US2359270A - Lubricants - Google Patents

Description

Patented Sept. 26, 1944 LUBRICANTS Richard S. Shutt and George R. Waitkins, Colum- Ohio, assignors to Battelie Memorial Institute, Columbus, Ohio, a corporation of Ohio No Drawint.

Serial No.

addition agents for heavy duty oils and high Claims.

Our invention relates to lubricants. It has to do, more particularly, with lubricants which are to be used under conditions Where the bearing pressures are comparatively high,'though it is v not necessarily limited thereto.

In recent years, the tendency in bearing design has been to increase operating pressures on the bearing surfaces to such an extent that ordinary mineral oil lubricants cannot be held between these surfaces and hence satisfactory inbrication is not attainable. Since a film of lubricant between rubbing surfaces is necessary to prevent wear, efforts have been made to obtain improved lubricants which will not be forced from between 'bearing surfaces even under comparatively heavy pressures.

It has been found that certain materials, such as sulfur, sulfur compounds, and certain soaps and acids, could be added to ordinary mineral oils and greases and thereby render these oils and greases useful under high pressure conditions. The exact mechanism of the eflect of these addition agents is not known but it has been suggested that these addition agents are adsorbed by or react with the metal bearing surfaces forming a film or plating which has a low coeiilcient of friction and great tenacity to the bearing metal. It appears that the lubricating eifect of the mixture is primarily due to the addition agent while the mineraloil lubricant acts more as a carrier and protective bath or wash. While there is some correlation between the composition of the addition agent and its effectiveness for use in heavy duty oils and extreme pressure lubricants, it is impossible to predict on the basis of composition whether or not a given type of compound will be satisfactory and extensive experimental work must be done to determine the suitability of any material used for this pur- One of the objects of our invention is to produce lubricants which will not break down or permit galling action when used under comparatively high pressure conditions.

Another object of our invention is to produce superior to oils and lubricants now available, particularly under high pressure conditions.

Another object of our invention is to provide a lubricating oil with an addition agent which is completely dispersed therein so that uniform and consistent results will be insured under all conditions of lubrication.

We have found that selenium dioxide and various selenocyanates are particularly suitable as lubricants which will have lubricating properties Application October 16, 1940,

pressure lubricants. We have found that by making certain small additions to these lubricants the lubricating properties of various oils and greases are improved. These materials are preferably added as a solution to the base lubricant. When added in this manner the addition agent is dispersed throughout the base lubricant in a much more thorough manner than can be done when solid additions are made. The lubricants resulting from this addition may be used at any place where lubrication under high pressures is required.

in some cases, while even smaller be effective for certain p poses. amount of addition required will exceed 1 per cent although larger be used.

To determine the effectiveness of various addition agents to lubricants of the type generally known as extreme pressure, special tests were made. In carrying out these tests a 600W oil was used as the base lubricant and various additions made to this base. The lubricant was then examined in performance on a wear testing machine.

In the particular type of machine used two carburized steel discs were used as the contacting specimens. When mounted in the machine these two discs were revolved in opposite directions with one disc mounted directly above the other.v They were pressed together by an ap- Dlied load which could be varied between 0 and 200 kg. Half of the lower disc was immersed in oil while the upper disc was only lubricated by the oil which clung to the surface of the lower disc as it rotated in the oil bath and was thus carried to the upper disc. Each disc was ground amounts may The maximum not ordinarily amounts may while the other ran 10 per cent slower thus pro ducing slippage between the two. The load was gradually increased by increments of 10 kg. at

disc was equal but applied in the opposite direction.

In all cases the lubricant was heated to 250 F. at the start of the run so that the temperature change during the run would not have a great effect upon the viscosity of the base lubricant and thereby invalidate comparison of results obtained at the different temperatures produced by the varying loads.

Where solid additions were made to the base lubricant, fine particles of the solid material were thoroughly dispersed in the oil while in liquid additions the desired compound Was dissolved in a suitable solvent and the resultant solution dissolved or dispersed in the lubricant base. Table I shows the results of various additions to a 600W base oil.

vention were compared with the base oil without these additions and with a commercially available oil carrying tricresylphosphate-as an addition agent. It was found that all of the oils gave about the same coefficient of friction at light bearing pressures but as the pressure increased, the coefficient of friction with oils containing selenium dioxide or seleno-cyanates remained about constant or increased only slightly while the coeflicient of friction in the case of oils without this addition increased to relatively high values. Thus, the action of these addition compounds with ordinary lubricating oils appears exactly analogous to their action with extreme pressure lubricants.

It is difiicult to propose a suitable hypothesis to explain the performance of the addition TABLE I.-E. P. Lubricant properties produced by various additions to a 600 W base oil Amount of Solvent for addi- Maximum Final oil Surface film Addltwn agent addition tion agent Tmque at Mme contact lo pon disc! Weight percent K F,

None (base oil alone) 40 270 None. Commercial sullurized lubr t 1% (S). 70 247 Partial.

Unknown... 130 295 Smooth blk. film. Flowers of sulfur a. 1 140 256 Do.

Se; (CN)2 257 None. (CoH5CH2); Se; 80 243 D0. (CsHs): SeCh. 254 D0. SeOC 130 242 Do. CdSe 30 255 Do. CdScOa 20-30 250 Do.

S002. l 200 308 Bluish film Do. 1 200 425 Do.

Do. 190 425 D0.

D0 e e i 1 200 345 D0. KSe ON. 1 200 425 Do.

Do l 200 460 Do. NaSeCN 200 460 Do. CH;(CH;) SeCN 200 445 Do.

1 Top limit or machine.

This Table I is divided into three sections. The first gives the performance of various extreme pressure lubricants now known to the art. The second section shows various. selenium compounds which were tried in the course of this work and were found to be unsuitable and the third section shows those selenium compounds of the types (oxides and seleno-cyanates) which have been found to be operable. It will be seen that the addition elements shown in this third section permit the use of very high bearing pressures without seizing or galling and confer excellent extreme pressure properties upon the base lubricant.

It has been found that the addition of these selenium compounds, such as oxides and selenocyanates, is not only effective in the extreme pressure lubricants but has a similar beneficial action in oils which are operated under relatively heavy bearing pressures, but not so high as to be termed extreme pressures. Tests were made with various oils to determine the amount of the improvement produced by these additions. In these tests a stationary bearing surface rested on a'revolving steel (S.-A. E. 1045) disc and the bearing load was increased at intervals. Both the steel disc and the bearing surface were constantly immersed in the oil which was heated to and held at 250 F. so as to duplicate motor operating conditions.

From the bearing-load, the area of the bearing surface and the torque on the rotating disc, the

coefficient of friction was calculated at various loadings. Tests were run at bearing pressures up to 3000-5000 #/in. Oils containing the selenium dioxide or seleno-cyanates of this inagents which have been found toiconfer these improved properties upon lubricants at high bearing pressures. plained as being due to the use of any selenium in the compound since certain selenium compounds are operable while still other selenium compounds are not satisfactory. Also the presence of the selenium in either the cation or anion of the compound cannot be said to be critical. As far as can be determined from the results of this work there is no definite way to specify the workable materials except by classes of compounds, which have been found to be workable.

As previously pointed out, it has been found that a. compound selected from the class composed of selenium dioxide and the seleno-cyanates has been found to be suitable. It has been further found that addition of these materials in suitable solvents confers improved lubricating properties to an oil base. By this addition in solution it is extremely easy to secure a uniform mixture of the oil base and the addition agent. As suitable solvents for selenium dioxide, dioxane, the aliphatic alcohols, glycols, glycerine, and other hydroxy-organi compounds may be mentioned. Acetone and other ketones have been found to be useful solvents for the inorganic seleno-cyanates where these are used while most organic seleno-cyanates being oil-soluble may be added directly to the oil. Examples of organic seleno-cyanates which are suitable for the practice of this invention are: methyl, butyl, octyl, lauryl, oleyl, stearyl, phenyl, tolyl, benzyl, and napthyl seleno-cyanates.

The additions of this invention are not only effective in producing improved lubricating prop- The action cannot be exerties but have been found to be effective in improving the oxidation resistance of the oil and decreasing its corrosive action on bearings which are particularly subject to corrosion by lubricating oils.

It will be seen that we have produced lubricants, particularly suitable for use at high hearing pressures although not limited thereto, which have properties superior to the lubricants which are now available. Moreover, these lubricants can be produced very easily and cheaply.

Having thus described our invention, what we claim is:

1. .A lubricant designed for use at comparatively high pressures consisting of a mineral 011 base and selenium dioxide to confer extreme pressure characteristics to said mineral oil base.

2. A lubricant designed for use at comparatively high pressures consisting of a mineral oil base and a seleno-cyanate to confer extreme pressure characteristics to said mineral oil base.

3. A lubricant designed for use at comparatively high pressures consisting of a lubricating oils and greases,

acteristics to said lubricating base selected from the group consisting of mineral oils and greases, and a substance selected from the group consisting of selenium dioxide and the seleno-cyanates in an amount sumcient to comer extreme pressure characteristics to said lubricating base.

4. A lubricant comprising a lubricating base selected from the group consisting of mineral oils and greases, and a compound selected from the group consisting of selenium dioxide and the seleno-cyanates in an amount suflicient to confer extreme pressure characteristics to said lubricating base.

5. A lubricant comprising a lubricating base selected from the group-consisting of mineral and containing, in efl'ective amounts up to 1%, a substance selected from the group consisting of selenium dioxide and the seleno-cyanates to confer extreme pressure charbase.

RICHARD s. sHU'rr. GEORGE R. WAITKINS.