US2758975A - Synthetic lubricants - Google Patents

Description

P'atented Aug. 14, 1956 United States Patent fire 2,758,975

simple or mixed carbonate depending on the character 2,753,975 of the second alcohol. The equation is as follows: SYNTHETIC LUBRICANTS ROH F il 0 Dehner L. Cattle, Highland Park, Frederick Knoth, in, Chlomiormic'ester Sayreville, and David W. Young, Westfield, N. J., assignors to Esso Research and Engineering Company, H01 a corporation of Delaware ll 1 No Drawing. Application July 2, 1952, Carbonate Serial No. 296,934 The organic carbonates which may be used for the 4 Claims 252-493) purposes of the invention have the general formula ROCOOR' wherein R and R are hydrocarbon radi- The present invention relates to organic materials usecals having at least 8 carbon atoms. While this broad ful as synthetic lubricants and for various other purposes. group of compounds has utility in the fields of synthetic More specifically, the invention pertains to improved synlubricants and plasticizers, those representatives of the thetic materials having excellent lubricating and plastigroup which have pour points below F. and flash cizing properties and to methods for making these 1113- points above 300 F. have been found to be most suitterials. In its broadest aspect, the invention provides 20 able as lubricating oil bases in general and for the profor the manufacture of lubricants and other valuable duction of low temperature greases in particular. materials, such as plasticizers for resins, rubbers, etc. on In accordance with the preferred embodiment of the the basis of certain organic carbonates having the general invention, the carbonates used have branched-chain hyforrnula ROCOOR'. drocarbon radicals R and R, each radical containing at Prior to the present invention it has been suggested least 8 carbon atoms. These compounds may be obto use certain synthetic oils, particularly certain esters tained by reacting phosgene with branched-chain monoof dibasic aliphatic acids as an oil constituent for greases, hydric or polyhydric alcohols in the manner described engine oils, extreme pressure lubricants and related maabove. Examples of such carbonates are those derived terials. While lubricants prepared on the basis of these from 6-methyl-l-heptanol, Z-n-propyl-l-pentanol, 3-nesters have highly desirable lubricating qualities as well 3 propyl-l-hexanol, 2,2-dimethyl-l-octanol, 10,10-dimethylas excellent high and low temperature characteristics, l-undecanol, 3-isopropyl-l-heptancl.

many of these esters are easily hydrolyzed. In addition, However, it has further been found that good results the field of available raw materials is rather limited. In are consistently obtained when using a group of new carview of the rapidly increasing demand for synthetic bonates which are derived from the product or bylubricating oils in many fields, a broadening of the raw product alcohols of the well known OX0 synthesis. material basis is highly desirable. Similar conditions J This process involves the catalytic reaction of olefins prevail in the field of plasticizers and related materials. with carbon monoxide and hydrogen at elevated tempera- It has now been found that certain organic carbonates tures of about 300400 F. and pressures of about2500 may be substituted for low boiling mineral oil fractions to 4000 p. s. i. g. to form, particularly in the presence and synthetic oils of the type described above in the mo of cobalt catalysts, aldehydes having one carbon atom duction of lubricants, plasticizers and for various other 40 more than the olefin originally used. The aldehyde is uses. These carbonates have excellent lubricating qualicatalyn'eally hydrogenated to the corresponding alcohol ties and combine relatively high boiling points with dewhich is recovered as overhead product by distillation of sirably low pour points, high flash points, low viscositythe reaction mixture. The distillation residue, i. e. the temperature coefficients and high chemical stability. so-called Oxo-bottoms, is rich in by-product alcohols Organic carbonates may be prepared by contacting of higher molecular weight. phosgene with a suitable alcohol at temperatures of about While the exact composition of all these alcohols is 260 to 350 F. Phosgene may either be bubbled through not known, it is well established that they are mixtures the alcohol maintained at reaction temperatures or the of primary alcohols, at least a substantial proportion of phosgene may be dissolved in a solvent, such as toluene, which is of the branched-chain type. The overhead and the alcohol added to the solution maintained at realcohol product consists of a mixture of such alcohols action temperatures, preferably in the presence of a base, averaging 1 carbon atom more than the olefin originally e. g. a tertiary amine such as trimethyl or triethylamine, fed to the Oxo synthesis. It has been found that these dimethylaniline, pyridine or an inorganic base such as alcohols may be reacted with phosgene as described alkali metal hydroxides or carbonates. above to produce new carbonates of the general type The process may be carried out in stages as follows. defined above. Oxo-alcohol carbonates which have The chloroformic ester of the alcohol used may first be branched-chain hydrocarbon radicals containing at least formed by adding 1 mol of alcohol to 1 mol-of phosgene 8, and preferably 10-20, carbon atoms each are preferred as described above. Thereafter, 1 mol of the same or for the purposes of the present invention. of a different alcohol may be added to this chloroformic Novel carbonates having excellent properties for the ester, preferably in the presence of a base to form a purposes of the invention may be obtained by the reaction of phosgene with Oxo-alcohols produced by reacting polymers and copolymers of C3 and C4 monoolefins in the presence of oxonation catalysts as described above. Suitable mixtures of these mono-olefins are readily available in refinery gases and processes for their conversion into liquid copolymers are well known in the art. In accordance with the most widely used of these processes, the olefins are contacted in liquid phase with a polymerization catalyst comprising phosphoric acid supported on kieselguhr. Other similar processes use as catalyst silica gel impregnated with phosphoric acid, or sulfuric acid, Friedel-Crafts catalysts, activated clays, and others. Polymerization conditions in the presence of phosphoric acid catalysts include temperatures of about 300 500 F. and pressures of about 250-5,000 p. s. i. g. The olefinic feed stocks normally contain about l5-60 mol percent of propylene, about 05-50 mol percent of butylenes and from 01-10 mol percent of isobutylene, the remainder being saturated hydrocarbons having 2-4 carbon atoms per molecule. In place of or together with these olefin mixtures the dimer and trimer of isobutylene as well as tri, tetra and penta propylene may be used.

The composition and structure of the C8 Oxo-alcohols obtained from a mixture of C7 olefins of the type described above and more specifically of C7 olefins derived from a refinery gas stream containing propylene and mixed normal and iso-butylenes "are now well understood. These Oxo-alcohols have the following analysis:

Structure of C3 Oxo-alcohols prepared from -04 copolymer Percent heptenes F i OCCCCOOH 29 i t CCCOCO-O-H 25 t i CCC-CCCOH 17 (I) COO-O-C-CGOH 16 C CCCGCC-OH G I i CCC-CCO-OH 2. 3

(I) C(iCCCC-OH 1. 4

2-alkyl-alkanols 4. 3 Others 5. 0

Total. 100. 0

Other Oxo-alcohols are believed to have compositions generally analogous to that specified above, chain lengths and degree of branching depending on the type of olefins used. It is noted in this respect that even when pure straight-chain olefins are used as the starting materials, the alcohols obtained consist predominantly of branched-chain compounds.

Examples of carbonates having utility as lubricating oil bases, plasticizers, etc. are tabulated below together with some of their more important characteristics.

Viscosity in centi- Pour, Flash, stokes at- Garbonate of- T. F.

C10 0x0 alcohol 75 355 2. 43 9. 27 01; 0x0 alcohol. 410 4. 32 23. 8 Cu 0x0 alcohol 40 455 8.32 78. 6

The addition of some polymers improves the viscosity of the 0x0 carbonates as shown in the table below.

Other carbonates having similarly desirable properties include those otbained by reacting phosgene with 0x0- alcohols to form di-isooctyl carbonate and diisoundecyl carbonate.

Some of the critical properties of carbonates prepared from OX0 alcohols in the manner described above are tabulated below in comparison with those of some prior art mineral and synthetic lubricants.

Viscosity in centistokes at- Lubricant Prepared by 0x0 synthesis from- Pour Flash Di'Oi 0x0 adipate C1 copolymer of butylene and propylene- 400 2. 81 9. 84 Di-Cm 0x0 adipate Co polypropylene- (75 465 4. 70 20. 83 Specifications for complex ester-type of lubricating oil 60 470 10. 1 52. 0 Extracted Mid-Continent mineral oil 5 410 4. 99 29. 8 Carbonate of (13 0x0 alcohol 0n polypropylene 70 410 4. 82 23. s Carbonate of C" 0x0 alcohol c polypropylene 40 465 8. 32 78. 6

The above table shows that the new Oxo carbonates of the invention compare favorably with synthetic lubricants as well as mineral oils.

These carbonates may also be used as plasticizers. The results on Mooney viscosity for C13 Oxo carbonate in GR-I butyl rubber (isobutylene-diolefin copolymer) and GR-S styrene butadiene copolymer rubber are recorded in table form below.

It is to be noted that the C13 Oxo carbonate at 25% as well as at 50% concentrations reduces the Mooney viscosity value of these rubbers at 212 F. to a very low value. The preferred range of plasticizer in these rubbers is about 1530%. Good results have also been obtained when adding C13 Oxo alcohol carbonate to ethyl cellulose. The carbonate is compatible with ethyl cellulose and acts as a plasticizer for the latter in concentrations as low as 10% As to other specific uses, extreme pressure lubricants may be produced by incorporating small percentages, e. g. 230 wt. percent of an extreme pressure agent containing sulfur, phosphorus and/or halogen, such as well known hydrocarbon derivatives containing both active halogen and active sulfur into the carbonates of the present invention. Carbonates such as those of the C10 to C16 Oxo alcohols are particularly suitable for this purpose.

For example, when 3% of tri cresyl phosphate was added to the carbonate of C16 Oxo alcohol the lubricant carried all 15 weights on the Almen machine, under both gradual and shock loading conditions.

Lubricating greases in accordance with the invention may be prepared by incorporating into the carbonate grease-making proportions, say about 5-40 wt. percent of a suitable metal soap, preferably an alkali or alkaline earth metal soap of a high molecular weight fatty acid having 30 carbon atoms per molecule or of a soapsalt complex consisting of the soaps of higher molecular Weight fatty acids and the salts of low molecular weight fatty acids, such as acetic, furoic, acrylic, or similar acids. The metal soap or soap-salt complex may be added as such particularly when carbonates are used which contain hydrocarbon radicals having only 5 carbon atoms or less which have a strong tendency to hydrolyze at soapforming conditions. In this case, the preformed dry soap or complex may be slurried into the carbonate and the mixture heated to 300 500 F. while stirring until a homogeneous mass is obtained which is cooled to form the finished grease.

The preparation of greases in accordance with the invention will be illustrated by the following example.

A C13 Oxo alcohol produced by catalytic oxonation of C12 olefin polymer was converted into the carbonate as follows: Phosgene was bubbled through the alcohol which was heated to 284 F. until HCl evolution ceased. The product was washed with water, hydrochloric acid and sodium hydroxide solutions and distilled, the fraction distilling at 338360 F. at 7 mm. pressure being taken as product. This carbonate had the following properties:

A lubricating grease of excellent stability was prepared as follows:

Ingredients: Wt. percent Complex lithium soap 20 C13 0x0 carbonate For preparing the complex lithium soap, a mixture of acetic acid and hydrofol acid (hydrogenated fish oil acids) in a 1:1 mol ratio was coneutralized with lithium hydroxide. The finished dry soap contained a small excess (about 1.0%) of free alkali.

The preformed dry soap was slurried in the carbonate and then stirred while heating to 450 F. The fluid molten grease was cooled without further agitation. The finished product was extremely hard and tended to become crumbly on homogenization. The soap concentration was further diluted with an equal weight of carbonate and reheated to 450 F. and allowed to cool. The finished inhibited grease had the following formulation:

ingredients:

Complex lithium soap 9.0 wt. percent. C13 Oxo carbonate 90.0 wt. percent.

Phenyl alpha naphthyl- 1.0 wt. percent.

amine oxidation inhibitor. inspection and properties:

Dropping point, F. 360. Penetrations,77F.mm./10:

Unworked 265.

Worked, 60 strokes 285. Worked, 60,000 strokes 290.

Water solubility Insoluble.

Appearance S m o o t h uniform, homogeneous grease. Light homogenization however results in greater smoothness.

It is noted that the above grease-making example is presented to illustrate the utility of the carbonates of the present invention as a synthetic lubricating oil base. Greases based on the carbonates of this invention and processes for preparing such greases are claimed and described in greater detail in the copending Morway, Cattle and Young application, Serial No. 296,935, filed of even date with the present application and assigned to the same interests.

The invention is not limited to the specific figures of the foregoing examples. The relative proportions of the materials used may be varied within the limits indicated in the specification to obtain products of varying characteristics.

What is claimed is:

1. A synthetic lubricating composition which comprises a major proportion of a mixture of organic carbonates of the formula wherein R and R are branched chain alkyl groups derived from C10 to C20 alcohols, containing combined therein a minor but extreme pressure-improving amount of tricresyl phosphate, said mixture of organic carbonates having a pour point below about 20 F. and a flash point above about 300 F., said alcohols being predominantly isomeric mixtures of branched-chain saturated aliphatic primary alcohols.

2. A synthetic lubricating composition according to claim 1 wherein said alkyl groups contain from about 13 to about 16 carbon atoms.

3. A synthetic lubricating composition according to claim 1 wherein said alkyl groups contain about 13 carbon atoms.

4. A synthetic lubricating composition according to claim 1 wherein said alkyl groups contain about 16 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS Mitchell Aug. 9, 1927 Kvalnes Aug. 24, 1937 Dickey et a1. Apr. 4, 1939 Wojcik Dec. 21, 1943 Knutson et a1. Feb. 1, 1944 OTHER REFERENCES Ind. and Eng. Chem, vol. 39, No. 4, pages 491-497. Ind. and Eng. Chem, vol. 42, No. 12, pages 2422, 10 2423, and 2426.

Claims (1)

1. A SYNTHETIC LUBRICATING COMPOSITION WHICH COMPRISES A MAJOR PROPORTION OF A MIXTURE OF ORGANIC CARBONATES OF THE FORMULA