WO2000048612A1

WO2000048612A1 - Method for producing chlorine dioxide using chemically impregnated expanded amorphous aluminum silicate

Info

Publication number: WO2000048612A1
Application number: PCT/US2000/004289
Authority: WO
Inventors: Neeraj Khanna; Theodore D. Head; Bryan D. Lowery
Original assignee: Bio-Cide International, Inc.
Priority date: 1999-02-18
Filing date: 2000-02-18
Publication date: 2000-08-24
Also published as: US6660287B1; EP1202740A1; EP1202740A4; WO2000048612B1; US6132748A; AU3600700A

Abstract

An important and central aspect of the present invention is the use of expanded amorphous aluminum silicate as a vehicle for a chlorite salt. This vehicle, when exposed to moisture, will release chlorine dioxide (C1O2) for purposes of deodorization or microbial suppression. Thus, where a particular area or volume is to be deodorized or made less microbially contaminated, the EAAS-chlorite salt (most preferably sodium chlorite) is placed in the area or volume to be treated and moisture is permitted to interact with the material. The result of the moisture is to permit the chemical reaction (presumably acidification) of the chlorite salt to yield chlorine dioxide gas. While normal EAAS has some inherent acidity, the inherent acidity is low enough so that, even when a chloride salt is encapsulated in the EAAS and the resultant mixture exposed to moisture, C102 release is very slow and over an extended period. Under most conditions, a more rapid release of C1O2 is desired for deodorization and/or sterilization. A more rapid release of chlorine dioxide may be accomplished by first treating the native EAAS with an acid, preferably a protic acid, to acidify chemical groups of the EAAS. After native EAAS is acidified and dried, if necessary, a chlorite salt such as sodium chlorite is incorporated therein.

Description

METHOD FOR PRODUCING CHLORINE DIOXIDE USING

CHEMICALLY IMPREGNATED EXPANDED

AMORPHOUS ALUMINUM SILICATE

Field of the Invention

The present invention relates to a method for producing chlorine dioxide using

expanded amorphous aluminum silicates ("EAAS") (CAS 93763-70-3).

Background of Invention

The present invention relates generally to a biocidal composition which releases chlorine dioxide for odor-diminishing biocidal or other purposes. The invention particularly relates to a composite formulated as a powder.

Chlorine dioxide (ClO₂) is a superior oxidizing agent widely used as a bleach, disinfectant, fumigant or deodorizer. It can penetrate the cell wall or membranes and cytoplasm of mold spores, bacteria and other microbiological contaminants at low

concentrations. The incorporation of chlorine dioxide or sodium chlorite in food packaging has

prompted studies to determine whether residual levels of such preservatives result in

a significant genetic or carcinogenic hazard to humans. Meier et al. studied the effect

of subchronic and acute oral administration of chlorine, chlorine dioxide, sodium

chlorite sodium chlorate and related substances on the induction of chromosomal

aberrations and spermhead abnormalities in mice. Only the highly reactive

hypochlorite resulted in a weak positive effect for mutagenic potential. The other

compounds, including chlorine dioxide and sodium chlorite, failed to induce any chromosomal aberrations or increased numbers of micronuclei in the bone marrow of mice. Richardson et al. reported that an extensive study of the reaction of chlorine

dioxide with water borne organics by the Environmental Protection Agency confirmed this observation.

Japanese Kokai Nos. 63/296,758, 63/274,434, and 57/168,977 describe

deodorants containing chlorine dioxide incorporated in a polymer, ceramic beads, or

calcium silicate wrapped in nonwoven cloth, respectively. Gels which generate chlorine dioxide for use as topical applications for disinfection are disclosed by

Kenyon, et. al. Chlorine dioxide generating gels are generally formed by mixing a gel

containing suspended sodium chlorite with a gel containing lactic acid immediately prior to use to avoid premature chlorine dioxide release. Chlorine dioxide releasing

gels have also been used in food preservation.

Encapsulation processes have also been used in preparing sources of chlorine

dioxide. Canadian Patent No. 959,238 describes generation of chlorine dioxide by

separately encapsulating sodium chlorite and lactic acid in polyvinyl alcohol and

mixing the capsules with water to produce chlorine dioxide.

Tice et al. describe gradual hydrolysis of alternating poly (vinyl methyl ether-

maleic anhydride) or poly(lactic-glycolic acid) to generate acid which can release

chlorine dioxide from sodium chlorite. A poly alcohol humectant and water are

encapsulated with the polyanhydride or polyacid in a nylon coating. After sodium

chlorite is diffused into the capsule through the nylon wall, an impermeable

polystyrene layer is coacervated around the nylon capsule. Solvents are required for

reaction and application of the capsules. The capsules can be coated onto surfaces to release chlorine dioxide. Although the capsules are said to provide biocidal action for several days to months, chlorine dioxide release begins immediately after the capsules

are prepared. The batchwise process used to prepare the capsules also involves numerous chemical reactions and physical processes, some of which involve

environmental disposal problems. Wellinghoff, et. al. describe methods of making a

powdered biocidal composition for the release of ClO₂.

There is a need for a composite that can be easily activated to initiate chlorine

dioxide release in use. A composition that is composed of and generates only FDA-

approved substances, or those generally recognized as safe (GRAS), is particularly needed for food packaging and other applications where the substances can be ingested

by or in contact with humans.

Summary of the Invention

An important and central aspect of the present invention is the use of expanded

amorphous aluminum silicate as a vehicle for a chlorite salt. This vehicle, when

exposed to moisture, will release chlorine dioxide (ClO₂) for purposes of deodorization or microbial suppression. Thus , where a particular area or volume is to be deodorized

or made less microbally contaminated, the EAAS-chlorite salt (most preferably sodium chlorite) is placed in the area or volume to be treated and moisture is permitted to

interact with the material. The result of the moisture is to permit the chemical reaction

(presumably acidification) of the chlorite salt to yield chlorine dioxide gas. While

normal EAAS has some inherent acidity, the inherent acidity is low enough so that,

even when a chloride salt is encapsulated in the EAAS and the resultant mixture

exposed to moisture, ClO₂ release is very slow and over an extended period. Under most conditions, a more rapid release of ClO₂ is desired for deodorization and/or

sterilization. A more rapid release of chlorine dioxide may be accomplished by first

treating the native EAAS with an acid, preferably a protic acid, to acidify chemical

groups of the EAAS. After native EAAS is acidified and dried, if necessary, a chlorite

salt such as sodium chlorite is incorporated therein.

In another embodiment of the present invention, the chlorite salt may be

incoφorated within the EAAS without prior acidification of the EAAS. In order to

accelerate ClO₂ release, the EAAS-chlorite salt mixture may be exposed to a volatile

acid such as acidic acid or the like. This may be prior to or in conjunction with the

exposure of the EAAS incorporated chloride salt to moisture as found in water vapor or water droplets.

Brief Description of the Drawings

Figure 1 shows ClO₂ release from accelerated release EAAS; optimized release EAAS; and extended release EAAS.

Detailed Description of the Invention

EAAS can be synthesized by heating naturally occurring siliceous volcanic

rock, known as Perlite. Perlite ore is extracted in the US and other countries,, and is

usually mined by scraping the earth's surface. Perlite is marketed by several

companies, such as Incon Corporation of Media, Pennsylvania and World Minerals,

Inc. of Santa Barbara, California. The elemental analysis indicates that Perlite consists

of 34% silicon and 7% aluminum and therefor falls under the category of aluminum silicate minerals. Perlite is chemically inert and has the ability to expand in volume by an order of magnitude when heated to certain temperatures, hence the adjective

"expanded" . To expand the Perlite, the Perlite crude is first crushed to a particle size

of approximately 5/8 inch in a primary crusher. The crushed Perlite is then passed

through an oil-fired rotary dryer and then undergoes a secondary grinding to produce the desired particle size. The heating temperatures may range between 1400° and

2000° F, depending on water content and rate of heating. The word amorphous in EAAS is used to reflect the absence of definite crystalline structure.

One form of EAAS used for this invention is marketed by Paradigm

International, Inc. of Irvine, California, under the brand name Stardust^*. Another expanded Perlite product that is expected to behave similarly is Harbolite^®, marketed

by World Minerals Inc. , of Santa Barbara, CA. These products are moisturized forms of EAAS. Moisturization is performed to induce aggregates that preclude accidental

inhalation. The Moisturized EAAS is soaked with an aqueous solution of from about

0.01 % to about 40% chlorite anion by weight. In particularly preferred embodiments

the countererion is sodium, potassium or calcium, however any suitable source of the

chlorite ion can readily be used in the alternative in accordance with the present

invention. In a preferred embodiment, soaking may be achieved by spraying a 5 %

solution of sodium chlorite solution (such as ProOxine^®, a product sold by BioCide International, Inc. of Norman, Oklahoma) while agitating the EAAS mechanically.

The soaked EAAS is then dried at a temperature of 120° C for about two hours and sealed in an air-tight container or desiccator to prevent moisture absorption. The activator is prepared in a similar manner by soaking EAAS in a protic acid

solution. Any suitable protic acid may be used such as, without limitation,

phosphoric, hydrochloric, sulphuric, nitric, acetic, citric, tartaric, gly colic, mandelic, salicylic, malic, maleic, aspartic, lactic, or other structurally similar acids. Persons skilled in the art will recognize other suitable protic acids, all of which are intended

to be suitable for use in the present invention. The concentration of the soaking

solution can range from about 0.01 M to saturated, depending on the desired potency of the activator.

The chlorite impregnated EAAS and the acid impregnated EAAS can be combined in a specific ratio to release a desired concentration of chlorine dioxide. A

most preferred embodiment is to first acidify EAAS, and then incorporate a chlorite

salt into the acidified EAAS. In a particularly preferred embodiment, the mixture is packaged in a spin bonded olefin bag, such as a Tyvek^* bag, of appropriate porosity.

Such bags are composed of porous material that allows moisture to diffuse into the bag, yet is able to retain the EAAS materials inside the bag. Upon contact with moisture,

the mixture releases ClO₂. Bags are best sealed from moisture until production of ClO₂

is desired, such as in a sealed plastic bag. In certain uses, the chlorite-impregnated EAAS and the acid- impregnated EAAS can also be mixed on site to produce ClO₂, as

opposed to premixing of the ingredients. Other suitable applications for the present

invention will be readily recognized by those skilled in the art, all of which are within

the spirit and scope of the present invention. For instance, in an alternative

embodiment a push/pull bottle can be used to store and activate the dry, chemically impregnated ingredients. Although the invention is not limited by a particular mechanism, a likely

mechanism of ClO₂ release may be explained as follows. The water molecules in the moisture provide the medium that facilitates the interaction of chlorite ions with the

protons. The chlorite ions then probably reacts with the protons according to the following equation.

5ClO₂ + 4H⁺ → 4ClO₂ (g) + CT + 2H₂O

One advantage of the present invention is the moisture-induced solid phase

release of ClO₂ that creates an antimicrobial and deodorizing atmosphere at the site of application. In low ambient moisture environments, moisture can be fogged or otherwise applied from outside to accelerate ClO₂ production; however, typically normal humidity will supply the necessary moisture. The amorphous nature of the

supporting phase, provides a much longer time-range for sustained release of ClO₂ as compared to a support that is homogeneous in nature. This occurs due to the existence

of a range of pore sizes (~ 10 to ~ lOOA) in the amorphous substance that expands the kinetic time scale for the penetration of the water molecules.

The product may be used for the microbial control of dry or semi dry goods

such as produce, cosmetics, medical devices, paper fabric, and fertilizers and other agricultural items. This product can be used for odor control, since ClO₂ has been shown to exhibit excellent deodorizing properties. EXAMPLE 1

One preferred embodiment is described as follows: EAAS is soaked with a

protic acid. The amount of protic acid is in the range of 5 to 100% of the weight of

EAAS. The exact quantity depends on the type of acid and the desired characteristics of the final product . In general , three different types of products can be manufactured .

These are i) accelerated release, ii) optimized release and iii) extended release. The ClO₂ release profiles for these products are shown in Figure 1. To make product that

will provide accelerated release, a greater amount of acid will be added. On the other hand, to make product that will provide optimized release, a lesser amount of acid will be added. On the other hand, to make product that will provide extended release,

comparatively lower amounts or no acid may be added.

After soaking with acid, EAAS is baked in the oven at a temperature between

80° C and 300° C for several hours. The optimum temperature and time for baking

is approximately 150° C and two hours, respectively. The temperature condition can be varied to produce different types of products. For example, lower temperatures

(- 100° C) and short baking times (under 30 minutes) will produce product that will demonstrate accelerated release.

Subsequent to baking, solid sodium chlorite is added to EAAS. The weight of sodium chlorite can range from 1 to 100% of the weight of EAAS. The weight of

sodium chlorite is added to the EAAS depends on the desired characteristics of the

product. In certain preferred embodiments, the quantity of sodium chlorite added to EAAS is between 4 to 15 % . Thus the amount of acid, strength of acid and baking time

are single variables to produce desired patterns or ClO₂ release. Of course the concentration and type of chlorite incorporated into the native or acid-treated EAAS

may also be varied to produce desired ClO₂ release patterns. The most commonly available form of sodium chlorite is its 80% pure form. One of the sources for this product is Vulcan Chemicals, Birmingham, Alabama. Other sources and other purities of the preferred NaClO₂ may be used.

The EAAS used in the following examples was obtained from two different sources; 1) Paradigm International, Inc., CA and ii) Aldrich Chemical Company,

Milwaukee, WI. These two materials are subsequently PI and P2, respectively. The density of P2 is much higher than that of PI .

To monitor the level of free ClO₂ produced from the EAAS product, gallon jars

made of poly(ethylene-terephthalate) commonly known as PET may be used. The EAAS product was packaged and used in a 50 cc wide-mouth bottle is made of high density polyethylene (HDPE). The cap on the bottle had a push-pull mechanism for

sealing or allowing the diffusion of air with the environment via an opening of 0.8 cm diameter. The ClO₂ gas that is generated by the product is discharged into the

environment through this opening.

To measure the concentration of ClO₂ released from the EAAS product, the

bottle was kept in the PET jar with a closed lid for a definite period of time and the

ClO₂ levels were measured with a ClO₂-monitoring device known as Tox-Array 1000 which is manufactured by Mil-Ram Technologies, Inc., San Jose, CA. This device

was calibrated to measure from 0.1 to 20 ppm of ClO₂. For each measurement the sample was drawn from the top of the jar by opening the lid slightly and allowing the

insertion of the sample suction tube into the jar. The suction tube was directly

connected to the monitoring device. The concentration of total available ClO₂ was measured by iodometric method

4500-C1O₂ B, as described in the standard methods (19th Edition) of American Water Works Association.

The jars were kept in the ambient lab environment and the inside temperature was monitored. The temperature was between 20 °C and 25 °C. The humidity of the inside of these jars was maintained between 80% and 95% RH by spraying calculated

amounts of water in the jars. The humidity was monitored with a hygrometer

manufactured by Radio Shack (model 63 -867 A).

EXAMPLE 2 230 mL of 0.6M hydrochloric acid was sprayed on each of the 230 g of PI and

P2. These substances were sprayed with a generic spray bottle, with thorough stirring between every few squirts. The acidified EAAS was allowed to bake at 250 °C for one

hour. The EAAS turned slightly brown in color. This may be due to oxidation of Fe²⁺ to Fe³⁺. Two bottles of each PI and P2 were kept in three different locations for trials

for odor removal. The results are reported in Tables 1 and 2. Samples A and B were kept in a toilet facility (100 sq. ft.), samples B and C were kept in the laboratory (1,600 sq. ft.), and sample E and F were kept in an office (1,500 sq. ft.). Table 1

Product made from PI

Table 2

Product made from P2

EXAMPLE 3

Mencaptoethanol is a fundamental molecule that is one cause for odors from rotten food substances. We tested the effect of our product in eliminating the odor

caused by this chemical substance. 25μ of 1-mercaptoethanol (Aldrich) was placed in each of two PET jars of the type described above. In the first jar, a bottle containing

5 g of PI. was placed. The second jar was treated as control, and no product was placed in it. The lids were placed back on both jars. After 12 hours, the product

bottle was taken out and the jars aired for 30 minutes. Subsequently, they were tested for mercaptan odor by 5 different individuals. None of them could detect any odor in the first jar, whereas the control-jar had strong odor of the mercaptan. The mechanism for the odor removal is believed to be the oxidation of the mercaptan by ClO₂.

EXAMPLE 4

This product is very effective in removing onion odors. 25 g of chopped white onions were stored in two PET jars overnight. The onions were removed the next day and the bottle with PI product was placed in one of the jars. After 12 hours, the jars

were inspected for odor by 5 different individuals. It was agreed that the odor was eliminated from the jar that was treated with the PI product.

EXAMPLE 5

Four samples, each containing 5 g of PI, were treated with 0.5 mL, 1 mL,

3mL and 5mL of 0.6 M HC1. Similarly, four examples each containing 10 g of P2, were treated with 0.5 mL, 1 mL, 3mL and 5 mL of 0.6 M HC1. These samples were allowed to air dry on the laboratory bench, and after one week. 0.5 g NaClO₂ was

added to them. These samples were packaged in the 50 cc bottles described in a prior Example. The ClO₂ levels were momtored in the similar manner as mentioned in

earlier examples. In these cases the characteristics of ClO₂ release matched that of accelerated release as shown in figure 1. The results are presented in Tables 3 and 4.

Table 3

Product made from PI

Table 4

Product made from P2

EXAMPLE 6

In this example, NaClO₂is mixed with PI and P2 that were not treated with any acid. The ratio of mixing was 0.5 g NaClO₂:5 g PI and 0.5 g NaClO₂: 10 g P2. In these cases the characteristics of ClO₂ release matched those of extended release as shown in figure 1. The ClO₂ level released from the 50cc bottle (described in Example 1) were below the detection limit of the Tox- Array monitoring device. However, when

bulk amounts of both PI and P2 formulations were left in the PET jars for

approximately 1 Vi months, - 10 ppm and ~6 ppm of ClO₂ was detected, respectively.

The following references as well as those separately cited above are incorporated in pertinent part by reference herein for the reasons cited.

References:

1) Greenwood, 'N. N. Eamshaw, A. In Chemistry of the Elements; Pergamon Press: New York, 1989, pp399-416.

2) Perlite Institute Inc., 88 New Drop Plaza, Staten Island, NY 10306-2994. 3) Masschelein, W. J. In Chlorine Dioxide, Chemistry and Environmental Impact of Oxychlorine Compounds; Ann Arbor Science: Ann Arbor, 1979. 4) Wellinghoff, et. al., U.S. Patent No. 5,695,814.

5) Tice, et al., U.S. Patent No. 4,585,482.

6) Meier, et al., Environ. Mutagenesis, 7, 201 (1985).

7) Richardson, et al., Environ. Sci. Technol., 28, 592 (1994). 8) Kenyon et al., Am. J. Vet. Res., 45(5), 1101 (1986).

Claims

That what is claimed:

1. A method for treating an area with ClO₂ , the method comprising placing in the area an acidified EAAS impregnated with a chlorite salt; and exposing said area to an amount of water sufficient to generate ClO₂.

2. A method for producing a source of ClO₂ activated by moisture, the

method comprising:

• treating EAAS with an acid;

• drying the acidified EAAS; and

• incorporating a chlorite salt into the dried acidified EAAS.

3. A composition of matter comprising expanded amorphous aluminum

silicate and a chlorite salt.

4. The composition of Claim 3 wherein the chlorite salt is sodium chlorite .

5. The composition of Claim 3 wherein the expanded amorphous aluminum silicate has been acidified.

6. The composition of matter of Claim 3 defined further as being

substantially anhydrous.

7. A composition of matter comprising acidified EAAS and NaClO₂.