Synthetic Oils

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.

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.

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.

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).

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.

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.

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.

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

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.