US2157079A - Lubricating oil - Google Patents

Description

Patented May 2, 1939 UNITED STATES PATENT OFFICE LUBRICATING OIL No Drawing. Application July 10, 1935, Serial No. 30.733

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Our invention relates to lubricating oils, possessing improved characteristics particularly 'lower pour points and greater load carrying ability, or film strength, than ordinary mineral 5 oils.

This application discloses but does not'claim certain matter disclosed and claimed in our copending application Serial No. 64,167, filed February 15, 1936.

One of the prime requirements for an automotive lubricating oil is that it be sufficiently fluid at all temperatures encountered in the operation of the equipment to be lubricated so that it may flow through pumps and feed lines to the bearings and other devices to be lubricated. No lubricant, however excellent, can lubricate unless it is properly applied to the part to be lubricated. The presence of any appreciable quantity of wax in hydrocarbon lubricants prevents g proper application in most instances and under many operating conditions such as are encountered in cold weather. It has been found that the removal of parafiln wax by various means such as filter pressing at a low temperature with 5 or without a solvent aids in producing a lubricating oil of a lower pour point which can be properly applied to the mechanism requiring lubrication. serves to raise the pour point, may be removed by centrifugal processes. 7

It is usually necessary in order to produce oils having pour points of approximately 0 F. to accomplish this removal of wax in two stages when neutral oils are being so treated. The first stage or hot pressing" consists in filter pressing the partly solidified oil cooled only to a relatively high temperature, say 45 to 50 F., when considerable wax is removed without the use of large amounts of refrigeration and without the necessity ofhandling a very solid mass of oil and wax such as would be obtained by chilling directly to a. lower temperature. The oil forming the filtrate .from this hot pressing from which considerable wax has been removed is then further chilled to approximately 5 F. below the pour point desired for the finished oil and. filtered again. This operation is known as cold pressing. These operations designed to remove paraflin wax from light oils are costly since they require expensive equipment including filter presses suitable for operation under high pressures, pumps capable of moving the semisolid oil-wax mixture, refrigerating systems for cool-- ing large quantities of the wax-bearing oil to extremely low temperatures, etc. The cost informed in the case of the lighter oils.

Wax and petrolatum, which also volved in removing part of the wax is not near as great as removing the latter small portions of wax. For example, an oil with F. to F. cold test may be dewaxed to a cold test of from 15F. to 50 F. at no greater cost than removing wax from a 15 to 20 F: cold test oil for 9, 5 to -+5 F. cold test.

The high cold test of bright stocks and such heavy oils is likewise due -to their content of waxy material which is, however, of a different sort known as petrolatum. Filter pressing of the chilled oil in this case is not suitable for removing petrolatum because in the pressing op eration the petrolatum behaves as a jelly-like material, packing tightly into the pores of the filter medium and stopping the fiow of oil through the cake. Furthermore this jelly-like mass is much more difflcult to pump to the presses than the slurry of wax crystals and oil Because of these difllculties it is preferred to dissolve the heavy stock in naphtha, chill, and centrifuge the precipitated petrolatum from the lighter naphtha solution of oil. After the centrifugal separation, it is necessary to remove the naphtha and recover it in order to make the process economical. Here again it is obvious that expensive equipment including blending tanks for dissolving the heavy oil in naphtha, refrigerating equipment for cooling both the oil and an equal weight or more of naphthato excessively low temperatures, pumps which can move the chilled solution and petrolatum to the centrifuges, and most expensive of all, the high speed centrifuge machines of which a large ,number are required. With a reasonable operating expense and with a reasonable amount of equipment an oil of from 15 to 50 F. cold test can be obtained but to produce 9. 0 F. cold test oil greater operating costs and much more-of the expensive equipment are required.

It is apparent .thatthe cost of manufacturing a lubricating oil using these methods of removing wax and petrolatum in order ,to obtain products having low cold tests is much greater than those manufactured by our method in which all these expensive processes and equipment are greatly reduced or rendered unnecessary. Furthermore, it is possible to obtain lubricants by our process which have equally low pour points but which contain part or all of the wax and/or petrolatum. From the point of view of improving the viscosity index of the oil it is a distinct advantage to have these waxy materials left in the oil, provided their action in-producing high,

cold test can be prevented. (See Dean and Davis, Chemical and Metallurgical Engineering, vol. 36, 1929, page 618).

These materials which tend to raise the pour point of a lubricating oil apparently act by partly crystallizing from the remainder of the oil in such a way that a lattice or honey-comb interlacing or interlocking structure is formed which prevents the free fiow of the oil. Another method of lowering the pour point of oils depends not on removing these materials responsible for such a lattice structure but on adding to the oil containing all or only part of them, such a material as will completely or partially inhibit or interfere with the formation of such a structure and thus permit the oil to flow freely at lower temperatures than it would without the added material. While we do not wish to be limited to this theory of how the materials covered in this invention act to lower the pour point, we believe they act somewhat in this manner.

We contemplate the use of our addition agents particularly in lowering the cold test and improving the film strength of partially dewaxed oils, though the additive materials here described are suited for use with any hydrocarbon oil whether wholly .dewaxed or whether containing all of its natural wax content. It is relatively inexpensive to dewax oils partially by the hot pressing process described above because the temperatures are comparatively easily attained and maintained during the pressing operation. A great lowering of the cold test of the oil is obtained in this way at little expense in contrast to the relatively small lowering of cold test obtained by the cold pressing process which is, at the same time, considerably more expensive because it is necessary to attain and maintain a much lower temperature in the oil by means of greatly increased refrigeration requirements. It is obvious that greater quantities of our addition agents will be required to lower the pour point of a wholly undewaxed oil than that of one which has been hot pressed. Thus in the preferred embodiment of our inven-' tion; we hot press and/or centifuge and/or partially dewax the oil by some other means, so as to remove large quantities of wax and lower the pour point in this manner since it is cheaper than the use of addition agents; but rather than use the relatively expensive cold pressing process or low temperature centrifuging for removing the remainder of the wax and simultaneously suffering the volumetric loss of lubricant involved, we add one of the addition agents here described so as to obtain the same lowering of the pour point .by this less expensive method and without loss of any of the lubricant. The blending stocks used in preparing the lubricant may be partially dewaxed, separately or after blending, for proper viscosity.

With regard to the desirability of producing lubricating oils of improved film strengths, it is well known that most lubricating oils are no better and many of them are poorer with respect to this characteristic than they were ten years and more ago. During this same period, engine speeds, compression ratios and horse power of automotive engines have increased considerably. All these advances in automotive engineering have increased bearing pressures and the demand made on lubricants. The necessity of a lubricant which has the ability to carry this load without permitting metal-to-metal contact is apparent. It has been found that certain classes of organic compounds, when blended in small concentrations with mineral oils serve to improve the load carrying ability of the mineral oils so that they are much better adapted to modern lubrication demands than the unblended oils. The film strengths of both'straight mineral and blended lubricating oils may be suitably measured by means of the Timken machine. The construction and operation of this machine is fully described in the literature.

One of the important features of our invention is that we have discovered a class of materials which when blended in small percentages, suitably 0.1 percent to 5 percent by weight, with mineral oils serves to produce both of these effects simultaneously. The advantage of lowering the pour point and raising the film strength by means of a single addition agent is at once apparent in decreasing the cost of manufacture because these materials are as readily prepared as addition agents designed for either purpose alone. They make necessary only one blending operation which will tend to reduce manufacturing costs.

The class of materials which we contemplate using to accomplish this dual purpose may be described as halogenated esters formed from organic acids containing ten or more carbon atoms and hydroxy cyclic organic compounds containing one or more hydroxyl groups for each cyclic group. These compounds may beprepared in any of the ways known to the art, for example, by the interaction of a higher fatty acid with a polyhydric phenol followed by halogenation. Another method which .may be used consists of esterifying the previously halogenated phenol with a higher fatty acid. Also the acid may first be halogenated and then converted into the ester by reaction with the polyhydric phenol or other cyclic. The reaction products are carefully refined by any of thewell known means such as washing with dilute caustic or carbonate solution. Washing with sodium sulfite solution serves to remove unstable halogen from the material which is then washed with water and suitably dried.

' These esters may be derived from saturated or unsaturated fatty acids having straight or branched chains which may be further substituted. The polyhydroxyl cyclics may be aromatic or cycloparaflinic in character. While chlorine is the cheapest and most readily available halogen, we contemplate using as well the other halogens,- fluorine, bromine and iodine since they are also suited to our purpose.

The hydrocarbon portions of these blended oils Example 1 Ninety-nine parts by weight of a well-refined Mid-Continent lubricating oil of S. A. E. grade No. 30 having a pour point of 2 F. and a'Timken film spetngth of 6000 pounds per square inch and one par by weight of dichlorohydroquinone distearate were blended together at F. by

mechanical agitation. The blended oil had a pour' point of 16 F. and a Timken film strength of 15,300 pounds per square inch.

Example 2- Example 3 One part by weight of trichlorophenyl stearate blended with 99 parts of S. A. E. 20 paraffin base mineral oil reduced the pour point of the latter .from 15 F. to 3 F. and raised the Timken film strength from 5600 to 11,800 pounds per square inch.

Example 4 The chlorinated and refined ester obtained from the action of lauric acid 4, 4', 4"-trihydroxy triphenylmethane in the presence of phosphorus oxychloride was blended with a mineral oil having a Timken film strength of 6500 pounds per square inch and a pour point of 2 F. 995 parts by weight of the oil was used with 5 parts of the addition agent. The blended material had a. Timken film strength of 22,800 pounds per square inch and a pour point of 10 F.

It willbe seen that we have accomplished the objects of our invention. By the addition of a small amount, that is, from one tenth to ten percent by weight of a chlorinated ester formed from an organic acid having ten or more carbon atoms per molecule, and a cyclic poly'hydroxy compound, which ester bears chlorine or one of the halogens in chemical combination, we lower the cold test and increase the film strength. Itwill be understood that, by the term polyhydroxy phenolic hydroxy compounds are to be understood as well as alcoholic hydroxy compounds or mixed phenolic alcoholic hydroxy cyclic or ring compounds.

Having thus described our invention, what we claim is:

A lubricating composition comprising in combination a major proportion of mineral lubricating oiland a minor proportion of trichlor phenyl stearate.

BERT H. LINCQLN. GQRDON D. BYRKIT.