US 2561232 A
Description (OCR text may contain errors)
- thetic lubricants.
Patented July 17, 1951 DIALKYLALKENYLSUCCINATES Barry W. Rudel, Roselle Park, and Jones I. Wasson, Union, N. J assignors to Standard Oil Development Company, a corporation of Dela- No Drawing. Application December 30, 1948, Serial No. 68,388
4 Claims. I
This invention relates to a new class of compounds which have been found to be particularly suitable for use as synthetic lubricants because of their low pour points and high viscosity indices.
In the lubricant art, considerable progress has been realized in recent years in the production of lubricants characterized by one or more specific properties and adapted for particular uses. In the main, this progress can be attributed to two developments: the first, new refining procedures, and the second, addition agents capable of imparting particular properties to available lubricants. Thus, viscosity index improvers and pour depressants are added to automotive lubricants to render the lubricants more adaptable to wide changes in temperature conditions, while other agents are added to improve the load carrying properties of a lubricant which is to be employed, for example, under extreme pressure conditions.
Recently, in an effort to obtain superior lubricants endowed with specific and superior characteristics, 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 syn- In general, they are characterized by higher viscosity indices, lower pour points, and higher flash points than mineral oils of corresponding viscosity. The esters described in the present specification have been found to exhibit high viscosity indices and in many cases very low pour points. Those esters which do not exhibit a pour point which is sufficiently low for use'without additive may be made useful by simply adding a pour depressant, as in the case of mineral oils. The esters possessing both high viscosity indices and low pour points are of special value in the lubrication of engines which are subjected to high temperatures such as combustion turbine engines, particularly those of the prop-jet type. Mineral oil lubricants containing added viscosity index improvers, thickeners or other highly non-volatile additives are undesirable for use in such engines because of the tendency to leave a residue which accumulates and interferes with the operation of the engine. A synthetic lubricant of the type described in the present specification is especially adapted to use under such conditions, since the lubricant contains no additives and thus tends to leave no residue upon volatilization.
The new compounds of the present invention which have been found to be particularly suitable for use as lubricating oils are esters of alkenyl dibasic and tribasic carboxylic acids in which the alkenyl group contains 3 to 24 carbon atoms and in which the total number of carbon atoms in the molecule, exclusive of the alkenyl group, is
mary monohydric alcohols containing 1 to 18' atoms or with monohydric alcohols containing oxygen or sulfur in ether or thioether linkages. In the latter case the oxygen or sulfur atoms are separated by a chain of at least two carbon atoms,
and there is always a chain of at least two carbon atoms between the hydroxyl group and the first atom of oxygen or sulfur. Itis not desirable to employ an alcohol contain'ingmore than two sulfur atoms, but there is no limit to the number of oxygen atoms which may be present. However, it is desirable, when employing alcohols containing oxygen or sulfur atoms, to employ alcohols in which the total number of carbon, oxyeen and sulfur atoms, exclusive of the hydroxyl group, is from 4 to 20. The esterifying groups in a given ester may be alike or different, but the acid and esterifying alcohols should be so chosen that the resulting ester has a molecular weight of at least 300.
The alkenyl dicarboxylic and tricarboxylic acids employed in preparing the esters of the present invention may be conveniently prepared by condensing monoolefins with suitable acids or acid anhydrides, employing an elevated temperature, for example, C. or higher, the acids or anhydrides having a double bond between two carbon atoms conjugated with one or more carboxyl groups. in the formation of an alkenyl substituted saturated polycarboxylic acid or acid anhydride. For example, when an olefin is condensed with maleic anhydride there is formed an alkenylsuccinic acid anhydride. Examples of acids or acid anhydrides which may be reacted with olefins in this manner are the following: maleic, citraconic, ethylmaleic, glutaconic, itaconic, methylitaconic, dimethylitaconic, hydromuconic, aconitic and methylaconitic.
For introducing the alkenyl groups desired in accordance with the present invention any monoolefin having from 3 to 24 carbon atoms may be employed. Such olefins include normal and branched chain olefins and polymers of the same, as well as mixtures of olefins occurring in technical products. Examples of suitable oleflns include propylene, n-butylene, isobutylene, 2-ethyll-butene, diamylene, 1-.-decene, l-tetradecene, loctadecene, ClS-Cl8 olefins from the Fischer synthesis, Cn-Cm polypropylene, C24 polypropylene, C24 .dechlorinated wax, cracked gasoline, and similar products.
All of the alkenyl substituted .dicarboxylic or tricarboxylic acids or anhydrides of the type described above may be esterified by reaction with an alcohol, employing the usual esterification methods, preferably with the aid of an esterifica- 7 tion catalyst such as p-toluene sulfonic acid, and
The condensation process results a water entraining agent. Typical examples of suitable alcohols which may be employed are the following Methyl alcohol Ethyl alcohol .n-Propyl alcohol n-Butyl alcohol Isobutyl alcohol n-Amyl alcohol Isoamyl alcohol n-Octyl alcohol Z-ethylhexyl alcohol Cetyl alcohol Oleyl alcohol B-n-Butylmercaptoethanol fl-Tert.-octylmercaptoethanol fi-n-Dodecylmercaptoethanol Diethylene glycol mono-n-butyl ether Diethylene glycol mono-2-ethylbutyl ether Diethylene glycol mono-2-ethylhexyl ether Propylene glycol mono-butyl thioether Propylene glycol mono-tert.-octyl thioether Propylene glycol mono-n-dodecyl thioether nButylmercaptoethoxyethanol Tert.octylmercaptoethoxyethanol n-Dodecylmercaptoethoxyethanol nButylmercaptopropoxypropanol Tert.octylmercaptopropoxypropanol n-Dodecylmercaptopropoxypropanol Propylene glycol mono-n-butyl ether Dipropylene glycol monomethyl ether Dipropylene glycol monoethyl ether Dipropylene glycol mono-n-butyl ether Tripropylene glycol monomethyl ether Tripropylene glycol monoethyl ether Tripropylene glycol mono-n-butyl ether Propylene glycol monoisopropyl ether Dipropylene glycol monoisopropyl ether Tripropylene glycol monoisopropyl ether by the reaction of ethylene oxide or propylene oxide with aliphatic alcohols, are known in the industry as Dowanols, Carbitols, Or Cellosolves.
A group of alcohols especially adapted for use in connection with the present invention are the so-called x0 alcohols, prepared by the reaction of carbon monoxide and hydrogen upon the olefins obtainable from petroleum products and hydrogenation of the resulting aldehydes. Materials such as diisobutylene and C7 olefins are suitable for this purpose; also higher molecular weight olefinic materials are sometimes employed. The alcohols obtained in this manner are primary alcohols and normally have a branched chain structure.
In the table below will be shown data obtained in the tests of various properties of a number of esters illustrating the present invention which indicate the usefulness of these esters as synthetic lubricating oils. All of these esters were derived from alkenylsuccinic acids having alkenyl groups of varying length. In some cases the two esterifying groups are of quite diflerent chain length. Where two alcohols are shown, one mol of each alcohol was reacted with one mol of the acid. The general method employed in preparing anhydrides of the alkenylsuccinic acids consisted in heating maleic anhydride in the presence of an olefin in a bomb overnight at a temperature of 220 C., after which the product was heated in a vacuum to strip off the excessive olefin and any unreacted maleic anhydride. The esterification was carried out by refluxing a mixture consisting of 1 gram mol of the alkenylsuccinic acid, 2.2 gram mols of alcohol (or 1.1 gram mols each of two different alcohols), 2.5 grams of p-toluene sulfonic acid monohydrate (catalyst) and 100 ml. toluene or similar hydrocarbon medium in an apparatus fitted with a refiux condenser and water trap until no more water collected in the trap, after which the resulting mixture was washed with a sodium carbonate solution andwater, dried by means of a desiccant, and stripped of solvent by heating under vacuum.
The results of tests of the properties of various esters are shown in the following table:
Esters of alkenyl succim'c acids Flash ArSTM Kinematic Viscosity ASTM our Viscosity Oleflns Employed m Alkylatlon Alcohol la n; Pomt Slope Index (F.) 100 F. 210 F.
Isobutylene 35 15. 572 3. 490 0. 752 115 2-Ethy1-1-butene 35 33. 980 5. 671 0. 727 117 D0; -35 34. 720 5. 570 0.742 108 180. 500 16. 820 0. 659 106 -35 6. 990 2.188 0.751 131 -35 26. 91 4.111 0.838 19 20 53. 948 6. 165 0. 813 51 35 38. 660 5. 631 0.769 80 35 31.35 4. 697 0.805 57 35 37. 800 5. 752 0.750 99 Methyl 35 35. 420 5. 146 0. 791 73 Methy1+C 435 ('2) 59. 753 6. 799 0. 791 65 nmyl 370 29. 11 4. 496 0. 809 53 2-Ethylhexyl.. 435 42. 72 5. 0. 803 69 n-Decyl 400 35 40. 73 6. 238 0. 728 Butyl cellosolve 410 35 33. 56 5.000 0.791 72 Butyl carbitol 430 35 35. 540 5. 681 O. 739 109 25 13. 720 3. 175 0. 767 106 35 28. 970 5. 257 0.718 126 10 35. 530 6. 246 0.687 132 25 33. 620 5. 702 0. 720 25 28. 260 5. 127 0. 723 123 D0 +35 38. 770 6. 467 0. 695 126 C o-01a Fischer olefins n-Decyl 415 15 235. 7 21. 51 0. 625 112 0 1-6 5 Polypropylened 420 20 152. 10 14. 010 0. 692 96 l-Octadecene ,d 460 +25 37. 270 6. 562 0. 676 134 C Dechloriuated wax do 480 +65 76.363 11. 085 0. 628 130 Do.- Methyl+n-decyl 435 +65 84. 400 11. 245 0. 645 123 Do Ca Oxo 435 +65 75. 963 10. 283 0.660 122 C14 Polypropylene. n-Decyl 395 10 271. 100 19. 960 0. 680 93 Do Methy1+n-decyl 455 5 230. 500 15. 442 0. 741 65 The above data indicate that the esters constituting the subject matter of the present invention possess characteristics, particularly with regard to the pour point, viscosity-temperature characteristics, viscosity index, and slope on the ASTM chart D341-32T, which indicate clearly their suitability for general use as lubricating oils. The esters of the present invention may also be blended with mineral lubricating oils to give lubricants of improved viscosity index and l pour point characteristics.
What is claimed is:
1. As a new composition of matter an aliphatic alcohol diesterof an alkenylsuccinic acid containing a single alkenyl group of 4 to 24 carbon atoms, in which the alcohol radicals are selected from the group consisting of 1) alkyl groups of 2 to 14 carbon atoms and (2) alkoxy radicals of the type C4H9(OCH2CH2-)nOI-I where n is an integer from 1 to 2.
2. Di-n-decyl isobutenylsuccinate. 3. Di-n-decyl ethylbutenylsuccinate. 4. Diethyl decenylsuccinate.
The following references are HARRY W. RUDEL. JONES I. WASSON.
REFERENCES CITED of record in the