US3223632A - Lubricating compositions containing metal salt of a bicyclo carboxylic acid - Google Patents

Description

United States Patent 3,223,632 LUBRIQATING COMPOSITIGNS CGNTAINTNG lliEl'lgdL SALT 0F A BICYCLO (JARBOXYLIC Hans G. Vesterdai, Elizabeth, and Rudolph Kassinger,

Westiield, NJ, assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawin Filed Mar. 22, 1963, Ser. No. 267,357 1 Claim. (Cl. 252--33.6)

This invention relates to lubricating compositions. In one aspect it relates to lubricating greases and concentrates containing metal salt of a bicyclo carboxylic acid. It also relates to the methods of preparation of these greases and concentrates. In a very specific aspect this invention relates to a fire resistant lubricant formed by thickening a silicone fluid with an alkaline earth metal salt of a halogenated bicyclo dicarboxylic acid.

Lubricating greases capable of operating under extreme pressure loading conditions and at temperatures above 400 F. are required in many operations, e.g., lubrication of aircraft, rocket engines, steel making facilities, etc. Many commercially available lubricants are not capable of functioning under these extreme conditions. Moreover, many of those commercially available lubricants present fire hazards, i.e., they are flammable.

DISCOVERY It has now been discovered, and this discovery forms the basis of the present invention, that lubricating oils, e.g., silicone fluids, may be effectively combined with metal salt of certain bicyclo carboxylic acids. These salt-containing lubricating compositions are effective both as extreme pressure and anti-wear additives in other lubricants, and as greases, per se. It will be realized, of course, that the relative proportion of the salt and lubricating oil will vary considerably, depending upon the ultimate use of the composition. For example, it has been found that lubricating greases containing these salts as substantially the only thickener will generally contain from about 38 to 82 wt. percent, e.g., 46 to 75 wt. percent of the salt based on the total formulation weight of the grease. it, however, it is desired to use these compositions as lubricant additives or in combination with other thickeners, etc., it is generally more advantageous to use from about 0.5 to 46 wt. percent, usually 2 to 35 wt. percent, e.g. 4 to 25 wt. percent of the salts based on the total formulation weight of the resulting composition. it should be understood, however, that depending upon the consistency of the composition desired and the properties required less than 0.5 Wt. percent or more than 82 wt. percent of the salt of the bicyclo acid may be employed.

It has been further discovered that these salts of bicyclo carboxylic acids may be advantageously used in combination with other thickeners, especially the metal salts of benzoic acid (which have recently been discovered to be effective in this respect). This is particularly true when it is desired to use the composition, per se, as a grease. Other auxiliary thickeners for use in the novel lubricating compositions of the present invention include the fatty acid soaps, carbon black, copper phthalocyanine, ammeline, indanthrene blue, polyaryl ureas, etc. When ICC used in combination with the salts of benzoic acid (which are preferred for certain applications) or other auxiliary thickeners, the combined amount of thickener (e.g., bicyclo dicarboxylic acid salt plus benzoic acid salt) will generally range from 5 to 82 Wt. percent, more usually from 15 to wt. percent, e.g., from 20 to 50 wt. percent etc. When used in combination with other thickeners, the bicyclo acid salts will generally be present in amounts of from 2 to 35 wt. percent, e.g., from 4 to 25 wt. percent based on the total formulation weight of the grease.

We do not, however, mean to limit ourselves to the use of the bicyclo acid salts, alone, or in combination with benzoic acid salts. Our invention resides in the fact that lubricating oils, particularly the silicone oils, may be effectively combined with metal salt of various bicyclo dicarboxylic acids to form novel lubricating compositions which can be used, per se, as lubricants, or as additives in other lubricating compositions. The particular combination of this lubricating composition (bicyclo acid salt plus oil) with benzoic acid salt, e.g., calcium benzoate, has been shown to illustrate the additive eitect of these novel compositions and because that particular combination produces a lubricant having certain desirable proper ties.

Lubricating compositions, e.g., greases, prepared according to the preferred form of the present invention will usually have a long lubrication life in high speed bearings operating at, for example, 10,000 rpm, and will function within the broad temperature range of from about -65 F. to 500 F. Additionally, these preferred greases may be used for shorter periods of time at temperatures of up to 700 F. Moreover, these preferred greases are fire resistant and are particularly suited for lubrication in places where there is a danger of fire such as kiln cars, oven hinges, electrical switches, etc.

BICYCLO CARB OXYLIC ACIDS The bicyclo carboxylic acids which are contemplated for use according to the present invention include the bicyclo dicarboxylic acids (or their anhydrides) represented as follows:

wherein X represents an atom of hydrogen, chlorine, fluorine, bromine or iodine. The Xs may be the same or different. It is preferred that all of the Xs be halogen atoms, and more preferably, that all be chlorine. When all of the Xs are chlorine, the acid is known as chlorendic acid and can be identified as 1,4,5,6,7,7-hexachlorobicyclo (2.2.1)-hept-5-ene-2,3-dicarboxylic acid.

This acid can be prepared in its anhydride form by reacting hexachlorocyclopenta-1,3-diene with maleic anhydride. The preparation of these bicyclo dicarboxylic acids does not constitute a part of the present invention. However, they may be prepared by the Diels-Alder addition of the corresponding halogenated cyclopentadiene and maleic anhydride. Chlorendic acid is commercially available from the Hooker Chemical Company, Niagara Falls, New York. This acid was used in the working examples of the present invention and is often referred to as HET acid. The use of this acid in the examples is for purposes of illustration only, and the present invention should not be limited thereby.

While the bicyclo acids of the type just described are all believed to be effective, it is not to be implied that all serve with equal efficiency, since the efliciency of the various compounds will vary to some extent depending upon the nature and severity of the service to which they are subjected as well as their inherent differences in chemical structure.

METAL COMPONENTS OF THE SALTS Although other metals may be used, e.g., Fe, the metal component of the salts should preferably be an alkali metal or alkaline earth metal, viz, Na, K, Li, Ca, Sr, etc. Of these metals, the alkaline earth metals are the more preferred and calcium is especially preferred. These metals may be conveniently used is such forms as their hydroxides, etc., e.g., hydrated lime.

It is surprising to note that when diesters of the previously described bicyclo carboxylic acids are employed (rather than the metal salts of the present invention) solid lubricating compositions do not result. For ex ample, US. Patent No. 2,771,423 describes cutting oils containing up to 75 wt. percent of the C -C alcohol diesters of chlorendic acid. US. Patent No. 2,985,644 describes sulfurized esters of chlorendic acid which are oil soluble and can be used in cutting oils in amounts up to 35 wt. percent.

SUITABLE LUBRICATING OI LS The lubricating oil base stock selected for use in the present invention is preferably a lubricant of the type which is, per se, best suited for the particular use for which the ultimate lubricating composition is designed. Since many of the properties possessed by lubricating oil are imparted to the ultimate lubricating composition, it is advantageous to employ an oil which is, itself, thermally stable at the contemplated temperature of lubrication.

The more preferred lubricating oils for use according to the present invention are the silicone fluids. They are particularly preferred because of their high thermal stability and compatibility with the salts of the present invention. Moreover, the preferred greases prepared from these fluids are fire resistant.

The silicone fluids which can be effectively used in the present invention include those silicone fluids having a viscosity of about 1 to 500, e.g., 30 to 400, centistokes at 100 F. although it may sometimes be desirable to use fluids having a viscosity outside of these ranges. These fluids are poly organo siloxanes having the general formula:

wherein R is an alkyl, aryl, alkaryl, aralkyl or hydrogen radical. The Rs need not be the same. Generally n is an integer of from about 2 to 50 or more, e.g., 6 to 35. The particular value of n is not critical as long as the fluid has the desired properties, e.g., viscosity, etc. Particular materials which have been found to be especially suited for the present invention are silicone fluids QF-6- 7012 and QF-67024 which are products of the Dow Corning Company, Midland, Michigan. These fluids are the most preferred base oils for use in the present invention. They are both polymethylphenyl siloxanes having the general formula previously indicated. QF6 7012 is a medium polymethylphenyl siloxane. QF-6- 7024 is a high viscosity silicone fluid which has a lower volatility than QF-6-7012 and is, therefore, better suited 4 for high temperature operation. The pour point of QF-6-7024 (+25 F.) makes it less suitable, however, for low temperature operation than QF67012 which has a pour point below minus F. Inspections obtained on these fluids are shown in Table I below.

TABLE I.-SILICONE FLUIDS QF-fi-7012 AND QF-fi-7024 Viscosity 100 F. (cs.) 64. 3 225. 4

Viscosity 210 F. (cs) 21. 2 20. 40

Viscosity Index (IOU-210 F.) 162 109 Evaporation Loss 400 F. (wt. percent after 0. 5 0.2

24 hrs). l00 +25 Pour Point F) According to the preferred form of present invention, a bicyclo carboxylic acid (in the presence or absence of an auxiliary thickening agent or its precursor, e.g., benzoic acid) is mixed with a lubricating oil, e.g., silicone flud, and usually heated to from 300 to 500 F., preferably above 350 F., at which point a suitable alkali or alkaline earth metal base is added, e.g., hydrated lime. Although neutralization may be accomplished at lower temperatures, e.g., 100 F., it is preferred that the neutralization of the bicyclo acid be done above 350 F. and even more preferably at 400 F. or higher. This high temperature neutralization improves the texture of the final grease and seems to enhance the thickening effect of the bicyclo acid salt. Additional heating (if required) and mixing is performed until the temperature reaches from about 375 to 500 F. The mixture is then cooled to, for example, 250 F. At this point, various additives, e.g., phenyl alpha naphthylamine, p,p-dioctyldiphenyl amine, dipyridylamine, etc., may be added, if desired. The mixture is then cooled to, for example, from about 100 F. to F. and milled. The additional heating after the metal base, e.g., hydrated lime, was added is required to remove the water of reaction. Optionally, and much less preferably, the water of reaction may be allowed to remain in the grease to form a cold-sett lubricant. This latter choice is not recommended where the grease is to be used above about 250 F. As another alternate, the metal salt may be preformed and added to the oil although this technique is not nearly as effective as the in situ technique.

As indicated, the lubricating compositions of the present invention may contain other lubricant additives, if desired, to improve specific properties of the lubricant without departing from the scope of the present invention. Thus, the lubricating compositions of the present invention may optionally contain corrosion and rust inhibitors, extreme pressure agents, anti-oxidants, dyes, etc. Whether or not such additives are employed, and the amounts thereof, depend to a large extent upon the severity of the conditions to which the composition is subjected and upon the original stability of the lubricating oil base. When such conventional additives are used, they are generally added in amounts between about 0.001 and 10 wt. percent or more based on the weight of the total composition.

The terms alkalinity and acidity as used herein refer to those phenomenon which are determined as follows: ten (10) ml. of 0.5 N HCl are added to a ten (10) gm.

charge of grease sample which is slurried in one hundred (100) ml. of naphtha and fifty (50) 1ml. of ethanol. This is then back-titrated with 0.5 N NaOH to a phenolphthalein end point. The results are then calculated and reported as percent NaOH or oleic acid. It is preferred that the maximum alkalinity be no more than about 0.40% and preferably that the lubricating compositions be substantially neutral. Even more preferably, the compositions are slightly acidic. This seems to enhance the effect of amine-type oxidation inhibitors. The effect is particularly pronounced in the case of silicone fluids.

EXAMPLES The present invention will be more clearly understood by reference to the following examples which include a preferred embodiment. All parts are by weight unless otherwise indicated.

Example 1 Six hundred parts of l,4,5,6,7,7 -hexachlorobicyclo (2.2.1)-hept-5-ene-2,3-dicarboxylic acid (hereinafter referred to as HET acid) were mixed with 240 parts of Dow Corning silicone fluid QF-6-7024 (a polyphenylmethyl siloxane) and rapidly heated in a grease kettle to 400 F. At 400 F. the acid formed a gel like mixture with the silicone fluid. One hundred sixty parts of hydrated lime were slowly added to the gel like mixture. Heating and mixing were continued for about 45 minutes as the reaction between the hydrated lime and HET acid progressed. A large part of the water of reaction was flashed during this time and dehydration was completed by soaking the reaction mixture at 300 F. until steam evolution subsided. The remaining mass was cooled to 110 'F. One hundred parts of silicone fluid QF-6-7024 were added to the mass at this point and the product was milled. The resulting composition had an excellent grease structure and its properties and formulation are shown in Table II.

Example 2 Two hundred ninety-four parts of silicone fluid QF-6- 7012 were mixed with 180 parts of benzoic acid and 60 about minutes until all of the water of reaction had been evaporated. Thirteen parts of p,p-dioctyldiphenyl amine and 19 parts of phenyl alpha naphthylamine were added after the mass had cooled to 250 F. The mass was then rapidly cooled to 110 F. and milled in a rolling mill. The finished grease had a tested acidity of 4.3% calculated as percent oleic acid. The resulting lubricant had the formulation and properties as shown in Table II.

Example 3 To later show the additive efiect of the metal salts of the bicycle acids, a test control grease was prepared as follows:

Two hundred forty parts of benzoic acid were mixed with 264 parts of silicone fluid QF-6-7012 and heated with mixing to 250 F. Sixty-six parts of hydrated lime and 285 parts of silicone fluid were added to this mixture while heating to 300 F. The resulting mass was then heated to 375 F. The heating was continued at that temperature for 1 hr. until the water of reaction had evaporated. The mass was then cooled to 250 P. where 26.6 parts of phenyl alpha naphthylamine and 17.7 parts of p,p'-dioctyldiphenyl amine were added. The mass was then rapidly cooled to 110 F. and milled in a Morehouse mill at a clearance at 0.001 inch. The formulation and properties of this lubricating composition are shown in Table II.

Example 4 To illustrate the efiectiveness of the calcium salt of HET acid as an extreme pressure additive, a lubricating grease was prepared by blending with a spatula and then milling in a laboratory grease worker (at ambient conditions) 47 parts of the lubricating composition of Example 1 with 260 parts of the test control grease of Example 3 and 114 parts of a silicone fluid (QF-6-7012). The resulting mixture was milled and tested. It had an alkalinity of 0.06%, calculated as percent NaOH (based on the weight of the finished grease). The grease thus prepared had the approximate formulation and properties as shown in Table II.

TABLE II Initial Charge Formulation (weight percent) 1 Example 1 Example 2 Example 3 Example 4 1 l. Silicone fluid 69.5. 2. Bicyclo dicarboxylic acid 4 7.42. 3. Benzoic acid 4 20.0. 4. Hydrated lime 5. Phenyl alpha naphthylamine 1.85. 6. P,p-dioctyldiphenyl amine 1.23. Properties:

1. Appearance Excellent, Smooth. Gray. Smooth. 2. ASTM penetration 77 F (mm./10)

Unworked 315 281. Worked 60X... 356 288. 3. ASlM dropping point, F 500+ 500+ 500+ 500+. 4. Extreme pressure values (mean Hertz load)- (a) EP value (kg) 84.6 39.0 21.1 29.7. (b) Weld point (kg) No weld point 315.

5. 4-Ball wear (scar dia., mm.) 5 6. AlgEgdgLGI Lubrication Life (10,000 r.p.m. 450. 566+.

u, rs. 7. Flammability Wont burn in open flame, carbonizes and glows.

1 Actual values in grease are somewhat different due to loss of water.

1 True formulation of grease.

3 Added to the finished grease.

4 Present as the calcium salt.

5 Steel on steel, 10 kg., 75 0., 1 hr., 1800 r.p.m.

It can be seen from Table II that the lubricating composition of Example 1 had some very desirable properties, viz, a smooth texture, a high dropping point, an extremely high weld point, excellent wear characteristics (when compared to the base oil, per se, which had a scar dia. of

about 400 F. Heating was continued at 400 F. for about 2.0 mm.), and was non-flammable. When exposed to the open fiame of a Bunsen burner, it would not support fire, but merely carbonized and glowed. This latter characteristic would be particularly useful where fire presents a problem, e.g., near blast furnaces, etc. Note that this unique lubricant does not require the use of secondary or auxiliary thickeners. The lubricant of Example 2, which contained calcium benzoate, was a harder grease having a good lubrication life. The test control grease of Example 3 does not contain any bicyclo acid salt. It has a good lubrication life, but the very poor extreme pressure properties which are characteristic of the silicone base oil. The addition of the lubricating composition of Example 1 to the test control grease of Example 3 produced the very much improved grease of Example 4. While the lubrication life decreased, it was still quite high. More importantly, however, the extreme pressure properties were substantially increased. This is very important since most applications are in loaded bearings. Many commercially available products of similar purpose, price, etc., have a good lubrication life at no load, but a very poor life under even minimal loading conditions. Note the surprising increase in load that the new composition could endure without reaching a weld point. Thus, it can be seen that lubricating compositions prepared according to the present invention have very desirable extreme pressure properties.

Having thus described our invention with a certain degree of particularity, it will be realized that numerous modifications and adaptations may be made within the spirit and scope of the invention as hereinafter claimed.

We claim:

A soap-free lubricating grease comprising a silicone lubricating fluid, as the base oil, and an amount sufficient to form a grease structure and within the range of from 20 to 65 wt. percent of a mixture of calcium salts of chlorendic acid and benzoic acid, the amount of calcium salt of said chlorendic acid being about 4 to 35 wt. percent of the totalweight of said grease.

References Cited by the Examiner UNITED STATES PATENTS 2,132,137 12/1939 Ricketts 252-41 2,880,174 3/1959 Morway et al 25239 2,976,242 3/1961 Morway 25239 3,113,849 12/1963 McCoy 44-7 OTHER REFERENCES HET Acid, Bulletin No. 40, July 1954, Hooker Electrochemical Co., New York, page 3.

HET Acid, Bulletin No. 40, July 1954, Hooker Electrochemical Co., New York, page 4.

DANIEL E. WYMAN, Primary Examiner.