atoms and the alkyl ester groups are derived from a primary alcohol having from six to fourteen carbon atoms, said alcohol being selected from the group consisting of 1 straight chain alcohols and branched chain alcohols having substituents no higher than ethyl on a'primary carbon chain.
References Cited in the file of this patent UNITED STATES PATENTS Graves et-alf Mar. 12, 1935 Wilder July 7, 1959 OTHER REFERENCES Murphy et al.: Ind. and Eng. Chem. vol. 42, Decem- 5 her 1950, pp. 2415-2420 relied on.
Cohen et al.: Ind. and Eng. Chem, p. 1771 relied on.
Tinker: J. Am. Chem. Soc. 73, 4493-4494. (1951). Talukdar et al.: J. Org. Chem. 20, 25-32 (1955). 1 Bergman et al.: J. Org. Chem. 21, 108 (1956).
vol. 45 (1953),
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1993736 *||Jun 10, 1931||Mar 12, 1935||Du Pont||Esters and process for producing them|
|US2893964 *||Dec 10, 1954||Jul 7, 1959||Johnson & Son Inc S C||Wax fortified paint and varnish compositions|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4287741 *||Oct 9, 1979||Sep 8, 1981||National Steel Corporation||Lubricated tinplate for drawing and ironing operation|
|US4695492 *||Oct 23, 1985||Sep 22, 1987||American Can Company||Forming lubricant for a coated metal container and method of making the same|
|USRE31349 *||Nov 28, 1980||Aug 16, 1983||National Steel Corporation||Lubricated metallic container stocks and method of preparing the same and applying organic coating thereto|
|U.S. Classification||508/496, 560/190, 560/204|
|Cooperative Classification||C10N2250/10, C10M2219/044, C10M2207/125, C10N2210/01, C10M3/00, C10M2207/286, C10M2215/042, C10M2207/283, C10M2219/024, C10M2223/041, C10M2209/084, C10M2207/129, C10N2240/08, C10N2230/08, C10N2240/12, C10N2240/121, C10M2207/34, C10M2207/281, C10M2219/00, C10M2207/287, C10M2207/30, C10N2210/00, C10M2219/108, C10M2215/227, C10M2207/023, C10M2207/282|