US2738328A

US2738328A - Complex grease containing hydrogenated castor oil

Info

Publication number: US2738328A
Application number: US446682A
Authority: US
Inventors: Arnold J Morway
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1954-07-29
Filing date: 1954-07-29
Publication date: 1956-03-13
Anticipated expiration: 1973-03-13
Also published as: NL109553C; FR1134151A; GB792767A; DE1091682B

Description

United States Patent Oiiice COMPLEX GREASE CONTAINING HYDROGENATED CASTOR 01L Arnold J. Morway, Clark Township, Union County, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application July 29, 1954, Serial No. 446,682

13 Claims. (Cl. 252-405) This invention relates to lubricating grease compositions and more particularly to high temperature lubricating grease compositions containing complex soap-salt thickeners and more particularly thickeners having high ratios of salt to soap. Still more particularly, this invention relates to lubricating grease compositions containing unsaponified hydrogenated castor oil in addition to the complex soap-salt thickeners, and to a method of preparing such lubricating grease compositions.

Soap-salt complexes are well known in the art for thickening lubricating oils to produce lubricating grease compositions. These complex thickeners have been employed for high temperature greases and consist of combinations of metal salts of low molecular weight car-. boxylic acids with metal soaps of high molecular weight fatty acids. Normally in the prior art the soaps and salts have been employed in proportions in therange of about 0.5 to 3 moles of salt per mole of soap since, in general, it was believed that in order to make greases of satisfactory penetration characteristics, it was necessary to employ a high proportion of the soap-salt thickener when the mole ratio of' salt to soap exceeded about 3 because of the low thickening effect of the salt.

However, recently it has been found that by drastically increasing the salt content and with it the metal content of soap-salt complexes, entirely new properties may be built into these new complexes which in addition to extending the scope of their utility to entirely new fields also greatly increase their value as grease thickeners. More specifically, it has been found that complexes of metal salts of low molecular weight carboxylic acids with metal salts of high molecular weight carboxylic acids which contain at least 7 moles and up to as much as 40 moles or more, preferably about 10 to moles, of the low molecular weight acid per mole of the high molecular weight acid have outstanding load carrying, dispersant and various other beneficial characteristics in addition. to thickening properties comparable to soap-salt complexes containing substantially lower proportions of low molecular weight carboxylic acids. These particular thickeners and their utilization in lubricating grease compositions are described in detail in the co-pending Morway and Kolfeneach application, Serial Number 387,527, filed October in these high metal content grease compositions, one of the high molecular weight carboxylic acids employed to form the soap portion of' the soap-salt complex has been derived from hydrogenated castor oil. A particularly preferred complex thickener has utilized a combination of hydrogenated fish oil acids and hydrogenated castor oil which were co-saponified with acetic acid in situ in the lubricating oil. In these grease compositions, the hydrogenated castor oil soap imparts not only structural stability to mechanical working but also prevents crust formation on the surface of'the grease when stored in a container. 3 t i i It has now been found in accordance with. this inven- 2,738,328 Patented Mar. 13, 1956 tion that excellent greases having improved structural stability to mechanical working and improved resistance to storage hardening and accompanying crust formation are prepared by employing unsaponified hydrogenated castor oil as such in the finished grease compositions. These greases of the present invention are softer, that is have higher penetration for given amounts of soap than do the other greases mentioned above, which makes the new greases easier to handle.

The greases of this invention comprise a major proportion of a lubricating oil and a grease-making proportion, generally about 8 to 35% by weight and preferably about 10 to 25% by weight based on the total composition, of a thickener consisting essentially of (l) a soap-salt complex of at least one alkaline earth metal soap of at least one high molecular weight carboxylic acid and at least one alkaline earth metal salt of at least one low molecular weight carboxylic acid, the molar ratio of low molecular weight carboxylic acid radical to high molecular weight carboxylic acid radical in the complex being in the range of about 7:1 to 40:1, preferably about 8:1 to 25:1, and (2) hydrogenated castor oil, the weight ratio of the hydrogenated castor oil to the soap in the thickener being in the range of about 1:4 to 4:1, preferably 1:2 to 2:1. The preferred alkaline earth metal is calcium, and acetic acid is the preferred low molecular weight carboxylic acid. Hydrogenated fish oil acids have been found to be especially useful as the high molecular weight can boxylic acid employed in forming the soap-salt complex.

The greases of this invention are generally prepared by mixing at least one high molecular weight carboxylic acid, at least one low molecular weight carboxylic acid, and a basic reacting compound of at least one alkaline earth metal with at least a portion of the lubricating oil and heating the mixture to an elevated temperature in the range of about 450 to 550 F. to dehydrate the mixture and form the soap-salt complex. Thereafter the mixture is cooled to a temperature below about 350 F. and the hydrogenated castor oil is added thereto. It has been found that in this method of preparation there is essentially no saponification of the hydrogenated castor oil.

Suitable low molecular weight carboxylic acids include saturated and unsaturated aliphatic monoand poly-carboxylic acids having about 1 to 6 carbon atoms such as formic, acetic, propionic, furoic, acrylic, adipic, and similar acids including their hydroxy derivatives such as lactic acid, etc. Acetic acid is particularly preferred.

The high molecular weight carboxylic acids useful for the purposes of the present invention are those having about 12 to 30 carbon atoms and preferably those having 18 to 22 carbon atoms per molecule. These acids may be derived from straight or unsaturated naturally-occurring or synthetic fatty materials. The fatty acids normally used in the manufacture of conventional greases, particularly the more saturated acids, are preferred. Examples of such acids include stearic, hydroxy stearic such as 12- hydroxy stearic, di-hydroxy stearic, poly-hydroxy stearic and other saturated hydroxy fatty acids, arachidic, hydrogenated fish oil and tallow acids, etc. However, unsaturated acids such as oleic, ricinoleic and similar acids may likewise be used. It will be understood, of course, that the naturally-occurring or synthetic fatty materials may themselves be used in the grease-making procedure to forms soaps.

Hydrogenated castor oil which is an essential ingredient in this invention is a synthetic wax-like compound obtained by the substantially complete hydrogenation of castor oil. The principal constituent is the glyceride of IZ-hydroxy stearic acid. There are also present minor quantities of mixed glycerides of this acid and di-hydroxy stearic and stearic acids. The hydrogenated castor oil which is a hard, brittle, high-melting point product is practically odorless and tasteless and is available commercially either in the form of uniform, free-flowing White flakes or as a powder. Typical physical and chemical properties of a particularly commercially available hydrogenated castor oil are as follows:

Physical properties:

Specific gravity C .99 Melting point, C 86 (187 F.) Ash content, percent .005 Di-electric constant (.IKC) at C 12 Flash point, COC, F 600 Fire point, COC, F 635 Chemical properties:

Acid value 2 Iodine value 4 Saponification value 180 It will be understood that other commercially available hydrogenated castor oils which have properties deviating within reasonable limits from those set out above may also be employed in the present invention.

The grease thickener of this invention consists essentially of (l) the soap-salt .complex of the aforementioned low and high molecular weight carboxylic acids and (2) the unsaponified hydrogenated castor oil. The proportion of this thickener employed in the lubricating grease composition will generally be in the range of about 8 to by weight and preferably about 10 to 25% by weight, based on the total composition. An especially desirable proportion is in the range of about 16 to 18% by Weight. In the soap-salt complex, the ratio of the low molecular weight carboxylic acid radical to high molecular weight carboxylic acid radical is about 7:1 to :1 and preferably about 8:1 to 25:1. In an especially desirable grease composition, this ratio is about 20:1. The preferred alkaline earth metals employed in this invention are calcium, barium, strontium and magnesium, calcium being especially preferred. The hydrogenated castor oil is employed in these lubricating grease compositions in an amount such that the Weight ratio of the hydrogenated castor oil to the soap in the thickener is in the range of about 1:4 to 4:1 and preferably about l:2 to 2:1. Approximately equal proportions by weight of the hydrogenated castor oil and the soap have been found to be particularly useful.

The lubricating oils useful in preparing the lubricating grease compositions of this invention generally should have a viscosity within the range of about 35 to 200 S. S. U. at 210 F. and flash points of about 350 to 600 F. A viscosity index of 100 or higher may be employed if desired. However, oils of lower viscosity index, such as below about 60 V. I., give better yields. The lubricating oil portion of the grease composition preferably comprises about 55 to 90% by weight of the finished grease.

The base oil employed in forming the mixture of the high and low molecular weight acids and the metal base prior to the grease-making process should be a nonsaponifiable oil, preferably a mineral lubricating oil. However, after the grease has been formed and cooled mineral oils as Well as synthetic lubricating oils having a viscosity of at least 30 S. S. U. at 100 F. may be added, such as esters of monobasic acids (e. g. ester of Ce Oxo alcohol with Ca Oxo acid, ester of C13 Oxo alcohol with octanoie acid, etc.), esters of dibasic acids (e. g. di-2- ethyl hexyl sebacate, di-nonyl, adipate, etc.), esters of glycols (e. g. C13 Oxo acid di-ester of tetraethylene glycol, etc.), complex esters (e. g. the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid, the complex ester formed by reacting one mole of tetraethylene glycol with two moles of sebacic acid and two moles of 2-ethyl hexanol, the complex ester formed by reacting together one mole of azelaic acid, one mole of tetraethylene glycol, one mole of Ca Oxo alcohol, and one mole of CB Oxo acid), esters of phosphoric acid (e. g. the ester formed by contacting three roles of the mono-methyl ether of ethylene glycol with one mole of phosphorus oxychloride, etc.), halocarbon oils (e. g. the polymer of chlorotrifluoroethylene containing twelve recurring units of chlorotrifiuoroethylene), alkyl silicates (e. g. methyl polysiloxanes, ethyl polysiloxanes, methyl-phenyl polysiloxanes, ethyl-phenyl polysiloxanes, etc.), sulfite esters (e. g. ester formed by reacting one mole of sulfur oxychloride with two moles of the methyl ether of ethylene glycol, etc.), carbonates (e. g. the carbonate formed by reacting Cs Oxo alcohol with ethyl carbonate to form a half ester and reacting this half ester with tetraethylene glycol), mercaptals (c. g. the mercaptal formed by reacting 2-ethyl hexyl mercaptan with formaldehyde), formals (c. g. the formal formed by reacting C13 Oxo alcohol with formaldehyde). polyglycol type synthetic oils (e. g. the compound formed by condensing butyl alcohol with fourteen units of propylene oxide, etc.), or mixtures of any of the above in any proportions.

Soap-salt complexes containing more than about 30 moles, for example 30 to 40 moles, of low molecular weight acid for each mole of high molecular weight acid have particular utility for converting synthetic oils of the ester type into excellent greases.

Although it will be understood that the soap-salt complex may be prepared in a separate step, in the preferred embodiment of this invention the high and low molecular Weight acids are co-neutralized with a basic reacting compound, such as a hydroxide and/or a carbonate of the alkaline earth metal in situ in a portion or all of the lubricating oil. A sufiicient amount of the alkaline earth metal basic reacting compound is employed to neutralize the high and low molecular weight carboxylic acids. After these three ingredients have been mixed with the lubricating oil, the mixture is heated to an elevated temperature in the range of about 450 to 550 F. or higher in order to dehydrate the product and to promote formation of the soap-salt complex. The lubricating oil employed in making the grease compositions of this invention should, of course, have a boiling point above the heating temperature. Generally a period of heating at about 500 F. of about 10 to 30 minutes will be required to promote formation of the complex. Heating of the mixture at this temperature may be continued for an additional period of time if desired.

After the mixture has been dehydrated and the complex has formed, the grease is then cooled to a temperature below about 350 F., at which point the hydrogenated castor oil is added. It is important that the hydrogenated castor oil not be added to the mixture prior to this point in the grease-making procedure. This is because hydrogenated castor oil is subject to saponification in the presence of water and/or excessive heat. In addition, the unsaponified hydrogenated castor oil may be decomposed at the high temperatures (450550 F.) involved in forming the soap-salt complex. It is, therefore, important that the hydrogenated castor oil be added after the mixture is substantially completely dehydrated and after the mixture is cooled to a temperature below about 350 F. After the hydrogenated castor oil is added, the resultant grease composition may then be cooled further, homogenized, filtered and packaged.

It will be understood that other conventional thickeners such as polyethylene, etc., anti-oxidants such as phenyl alpha-naphthylamine, N-lauryl para amino phenols; etc., tackiness agents such as polybutene, etc. and the like may be added prior, during or after the heating step as will be apparent to those skilled in the art.

The following example is presented as a specific embodiment of this invention but it will be understood that (it is not intended that this example limit theprese'nt invention in any way. i

EXAMPLE Two greases having'identical ingredientformulations, one prepared in accordance with this invention (grease A) and the other prepared in accordance with conventional grease-making procedures. (grease B) were prepared. These greases were formulated from. the following ingredients:

Formulation Ingredientsz Percent weight Hydrogenated castor oil 2.0 Hydrofol acids 51 2.0 Acetic acid (glacial) Q 8.0 Hydrated lime h 6.0

. Phenyl alpha-naphthylamine 0.5

. Lubricating oil 81.5

Hydrogenated fish oil acids corresponding to commercial stearfit acid in degree of saturation and average molecular we1 aphthenic-type mineral oil distillate having a viscosity of about 55 S. S. U. at 210 F. i

Preparation Grease A (prepared in accordance with this invencharged and the mass heated to about 500 F. and held at this temperature until all water was removed and the soapsalt complex was formed. This requiredabout 2 hours. The grease was then cooled to about 300 F. at which point the hydrogenated castor oil was addedand the grease was then cooled to about 250 F., at which point the phenyl alpha-naphthylamine was charged. The grease was then cooled to about 200 F., homogenized, filtered and packaged.

Grease B (conventional preparatin).The hydrogenated castor oil, Hydrofol acids, lime and lubricating oil were charged to a fire heated grease kettle and heated to about 500 F. The mass was maintained at this temperature for about 0.25 hours. Thereafter, the grease was cooled to about 250 F. while agitating, at which point the phenyl alphamaphthylamine was added. The grease was then further cooled to about 200 F., homogenized, filtered and packaged.

The following properties of these two greases were determined:

Properties Grease A Grease B Appearance r Penetration, 77 mm Worked, 60 Strokes 258 238 Worked, 100,000 Strokes 350 308 Dropping Point, F 500+ 500+ Norma Hottmann Oxidation Test, H to p. s. i. drop .4 372+ 320 Lubrication Life (Hrs) 250 F.l0,000 R. P.

M 407 510 Wheel Bearing Test, 6 hours at 220 F Pass Pass Water Emulsion Test, Penetration after working 310 Fluid 1 Excellent, uniform, homogeneous.

3 200 grams of grease and 20 grams of water are placed in an A.S.T.M. worker and worked 1,000 strokes. Penetrations are taken on the emulsified grease.

Grease A, due to its softer consistency, is superior to grease B as it is easier to handle in dispensing equipment, particularly centralized lubrication systems which are particularly susceptable to grease consistency. Also, it will be noted that the unsaponified hydrogenated castor oil has a water-proofing effect on grease A, keeping it from going to a fluid on working in the presence of water, although in static tests both greases are water-insoluble in boiling water.

Greases A and B were then subjected to identical analyses in order to determine how much of the hydrogenated castor oil was saponified in each of the two greasemaking procedures. Both greases were extracted in a Soxhlet extraction apparatus with acetone for eight hours the ,insolubility of the calcium soaps of the hydrogenated castor oil and the hydrofol acids and calcium acetate in the same medium. The respective extracts were then evaporated to dryness and saponification values run on the oily extractions. From the saponification values, the following fatty acid contents were calculated as oleic acid:

. Percent Grease A 2.28 Grease B 0.31

It will be noted that there was a dilference in unreacted or unsaponified materials of about 2% (based on total grease) between greases A and B. This difference of 2% can be attributed to the 2% of hydrogenated castor oil employed in the formulation which in grease A, due to the grease-making procedure, was unsaponified because of the absence of water and the existence of a relatively low temperature but which in grease B, because of the grease-making procedure, was saponified together with the hydrofol acids and acetic acids.

The following percentages of the two greases were found to be insoluble in acetone:

Percent Grease A 14.4 Grease B 16.7

Percent Grease A 2.17 Grease B 3.93

Thus this further analysis confirmed and checked the results of the initial analysis indicating that in grease A only about 2% (based on total grease) of the high molecular weight carboxylic acids were saponified whereas in grease B about 4% (based on total grease) of the high molecular weight carboxylic acids were saponified. The difference of 2% (based on total grease) between greases A and B can, therefore, be attributed to the hydrogenated castor oil which in grease A was unsaponified and in grease B was saponified.

What is claimed is:

l. A lubricating grease composition comprising a major proportion of a lubricating oil and a grease-making proportion of a thickener consisting essentially of (l) a soap-salt complex of alkaline earth metal soap of at least one high molecular weight carboxylic acid and alkaline earth metal salt of at least one low molecular weight carboxylic acid, the molar ratio of low molecular Weight carboxylic acid radical to high molecular weight carboxylic acid radical in said complex being in the range of about 7:1 to 40:1, and (2) hydrogenated castor oil, the weight ratio of said hydrogenated castor oil to said soap in said thickener being in the range of about 1:4 to 4:1.

2. Composition according to claim 1 wherein said lubricating oil is a mineral oil.

3. A lubricating grease composition comprising a major proportion of a lubricating oil and in the range of about .8 to 35% by weight, based on the total composition, of a thickener consisting essentially of (l) a soapsalt complex of an alkaline earth metal soap of a high molecular weight carboxylic acid having 12-30 carbon atoms per molecule and an alkaline earth metal salt of a low molecular weight carboxylic acid having 1 to 6 carbon atoms per molecule, the molar ratio of low molecular weight carboxylic acid radical in said complex being in the range of about 7:1 to 40:1, and (2) hydrogenated castor oil, the weight ratio of said hydrogenated castor oil to said soap in said thickener being in the range of about 1:4 to 4:1.

4. Composition according to claim 3 wherein said lubricating oil is a mineral oil.

5. Composition according to claim 3 wherein said alkaline earth metal is calcium.

6. Composition according to claim 3 wherein said low molecular weight carboxylic acid is acetic acid.

7. Composition according to claim 3 wherein said high molecular weight carboxylic acid comprises hydrogenated fish oil acids.

8. A lubricating grease composition comprising a major proportion of a mineral lubricating oil and in the range of about 10 to 25% by weight, based on the total composition, of a thickener consisting essentially of l) a soap-salt complex of an alkaline earth metal soap of a high molecular weight carboxylic acid having about 18 to 22 carbon atoms per molecule and an alkaline earth metal salt of acetic acid, the molar ratio of acetic acid radical to high molecular weight acid radical in said complex being in the range of about 8:1 to 25:1, and (2) hydrogenated castor oil, the weight ratio of said hydrogenated castor oil to said soap in said thickener being in the range of about 1:2 to 2:1.

9. Composition according to claim 8 wherein said alkaline earth metal is calcium.

l0. Composition according to claim 8 wherein said high molecular Weight carboxylic acid comprises hydrogenated fish oil acids.

11. A lubricating grease composition comprising a major proportion of a mineral lubricating oil, about 14 to 16% by weight, based on the total composition, of a soap-salt complex of the calcium soaps of hydrogenated fish oil acids and calcium acetate, the molar ratio of acetic acid radical to fish oil acid radical in said complex being about 20:1, and about 2% by weight, based on the total composition, of hydrogenated castor oil.

12. A method for preparing an improved lubricating grease composition containing a complex soap-salt thickener which comprises mixing at least one high molecular weight carboxylic acid, at least one low molecular weight carboxylic acid and a basic reacting compound of alkaline earth metal with a lubricating oil in grease-making proportions, the molar ratio of low molecular weight carboxylic acid radical to high molecular weight carboxylic acid radical in said mixture being in the range of about 7:1 to 40:1, heating said mixture to a temperature in the range of about 450 to 550 F. to dehydrate said mixture and form a soap-salt complex, cooling said mixture to a temperature below about 350 F. and adding thereto hydrogenated castor oil, the weight ratio of hydrogenated castor oil to said soap in the resultant grease composition being in the range of about 1:4 to 4:1.

13. A method for preparing an improved lubricating grease composition which comprises mixing hydrogenated fish oil acids, glacial acetic acid and hydrated lime together in a mineral lubricating oil in grease-making proportions, the weight ratio of glacial acetic acid to hydrogenated fish oil acids being about 4:1, heating the mixture to about 500 F. until the mixture is dehydrated, cooling the mixture to about 300 F. and adding thereto hydrogenated castor oil, the weight ratio of hydrogenabout 1:1.

No references cited.

Claims

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND A GREASE-MAKING PROPORTION OF A THICKENER CONSISTING ESSENTIALLY OF (1) A SOAP-SALT COMPLEX OF ALKALINE EARTH METAL SOAP OF AT LEAST ONE HIGH MOLECULAR WEIGHT CARBOXYLIC ACID AND ALKALINE EARTH METAL SALT OF AT LEAST ONE LOW MOLECULAR WEIGHT CARBOXYLIC ACID, THE MOLAR RATIO OF LOW MOLECULAR WEIGHT CARBOXYLIC ACID RADICAL TO HIGH MOLECULAR WEIGHT CARBOXYLIC ACID RADICAL IN SAID COMPLEX BEING IN THE RANGE OF ABOUT 7:1 TO 40:1, AND (2) HYDROGENATED CASTOR OIL, THE WEIGHT RATIO OF SAID HYDROGENATED CASTOR OIL TO SAID SOAP IN SAID THICKENER BEING IN THE RANGE OF ABOUT 1:4 TO 4:1.