US2739127A - Lubricating grease containing organic carbonates - Google Patents

Description

LUBRICATING GREASE CONTAINING ORGANIC CARBONATES No Drawing. Application July 2, 1952, Serial No. 296,935

Claims. (Cl. 252-41) The present invention relates to organic materials useful as synthetic lubricants. More specifically, the invention pertains to improved synthetic lubricating greases having excellent lubricating properties over a wide temperature range, particularly at extremely low temperatures, and to methods for making the same.

In its broadest aspect, the invention provides for the manufacture of lubricating greases on the basis of certain organic carbonates having the general formula RO-CO-OR'. One of the most important phases of the invention pertains to improved lubricating greases, particularly low temperature greases containing such carbonates as a lubricating oil constituent and to methods for making such greases.

Prior to the present invention, low temperature greases have been prepared by compounding low boiling mineral oil fractions having low viscosities with metal soaps in grease making proportions. However, such greases are frequently subjected to relatively high temperatures in normal use. The mineral oil used in making the grease should, therefore, combine low viscosity with low volatility in order to provide efficient low temperature lubrication and at the same time prevent oil losses at relatively high temperatures. Since most low boiling mineral oils of sufficiently low viscosity have high volatilities, the number of mineral oils suitable for the production of low temperature greases is very limited.

More recently it has been suggested to use certain synthetic oils, particularly certain esters of dibasic aliphatic acids as an oil constituent for low temperature greases. While greases prepared on the basis of these esters have highly desirable lubricating qualities as well as excellent high and low temperature characteristics many of these esters are easily hydrolized. The soap and the grease, therefore, must be made in separate stages. In addition, the field of available raw materials is rather limited. In view of the rapidly increasing demand for greases having utility over a wide range of temperatures, a broadening of the raw material basis is highly desirable.

It has now been found that certain organic carbonates may be substituted for low boiling mineral oil fractions and synthetic oils of the type described above in the pro duction of low temperature greases. These carbonates have excellent lubricating qualities and combine relatively high boiling points'with desirably low pour points, high flash points, low viscosity-temperature coefiicients and high chemical stability.

Organic carbonates may be prepared by contacting phosgene with a suitable alcohol at temperatures of about 260 to 350 F. Phosgene may either be bubbled through the alcohol maintained at reaction temperatures or the phosgene may be dissolved in a solvent, such as toluene, and the alcohol added to the solution maintained at reactioii temperatures, preferably in the presence of a base, e. g. a tertiary amine such as trimethyl or triethylamine, dimethylaniline, pyridine or an inorganic base such as alkali metal hydroxides or carbonates.

The process may be carried out in stages as follows.

, masher Patented Mar. 20, lfififi The chloroformic ester of the alcohol used may first be formed by adding 1 mol of alcohol to 1 mol of phosgene as described above. Thereafter, 1 mol of the same or of a different alcohol may be added to this chloroformic ester, preferably in the presence of a base to form a simple or mixed carbonate depending on the character of the second alcohol. The equation is as follows:

0 hlorolormic ester RO-C-Cl HOB -t RO-C-OR' 1101 Carbonate sentatives of the group which have pour points below 20 F. and flash points above 300 F. have been found to be most suitable as lubricating oil bases for greases in general and for the production of low temperature greases in particular. For the latter purpose it has been found desirable to use carbonates wherein R and/or R have at least 8 carbon atoms because carbonates of lower molecular weight are easily hydrolyzed and, therefore, not well suited for commercial grease manufacture wherein saponification or acid neutralization is carried out in the lubricating oil base.

In accordance with the preferred embodiment of the invention, the carbonates used have branched-chain hydrocarbon radicals R and R, each radical containing at least 8 carbon atoms. These compounds may be obtained by reacting phosgene with branched-chain monohydric or polyhydric alcohols in the manner described above. Examples of such carbonates are those derived from 6- methyl-l-heptanol, 2-n-propyl-l-pentanol, 3-n-propyl-1- hexanol, 2,2-dimethyl-l-octanol, 10,10-dimethyl-1-undecanol, 3-isopropyl-l-heptanol.

However, it has further been found that good results particularly in the production of low temperature greases are consistently obtained when using a group of new carbonates which are derived from the product or by-product alcohols of the well known Oxo" synthesis. This process involves the catalytic reaction of olefins with carbon monoxide and hydrogen at elevated temperatures of about 300-400 F. and pressures of about 2500-4000 p. s. i. g. to form, particularly in the presence of cobalt catalysts, aldehydes having one carbon atom more than the olefin originally used. The aldehyde is catalytically hydrogenated to the corresponding alcohol which is recovered as overhead product by distillation of the reaction mixture. The distillation residue, i. e., the so-called 0x0- bottoms, is rich in by-product alcohols of higher molecular weight.

While the exact compositions of all these alcohols is not known, it is well established that they are mixtures of primary alcohols, at least a substantial proportion of which is of the branched-chain type. The overhead alcohol product consists of a mixture of such alcohols averaging 1 carbon atom more than the olefin originally fed to the 0x0 synthesis. alcohols may be reacted with phosgene as described above to produce new carbonates of the general type defined above. Oxo-alcohol carbonates which have branchedchain hydrocarbon radicals containing at least 8, and preferably 10-20, carbon atoms each are preferred forthe purposes of the present invention.

Novel carbonates having excellent properties for the purposes of the invention may be obtained by the reac- It has been found that these tion of phosgene with UXO-Blcoiltlia produced by reactstraight-chain oleflns are used as the starting materials ing polymers and copolymers of Ca and Cs mono-oleflns the alcohols obtained consist predominantly of branchedin the presence of oxonation catalysts as described above. chain compounds.

Suitable mixtures of these mouo-olefins are readily avail- Examples of carbonates having utility as lubricating able in refinery gases and processes for their conversion oil bases for greases are tabulated below together with into liquid copolymcrs are well known in the art. In some of their more important characteristics. 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 Vmsitym mm Ccntlstokes kieselguhr. Other similar processes use as catalyst silica l Carbonate oto o gel impregnated with phosphoric acid, or sulfuric acid, mo mo F. Friedel-Crafts catalysts, activated clays, and others. Polymerization conditions in the presegge 00%l:0s5ph0 ril(=: acig g g ;g 355 catalysts include temperatures of a ut 00 an n X0 00 0 410 23-8 pressures of about 250-5,000 p. s. i. g. The olefinic feed stocks normally contain about 15-60 mol percent of propylene, about 0.5-50 moi percent of butylenes and Other carbonates having similarly desirable properties from 0.1-10 mol percent of isobutylene, the remainder include those obtained by reacting phosgene with Oxo-albeing saturated hydrocarbons having 2-4 carbon atoms cohols to form di-iso octyl carbonate and di-"iso" unper molecule. In place of or together with these olefin decyl carbonate. 7 mixtures the dimer and trimer of isobutylene as well as Some of the critical properties of carbonates prepared tri, tetra and penta propylene may be used. from Oxo alcohols in the manner described above are The composition and structure of the Cs Oxo alcohols tabulated below in comparison with those of some prior obtained from a mixture of C1 olefins of the type deartmineral and synthetic lubricants.

Viscosity in m b o Oentistokee so Lnbrlmnt ag a Pour Flash Q 210 6 100' F. I.

Dl-Os Oxo Adlpete C1 eopol mer oi butyl- (-75 I!) 2.81 9.8 one an Dl-Ou 0x0 Adlpate Os Polypropy (-76 466 4. 70 ll. 88 Specifications for Oomglax Ester- -so 470 10.1 62.0

Type of Lubricating Extracofl ted Mid-Oontinmt Mineral -5 410 L99 Carbonate of 0 0x0 Alcohol o Polypropylene -10 410 4.32 ass Carbonate 010:: 0x0 Aloohol.--... cl: Polypropylene --so use a 32 n. o

scribed above and more specifically of C1 olefins derived The above table shows that the new 0x0 carbonates from a refinery gas stream containing propylene and of the invention compare favorably with synthetic lubrimixed normal and isobutylenes are now well understood. cants as well as mineral oils with respect to their utility These Oxo alcohols have the following analysis: asgreasebases.

' Lubricating greases in accordance with the invention may be prepared by incorporating into the carbonate Structure ot 0; 0x0 alcohols paepared trom C1-C4 c p r hapwnes Perm grease-making proportions, say about 5-40 wt. percent of a suitable metal soap, preferably an alkali or alkaline C C earth metal soap of a high molecular weight fatty acid Q J: C C OH 2 having 1.0-30 carbon atoms per molecule or of a soap-salt C c so complex consisting of the soaps of higher molecular J: weight fatty acids and the salts of low molecular weight 0- CCC0H 25 fatty acids such as acetic, furoic, acrylic or similar acids. 0 c The metal soap or soap-salt complex may be added as such particularly when carbonates are used which conat" 63 tain hydrocarbon radicals having only 5 carbon atoms or C less which have a strong tendency to hydrolyze at soapc-o-d-o-c-c-c-o-n forming conditions. In this case, the preformed dry soap 0 or complex may be slurried into the carbonate and the mixture heated to 300'-500 F. while stirring until a w homogenous mass is obtained which is cooled to form 0 the finished grease. I Wheat; carbgrngges with hydrocarbon radicals having more an 8 c n atoms are used, the grease thickening soap 'or soap-salt complex may be formed in situ in the c u carbonate which is not hydrolyzed at the soap-forming u conditions. For this purpose, suitable fatty acids may be mixed with the carbonate in grease making proportions and heated toabout 100'-200' F. A metal hygatgt-dhnots t3 droxide, preferably caustic alkali, is then added in aqueous solution and in amounts at lerst sufiicient to neutralize the'acids. The mixture is heated to about 300'400' F. until neutralization is completed and the mixture is com- Other 0x0 alcohols are believed to have compositions p e y dehydrated. p cooling. the c e s i he generally analogous to that specified above, chain lengths For the production of low temperature greases lithium and degree of branching depending on the type of olen soaps or lithium soap-salt complexes are preferred.

fins used. It is noted in this respect that even when pure After completion of the neutralization process, the

spoons? greases may be further med by the addition of other lubricating oils, particularly synthetic oils, such as the more readily hydrolyzable esters of dibasic acids, complex esters and others. Other eonventionai modifying agents may be added to the carbonates of the invention in a man- 5 per known to the art. These include thickeners, such as N-stearyl-p-arnino phenol, antioxidants, such as phenyl alpha naphthylamine, phenothiazine, corrosion inhibitors, such as zinc naphthenate or sulfonate soaps, tackiness agents, such as polybutenes, poly acrylate and poly methi acrylate esters, load carrying compounds, such as sulfochlorinated hydrocarbons or lead oleate or naphthenate, viscosity index improvers, such as polybutenes or poly acrylate esters.

The preferred thickeners for low temperature greases iii in accordance with the present invention are lithium soaps of hydrogenated fish oil acids or complexes of such soaps with lithium salts of low molecular weight fatty acids of the type described above. It may also be desirable to add small amounts, say, about 0.5- wt. percent of a stabilizer to these greases to improve their texture and consistency. The oxides, carbonates, or soaps of metals forming amphoteric oxides, such as the soaps of zinc, tin and aluminum, are useful for this purpose.

The invention will be further illustrated by the follow- 25 ing specific examples.

Example I Example Ii the greases. This is borne out by the following data.

llnents: Wt. lercent lhlydrofol acid i0.0 LiOH-HzO 1.7 Cu Oxo carbonate of Example I 30.0 Di-Z-ethyl hexyl sebacate 57.3

Phenyl alpha-naphthylamine oxidation inhibitor 1.0

The Hydrofol acids and the carbonate were charged to a fire heated grease kettle and warmed to 150 F. The lithium hydroxide in a 10% aqueous solution was added and heating continued. When the acid was completely neutralized and dehydrated after extended heating at about 300 F. the dibasic ester di-Z-ethyl hexyl scbacate was charged and the mass heated to 420 F. The inhibitor was added and heating and mixing discontinued. The fluid grease was drawn into pans for cooling in thin layers.

A C13 0x0 alcohol produced by catalytic oxonation of 80 Proparflea:

C1: olefin polymer was converted into the carbonate as follows: which was heated to 284 F. until H C1 evolution ceased.

The product was washed with water, hydrochloric acid and sodium hydroxide solutions and distilled, the fraction 85 distilling at 338-360 F. at 7 mm. pressure being taken as product. This carbonate had the following properties:

Flash, F. 405

Viscosity, centistokes:

210 F. 4.38 100 F. 23.8 4 F, 23765 Pour, F. -65

A lubricating grease of excellent stability was prepared as follows:

Ingredients: Wt. Percent Complex lithium soap C13 0x0 carbonate 80 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:

rease Light homage ration howev'er results in 'sm thnass.

Phosgene was bubbled through the alcohol greater 1 Appearance Smooth uniform grease cake. Completely homogeneous short fibered product alter homogenization.

Dropping int, F 365.

Water so u llity Insoluble in boiling water.

Penetration, 77 F. mm./l0:

Unworkad 285. Worked 60 strokes.

flmann bomb dil'dt'l'riri' (hrs. to 5 p. s. 1. drop in oxygen pressure) Cu corrosion 24 hrs. at 210 F None.

Reference is made to the copending Cottle, Knuth and Young application, Serial No. 296,934, filed of even date with the present application and assigned to the same interests, wherein the carbonates used as lubricating oil bases for greases in accordance with the present invention are claimed broadly and for various other uses.

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:

l. A lubricating grease comprising a major proportion of a liquid organic carbonate having the formula RO-CO-OR' in which R and R are hydrocarbon radicals each having at least 8 carbon atoms, said carbonate having a pour point below 20 F. and a flash point above 300 F.; and about 5 to 40% by weight, based on the total composition, of a grease thickener selected from the group consisting of (1) metal soaps of high molecular weight fatty acids having 10 to 30 carbon atoms per molecule and (2) complexes of such metal soaps with metal salts of low molecular weight fatty acids, said metal being selected from the group consisting of alkali metals and alkaline earth metals.

2. The grease of claim 1 in which said metal is lithium.

3. The grease of claim 1 in which said metal is lithium and said high molecular weight fatty acids are hydrogenated fish oil acids.

4. The grease of claim 1 in which said metal is lithium and said low molecular weight fatty acid is acetic acid.

5. The grease of claim 1 which comprises a second lubricating oil constituent other than an organic carbonate.

6. The grease of claim 1 in which R and R are radicals each derived from a primary branched-chain alcohol assume? 0 having in the range of 8 to 20 carhonatoms per molecule. 7. The grease of claim 6 in which said alcohol is an Oreo-alcohol obtained by reacting an olefin with carbon monoxide and hydrogen at an elevated temperature and pressure in the presence of a cobalt catalyst.

8. The grease of claim 7 in which R and R are the radical of a C10 Ciro-alcohol.

9. Ike grease of claim 7 in which R and R are the radical of a C13 Om-alcohol.

10. The grease of claim 7 in which R and Rere the radical of a Cu Oxo-alcohol.

References Citctl in the file of this patent UNITED STATES 1,638,014 Mitchell Aug. 9, 1927 8 Dickey et al. Apr. 4, 1939 Wojcik Dec. 21, 1943 Knutson et a1. Feb. 1, 1944 Zimmer et a1. Feb. 17, 1948 Morway et al Nov. 13, 1951 Owen et a1 Apr. 29, 1952 Mikcska. et a1. Sept. 8, 1953 OTHER REFERENCES

Claims (1)

1. A LUBRICATING GREASE COMPRISING A MAJOR PROPORTION OF A LIQUID ORGANIC CARBONATE HAVING THE FORMULA RO-CO-OR'' IN WHICH R AND R'' ARE HYDROCARBON RADICALS EACH HAVING AT LEAST 8 CARBON ATOMS, SAID CARBONATE HAVING A POUR POINT BELOW 20* F. AND A FLASH POINT ABOVE 300* F.; AND ABOUT 5 TO 40% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF A GREASE THICKENER SELECTED FROM THE GROUP CONSISTING OF (1) METAL SOAPS OF HIGH MOLECULAR WEIGHT FATTY ACIDS HAVING 10 TO 30 CARBON ATOMS PER MOLECULE AND (2) COMPLEXES OF SUCH METAL ATOMS PER METAL SALTS OF LOW MOLECULAR WEIGHT FATTY ACIDS, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS.