US3106532A - Process for preparing improved compositions of lubricating greases - Google Patents

Description

Oct. 8, 1963 IU 1 ,106,532

BC T 3 PROCESS FOR PREPARING IMPROVED COMPOSITIONS OF LUBRICATING GREASES Filed May 9, 1961 2 Sheets-Sheet l 29 Co(Fe) '40 Bw-unello C/UC 1' INVENTOR ATTORNEY Oct. 8, 1963 B. CIUTI 3,106,532

PROCESS FOR PREPARING IMPROVED COMPOSITIONS 0F LUBRICATING GREASES Filed May 9, 1961 2 Sheets-Sheet 2 Bvunello CI'u-bi INVENTOR ATTORNEY 3,19%,53-2 Fatented Oct. 8, 1%63 tree 3,106,532 PROCESS FOR PREPARENG EMPROVED COMPO- SKTIONS OF LUERHCATING GREASES Bruneiio Ciuti, San Donate Milanese, Italy, assignor to Laboratori Riuniti Studi E Ricerche S.p.A., San Donate Milanese, italy, a company of Italy Filed May 1961, Ser. No. 103,896 Claims priority, application Italy May 12, 196i 7 Claims. ((31. 25221} It is known that greases based on lithium soaps are normally employed for lubricating rolling bearings, since they possess special characteristics which contribute to impart to said greases great resistance to mechanical wear, at low temperatures as well as at fairly elevated temperatures.

There are also known greases based on organophilic bentonites which possess particular properties such as to make them unreplaceable for some kinds of lubrication such as for instance in the case of the lubrication of members which work at temperatures higher than those which greases based on lithium soaps can stand.

Under those conditions in fact greases based on organophilic bentonites not only do not melt, but still keep sol-idly bound the lubricating liquid that constitutes them for the greatest part.

Together with their excellent qualities, lithium greases as well as greases based on organophilic bentonites present some inconveniences. It can be said, for instance, that some types of lithium greases tend to separate oil, during operation as well as during storage, while with greases based on organophilic bentonites the main inconvenience is constituted by a certain difficulty in yielding the oil necessary for lubrication, also apart from the high cost of said organophilic bentonites.

It has also been proposed to prepare greases by mixing in variable proportions a grease based on soaps with an organophilic bentonite (Bentone) grease, to obtain a product wherein the negative properties of the two components are eliminated.

However experience has shown that such compositions still present deficiencies, such as for instance consider-able losses of grease, to be detected by the ASTM D l263-53 T test and fairly high values for penetration. These defects prove mainly obnoxious and in a very marked manner with bearings for hubs of motor vehicles and generally with bearings subjected to considerable stress for long duration.

It is an object of the present invention to provide a process for the preparation of an improved composition of lubricating grease.

It has been found in fact that by preparing in one single operation and with suitable specifications as described hereinafter, greases based on mixtures of lithium soaps and organoph-ilic bentonites, the products obtained have different characteristics definitely superior as compared with those displayed by greases obtained by starting from the same raw materials but preparing separately -a lithium soap grease and one based on organophilic bentonites and then mixing them with each other.

According to the process of the present invention the operating procedure is as follows: the organophilic benteonite and lithium stearate, both conveniently dosed, are incorporated with the mineral oil, heating between 50 and 100 C. if oils having elevated viscosity are involved, in such a manner as to obtain a homogeneous mixture free from nodules, whose consistency may vary according to the kind of oil employed and to the concentrations of the thickeners; anhydrous methanol is added, acetone and one of the other dispersing agents normally employed in the proportion of 1-2% and the mixture is treated in a colloid mill or other analogous apparatus in such a mannet as to obtain maximum consistency, in relationship to the content of thickeners; the mixture is heated slowly under continuous agitation to expel the dispersing agent; heating is continued as well as agitation until attaining a temperature not lower than 225 C. and not higher than 280 C. On reaching the desired temperature, the grease is poured into a special container wherein it is cooled down.

By this process a whole series of greases with diiferent percentages of lithium stearate and of Bentone Were prepared and always highly stable greases were obtained, which were stable during storage as well as during operation on test hearings in the laboratory and on the road.

In general it can be said that greases so prepared have shown a behavior in duration and in lubricating quality higher than that of the best greases already existing in the trade, in the course of comparative tests carried out on the bearings of the front wheels of motor vehicles.

In the lubricating greases prepared according to the present invention, it has been found that, in addition to the composition, the method of preparation is mainly determining, since the latter has influence upon the intimate structure of the product and, therefore, upon its exploits.

it has also been found that :difierences are noted according to the kind of oil used, and said diiferences are more marked and the grade of the grease is better, if the oils employed have higher viscosity. In general the lubrieating oil employed is an oil having a viscosity higher than 40 Engler at 50 C.

The greases prepared by us have, as compared with those of identical analytic composition but obtained by mere mixing of a lithium soap greases with a bentone grease:

(l) Diiierent appearance and colour;

(2) Higher consistency;

(3) Superior adhesion to the bearing.

Observation in the infrared confirms, in a reproducible manner, strict qualitative differences between said greases. Though in fact in the grease as prepared according to the process of the present invention there is not observed the formation of chemical bonds proper, there is noted a perturbation of the SiO bonds of the Bentone, not observed in the greases prepared by mere mixing.

X-ray observation permits to establish that the grease prepared according to the process of the present invention undergoes a structural modification: Bentone 34 in fact presents a structure diiierent from that obtainable by mere absorption of the hydro-carbon molecules constituting the oil, at low temperature as well as at elevated temperature, as commonly found in known greases of the prior art.

The new structure is determined by the interaction of soap with Bentone 34.

The greases prepared according to the present invention are finally adapted to be corrected by additives such as graphite, molybdenum sulfide and other solid lubricants, In general revealing improved technical characteristics. the total content of lithium soap vand of organophilic ben tonite, with any ratios of the former to the latter, varies from 3 to 20% A series of experiments is reported hereinafter by way of example without limitation.

EXAMPLE 1 The technological tests efl'ected on this grease gave the following results:

Initial Penetration Loss in the penetration, after 100,000 A STM 1203 drum. double blows, 53 T test dram.

195 300 nil EXAMPLE 2 A sample of grease having the following composition:

% of Bentone 34 4% of lithium stearate 91% of mineral oil with high viscosity (VE =S3) was prepared operating as in Example 1, varying only the temperature, which was brought up to 240 C.

The technological tests gave the following results:

Initial Penetration Loss in the penetration, after 100,000 ASlM 1203- dmrn. double blows, 53 '1 test drnni.

260 330 traces EXAMPLE 3 A sample of grease having the following composition:

2% of Bentone 34 of lithium soap 88% of mineral oil (VE =l6) was prepared while operating as in Example 1.

The technological tests effected on this grease gave the following results:

Initial Penetration Loss in the penetration, after 100,000 ASTM 1263- dinin. double blows, 53 T test,

dninl. percent EXAMPLE 4 A sample of grease having the following composition:

4% of Bentone 34 10% of lithium soap 86% of mineral oil (Vi-3 :7)

was prepared While operating as in Example 1.

The technological tests efiected on this grease gave the Operating as in Example 1, a sample of grease having the following composition was prepared:

10% of Bentone 34 2% of lithium soap 88% of mineral oil (VE =l6) The technological tests carried out on this grease gave the following results:

Initial Penetration Loss in the 5 penetration, after 100,000 xsmr 1203- dmm. double blows, 53 '1 test dmin.

235 313 I absent EXAMPLE 6 Operating as in Example 1, a sample of grease having the following composition was prepared:

2% of Bentone 34 3% of lithium soap 95% of mineral oil (VE =7) The technological tests effected on this grease gave the following results:

Initial Penetration Loss in the penetration, after 100,000 ASTM 1263 (1mm. double blows, 53 '1 test,

drnrn. percent EXAMPLE 7 30 Greases corrected by additive molybdenum sulfide gave in the technological tests the results reported in the following table:

Table 1 Specific lead pressure Sample Percent of without at max. Type of additive seizure, lead withadditive kg. out seizure,

lrg/em.

40 1A 2 115 22, 990 975% Semicolloidal MoSz. 2B 1 21,800 As above. 413 1 95 20, 570 M08: in

powder form. Ninja corrected by addi- 00 15,600

From this table it will be seen that with the addition of a semicolloidal product definitely better results are obtained with 2% of additive, in fact an increase of the seizure load is noted by 25 kg. and a diminution of wears, working be it with medium loads, be it with elevated It will be noted that besides the consistency also the structure of the two types of grease is considerably different; the sample A appears nearly spinning (while the other one has gelatinous structure) and resists mechanical Work better. Hence it is possible to conclude that using a high viscosity oil for the preparation of a grease based on lithium and Bentone, there is obtained a product of a structure particularly suitable to avoid phenomena of canalization during operation on bearings.

EXAMPLE 9 Greases having the following compositions:

(a) 4% of lithium stearate 5% of Bentone 34 91% of high viscosity oil VE =30 (b) 4% of lithium stearate 5% of Bentene 34 91% of low viscosity oil VE =7.5

were prepared in the following manner:

(1) The two samples 1:: and 1b were prepared operating according to process known from the prior art, namely by dispersing the stearate in 50% of the oil, in the presence of 2% of methyl alcohol, heating up to 225 C.

v and cooling rapidly. In the other half of the oil, in the presence of 2% of methyl alcohol, there is dispersed Bentone 34; the mixture is ground to maximum consistency and the two greases so obtained are mixed and ground at room temperature.

(2) For other two samples 2a and 2b the lithium stearate grease was prepared as in (1), then the Bentone 34 grease was subjected to heating up to 225 C., after grinding; after the cooling down to room temperature, the two greases were mixed and ground.

(3) Finally the samples 3a and 3b were obtained by mixing lithium stearate, oil and Bentone 34 in the cold and in the presence of 2% of methyl alcohol, grinding the mass obtained and heating it up to 225 C., cooling then rapidly in a metallic vessel. Subjecting the above cited examples to tests of mechanical manipulation, the following results were obtained:

Table 2 From Table 2 there are noted between the greases of types 1 and 2 and the greases of type 3, be it utilizing high viscosity oils be it utilizing lower viscosity oils or, differences of characteristics to the entire advantage of greases of type 3, prepared according to the present invention, be it in the initial behaviour or be it in that during long-lasting tests.

The greases of Example 9 were observed by X-rays. The X-ray diffraction spectra obtained with the difiractometer equipped with Geiger are reported in FIGS. 1 and 1a of the appended drawings (for the samples 1a, 2a, 3a and 1b, 2b, 3b respecively).

The spectra are characterized by an intensive and common band due to the oil and by some more or less widened peaks due to the thickener; as can be observed from the following table, they differentiate two types of structure which we shall call at and ,8.

Table 3 Structure 0: Structure ,3 Greases 1 and 2 (a and b) Greases 3 (a and b) d (A) Intensity d (A Intensity observed observed strong 4244 Weak. medium medium-weak-.. 14-15 strong.

(1) Though the Bentone 34 has adsorbed, in all of the cases, some organic fluid bringing the distance of the siliceous layers from 24 A. to 42 A. approximately, the structural distribution or the type of fluid adsorbed are equal for the greases Nos. 1 and 2 (a and b) but differ for those No. 3 (a and b). During the preparation of the greases of type 3, samples were taken at various conditions of heating: the X-ray spectra reported in FIG. 2 of the appended drawings, show that:

(2) The structure of the on type begins forming with the mere mixing of the products;

(3) The passage from the a structure to the B structure begins at about 180 C. and is completed at about 220 C.;

(4) At about 180 C. the reflexions of the crystalline stearate disappear owing to the melting of the product which forms an isotropic solution with the oil.

The conclusion is that:

(a) The formation of the 5 structure is determined by the soap.

(b) The interaction between soap and Bentone is caused when the former, at elevated temperature, finds itself in solution in the oil: the adsorption of the oil, under these conditions, involves also the introduction of soap molecules between the Bentone layers.

(c) The presence of polar molecules such as those of the stearate disturbs the organization of the hydrocarbon molecules constituting the oil by varying the distribution of the electronic density among the siliceous layers of the Bentone.

These structural modifications are at the basic of the synorgism observed in the technological properties of the greases of type 3.

I claim: 7

1. A process for preparing improved lubricating greases comprising lubricating oil, lithium soap and organophilic bentonite, characterized in that the lithium soap and the organophilic bentonite total content, in any ratio of the former to the latter, varies from 3 to 20%, and in that the lithium soap and the organophilic bentonite are homogenized in the lubricating oil and heated to a temperature of between 50 and C. until disappearance of nodules; then mixing with the mixture previously obtained a dispersing agent, selected from the group consisting of alcohols, ketones and esters, in the proportions of 1 to 2%, then treating the mixture obtained until the maximum possible consistency in relationship with the content of the thickeners is obtained, expelling the dispersing agent from the mixture by slow heating and under continuous stirring, and continuing heating and stirring until a temperature not lower than 225 C. and not higher than 280 C. is attained, and when that temperature is attained cooling the grease.

2. A process according to claim 1, characterized in that the lubricating oil employed is an oil having viscosity higher than 0 Engler at 450 C.

3. An improved lubricating grease obtained by the process according to claim 1.

4. An improved lubricating grease obtained by the process according to claim 1, and including from about 1% to 2% of a workable solid lubricating grease additive.

5. An improved lubricating grease obtained by the process according to claim 1, and including from about 1% to 2% of a solid lubricating grease additive selected '1? from the "roup consisting of molybdenum sulfide, and graphite.

6. An improved lubricating grease obtained by the process according to claim 1, and including from about 1% to 2% of a workable liquid lubricating grease dispersing agent.

7. An improved lubricating grease obtained by the process according to claim 1 and including from about References Cited in the file of this patent UNITED STATES PATENTS McCarthy June 14, 1955 Sawyer et a1. June 27, 1961

Claims (1)

1. A PROCESS FOR PREPARING IMPROVED LUBRICATING GREASES COMPRISING LUBRICATING OIL, LITHIUM SOAP AND ORGANOPHILIC BENTONITE, CHARACTERIZED IN THAT THE LITHIUM SOAP AND THE ORGANOPHILIC BENTONITE TOTAL CONTENT IN ANY RATIO OF THE FORMER TO THE LATTER, VARIES FROM 3 TO 20%, AND IN THAT THE LITHIUM SOAP AND THE ORGANOPHILIC BENTONITE ARE HOMOGENIZED IN THE LUBRICATING OIL AND HEATED TO A TEMPERATURE OF BETWEEN 50 AND 100*C. UNTIL DISAPPEARANCE OF NODULES; THEN MIXING WITH THE MIXTURE PREVIOUSLY OBTAINED A DISPERSING AGENT, SELECTED FROM THE GROUP CONSISTING OF ALCOHOLS, KETONES AND ESTERS, IN THE PROPORTIONS OF 1 TO 2%, THEN TREATING THE MIXTURE OBTAINED UNTIL THE MAXIMUM POSSIBLE CONSISTENCY IN RELATIONSHIP WITH THE CONTENT OF THE THICKENERS IS OBTAINED EXPELLING THE DISPERSING AGENT FROM THE MIXTURE BY SLOW HEATING AND

Images