US3437594A - Alkaline earth metal carboxylate dispersions - Google Patents

Description

3,437,594 ALKALINE EARTH METAL CARBOXYLATE DISPERSIONS Berti] Albin Peterson, Amityville, N.Y., assignor to Mobil Oil Corporation, a corporation of New York No Drawing. Filed Nov. 25, 1966, Ser. No. 596,785 Int. Cl. C10m ]/08, 1/24; B01} 13/00 US. Cl. 25240.7 17 Claims ABSTRACT OF THE DISCLOSURE This invention relates to lubricating compositions containing a dispersed phase. More particularly this invention concerns providing stable dispersions of oil-insoluble alkaline earth metal carboxylates for use in lubricants.

It is known that certain alkaline earth metal carboxylates, such as calcium acetate, provide extreme pressure properties for lubricants. These properties include load carrying and anti-Wear characteristics which enable the oil to lubricate engines and other machines operating under great pressure.

These carboxylate salts, being insoluble in oil, are either relatively difficult to disperse therethrough uniformly, and they tend to separate from the oil, or once the dispersion is formed, the viscosity of the finished dispersion may increase in storage. Moreover, the dispersion techniques known in the industry are not always effective to yield long-lasting dispersions. Quite often the dispersion is nonuniform and portions of the lubricant compositions possess almost no load-carrying properties at all.

In the past, dispersing agents have been used to stabilize these metal carboxylates in oil with a large measure of success. However, since it is often necessary to obtain a lubricant dispersion capable of being stored for long periods of time, a method of further ensuring stable dispersions would be desirable. Furthermore, obtaining a uniform dispersion in a short period of time and under moderate mixing conditions would also be desirable. Sometimes a dispersion cannot be readily obtained at temperatures over 200 F. or even after hours of mixing. A convenient and effective means of providing a stable oil dispersion is required.

Many known additives used as dispersing agents tend to be acidic in nature and it has been observed that the metal surfaces with which the oil dispersions have come in contact may become corroded. A need to reduce the corrosive tendencies of the oil dispersion without adversely alfecting the performance of the dispersing agents represents yet another aspect of the problem.

A major object of this invention is to provide a means of obtaining stable dispersions of alkaline earth metal carboxylates in oil. A further object is to provide stable alkaline earth metal carboxylate dispersions in oil which are stable for a long period in storage. Another object is to provide a method of obtaining alkaline earth metal carboxylates in oil that are relatively non-corrosive to metal.

It has now been discovered that stable oil dispersions of alkaline earth metal carboxylates of carboxylic acids having from 1 to carbon atoms may be prepared by the presence in the oil mixture of at least 0.55 mole of water per mole of water-free metal carboxylate. If the carboxylnited States Patent 0 ate-oil mixture has less than 0.55 mole of water per mole of water-free carboxylate, a uniform dispersion cannot be produced. It is most preferred that there be present from about 0.55 to about 1.0 mole of water per mole of waterfree metal carboxylate. Dispersions containing from about 0.01% to about 60% by weight of carboxylate may be prepared by this invention.

Surprisingly, the addition of the small amount of water in accordance with this invention provides oil dispersions of oil-insoluble metal carboxylates having less than about 0.55 mole of water present at temperatures ranging as low as about F. up to about 200 P. On the other hand, it has been unexpectedly found that if the amount of water present during the dispersion procedure is excessive or if the maximum temperature for dispersion is over 250 F., although the dispersion may be obtained, the viscosity of the lubricant may increase.

The carboxylates of this invention include metal salts of formic, acetic, propionic, isopropionic, butyric, isobutyric, valeric and isovaleric acids. The suitable metals include calcium, magnesium, strontium and barium. The most preferred salt is calcium acetate, especially calcium acetate hemihydrate. With the use of a calcium acetate salt, the amount of water critical for obtaining the stable dispersions of this invention is at least 6% by weight of water based on the total weight of dry calcium acetate and water. Preferably from 6% to about 10% may be present. Higher concentrations of water may of course be present during the dispersing step, and if desired the water may be removed by subsequent dehydration.

A number of dispersing agents for these oil-insoluble metal carboxylates are employed according to the method of this invention. One of the more effective classes of agents is the long-chain carboxylic acid having from about 8 to about 18 carbon atoms. Such acids as oleic, palmitic, stearic, linoleic, capric, lauric, myristic and the like have been found to be excellent dispersants as disclosed in US. Patent No. 3,121,689. The preferred of these acids is oleic acid in concentrations about 0.005% to 10% by weight of final dispersion. Another extremely successful class of dispersing agents is the N-acyl-substituted sarcosine disclosed in US. Patent No. 3,182,020. These sarcosines have the formula:

0 R-C-IIT-CHzC O OH wherein R is an aliphatic hydrocarbon radical having from about 8 to about 24 carbon atoms. These sarcosines include N-pelargonoyl sarcosine, N-lauroyl sarcosine, N- myristol sarcosine, N-palmitoyl sarcosine, N-oleoyl sarcosine, and N-arachidoyl sarcosine. The preferred of this group is oleoyl sarcosine.

Even with the use of these dispersing agents it had sometimes been found that alkaline earth metal carboxylate dispersions in oil either cannot be made readily, or, if made, would not be stable after weeks or months in storage. The use of special equipment such as homogenizers, grease kettles, high speed dissolvers and the like are of no avail in producing uniform, long'lasting dispersions. The commercial calcium acetate hemihydrate ordinarily contains only small amounts of water, and the water content of these commercial materials is not always consistent. With the addition of a small amount of water to arrive at the critical total-water content in the dispersion based on the metal carboxylate present, it is surprising indeed to find that stable dispersions can be readily prepared at very low temperatures.

Broadly, the method of this invention involves mixing the oil, dispersing agent, carboxylate and Water together in any desired fashion and then mixing. Preferably, the oil,

dispersing agent, and water are mixed together initially as uniformly as possible, and then the alkaline earth metal carboxylate is dispersed therein by means of any convenient mixing device. The temperature during the mixing may be held between about 100 and 200 F. The dispersions are usually prepared first in the form of a concentrate, containing from about to about 60% by weight of the carboxylate, preferably to 50%, and the rest oil and dispersing agent.

In another aspect of this invention, it has been unexpectedly found that the dispersing agent continues to react with the metal carboxylate after dispersion occurs to produce excess free carboxylic acid. For example, in the sarcosine and metal carboxylate system, metal sarcosinate is produced leading to the formation of small amounts of carboxylic acid. However, the increasing presence of these short-chained acids, such as formic, acetic, propionic and butyric acids, can cause corrosion of the metals used in engine construction. Thus, the very dispersion additives contribute somewhat to the corrosion problem. Since the reaction between the dispersing agent and the metal carboxylate can continue after the dispersion is effected, prevention of corrosive acid formation is desirable as soon as the required dispersion is achieved. This reaction also promotes the formation of extremely fine metal carboxylate particle which tends to thicken the dispersion. In accordance with this aspect of the invention, a small amount preferably from 0.05% to about 5% by weight of metal carboxylate, of a basic, alkaline material, including alkali metal hydroxides and carbonates, alkaline earth metal hydroxides, ammonia, and any other suitable base, is added to the oil blend after obtaining the carboxylate dispersion. The corrosion and viscosity problems are considerably reduced. This treatment maintains the dispersed carboxylate particle in the desired size; for calcium acetate the longest dimension of the particle is preferably in the range of about 0.5 micron to about 5 microns. Calcium hydroxide or hydrated lime is preferred.

The following examples serve to illustrate the invention although they are not intended to limit the invention in any way.

EXAMPLE 1 Into a suitable mixing vessel was added 4.56 lbs. of a 500 S.U.V. (at 100 F.) solvent-refined naphthenic mineral oil. To this oil were added together 0.24 lb. of oleoyl sarcosine (containing 0.6% of water) and 0.03 lb. of water. A Cowles Dissolver mixing mechanism operating at 1900 r.p.m. was used to mix the components. As the mixer was operated, 3.2 lbs. of calcium acetate hemihydrate (containing 5.08% water) was added. After all of the calcium acetate was added the mixing was continued until the power requirement for the mixer began to increase the temperature of the batch. The mixing temperature reached a maximum of 180 F.

The resulting dispersion was a smooth concentrate. Upon addition of further amounts of a lubricating oil to produce an oil having a total base number (A.S.T.M. Method D-664) of 40, the calcium acetate remained in dispersion with no evidence of separation. The total amount of water in the dispersion concentrate prior to dilution in the remainder of the oil was 2.44% or about 6.1% by weight of the calcium acetate.

Comparative examples Using the same equipment as in Example 1, and the same amounts of additives, except that no additional water was added to the dispersion batch, the mixing was performed until the temperature of mixing reached a maximum of 280 F. After completion of the mixing calcium acetate had not been dispersed. The amount of water in the entire batch obtained from the calcium acetate hemihydrate and the oleoyl sarcosine was 2.06%, about 5.15% by weight of the calcium acetate.

The above steps were repeated and 0.25% of water was added to the mixture, yielding a total water concentration of 2.31%, about 5.75% by weight of calcium aectate, in the batch. The mixing temperature rose to 296 F. The calcium acetate was not dispersed.

These two examples indicate that calcium acetate cannot be dispersed readily unless a critical amount of water is present.

EXAMPLE 2 Using the same amounts of additives as in Example 1 and the same procedure 0.5% of water was added to the batch yielding a total water concentration of 2.56%, about 6.4% by weight of calcium acetate. The calcium acetate began to disperse into the oil at F. Complete dispersion occurred at 180 F.

EXAMPLE 3 The steps of Example 1 were repeated except that in addition to the calcium acetate, 0.3 lb. of commercial lime was also added to the batch, when the temperature of mixing reached 174 F. The mixing was continued for an additional 10 minutes. The final temperature reached 180 F. This concentrate was diluted in further amounts of oil to produce a 40 T.B.N. oil blend; the blend was found to be stable in storage and the dispersion contained no evidence of separation. Moreover, this oil blend passed the A.S.T.M. Rust Test D-665.

The following examples indicate the adverse effect of dispersion temperature on the viscosity of the diluted oil dispersions. The presence of commercial lime reduces viscosity increase.

EXAMPLE 4 Using the same concentrates of calcium acetate, oleoyl sarcosine and oil, as in the previous examples, 1.0% and 2.0% water were added to two different batches. The total water in the concentrates were (1) 3.06% and (2) 4.05%, respectively. Duplicate dispersions of the two were made with 0.4% by weight of commercial lime added as soon as dispersion was obtained, at about 175 F. The dispersions were subjected to heat at two different temperatures as noted in the table below. After the six dispersions were prepared, they were further diluted in the same solvent-refined mineral oil to produce a 40 T.B.N. lubricant composition. Viscosity measurements were taken after the dilution and again after a period of storage time. The results are tabulated below:

1 A desired maximum viscosity is 100.

Although this invention has been described in the light of specific examples and working embodiments, the invention is subject to modifications not necessarily disclosed herein but which would be obvious to One skilled in the art; the scope of the invention is not to be limited by these examples or embodiments except as limited by the following claims.

I claim:

1. A method of producing stable dispersions of preformed calcium monocarboxylate containing from 1 to 5 carbon atoms in mineral oil wherein the said calcium carboxylate contains less than 0.55 mole of water per mole of dry carboxylate comprising the step of adding sufiicient water to obtain a final water concentration of between 0.55 and 1.0 mole of water per mole of dry carboxylate.

2. The method of claim 1 wherein the dispersion mixture contains a dispersing agent selected from the group consisting of a fatty acid containing from 8 to 18 carbon atoms and an N-acyl sarcosine containing from about 8 to about 24 carbon atoms in the acyl group, wherein the said dispersing agent is capable of reacting with the said calcium carboxylate thereby producing a minor amount of the free carboxylic acid derived from the said calcium carboxylate.

3. The method of claim 2 wherein there is added a basic neutralizing compound after the calcium carboxylate is dispersed in the oil with the said dispersing agent, the said neutralizing compound being present in just suflicient amount to react with the said free carboxylic acid.

4. The method of claim 3 wherein the compound is an alkaline earth metal hydroxide.

5. The method of claim 4 wherein the said hydroxide is lime.

6. The method of claim 2 wherein the dispersing agent is oleic acid.

7. The method of claim 2 wherein the dispersing agent is oleoyl sarcosine.

8. The method of claim 1 wherein the dispersion is first produced as a concentrate containing 15% to 60% by weight of calcium carboxylate.

9. A composition consisting of calcium acetate dispersed in oil according to the method of claim 8.

10. A composition according to claim 9 wherein the largest dimension of the calcium acetate particle is in the range of from about 0.5 micron to about 5.0 microns.

11. The method of claim 8, wherein the concentrate contains 20% to 50% by weight of calcium carboxylate.

12. The composition consisting of calcium carboxylate dispersed in oil according to the method of claim 1.

13. The composition of claim 12 wherein the said carboxylate is calcium acetate.

14. The composition of claim 12 wherein the dispersion contains from 0.01% to about by weight of carboxylate.

15. The method of claim 1 wherein the carboxylate is acetate.

16. The method of claim 1 wherein the said final concentration of water is about 0.55 mole of water per mole of dry carboxylate.

17. The method of claim 1 wherein the temperature of dispersing is from to about 200 F.

References Cited UNITED STATES PATENTS 2,514,331 7/1950 Morway 25240.7 X 2,831,811 4/1958 McCormick et a1. 252-39 2,846,392 8/1958 Morway et a1. 25239 X 3,036,901 5/1962 Sanders et a1. 252-39 X 3,152,079 10/1964 Morway 25240.7 X 3,182,020 5/1965 Davis 25240.7 3,250,709 5/1966 Morway et a1. 252-39 X DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner.

US. Cl. X.R. 252-39, 308