US2801974A - Grease process utilizing the alkali fusion products of cyclic alcohols - Google Patents

Description

nited States Patent GREASE PROCESS UTILIZING THE ALKALI FUSION PRODUCTS OF CYCLIC .ALCOHOLS Arnold J. Morway, Rahway, and Jeffrey H. Bartlett, Westfield, N. 3., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application December 22, 1952, Serial No. 327,436

5 Claims. .(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 thickeners by fusing cyclic alcohols with caustic alkali, producing a metal salt from the acid so formed and incorporating this metal salt into a lubricating oil in greasemaking 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 are generally prepared by the neutralization of high molecular weight fatty acids or by the saponification of fats which is usually carried out ina 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 lubricating oils a grease thickener obtained by fusing cyclic primary alcohols with alkali, particularly caustic soda or potash at temperatures of about 450- 650 F., preferably about 500-560 F., for a time sulficient to form the alkali metal salt of the acid corresponding to the alcohol used. The chemical reaction taking place during the fusion process may beillustrated by the following equation:

wherein M is an alkali metal such as sodium or potassium.

The discovery of the utility of alkali fusion of cyclic alcohols 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 been used 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, a situation conducive to the development of shortages forcing frequent variations in grease making procedures and grease characteristics. The discovery of an entirely new raw material eases this situation.

The use of cyclic primary alcohols as a grease-making material introduces no complication into the grease making procedure. While alkali fusion of the alcohol 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 cyclic primary alcohol 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.

The alcohols used in. accordance with this invention have the formula R-CH2OH, where R contains a monoor bi-cyclic group which may be naphthenic or terpenic, for example, cyclohexyl, cyclohexenyl, cyclopentyl, dipentenyl, camphenyl, fenchenyl, 6, 6-dimethylbicyclo-(l,1,3)-heptenyl, etc. Alcohols having 7-20 carbon atoms can be used, those having 10 or more being especially preferred. The alcohols can be derived from any source. However, an especially useful method for preparing the alcohols comprises the addition of formaldehyde to an appropriate olefinic hydrocarbon. This reaction was discovered by Kriewitz (Ber. 32, 57 (1899)) and was studied extensively by Prins (J. Chem. Soc. 118 (1), 42 (1920)). The modifications of this Prins Reaction that yield unsaturated alcohols rather than diols or dioxanes are preferred, for example thermal condensation as described by'Bain (J. Chem. Soc. 68, 638 (1946)), or in the presence of catalysts, such as stannic chloride or zinc chloride under anhydrous conditions as described by Mikeska and Arundale in U. S. Patent No. 2,308,192; Another useful method for preparing the alcohols used in the invention is the well-known Oxo process wherein a primary alcohol is produced by reacting an appropriate olefin with carbon monoxide and hydrogen and hydrogenating the aldehyde formed. p

A commercially available cyclic primary alcohol which is very useful in preparing the improved greases of this inventionis known as Nopol. This is produced by the condensation of formaldehyde and beta pinene, as follows:

011 CH: 0 0H oH3ocH. +oH,o cnr-o-om om\ /on, s r. H, h on,

CH \CH/ Beta plnene N opol During alkali fusionthe. Nopol is converted to a salt of Nopol acid:

rim-doom z Hydronopol which is prepared by simplehydrogenation of Nopol behaves simil'arly in alkali fusion, Nopol undergoes some of the reactions of alpha pinene, for example isomerization on heating. Therefore, the product obtained on alkali fusion probably contains not only the salt of the acid corresponding to Nopol, but salts of other acids corresponding to dipentene-7-carbinol and allocimehe carbinol'. h y

In addition to beta pinene, other unsaturated cyclic compounds which may be converted by reaction with formaldehyde or CO -l-Hz to alcohols useful in the invention include dipentene, alpha and beta fenchene, methyl fenchene, propyl camphene, methylene cyclohexane, cyclohexyl ethylene, etc. Of course, other synthetic or naturally occurring cyclic alcohols can be employed, for example, myrtenol, IO hydrOXycamphane, endo-2-5-methylene \-tetrahydrobenzyl alcohol and 2: lcyclopentyl)'-etliaiTol.

When carrying out the alcohol fusion in the lubricating oil itself. so as to form the grease thickening salt in situ in accordance with the preferred embodiment of the in= vention, 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 efficient stirring or agitation will counteract this tendency. However, in many cases more efiicient stirring is required than may be obtained in conventional grease kettles and special equipment would have to be used.

It has been found that the settling tendency of the alkali in the lubricating oil-alcohol mixture is negligible when a suflicient 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 difficulty may be overcome 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 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 alcohol-oil mixture with alkali added in amounts sufiicient for this neutralization and the subsequent fusion which takes place at considerably higher temperatures. High molecular weight acids useful for this purpose include hydrogenated fish oil acids, Crz-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 nonvolatile 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 alkali fusion of x0 products.

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. Thus, it has been found that the use of salts derived from cyclic alcohol as the sole grease thickener tend to form rubbery or cohesive structures which may be undesirable. However, when these salts are mixed with straight chain soaps derived from fatty acids, this cohesive structure is largely eliminated or modified to an extent that is desirable for certain purposes.

, The salts formed by alkali fusion of the alcohols herein described in the presence of other fatty acid soaps consistently yield excellent smooth greases. Other conventional thickeners, anti-oxidants, corrosion inhibitors, tackiness agents, load-carrying compounds, viscosity index improvers, oiliness agents, and the like may be added prior, during and/or after the fusion process as will b 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-Z-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 process of the invention may be carried out in two stages. When so operating, the alcohol to be fused may be added over a period of several hours, say 5-15 hours, in substantially stoichiometric proportions, to a molten mixture of alkali and mineral oil, preferably a heavy oil, maintained at fusion temperatures of, say, about 450-600 F. When all the alcohol 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 alcohol with a light hydrocarbon solvent, such as pentane, hexane, heptane or the like, and acidification of the aqueous raftinate. 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 350500 F. may be used in this stage. The salt derived from the alcohol by alkali fusion should form at least 20 wt. percent and preferably about 30-50 wt. percent of the grease thickener or about 2.0-2.0 wt. percent of the finished grease. The remainder of the grease thickener is preferably made up by a suitable soap-salt complex of the type described above. The proportion of soap derived from alcohol 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 alcohol 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 solid alkali, preferably in flake or pellet form. The mixture is heated to about 450 -500 F. whereupon the alcohol is slowly added in increments or continuously over a period of about 1-20 hours under vigorous stirring. A reaction temperature of about 475600 F., preferably about 500-580 F, is maintained throughout the alcohol addition. After all the alcohol has been added, heating at these temperatures is continued until evolution of hydrogen ceases or until the desired conversion has been obtained. The reaction mixture is quenched or allowed to cool and may then be diluted with further amounts of lubricating oil to the desired grease consistency.

A similar procedure is employed when the alcohol 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, all the acids needed to form the suspending agent are added to the mineral oil together with the alcohol. Thereafter, sufficient caustic alkali to neutralize the acids and convert the alcohol to salt 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 stirring is required. i i

The invention will be best understood by reference to the following specific examples which represent preferred modifications of the invention.

substantially as described above, except that less violent EXAMPLE I Ingredients: Weight percent Nopol (commercial product) ..s 10.00 Hydrofol Acids 54 10.00 Glacial acetic acid 4.00 Sodium hydroxide 6.50 Phenyl alpha-naphthylamine 1.00 Blend of naphthenic mineral oils having a viscosity of 50 S. S. U. at 210 F 68.50

' Time (Hours) Tempera- Remarks ture, F.

Started Timing 240 :33 340 Added Balance of Mineral Oil.

Started Cooling.

240 Added Phenyl alpha-Naphthylamine.

Properties: 1

Appearance Excellent, smooth, uniform product. Dropping point, F 520+.

Before After Homog- Homogenizaenization tion Penetrations, 77% F., min i0:

Unworked 180 155 Worked 60 Strokes 215 158 Worked 100,000 Strokes 155 175 Water Washing Test, Percent Los None N orma-Hofiman Oxidation Test, Ht 5 1.

Drop in 02 Pressure 126 EXAMPLE II The grease as described in Example I is an excellent channelling type product. However, on homogenization at high rates of shear it tends, like other good channelling greases, to become excessively stiif or hard for certain lubrication services. In addition, the mineral oil employed in its manufacture was chosen for its ability to disperse soap and as a medium for proper crystal nucleation and growth. This type mineral oil is not as stable and is more volatile than desired for long lubrication service at elevated temperatures. Therefore, after homogenization of the grease in Example I to ultimate hardness, this grease was cut back to desired softer consistency with an excellent stable mineral oil of good viscositytemperature characteristics, low volatility and proper viscosity.

6 Ingredientsi Weight percent Nopol 6.00 Hydrofol Acids 54 6.00 Glacial acetic acid 2.40 NaOI-I 3.90 Phenyl alpha-naphthylamine 1.00 Blend of naphthenic mineral oils having a viscosity of 50 S. S. U. at 210 F 41.10 Cut-back oil (highly solvent refined Mid-Continent distillate blended with a small amount of bright stock, viscosity at 210 F., 45 S. U. S.) 39.60

The above grease was prepared by mixing together the cut-back oil containing sufiicient phenyl alpha-naphthylamine to bring the finished grease to a 1.00% content, and the homogenized grease of Example 1. After thorough mixing, the grease was again homogenized.

Properties:

Appearance Excellent, smooth, short fiber, uniform product. Dropping point, F 406. Penetrations, 77 F.,

mm./l0:

Unworked 245. W o r k e d 6 0 strokes 272. Worked, 100,000

strokes 360. Water washing test,

percent loss l0.

Norma-Hoffman oxidation test, hrs. to. 5 p..s. i. drop in 02 pressure 116.

The oxidation tests obtained on the two lubricants described. in. Examples I and II show less than a 5 p. s. i. drop in oxygen pressure in 100 hours. These data indicate excellent oxidation stability since only a 5 lb. 02 pressure drop in 100 hours in this test is required in all of the more stringent government specifications.

B. E. C. bearing test data show the greases of both Examples I and II are excellent lubricants showing no leakage through the bearing seal even at the elevated temperature of 250 F. These data are shown below.

B. E. C. bearing test [204 bearing operating at 3,600 R. P. M.]

Temperature F. 200F. 250F.

Examples I I II I I I II I II Appearance of Grease During Test.

Excellent channelling type grease. N0 tendency to become fibrous or throw out of cup or thin out.

'7 Preparation-The preparation of this grease was similar to that described in Example I. The heating schedule Was as follows:

Time Temp, Remarks 45 Start 800 Started Heating. 10 150 Added Acetic Acid Followed by NaOH Solution.

200 330 490 570 570 Started Cooling. 200 Shut Ofi Agitation.

Properties:

j Appearance Excellent, smooth hard grease. Free alkalinity, percent (as NaOH) 0.53. Dropping point, F 450. Penetration, 77 F., mm./ 10:

Unworked 115. Worked, 60 strokes 101;

EXAMPLE IV The base grease of Example 111 was cut back 200% with an excellent high viscosity index, non-volatile, oxidation stable type mineral oil. This oil is not sutficiently polar to give a good grease structure when employed in the grease manufacture. This cut-back was then homogenized.

Ingredients: Weight percent Hydronopol 3.33 Hydrofol Acids 53. 3.33 Glacial acetic acid 1.33 Sodium hydroxide 2.17 Phenyl alpha-naphthylamine 0.33

Blend of naphthenic mineral oils having a viscosity of 50 S. S. U. at 210 F 22.83 Cut-back oil (highly solvent refined Mid-Continent distillate blended with a small amount of bright stock, viscosity at 210 F. 45

S. U. S.) 66.68

. The cut-back was prepared by mixing the base grease in the kettle (cold) with the cut-back oil. The blend was then finished by Gaulin homogenization at high rates of shear without concurrent mixing.

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. A process for preparing a lubricating grease which comprises: admixing a mineral lubricating oil with 2-30 weight percent, based on final composition, of a fatty acid having from 12 through 22 carbon atoms, 1-10 weight percent, based on final composition, of a low molecular weight carboxylic acid, and a cyclic primary alcohol having 10 through 20 carbon atoms, the amount of said alcohol being suificient for the salt derived therefrom by subsequent alkali fusion to amount to 2-20 weight percent of the final composition, and the mol ratio of the salt derived from said alcohol to the soap and salt derived from said fatty and carboxylic acids being in the range of 1:4 to 4: 1; adding to the resulting admixture sufiEicient sodium hydroxide to neutralize all acids present and to convert by subsequent alkali fusion said alcohol into the corresponding acid salt; heating the admixture to a saponification temperature in the range of 300 to 400 F. until all acids originally added are converted to soaps and salts, and the water present is substantially removed by volatilization; then further heating the admixture to an alkali fusion temperature in the range of 500 to 580 F.; maintaining the admixture at said alkali fusion temperature until gas evolution recedes substantially; and cooling the thus heated admixture to obtain a lubricating grease composition.

2. The process of claim 1 wherein said alcohol is a terpenic alcohol.

3. The process of claim 2 wherein said terpenic alcohol has the following structural formula (I3H2CH:OH i 0 HO OH CHEr-C-CEH /CH2 CH 4. The process of claim 2 wherein said terpenic alcohol is hydrogenated.

5. The process of claim 1 wherein said fatty acid is a hydrogenated fish oil acid and wherein said carboxylic acid is acetic acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,425,882 Maitland Aug. 15, 1922 1,529,658 McKee et a1 Mar. 17, 1925 1,530,386 McKee et a1. Mar. 17, 1925 2,055,795 Kaufman Sept. 29, 1936 2,069,626 Roehner Feb. 2', 1937 2,169,155 Lincoln et al. Aug. 8, 1939 2,182,137 Ricketts Dec. 5, 1939 2,196,581 Stephenson et a1 Apr. 9, 1940 2,285,453 Markle June 9, 1942 2,384,817 Chitwood Sept. 18, 1945 2,390,450 Morgan Dec. 4, 1945 2,425,343 Pelton et al. Aug. 12, 1947 2,427,344 Bain Sept. 16, 1947 2,455,892 Fraser Dec. 7, 1948 2,567,026 Pelton et al. Sept. 4, 1951 2,576,031 Morway et al Nov. 20, 1951 2,576,032 Morway et al. Nov. 20, 1951 2,586,693 Morway et al. Feb. 19, 1952 2,690,429 Morway et al. Sept. 28, 1954 2,692,232 Bartlett et al. Oct. 19, 1954 2,695,878 Entwistle Nov. 30, 1954 OTHER REFERENCES Bain et al.: J. Am. Chem. Soc., vol. 68, M. 638-4l (1946).

Claims (1)

1. A PROCESS FOR PREPARING LUBRICATING WHICH COMPRISES: ADMIXING A MINERAL LUBRICATING OIL WITH 2-30 WEIGHT PERCENT, BASED ON FINAL COMPOSITION, OF A FATTY ACID HAVING FROM 12 THROUGH 22 CARBON ATOMS, 1-10 WEIGHT PERCENT, BASED ON FINAL COMPOSITION, OF A LOW MOLECULAR WEIGHT CARBOXYLIX ACID, AND A CYCLIC PRIMARY ALCOHOL HAV-7 ING 10 THROUGH 20 CARBON ATOMS, THE AMOUNT OF SAID ALCOHOL BEING SUFFICIENT FOR THE SALT DERIVED THEREFROM BY SUBSEQUENT ALKALI FUSION TO AMOUNT TO 2- 20 WEIGHT PERCENT OF THE FINAL COMPOSITION, AND THE MOL RATIO OF THE SALT DERIVED FROM SAID ALCOHOL TO THE SOAP AND SALT DERIVED FROM SAID FATTY AND CARBOXYLIC ACIDS BEING IN THE RANGE OF 1:4 TO 4:1; ADDING TO THE RESULTING ADMIXTURE SUFFICIENT SODIUM HYDROXIDE TO NEUTRALIZE ALL ACIDS PRESENT AND TO CONVERT BY SUBSEQUENT ALKALI FUSION SAID ALCOHOL INTO THE CORRESPONDING ACID SALT; HEATING THE ADMIXTURE TO A SAPONIFICATION TEMPERATURE IN THE RANGE OF 300* TO 400* F. UNTIL ALL ACIDS ORIGINALLY ADDED ARE CONVERTED TO SOAPS AND SALTS, AND THE WATER PRECENT IS SUBSTANTIALLY REMOVED BY VOLATILIZATION; THEN FURTHER HEATING THE ADMIXTURE TO AN ALKALI FUSION TEMPERATURE IN THE RANGE OF 500* TO 580 F.; MAINTAINING THE ADMIXTURE AT SAID ALKALI FUSION TEMPERATURE UNTIL GAS EVOLUTION RECEDES SUBSTANTIALLY; AND COOLING THE THUS HEATED ADMIXTURE TO OBTAIN A LUBRICATING GREASE COMPOSITION.