Synthetic oils

Abstract

Synthetic base oils for functional fluids and greases are provided comprising a mixture of monoalkylated naphthalenes and polyalkylated naphthalenes, said naphthalenes represented by the formula: ##STR1## wherein the R' groups are independently selected from H and methyl, the monoalkylated naphthalenes have three R groups which are H and one R group which is a 12-26 carbon alkyl, the polyalkylated naphthalenes have from two to four R groups which are 12-26 carbon alkyl and any remainder R groups H, and the weight ratio of monoalkylated naphthalenes to polyalkylated naphthalenes is from 5:95 to 70:30 when the average alkyl group is C.sub.12 -C.sub.16 and from 5:95 to 99:1 when the average alkyl group is C.sub.17 -C.sub.26. In the preferred mixture, the polyalkylated naphthalenes have a numerical ratio of .alpha./.beta. substitution of from 50/50 to 10/90 when the R' groups are both H.

Description

BACKGROUND OF THE INVENTION

There is a continuous need for synthetic oils such as lubricants and base stocks for greases of moderate cost with a combination of low volatility at high temperatures (>200.degree. C.), high flash points (>260.degree. C./500.degree. F.), high fire points (>530.degree. F.), excellent viscosity indices (.gtoreq.100), good pour points (as low as -40.degree. F.), good lubricity and good response to additives.

A group of synthetic oils have now been discovered that fulfills all or most of the above requirements.

BRIEF DESCRIPTION OF THE INVENTION

Synthetic oils have been discovered comprising a mixture of monoalkylated naphthalenes and polyalkylated naphthalenes, said naphthalenes represented by the formula: ##STR2## wherein the R' groups are independently selected from H and methyl, the monoalkylated naphthalenes have three R groups which are H and one R group which is a 12-26 carbon alkyl, the polyalkylated naphthalenes have from two to four R groups which are 12-26 carbon alkyl and any remainder R groups H, and the weight ratio of monoalkylated naphthalenes to polyalkylated naphthalenes is from 5:95 to 70:30 when the average alkyl group is C.sub.12 -C.sub.16 and from 5:95 to 99:1 when the average alkyl group is C.sub.17 -C.sub.26. In the preferred mixture, the polyalkylated naphthalenes have a numerical ratio of .alpha./.beta. substitution of from 50/50 to 10/90 when the R' groups are both H.

Thus, the mixture comprises naphthalenes, methyl naphthalenes and dimethyl naphthalenes and their mixtures alkylated with C.sub.12 to C.sub.26 alkyl groups.

DETAILED DESCRIPTION OF THE INVENTION

In formulating the synthetic oils of the invention, the amount of monoalkylated naphthalene employed in the oil will depend upon the use contemplated for the oil, the particular olefins employed, whether a single olefin or a mixture of olefins is employed to make the polyalkylated naphthalene, and whether a single or mixture of monoalkylated naphthalenes is employed.

Generally, however, the ratio of monoalkylated naphthalene to polyalkylated naphthalene should be from 5:95 to 70:30 by weight, preferably from 5 to 30% monoalkylnaphthalene when the monoalkylated and the polyalkylated alkyl groups are C.sub.12 to C.sub.16 and 15 to 99% monoalkylnaphthalene when said alkyl groups are greater than C.sub.16.

The synthetic oils are manufactured by reacting naphthalene with an .alpha.-olefin (to include mixtures) in a molar ratio of from 1 naphthalene:0.8 olefin to 1 naphthalene:5 olefin at elevated temperatures between about 150.degree. C. and about 260.degree. C. for a time between about 0.25 hrs. and about 6 hrs. in the presence of a catalyst. The ratio of monoalkylated naphthalene to polyalkylated naphthalene can be varied by adjusting the mole ratio of reactants. For example, if it is desired to prepare mixtures high in monoalkylated naphthalene of 50% or more by weight then a mole ratio of naphthalene to olefin of about 1:1 is employed. If it is desired to prepare dialkylated naphthalenes, a mole ratio of naphthalene to olefin of about 1:2.2 is employed. For trialkylated naphthalenes, a mole ratio of naphthalene to olefin of about 1:4 is employed, and a ratio of 1:5 naphthalene to olefin is employed for tetraalkylated naphthalenes. An inert diluent, such as an aliphatic hydrocarbon, may be used. Suitable catalysts include the activated clay alumina silicates and high silica zeolites which are used in an amount from between about 10 wt.% and about 100 wt.% based on the naphthalene. The products are essentially free of unsaturated by-products which would increase their susceptibility to oxidation. The synthetic base oils can be used for making lubricants, hydraulic fluids, vacuum pump oils, heat transfer fluids, and other functional fluids and lithium, aluminum, bentonite and urea complex greases.

The invention will be illustrated in more detail in the following examples. All parts and percentages in said examples and elsewhere in the specification and claims are by weight unless otherwise specified.

EXAMPLE 1

A 1-l glass reactor was charged with 130.0 g. (1.02 m) of naphthalene, 564.0 g. (2.25 m) of Chevron Chemical Co. C.sub.15-20 .alpha.-olefin, which consists of 1% C.sub.14, 17% C.sub.15, 18% C.sub.16, 17% C.sub.17, 17% C.sub.18, 15% C.sub.19, 12% C.sub.20, and 3% C.sub.21 olefin, and 70.0 g. of Filtrol-13 acid activated silica alumina clay (low moisture catalyst). The charge was agitated and heated to 200.degree. C., held at this temperature for six hours, then allowed to cool to room temperature (25.degree. C.) and discharged. The resultant slurry was filtered and the filtrate was distilled to a pot temperature of 260.degree. C. at 1 torr to provide 456.7 g. (65.8% yield on the organics charged; 79.5% yield corrected for losses, mostly holdup in the filter cake) of a residual product as a light amber oil. By IR/NMR (.sup.1 H and .sup.13 C) analysis this residue consisted of 73% of polyalkyl(C.sub.15 -C.sub.20) substituted naphthalenes with about 80% beta substitution and 27% monoalkylated naphthalenes (determined by IR/NMR and GC analysis).

The product had a viscosity of 84 SUS at 210.degree. F., flash point 520.degree. F. (ASTM D92), viscosity index 110, and pour point -5.degree. F. (ASTM D97).

EXAMPLE 2

A 2-l glass reactor was charged with 130.0 g (1.02 m) of naphthalene, 504.0 g. (2.25 m) of hexadecene-1 (Shell Chemical's Neodene-16), and 70.0 g. of Filtrol-13. The mixture was agitated and reacted at 200.degree. C. for 6 hrs., then allowed to cool to room temperature (25.degree. C.) and filtered. The filtrate was distilled to a pot temperature of 260.degree. C. at 1 torr to provide 490.7 g (77.4% yield based on the organics charged; 86.8% yield corrected for losses) of a gold-colored oil. The product was identified by IR/NMR analysis as a naphthalene having an average of two C.sub.16 -alkyl substituents with 34/66 ratio of .alpha.- to .beta. substitution, and containing 24% of C.sub.16 -monosubstituted naphthalene. No olefinic double bond was detectable in this oil. The oil had a flash point of 515.degree. F.; a fire point of 575.degree. F.; a pour point of - 30.degree. F.; a viscosity of 545 SUS and 69.8 SUS at 100.degree. F. and 210.degree. F., respectively, and a viscosity index of 110.

To test for lubricity, the products of Examples 1 and 2 were compared with a commercial mineral oil and two synthetic ester oils in industrial lubricant evaluation tests according to ASTM D2596 and D2266. The results are shown in the following Table I.

TABLE I__________________________________________________________________________ Products of Sohio HUMKO SYNLUBE Ex. 1 Ex. 2. 600.sup.1 3681.sup.2 500.sup.3 TMPTH.sup.4__________________________________________________________________________Four-Ball EPLoad Wear Index, Kg 21.09 19.96Weld, Kg 126.0 80.0Four-Ball Wear 0.27 0.30Scar, mm at 20 Kg1800 rpm, 130.degree. F., 1 hr.Oxidation Stability Test (neat oil)% Evaporation at 400.degree. F.after 24 hrs. 22.9 23.0 34.3 82.2 87.8 Solidafter 48 hrs. 29.8 29.3after 72 hrs. 32.6 31.6after 96 hrs. Solid 35.4Hours to Solidification 96 103 48 24 24 24at 400.degree. F.Viscosity, SUS100.degree. F. 546 600 87210.degree. F. 70 69 66 40% Sludge (Hexane) -- 18 -- -- -- 51.0Insolubles after #Hrs. at 400.degree. F.Flash Point (COC), .degree.F. -- 515 515 -- 490 460__________________________________________________________________________ .sup.1 product of Standard Oil Company of Ohio .sup.2 product of Humko Chemical Company .sup.3 product of Synlube International Co. .sup.4 trimethylolpropane trin-heptanoate, Product of Stauffer Chemical Co. From the results, it can be seen that the products of the invention compare favorably with or are better than the commercial products.

Other useful synthetic oils and their properties are shown in the attached Table II. The alkylated naphthalenes were prepared in a manner similar to Examples 1 and 2.

TABLE II__________________________________________________________________________ Product Reaction % Temp/ Number Ratio Mono Flash PourCatalyst Reactant.sup.a Time Ex. Alkyl .alpha.-.beta. alky- pt., pt., Viscosity, SUS(gm) Quantities .degree.C. hr. No Olefin.sup.b Grps. Substit. late .degree.F. .degree.F. 100.degree. F. 210.degree. V.I.__________________________________________________________________________ALKYNAPHTHALENES-STRUCTURE VS. PROPERTIES70.0 Filtrol 13 1.0mN;4.0mC.sub.14 150 5.5 3 C.sub.14 S 3.0 43:57 10 512 -- 39 62 11357.0 Filtrol 13 0.5mN;2.5mC.sub.14 200 4 4 C.sub.14 S 3.6 36:64 12 525 -40 700 79 10965.0 Filtrol 13 2.0mN;2.0mC.sub.18 220 1 5 C.sub.18 S 1.5 5:95 50 508 +5 389 61 11460.0 Filtrol 13 0.42mN;2.25mC.sub.18 200 4 6 C.sub.18 S 2.8 20:80 -- 535 -- 460 69 11870.0 Filtrol 13 1.0mN;2.25mC.sub.16 200 6 7 C.sub.16 G 2.0 34:66 24 515 -30 525 68 1103.56 lb. Filtrol 13 6.6 lb.N;25.6 lb.C.sub.16 175 6 8 C.sub.16 S 2.1 54:46 20 520 -5 571 72 111100 Filtrol 13 0.8mN;4.0C.sub.16 175 5 9 C.sub.16 S 3.0 39:61 16 535 -- 560 75 12070.0 Filtrol 13 1.0mN;3.5mC.sub.12-14 175 6 10 C.sub.12-14 E 3.0 -- -- 520 -- 480 65 10678 Filtrol 13 0.9mN;2.1mC.sub.12-14 200 4 11 C.sub.12-26 E 2.4 33:67 -- 560 +5 791 84 11770 Filtrol 13 1.0mN;2.5mC.sub.14-16 200 4 12 C.sub.14-16 S 2.3 -- 17 545 -- 525 69 10956 Filtrol 13 2.0mN;4.4mC.sub.14-16 220 1 13 C.sub.14-16 S -- -- 17 520 -- 562 88 13670 Filtrol 13 1.0mN;2.5mC.sub.14-18 200 4 14 C.sub.14-18 S 2.4 24:76 -- 545 -- 580 77 11252 Filtrol 13 1.0mN;2.2mC.sub.14-18 220 3 15 C.sub.14-18 E 2.0 12:88 24 520 -- 510 69 10556 Filtrol 13 2.0mN;4.5mC.sub.14-18 220 1 16 C.sub.14-18 S -- -- 17 545 -- 585 74 114280 Filtrol 13 3.5mN;7.9mC.sub.15-20 200 4 17 C.sub.15-20 C 2.0 37:63 26 533 -- 640 77 11045 Filtrol 13 0.5mN;1.6mC.sub.16-18 175 6 18 C.sub.16-18 E 2.2 50:50 26 530 -- 510 72 11475 Filtrol 13 1.0mN;3.0mC.sub.18-20 200 4 19 C.sub.18-20 E 2.0 40:60 22 540 -- 590 77 11778 Filtrol 13 1.0mN;2.2mC.sub.20-24 200 4 20 C.sub.20-24 G 2.1 37:63 -- 550 -- 625 80 116COMPARISON OILS36 Filtrol 13 0.8mN;3.2mC.sub.8 200 3 21 C.sub.8 F 2.9 30:70 -- 485 -- 200 74 69 220 145 Filtrol 24 1.0mN;2.2mC.sub.10 200 4 22 C.sub.10 G 2.2 23:77 5.3 485 -- 550 60 7865 Filtrol 13 2.0mN;2.0mC.sub.16 220 0.5 23 C.sub.16 G 1.1 12:88 100* 453 -- 140 45 136__________________________________________________________________________ .sup.a N = naphthalene; .sup.b S = Shell Oil Corp.; G = Gulf Oil Corp.; E = Ethyl Corp.; F = Fisher Scientific Corp.; and C = Chevron Corp. .sup.* = Distilled to obtain monoalkylate

In the following Table III base oils of the invention are compared with commercial oils. The base oils of Examples 24-34 were made in accordance with the general procedure of Examples 1 and 2. The resultant products had a weight ratio of monoalkylated naphthalene to polyalkylated naphthalene within the claimed range and the polyalkylated naphthalenes had a numerical ratio of .alpha./.beta. substitution within the preferred range. The olefins employed are listed by carbon number, or carbon number range for mixed olefins, in the table.

TABLE III__________________________________________________________________________COMPARATIVE EVALUATION OF ALKYLNAPHTHALENES OF THEINVENTION WITH COMMERCIAL OILS__________________________________________________________________________Product Monsanto OS-124 Stauffer TMPTHIdentification Sohio 600 Mineral Oil Poly (phenyl ether) Triol triester__________________________________________________________________________Flash pt., .degree.F. 450 550 460Pour pt., .degree.F. -8 +40 -90Viscosity,SUS, 100.degree. F. 1682 77.0Viscosity,SUS, 210.degree. F. 70.2 37.5Viscosity Index -70Evaporation loss, wt. %, 400.degree. F., 24 hrs. 23.2 5.3 92.7Evaporation loss, wt. %, 400.degree. F., 48 hrs. 14.3Evaporation loss, wt. %, 400.degree. F., 72 hrs. 23.1Evaporation loss, wt. %, 400.degree. F., 96 hrs. 30.0Evaporation loss, wt. %, 400.degree. F., 103 hrs. 31.5Evaporation loss, wt. %, 400.degree. F., 127 hrs.Hours to solidify 48 200+ 24Sludge, wt. % at 103 hrs. 1.1Sludge, wt. % at 150 hrs. 10.4__________________________________________________________________________ NASA SynlubeProduct Mil. Spec. 23699 Oil Humko 3681 500 501Identification Fully formulated polyolester Ester Di-ester Di-ester__________________________________________________________________________Flash pt., .degree.F. 490 490 490Pour pt., .degree.F. -90 -36 -70Viscosity,SUS, 100.degree. F. 78.2 86.5 80Viscosity,SUS, 210.degree. F. 37.8 66 39.5 38Viscosity Index 125 177 154Evaporation loss, wt. %, 400.degree. F., 24 hrs. 100 82.2 87.8 91.0Evaporation loss, wt. %, 400.degree. F., 48 hrs.Evaporation loss, wt. %, 400.degree. F., 72 hrs.Evaporation loss, wt. %, 400.degree. F., 96 hrs.Evaporation loss, wt. %, 400.degree. F., 103 hrs.Evaporation loss, wt. %, 400.degree. F., 127 hrs.Hours to solidify 24 24 24 24 72Sludge, wt. % at 103 hrs. 51(24 hrs.)Sludge, wt. % at 150 hrs.__________________________________________________________________________Example 24 25 26 27 28 29Identification 2.8C.sub.12- 3.6C.sub.14- 3.0C.sub.14- 2.2C.sub.16- 2.0C.sub.16- 3.0C.sub.16-__________________________________________________________________________Flash Pt., .degree.F. 535 525 525 525 515 535Pour pt., .degree.F. -40 -40 -40 -5 -30 0Viscosity,SUS, 100.degree. F. 849 699 668 571 546 560Viscosity,SUS, 210.degree. F. 84.0 79.3 77.7 71.8 69.8 74.6Viscosity Index 102 110 95 111 110 119Evaporation loss, wt. %, 400.degree. F., 24 hrs. 13.8 16.2 16.5 18.3 23.0 14.1Evaporation loss, wt. %, 400.degree. F., 48 hrs. 29.8 21.4 26.5 25.2 29.3 19.5Evaporation loss, wt. %, 400.degree. F., 72 hrs. 40.3 26.8 29.9 31.6 24.9Evaporation loss, wt. %, 400.degree. F., 96 hrs. 45.9 31.0 33.8 35.4 28.6Evaporation loss, wt. %, 400.degree. F., 103 hrs. 32.0 34.5 28.7Evaporation loss, wt. %, 400.degree. F., 127 hrs. 32.1Hours to Solidify 96 72 103 103Sludge, wt. % at 103 hrs. 4.2 4.0 41.1**Sludge, wt. % at 150 hrs. 24.5 2.7*__________________________________________________________________________Example 30 31 32 33 34Identification 2.0C.sub.18- 2.4C.sub.12-26 2.1C.sub.14-26 C.sub.14-28 C.sub.15-20__________________________________________________________________________Flash Pt., .degree.F. 525 560 570 520Pour pt., .degree.F. 0 +5 +10 wax -5Viscosity,SUS, 100.degree. F. 603 791 750 -- 700Viscosity,SUS, 210.degree. F. 75.3 84.3 82.9 89.1 83.5Viscosity Index 114 117 111 -- 110Evaporation loss, wt. %, 400.degree. F., 24 hrs. 17.1 9.9 10.4 11.2 27.7Evaporation loss, wt. %, 400.degree. F., 48 hrs. 24.2 15.0 15.8 14.8 33.1Evaporation loss, wt. %, 400.degree. F., 72 hrs. 29.2 20.8 20.3 18.5 46.2Evaporation loss, wt. %, 400.degree. F., 96 hrs. 32.5 24.9 24.1 21.4 50.2Evaporation loss, wt. %, 400.degree. F., 103 hrs. 26.0 25.4 21.7Evaporation loss, wt. %, 400.degree. F., 127 hrs. 30.2 29.2Hours to Solidify 103 127 127 103 96Sludge, wt. % at 103 hrs. 23.2** 55.6** 2.4 26.5***Sludge, wt. % at 150 hrs.__________________________________________________________________________Example 35 36 37 38 39Introduction 2.0C.sub.15-20 1.8C.sub.15-20 2.0C.sub.15-20 1.7C.sub.18-24 2C.sub.24-28__________________________________________________________________________Flash pt., .degree.F. 505 515 540 550 545Pour pt., .degree.F. 0 +25 +10 waxViscosity,SUS, 100.degree. F., 698 588 644 692 --Viscosity Index 79.0 71.5 79.0 80.2 91.0Evaporation loss, wt. %, 400.degree. F., 24 hrs. 109 107 116 113 --Evaporation loss, wt. %, 400.degree. F., 48 hrs. 22.9 29.9 15.5 15.3 9.0Evaporation loss, wt. %, 400.degree. F., 72 hrs. 29.8 36.9 22.9 23.9 13.0Evaporation loss, wt. %, 400.degree. F., 96 hrs. 32.6 43.8 26.0 30.9 17.6Evaporation loss, wt. %, 400.degree. F., 103 hrs. 48.3 29.2 32.9 21.0Evaporation loss, wt. %, 400.degree. F., 127 hrs. 33.6 21.6Hours to Solidify 96 96 103 103 103Sludge, wt. % at 103 hrs.Sludge, wt. % t 150 hrs. 25.0*** 4.5 15.2__________________________________________________________________________ *Added 1 wt. % phosphite of 4, 6di-t-butylresorcinol **% Sludge at 127 hrs. ***% Sludge at 96 hrs.

The following grease formulations (components in parts) are illustrative of the use of the synthetic oils of the invention.

__________________________________________________________________________GREASES Commercial Bentone 40 41 42 43 44 Grease with Mineral Oil__________________________________________________________________________Bentone Clay.sup.1 6.4 8.8 6.4 6.4Polyalkylated 92.2 88.8 84.1 83.2Naphthalene.sup.2Oxidation Inhibitor.sup.3 1.0 1.0Stearic Acid 5.2 6.7Azelaic Acid 5.1Benzoic Acid 2.9Mineral Oil 92.2Anti Wear Vanlube 71.sup.4 2.0Acetone & H.sub.2 O 1.4 1.4 1.4 1.4Aluminum Hydrate 5.2Alpha-olefine polymer.sup.5 92.2Lithium Hydroxide 4.6ASTM D1263-61 modified 308 493 409 576 168 103at 305.degree. F. in hours-Bearing Life__________________________________________________________________________ .sup.1 Product of National Lead Co. .sup.2 2C.sub.16 alkyl groups & 20% C.sub.16 monoalkyl; pour point -5.degree. F., Flash pt. 525.degree. F.;.alpha./.beta. substitution 54/46 .sup.3 Tris(4,6di-t-butyl-3-hydroxyphenyl) phosphite .sup.4 Product of R. T. Vanderbilt Co. .sup.5 A 6 cSt synfluid of Gulf Chemical Co.

From the above, it can be seen that the compositions of the invention have a number of useful properties. Obvious modifications may be apparent to one or ordinary skill, however, and thus the invention is intended to be limited only by the appended claims.

Claims

1. A synthetic base oil for functional fluids and greases comprising a mixture of monoalkylated naphthalenes and polyalkylated naphthalenes, said naphthalenes represented by the formula: ##STR3## wherein the R' groups are independently selected from H and methyl, the monoalkylated naphthalenes have three R groups which are H and one R group which is a 12-26 carbon alkyl, the polyalkylated naphthalenes have from two to four R groups which are 12-26 carbon alkyl and any remainder groups H, the weight ratio of monoalkylated naphthalenes to polyalkylated naphthalenes is from 5:95 to 70:30 when the average alkyl group is C.sub.12 -C.sub.16 and from 5:95 to 99:1 when the average alkyl group is C.sub.17 -C.sub.26 and the oil has a viscosity at 210.degree. F. between 61 and 88 SUS, a viscosity index between 105 and 136, and a flash point (COC=Cleveland open cup) of between 508.degree. F. and 560.degree. F.

2. The base oil of claim 1 wherein a mixture of different polyalkylated naphthalenes is employed.

3. The base oil of claim 1 wherein a mixture of different monoalkylated naphthalenes is employed.

4. The base oil of claim 1 wherein the ratio of monoalkylated naphthalene to polyalkylated naphthalene is from 5:95 to 30:70 and the alkyl groups are C.sub.12 to C.sub.16.

5. The base oil of claim 1 wherein the ratio of monoalkylated naphthalene to polyalkylated naphthalene is from 15:85 to 99:1 when the alkyl groups are C.sub.17 to C.sub.26.

6. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of two 16-carbon alkyl groups.

7. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of three 14-carbon alkyl groups.

8. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 3.6 14-carbon alkyl groups.

9. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 1.5 18-carbon alkyl groups.

10. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.8 18-carbon alkyl groups.

11. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.0 16-carbon alkyl groups.

12. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.1 16-carbon alkyl groups.

13. The base oil of claim 1 wherein the polyalkylated napthalene has an average of 3.0 alkyl groups with 12-14 carbon atoms each.

14. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.4 alkyl groups with 12-26 carbon atoms each.

15. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.3 alkyl groups with 14-16 carbon atoms each.

16. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.4 alkyl groups with 14-18 carbon atoms each.

17. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.0 alkyl groups with 14-18 carbon atoms each.

18. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.0 alkyl groups 15-20 carbon atoms each.

19. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.2 alkyl groups with 16-18 carbon atoms each.

20. The base oil of claim 1 wherein the polyalkylated naphthalene has an average of 2.0 alkyl groups with 18-20 carbon atoms each.

21. The base oil of claim 1 wherein the polyalkylated naphthalenes have a numerical ratio of .alpha./.beta. substitution of from 50/50 to 10/90 and the R' groups are both H.