US2559521A - Synthetic lubricant - Google Patents

Description

Patented July 3, 1951 SYNTHETIC LUBRICANT Paul V. Smith, Jr., Westfield, N. J .,'and Alexander H. Popkin, New York, N. Y., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application November 27, 1948, Serial No. 62,418

6 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 vis- V cosity 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 synthetic lubricants. 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 nonvolatile 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 dicarboxylic acids which contain one or more atoms of oxygen and/or sulfur in ether or thioether linkages, and in which the alcohol residue is a long chain aliphatic hydrocarbon radical ora hydrocarbon radical containing oxygen and/or sulfur in ether or thioether linkages. More precisely, the new class of compounds may be defined by the general formula where R is an organic group which consists of hydrocarbon radicals interlinked by at least one atom of oxygen and/or sulfur, the total number of carbon and oxygen or sulfur atoms in the group being from 3 to and the number of sulfur atoms being not greater than 2. In this group there is at least one carbon atom between each carboxyl group and the nearest oxygen or sulfur atom and at least two carbon atoms between any two oxygen and/or sulfur atoms. The hydrocarbon radicals in group R may be of any hydrocarbon type, whether aliphatic, cycloaliphatic, aromatic, or aliphatic-aromatic, whether straight or branched, and whether saturated or unsaturated, although compounds in which such hydrocarbon radicals are saturated aliphatic radicals are generally preferred. Rand R" of the formula are organic groups, alike or unlike, and may consist of aliphatic hydrocarbon radicals containing a total in the two groups of 16 to 40 carbon atoms, or they may be groups each consisting of a series of saturated aliphatic hydrocarbon radicals interlinked by l to 5 oxygen 3 V and/or sulfur atoms (not more than 2 sulfur atoms), the total number of carbon, oxygen, and sullur atoms in the two groups being from 8 to 40. When the groups contain oxygen or sulfur atoms, there should be at least two carbon atoms between any two such non-carbon atoms and between the carboxyl group and the nearest atom of oxygen or sulfur. The hydrocarbon group at the end of a chain may contain one or more carbon atoms. To produce a composition which will have a sufficiently high viscosity to be useful as a lubricant the components of thecomposition should be chosen so that the molecular weight thereof is at least 300. It is also preferable to prepare compounds having a viscosity not greater than 150 seconds (Saybolt) at 210 F.

The esterification process can be carried out by the usual methods, preferably employing anesterification catalyst, such as p-toluene sulfonic acid, and a water-entraining agent.

Illustrative examples of the dibasic acids which may be employed in the synthesis of the esters of the present invention are the following: diglycolic acid, thiodiglycolic acid, ethylene-bis-glycolic acid, s-oxydipropionic acid, o-di(2-thia-4- carboxybutyDbenzene, 4,7-di-oxa--l,10-decanedioic acid, 4,7,10,13-tetra-oxa-1,16-hexadecanedloic acid, 4,10-di-oxa-7-thia1,13-tridecanedioic acid, 4,7,10,13,16-penta-oxa-1,19-nonadecanediic acid, and 4,7-di-thia-1,10-decanedioic acid.

In addition to the above, it has been found advantageous to prepare esters from dibasic acids which are addition products of unsaturated dibasic acids and alcohols or mercaptans or of monobasic hydroxy and/or mercapto aliphatic acids and diolefins. For example, two mols of thioglycolic acid and one mol of cyclopentadiene may be reacted together to form a product probably having a composition of the type and such an acid may be reacted with alcohols to form esters suitable for use in accordance with the present invention. Similarly, thioglycolic acid may be reacted with vinyl cyclohexene or other diolefins. In a similar manner, addition products may be formed between unsatu rated acids, e. g., maleic acid, and alcohols or mercaptans. The addition product of a maleic acid ester and dodecyl mercaptan is an example.

CHzSCHzCHzC O OH CHzS C'HzCHaC O OH The monohydric alcohols employed in esteritying the dibasic acids described above are typifled by the following:

Methyl alcohol Ethyl alcohol n-Propyl alcohol I I n-Butyl alcohol Isobutyl alcohol n-Amyl alcohol Isoamyl alcohol n-Octyl alcohol 2-ethy1hexyl alcohol Cetyl alcohol Oleyl alcohol Ethylene glycol mono-n-butyl ether Ethylene glycol mono-2-ethylbutyl ether Ethylene glycol mono-2-ethylhexyl ether Many of the above listed ether alcohols, formed 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 Oxo 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 C1 olefins are suitable for this purpose; also higher molecular weight olefinic materials are sometimes employed. Thev 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 tests of the properties of severaltypical esters illustrating the present invention. The esterification process was carried out in each case by the following procedure: A mixture of I one mol of dlbasic acid, 2.2 mols' of alcohol, 0.5 weight percent of p-toluene-sulfonic acid monohydrate, and to 200 mls. of a water-entraining agent such as naphtha, benzene, toluene or the like, is refluxed until no more water is collected in an esterification water trap. The product is washed untilneutral with saturated aqueous NazCOs solution'and then with water. After drying over a desiccant, such as anhydrous CaSO4, the material is stripped at a pressure of 5 mm. to a bath temperature of, 200-225 C.

5 The data obtained in the tests of properties of the esters obtained as described are shown in the following table:

. 6 two carbon atoms between each pair 01' said oxygen atoms and at least one carbon atom between the carboxyl group and the nearest of said oxygen I Kinematic Components of Ester Flash Viscosity AqTM A Point, cosity Z F. Index Acid Alcohol 100 F. 210 F.

Diglvoolic 410 16. 360 3. 696 0. 731 130 80 Do 390 21. 840 4. 083 0. 773 91 -35 fl-0xydlprop1omc 25. 540 5. 298 0 673 150 -35 o 415 226.000 25 160 0565 1'26 Ethvlene-bis-glycohc 445 19 230 6'000 0'41 120 4 I D o 440 23. 950 4. 590 0. 732 121 35 4,7-D1-oxa-Ll0demne-d1o1c 012-011 "0x9 410 22. 97 4. 97 0.672 155 0 Do Butvl Carbltol. e 16. 600 3. 962 0. 094 158 -35 4,7,10,13-letra-oxa-l,l6-hexadecaned1olc... C 0110". 355 13.700 3. 487 0. 702 154 -35 4,7,10,l3,16'le11taoxa-1,lll-nonadecanedioie do. 32. 610 6. 578 0. 634 152 Q-35 Th1od1p1-op1on1c 2-E t hvlbexyl 11. 596 2. 911 0. 760 113 -35 D0 C3 OX0" 13. S90 3. 480 O. 710 148 (-35 D0. C6 "OX0 1' 18. 410 4. 133 0. 705 148 35 Em Cm OX0 19. 880 4.38 0 695 152 (-35 Ds- 266124101? 11-16 4-64 8233 11: 43-1114: emne411616 But vl 26. 580 5:449 0' 670 149 2 filil'ggciioxaJ-thiaq,13-tr1decaned1o1c 01 0x0 22. 840 4. 782 0. 692 146 -35 2 111615 T1116 lycolic 1 ml lsopngle }n-Decyl 32. 210 s. 973 0.681 133 35 Adduct:1 Th 8] 1 2mos io ycoic 1. d m1 cyclopemadiene do 19. 660 4. 306 0. 703 14s 35 not: 2 mols 'Ihioglycolic 1 mo] Vinylcyclohexene 2L4) 680 0'683 154 35 Adduct:l Th

1 mo colic 1 mm undgglenic }Isoamyl 415 13. 990 3. 642 0. 683 167 --10 Adduct:I Th 1 1 1 mo 10 00 ie 1 mo] g gf }Butyl Carbltol 20. 660 4. 722 0. 666 164 -35 Adduct:l Th 1 1 1 1 mo 1 m0] if gg g }Butyl Cellosolve 16.55 4. 061 0.677 169 5 Adduct:l Th 1 l 1 mo 10 co ic M 1 mol 5}: }c "0X0" 455 30.610 5.993 0.664 146 -15 duct:

1 mol Maleic 1 m0] mDodecYlmercaDtan }n-Decanol 475 24. 760 s. 156 0. 676 150 Adductzl M I 1 mo a eie v 1 m0] mDodecmmercaman }C1 OX0 460 23. 970 4. 742 0. 714 133 25 Adduct:l M l 1 mo a eie 'Iri ro ylenc 2] col monois 1 mol n-Dodecylmercaptan $1 e ther. 3 0pm 355 91 31 683 120 5 Adduct' D 1 11161 Itaco 16 Add mmgecylmemman }01 "0x0 440 32v 010 5.882 0. 697 131 uc 1 mol Itaconic 1 m0! n Dodecyl mercaptamuu }Butyl Carb1tol 415 55. 950 9. 822 0.599 144 Adduet:1 I

1 mo taconic 1 Ma 2 tert D0decy1 mmamm }c11-O11 "0x0 s95 50. 84 v. 63 0. 689 -3 I10 I 1 mol Iteconic Tri r0 vlene 1 col monois 1 mo] tert=Dodecyl mercapta p51 -her. g y 0pm 360 1349 754 71 5 Adduct:l O]

1 mo clc I mo1 Thiog1yc0nc }Butyl Carbltol 460 31. 780 6. 471 o. 634 15a 10 0-D1(2-th1a4-carboxy-butyl) b C C12n 0110" 27. 660 5.197 0.709 131 40 The above data indicate that the esters constituting the subject matter of the present invenmay also be blended with mineral lubricating oils C0 to give lubricants of improved viscosity index and pour point.

What is claimed is:

1. As a new composition of matter a compound of the formula 65 where R is an organic group consisting of sat- 7i urated aliphatic hydrocarbon radicals interlinked by at least two oxygen atoms, the total number of carbon and said oxygen atoms in the group R being from 3 to 85, the number of oxygen atoms being at least 2, in which there are at least 7.1

atoms; where R and R are organic groups selected from the class consisting of (1) saturated branched chain aliphatic hydrocarbon radicals containing a total in the two groups of 16 to 40 carbon atoms and (2) radicals consisting of a series of saturated aliphatic hydrocarbon radicals linked through 1 to 5 non-carbon atoms in each group of the class of elements consisting of oxygen and sulfur, the number of sulfur atoms being not greater than 2, and the total number of carbon and said non-carbon atoms in the two groups R and R" being from 8 to 40, there being at least 2 carbon atoms between each pair of said non-carbon atoms and between the carboxyl group and the nearest such non-carbon atom; the components of the composition being so chosen that the molecular weight thereof is at least 300.

2. A composition according to claim 1 in which the groups R and R" are each saturated branched chain aliphatic hydrocarbon radicals and contain a total in the two groups of 16 to 40 carbon atoms.

3. A composition according to claim 1 in which each of the groups R, and R" consists of a series oi. saturated aliphatic hydrocarbon radicals linked through 1 to 5 non-carbon atoms of the class of elements consisting of oxygen and sulfur.

4. As a new composition of matter the ester formed by reacting one molecular proportion 4,7-di-oxa-1,10-decanedioic acid and two molecular proportions of butyl carbitol.

5. As a new composition of matter the ester formed by reacting one molecular proportion of 4,7,10,13 tetra-oxa 1,16 hexadecanedioic acid with two molecular proportions of Ca "Oxo alcohol.

6. As a new composition of matter the ester formed by reacting one molecular proportion of 4,7,10,13,16-penta-oxa-1,19-nonadecanedioic acid with two molecular proportions of Ca 0x0 alcohol.

PAUL V. SMITH, JR. ALEXANDER H. POPKIN.

8 REFERENCES cn'En The following references are of record in the- Number Name Date 2,063,620 Persiel Dec. 8, 1936 2,262,686 Kyrides Nov. 11,1941 2,283,764 Rosefibach May 19, 1942 2,327,652 Kyrides Aug 24, 1943 2,341,846 Meincke Feb. 15, 1944 2,347,627 Bruson Apr. 25, 1944 2,393,327 Langkammerer Jan. 22, 1946 2,425,225 Bearse Aug. 5, 194! 2,468,725 Gresham May 3, 1949 2,469,317 Shokal May 3, 1949

Claims (1)

1. AS A NEW COMPOSITION OF MATTER A COMPOUND OF THE FORMULA