US2382115A - Lubricant - Google Patents

Description

Patented Aug. 14, 1945 LUBRICANT I Joseph B. Stucker, Wilmington, DeL, assignor to The Pure Oil Company, Chicago, Ill., a corporation of Ohio No Drawing. Application July 16, 1942, Serial No. 451,217

9 Claims.

This invention relates to lubricants and is more particularly concerned with lubricants for use in lubricating moving metallic parts which are subjected to extreme pressure conditions such as are encountered in the transmission and differential of automobiles and trucks having hypoid gears.

In Patents Nos. 2,142,998 and 2,211,306 are disclosed lubricants and lubricant additives made by phosphorizing and sulfurizing and phosphorizing fatty bodies. Additives and lubricants made in accordance with these patents have been widely and successfully used for many years for lubrication of hypoid gears and other mechanism in which the lubricant is subjected to extreme pressure conditions.

In recent years, however, a testing machine has been devised known as the S. A. E. testing machine for testing load carrying ability of lubricants. Some automobile manufacturers will not approve a lubricant for use in the transmission and differential of their automobiles unless the -lubricant passes the S. A. E. test. Lubricants made in accordance with the aforesaid patents while giving eminently satisfactory service in actual use and while being able to give an extremely high rating on the Timken test give a low rating on the S. A. E. testing machine. Both the Timken and S. A. S. test and the machines used in these tests are widely known and used in the automotive and lubricating oil industries and have been described in various publications. Various additives have been experimented with for producing a lubricant which will not only g 8 d performance under actual service conditions but which will pass the Timk'en and S. A. E. tests and at the same time not be too corrosive. It has been found cliflicult, however, to realize all of these conditions for generally those materials which give good S. A. E. tests are corrosive, whereas the materialswhich give good Timken tests generally do not give good S. A. E. tests and vice versa.

I have discovered a composition which substantially meets the required condition of good performance in service, good Timken and S. A. E. tests and low corrosion. I have discovered that by adding a small amount of an organic polysulfide, particularly an aryl or aralkyl disulfide. to a mineral oil lubricant containing a phosphorized or sulfurized and phosphorized fatty body,

the resulting product not only has a satisfactory Timken test but also satisfactory S. A. E. and corrosion tests.

In order to prepare compositions in accordance with my invention it is merely necessary to blend with mineral oil containing the phosphorized or sulfurized-phosphorized fatty body as disclosed and claimed in Patents Nos. 2,142,998 and 2,211,306. the organic polysulfide in amounts of approximately .5 to but preferably 2 to 5% byweight. As organic polysulfides which are useful in accordance with my invention may .be mentioned the aryl and aralkyl polysulfides such as dibenzyl disulfide. phenyl disulfide, tolyl disulfide and xenyl disulfide. I may also use polysulfides having more than two sulfur atoms in the molecule. For example I have prepared polysuliides from the disulfides of the various compounds mentioned above by reacting one mo1 of the disulfide with 1 to 4 mols of sulfur at temperatures of approximately 300 to 310 F. By heating the aryl or aralkyl disulfldes with sulfur at this temperature with intermittent stirring for a period of- 5 to hours the sulfur can be completely reacted with the disulfide to form polysulfides from which sulfur does not crystallize out upon standing.

In addition to the aryl and aralkyl polysulfides I may use aryl-alkyl polysulfldes and aralkyl-aryl 88 polysulfides, aralkyl-alkyl polysulfides, and dialkyl polysuliides. In the case of the di-alkyl polysulfldes the alkyl chains should contain at least six carbon atoms in the combined chains and preferably at least six carbon atoms in at least one chain. Thus, although I-may use dipropyl di or polysulfides, I prefer to use ,dihexyl 01' higher polysulfides.

In order to make a stable lubricating oil blend, the mineral oil containing the phosphorized or suliurized fatty body is mixed with the poly. sulfide and the mixture heated to a temperature of approximately to F. for a period of approximately 30 minutes. If the blending is carried out under these conditions no separation takes place in the material upon standing. In order to obtain a product having desirable characteristics the mineral lubricating oil should be blended with from approximately 10 to 20% of the phosphorized' or sulfurized-phosphorizcd fatty oil E. P. base and with approximately 2 to 5% of the polysulfide. Although lesser amounts of the additives show improved load carrying ability, they will not as a general rule give Timken and S. A. E. tests which are considered high enough to indicate their usefulness under all service conditions. Onthe other he: 1d amounts of additive: in excess of those indicated do not appear to further enhance the load carrying ability of the mineral oil.

A series of tests was made to demonstratethe in accordance with my invention. The results on these tests are tabulated in Table I. 1

Table! 8 i l fif l f fi. tests in lbs.

Test Oil Additive B P cam ressure loadin lbs. per

m inch R. P. R. P. M.

1 2 7,500 60 85 59 33,750 10 145 1r #2-. 90 85 2 a #2.. 25 13,000 75 9O 3% #2.. as 14, 90 #2... 33 13,50 1 m i :511} 51 3 .150 100 (I) VZ II 51 291750 97.5 2333 (1) II'I- 51 0 315 375 0 it," 51 e as it ii-J a 00 a (a }8%#1 00 175 nnuflh /%#4 0 321 31333 33 16.500 2 5 w it?*.::- 43 24,500 woo (a) 18% l 33 ,250 102.5

\ 2000 viscosity 100 F. Gulf Coast pale.

1 Average.

I 1200 viscosity 100 F. Gulf Coast pale.

4 Seized during run-in.

#1 Lard oil sulfurized and Patent No. 2,211, 306.

#3 P-ditolyl disulflde reacted with 3 mols sulfur.

#4 D benzyl d sulflde reacted with 3 mols sulfur.

#5 D benzyl d sulflde reacted with 2 mols sulfur.

#6 Dibenzyl disulflde reacted with 1 mols sulfur.

phosphorized in accordance with 15. It will be seen from a comparison of tests 1 and 2 that sulfurized-phosphorized lard oil greatlyimproves the Timken test of the mineral oil, but does not materially improvethe S. A. E. test. It is likewise apparent from tests 3 to 6 that dibenzyl disulflde in amounts varying from 1 to 5% improves both the Timken and the S. A. E. to some extent, but not nearly sufllciently to be satisfactory for service. Experience with phosphorized-sulfurized fatty oil. type lubricants has shown that when such lubricants carry a beam load 01' 50 lbs. or more and hold a pressure of approximately 25,000 lbs. per square inch and upward on a Timken machine the lubricant is entirely satisfactory for use under actual service conditions. Those who rely on the S. A. E test as a measure of load carrying ability of extreme pressure lubricant regard 250 to 300 lbs. at 1000 R. P. M. as being the minimum load which the lubricant should carry. 550 lbs. is the maximum load which the machine will measure at 1000 R. P. M.

From a consideration of theresults given in the table it is apparent that the addition of the polysulfide lowers the Tinken test to some extent, but does not affect it to such an extent as to bring it below the point which is: considered satisfactory. Whereas when sufllcient polysulfide is added the S. A. E. test is improved to an extent far beyond that which would be expected from S. A E. tests 1 to 6. Note particularly the results on tests 9 and 10. I

Although polysulfides having more than two sulfur. atoms in the molecule have a more marked effect on the S. A. E. test, I prefer to use the disulfldes for the reason that the disulfldes are not as corrosive and do not ailfect the Timken test adversely to the same extent as the higher polysulfldes. Thus, although it requires a larger amount of the disulflde to achieve the same S. A. E. test as in the caseof the higher polysulflde, the extra amount of disulflde used does not adversely affect the Timken test to the same extent as the higher polysulfldes do in smaller amounts. Moreover the disulfides are not as corrosive as the higher polysulfides and consequently less wear on the metallic parts is experienced when'using the disulflde rather than the higher polysulfides. I

In accordance with my invention it is possible by judicious blending of the additives to meet almost any requirements for extreme pressure lubricants. Thus, if both high Timken test and high S. A. E. tests are required with low corrosion, these conditions can be met by. blending with the mineral oil 18% by weight of sulfurized phosphorized fatty material and 5% by weight of dibenzyl disulflde. If the emphasis is on the S. A. E. test without the' necessity of having a very high Timken test and low corrosion the higher polysulfides such as tri-, tetra-, penta-, and hexa polysulfides may be used. .For example I have found that when using dibenzyl disulflde reacted with 3 mols of sulfurin the manner previously set forth the resultant polysulflde when added in the amounts of 2 to 3% by weight to mineral lubricating oil containing 18% of sulfurized phosphoriz'ed lard oil will carry the full load on the S. A. E. machine but is somewhat more corrosive than the disulfides.

In order to determine'the corrosiveness of a lubricant containing dibenzyl disulflde a metallic copper strip was immersed in this andwother lubricants and kept immersed at temperatures of 250 and 300 F. for a period of one hour. The sample of mineral oil containing 18% of sulfurized-phosphorized fatty oil and 3% of dibenzyl disulflde showed no stain or deposit at 250 F.

and at 300 F. showed only a light, sooty deposit which was easily removed. After the deposit stain as at 250 only both were heavier.

A number of commercial additives were also tested by adding to mineral oil containing 18% of sulfurized-phosphorized lard oil, suifllcient additive'to obtain --the desired S. A. E. test and in each case the copper strip corrosion tests showed considerable dep t and staining.

Thus, I have discovered lubricant compositions which meet the required laboratory and service tests without having the disadavntages which are inherent in other lubricants.

being present in aralkyl-aryl, aralkyl-alkyl and .dialkyl poly fldes, excluding dialkyl polysuliides than 6 carbon atoms in the combined cals, said substances from groups (1) and (2) suiiicient amounts to materially improve the load carrying ability of the mineral lubricatin oil.

havingless 2; A lubricant in accordance with claim 1 in: which the substance from group (1) is present in amounts of 10 to 20%by weight based on the mineral oil and the substance irom group (2) by weight 01 the mineral oil.

- 3. A lubricant in sulfide. 4 4; lubricant in accordance with claiml in alkyl radi-v to 20% by weight 0! is present in amounts of approximately 3 to 5% accordance with claim 1 in which the substance from group (2) is an aralkyl a as than 2 sulfur atoms which the substance from group (2) is an aralkyl disulflde.

5. A lubricant in accordance with claim 1 in which the substance from group (2) is dibenzyl disuliide.

8. A lubricant in accordance with claim 1 in" which the substance from group (i) is sulturised and phosphorined lard oil in the amount of 10 the mineral oil and the substance from group (2) is dibenzyl disulnde in the amount of 3 to 5% by weight of the mineral oil.

7. A lubricating oil in accordance with claim 1 in which the substance. from group (2) is an aryl poiysulnde. 4

8-. A lubricating oil in accordance with claim l in which the substance from group (1') is a suliurized and phosphorized fatty oil and the substance tronigrcu'p (2) is an aralkyl polysuliide.

9. A lubricating oil in accordance wiui'ciaim ,l

in which the'substance from group (1) is sulturised and phosphorised lard oil in amounts of 10 to 20% by weight and the substance from group (2) is an aralkyl p lysulilde, having more per molecule. J B. BTUCER.