US2801973A - Grease process utilizing the alkali fusion of aldehydes - Google Patents

Description

asthma GREAdE PRUQES UTllLlZlNG THE ALKAILI FUSKUN @F ALDEHYDES Arnold J. lliorv /ay, Railway, and .letirey H. Bartlett and Louis A. Mikeslra, Westiieid, N. 3., assignors to Essa Research and Engineering Company, a corporation of Delaware No Drawing. Application December 25,-, 1952, Serial No. 327,166

'7 (Ilaims. (Cl. 252-41) The present invention relates to an improved method of preparing lubricating greases and to grease compositions produced by this method. More specifically, the invention pertains to improvements in the manufacture of grease thickeners and to greases containing such thickeners. The invention provides for making grease thickenersby fusing aldehydes, particularly branched-chain aldehydes with caustic alkali, producing a metal soap fromthe acid so formed and incorporating this metal soap into a lubricating oil in grease making proportions. In a preferred embodiment of the invention, the fusion is carried out in the presence of lubricating oil.

Lubricating greases normally consist of lubricating oils thickened by alkali and alkaline earth metal soaps or other thickeners to a solid or semi-solid consistency. The soaps may be prepared by the neutralization of high molecular weight fatty acids or by the saponification of fats which is usually carried out in a portion of the oil to be thickened.

The present invention pertains to highly valuable, stable lubricating greases in which the high molecular weight fatty acids are replaced or at least supplemented by a new grease making material. It has now been found that such greases may be prepared by incorporating into lubricatingloils a 'grease' thickener obtained by fusing suitable aldehydeaparticularly branched-chain aliphatic aldehydes with alkali, particularlycaustic soda or potash at temperatures of about 350-620" R, preferably about 500-560 R, for a time sufiicient to form the alkali metal salt of the acid corresponding to the aldehyde used. The chemical reaction taking place during the fusion process may be illustrated by the following equation? RCl-lO+MOH- H2+RCOOM wherein R maybe a branched-chain aliphatic radical and M is analkali metal such as sodium or potassium.

The discovery of the utility of alkali fusion of aldehydes for grease making increases the wealth of raw materials available for grease production. Heretofore, ester-type fats, oils or high molecular weight fatty acids have beenused almost exclusively in the manufacture of soap-thickened greases and these starting materials have been believed indispensable'for the purpose. All these materials have numerous other industrial uses, asituation conducive to the development of shortages forcing frequent variations in grease making procedures and grease characteristics. The discovery of an entirely new and large class of suitable raw materials cases this situation considerably. i

"Theme of aldehydes introduces no complication into the grease making procedure. While alkali fusion of 2 the aldehyde may be carried out in a separate preliminary acid-forming stage, the greases are preferably produced essentially in a single process step in which the aldehyde is fused with alkali in the lubricating oil base in grease making proportions and at grease making conditions, although at somewhat higher temperatures. At the conclusion of the fusion process a finished grease is obtained.

Aldehydes useful for the purposes :of the present invention have become available in large quantities as intermediate or final products of various synthesis processes and more particularly as products and by-products of the well-known 0x0 synthesis. The last-named process involves the catalytic reaction of olefins with carbon monoxide and hydrogen at elevated temperatures, say about BOW-400 F, and pressures of about 2500 to 4000 p. s. i. g. in the presence of group VIII metal catalysts, particularly cobalt catalysts, to form saturated oldehydes having one carbon atom more than the olefin originally used.

Quite generally, aldehydes may be used which, upon alkali fusion, yield acids or salts having about l030 carbon atoms per molecule. As to the type of aldehydes suitable for the invention, straight or branched-chain aldehydes may be used. Oxo-aldehydes having 10 or more carbon atoms are preferred. However, lower molecular weight aldehydes, such as Cs andCq aldehydes may be used by promoting an aldol condensation in the course containing 10 or more carbon atoms.

of the soapunaking process. Also,.in.a closed system,

aldehydes of even lower molecularweight; such as C2 or C3 aldehydes, may be used in this case in combination with aldehydes of higher molecular weight to form aldols Examples of such aldehydes are acetaldehyde, propionaldehyde, butyr-aldehyde, etc.

In aldolization, two molecules of aldehyde condense with the elimination of water to yield an unsaturated aldehyde of higher molecular weight. In carrying out the invention, aldolization generally occurs to some extent with all aldehydes that have an alpha hydrogen atom. Thus, the alkali-fused product consists of a mixture of soaps of the acid corresponding to the original aldehyde and of the acid corresponding to the aldol product.

Particularly desirable starting materials are the 0x0 aldehydes obtained by oxonation of polymerized olefins or olefins from cracked waxes, cracked petrolatums and other high molecular Weight hydrocarbon products, for example Fischer-Tropsch olefins. Especially useful are the branched-chain oldehydes produced by oxonation of olefin polymers, such as polymers of propylene, butylene, isobutylene, amylene, etc., for example tetrapropylene, triisobutylene, pentapropylene, tetraisobutylene, hexapropylene, pentaisobutylene, etc., as Well as copolymers such as those produced from propylene and butylene, etc. Among the suitable aldehydes are decanal, dodecanal, isododecanal, isotridecanal, tetradecanal, isopentadecanal, isohexadecenal, octadecanal, iso-octadecanal, isooctaclecenal, iso-nonadecanal, iso-pentacosanal, iso-hexacosenal,etc.

While the composition and structure of many Oxo aldehydes are not fully known, those of the Ca aldehyde ob tained from a mixture of C olefins of the type described above and more specifically of C7 olefins derived from arefinery gas stream containing propylene and mixed normal and iso-butylenes are now Well understood. This Ciro-aldehyde is a mixture of aldehydes having the following composition:

Other Oxo-aldehydes are believed to have compositions generallyanalogous 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 aldehydes have some branching.

-When carrying out the aldehyde fusion in the lubricating oil itself so as to form the grease thickening soap in situ in accordance with the preferred embodiment of the invention, it has been observed that the alkali has a strong tendency to settle out of the reaction mixture to the bottom of the reactor in the form of a cake which does not fully participate in the reaction. Highly efiicient stirring or agitation will counteract this tendency. However, in many cases more efficient stirring is required than may be obtained .in conventional grease kettles and special equipment would have to be used.

This settling tendency of the alkali in the lubricating oil-aldehyde mixture is negligible when a sufficient amount of a solid suspending agent is present in the reaction mixture. Most desirable suspending agents are those which serve simultaneously as grease thickeners, such as soaps of high molecular weight fatty acids, silica gel, carbon black, bentones, Attapulgus clay modifications, etc. Soaps, particularly sodium soaps of high molecular weight fatty acids are preferred for this purpose. However, the melting points of most of these soaps in lubricating oil is rather low, usually below 400 F. Thus, at the high reaction or fusion temperature of about 500 F. or thereabove, these soaps are liquid when used as such and do not entirely counteract the settling tendency of the alkali. This difliculty may be overcome in accordance with a specific embodiment of the invention by using the salt, preferably the alkali metal salt, of a low molecular weight acid in addition to the high molecular weight. fatty acid soap. In this manner, soap-salt complexes are formed 4 which melt well above 500 F. and thus form an excellent suspending agent.

These soaps or soap-salt complexes are preferably formed in situ by neutralization of the corresponding acids in the aldehyde-oil mixture with alkali added in amounts suflicient for this neutralization and for the subsequent fusion which takes place at considerably higher temperatures. High molecular weight acids useful for this purpose include hydrogenated fish oil acids, Cm-Czz naturally occurring acids of animal or vegetable origin, etc. These acids may be used in amounts ranging from about 2-30 wt. percent based on the finished product. Suitable low molecular weight acids include acetic, furoic, acrylic and similar acids to be used in proportions of about 1-10 wt. percent based on the finished product. Esters of the high and/ or low molecular weight acids, particularly those containing mono basic acid esters may be used in place of the free acids in corresponding proportions. In this case, the alcohol portions of the esters are converted into acids and the corresponding soaps by alkali fusion. If esters of low molecular weight alcohols are used, elevated pressures may be employed to prevent volatilization of the alcohols. Of course, esters of non-volatile low molecular weight alcohols, such as polyhydroxy alcohol esters, e. g. sorbitol acetate, glycol acetate, etc. may be used. Particularly the high molecular weight type of acids or their esters used for this purpose may also be prepared by alakil fusion of 0x0 aldehydes. In this case, a portion of the product of the alkali fusion process in which the principal grease thickener is prepared in accordance with the invention may be returned to the fusion stage to serve as an agent preventing settling of the alkali.

Soaps of high molecular weight fatty acids and/or soap-salt complexes of the type specified may be incorporated in the greases of the present invention to improve high temperature or other characteristics even if no suspending agents are required. This is useful when branched-chain aldehydes are employed, since it has been found that the use of soaps of branched chain acids as the sole grease thickeners often tend to form rubbery or cohesive structures which may be undesirable. However, when these branched chain soaps are mixed with straight chain soaps derived from fatty acids, this c-ohesive structure is largely eliminated or modified to an extent that is desirable for certain purposes.

The soaps formed by alkali fusion of aldehydes in the presence of other fatty acid soaps consistently yield excellent smooth greases. Other conventional thickeners, anti-oxidants, corrosion inhibitors, tackiness agents, loadcarrying compounds, viscosity index improvers, oiliness agents, and the like may be added prior, during and/or after the fusion process as will be apparent to those skilled in the art.

The base oil used as menstruum during the fusion process should be a mineral lubricating oil. After the fusion is completed, synthetic lubricating oils, such as a dibasic acid ester (e. g. di-2-ethyl hexyl sebacate, adipate, etc.), polyglycol type synthetic oils, esters of dibasic acids and polyhydric alcohols, etc., as well as alkyl silicates, carbonates, formals, acetals, etc., may be used alone or in addition to mineral lubricating oil to bring the grease to the desired consistency. The oil base preferably comprises about 50 to about of the total weight of the finished grease.

.As indicated above, the alkali fusion of the invention may be carried out in two stages. When so operating, the aldehyde to be fused may be added to a molten mixture of alkali and mineral oil, preferably a heavy paraflinic oil maintained at fusion temperatureof, say, about 400- 620 F. The aldehyde and alkali may be used in substantially stoichiometric proportions, When all the aldehyde has been added, heating may be continued at these temperatures until gas evolution substantially ceases.

The acid formed may be recovered from the reaction mixture after cooling, by dilution with water followed by extraction of the oil and any unreacted aldehyde with a light hydrocarbon solvent, such as heptane or the like, and acidification of the aqueous rafiinate. If desired, the free acid may be purified by vacuum distillation. The acid so prepared may then be introduced into a lubricating oil base stock, other high and/or low molecular weight fatty acids as well as other grease additives may be added and the mixture may be converted into a grease by the addition of at least sufficient caustic alkali, preferably in aqueous solution, to neutralize the acids present. Conventional grease making conditions including temperatures of about 350-500 F. may be used in this stage. The soap derived from the aldehyde by alkali fusion should form at least 20 wt. percent and preferably about 30-50 wt. percent of the grease thickener or about 2.020 wt. percent of the finished grease. The remainder of the grease thickener is preferably made up by a suitable soapsalt complex of the type described above. The proportion of soap derived from aldehyde to soaps and salts derived from other acids may be about 1:4 to 4:1 and preferably is about 1:1.

In order to prepare a grease by alkali fusion of the aldehyde in situ in accordance with a more desirable embodiment of the invention, the grease making procedure may be quite generally as follows. A mineral lubricating oil base is mixed with the aldehyde and the mixture is heated to about 130180 F. The alkali is added preferably in the form of an aqueous solution of about 30-50% concentration. The mass is then dehydrated at temperatures of about 300 400 F. for about 24 hours. Thereafter, the temperature is increased to a fusion temperature of about 400620 F. and maintained Within this range until gas evolution has receded appreciably, which takes place usually after about 1-3 hours. The grease may then be allowed to cool under stirring to about 200-250 F. at which level further additives may be introduced. Finally, the grease may be poured into pans toibe cooled to room temperature.

A similar procedure is employed when the aldehyde is subjected to alkali fusion in situ in the presence of suspending agents, such as soaps of high molecular weight fatty acids or complexes of such soaps with low molecular Weight fatty acid salts in accordance with the preferred embodiment of the invention. In this case, the high molecular weight acids are added to the mineral oil together with the aldehyde while the low molecular weight acid may be added after the initial heating stage immediately prior to the alkali addition. Thereafter, suliicient caustic alkali to neutralize the acids and convert the aldehyde to soap is added, preferably in the form of an aqueous solution of about 40-50% and the mixture is heated at a saponification temperature of about 300-400 F. until the acids are converted to soaps and salts and all the Water is volatilized. Alkali fusion is then carried out substantially as described above, except that less violent stirring is required.

The invention will be best understood by reference to.

the following specific examples which represent preferred modifications of the invention.

Example I Octadecenyl aldehyde prepared by oxonation of diisobutylene followed by aldolization of the Oxo-nonylaldehyde was used in preparing a grease as follows:

Ingredients: Weight percent Octadecenyl aldehyde 10.00 Hydrofol Acids 54 1 10.00

1 Hydrogenated fish oil acids corresponding in unsaturation to commercial stearic acid.

Preparati0n-.'The aldehyde, the nydrofol Acids 5 4 and /z of the mineral oil was charged tofa grease kettle and warmed to 150 F. The glacial acetic acid was added Properties Unhomoge- Homoge nlzed nized Appearance Excellent smooth somewhat fibrous rease Penetrations, 57 F., 111111.]102

Unworke 154 158 Worked 60 Strokes 179 166 Worked 100,000 Strokes 1 210 Dropping Point, F 500+ 500+. Water Washing Test, Percent Loss None N one Norma-Hoffman Oxidation Test, Hours to 5 p. s. 1. Drop in Oxygen Pressure 114 1 270- }t a hole worker plate.

Example II The grease of Example I was mixed with an equal quantity of a high viscosity index, solvent extracted highly parafiinic lubricating grade mineral oil having a viscosity of 383.9 5. S. U. at F. and of 58.2 S. S. U. at 210 F. with a V. I. of 1032. A grease could not be prepared as described in this oil due to the poor solvency and crystallization of the soap in this non-polar medium, However, as large "a quantity of this oil is desirable in the grease as is compatible with structural stability due to its low volatility, good oxidation stability and excellent viscositytemperatur e relationship. This semi-fluid grease, after mixing, was then homogenized by passage through a Gaulin homogenizer at 5000 p. s. i., very high rates of shear and without concurrent mixing. The resultant product was of excellent, smooth uniform structure.

Properties:

Penetrations, 77 F., mm./10:

Unworked 275. Worked, 60

strokes 310. Worked, 100,000

1 270 ,i hole worker plate.

The invention is not limited to the specific figures of the foregoing examples. The relative proportions of the grease constituents may be varied within the limits indicated above to obtain greases of different consistency and varying characteristics.

What is claimed is:

1. The process of preparing lubricating grease compositions which comprises mixing an aliphatic aldehyde having an alpha hydrogen and from about 10 to 30 carbon atoms per molecule and a high molecular weight carboxylic acid having from about 12 to 22 carbon atoms per molecule with a dispersing proportion of mineral lubricating oil, heating the mixture to about 130 to 180 F., adding a low molecular weight carboxylic acid and alkali sufiicient for neutralization of said acid and for alkali fusion of said aldehyde to said heated mixture, dehydrating the mixture at a temperature of about 300 to 400 F., heatingv the dehydrated mixture at a fusion temperature of about 400 to 620 F. sufficient to cause fusion between said alkali and said aldehyde until gas evolution recedes, and then cooling the grease mixture to obtain said lubricating grease composition.

2. The process of claim 1 wherein said aldehyde is an octadecenyl aldehyde made by aldolization of x0 nonyl aldehyde prepared by reacting a Ca olefin with carbon monoxide and hydrogen at elevated carbonylation temperatures and pressures in the presence of a group VIII catalyst.

3. The process of claim 1 wherein about 2 to 30 wt. percent of hydrogenated fish oil acids is employed as the high molecular weight carboxylic acid and about 1 to wt. percent of acetic acid is employed as the low molecular weight carboxylic acid.

4. The process of claim 1 wherein the mol ratio of soap derived from the aldehyde to the soap and salt derived from the high and low molecular weight carboxylic acids is within the range of about 1:4 to 4: 1.

1 5. The process of claim 1 wherein said lubricating grease composition is homogenized at a high rate of shear.

6. The process of preparing lubricating greases which comprises admixing a branched chain aliphatic aldehyde containing an alpha hydrogen and having 10 to 30 carbon atoms per molecule with a mineral lubricating oil, heat ing the admixture to a temperature in the range of 120 to 180 F., adding an aqueous solution of an alkali in an amount sufficient foralkali fusion of said aldehyde, dehydrating the mixture at a temperature in the range of 300 to 400 F., then raising the temperature to a fusion temperature in the range of 400 to 620 F., maintaining 1 8 said fusion temperature until gas evolution has appreciably receded and fusion between said alkali and said aldehyde has occurred.

7. The process of preparing lubricating greases which comprises admixing an aldehyde, as defined below, with a mineral lubricating oil, heating the mixture to a temperature in the range of to F., adding an aqueous solution of an alkali sufficient for alkali fusion of said aldehyde, dehydrating the mixture at a temperature in the range of 300 to 400 F., then raising the temperature to a fusion temperature in the range of 400 to 620 F., maintaining said fusion temperature until gas evolution has receded appreciably and alkali fusion has occurred between said alkali and said aldehyde, said aldehyde being a branched chain aliphatic aldehyde containing an alpha hydrogen and 10 to 30 carbon atoms per molecule, and being prepared by reacting an olefin containing one carbon atom less than said aldehyde with carbon monoxide and hydrogen at an elevated carbonylation temperature and pressure in the presence of a group VIII metal catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 2,449,312 Murray et al. Sept. 14, 1948 2,454,047 Finch et al. Nov. 16, 1948 2,468,099 Morway Apr. 26, 1949 2,470,859 Pavlic May 24, 1949 2,516,137 Morway et al. July 25, 1950 2,537,577 Fasce Jan. 9, 1951 2,575,286 Morway et al. Nov. 13, 1951 2,576,032 Morway et al. Nov. 20, 1951 2,591,586 Morway et a1. Apr. 1, 1952 2,594,341 Owen et al. Apr. 29, 1952 2,606,153 Holdstock Aug. 5, 1952 2,628,195 Allison et al. Feb. 10, 1953 2,628,202 Allison et a1. Feb. 10, 1953 2,628,938 Whitney Feb. 17, 1953 2,648,694 Mason Aug. 11, 1953

Claims (1)

1. THE PROCESS OF PREPARING LUBRICATING GREASE COMPOSITIONS WHICH COMPRISES MIXING AN ALIPHATIC ALDCHYDE HAVING AN ALPHA HYDROGEN AND FROM ABOUT 10 TP 30 CARBON ATOMS PER MOLLECULE AND A HIGH MOLECULAR WEIGHT CARBOXYLIC ACID HAVING FROM ABOUT 12 TO 22 CARBON ATOMS PER MOLECULE WITH A DISPERSING PROPORTION OF MINERAL LUBRICATING OIL, HEATING THE MIXTURE TO ABOUT 230* TO 180* F., ADDING A LOW MOLECULAR WEIGHT CARBOXYLIC ACID AND ALKALI SUFFICIENT FOR NEUTRALIZATION OF SAID ACID AND FOR ALKALI FUSION OF SAID ALDEHYDE TO SAID HEATED MIXTURE, DEHYDRATING THE MIXTURE AT A TEMPERATURE OF ABOUT 300* TO 400* F., HEATING THE DEHYDRATED MIXSTURE AT A FUSION TEMPPERATURE OF ABOUT 400* TO 620* F. SUFFICIENT TO CAUSE FUSION BETWEEN SAID ALKALI AND SAID ALDEHYDE UNTIL GAS EVOLUTION RECEDES, AND THEN COOLING THE GREASE MIXTURE TO OBTAIN SAID LUBRICATING GREASE COMPOSITION.