US 3607746 A
Description (OCR text may contain errors)
United States Patent 11113,607,746
 Inventor Gerard P. Caruso  Reference Cited A 1 N xg'g g UNITED STATES PATENTS fi 29 1968 Re. 26,088 9/1966 Rulon-Miller et al 252/12  Patented Se 1971 3,078,237 2/1963 Creech et al 252/59  Assi nee oucom an 3,080,330 3/1963 Rudel et 31.... 252/59 g New York y 3,264,215 8/1966 Smith etal.... 252/12 2 .'.1 V 3, 3,258,319 6/1966 Cox 252/59 3,438,896 4/1969 Council at al 252/12 541 SURFACE COATED WAX-POLYMER LUBRICANT "9" 'W- wyma" COMPOSITIONS Assistant Examiner-l. Vaughn 6 Claims No Drawings Attorney-Harold L. Denkler  US. (I 252/12  Int. Cl Cl0m 5/22, ClOm 5/ l2, ClOm 5/02 ABSTRACT: Lubricant compositions consisting essentially of  Field of Search 252/12, free-flowing discrete particles of wax-polymer, the surface of 12.2, 12.4, 12.6 which is coated with a wetting agent and a solid lubricant.
SURFACE COATED WAX-POLYMER LUBRICANT COMPOSITIONS This invention relates to compositions to be used for lubricating railroad centerplates and for other heavy duty applications such as on caterpillar tractors, earth-moving equipment, etc., in which solid lubricants are necessary for satisfac tory performance. More specifically, this invention relates to lubricating compositions consisting essentially of free-flowing discrete particles of wax-polymer, the surface of which is coated with a wetting agent and a solid lubricant.
Changes in railroad car design and operating practices have demonstrated the need for lubricants of greater serviceability than those used in the past. With the addition of high-tonnage railroad cars into service, the problems of wheel-flange wear, lateral thrust on general bearings, centerplate wear, etc., have become more and more acute. To overcome these problems, there has been a general shift away from greases to the use of solid lubricants such as molybdenum disulfide, graphite, powdered lead, etc., as centerplate lubricants. A satisfactory means of conveying the solid lubricant to the centerplate, however, has not been found. When solid lubricants are applied in a grease mixture, the force on the centerplate quickly extrudes the grease carrying the solid lubricant with it before the solid lubricant can bond to the metal surfaces. Mixtures of solid lubricants and wax have offered some improvement but they still have a tendency to extrude, also the dispersion of the solid lubricant is not always homogeneous. The development of wax-polymer systems containing a homogeneous dispersion of solid lubricant, such as described in application Ser. No.
746,772 Smith-Cokes filed July 23, 1968 and now abandoned, has resolved some of these problems. Other approaches included utilizing plastic liners which proved to be relatively successful in reducing extrusion, but were extremely expensive and therefore have limited practical use. Petroleum solvents were also employed as carriers for solid lubricants, but these are relatively volatile and do not provide secondary lubrication as does a system employing grease, wax, or waxpolymer.
It has now been found that the problems of the prior art can be substantially overcome by employing lubricant compositions consisting essentially of discrete particles of waxpolymer coated with a wetting agent having a solid lubricant dissolved or dispersed therein.
The advantages of the compositions of this invention are immediately apparent. The wax-polymer particles, e.g., pellets, serve not only as the carrier-vehicle but also impart a tough lubricating film which adheres to the centerplate and allows sufficient time for the solid lubricant to bond to the metallic surfaces. It has an advantage over the homogeneous waxpolymer solid lubricant system, in that the solid lubricant is readily available on the surface of the pellets and thus increases the efficiency of use of the solid lubricant. The waxpolymer pellets are of sufficient consistency to resist extrusion from the centerplate as is often experienced with grease or simple wax carriers.
The wax-polymer pellets used in accordance with this invention can be prepared from any conventional wax by adding thereto sufi'icient polymer to enable the resultant mixture to be pelletized. The preferred waxes for this invention are petroleum waxes, either distillate or residual waxes, or any combination thereof. Distillate waxes are defined as those waxes which are derived from the refining of distillate lubricating oils, while the term residual waxes" refers to those waxes which are removed during the refining of residual lubricating oils. The preferred petroleum waxes generally have melting points of from about 120 to 180 F. The distillate waxes are generally paraffinic in nature, while the residual waxes may contain microcrystalline wax or high-melting point paraffins or both. Residual waxes may, however, be further refined (split) to produce separate wax fractions which are essentially microcrystalline or parafiinic in character.
The polymers used in the present invention can be characterized generally as having long chain backbones to which randomly and irregularly are attached side chains of no more than about 4 carbon atoms in length. Particularly advantageous polymers are copolymers of ethylene with terminally ethyleniliiil Rt lti 1.
wherein n ranges from about 15 to about 250. The acetate substituent occurs at random along the hydrocarbon chain, and thus the letter m" denotes the average number of ethylene units per vinyl acetate unit in the molecule, rather than the presence of regularly recurring units having the composition given within the brackets. The value of m ranges from 6.5 to 30, preferably from about 8 to 14.
The ethylene alpha-olefin copolymers which may also be used in accordance with the invention have the general linear configuration wherein n is an average integer from about 10 to about 50 (preferably 10 to 40), R is a hydrocarbyl radial having 1 to 4 carbon atoms and the unit (CH is an unbranched chain, the average molecular weight of the copolymers being between about 20,000 to 800,000 (preferably between about 200,000 and 400,000). Expressed as intrinsic viscosity (deciliters per gram), copolymers having intrinsic viscosities of between about 1.0 and 6.0 are preferred. Intrinsic viscosity is determined in decalin at 150 C. The mole ratio of ethylene to higher alkylene in the copolymer can be carried from about 60% to about 95%; however, more highly crystalline copolymers, i.e., those having from about to ethylene are preferred in order to avoid tackiness.
The aforementioned wax-polymer compositions are old and well known in the art. Also known are methods of preparing pellets (sometimes referred to as nibs) from these waxpolymer blends. An often-employed method involves pumping the molten wax-polymer blend through a die forming long strings" which are cooled then cut into desired lengths. The size and shape of the pellets are not critical in the present invention. Pellets must of course be large enough to be free flowing and avoid agglomeration after the solid lubricant is applied, but not so large as to make them difficult to use in the desired application. Especially suitable pellets are cylindrical in shape, and are approximately one-eight inch in length by one-eighth inch in diameter. The pellets generally comprise from about 5% to 30% of ethylene-vinyl acetate copolymer blended with petroleum wax. The copolymer contains approximately 25 to 28 mole percent of vinyl acetate.
Various types of solid lubricants are known to be useful in the lubrication of railroad centerplates. Solid lubricants which can be coated on wax-polymer pellets include but are not restricted to the following: molybdenum disulfide, graphite, red lead, zinc oxide, copperflake, powdered lead, and powdered zinc. Many other solid lubricants can also be applied to the surface of wax-polymer pellets employing the method of the present invention. The amount of solid lubricant coated on the pellets can vary from about 5% to about 30% by weight.
The lubricating compositions of the present invention can be prepared by moistening the wax-polymer pellets with a wetting agent, then stirring or mixing them in a vessel containing a predetermined amount of solid lubricants. An alternative method is to mix the wax-polymer pellets with the solid lubricant then slowly add the wetting agent which would complete the adhesion of the solid lubricant to the surface of the waxpolymer pellets. One other method of preparation is to blend the solid lubricant and wetting agent together and then add the wax-polymer pellets and stir until the pellets are completely coated.
The wetting or adhesive agent can be any material capable of causing the solid lubricant to adhere to the wax-polymer surface. Such materials include but are not restricted to mineral lubricating oils, synthetic lubricating oils such as polymerized olefins, esters and others, and synthetic fluids such as propylene oxide or silicon polymers. Mineral lubricating oil is especially preferred and can be obtained from any paraffinic, naphthenic, asphaltic, or mixed base crude. The viscosity of these oils may vary over a wide range, such as from about 50 to 6,500 SUS at 100 F. Mineral oils having viscosities of about 57 to 3,000 SUS at 100 F. are preferred. The coating operation can be performed at room temperature or any other temperature which is convenient.
The amount of wetting agent used should be sufficient to provide adhesion of the desired amount of solid lubricant to the surface of the wax-polymer pellet, yet should not be so great as to cause sticking or agglomeration of the pellets and retard their free flow properties. The percentage of wetting agent can vary from about 1% to by weight depending on its viscosity and the nature and amount of solid lubricant desired to be coated. For example, when mineral oil is used as the wetting agent with a relatively large amount of solid lubricant, e.g., of molybdenum disulfide as described in Example l, the amount of mineral oil which could be used ranged from 5.5% to 6.0% by weight. Compositions containing less than 5.5% by weight mineral oil resulted in the solid lubricant not completely adhering to the surface of the pellets, which compositions containing greater than 6% by weight resulted in agglomeration of the pellets.
The waxpolyrner pellets used in examples 1 to 7 were formed from a blend comprising distillate and residual petroleum waxes blended with ethylene-vinyl acetate copolymer. Typical composition of the pellets is as follows:
38.6% by volume, l40
refined wax) 12.8% by volume, 160 F.m.p., FRW
38.6% by volume l40 F.m.p. microcrystalline wax 10.0% ethylene-vinyl acetate copolymer containing about 25 mole percent of vinyl acetate(Elvax 360, commercially available from E. l. Dupont De Nemours Co.)
The following examples are illustrative of the invention:
F .m.p. (melting point), FRW (fully EXAMPLE l Wax-polymer pellets were moistened with 500 l-lVl (High Viscosity Index, viscosity index of 85 or greater) solvent neutral mineral oil then coated with 25% by weight molybdenum sulfide by mixing the components in a vessel at room temperature. The resultant product was freeflowing coated wax-polymer pellets position:
25.0% by weight molybdenum disulfide 69.5% by weight wax-polymer pellets 5.5% by weight 500 l-lVl neutral mineral oil having the following approximate com- EXAMPLE 2 5.5% by weight 500 l-lVl neutral mineral oil EXAMPLE 3 Wax-polymer pellets were moistened with 500 l-lVl neutral mineral oil then coated with 25% by weight red lead by mixing the components in a vessel at room temperature. The resultant product was free-flowing coated wax-polymer pellets having the following approximate composition:
25.0% by weight red lead 69.5% by weight wax-polymer pellets 5.5% by weight 500 l-lVl neutral mineral oil EXAMPLE 4 Wax-polymer pellets were moistened with 500 HVl neutral mineral oil then coated with 25% by weight zinc oxide by mixing the components in a vessel at room temperature. The resultant product was free-flowing coated wax-polymer pellets having the following approximate composition:
25.0% by weight zinc oxide 69.5% by weight wax-polymer pellets 5.5% by weight 500 l-lVl neutral mineral oil EXAMPLE 5 Wax-polymer pellets were moistened with 500 V1 neutral mineral oil then coated with 25% by weight copperflake by mixing in a vessel at room temperature. The resultant product was free-flowing coated wax-polymer pellets having the following approximate composition:
25.0% by weight copperflake 69.5% by weight wax-polymer pellets 5.5% by weight 500 l-lVl neutral mineral oil EXAMPLE 6 Wax-polymer pellets were moistened with 500 HW neutral mineral then coated with 25% by weight of powdered lead by mixing the components in a vessel at room temperature. The resultant product was free-flowing coated wax-polymer pellets having the following composition:
25.0% by weight powdered lead 69.5% by weight wax-polymer pellets 5.5% by weight 500 l-lVl neutral mineral oil EXAMPLE 7 Wax-polymer pellets were moistened with 500 HVl neutral mineral oil then coated with 25% by weight of powdered zinc by mixing the components in a vessel at room temperature. The resultant product was free-flowing coated wax-polymer pellets having the following composition:
25.0% by weight powdered zinc 69.5% by weight wax-polymer pellets 5 .5% by weight 500 HVl neutral mineral oil Further examples which are illustrative of the invention are:
EXAMPLE 8 Wax-polymer pellets are moistened with synthetic ester lubricant then are coated with 30% of molybdenum disulfide.
EXAMPLE E9 Wax-polymer pellets are moistened with a propylene oxide polymer then are coated with 5% of copperflake.
EXAMPLE l0 Wax-polymer pellets are moistened with a silicone polymer than are coated with 10% of powdered lead.
To demonstrate the effectiveness of the lubricating compositions of this invention, the coated pellets of Example 1 were applied to railway car centerplates. This lubricant composition has now performed satisfactorily for over 6 months.
1 claim as my invention:
1. A lubricant composition consisting essentially of freeflowing discrete particles of wax-polymer, the surface of which is coated with 1% to by weight lubricating oil wetting agent and 5% to 15% by weight solid lubricant, said wax-polymer comprising a blend of petroleum wax and 5% to 30% by weight of a copolymer of ethylene and a member selected from the group consisting of the ester of a saturated mono-carboxylic acid and a terminally ethylenically unsaturated aliphatic alcohol, and the ester of a saturated aliphatic alcohol and a terminally ethylenically unsaturated monocarboxylic acid and wherein said solid lubricant is a member selected from the group consisting of molybdenum disulfide, graphite, red lead, zinc oxide, copperflake, powdered lead and powdered zinc.
2. The composition of claim 1 wherein the copolymer is a member selected from the group consisting of ethylene-vinyl