MXPA99010611A - High-temperature, water-based lubricant and process for making the same - Google Patents

Abstract

It is disclosed a high-temperature lubricant comprising a water-base and minor effective amounts of borate, dextrin, graphite, xanthan gum, and an organic preservative. A powder for preparing a water-based high temperature lubricant is disclosed in which the powder comprises graphite and minor effective amounts of borate, dextrin, and xanthan gum. A continuous process for making the lubricant is also disclosed.

Description

LUBRICANT RESISTANT TO HIGH TEMPERATURES WITH WATER BASED, AND PROCEDURE TO PRODUCE THE SAME TECHNICAL FIELD The present invention relates to a water-based high temperature resistant lubricant and, more particularly, to a suspension of water-based graphite useful in metal and mineral shaping applications, and to a continuous process for producing the same .

BACKGROUND OF THE INVENTION Many metal forming operations are performed at a high temperature using dies, molds and the like. In such operations, lubricants and / or release agents are often used to reduce wear on the dies or molds, and to prevent the resulting metal products from adhering to the dies or molds. For example, a processing plant for fluidized iron ore reduction (FIOR) includes a hot briquette fabrication assembly, in which direct reduced iron briquettes (DRI) are formed using iron ore fines as feed. Such a process is described in the U.S. Patent. No. 5,082,251 given to hipp, which is incorporated herein by reference. The briquettes are resistant to oxidation during storage and shipping, and can be easily handled and loaded in steelmaking operations. In the briquetting process, fines, pieces, or pellets of reduced iron ore are typically dosed from a storage drum to a briquette making machine, such as those generally described in US Pat. No. 3,988,095 given to Mersh et al., And the U.S. Patent. No. 1,272,617, which are incorporated by reference. In a briquette machine, the material to be molded into briquettes is introduced by rollers that rotate in opposite directions, and compressed into briquettes in the line of contact between the pair of rollers, by means of molds or matrices with form of briquette embedded in the rollers. The fines, pieces or nodules of iron enter a feeding drum that is in the upper part of the briquette making machine, and are forced between the two counter-rotating rollers by a feeding screw. The rollers are equipped with briquette molds, which compress the fines into briquettes. The compaction is achieved by a combination of the high pressure between the rollers and the high temperature of the iron feed (approximately 900 ° C), which makes them more compressible. The roller temperatures are typically in the range of about 200 ° to 450 ° C. The pressure is maintained by means of hydraulic cylinders, which exert force against one of the two cylinders, one cylinder is fixed and the other cylinder is allowed to move, to prevent breakage if a piece of metal passes through the machine. Briquettes leave the machine in a coil, and then separate into individual briquettes. The briquettes can then be cooled in a tank full of water, and discharged on a conveyor, where moisture is removed by the heat remaining in the briquettes. In the past, dry powdered graphite has been used as a release agent on the briquette rollers used for the manufacture of DRI hot briquettes. However, dry graphite has not proved satisfactory because it does not consistently and uniformly adhere to the rollers, resulting in inefficient application of graphite, and a large loss of graphite during application, and a concomitant problem of dust control. of graphite. In addition, dry graphite is also relatively abrasive, resulting in greater wear on the rolls than is desired. Accordingly, it is an object of this invention to provide a lubricant and release agent for metal working which will do both, minimize wear on the forming rolls, and facilitate the release of the formed metal product. It is a further object to provide such a lubricant that can be applied efficiently to the rollers. It is a still further object to provide a continuous process for producing such a lubricant.

BRIEF DESCRIPTION OF THE INVENTION These objects, as well as others that will become apparent with reference to the following detailed description are achieved by a lubricant resistant to high temperatures, comprising a water base and effective lower amounts of borate, dextrin, graphite , xanthan gum, and an organic preservative. Additionally, a powder for preparing a water-based lubricant, resistant to high temperatures, comprising graphite and lower effective amounts of borate, dextrin, and xanthan gum is disclosed. The ranges for the components and preferred embodiments are described for both the liquid lubricant and the powdered precursor, as well as the procedures for producing the lubricant.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic representation of a continuous process for producing the lubricant of the present invention. Figure 2 is an alternative method to that shown in Figure 1 to produce the lubricant of the present invention.

DESCRIPTION OF THE PREFERRED MODALITY The high temperature resistant lubricant according to the present invention is exemplified by the following examples, which show ranges for the various components, expressed as a percentage of the total weight.

TABLE 1 The tap water can be any water of a quality suitable for industrial applications, and without harmful impurities. Its purpose is to transport the solid materials to the work zone, and to decrease the temperature of the matrix due to its evaporation. The preservative can be any material classified as a preservative, such as a biocide, that is suitable for fluids for metal work, paints, coatings, and / or suspensions. Its purpose is to protect the organic components of the microbiological decomposition suspension. Preferably, the preservative is a 50% solution of glutaraldehyde, such as Ucarcide 250 preservative available from Union Carbide or Ucar Carbon Company. Borax can be any material from the chemical family of inorganic borate, and preferably it is sodium tetraborate decahydrate, 10 molar powder. Its purpose is to control the pH of the suspension during storage and handling, and improve the lubricating power. This material can be obtained from U.S. Borax Co. Dextrin includes all the materials of the chemical family of dextrin, and is preferably more than 90% soluble in water. With the heat, the dextrin becomes a sticky adhesive, and finally decomposes into carbon, gases and ash. Dextrin Stadex 126, available from Staley Co. has provided satisfactory results. The graphite can be any material of the graphite chemical family, both natural and synthetic, and preferably has an average particle size of 30 microns, with a loss on calcination (LOI) greater than or equal to 70%, and more preferably 95 % and more. The graphite prevents the adhesion between the briquettes of iron and the mold of the briquettes. In practice, the synthetic graphite 5033 of Superior Graphite Co. It has provided excellent results. The xanthan gum can be any material from the chemical family of xanthan gum, and preferably has an average particle size of 175 microns. Xanthan gum is a suspending agent, and prevents solid particles from settling. Xanthan gum is available from Kelco under the trademark Kelzan. The preferred composition for the lubricant is as follows: TABLE 2 A powder for preparing a water-based lubricant, resistant to high temperatures according to the present invention is set forth in the following Table 3, which shows ranges for the various components as a percentage of the total weight.

TABLE 3 The preferred composition for the powder is set forth in Table 4.

TABLE 4 The lubricant can be produced in a batch process, using a tank and a propeller-type mixer. Preferably, the suspension is manufactured in a continuous automated process, which helps control costs through the minimization of labor, and the elimination of multiple start-up and shut-down procedures. In such a continuous process, the six raw materials are used (water, preservative, borax, dextrin, graphite and xanthan gum). With reference to Figure 1, a schematic representation of the generally designated process 10 is seen. The water is collected in a holding tank 12, and is pumped from the holding tank 12 by a metering pump 14 to an injection point 16 of liquid. A drum 18 containing the preservative is connected to a metering pump 20, and the preservative is combined with the water at the liquid ejection point 16. The combined stream of preservative and water is fed to a powder injector 22. The graphite, dextrin, borax, and xanthan gum are automatically unloaded from bulk bags, or similar bulk cargo containers, by screw conveyors 24a, 24b, 24c, and 24d, which are associated with the feeder hoppers 26a, 26b, 26c, and 26d, respectively. The screw conveyors automatically dose the respective ingredients to the powder injector 22, which combines the flow of water / preservative with the other ingredients with a minimum of air occlusion. The suspension is then transported from the powder injector 22 by a pump 28 to a high shear in-line mixer 30, which completely wet the insoluble solid particles, and completely dissolves the soluble solids in the fluid. The suspension is then transported via pipe to a container 32, which may be, for example, a tank truck or a large capacity tank. The ratio of the preservative to water is controlled by the dosing pumps 20, 14, while the ratio of the graphite, dextrin, borax, and xanthan gum is controlled by the speed of the screw feeder of each component, and the resulting velocity of the water / conservative combination pump. The speeds of the pumps 14, 20 and the screw feeders 24a, 24b, 24c, and 24d are controlled by computerized electronic motor frequency controls, which are well known. This general procedure can also be advantageously used to continuously produce lubricating suspensions in which the lubricating particles are not graphite, but are other solid lubricants, for example borax, boron nitride, molybdenum disulfide, talc, etc., and the liquid in which the lubricating particles are suspended is any of water, oil, or other hydrocarbon solvents and / or solvents. In an alternative process, the dry ingredients (graphite, dextrin, borax, and xanthan gum) are previously combined and added to the water / preservative in the powder injector 22 from a single screw conveyor 34 and hopper 36 feeder (see Figure 2). To prepare the powder, a powder mixer (not shown) is required. All components are added to the mixer, and mixed together until a uniform mix is achieved. The water-based suspended graphite lubricant described above has found particular utility in the manufacture of hot iron briquettes used in direct reduced iron processing plants. The application of the lubricant suspended in water directly to the sprinkler dies has resulted in energy savings due to the reduction in torque energy needed to rotate the briquette making rollers, and has extended the life of the rollers, reducing the friction between the rollers and the briquettes. The long life of the rollers has also increased production, due to the shorter time of work interruption and maintenance. The spray has proven to be an efficient method of applying the lubricant to the rollers, and the graphite lubricant is attached to the surface of the roller after the carrier evaporates. Because the lubricant is water based, evaporation of the carrier is environmentally safe. In addition, the use of the water-based suspension has reduced the problems of graphite powder control associated with the use of dry powdered graphite. While the invention has been described as particularly useful for the hot briquette manufacturing process, it should also prove to be equally useful as a matrix lubricant or mold release agent in forging and other metal and mineral forming operations in hot .

Claims (12)

1. RE IVINDICATIONS 1. A lubricant resistant to high temperatures, characterized in that it comprises a water base and effective minor amounts of borate, dextrin, graphite, xanthan gum, and an organic preservative.
2. 2. A lubricant resistant to high temperatures, comprising: between about 60% by weight and 80% by weight of water; between about 0.1% by weight and 1.0% by weight of borate; between about 5.0% by weight and 15.0% by weight of dextrin; between about 10.0% by weight and 30.0% by weight of graphite; between about 0.5% by weight and 1.0% by weight of xanthan gum; and between about 0.1% by weight and 0.3% by weight of an organic preservative.
3. 3. The lubricant according to claim 2, comprising about 69.8% by weight of water; approximately 0.5% by weight of borate; about 10.0% by weight of dextrin; about 19.3% by weight of graphite; about 0.2% by weight of xanthan gum; and about 0.2% by weight of an organic preservative.
4. 4. The lubricant according to claim 2 or 3, wherein the preservative is a 50% solution of glutaraldehyde; borate is a 10 molar pulverized borax; Dextrin is between 95% and 100% soluble in water; the graphite has an average particle size of 30 microns; and the xanthan gum has an average particle size of 175 microns.
5. 5. A powder for preparing a water-based lubricant resistant to high temperatures, comprising graphite and effective minor amounts of borate, dextrin, and xanthan gum.
6. 6. A powder for preparing a water-based lubricant resistant to high temperatures, comprising: between about 0.5% by weight and 2.0% by weight of borate; between about 31.0% by weight and 34.0% by weight of dextrin; between about 63.0% by weight and 66.0% by weight of graphite; and between about 0.5% by weight and 1.3% by weight of xanthan gum.
7. 7. The powder according to claim 6, comprising about 1.7% borate; about 33.3% by weight of dextrin; approximately 64.3% by weight of graphite; and about 0.7% by weight of xanthan gum.
8. 8. The powder according to claim 6 or 7, wherein the borate is a 10 molar pulverized borax; Dextrin is between 95% and 100% soluble in water; the graphite has an average particle size of about 30 microns; and the xanthan gum has an average particle size of 175 microns.
9. 9. A process for continuously producing a water-based lubricant containing suspended graphite, comprising: supplying water at a pre-determined rate and controllable by means of a first metering pump; supplying a conservator at a predetermined speed and controllable by means of a second metering pump; combine the water and the preservative, and inject the combined water and preservative into a powder injector; introduce pre-determined amounts of graphite, dextrin, borax, and xanthan gum to the powder injector, to combine them with the water and the preservative; pump water, preservative, graphite, dextrin, borax and xanthan gum to a high shear mixer; and introducing the resulting suspension in a container.
10. 10. The process according to claim 9, wherein the graphite, dextrin, borax, and xanthan gum are separately introduced to the powder injector by means of separate dosing worm feeders.
11. 11. The method according to claim 9, wherein the graphite, dextrin, borax, and xanthan gum are combined and introduced to the powder injector by means of a single dosing screw feeder.
12. 12. A continuous process for producing a lubricating suspension, comprising: supplying a liquid selected from the group consisting of water, oil, hydrocarbons and solvents at a pre-determined rate and controllable by means of a metering pump, and injecting the liquid into an injector of powders; introducing pre-determined quantities of lubricating particles from the group consisting of graphite, borax, boron nitride, molybdenum disulfide and talc to the powder injector, to combine the powder with the liquid; pump the liquid and lubricating powder to a high shear mixer; and introducing the resulting suspension to a container.