US 2201258 A
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Patented May 2t,
.PATVENT ore-[cs I mgmnma ranssuan LUBRICANT 9 Warren F. Busse, Akron, Ohio, assignor to The B. F; Goodrich Company, New York, corporation of New York Application August 11, 1936, Serial No. 95,431 I No Drawing.
This invention relates to methods of improving the film strength or load-carrying power of lubricating oils.
The use of smaller gears and greaterpower in modern automobiles has increased the gear toothpressures to a point where in many cases pure petroleum lubricants are no longer able to keep the metal surfaces apart. 7 As a result the surfaces of the gears may actually fuse or weld 10" together in spots, resulting in rapid wear and scoring which soon makes the gears very noisy, and ultimately may cause a complete failure. Similar problems are encountered in the lubrication of other bearing surfaces which are subjected to high pressures.
*Itisknown that the addition of materials such as carbon tetrachloride, sulfur or lead soaps will increase the film strength of lubricants, but these materials have disadvantages such as corrosive- ,ness, instability in the presence of moisture, or an abrasive action, etc., which often makes them unsatisfactory for commercial lubricants.
I have found that the addition of oil-soluble thiuram monosulfide; tetraphenyl thiuram disulfide; the lead salt of mercaptobenzothiazole; the zinc salt of diphenyl dithiocarbamic acid; benzothiazyl thio'benzoate; thiocarbanilid; 2-chlor,
fi-nitro benzothiazol; 2-chlor naphthothiazole; etc. Some of the chemicals, such as the benzothiazyl disulflde and some of the lead salts, tend to thicken or gel lubricants which contain considerable am'ountsoi naphthenic or unsaturated compounds, so they are particularly useful in making greases. 'I'hesolubility of the chemicais will vary'to some extent with the viscosity and chemical nature of the oil. Two per cent mercaptobenzothiazoie, for example, does not dissolve completely in an S. A. E. 30 paramn-base motor oil, even after heating to C. for several hours. However, it does dissolve at elevated temperatures in a summer black oil and in a compounded oil made by adding tallow to 9. Gulf Coastoil. When the solutions oi the chemical ence of acids such as stearic, benzoic, etc.
'I'he'term oil soluble" as used in this patent is understood to mean that the chemical is soluble in the particular oil or grease used under the temperature conditions prevailing in service. The term lubrican is intended to include both animal and vegetable fats and ofls as well as oils and greases derived from shale, petroleum. etc.
The solubility of the chemicals in the oil is due, in some cases, to a chemical reaction which often increases the eflectiveness of the chemicals in raising the load-carrying power or film strength oi the lubricant. Probably because of this reaction the effectiveness of many of the chemicals may be increased by heating them with the oil to temperatures above 200 F. before use. I In other cases the chemicals may only be active when the oil is hot, due to the increased rate of difiusion and greater reactivity at the higher temperatures.
In the following examples illustrating specific embodiments of this invention, the film strength of the lubricants is expressed as the maximum load which can be applied to the lever arm of a Timken lubricant tester without producing scoring on the ring.
In one test, the film strength of an S. A. E. 50 naphthenic base motor oil is 10 lbs. on the Timken tester. After one per cent of tetramethyl thiuram disulfld CH: CH:
is dissolved in the oil, it supports a load of '15 with the viscosity of oil used as with the kind of oil. This maybe due in part to the reaction of the chemicals with certain constituents of the oil and in part to the fact that the Tlmken lubricant tester is not sensitive in the region of low film strengths. In a test of a pale neutral oil having an original score point of about five pounds. the increase in film strength on adding two per cent g-chlorbenzothialolo is too small to be measured, but the addition of two per cent 2-chlorbenzothiazole.
N CCl to a compounded gear lubricant containing tallow and fatty acids raises the score point from 15 to 52 pounds and five per cent of this compound raises the score point to over pounds.
When five percent of 2-chlorbenzothiazole is added to' a summer black oil, the score point is raised from 14 to 20 lbs. However, if the oil and chemical are heated to a temperature of around 240 F. for five or ten minutes, only 2 per cent of the chemical is required to raise the score point to 25 lbs.
The results obtained with the Timken tester have been verified by service tests. For example, one per cent of mercaptobenzothiazole bodiments of this invention, and are not intended to limit its scope.
This oil was then used in the motor of a,
1. A composition comprising an oleaginous lubricant and about 1 to 5% of an oil-soluble compound containing at least one carbon atom attached directly to both nitrogen and sulfur.
2. A composition comprising an oleaginous lubricant and about 1 to 5% of an oil-soluble compound containing at least one carbon atom attached directly to both nitrogen and sulfur and to more than one atom of one of these elements. i
3. A composition comprising an oleaginous lubricant and. about 1 to 5% of an arylenethiazole compound.
4. A composition comprising an oleaginous lubricant and about 1 to 5% of mercaptobenzothiazole.
5. A composition comprising an oleaginous lubricant and about 1 to 5% of mercaptobenzothiazole and an organic acid.
6. A composition comprising an oleaginous lubricant and about 1' to 5% of chlorbenzothiazole.
7. A composition comprising an oleaginous lubricant and about 1 to 5% of a substituted thiuram sulfide. l
8. A composition comprising an oleaginous lubricant and about 1 to 5% of a tetrasubstituted thiuram disulfide.
9. A composition comprising an oleaginous lubricant and about 1 to 5% of tetramethyl thiuram disulfide.
10. A composition comprising a lubricating oil and 1% to 5% mercapto benzo thiazole.
'11. A composition comprising a lubricatingoil and a small proportion, sufficient to impart ex-,
'treme pressure characteristics to said oil, of
mercapto benzo thiazole.
WARREN F. BUSSE.