EP2978458A1

EP2978458A1 - Pigmented decontaminating gel and method for decontaminating surfaces using said gel

Info

Publication number: EP2978458A1
Application number: EP14714661.7A
Authority: EP
Inventors: Amélie LUDWIG; Frédéric GOETTMANN; Fabien FRANCES
Original assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2013-03-29
Filing date: 2014-03-27
Publication date: 2016-02-03
Also published as: JP2016521199A; US20160057993A1; WO2014154817A1; JP6757774B2; US10653131B2; FR3003869A1; FR3003869B1; KR102286086B1; JP2019048978A; JP6685220B2; KR20150140712A

Abstract

A decontaminating gel consisting of a colloidal solution comprising, preferably consisting of: - 0.1% to 30% by weight, preferably 0.1% to 25% by weight, more preferably 5% to 25% by weight, better still 8% to 20% by weight, relative to the weight of the gel, of at least one inorganic viscosifying agent; - 0.1 to 10 mol/l of gel, preferably 0.5 to 10 mol/l of gel, more preferably 1 to 10 mol/l of gel, of at least one decontaminating active agent; - 0.01% to 10% by weight, preferably 0.1% to 5% by weight, relative to the weight of the gel, of at least one mineral pigment; - optionally, 0.1% to 2% by weight, relative to the weight of the gel, of at least one surfactant; - optionally, 0.05% to 5% by weight, preferably 0.05% to 2% by weight, relative to the weight of the gel, of at least one superabsorbent polymer; - with the rest being solvent. A decontaminating method using said pigmented gel.

Description

PIGMENT DECONTAMINATION GEL AND DECONTAMINATION METHOD OF

SURFACES USING THIS GEL.

DESCRIPTION TECHNICAL FIELD

The present invention relates to a pigmented decontamination gel used for the decontamination of surfaces.

The present invention further relates to a process for decontaminating surfaces using this pigmented gel.

The method and the gel according to the invention allow the decontamination of all kinds of surfaces such as surfaces made of metallic materials, plastics, minerals such as vitreous materials.

The method and the gel according to the invention apply in particular to the decontamination of surfaces of porous materials such as cementitious materials such as mortars and concretes; the bricks ; plasters; and natural stone.

The process and the gel according to the invention also allow the elimination of all kinds of contaminants and in particular chemical, biological, or nuclear, radioactive contaminants.

The process and the gel according to the invention can therefore be qualified as a process and a N RBC decontamination gel (Nuclear, Radiological, Biological, Chemical).

The technical field of the invention can thus generally be defined as that of the decontamination of surfaces in order to eliminate the pollutants, contaminants which are on this surface and possibly under this surface, and whose presence on and under these surfaces is not desired.

STATE OF THE PRIOR ART

For a few decades, the succession of terrorist acts using chemical agents and more recently biological, for example the attack on gas sarin in the Tokyo subway in 1995, and the anthrax in US Postal mail bombs in the United States in 2001, prompted many countries to develop strategic means, so-called post-event intervention, to respond effectively the consequences of possible terrorist attacks using biological, chemical or radiological agents, and to limit the effects of such attacks, particularly in public areas.

Essentially chemical nature at the beginning of XX ^th century, the threat agents have evolved into the arms of stronger impacts, simpler to implement and especially not detectable before the first symptoms appear on the body.

The fear is therefore rather today about the particularly contagious biological terrorist attacks, but also on chemical, nuclear or radiological terrorist attacks. Toxic biological species such as Bacillus anthracis (anthrax or anthrax), the bacterium that causes plague Yersinia pestis, or botulinum toxin are considered to be the weapons with the highest probability of use.

In the event of such an event, the priority for the authorities is to limit the effects of the attack on the civilian population by rapidly decontaminating and rehabilitating the exposed infrastructure, in order to prevent the spread of toxic species through technical installations and equipment, such as ventilation ducts and sewage pipes, and then return buildings to their use as quickly as possible without any risk of exposure to toxic species persisting for users of these buildings.

This decontamination can go through one of the following two steps, potentially implemented in parallel:

- the neutralization, or even the destruction of the species, agent, toxic, when this is possible.

transfer of the species, toxic agent to a solid or liquid phase allowing its elimination. In general, remediation techniques for contaminated materials, including biological contamination, include contacting a liquid containing a decontaminant, such as a biocidal agent, with the contaminated surfaces. The application of the decontamination solution, for example the biocidal solution, is generally carried out by spraying or washing, which may or may not be coupled with a mechanical effect such as brushing.

An overview of these techniques is provided in documents FR-A1-2962046 and WO-A1-2012 / 001046 [1].

In particular, it states that the decontamination products, which are in the form of a gel, generate a solid waste and thus make it possible to overcome the use of liquid solutions for sanitizing parts of large areas and geometries. complex.

These gels are generally used by spraying them on the surface to be decontaminated.

After a contact time of the gel with the surface to be decontaminated, equivalent to the evaporation time of the solvent, the dry waste obtained is removed by brushing and / or aspiration. The major advantage of these methods is their ability to treat large areas and uneven geometries.

Thus, document [2] describes a gel composition containing oxidizing agents for the chemical or biological decontamination of contaminated areas. This composition is prepared by adding thickening or gelling agents in the form of colloids to an oxidizing agent solution to form a viscous colloidal gel.

The thickening or gelling agents may be chosen from silica, alumina, aluminosilicates, mixtures of silica and alumina, and clays such as smectite.

It is stated that these gels can be used to remove biological agents such as microorganisms such as bacteria, fungi, viruses, and spores, or chemical agents such as neurotoxic gases.

The gels are then sprayed onto the surfaces to be treated and then recovered by suction after drying. The gelled formulations developed by the Lawrence Livermore National Laboratory under the names of L-Gel 115 and L-Gel 200 are analogous to the formulations developed in document [2] and are implemented with the so-called "L-Gel" process. This method appears to be somewhat effective against biological contamination such as contamination by Bacillus globigii spores [3].

These gels are formulated from oxidizing acid solutions to which organic solvents and a silica filler are added. The gels are then sprayed onto the surfaces to be treated and then recovered by suction after drying. Among the critical points of this process, appears first of all the presence of powerful oxidizing agents whose chemical stability is often very limited in time.

In addition, in order to prevent run-off, particularly when the gel is applied to walls or ceilings, it is applied in the form of very thin films with a thickness not exceeding, in document [2], 125 μιη. The result is a dry powdery waste that can result, if the effectiveness of the treatment is not total, a dissemination of biotoxic and chemical species, such as oxidizing compounds, in the atmosphere.

Furthermore, in the context of nuclear decontamination, gelled formulations that make it possible to overcome the problems related to the pulverulent character of the dry waste, and to increase the efficiency of the process using a gel have been the subject of documents [4] and [5].

These documents describe inorganic colloidal gels called "aspirable gels", specifically formulated to be sprayed, then to dry by fracturing, while trapping and confining radioactive contamination in the form of aspirable and storable flakes (see Figure 1).

Document [4] describes a gel consisting of a colloidal solution comprising an inorganic viscosifying agent, generally silica or alumina, an active treatment agent which is, for example, an acid or an inorganic base such as sodium hydroxide or potash, and optionally an oxidizing agent having a normal redox potential E ₀ greater than 1.4 V in a strong acid medium such as Ce (IV), Co (III), or Ag (II). Document [5] describes a gel consisting of a colloidal solution comprising an organic viscosity agent, generally silica or alumina, a surfactant, an acid or an inorganic base, optionally an oxidizing agent having a normal potential. oxidation-reduction E ₀ greater than 1.4 V in strong acid medium such as Ce (IV), Co (III), or Ag (II).

These inorganic colloidal gels, because of the different constituents used in their composition have a rheology that allows their spraying on a contaminated surface, then their adhesion to this surface, even vertical, without sinking.

This thus allows prolonged contact between the contaminant and the active decontamination agent, without the mechanical properties of the substrate being altered.

Following its spraying, the gel dries, fractures, and produces dry residues, called "flakes", adhering to the substrate and which are subsequently removed by brushing or aspiration to be directly conditioned.

The decontamination processes that use these suction gels are therefore dry decontamination processes, generating no liquid effluent and few dry solid residues. Indeed, these dry solid residues represent on average only a quarter of the initially sprayed gel mass. In addition, these methods limit the time of exposure of operators to radioactive contamination, because of their easy implementation by spraying and suctioning of dry residues, and the fact that the presence of the operator is not required during the drying of the gel.

Documents FR-A1-2962046 and WO-A1-2012 / 001046 [1] relate to an "aspirable" biological decontamination gel and a process for the biological decontamination of surfaces using this gel.

This gel consists of a colloidal solution comprising at least one inorganic viscosifying agent, at least one biological decontamination agent, at least one superabsorbent polymer, and at least one surfactant.

The superabsorbent polymer, such as sodium polyacrylate, makes it possible to improve the gel efficiency on porous materials, for example mortars. However, the practical implementation of these aspirable decontamination gels, such as those described in documents [1], [4], and [5] under real conditions could encounter a number of difficulties.

Indeed, in the hypothesis of the use of aspiratable decontamination gels for the "post-event" treatment of civilian installations, such as railway stations or subway stations, the intervention of the operators would be made difficult mainly because of of the following three factors:

the stress, the intervention must be carried out quickly without being able to be prepared meticulously.

- the wearing of personal protective equipment ("PPE"), such as NRBC suits, which sometimes impede vision and movement.

the color of the media to be decontaminated, which does not necessarily vary much with the colors of conventional formulations of decontamination gels, is that we can call the effect "white on white".

Thus, the photograph of FIG. 4 shows the spraying of a conventional white unpigmented decontamination gel on a support to be decontaminated constituted by white ceramic tiles. This photograph shows that it is difficult to distinguish areas of the support covered by the gel, whether dry or wet, areas of the support that are not covered by the gel. In other words, it is difficult to visualize the wet gel, then the dry residues obtained by drying this gel, when the support to be decontaminated has a color, usually white, similar to that of the gel, or when the support to decontaminate is in a confined environment and / or in which the visibility is reduced, for example a dark, poorly lit place. This visualization is all the more difficult as the operator wears an outfit that can interfere with his vision such as a NRBC suit.

Figure 5 shows a white ceramic tile wall of the Paris metro covered with white gel. It is very difficult to distinguish areas of the wall from areas that are not covered. From the foregoing, it is essential to facilitate and simplify the intervention of decontamination operators under critical emergency conditions.

There is therefore a need for a decontamination gel which makes it possible to better visualize the wet gel applied to a substrate, substrate to be decontaminated as well as the dry residues obtained by drying this gel on this substrate, a decontaminated support.

In other words, there is a need for a decontamination gel which makes it possible to easily distinguish the zones of a substrate, support, covered by the gel, whether they are dry or wet, areas of the substrate, support, which are not covered by the gel.

This decontamination gel must ensure such an improvement in the visualization of the gel applied or dry residues which (s) that the substrate, and in particular the color thereof, the contaminants to be eliminated, the medium in which the substrate to be decontaminated, especially in the case of a confined or reduced-visibility environment, the circumstances in which decontamination is carried out, for example, in disaster-affected areas and in emergency emergency situations, and whatever the situation. holding of the decontamination operator, especially if the latter is wearing an NRBC suit that may hinder his vision.

These improvements in terms of visualization of the wet or dry gel must be obtained without the other physicochemical properties of the gel such as its rheology or others are affected.

In particular, this gel must have all the properties of a suction gel with all the advantages associated with the implementation of such a gel in a decontamination process that have already been described above.

Among others, the gel must have the following properties:

ease of application on the surface to be treated and formation of a homogeneous layer;

good adhesion to the surface to promote optimal decontamination; rapid drying, for example in a period of the order of a few hours;

formation of flakes adhering to the surface to be treated, but easily recoverable by brushing and / or suction and not pulverulent.

This decontamination gel, for example biological, must produce dry waste, easy to eliminate without dissemination of contaminants, for example biological contaminants, and must allow to treat with the same efficiency a wide variety of surfaces regardless of their shape, geometry, their size and their nature.

There is still a need for a decontamination gel that does not produce any alteration, chemical, mechanical or physical surfaces treated.

The purpose of the present invention is to provide a biological decontamination gel that meets the needs and requirements listed above, among others.

The object of the present invention is still to provide a decontamination gel which does not have the disadvantages of the defects, limitations and disadvantages of the decontamination gels of the prior art and which solves the problems of the decontamination gels, in particular nuclear and biological gels. prior art, in particular gels which are the subject of documents [1], [4] and [5].

STATEMENT OF THE INVENTION

This and other objects are achieved, according to the invention, by a decontamination gel consisting of a colloidal solution comprising, preferably consisting of:

- 0.1% to 30% by weight, preferably 0.1% to 25% by weight, more preferably 5% to 25% by weight, more preferably 8% to 20% by weight, based on the mass of the gel at least one inorganic viscosifying agent;

0.1 to 10 mol / l of gel, preferably 0.5 to 10 mol / l of gel, more preferably 1 to 10 mol / l of gel, of at least one active agent for decontamination; 0.01% to 10% by weight, preferably 0.1% to 5% by weight, based on the weight of the gel, of at least one mineral pigment;

optionally, 0.1% to 2% by weight, based on the weight of the gel, of at least one surfactant;

- optionally, 0.05% to 5% by weight, preferably 0.05% to 2% by weight relative to the weight of the gel, of at least one superabsorbent polymer;

and the remainder of solvent.

"Solvent residue" means that the solvent is always present in the colloidal solution and that the amount of solvent is such that, when it is added to the quantities of the components of the colloidal solution other than the solvent (that these components are mandatory or optional components mentioned above, or other additional optional components mentioned or not mentioned), the total amount of all the components of the colloidal solution is 100% by weight.

The gel according to the invention differs fundamentally from the gels of the prior art, such as those of documents [1], [4], and [5] in that it contains a mineral pigment.

The decontamination gel according to the invention may thus be called pigmented gel.

The incorporation of a mineral pigment in a decontamination gel has never been described or suggested in the prior art and in particular in the documents [1],

[4], and [5] cited above.

There is no limitation on the mineral pigment that is incorporated in the decontamination gel according to the invention.

Generally, the inorganic pigment is chosen from mineral pigments which are stable in the gel, especially with regard to the active decontamination agent that the gel contains.

By stable pigment, it is generally meant that the pigment does not exhibit a stable change in color over time, during storage of the gel for a minimum of 6 months. There is no limitation on the color of this pigment, which is usually the color that it will communicate to the gel. This pigment can be black, red, blue, green, yellow, orange, violet, brown, etc., and even white.

Generally, the gel therefore has a color identical to the color of the pigment it contains. It is possible, however, that the gel has a color that differs from the color of the pigment it contains, for example in the case where the pigment reacts with the decontamination active, but this is not desired.

The pigment, especially when it is white, is generally different from the inorganic viscosifying agent.

Advantageously, the mineral pigment is chosen so that it gives the gel (that is to say the gel in the wet state as defined above, before drying) a color different from the color of a surface to decontaminate on which the gel is applied.

Advantageously, the inorganic pigment is a micronized pigment, and the average particle size of the inorganic pigment may be from 0.05 to 5 μιη, preferably from Ο, ΐ μιη.

The fact that the pigment is micronized prevents it from modifying the rheology and the spraying ability of the gel ("sprayability") because the pigment then has the same micrometric size, which is generally that of the viscosifying agent. inorganic, such as alumina aggregates.

Advantageously, the mineral pigment is chosen from metal oxides

(metal) and / or metalloid (s), metal (metal) and / or metalloid (s) hydroxides, metal (metal) and / or metalloid (s) oxyhydroxides, ferrocyanides and ferricyanides of metal (metals), metal aluminates (metals), and mixtures thereof.

Preferably, the inorganic pigment is chosen from iron oxides, preferably micronized, and mixtures thereof.

The iron oxides can have different colors, they can be for example yellow, red, purple, orange, brown, or black.

Indeed, the iron oxide pigments are known to have a good hiding power and a high resistance to acids and bases. For incorporation into a decontamination gel, the iron oxides have the best performance in terms of stability and coloring power. Thus, an iron oxide content of 0.1% or even 0.01% by weight is sufficient to strongly color the gel without modifying its properties.

As already mentioned above, the fact that the iron oxide pigment is preferably micronized makes it possible to prevent it from modifying the rheology and the sprayability of the gel ("sprayability") because the pigment then has a micrometric size, ie a size which is generally that of the inorganic viscosifying agent, such as alumina aggregates.

Micronized iron oxides are available from the company

Rockwood ^® under the trade name Ferroxide ^® .

There may be mentioned inter alia the Ferroxide ^® 212M which is a red iron oxide micronized ave an average particle size of 0.1 μιη and Ferroxide ^® M 228 which is a micronised red iron oxide with an average particle size of 0.5 μιη.

In addition to and / or instead of the iron oxides, other oxides or hydroxides of metals or of colored metalloids may be incorporated in the gel according to the invention, depending on the pH of the gel, mention may in particular be made of the oxide vanadium (V ₂ O ₅ ) which is orange, manganese oxide (MnO ₂ ) which is black, cobalt oxide which is blue or green, and rare earth oxides. However, iron oxides are preferred for the reasons specified above.

Among the oxyhydroxides, there may be mentioned goethite, that is iron oxyhydroxide FeOOH, which is very colored.

By way of example of metal ferrocyanide, mention may be made of Prussian blue, ie ferric ferrocyanide, and by way of example of aluminate, mention may be made of cobalt blue, that is, cobalt aluminate.

The inclusion in the gel according to the invention of a mineral pigment makes it possible to better visualize the wet gel then the dry residues whatever the substrate on which the gel is applied.

Thus Figure 6, to compare with Figure 5 (white ceramic tiles covered with a white gel, without pigment), shows a white ceramic tile of which part is covered by a pigmented gel colored according to the invention, which contains the pigment Ferroxide ^® 212M, dry and fractured. The part of the tile covered by the pigmented dry gel is easily distinguished from the white part which is not covered by the gel.

Surprisingly, it has been demonstrated, according to the invention, that the specific coloring substance incorporated in the gel according to the invention, which is a mineral pigment, does not affect the decontaminating and physicochemical properties of the decontamination gel. according to the invention which is, like the pigment-free gels of documents [1], [4], and [5] inorganic (inorganic), sprayable, aspirable after drying and usable in many situations over a wide range of contaminants and substrates.

In other words, it has been demonstrated, according to the invention, that of all the dyes and pigments that could have been used to give a color to the projectable and aspirable decontamination gels, only the inorganic pigments, more particularly the pigments with metal (metal) and / or metalloid (s), metal hydroxide (metal) and / or metalloid (s), metal oxyhydroxide (metal) and / or metalloid (s) ), ferrocyanides and ferricyanides of metal, metal aluminates (metals), and mixtures thereof; and even more particularly pigments based on micronized iron oxides, were compatible with the formulation of the decontamination gels, that is to say did not affect in any way the necessary properties of these gels (see above) and the benefits that flow from it.

Indeed, it has been found that the decontaminating properties of the decontamination gels according to the invention are generally due to an aggressive formulation, for example a very low or very high pH, and / or to the presence of oxidants and, as a result, organic dyes deteriorate rapidly, which leads to a loss of properties of the gel in storage conditions.

Surprisingly, only mineral pigments, more particularly pigments based on oxides, hydroxides, oxyhydroxides, ferrocyanides, ferricyanides, and aluminates, more particularly pigments based on iron oxides. micronized, offer a good coloring power and good preservation of the staining over time without significantly modifying the properties (see above) of the formulated gel.

The gels according to the invention meet all the needs and requirements mentioned above, they do not have the disadvantages, defects, limitations and disadvantages of the gels of the prior art such as those described in the documents mentioned above.

The gels according to the invention solve the problems presented by the decontamination gels of the prior art such as those described in the documents [1], [4] and [5] without presenting the drawbacks in particular in terms of visualization on a substrate areas covered or not wet and dry gel, but retaining all the known advantageous properties of these gels.

The addition of mineral pigments to the known conventional formulation of the projectable and aspirable decontamination gels in many ways makes it possible to facilitate and improve their implementation, particularly with regard to their use in disaster areas, in particular emergency situation in confined or reduced-visibility environments, particularly for NRBC operators.

The presence of mineral pigments in the gel according to the invention ensures not only a better visualization of the areas covered by the wet gel after spraying but also a better visualization of the dry flakes on the decontaminated support.

Another additional advantage of the pigmented gels according to the invention is that it makes it easy to distinguish the dry zones, namely the areas covered by the flakes of dry gel, areas of still wet gel.

This is possible due to discoloration of the gel during drying if, of course, the pigment is not a white pigment.

It can thus be visually, easily, and certainly ascertained that the action of the gel is complete and that the time during which it has remained on the substrate has been sufficient to allow complete drying of the gel, even though this duration is random and varies with climatic conditions, including temperature, relative humidity, and ventilation (Figures 5, 6). The gel according to the invention may further optionally comprise a superabsorbent polymer.

The incorporation of a superabsorbent polymer into a decontamination gel and a fortiori the combination in such a gel of such a superabsorbent polymer with a decontaminating agent, such as a biological decontamination agent, and with a mineral pigment have never been described in the prior art, as represented in particular by the documents cited above.

The gel according to the invention is a colloidal solution, which means that the gel according to the invention contains inorganic solid particles, mineral, viscosity agent whose elementary particles, primary, have a size generally of 2 to 200 nm.

Due to the use of a generally exclusively inorganic viscosifying agent, without organic viscosity agent, the organic matter content of the gel according to the invention is generally less than 4% by weight, preferably less than 2% by weight, which constitutes yet another advantage of the gels according to the invention.

These inorganic, solid inorganic particles act as a viscosity agent to allow the solution, for example the aqueous solution, to gel and thus adhere to the surfaces of the part to be treated, decontaminate, whatever their geometry, their shape. , their size, and where are the contaminants to be removed.

Advantageously, the inorganic viscosifying agent may be chosen from metal oxides such as aluminas, metalloid oxides such as silicas, metal hydroxides, metalloid hydroxides, metal oxyhydroxides, metalloid oxyhydroxides, aluminosilicates, clays such as smectite, and mixtures thereof.

In particular, the inorganic viscosifying agent may be chosen from aluminas (Al ₂ O ₃ ) and silicas (SiO ₂ ).

The inorganic viscosifying agent may comprise only one silica or alumina or a mixture thereof, namely a mixture of two or more different silicas (SiO ₂ / SiO ₂ mixture), a mixture of two different aluminas, or more (mix AI2O3 / Al2O3), or a mixture of one or more silicas with one or more aluminas (mixture S102 / Al2O3).

Advantageously, the inorganic viscosifying agent may be chosen from pyrogenic silicas, precipitated silicas, hydrophilic silicas, hydrophobic silicas, acidic silicas, basic silicas, such as Tixosif 73 silica, marketed by Rhodia, and mixtures thereof.

Among the acidic silicas, mention may be made especially of fumed silica or fumed silica "Cab-O-Sil" ^¾ M5, H5 or EH5, sold by CABOT, and pyrogenic silicas sold by the company Evonik Industries under the name AEROSIL ^* .

Among these fumed silicas, AEROSIL ^* 380 silica with a specific surface area of 380 m ² / g, which offers the maximum viscosity properties for a minimum mineral filler, will be preferred.

The silica used may also be a so-called precipitated silica obtained for example by the wet route by mixing a solution of sodium silicate and an acid. The preferred precipitated silicas are sold by the company Evonik Industries under the name Sipernat ^* 22 LS and FK 310 or by the company Rhodia under the name Tixosil ^* 331, the latter is a precipitated silica whose average surface area is between 170 and 200 m ² / g

Advantageously, the inorganic viscosifying agent consists of a mixture of a precipitated silica and a fumed silica.

The alumina may be chosen from calcined aluminas, crushed calcined aluminas, and mixtures thereof.

By way of example, mention may be made of the product sold by EVONIK INDUSTRIES under the commercial designation "Aeroxide Alumine C" which is fine-pyrogenic alumina.

Advantageously, according to the invention, the viscosing agent is constituted by one or more alumina (s) generally representing from 5% to 30% by weight relative to the mass of the gel. In this case, the alumina is preferably at a concentration of 8% to 17% by weight relative to the total mass of the gel in order to ensure drying of the gel at a temperature of between 20 ° C. and 50 ° C. and at a humidity of relative between 20% and 60% on average in 30 minutes to 5 hours.

The nature of the mineral viscosifying agent, especially when it consists of one or more alumina (s), unexpectedly influences the drying of the gel according to the invention and the particle size of the residue obtained.

Indeed, the dry gel is in the form of particles of controlled size, more precisely millimetric solid flakes, the size of which generally ranges from 1 to 10 mm, preferably from 2 to 5 mm, in particular by the above-mentioned compositions of the present invention. invention, especially when the viscosing agent is constituted by one or more alumina (s).

Note that the size of the particles generally corresponds to their largest dimension.

In other words, the inorganic solid particles of the gel according to the invention, for example of the silica or alumina type, in addition to their role of viscosity, also play a fundamental role during the drying of the gel because they ensure the fracturing of the gel to achieve to a dry waste in the form of flakes.

The gel according to the invention contains an active decontamination agent. This active decontaminating agent can be any active decontamination agent for removing a contaminant whatever the nature of this contaminant: whether this contaminant is chemical, biological or even nuclear, radioactive -in other words, this decontamination agent may be any decontaminant "NRBC" (Nuclear, Biological, Radiological, Chemical) - or that this contaminant is organic or mineral, liquid or solid; or whatever the form of this contaminant: that this contaminant is in a solid or particulate form, contained in a surface layer of the material of the part, in the form of a film or contained in a film, for example a film grease on the surface of the workpiece, in the form of a layer or contained in a layer, for example a layer of paint on the surface of the workpiece, or simply deposited on the surface of the workpiece. Depending on the nature of the contamination, the modes of action of the gels differ: erosion of the support material containing the contamination, solubilization of the contaminating film, for example grease, or covering for example of paint, or in situ inactivation of contaminants chemical or biological in the case of pathogenic species (anthrax).

The gel according to the invention may thus contain an active agent for biological or chemical decontamination or else nuclear, radioactive decontamination; the active decontamination agent may also be a degreasing agent, pickling. Some active decontamination agents can simultaneously perform several decontamination functions.

By biological decontamination agent which can also be described as biocidal agent is any agent, which when it is brought into contact with a biological species and in particular a toxic biological species is likely to inactivate or destroy it. this.

By biological species, we mean any type of microorganism such as bacteria, fungi, yeasts, viruses, toxins, spores including Bacillus anthracis spores, prions, and protozoa.

The biological species that are eliminated, destroyed, inactivated by the gel according to the invention are essentially biotoxic species such as pathogenic spores, for example Bacillus anthracis spores, toxins such as botulinum toxin or ricin, bacteria such as Yersinia pestis bacteria and viruses such as vaccinia virus or haemorrhagic fever viruses such as Ebola.

By chemical decontamination agent is meant any agent which when it is brought into contact with a chemical species and in particular a toxic chemical species is likely to destroy or inactivate it.

The chemical species that are removed by the gel according to the invention are in particular toxic chemical species such as toxic gases, in particular neurotoxic or vesicants. These toxic gases include organophosphorus compounds, among which mention may be made of Sarin or GB agent, VX, Tabun or GA agent, Soman, Cyclosarin, diisopropyl fluoro phosphonate (DFP), Amiton or VG agent, Parathion. Other toxic gases are mustard gas or agent H or agent HD, Lewisite or agent L, agent T.

The radioactive nuclear species that can be removed by the gel according to the invention can be chosen for example from metal oxides and hydroxides, especially in the form of solid precipitates.

It should be noted that in the case of radioactive species, there is no mention of destruction or inactivation but only elimination of the contamination by dissolution of the irradiating deposits or corrosion of the materials supporting the contamination. So there is a real transfer of nuclear contamination to dry gel flakes.

The active decontamination agent, for example the active agent for biological or chemical decontamination may be chosen from bases such as sodium hydroxide, potassium hydroxide, and mixtures thereof; acids such as nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydrogen oxalates such as sodium hydrogenoxalate, and mixtures thereof; oxidizing agents such as peroxides, permanganates, persulfates, ozone, hypochlorites such as sodium hypochlorite, cerium IV salts, and mixtures thereof; quaternary ammonium salts such as hexacetylpyridinium salts, such as hexacetylpyridinium chloride; reducing agents; and their mixtures.

Some active decontamination agents can be classified among several of the categories defined above.

Thus, nitric acid is an acid but also an oxidizing agent.

The active decontaminating agent, such as a biocidal agent, is generally used at a concentration of 0.5 to 10 mol / L of gel, preferably of 1 to 10 mol / L, and more preferably of 3 to 6 mol / L gel to ensure a decontamination power, for example a power of inhibition of biological species, especially biotoxic, compatible with the drying time of the gel, and to ensure for example a drying of the gel at a temperature between 20 ° C and 50 ° C and at a relative humidity of between 20% and 60% on average in 30 minutes to 5 hours.

In order to achieve total efficiency, including under the most unfavorable temperature and humidity conditions with respect to drying time, the formulation of the gel of the present invention supports different concentrations of active agent. It may be noted, in fact, that the increase in the concentration of decontamination agent more particularly acidic or basic decontamination agent significantly increases the gel drying time and therefore the efficiency of the process. In order to take into account the kinetics of erosion of the materials and the kinetics of inhibition of the contaminating species, in particular the biotoxic species, the active decontamination agent, in particular the biological decontamination agent, will preferably be present in the gel at a concentration of between 3 and 6 mol / l in order to achieve the maximum efficiency of the process.

The active decontamination agent can be an acid or a mixture of acids. These acids are generally selected from mineral acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

A decontaminating agent, especially a particularly preferred biological decontaminating agent is nitric acid.

Indeed, it turned out surprisingly that nitric acid destroyed, inactivated, biological species including biotoxic.

In particular, it has been surprisingly demonstrated that nitric acid ensures the destruction, inactivation, of spores such as Bacillus thuringiensis spores which are particularly resistant species.

The acid (s) is (are) preferably present in a concentration of 0.5 to 10 mol / L, more preferably 1 to 10 mol / L, more preferably 3 to 6 mol / L to ensure drying the gel generally at a temperature between 20 ° C and 50 ° C and at a relative humidity of between 20% and 60% on average in 30 minutes to 5 hours.

For this type of acid gel, the inorganic viscosity agent is preferably silica or a mixture of silicas. Alternatively, the active decontamination agent, for example the active biological decontamination agent, may be a base, preferably a mineral base, preferably chosen from sodium hydroxide, potassium hydroxide and mixtures thereof.

In the case of such a basic gel formulation, the gel according to the invention has, in addition to the decontamination action, a degreasing action.

As already mentioned above, so as to achieve total efficiency, including in the most unfavorable climatic conditions vis-à-vis the drying time of the gel, the gel according to the invention can have a wide range concentration of basic decontamination agent (s).

Indeed, increasing the concentration of basic decontamination agent such as NaOH or KOH, generally acting as a biocidal agent, considerably increases the inhibition rates of biological species, as has been demonstrated for spores. of Bacillus thuringiensis.

The base is advantageously present at a concentration of less than 10 mol / l, preferably between 0.5 and 7 mol / l, more preferably between 1 and 5 mol / l, more preferably between 3 and 6 mol / l, to ensure gel drying at a temperature between 20 ° C and 50 ° C and at a relative humidity of between 20% and 60% on average in 30 minutes to 5 hours.

For this type of alkaline, basic gel, the inorganic viscosifying agent is preferably an alumina or a mixture of aluminas.

In order to achieve maximum efficiency on a wide range of materials while ensuring the safety of the treatment, the decontaminating agent, especially when it comes to a biological decontamination agent, is preferably hydroxide. sodium or potassium hydroxide.

In the case of the treatment of a cement matrix, the basic pH of the gel, which is induced by the use of soda or potassium hydroxide, makes it possible to avoid acid-base reactions, between the material to be decontaminated and the gel , which affect the integrity of the gel on the surface and therefore the efficiency of the process.

The hygroscopic nature of sodium hydroxide or potassium hydroxide is also a considerable asset in slowing down the phenomenon of gel drying. The contact time between the gel according to the invention, for example containing a biocidal solution, and the biological contamination, is then considerably increased.

Indeed, the competition between the evaporation process of the aqueous phase and the water recovery of the sodium hydroxide or potassium hydroxide crystals favorably modifies the drying kinetics of the gel.

With regard, for example, to the kinetics of the inhibition of spores and the drying times of the gels as a function of temperature, the active agent for decontamination, especially when it is a biocidal agent, will preferably be hydroxide. of sodium at a concentration of between 1 and 5 mol / L.

The gel according to the invention may also contain, optionally, a superabsorbent polymer.

The term "superabsorbent polymer" also referred to as "PSA" or "SAP" generally means a polymer capable, in the dry state, of spontaneously absorbing at least 10 times, preferably at least 20 times its weight of aqueous liquid. , in particular water and especially distilled water.

Some "SAP" can absorb up to and even over 1000 times their weight of liquid.

Such superabsorbent polymers are in particular described in the book "Absorbent Polymer Technology, Studies in Polymer Science 8" by L. BRANNON-PAPPAS and R. HARLAND, Elsevier edition, 1990, to which reference may be made.

Spontaneous absorption is understood to mean an absorption time of up to about one hour.

The superabsorbent polymer can have a water absorption capacity ranging from 10 to 2000 times its own weight, preferably from 20 to 2000 times its own weight (ie 20 g to 2000 g of water absorbed per gram of polymer absorbent), more preferably from 30 to 1500 times, and in particular from 50 to 1000 times.

These water absorption characteristics are understood under the normal conditions of temperature (25 ° C) and pressure (760 mm Hg or 100000 Pa) and for distilled water. The PSA optionally contained in the decontamination gel according to the invention may be chosen from sodium poly (meth) acrylates, starches grafted with a (meth) acrylic polymer, hydrolyzed starches grafted with a (meth) acrylic polymer; polymers based on starch, gum, and cellulose derivative; and their mixtures.

More specifically, the PSA that can optionally be used in the gel according to the invention can be, for example, chosen from:

the polymers resulting from the polymerization with partial crosslinking of hydrosoluble ethylenically unsaturated monomers, such as acrylic polymers, methacrylic polymers (resulting especially from the polymerization of acrylic and / or methacrylic acid and / or acrylate and / or methacrylate monomers) or vinyl, especially crosslinked and neutralized poly (meth) acrylates, especially in gel form; and the salts, in particular the alkaline salts such as the sodium or potassium salts of these polymers;

starches grafted with polyacrylates;

acrylamide / acrylic acid copolymers, especially in the form of sodium or potassium salts;

acrylamide / acrylic acid grafted starches, especially in the form of sodium or potassium salts;

sodium or potassium salts of carboxymethylcellulose; salts, especially alkaline salts, of crosslinked polyaspartic acids; salts, especially alkaline salts, of crosslinked polyglutamic acids.

In particular, it is possible to use as "SAP" a compound chosen from:

crosslinked sodium or potassium polyacrylates sold under the names SALSORB CL 10, SALSORB CL 20, FSA type 101, FSA type 102 (Allied Colloids); ARASORB S-310 (Arakawa Chemical); ASAP 2000, Aridall 1460 (Chemdal); KlGEL 201-K (Siber Hegner); AQUALIC CA W3, AQUALIC CA W7, AQUALIC CA W10; (Nippon Shokuba); AQUA KEEP D 50, AQUA KEEP D 60, AQUA KEEP D 65, AQUA KEEP S 30, AQUA KEEP S 35, AQUA KEEP S 45, AQUA KEEP Al Ml, AQUA KEEP Al M3, AQUA KEEP HP 200, NORSOCRYL S 35, NORSOCRYL FX 007 (Arkema); AQ.UA KEEP 10SH-NF, AQ.UA KEEP J-550 (Kobo); LUQUASORB CF, LUQUASORB MA 1110, LUQUASORB MR 1600, HYSORB C3746-5 (BASF); COVAGEL (Sensient Technologies), SANWET IM-5000D (Hoechst Celanese);

grafted polyacrylates of starch sold under the names SANWET IM-100, SANWET IM-3900, SANWET IM-5000S (Hoechst);

Acrylamide / acrylic acid copolymers grafted with starch in the form of sodium or potassium salt sold under the names WATERLOCK A-100, WATERLOCK A-200, WATERLOCK C-200, WATERLOCK D-200, WATERLOCK B-204 (Grain Processing Corporation);

acrylamide / acrylic acid copolymers in the form of the sodium salt sold under the name WATERLOCK G-400 (Grain Processing Corporation);

carboxymethylcellulose sold under the name AQUASORB

A250 (Aqualon);

cross-linked sodium polyglutamate sold under the name GELPROTEIN (Idemitsu Technofine).

Superabsorbent polymers, in particular superabsorbent polymers (polyelectrolytes) which contain alkaline ions such as sodium or potassium ions, for example of the sodium or potassium poly (meth) acrylate type, give many properties to the decontamination gels. according to the invention.

They first influence the rheology of the product, especially its flow threshold. In terms of implementation of the process, the advantage of superabsorbent polymers is to guarantee a perfect gel hold on the treated materials, especially on the vertical and overhanging surfaces when the sprayed gel thickness is greater than 1 mm.

In the context of a decontamination process including biological gel decontamination, the superabsorbent polymer is particularly interesting because it absorbs hydrogen bonding part of the solution, for example the biocide solution contained in the gel. The number of hydrogen bonds formed between the solution, for example the biocidal solution, of the gel and the superabsorbent polymer such as the sodium polyacrylate being a function of the saline load, absorption / desorption phenomena appear when the saline load of the decontamination gel is modified.

This mechanism is particularly interesting when it comes to decontaminate inorganic and porous materials such as cementitious matrices, for example.

Indeed, in contact with the material, the salt load of the gel increases due to the presence of mineral particles very often calcium-based. Within the superabsorbent polymer such as sodium polyacrylate, the substitution of the Na ⁺ counterion by calcium-derived Ca ²⁺ instantly generates a solution re-release phenomenon, for example of a biocidal solution, because of the greater steric hindrance of the calcium ion.

The amount of solution, for example biocidal solution released by the superabsorbent polymer such as sodium polyacrylate can then diffuse instantly in the porosity of the material and penetrate deeply.

The phenomenon of diffusion of the decontaminating agent, for example of the biocidal agent towards the core of the material is much more limited in the case of a gel containing no superabsorbent.

The addition of superabsorbent polymer to the gel according to the invention thus makes it possible to significantly increase the effectiveness of the gel and the process according to the invention in the presence of porous materials contaminated in depth over a thickness of one to several millimeters, for example. example up to 2, 5, 10, 20 or even 100 mm.

The superabsorbent polymer may be chosen preferably from the Aquakeep ° or Norsocryl ° ranges sold by the company Arkema.

The gel may optionally also contain a surfactant or a mixture of surfactants, preferably selected from the family of nonionic surfactants such as block copolymers, sequenced as the block copolymers of ethylene and propylene oxide, and ethoxylated fatty acids; and their mixtures. For this type of gel, the surfactants are preferably block copolymers marketed by BASF under the name PLURONIC ^* .

Pluronics ^* are block copolymers of ethylene oxide and propylene oxide.

These surfactants influence the rheological properties of the gel, in particular the thixotropic character of the product and its recovery time and avoid the appearance of sagging.

The surfactants also make it possible to control the adhesion of the dry waste, and to control the size of the flakes of dry residue to ensure the non-dustiness of the waste.

The solvent according to the invention is generally selected from water, organic solvents, and mixtures thereof.

A preferred solvent is water, and in this case the solvent is therefore water, comprises 100% water.

The invention further relates to a method for decontaminating at least one surface of a substrate of a solid material, said surface being contaminated by at least one contaminating species on said surface and optionally under said surface in the depth of the substrate, in which at least one cycle comprising the following successive steps is carried out:

a) applying the gel according to the invention as described above on said surface;

b) the gel is maintained on the surface for at least sufficient time for the gel to destroy and / or inactivate and / or absorb the contaminating species, and for the gel to dry and form a dry and solid residue containing said contaminating species ;

c) removing the dry and solid residue containing said contaminating species.

It should be noted that, in the case of a non-porous surface, the contamination, for example the biological contamination, "inactivated", is recovered by the flakes of dry gel. On the other hand, in the case of deep contamination, as is the case in porous materials such as cementitious matrices, the dry gel will contain only the surface contamination residue.

Deep internal contamination, "inactivated" in situ following the action of the superabsorbent polymer which is then advantageously incorporated into the gel, will remain at the heart of the material substrate.

Advantageously, the mineral pigment contained in the gel is chosen such that it gives the gel a color different from the color of the surface to be decontaminated on which the gel is applied.

The solid substrate may be a porous substrate, preferably a porous mineral substrate, and the gel according to the invention then advantageously contains a superabsorbent polymer.

However, the effectiveness of the gel and the method according to the invention is equally good in the presence of a non-porous and / or non-mineral surface.

Advantageously, the substrate is in at least one solid material selected from metals and metal alloys such as stainless steel, painted steels, aluminum, and lead; polymers such as plastics or rubbers such as polyvinyl chloride or PVC, polypropylenes or PPs, polyethylenes or PEs, in particular high density polyethylenes or HDPEs, poly (methyl methacrylates) or PMMA, polyvinylidene fluoride or PVDF, polycarbonates or PCs; the glasses ; cement and cementitious materials; mortars and concretes; plasters; the bricks ; natural or artificial stone; ceramics.

Advantageously, the contaminating species is chosen from the chemical, biological, nuclear or radioactive contaminating species already listed above and in particular from the toxic biological species already listed above.

Advantageously, the gel is applied to the surface to be decontaminated at a rate of 100 g to 2000 g of gel per m ² of surface, preferably of 500 to 1500 g of gel per m ² of surface, more preferably of 600 to 1000 g of gel per m ² of surface, which generally corresponds to a thickness of gel deposited on the surface of between 0.5 mm and 2 mm. Advantageously, the gel is applied to the solid surface by spraying, with a brush or with a trowel.

Advantageously (during step b)), the drying is carried out at a temperature of 1 ° C. to 50 ° C., preferably of 15 ° C. to 25 ° C., and at a relative humidity of 20% to 80%. preferably from 20% to 70%.

Advantageously, the gel is maintained on the surface for a period of 2 to 72 hours, preferably 2 to 48 hours, more preferably 3 to 24 hours.

Advantageously, the gel is maintained on the surface until it has a decrease in its absorbance in the visible and the ultraviolet, for example discoloration. This decrease in absorbance generally indicates that the drying has come to an end, and that the decontamination is complete.

By absorbance decrease, it is generally meant that the absorbance of the dry gel (flakes) decreases by 30% to 99% compared to the initial absorbance of the gel -humid- when applying the gel on the surface to be decontaminated.

Advantageously, the dry and solid residue is in the form of particles, for example flakes, of a size of 1 to 10 mm, preferably 2 to 5 mm.

Advantageously, the dry and solid residue is removed from the solid surface by brushing and / or suctioning.

Advantageously, the cycle described above can be repeated for example from 1 to 10 times using the same gel during all the cycles or by using different gels during one or more cycle (s).

Advantageously, during step b), the gel, before total drying, is rewetted with a solution of a decontamination agent, preferably with a solution of the active agent for decontaminating the gel applied during step a ) in the solvent of this gel which then generally avoids repeating the application of the gel on the surface and causes a reagent saving and a limited amount of waste. This rewetting operation can be repeated for example from 1 to 10 times. The method according to the invention has all the advantageous properties inherent in the decontamination gel that it implements and which have already been widely discussed above.

In summary, the process and the gel according to the invention have among other things, besides the advantageous properties specifically due to the mineral pigment contained in the gel, the other advantageous properties:

application of the gel by spraying,

adhesion to the walls,

obtaining the maximum effectiveness of decontamination at the end of the drying phase of the gel, including penetrating contamination in particular in the case of porous surfaces.

In general, it is ensured that the drying time is greater than or equal to the time required for inactivation. In the case of deep inactivation, rewetting is generally used.

the treatment of a very wide range of materials,

the absence of mechanical or physical alteration of the materials at the end of the treatment,

implementing the process under varying climatic conditions, reducing the volume of waste,

the ease of recovery of dry waste.

Other features and advantages of the invention will appear better on reading the detailed description which follows, this description being given for illustrative and non-limiting, in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 (A, B) shows schematic sectional views illustrating the main steps of the method according to the invention for the decontamination of a solid material. Figure 2 (A, B, C) shows schematic sectional views showing the mode of action of a superabsorbent polymer-free gel on a cementitious material deeply contaminated by contamination in liquid form.

Figure 3 (A, B, C) shows schematic sectional views showing the mode of action of a gel containing a superabsorbent polymer on a cementitious material deeply contaminated by contamination in liquid form.

Figure 4 is a photograph showing the spraying of a conventional white unpigmented decontamination gel on a support to decontaminate constituted by white ceramic tiles. This photograph shows that it is difficult to distinguish areas covered by frost, whether dry or wet, from areas that are not covered by frost.

Figure 5 is a photograph showing a ceramic tile wall of the Paris metro covered with white unpigmented gel.

Figure 6 is a photograph showing a ceramic tile coated with pigmented gel according to the invention, dry and fractured.

FIG. 7 is a graph which represents the absorbance curves in the UV and the visible of the GB62 alkaline pigmented gel according to the invention, wet (curve A), of the pigmented gel GB62 according to the invention, dry (curve B) , and white gel without GB61 pigment, wet (curve C).

On the abscissa is the wavelength (in nm), and on the ordinate is the absorbance.

FIG. 8 is a graph which represents the absorbance curves in the UV and the visible of the GB63 alkaline pigmented gel according to the invention, wet (curve A), of the pigmented gel GB63 according to the invention, dry (curve B) , and white gel without GB61 pigment, wet (curve C).

FIG. 9 is a graph which represents the absorbance curves in the UV and the visible of the acidic gel pigment GB75 according to the invention, wet (curve A), GB75 pigmented gel according to the invention, dry (curve B), and white gel without pigment GB61, wet (curve C).

FIG. 10 is a graph which represents, in logarithmic scale, the viscosity (in Pa.s) of gels GB61 (curve 1), GB62 (curve 2) and GB63 (curve 3) as a function of the shear rate (in s ^"1 ).

Figure 11 is a graph that represents the frost threshold stress

GB61.

Curves 1, 2, 3, and 4 respectively represent the stress measured for a 100 s ^{1 setting} for 100 s, then a rest period of 10 s (curve 1), a rest period of 100 s (curve 2) , a rest period of 500 s (curve 3), and a rest period of 1000 s (curve 4).

In abscissa, the deformation is carried and in ordinate is carried the stress (in Pa).

Figure 12 is a graph that represents the frost threshold stress

GB62.

On the abscissa, the deformation is carried and the ordinate is carried

(in Pa)

Figure 13 is a graph which shows the drying kinetics of gels GB61 (curve A), GB62 (curve B), and GB63 (curve C).

On the abscissa is the drying time (in min.) And the ordinate is the weight loss (in%).

Figure 14 is a graph that shows the fracking of GB61 gels,

GB62, and GB63. For each gel GB61, GB62, and GB63 is given the average area of flakes (left bar), the number of straws (middle bar), and the median area of flakes (right bar).

On the left scale is the number of flakes, and on the right scale is the flake area (in mm ² ).

FIG. 15 is a graph which represents the absorbance in the ultraviolet and the visible of the fresh, wet, freshly prepared pigmented alkaline gel GB62 according to the invention (curve 2), of the GB62 pigmented alkaline gel according to FIG. wet invention, after storage for 4 months at the end of its preparation (curve 1) and wet ungelled alkaline gel GB61 (curve 3).

FIG. 16 shows photographs of petri dishes in which cultures resulting from the decontamination of Bacillus thuringiensis contaminated stainless steel supports by the GB62 pigmented gel according to the invention (16A) and by an unpigmented white gel (FIG. 16B).

In each of FIGS. 16A and 16B, the left petri dish is a petri dish containing a culture derived from the decontaminated support free of straws while the right petri dish is a petri dish containing a culture derived from gel flakes. dry recovered on the support.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The gel according to the invention can be easily prepared at room temperature.

For example, the gel according to the invention can be prepared by preferably adding progressively, the inorganic viscosity agent (s), for example the alumina (s) and / or the silica (s). (s), a mixture of the decontaminating active agent, the surfactant (s), if any, and the mineral pigment (s) such as iron oxides. This mixture can be produced by mechanical stirring, for example by means of a mechanical stirrer equipped with a three blade propeller. The rotational speed is for example 200 rpm, and the duration of the stirring is for example 3 to 5 minutes.

The addition of the inorganic viscosity agent (s) to the mixture containing the active biological decontamination agent, the surfactant (s), if any, and the pigment (s) ) can be performed by simply pouring the viscosity agent (s) into said mixture. During the addition of the inorganic viscosity agent (s), the mixture containing the biological decontamination active agent, the surfactant (s), if any, and the pigment (s) is usually kept under mechanical stirring.

This agitation can be, for example, carried out by means of a mechanical stirrer equipped with a three blade propeller.

The stirring speed is generally increased gradually as the viscosity of the solution increases, finally reaching a stirring speed of, for example, between 400 and 600 rpm, without there being projections.

After the end of the addition of the mineral viscosity (s) (s), stirring is still maintained, for example for 2 to 5 minutes, so as to obtain a perfectly homogeneous gel.

It is obvious that other gel preparation protocols according to the invention can be implemented with an addition of the gel components in a different order from that mentioned above.

Generally, the gel according to the invention must have a viscosity of less than 200 mPa.s under a shear of 1000s ¹ so as to allow spraying on the surface to be decontaminated, remotely (for example at a distance of 1 to 5 m) or near (for example at a distance less than 1 m, preferably from 50 to 80 cm). The recovery time of the viscosity should generally be less than one second and the viscosity under low shear greater than 10 Pa s to not flow on a wall.

It should be noted that the surfactant of the gel according to the invention has a favorable and noticeable influence on the rheological properties of the gel according to the invention. This surfactant allows in particular that the gel according to the invention can be implemented by spraying and avoids the risk of spreading or sagging during the treatment of vertical surfaces and ceilings.

The gel according to the invention thus prepared is then applied (1) (FIG. 1A) on the solid surface (2) to be decontaminated with a substrate made of a solid material (3), in other words on the surface (2). having been exposed to contamination eg biological contamination (4). This contamination has already been described above. In particular, the biological contamination (4) may consist of one or more of the biological species already defined above.

As already indicated above, the active decontamination agent, for example the active biological decontamination agent, is chosen according to the contaminating species, for example the biological species to be eliminated, destroyed, or inactivate.

With the exception of alloys of aluminum-type light metals, in the case where basic or acidic gels are used, there is no limitation as to the material which constitutes the surface (2) to be decontaminated, in fact the gel according to the invention can treat without any damage, all kinds of even fragile materials.

The gel according to the invention does not generate any alteration, erosion, attack, chemical, mechanical or physical of the treated material. The gel according to the invention is therefore in no way detrimental to the integrity of the treated materials and even allows their reuse. Thus, sensitive materials such as military equipment are preserved and may after their decontamination be reused, while the monuments treated with the gel according to the invention are absolutely not degraded and see their visual and structural integrity preserved.

This material of the substrate (3) can therefore be chosen from, for example, metals and alloys such as stainless steel, aluminum and lead; polymers such as plastics or rubbers, among which mention may be made of PVC, PP, PE in particular HDPE, PMMA, PVDF, PC; the glasses ; cements and cementitious materials; mortars and concretes; plasters; the bricks ; natural or artificial stone; ceramics. In any case, whatever the material, the decontamination efficiency by the gel according to the invention is total.

The treated surface can be painted or unpainted.

In a particularly surprising manner, it has been found that the gel according to the invention, when it contained a superabsorbent polymer, was particularly effective on porous materials such as cementitious matrices such as pastes, mortars and concretes, bricks, plaster, or natural or artificial stone.

Indeed, the presence in the gel according to the invention of a superabsorbent polymer allows a decontamination of a porous material to a much greater depth than with an equivalent gel without superabsorbent polymer.

In other words, the presence of a superabsorbent polymer in the gel according to the invention facilitates the diffusion of the active agent for decontamination, for example of the biocidal agent in the depth of the material when it is It acts to treat porous substrates, in particular minerals.

The effectiveness of the treatment with the gel according to the invention is generally total, including contaminated materials several millimeters deep; in the latter case a superabsorbent polymer is then preferably included in the gel.

There is also no limitation as to the shape, the geometry and the size of the surface to be decontaminated, the gel according to the invention and the process implementing it allow the treatment of large surfaces of complex geometries, presenting for example, hollows, angles, recesses.

The gel according to the invention provides effective treatment not only of horizontal surfaces such as floors, but also of vertical surfaces such as walls, or inclined or overhanging surfaces such as ceilings.

Compared to decontamination processes, for example existing biological decontamination processes which implement liquids such as solutions, the decontamination method according to the invention which implements a gel is particularly advantageous for the treatment of materials of great importance. surface, not transportable and implanted outside. Indeed, the process according to the invention because of the implementation of a gel, allows the decontamination in situ by avoiding the spreading of chemical solutions in the environment and the dispersion of the contaminating species.

The gel according to the invention can be applied to the surface to be treated by all the application methods known to those skilled in the art.

Conventional methods are spraying, for example by spraying, or applying by means of a brush, or a trowel.

For the spraying application of the gel according to the invention on the surface to be treated, the colloidal solution may for example be conveyed via a low pressure pump, for example a pump which implements a pressure less than or equal to at 7 bar, about 7.10 ⁵ Pascals.

The burst of the gel jet on the surface can be obtained for example by means of a jet nozzle or round jet.

The distance between the pump and the nozzle may be arbitrary, for example it may be from 1 to 50 m, in particular from 1 to 25 m.

The sufficiently short viscosity recovery time of the gels according to the invention allows the spray gels to adhere to all surfaces, for example to walls.

The amount of gel deposited on the surface to be treated is generally from 100 to 2000 g / m ² , preferably from 500 to 1500 g / m ² , more preferably from 600 to 1000 g / m ² .

The amount of gel deposited per unit area and, consequently, the thickness of the deposited gel influences the rate of drying.

Thus, when spraying a film, layer of gel with a thickness of 0.5 mm to 2 mm on the surface to be treated, the effective contact time between the gel and the materials is then equivalent to its drying time period during which the active ingredient contained in the gel will interact with the contamination.

In the case of porous substrates, for example cementitious matrices, the action time of the decontamination solution, for example of the biocidal solution - which preferably contains in this case a superabsorbent polymer having penetrated into the core of material - Due to the action of the super-absorbent polymer may be greater than the gel drying time, in which case it is usually necessary to either perform a rewetting with the contamination solution, for example with the biocidal solution, or repeating a spray of the gel.

In addition, it has been surprisingly shown that the amount of gel deposited when it is in the ranges mentioned above and in particular when it is greater than 500 g / m ² and in particular in the range of 500 to 1500 g / m ² , which corresponds to a minimum thickness of deposited gel for example greater than 500 μιη for a deposited gel quantity greater than 500 g / m ² , allowed after drying of the gel to obtain fracking of the gel in the form millimetric flakes, for example of a size of 1 to 10 mm, preferably 2 to 5 mm aspirable.

The amount of gel deposited and therefore the deposited gel thickness, preferably greater than 500 g / m ^2, ie 500 μιη, is the fundamental parameter which influences the size of the dry residues formed after drying of the gel and which thus ensures that residues Millimeter sized and not powdery residues are formed, such residues being easily removed by a mechanical process and preferably by suction.

However, it should also be noted that, thanks to the low concentration surfactant, generally from 0.1% to 2% of the total mass of the gel, the drying of the gel is improved and leads to a homogeneous fracturing phenomenon. with a size of the mono-dispersed dry residues and an increased ability of the dry residues to separate from the support.

The gel is then held on the surface to be treated for the duration necessary for drying. During this drying step, which can be considered as constituting the active phase of the process according to the invention, the solvent contained in the gel, namely generally the water contained in the gel evaporates to the obtaining a dry and solid residue.

The drying time depends on the composition of the gel in the concentration ranges of its constituents given above, but also, as already mentioned, on the amount of gel deposited per unit area, that is to say the deposited gel thickness. The drying time also depends on the climatic conditions, namely the temperature and the relative humidity of the atmosphere in which the solid surface is located.

The process according to the invention can be carried out under extremely wide climatic conditions, namely at a temperature T of 1 ° C. to 50 ° C. and at a relative humidity RH of 20% to 80%.

The drying time of the gel according to the invention is therefore generally from 1 hour to 24 hours at a temperature T of 1 ° C. to 50 ° C. and at a relative humidity RH of 20% to 80%.

It should be noted that the formulation of the gel according to the invention essentially because of the presence of surfactants such as "Pluronics °" generally provides a drying time which is substantially equivalent to the contact time (between the agent of decontamination, such as a biocidal agent, and the contaminating species, for example biological species including biotoxic to be eliminated) that is necessary, required to inactivate and / or absorb the contaminating species polluting the material, and / or to carry out sufficiently the reactions surface erosion of the material.

In other words, the formulation of the gel ensures a drying time which is nothing other than the inactivation time of the contaminating species, for example biological species, which is compatible with the kinetics of inhibition of the contamination, by example of biological contamination.

Or the formulation of the gel provides a drying time which is none other than the time required for the erosion reactions to remove a contaminated surface layer of the material.

In the case of radioactive contaminant species, the contamination is eliminated by dissolving the irradiating deposits or by corrosion of the materials supporting the contamination. So there is a real transfer of nuclear contamination to flakes of dry gels.

The specific surface area of the generally used inorganic filler which is generally from 50 m ² / g to 300 m ² / g, preferably 100 m ² / g and the capacity absorption of the gel according to the invention can trap the labile (surface) and fixed contamination of the material constituting the surface to be treated.

If necessary, the contaminating species, for example the biological contaminating species are inactivated in the gelled phase. After drying the gel, the contamination, for example the inactivated biological contamination is removed during the recovery of the dry gel residue described below.

After the drying of the gel, the gel fractures homogeneously to give millimetric solid dry residues, for example of a size of 1 to 10 mm, preferably 2 to 5 mm non-pulverulent, generally in the form of solid flakes (5) (Figure 1B).

Dry residues may contain the inactivated contaminant (s) (6).

The dry residues, such as flakes (5), obtained after drying have a low adhesion to the surface (2) of the decontaminated material. As a result, the dry residues obtained after drying of the gel can be easily recovered by simple brushing and / or aspiration. However, the dry residues can also be evacuated by gas jet, for example by compressed air jet.

Thus, no rinsing with a liquid is generally necessary, and the process according to the invention does not generate any secondary effluent.

However, it is possible, although not preferred, and if desired, to remove dry residues by means of a jet of liquid.

The method according to the invention thus firstly achieves a significant saving of chemical reagents compared to a decontamination process by washing with a solution. Then because a waste in the form of a directly aspirable dry residue is obtained, a rinsing operation with water or with a liquid, generally necessary for the removal of traces of chemical agents from the part, is usually avoided. This obviously results in a decrease in the amount of effluents produced but also a significant simplification in terms of waste treatment and outlet. Due to the predominantly mineral composition of the gel according to the invention and the small amount of waste produced, the dry waste can be stored or directed to an evacuation die ("outlet") without prior treatment.

The dry gel flakes obtained at the end of the process according to the invention were approved by ANDRA as a heterogeneous waste immobilizable in an HTC mortar slurry.

At the end of the process according to the invention, a solid waste is recovered in the form of flakes that can be packaged in the state, directly conditionable, it results as already indicated above a significant decrease in the amount of effluents produced as well as a significant simplification in terms of waste treatment and outfall treatment.

Moreover, in the nuclear field, the fact of not having to reprocess the flakes before the conditioning of the waste is a considerable asset; this allows the use of active active agents hitherto prohibited in the decontamination liquids due to the operating constraints of liquid effluent treatment plants ("STEL").

The gel may therefore contain powerful oxidizing agents such as cerium IV which can very easily be regenerated from the electrolysis of cerium III.

By way of example, in the current case where 1000 grams of gel are applied per m ² of treated surface, the mass of dry waste produced is less than 200 grams per m ² .

In Figure 2, there is illustrated the decontamination by a gel containing no superabsorbent polymer of a porous substrate (21) contaminated for example by spores in aqueous solution (22). The contamination front (23) extends in the depth of the substrate (Figure 2A). When applying a decontamination gel, for example a biocide gel (24) to the surface (25) of the substrate, the diffusion front (26) of the decontaminating agent, for example the biocidal agent extends little in the depth of the substrate and remains below the contamination front (23) (Figure 2B). As a result, when the gel is removed (Figure 2C) the sanitized area (27) extends little deep and residual contamination remains (28) in the porous substrate (21). In Figure 3, there is illustrated the decontamination, by a gel according to the invention containing a superabsorbent polymer, a porous substrate (31) contaminated, for example by spores in aqueous solution (32). The contamination front (33) extends into the depth of the substrate (Figure 3A). When applying a decontamination gel, for example a biocidal gel, containing the superabsorbent (34) on the surface (35) of the substrate, the diffusion front (36) of the decontamination agent, for example the biocidal agent extends into the depth of the substrate and goes beyond the contamination front (33) (Figure 3B). As a result, the sanitized zone (37) extends in depth (P) and no residual contamination remains in the porous substrate.

The invention will now be described with reference to the following examples given for illustrative and non-limiting.

EXAMPLES

Example 1

In this example, we study the discoloration of basic gels during their drying.

The gels analyzed in this example are basic mineral gels composed of 14% Aeroxide ° Alu C alumina marketed by EVONIK INDUSTRIES and having a specific surface area of 100 m ² / g (BET), 0.2% of surfactants. (Pluronic ^® PE6200 from BASF, and Empilan ^® KR8 from HUNTSMAN), and 1M soda supplement.

According to the gels (Table 1), the formulation may also contain a pigment, namely 0.1% by mass of ferroxide® micronized red iron oxides of the company Rockwood Pigments Ltd of formula Fe ₂ O ₃ with an average size of particles of 0.1 μιη or 0.5 μιη.

The surfactants, the possible oxides of iron, and the sodium hydroxide are firstly mixed using a mechanical stirrer equipped with a three-bladed stirrer at a speed of 200 rotations / min for 3 to 5 minutes. .

The alumina is then gradually added to the reaction mixture by gradually increasing the stirring as the viscosity increases for arrive at about 400 to 500 revolutions / min without projections. The gel is then stirred for 5 minutes.

The gels thus manufactured are then analyzed in the wet state and in the dry state using a UV-3600 Shimadzu ^® spectrometer to measure their UV-Visible absorbance by reflection. The measurements are made in the wavelength range of 240 to 800 nm. The baseline is performed on a barium sulfate pellet.

Three gels named GB61, GB62, and GB63 were prepared, the staining of these gels is shown in Table 1 below.

Table 1: Staining of the tested gels

The absorbance of the GB61 white gel without pigment is measured in the wet state only.

On the other hand, for the two colored gels GB62 and GB63 according to the invention, the absorbance of the wet gels but also that of the flakes obtained at the end of their drying is measured.

In order to carry out the analyzes on the wet gels, they are deposited on the support of the spectrometer placed vertically the time of the analysis. The gels adhere to the walls of the analysis chamber.

In order to carry out the analyzes on dry flakes, they are crushed with mortar to give a powder. The powder is then deposited on a pellet of barium sulfate and compacted before being placed vertically in the analysis chamber.

The results of the analyzes are shown in Figures 7 and 8. First of all, it is obvious that the GB62 and GB63 color-pigmented gels according to the invention have a higher absorbance than the GB61-free white gel.

Despite a low concentration of pigments (0.1%), it is easy to appreciate the strong coloring of these gels according to the invention, linked to the high coloring power of red iron oxide pigments.

Depending on the surface to be decontaminated which must be covered by the gel, this strong coloration of the gels according to the invention is a particularly advantageous property for NRBC operators. For example, it makes it possible to avoid tonal effects in areas with reduced visibility and thus facilitates the visual detection of areas covered or not by frost.

Moreover, the comparison of the absorbance of the wet gels and the dry flakes obtained after drying of these gels makes it possible to demonstrate that the desired objective in terms of decontamination has been achieved.

Indeed, the absorbance of flakes of dry gels is less than that of wet gels, the absorbance curves, however, showing completely similar shapes.

This lower absorbance of straws reflects a discoloration of the gel during drying, and confirms the results of visual observations.

This discoloration, linked to the addition of pigments in the gels according to the invention, is one of the main advantageous effects obtained with the gels according to the invention, since it makes it possible to easily and quickly identify the wet zones and the zones. dry on the surfaces covered by the decontamination gels according to the invention.

It should be noted that the shape of the absorbance curves depends on the pigment present in the gel.

In fact, the absorbance curves obtained with the gel containing the red, wet or dry Ferroxide 212M pigment in the form of flakes look the same, and this appearance is different from that of the absorbance curves obtained with the gel containing the pigment. Ferroxide 228M violet, wet or dry in the form of flakes. Example 2

In this example, the discoloration of an acid gel according to the invention during its drying is studied.

A colored acid gel containing red iron oxide pigments is formulated to show that discoloration during drying also occurs when the gel is an acidic gel.

This gel, called GB75 gel, is composed of 14% Tixosif 331 silica marketed by RHODIA which has a specific surface area of 200m ² / g (BET), 0.2% surfactants (Pluronic ^® PE6200 from BASF, and Empilan ^® KR8 by HUNTSMAN), 0.1% Ferroxide ^* 212M micronized red iron oxides from ROCKWOOD PIGMENTS LTD with formula Fe ₂ 0 ₃ , and the nitric acid supplement IN.

The gel is manufactured according to the same method as in Example 1.

The dry and wet GB75 gels were analyzed by UV-3600 ^® Shimadzu spectrometer according to the same method as in Example 1.

The results of these analyzes are shown in Figure 9.

It appears, as in Example 1, that the acid gel GB75 is more colored than the white basic gel without pigment GB61.

In addition, the flakes of this acid gel GB75 have a lower absorbance than that of the same wet gel, which again shows the discoloration of the gel following drying.

This example shows that the gels according to the invention can be both basic gels and acid gels which in both cases have the same advantageous properties.

Example 3

In this example, the rheology of the pigmented gels according to the invention is studied. More precisely, in this example, the rheology of the two basic colored gels GB62 (red) and GB63 (violet) according to the invention described in Example 1 is compared, as well as the rheology of the GB61-free white basic gel described in Example 1, in order to observe the impact of the addition of pigments to 0.1% by weight on the viscosity of the gel.

Indeed, it is essential that the rheological properties of the gel, which is a gel called "sprayable" are preserved so that said gel can be sprayed and still adheres to the support.

Thus, it should be verified that the addition of micronized particles - in this case the pigments - in no way modifies the viscosity of the colloidal gel which is itself composed of micrometric size alumina aggregates.

For this, two viscosimetric and rheological measurements are made.

The first measurement that can be qualified as a viscosimetric measurement consists in measuring the viscosity as a function of the shear rate using a Rheomat ^* RM100 viscometer of the company LAMY RHEOLOGY.

The viscometer is equipped with an anchor type measurement system MS-R3. After a 10 second skew at a shear rate of 1 s ^-1 , 15 shear rate steps ranging from 1 s ¹ to 100 s ¹ are performed with a viscosity measurement every 20 seconds.

The second measurement, which can be qualified as rheological measurement, consists of measuring the threshold stress of GB61 and GB62 gels using a TA Instruments AR-1000 rheometer in "Vane" geometry.

A low shear rate, ie 6.7 x 10 ^-3 s ^-1 , is applied to the gels in a constant manner in order to deform them from the rest, and thus to determine their flow threshold.

The results of viscosimetric measurements on gels GB61, GB62, and GB63 are shown in logarithmic scale in Figure 10.

Figures 11 and 12 represent the results of the rheological measurements.

It appears in Figure 10 that the three curves are very close and parallel. In this range of shear rates, it is therefore impossible to perceive a difference, from a rheological point of view, between the white gel without pigment and the gels according to the invention containing 0.1% by mass of oxide pigments. of red iron. Thus, the addition of a small amount of micronized pigments does not fundamentally alter the rheology of colloidal mineral gels.

Figure 11 and Figure 12 show the shear stress, as a function of deformation, respectively for the gels GB61 (Figure 11) and GB62 (Figure 12).

In both cases, two regimes can be observed.

First of all the stress increases linearly, the material is in solid regime (elastic deformation).

Then, a drop is observed, the stress reaches the flow threshold and the material goes into the liquid regime (stationary flow).

The threshold stress corresponds to the yield stress, ie 43 Pa maximum for the gel GB61, and 40 Pa maximum for the gel GB62.

It should be noted that the measurements were carried out four times for each gel, namely for a precision at 100s ¹ for 100s, then a rest period of 10s (curve 1), 200s (curve 2), 500s (curve 3 ), and 1000s (curve 4). The reproducibility of the measurements is good.

Thus, it appears that the addition of pigment to the formulation has little influence on the threshold stress, and that the gel still fulfills the specifications of the "aspirable gels", ie a threshold stress greater than 15-20 Pa for the gel to does not flow under the effect of gravity on a vertical wall for 0.5-2mm applied gel thicknesses.

Example 4

In this example, the drying kinetics of the pigmented gels according to the invention are studied.

Indeed, another fundamental feature of decontamination gels is their drying time which is very closely related to the climatic conditions of the drying environment, namely temperature, relative humidity, ventilation / aeration. In this example, the three basic gels GB61 (white without pigment), GB62 (red, pigmented according to the invention) and GB63 (violet, pigmented according to the invention) are dried one after the other in a Binder ^® climate chamber set at 25 ° C and 50% relative humidity.

The gels are spread on stainless steel nacelles machined to obtain a controlled thickness of 0.5 mm of gel in the nacelle.

In the climate chamber, a Sartorius precision balance is installed, as well as a Moticam ^® camera surrounded by a circular LED lamp (VWR ^® ) which is placed on the top of the scale. The balance and the camera Moticam are connected to a computer placed outside the climatic chamber allowing the simultaneous acquisition, during the drying in controlled atmosphere, the mass and images of the nacelle filled with gel.

It should be noted that the basket containing the gel is placed in the precision scale, and that all the doors of the scale are closed, except for the door opposite the blower, which is open by 3 cm to maintain the balance. Controlled atmosphere in the enclosure of the balance while limiting the flow of air related to the operation of the climatic chamber.

The results, shown in Figure 13, show a loss of mass between the completely identical gel without GB61 white pigment and gel Ferroxide ^® 228M GB63 according to the invention.

Indeed, in 200 minutes, or 3:20, the gel is completely dry and has lost a little less than 80%, namely 78% of its initial mass.

Regarding the GB62 gel Ferroxide ^® 212M according to the invention, the gel dries very slightly faster but the 78% mass loss level is reached just in less than 200 minutes. This difference between the times required to reach this level of 78% mass loss can be related to a very slight variation in the opening of the door of the balance for example.

This example therefore shows that the addition of a low concentration of pigment to gels does not fundamentally modify the drying kinetics of these both the total drying time and the general appearance of the curves representing the drying kinetics of the gels.

Example 5

In this example, the fracturing of the pigmented gels according to the invention is studied.

Indeed, in addition to their rheology (so that they are sprayable and adherent) and their drying time, a third important characteristic of the so-called "aspirable" gels of decontamination is their fracturing, in the dry state, in the form of flakes. millimeter solids not pulverulent.

It is therefore in this example to verify that the addition of pigments in a gel does not alter its fracturing.

This manipulation is carried out in parallel with the measurements carried out in Example 4 in a climatic chamber under a controlled atmosphere.

Indeed, during drying, according to the protocol and with the device detailed in example 4, the images (FIG. 14) and the mass of the gel (FIG. 13) are recorded simultaneously during the drying of the gel in the pod. . The MoticarrT camera regularly takes pictures over time.

The photo of the totally dry gel is then analyzed using an image processing software that detects flakes and counts them while calculating their area.

The results are shown in Figure 14.

Admittedly, the number of flakes is slightly greater for the two gels GB62 and GB63 according to the invention which contain 0.1% of pigments than for the gel GB61 which does not contain any.

Nevertheless, the difference in terms of number of flakes and average area is not significant. The straws have a millimetric size, with an average size around 1 mm ² as desired in the specification of "suction gels". According to this example, the pigments of red iron oxides do not therefore fundamentally alter, at such concentrations, frost fracturing.

Example 6

In this example, it is shown that the coloration of the gels according to the invention is preserved over time.

More precisely, in this example, it is necessary to show that the coloration is constant between a gel stored several weeks and a fresh gel, which has just been prepared.

For this, two gels GB62 (red) are manufactured according to the method described in Example 1, and they are then analyzed in the wet state with the UV-3600 spectrometer according to the same method as in Example 1.

The first of these gels GB62 (red) is stored, stored for 4 months following its manufacture, before carrying out the analysis. This gel is called old gel, preserved.

The second of these gels GB62 is manufactured the day before the measurement. This gel is called fresh gel, fresh.

The results of the analyzes are shown in Figure 15.

The two curves, respectively for the preserved gel and the fresh gel have a similar appearance because these gels contain the same Ferroxide ^® 212M pigment at the same concentration.

However, the fresh gel has a much lower absorbency than the old gel. This may be due to the high coloring power of the micronized red iron oxide pigments. Indeed, a very small difference in the added pigment mass (and up to 0.1% by weight) can strongly modify the color of the pigmented gel. Example 7

In this example, the biocidal properties of the gel according to the invention are studied.

Indeed, it should be verified that the biocidal properties of the gel are not impaired by the addition of pigments in its formulation.

To do this, the biocidal efficacy of the GB62 pigmented gel according to the invention and the white gel without GB61 pigment on a contaminating biological species are tested, that is, spores of Bacillus thuringiensis, non-pathogenic fake spores of Bacillus anthracis.

Under a sterile laminar flow hood, two autoclaved stainless steel supports were contaminated with 10 ⁷ Bacillus thuringiensis spores by depositing 100 μl of a liquid contaminating solution containing 10 ⁸ Bacillus thuringiensis (BT) spores. per mL.

Once the media are dry, the test gels are spread on the media with an average thickness of 0.6mm and are dried under the hood for 3h-3h30. Then, the dry gel flakes are brushed and recovered in 30 mL of LB nutrient medium. Likewise, the supports freed from flakes are placed in tubes with 30 ml of LB nutrient medium. After incubating the tubes at 30 ° C. with stirring, 30 μl of LB are taken from each of the tubes and then plated at the center of Petri dishes containing gelled LB. The dishes are then placed in the incubator at 30 ° C. for 24 hours.

The results obtained are shown in Figure 16 (A, B). It appears that the number of colonies present after 24 hours of incubation on the surface of the gelled LB of the different boxes is of the same order of magnitude. Indeed, the development of a colony corresponds to the growth of a spore not inactivated by the biocide gel.

Knowing that 30 μl of the 30mL of LB recovery medium were spread on the boxes, ie 1 / ^1000th , we can estimate that of the 4 boxes presented, there remains after decontamination of the supports by the gel, approximately 10 ⁴ spores of BT active on the 10 ⁷ spores initially deposited on the supports, or 3 log of abatement due to the effect of the gels, whether they are pigmented or not (these counts in biology have a precision to the power of nearly ten).

This example shows that the biocidal efficacy of the basic gel is therefore not significantly altered by the addition of the red iron oxide pigments.

Conclusion of examples:

The examples provided above show that the addition of micronized iron oxide pigments to a decontamination gel provides a real improvement for the implementation of the technology "aspirable gel" in the context of a post-event use, following for example an industrial accident, or a terrorist attack.

Indeed, the addition in the gels according to the invention of a small amount of pigments makes it possible to improve the visualization, by the CBRN equipment response teams, of the areas of the surface of a contaminated material covered by the gel relative to other areas of the surface of this material.

Moreover, the possible discoloration of the pigmented gel following the drying of the latter is another of the advantages of the pigmented gels according to the invention. Indeed, this discoloration makes it possible to evaluate clearly and precisely the state of progress of the drying of the gel which goes hand in hand with the progress of the decontamination process. This ensures complete and complete drying of the decontamination gel before its aspiration / conditioning.

These advantageous properties of the gels according to the invention, due to the presence in the gels according to the invention of mineral pigments and in particular of micronized iron oxide pigments, are obtained without altering the physicochemical properties of these gels which make them suitable for their implementation in the context of a so-called "suction gel" process. Indeed, the fracturing and drying properties of the gels according to the invention as well as their viscosity and their threshold stress are not deteriorated by the addition of the pigments.

REFERENCES

CUER F., FAURE S., "Biological decontamination gel and method for decontaminating surfaces using this gel", FR-A1-2962046 and WO-A1-2012 / 001046.

HOFFMAN D., GU IRE R., "Oxidizer gels for detoxification of chemical and biological agents", US-B1-6,455,751.

HARPER B., LARSEN L, "A comparison of decontamination technologies for biological agents on selected commercial surface materials," Biological weapons improved response program, April 2001.

FAURE S., FOURNEL B., FUENTES P., LALLOT Y., "Method of treating a surface with a treatment gel, and treatment gel", FR-A1-2 827 530.

FAURE S., FUENTES P., LALLOT Y., "Aspirable gel for the decontamination of surfaces and use", FR-A1-2 891 470.

Claims

1. Decontamination gel, consisting of a colloidal solution comprising, preferably consisting of:

0.1% to 30% by weight, preferably 0.1% to 25% by weight, more preferably 5% to 25% by weight, more preferably 8% to 20% by weight, based on the weight of the gel, at least one inorganic viscosifying agent;

0.1 to 10 mol / l of gel, preferably 0.5 to 10 mol / l of gel, more preferably 1 to 10 mol / l of gel, of at least one active agent for decontamination;

0.01% to 10% by weight, preferably 0.1% to 5% by weight, based on the weight of the gel, of at least one mineral pigment;

optionally, 0.05% to 5% by weight, preferably 0.05% to 2% by weight, based on the weight of the gel, of at least one superabsorbent polymer;

and the remainder of solvent.

2. Decontamination gel according to claim 1, wherein the inorganic pigment is chosen such that it gives the gel a color different from the color of a surface to be decontaminated on which the gel is applied.

3. decontamination gel according to claim 1 or 2, wherein the inorganic pigment is a micronized pigment, and the average particle size of the inorganic pigment is from 0.05 to 5 μιη, preferably from 0.1 to 1 μιη.

4. Decontamination gel according to any one of the preceding claims, in which the inorganic pigment is chosen from metal (metal) and / or metalloid (s) oxides, metal (metal) and / or metalloid hydroxides. (s), oxyhydroxides of metal (metal) and / or metalloid (s), ferrocyanides and ferricyanides of metal (metals), metal aluminates (metals), and mixtures thereof.

5. Decontamination gel according to claim 4, wherein the inorganic pigment is selected from iron oxides, preferably micronized, and mixtures thereof.

6. Decontamination gel according to any one of the preceding claims, wherein the inorganic viscosifying agent is selected from metal oxides such as aluminas, metalloid oxides such as silicas, metal hydroxides, hydroxides of metalloids, metal oxyhydroxides, metalloid oxyhydroxides, aluminosilicates, clays such as smectite, and mixtures thereof.

7. decontamination gel according to claim 6, wherein the inorganic viscosifying agent is selected from pyrogenic silicas, precipitated silicas, hydrophilic silicas, hydrophobic silicas, acidic silicas, basic silicas, and mixtures thereof.

8. Decontamination gel according to claim 7, wherein the inorganic viscosifying agent consists of a mixture of a precipitated silica and a fumed silica.

9. Decontamination gel according to claim 6, wherein the inorganic viscosifying agent is constituted by one or more alumina (s) representing from 5% to 30% by weight, preferably from 8% to 17% by weight relative to the mass of the gel.

10. Decontamination gel according to any one of the preceding claims, wherein the active decontaminating agent is selected from bases such as sodium hydroxide, potassium hydroxide, and mixtures thereof; acids such as nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, hydrogenooxalates such as sodium hydrogenoxalate, and mixtures thereof; oxidizing agents such as peroxides, permanganates, persulfates, ozone, hypochlorites such as sodium hypochlorite, cerium IV salts, and mixtures thereof; quaternary ammonium salts such as hexacetylpyridinium salts, such as hexacetylpyridinium chloride; reducing agents; and their mixtures.

11. decontamination gel according to any one of the preceding claims, wherein the superabsorbent polymer is selected from sodium poly (meth) acrylates, starches grafted with a (meth) acrylic polymer, hydrolysed starches grafted with (meth) acrylic polymer; polymers based on starch, gum, and cellulose derivative; and their mixtures.

The decontamination gel according to any of the preceding claims, wherein the surfactant is selected from nonionic surfactants such as block copolymers, such as block copolymers of ethylene oxide and propylene oxide, and ethoxylated fatty acids; and their mixtures.

13. Decontamination gel according to any one of the preceding claims, wherein the solvent is selected from water, organic solvents and mixtures thereof.

A method for decontaminating at least one surface of a substrate of a solid material, said surface being contaminated by at least one contaminating species on said surface and optionally under said surface in the depth of the substrate, wherein at least one cycle comprising the following successive steps:

a) the gel according to any one of claims 1 to 13 is applied to said surface; b) the gel is maintained on the surface for at least sufficient time for the gel to destroy and / or inactivate and / or absorb the contaminating species, and for the gel to dry and form a dry and solid residue containing said contaminating species ;

c) removing the dry and solid residue containing said contaminating species.

15. The method of claim 14, wherein the inorganic pigment contained in the gel is chosen such that it gives the gel a color different from the color of the surface to be decontaminated on which the gel is applied.

The method of any of claims 14 and 15, wherein the substrate is a porous substrate, preferably a porous mineral substrate.

17. A method according to any one of claims 14 to 16, wherein the solid material is selected from metals and metal alloys such as stainless steel, painted steels, aluminum and lead; polymers such as plastics or rubbers such as polyvinyl chloride or PVC, polypropylenes or PPs, polyethylenes or PEs, in particular high density polyethylenes or HDPEs, poly (methyl methacrylates) or PMMA, polyvinylidene fluoride or PVDF, polycarbonates or PCs; the glasses ; cements and cementitious materials; mortars and concretes; plasters; the bricks ; natural or artificial stone; ceramics.

18. A method according to any one of claims 14 to 17, wherein the contaminating species is selected from the chemical, biological, nuclear or radioactive contaminant species.

19. The method of claim 18, wherein the contaminating species is a biological species selected for example from bacteria, fungi, yeasts, viruses, toxins, spores and protozoa.

20. The method of claim 19, wherein the biological species is selected from bio-toxic species such as pathogenic spores such as Bacillus anthracis spores, toxins such as botulinum toxin or ricin, bacteria. such as Yersinia pestis bacteria and viruses such as vaccinia virus or haemorrhagic fever viruses, for example of the Ebola type.

21. A method according to any one of claims 14 to 20, wherein the gel is applied to the surface at a rate of 100 g to 2000 g of gel per m ² of surface, preferably from 500 g to 1500 g of gel per m ² of surface, more preferably from 600 g to 1000 g of gel per m ² of surface.

22. Process according to any one of claims 14 to 21, wherein during step b), the drying is carried out at a temperature of 1 ° C to 50 ° C, preferably 15 ° C to 25 ° C and at a relative humidity of 20% to 80%, preferably 20% to 70%.

23. A method according to any one of claims 14 to 22, wherein the gel is held on the surface for a period of 2 to 72 hours, preferably 2 to 48 hours, more preferably 3 to 24 hours.

The method of any of claims 14 to 23, wherein the gel is held on the surface until it exhibits a decrease in its visible and ultraviolet absorbance, for example discoloration.

25. Process according to any one of claims 14 to 24, in which the dry and solid residue is in the form of particles, for example flakes, of a size of 1 to 10 mm, preferably of 2 to 5 mm. mm.

26. A process according to any one of claims 14 to 25, wherein the dry and solid residue is removed from the solid surface by brushing and / or suctioning.

The method of any one of claims 14 to 26, wherein the cycle described is repeated from 1 to 10 times using the same gel in all cycles or using different gels in one or more cycles. (s).

28. A method according to any one of claims 14 to 27, wherein in step b), the gel, before total drying, is rewetted with a solution of a decontaminating agent, preferably with a solution of active agent for decontaminating the bath gel of step a) in the solvent of this gel.