US2488618A - Lubricants of the extreme pressure type - Google Patents

Description

Patented Nov; 22, 1949 LUBRICANTS or 'rrm e craemr. rmissuae Elmer B. Cyphers, Craniord, and George M. Mc-

Nulty, Union, N..J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing.

The present invention relates to lubricants of the extreme pressure type and particularly to extreme pressure lubricants containing materials such as phosphorus, sulfur and compounds thereof in mineral and/ or fatty oil bases.

In many types of modern machinery very high unit pressures occur between the adjoining sur-' faces of moving metallic parts. Unless such surfaces are effectively and continuously lubricated, rapid wear and early destruction occur. At the pressures which aresometimes employed, and particularly when metal parts such as hypoid gears in automotive vehicles are operated at high speeds, or, more particularly, at high torques, as in heavy duty automotive vehicles, conditions arise where ordinary lubricants are not capable of maintaining effective lubricating films. Mo-

mentary rises in temperature also cause the prowith the metal to form thin protective layers of chemical reaction products. Thus, as is well known in the art, certain substance such as sulfur, chlorine, phosphorus and the like, when added to lubricating oils and when rendered reactive by rise in temperature, combine in some chemical manner with the metal to produce protective films of approximately molecular thickness-or thickness of that general order. These films adhere tenaciously to the metal, preventing metal to metal contact momentarily until the normal oil film can be restored.

Lubricants of the general character referred to above usually consist of blends of petroleumoil with a saponifiable oil, usually an animal or vegetable oil, containing asextreme pressure agents either free elements or chemical compounds of sulfur, chlorine, phosphorus and related materials. It is desirable that at ordinary temperatures these materials be relatively inactive, being adapted'to react vigorously with the metal surfaces upon temperature increases which result, as on momentary failure of the lubricating oil film.

In the past, it has been necessary to compromise between extreme pressure additives which, on the one hand, are effective when needed to provide the type of chemical film mentioned above, but are objectionably corrosive, over a period of time, to metals such as copper and steel, and those, on the other hand, which are relatively non-corrosive but are only moderately effective as extreme pressure agents.

Application November 25, 1945, Serial No. 712,050

4 Claims. (Cl. 252-46.6)

probably consist of metal sulfides, chlorides,

' phosphides and the like. Thus when materials The thin protective films referred to above which this invention pertains.

such as sulfur, chlorine or phosphorus are used in an active form in a lubricant for steel gearin iron sulfides, chlorides or phosphides may be formed on the gear teeth. Analogous reactions occur with other metals and with other extreme pressure additives.

In the past, numerous compounds have been used for the purpose described above; among them are not only inorganic materials such as free sulfur, free phosphorus, sulfides, etc., but also aryl and alkyl chlorides and various other organic as well as inorganic compositions of sulfur, phosphorus, chlorine, arsenic, selenium, lead, etc. These materials have usually been added to fatty oils which in themselves have certain extreme pressure properties. Certain animal and vegetable oils have very desirable film strength properties but often are somewhat unstable and in some respects not entirely satisfactory as lubricant additives. It is therefore an object of the present invention to use materials other than, or in addition to, fatty oils in mineral oil lubrieating compositions, as extreme pressure additives.

A furtherv object is to combine certain organic materials which have been found desirable substitutes for fatty materials, with sulfuror phosphorus-containing materials in a manner to provide extreme pressure lubricants and additives therefor having useful, and superior properties.

Still a further object is to use organic materials in lubricants which have certain economic advantages over fatty oils and the like previously used in .lubricants of the general character to The materials proposed for use according to the present invention are, in some instances, at least less costly and in some cases more abundant than fatty materials conventionally used.

We have discovered that by treating certain I esters of abietic acid, or'hydrogenated abietic acid with phosphorus-containing materials, lubricants may be produced which have useful extreme pressure properties and which are free from certain of the objections to which fattyoils are subject. Also, in lieu of simple esters of abietic acid or hydrogenated abietic acid, sulfurized esters of the same may be combined with phosphorus containing materials.

In a copending application, Serial No. 708,794, filed November 8, 1946, by Elmer B. Cyphers and Louis J. Osborne, there is disclosed an extreme found useful since it has desirable properties as an oiliness" agent and also as an anti-oxidant. In lieu of tricresyl phosphate, various esters of phosphoric and phosphorous acids may be used as organic additives, and the substitution of hydrogen atoms in such materials byalkyl or aryl additives, to form either complete or partial esters. is contemplated.

The process just described is also applicable to esters of abietic acid, hydrogenated abietic acid ,or sulfurized esters of the same. It is to be understood, however, that the present invention is not dependent upon the use of a second added phosphorus compound such as tricresyl phosphate and the like, although such may be used if desired to improve the effectiveness of our compositions. A suitable composition may be provided by merely treating the esters or sulfurized esters of abletic acid and/or hydrogenated abietic acid with phosphorus-containing materials such as the phosphorus sulfides as, for example, P453. .Other phosphorus compounds, such as PCls, PCls. POCl, POCls, POCls, P205, P203, etc. may be employed but we prefer to use the phosphorus sulilde such as P285, P481 and P483, the last being particularly preferred.

The abietic acid derivatives have a notable advantage over the fatty oils conmentioned above ventionally used in extreme pressure lubricants as regards treatment with phosphorus sulfides. Fatty oils must be sulfurized, for example. by cooking free sulfur into them, before they can be treated satisfactorily with a phosphorus sulfide such as P483. The abietic acid derivatives, however, can be treated directly and the reaction product is found to be a rather effective extreme pressure agent, capable of carrying fairly .high loads.

It will be understood that an extreme pressure additive such as described above, consisting of alkyl esters of abietic acid. and related compounds reacted with phosphorus-containing materials, is not only useful in lubricants designed especially for extreme pressure functions, but may be useful generally in various types of lubricating oils and greases. Thus it may be used in mineral oils,

fatty oils, or synthetic oils, or mixtures thereof.

It may be used in greases prepared, for example, by the addition of soaps to lubricating oils, or by the addition of carbon black and like thickeners to oils. It may be used alone or in conjunction with other extreme pressure additives and along with corrosion inhibitors, anti-oxidants, pour point depressants and the like, as will be readily understood in the art. v

Ordinarily the material resulting from the-reaction of methyl abietate and the like with a phosphorus sulfide will be used in quantities of 5'to 15%, based on the total lubricant, but these name Abalyn."

base lubricant will usuallyrun or more. to

as much as 99.9%. Specific examples of suitable compositions are as.follows: I EXAMPLE 1 940 grams of a commercial grade of methylawd rosin produced by esteriflcation of rosin with methyl alcohol was heated in an open beaker to 280 F. and 60mm of sulfur added with good agitation. Such a material is sold commercially by the Hercules Powder Company under the trade The temperature was raised to 385 F. and held at this point for 2 hours, after which the sulfurized product was cooled. Next day itwas heated at 210 It, 5 grams of phosphorus sesquisulilde was added, and the temperature was maintained at 210-220 I". for eight hours with continuous agitation, followed by natural cooling. 7 a

10 partsof the above product were blended with 90 parts of SAE 90 grade mineral oil and the blend was tested on the Timken machine with the results shown in the table.

. product was then removed and cooled, after which 4 grams of phosphorus sesquisuliide were added to 1000 grams of the sulfurized product, and the a mixture stirred and heated in an open beaker at 2l0-220 F. for fivehours.

10 parts of the resulting product and 90 parts of the SAE 90 grade mineral oil were blended and tested on the Timken machine with the results shown in the table below. EXAMPLE 3 6 grams of phosphorus sesquisulfide and 294 grams of a methyl dihydroabietate, produced by. the methylation of rosin, were mixed and heated in an open beaker to 300 F. in one hour and then held at 300 1''. for hour. Such a hydrogenated and methylated rosin as just described is available commercially being sold under the trade name Hercolyn by the Hercules Powder Company. 10 parts of the resulting product and 90 parts of the SAE 90 grade mineral oil were blended and tested with the results shown in the table.

TABLE Timken machine test data ox Load, Scar Width Lubricant Lbs. m m Inch: Lbisi/sq.

SAE 90 Grade base oil.... 10 1. 10% Example 1 in above 65 base oil 43 l. 65 33,400 10% Example l+0.l7 trigresyli lahosphateina ve 5 ace 0 1 l. 65 10K, Example 2 in above 39,500 0 rii seia'aliwfis' o a eresyl phosphatein above baseo 51 1.8 30,3(10 10% Example 3 in above I base oil 4a 2. 4 22, coo 10% Example 3+0.1% tricresyl phosphate in above baseoil 5i 2.1 31,100

ates-gems lieved to be substantially as follows:

' I Per cent Methyl esters'of 'abietic and neoabietic acid (contain 2 conjugated double bonds per mol) g '23 Methyl ester of dihydroabietic acid (contains 1 double bond per mol) Y 22 Methyl ester of-tetrahydroabietic acid (contains no double bonds) 22 Methyl ester of dehydroabietic acid (contains onebenzenoid ring) 17 nsaponifiable matter (pinenes, ethers, etc.) 16

' This composition may be described roughlyas a methyl abietateor more accurately as a methylester of rosin having an average double bond content of approximately 0.80 active double bond per mol not counting benzine type bonds. The ester of Example 1 has an average value of 8.0 and an equivalent molecular weight of 358 based on' the saponification value determination.

'In lieu' of the methyl ab'ietate the related material mentioned above in connection with Example 3 may be used. This is also a proprietary product marketed by the Hercules Powder Company. Whereas the former appears to be a mixture of methyl esters of abietic acid derivation, the latter is somewhat more fully hydrogenated, having roughly the following formula:

that they can be treated directly with a phosphorus sulfide without sulfurization.

It will be understood from the foregoing that the esters and sulfurized esters of abietic acid have been found to serve very satisfactorily as substitutes for fatty oils and sulfurized fatty oils which in the past have been considered essential in certain types of lubricants. By the use of these materials, unstable fatty bodies may be eliminated from oils and greases while their desirable oiliness and film forming characteristics may be retained. It will be understood, however, that the abietic' acid esters, sulfurized or otherwise, are 5 compatible with fatty bodies and may be used in conjunction with vegetable and/or animal oils as well as in mineral oils with or without fatty constituents.

Thus, a satisfactory lubricant may be formed 1" by combining sulfurized or unsulfurized the methylated rosin, referred to generally herein as a methyl abietate, or methylated hydrogenated.

abietate, referred to herein by its approximate formula methyl dihydro abietate, with phosphorus sesquisulfide, or other phosphorus sulfides, with or without the addition of tricresyl phosphate or an analogous phosphorus containing organic "compounds.

Various other organic abietates, such as other alkyl esters of abietic acid may be used. It will.

- of course, be understood that materials as described above may be included in oils" contain ing or even consisting largely or entirely of fatty oils, sulfurized fatty oils and the like. sulfurized mineral oils, which themselves have mild extreme pressure properties, may also be so treated, and

the percentage of sulfur in active form may be up to or exceeding 1%.

Extreme pressure compositions consisting of mineral and/or fatty oils including various percentages of the materials described above may be used per se as lubricants or maybe added to lubricating oils in various proportions to secure the characteristics desired for a particular purpose; Synthetic oils of the ethylene glycol type, for example, may be used in lieu of or in addition to mineral and/or fatty oils. Referring to the example given above when 10% of P48: treated sulthat the load carrying characteristics were considerably increased by the addition of 0.1% of tricresyl phosphate. For some purposes, the use of the latter material may not be necessary or desirable but it appears to have merit where high load carrying qualities are required and where corrosivity must be held to a minimum. Since it is usually desirable to keep corsosivity to a minimum while imparting extreme pressure qualities to a lubricant, it will frequently be found advantageous to ,add a part of the reactive phosphorus in the form of an organic phosphate or phosphite, as described in the above mentioned copending application of Cyphers and Osborne.

The quantity of organic phosphate or phosphite which may be included in compositions according to the present invention may vary considerably. Ordinarily a small amount is sufllcient, suitable percentages being from 0.01 to 5%, based on the total composition.

The amount of the phosphorus sulfide treated abietic ester may vary from as little as 0.5 to 20% or more. based on the total composition. The reaction product may be sulfurized after the reaction has been completed, in the same manner that fatty oils are commonly sulfurized. Such a sulfurized product may be found to have desirable extreme pressure properties for certain applicatlons.

- As indicated above, this invention deals broadly with the addition of the reaction products of phosphorus sulfides with esters of abietic acid to hibricants of various types. Mineral oils, synthetic oils, fatty oils, and greases comprising various bodying agents may be treated with various quantities of such reaction products, depending on their respective characters and purposes. The reaction between the phosphorus sulfides and the various abietic acid derivativesenumcrated hereinabove appears to proceed over a rather wide temperature range and the invention is not to be limited either to the specific compositions or the reaction conditions mentioned hereinabove. Thus reactions may proceed at moderate temperatures, 60 F., for example, or at any temperatures up to 400 F. or more. The derivative of abietic acid, whether of the methyl ester type or the di- 4 hydro-methyl ester type, as described above, or related composition, may be sulfurized by heating with sulfur as is common practice with fatty oils and mineral oils, and this may be effected either before, during or after treatment with a phosphorus sulfide. The time of heating will be varied as required to obtain a reaction product which is efiective as an extreme pressure agent.

The methylated and hydrogenated abietic acid derivatives mentioned above appear to be excellent for the purposes of the present invention, but ethyl and higher alkyl esters of abietic acid, sulfurized abietic acid, hydrogenated abietic acid and its esters, and the like are contemplated as being within the spirit of our invention.

While we have described our invention in terms of specific compounds prepared in specific ways, the inventionis not limited thereto or'otherwise, except as indicated in the appended claims.

We claim:

1. A composition consisting essentially of 80 to 99.5% of petroleum base lubricating oil and 0.5 to 20% of the phosphorus containing reaction product oi a sulfide of phosphorus with a methyl ester of abietic acid which has been substantially saturated with a material selected from the class which consists of hydrogen and sulfur, said reactant ester and sulfide of phosphorus being reacted for a substantial period or time at a temperature between about 60' F. and about 300 1".

2. An extreme pressure lubricating composition consisting essentially oi 80 to 99.5% 01 petroleum base lubricating'oil and 0.5 to 20% oi material reacted with phosphorus sulfide is Hercolyn.

ELMER B. CYPHERS. GEORGE M. McNULTY.

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

UNITED STATES PATENTS Number Name Date 2,252,133 Morway et al. Aug. 12, 1941 2,347,592 Cook et al --Apr. 25, 1944 2,357,211 Lincoln et a1. Aug. 29, 1944 2,415,837 Musselman et al Feb. 18. 1947

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