US2536685A - Synthetic lubricant - Google Patents

Description

PM. Jan. 2, 1951 SYNTHETIC LUBRICANT Denham' Harman and William E. Vaughan,

Berkeley, Calif., assignors to Shell Development\ompany, San Francisco, Guilt, a corporation of Delaware 1 No Drawing. Application June 2, 1947,

Serial No. 751,977

This invention relates to novel products and to "their preparation and use. More particularly, it

pertains to the use of certain sulfur-containing linear polymers especially useful as synthetic lubricants or as lubricant additives.

Mineral oil fractions are suitable for many lubricating purposes, but it is well known that such lubricants possess certain inherent limitations such as tendency to oxidize, thickening at low temperatures and poor inherent lubricating characteristics under conditions of relatively extreme pressure such as t'n hypoid gear lubrica tion. A large number of additives have been employed with mineral oils in order to improve these shortcomings with a certain degree of success.

Various synthetic materials have been proposed for use as synthetic lubricants. These include polymers of cracked wax olefins and alkylated aromatics such as alkylated naphthalenes. some of these are useful for special purposesbut, especially if the synthetic lubricants are derived from olefinic sources, they usually possess corrosion and oxidization characteristics limiting their utilization to a, substantial degree. Another type of synthetic lubricant which has been investigated is the alkylene oxide polymer type such as polymerized propylene oxide. This latter type of synthetic lubricant is suitable for use only under mild operating conditions. If even moderate extreme pressure conditions are encountered this type of polymeric lubricant fails to function satisfactorily and results in rapid wear of the machinery or engine being lubricated.

It is an object of this invention to provide novel phosphorus containing products. It is another object of this invention to provide a, process for the production of such materials. It is a further object of this invention to provide novel synthetic lubricants. A further object of this 8 Claims. (Cl- 252-48.6)

- or a phosphorus containing compound. Still in invention is to provide novel additives for lubriwherein R is an organic radical (especially a hydrocarbon radical) when treated with phosphorus accordance with this invention, it has been found that such polymers add extreme pressure characteristics in an unexpected degree to oxygencontaining oleaginous materials and may be used therewith in substantially any portion. Thus, these phosphorized polymers comprise unusually effective lubricants in themselves or modifiers for oxygen-containing lubricants.

Polymers which maybe phosphorized for the purpose of the present invention include especially those prepared from alkylene oxides and alkylene glycols.

Alkylene oxides. and particularly the alkylen oxides having the oxygen bound to adjacent carbon atoms, form polymers of the above configuration. These monomeric oxides have the general configuration wherein the free valences are satisfied with hydrogens or organic radicals.

* Alkylene oxides which form such polymers include ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, isobutylene oxide, tetramethylethylene oxide, methyiphenylethylene oxide, cyclohexene oxide, methylcyclohexene oxide, 1,2-cetene oxide; and other substances containing the epoxide linkage such as epichlorohydrin, epibromohydrin, and glycides such as glycidol and 1,2-epoxy-2-butanol, as well as derivatives and polymerizablehomologs and analogs of the aforementioned substances.

Copolymers of the alkylene oxides useful in compositions of the present invention include for example, the copolymers of ethylene oxide and propylene oxide; and copolymers of ethylene oxide and isobutylene oxide; the copolymers of propylene oxide and epichlorohydrin'; the copolymers of propylene oxide and l,2-butylene oxide; the copolymers of propylene oxide and glycidol; and the copolymers of propylene oxide and isobutylene oxide.

Polymers similar to those above are formed from the alkylene glycols, including the polymethylene glycols and the ethylene glycols. The monomeric and lower polymeric glycols have the general configuration i -rail ing the glycollic hydroxyls are derived from 1,3- propanediol (trimethylene glycol) and have the general formula:

wherein n is an integer and R1 and R: are hydrogens or organic radicals. v

11' R1 and/or R: are not hydrogen atoms, they may be organic radicals such as alkyl, aralkyl, aryl, etc. Preferably. if they are not hydrogens, they are aliphatic radicals, especially saturated lower aliphatic radicals, but mayalso be groups which contain oleflnic or acetylenic links. Typical of the trimethylene alkyl substituted glycols are the methylated trlmethylene glycols, including l-methyl-l,3-propanediol; 2-methyl-1,3-propanediol; 1,1-dimethyl-1,3-propanediol; 1,2-dimethyl-1,3-propanediol; 1,3-dimethyl 1,3 propanediol; 2,2-dimethyl-l,3-propanediol: 1,1.2-trimethyl-1,3-propanediol; 1,1,3-trimethyl-1,3-propanediol; 1,2,2-trimethyl-l,3-propanediol; 1,2.3- trimethyl-l,3-propanediol; l,1,2,2-tetramethyl- 1,3-propanediol; 1,l,3,3-tetramethyl 1,3 propane'diol; 1,2 3 3 tetramethyl 1,3 propanediol; 1,1 ,2,2,3 pentamethyl-l,3-propanediol; 11.2.3.3- pentamethyl-1,3-propanediol; and hexamethyl- 1,8-propanediol.

In place of the methyl groups other alkyl groups may be utilized such as ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl. etc.. as well as their isomers. Preferably, when alkyl groups are the substituents R1 and R2, they have from 1 to lottfarbon atoms, and still more preferably from 1 5.

It will be understood that R1 and B: may be similar or dissimilar groups. Thus, when expanding the general formula given hereinbefore to its indicated number of carbon atoms, it then becomes wherein B: through Rs are either hydrogen atoms or similar or dissimilar organic radicals. Those derivatives of trimethylene glycol, other than trimethylene glycol itself. which gives the most satisfactory polymers for general use h ve either one or two of the R's as lower alkyl groups. Thus, 2-methyl-L3-propanediol and 2,2-dimethyl-l,3-propanediol form excellent polymers when treated according to the method of the present invention.

Other lower alkyl substituted trimethylene glycols which polymerize readily are 1-methyl-2- ethyl 1,3 propanediol: 2-methyl-2-ethyl-l, 3- propanediol; l-methyl-3-ethyl-1,3-propanediol; 2-methyl-2-propyl-1,3-propanediol; l-methyl-2- isopropyl-1,3-propanediol; 2-methyl-2-but l-l3- propanediol; 2-methyl-3-butyi-l 3-propanediol; and the homologs, analogs and derivatives of the same.

Cycloaliphatic radicals may be one or more of the substituents represented b R3 to Rs in the above general formula. Thus R: thro gh Rs may be such radicals as cyclohexvl. methylcyclohexyl, dimethylcyclohexyl, ethyleyclohexyl, etc. However, open chain alkyl substituents form polymers having preferred properties.

The polymers have modified properties it the trimethylene glycol derivative contains other active groups, such as additional hydroxyls, carboxyls, carbonyls, halogens, sulfur. phosphorus, nitrogen, etc.

Polymethylene glycols having 6 or more carbon atoms separating the glycollic hydroxyls also form olymers and copolymers which are readily treated as described herein.

The polymethylene glycols from which such polymers are prepared have the general formula wherein Z is an integer, u is an integer greater than 5 and the Rs are substituents attached to each carbon atom, such as hydrogen atoms or organic radicals, especially hydrocarbon radicals. Preferably Z is an integer less than 10, and more preferably is an integer between 1 to 4. Actually, when Z is more than 1, the glycol is a dimer, trimer. etc., of the corresponding monomeric glycol. The polymethylene glycols p lymerizing most readily are those in which 1! is an integer Iron. 6 to 20.

Monomeric, unsubstituted polymethylene glycols falling within the above formula include 1,6- hexanediol: 1,7-heptanediol; 1,8-octanediol; 1,9- nonanediol; LIO-decanedioi; 1,12-dodecanediol: and polymerizable homologs, analogs and derivatives of the same.

The above glycols are those in which all of the R. substituents attached to the carbon atoms are hydroeenatoms. When one or more of the R's are substituents other than hydrogen atoms they may be hydrocarbon radicals, such as allphatic, aromatic, or alicyclic hydrocarbon radicals, or radicals containing non-hydrocarbon members, such as hydroxyl. carboxyl, or carbonyl groups, or sulfur, selenium, tellurium, phosphorus or nitrogen atoms. Preferably. however. anv organic radicals attached to the polymethylene glycol are hvdrocarbon radicals. Of these, the aliphatic hydrocarbons are preferred. and the saturated lower aliphatic radicals give the most stable polymers and have the widest utility. Hence, the preferred R's, other than hydro en, are the lower alkvls. such as methyl, ethyl, propyl, isopropwl. butyl, secbutyl, terbutyl. amyl. isoamvl. hexyl, etc. groups. Again even when R's other than hydrogen are present, it is preferred that the monmeric gl col conta n a p enonderance of hydro en substituent Rs. The most reactive glycols are those in w ich less than 4 R's are other than hydrogen, and the greatest reactivitv is possessed by those having 2 or le s R's which are organic radicals.

Glycols which fall within the above classification include LG-heptanediol: 1,6-octanediol; 1 .fi-nonanediol: 1 .G-dodeeanediol: 1,6-deemediol; 1.7-octanediol; 1,7-nonanediol; 1,7-decanediol: 1,7-dodecanediol: 1,8-nonanediol; 1,8- decanediol; 1.9-decanediol; 1.9-dodecanediol: 1.10-dodecanediol: ZF-octanediol: 2,7-nonanediol: 2,7-decanedio1; 2.7-dodecanediol: 2,8-nonanediol: 2,8-decanediol; 2,8-dodecanediol: 2,9- decanediol; 2,9-dodecanediol; 2,3-dimethyl-l,8- hexanediol; 2,4-dimethyl-1,6-hexanediol; 2,5- dimethyl 1,6 hexanediol; 4,4-dimethvl-L6- hexanediol; 5,5 dimethyl 1,6 hexanediol: 2- methyl 3 ethyl-1,7-heptanediol: 2-ethyl-3- methyl 1,7 heptanediol; 3,3-diethyl-1,'7-heptanediol; 3,4 diisopropyl-1,8-octanediol; etc., and their polymerizable homologs, analogs and derivatives.

The polymers described hereinbei'ore may be lhomopolymers or may be copolymers. For example, an ethylene glycol may be copolymerized with a trimethylene glycol to give copolymers having units of the general configuration:

whe ein m and n are integers and the free vale es within the brackets are satisfied with hydrogen atoms or organic radicals. These include olymers of ethylene glycol and trimethylene glycol; ethylene glycol and l-methyl- 1,3-propanediol; ethylene glycol and 2-methvl- 1,3-propanediol; ethylene glycol and 2,2-dimethyl-1,3-propanediol; ethylene glycol and l,3-'

diethyl 1,3 propanediol; 1,2-dimethylethylene glycol and trimethylene glycol; 1,2-dimethylethylene glycol and 1,3-dibutyl-1,3-propanediol, etc.

Other copolymers falling within the general formula of substances stabilized according to the present invention include the copolymers of an ethylene glycol or a trimethylene glycol with a polymethylene glycol having more than 5 carbon atoms separating the glycollic hydroxyis. These copolymers have units of the general configuradrogen halides such as hydrogen iodide or hydrogen chloride; or organic sulfonic acids such as para-toluene sulfonic acid. a

In producing the phosphorized polymers for' use as lubricants or as modifiers for oxygencontaininglubricants it is preferred practice to heat one or' more of the polymers at a temperature from about 50 C. to about 200 C. for a period of about 3 hours with an agent selected from the group consisting of phosphorus. phosphorus halides and phosphorus oxyhalides. Suitable halides include e pecially phosphorus trichloride, while the most effective oxyhalide is phosphorus oxvchloride. However, the iodides, bromides and fluorides as well as the corresponding oxyhalides may be used for the present purpose. The reaction mixture may be heated in the absence of other materials or in the presence of solvents for one or more of the ingredients or products.

An especially suitable means of preparing the subject lubricants comprises heating alarge excess of the polymer with phosphorus or a phosphorus compound in such a manner that only a minor amount 01' the product obtained has been phosphorized while the remainder is in an 7 unmodified condition. Thus lubricants having any predetermined degree of extreme pressure characteristics may be prepared.

In carrying out the preparation of these ph0$* phorlzed lubricants therefore, any desired degree of phosphorization may be effected by controlling the ratio oi phosphorus 'or phosphorus compound to the polymer. Preferably the amount of phosphorus in the product will vary from about 1% to about 20% by weight of the polymer. However, higher or lower percentages may be employed. In order to obtain a synthetic lubricating material having satisfactory extreme pressure properties at high loads it is usually preferred that the percentage of phosphorus be from about 3% to about 10%, based on the weight of the polymer.

, Under normal operating conditions it is advisable to employ an amount of phosphorus in excess of that amount with which it is desired to modify the polymer. By the use of such an excess the rate of reaction is increased to a satisfactory degree. If an excess is used it becomes necessary at the end of the heating period to separate the unreacted phosphorus or phosphorus compound from the modifier polymeric material. Ordinarily the excessvagent will remain in suspension and may be separated by a filtration or centrifuging operation. Under some conditions, however, the excess agent dissolves in the polymer and, if it is necessary to separate therefrom, it must be removed by such means as solvent extraction. For many lubricating pur; poses an excess of phosphorus is not objectionable if it is dissolved in the body of the lubricant.

The phosphorizing operation normally may be effected without undue discolorization or other adverse effects on the subject polymers. However, it may be desirable to colorize or decolorize the product by subjecting it to an operation such as filtration through activated carbon, treatment with an absorbent clay or by chemical means of decolorization.

The products obtained by the phosphoriza-.

tion of polymers, such as those described above, are solids or liquids useful for a number of purposes. The solids are particularly effective as extrem pressure additives in oxygen-containing lubricants, while the liquid members of the phosphorized series are effective not only as ex treme pressure additives but as lubricants themselves. The oily products have satisfactory lubricating characteristics, having high viscosity indices and low pour oints.

Lubricants which n' y be modified by the addition of a solid or liquid phosphorized polymer as described hereinbefore include oxygen-com taining oleaginous materials such as fatty oils; vegetable oils such as corn oil, cottonseed oil and castor oil; animal oil such as neats-foot oil; and fish oils such as sperm oil. Oleaginous materials when modified by such means as halogenation, hydrogenation, alkylation and other means may be modified by the phosphorized polymers of the present invention. Depending upon the application intended, oleaginous materials of extreme low or extrme high viscosities may be used successfully. Lubricating oils having a viscosity from about 30 seconds at F. to about 250 seconds at 210 F. and higher may be used if desired.

A special type of lubricant which is particularly suited to modification with the subject phosphorized polymers includes lubricants comprising or derived from the alkylene oxide or alkylene glycol polymers listed above. These polymers Polymer-iced:

vail. It has been discovered that by the-phosphorization as described hereinabove pressure characteristics are imparted to the alkylene oxide and glycol polymers. The examples which follow describe the preparation and use of this invention. It is not intended that the invention be limited specifically to these examples, but that they be treated as specific illustrations thereof.

Example I 100 parts of a polymerized propylene oxide were heated with parts by weight of phosphorus trichloride at a temperature of 170 for 3 hours. The product was filtered and was I found to have the following characteristics:

Phosphorus. percent by weight 1.42 Chlorine, percent by weight 1.16 Viscosity index 149 Pour point, F Example II 100 parts of a polymerized propylene oxide were heated with 5 parts by weight of phosphorus oxychloride at a temperature of 190 for 3 hours. The product was filtered and was found to have the following characteristics:

Phosphorus, percent by weight 1.28 Chlorine, percent by weight 1.66 Viscosity index 140 Pour point. "P -25 Example III The propylene oxide polymer and the phosphorized product thereof formed as described in Examples I and II were tested for extreme pressure properties, using the 4-ball machine described by Boelage in "Engineering (July 14, 1933). The following data were obtained.

Wear in mm. at Various Loads mums W indicates welding.

We claim as our invention: 1. As an extreme pressure agent suitable for assess! imparting extreme pressure properties'to oxygen-containing lubricating oils, the reaction product of a propylene oxide polymer with a phosphorus halide, said product having both phosphorus and. halogen substituents, the composition having a phosphorus content'of and a chlorine content of at least 1%, said reaction produet being obtained by heating a propylene oxide polymer and a phosphorus halide at a temperature between 50 and 200 C.

2. The process for the preparation of an extreme pressure lubricant which consists essentially of heating 100 parts by weight of propylene oxide polymers with 5 parts by weight of phosphorus trichloride for 3 hours at a temperature of C.

3. The process for the p p ration of an extreme pressure lubricant which consists essentially of heating 100 parts by weight of propylene oxide polymers with 5 parts by weight of phosphorus oxychloride for 3 hours at a temperature of C.

4. As an extreme pressure agent suitable for imparting extreme pressure properties to oxygen-containing lubricating oils, the reaction product prepared according to the process of claim 2. v

5. As an extreme pressure agent suitable for imparting extreme pressure properties to oxygen-containing. lubricating oils, the reaction product prepared according to the process of claim 3.

6. The process for the preparation of an extreme pressure lubricant which consists essentially of heating polyoxy lkylene fiuids at a temperature between 50 C. and 200 C. with a phosphoru halide, the proportion of said phosphorus halide being sufiicient to impart a phosphorus content to the reaction product of the agent and gfig of between 1% and 20% by weight of the 7. As an extreme pressure agent suitable for imparting extreme pressure properties to oxygencontaining lubricating oils, the reaction product prepared according to the process or claim 6.

8. An extreme pressure lubricating composition consisting essentially of an oxygen-containing lubricating oil and a reaction product prepared according to the process of claim 6, the proportion of said reaction product being suillcient to impart extreme pressure properties to said composition.-

DENHAM HARMAN. WILLIAM E. VAUGHAN.

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

UNITED STATES PATENTS

Claims (1)

1. AS AN EXTREME PRESSURE AGENT SUITABLE FOR IMPARTING EXTREME PRESSURE PROPERTIES TO OXYGEN-CONTAINING LUBRICATING OILS, THE REACTION PRODUCT OF A PROPYLENE OXIDE POLYMER WITH A PHOSPHORUS HALIDE, SAID PRODUCT HAVING BOTH PHOSPHORUS AND HALOGEN SUBSTITUENTS, THE COMPOSITION HAVING A PHOSPHORUS CONTENT OF 1-20% AND A CHLORINE CONTENT OF AT LEAST 1%, SAID REACTION PRODUCT BEING OBTAINED BY HEATING A PROPYLENE OXIDE POLYMER AND A PHOSPHORUS HALIDE AT A TEMPERATURE BETWEEN 50 AND 200* C.