US2761844A - High temperature lubricating compositions - Google Patents

Description

Patented Sept. 4, was

HIGH TEMPERATURE LUBRICATING COMPOSITIONS Carl D. Ackerman, Indiana Township, Allegheny County, Paul R. McCarthy, Allison Park, and Thomas R. Orem, Blawnox, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application November 7, 1951, Serial No. 255,328

3 Claims. (Cl. 252-29) This invention relates to improved lubricants and, more particularly, to the class of lubricants existing as plastic solids or jellies adapted for lubricating mechanisms operated at temperatures of 500 to 900 F.

Compositions are available for lubricating purposes at room temperature and atmospheric pressure. Lubricants are also available for use at temperatures between room temperature and 450 to 500 F. However, so far as we know, no satisfactory grease-like lubricants have been developed for lubrication at temperatures up to 900 F. While some lubricants have been suggested for use at these higher temperatures, they have not been entirely satisfactory in that either they are diflicult to handle and apply at room temperature or they decompose at elevated temperatures leaving in some instances, resinous deposits, and in other instances where complete evaporation occurs, only metal to metal contact. In either of the latter instances seizure of the moving parts results for want of adequate lubrication.

The lubricating compositions of our invention can be used where temperatures below 500 F. are encountered. However, their main advantage lies in their applicability at temperatures in excess of 500 F. One important use for the compositions of our invention is in the lubrication of plug valves. Many of the advantages of plug valves flow from the effective lubricating means provided by their design. Efficient operation of these valves is therefore dependent upon the lubricant employed. Naturally, when these valves are placed in lines carrying materials which have been heated to temperatures of 500 to 900 F., a lubricant is required which will not break down at these high temperatures. It the lubricant breaks down,

en frequent valve replacement is required as a result of seizure and galling. Valves which are lubricated with the compositions of our invention can be operated over prolonged periods of time at temperatures of 500 to 900 F.

We have discovered that lubricating compositions which are easy to handle and apply at room temperature and which give adequate lubrication of moving parts at temperatures of 500 to 900 F., can be prepared by dispersing graphite and a compound of a bentonite and an organic base in an ester of a dibasic acid. Thus, we have found that a dispersion of graphite and a compound of a bentonite and an organic base in an ester of a dibasic acid results in a lubricant having good lubricating characteristics at temperatures up to 900 F. We have found that the operating life of a valve when lubricated with a composition of our invention is increased over the. operating life of a valve lubricated with competitive compositions.

The bentonite compounds employed in accordance with the invention are compounds composed of a montmorillonite mineral in which at least a part of the cation content of the mineral has been replaced by an organic base. Clays that swell at least to some extent on being contacted with water and contain as a primary constituent a mineral of the group known as montmorillonites are generally referred to as bentonites. Such clays, which contain exchangeable alkali metal atoms either naturally or after treatment, constitute the raw materials employed making the bentonite-organic base compounds used in the compositions of this invention. So far as known, all naturally occurring montmorillonites contain some magnesium and certain of them, as exemplified by Hector clay, contain such a high percentage of magnesium that they largely have magnesium in place of the aluminum content characteristic of the more typical montmorillonites.

The bentonite-organic base compounds are preferably prepared as described in U. S. Patent No. 2,033,856, issued March 10, 1936, by bringing together the bentonite and the organic base in the presence of aqueous mineral acid to eliect base exchange. The organic bases should preferably be titratable with mineral acids. Among these reactive bases are many alkaloids, and cyclic, aliphatic, and heterocyclic :amineS. The bentonite-organic base compounds used preparing the lubricating compositions of this invention are preferably those prepared by bringing together a bentonite clay and such organic bases as aliphatic amines, their salts, and quaternary ammonium salts. Examples of such amines and salts are: decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, hexadecyl ammonium acetate, octadecyl ammonium acetate, dimethyldidodecyl ammonium acetate, dimethylhexadecyloctadecyl ammonium acetate, dimethyldodecylhexadecyl ammonium acetate, dimethyldicetyl ammonium acetate, dimethyldioctyl ammonium acetate, dimethyldioctadecyl ammonium acetate, and the corresponding chlorides and quaternary ammonium chlorides. The organic bases employed should be such as to impart substantial organophilic properties to the resulting compounds. The preferred bentonite compounds are prepared from quaternary ammonium compounds in which the N-substituents are aliphatic groups containing at least one alkyl group with a total of at least 10 to 12 carbon atoms. When aliphatic amines are used they preferably contain an alkyl group with a total of at least 10 to 12 carbon atoms.

The amount of the bentonite compound used may vary over wide limits depending upon the particular ester or esters with which the bentonite compound is to be blended and upon the properties desired in the final lubricating composition. Ordinarily the bentonite compound is employed in an amount between about 5 and about 20 per cent by weight of the total composition. The exact amount may vary depending upon the consistency of the composition desired, but in any case the bentonite compound is dispersed together with the graphite in the ester in an amount sufiicient to produce a plastic solid or composition having the consistency of a grease. When a bentonite compound is mentioned, it is understood, of course, that one or more of such compounds is intended. a

The esters which we employtare those which have a majority of the properties of hydrocarbon oils of lubricating grade such as the lubricating oils customarily used in compounding greases. While esters having viscosities as high as 4000 SUS at F. may be used, we prefer to use esters having viscosities of about 45 to about 400 SUS at 100 F. If desired, a mixture of esters of suitable viscosity may be employed instead of a single ester, by means of which any desired viscosity within the range of 45 to 4000 SUS at 100 F. may be secured. The viscosity of the ester has little etfect on the dropping point of the compositions, but more viscous esters produce compositions having greater stickiness and adhesive properties than do the less viscous esters. Ordinarily the more viscous esters are used in producing lubricants of greater consistency,- However, the consistency can also be adjusted by the amount of the bentonite compound used. In addition to possessing lubricating properties, the esters should be substantially neutral. Free acids tend to catalyze the oxidation of the esters, resulting in compounds which are corrosive to metals. Therefore, to produce a grease-like lubricant which is stable and which is substantially non-corrosive to metals, we employ esters preferably having a neutralization number below about 0.2.

Exemplary of some of the preferred esters used in making the compositions of the present invention are the diesters of aliphatic dibasic acids and alcohols containing at least four aliphatic carbon atoms, preferably between 6 and 16 carbon atoms. Examples of some of the alcohols which can be used are 1-butanol; Z-butanol; Z-methyl-Z-propanol; l-pentanol; ll-pentanol; Z-methyl- Z-butanol; l-hexanol; Z-hexanol; 3-hexanol; 2-methyl-lpentanol; 3-methyl-l-pentanol; 4-methyl-1-pentanol; 2,4- dimethyl-Z-pentanol; 2,3dimethyl-3-pentanol; 2,4-dimethyl-3-pentanol; 3-ethyl-3-pentanol; Z-methyl-l-hexanol; S-methyl-l-hexanol; 2-methyl-2-hexanol; S-methyl- 2-hexanol; 3-methyl-3 hexanol; 5-methy1-3-hexan0l; lheptancl; Z-heptanol; 4-heptanol; Z-me'thyl-Z-heptanol; 3-methyl-2-heptanol; 4-methyl-4-heptanol; Z-ethyl-lhexanol; 3-ethyl-3-hexanol; 3-ethyl-2-methyl-3-pentanol; l-octanol; 2-octanol; 2-methyl-2-octanol; 2,6-dimethyl-4- heptanol; 4-ethyl-4 heptanol; 3-ethyl-5-methyl-3-heptano1; l-nonanol; Z-nonanol; 3-nonanol; 4-nonanol; S-nonanol; Z-methyl-l-nonanol; 3,7-dirnethyl-l-octanol; 3-ethyl-3- octanol; 4-propyl-4-heptanol; 3-isopropyl-5-methyl-l-hexanol; l-decanol; 4-decanol; lauryl alcohol; myristic alcohol; cetyl alcohol; stearyl alcohol; glycol; glycerol; and the like.

'As examples of some of the dibasic acids suitable for the preparation of the esters used in making the compositions of the present invention there may be mentioned oxalic, malonic, succinic, isosuccinic, glutaric, ethyl malonic, pyrotartaric, adipic, pimelic, suberic, azelaic, sebacic, and phthalic acid. When a low molecular'weight acid is esterfied, a high molecular Weight alcohol .is preferred in order to produce an ester having a majority of the properties'of hydrocarbon oils of lubricating grade. While the diesters of the aliphatic dibasic acids are preferred, the esters of aromatic dibasic acids such as the phthalic acid ester of a material such as castor oil :or other high molecular weight alcohols may be used.

7 The esters may be prepared by any of the methods known in the art. According to one meflaod, as described in U. S. Patent No. 2,09'LM1, issued August 24,

1937, a dicarboxylic acid or its anhydride is dissolved :in

an inert solvent, after which the resulting mixture is heated to its boiling point. While maintaining themixture at its boiling point, an alcohol to give the desired ester is added gradually. When addition of the alcohol is completed, the solvent is distilled off and esterification is carried out at a temperature above 150 C. According to another suitable method, the alcohol :and acid are reacted at an elevated temperature in the presence of a sulfuric acid catalyst. As the reaction proceeds, water iscontinuously removed by .azeotropic distillation with a solvent such as benzene or toluene. When the reaction is substantially complete, the product is washed with dilute alkali to remove any acidic substances. Purification of the product may be accomplished by .tractional distillation.

The particular ester employed, as well as the exact amount of the ester, depends upon the characteristics desired in the final lubricating composition. In most instances, however, the ester content comprises about 50 to about 70 per cent by weight of the total composition.

The graphite which we employ is finely divided, 1. e., 50 mesh or finer, and advantageously finer than about 200 mesh. The amount :of graphite in the compositions of-our invention can be varied over a wide range without all? cting its beneficial eifects. However, we prefer to incorporate graphite in the compositions in an amount between about 20 and about 40 per cent by weight.

While the compositions produced according to this invention are generally satisfactory with respect to oxygen stability, it may be desirable in certain instances, as when the composition is subjected to severe operating conditions over prolonged periodsof time to incorporate in the composition a small amount of a diaryl amine. As examples of some of the diaryl amines which may .be used in the compositions of this invention may be mentioned diphenylamine, phenyl alpha naphthy-lamine, phenyl beta naphthylamine, alpha alpha, alpha beta, beta beta dinaphthylamines, and the like. Other diaryl amines as well as their derivatives wherein one or more hydrogen atoms on one or both of the aromatic nuclei are replaced by a substituent group may be used. The substituting group :may,'for'.example, he one selected from the class of aryl, alkyl, amino, aryloxy and alkyloxy radicals, so long as the presence of the substituent does not render the diaryl amine insoluble in the ester, or soluble in water or otherwise adversely'afiect the effectiveness of the diaryl amine. The amount of the diaryl amine employed will depend to a large extent upon the severity of the conditions to which the composition is subjected, as well as the particular diaryl amine used. For instance, when the composition is subjected to prolonged use under oxidizing conditions, the dhiryl amine requirement will be much greater than when relatively mild non-oxidizing conditions are encountered. When a diaryl amine is desired, it -is amployed in an amount between about 0.1 and 1.5 per cent by Weight based upon the weight of the total composition. In any case, when,

an inhibitor is used, it is added in an amount sufiicient to .substantially inhibit oxidational deterioration.

In compounding the compositions of the present invention, Various compounding and blending procedures may be used. In accordance with one embodiment, the ester and the bentonite compound are introducedinto a suitable mixing device such as .a paint mill or a colloid The mixture is then repeatedly passed through the mill until the desired degree of dispersion of the bentonite compound in the ester is obtained. The graphite .is then stirred into the plastic mixture thus formed until a uniform composition isobta-ined.

In order to illustrate the advantageous properties of the compositions of this invention, .a greasealike lubricant was prepared by dispersing 9.8 parts by weight of dimethyldicetyl ammonium bentonite and 3.3.8 parts by weight of graphite, 9.8 per cent of which passed a 325- mesh screen, in 56.4 parts by weight of di-Z-ethylhexyl sebaeate. The 'di-Z-ethylhexyl sebacate had :a viscosiry of $115 at F., a flash point of 490 F. and .a pour point below 60 :F. The resulting lubricant had I a consistency (ASTM) of 232 nnworked and 2A5 Worked. This lubricant was easy to handle at room temperature and was easy to apply by means of a pressure gun through a ball-type fitting to parts requiring lubrication. When this lubricant was applied to plug valves which were in use in a fluid catalytic cracking uni-t, these valves did not fail even after being operated at 700 to 900 F. for several months. When competitive commercial greases were employed, valve failure occurred after the valve had been in use for only a few hours.

While this inventionhas been described with reference to specific details and examples of the production and properties of the compositions of our invention, it is to be understood that the invention is not intended to be limited to such details and examples except as recited hereinafter in the appended claims.

We claim:

1. A lubricating -.composition consisting of a uniform mixture of about .3328 per cent by weight of powdered graphite, about 9.8 per cent by weight of dimethyldicetyl ammonium bentonite and about 56.4 per-cent lby weight of di-Z-ethylhexyl sebacate.

2. A lubricating composition consisting of a uniform mixture of about to about per cent by weight of powdered graphite, about 5 to about 20 per cent by weight of dimethyldicetyl ammonium bentonite, and about to about per cent by weight of di-Z-ethylhexyl sebacate.

3. The composition of claim 2 containing about 0.1 to about 1.5 per cent by weight of a diaryl amine.

References Cited in the file of this patent UNITED STATES PATENTS Brunstrum Nov. 27, 1934 Vande Bogart Dec. 17, 1946 Zimmer et a1. Feb. 17, 1948 Jordan Nov. 28, 1950 Stross May 22, 1951 Peterson Dec. 30, 1952 Sparks et a1. Jan. 20, 1953 Abrams et a1. Jan. 27, 1953

Claims (1)

1. 2. A LUBRICATING COMPOSITION CONSISTING OF A UNIFORM MIXTURE OF ABOUT 20 TO ABOUT 40 PER CENT BY WEIGHT OF POWDERED GRAPHITE, ABOUT 5 TO ABOUT 20 PER CENT BY WEIGHT OF DIMETHYLDICETYL AMMONIUM BENTONITE, AND ABOUT 50 TO ABOUT 70 PER CENT BY WEIGHT OF DI-2-ETHYLHEXYL SEBACATE.