MX2008007429A - Barium sulfate product - Google Patents

Abstract

This invention generally relates to a barium sulfate product particularly useful as an X-ray contrast agent in preparations administered for examination of the gastrointestinal tract and to processes for making the product from naturally occurring barite ore containing barium sulfate crystals and gangue materials. The process includes treating or contacting the barium sulfate-containing particles obtained from barite ore with a fluidizing agent in a liquid medium to remove gangue materials present therein.

Description

BARIUM SULPHATE PRODUCT FIELD OF THE INVENTION In general, the present invention relates to a barium sulfate product and to processes for manufacturing the product from a barite ore containing barium sulfate crystals and gangue materials. The barium sulfate product can be used in the production of paints, rubbers and drilling fluids for the exploitation of oil and gas and is conveniently of medical grade and can be used in other different applications, including as a component of the pharmaceutical, veterinary compositions and cosmetics, particularly when a barium sulfate product having a "whiter" appearance is desired.

BACKGROUND OF THE INVENTION Barium sulfate is a radiopaque medium widely used as an X-ray contrast agent in the medical examination of the gastrointestinal tract. In general, for a gastrointestinal examination, the patient undergoing examination takes a suspension of barium sulfate in water, alone, or in combination with a carbon dioxide producing agent, such as BAROS effervescent granules (Mallinckrodt, Saint Louis, MO). The barium sulfate used is REF. : 191256 a voluminous fine, white, odorless, tasteless powder that is practically insoluble in water, in organic solvents and in acid and alkaline solutions. However, it exhibits some solubility in hot concentrated sulfuric acid. This extremely inert quality of barium sulfate makes it ideal as a radiopaque medium, since it is not absorbed by an intact mucosa and, therefore, is considered safe to administer for radiological use. A method used to produce medical grade barium sulfate, often referred to as the Mallinckrodt process, involves dissolving a finely divided barite ore in solution by means of an acid and then precipitating the barium ions from the solution as barium sulfate. using sulfuric acid. Due to the inert nature of barium sulfate, this is a very difficult and expensive procedure. Often, the formed barium sulfate precipitate still contains many impurities and must undergo a number of additional purification steps including leachate. In addition, in general, such precipitation processes produce a barium sulfate product comprised largely of particles of a size much less than about 1 micrometer. For use as a contrast agent in preparations for examination of the gastrointestinal tract, particularly examination of the upper gastrointestinal tract, it is often preferred that medical barium sulfate particles be larger than those typically produced by precipitation techniques. . Stone, U.S. Patent No. 4,119,700, discloses an alternative process for producing a medical barium sulfate product from a barite ore that does not require dissolution for purification, but instead isolates substantially pure barium sulfate crystals present in the ore. The process includes crushing the naturally occurring barite ore containing barium sulfate crystals and the gangue minerals to form a granular ore material, passing this granular ore through a high intensity wet magnetic separator to remove the particles magnetic particles and subjecting the non-magnetic fraction containing barium sulfate and minerals of low specific gravity to a gravity separation to separate a substantially pure barium sulfate fraction. The process further includes subjecting this barium sulfate fraction to additional grinding to achieve the desired particle size distribution (e.g., in the order of about 1 micron), leaching the finely divided barium sulfate fraction with a mineral acid. such as sulfuric or hydrochloric acid and wash the product leached with water to neutralize the leached acid. Although the teachings of Stone are useful to face some of the problems that are in charge of the production of medical barium sulfate by the techniques of precipitation, the product is not always satisfactory. Often the barium sulfate produced in this manner has a less desirable white or gray coloration. The gray coloration is believed to be attributed to impurities, such as silica and other persistent barite materials of barite ore. In addition, during the examination and investigation of the gastrointestinal tract, medical barium sulfate preparations are typically suspended in water for ingestion by the patient. The persistent gangue materials present in the barium sulfate component of the preparation can be separated and form an almost white or gray floating material in the suspension to be ingested by the patient undergoing examination. Therefore, there remains a need for more effective techniques for the manufacture of a medical barium sulfate product from a barite ore having an improved appearance (eg, a more "whiter" color more consistent) and other properties which make it more suitable for use as an X-ray contrast agent in preparations for examination of the gastrointestinal tract, as well as in other applications that require a cleaner, whiter barium sulfate product.

BRIEF DESCRIPTION OF THE INVENTION Briefly, the present invention relates to a process for the preparation of a barium sulfate product from a barite ore containing barium sulfate particles and gangue materials. The process comprises mixing barium sulfate-containing particles obtained from a barite ore with a fluidizing agent in a liquid medium to form a treated mixture comprising particles containing barium sulfate and fluidized gangue materials released from the sulphate-containing particles. of barium. The fluidized gangue materials are separated from the treated mixture and the particles containing barium sulfate are dried to produce the barium sulfate product. According to a preferred embodiment, the process for making a barium sulfate product from a barite ore containing barium sulfate particles and gangue materials comprises contacting the barite ore particles with a barite. leaching acid to leach the acid soluble impurities and produce a suspension comprising leached barium sulfate-containing particles having a reduced concentration of acid-soluble impurities, followed by washing the barium sulfate-containing particles leached with water. The washed barium sulfate-containing particles are mixed with a fluidization agent in a liquid medium to form a treated mixture comprising particles containing barium sulfate and fluidized gangue materials from the particles containing barium sulfate. The fluidized gangue materials are separated from the treated mixture and the particles containing barium sulfate are dried to produce the barium sulfate product. Other features of this invention will be partly evident and partly visualized below.

BRIEF DESCRIPTION OF THE FIGURE Figure 1 is a schematic diagram of a process for making a barium sulfate product from a barite ore containing barium sulfate and gangue materials according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, improved processes for producing barium sulfate products, which are particularly useful as X-ray contrast agents in gastrointestinal tract examinations, have been visualized. More specifically, the use of particular fluidization agents or fluidizers has been found to be a useful means of reducing the concentration of unwanted gangue materials in the medical grade barium sulfate products obtained from a barite ore that occurs naturally or that otherwise they undermine the appearance and other desired properties of the product. The use of a fluidizing agent according to the present invention is easily integrated into the processes known for the production of barium sulfate products from a barite ore that does not require dissolution and precipitation for the purification of the sulfate product of barium, but instead they insulate substantially pure barium sulfate crystals in the barite ore. These processes, including that described by Stone in U.S. Pat. No. 4,119,700, the disclosure of which is incorporated herein by reference, are generally known in the art and typically include milling (eg, grinding and pulverizing) of barite ore, classification of sulfate-containing particles, barium ground to the desired particle size, contact the barium sulfate-containing particles with an acid to leach and remove the acid-soluble impurities and wash and dry the barium sulfate product. In the practice of the present invention, these process operations can be carried out in a batch, semi-continuous or continuous manner. The operations can be carried out appropriately using a variety of apparatuses and process techniques well known to those skilled in the art and in some cases can be omitted or combined with other operations without departing from the scope of the present invention. In general, the process for isolating substantially pure barium sulfate crystals present in the barite ore is modified according to the present invention by mixing the barium sulfate-containing particles obtained directly from the barite ore (i.e., without requiring precipitation from the barite. barium sulfate) with a fluidizing agent in a liquid medium to form a treated mixture comprising particles containing barium sulfate and fluidized or released gangue materials from barium sulfate-containing particles. Fluidized gangue materials are typically present in the mixture treated as part of a floating layer. The fluidized gangue materials are separated from the treated mixture and subsequently the particles containing barium sulfate are dried to produce the barium sulfate product. As will be described in more detail below, the treatment of the barium sulfate-containing particles obtained from the barite ore with a fluidizer in a liquid medium to release and separate the gangue materials that form color can be integrated in different ways in a different manner. process for isolating the substantially pure barium sulfate crystals present in the barite ore.In addition to the substantially pure barium sulfate crystals, naturally occurring barite ore or barites contain many gangue materials, such as long pieces of iron oxides or hydrated iron oxides, iron carbonate, quartz or crystals. of silica, together with impurities of aluminum and chromium compounds. Iron compounds and silica are sometimes associated with each other (that is, as nodules or relatively large pieces of iron silicates). The types of gangue materials and their proportions can vary widely in relation to the barium sulfate content of the ore, being appreciated that the smaller amount of barium sulfate present in the ore, the greater the amount of ore that will have to be processed to obtain a given amount of barium sulfate product. An example of an analysis of a barite ore given by Stone in U.S. Pat. No. 4,119,700 described the following components: 74.4% of BaSO4; 18.6% FeC03; 5.6% of S? 02 and other miscellaneous gangue materials 1.4%. In general, the impurities based on oxide and carbonate present in the ore are removed by acid treatment leaving behind gangue materials not soluble in acids. Without considering the exact composition of the barite ore, it is the silica and other gangue materials present in the ore that may otherwise persist in the barium sulfate product and are believed to cause undesired coloring of the product and the floating material undesirable in barium sulfate suspensions administered for gastrointestinal tract examinations. The fluidization agent combined with the barium sulfate particles obtained from the barite ore is selected to be capable of fluidizing or releasing at least a portion of the present gangue materials and, should be relatively inert and non-harmful, should persist to any significant degree in the barium sulfate product intended for ingestion as part of an examination preparation of the gastrointestinal tract. The fluidizing agent can be in the solid or liquid form (for example, dissolved in solution) and dispersed or is at least partially soluble, preferably substantially soluble, in the liquid medium in which the particles containing barium sulfate are treated with the fluidizing agent. Preferably, an aqueous liquid medium comprising water is used. According to the present invention, the different fluidization agents have been identified that effectively reduce the concentration of gangue materials in barium sulfate-containing particles obtained from barite ore, particularly silica impurities. These suitable fluidizing agents include neutral gums, synthetic and semi-synthetic gums or polymers, biopolymers, chelating agents, salts of polyacid monomers, inorganic salts and mixtures thereof. Polymer fluidizers include natural gums, synthetic and semi-synthetic gums or polymers and biopolymers. Examples of the appropriate natural gums include carrageenan, alginate, gum arabic, gum arabic treated with NaOH, pectin and the like and mixtures thereof. Examples of suitable synthetic and semi-synthetic gums or polymers include low viscosity carboxymethylcelluloses, copolymers of ethylene and maleic anhydride or maleic acid, such as EMA 31, EMA 31 Na +, EMA 21, EMA 21 Na +, copolymers of methyl vinyl ether and maleic anhydride, such as GANTREZ Na + (GAF Corporation, New York, NY) and the like and mixtures thereof. Examples of suitable biopolymers include heparin, chondroitin sulfate and the like, and mixtures thereof. Other fluidizing agents include chelating agents, salts of polyacid monomers (eg, polycarboxylate salts) and inorganic salts. As used herein, polyacid monomers are polycarboxylic acid compounds having from 2 to 5 -COOH groups. As used in this, the salts are pharmaceutically acceptable salts. These suitable pharmaceutically acceptable salts include alkali metals (e.g., sodium and potassium), alkaline earth metals (e.g. calcium and magnesium) and organic bases (e.g., meglumine). Examples of the appropriate chelating agents include salts of polyaminocarboxylic acids, such as ethylenediaminetetraacetic acid (EDTA), cyclohexane-trans-1,2-diamintetraacetic acid (CDTA), diethylenetriaminpentaacetic acid and the like, other chelating agents such as lactic acid, acid N-β-ethanolamin-N, N-diacetic (for example, N-β-ethanolamin-N, N-disodium diacetate) and the like, and mixtures thereof. Examples of suitable acids of the polyacid monomers include alkali and alkaline earth metal salts of citric acid (eg, sodium citrate), nitrilotriacetic acid (eg, trisodium nitrilotriacetate), nitrile-trimethylene triphosphoric acid (eg, nitrile) Trimethylen triphosphite trisodium), inositol hexaphosphoric acid, N-β-ethanolamine-N, N-diacetic acid (for example, N-β-ethanolamin-N, N-disodium diacetate) and the like and mixtures thereof. Suitable inorganic salts include, for example, sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and the like and mixtures thereof. According to a preferred embodiment, the fluidizing agent comprises an alkali metal or alkaline earth metal polycarboxylate salt. Suitable polycarboxylate salts include salts of dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid and the like, and mixtures thereof, as well as salts of tricarboxylic acids, which include, but are not limit to, citric acid. Preferably, the polycarboxylate salt includes a hydroxyl substituent. Preferred polycarboxylate salts having a hydroxyl group include the salts of citric acid, isocitric acid, tartaric acid and malic acid. Examples of particularly suitable fluidization agents include EMA 21 Na +, GANTREZ Na +, gum arabic treated with NaOH, sodium citrate, trisodium nitrilotriacetate, trisodium nitrile-trimethylene triphosphite, sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and hexaphosphorate. of inositol. In a preferred embodiment, the fluidizing agent comprises sodium pyrophosphate. According to an especially preferred embodiment, the fluidizing agent comprises sodium citrate. Sodium citrate has been found to be especially effective in fluidizing or releasing gangue materials, particularly silica, from barium sulfate-containing particles obtained from a barite ore. Sodium citrate is often included as a component of conventional gastrointestinal tract examination preparations to produce a free-flowing X-ray contrast composition. Therefore, the persistence of some amount of sodium citrate used as a fluidizer in the barium sulfate product can provide an additional benefit. For the purpose of illustration of some embodiments of the present invention, a process for making a barium sulfate product from a barite ore containing barium sulfate and gangue materials will be described with reference to FIG. Figure 1 is a schematic diagram of a process for making a barium sulfate product from a barite ore including using a fluidizing agent to reduce the concentration of unwanted gangue materials. In the embodiment shown in Figure 1, the particles containing barium sulfate are treated with a fluidizing agent in a liquid medium, then the particles are subjected to an acid leaching operation and then to the neutralization of the leached material. Barite 1 ore containing barium sulfate and gangue materials, as obtained from the mine, it undergoes a grinding and sorting operation 3 until obtaining the particles of the ore containing barium sulfate 5 of desired size distribution. The barite ore, for example, can be subjected to an initial crushing taking care to keep the production of fine particles to a minimum. This can be done by means of a jaw crusher followed by a rotary shredder or other means known in the art. These coarse ore particles can then be subjected to grinding, for example, in a ball mill, roller mill or hammer mill, to further reduce their size and produce a granular ore, again with appropriate care to avoid overproduction of fines. After the particles are crushed and ground, the particles are then sorted by size to separate the fine particles and oversize particles from the barium sulfate-containing ore particles of the desired size. In general, barium sulfate-containing ore particles subjected to further processing have a particle size distribution that provides efficient acid leaching and allows the recovery of a final barium sulfate product having the size distribution of desired particle. However, because the final barium sulfate product is usually subjected to an additional grinding and classification operation, the particle size distribution of the barium sulfate-containing ore particles subjected to an active ingredient is not strictly critical. additional processing. The milled and graded barium sulfate-containing particles of the ore are then subjected to an acid leaching operation 7 to reduce the concentration of any acid-soluble gangue materials or impurities, such as salts and barium oxides soluble in acidic acids. iron and / or manganese, to meet applicable USP specifications. In general, the acid leaching operation comprises contacting barium sulfate-containing ore particles with a leaching acid in a suitable vessel (s) to leach acid-soluble impurities from the particles and produce a suspension 9 comprising particles containing leached barium sulfate having a reduced concentration of acid soluble impurities. Preferably, the leaching acid comprises a mineral acid. Examples of the appropriate mineral acids are sulfuric acid and hydrochloric acid. The proportion or concentration of the leaching acid used in the leaching operation can vary depending on the composition of the inlet barite ore and the desired composition of the final barium sulfate product. In general, higher concentrations of the leaching acid are required since the concentration of the acid-soluble impurities in the barite ore and / or the desired purity of the barium sulfate product increases with respect to the increase in the acid-soluble impurities. Typically, appropriate results are obtained in the leachate operation by contacting the barium sulfate-containing ore particles with sulfuric acid or hydrochloric acid at a concentration sufficient to produce a leached mixture or suspension having a pH of less than about 3, more preferably less than about 2. The leaching operation can be carried out in a single-stage leaching system in which a suspension comprising ore particles containing barium sulfate and the leaching acid is mixed in a drum that rotate slowly The leach drum can be adapted to lean at an angle to drain or decant and recover the leach acid after completion of the leaching operation. To reduce the consumption of acid, the leaching operation can be carried out in multiple stages, for example, a three-stage countercurrent leachate operation. In one example of such an operation, the barium sulfate-containing ore particles pass from the first stage through the second and third stages and are brought into contact with the leaching acid of increased concentration. That is, the fresh leaching acid is introduced into the third or final stage and recovered and passes countercurrently with the ore particles containing barium sulfate through the second and then the first stage. The resulting suspension 9 of the leached barium sulfate-containing particles is washed with water to at least partially neutralize the leached acid retained in the suspension. The wash water can be tap water or purified water, such as distilled or deionized water. As illustrated in Figure 1, the suspension of the leached barium sulfate-containing particles 9 is washed with water in a washing operation 11 to produce a washed suspension 17 comprising leached barium sulfate-containing particles. As the leaching operation, the washing of the suspension can be carried out in one or several steps until the desired pH is obtained. If the washing is carried out in multiple stages, wash water of different purity can optionally be used in different stages. For example, the leached barium sulfate-containing particles can be washed with water in the drum or other container used in the leaching operation by introducing wash water into the container and allowing the water and acid mixture to spill out of the drum. When the washing operation is completed, the container can be tilted at an angle to drain or decant the wash water and recover the leached and washed barium sulfate-containing particles. Alternatively, the suspension of the leached barium sulfate-containing particles can be transferred to a separate container for the washing operation. Regardless of how the washing operation is performed, the washing is preferably continued to neutralize and substantially increase the pH of the leached material to at least about 6, more preferably from about 6 to about 7. In accordance with the embodiment herein invention illustrated in Figure 1, the barium sulfate-containing particles washed from suspension 17 are subjected to a fluidization or peptization treatment 21, in which the particles are mixed with an appropriate amount of fluidizing agent 19 in a liquid medium to fluidize or release the gangue materials from particles containing barium sulfate. The particular construction and configuration of the equipment used to mix the washed particles containing barium sulfate and the fluidizing agent are not critical in the practice of the present invention. The apparatus used may comprise an appropriate container, preferably equipped with a stirring device (eg, a stirred tank). Preferably, an aqueous liquid medium comprising water in the fluidization treatment is used. In general, the amount of the fluidizing agent added to the barium sulfate-containing particles varies depending on the composition of the incoming barite ore used, the desired purity of the barium sulfate product, and the concentration of the sulfate-containing particles. barium in the treated mixture. In general, as the concentration of the barite materials in the barite ore increases, more fluidizing agent may be required. Similarly, if a lower concentration of the gangue materials in the barium sulfate product is required, it may be necessary to use more fluidizing agent. Although higher or lower concentrations may be employed, depending particularly on the effectiveness of the specific fluidizing agent used, in general, appropriate results are obtained when the concentration of the particles containing barium sulfate is from about 15% to about 65% by weight in the treated mixture, and the fluidizing agent used to treat the particles containing barium sulfate is added in a proportion of at least about 0.03% by weight of the treated mixture, preferably from about 0.05% to about 5% by weight, more preferably from about 0.05% to about 0.5% by weight. The liquid medium in which the washed barium sulfate-containing particles are mixed with the fluidizing agent is conveniently maintained at typical temperatures, for example, from at least about 5 ° C to about 50 ° C and preferably at ambient temperatures from at least about 15 ° C to about 30 ° C. The fluidization treatment is allowed to proceed for a sufficient time to thoroughly mix the barium sulfate-containing particles and the fluidizing agent in the liquid medium and allow the fluidizing agent to release at least a portion of the gangue materials present. in the particles to be treated. Usually, the mixture of the barium sulfate-containing particles and the fluidizing agent is contacted for a sufficient period until the desired results are achieved, for example, for a period of at least about 15 minutes and preferably of at least about 60 minutes. The fluidization treatment produces a treated mixture 23 comprising particles containing barium sulfate and fluidized gangue materials released from the particles containing barium sulfate. Fluidized gangue materials mainly include silica and other optional impurities, such as aluminum, chromium and iron compounds. Once the fluidization treatment is completed, the fluidized gangue materials are separated from the treated mixture. The equipment and techniques used to separate the fluidized gangue materials from the treated mixture can be any conventional equipment or technique known in the art, and one skilled in the art would be able to easily select an appropriate separation operation from the point of view of the global process considerations. For example, fluidized gangue materials can be properly separated from the treated mixture by decanting, filtration, centrifugation or even a combination of such operations. Typically, at least a portion of the gangue materials released from the barium sulfate-containing particles using the fluidization agents according to the present invention are present in a floating layer in the treated mixture. Therefore, the separation of the fluidized gangue materials from the treated mixture often includes decanting the floating layer as a viable means to separate at least a portion of the fluidized gangue materials. In the embodiment shown in Figure 1, the treated mixture 23 comprising particles containing barium sulfate and the fluidized gangue materials is first subjected to a decanting operation to remove such a floating layer 27 from the treated mixture and form a mixture. Decanted treatment 29 which is then subjected to a filtration operation 31 to further remove the fluidised gangue materials and other impurities. Decanting the gangue materials containing the floating layer released from the barium sulfate-containing particles before filtering the decanted treated mixture reduces the risk of premature mixing of the filtration device.

The particular construction and configuration of the equipment used to decant the floating layer 27 of the treated mixture 23 is not critical in the practice of the present invention. For example, the equipment used may comprise an appropriate container adapted to be inclined at an angle to pour the floating layer or the container may be provided with a decanting port at an appropriate elevation through which the floating layer may be extracted from the treated mixture. . In addition, the decanting of the floating layer can be achieved in a container provided with an appropriate vacuum means. The settling operation can be carried out in the same vessel in which the fluidizing agent is mixed with the particles containing barium sulfate. In another embodiment, the treated mixture 23 with the floating material can be transferred to another vessel in which the floating material is decanted from the treated mixture. The decanting step can optionally be carried out in a single step or in multiple stages. The water used in the fluidization treatment and the decanting steps may be tap water or purified water, such as distilled or deionized water. In a multi-stage process, water of different purity can be used in different stages, for example, the final stage can optionally use purified water. In the embodiment shown in Figure 1, the decanted treated mixture 29 is subjected to a filtration operation 31 to further remove any additional impurities and produce a filtrate or feed stream of the dryer 33 comprising particles containing barium sulfate. The filtration device is constructed and configured to maintain undesirable impurities larger than particles containing barium sulfate. In one embodiment, the decanted treated mixture can be filtered through a mesh filter such as a Standard Sieve U.S. Series screen. 325 mesh or a similar device. After separation of the fluidized gangue materials from the treated mixture 23, the particles containing barium sulfate in the feed stream of the dryer 33 are subjected to a drying operation to produce a dried barium sulfate product 37, which typically has a moisture content of not more than about 2% by weight and which contains particles ranging in size from about 0.5 μm to about 15 μm, although smaller and larger particles may also be present. The particular construction and configuration of the equipment used for the drying of particles containing barium sulfate is not critical in the practice of the present invention and may comprise a steam pipe dryer or other suitable industrial drying device. Once dry, the barium sulfate product 37 can be subjected to an additional grinding and classification operation 39 to separate and obtain one or more barium sulfate products 41 and 43 having the desired particle size distribution. Alternatively, the drying, grinding and sorting operations can be carried out simultaneously. In one embodiment, the particles of the medical barium sulfate product intended for use in a pharmaceutical gastrointestinal examination formulation have an average particle size of at least about 3 μm, preferably from about 3 μm to about 4.5 μm. In another embodiment, the particles of the medical barium sulfate product have an average particle size of about 8 μm to about 11 μm. Although the process for making a barium sulfate product from a barite ore illustrated in Figure 1, it shows a preferred embodiment that includes the treatment of the barium sulfate-containing particles with a fluidizing agent after the acid leaching operation and washing with water to neutralize the leached material, it should be recognized that the fluidizer treatment can be integrated into the process in other ways, without departing from the scope of the present invention.

The pH during the fluidization treatment can impact the capacity if the fluidizing agent releases the gangue materials from the particles containing barium sulfate. If the fluidization treatment is presented before the neutralization of the leached material is completed, it is preferable to choose a fluidizer that is not capable of substantially completing the protonation at a given pH. For example, in such an embodiment, a fluidizing agent comprising an alkali metal or alkaline earth metal polycarboxylate salt may be less preferred. In addition, a conventional process for producing a barium sulfate product from a barite ore can be modified in accordance with the present invention by subjecting the dried product to a fluidization treatment which includes mixing the particles of the barium sulfate product with a fluidizing agent in a liquid medium (e.g., water) and subsequently separating the fluidized gangue materials from the treated mixture and drying the treated product. However, this latter alternative mode is much less preferred since it would require an additional drying operation and would increase the overall operating cost of the process. Furthermore, it should be understood that the treatment of particles containing barium sulfate with a fluidizer can be carried out multiple times (eg, in series) within the process scheme, to improve the removal of persistent gangue materials from the sulfate product of barium. For example, a first treated mixture can be prepared by first mixing the barium sulfate-containing particles with a fluidizing agent and then mixing the treated barium sulfate-containing particles with a second fluidizing agent to form a second treated mixture comprising particles that they contain barium sulfate and additional fluidized gangue materials. Fluidised gangue materials (eg, floating layer) can be separated from the first treated mixture before contacting the treated barium sulfate-containing particles contained therein with a second fluidizing agent and / or fluidized gangue materials. they can be separated from the second treated mixture. The fluidization agents used in each of the fluidization treatments may be the same, or different fluidization agents may be employed in the fluidization treatments. The barium sulfate product produced in accordance with the present invention is suitable for use in the production of paints, rubbers and drilling fluids for the exploration of oil and gas, but is particularly suitable for use as a contrast agent of radiopaque x-rays in the preparations administered to patients undergoing medical examination of the gastrointestinal tract. The barium sulfate product of the present invention can be used in liquid formulations as well as in dry formulations that are constituted (eg, suspended in water) prior to ingestion by the patient. The quality and particle size exhibited by the barium sulfate product of the present invention has been found to be particularly useful in medical examinations of the upper gastrointestinal tract because it provides a uniform coating of the gastrointestinal tract and proper opacification during the X-ray examination. In addition, the barium sulfate product of the present invention has a substantially desirable white coloration and is less susceptible to the formation of an almost white or gray flotation when suspended in water to form a suspension of barium sulfate. for ingestion by a patient undergoing gastrointestinal examination. This latter feature is particularly advantageous in gastrointestinal tract examination formulations that do not contain a viscosity modifier to maintain the barium sulfate particles in suspension. Dry formulations usually do not contain a viscosity modifier. In the absence of a viscosity modifier, the appearance and severity of the gray float is often more pronounced due to the suspension of a dry formulation in water. Therefore, the barium sulfate product of the present invention is particularly useful as a radiopaque X-ray contrast agent in the gastrointestinal tract examination formulations. In addition to the barium sulfate product described herein, pharmaceutical preparations for use in gastrointestinal examinations may include other additives known to those skilled in the art to improve the properties of the suspension, adhesion of the mucosal lining, film thickness and patient acceptance and tolerance. These include, for example, stabilizing and suspending agents to prevent settling, viscosity modifiers (eg, some gums), fluidizing agents, such as sodium citrate and sodium tripolyphosphate, sweeteners, such as sucrose and sorbitol and agents flavors to improve flavor, water soluble salts to prevent foam and preservatives and antimicrobial agents to prolong the shelf life of the product. In one embodiment, the barium sulfate product prepared in accordance with the present invention has a substantially reduced concentration of some gangue materials, particularly silica impurities, which may persist and undermine the desired appearance (e.g., color) properties of the product. The amount of unwanted color formation gangue materials removed in accordance with the present invention are related to the incoming barite ore will vary depending on the composition of the ore, the selection of the fluidizing agent and the manner in which the or Fluidization treatments are carried out. For example, by practicing the techniques described above, it is possible to remove at least about 80% by weight of silica and other gangue materials from the barium sulfate initiator material, more preferably at least about 90%. The following examples are intended merely to illustrate and further explain the present invention. The invention, therefore, should not be limited to any of the details in these examples.

EXAMPLE 1. Elemental analysis of crude barite ore, barium sulfate product and "gray flotation" Raw barite ore is processed in a conventional manner (eg, without fluidizer treatment) to produce a barium sulfate product . During the processing, samples of washing liquid and residual liquid were collected. To determine the elemental components as well as the relative levels of each element in the crude barite ore, the barium sulfate product, the wash liquid, the residual liquid and the "gray float" samples derived from each were subjected to Spectrographic analysis using qualitative DC arc emission techniques. The results of the spectrographic analyzes are shown in Table I. In Table I, the measured levels of each element are qualitatively defined using the abbreviations defined below in Table II. In Table I, the sample represented "Wash water" was derived from a collection of wash liquid samples from the production process described above. The collected samples were allowed to settle and formed a mixture comprising a clear liquid and solid white powder. The "residual stream" represents a sample derived from a collection of residual liquid from the acid wash tank of the production process described above that contained large gray pieces of solid material. The wet insoluble powder and the gray pieces were isolated from the collected samples of wash liquid and residual liquid, respectively, and dried. The samples represented "Flotation # 1" and "Flotation # 2" in Table I are the "gray float" samples comprising the isolated gray flotation produced by suspending the pilot formulations containing the barium sulfate product in water.

After suspension in water, the gray floating material was isolated and allowed to settle to form a mixture comprising an insoluble powder. The wet insoluble powder was removed and dried in a similar manner. The four dried samples, as well as the crude barite ore and the barium sulfate product were subjected to analysis using DC arc emission techniques. The specimens from each were added to # 44UC graphite electrodes. The white electrodes were prepared in almost the same way by comparison. The white electrodes and electrodes containing the specimens were burned and the emission spectra were collected using a Thermo Jarrell Ash AtomComp 2000 DC Arc Spectrometer, which uses a charge injection device (CID) detector. The instrumental parameters were as follows: Gas level 3.00 s (covering gas 30% of 02 in argon); Pre-combustion - 0.00 s; Arc current sequence - 25.0 s at 15 amperes and total integration time - 25.0 s.

Table I Qualitative elemental analysis of barite ore, barium sulfate product and other samples Table II Abbreviations that designate the relative levels of the elements in the samples of Table I The elements not detected in any of these samples included: Ag, As, Au, Be, Bi, Cd, Co, Cs, Gd, Hg, Li, Mo, Ni, Pd, Pt, Rb, Sb, Ta, Ti, V , W and Zn. Based on the qualitative analysis presented in the Table I, the conventional processing of barite ore resulted in the reduction and in some cases the elimination, of many of the impurities elements in the barium sulfate product. However, the levels of substantial impurities, especially silicon and calcium, persist in the barium sulfate product. These results merit additional quantitative research. The crude barite ore, the barium sulfate product and the isolated gray parts of the residual stream were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to determine the concentrations of elemental impurities in each sample. In preparation for the analysis, a portion of each sample was fused with a mixture of sodium carbonate / boric acid in a flask and the resulting melt was dissolved using dilute hydrochloric acid. However, it is observed that the preparation of the sample for the ICP-AES analysis was not completely successful since a precipitate formed during the dissolution of the melt, although the melt itself appeared clear once it was removed from the muffle. The dissolved samples were filtered or decanted and the clear or decanted filtrate was subjected to ICP-AES analysis using a Thermo Jarrell Ash AtomComp 25 inductively coupled plasma atomic emission spectrometer. The results of the ICP-AES analysis are shown in Table III . Due to the difficulty to completely dissolve the samples submitted to ICP-AES, it is possible that some analytes were lost with the precipitates that were formed during the sample preparation, which would impact the quantitative analysis and the reproducibility of the results reported in the Table III. However, the trends observed during the ICP-AES analysis are consistent and confirm the results of the qualitative analysis generated during DC arc emission techniques.

Table III Quantitative analysis of barite ore, barium sulfate product and residual current As can be seen from the quantitative analyzes, the conventional processing of crude barite ore without the fluidization treatment can reduce the concentrations of the main impurities, such as silicon, calcium and iron. These elements appear in a high concentration in the residual stream and in a lower concentration in the barium sulfate product. However, it is difficult using conventional processing to adequately remove elements, such as silicon, which is believed to impart the appearance of the barium sulfate product and cause a "gray float" due to the suspension of the barium sulfate product in water. .

EXAMPLE 2. Fluidization treatment of the barium sulfate product to remove impurities from "gray flotation" A barium sulfate product (11 g) conventionally processed (for example, without fluidizer treatment) from a barite ore, it was mixed with water (500 mL) and sodium citrate (3 g) in a beaker. The solution was stirred with a mechanical stirrer and a "gray float" layer formed above the suspension. The suspension was passed through a 120 mesh (125 μm) screen, which easily separated the "gray float" material. The filtrate, which comprises the suspended barium sulfate particles was substantially clear and free of the "gray float" material. The above description of the preferred embodiments is intended only to inform others skilled in the art with the invention, its principles and its practical application, so that others skilled in the art can adapt and apply the invention in its many forms, as adapt better to the requirements of a particular use. The present invention, therefore, is not limited to the above embodiments and can be varied in a variety of ways. With reference to the use of the terms "comprise" or "comprises" or "comprising" in this specification (including the claims), the Applicants observe that, unless the context otherwise requires, these terms are used on the basis and clear understanding that they are interpreted in an inclusive manner, rather than exclusively, and that the Requesters intend that each of these terms be interpreted in the construction of this specification (including the claims). It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (26)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. Process for the production of a barium sulfate product from a barite ore containing barium sulfate particles and gangue materials , characterized in that it comprises: mixing barium sulfate-containing particles obtained from a barite ore with a fluidizing agent in a liquid medium to form a treated mixture comprising particles containing barium sulfate and fluidized gangue materials released from the particles which they contain barium sulfate; separating the fluidized gangue materials from the treated mixture; and drying the particles containing barium sulfate to produce the barium sulfate product; wherein the fluidizing agent is selected from natural gums, synthetic and semi-synthetic gums or polymers, biopolymers, chelating agents, salts of polyacid monomers, inorganic salts and mixtures thereof.
2. 2. Process for the production of a barium sulfate product from a barite ore containing barium sulfate particles and gangue materials, characterized in that it comprises: contacting the particles of the barite ore with an acid of barium. leaching to leach the acid-soluble impurities and produce a suspension comprising leached barium sulfate-containing particles having a reduced concentration of acid-soluble impurities; wash particles containing barium sulfate leached with water; mixing the washed barium sulfate-containing particles with a fluidization agent in a liquid medium to form a treated mixture comprising particles containing barium sulfate and fluidized gangue materials released from the barium sulfate-containing particles; separating the fluidized gangue materials from the treated mixture; and drying the particles containing barium sulfate to produce the barium sulfate product; wherein the fluidizing agent is selected from natural gums, synthetic and semi-synthetic gums or polymers, biopolymers, chelating agents, salts of polyacid monomers, inorganic salts and mixtures thereof.
3. 3. The process according to claim 1 or 2, characterized in that the fluidizing agent comprises a natural gum selected from carrageenan, alginate, gum arabic, pectin and mixtures thereof.
4. The process according to claim 1 or 2, characterized in that the fluidizing agent comprises a synthetic or semi-synthetic gum selected from low viscosity carboxymethyl celluloses, copolymers of ethylene and maleic anhydride, copolymers of ethylene and maleic acid, copolymers of methyl vinyl ether and maleic anhydride and mixtures thereof.
5. 5. The process according to claim 1 or 2, characterized in that the fluidizing agent comprises a biopolymer selected from heparin, chondroitin sulfate and mixtures thereof.
6. The process according to claim 1 or 2, characterized in that the fluidizing agent comprises a chelating agent selected from salts of ethylenediaminetetraacetic acid, salts of cyclohexane-trans-1,2-diamintetraacetic acid, salts of diethylenetriaminpentaacetic acid and mixtures thereof.
7. The process according to claim 1 or 2, characterized in that the fluidizing agent comprises an inorganic salt selected from sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and mixtures thereof.
8. 8. The process according to claim 1 or 2, characterized in that the fluidizing agent comprises a salt of a polyacid monomer.
9. The process according to claim 8, characterized in that the fluidizing agent comprises a salt of a polyacid monomer selected from alkali metal and alkaline earth metal salts of nitrilotriacetic acid, nitrile-trimethylene triphosphoric acid, inositol hexaphosphoric acid, N-β-ethanolamine-N, N-diacetic acid and mixtures thereof.
10. 10. The process according to claim 8, characterized in that the fluidizing agent comprises a polycarboxylate salt.
11. The process according to claim 10, characterized in that the fluidizing agent comprises a polycarboxylate salt selected from alkali metal and alkaline earth metal salts of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, citric acid, isocitric acid, tartaric acid, malic acid and mixtures thereof.
12. 12. The process according to claim 11, characterized in that the fluidizing agent comprises sodium citrate.
13. The process according to any of claims 1 to 12, characterized in that the treated mixture comprises from about 15% to about 65% by weight of the particles containing barium sulfate and the fluidizing agent is added in a proportion of at least about 0.03% by weight of the treated mixture.
14. The process according to claim 13, characterized in that the fluidizing agent is added in a proportion from about 0.05% to about 0.5% by weight of the treated mixture.
15. 15. The process according to any of claims 1 to 14, characterized in that the fluidized gangue materials released from the barium sulfate-containing particles are present in a floating layer in the treated mixture.
16. The process according to claim 15, characterized in that the fluidized gangue materials are separated from the treated mixture by decanting at least a portion of the floating layer of the treated mixture.
17. The process according to claim 1, characterized in that it further comprises contacting the barium sulfate-containing particles obtained from the barite ore with a leaching acid to leach the acid-soluble impurities and produce a suspension comprising particles containing leached barium sulfate having a reduced concentration of acid soluble impurities; and wash the barium sulfate-containing particles leached with water.
18. 18. The process according to claim 17, characterized in that the leaching acid comprises a mineral acid.
19. 19. The process according to claim 2, characterized in that the leaching acid is a mineral acid selected from hydrochloric acid and sulfuric acid.
20. 20. The process according to claim 2 or 17, characterized in that the leached barium sulfate-containing particles are washed with water to at least partially neutralize the suspension before mixing the barium sulfate-containing particles leached with the spent agent. fluidization in the liquid medium to form the treated mixture, the liquid medium comprising water.
21. 21. The process according to claim 20, characterized in that the pH of the at least partially neutralized suspension is at least about 6.
22. 22. The process according to claim 21, characterized in that the pH of the suspension by The least partially neutralized is from about 6 to about 7.
23. 23. The process according to any of claims 20 to 22, characterized in that the temperature of the liquid medium in which the leached barium sulfate-containing particles are mixed with the fluidizing agent is from about 15 ° C to about 30 ° C.
24. 24. The process according to any of claims 20 to 23, characterized in that the treated mixture comprises a first treated mixture, the process further comprising mixing barium sulfate-containing particles obtained after separation of the fluidized gangue materials from the first mixture treated with a second fluidizing agent to form a second treated mixture comprising particles containing barium sulfate and fluidized gangue materials released from the particles containing barium sulfate; and separating the fluidized gangue materials from the second treated mixture.
25. 25. The process according to any of claims 2 or 19 to 24, characterized in that the barium sulfate product comprises particles having an average particle size of about 3 μm to about 4.5 μm or about 8 μm to about 11 μm. μm.
26. 26. Pharmaceutical formulation for use in gastrointestinal examinations comprising an X-ray contrast agent comprising the barium sulfate product produced according to any of claims 1 to 25.