US3071543A

US3071543A - Solid lubricant containing compositions

Info

Publication number: US3071543A
Application number: US42238A
Authority: US
Inventors: Zell G Mcgee
Original assignee: MCGEE CHEMICAL Co Inc
Current assignee: MCGEE CHEMICAL Co Inc; MCGEE CHEMICAL COMPANY Inc
Priority date: 1960-07-12
Filing date: 1960-07-12
Publication date: 1963-01-01
Anticipated expiration: 1980-01-01

Description

annals Patented Jan. 1, 19613 3,071,543 SOLlD LUBRICANT CGNTAENENG CDMPOSITISNS Zeil G. McGee, Haverford, Pa, assignor to McGee Chemical Company, Inc, Upper Darby, P3,, a corporation of Pennsylvania No Drawing. Filed July 12, 1960, Ser. No. 42,238 8 Claims. (til. 252-45) This invention relates to lubricating compositions and more specifically it relates to lubricating compositions containing a solid lubricant suitable for use at high temperatures under extreme pressure loads. This application is a continuation-in-part of my copending application Serial No. 772, 634, filed November 10, 1958, and now abandoned, entitled Solid Lubricant Containing Compositions.

The lubrication of the chains in bakery ovens is a typical example of a difficult problem in lubrication since high temperatures, i.e. up to 500 F. are regularly encountered with loadings in the extreme pressure range. Numerous types of lubricants have been developed heretofore to solve such problems of lubrication but each proved to be inadequate for one or more reasons.

One of the earliest lubricants and one which is still in use comprises a solid lubricant such as graphite dispersed in kerosene. In order to apply this lubricant, however, it is necessary to cool the oven chains to at least 200 F. and preferably lower because of the low flash point of the kerosene. Once the lubricant has been applied the kerosene must be removed by heating in order to deposit the graphite onto the bearing surfaces. On numerous occasions when the chains have been heated too rapidly after lubrication, explosions and fires have occurred which have resulted in severe injuries to personnel. Moreover, the kerosene smokes badly as it is being removed and it also gives off very obnoxious odors. Since the flavor of bread as well as the flavor of other bakery products is extremely sensitive to odors, it is necessary to employ lubricating compositions which will not give off obnoxious odors when the liquid vehicle is vaporized. Kerosene and similar petroleum hydrocarbons generally contain mercaptans and other sulfur compounds which, although they may be present in very small amounts, have such obnoxious odors that when the hydrocarbons containing them are vaporized strong and penetrating odors are produced. In addition they carbonize some- What on the metal surfaces, which interferes with smooth lubrication and operation of the chains.

Polymer oils such as the polyisobutylenes were thought to be suitable as a vehicle for solid lubricants since these were produced synthetically from compounds free of sulfur and similar odor causing elements and since they decomposed upon heating into their monomers, i.e. they depolymerized, so that carbonizing was avoided. Lubricants containing polyisobutylene as the dispersing agent for the solid lubricant were found to be unsuitable since at the lower viscosity levels which would provide suflicient lubrication and penetration of the lubricant, the fire and explosion hazard was too great, while if a higher molecular weight polyisobutylene was employed to reduce the fire hazard the lubricant did not penetrate because of its high viscosity and thus the solid lubricant could not form a film over the bearing surfaces. Subsequently to avoid the fire hazard and provide a sufficiently low viscosity a third type of lubricant was formulated which consisted of a dispersion of the solid lubricant in water. It was found that the evaporation rate was too rapid to permit the lubricant film to penetrate and form over the bearing surfaces and since the metal surfaces were not covered completely they developed rust and seized.

A composition now has been found which can be applied without cooling the ovens from their normal operating temperatures of around 400 F. and which substantially completely avoids the dangers of fire and explosions. This lubricant composition provides an improved vehicle for depositing the solid lubricant onto the hot bearing surfaces. This vehicle does not carbonize, its viscosity and evaporation rate are controlled to provide maximum contact of the solid lubricant with the bearing surfaces and it prevents rusting and corrosion of adjacent parts of the machinery. Moreover, the vehicle may be vaporized from the hot bearing surfaces without the projection of any objectionable smoke or odors.

Accordingly it is an object of this invention to provide ew and improved lubricating compositions.

It is another object to provide new and improved extreme pressure lubricants.

It is another object to provide new and improved extreme pressure lubricants capable of high temperature application and use.

It is another object to provide a new and improved lubricating composition which Will deposit a solid lubri cant uniformly over hot bearing surfaces which are sub ject to extreme pressure loads such that wear and corrosion are minimized.

Additional objects of this invention will be apparent from the description and claims that follow.

in accordance with the present invention, and in its broadest aspects, a lubricating composition is provided wherein a solid lubricant is dispersed in an emulsion of a specific synthetic oil and water. In its more specific aspects, the lubricating composition described may also contain certain other components which may or may not be required dependent upon the specific use of the lubricant but which add to the usefulness of the finished composition as will be described in detail.

The solid lubricants which may be used in the present composition are those materials which because of their plate-like molecular structure are peculiarly suited for the dry lubrication of metal bearing surfaces. Graphite and molybdenum disulfide are examples of these materials which are useful for lubricating metal bearing surfaces and are the preferred solid lubricants for this invention. j

The specific synthetic oils which are emulsified with Water to provide a vehicle for the graphite or molybdenum disulfide solid lubricant are the polyalkylene glycols such as the polyethylene glycols and the polypropylene glycols. The polyethylene glycols are particularly preferred. These pre-erred glycols are the oil soluble high molecular weight glycols which range in molecular weight from to about 2000. A particularly preferred glycol is a polyethylene glycol having a viscosity of 400- Saybolt Seconds Universal at 000 F., a flash point of 490 F. and a fire point of 585 F. A second preferred glycol is a polyethylene glycol having a viscosity of 300 Saybolt Seconds Universal at 100 F. These glycols are the wellknown commercially available polyalkylene glycols sold under the trade name of Ucon fluids. The first of the above-mentioned preferred compounds has the specific designation Ucon LB-400X and the second preferred compound, Ucon LB-300-X. In particular, those glycols having a viscosity ranging between about '70 and 500 Saybolt Seconds Universal at 100 F. are suitable for use in the composition of this invention.

It has been found necessary to employ an agent which will assist in emulsifying the above described synthetic oils and water to produce a stable emulsion. In addition, it is necessary that such emulsifying agent when vaporized along with the water and oil from the hot bearing surface will not decompose to give compounds having obnoxious odors.

Certain polyoxyalkylene compounds have been found to be particularly suitable as emulsifying agents for the synthetic oil, solid lubricant and water composition of this invention. In addition, these polyoxyalkylene compounds because of their surface activity, behave as wetting agents which promote the uniform distribution of the water emulsion over the metal surfaces and thus promote proper coverage and adherence of the solid lubricant to the metal bearing surfaces. The specific polyoxyalkylene compounds which provided the combination of emulsification characteristics and wetting characteristics are those compounds which are sold under the trade name of Pluronics, These preferred compounds are so-called block polymers. They are prepared by adding propylene oxide to the two hydroxyl groups of propylene glycol. The resulting polyoxypropylene chain has hydrophobic properties and can be made to any controlled length varying in molecular weight from 800 to several thousand. Ethylene oxide is added to both ends of the polyoxypropylene hydrophobic base to give the polyoxyethylene hydrophilic groups on the ends of the molecule. This reaction may be controlled so that the hydrophilic groups have a controlled length such that they constitute from percent to 90 percent by weight of the final molecule. The Pluronics particularly preferred for the combination emulsification and wetting agent of this invention are the liquids in which polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 and preferably about 1750 with from 10 weight percent to approximately 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups. A particularly preferred Pluronic is the Pluronic L62 wherein the hydrophobic base has a molecular weight of 1750 and percent by weight of the molecule consists of the hydrophilic polyoxyethylene groups.

It has been found that at the high temperatures of application and use the instant lubricating compositions have a tendency to foam, consequently it is preferable although not necessary to employ an anti-foam agent. Agents particularly suitable are the silicones such as dimethyl silicone and other commercially available materials. They are preferably introduced into the oil prior to emulsification in amounts ranging between 5 and 50 parts per million based on the oil. By introducing anti-foam agents prior to emulsification excessive foaming during the emulsification stage is avoided.

Since these emulsion lubricating compositions often develop mold upon standing for any appreciable length of time before use, it is preferable to prevent this by the addition of an anti-mold agent such as thymol, chlorthymol or similar compound, generally contained in alcoholic solutions, in amounts ranging between 0.01 percent and 0.1 percent by weight based on the weight of the final composition. It is preferable to add the thymol solution to the mixture after the introduction of the solid lubricant into the emulsion.

The compositions of this invention are prepared by emulsifying from 3 to 300 parts by weight of the polyalkylcne glycol in 375 parts by weight of water using from 0.2 to 125 parts by weight of one of the above described polyoxyalkylene emulsifiers. The weight of the glycol should not be more than 15 times the weight of the emulsifier, and preferably the weight of the glycol should range from about 2 to about 4 times the weight of the emulsifier. The oil is preferably emulsified with the water by means of a homogenizer, colloid mill or similar device in order to produce a stable emulsion. From 1 to 100 parts by weight of the solid lubricant, i.e. graphite or molybdenum disulfide, is dispersed in the emulsion of oil and water by conventional means such as a colloid mill. The antifoam agent is added to the glycol preferably before emulsification and the anti-mold agent is added to the final composition.

The composition thus prepared is stable and may be used directly for the lubrication of hot bakery chains. If desired and for certain particular conditions of use the described emulsion may be diluted with additional quantities of water immediately prior to use, for example, with a quantity of water ranging from 2 to 20 times the weight of the original emulsion. It will be understood, however, that such diluted emulsions do not possess the same stability characteristics or lubrication characteristics as the aforementioned original emulsion.

The following example will serve to illustrate a specific embodiment of the invention.

Example An emulsion containing 56 pounds of polyethylene glycol having a viscosity of 62.7 Saybolt Seconds Universal at 210 F. and 300 Saybolt Seconds Universal at 100 F., a flash point of 490 F. (ASTM Method D9252) and a fire point of 585 F. (ASTM Method D9252) designated by the trade name Ucon-LB-300X was emulsified in 375 pounds of water using 22 pounds of polyoxyethylene-polyoxypropylene emulsifying agent (Pluronic L62). Prior to emulsifying the glycol with the water, 10 parts by million by weight of dimethyl silicone were added to the glycol. After the emulsion of glycol and water had been produced, pounds of finely divided molybdenum disulfide were dispersed therein by means of a colloid mill to produce the lubricant composition. Approximately 25 grams of thymol dissolved in 50 cc. of isopropyl alcohol were added to the final composition as an antimold agent.

This composition was found to be completely successful in overcoming the disadvantages outlined hereinbefore of prior art lubricants. When applied on the hot surfaces of bakery oven chains, rollers and bearing surfaces the rate of evaporation was sufficiently low so that the lubricant penetrated the remotest parts before the evaporation of the water and oil was completed. Upon completion of the evaporation of the water portion of the lubricant leaving a thin, durable coating of molybdenum disulfide was completely dispersed.

The molybdenum disulfide was deposited throughout the various parts and when the temperature reached approximately 490" F., the glycol was completely volatilized leaving a thing, durable coating of molybdenum disulfide bonded to the bearing surfaces.

As an added advantage it was found that upon application of this lubricant composition the various parts were flushed clean of rust and other corrosive products which had developed previously during the use of inadequate lubricating compositions. It was found after successive applications of the lubricant of this invention that the bearing surfaces and adjacent parts were thoroughly cleaned and freed of rust with the result the molybdenum sulfide lubricant was bonded to the clean bearing surfaces and provided a durable efficient lubricating film.

It was also found that the volatilization of the liquid portion of the lubricant composition was accomplished without the formation of any obnoxious odors or smoke since there were no sulfur or similar odor producing compounds either in the oil phase of the emulsion or in the emusifying agent. In addition the composition provided rust protection throughout its period of use.

For most efficient lubrication, if graphite is used as the solid lubricant, it should be as pure as possible and free of abrasive type materials such as silica-containing materials. Either the so-called fine or coarse grades of molybdenum disulfide may be used although it is preferable that the particle size of the molybdenum disulfide have an average size of approximately one-half micron in cross sectional diameter since this material is more easily dispersed in the lubricant composition and bonded to the bearing surfaces.

I claim:

1. A lubricating composition consisting essentially of from 1 to parts by weight of a solid lubricant having a plate-like molecular structure selected from the group consisting of graphite and molybdenum disulfide dispersed in an emulsion of 3 to 300 parts by weight of a polyalkylene glycol synthetic oil selected from the group consisting of polyethylene glycols and polypropylene glycols, said glycols having a molecular weight in the range from 100 to about 2000 and having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from weight percent to about 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyalkylene glycol is not more than times the Weight of the polyoxyalkylene emulsifier.

2. A lubricating composition consisting essentially of from 1 to 100 parts by weight of molybdenum disulfide dispersed in an emulsion of 3 to 300 parts by weight of a polyalkylene glycol synthetic oil selected from the group consisting of polyethylene glycols and polypropylene glycols, said glycols having a molecular weight in the range from 100 to about 2000 and having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from 10 weight percent to about 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyalkylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier.

3. A lubricating composition consisting essentially of from 1 to 100 parts by weight of graphite dispersed in an emulsion of 3 to 300 parts by weight of a polyalkylene glycol synthetic oil selected from the group consisting of polyethylene glycols and polypropylene glycols, said glycols having a molecular weight in the range from 100 to about 2000 and having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from 10 weight percent to about 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyalkylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier.

4. A lubricating composition consisting essentially of from 1 to 100 parts by weight of a solid lubricant having a plate-like molecular structure selected from the group consisting of graphite and molybdenum disulfide dispersed in an emulsion of 3 to 300 parts by weight of polyethylene glycol having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from 10 weight percent to about 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of Water wherein the weight of the polyethylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier.

5. A lubricating composition consisting essentially of from 1 to 100 parts by weight of molybdenum disulfide dispersed in an emulsion of 3 to 300 parts by weight of polyethylene glycol having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at F., 0.2 to parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from 10 weight percent to about 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyethylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier.

6. A lubricating composition consisting essentially of from 1 to 100 parts by weight of graphite dispersed in an emulsion of 3 to 300 parts by weight of polyethylene glycol having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from 10 weight percent to about 40 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyethylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier.

7. A lubricating composition consisting essentially of from 1 to 100 parts by weight of a solid lubricant having a plate-like molecular structure selected from the group consisting of graphite and molybdenum disulfide dispersed in an emulsion of 3 to 300 parts by weight of a polyalkylene glycol synthetic oil selected from the group consisting of polyethylene glycols and polypropylene glycols, said glycols having a molecular weight in the range from 100 to about 2000 and having a viscosity ranging between about 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight ranging from about 1200 to about 2100 with from 10 weight percent to about 40 Weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyethylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier and the emulsion contains minor amounts of anti-foam and anti-mold agents.

8. A lubricating composition consisting essentially of from 1 to 100 parts by weight of molybdenum disulfide dispersed in an emulsion of 3 to 300 parts by weight of polyalkylene glycol selected from the group consisting of polyethylene glycol and polypropylene glycol and having a viscosity of 300 Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agent consisting of a liquid block polymer in which the polyoxypropylene hydrophobic base has a molecular weight of about 1750 with 20 weight percent of the molecule consisting of hydrophilic polyoxyethylene groups and 375 parts by weight of water wherein the weight of the polyethylene glycol is not more than 15 times the weight of the polyoxyalkylene emulsifier.

References Cited in the file of this patent UNITED STATES PATENTS 1,428,148 De Cew Sept. 5, 1922 FOREIGN PATENTS 716,354 Great Britain Oct. 6, 1954 OTHER REFERENCES Ucon Brand Fluid and Lubricants, booklet by Carbide and Carbon Corp, N.Y., 1957, pages 3 and 16.

Claims

1. A LUBRIACATING COMPOSITION CONSISTING ESSENTIALLY OF FROM 1 TO 100 PARTS BY WEIGHT OF A SOLID LUBRICANT HAVING A PLATE-LIKE MOLECULAR STRUCTURE SELECTED FROM THE GROUP CONSISTING OF GRAPHITE AND MOLYBDENUM DISULFIDE DISPERSED IN AN EMULSION OF 3 TO 300 PARTS BY WEIGHT OF A POLYALKYLENE GLYCOL SNYTHETIC OIL SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE GLYCOLS AND POLYPROPYLENE GLYCOLS, SAID GLYCOLS HAVING A MOLECULAR WEIGHT IN THE RANGE FROM 100 TO ABOUT 2000 AND HAVING A VISCOSITY RANGING BETWEEN ABOUT 70 AND 500 SAYBOLT SECONDS UNIERSAL AT 100*F., 0.2 TO 125 PARTS BY WEIGHT OF POLYOXYALKYLENE EMULSIFYING AGENT CONSISTING OF A LIQUID BLOCK POLYMER IN WHICH THE POLYOXYPROPYLENE HYDROPHOBIC BASE HAS A MOLECULAR WEIGHT RANGING FROM ABOUT 1200 TO ABOUT 2100 WITH FROM 10 WEIGHT PERCENT TO ABOUT 40 WEIGHT PERCENT OF THE MOLECULE CONSISTING OF HYDROPHILIC POLYOXYETHYLENE GROUPS AND 375 PARTS BY WEIGHT OF WATER WHEREIN THE WEIGHT OF THE POLYALKYLENE GLYCOL IS NOT MORE THAN 15 TIMES THE WEIGHT OF THE POLYOXYALKYLENE EMULSIFIER.