US2529304A - Extreme pressure lubricants - Google Patents

Description

Patented Nov. 7, 1950 ICE 4 EXTREME PRESSURE LUBRICANTS Louis A. Mikeska, Westfield, and Elmer B. Cypher-s, Cranford, N. .L, assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application February 19, 1948, Serial No. 9,617

- 13 Claims. 1

The present invention relates to improvements in extreme pressure lubricants and particularly to improvements in compositions which may be blended with ordinary lubricating oils, greases, and the like, to enhance their load-carrying properties.

It has long been recognized that ordinary mineral oil lubricants while highly satisfactory for many lubricating functions are not entirely satisfactoryfor the lubrication of machine parts, such as hypoid gears, worm gears, and the like, where extremely high unit pressures are encountered. It is also known in the prior art that by the addition of certainsubstances, such as fatty oils, fatty acids, and the like, and particularly by the addition of compounds containin certain reactive elements such as sulfur, chlorine, or phosphorus, the load-carrying capacity of a mineral base lubricating oil can be greatl increased. It is known further that compounds including such active sulfur, chlorine, or phosphorus, will react with-the metals which are being lubricated to form on the surface thereof an extremely thin but effective lubricating film which apparently consists of the metal sulfide metal chloride, or metal phosphide. This film is produced when the ordinary oily film starts to break and permits direct metal-to-metal contact with a consequent rise in temperature. It provides momentary lubrication and prevents seizure between the metal parts pending re-establishment of the normal oil film which separates them.

Oil compositions including sulfur, chlorine, and /or phosphorus which have the desirable loadcarrying properties mentioned above are frequently objectionable because they are corrosive to the metals they are designed to protect. Many efforts have been made in the prior art to incorporate into the lubricating compositions various materials which will provide the necessary reactive sulfur, halogen, or phosphorus, or at least two of these, when a protective film is required, but will otherwise remain inert and inactive. Some of the compositions have been quite successful but most of them are subject to various objections in that they do not aiford sufficient load-carrying capacity, or they are too corrosive, or the ingredients used are expensive or hard to obtain. Hence, although various suggestions have been made for combining reactive and unreaczive sulfur, phosphorus, etc., in various ways, the resulting compositions have not always been satisfactory, many of these either lacking in load- ,carrying properties, or being subject to oxidation,

sludging and the like. Some of the prior art compositions have been satisfactory for high speedlow torque service but not for high torque-low speed service. It is obviously desirable that a single composition be suitabl for both. It is also desirable that the compositionbe such that the 2 protective sulfide, phosphide, or chloride or other halide film will be formed instantly, upon temperature rise due to metal-to-metal contact, but that otherwise the sulfur, etc., remain quite inert. To obtain these properties is an object of this invention.

Some fairly satisfactory complex compositions of the prior art have the requisite properties and have been used with some success, but the industry as a whole, for reasons of economy and other considerations, has shown a tendency to use simple additives for extreme pressure lubrication. Hence, more commonly, use has been made in the prior art of simple sulfurized fatty oils such as sulfurized lard oil, sperm oil, and the like, together with simple phosphorus, phosphorus sulfide and/or chlorinated wax, etc., blended inappropriate quantities into lubricating oils of mineral base, e. g., ordinary motor oils, cutting oils,

greases, etc., to increase the load-carrying capacity. It has now been discovered, however, that products which are more satisfactory may be prepared simply and economically from readily available materials and to accomplish the foregoing is another object of this invention.

As a starting material for an extreme pressure additive, which can be blended in ordinary mineral lubricating oils, cutting oils, greases and the like, in various proportions as may be required for the specific purpose, halogenated and especially chlorinated esters of aliphatic carboxylic acids (including both saturated and unsaturated, straight and branched chains) are suitable. The

alcohol portion of the esters may include primary, secondary, or tertiary alcohols or polyhydroxy alcohols such as glycerin. For the carboxylic acid constituent, the higher fatty acid esters or glycerides having one or more chains of 12 to 22 carbon atoms each, such as the natural fats, for example, animal, vegetable, and marine oils are preferred because of their low cost and availability, but other aliphatic carboxylic acid esters of the same general type are also suitable. Compounds with carboxylic radicals of 2 to 22 carbon atoms are useful, broadly, such as those containing acetic, propionic, butyric, acrylic, and other low acids, saturated or unsaturated. Such esters, after being chlorinated or otherwise halogenated, are thereafter treated to incorporate sulfur and phosphorus into them.

Thus an extreme pressure additive according to this invention may be obtained by at least partially reacting a halogenated aliphatic carboxylic acid ester of the type just described with a partially hydrocarbon substituted dithiophosphate. Thus a chlorinated aliphatic carboxylic acid material such as a fatty oil, e. g. lard oil, sperm oil, cottonseed oil, fish oil (partly hydrogenated or otherwise) may be reacted, or partially reacted,

with a dialkyl dithiophosphate, or with a diaryl dithiophosphate, or with mixtures of the two to secure the desired additive. Alternatively, a single dithiophosphate may have two dissimilar groups, e. g. one alkyl and one aryl. Such groups should be of proper chain length or molecule siZ3 for oil solubility without undue thickening effect. Thus an aliphatic fatty ester, and preferably one having say 12 to 22 carbon atoms in the fatty chain may be treated to contain 2 to 4 halogen atoms in the chain, or in each chain where more than one is involved. This halogenated material, preferably in excess, is then reacted with a suitable monovalent or .divalent metal salt, preferably the alkali metal salt, of the dithiophosphate. The metal combines with a part of the halogen (usually chlorine, though others, especially bromine or iodine, may be substituted as indicated above The resulting salt, which commonly is not oil soluble, may be filtered out of the resulting product which may well be a mixture of the halogenated fatty material and the reaction product. The latter may have the approximate formula where R1 is an aliphatic carboxylic acid radical having one or more chains of 2 to 22 carbon atoms each, preferably 12 to 22, X is a halogen, preferably chlorine, y is an integer of say 1 to 12, and R2 and R3 are like or dissimilar alkyl or aryl or alkaryl radicals of such configuration that the material is liquid or readily'soluble in oil. Preferably the radicals R and Rs are similar. If aryl, they preferably have alkyl substituents of 2 to carbon atoms attached to the benzene nucleus.

More specifically, the extreme pressure addition agent is the product obtained by adding chlorinated fatty oil in excess to a dialkyl dithiophosphate or a dialkaryl dithiophosphate, where the alkylsubstituents or the aliphatic substituents on aryl nucleus, are short chains, straight or branched, having, for example, not more than 2 to 10 carbon atoms. More particularly, as a very satisfactory example, the alkyl radical is an isopropyl radical, in which case the formula becomes accompanied by some of the unreacted chlorinated fatty material, RCILUH).

More particularly, lard oil or sperm oil, halogenated, e. g. chlorinated to contain about of halogen are preferred, although other proportions, from about 5 to 50% halogen may be used. Chlorine is the preferred halogen but bromine and iodine, and for some purposes, fluorine, have utility. These halogenated fatty materials may be produced in conventional manner as is well known in the prior art, for example, by passing gaseous chlorine through oils heated to temperatures from room temperature up to 300 F., preferably 150 to 200 F. They preferably are'prO- .duced by halcgenating vegetable or animal fats and oils, or mixtures thereof, containing as a rule between 12 and 22 carbon atoms in the fatty acid chain.

A halogenated ester of the character described above, for example, a chlorinated ester, is next treated with an alkali salt of an organic thiophosphoric acid, particularly of a dialkyl or dialkaryl dithiophosphoric acid, in such a way as to replace part of the chlorine with a diester dithiophosphate group. Dithiophosphoric acid salts of suitable metals, especially alkali and alkaline earth metals, prepared by combining a phosphate radical with branched chain alcohols, phenols, alkyl substituted phenols, alkyl phenol sulfides, and the like are also suitable for this purpose. This reaction takes place at moderately elevated temperatures, preferably in the presence of a solvent, as will be described later, the product being appropriately described as a condensation product of chlorinated esters and the aryl or alkyl diesters of metal salt of dithiophosphoric acid. The reaction temperature of reflux, e. g. the normal boiling point of isopropyl alcohol, about 178 F., is a convenient reaction temperature, although it may be varied considerably. The resulting product contains all of the desirable extreme pressure addition agents mentioned above, namely chlorine, phosphorus, and sulfur. It is highly effective as an extreme pressure agent when blended with an appropriate lubricating oil, that is an oil suitable for lubricating the type of mechanism involved, being of appropriate viscosity at the temperatures of operation. The proportions in which the additives are used will vary; ranging from as little as 1%, for some purposes, to as much as 20 f-b for others.

Also, if desired, in lieu of the simple sodium or potassium salt, a mixture of various salts may be used for reaction with the glyceride or the fatt acid. For example, a. mixture of a sodium salt of the diester of a dithiophosphoric acid and a sodium or potassium polysulfide may be used in conjunction with chlorinated lard oil, sperm oil, and the like. Other oils, suitably chlorinated, such as cottonseed oil, hydrogenated fish oil, and the like, may be used to obtain analogous reaction products. Addition agents, prepared as above indicated, will normally be used in proportions of about 5 to 15% although proportions may range from 1 to 20% in mineral base lubricating oils. For heavy duty operation percentage limits will ordinarily run between 7 and 12%, depending upon the type of operation and the effective active sulfur, phosphorus, and chlorine in the reaction or condensation product. The finished lubricant may also contain other addition agents such as oxidation inhibitors, sludge dispersers, pour point depressors, adhesive or stringiness agents and the like, as will be understood by those skilled in the art. The oil used is of appropriate type and viscosity for the purpose intended, for example a conventionall refined Mid- Continent oil having a viscosity of from 50 to 250 S. S. U. at 210 F., a narrower range of to S. S. U. viscosity being somewhat preferable. The oil may or may not be thickened with suitable soaps, polybutene compositions, methacrylate polymers, etc., as will be obvious to those skilled in the art.

In the prior art, phosphorus, sulfur and chlorine have all been combined in certain ways in single compositions for addition to lubricating oils and greases, as for example in Zimmer and Morway Patent No. 2,307,183. This present invention represents a new and specific improved type of composition having novelty and practical merit. The invention will be more fully understood by reference to the following examples:

EXAMPLE I A. Chlorination 1800 grams of No. 1 lard oil were placed in a 3-neck flask and gaseous chlorine was introduced through a, diffusion stone. The temperature rose rapidly to F. after which the rate of chlo- Chlorine, per cent 18.74 Acid No. 38.2 Saponiflcation No. 263.3

B. Preparation of dithiophosphoric acid 480 grams of 99% isopropyl alcohol were placed in a glass flask equipped with a stirrer and reflux condenser. 444 grams of phosphorus pentasulflde (P285) were added in about equal portions over a period of minutes. The temperature rose spontaneously to about 120 F., and heat was then supplied, and refluxing began at 130 F. The low initial refluxing temperature was due apparently to the release of free gases, such as hydrogen sulfide. The temperature continued to rise to the boiling point of the alcohol, about 178 F.

As the reaction proceeded further, the temperature was raised to 210 F. and held at this point for 2 hours, at which time no refluxing could be observed, indicating substantially complete conversion of the'alcohol to the dithiophosphoric acid. The product was then cooled and filtered and was found to contain 14.82% phosphorus and 28.41% sulfur, corresponding approximately to the following formula:

CaH7O S oam-o SH (Theoretical P: 14.5% 8229- C. Condensation 60 grams of the product from B above and 10 grams of NaOl-I dissolved in grams of water were mixed with 540 grams of 91% isopropyl alcohol as solvent, heated to reflux temperature, about 178 F., to promote reaction. and cooled to 140 F. 540 grams of the chlorinated ester from A were then added and the mixture was stirred andheatedto reflux, maintaining reflux for 4 hours. The alcoholic solvent and water were stripped off under vacuum and the residue was filtered. The'product was a clear brown oily liquid having the following analysis:

Per cent Phosphorus 1.04 Sulfur 1.27 Chlorine 16.97

It is believed that the reaction proceeds approximately according to the following equation:

(final product) where R represents lard oil. In the exp riments just described the RC1: appeared to be RCls.

EXAMPLE II 15 grams of diisopropyl dithiophosphoric acid prepared as in Example 13, 2.5 grams of NaOH in 7.5 grams of water, and 540 grams of chlorinated lard oil prepared as in Example IA, were condensed in the manner of Example IC. The difference between Examples I and II is merely in the quantity of the dithiophosphoric acid used.

The product showed the following analysis:

I Per cent Phosphorus 0.29 Sulfur 0.38 Chlorine 18.53

EXANIPLE III A product was prepared as in Example I except that sperm oil was substituted for lard oil. The analysis of the product was;

Per cent Phosphorus 0.88 Sulfur 1.62 Chlorine 17.22

EXAMPLE IV Condensation of chlorinated sperm oil with sodiam salt of ditertzaryoctylphenyl dithtophosphoric acid A 3-way flask equipped with a stirrer, and a return condenser was charged with 540 gms. of 91% isopropyl alcohol and 28.4- ml. (0.178 mol) of 25% sodium hydroxide. The mixture was warmed and stirred for a, while, whereupon 540 gms. of chlorinated sperm oil (containing 20% chlorine) was added, which was followed with 99 gms. (0.178 mol) of ditertiaryoctylphenyl dithioplzosphoric acid. The latter had been prepared-in the usual manner by condensing tertiaryoctylphenol with phosphorus pentasulfide in an inert solvent. When all the ingredients had been added as indicated above, the mixture was refluxed with rapid stirring for 4 hours,

The alcohol was then removed under reduced pressure, the residue was filtered, and this flltrate was extractedwith naphtha and the extract dried over sodium sulfate. The naphtha was removed under reduced pressure with final topping at 220 0. bath temperature. The residue consisted of a dark brown liquid which rroved to be readily soluble in lubricating oils.

EXAMPLE V Condensation of chlorinated sperm oil with d.i( tertiary octylphenol) sulfide phosphorus pentasulfide condensate The di(tertiaryoctylphenol) sulfide-phosphorus pentasulfide condensate was prepared by condensing tertiaryoctylphenol with sulfur dichloride and phosphorus pentasulfide in the usual manner in an inert solvent. The dithiophosphoric acid derivative thus obtained was condensed with chlorinated sperm oil as described below:

A 3-way flask equipped with a stirrer, and a return condenser was charged with 280 ml. of 91% isopropyl-alcohol. 278.7 gms. (1.57 mol) of chlorinated sperm oil (2% chlorine), 14.7 ml. (0.117 mol) of 25% sodium hydroxide, and 89.5 gms. (0.092 mol) of the above described dithiophosphoric acid. The mixture was then refluxed with rapid stirring for 4 hours. The reaction product, which consisted of 339 gms, of dark brown oil, was isolated as described in the preceding experiment. The product proved to be readily soluble in mineral oils.

The performance of the various products previously described is shown in the following table. It will be observed that the performance of these products is excellent on both the Timken and the SAE machines, whereas the performance of products previously known in the art may be good on either one or the other machine, but not on both. Since the Timken machine indicates the performance to be expected in heavy duty truck service and the like, and the SAE machine indicates the performance to be expected in high speed passenger car service, it is obvious that a single lubricant which can be used interchangeably for either type of service is of distinct advantage This is especially true in military operations where the problems of supply are acute.

It will also be seen that it is possible to vary somewhat the relative performance on the two machines to permit some extra emphasis to be placed on either one or the other type .of service, as is shown by the data for the several examples, but in all cases the performance on both machines appears to be more equally balanced than has been possible heretofore. Conventional extreme pressure additives of the prior art, of good recognized quality, as indicated on the SAE machine and the Timken machine respectively, were tested as Additive A and Additive B.

Performance of extreme pressure lubricants Timken Machine SAE Machine Additives (in Scar (Scale Lbs.

SAE 90 oil) K Load Width Unit Load at 1,000

(Lbs. on (in 1,6 (Lbs/Sq. R. P. M.)

Lever) inch) In.)

None l0 1. 65 7, 350 220 I0. Additive A 61 i. 8 37, 400 90 Additive B 33 4. 0 10, 600 325 10% Example I 51 2. 3 28, 500 400 10% Example IL- 49 l. 95 38, 800 285 10% Example III- 77 2. 45, 900 220 107 Example IV. 51 2. l 31, 200 250 l 0 Example V. 51 2. 25 29,100 200 In the foregoing table the SAE 90 oil is a blend of two base stocks having the following characteristics:

Stock X Stock Y Per cent used 5O 50 Crude t Refining method Gravity, 21. 9 29. 8 Flash 585 445 Vis./l00. 4809. 4 375. 1 Vis./2l0. 204. 3 58.0 Viscosity Index 85 105 (Jon. Carbon 2. 86 0. 07 Sulfur 0. 92 0. 34

I Mid-Continent. 1 Propane-extracted. 3 Phenol extracted.

1. An extreme pressure additive composition for mineral oil base lubricants consisting essentially of the condensation product of a halogenated fatty material containing at least two halogen atoms with an alkali metal salt of a dithiogroups of said ester being selected from the class which consists of alkyl and alkaryl radicals of 2 to 10 carbon atoms in the alkyl chain.

2. An extreme pressure additive composition for mineral base lubricants and the like, consisting essentially of a chlorinated aliphatic fatty ester containing at least 2 atoms of chlorine, condensed at least in part with a composition having the general formula where M is a metal having a valence of 1 or 2, and R1 and R2 are hydrocarbon radicals selected from the class which consists of alkaryl and alkyl groups having 2 to 10 carbon atoms in the alkyl chain.

3. An extreme pressure additive composition for mineral oil lubricants consisting essentially of the condensation product of a chlorinated aliphatic fatty material containing at least 2 atoms of chlorine and having at least one chain of 12 to 22 carbon atoms and a metal salt of dialkyl dithiophosphate having 2 to 10 carbon atoms in each alkyl group.

4. An extreme pressure additive composition for mineral oil lubricants consisting essentially of the condensation product of a chlorinated aliphatic fatty material containing at least 2 atoms of chlorine and having at least one chain of 12 to 22 carbon atoms each and a metal salt of dialkaryl dithiophosphate having 2 to 10 carbon atoms in the alkyl chain of each alkaryl group.

5. An extreme pressure additive composition for mineral oil lubricants consisting essentially of the condensation product of a halogenated aliphatic carboxylic acid ester containing at least 2 atoms of halogen and having at least one aliphatic chain of 12 to 22 carbon atoms each and a metal salt of diisopropyl dithiophosphate.

6. An extreme pressure lubricant composition consisting essentially of a mineral oil of lubricating grade containing from 1 to 20% of a condensation product of a halogenated aliphatic ester containing at least 2 atoms of halogen and having from 12 to 22 carbon atoms, with an alkali metal salt of a diester of dithiophosphoric acid containing 2 to 10 carbon atoms in each esterifying radical said esterifying radicals being selected from the class which consists of alkyl and alkaryl radicals having 2 to 10 carbon atoms in the alkyl chain.

7. Composition as in claim 1 wherein the ester compound is lard oil.

8. Composition as in claim 1 wherein the ester compound is sperm oil.

9. Composition as in claim 6 wherein the aliphatic carboxylic acid ester is lard oil.

10. Composition as in claim 6 wherein the ester is sperm oil.

11. A lubricating composition consisting essentially of a mineral oil base lubricant containing 1 to 20% by weight of the product obtained by at least partially reacting a halogenated aliphatic carboxylic acid ester containing at least 2 halogen atoms with a dihydrocarbon substituted metal salt of dithiophosphoric acid, said dihydrocarbon substituent consistin of like hydrocarbon radicals selected from the class which consists of alkyl and alkaryl radicals having 2 to 10 carbon atoms in the alkyl chain.

12. A process which comprises halogenating an phosphoric acid diester, each of the esterifying al hat c est r, hav n one or m re chains of 12 to 22 carbon atoms each, to a halogen content of 5 to 50% by weight, reacting a phosphorus sulfide and an aliphatic alcohol of 2 to 10 carbon atoms at temperatures between room temperature and 210 F. to obtain a dithiophosphoric acid diester, neutralizing said acid ester with a metal base, and condensing the resulting metal salt of acid ester and said halogenated ester to obtain an extreme pressure additive composition for lubricating oil and the like which contains active sulfur, chlorine and phosphorus.

13. The process which comprises chlorinating a fatty oil having at least one alkyl chain of 12 to 22 carbon atoms to a chlorine content of 5 to 50% by weight, and at a temperature not exceeding 300 F., combining an aliphatic alcohol of 2 to 10 carbon atoms with phosphorus pentasulfide, at a temperature not greater than about 210 F. to prepare an alkyl diester of thiophosphoric acid, neutralizing said acid with an alkali to form an alkali salt, and condensing said salt with said chlorinated fatty oi1 by heating to a temperature suflicient to evaporate and remove water to obtain a condensate containing active chlorine, phosphorus and sulfur.

LOUIS A. IMIKESKA. ELIVIER B. CYPHERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Musselman et al. July 13, I948

Claims (2)

1. AN EXTREME PRESSURE ADDITIVE COMPOSITION FOR MINERAL OIL BASE LUBRICANTS CONSISTING ESSENTIALLY OF THE CONDENSATION PRODUCT OF HALOGENATED FATTY MATERIAL CONTAINING AT LEAST TWO HALOGEN ATOMS WITH AN ALKALI METAL SALT OF A DITHIOPHOSPHORIC ACID DIESTER, EACH OF THE ESTERIFYING GROUPS OF SAID ESTER BEING SELECTED FROM THE CLASS WHICH CONSISTS OF ALKYL AND ALKARYL RADICALS OF 2 TO 10 CARBON ATOMS IN THE ALKYL CHAIN.

11. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL OIL BASE LUBRICANT CONTAINING 1 TO 20% BY WEIGHT OF THE PRODUCT OBTAINED BY AT LEAST PARTIALLY REACTING A HOLOGENATED ALIPHATIC CARBOXYLIC ACID ESTER CONTAINING AT LEAST 2 HALOGEN ATOMS WITH A DIHYDROCARBON SUBSTITUTED METAL SALT OF DITHIOPHOSPHORIC ACID, SAID DIHYDROCARBON SUBSTITUENT CONSISTING OF LIKE HYDROCARBON RADICALS SELECTED FROM THE CLASS WHICH CONSISTS OF ALKYL AND ALKARYL RADICALS HAVING 2 TO 10 CARBON ATOMS IN THE ALKYL CHAIN.