US2388047A - Lubricating oil - Google Patents

Description

place when the pressure a that described in -2,1e4,sss.-

Patented Oct. 30, 1945 Elliott Alfred Evans and John Scotchford Elliott Beaconsileld,

England, assignors to C. 0. Wakefield & Company Limited, Bea'consileld, England, a British company Application April 16, 1943, Serial No In Great Britain April 2, 1942 No Drawing.

Claims. x01. zoo-sac) This invention is for improvements in or relating to lubricants which are to be used under conditions which tend to disrupt the lubricant film, which disruption more particularly takes between the bearing surfaces is very great. I

Where the lubricant is required to lubricate surfaces under the above conditions, the flimrupture strength becomes more important than 'the coeilicient of friction. For example, under the extreme pressures obtaining in hypoid gears,

it the oil film is ruptured the metal surfaces will contact one with the-other}, thereby leading to loss of efllcie excessive "syear'and iailure oi There have already, been provided lubricants which have a high film-rupture strength. Such lubricants are generally known in the trade as "extreme-pressure" lubricants.

These extreme-pressure lubricants originally consisted o! lubricating oil. which contained sulphur either in the form oi flowers of sulphur. or

* as a colloidal dispersion. The sulphur, however,

was liable to precipitation and it was later proposed to, prepare these extreme-pressure lubricants by treating a fatty oil, for example an animal oil. with thionyl-chloride or with similar reagents. such as sulphur monochloride, sulphur dichloride, etc... and then adding the product of this reactlonto a mineral oil. f'

A theory as to the action of extreme-pressure lubricants has been that thesulphur reacts with metallic surfaces and forms a. very thin coatina of iron sulphide and 'that-this sulphide him is sumcient toprevent the metallic surfaces coming into contact with one another should the lubricant film he ruptured. If this theory is, in fact, correct, then it is obvious that the sulphur conhand, the sulphur compound must not be so reactive as to induce corrosionjof the surfaces.

It. found, however. that with these prior which would ensure a uniform productalways being obtained and it was therefore always necesmry when preparing anextreme-pressure lubricant to app llthe method of trial and error in arriving at a satisfactory composition.

The present invention is a development from. United States Patent No.

. It is a further object .of this invention to proyids lubricants which no set conditions could be determined "active" sulphur, i. e. sulphur which will react they may contain a substantial quantity of chemically with metals such as copper at high temperatures, yet are relatively noncorrosive towards metals. especially copper, in practice under the conditions in which they are used.

It is" a further object 01' this invention to provide new sulphur-containing addition agents for extreme-pressure lubricants, characterised by imparting a high film rupture strength to the oll ill which they are dissolvedtogether wlthllttle corrosive action on metalsurfsces.

According to this invention an extreme-pres? sure lubricant comprises a lubricating oil havins dispersed therein an aromatic'hydroxy-substi- .tuted' polysulphide comprising an ester substituent.

Said polysulphlde comprises two aromatic radicals each of which contains both a hydroxyl and an ester substituent. Preferably the hydroxyl substituent in each aromatic radical is located tamed in'the oil mustbe in such form as to be I capable of rcactingwlth the metallic surfaces which it is desired to lubricate. the other in the paraposition to the 'polysulphide sroup.

More specifically the invention contemplates the use of disulphides, trisulphides and tetrasulphides and of mixtures of such polysulphides in varying amount, and" also of mixtures of such polysulphides with varying amounts of the corresponding thioetherand of minor amounts of free sulphur. v

The formulae for typical disulphide, trisulphide and tetrasulphlde compounds are-as follows. al-

though triand tetra-sulphides having other arrangements of sulphur atoms may exist:

.(1) no-Qs-s-Qon ,1

omooc v i coocn. 27 HOG-544G013" CHibOC l coocm CHsOOC L v 00003::

The following procedure was adopted for determiningthe amount of elementary sulphur present in the solid described. v v I v An accurately-weighed quantity or the solid (about 1 gram) was dissolved in 20 cc. tetrahydronaphthalene in a cc. beaker, and a weighed amount of copper powder (about 3 grimsl-was added. The beaker was placed in addition adents hereinafter an oven at"100 C. and removed after half an hour. a I I I The copper powder was then washed into, a weighed filter paper which was well washed with ether to remove tetrahydronaphthalene, driedin an oven at 100 C. and reweighed.

It was found that by this method the whole of th e elementary sulphur present in any such mixture could be determined with reasonable accuracy, whereas the short time of heating did not cause appreciable decomposition of the higher polysulphides.

By employing the method of Ormandy and Craven (described in the Journal of Industrial I andEngineering Chemistry, 1927, page 1281) i. e. shaking a'solutionoi the material with mercury until formation of mercury sulphide ceased, the whole of what may be termed the loosely held" sulphur was removed, although the time of shaking required was two days instead or half an hour. This loosely held sulphur is believed' byus to consist of sulphur atoms combined in the form of trisulphide and tetrasulphide. .In addition, of course, the free sulphur is also removed. After the removal of all the loosely held and .free. sulphur inthis way from a known amount ofthe material in solution, the disulphide present was reduced to mercaptan with zinc dust and aceticacid, andthe mercaptan removed by shak- 111g with-.50% alcoholic plumbite. solution. The residual sulphur content oi. the solution. was then determined.

l .A' rough confirmation of the amount of disulphide was obtained by the method of Bond (Journal of Industrial and Engineerin Chemistry,

: Analytical, 1933, page 257).

'Ezamplel Q A mixture of 20.2 grams of methyl salicylate,

9.1 grams of sulphur menochloride and 2.12 grams of flowers ot'sulphur was warmed gentlyand a small amount or copper powder added. v A vigorous reaction ensued during which the s'ulphurdissolved. After heating for ten minutes at 120 C. .the product was allowed to cool and set to a hard yellow solid.

It is believed that the reactions involved are similar to those already outlined, but that some or .theadded sulphur takes part in the reaction causing an increase in the amounts .of .tri-and tetrasulphides and a corresponding decrease in the amount 01' disulphide produced.-

An analysis, similar to that heretofore described, indicated the following approximate composition! g v Per cent Di(3-carbomethoxy-4-hydroxyphenyl) triand tetrasulphide 40-50 Di(3-carbomethoxy-4-hydroxyphenyl) dilsulphide l 20-30 Di(3-carbomethoxy-4-hydroxyphenyl) thioether 20-30 Elementary sulphur 6 ("Loosely held sulphur) 10 Example 2 l I Methyl salicylate (00.8 grams-1 mol.) "was mixed with 32.4 grams (0.6 moi.) of sulphur monochloride and 15.2v grams (1.2 gm.-atoms),ot sul- Dhur were added. Y

, A'little copper powder wasadded, and there- @action started by gentle warming. v After the. reaction had been completed asbe- 3. lore theproduct was'cooled, and set to an opaque ye l w plastic l d- Such plastic characteristics may be imparted to any of these products by employing more than the theoretical quantity of sulphur monochloride, thus giving rise to secondary reaction products.

An analysis of this material indicated the 101- lowing composition: ,2

1 Per cent Di(3-i:arbomethoxy-e-hydroxyphenyll triand tetrasulphide 50-60 Di(3-carbomethoxy-4-hydroxyphenyl) disulphide 5-10 Di 3-carbomethoxy-4-hydroxyphenyl) I ,thioether -30 Elementary sulphur 11.5. 15, ("Loosely held sulphur) -1--- 13.5

' It will be understood that in this list, the polymers and secondary reaction products are included with the simple compounds. I

A varying degree of chlorination also takes place during these reactions. Thus the material prepared as outlined-in this example contained Whereas the formulae forthe triand tetrawe do not wish to be restricted in any way, as

the actual mode of attachment of the sulphur atoms is not known with certainty. I The products of. this invention are extremely effective for increasing the film-rupture strengths In the following table, the efiect of typical materialson the film-rupture strength (F. R. S.) of a parafflnic mineral oil is shown. I

The testing machine employed was the wellknown Almen machine.

Material added to oil g f 3 per 40 Emma-.. 4,000

Product of Example 1 1. 0 More than Product of Erample 2 1.0 More than v 15, (XX) 4 It willbe seen from the foregoing table that the products of this invention are eminently suitthe extreme-pressure activity of these materials is due to a combination of desirable features, viz. Y

6 the. presence of firmly-bound sulphur rendered active by the presence of electronegative groups,

the presence of loosely held sulphur, andthe presence of the ester groups themselves. Thus in general the compounds of this invention impart a higher film-rupture strength to oils in which they are dissolved than the correspondin polysulphides made from phenols.

Some of the materials contemplated inthis irik,

vention contain as has already been shown minor amounts 0f free sulphur. Although this assists in producing a high film-rupture strength ofthe oil in which the material is dissolved, it is undesirableonaccount of its corrosive propensities,

particularly towards copper and, its alloys. Ac-' 05 cordingly it is desirable to have as much "loosely hel sulphur and as little free sulphur as possible. In any case the free sulphur should :not

exceed about 15% of the total composition. I If desired,-the free sulphur may be removed, 7 at least in part, by maintaining the material at a temperature just above its melting point, and

' 'allowin 'the sulphur to settle out, butit is not w giv n a' 15 8006 indication orthe corrosiveness or an 'oil' in generalnecessary to do this. I l

v A. simple test which is recognised as sulphides have been written in the manner shown,

of lubricatin oils, e. g..mineral 'lubricating oils.

able extreme-pressure agents. We believe'that L It W111 be that the materials 01 this" towardscopper when in use consists in heating a strip or copper toil, polished with carborundum powder in 100 grams oi the oil at 100 C. for one hour.

I The following table indicates the superiority or g oils 'containingour materials over oils containing elementary sulphur in the same the "active sulphur" introduced in our addition a nounts as These results would indicate not only the ad.- vantage of having as much of the "active sulphur as possible chemically combined, but also that the polysulphides of this invention exert a highly beneficial inhibitory influence at the metal In preparing lubricating oils for extreme-pres:- sure purposes'we.may en' ploy any of the compounds or this invention ormixtures thereof in a concentration 01' or less, and preferably 0.5

to 2%, or we may employ mixtures ,of these materials with the compounds of Patent No. 455,235 '(e. g. $(3-carbomethoxy-4-hydroxyphcnyl) thioe'ther)! Excellent results are also obtained by employ- 01 these compounds with halogenated organic compounds, e. g. chlorinated paramn wax and other hydrocarbons, haloaenated ouinones andthe nitro-polychlor-benaenes. Y

' Inone example a blend oi a mineral oil, classiflcation 90 (Society of Automotive Engineers) containing one per cent or the product of, Example 2 and eight per cent of a chlorinated paratlin wax containing about 40% chlorine, when tested on the well-known Society of Automotive Engineers machfiie at 1,000 B. P. M. and standard rubbing ratio 0114.6, the rate-oi loading being 83.5 lbs./second,-.withstood loads up to 460 lbs.

The normal requirement for a good extremepressure oil 0! this type lethat it should withstand loads upon to 325 lbs. imder these condiinvention may be added tomineral-oilg which may be parafllnic; naphthenic or asphaltic in type, or which may contain varying amounts of iatty oils (e. g. animal, vegetable and fish oils) 1 i or known addition agents such as pour-point depressants, viscosity index improvers, anti oxb. dants, sludge disperser-s and detergents and corrosion inhibitors gnch as mercaptobenzothiamle. Weclaim: g 1. extreme-premise lubricating composition mlmmdl'mhfimdmd therein-a oi sulphurmonochlo stituted ester, said reaction product comprising a substantial proportionof aromatic hydroxystituted polysulphide containing at least three sulphur atoms to the molecule and having an ester substituent, said reaction product being in sufiicient amount to substantially increase the film-rupture strength of said lubricating oil base.

2. An extreme-pressure lubricating composition comprising a lubricating oil base having dispersed therein a reaction product or sulphur monochloride and sulphur with an alkyl salicylate, said reaction product comprising a substantial proportion of hydroxyphenyl polvsulphide containaromatic radicals each of which contains both a ing at least three. sulphur atoms to the molecule and having an ester substituent, said reaction product being in sufiicient amount to substantially increase the film-rupture strength of said lubricating oilbase.

3. An extreme-pressure lubricating composition as claimed in claim 1 in which the aromatic hydroxy-substituted polysulphide comprises two hydroxyl substituent and an ester substituent.

An extreme-pressure lubricating composition as claimed-inclaim 1 in which the hydroxyl substituent is located in the p lysulphide group.

para position to the 5. An extreme-pressure-lubricatingcomposition as claimed in claim 1 in which the aromatic hydroxy-substltuted polysulphide is admixed with the corresponding thioether.

6. An extreme-pressure lubricating composition as claimed in claim 1 in' which the aromatic byoitheoilbase. t a I 8. A process for producing an extreme-pressure lubricating composition which comprises reacting sulphur monochloride and sulphur with droxy-substituted polysulphideis associated with minor amounts of free sulphur.

'1. A process for producing an extreme-pressure lubricating composition which comprises reacting sulphur monochloride and sulphur with an aromatic hydroxy-substitutd ester to form a reaction product comprising a substantial proportion of-aromatic hydroxy-substituted pb ysulphide containing at least three sulphur atomsPto the molecule and having an ester substituent, and dispersing a sufllcient amount of said reaction product in a lubricating 011 base to substantially. increase the film-rupture strength an alkylsalicylate to form a reaction :product comprising asubstantial pro rtion 0! hydroxyphenyl poliwu phide containing at-least three sulphur atoms. to the molecule and having an ester substituent, and dispersing a sumcient amount oi' said reactionproduct in alubricating amount o! from about 0.5% to 011 base to substantially increase the film-rap I ture strength of the 011 base.

'- 9.- The composition as defined in claim 1 tin-- ther characterized in that said reaction product is dispersed in the lubricating oil baseinthe amount of from about 0.5%. to about 5%.

wedincli'lim2fur- 10. The composition as d ther characterized in-that d reaction.product is dispersed in the lubricating about 0%.

ems.

oil base in the