MXPA99008072A - Method, composition and system for the controlled release of chlorine dioxide gas - Google Patents

Abstract

Method, composition and system for generating chlorine dioxide gas in a controlled release manner by combining at least one metal chlorite and a dry solid hydrophilic material that reacts with the metal chlorite in the presence of water vapor, but does not react with the metal chlorite in the substantial absence of liquid water or water vapor to produce chlorine dioxide gas in a sustained amount of from about 0.001 to 1,000 ppm.

Description

METHOD, COMPOSITION AND SYSTEM FOR CONTROLLED CHLORINE DIOXIDE GAS RELEASE DESCRIPTION D? THE INVENTION This application is a Request for Continuation in Part of the United States Serial No. 08 / 961,488 filed on October 30, 1997, which is a Request for Continuation in Part of the United States Serial No. 08 / 891,665 filed on July 11, 1997, which is in itself a Request for Continuation in Part of the United States Serial No. 08 / 808,768 filed on March 3, 1997, now abandoned. The present invention is generally directed to the controlled release of chlorine dioxide gas from the reaction of metal chlorite and a second material, which reacts with the metal chlorite in the presence of water vapor, but will not react with the metal chlorite. metal chlorite in the substantial absence of liquid water or water vapor. Once the reaction begins, the chlorine dioxide gas is produced in a sustained concentration of about 0-001 to 1,000 ppm. Gaseous chlorine dioxide at low concentrations (ie, up to 1,000 ppm) has long been recognized as useful for the treatment of odors and microbes. Its use is particularly advantageous when seeking to control microbes and / or organic odors in and around food products, since chlorine dioxide functions without the formation of unwanted by-products such as chloramides or chlorinated organic compounds that can be produced when uses elemental chlorine for the same or similar purposes. For example, if a low concentration of chlorine dioxide gas can be kept in contact with fresh products for several days during shipment from the farm to the local buyer, the rate of deterioration of the product may be reduced. In addition, chlorine dioxide gas is also generally considered safe for human contact at low concentrations that are effective for deodorization and antimicrobial applications. The chlorine dioxide gas can be toxic to humans at concentrations greater than 1,000 ppm and can be explosive at concentrations above about 0.1 atmosphere. Therefore, chlorine dioxide gas is not manufactured and shipped under pressure like other industrial gases, and conventional on-site manufacturing methods require not only expensive generation equipment but also high levels of operator experience. to avoid the generation of highly dangerous concentrations. These problems have substantially limited the use of chlorine dioxide to large commercial applications, such as water treatment and poultry processing, where the chlorine dioxide consumption is sufficiently large that it can justify the capital and operating costs of expensive equipment and Experienced operators for onsite manufacturing. Commercially, chlorine dioxide is produced from a variety of aqueous solutions of chlorine-containing salts for example, see U.S. Patent 5,009,875. Attempts have also been made to produce chlorine dioxide using mixtures of solid reagents. In general, the prior art has focused on three systems for the production of chlorine dioxide using solid reagents. A system employs a solid mixture of a metal chlorite and an acid in a liquid, aqueous environment. A second system combines a metal chlorite and an acid, where the chlorine dioxide gas is released, under dry conditions. A third system employs the combination of a metal chlorite and a solid organic acid anhydride to generate a highly concentrated flow of chlorine dioxide, which must be diluted, with a constant stream of inert gas flow. Solid reagents are disadvantageous for any one or more of the following reasons: a) after mixing there is a normally concentrated, usually sudden stream of generated chlorine dioxide; b) the reagent mixture produces chlorine dioxide gas under dry conditions thus reducing the life of the reagents; c) an inert gas stream must be used to reduce the concentration of chlorine dioxide gas in the atmosphere. For example: the United States patent 2,022,262 describes the use of chlorine in an aqueous solution in a strain removal process, wherein the chlorine dioxide is produced after the acidification of an aqueous solution of alkali metal or alkaline earth metal chlorite (ie chlorites), with oxalic acid. U.S. Patent 2,071,091 discloses that chlorous acid which is produced after the acidification of solutions of chlorite salts of alkali metal and alkaline earth metal is an effective fungicide and bactericide. This patent discloses solid compositions of metal chlorites and solid acids that will produce chlorine dioxide when dissolved in water. However, the materials of the '091 patent are useful only in "wet" applications, where liquid water is available and is in contact with a material that will be treated with chlorine dioxide dissolved in liquid water, and is acceptable. U.S. Patent 2,071,094 discloses deodorizing compositions in the form of dry briquettes comprising a dry mixture of a soluble chlorite, an acidifying agent, and a filler of lower solubility, so that the disintegration of a briquette is inhibited in the presence of liquid water. The generation of chlorine dioxide begins as the briquette dissolves in the water. Such materials are subject to the same limitations of use as those of the? 091 patent. U.S. Patent 2,482,891 discloses a material comprising a solid organic acid anhydride and an alkali metal or alkaline earth metal chlorite salt, which is stabilized through the addition of a desiccant material. The combined solid material is described as the one that develops chlorine dioxide on contact with water. Example 1 describes the production of chlorine dioxide by contacting a mixture of sodium chlorite, ophthalmic anhydride and sodium monoxide with steam. It is not clear from the example if the solid mixture was already in contact with the liquid water or not. The resulting exit gas in this example contains a high concentration of chlorine dioxide gas. Also, the organic acid anhydride is potentially explosive in combination with the chlorite salt, as well as being a relatively expensive constituent. Therefore, this material has not been commercially successful. U.S. Patent 3,591,515 discloses solid powdery compositions comprising solid carriers which have stabilized chlorine dioxide or chlorite solutions impregnated therein. When the compositions impregnated with the solution are contacted with solid acids, they release chlorine dioxide gas. These materials are currently sold commercially under the trade names of OSTOBON © and ABSCENT © (by International Dioxide Inc., Clark, NJ), but their commercial acceptance has been limited because they release prematurely small amounts of chlorine dioxide through the packaging in the warehouse, or require a relatively complicated mixing of two ingredients per part of the user at the point of application. U.S. Patent 4,585,482 describes a long-acting biochemical composition comprising a chlorite and an organic salt such that the pH of the composition is < 7. Said compositions release the chlorine oxide in the presence of liquid water. This patent also discloses methods for producing dry microcapsules of such compositions with water having polymer shells such that the resulting dry materials release chlorine dioxide. U.S. Patent 4,547,381 discloses dry compositions for the controlled and sustained release of gaseous chlorine dioxide comprising a dry inert diluent, a chlorite salt and a drying agent capable of reacting with a chlorite in a dry state to produce the chlorine dioxide gas. Such materials have not achieved substantial commercial success as they begin to release the chlorine dioxide gas immediately after the formulation and, therefore, they must be mixed and used for a short period. U.S. Patent 5,360,609 discloses the incorporation of a chlorine dioxide generating compound into a polymer or oligomer film, which is then coated on a substrate. The chlorite constituent is dissolved in a phase bound by hydrogen containing an amide or monomeric or polymeric alcohol. The hydrogen-binding phase is then mixed with an incompatible apolar phase containing an acid anhydride. The chlorine dioxide gas is released through the direct reaction of the acid anhydride with the chlorite anion through the boundary of the phase. However, the process described in the '609 patent employs relatively expensive materials and the reaction is potentially explosive due to the proximity of the strongly oxidizing metal chlorite to the carbonbonic polymers. U.S. Patent 5,567,405 describes the generation of chlorine dioxide gas from mixed beds of zeolite catalysts, wherein the first bed comprises a zeolite which has been impregnated with an aqueous solution of sodium chlorite and the second bed it comprises a zeolite which has been impregnated with phosphoric acid, or acetic acid. The chlorine dioxide gas is released when the acid migrates from the second bed and comes into contact with the chlorite in the first bed. The first and second beds can be physically mixed together. The process described in the patent 05 requires expensive equipment and results in a product that has a relatively short life. Therefore, it can be a significant advance in the general chlorine dioxide gas technique for commercial applications and that there is a method, position and system where the chlorine dioxide gas can be generated under controlled conditions at low concentrations. In addition it could be a breakthrough in the art to provide a method, composition and system wherein the reagents do not generate the chlorine dioxide gas in the absence of water, but provide a controlled sustained release of the chlorine dioxide gas in the presence of water vapor . As a result, the composition of the present invention can be prepared in advance and stored under dry conditions without the premature release of the chlorine dioxide gas. In this way, the need for experienced personnel to prepare the mixture on site is avoided and life is improved. The present invention is generally directed to a method, composition and system useful for the controlled release of chlorine dioxide gas, the concentration is low when in the presence of water vapor. The reagents that generate the chlorine dioxide gas when combined to form the composition do not generate a significant amount of chlorine dioxide gas when the water vapor is not present. The reagents, therefore, can be stored for long periods in a substantially dry atmosphere. In particular, the present invention is directed, in part, to a method for generating chlorine dioxide gas in controlled release form, comprising: a) forming a mixture of at least one metal chlorite and at least one second material, a dry solid hydrophilic material capable of reacting with metal chlorite to produce chlorine dioxide gas in the presence of water vapor, but not in the substantial absence of liquid water or water vapor (hereinafter, "Second Material" ); and b) exposing said mixture to an atmosphere comprising steam to produce chlorine dioxide gas in a sustained concentration of about 0.025 to 1,000 ppm. The present invention is also directed to compositions for the generation of chlorine dioxide gas in the form of a mixture of reagents. The reagents can be selected to control both the speed and the duration of the generation of the chlorine dioxide gas. BRIEF DESCRIPTION OF THE DRAWINGS The following drawings are illustrative of the embodiments of the invention and are not intended to limit the invention as encompassed by the claims forming part of the application. Figure 1 is a graph showing the production of low chlorine dioxide gas dry and wet conditions for the first mixture prepared according to Example 1; Figure 2 is a graph showing the production of the chlorine dioxide gas under dry and wet conditions for the second mixture prepared according to Example 1; and Figure 3 is a graph showing the concentrations of chlorite and chlorate anions in powdered samples during storage under dry conditions for various mixtures prepared in accordance with the present invention. The present invention is directed to a method, composition and system for generating chlorine dioxide gas in a controlled release form. As used herein, the phrase "controlled release form must represent that the reagents comprising the composition produce the chlorine dioxide gas at a production rate that results in low gas concentrations as compared to systems of the art. above, wherein the generation of the chlorine dioxide gas is made at high concentrations in a possibly explosive and sudden manner.According to another aspect of the present invention, solid compositions are provided to produce the chlorine dioxide gas wherein the The speed and duration of the generation of the chlorine dioxide gas can be controlled The first step of the method is the formation of a composition in the form of a mixture of at least one metal chlorite and at least one second material. The metal chlorites used in the present invention can generally be any metal chlorite The preferred metal chlorites on alkali metal chlorites, such as sodium chlorite and potassium chlorite. Alkaline earth metal chlorite can also be used. Examples of alkaline earth metal chlorite include barium chlorite, calcium chlorite and magnesium chlorite. The most preferred metal chlorite is sodium chlorite. The Second Material is a dry solid hydrophilic material, preferably a dry solid inorganic hydrophilic material. The preferred dry solid hydrophilic material produces a pH no greater than about 10.5 when the aqueous portion of a 30 weight percent mixture of that material in ionized water is measured. More preferred solid hydrophilic materials produce a pH less than 9 and more preferably less than 7. Examples of such dry solid hydrophilic materials suitable for reacting with metal chlorites include, but are not limited to, synthetic zeolites such as A, X, And, and mordenita; natural zeolites such as cabazite and clinoptilolite; hydrated clays, such as bentonite, kaolin, attapulgite, and haloysite; calcined clays such as metacaolin, spinel phase kaolin, calcined bentonite, calcined haloysite and calcined attapulgite; acidic synthetic zeolites such as A, X, Y, and mordenite which have been contacted with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid or other acidic compound (for example calcium chloride) so that the pH of the aqueous phase resulting from the mixture is below 10.5; acidic natural zeolites such as cabazite and clinoptilolite; acidic clays, such as bentonite, kaolin, attapulgite and haloysite which have been contacted with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid or other acidic compounds (for example, lanthanum chloride) so that the pH of the aqueous phase resulting from the mixture is below 10.5; calcined acidic clays, such as metacaolin, spinel phase kaolin, calcined bentonite, calcined haloysite and calcined attapulgite which have been contacted with one or more acid solutions containing sulfuric acid, hydrochloric acid, nitric acid and other acidic compounds (e.g. , acetic acid) so that the pH of the aqueous phase resulting from the mixture is below 10.5; salts such as aluminum sulfate, magnesium sulfate, calcium carbonate, and particularly acid salts of deliquescents, such as calcium chloride, magnesium chloride, lithium chloride, and magnesium nitrate; solid acids, such as boric acid, tartaric acid, and citric acid; organic acid anhydrides such as italic anhydrides, maleic anhydride, succinic anhydride and glutaric anhydride; and mixtures thereof.

A second preferred material is metacaolin microspheres as used herein, the term "microspheres" represents nominally spherical particles having an average particle size of about 50 to 100 microns. The metakaolin microspheres are substantially composed of metakaolin and can be prepared through the process described in the Preparation of the Partition Materials section set forth below. The following procedure can be used to find out if a material is a Second Material suitable for forming a mixture with the metal chlorite for the purposes of the present invention. Dry Air: An intimate physical mixture of the desired amounts of the metal chlorite (eg, sodium chlorite) and a proposed Second Material was prepared and stored under dry conditions. A one-gram portion of the mixture was placed, at room temperature, in a sealed, dry 3,784-liter polyethylene enclosure, which was purged at a flow rate of approximately 10cc / min with dry air (i.e. of spray not greater than -50 ° C). The chlorine dioxide concentration of the gas within the enclosure was periodically measured over a period of about 72 hours. The Second Material has an acceptable dry stability if the resulting chlorine dioxide gas concentration is less than approximately 0.025 ppm during this Dry Air test even if the Second Material exhibits an initial and brief release of chlorine dioxide gas which gives as a result a concentration in excess of 0.025 ppm, due to the presence of a small amount of residual water in the solids and / or the enclosure. Wet Air: A second portion of a gram of the mixture used in the previous dry air test step was exposed to approximately 80% relative humidity at room temperature in a sealed 3,784-liter polyethylene enclosure, which was purged at a rate flow rate of approximately 10cc / min with an air of relative humidity of 80%. The gas concentration enclosed by chlorine dioxide inside periodically was measured over a period of about 7 days. A material is considered a Second Material acceptable for use in the present if it exhibits both acceptable stability in the previous Dry Air test and if at any time during the previous Wet Air test it produces a sustained concentration (defined below) of Chlorine dioxide equal to or in excess of about 0.025 ppm in a controlled release form. According to the present invention, the mixture of the metal chlorite and the Second Material generates the chlorine dioxide gas in a sustained concentration of from about 0.001 to 1,000 ppm, preferably from about 0.001 to 100 ppm from about 0.1 to 10 ppm. The measurement of the chlorine dioxide gas is made in an atmosphere where the chlorine dioxide gas is generated. For example, if the mixture in generation is exposed to water vapor in the air, the concentration of chlorine dioxide gas in ppm will be measured based on the total atmosphere including air and water vapor. As previously indicated, the chlorine dioxide gas is produced according to the present invention in a sustained concentration and from about 0.001 to 1,000 ppm. The phrase "sustained concentration" means that at all times during production, the concentration of the chlorine dioxide gas is within the range of 0.001 to 1,000 ppm. The generation of chlorine dioxide gas does not need to be at a constant speed. A fluctuation rate is allowed, provided that the concentration of chlorine dioxide gas does not exceed 1,000 ppm, and that it is within the range of approximately 0.001 to 1,000 ppm during a sustained period as defined above. According to the invention, the generation of chlorine dioxide gas within the specific scale will vary depending on the relative humidity of the atmosphere, surrounding, the ratio of the reactants in the mixture, the flow velocity of diluent gas (eg, air) through the treated space, and the ratio of the amount of the chlorine dioxide gas release material to the volume of the treated space. In general, the higher the relative humidity, the higher the production rate of chlorine dioxide gas. The lower the velocity of the diluent gas through the treated space, the greater the concentration of the resulting chlorine dioxide gas. The higher the ratio of the chlorine dioxide gas release material to the volume of the treated space, the higher the concentration of chlorine dioxide gas. In a preferred embodiment of the invention, the sustained amount of chlorine dioxide gas is from about 0.001 to 1000 ppm, most preferably about 0.001 to 100 ppm. Especially good results are obtained when the production of chlorine dioxide gas is in the range of about 0.01 to 10 ppm. The amount of each of the metal chlorite and the Second Material will depend on several factors, including, but not limited to, the amount of chlorine dioxide gas needed for a particular application, the metal chlorite alkalinity and the acidity of the second. Material. In general, it is preferred to use chlorite in a concentration as consistent as possible with a sufficient rate of release. As a consequence, the production of chlorine dioxide per unit mass of the mixture is maximized. In general, the weight ratio of metal chlorite and Second Material is on the scale of about 0.001 to 0.25: 1.0. It is within the experience of the technique to select the appropriate relationship for a particular application. The mixture formed according to the present invention can optionally contain at least one desiccant, which absorbs the water to minimize or eliminate an initial short-term production of chlorine dioxide gas due to the residual water vapor present in the atmosphere or in solids when the mixture is packaged. Suitable desiccants include, but are not limited to, activated calcium chloride, activated calcium sulfate, activated X zeolite, activated zeolite A, activated bentonite clay, activated silica gel, activated attapulgite, and mixtures thereof. The term "activated" means that the particular material has been substantially dehydrated, for example, by heating at 300 ° C for one hour. The total amount of desiccant can vary depending on several factors, for example, the environmental humidity when the material is packaged, the water permeability of the packaging material and the desired storage life of the product. In general, the desiccant is present in a total amount of about 0.1% to 25% by weight based on the total weight of the mixture. In the practice of the present invention, the relative humidity of the atmosphere at which the composition is exposed during use may vary from low to high humidity conditions. The method of the present invention can be conducted at a low humidity (eg, 10% relative humidity) to a relative humidity of 100%. As indicated previously, the amount of the chlorine dioxide gas generated per given amount of the mixture will depend, in part, on the relative humidity of the surrounding atmosphere. In general, higher humidity will result in a higher concentration of chlorine dioxide gas. For example, it has been observed that the production of chlorine dioxide gas will approximately double when the relative humidity is increased from about 10% to about 80% at room temperature. It has also been observed that at room temperature compared to 0 ° C, there is no significant change in the production rate of chlorine dioxide. It will be understood that for a given unit of the mixture, a sustained amount of chlorine dioxide gas will be produced. For commercial applications, it may be desirable to employ multiple units of the mixture. In some cases, it will be desirable to start production of the chlorine dioxide gas from one or more units of the mixture and then have a second group or multiple groups of units of the mixture to be added at a last moment. In addition, one of the constituents of the composition of the present invention may be present in excess and the second of the constituents may be added as necessary. For example, the composition may initially contain an excess of the Second Material, such as, for example, kaolin metal microspheres treated with acid, and additional amounts of metal chlorite may be added periodically. The mixture of metal chlorite and the Second Material can be formulated in various ways. The preferred method is to prepare in a dry atmosphere an intimate physical mixture of fine powders of both constituents having particle sizes preferably below about 200 μm. Larger particles can be used and a lower rate of release of chlorine dioxide gas can be obtained in certain cases. The mixture can also be formed by combining one of the constituents in liquid form with other constituents. For example, a paste of a fine powder of calcined kaolin microspheres in a non-polar liquid such as dodecane can be combined with the metal chlorite. The mixture is then dried to remove the non-polar liquid. If the water is used as the liquid, then the mixture should be quickly dried to a sufficient degree to avoid excessive release of the chlorine dioxide gas. The reaction of the metal chlorite and the Second Material may last at least for a sustained period. The term "sustained period" represents that the chlorine dioxide gas will be generated for a short period (several minutes) over a long period that extends to many hours. The duration of the sustained period will depend, for example, on the relative amounts of the constituents in the mixture. Eventually, of course, one of the reaction constituents (either the metal chlorite or the Second Material) will run out and the reaction will cease however, during the course of the reaction, the chlorine dioxide gas will be produced in a sustained concentration as defined herein. A preferred composition for producing a slow release rate of long duration is a mixture of about 5% sodium chlorite and about 95% metacaolin microspheres. A preferred composition for a shorter duration, a higher rate of generation of chlorine dioxide is a mixture of about 5% sodium chlorite, about 10% activated calcium chloride and the rest metacaolin microspheres treated with acid.

The duration of the reaction also depends on, in part, how much water vapor is present in the atmosphere contained within the package. The optional use of desiccants to minimize the production of chlorine dioxide gas in the packaging during storage can ensure that the mixture will react for the longest period when exposed to water vapor under operating conditions. However, the presence of a desiccant can delay the desired start of production of the chlorine dioxide gas when the mixture is exposed to water vapor. The present invention can be used for a variety of commercial applications involving solid, liquid / gaseous environments. For example, the chlorine dioxide gas can be used to treat solids such as those having metal, cloth, wood, and / or plastic surfaces. Chlorine dioxide gas can also be used to treat animal waste, pet litter and livestock, medical devices including bandages, ostomy devices and medical instruments, food products, such as meat, vegetables, fruits, grains and nuts; as well as items made of fabric including wraps, wall brackets, upholstery and fabric. Examples of liquids that can be treated with chlorine dioxide gas, waste, liquid and water, including drinking water.

Examples of gaseous environments that can be treated include those that contain noxious and / or objectionable gases such as animal environments, smoke-laden environments (eg, tobacco smoke), and exhaust systems for noxious gas production facilities (eg. example, chemical plants). The materials of this invention can also be used to help prevent the incorporation of undesired substances (including potentially toxic substances), which can affect the taste and smell of ice produced by ice-making machines, particularly in a production of large volume of ice such as in commercial applications. It is well known that after prolonged use, the ice producing chambers of such machines that make ice can accumulate microbes - (including pathogenic microbes) and microbial films, which can emit a harmful or unpleasant odor and a gas and other flavor. byproducts. Such by-products can accumulate in or on the ice that is being produced either before, during, or after the water freezing process. However, it is believed that the taste and odor that is being produced will be less affected and will not deteriorate to a substantial degree when the materials of the present invention are used to generate and maintain a concentration of chlorine dioxide gas within from about 0.01 to 10.0 ppm, and preferably about 0.01 to about 1.0 ppm within the ice making chamber of an ice machine. It is believed that the chlorine dioxide gas produced according to the practice of this invention destroys the unpleasant odor and flavor microbial byproducts so that they do not contaminate the ice. At the highest concentrations of chlorine dioxide gas, it is believed that the microbes themselves will be destroyed by the chlorine dioxide gas. The metacaolin microspheres possess a spectrum of physical and chemical properties that make them uniquely valuable in uses such as cleaning of fabrics and carpets and deodorization, where the Second Material and the gas source of chlorine dioxide must be applied to a surface such as a solid to provide a gradual and controlled release of chlorine dioxide and spent reagents must be removed as a solid without significant generation of dust and without adhering to or forming an embedding either on the material in which the composition is applied or on internal parts of a vacuum cleaner or a mechanical sweeper. Metakaolin powder has a low surface area, as measured by the BET method. In this way, there is a minimum microporosity. When supplied in the form of spray-dried microspheres, however, the surface area remains low but voids are created and the microspheres have an appreciable content of large pores (voids). Reference is made to U.S. Patent 4,214,978, Kennedy et al. As described in this and other patents, the surface area (BET, using nitrogen) is typically between 10 to 15 m2 / g, but a total pore volume (reflection voids) is on the scale of 0.06 cc / g 0.09 cc / g. The microspheres produce an acidic pH in the liquid portion of an aqueous paste of microspheres. When exposed to moisture, water vapor can condense in the gaps in the calcined clay microspheres, thereby generating protons, which can then be reacted with the chlorite salt to generate chlorine dioxide gas. The gas is then released into the environment. In the case of carpets or similar, the gas then penetrates the material that is going to be treated in this way, it is believed that the water is transferred, as vapor in the air, to the microspheres where it condenses forming protons that react later with a chlorite salt to generate chlorine dioxide gas. Since the microspherical particles are larger than the chlorine salt particles, it is believed that the chlorine salt adheres to the surface of fresh (unused) microspheres and the salt residue adheres to the spent microspheres. This, taken with the fact that the microspheres are adherent and maintain their integrity during use as well as final removal through a vacuum cleaner or mechanical sweeper, results in compositions that do not generate significant amounts of dust since the microspheres do not crumble or during use, an undesirable film of the residue or incrustation of the carpet material is not found. The compositions of the invention which are based on metacaolin microspheres as the Second Material may, optionally, contain ingredients other than chlorite salt powder. Optional ingredients include desiccants such as sodium chloride and zeolitic molecular sieves or particulate solid acids such as citric acids to adjust the rate of liberation of chlorine dioxide. Mineral acids such as sulfuric acid can be applied to metacaolin microspheres through spraying or other means that do not decompose the physical form of the microspheres. This can be followed by drying preferably at temperatures below which any aluminum salt generated could decompose. The mixture of metal chlorite, Second Material and any desired additive can be packaged by shipping and storage in containers made of materials that are resistant to the passage of liquid water and water vapor. Examples of such materials include metal cans, glass containers, aluminum bags and laminates of barrier layer polymers. The mixture of metal chlorite and the Second Material can be used as a powder, used as formed configurations, or packaged or retained for use in any material, which is permeable to gas. Preferably, any packaging material for retained use is substantially impermeable to liquid water. Examples of such materials include TYVEK © and GORTEXT. These materials allow water vapor to enter the package and react with the mixture and also allow the resulting chlorine dioxide gas to be released from the package and into the atmosphere. Said materials are substantially impervious to liquid water. Test Procedure Unless otherwise indicated, the following test procedure is used to evaluate the samples prepared in the following examples. One gram of the specified material was placed in a layer thin in a crystallization box with a diameter of 5.08 centimeters. This box was placed in a 3,784-liter resealable polyethylene bag that was fixed with gas at the inlet and outlet ports near the opposite corners. The bag was purged and moderately pressurized to a pressure of approximately 0.254 cm (0.1 inches) of water column through the gas inlet fitting with dry air or air of the desired moisture. The bag was then hung continuously at a flow rate of about 10 cc / min with air. A pressure of approximately 02.254 cm (0.1 inches) of water column was maintained by venting the purge gas through a tube that was held just below the surface of a water reservoir. The chlorine dioxide gas inside the bag was analyzed by replacing the gas outlet vent tube with a gas sampling tube and removing a sample through a gas analysis tube (Draeger © model CH24301). The dry gas was supplied through a laboratory compressed air system and was further purified by passing it through a 13X molecular sieve trap (Hewlett Packard model GMT-4-HP). Air was prepared having a relative humidity of about 80% by bubbling compressed laboratory air at a rate of approximately 200 cc / min through a one liter beaker filled with 500 cc of saturated ammonium sulfate solution., stirred at room temperature inside a polyethylene bag having an internal volume of approximately 20 liters. An internal pressure of approximately 1.27 cm (inch) of water column was maintained inside the bag by venting a portion of the gas through a submerged side arm approximately 1.27 cm (H inch) into a column of water. Preparation Examples I. Sodium Chlorite in technical grade flakes, with a nominal purity of 80% with the remaining 20% reported as sodium chloride (available from Acros Aldrich Chemical Co. and "Alfa Aesar) dried for 3 hours at 150 ° C, and cooled to room temperature in a sealed container. II. Sodium chlorite was impregnated using a saturated solution of sodium chlorite which was prepared by mixing an excess of granulated sodium chlorite with deionized water for one hour at 35 ° C, cooling to room temperature, stirring overnight at room temperature, and then filtering the resulting solids containing a solution to remove the solids and leave a saturated, transparent solution. III. Dry calcium chloride and potassium chloride were supplied as technical grade granulated solids (supplied by T J Baker Co. and Aldrich Chemical Co., respectively). Each was dried for 3 hours at 300 ° C and then cooled in sealed containers before use. IV. Metakaolin microspheres were prepared by spray-drying an aqueous hydrous Georgia kaolin clay slurry having a solids content of approximately 28-44% and a particle size distribution of approximately 80% by weight finer than an um , and was dispersed with up to 2% by weight of the clay from a solution of up to 25% to 30% sodium silicate having a molar ratio of Si? 2: Na2? from 2.0 to 3.3 using a spray atomizer spray wheel to produce spherical kaolin agglomerates having an average particle size of about 70 um. The agglomerates were calcined in a commercial rotary calciner for a sufficient time and temperatures to substantially convert all of the hydrous kaolin to metacaolin (e.g., one hour at 700 ° C). V. Kaolin clay microspheres were produced that were calcined through the characteristic kaolin exotherm in a manner similar to the metakaolin microspheres prepared as in the preceding paragraph IV, except that the calcination temperature was higher (e.g. one hour at 1,000 ° C). The hydrated kaolin clay underwent the characteristic exothermic transformation to the well-known spinel phase of kaolin without the formation of a substantial amount of mulite. The resulting material was called "spinel phase microspheres". SAW. Acid-treated metakaolin microspheres were prepared by impregnating about 300 grams of metakaolin microspheres as in the preceding IV with 280 grams of a 2.16 N sulfuric acid solution, drying at 100 ° C, and calcining at 350 ° C for 3 hours. Prior to incorporation into the blends of the present invention, the metacaolin microspheres and the spinel phase microspheres were heat treated 300 ° C for 3 hours in a laboratory oven and then cooled to room temperature in a sealed container. The following examples are illustrative of the embodiments of the invention and are not intended to limit same as encompassed by the claims forming part of the application. EXAMPLE 1 First Mix: 200 grams of metakaolin microspheres prepared as in preparative example IV were mixed with 12.5 grams of dry sodium chlorite prepared as in preparative example I with moderate manual milling with a mortar under ambient air conditions. The mixed sample was placed in a sealed glass jar wrapped with an opaque tape. Second Mixture: 200 grams of metacaolin microspheres were mixed with 12.5 grams of dry sodium chlorite with moderate manual grinding with a mortar under dry air conditions to a point of spray below -20 ° C in a glove bag. The mixed sample was placed in a sealed glass jar wrapped with an opaque tape.

One gram of the First Mix was tested under conditions as described in the test procedure. The results are shown in Figure 1. An initial trace (0.3 ppm) of chlorine dioxide gas was detected during the first five hours, which was probably due to water initially present in the sample, but no gas was detected. of chlorine dioxide during 195 hours. At that point, the dry air stream was wetted at a relative humidity of 80%. The concentration of chlorine dioxide gas was increased to 1 ppm and remained at 1 ppm until the test was conducted at approximately 250 hours. Another sample of one gram of the First Mix was tested under 80% relative humidity conditions as described in the test procedure. The results are also shown in Figure 1. The concentration of the chlorine dioxide gas was increased from 0 to 2 ppm in 19 hours, and varied between 1 and 2 ppm through approximately 360 hours of the test. One gram of the Second Mixture was tested under dry conditions as described in the Test Procedure. The results are shown in Figure 2. No chlorine dioxide gas was detected during the 313 hours of testing under dry conditions. At that point, the dry air stream was wetted at a relative humidity of approximately 80%. The concentration of chlorine dioxide gas was increased to 1 ppm and remained within 1 and 1.1 ppm, until the test was conducted at 450 hours. The results shown in Figures 1 and 2 illustrate that the mixtures prepared with Example 1 both have stability under dry conditions and have the ability to release chlorine dioxide gas after exposure to moisture. In addition, it is shown that the initial release of traces of the first mixture was probably the result of the water absorbed during sample preparation in ambient air, and, if desired, even that lower degree of premature release can be eliminated by preparing the material under dry conditions. Example 2 A. 200 grams of spinel phase microspheres prepared as in Preparative Example V were mixed with 12.5 grams of dry sodium chlorite with moderate manual grinding with a mortar under ambient air conditions. The mixed sample was placed in a glass jar wrapped with an opaque ribbon. B. One gram of the mixture prepared as in paragraph A above was tested at a relative humidity of about 80%. The chlorine dioxide gas was first detected after 5.5 hours. The concentration of the chlorine dioxide gas reached the maximum at 1 ppm after 94 hours, and the concentration of the chlorine dioxide gas was 0.15 ppm after 364 hours. Example 3 A. An acid-activated bentonite clay was prepared as follows. A paste containing bentonite clay of the brand Engelhard F 100 ™ and oxalic acid (1 gm clay / 10 ml of a 2 M oxalic acid solution) was prepared. The paste was heated at 90 ° C for 6 hours, it was filtered, washed 3 times with deionized water, dried at 105 ° C, and then calcined for 3 hours at 350 ° C. B. 50 grams of activated bentonite clay was mixed with acid prepared as in paragraph A above, with 3.2 grams of dry sodium chlorite with moderate manual grinding with a mortar under dry air inside a glove bag. The mixed sample was placed in a sealed glass jar wrapped with opaque tape. C. The sample prepared in paragraph B above was treated as described in the Test Procedure. Under dry conditions no chlorine dioxide gas was detected after 72 hours of testing. Under wet conditions, a trace (0.1 ppm) of chlorine dioxide gas was detected after 5 hours; the peak concentration was 2.25 ppm after 72 hours when the test ended.

Example 4 A. Microspheres of an intermediate stage of the manufacturing process of a catalyst constituent of commercial fluid catalytic cracking comprising about 70% by weight of zeolite Y in its interchangeable form of sodium ion (NaY, Si / Al = 2.58 ) and 30% of a non-crystalline sodium-silica-alumina residue from the zeolite crystallization reaction were dried for 3 hours at 450 ° C (see, for example, Example 4 in U.S. Patent 5,395,809). When they were mixed at a concentration of about 30% by weight solids in water, the pH of the aqueous pulp of the resulting pulp was about 8. B. 200 grams of the dry NaY-containing microspheres prepared as in US Pat. Paragraph A above, with 12.5 grams of dry sodium chlorite with moderate manual grinding with a mortar under conditions at room temperature. The mixed sample was placed in a sealed glass jar wrapped with an opaque ribbon. C. The mixture prepared in paragraph B above was treated as described in the Test Procedure. Under dry conditions, no chlorine dioxide gas was detected during the first 196 hours of testing, but chlorine dioxide gas (0.5 ppm) was detected after 313 hours and a much smaller amount (0.1 ppm) was still present. at 337 hours when the test ended. This result shows that the material has approximately one to two weeks of storage life, so that it could be satisfactory for use in applications where there is only a slight delay between mixing and use. When the mixture prepared as in paragraph B above was exposed to wet conditions, the chlorine dioxide gas was first detected after 54 hours of exposure (2.6 ppm). The remaining concentration between about 1 and about 3 ppm through 364 hours when the test ended. Example 5 A. A powder of sodium hydrogen zeolite Y (NaHY) was prepared as follows: They were formed into a paste in 25 grams of sodium zeolite Y powder (Si / Al = 2.34 Aldrich) in 250 ml of a solution at 5% ammonium sulfate. The aqueous phase of the resulting paste had a pH of 6.5. The pulp was heated to 90 ° C with stirring for 2 hours, and filtered to separate the solid zeolites from the solution. The solid was washed with approximately 200 grams of deionized water 5 times and dried, at room temperature for about 105 ° C. The dried solid was calcined for 2 hours at a temperature of 450 ° C in a thin layer on an open tray, and cooled to room temperature in a sealed container.

B. Another material was prepared by impregnating 8 grams of NaHY powder prepared as in paragraph A above with 1. 6 grams of a saturated solution of sodium chlorite. The impregnation was done by adding the solution to the powder, drop by drop, with rapid agitation to maximize the rapid distribution of the solution through the powder. The sodium chlorite mixture impregnated with zeolite was not dried after the impregnation step. It was stored in a sealed glass container covered with an opaque tape. C. The mixture prepared in paragraph B above was treated according to the Test Procedure. Under dry conditions, the chlorine dioxide gas was released for 2 hours and the concentration of chlorine dioxide gas remained between 3 and 4.5 ppm throughout the 26 hour test. Under humid conditions, the mixture generated between 3 and 4.5 ppm of chlorine dioxide gas during the first 48 hours. The concentration of the chlorine dioxide gas slowly decreased after zero after 150 hours of exposure to the humid atmosphere. Example 6 A. 10 grams of dry calcium chloride prepared as in Preparative Example III was mixed with 0.75 grams of dry sodium chlorite with moderate manual milling in a mortar under ambient air conditions. The mixed sample was placed in a glass jar wrapped with an opaque ribbon. B. The mixture prepared as in paragraph A above was tested in accordance with the Test Procedure. Under dry conditions, no chlorine dioxide gas was detected during the 72 hours of testing. Under humid conditions, no chlorine dioxide gas was detected for 54 hours, and an amount (0.25 ppm) was detected at 94 hours, and the generation of the chlorine dioxide gas remained stable at a concentration of between about 1 and 2 ppm for 364 hours. Example 7 A. 84 grams of the acid-treated metakaolin microspheres prepared in Preparative Example VI were mixed with 10 grams of dry calcium chloride with moderate manual milling with a mortar under ambient air conditions. The resulting mixture was dried for 2 hours at 200 ° C and cooled to room temperature in a glass jar wrapped with opaque tape. B. The mixture prepared as in paragraph A above was combined with 5.25 grams of dry sodium chlorite with moderate manual grinding with a mortar under ambient air conditions. The mixed sample was placed in a sealed glass jar wrapped with opaque tape.

C. The sample prepared as in paragraph B above was tested in accordance with the Test Procedure. Under dry conditions, no chlorine dioxide gas was detected during the 72 hours of testing. Under wet conditions, a trace (0.05 ppm) of chlorine dioxide gas was detected after 4 hours. The peak concentration of chlorine dioxide gas was 6.25 ppm after 26 hours, and dropped to zero after 172 hours. Example 8 A. A material was prepared as follows. They mixed grams of stearic acid (Aldrich) with 0.75 grams of dry sodium chlorite with moderate manual grinding with a mortar under ambient air conditions. The mixed sample was placed in a sealed glass jar, wrapped with opaque tape. B. The mixture prepared as in paragraph A above was tested at a relative humidity of 80% according to the test procedure. No chlorine dioxide gas was detected during the 8 days of the test. Example 9 A. A mixture according to the present invention was prepared as follows. A commercial 13X zeolite powder (Aldrich) was dried for 3 hours at 300 ° C and cooled to room temperature in a sealed container. When a paste was formed at a solids content in water of 30% by weight, the aqueous phase of the paste had a pH of 9.7. 10 grams of the dry 13X powder was mixed with 0.8 grams of dry sodium chlorite with moderate manual grinding with a mortar under ambient air conditions. The mixture was stored in a sealed glass container covered with an opaque tape. B. The mixture prepared in paragraph A above was tested according to the test procedure. Under dry conditions, no chlorine dioxide gas was detected during the 144 hours of the test. Under wet conditions, a trace (0.05 ppm) of chlorine dioxide gas was detected after 96 hours. The concentration of chlorine dioxide gas varied between 0.025 and 0.05 ppm throughout the rest of the 168-hour test. Example 10 A. 50 grams of acid-treated metakaolin microspheres were mixed with 5 grams of dry potassium chloride prepared as in Preparative Example III with moderate milling in a mortar under ambient air conditions. The resulting mixture was dried for 2 hours at 200 ° C and cooled to room temperature in a sealed container. B. The mixture prepared in paragraph A above was combined with 3.125 grams of dry sodium chlorite with moderate manual grinding with a mortar under ambient air conditions. The resulting mixture was placed in a sealed glass jar wrapped with an opaque tape. C. The sample prepared in paragraph B above was tested in moist air according to the Test Procedure. A trace (0.1 ppm) of chlorine dioxide gas was detected after 45 minutes, and the concentration of chlorine dioxide gas ranged from about 3 to 1 ppm between about 4 and 290 hours when the test ended. Example 11 Microspheres comprising 80% of zeolite X (having a ratio of Si02 to AI2O3 equal to 1) in their interchangeable forms of sodium and potassium ion mixed and % crystallization residues of calcined kaolin clay were produced by reacting metacaolin microspheres in an aqueous solution of sodium hydroxide, potassium hydroxide and sodium silicate at 75 ° C. The solids were filtered and washed with deionized water until the effluent pH was about 10.5. The solids were then dried for 3 hours at 300 ° C and cooled to room temperature in a sealed container. When a paste was formed at a solids content in water of 30% by weight, the aqueous phase of the paste had a pH of 10.3. 12 grams of the dried microspheres were mixed with 0.8 grams of dry sodium chlorite with moderate manual milling in a mortar under ambient air conditions. The mixture was stored in a sealed glass container covered with an opaque tape. The mixture was tested according to the test procedure. Under dry conditions, no chlorine dioxide gas was detected during the 142 hours of testing. Under humid conditions, a trace (0.1 ppm) of chlorine dioxide gas was detected after 46 hours. The release of chlorine dioxide gas slowly increased to a peak of 0.5 ppm at 124 hours, and was at 0.4 ppm after 143 hours when the test ended. Example 12 Three samples were tested, each in the form of a powder prepared according to Examples 1, 4 and 7, respectively, to determine the storage stability of the composition of the present invention through the following procedure. Single gram samples were stored in sealed glass jars. A chemical analysis of each of the samples was carried out extracting the water soluble constituents to an aqueous solution regulated in its pH with a pH of 7 at room temperature. The respective solutions were analyzed for the concentration of chlorate, chlorite and chloride anions using chromatography following the general procedures of the EPA 300 test method. The chlorite analytical standard was prepared from solid technical grade sodium chlorite, which it assumed that it comprises approximately 80% by weight of the pure sodium chlorite. The results are shown in Figure 3. As shown in Figure 3, except for a small initial reduction in chlorite concentration, the chlorite and chlorate concentrations of each sample did not change during a period of 112 days of storage, indicating that the samples possessed an excellent storage stability.

Claims (61)

1. CLAIMS 1. A method for generating chlorine dioxide gas in a controlled release form, characterized in that it comprises: (a) combining at least one metal chlorite and a second material, which is at least one dry solid hydrophilic material capable of reaction with the metal chlorite in the presence of water vapor, but which is not capable of reacting in the substantial absence of liquid water or water vapor to thereby produce the chlorine dioxide gas; and (b) exposing said mixture to an atmosphere containing water vapor to produce chlorine dioxide gas in a sustained amount of about 0.001 'to 1,000 ppm of the atmosphere.
2. 2. The method of compliance with the claim 1, characterized in that the metal chlorite is selected from the group consisting of alkali metal chlorites and alkaline earth metal chlorite.
3. 3. The method according to claim 2, characterized in that the metal chlorite is sodium chlorite.
4. The method according to claim 1, characterized in that the dry solid hydrophilic material produces a pH no greater than about 10.5 when measuring an aqueous portion of a mixture of 30% by weight of the dry solid hydrophilic material in deionized water.
5. The method according to claim 4, characterized in that the dry solid hydrophilic material produces a pH less than 9.
6. The method according to claim 1, characterized in that the second material is selected from the group consisting of zeolites, hydrated clays, calcined clays, acid zeolites, acid clays, acid calcined clays, salts, solid acids, organic acid anhydrides, and mixtures thereof.
7. The method according to claim 1, characterized in that the second material is at least an inorganic material.
8. 8. The method of compliance with the claim 6, characterized in that the second material are metacaolin microspheres.
9. 9. The method according to claim 1, characterized in that it comprises adding at least one desiccant to the mixture.
10. The method according to claim 9, characterized in that at least one desiccant is selected from the group consisting of activated calcium chloride, activated calcium sulfate, activated zeolite X, activated zeolite A, activated bentonite clay, activated activated silica, active attapulgite and mixtures thereof.
11. The method according to claim 1, characterized in that the sustained amount of the chlorine dioxide gas produced is from about 0.001 to 500 ppm.
12. 12. The method according to claim 1, characterized in that the sustained amount of the chlorine dioxide gas produced is from about 0.001 to 100 ppm.
13. The method according to claim 1, characterized in that the sustained amount of the chlorine dioxide gas produced is from about 0.001 to 10 ppm.
14. 14- A system for generating chlorine dioxide gas in a controlled release form characterized in that it comprises: (a) a combination of at least one metal chlorite and at least one second material, which is a dry solid hydrophilic material capable of reacting with the metal chlorite in the presence of water vapor, but which is not capable of reacting with a metal chlorite in the substantial absence of liquid water or water vapor; and (b) an atmosphere comprising water vapor, wherein the combination reacts to produce chlorine dioxide gas in a sustained amount of about 0.001 to 1,000 of said total atmosphere.
15. 15. The system in accordance with the claim 14, characterized in that the metal chlorite is selected from the group consisting of alkali metal chlorites and alkaline earth metal chlorites.
16. 16. The system in accordance with the claim 15, characterized in that the metal chlorite is sodium chlorite.
17. 17. The system in accordance with the claim 14, characterized in that the dry solid hydrophilic material produces a pH of no greater than about 10.5 when an aqueous portion of a mixture of 30% by weight of the dry solid hydrophilic material in deionized water is measured.
18. 18. The system in accordance with the claim 14, characterized in that the second material is at least an inorganic material.
19. 19. The system according to claim 14, characterized in that it comprises at least one desiccant.
20. 20. A dry solid composition for generating chlorine dioxide gas in a controlled release manner comprising a mixture of an effective amount of at least one metal chlorite and at least one second material, which is dry solid hydrophilic material able to react with the metal chlorite in the presence of water vapor, but is not able to react in the substantial absence of liquid water or water vapor.
21. The composition according to claim 20, characterized in that the metal chlorite is selected from the group consisting of alkali metal chlorites, alkaline earth metal chlorites and mixtures thereof.
22. 22. The composition according to claim 21, characterized in that the metal chlorite is sodium chlorite.
23. 23. The composition according to claim 20, characterized in that the dry solid hydrophilic material produces a pH no greater than 10.5 when measuring an aqueous portion of a mixture of 30% by weight of the dry solid hydrophilic material in deionized water.
24. The composition according to claim 23, characterized in that a pH of less than 9 is produced.
25. 25. The composition according to claim 20, characterized in that the second material is selected from the group consisting of zeolites, hydrated clays, clays calcined, acid zeolites, acid clays, acid calcined clays, salts, solid acids, organic acid anhydrides and mixtures thereof.
26. 26. The composition according to claim 25, characterized in that the second material is at least an inorganic material.
27. 27. The composition according to claim 25, characterized in that the second material is metakaolin microspheres.
28. 28. The composition according to claim 25, characterized in that the salts are deliquescent salts.
29. 29. The composition according to claim 28, characterized in that the deliquescent salt is calcium chloride.
30. 30. The composition according to claim 26, characterized in that the second material is at least one inorganic material.
31. The composition according to claim 20, characterized in that it also comprises an effective amount of at least one desiccant.
32. 32. The composition according to claim 31, characterized in that the amount of the desiccant is from about 0.1 to 25% by weight based on the total weight of the composition.
33. The composition according to claim 31, characterized in that the desiccant is selected from the group consisting of activated calcium chloride, activated calcium sulfate, activated zeolite X, activated zeolite A, activated bentonite clay, activated silica gel, activated attapulgite and mixtures thereof.
34. 34. The composition according to claim 20, characterized in that the weight ratio of the metal chlorite to the second material is from about 0.001 to 0.25: 1.0.
35. 35. The composition according to claim 20, characterized in that it comprises a mixture of sodium chlorite and metakaolin microspheres.
36. 36. The composition according to claim 35, characterized in that the amount of sodium chlorite is about 5% by weight based on the total weight of the composition.
37. 37. The composition according to claim 20, characterized in that it consists essentially of about 5% by weight of sodium chlorite, about 10% by weight of activated calcium chloride with the remainder being metacaolin microspheres treated with acid.
38. 38. A method for sanitizing, deodorizing or both sanitizing and deodorizing a solid surface, liquid or gaseous environment characterized in that it comprises exposing said surface or environment to the combination of at least one metal chlorite and at least one second material, which is a dry solid hydrophilic material capable of reacting with the metal chlorite in the presence of water vapor, but which is not capable of reacting with the metal chlorite in the substantial absence of liquid water or water vapor, and exposing the combination to a an atmosphere that contains water vapor to produce chlorine dioxide gas in a sustained amount of about 0.001 to 1,000 ppm of said atmosphere.
39. 39. The method according to claim 38, characterized in that the environment is a medical device.
40. 40. The method according to claim 38, characterized in that the environment is a food product.
41. 41. The method according to claim 38, characterized in that the environment is animal waste.
42. 42. The method according to claim 38, characterized in that the environment is liquid waste.
43. 43. The method according to claim 38, characterized in that the environment is water.
44. 44. The method according to claim 38, characterized in that the environment is potable water.
45. 45. The method according to claim 38, characterized in that the environment is a fabric.
46. 46. The method according to claim 38, characterized in that the environment is an atmosphere containing at least one objectionable and objectionable gas.
47. 47. The method according to claim 46, characterized in that the gas includes smoke.
48. 48. The method according to claim 47, characterized in that the smoke includes tobacco smoke.
49. 49. A method for producing ice that substantially has no undesirable taste and odor characteristics, which comprises freezing water in the presence of a chlorine dioxide gas.
50. 50. The method according to claim 49, characterized in that the chlorine dioxide gas is present in a concentration from about 0.01 ppm to about 10.0 ppm.
51. 51. The method according to claim 49, characterized in that the chlorine dioxide is present in a concentration of about 0.01 ppm to about 1.0 ppm.
52. 52. The method of compliance with the claim 49, characterized in that the chlorine dioxide gas is generated in a controlled release form, comprising: (a) combining at least one metal chlorite and a second material, which is at least one dry solid hydrophilic material capable to react with the metal chlorite in the presence of water vapor, but which is not capable of reacting in the substantial absence of liquid water or water vapor to thereby produce a chlorine dioxide gas; and (b) exposing the mixture to an atmosphere containing water vapor to produce a chlorine dioxide gas in a desired sustained amount.
53. 53. The method according to claim 52, characterized in that the chlorine metal is selected from the group consisting of alkali metal chlorites and alkaline earth metal chlorites.
54. 54. The method according to claim 52, characterized in that the metal chlorite is sodium chlorite.
55. 55. The method according to claim 52, characterized in that the sustained amount of the chlorine dioxide gas produced is from about 0.01 ppm to about 10.0 ppm.
56. 56. The method according to claim 49, characterized in that the chlorine dioxide gas is generated from a dry solid composition in a controlled release form, said composition comprising a mixture of an effective amount of at least one chlorite. of metal and at least one second material, which is a dry solid hydrophilic material capable of reacting with metal chlorite in the presence of water vapor, but which is not capable of reacting in the substantial absence of liquid water or water vapor .
57. 57. The composition according to claim 56, characterized in that the metal chlorite is selected from the group consisting of alkali metal chlorites, alkaline earth metal chlorites and mixtures thereof.
58. 58. The composition according to claim 56, characterized in that the metal chlorite is sodium chlorite.
59. 59. The composition according to claim 56, characterized in that the second material is selected from the group consisting of zeolites, hydrated clays, calcined clays, acid zeolites, acid clays, acid calcined clays, salts, solid acids, organic acid anhydrides. and mixtures thereof.
60. 60. The composition according to claim 56, characterized in that the second material is metacaolin microspheres.
61. 61. The composition according to claim 56, characterized in that the weight ratio of the metal chlorite to the second material is from about 0.001 to 0.25: 1.0.