METHOD FOR PREPARING A SOLID MATERIAL FOR STORING OZONE, THE MATERIAL AND THE USES THEREOF

Abstract

The present invention relates to a method and a unit for preparing a solid material for storing ozone, said method comprising contacting cyclodextrins and/or derivatives of cyclodextrins in solid form with a gas comprising ozone, by means of which a solid material for storing ozone is obtained. The present invention also relates to the material thus prepared and to the uses thereof.

Claims

1. A process for preparing a solid ozone storage material comprising contacting cyclodextrins and/or cyclodextrin derivatives in solid form with a gas comprising ozone, whereby a solid ozone storage material is obtained.

2. The process of claim 1, characterised in that said cyclodextrin derivative is a chemically modified, cross-linked, immobilized cyclodextrin and/or organised in a molecular superstructure.

3. The process of claim 1, characterised in that said cyclodextrins and/or said cyclodextrin derivatives are selected from the group consisting of α-CDs, β-CDs, γ-CDs, hydroxypropylated α-CDs, hydroxypropylated β-CDs, hydroxypropylated γ-CDs, dimethylated α-CDs, dimethylated β-CDs, dimethylated γ-CDs; sulfobutylether α-CDs, sulfobutylether-β-CDs, sulfobutylether γ-CDs, sulfated α-CDs, sulfated β-CDs, sulfated γ-CDs, phosphated α-CDs, phosphated β-CDs, phosphated γ-CDs; carboxymethylated α-CDs, carboxymethylated β-CDs, carboxymethylated γ-CDs, carboxymethylether α-CDs, carboxymethylether β-CDs, carboxymethylether γ-CDs, 3-trimethylammonium-2-hydroxypropyl-ether α-CDs; 3-trimethylammonium-2-hydroxypropyl-ether β-CDs; 3-trimethylammonium-2-hydroxypropyl-ether γ-CDs; cross-linked cyclodextrin derivatives and mixtures thereof.

4. The process of claim 1, characterised in that said process has a step prior to contacting said cyclodextrins and/or said cyclodextrin derivatives with said gas comprising ozone aiming at either removing all or part of water molecules present in the cavities of said cyclodextrins and/or said cyclodextrin derivatives, or replacing all or part of water molecules present in the cavities of the cyclodextrins and/or cyclodextrin derivatives with a non-ozone reactive substance.

5. The process of claim 1, characterised in that said gas comprising ozone is a gas mixture comprising ozone and at least one other gas such as dioxygen, carbon dioxide, nitrogen or a mixture thereof.

6. The process of claim 1, characterised in that contacting between said cyclodextrins and/or said cyclodextrin derivatives and said gas comprising ozone is carried out at a temperature between 0° C. and 80° C.

7. The process of claim 1, characterised in that contacting between said cyclodextrins and/or said cyclodextrin derivatives and said gas comprising ozone lasts between 1 min and 8 h.

8. A facility capable of being implemented in a preparation process as defined in claim 1, said facility comprising at least one reactor containing cyclodextrins and/or cyclodextrin derivatives in solid form in fluid connection with a source of a gas comprising ozone.

9. The facility of claim 8, characterised in that said reactor is a gas/solid contactor, operating in a fixed or fluidized bed, a powder mixer or a stirred reactor and/or in that said ozone source is an ozone generator.

10. The facility of claim 8, characterised in that it further comprises one or more elements selected from the group consisting of a filter, an ozone scavenger, a flow meter, temperature probes, ozone analysers and valves.

11. A solid ozone storage material prepared by the process of claim 1.

12. The solid ozone storage material of claim 11, characterised in that it comprises cyclodextrins and/or cyclodextrin derivatives in solid form, at least some of the cavities of which contain ozone.

13. The solid ozone storage material of claim 11, said material being in compacted form and/or in packaged form.

14. The solid ozone storage material of claim 11, which is a disinfectant, depollutant, cleaner or biocide.

15. A method of disinfecting, depolluting or cleaning a fluid or a surface comprising contacting the solid ozone storage material of claim 11 with said fluid or a surface.

16. The method of claim 15, characterised in that said fluid is selected from the ambient air or gaseous atmosphere of a site such as a domestic room, a cold room or an industrial confined space; city water, river water, well water, ground water, pond water, lake water, swimming pool water, aquarium water, cooling water from air conditioning systems or cooling towers; a sample from a chemical reactor; domestic waste water; a product, especially a liquid, effluent or waste water from intensive livestock farming or from industries or facilities in the chemical, pharmaceutical, cosmetic, agricultural, agri-food, maritime, aeronautical or space sectors; or a mixture thereof

17. The method of claim 16, characterised in that said surface is selected from an industrial object such as an electronic device or a machine used in the agri-food industry, a vehicle, a carcass, an aircraft, a tank, a restaurant kitchen, a cold room, a sanitary facility, a container, a part of a dwelling such as a roof, a facade, a terrace, a driveway, systems embarked in space, in ships or in submarines, medical devices, pipes, soil or earth, wood and a plant surface.

18. The solid ozone storage material of claim 11, which is a medicine.

19. The solid ozone storage material of claim 11, which is a chemical reagent.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0088] FIG. 1a shows a diagram of a facility capable of being implemented within the scope of the invention with 1. Ozoniser; 2. Reactor; 3. Filter; 4. Scavenger; F1. Flow meter; T1, T2. Temperature probes; A1. Ozone analyser; V1, V2, V3. Valves.

[0089] FIG. 1b shows a schematic diagram of a facility capable of being implemented within the scope of the invention with 1. Ozoniser; 2. Reactor; 3. Thermostatic bath; 4. Vacuum pump; 5. Filter; 6. Scavenger; F1, F2. Flow meters; T1. Temperature probe; P1, P2. Pressure sensors; A1. Ozone analyser; V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11. Valves.

[0090] FIG. 2 shows the results of a potassium iodide (KI) test performed with native HP-β-CD before reaction (middle vial=negative test) and after reaction (right vial=positive test), the left vial being a negative control containing only KI. The test was performed immediately after synthesis (at D.sub.0).

[0091] FIG. 3 shows the results of biological tests under the conditions detailed in Table 1.

[0092] FIG. 4 shows the results of biological tests under the conditions detailed in Table 2.

[0093] FIG. 5 shows the results of a potassium iodide (KI) test as a function of the storage time of β-CD after reaction. From left to right: KI alone (negative control), KI+native 13-CD before reaction, KI+β-CD after reaction at t.sub.0, KI+β-CD after reaction at t.sub.0+1 day, KI+β-CD after reaction at t.sub.0+2 days, KI+β-CD after reaction at t.sub.0+5 days and KI+β-CD after reaction at t.sub.0+6 days.

[0094] FIG. 6 shows the course of the ozone mass concentration in the material over time for 3 tested storage temperatures (−19° C., 2° C. and 21° C.).

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

I. Facility and Process for Preparing the Material According to the Invention

I.1. Example 1 of a Facility and Process for Preparing the Material According to the Invention

[0095] A particular example of a facility implemented to prepare an oxidatively active material according to the invention is described in FIG. 1a.

[0096] This facility is comprised of an ozoniser (1), a reactor (2), a filter (3) and an ozone scavenger (4). The 3 valves (V1), (V2), (V3) allow the gas to be directed or not to the reactor. The process parameters are monitored using various sensors, some of which are connected to displays: a gas flow meter (ball rotameter (F1)) placed at the outlet of the ozone scavenger, a temperature probe (T1) at the inlet of the reactor, a temperature probe (T2) at the outlet of the reactor, and an ozone analyser (A1) placed between the filter and the scavenger.

[0097] The synthesis of the material of interest is done by direct gas/solid reaction between cyclodextrins and a gaseous dioxygen/ozone (O.sub.2/O.sub.3) mixture. Cyclodextrins used in the following experimental section are β-cyclodextrin (β-CD, supplied by Sigma-Aldrich, manufactured by Wacker Chemie AG, Burghausen, Germany, Life Science, batch BCBG7824V, 98, 6% pure) and (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD, supplied by Sigma-Aldrich, manufactured by Wacker Chemie AG, Burghausen, Germany, Life Science, batch BCBV0722, more than 94% pure) which is much more soluble in water than β-CD. These cyclodextrins are in the form of fine-grained powder with a mean grain diameter of less than 100 μm and, in particular, of 60 μm for β-CD and 13 μm for HP-β-CD.

[0098] The reactor (2) used is comprised of a glass tube 20 cm high, 6 mm outer diameter and 1 mm thick. The tube is crimped at the ends with PTFE “double ring” fittings. The glass tube with the fittings is attached to stainless steel supports in a vertical position with a gas supply at the bottom. This reactor is positioned in an oven (Heratherm oven OGS60) to vary the temperature if necessary.

[0099] The material before reaction, for example native cyclodextrins, is initially fed into the reactor (2) manually. The solid in powder form is held in the reactor via two filters positioned upstream and downstream of the powder. The two filters used are made of cotton in the experiments and are positioned so that the powder can be fluidised by the gas supplying the reactor.

[0100] The filter (3) avoids fine particles being entrained into the scavenger.

[0101] The ozone scavenger (4) is a COD 8 type thermo-catalytic scavenger of stainless steel 316 Ti, able to instantaneously treat a maximum gas flow of 8 Nm.sup.3/h. The catalyst consists of manganese dioxide and copper oxide deposited on alumina oxide. On contact with this catalytic mass, the ozone molecules are decomposed into oxygen molecules before being released into the atmosphere (vent).

[0102] For the start-up phase, the valves are initially positioned in such a way that the gas leaving the ozoniser is directed towards the ozone scavenger: valves (V1) and (V3) closed and (V2) open.

[0103] The ozone gas is generated by an electric discharge Labo5LO type Trailigaz ozoniser, supplied with pure dioxygen (O.sub.2). The ozone production is modified and controlled by adjusting voltage on the potentiometer. The gas produced at the outlet of the ozoniser is an O.sub.2/O.sub.3 mixture. The flow rate of this gas at the outlet of the ozoniser is adjusted and measured using the flow meter (F1) and the ozone concentration is measured by means of the analyser (A1).

[0104] The voltage of the ozoniser is increased until the desired ozone concentration in the gas is reached. This concentration has been set between 55 and 75 g/Nm.sup.3 for the experiments. During this transitional phase, the gas flow does not pass through the reactor.

[0105] Once the ozone concentration on the analyser (A1) and the temperatures (T1) and (T2) are stable and in accordance with the desired values (between 23 and 26° C. for the experiments), the gas leaving the ozoniser is directed to the reactor by closing the valve (V2) and opening the valves (V1) and (V3). In the experiments carried out, the gas flow rate has been set to 30 L/h with the flow meter (F1). Under these conditions, the gas flow rate (0.66 m/s) is sufficient to fluidise the material in the reactor. The passage time of the gas mixture through the reactor is then 0.3 s.

[0106] The contacting time of the powder with the ozone-containing gas has arbitrarily been set to 3 hours for these experiments.

[0107] When the desired reaction time is reached, the valves are positioned so that the gas leaving the ozoniser is directed to the scavenger. The reactor is then taken off from the support, the cotton filters are removed with tweezers and the ozone-treated powder is recovered in a glass vial.

[0108] The material obtained at the end of the synthesis is a fine white powder, resembling, to the naked eye, the material prior to the process according to the invention.

[0109] The product is stored without special precautions in vials closed with a plug. Two storage conditions have been tested: “ambient” conditions (atmospheric pressure and temperature of about 25° C.) or cold storage (atmospheric pressure and temperature of about 6° C.).

I.2. Example 2 of a Facility and Process for Preparing the Material According to the Invention

[0110] Another particular example of a facility implemented to prepare an oxidatively active material according to the invention is described in FIG. 1b.

[0111] This facility is comprised of an ozoniser (1), a reactor (2), a thermostatic bath (3), a vacuum pump (4), a filter (5) and an ozone scavenger (6). Valves (V1) and (V2) allow the selection of the supply gas (oxygen or air) to the ozoniser. Valves (V3) and (V10) allow the circulation of nitrogen or CO.sub.2 in the process, if required. Valve (V4) allows the gas coming from the ozoniser to be directed to the reactor (2). Valve (V5) directs the gas to the scavenger (5). Valves (V6) and (V8) isolate the reactor (2), and valve (V7) opens the bypass of reactor (2). Valve (V9) allows the vacuum pump (4) to be connected to the process, and valve (V11) allows the purge circuit of the reactor (2) to be closed in order to vacuumize the facility. The process parameters are monitored using various sensors, some of which are connected to an acquisition system and a computer: a volume flow meter (ball rotameter (F1)) placed at the outlet of the ozoniser for adjusting the supply gas flow rates to the reactor (2), a mass flow meter (F2) to precisely measure the supply flow rate to the reactor (2), an ozone analyser (A1) for measuring the ozone concentration of the supply gas to the reactor (2), two pressure sensors (P1) and (P2) for measuring the pressure upstream and downstream of the reactor (2), and a temperature probe (T1) for measuring the temperature within the reactor (2).

[0112] The synthesis of the material of interest is carried out by direct gas/solid reaction between cyclodextrins (CDs) and a gas mixture containing ozone (O.sub.3). Cyclodextrins (CDs) used in the experimental section in connection with this facility are α-cyclodextrin (α-CD, supplied by Sigma-Aldrich, manufactured by Wacker Chemie AG, Burghausen, Germany, Life Science, batch BCBQ5117V, 98% pure), β-cyclodextrin (β-CD, supplied by Sigma-Aldrich, manufactured by Wacker Chemie AG, Burghausen, Germany, Life Science, batch BCBG7824V, 98.6% pure), γ-cyclodextrin (γ-CD, supplied by Sigma-Aldrich, manufactured by Wacker Chemie AG, Burghausen, Germany, Life Science, batch BCBG7825, 99.5% pure), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD, supplied by Sigma-Aldrich, manufactured by Wacker Chemie AG, Burghausen, Germany, batches BCBV0722 and BCBX5180, more than 94% pure), Sulfobutylether-β-Cyclodextrin (SBE-β-CD, supplied by ABMole, batches M4837-07, 98.08% pure) and a cyclodextrin polymer (β-CD polymer, supplied by Sigma-Aldrich, product number C2485, batch BCBX7555).

[0113] The reactor (2) used is entirely of stainless steel. It is a tubular reactor with a diameter of 17 mm, a total length of 150 mm and a working length of 50 mm, which can hold up to about 5 g of cyclodextrin powder. It has a double stainless steel jacket in which a heat transfer fluid circulates through flexible pipes. These pipes are connected to the thermostatic bath (3), which ensures temperature setting and circulation of the heat transfer fluid in the double jacket of the reactor. The reactor is mounted in a vertical position, with a gas supply at the bottom, and is connected to the rest of the process by stainless steel double ring fittings.

[0114] The material before reaction, consisting of native cyclodextrins, is initially fed into the reactor (2) manually. The solid in powder form is held in the reactor via two sintered parts positioned upstream and downstream of the powder.

[0115] The vacuum pump (4) allows the reactor and part of the facility to be vacuumized when necessary.

[0116] The filter (5) avoid fine particles being entrained into the scavenger.

[0117] The ozone scavenger (6) is a thermo-catalytic scavenger. On contact with the catalyst and under the effect of temperature, the ozone molecules are decomposed into oxygen molecules before being released into the atmosphere (vent).

[0118] For the start-up phase, the valves are initially positioned in such a way that the gas leaving the ozone generator is directed to the ozone scavenger via the reactor bypass: valves (V5), (V6) and (V8) closed, and valve (V7) open.

[0119] The ozone gas is generated by an ozoniser (1) (model CFS-01-2G from Ozonia). It uses a dielectric discharge process from dry air or oxygen. The ozone production is set directly on the ozoniser by a power value. The gas produced at the outlet of the ozoniser is either an O.sub.2/O.sub.3 mixture when pure oxygen is used as the supply gas to the ozoniser, or an N.sub.2/O.sub.2/O.sub.3 mixture if air is used instead of pure oxygen. The flow rate of this gas at the outlet of the ozone generator is adjusted and measured using first the rotameter (F1) and then the flow meter (F2). The ozone concentration is measured by means of the analyser (A1).

[0120] The power of the ozoniser is increased until the desired ozone concentration in the gas is reached. During this transitional phase, the gas flow does not pass through the reactor. In experiments with this facility, the ozone concentration can be very high, for example 165 g O.sub.3/Nm.sup.3.

[0121] The temperature in the reactor is controlled by the thermostatic bath (3). The temperature range of the experiments carried out with this facility is between 7 and 77° C.

[0122] Once the ozone concentration on the analyser (A1) and the temperature (T1) are stable and in accordance with the desired values, the gas leaving the ozoniser is directed to the reactor by closing valve (V7) and opening valves (V6) and (V8). In the experiments carried out, the gas flow rate can be variable, and varied from 33 to 723 Normal litres per hour (Nl/h) with the flow meters (F1) and (F2). The contacting time of the powder with the ozone-containing gas can also be variable, ranging from 0.5 to 6 h for these experiments.

[0123] When the desired reaction time is reached, the valves are positioned so that the gas leaving the ozoniser is directed to the scavenger. The reactor is then taken off from the support and the sintered parts are removed.

[0124] The material obtained at the end of the synthesis is a fine powder, resembling, to the naked eye, the material prior to the process according to the invention.

[0125] The ozone-treated powder is then recovered and stored in a glass vial or shaped (in the form of a pellet, for example).

II. Characterisation of the Material According to the Present Invention

II.1. Characterisations and Assays

[0126] Characterisation tests (thermogravimetric analysis coupled with a differential calorimetric analysis, Infrared spectroscopy . . . ) and assays (potassium iodide/sodium thiosulphate assay—assay method called “KI method” or “KI test”—allowing the amount of ozone contained in the powder to be determined) have been carried out on some of the materials.

[0127] Note that dissolving native cyclodextrins (commercial product) in a KI solution does not produce any staining of the solution (negative KI test). Only the cyclodextrins reacted with ozone obtained according to the process of the invention have a “positive” KI test: the solution becomes yellow/orange as illustrated in FIG. 2.

II.2. Detailed Protocol for Biological Tests

[0128] The purpose of the microbiological tests is to verify the biocidal effect of the material according to the present invention and thus to evaluate its potential for use in crop protection for example.

II.2.1. Protocol A

[0129] Artificial supports are first placed in Petri dishes (2 dishes/modality tested) without agar medium and then inoculated with a solution of micro-organisms (fungi or bacteria), for example conidia of Venturia inaequalis, the fungus responsible for apple scab. These supports are then placed in an incubation chamber for 24 hours in order to initiate development of the micro-organisms.

[0130] Treatments with a material according to the present invention are applied by sprinkling (0.1 g/dish) 24 h after the beginning of germination.

[0131] After approximately one hour of contacting the micro-organisms with the material, the artificial supports are moved to an agar medium (Patato Dextrose Agar) in order to ensure the nutrient supply necessary for the proper development of the micro-organisms. The inoculated Petri dishes treated are then placed in an air-conditioned chamber (12 h/12 h day/night cycle, night temperature: 8° C., day temperature: 17° C.).

[0132] From the 3rd day of incubation, regular observations and counts are carried out in order to evaluate and compare the different modalities.

II.2.2. Protocol B

[0133] Fungal Strains:

[0134] Three fungal strains have been tested. Strains 110.712 and 100.398 belong to the species Pheaoacremonium minimum. Strain 239.74 corresponds to the species Phaeomoniella chlamydospora. They are referred to as P. min 110.712, P. min 100.398 and P. ch 239.74 respectively below. All three are associated with the grapevine wood diseases known as Esca.

[0135] They have been first grown for four weeks on agar medium (Malt Extract Agar MEA) to allow them to reach the sporulation stage. On the day of the test, a spore suspension with a concentration of approximately 1.10.sup.5 spores/mL has been prepared for each strain. Count was carried out on Malassez cells. The spore suspensions thus obtained are distributed in 8 eppendorf tubes (1.5 mL of suspension per eppendorf tube).

[0136] The native or ozonated powder and the spore suspensions are contacted for 20 min on ice. The samples are then diluted and seeded on agar medium (MEA). Petri dishes are incubated for 5 days in the dark at 26° C. Counts are carried out after this incubation time and will allow comparison of samples that received native powder without ozone versus those that received ozonated powder.

[0137] Bacterial Strains:

[0138] Two species have been tested: Escherichia coli and Streptococcus uberis (E. coli and S. uberis). The bacteria, which had previously been stored in glycerol milk at −80° C., have been deposited in a liquid BHB (Brain Heart Broth) medium, previously autoclaved for 15 min at 121° C.

[0139] In order to bring them out of the latent phase and allow them to reach the exponential growth phase, the bacteria have been pre-cultured for 4 h and 4 h30 respectively at 37° C. under 150 rpm stirring.

[0140] As soon as they were contacted with the native or ozonated material, 150 μL of spore suspension have been deposited on 96-well plates in order to read absorbance every 10 min for 4 h at 600 nm using the TECAN (150 rpm stirring, 37° C.). The different modalities have then been compared.

II.3. Results.

[0141] Three series of tests (Test Runs No. 1, No. 2 and No. 3) have been carried out (3 h of reaction at ambient temperature (T.sub.am) approximately 25° C., with native products used without any prior treatment) in order to evaluate: (i) the effect of the type of cyclodextrins (β-CD and HP-β-CD); (ii) the influence of the storage conditions of the material after reaction (T.sub.am or 6° C.); (iii) the amount of ozone contained in the material; (iv) the reproducibility; (iv) the efficiency of the material (biological tests according to protocol A (point II.2.1. above).

[0142] Additional tests (Test Run No. 4), have been carried out to make sure that the disinfecting capacities of the oxidising β-CDs that is prepared according to the process of the invention are verified on several bacterial and fungal strains. These tests have been carried out according to protocol B (point II.2.2. above) with oxidising CDs obtained from HP-β-CD according to process example 2 (point I.2. above).

II.3.1. Test run No. 1: β-CD

[0143] The syntheses were carried out with the β-CD according to process example 1 (point I.1. above). The batch of powder at the end of the synthesis was divided into two parts: one stored under ambient conditions and one at 6° C. The analytical characterisations of the product formed were carried out 48 h after the end of the synthesis (D.sub.0+2) at the time of the biological tests (Bio Tests). The results are summarised in Table 1 below.

TABLE-US-00001 TABLE 1 Summary of tests No1 BIO TESTS (*) [O.sub.3] m.sub.powder Biological Exp Sample Storage T KI Test μg/g.sub.powder Bio test Pathogens efficiency 1 1 T.sub.am — 0.1 g Bacteria + Partial fungi (growth 1 2 6° C. — 0.1 g Bacteria + slowdown) fungi 2 3 T.sub.am Positive 725(*) 0.1 g Bacteria + fungi 2 4 6° C. Positive 817(*) 0.1 g Bacteria + fungi (*) done at D.sub.0 + 2

[0144] The results of biological tests are also set forth in FIG. 3. The control dishes show an uncountable number of micro-organisms (carpet-like appearance). On the other hand, the dishes that received oxidising β-CDs, that is prepared according to the process of the invention, are in turn much more sparse. The effect is therefore proven, even if it is only partial, as not all the micro-organisms could be constrained.

II.3.2. Test Run No. 2: HP-β-CD

[0145] The syntheses have been carried out with HP-β-CD according to example 1 of the process (point I.1. above). The batch of powder at the end of the synthesis was divided into two parts: one stored at ambient conditions (about 25° C.) and one at 6° C. Analytical characterisations of the product formed were made 24 h after the end of the synthesis (D.sub.0+1) at the time of the biological tests (Bio Tests). The results are summarised in Table 2 hereinafter.

TABLE-US-00002 TABLE 2 Summary of tests No2 BIO TESTS)*) [O.sub.3] m.sub.powder Biological Exp Sample Storage T KI test μg/g.sub.powder Bio test Pathogens efficiency 3 5 T.sub.am — 0.1 g Bacteria + Total fungi 3 6 6° C. — 0.1 g Bacteria + Total fungi 4 7 6° C. Positive 5716(*) 0.1 g Bacteria + Total fungi (*) done at D.sub.0 + 2

[0146] The results of biological tests are also set forth in FIG. 4. The control dishes again show an uncountable number of micro-organisms. On the other hand, no micro-organisms at this stage, that is at D.sub.0+1, are visible on the dishes that have been treated with oxidising HP-β-CDs, that is prepared according to the process of the invention.

II.3.3. Test Run No. 3: HP-β-CD

[0147] The syntheses have been carried out with HP-β-CD according to process example 1 (point I.1. above). The batch of powder at the end of the synthesis was kept in its entirety under ambient conditions. Ozone assay in the material has been carried out immediately after synthesis (D.sub.0), 24 h after synthesis (D.sub.0+1) and 48 h after synthesis (D.sub.0+2). The results are summarised in Table 3 hereinafter.

TABLE-US-00003 TABLE 3 Summary of tests No3 BIO TESTS [O.sub.3] m.sub.powder Biological Exp Sample Date KI test μg/g.sub.powder Bio test Pathogens efficiency 5 8_0 D.sub.0 Positive 5700 +− 0.05 g fungi Total 100 (*) 8_1 D.sub.0 + 1 Positive 4713 (**) — — — 8_2 D.sub.0 + 2 Positive 3743(**) — — — (*) mean value and uncertainty obtained with 3 assays

[0148] The values indicated (**) are those obtained on the first decolourising of the solution. It can be seen that the solution gradually recolourises yellow again after the end of the assay. The indicated value is therefore probably underestimated if recolouring is due to a gradual release of stabilised ozone into the liquid phase. Organised structures in the solution are clearly visible under the microscope: it is possible that cyclodextrins in solution stabilise some ozone, which hence does not react immediately during the assay.

II.3.4. Test Run No. 4

[0149] Synthesis of the Materials According to the Invention:

[0150] The syntheses have been carried out with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), Sulfobutylether-β-Cyclodextrin (SBE-β-CD) and a cyclodextrin polymer (β-CD polymer) according to process example 2 (point I.2. above).

[0151] The operating conditions for these tests are summarised in Table 4 below. Notations are: Tr (reactor temperature); [O.sub.3]g supply: ozone concentration in the supply gas; Q=gas flow rate; t.sub.s=synthesis time; m=mass of powder introduced into the reactor; [O.sub.3].sub.p=amount of stored ozone obtained by KI volumetric assay; Pre-treatment: pre-treatment of the powder before reaction; Ozoniser supply=nature of the supply gas to the ozoniser.

TABLE-US-00004 TABLE 4 Operating conditions of syntheses during tests No4 [O3].sub.g Tr supply Q Pre- Ozoniser Mean σ Mean σ Mean σ t.sub.s m [O3].sub.p Δ.sub.[O3]P Product treatment supply ° C. g/Nm.sup.3 Nl/h h g Mg.sub.O3/g.sub.product / / / 25.6 0.2 77 1 185 3 2 1.05 1.47 0.17 α-CD none O2 25.1 0.3 76 5 186 5 2 1.07 0.99 0.15 β-CD none O2 25.4 0.1 76 1 186 7 2 1.05 5.71 0.31 HP-β- none O2 CD 25.7 0.1 77 1 185 3 2 1.02 0.26 0.13 SBE-β- none O2 CD 25.3 0.1 78 1 182 4 2 1.02 5.44 0.31 β-CD- none O2 Polymer 25.1 0.1 77 1 188 3 2 1.01 0.91 0.15 γ-CD none O2

[0152] Under identical operating conditions, it is noted that the ozone storage capacity is strongly dependent on the nature of the CD used for the synthesis, the best results being obtained with HP-β-CD and the β-CD polymer.

Evaluation of the Biocidal Character of a Material Thus Prepared on Several Bacterial and Fungal Strains

[0153] The results are summarised in Table 5 below.

TABLE-US-00005 TABLE 5 Biocidal character of the material according to the invention Pathogens Biological efficacy Fungi P.min 110.712 Confirmed P.min 100.398 (spores unable to grow P.ch 239.74 after 5 days incubation) Bacteria E.coli Confirmed S.uberis (Growth arrest)

[0154] Concerning the fungal strains, the control dishes exhibit an uncountable number of micro-organisms (carpet-like appearance). On the other hand, dishes that received oxidising β-CDs, that are prepared according to the process of the invention, are largely sparser or completely free of mycelial spots. At 100-fold dilution, the control agar media still contain numerous mycelial starts (on average 990/ml deposited) whereas the agar media that have received oxidising β-CDs, that are prepared according to the process of the invention, no longer contain any for the strains P. min 100.398 and P. ch. 239.74. Only a few mycelial starts are visible for the strain P. min 110.712, which seems to be a little less sensitive. The fungicidal effect is therefore confirmed.

[0155] As far as the bacterial strains are concerned, the addition of oxidising β-CDs, that are prepared according to the process of the invention, stops development of the bacteria in both cases, whereas the controls continue growing during the hours of analysis. Again, it can be concluded that the newly obtained material has a bactericidal effect.

II.3.5. Stability of the Material According to the Present Invention

[0156] In order to test the stability of the material according to the present invention, a synthesis has been carried out with β-CD and a contacting time with ozone of 2 h (according to process example 1 of point I.1. above). The batch of powder at the end of the synthesis has been stored at 6° C. (open vial).

[0157] FIG. 5 sets forth a series of KI tests performed on the powder at different storage times (1 day, 2 days, 5 days and 6 days). A yellow colour can be seen for all samples containing β-CD subjected to the process according to the invention, to be compared with the transparent colour of KI alone (left-hand vial) or KI with β-CD before the reaction (second vial from the left).

[0158] This stability test has been repeated with the ozone-treated HP-β-CD according to process example 2 (section I.2. below) under the following conditions: synthesis time=6 h; ozone concentration in supply gas=69±18 g.sub.O3/Nm.sup.3; gas flow rate=335 ±7 Nl/h; reactor temperature=27.1° C.±0.5° C. The material was packaged in closed glass vials. The stability of the material has been evaluated over a period of 65 days under different temperature conditions: under ambient conditions at a mean temperature of 21° C.±2° C.; in a refrigerator at a mean temperature of 2° C.±2° C., and in a freezer at a mean temperature of −19° C.±2° C. The ozone concentration in the material has been evaluated by volumetric assay (“KI method”).

[0159] The results of the course of ozone mass concentration in the material over time for the 3 storage temperatures tested (−19° C., 2° C. and 21° C.) are set forth in FIG. 6.

[0160] It can therefore be concluded that the material prepared according to the present invention stabilises ozone, thus keeping its oxidative properties at a minimum for several weeks. It should be noted that the lower the storage temperature, the more stable the material. For example, the ozone mass loss rate (calculated as 100×[1−(C/C.sub.0)], where C is the ozone mass concentration at time t and C.sub.0 is the initial ozone mass concentration) is less than 20% after 65 days of storage if the material is kept at a temperature of −19° C.

[0161] In further tests with HP-β-CD stored at ambient temperature for 33 days, it has also been shown that the stability of the material over time was not affected by either primary vacuum conditioning or conditioning under 3.5±0.2 bar absolute CO.sub.2.

II.3.6. Ozone Storage By the Material According to the Present Invention

[0162] In order to validate ozone storage in the material according to the invention, two tests have been carried out with HP-β-CD treated according to process example 2 (point I.2. above).

[0163] First Test:

[0164] In the first test, about 1.5 g of ozone storage material in powder form have been placed in a glass cup, which in turn has been placed in a glass reactor of volume 1.4 litres. The reactor can be hermetically closed and has been maintained at ambient temperature (˜20° C.).

[0165] A portable ozone detector (model X-an-5000 from Dräger, equipped with an XXS O.sub.3 cell specifically for ozone detection, detection limit equal to 0.02 ppm and resolution equal to 0.01 ppm, response time <10 s at 20° C.) has been introduced into the reactor and switched on near the powder cup. The detector thus placed makes it possible to continuously emphasise the presence of ozone in the reactor, from an ozone concentration higher than the detection limit of 0.02 ppm.

[0166] Firstly, it has been noted that the detector indicates zero ppm of ozone when the powder is left as is (that is the detector is switched on next to the powder for several minutes and does not detect any ozone).

[0167] Secondly, using a graduated glass pipette, a volume of approximately 3 ml of distilled water has been introduced onto the powder through one of the upper openings of the reactor. The reactor has then been immediately hermetically closed again to monitor the course of the vapour phase composition of the reactor with the detector over time. The dissolution of part of the material (about ⅓ of the initial amount) by this addition of water (as the material is relatively soluble in water), caused a rapid increase in the ozone concentration over time as read on the detector (for example 0.1 ppm measured in 40 s; 0.2 ppm in 100 s). The maximum concentration reached was 0.48 ppm ozone for this experiment (well above the detection limit of the measurement device).

[0168] In another experiment performed under exactly the same conditions, no ozone release was observed on the detector when native product (that is non-ozonated HP-β-CD) has been used. These experiments therefore confirm that the material manufactured according to the present invention does store ozone, and that ozone in gaseous form is released when the material is contacted with water.

[0169] Second Test:

[0170] In the second test, approximately 2 g of ozone storage material in powder form have been placed in a glass cup, which was in turn placed in a glass reactor of volume 1.7 litre. The hermetically closed reactor has been placed in a stove initially at ambient temperature.

[0171] A portable ozone detector (Micro IV model from GIG, calibrated specifically for ozone, detection limit equal to 1 ppm and resolution equal to 0.01 ppm, response time <60 s) has been introduced into the reactor and switched on near the powder cup. The detector thus placed makes it possible to continuously detect the presence of ozone in the reactor, from an ozone concentration higher than the detection limit of 0.01 ppm. Firstly, it has been noted that the detector indicates zero ppm of ozone when the powder is still at ambient temperature.

[0172] Secondly, the temperature of the stove is gradually increased (in about one hour) until it reaches 40° C. The purpose of this increase is to facilitate degassing. The course of the vapour phase composition of the reactor is monitored with the detector over time.

[0173] At ambient temperature, the detector displayed 0 ppm. On the other hand, the increase in temperature caused an increase in the ozone concentration over time as read on the detector (example: 0.12 ppm measured in 1.5 hours). These experiments therefore confirm that the material manufactured according to the present invention does store ozone, and that ozone in gaseous form is released when the material is subjected to a temperature higher than the ambient temperature.

[0174] Conclusion:

[0175] These two tests show that the material manufactured according to the present invention does store ozone, and allows the release of ozone gas when this material is dissolved in part in a solvent (in water in the first test), and/or is put under thermodynamic conditions (here a temperature of 40° C. under 1 bar, in the second test) unfavourable to the ozone storage, making the ozone less stable in the material and thus allowing in these conditions the release of a measurable amount of O.sub.3 in the given time.

II.4. Conclusions

[0176] Contacting ozone with cyclodextrins such as β-CD and HP-β-CD in the solid phase leads to a material with strong oxidative properties. The syntheses as well as the results obtained (assays, biological efficiency, etc) are reproducible. The product obtained at the end of the synthesis is a fine powder that can easily be used for the targeted applications (see biological tests).

[0177] Hypothesising that ozone molecules are encapsulated within the material, the ozone concentrations obtained by assay are very high (100 to 1000 times those obtained with ozonated water). This concentration depends on several parameters, including the nature and properties of the CD.

[0178] The storage capacity of the material is highly dependent on the CD used as raw material. The best results have been obtained with HP-β-CD (a modified β-CD much more soluble in aqueous phase than simple β-CD) for which an ozone concentration equal to 5700±100 μg/g powder (three assays performed) has been found with process example 1 and 11540±540 g/g powder (three assays performed) with process example 2 (point I.2. above). These values are equivalent to a concentration about 400 and 800 times higher than for ozonated water at ambient temperature and pressure ([O.sub.3] ozonated water, 25° C., 1 bar, at 60-80 g/Nm.sup.3 (pH=7) about 14 mg/L water), respectively.

[0179] It has also been shown that the material maintains its oxidative properties for several months, even with rudimentary storage under ambient conditions (temperature of about 21° C. under air). Nevertheless, the ozone concentration in the material stored under ambient conditions (temperature of about 25-30° C. and synthesis process example 1) decreases over time: the estimated loss is about 20% per day as regards the “immediate” assay of the powder (first decolourising of the KI solution). Measurements carried out with powders synthesized with process example 2 and stored at different temperatures show that low storage temperatures (2° C., −19° C.) allow ozone loss to be limited over time, the best results being obtained with the lowest storage temperature tested (that is −19° C.).

[0180] Furthermore, the assay results could also suggest that the solid, once dissolved in water, stabilises some of the ozone, initially contained in the material, within the liquid solution which gradually recolours over time. Predicted concentrations and kinetics could thus be underestimated as compared to reality.

REFERENCES

[0181] [1] McTurk & Waller, 1964, “Ozone carbon tetrachloride double hydrate”, Nature, vol. 202, page 1107.

[0182] 2] Nakagima et al, 2012, “Molecular storage of ozone in a clathrate hydrate: an attempt for preserving ozone at high concentrations”, PlosOne, vol. 7: e48563.

[0183] 3] Patent application JP 2007/210881 on behalf of Kurita Water Ind. Ltd, published on 23 Aug. 2007.

[0184] [4] Dettmer et al, 2017, “Stabilization and prolonged reactivity of aqueous phase ozone with cyclodextrin”, Journal of Contaminant Hydrology, vol. 196, pages 1-9.

[0185] [5] Patent application US 2018/0178263 on behalf of OXYTEC LLC, published on 28 Jun. 2018.

[0186] [6] Patent application US 2016/0367967 on behalf of Temple University of the Commonwealth System of Higher Education, published on 22 Dec. 2016.

[0187] 7] International application WO 2006/134299 on behalf of Université de Franche-Comté, published on 21 Dec. 2006.