US2692233A - Synthetic lubricant - Google Patents

Description

Patented Oct. 19, 1954 SYNTHETIC LUBRICANT Delmer L. Cottle, Highland Park, David W. Young, Westfield, and Frederick Knoth, Jr., Sayreville, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application February 16, 1952, Serial No. 271,974

1 Claim. 1

This invention relates to synthetic lubricating compositions. Particularly it relates to synthetic lubricants having utility at both high and low temperatures. More particularly the invention relates to new and improved synthetic lubricants of the ester type which exhibit outstanding characteristics as to pour point and low temperature viscosity.

In the lubricating art, considerable progress has been realized in recent years in the production of lubricants characterized by one or more specific properties and adapted for specific uses. In general, this progress is attributed to two developments, new and improved refining techniques, and addition agents capable of imparting particular properties to available lubricants. Thus, viscosity index 'improvers and pour point depressors are added to available automotive lubricants to render the lubricants more adaptable to change in temperature conditions. There are, of course, limits upon the range of effectiveness of these addition agents, and certain requirements cannot be met in every instance.

With the development of the turbo-jet and turbo-prop type aircraft engines, which operate at peak efliciency at extremely high altitudes, there has developed a corresponding need for a lubricant which is efiicacious at the extremely low temperatures encountered at high altitudes or in frigid areas. Engine manufacturers and operations personnel dealing with these turbine engines must be supplied with a lubricant possessing exceptionally low viscosities at low temperatures and at the same time having satisfactory lubricating qualities at high temperatures.

The mineral lubricating oils which exhibit satisfactory low temperature viscosities have generally been found to have flash points that are dangerously low and high temperature viscosities that are below those required. In other words, when the mineral oil is thin enough at low temperatures, it is too volatile at higher temperatures, where it is also too thin to possess satisfactory lubricity. It has been found that, generally speaking, additive agents do not satisfactorily furnish the required characteristics.

Recently, in an effort to obtain the superior lubricants needed for these uses, a new field has been explored, namely, the synthesis of lubricants from various materials. Esters represent one class of materials which have attracted unusual interest as synthetic lubricants. Esters are generally characterized by high viscosity indices and flash points and lower pour points than mineral oils of a corresponding viscosity. It is with a synthetic lubricant of the ester type that this invention is concerned.

The new synthetic lubricants of the ester type to which the instant invention is directed are highly branched chain esters of adipic acid having the following general structural formula:

R in the above formula are highly branched chain aliphatic radicals containing '7 carbon atoms and corresponds to those of alcohols prepared by interaction of propylene dimer with carbon monoxide and hydrogen according to the 0x0 process.

The oxo process may be described as being the catalytic reaction of a mono-olefin with carbon monoxide and hydrogen. This interaction occurs at temperatures in the order of 300 F. to 400 F. and at pressures in the order of about 1000 to 3000 p. s. i. In the presence of a suitable catalyst such as a heavy metal carbonyl, cobalt carbonyl, for example, there is formed an aldehyde which is subsequently hydrogenated to form a primary alcohol. This process was first developed in Germany and is described in U. S. Patent No. 2,327,066, issued to Roelen in 1943.

It has been found that diesters of adipic acid formed by reacting said acid with the mixture of alcohols obtained by subjecting a C6 olefin to the 0x0 process has outstanding properties as a synthetic lubricant. The C6 olefin, ordinarily a dimer of propylene, is ordinarily obtained from the subjection of certain refinery streams containing a substantial percentage of propylene to separation processes and polymerizing or dimerizing the propylene component by polymerizing procedures. One such process, known as U. 0. P.

polymerization, consists of passing the olefin stream in liquid form in contact with an acid catalyst comprising phosphoric acid on kieselguhr. Other acidic catalysts such as liquid phosphoric acids, phosphoric acid or copper phosphate impregnated on silica gel, sulfuric acid, Friedel-Crafts catalysts, activated clays, silicaalumina, pyrophosphate, etc. may also be used. Suitable conditions when employing the phosphoric acid catalysts of the U. 0. P. type are temperatures of 300 to 500 F. and pressures of 250 to 5000 p. s. i.

It has been demonstrated that the propylene dimers prepared in accordance with the polymerization processes familiar in the art contain the following two olefins in predominant amounts.

0133- H=CHCH2CH2 Variousother methyl pentenes and dimethyl bu tene constitute the remainder.

Upon reaction with carbon monoxide and excess hydrogen in the x0 process the mixture of olefins obtained as above result in a series of branched chain alcohols of a great number of 4 tures at high altitudes. It is essential that the engine lubricant be sufiiciently labile at low temperatures to be capable of being circulated in the lubrication system. As is clearly pointed out in the table above, esters ofzinvention have excellent viscosity characteristicsat all test temperatures and a flash point and pour point that is outstanding. It will be noted that as the esterifying alcohol chain length decreases the 'flash point also structural configurations. For instance, it has 110 decreases. one qutstanffing t of the C7 9 been determined that when 2 'methy1 pentene 3 alcohol diester mixture is that it has a flash po nt is the olefin that is subjected tothe oxo process a hlghras the C8 OX0 alcohol esters fact whlch there is formed the following mixture of alcohols: oconjpletely, unexpectefl m the hght of the CH3 30 -35 drop 1n flash points between any other 4 Percent 15 tWO'COIlSGClltlVG esters. CH3- H CH-CH CH CH2OH 40 The C7 0x0 ester mixture is also outstanding in CH3 CH3 its viscosities at 40 F. and -65 F. The viscos- (b) C s 2 -C 2O 30 ity of this mixture at these temperatures is also CH3 completely unexpected in the .light of the viscosity (6) OH CH H H H CH 0H 30 of the Cs 0x0 alcohol esterat'these temperatures. The other olefins present gjve a proportionate be noted ViSLOSity at -4:0 F; numberof alcohols so that the total C1 oxo alcoand of those esters below Ci 0X0 estersin h mixture is composed of a great number f the table are higher than the Ci oxo ester .mixe variations as'to' structure, each having one hyture- The flash points of these esters m them droxyl group and 7 carbon atoms less desirable for jet lubrication- These flash and 7 w a doume molecumr proportion of this viscosity results on the esters have been checked mixture-of alcohols is used to esterify a molecular Several times on several Synthesespmportion of adipic acid the ,0, adipate To summarize briefly, this invention relates to formed has a molecular configuration which rea Synthetic lubricating composition having 011t- Sults in properties that make the Compound an standing lubricating characteristics at low tem outstanding synthetic lubricating oil. This will pemtlll'es which Comprlses a ImXtU-Te of 0X0 be more completely shown in the following table. alcohol esters of adipic acid In the table below the properties of seven adipic What is c m 153 acid diesters are set out in detail. These esters A Synthetic lubricating o l v Outsta din were n prepared a procedure familiar to the lubricating characteristics at low temperatures art of which the following is typical. which consists essentially. of a mixture ofdiesters DisCTQXO adipate was prepared by mixing 975 of adipic acid, each ester having the formula g. (8.4 moles) of C1 0x0 alcohol, 584 g. (4 mole) 4 COOR V of adipic acid, in the presence of 1 g. of toluener sulfonic acid. This mixture was refluxed and 149 40 wherein R is the combiningradical of an alcohol ml; of water removed with the aid of 200 ml. of obtained upon reaction of a propylene dimer with toluene as water entrainer. The residue was percarbon monoxide and hydrogen in the presence of colated through Attapulgus clay, stripped of a heavy metal carbonyl catalyst at temperatures toluene and excess alcohol and'distilled at 2mm. of about 300 to 400 F. and pressures of from pressure. The product distilled sharply at 175 1,000 to 3,000 atmospheres to form an aldehyde C. d We 1200 which Was 7.5% of the and hydrogenation of said aldehyde to said alcotheoretical based on the adipic acid charged. hol.

vT0iZ )Ze'.-Adipic acid esters Kii1e'maticZVlcosity(C.S.) Flash Pour ffifigi fg E'steriiying alcohol 7 PJiFI lt, P oirnt, 210W. 100 F. -40 F -s5 F; Seiz. Weld;

oltjoxo Alcohol s. '15. 20- 3,4300 20, 000 450 3.45. 12.81 1, 955.0 10,000 420 -75- 2.80 10.0 1, 040.0 6, 400 395 -110. 50 100,, 2. 30 7.4 460.0 2,290 395 so 95 ZethYl-butylalcohol-.. 1.77 5.35 465.0 2, 310 301 -98 i isohexyl alcohol n 1. 98 5. 68 510.0 Solid 372 54 n-amyl alcohol 1.75 4. 76 462. O 329 -l08 temperature viscosity since equipment utilizing jetengines operate at extremely low tempera- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 65 2,417,281 Wasson et al Mar. 11, 3947 2,481,372 Fuchs et a1 Sept. 6, 1949 2,491,028

Beerbower Dec. 13, 1949 OTHER REFERENCES Symposium on Synthetic Lubricants, A. S. T. M., Special tests, Pub. No. 77- -1947.