US1944941A - Lubricating oil - Google Patents

Description

Patented 30, 1934 UNITED STATES LUBRICATING on.

' Bert H. Lincoln and Alfred Henriksen, Ponca City, Okla", assignors to Continental Oil Company, Ponca City, kla., a corporation of:

\ Delaware No Dre.

'5 Claims.

Our invention relates to lubricating oils and more particularly to improved methods for the production of high quality lubricating oils and such products as new compositions of matter.

a It is well known that mineral lubricating oils are deficient in oiliness characteristics, which is the most important character of the lubricant when used under conditions of boundary lubrication, where the viscosity of the lubricant plays little or no part in lubrication. Boundary lubrication conditions are obtained when engines are operating at heavy load, low' speeds or, if for any reason, the supply of lubricant is cut off or not suflicient. This last condition may exist when for mechanical reasons the lubricant pump is not functioning properly or when the lubricant feed line is clogged with foreign matter.

One object of our invention is to provide a lubricant of high oiliness character, low coeflicient of friction, and one which will act as a safety factor in lubrication when abnormal conditions exist for one reason or another.

Another object of our invention is to provide a lubricant which will maintain a very low coefficient of friction when diluted with light hydrocarbons such as are obtained in an automobile crank case by incomplete combustion of the fuel.

A further object of our invention is to provide a lubricant having penetrative lubricity characteristics. It has been found that our lubricant does not drain off the rubbing surfaces when idle, thereby providing a lubricating film on the rubbing surfaces at all times and being of great value to-the life of the machine in cold weather starting when the lubricant is very viscous and sluggish.

It has been demonstrated a number of times that hydrocarbon lubricants of the very best quality are not constant in coefficient of friction with slightly changing loads or speeds, and in some cases the coefiicient of frictionvaries over rather v wide limits with some lubricants when all operating conditions are held constant.

Another object of our invention is to provide a lubricant which shows a more nearly constant coefflcient of friction, thereby insuring, smoother engine operation.

The method we have discovered and the lubricant prepared thereby for accomplishing the above objects consists broadly of adding organic fatty acid esters to mineral hydrocarbon lubricants. We have found that a certain type organic ester gives a muchlmore constant coefficient of friction when added to a mineral lubricantlhan. is obtained by adding organic fatty acids to the Application June 11, 1932 Serial No. 616,741

same lubricant. Another advantage of the organic esters over fatty acids as addition products to lubricants is that organic esters may be used when an acid free lubricant is required for one cause or another, such as in the presence of easily corroded metals or alloys.

The theory of our invention is not fully understood, but we assume that the organic esters function due to their molecular polarity, whereas the organic acids act entirely differently and. probably by soap formation on the metal surface with the free carboxyl group and residual metal aflinity. It has been proved by spectrum analyses and spectograms that the fatty acid carboxyl group forms a new compound (soap) with the metal surface. The carboxyl is rooted in the metal and the long chain hydrocarbon radical standing on the carboxyl base perpendicular to the metal and parallel to each other. With the carboxyl acid afiinity neutralized by ester formation, the action of esters in reducing friction must be different.

We are aware that fatty oils containing glycerides of fatty acids have been sulpho-chlorinated in order to improve the oil. An example of an 0 oil thus sulpho-chlorinated is shown in U. S. patent to Sommer, 461,513, bearing date of October 20, 1891. It is to be observed, however, that the sulpho-chlorination of oils is not the equivalent of the chlorination of oils inasmuch as no 5 sulphuretting takes place in the chlorination of the oil. Furthermore, the glycerides are esters of the tri-atomic alcohol glycerol, while we employ esters of di-hydric or mono-hydric alcohols which are chlorinated.

In practicing our invention only small quantities of the various esters are added to hydrocarbon lubricants. The ester is well blended with the hydrocarbon and the mixture is ready for use. To prove the efficiency and value of our invention, we determine the coefiicient of friction of the original hydrocarbon lubricant bytesting on the Herschel friction testing machine, which was developed by Dr. W. H. Herschel of the United States Bureau of Standards and is well known to the art. The coefficient of friction of the mixture of hydrocarbon oil and ester is then determined by the same machine. The following examples clearly demonstrate the value and efliciency of this invention:

Example 1.--A very good quality, of 350 pale oil was selected as' the hydrocarbon lubricant for the test. Testing this product on the Herschel friction machine gave a' coeflicientoffriction of 1 0.135, indicating that the original lubricant was of ver' high quality.

To t hydrocarbon lubricant 0.5% of commercial ethyl oleate was added and well mixed. Testing this mixture on the Herschel machine gave a coefficient of friction of 0.065, or less than half the friction of the original hydrocarbon lubricant. During the test the machine lubricated with the mixture gave very smooth operation. The indicating pointer reached the point 0.065 on the scale and was held at a constant point throughout the test. Hydrocarbon lubricants and hydrocarbon lubricants blended with fatty acids have a tendency to fluctuate over rather wide limits when tested on this machine, their action being variable and jerky while the esters blended in accordance with our invention give very smooth operation.

Example 2.Another sample of the hydrocarbon lubricant mentioned in Example 1 was blended with 0.5% of N-butyl oleate. This mixture gave a coefilcient of friction of 0.073, or a reduction in the coefficient of friction of about 46%. In this case as before, the operation of the machine was extremely smooth.

Example 3.-To another sample of the same hydrocarbon lubricant mentioned in Example 1, 0.5% ethyl palmitate was added. This mixture gave a very smooth operation and a coefiicient of friction reading of 0.071% or about &8% reduction.

but the above examples show Example 4.0.75% of ethyl stearate gave in the same hydrocarbon lubricant a coefiicient of friction of 0.075 and very smooth operation.

Example 5.-To another sample of the hydrocarbon lubricant mentioned in Example 1, 0.5% phenyl stearate was added. a This aromatic alcohol ester gave a coemcient of friction reading of 0.075 and the operation was extremely smooth.

Any number of other examples might be given that esters of fatty acids with either aliphatic or aromatic alcohols are efficient in our process. It should be pointed out that the lower molecular weight fatty acid esters are not as efficient as the higher molecular weight fatty acid esters. For example, 0.50 ethyl butyrate in the same hydrocarbon lubricant as mentioned in Example 1 above gave a coefilcient of friction reading of 0.080 and the operation was very irregular. 0.50 isopropyl oxalate gave a very, high coemcient of friction, 0.130, and was very irregular. 0.5% isopropyl acetate gave a reading of 0.085 but was irregular in operation.

It is to be understood that the term esters" as used in the claims and in this specification is intended to cover all esters broadly, excluding those low molecular weight acids which do not lower the coeflicient of friction. The commercial esters are satisfactory for this process; the impurities present do not affect the efficiency. The esters may be prepared by any of the commercial esterification processes wherein commercial fatty acids and commercial alcohols are used as raw materials.

We have further found that original hydrocarbon lubricants and hydrocarbon lubricants blended with esters have low film strength and have a tendency to break down and allow seizure of metals at relatively low pressures. The film strength of a lubricant is of great importance when the lubricant is used under heavy loads and slow speeds. By halogenating the esters of this invention prior to blending with hydrocarbon lubricants the film strength is greatly improved,

The halogen may be added to the ester in any manner, the only requirement being that the halogen is introduced in the molecule. With esters of unsaturated fatty acids, the halogen may be added directly until the unsaturated bonds are saturated with halogen. With further halogenation, hydrogen is replaced by halogen by substitution. Saturated molecules are halogenated entirely by substitution. The halogen may be introduced into the alcohol radical or the fatty acid radical prior to or after esterification.

As an example of one method of carrying out this phase of our invention, but not as a limitation thereto, the following demonstration is cited.

A sample of ethyl oleate was chlorinated until it was a liquid at room temperature. Excess chlorine and hydrogen chloride were removed by warming and washing with solvents. The product thus prepared was added to a sample of high quality lubricant and tested on the Timken machine, which is a machine for determining film strength of lubricants developed and manufactured by the Timken Roller Bearing Company and well known in the art. A sample of the original hydrocarbon lubricant was also tested on the Timken machine. The original hydrocarbon lubricant broke down and allowed seizure of the metal rubbing surfaces when 18.2 pound weights had been added, which is equivalent to'approximately 10,500 pounds per square inch on the rubbing -surfaces. To another sample of this same hydrocarbon lubricant 0.5% of halogenated ethyl oleate was added. This product did not break down until 35.2 pound weights had been added, which represents a pressure of approximately 22,000 pounds per square inch on the rubbing surfaces; thus by adding 0.5% of the product of this invention, the film strength of a lubricant can be practically doubled.

The degree of halogenation of the esters may be varied over wide'limits depending upon the ester used and the service in which the bed lubricant is to be used. In some cases small percentages of halogen in the molecule are sufficient; in others a large percentage of halogen is required.

When using poorer quality original hydrocarbon lubricants, larger quantities of ester and halogenated ester are required to obtain the desired result. Quantities as high as 2% or more may be used. With any given hydrocarbon lubricant one skilled in the art of preparing lubricants can easily determine the percentage of ester or halogenated ester required to give the smooth operation, low coefiicient of friction and/or high film strength. In most cases the quantity will vary between 0.1% and 2%.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It

is, therefore, to be understood that our inven- 3. A lubricating 011 comprising in combination a hydrocarbon oil and a small quantity of a chlorinated ester of a fatty acid and a dihydric alcohol.

tion a hydrocarbon oil and a small quantity of chlorinated ethyl oleate.

4. A lubricating oil comprising in combina,

5. A lubricating 011 comprising in-combination a hydrocarbon oil and a small quantity of chlorinated methyl stearate. a

BERT H. LINCOLN.