US3432431A - Grease - Google Patents

Description

United States Patent 3,432,431 GREASE Bill Mitacek, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Mar. 14, 1966, Ser. No. 533,851 U.S. Cl. 252-16 4 Claims Int. Cl. Cm 5/10 ABSTRACT OF THE DISCLOSURE A grease is improved as to at least one desirable property thereof without substantially further thickening same by cold dispersing in the grease at least one powdered polymer.

' This invention relates to an improved grease and the method for making same.

Heretofore greases have been made by thickening a suitable oil by use of soaps and/or by dissolving polymers in the oil at temperatures of at least 245 F. (U.S. Patents 3,169,114 and 3,112,270 to Mitacek and Graham).

Quite surprisingly, it has now been found that the grease of US. Patents 3,169,114 and 3,112,270 and other greases can be improved as to at least one desirable property thereof without substantially further thickening the grease by cold dispersing in the grease, i.e. not dissolving in the grease at temperatures of at least 245 F., at least one powdered polymer selected from the group consisting of ethylene polymers and propylene polymers, the at least one powdered polymer being subdivided so that the average particle diameter, defined as that diameter whereby all the polymer particles having smaller diameters constitute 50 weight percent of the at least one powdered polymer, is less than 300, preferably less than 150, still more preferably less than 100 microns.

Accordingly, the improved grease of this invention comprises a grease having dispersed therein in a powdered state the at least one polymer as above defined in an amount effective to improve at least one property of the grease without substantially thickening same.

It is important not to excessively thicken a grease because the grease must not be so viscous as to hinder the dispensing and/or the functioning of the grease. Thus, a problem solved by this invention is to improve at least one property of an already formed grease without further thickening same substantially.

Accordingly, it is an object of this invention to provide a new and improved grease. It is another object of this invention to provide a new and improved method for making grease.

Other aspects, objects, and the several advantages of this invention will be apparent to those skilled in the art from the description and appended claims.

Generally, any conventional and commercially available grease is amenable to this invention. The grease employed can have been thickened in any known manner such as by the use of soaps and/or by dissolving polymers in the oil at temperatures of at least 245 F., and the like.

Suitable greases includesubstantially any grade of flowable grease as defined by the National Lubricating Grease Institute (NL'GI). For example, NLGI grade grease from 000 to 6 can be employed in this invention. Also, greases having an ASTM D 217-52T penetration at 60 strokes in the range of 85 to 475 can be employed.

The lubricating oil bases which can be employed to make greases of this invention can be mineral, vegetable, or animal in nature, preferable lubricant bases having at least a major amount of mineral origin. Such oils include refined oils having a viscosity of from about 35 to about 240 SUS at 210 F. White mineral oil as well as other specialty oils can be used and among the preferred oils. Paraffinic oils which produce greases of low graininess are frequently used.

Thickeners for the oils can be employed in amounts up to 20 weight percent of the oil. Various soaps normally used to thicken greases can be used and they include metal salts of high molecular weight acids, for example, acids of 10 to 30 and preferably 16 to 24 carbon atoms, either synthetic or of animal or vegetable origin. Other carboxylic acids useful for making soaps of metal salts include those derived from tallows, hydrogenated fish oil, castor oil, wool grease, and rosin. Generally the alkali metal or alkaline earth metal or aluminum or lead salts of acids such as lauric, palmitic, oleic, stearic, and the like are used. One of the preferred soaps is the lithium soap of l2-hydroxystearic acid. While soaps of a general nature can be used in the greases of this invention, it should be understood that the invention is of use with soapless greases formed essentially from polymers and oil alone, with or without small amounts of additives such as rust inhibitors, antioxidants, and the like. Thus, polymers such as polyethylene and polypropylene can be employed as thickeners, together, alone, or in conjunction with other thickeners such as soap.

In preparing the greases applicable to this invention the thickeners can be dispersed in the oil using heat and agitation generally followed by milling which produces shearing of the mixture, and improves properties of the grease such as work stability. When polymers are employed as thickeners the oil is heated at a temperature sulficiently elevated so as to dissolve the polymer in the oil. For example, when polypropylene is used as at least part of the thickening agent, the oil is heated with stirring to a temperature of about 400 F. and stirred for from 30 to 40 minutes in order to dissolve the polymer. The greases are then cooled from the dispersing temperature to the milling temperature or they can be cooled to below the milling temperature and reheated either prior to or during milling, all of which is conventional in the art.

The milling can be carried out in colloid mills operated at high speed and relatively close clearance, for example, on the order of 3000 to 9000 rpm. and 0.001 to 0.003 inch clearance. Any conventional grease mill can be employed. A fulland complete discussion of grease milling is found in US. Patents 3,169,114 and 3,112,270, the disclosures of which are incorporated herein by reference.

Other materials normally used in greases can also be employed in the greases applicable to this invention. For example, additives such as rust inhibitors, antioxidants, fillers, pigments, perfumes and the like can be employed. Some examples of such materials include propylenediamine, phenyl-ot-naphthylamine, phenothiazine, mica, asbestos, powdered lead, powdered zinc, talc, alumina, titanium dioxide, molybdenum, disulfide, bentones, carbon black, nitrobenzene and the like. Generally, the amount of these modifiers is less than about 10 percent of the total weight of the grease.

The sub-divided polymers employed according to this invention are preferably homopolymers of ethylene, homopolymers of propylene, and non-rubbery copolymers of ethylene and propylene. Mixtures of homopolymers and/ or copolymers can also be employed. The ethylene polymers used in this invention are high density polymers, i.e. have a density at 25 C. of at least 0.94 grams per cubic centimeter. The propylene polymers can have a density at 25 C. of from 0.890 to 0.920 gram per cubic centimeter. The amount of sub-divided polymer incorporated in the grease will generally be in the range of from about 0.1 to about 10, preferably from about 0.5 to about 5, weight percent based on the total Weight of the greases.

Although any procedure giving equivalent results can be used, a preferred density determination method for the polymers employed in this invention is set forth in U.S. Patent 3,112,270, column 2, lines 39-64.

The ethylene polymers employed in this invention can include copolymers formed of ethylene with at least one other olefin of higher molecular weight, e.g. up to 8 carbon atoms per molecule. Examples of suitable comonomers include propylene, l-butene, Z-butene, l-pentene, l-octene, 4-methyl-l-pentene, 4-methyl-1-hexene, fi-methyl-l-heptene, 4-ethyl-1-hexene, and the like. Preferred copolymers include ethylene with propylene or l-butene. In general, ethylene makes up at least 95 weight percent of the copolymer. In forming such a polymer the monomer feed to the polymerization zone will ordinarily be at least 80 percent by weight ethylene. As the percent of ethylene in the copolymer is decreased the density of the polymer likewise is decreased 50 that the density limitation can be used as an indication of copolymer composition. In other words, if the density of the ethylene-containing copolymer is 0.940 or above, it will be suitable for the invention. The propylene polymers include copolymers as defined hereinabove for ethylene polymers including the propylene making up at least 95 weight percent of the copolymer. The melt index of the propylene polymer can vary widely; for example, from about 0.1 to about 25, preferably from 1 to 6 as determined by ASTM D 1238-62T, Procedure E.

The sub-divided polymers will have an average particle diameter as defined hereinabove. By average particle diameter it is meant the diameter of the particle if it is substantially spherical in which case the length, breadth, and thickness of the particle are all substantially equal. However, when the particle is irregular in external configuration so that the length is greater than the breadth and the breadth is greater than the thickness, the average particle diameter is taken to be the breadth since it is the intermediate dimension and it is this intermediate dimension which is generally the controlling medium in sieving and is almost always visible under the microscope. The average particle diameter whereat all those particles in the sub-divided polymer which have a smaller average diameter add up to 50 weight percent of the total weight of the sub-divided polymer can be obtained in any conventional and Well known manner such as by sedimentation, electronic analysis, or visual techniques such as the ASTM technique designated E20-51T and entitled Analysis by Microscopical Methods for Particle Size Distribution of Particulate Substances of Sub-Sieve Size. From these analysis techniques a plot can be made employing weight percent as the ordinant and particle diameter as the abscissa so that the particular particle diameter at which 50 weight percent of the sample is made up of particles having smaller diameters can be readily determined.

The sub-divided polymer or polymers can be incorporated into the grease by conventional blending machines, as in grease manufacturing discussed hereinabove. The incorporation of these sub-divided polymers must be carried out at temperatures below that which allow melting and/or dissolving of the polymer in the grease. In other words, the temperature of dispersion should be that which allows dispersion and retention of the polymers in the grease in the sub-divided, solid state. Generally, the dispersing operation should not be carried out at a temperature substantially exceeding 225, preferably 200 F. Good dispersions can be obtained by operating substantially at room temperature.

Example I Powdered polyethylene (Microthene 608) having an average particle diameter as defined above of less than 74 microns was incorporated into two greases in the amount of 1 weight percent based on the total weight of the grease. The powdered polyethylene was obtained from polyethylene having a density of 0.96 gram per cubic centimeter at 25 C. (ASTM D 1505-63T) and a melt index of 19.5 grams/10 minutes, (ASTM D 1238- 62T, Procedure E). The first grease, grease A, was prepared from solvent refined neutral Mid-Continent base oil of about 75 SUS at 210 F. which had been thickened with about 12 weight percent based on the total weight of the grease of mixed lithium fatty acid soaps of mixed even-numbered fatty acids whose carbon atom range per molecule varied from 14 to 22. The second grease, Grease B, was prepared from a solvent refined neutral Mid-Continent base oil of about 500 SUS at 100 F., a viscosity index of about 89. Grease B had been thickened by dissolving in the oil 1 weight percent based on the total weight of the grease of high density polyethylene (the pellets having a density of about 0.96 and a melt index of about 5) and by 9 Weight percent based on the total weight of the grease of a soap formed by saponifying a mixture of 3 parts methyl l2-hydroxystearate and 1 part of castor oil with a stoichiometric quantity of lithium hydroxide.

Grease A was formed by adding the soap-forming ingredients to the oil and heating the mixture to about 400 F. with agitation followed by cooling and milling at about 180 F. Grease B was formed by adding the high density polyethylene and the soap-forming ingredients to the oil and heating the mixture to about 400 F. with agitation followed by cooling and milling at about 180 F.

The powdered polyethylene was incorporated in separate portions of both greases A and B by blending in a Hobart mixer at about 75 F. for about 60 minutes.

Grease A and Grease B both with and without powdered polyethylene incorporated therein were then tested and the results were as follows:

TAB LE I n+1 wt. B+1 wt. percent percent Grease A powdered B powdered polyethpolyethylene ylene ASTM penetration, 60 strokes 273 281 272 265 Tlmken endurance, minfl. 3 72 5 7 5 Wheel bearing tests, grams leakage:

ASTM test 3 0.7 0. 4 Phillips modified test 4 15. 6 15. 1

Example II Several samples of a Mid-Continent solvent refined neutral oil which had a viscosity of 500 SUS at F. and a viscosity index of about 80 were thickened using varying amounts of conventional high density pelleted polyethylene having a density of about 0.96 gram per cubic centimeter at 20 C. (ASTM D 1505-63T) and a melt index of about 5 grams/ 10 minutes (ASTM D 1238- 62T, Procedure E), and using in each sample the same amount of a soap formed by saponifying a mixture of 3 parts of methyl 12-hydroxystearate and 1 part castor oil with a stoichiometric quantity of lithium hydroxide.

In Run 1 the oil was thickened into grease by adding 9 weight percent of the soap based on the total weight of the grease, the oil and soap being mixed with heating until the temperature reached 400 F. after a period of about 1 hour, 45 minutes.

In Run 2 the oil was thickened with 9 weight percent soap in the same manner as Run 1. To the grease of Run 2 was added 1 weight percent based on the total weight of the grease of powdered polyethylene having an average particle diameter of less than 74 microns and formed from the same polyethylene as defined in Example I. The powdered polyethylene was incorporated in the resulting grease by agitation at room temperature for about 60 minutes.

In Run 3 the oil was thickened with 9 weight percent soap based on the total weight of the grease and 1 weight percent of the pelleted conventional high density polyethylene thickening agent by adding the pelleted polyethylene simultaneously with the soap forming ingredients and heating, cooling, and milling as with Run 1. Thus, in Run 3 the pelleted polyethylene added was dissolved in the hot base oil as opposed to the powdered polyethylene in Run 2 being dispersed in cold base oil and retaining its original particulate form.

In Run 4 the oil was thickened by the high temperature incorporation of 9 weight percent soap and 2 weight percent conventional high density pelleted polyethylene using the same method as Run 3.

In Run 5 the oil was thickened by the high temperature incorporation of 9 weight percent soap and 1 weight percent conventional high density pelleted polyethylene using the procedure of Run 3 and thereafter I weight percent of powdered polyethylene was incorporated in the resulting grease at room temperature using the same method as Run 2.

Thus, in Runs 4 and 5 the same amount of polyethylene was present in the resulting grease. However, for Run 4 all the polyethylene was dissolved in oil during the preparation of the grease and for Run 5 half the polyethylene was present in the resulting grease in substantially the original particulate state. A table of the thickeners and powdered polyethylene present in the greases of Runs 1 through 5 is presented in Table II.

The greases from Runs 1 through 5 were tested with results as follows:

TABLE III ASTM Timken Apparent viscosity Run No penetration, Endurance, at 20 F., poise,

60 strokes 1 mini shear rate 200 sec: 3

1 ASTM D 217-521.

2 NLGISpokesman, Vol. XX, No. 9, p. 36 (1956), 7.5 lb. load.

8 ASTM D 1092452.

From Table HI a comparison of Runs 2 and 3 with Run 1 shows that with the grease having powdered polyethylene therein according to this invention, Run 2, the hardness of the grease was substantially the same (all falling in the NLGI range for grade 2 grease) while the lubrication endurance of the grease of Run 2 was substantially improved over that of the greases of Runs 1 and 3. Similarly, a comparison of Runs 1, 4, and 5 shows that the' grease according at this invention, Run 5, had substantially the same hardness as the other greases but also a substantially improved lubrication endurance over the greases of Runs 1 and 4. Thus, it is apparent that the improved results of this invention are obtained from the presence of this particulate, cold-dispersed polymer in the grease. Further, the higher apparent viscosity of the greases of Runs 3 and 4 show that those greases did not flow as well as the greases of this invention, i.e. Runs 2 and 5. Also, comparison of Runs 2 and 3 and Runs 4 and 5 show that the invention Runs 2 and 5 have advantageous apparent viscosities. Thus, the invention offers a new means for incorporating greater quantities of desirable polymer into a grease and enjoying its beneficial influence on lubricity yet without substantially changing the hardness (grade) or viscosity of the grease.

Reasonable variations and modifications are possible within the scope of this disclosiure without departing from the spirit and scope thereof.

I claim:

1. An improved grease consisting essentially of at least one polymer selected from the group consisting of ethylene polymers and propylene polymers in a sub-divided, substantially solid, dispersed state, said at least one polymer being present in an amount elfective to improve at least one property of said grease without substantially thickening same, said at least one polymer being sub-divided so that the average particle diameter, defined as that diameter whereat all the polymer particles having smaller diameters constitute 50 Weight percent of said at least one polymer, is less than 300 microns, said at least one polymer is dispersed in said grease at a temperature not greater than 225 F. to prevent melting and dissolving of said polymer, and said polymer is present in the amount of from about 0.1 to about 5 weight percent based on the total weight of the grease.

2. The grease according to claim 1 wherein said grease is formed from at least one grease having an ASTM D 217-52T penetration at 60 strokes in the range of to 475, said at least one polymer is present in the range of from about 0.1 to about 10 weight percent based on the total weight of the grease, and said at least one polymer is selected from the group consistig of polyethylene having a density at 25 C. of at least 0.94 gram per cubic centimeter, and copolymers of ethylene and l-olefins having a density at 25 C. of at least 0.94.

3. The grease according to claim 1 wherein said at least one polymer is a homopolymer of ethylene having a density at 25 C. of at least 0.940 gram per cubic centimeter, said polyethylene is dispersed in said grease at about room temperature and is present in the amount of from about 0.1 to about 5 weight percent based on the total weight of the grease, the average particle diameter of the polyethylene in said grease is less than microns and said grease was formed at least in part by dissolving at least one polymer in the base oil.

4. The grease according to claim 1 wherein said at least one polymer is a homopolymer of propylene having a density at 25 C. of at least 0.89 gram per cubic centimeter, said polypropylene is dispersed in said grease at about room temperature and is present in the amount of from about 0.1 to about 5 weight percent based on the total weight of the grease, the average particle diameter of the polypropylene in said grease is less than 100 microns, and said grease was formed at least in part by dissolving at least one polymer in the base oil.

References Cited UNITED STATES PATENTS 2,791,576 5/ 1957 Field et al. 25259 2,810,695 10/1957 Young et al. 25228 2,887,472 5/1959 Fotis 252-59 2,917,458 12/1959 Morway et al 25259 3,080,330 3/1963 Rudel et a1 25259 3,112,270 11/1963 Mitacek et al 25259 3,114,708 12/1963 Morway et a1 25212 3,169,114 2/1965 lMitacek et al. 25259 3,216,935 11/1965 MOP-Way et al 25259 3,271,311 9/1966 Morway et al. 25259 3,290,244 12/ 1966 Polishuk et al 25259 PATRICK P. GA-RVIN, Primary Examiner. I. VAUGHN, Assistant Examiner.

U.S. Cl. X.R. 25217, 59