Method, composition and system for the controlled release of chlorine dioxide gas

Method, composition and system for controlled release of chlorine dioxide gas

<u>Related applications</u>

This application is part of the U.S. serial number 08/961,488 filed on October 30, 1997. The U.S. serial number 08/961,488 is the part of the U.S. serial number 08/891,665 filed on July 11, 1997. Continue to apply, US serial number 08/891,665fi, the part of US serial number 08/808,768 filed on March 3, 1997, continue to apply, the latter has now been abandoned.

<u>Field of invention</u>

The present invention is generally directed to the controlled release of chlorine dioxide gas by the reaction of metal chlorite with a second material. The second material reacts with metal chlorite in the presence of water vapor, but in essence Without the presence of liquid water or water vapor, it will not react with metal chlorite. Once the reaction starts, chlorine dioxide gas is generated at a continuous concentration of about 0.001 to 1000 ppm.

<u>Background of the invention</u>

It has long been known that gaseous chlorine dioxide at low concentrations (that is, up to 1000 ppm) can be used to treat odors and microorganisms. For trying to control the microbial and/or organic odor of food, its use is particularly advantageous, because the role of chlorine dioxide does not form undesirable by-products such as chloramines or chlorinated organic compounds, and elemental chlorine is used for the same purpose Will produce these by-products. For example, during the shipment from the farm to the regional retailer, if the low concentration of chlorine dioxide gas can be kept in contact with fresh agricultural products for several days, the damage rate of the agricultural products can be reduced. In addition, human exposure to low concentrations of chlorine dioxide gas is generally regarded as safe, which is effective for deodorization and most antimicrobial applications.

Chlorine dioxide gas may be toxic to humans when the concentration is greater than 1000 ppm, and it may explode if the concentration is above about 0.1 atmosphere. Unlike other gases, the chlorine dioxide system is not manufactured and shipped under pressure, and the conventional method of on-site manufacturing requires not only expensive production equipment but also the high skill of the operator to avoid dangerously high concentrations. These problems have considerably restricted the use of chlorine dioxide gas for large commercial applications, such as water treatment and poultry treatment, where the consumption of chlorine dioxide is large enough to allow the expensive equipment manufactured on-site and the capital of skilled operators And the operating cost becomes reasonable.

Commercially, chlorine dioxide is produced from various aqueous solutions of chlorine-containing salts. In general, the prior art has focused on three chlorine dioxide production systems using solid reagents. One system uses a solid mixture of metal chlorites and acid in a liquid, aqueous environment. The second system combines metal chlorite and acid, where chlorine dioxide is released in a dry state. The third system uses a combination of metal chlorite and solid organic anhydride in order to generate a highly concentrated stream of chlorine dioxide, which must be diluted by a constant flow of inert gas stream.

These solid reagent systems have their own disadvantages for one or more of the following reasons:

a) Once mixed, a highly concentrated stream of chlorine dioxide is usually suddenly generated;

b) The mixture of reactants produces chlorine dioxide gas in a dry state, thereby reducing the useful life of the reactants; and c) an inert gas stream must be used to reduce the concentration of chlorine dioxide gas in the atmosphere.

For example, US Patent No. 2,022,262 discloses the use of chlorine dioxide in an aqueous solution in the decontamination process, in which oxalic acid is used to acidify an aqueous solution of alkali metal or alkaline earth metal chlorite (that is, chlorite) to produce two Chlorine oxide.

U.S. Patent No. 2,071,091 discloses that chlorous acid produced by acidifying alkali metal or alkaline earth metal chlorite is an effective fungicide and bactericide. This patent discloses a solid composition of metal chlorite and solid acid that produces chlorine dioxide when dissolved in water. However, the material of the '091 patent can only be used in "wet" applications where liquid water is available and what is acceptable is that the material to be treated is brought into contact with chlorine dioxide dissolved in liquid water.

U.S. Patent No. 2,071,094 discloses a deodorant composition in the form of dry briquettes, including a dry mixture of soluble chlorite, acidulant and a low-solubility filler, in order to prevent the briquettes from collapsing and dispersing in the presence of liquid water. This material is subject to the same usage restrictions as the '091 patent.

US Patent No. 2,482,891 discloses a material containing solid organic acid tincture and alkali metal or alkaline earth metal chlorite. The solid material combined by adding a desiccant material is said to release chlorine dioxide when it comes into contact with water. Example 1 Describes the production of chlorine dioxide by contacting a mixture of sodium chlorite, anhydride, and sodium monoxide with water vapor. The example does not clearly show whether the solid mixture has been in contact with liquid water. The gas produced in this example contains a high concentration of chlorine dioxide gas. Moreover, the combination of organic acid anhydride and chlorite may be explosive, and it is a rather expensive component. Therefore, this material has not been commercially successful.

U.S. Patent No. 3,591,515 discloses a solid powder composition comprising a solid carrier impregnated with a stable solution of chlorine dioxide or chlorite. When the composition impregnated with the solution comes into contact with the solid acid, they release chlorine dioxide gas. The materials are currently sold on the market under the trade names OSTOBON and ABSCENT (International Dioxide Company, Clark, NJ), but their market acceptance is limited because they are prematurely on the store shelf packaging A small amount of chlorine dioxide is released, or the user needs to mix the two components quite complicatedly during application.

U.S. Patent No. 4,585,482 discloses a long-acting microbicidal composition, including chlorous acid and organic acid, so that the pH of the composition is less than 7. The composition releases chlorine dioxide in the presence of liquid water. This patent also discloses a method for producing microcapsules containing water in the composition, the microcapsules having a polymer shell so that the synthesized dry material releases chlorine dioxide.

U.S. Patent 4,547,381 discloses a dry composition for continuous and controlled release of gaseous chlorine dioxide, including a dry inert diluent, chlorite and a desiccant that can react with chlorite in a dry state to produce two Chlorine oxide gas. The materials have not yet achieved substantial commercial success, so they release chlorine dioxide gas immediately after being formulated, so they must be mixed and used within a short period of time.

U.S. Patent No. 5,360,609 discloses mixing a compound that generates chlorine dioxide into a polymer or oligomer film, which is then coated on a substrate. The chlorite component is dissolved in a hydrogen-bonded phase containing monomeric or polymerized amide or alcohol. The hydrogen-bonded phase is then mixed with an incompatible non-polar phase containing acid tincture. Chlorine dioxide gas is released by the direct reaction of acid anhydride and chlorite anion crossing the phase boundary. However, the method described in the '609 patent uses relatively expensive materials and the reaction system may be explosive because the strongly oxidizing metal chlorite is close to the carbon-containing polymer.

U.S. Patent No. 5,567,405 discloses the generation of chlorine dioxide gas from a mixed bed of zeolite crystals. The first bed includes zeolite impregnated with an aqueous solution of sodium chlorite, and the second bed includes phosphoric acid, citric acid or acetic acid. When the acid migrates out of the second bed and contacts the chlorite in the first bed, chlorine dioxide gas is released. The first bed and the second bed can be physically mixed together. The method disclosed in the '45 patent requires expensive equipment, and the resulting product has a relatively short useful life.

Therefore, a method, composition and system for generating chlorine dioxide gas at a low concentration under a controlled state will be one of the major advances in the technology of generating chlorine dioxide gas in commercial applications. One of the further advances of this technology will be to provide a method, composition and system in which the reactant will not produce chlorine dioxide gas in the absence of water, but will continue to release chlorine dioxide in a controlled manner in the presence of water vapor gas. As a result, the composition of the present invention can be prepared in advance and stored in a dry state without premature release of chlorine dioxide gas. In this way, the need for skilled personnel to prepare the mixture on site is avoided, and the useful life is increased.

Summary of the invention

The present invention is generally directed to a method, composition and system, which is suitable for the controlled release of low-concentration chlorine dioxide gas in the presence of water vapor. When combined into a composition, the reactant that produces chlorine dioxide gas will not produce a large amount of chlorine dioxide gas in the presence of water vapor. The reactants can therefore be stored for a long time in a substantially dry atmosphere.

In particular, the present invention is partially directed to a method for generating chlorine dioxide gas in a controlled release manner, including:

a) forming a mixture of at least one metal chlorite and at least one second material, the second material being a dry solid hydrophilic material that can react with metal chlorite in the presence of water vapor to produce chlorine dioxide gas but It will not react in the substantial absence of liquid water or water vapor (hereinafter the second material"); and b) exposing the mixture to an atmosphere containing water vapor so as to produce two at a continuous concentration of about 0.025 to 000 ppm Chlorine oxide gas.

The present invention is also directed to a composition for generating chlorine dioxide gas, which is a mixed form of reactants. The reactants can be selected to control the rate and duration of chlorine dioxide gas generation.

<u>Detailed description of the invention</u>

The present invention is directed to a method, composition and system for generating chlorine dioxide gas by a controlled release method. As used here, the term "controlled release" means that the composition containing reactants is manufactured at a low gas concentration compared with the previous technological system (in which chlorine dioxide gas is generated in a sudden high concentration and possibly explosive manner) The rate produces chlorine dioxide gas. According to another aspect of the present invention, a solid composition for producing chlorine dioxide gas is provided, in which the generation rate and duration of chlorine dioxide gas can be controlled.

The first step of the method is to form a composition, which is a mixture of at least one metal chlorite and at least one second material. The metal chlorite used in the present invention can generally be any metal chlorite. Preferred metal chlorites are alkali metal chlorites, such as sodium chlorite and potassium chlorite. Alkaline earth metal chlorites can also be used. Examples of alkaline earth metal chlorites include barium chlorite, calcium chlorite, and magnesium chlorite. The best 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 has a pH of no more than about 10.5 when the aqueous portion of the 30 weight percent material mixture is measured in deionized water. More preferably, the pH of the solid hydrophilic material is less than 9, and most preferably less than 7. Examples of the dry solid hydrophilic material suitable for reacting with metal chlorite include (but not limited to) synthetic zeolites such as A, X, Y and mordenite; natural zeolites such as chabazite and clinoptilolite ; Water-containing clay, such as bentonite, kaolin, attapulgite and halloysite; burnt clay, such as metakaolin, spinel phase kaolin, burned kaolin, burned hallowed clay and burnt green Palygorskite; acidified synthetic zeolites, such as A, X, Y and mordenite, which have been in contact with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid or other acidic compounds (such as calcium chloride), and are produced by mixtures The pH of the aqueous phase is below 10.5; acidified natural zeolites, such as chabazite and cloparite; acidified clays, such as bentonite, kaolin, attapulgite and halloysite, which have been combined with one or more sulfuric acid , Hydrochloric acid, nitric acid or other acidic compounds (such as lanthanum chloride) in contact with an acidic solution, the pH of the aqueous phase produced by the mixture is lower than 10.5; acidified burnt clay, such as metakaolin, spinel phase kaolin, Burned kaolin, burned halloysite and burned attapulgite, which have been in contact with one or more acidic solutions containing sulfuric acid, hydrochloric acid, nitric acid or other acidic compounds (such as acetic acid), and the water produced by the mixture The phase pH is lower than 10.5; salts, such as aluminum sulfate, magnesium sulfate, calcium carbonate, and especially deliquescent acid salts, 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 acid anhydride, maleic anhydride, succinic anhydride, and glutaric anhydride; and mixtures thereof.

The preferred second material is metakaolin microspheres. As used herein, the term "microspheres" shall mean nominal spherulites with an average particle size of about 50 to 100 microns. Metakaolin microspheres are essentially composed of metakaolin, and can be prepared by the procedure described in the following section of raw material preparation.

The following procedure can be used to determine whether the material is a suitable second material for forming a mixture with metal chlorite for the purpose of the present invention.

Dry air: Prepare an intimate mixture of the desired amount of metal chlorite (such as sodium chlorite) and the recommended second material and store it in a dry state. A one gram portion of the mixture is placed in a dry and sealed one-gallon polyethylene container at room temperature, and the container is flushed with dry air at a flow rate of about 10 cc/min (that is, the dew point is not greater than -50°C). Regularly measure the chlorine dioxide concentration of the gas in the container for a period of 72 hours. In this dry air test, if the concentration of the generated chlorine dioxide gas is less than about 0.025ppm, the second material has acceptable dry stability, even if the second material releases chlorine dioxide gas for a short period of time initially. When the concentration exceeds 0.025 ppm, it is due to the presence of solids and/or a small amount of residual water in the container.

Humid air; expose another gram portion of the mixture used in the above dry air test step to a sealed one-gallon polyethylene container with a relative humidity of about 80% at room temperature, and the container is subjected to 80% relative temperature air at a flow rate of about 10cc/min The flushing. Regularly measure the concentration of chlorine dioxide gas in the container for a period of 7 days.

If the material exhibits acceptable stability in the above dry air test and if the continuous concentration of chlorine dioxide gas (defined below) generated by the material at any time during the above wet air test is equal to or more than about 0.025 ppm (to control Type release mode), the material is regarded as an acceptable second material.

According to the present invention, the mixture of metal chlorite and the second material will generate chlorine dioxide gas at a continuous concentration of about 0.001 to 1000 ppm, preferably about 0.001 to 100 ppm, and more preferably about 0.01 to 10 ppm.

The chlorine dioxide gas is measured in an atmosphere where chlorine dioxide gas is generated. For example, if the resulting mixture is exposed to water vapor in the air, the concentration (ppm) of chlorine dioxide gas will be measured based on the total atmosphere containing air and water vapor.

As mentioned above, according to the present invention, chlorine dioxide gas is produced at a continuous concentration of about 0.001 to 1000 ppm. The term "continuous concentration" means that the concentration of chlorine dioxide gas during manufacturing is always in the range of 0.001 to 1000 ppm. The fluctuation rate is allowed as long as the concentration of chlorine dioxide gas does not exceed 1000 ppm, and it undergoes the duration defined below in the range of about 0.001 to 1000 ppm.

According to the present invention, the generation of chlorine dioxide gas within a specific range will vary depending on the relative humidity of the surrounding atmosphere, the proportion of reactants in the mixture, the flow rate of the dilution gas (such as air) passing through the space to be treated, and the chlorine dioxide gas releasing material. The amount changes in proportion to the volume of the space to be processed. Generally, the higher the relative humidity, the higher the production rate of chlorine dioxide gas. The lower the flow rate of the dilution gas flowing through the space to be treated, the higher the concentration of chlorine dioxide gas produced. The higher the ratio of the amount of chlorine dioxide gas releasing material to the volume of the space to be treated, the higher the concentration of chlorine dioxide gas. In a preferred embodiment of the present invention, the continuous amount of chlorine dioxide gas is about 0.001 to 1000 ppm, more preferably about 0.001 to 100 ppm. Particularly good results are obtained when chlorine dioxide gas is produced in the range of about 0.01 to 10 ppm.

The amount of each metal chlorite and the second material will depend on many factors, including (but not to limit) the amount of chlorine dioxide gas required for a particular application, the alkalinity of the metal chlorite and the second The acidity of the material. In general, it is better to use as much metal chlorite as possible in order to accommodate a sufficient release rate. As a result, the output of chlorine dioxide per unit mass of the mixture is maximized. Generally, the weight ratio of the metal chlorite to the second material is in the range of about 0.001 to 0.25:1.0. Those who are familiar with the art can choose the appropriate ratio for a particular application.

The mixture formed according to the present invention may optionally contain at least one desiccant, which can absorb water so as to eliminate the chlorine dioxide gas produced during the initial brief period due to residual water vapor in the atmosphere or solids when the mixture is packaged. Suitable desiccants include (but are not limited to) activated calcium chloride, activated calcium sulfate, activated zeolite X, activated zeolite A, activated bentonite clay, activated silica gel, activated attapulgite, and mixtures thereof. The term "active" means that the particulate matter has been substantially dehydrated, for example heated at 300°C for about one hour. The total amount of desiccant varies depending on several factors, such as the ambient humidity when the material is packaged, the water permeability of the packaging material, and the desired service life of the product. Generally, the total amount of desiccant present is about 0.1% to about 25% by weight of the total weight of the mixture.

When implementing the present invention, the relative humidity of the atmosphere to which the composition is exposed during use can range from low to high humidity. The method of the present invention can be performed at low humidity (for example, 10% relative humidity) to 100% relative humidity. As mentioned above, the amount of chlorine dioxide gas produced by each specific amount of mixture will partly depend on the relative humidity of the surrounding atmosphere. Generally, higher humidity will produce a higher concentration of chlorine dioxide gas.

For example, it has been observed that when the relative humidity increases from about 10% to about 8.0% at room temperature, the production of chlorine dioxide gas will approximately double. It has also been observed that there is no significant change in the production rate of chlorine dioxide at ambient room temperature compared to 32°F.

It will be understood that a mixture of a specific unit will produce a continuous amount of chlorine dioxide gas. For commercial applications, it is appropriate to start the production of chlorine dioxide gas from a mixture of one or more units, and then add a second group or groups of mixture units at a later time. Furthermore, one component in the composition of the present invention may be present in excess, and a second component may be added if necessary. For example, the composition may initially contain an excess of the second material, such as acid-treated metakaolin microspheres, and periodically add additional amounts of metal chlorite.

The mixture of metal chlorite and the second material can be formulated in several ways. The preferred method is to produce an intimate physical mixture of fine powders in a dry atmosphere. Both components preferably have a particle size below about 200 microns. Larger particles can be used, and in some cases a slower release rate of chlorine dioxide gas can be achieved.

It is also possible to combine liquid components with other components to form a mixture. For example, a slurry of -fired kaolin fine powder in a non-polar liquid such as dodecane can be combined with metal chlorite. Then, the mixture is dried to remove the non-polar liquid. If water is used as the liquid, the mixture should be quickly dried to a sufficient degree to avoid excessive release of chlorine dioxide gas.

The reaction of the metal chlorite with the second material can continue for a period of time. The term "duration" means that chlorine dioxide gas will be generated in a short time (a few minutes) to a long time (many hours). The length of the duration will depend, for example, on the relative amounts of ingredients in the mixture. The result is of course that one of the reaction components (metal chlorite or the second material) will be used up to terminate the reaction. However, during the long reaction period, chlorine dioxide gas will be produced at a continuous concentration as defined herein.

A preferred composition that produces a long-term slow release rate is a mixture of about 5% sodium chlorite and about 95% metakaolin microspheres. A preferred composition that produces chlorine dioxide with a shorter duration and a higher rate is a mixture of about 5% sodium chlorite, about 10% active calcium chloride and the rest are acid-treated metakaolin microspheres .

The length of the reaction time also depends in part on how much water vapor is present in the atmosphere contained in the package. The desiccant may be selected as needed to minimize the production of chlorine dioxide gas in the package during storage, and to ensure that the mixture will have the longest reaction time when exposed to water vapor under operating conditions. However, when the mixture is exposed to water vapor, the presence of the desiccant can delay the start of the production of chlorine dioxide gas.

The invention can be used in a variety of commercial applications, including solid, liquid and/or gaseous environments. For example, chlorine dioxide gas can be used to treat solids such as those with metal, fabric, wood, and/or plastic surfaces. Chlorine dioxide gas can also be used to treat animal waste, pets and domestic animal debris; medical devices, including bandages, stoma devices and medical equipment, food, including meat, vegetables, fruits, grains and nuts: and fabric manufacturing items, Including diapers, wall hangings, upholstery materials and clothes. Examples of liquids that can be treated with chlorine dioxide include liquid waste and water containing drinking water. Examples of treatable gas environments include those containing toxic and/or unpleasant gases such as animal environments, smoke-containing environments (such as tobacco smoke), and exhaust systems of toxic gas manufacturing facilities (such as chemical factories).

The material of this invention can be used to help prevent the incorporation of unwanted substances (including potentially toxic substances), which may have an adverse effect on the taste and smell of ice produced by ice machines, especially in large-scale ice production such as commercial applications of. It is well known that after a long period of use, the ice making chamber of the ice maker may accumulate microorganisms (including pathogenic microorganisms) and may emit harmful or unpleasant odors or smells and other by-products. Before, during or after the water freezing process, these by-products may accumulate in or on the ice produced. However, it is believed that when the material of the present invention is used to generate and maintain a chlorine dioxide gas concentration of about 0.01 to about 10.0 ppm, preferably about 0.01 to about 1.0 ppm, in the ice making chamber of an ice maker, it will less affect the manufactured The taste and smell of the ice will not be damaged to a substantial degree. It is believed that the chlorine dioxide gas produced according to the implementation of the present invention will destroy the microbial by-products with unpleasant odor and taste, so that they will not contaminate the ice. At higher concentrations of chlorine dioxide gas, I believe that the microorganisms themselves will be destroyed by the chlorine dioxide gas.

The range of physical and chemical properties of metakaolin microspheres makes them particularly valuable for their applications, such as cleaning and deodorizing fabrics and carpets, where the second material and chlorine dioxide gas source must be applied to the surface in solid form. Provides a gradual and controlled release of chlorine dioxide, and the used reactant must be recycled as a solid, will not produce obvious dust and will not adhere or form on the material applied to the composition or inside the vacuum cleaner or machine sweeper Crusty.

Metakaolin powder has a low surface area, as measured by the BET method. Therefore, there is minimal microporosity. However, when supplied in the form of spray-dried microspheres, the surface area is still low, but voids are generated, and the microspheres have a considerable amount of macropores (voids). See U.S. Patent No. 4,214,978 by Kennedy et al. As disclosed in this patent and other patents, the surface area (BET, using nitrogen) is typically between to and 15 cm²/g, but the pore volume (reflective void) is between 0.06cc/g and 0.09cc/g. Within the range of grams.

In the liquid part of the aqueous slurry of microspheres, the microspheres generate an acidic pH.

When exposed to humidity, water vapor can condense in the voids of the microspheres of the burnt clay, thereby generating protons, which can then react with chlorite to produce chlorine dioxide gas. This gas is then released into the environment. In the case of carpets or the like, this gas penetrates into the material to be processed. Therefore, it is believed that water is transported as vapor in the air into the micropores, where it condenses to form protons, and then reacts with chlorite to produce chlorine dioxide gas.

Because the microsphere particles are larger than the chlorate particles, we believe that the chlorite is attached to the fresh (unused) microspheres. This is combined with the fact that the particles are agglomerated and maintain their integrity during use and finally removed by a vacuum or machine sweeper, resulting in the composition not generating a significant amount of dust. Because the microspheres will not disintegrate or burst during use, they will not encounter unpleasant residue films or carpet material skins.

The composition of the present invention based on metakaolin as the second material may optionally contain components other than chlorite powder. Optional ingredients include desiccants such as calcium chloride and zeolite molecular sieves or granular solid acids such as citric acid to adjust the release rate of chlorine dioxide.

Mineral acid such as sulfuric acid can be applied to the microspheres by spraying or other physical forms that will not disrupt the microspheres. This is followed by drying, preferably at a temperature below which any aluminum salt produced will decompose.

The metal chlorite, the second material and any suitable additives can be packaged, shipped and stored in a container made of a material resistant to liquid and water vapor. Examples of such materials include metal cans, glass bottles, aluminum foil bags, and barrier polymer laminates.

The mixture of metal chlorite and the second material can be used as a powder, used as a shaped shape, or packaged or retained in any breathable material. Preferably, any packaging materials used for retention purposes are substantially impermeable to liquid water. Examples of this material include TYVK. and GORTE. These materials enable water vapor to enter the package and react with the mixture and also release the chlorine dioxide gas generated from the package into the atmosphere. The material is substantially impermeable to liquid water.

<u>Test procedure</u>

Unless otherwise indicated, the following test procedure was used to evaluate the samples prepared in the following examples. Place one gram of the specified material as a thin layer into a 2-inch diameter crystallizing dish. Place the disc in a one-gallon resealable polyethylene bag with gas inlet and outlet near the opposite corners. The bag is flushed with dry air or air with a predetermined humidity through the gas inlet and gently pressurized to about 0.1 inches of water column. The bag is then continuously flushed at a flow rate of about 10 cc/min. The flushing air is discharged through a pipe just below the surface of the water tank to maintain a back pressure of about 0.1 inches of water column. Replace the gas outlet exhaust pipe with a gas sampling tube and draw samples through a gas analysis tube (Draeger type CH24301) to analyze the chlorine dioxide gas in the bag.

The dry air is supplied by a laboratory compressed air system, which is further purified by passing through a 13X molecular sieve trap (Hewlett Packard type GMT-4-HP). Pass the laboratory compressed air at a rate of about 200 cc/min through a one-liter beaker containing 500 cc of agitated saturated ammonium sulfate solution at room temperature, which is in a polyethylene glove bag with an inner volume of about 20 liters. A side wall is immersed in the water column for about 1/2 inch and part of the gas is discharged to maintain the internal pressure in the bag about 1/2 inch of water column.

<u>Preparation example</u>

I. Industrial-grade flake sodium chlorite, nominally 80% pure and the rest is reported as 20% sodium chloride (available from Acros, Aldrich Chemical Company and AlfaAesar), dried at 150°C for 3 hours, and Cool to room temperature in a sealed container.

II. Use a saturated solution of sodium chlorite to immerse sodium chlorite in water. The saturated solution is prepared by mixing excess granular sodium chlorite with deionized water at 35°C for one hour and cooling to room temperature After stirring overnight at room temperature, the resulting solid-containing solution was filtered to remove the solids and leave a clear saturated solution.

III. Supply dry calcium chloride and potassium chloride as industrial grade granular solids (supplied by TJ Baker Company and Aldrich Chemical Company, respectively). Each was dried at 300°C for 3 hours, and then cooled in a sealed container before use.

IV. Spray-dry the aqueous slurry of the white water-containing Georgia kaolin clay to prepare metakaolin microspheres. The slurry has a solid content of about 28-44% and a particle size distribution of about 80% by weight finer than one micron. Dispersed up to 2% by weight of clay, the clay is 25% to 30% sodium silicate solution (SiO₂: Na2_OThe molar ratio is 2.0 to 3.3), and a wheel atomized spray dryer is used to produce spherical kaolin clay with an average particle size of about 70 microns. The viscous polymer is burnt in a commercial rotary burner for a period of time and at a temperature sufficient to convert substantially all of the hydrous kaolin into metakaolin (for example, at 700°C for one hour).

V. Manufacture the kaolin clay microspheres that have undergone the characteristic kaolin exothermic calcination in the same manner as in the preparation of metakaolin microspheres in the above IV, except that the calcination temperature is relatively high (for example, at 1000°C for one hour). Water-containing kaolin undergoes characteristic exothermic transformation into mature spinel phase kaolin, and no substantial mullite is formed. The resulting material is called "spinel phase microspheres

VI. Soak about 300 grams of metakaolin microspheres prepared in the above IV in 280 grams of 2.1N sulfuric acid solution, dry at 100°C and burn at 350°C for 3 hours to prepare acid-treated metakaolin microspheres.

Before being mixed into the mixture of the present invention, the metakaolin microspheres and spinel phase microspheres were heated at 300°C for 3 hours in a laboratory oven, and then cooled to room temperature in a sealed container.

The following examples are used to illustrate the embodiments of the present invention, but are not intended to limit the present invention, such as those included in the scope of the patent application that forms part of this application.

<u>Example 1</u>

The first mixture; in the ambient room air condition, use a mortar and pestle to grind with gentle hands to mix 200 g of the metakaolin microspheres prepared in Preparation Example IV with 12.5 g of the dry chlorous acid prepared in Preparation Example I Place the mixed sample in a sealed glass bottle wrapped with opaque tape

<u>Second mixture</u>: In dry air with a dew point of about -20°C or less, use a mortar and pestle in a glove bag to grind with gentle hands to mix 200 grams of metakaolin microspheres with dry sodium chlorite. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

One gram of the first mixture was tested in the dry state as described in the test procedure. The results are shown in Figure 1. The initial trace amount (0.3PP) of chlorine dioxide gas was detected in the first five hours, which may be caused by the water originally present in the sample, but no other chlorine dioxide gas was detected after 195 hours. At this point, the dry air stream is humidified to approximately 80% relative humidity. The concentration of chlorine dioxide gas was increased to 1 ppm and kept at 1 ppm until the end of the test in about 250 hours.

Test another gram sample of the first mixture at 80% relative humidity as described in the test procedure. The results are also shown in Figure 1. The concentration of chlorine dioxide gas increased from 0 to 2 ppm in 19 hours, and it was in the range between 1 and 2 ppm after about 360 hours of testing.

The result of testing one gram of the second mixture in the dry state described in the test procedure is shown in Figure 2. No chlorine dioxide gas was detected in the test for 313 hours in a dry state. At this point, the dry air stream is humidified to approximately 80% relative humidity. The concentration of chlorine dioxide gas was increased to 1 ppm and stayed between 1 and 1.1 pp until the end of the test at 450 hours.

The results shown in Figures 1 and 2 show that the mixture prepared according to Example 1 has stability in a dry state and the ability to release chlorine dioxide gas when exposed to humidity. Furthermore, they show that the initial release of the trace amount of the first mixture may be the result of water absorbed during sample preparation in the surrounding air, and if necessary, the material can be prepared in a dry state in order to even eliminate this trace level of premature release .

<u>Example 2</u>

A. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to mix 200 grams of the spinel phase microspheres prepared in Preparation Example V with 12.5 dry sodium chlorite. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

B. Test one gram of the mixture prepared in paragraph A above at 80% relative humidity. Chlorine dioxide gas was first detected after 5.5 hours. The peak of the chlorine dioxide gas concentration after 94 hours was 1 ppm, and the chlorine dioxide gas concentration after 364 hours was 0.15 ppm.

<u>Example 3</u>

A. The acid-activated bentonite clay was prepared as follows. Preparation one contains Engelhard F100^TMThe paste of brand bentonite clay and oxalic acid (1g clay/10ml 2M oxalic acid solution). The slurry was heated at 90°C for 6 hours and filtered, washed three times with deionized water, dried at 105°C, and then fired at 350°C for 3 hours.

B. Use a mortar and pestle in a glove bag under dry air to mix 50 grams of the acid-activated bentonite clay prepared in paragraph A above with 3.2 grams of dry sodium chlorite with gentle hands. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

C. Test the mixture prepared in paragraph B above as described in the test procedure. In the dry state, no chlorine dioxide gas was detected after 72 hours of testing. Under humidity conditions, a trace amount of chlorine dioxide gas (&lt;0.1 ppm) was detected after 5 hours: the peak concentration was 2.5 ppm after 45.5 hours, and it was 2.25 ppm at the end of the test after 72 hours.

<u>Example 4</u>

A. The microspheres from the intermediate stage of the production process of the components of the commercial fluid catalytic cracking catalyst are dried at 450°C for 3 hours, and they contain about 70% by weight of zeolite Y in the form of sodium ion exchange (NaY, Si/A1 = 2.58) And 30% by weight of the zeolite crystallization reaction of amorphous sodium-silica-alumina residue (see, for example, Example 4 in U.S. Patent No. 5,395,809). When mixed at a concentration of about 30% by weight solids in water, the pH of the aqueous phase of the resulting slurry is about 8.

B. In the surrounding room, use a mortar and pestle to grind with gentle hands to mix 200 grams of the dry NaY-containing microspheres prepared in paragraph A above with 12.5 grams of dry sodium chlorite. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

C. Test the mixture prepared in paragraph B above as described in the test procedure. In the dry state, no chlorine dioxide gas was detected during the first 196 hours of the test, but chlorine dioxide gas (0.5 ppm) was detected after 313 hours, and there was still a small amount at the end of the 337 hour test. Quantity (0.1ppm). This result shows that the material has a pot life of about one to two weeks, so it should be satisfactorily used in applications where there is only a slight delay between mixing and use.

When the mixture prepared in paragraph B above was exposed to moisture, chlorine dioxide gas (2.6 ppm) was initially detected after exposure 54.

At the end of the test after 364 hours, the concentration remained between about 1 and about 3 ppm.

<u>Example 5</u>

A. The sodium hydrogen zeolite Y (NaHY) powder is prepared as follows: 25 grams of sodium Y zeolite powder (Si/A1 = 2.34 Aldrich) is slurried in 250 ml of 5 weight percent ammonium sulfate solution. The aqueous phase of the resulting slurry has a pH of 6.5. The slurry was heated to 900C and stirred for 2 hours, and filtered to separate the solid zeolite from the solution. The solid was washed five times with about 200 grams of deionized water and dried at a temperature of about 105°C. The dry solid was burned in a thin layer of an open pan at a temperature of 4500C for 2 hours, and cooled to room temperature in a sealed container.

B. Immerse 8 grams of the NaHY powder prepared in paragraph A above with a saturated solution of 1.6 grams of sodium chlorite to prepare another material. Add the solution dropwise to the powder and stir quickly so that the solution is distributed to the powder most quickly. After the impregnation step, the mixture of zeolite impregnated with sodium chlorite is not dried. It is stored in a sealed glass container covered by opaque tape.

C. Test the mixture prepared in paragraph B above according to the test procedure.

In the dry state, chlorine dioxide gas was released within 2 hours, and the concentration of chlorine dioxide gas remained between 3 and 4.5 ppm in the 26-hour test. In a wet state, the mixture produces 3 to 4.5 ppm chlorine dioxide gas in the first 48 hours. After 150 hours of exposure to moisture, the concentration of chlorine dioxide gas slowly decreased to zero.

<u>Example 6</u>

A. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to mix 10 grams of dry calcium chloride prepared in Preparation Example III with 0.75 grams of dry sodium chlorite. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

B. Test the mixture prepared in the above paragraph A in a dry state according to the test procedure. After 72 hours of test, no chlorine dioxide gas was detected. In a humid state, no chlorine dioxide gas was detected for 54 hours, the amount (0.25 ppm) was detected for 94 hours, and chlorine dioxide gas was generated stably at a concentration of about 1 to 2 pp after 364 hours.

<u>Example 7</u>

A. In the ambient room air condition, use a mortar and pestle to grind with gentle hands so that 84 grams of the acid-treated metakaolin microspheres prepared in Preparation Example VI are mixed with 10 grams of dry calcium chloride. The resulting mixture was dried at 200°C for 2 hours and cooled to room temperature in a sealed glass bottle wrapped with opaque tape.

B. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to combine the mixture prepared in the above paragraph A with 5.25 grams of dry sodium chlorite. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

C. Test the mixture prepared in paragraph B above according to the test procedure.

In the dry state, no chlorine dioxide gas was detected after 72 hours of testing. In a humid state, a trace amount (0.05 ppm) of chlorine dioxide gas was detected after 4 hours. The chlorine dioxide concentration peaked at 6.25 pp after 26 hours, and dropped to zero after 172 hours.

<u>Example 8</u>

A. The materials are prepared as follows. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to mix 10 grams of stearic acid (Aldrich) with 0.75 grams of dry sodium chlorite. Place the mixed sample in a sealed glass bottle wrapped with opaque tape.

B. Test the mixture prepared in paragraph A above at 80% relative humidity according to the test procedure. After 8 days of the test, no chlorine dioxide gas was detected.

<u>Example 9</u>

A. The mixture according to the invention is prepared as follows. Commercial 13X zeolite powder (Aldrich) was dried at 300°C for 3 hours and cooled to room temperature in a closed container. When slurried in water at 30 weight percent, the aqueous phase of the slurry has a pH of 9.7. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to mix 10 grams of dry 13X powder with 0.8 grams of dry sodium chlorite. Place the mixture in a sealed glass container covered with opaque tape.

B. Test the mixture prepared in paragraph A above according to the test procedure. In the dry state, no chlorine dioxide gas was detected after 144 hours of testing. In a humid state, a trace amount (0.05 ppm) of chlorine dioxide gas was detected after 96 hours. After the remaining 168 hours, the concentration of chlorine dioxide fluctuated between 0.025 and 0.05 ppm.

<u>Example 10</u>

A. In the surrounding room air, use a mortar and pestle to grind with gentle hands to mix 50 grams of acid-treated kaolin microspheres with 5 grams of the dry potassium chloride prepared in Preparation Example III. Place. The resulting mixture was dried at °C for 2 hours and cooled to room temperature in a sealed container.

B. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to combine the mixture prepared in paragraph A above with 3.125 grams of dry sodium chlorite. The resulting mixture is placed in a sealed glass bottle wrapped with opaque tape.

C. Test the mixture prepared in paragraph B above in moisture according to the test procedure. A trace amount (0.1 ppm) of chlorine dioxide gas was detected after 45 minutes, and the concentration range of chlorine dioxide gas was between about 1 and 3 ppm between about 4 and 290 hours at the end of the test.

<u>Example 11</u>

The metakaolin microspheres were reacted in an aqueous solution of sodium hydroxide, potassium hydroxide and sodium silicate at 75°C to produce 80% zeolite X (with SiO₂To A1₂O₃The ratio is equal to one, which is the mixed sodium and potassium ion exchange form) and 20% microspheres of the crystalline residue of burnt kaolin clay. The solid was filtered and washed with deionized water until the pH of the effluent was about 10.5. The solid was then dried at 3000C for 3 hours, and cooled to room temperature in a sealed container. When slurried in water at 30 weight percent, the aqueous phase of the slurry has a pH of 10.3. In the ambient room air condition, use a mortar and pestle to grind with gentle hands to mix 12 grams of dry microspheres with 0.8 grams of dry sodium chlorite. Store the mixture in a sealed glass container covered with opaque tape.

Test the mixture according to the test procedure. In the dry state, no chlorine dioxide gas was detected after 144 hours of testing. In a humid state, a trace amount (0.1 ppm) of chlorine dioxide gas was detected after 40 hours. The release of chlorine dioxide gas slowly increased, reaching a peak of 0.5 ppm at 124 hours, and 0.4 ppm at the end of the test after 143 hours.

<u>Example 12</u>

Three samples, each in the form of powder prepared according to Examples 1, 4, and 7, were tested by the following procedures to determine the storage stability of the composition of the present invention.

Store individual one gram samples in sealed glass bottles. The water-soluble components were extracted into a buffered aqueous solution of pH 7 at room temperature for chemical analysis of each sample. According to the general procedure of EPA Test Method 300, ion chromatography was used to analyze the concentration of chlorate, chlorite, and chloride anion in each solution. The chlorite analysis standard is prepared from industrial-grade solid sodium chlorite, which is deemed to contain about 80% by weight of pure sodium chlorite. The results are shown in Figure 3.

As shown in Figure 3, in addition to the small initial decrease in chlorite concentration, the chlorite and chlorate concentrations of each sample remained unchanged after 112 days of storage time, indicating that the sample has excellent storage stability sex.

The first figure is a graph showing the production of chlorine dioxide gas in the dry and wet state of the first mixture prepared according to Example 1;

The second figure is a graph showing the production of chlorine dioxide gas in the dry and wet state of the second mixture prepared according to Example 1;

The third figure is a graph showing the concentration of chlorite or chlorate anion in the powdered sample during storage of the mixture prepared according to the present invention in a dry state.