US 3069387 A
Description (OCR text may contain errors)
3,06%,337 THTXQTRQPMZ THREAT) LUBRHCANT Lloyd it. Alien, Eelmont, and Dudley H. Woodard, Cambridge, Mass, assignors, by rnesne assignments, to Kenmore Research Company, Framingham, Mass., a corporation of (thin No Drawing. Filed June 1, 1956, Ser. No. 588,626 3 (Claims. (Cl. 252-495) This invention, relating as indicated to thixotropic lubricants, is particularly directed to a thixotropic thread lubricant adaptable for use over a Wide range of temperatures, especially under 400 F. The lubricant is characterized by reducing the galling between threaded members of stainless steel, titanium, aluminum and the like, and employs a relatively high concentration of powdered polytetrafiuoroethylene, i.e., Teflon, and a mild pressure lubricant in a thixotropie gelling agent, such as Bentone 34.
in the prior art, various types of lubricants, greases and thread lubricants have been known, but these have had certain limiting conditions and have not had as low a co-eflicient of friction as was desirable, particularly over a wide temperature range.
This invention relates, then, to a thread lubricant having a mild pressure, wetting type lubricating oil, such as castor oil with an organophilic gelling agent, such as Bentone 34, and powdered polytetrafiuoroethylene, which will be referred to hereinafter for simplicity as Teflon.
An object of this invention is to provide a new and improved lubricant, particularly a thread lubricant, having a spacer or cushioning element which will prevent locking of the threads A further object of this invention is to provide a nonsettling thixotropic lubricant which will have permanently suspended therein spacer particles of small size of polytetrafiuoroethylene to cushion the locking action of the threads.
In connection with this invention, Teflon is employed because of its good anti-friction properties, and it is intended to be used in specific sizes, viz., 1 to 20 microns in "dimension, i.e., 1 to 20 millionths of a meter. This will be less than the average (root mean square) size of the asperites of the threaded particles, yet small enough to fill depressions on the tops of the asperites.
in this connection Teflon is characterized by its low modulus of elasticity and its extremely low co-efflcient of friction. The modulus of elasticity of Teflon is important because it means that each of these little particles of Teflon serves as a rider or cushioning element for the asperite and can be deformed by the asperite rather than serving as rigid particles which would increase the friction. When they are small enough and have a low enough modulus, they tend to bend elastically and permit the surfaces to glide with respect to one an other. A partial explanation of the low co-eflicient of friction of Teflon with steel may be due to the low surface shear stress of Teflon.
Further in connection with this composition of Teflon particles of small size in a thixotropic lubricant containing a fatty acid base, mild pressure lubricating oil, it is intended to use castor oil. Castor oil is a good lubricant in that it bonds to the metallic surfaces, forming both a physical and a chemi-sorbed bond. With this lubricant, we intend to use a thixotropic gelling agent, such as Bentone 34, and Teflon.
The Teflon serves as a lubricating medium in itself, having a very low co-eflicient of friction. However, it would be ineffective if not held in position, i.e., in the thixotropic thread lubricant, so that it is ready to perform its function at the surface of the moving or gelling parts. It further will be held to the surface by the wetting action of the lubricating material such as castor oil. The combination of the thixotropic gelling agent and the mild pressure lubricant, which in this particular instance is a castor oil-Bentone mixture, has a considerably lower frictional co-eflicient with the Teflon than without it.
It will be seen from the foregoing that the Teflon in this combination acts in several ways. First, it acts as a barrier particle or spacer element so that the metal particle, such as steel, never would rub against the oppositely disposed surface and, in performing this function, it reduces the co-efiicient of friction. The material itself and in combination with the mild pressure lubricant has a particularly low co-eflicient of friction with a metal such as steel. The Teflon stays in position because of the wetting action of the mild pressure lubricant. The thixotropic gelling agent further increases the adherence of the mild pressure lubricant to the Teflon.
Under tests of threaded parts employing this combination of materials, the galling was greatly reduced by the action described.
As an example of these compositions and how they are made, the following is given. A standard composition for one batch might be 2000 cc. of castor oil; 160 grams of a thixotropic gelling agent, such as Bentone 34, which is dimethyldioctadecyl ammonium bentonite; cc. of acetone; and 730 grams of Teflon. The followlog are examples of the ranges that may be employed:
From the foregoing, it will be seen that Teflon may be used from 20 to 50 percent of the mixture with the balance being fluid, principally lubricating oil and the thixotropic gelling agent.
in these compositions, the powdered Teflon is processed as follows. Teflon is stored in a deep-freeze to prevent agglomeration. It is scraped through a stainless steel screen into the media, castor oil. This is to break up any agglomeration that may have been formed. If particles have been agglomerated in spite of these precautions by being stored for a time at higher temperatures, it is recommended that the Teflon be frozen and screened again. A limited amount of mixing and stirring is performed in the castor oil after the Bentone and acetone have been added, and these effectively make a thixotropic gelling agent and carrier for the Teflon; The Bentone 34 is, of course, an organophilic gelling agent suitable for use with castor oil. A Manton-Gaulin homogenizer was used to impart shear into the mixture. It may be possible under some conditions to use a high speed ball or rod mill, propeller agitation and heaters. A limited amount of agglomeration takes place in this means, but does not seem to harm the final product,
As additional examples of the manner in which this invention may be carried out, the minimum and maximum ranges may be used and have been used as examples, and compositions at varying points within the preferred range have been used.
While only a few examples have been given herein, other thixotropic lubricants containing Teflon are satisfactory, that is, any lubricant that is a wetting, mild pressure lubricant may be substituted for the castor oil if suitable thixotropic agents may be used in connection therewith. Examples of these might be sperm oil, soybean oil or mineral oil. Examples of other fluids that may be used are the diester fluids normally used as plasticizers, examples of which are trioctyl phosphate, ethyl azelate and diethylhexyl sebacate.
In connection with thread lubricants, particularly in the food and drug industries, we may use a lubricant of cottonseed oil and bentone, water and bentonite, or other combinations of these materials which would not contaminate the food or products with which they are used.
In addition to Teflon, We may also use Du Pont Teflon 3086, a sticky polytetrafluoroethylene polymer, in a proportion usually ranging from to 40 percent of the T efion powder used, i.e., this material may be used up to 40 percent of the entire mixture. As an example of this, we may use the following: castor oil, 1000 cc.; Teflon, 350 grams; Du Pont Teflon 3086, 34 grams; Bentone 34-, 80 grams; acetone, 40 cc. and possibly suitable coloring matter.
This invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments and examples are, therefore, considered in all respects to be illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.
1. A thixotropic thread lubricant having a proportion f. of ingredients as specified; castoroil 2000 cc. and additional ingredients in the following varying proportions: dimethyldioctadecyl ammonium bentonite from to 400 grams; acetone from 25 to 200 cc.; finely powdered polytetrafluoroethylene from 1 to 20 microns in size from about 500 to 850 grams.
2. A thixotropic thread lubricant having a proportion of ingredients as specified: castor oil 2000 cc.; dimethyldioctadecyl ammonium bentonite from 120 to 170 grams; actone from about to cc.; finely powdered polytetrafluoroethylene from 1 to 20 microns in size from about 700 to 800 grams.
3. A thixotropic thread lubricant having a proportion of ingredients as specified: castor oil, 2000 cc.; dimethyldioetadecyl ammonium bentonite, of grams; acetone, 85 cc.; finely powdered polytetrafluoroethylene, from 1 to 20 microns in size, 730 grams.
References Cited in the tile of this patent UNITED STATES PATENTS 2,510,078 Compton et al June 6, 1950 2,510,112 Holbrook lune 6, 1950 2,531,440 iordan Nov. 28, 1950 2,644,802 Lontz July 7, 1953 2,679,479 Peterson et al May 25, 1954 2,746,887 ONeil May 22, 1956 2,824,060 White Feb. 18, 1958 2,833,720 Stratton May 6, 1958