US3107220A - Lubricant containing a hindered phenol - Google Patents

Description

3 ,17,220 .Patented Oct. 15, 1963 3,107,220 LUBRICANT CONTING A HINDERED PHENOL Arnold .I. Morway, Clark, NJ assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Get. 3, 1960, Ser. No. 59,800 5 Claims. (Cl. 252-18) This invention relates to lubricants containing 4,4- methylenebis (2,6-di-tertiary butyl phenol). Particularly, the invention relates to lubricating fluids and greases containing calcium salts of fatty acids and also containing a minor amount of 4,4-methylenebis (2,6- di-tertiary butyl phenol). The invention also relates to the use of said phenol in the manufacture of lubricants.

4,4'-methylenebis (2,6-di-tertiary butyl phenol) is known as an oxidation inhibitor. However, it has been found that when used in lubricating greases thickened with calcium salts of fatty acids, that it also has a plasticizing effect and inhibits hardening and crust formation of the grease during storage. Thus, greases containing calcium fatty acid salts, particularly calcium acetate in combination with calcium salts of C to C fatty acids, frequently form a hard crust during storage, particularly when in a static condition at elevated temperatures. This crust formation, of course, is quite undesirable since the hardened grease usually has to be discarded.

It has been further found that 4,4'-methylenebis (2,6- di-tertiary butyl phenol) imparts a deep red color to lubricants containing these salts, when the lubricant is alkaline. When the lubricant is acid or neutral, the red color disappears and the lubricant reverts to its normal color. Because of this property of acting as an indicator, the alkalinity or acidity of the lubricant is readily determined. Most calcium salt lubricants are prepared by neutralizing the acid with calcium base in situ in lubricating oil. By the addition of the phenol before or during the neutralization, the lubricant maker has a builtin indicator which determines when neutralization is complete. If the lubricant is manufactured so as to be on the alkaline side with a red color, it has been further found that this color disappears upon heating the lubricant to a temperature above about 200 P. On cooling the lubricant, the red color reappears. This property is important in many applications, since it provides a ready means of visually determining whether or not equipment lubricated with the phenol-containing alkaline lubricant is running hot and thereby gives warning of a pending failure. For example, most bearings operate at temperatures considerably below 200 F., and temperatures above this appear only if breakdown or failure of the equipment is occurring. In this case, the user of the lubricant by a simple visual inspection, i.e. by observing the lubricant losing its red color, is given Warning of possible failure.

Surprising, while the 4,4'-methylenebis (2,6-ditertiary butyl phenol) has been found to have all the above properties, other very closely related hindered phenols such as 2,2'-methylene bis (4-methyl, 6-ter-tiary butyl phenol), and 2,6-ditentiary butyl u-dimethyl amino para cresol are lacking in one or more of the above properties.

Specifically, the compositions of the invention are those comprising a major proportion of oil, a thickening amount of a fatty acid salt and an indicating and oxidation inhibiting amount of 4,4'-methylenebis (2,6-ditertiary butyl phenol). More specifically, compositions of the invention will usually contain a major amount of lubricating oil, about 3.0 to 40 Wt. percent of a calcium fatty acid salt and about 0.1 to 3.0 wt. percent of 4,4'-methylenebis (2,6-di-tertiary butyl phenol). Preferred compositions will contain 8 to 30 Wt. percent of salt and 0.5 to 1.0 Wt. percent of the phenol; all of said preceding weight percents being based on the total weight of the composition.

The oil portion of the lubricant can be either a synthetic or mineral lubricating oil. Included among the synthetic oils are diesters, e.g. di(2-ethylhexyl) sebacate; polysilicones, eag. polymethylsilicone; formals; carbonates; polyglycols; etc.

The salt portion of the lubricant is usually formed by the co-neutralization in oil, by calcium base, of the desired fatty acids. Frequently, these thickeners are formed from various mixtures of high molecular Weight fatty acids and/or intermediate molecular weight fatty acids with low molecular weight fatty acids. Salts prepared from the high molecular Weight fatty acid as the sole thickening agents are also operable.

The high molecular weight fatty acids useful for forming salt thickeners include naturally-occurring or synthetic, substituted and unsubstituted, saturated and unsaturated, mixed or unmixed fatty acids having about 14 to 30, e.g. 16 to 22, carbon atoms per molecule. Examples of such acids include stearic, hydroxy stearic, such as l2-hydroxy stearic, di-hydroxy stearic, polyhydroxy stearic and other saturated hydroxy fatty acids, arachidic, oleic, ricinoleic, hydrogenated fish oil, tallow acids, etc.

Intermediate molecular weight fatty acids useful for forming salts include those aliphatic, saturated, unsubstituted, mono-carboxylic acids containing 7 to 12 carbon atoms per molecule, e.g., capric, lauric, caprylic, nonanoic acid, etc.

Suitable loW molecular weight acids used to form salts include C to C fatty acids. Acetic acid or its anhydride is preferred.

Calcium bases which can be used to neutralize the above acids include the hydroxides, oxides and carbonates. The color changes obtained from the bis phenol when used with a calcium salt, is not obtained by salts of other metals such as sodium, lithium and barium. Thus, it is essential that calcium salt be present, although, of course, salts of other metals may also be present as supplemental thickeners.

The lubricants of the invention may also contain other supplemental thickeners such as polymeric thickeners, e.g. polymers of C to C monoolefins of 10,000 to 1,000,000 molecular Weight such as polyethylene; inorganic thickeners, e.g. clay, carbon black, silica gel; salt thickeners of other metals such as sodium, lithium, barium, etc.

A specific high molecular weight acid used in several of the working examples ofthe invention was iso-oleic acid. Iso-oleic acid is a very low price fatty acid material comprising chiefiy elaidic acid with minor amounts of oleic acid (9-octadeceneoic acid), and other isomers of oleic acid, e.g. l2-octadeceneoic acid and linoleic acid, etc. This acid primarily dilfers from pure oleicacid in that its chief component, i.e. elaidic acid, is in the cis or syn isomeric form, rather than in the more common trans or auto form of oleic acid.

The specific iso-oleic acid used is commercially available under the tradename of Emery 32866 acid. This acid had the following characteristics:

Titer, C 30 Iodine value (Wijs) 94.0 Free fatty acids (percent as oleic) 91.6 Acid value 182.0 Saponification value 2 189 Color, Gardner 1 The titer noted above is a false titer, since in derivatives, the acid acts as a lower titered acid. 1

2 Contains an inter-ester easily broken by saponification techniques.

The salt materials of the invention are best prepared in the lubricating oil by adding the acids and neutralizing .metal base to at least a portion of the oil and heating the resultant composition for a time and at a temperature sufficient to form the salt, e.g. 250 to 550 F. The

phenol is preferably present during the neutralization, although it may be added anytime during the subsequent heating or cooling steps. In'some cases, no external heating is applied at all, and a so-called cold-set lubricant is formed which still contains the water of reaction. In any event, the lubricant may next be homogenized and finished in the usual way. Also, the phenol may be simply mixed into a cold (e.g. room temperature) preformed grease or into a preformed grease which is warmed to about ISO-250 F.

Mixed salt lubricants prepared by neutralizing various 8 mixtures of fatty acids are becoming of increasing importance. Lubricants of this type are prepared by neutralizing mixtures of 40 to 90 wt. percent, preferably 60 to 80 wt. percent, of low molecular Weight fatty acid or anhydride thereof, 0 to 60 wt. percent, preferably 0 to 40 wt. percent, intermediate molecular weight fatty acid and 0 to 60 wt. percent, preferably 0 to 40 wt. percent of high molecular weight acid, based on 100% total acid.

Various additives can be added to the finished lubricant in amounts of 0.1 to 10.0 wt. percent, based on the weight of the finished lubricant. Among additives that can be added are corrosioninhibitors such as sodium nitrite, lanolin, wool grease stearine; extreme pressure agents; 'dyes; etc.

The invention will be further understood by the following examples which include preferred forms of the invention and wherein all parts are by weight.

Example IA 12.8 parts of hydrated lime, 8.4 parts of iso-oleic acid (Emery 3286-8) and 62.8 parts of a mineral lubricating oil having a viscosity at 210 F. of 55 SSU were added to a steam heated jacketed grease kettle and intimately mixed. 1 part of 4,4' methylenebis (2,6-di-tertiary butyl phenol) was dissolved in 15 parts of acetic anhydride by Example I-B Example IA was repeated except that no phenol was used, but instead 1 part of phenyl-alpha-naphthylamine was added as the oxidation inhibitor after the grease had been formed at 320 F. and was cooled down to 200 F.

Example II Example IA was repeated except that a slightly lesser amount of lime was added so that the acetic anhydride and the fatty acid were insufiiciently neutralized. This resulted in a grease having an acidity equivalent to .05

wt. percent, calculated as free oleic acid. This grease showed no-red coloration at any time.

Example III Example IA was repeated except that 1 part of 2,2- methylene bis (4-methyl, 6-tertiary butyl phenol) (Cyanamid 2246) was employed, replacing the 4,4'-methylenebis (2,6-di-tertiary butyl phenol). No red color occurred.

Example I V-A A grease kettle was charged with 20 parts hydrated lime, .66 part of polypropylene having a molecular weight of 250,000 and 52.70 parts of mineral lubricating oil. Then 26.64 parts of acetic anhydride was slowly added. Next, external heating was applied and the temperature of the composition raised to 400 F.

Example IV-B In a second kettle, 14.66 parts of rapeseed oil was reacted with 3.16 parts of sodium hydroxide (as a 40 wt. percent aqueous solution, i.e. 3.16 parts NaOH and 7.90 parts of water) in 80.22 parts of mineral lubricating oil containing 2.0 parts of sodium petroleum sulfonate concentrate. This mixture was heated to 200 F. where .66 part of 4,4'-methylenebis (2,6-ditertiary butyl phenol) was added. 'I heltemperature of the composition was next raised to 500 F. by external heating and maintained until hydrogen evolution, as evidenced by foaming, had ceased. This hot product was then pumped and mixed into grease IV-A which was maintained at a temperature of 400 F. After complete mixing, the blended mass was cooled and an excellent deep red color resulted. This combined blend is designated Example IV.

The sodium sulfonate concentrate used above was a 50/50 concentrate of a sodium petroleum sulfonate of 450 molecular weight in mineral lubricating oil.

Example I V-C Example lV-D A sample of the product of IV-B was cooled to room temperature and showed no color change.

The formulations of the products of Examples I to IV,

and their properties are summarized in the following table:

kalinity of 0.10 wt. percent calculated as free oleic acid, and wherein said alkalinity is due to excess lime.

Examples I-A I-B II III IV Composition (parts by weight):

Acetic anhydride 15.0 15.0 15.0 15.0 13. 32. Iso-olcic acid 8. 4 8. 4 8. 4 8. 4 Hydrated lime 12. 8 12. l 12. 0 12. R 10. 00. 4,4-rnethylene bis (2,6 diter'tiary butyl phenol) l. 0 1. 0 0. 33. Phenyl a-nflphthyllminp n 2,2-methylene bis i-methyl,

G-tertiary butyl phenol) 1, 0 Mineral lubricating oil 55 SUS at 210 F 62. 8 62. 8 63. 6 62. $1 66. 11. Rapeseed oil 7. 33. Sodium hydroxide 1. 58. Polypropylene (250,000 mol.

weight) 0. 33. Sodium petroleum sulionate 1. 00. Properties:

Alkali ity Alkaline Alkaline Acid- Alkaline Alkaline. Appearance Smooth deep red Smooth brown Smooth brown Smooth brown Smooth red grease. grease. grease. grease. grease. Dropping Point, "F 500+ 0+ 0 500+. AS'IM Penetration 77F.

Unwotked 308 310 325 233. Vforked 60 Str ke 310 3]? 124 265. Worked 10,000 Strokes 300 sno M0 300. Color on heating above 200F Lost red color No color change No color change Lost red color above 200F. above 200F. Oven hardening test at 300F Tends to harden Hardens excessively Hardcus faster than Slightly hardcns.

slightly over 3 in 7 days. I-A. week period. Lubrication lil'e, hours:

r p 1, 500 980 Water solubility Insoluble In o u In olu Insoluble.

2 ABEC-NLGI spindle test.

As illustrated by Example I-A, the his phenol of the invention when used in an alkaline grease resulted in a red grease which lost its color upon heating above 200 F., but which regained its color upon cooling below this temperature. In addition this grease showed only a slight endency to harden, even when maintained in an oven for three Weeks at 300 F., and it also has an excellent lubrication life. In comparison, Example 143 shows a grease containing phenyl-alpha-naphthylamine which showed no unusual coloring, which hardened excessively in the oven hardening test and which had a shorter lubrication life when used at 300 F. Example II shows that if a grease of the type of Example LA is maintained on the acid side, that it does not obtain a red color. Example III shows that a closely related bis phenol, namely 2,2- methylene bis (4-methyl, G-tertiary butyl phenol) even when alkaline, did not result in any red color. Example IV illustrates the use of the his phenol of the invention in a mixed sodium-calcium grease system which resulted in a red colored grease. On the other hand, as demon strated by Example IV-D, a sodium mixed salt grease containing the bis phenol showed no color change even though alkaline. Thus, the red color cannot be achieved by alkali metals as the sole metal component of the salt thickener.

Lubricants containing a salt of a high molecular weight fatty acid as the sole thickening agent are also within the scope of the present invention. For example, a grease can be prepared using the mineral oil of Example I-A,

What is claimed is:

1. A lubricant comprising a major proportion of lubricating oil, about 3 to 40 wt. percent of calcium salt of C to C fatty acid and about 0.1 to 3 wt. percent of 4,4-methylenebis (2,6-di-tertiary butyl phenol), wherein said lubricant contains free calcium base to thereby form a slightly alkaline lubricant.

2. A lubricant comprising a major proportion of mineral lubricating oil, about 8 to 30 wt. percent of calcium salt of C to C fatty acid, about .5 to 1 wt. percent of 4,4-methylenebis (2,6-di-ter-tiary butyl phenol) and free calcium base sufiicient to form a slightly alkaline lubricant.

3. A lubricant according (to claim 1, wherein said fatty acid is a mixture of 40 to percent of a material selected from the group consisting of C to 0.; fatty acids and anhydrides thereof, and 60 to 10 wt. percent of an acid selected from the group consisting of C to C fatty acid, C to C fatty acid and mixtures thereof.

4. A lubricant according to claim 3, wherein said anhydride is acetic anhydride.

5. A method of lubricating a hearing so as to obtain a color change when the operating temperature of said bearing exceeds 200 F. which comprises lubricating said bearing with the lubricant of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A LUBRICANT COMPRISING A MAJOR PROPORTION OF LUBRICATING OIL, ABOUT 3 TO 40 WT. PERCENT OF CALCIUM SALT OF C2 TO C30 FATTY ACID AND ABOUT 0.1 TO 3 WT. PERCENT OF 4,4''-METHYLENEBIS (2,6-DI-TERTIARYL BUTYL PHENOL), WHEREIN SAID LUBRICANT CONTAINS FREE CALCIUM BASE TO THEREBY FORM A SLIGHTLY ALKALINE LUBRICANT.