CLAIM OF PRIORITY

[0001] This application claims priority from United States Provisional Patent Application Serial No. 63/069,486, filed on August 24, 2020, which is incorporated herein in its entirety.

FIELD OF THE INVENTION

[0002] This invention relates to a solid lubricant bar for lubricating the interface between the support pads of the cylindrical kiln shell and the inside diameter of the kiln tires of a hot rotary kiln.

BACKGROUND OF THE INVENTION

[0003] Hot rotary cylindrical kilns are used in cement plants, paper mills, and mineral processing plants to dry materials and to help chemical reactions take place. A hot rotary cylindrical kiln comprises a cylindrical kiln shell supported at axial intervals by kiln tires. The kiln tires in turn are supported on rotating trunnions. Filler bars or support pads are attached around the circumference of the cylindrical shell and frictionally engage the inside bore of the kiln tires. The resulting interface between the support pads of the kiln shell and the inside bore of the kiln tires requires lubrication. Because of the heat generated by the kiln, the lubrication may be provided in the form of solid lubricant bars placed between the support pads and the inside diameter of the kiln tires. The temperature of the kiln shell causes the solid lubricant bars to melt and distribute lubricant along the interface between the support pads and the inside bore the kiln tires.

[0004] The assignee of the present invention manufactures and sells a solid lubricant bar that comprises by weight: soy wax (60%), regular graphite (35%), and copper (5%). In addition, the prior art includes Lockett United States Patent No. 6,767,870 (the “870 patent”) and Lockett United States Patent No. 7,030,065 (the “065 patent”). Both the 870 patent and the 065 patent use an organophosphate (including triphenyl phosphate (TPP)) in their formulations. Such organophosphates are toxic and hazardous to the health of personnel, who must handle the solid lubricant bars. The TPP is added to the lubricant bar formulation of the 870 patent and the 065 patent in order to raise the auto-ignition temperature of the lubricant bars. Particularly, the formulations disclosed in the 870 patent and the 065 patent claim to have auto-ignition temperatures above 1000° Fahrenheit (F) (538° C). SUMMARY OF THE INVENTION

[0005] The present invention is a solid lubricant bar useful for lubricating the interface between the support pads of the kiln shell and the inner diameter of the kiln tires. The formulation of the solid lubricant bar of the present invention is free of toxic materials and has an auto-ignition temperature above 1000° F (538° C). The solid lubricant bar of the present invention is generally formed of hydrogenated castor oil or castor wax, expandable flake graphite, and copper. Alumina trihydrate (ATH) and magnesium hydroxide (MDH) can also be added to the formulation to enhance fire retardancy and suppression.

[0006] Further objects, features and advantages will become apparent upon consideration of the following detailed description of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0007] A solid lubricant bar in accordance with the present invention comprises the following formulation (1) by weight:

Hydrogenated castor oil or wax 60% Expandable flake graphite 35% Copper powder 5%

[0008] In the above formula, the hydrogenated castor oil or wax can range from 35% - 65% by weight, the expandable flake graphite can range from 30% - 60% by weight, and the copper can range from 5% - 15% by weight.

[0009] The specification for the hydrogenated castor wax MP 70 flakes is set forth in Table 1 below.

TABLE 1

Castor Wax MP 70 Flakes [0010] The hydrogenated castor wax MP 70 flakes can be procured from Acme Hardesty Oleochemicals of Bluebell, Pennsylvania. The designation MP 70 pertains to the melting point, 70° C. Other versions, including MP 60 and MP 80, are available with melting points of 60° C and 80° C respectively. [0011] Grade 3626 of expandable flake graphite is useful in preparing the formulation (1) above. The properties of the expandable flake graphite is set forth in Tables 2, 3, and 4 below.

TABLE 2 General Product Description Expandable Flake

TABLE 3

Typical Analysis (U.S. Standard Test Sieves) TABLE 4 Test Methods [0012] The grade 3626 expandable flake graphite can be procured from Asbury Graphite of

North Carolina Inc., 191 Magna Blvd., Lumberton, NC 28360.

[0013] Other grades of expandable flake graphite, shown in Table 5 below are also suitable for the formulation (1) above.

TABLE 5 Expandable Flake Graphite Grades [0014] The specification for the copper powder of formula (1) is shown in Table 6 below. TABLE 6 BR-83 UP Copper Color shade: Copper Pigment type: Cornflake pigment [0015] America Corporation, 4101 Camp Ground Road, Louisville KY 4021. [0016] The above formulation (1) may also include other solid lubricants instead of copper including sulphides, selenides, and tellurides (chalcogenides) of molybdenum, tungsten, niobium, tantalum, titanium (eg. WS2, WS2, MoSe2, TaSe2, TiTe2), monochalcenides (GaS, GaSe, SnSe), chlorides of cadmium, cobalt, lead, cerium, zirconium (eg. CdCl2, CoCl2, PbCl2, CeF3, PbI2), borates (eg. Na2B4O7), sulfates (Ag2SO4), or oxides (B2O3, MoO2, ZnO, Re2O7, TiO ₂ , CuO-MoO ₂ , NiO-Mo ₂ , PbO-B ₂ O ₃ , CuO-Re ₂ O ₇ ). [0017] When tested, the formulation (1) above achieved an auto-ignition temperature above 1000° F (538° C) and approached 1200° F (538° C). Because the formulation (1) comprises individual ingredients, each with proven lubrication properties, the combination of formula (1) provides a synergistic solid lubrication bar that is eco-friendly and avoids the use of toxic flame retardant compounds. Consequently, the formulation (1) provides superior lubrication performance when used with high temperature kilns. [0018] In some cases, a blend of zinc borate Zn[B3O4(OH)3], magnesium hydroxide (MDH), and alumina trihydrate (ATH) can assist in providing additional flame retardancy and fire suppression because of the different temperatures at which zinc borate, ATH, and MDH decompose to generate water molecules. The following formula (2) by weight is useful in implementing the solid lubrication bar of the present invention. Hydrogenated castor oil or wax 50% Expandable flake graphite 40% Copper powder 5% ATH 1% MDH 2% Zinc borate 2% [0019] In the above formula (2), the hydrogenated castor oil or wax can range from 40% - 60% by weight, the expandable flake graphite can range from 30% - 50% by weight, the copper can range from 3 % - 6 % by weight, the ATH can range from 2% - 5% by weight, and MDH can range from 2% - 3% by weight and zinc borate can range from 2% – 3% by weight. Formula (2) above has an auto-ignition temperature above 1000°F and provides superior lubrication performance when used with high temperature kilns. [0020] A formula (3) below is also useful in implementing the solid lubrication bar of the present invention. Hydrogenated Casor oil or wax 50% Expandable flake graphite 40% Copper Powder 5% ATH 1% MDH 1% Zinc borate 3% [0021] In the above formula (3), the hydrogenated castor oil or wax can range from 40% - 60% by weight, the expandable flake graphite can range from 30% - 50% by weight, the copper can range from 3 % - 6 % by weight, the zinc borate can range from 1% - 3%, by weight, and MDH can range from 1% - 2% by weight and ATH can range from 1% – 2% by weight. Formula (3) above has an auto-ignition temperature above 1000°F and provides superior lubrication performance when used with high temperature kilns. [0022] While this invention has been described with reference to preferred embodiments thereof, it is to be understood that variations and modifications can be affected within the spirit and scope of the invention as described herein and as described in the appended claims.