EP2097502A1

EP2097502A1 - Solid material and a gel forming a hydrogen peroxide and/ot acid source, method for the preparation and the use thereof

Info

Publication number: EP2097502A1
Application number: EP05793058A
Authority: EP
Inventors: Rémi WILMOTTE; Bernard Lebeau; Francoise Marechal
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-07-28
Filing date: 2005-07-28
Publication date: 2009-09-09
Also published as: WO2006018549A1

Abstract

The invention relates to a solid material, preferably in powder form, useful, in particular in the form of a gel-type hydrogen peroxide and/or acid source, wherein said material comprises intimately associated (A) a gelling agent which forms a gel in the presence of stirred water and is embodied in the form of hydrophilic silica, (B) a substance which is harmful in an aqueous solution and is selected from an assembly formed by (B1) a hydrogen peroxide, (B2) acids, (B3) the mixtures thereof and (C) an agent for homogeneously dispersing the substance (B) in the gel produced by bringing into contact (i) the mixture of (A) and (B) or (ii) said solid material with the stirred water. A method for the preparation and the use of said material is also disclosed.

Description

Solid material and gel constituting a source of hydrogen peroxide and / or acid, method of preparation and use

Field of the Invention The present invention relates to the gelation of an aqueous composition of hydrogen peroxide, at least one acid or a mixture thereof, which can be harmful when concentrated.

More specifically, it aims as a new industrial product, (i) a solid material, prepared by dehydration of a gel, and (ii) said gel, this solid material constituting a source of H ₂ O ₂ and / or acid in gel form after being contacted with stirring with water.

It also relates to the method of preparation of this solid material, as well as its. use especially in the field of cleaning, hygiene, disinfection, descaling, pickling, electrolytes for batteries or accumulators, and the paper industry (especially for the refining of cellulosic fibers). Prior art

Aqueous solutions of H ₂ O ₂ and acids have two main disadvantages. On the one hand, when you pour them, you can get splashes, which is a risk for the staff. On the other hand, when used to treat surfaces, they flow very (or even too much) quickly on surfaces that are not horizontal.

To overcome these two disadvantages and in particular to have a longer contact time on the vertical surfaces, curved or inclined, it would be desirable to use (i) H ₂ O _{2 solutions} and / or from at least one acid which is gelled, on the one hand, and (ii) solid (advantageously pulverulent) compositions containing H ₂ O ₂ and / or at least one acid which are gellable by contact with water with stirring, on the other hand. It is known from EP 1175149 B9 (see for this purpose examples 7-10 and 12 of this document) that gels have already been prepared which are stable during storage and constitute a source of H ₂ O _{2 which} can be used at the time of storage. use, from silica, of demineralized water, and of an aqueous solution containing H ₂ O ₂ , at least one acid (in particular H ₃ PO ₄ or a pyridinecarboxylic acid for stabilize H ₂ O ₂ in said aqueous solution), metal ions (from Ag ¹¹ ,

Ag ^m , V ^v , Nb ^v , Ta ^v , Mo ^VI , W ^VI , Co ^m , In ¹¹¹ and / or T1 ¹¹¹ ) and a surfactant.

It is also known that, when a finely divided hydrophobic silica is contacted with stirring with hydrogen peroxide having a content of z% w / w in H ₂ O ₂ , a gel of H ₂ O ₂ :

(A) if z <20% w / w, an H ₂ O ₂ gel will never be obtained, but a precipitate of SiO ₂ may be obtained;

(B) if z> 20% w / w, there will be obtained (according to Examples 1-2 of FR 1192908 A and Examples 1-4 of DE 2013762 A) powders containing silica and hydrogen peroxide; and

(C) if the powders of point (B) are brought into contact with water with stirring, gels containing H ₂ O ₂ will be obtained, which will hardly be stable over time, the gel becoming destabilized as soon as the content of H ₂ O ₂ in the water of said gel will become less than 20%

It is furthermore known that the product, containing silica and H ₂ O ₂ , which is obtained according to a particular process [described in WO 2004/10358 (which can only be used as novelty)] and comprising the mixing under strong

® Hydrophobic silica shear (Aerosil R812S) with an aqueous solution of H ₂ O ₂ to form a pulverulent product consisting of silica-coated oxygenated water droplets, releases on contact with water the hydrogen peroxide it contains and dissolves in water.

To complete the technological background, we can also point out CH 406123 A, which recommends obtaining a stable powder, containing active and water-soluble oxygen when it is brought into contact with water, according to a process comprising mixing H ₂ O ₂ with sodium metasilicate in the presence of an absorbent (sodium carbonate); US 4313932 A, which describes obtaining a powder from an H ₂ O ₂ generator (for example sodium peroxydisulfate), a thickener (which may be silica), a salt inorganic ammonium [e.g. (NH ₄ ) ₂ SO ₄ ] and an alkaline compound, this powder is contacted with water to provide a hair detergency composition [at a pH of 9.3 indicated in Example 3 of this document, the hydrogen peroxide capable of being released is no longer oxidizing, since it can act as a reducing agent at a pH greater than 8.5]; and US 6218352 B, which proposes a composition an improved solubility detergency containing H ₂ O ₂ or an H ₂ O ₂ generator.

It would be desirable to provide a powdery solid composition containing silica and H ₂ O ₂ , which (a) is substantially stable for a long period of time during storage, and (b) can be contacted by contacting with water a gel that contains H ₂ O ₂ and is substantially stable over time, regardless of the H ₂ O _{2 content} . Purpose of the invention

It is proposed to provide according to the invention a new technical solution to solve the problem of gelling an aqueous composition of hydrogen peroxide and / or at least one acid, in order to make available, whatever the content of H ₂ O ₂ ,

An H ₂ O ₂ gel and / or at least one acid, on the one hand, and

A solid material, powdery, dehydrated, convenient for transport and especially the dosage of the active ingredient (H ₂ O ₂ and / or at least one acid), and capable of providing a gel by contacting with water on the other hand, said gel and said material each constituting a source of H ₂ O ₂ and / or acid. According to the invention, it is also proposed to provide a process for preparing said gel and said solid material.

The new technical solution, developed with the present invention, comprises

the gelling of an aqueous solution of a harmful substance [ie likely to be corrosive when this substance is an acid, or explosive when this substance is H ₂ O ₂ ] in high concentration,

the dehydration of the resulting gel without loss of the physical and chemical properties of its components, then,

- The gel transformation of the resulting solid material at the time of use.

It implements a hydrophilic silica, not described or suggested by the teaching of the aforementioned prior art. Indeed, the prior art did not make it possible to presume that the gel according to EP 1175149 B9 could be dehydrated in the form of a stable powder, and that the powder thus obtained could, with water, give a stable gel identical or equivalent to the starting gel. . Object of the invention

According to a first aspect of the invention, there is provided, as a new industrial product, a solid material, advantageously in pulverulent form, useful in particular as a source of hydrogen peroxide and / or gel acid. , said material being characterized in that it comprises in intimate association:

(A) a gelling agent forming a gel in the presence of stirring water, which is a hydrophilic silica,

(B) a substance that may be harmful in aqueous solution, which is selected from the group consisting of

(B1) hydrogen peroxide, (B2) acids, and (B3) mixtures thereof; and

(C) an agent ensuring a homogeneous dispersion of the substance (B) in the gel resulting from the contacting with water with stirring (i) of the mixture of (A) and (B) or (ii) of said material solid. This material is obtained by dehydration of a gel produced by mixing with stirring of the gelling agent (A) with an aqueous solution of (B) +

(VS). According to a second aspect of the invention, it is recommended to use this solid material for the preparation of a gel, said use being characterized in that said material is brought into contact with water with stirring until forming a homogeneous gel, which is likely to be used in the field of hygiene, decontamination, cleaning, surface treatment including passivation, stripping, making electrolytes for batteries and accumulators , or the refining of cellulosic fibers.

According to a third aspect of the invention, there is provided a method for the preparation of said solid material, this method being characterized in that it comprises:

(α) the formation of a gel with stirring from a mixture:

A gelling agent (A), which is a hydrophilic silica, with

• an aqueous solution of (B) + (C), then (β) the dehydration of the resulting gel. In this process, said formation of the gel is carried out with stirring at an angular rate of 1000 to 2500 revolutions / minute, preferably with stirring at an angular speed of 1500 to 2000 revolutions / minute, for 10 to 20 minutes. According to a fourth aspect of the invention, there is also provided a method for preparing a gel from said solid material, said method being characterized in that it comprises bringing said material into contact with water (preferably distilled water, or better deionized water) with stirring at an angular rate of 1000 to 2500 rpm, preferably with stirring at an angular rate of 1500 to 2000 rpm, for 10 to 20 minutes.

Finally, according to a last aspect of the invention, a gel is provided, as a new industrial product, which is obtained from a starting aqueous hydrogen peroxide solution preferably containing at most 60% w / w of H ₂ O ₂ .

Detailed description of the invention

Among the gelling agents which are suitable according to the invention, it is essential to use a finely divided hydrophilic silica. From this point of view, a hydrophilic fumed silica having a submicron granulometry, advantageously a particle size of less than or equal to

0.1 μm, and better a particle size less than or equal to 60 nm.

Pyrogenic hydrophilic silicas, marketed by the company known as dR)

CABOT under the CAB-O-SIL nomenclature (in particular the hydrophilic products CAB-O-SIL® L-90, LM-150, M-5, H-5, EH-5 and M-7D), which have a surface mass of 80 to 460 m ² / g (in particular, for the 6 CAB-O-SIL mentioned above, a specific mass of 2.2 g / cm ² ) and an average particle size of 7 to 20 mm, are particularly useful according to the present invention. invention.

When using such a hydrophilic silica, it is imperative that the acid or acids present in B2 or B3 are free of fluorine, and that the agent C is also free of fluorine. Indeed, the presence of at least one fluorine atom in the molecule of these products would be likely to destabilize or destroy the silica of the solid material and of the gel which is involved in the preparation of said solid material or which is regenerated from said solid material. Hydrogen peroxide in aqueous solution, which is used as a starting material, can have a practical H ₂ O ₂ concentration of 0.5% w / w to 60% w / w. Advantageously, this concentration of H ₂ O ₂ will be greater than or equal to 0.5% w / w, for example less than or equal to 8% w / w as indicated in EP 1175149 B9 cited above. According to the invention, this starting solution may have an H ₂ O ₂ concentration greater than or equal to 12% w / w and better still a concentration greater than or equal to 20% w / w. This solution may contain up to 50% w / w H ₂ O ₂ , or even up to 60% w / w H ₂ O ₂ . B2 substance is a mineral acid (especially a strong acid such as

HCl, H ₂ SO ₄ , H ₃ PO ₄ ) or an aliphatic organic acid (in particular CH ₃ CO ₂ H, CH ₃ CH ₂ CO ₂ H, a mixture CH ₃ CO ₂ H ₂ CH ₃ CO ₃ H, or an ethylenically unsaturated acid ), aromatic (especially a hydroxybenzoic acid, such as 2, 3- and 4-hydroxybenzoic acids) or heterocyclic (especially a pyridinecarboxylic acid such as nicotinic, isonicotinic and picolinic acids).

According to the invention these acids are used alone or in combination with

H ₂ O ₂ , In practice, the substance B2 will comprise at least one acid, pyridinecarboxylic acid, or will be an acid mixture comprising at least 0.1% by dry weight and better still at least 0.2% by dry weight. of pyridinecarboxylic acid relative to the dry weight of said acid mixture.

Alternatively, the substance B is a mixture B3 containing hydrogen peroxide and at least one acid which is a pyridinecarboxylic acid.

In such a mixture, the B2 acid (s) intervene to stabilize the hydrogen peroxide, as indicated in the prior art.

The pyridinecarboxylic acid plays here an interesting role in view of the fact that it comprises in its molecule two functional groups: a tertiary amine function and a carboxylic acid function both useful for the cohesion of the gel and the solid material of the invention . The agent C which ensures a homogeneous dispersion of B in the solid material and the gel is advantageously chosen from: (Cl) surfactants, (C2) sequestering agents, (C3) polyols, (C4) ₅ NaOH KOH and their salts, in particular their salts with mineral acids, and (C5) mixtures thereof.

The preferred surfactants (C1) are (i) anionic surfactants and (ii) nonionic surfactants. For example, with regard to anionics, mention may be made of dihexyl sodium sulphosuccinate of formula

its dialkyl analogs, linear alkylsulfonates, fatty acid salts with a metal (sodium, potassium, cobalt), and sulfated castor oil; and for nonionics, polyglycol esters, polyoxyalkylenated alcohols, sorbitan esters and polyoxyalkylenated sorbitan esters.

The sequestering agents (C2) include, in particular, substances selected from the group consisting of (i) ethylenediaminetetraacetic acid and its sodium and / or calcium salts, and (ii) benzotriazole.

In the context of the present invention, benzotriazole acts mainly as a corrosion inhibiting agent for copper and its alloys; it can also intervene as illustrated below as a sequestering agent.

The polyols (C3), which are suitable here, are mainly C ₂ -C ₆ short-chain aliphatic alcohols with at least 2 and at most 6 groups

OH, especially a diol, triol, tetrol, pentol or hexol, and / or • long chain, in particular of the (polyoxyalkylene) diol type, in particular a polyethylene glycol or a polypropylene glycol. The polyols (C3) are interesting in terms of homogenization and stability due to the fact that they are polyfunctional products. The ethers and esters of these polyols are classified as non-ionic surfactants referred to above. The alkalis (C4), namely mainly NaOH and KOH, are favorably used to obtain a homogeneous dispersion in the solid material and in the gel. They act for this purpose as (i) pH regulators and (ii) products increasing the ionic strength of low polarity systems.

It is important that the aqueous solution that contains H ₂ O ₂ does not exceed a pH value greater than 8.5. Beyond this threshold, the hydrogen peroxide, which would be associated with an alkali, would become a reducing agent while it is its oxidizing properties that is sought according to the invention.

In practice, the addition of an alkali such as NaOH or KOH will only occur if and only if it is desired to have an included pH, if necessary, between 6 and 7.5.

The agents (C) which are preferably recommended according to the invention are anionic surfactants, nonionic surfactants, polyols and mixtures thereof.

According to a particular mode of implementation, the solid material comprises:

(A) a gelling agent forming a gel in the presence of stirring water, which is pyrogenic hydrophilic silica,

(Bl) hydrogen peroxide,

(B2) inorganic and organic acids lacking fluorine, and (B3) their mixtures; and

(C) an agent ensuring a homogeneous dispersion of the substance (B) in the gel resulting from the contacting with water with stirring (i) of the mixture of (A) and (B) or (ii) of said material solid. In this case the silica is, as indicated above, a hydrophilic silica having a mean granulometry in the dry state which is submicron.

When forming the gel to be dehydrated according to the invention, it is recommended to stir the mixture of A with the aqueous solution of B + C, with a low angular velocity. It is recommended for this purpose a speed angular from 1000 to 2500 rpm, and preferably an angular velocity of 1500 to 2000 rpm, for 10 to 20 minutes. If the angular velocity is greater than 2500 revolutions / minute, there is a risk of destabilizing the gel formed. The dehydration of the gel to obtain the solid material can be carried out by an appropriate method, in particular:

(i) at atmospheric pressure

(ii) under reduced pressure, or

(iii) lyophilization. Lyophilization is the most practical in the context of the invention. The freeze-drying phase is implemented here in a conventional manner, the sublimation phase is advantageously achieved by limiting the maximum temperature of heating under vacuum.

Lyophilization leads to a solid powdery material, which is an advantage for the future regeneration of the gel.

Regeneration of the gel from said material is carried out under conditions similar to those of formation of the gel to be dehydrated. These conditions are, as indicated above, stirring at an angular rate of 1000 to 2500 rpm, preferably stirring at an angular speed of 1500 to 2000 rpm for 10 to 20 minutes.

According to a particular embodiment of the preparation of the solid material, it is carried out according to a process comprising the steps of: (1) contacting with stirring • a gelling agent (A), which is a hydrophilic silica pyrogenous, with

An aqueous solution of a mixture of a substance (B) which may be harmful in aqueous solution, which is chosen from the group consisting of (B1) hydrogen peroxide,

(B2) inorganic and organic acids lacking fluorine, and (B3) their mixtures, and

An agent (C) chosen from the group consisting of (C1) anionic and nonionic surfactants, (C2) sequestering agents, (C3) polyols, (C4) NaOH or KOH, and (C5) mixtures thereof; then (2) lyophilize the gel thus obtained.

According to a particularly preferred embodiment, the solid material acts as an intermediate product that can be used in the preparation of the final gel. In this case, a gel is prepared according to a process comprising the steps of: (1) contacting with stirring

A gelling agent (A), which is a pyrogenic hydrophilic silica, with

An aqueous solution of a mixture of a substance (B) which may be harmful in aqueous solution, which is chosen from the group consisting of

(Bl) hydrogen peroxide,

(B2) inorganic and organic acids lacking fluorine, and (B3) mixtures thereof, and • an agent (C) selected from the group consisting of

(C1) anionic and nonionic surfactants, (C2) sequestering agents, (C3) polyols, (C4) NaOH or KOH, and (C5) mixtures thereof;

(2) lyophilize the gel, thus obtained, to obtain a powder that can be stored (advantageously in sealed packaging or packaging); then

(3 °) put in contact with demineralized water, with stirring, the powder obtained at the end of step (2 °) to obtain at the time of use a gel identical or equivalent to that of the from step (1 °).

It has also been possible to obtain stable and effective powders by gelling and desiccating (by lyophilization) according to the process of the present invention aqueous compositions based on H ₂ O ₂ and metal ions (such as Ag-VAg ^{4 ",} MoO ₄ ^2" or WO ₄ ^{2 "),} including those described in Examples 1-6 of EP 1175149 B9 supra.

The powder and the gel according to the invention are particularly useful, topically, in therapeutics and cosmetics vis-à-vis dermatitis, dermatoses (especially mycoses), particularly vis-à-vis unsightly conditions due to bacterial strains (in particular Staphylococcus aureus and Propionibacterium acnes), fungal (in particular Candidd) or viral strains (in particular Herpes simplex virus).

Other advantages and features of the invention will be better understood on reading the following examples of embodiments. Of course, these elements are not limiting, but are provided by way of illustration. Example 1 Manufacture of a powder material from an aqueous solution of H ₂ O ₂ at 50% w / w

In a mixture of 876 g of 50% w / w hydrogen peroxide, 1 g of HEDP and 1 g of picolinic acid (the latter two products being H ₂ O ₂ stabilizers), 1 g is added. wetting agent (nonionic surfactant,

GOLD)

PLURONIC P, marketed by the so-called BASF company). With stirring at 1500 rpm, 120 g of hydrophilic silica are gradually added

(S) fumed (type CAB-O-SIL) until a homogeneous gel is formed. The gel thus obtained is then lyophilized under reduced pressure until 450 g of stable powder are obtained.

This powder retains all the oxidizing properties of hydrogen peroxide and found the same physical and chemical properties of the original gel after addition with stirring of 550 g of demineralized water of conductivity 1 μS.cm ^-1 .

Example 2 Manufacture of a Powdered Material from a 50% w / w aqueous H ₂ O ₂ Solution to Strip and Pass Stainless Steels to the Following Formulation Prepared from an Aqueous Solution of H ₂ O ₂ at 50% w / w:

Water 166 g

Phosphoric acid (85% w / w) 350 g

Hydrogen Peroxide (50% w / w) 400 g

Picolinic acid: 2 g Ethylene glycol 2 g 80 g of pyrogenic hydrophilic silica are added with stirring at an angular speed of 2000 rpm until a homogeneous gel is formed. The gel thus obtained is lyophilized under partial pressure until 570 g of stable powder is obtained. This powder retains all the oxidizing properties of hydrogen peroxide and found the same physical and chemical properties of the original gel after addition with stirring of 430 g of deionized water of conductivity 1 μS.cm ^"1 .

EXAMPLE 3 Manufacture of a Powdered Material from a 35% aqueous H ₂ O ₂ solution for pickling-brightening copper and its alloys to the following formulation made from an aqueous solution of H ₂ O ₂ to 35% w / w:

Water 720 g Sulfuric acid (98% w / w) 100 g

Picolinic acid 2 g

Hydrogen peroxide (35% w / w) 90 g

Benzotriazole 30 g 60 g of hydrophilic fumed silica are added with stirring at an angular speed of 2000 rpm until a homogeneous gel is formed. The gel thus obtained is lyophilized under reduced pressure to obtain 140 g of stable powder.

This powder retains all the oxidizing properties of hydrogen peroxide and found the same physical and chemical properties of the original gel after stirring addition of 860 g of deionized water of conductivity 1 μS.cm ^"1 .

In Example 3, benzotriazole acts as a sequestering agent on the one hand and as a corrosion inhibitor on copper on the other hand. In the following example, a portion of the benzotriazole was replaced by a C3 polyol.

Example 4 Manufacture of a Powdered Material from a 35% w / w aqueous solution of H ₂ O ₂ for pickling-brightening copper and its alloys To the following formulation made from an aqueous solution of H ₂ O ₂ at 35% w / w: 720 g water

Sulfuric acid (98% w / w) 100 g

Picolinic acid 2 g

Hydrogen Peroxide (35% w / w) 90 g Ethylene Glycol 2 g

Benzotriazole 28 g 60 g of hydrophilic fumed silica are added with stirring at 2000 rpm until a homogeneous gel is formed. The gel thus obtained is lyophilized under reduced pressure to obtain 140 g of stable powder. This powder retains all the oxidizing properties of hydrogen peroxide and found the same physical and chemical properties of the original gel after stirring addition of 860 g of deionized water of conductivity 1 μS.cm ^"1 .

Example 5 Manufacture of a powdered material from a 1% w / w aqueous H ₂ O ₂ solution for antimycotic use

To the following formulation prepared from an aqueous solution of H ₂ O ₂ at 1% w / w:

Water 150 g Phosphoric acid (85% w / w) 350 g

Hydrogen peroxide (at 1% w / w) 90 g

Picolinic acid: 2 g

Ethylene Glycol 2 g is added 70 g of hydrophilic fumed silica with stirring at an angular speed of 2000 rev / min until a homogeneous gel is formed. The gel thus obtained is lyophilized under partial pressure until a stable storage powder is obtained.

This powder was applied once a day for 15 days on the zone of a mycosis of the feet of 6 patients. At the end of the 15-day treatment, the feet of all patients no longer had fungal infection.

Claims

1. Solid material, advantageously in pulverulent form, useful in particular as a source of hydrogen peroxide and / or acid in gel form, said material being characterized in that it comprises in intimate association:

(B1) hydrogen peroxide, (B2) acids, and (B3) mixtures thereof; and

(C) an agent ensuring a homogeneous dispersion of the substance (B) in the gel resulting from the contacting with water with stirring (i) of the mixture of (A) and (B) or (ii) of said material solid.

2. Solid material according to claim 1, characterized in that it comprises:

(Bl) hydrogen peroxide,

(B2) inorganic and organic acids lacking fluorine, and (B3) their mixtures; and

3. Material according to claim 2, characterized in that said gelling agent (A) is a hydrophilic silica having in the dry state a mean submicron granulometry.

4. Material according to any one of claims 1 to 3, characterized in that said agent (C) is chosen from:

(Cl) surfactants, (C2) sequestering agents, (C3) polyols,

(C4) NaOH, KOH and their salts, especially their salts with mineral acids, and (C5) their mixtures.

5. Material according to claim 4, characterized in that said agent (C) is selected from the group consisting of anionic surfactants, nonionic surfactants, polyols and mixtures thereof.

6. Material according to claim 4, characterized in that said agent (C) is selected from the group consisting of (i) ethylenediamine tetraacetic acid and its sodium and / or calcium salts, and (ii) benzotriazole .

7. Material according to claim 1 or 2, characterized in that the substance (B2) comprises at least one acid, which is a pyridine-carboxylic acid.

8. Material according to claim 1 or 2, characterized in that the substance (B2) is a mixture of acids comprising at least 0.1% by dry weight and better still at least 0.2% by dry weight of pyridinecarboxylic acid relative to the dry weight of said acid mixture.

9. Material according to any one of claims 1, 2, 7 and 8, characterized in that said substance (B) is a mixture (B3) containing hydrogen peroxide and at least one acid which is a pyridinecarboxylic acid.

10. Material according to any one of claims 1 to 9, characterized in that it is obtained by dehydration of a gel made by stirring mixture of the gelling agent (A) with an aqueous solution of (B) + (VS).

11. Use of the solid material according to any one of claims 1 to 10 for the preparation of a gel, said use being characterized in that said material is brought into contact with water with stirring until formation a homogeneous gel, which is likely to be used in the field of hygiene, decontamination, cleaning, surface treatment especially for passivation, stripping, the production of electrolytes for batteries and accumulators, or the refining of cellulosic fibers.

12. Process for the preparation of a homogeneous gel from the solid material according to any one of claims 1 to 10, said method being characterized in that it comprises bringing said material into contact with water (preferably distilled water, or better deionized water) with stirring at an angular rate of 1000 to 2500 rpm, preferably with stirring at an angular speed of 1500 to 2000 rpm, for 10 to 20 minutes.

13. Process for the preparation of a solid material according to any one of claims 1 to 10, said process being characterized in that it comprises: (α) the formation of a gel with stirring from a mixture :

A gelling agent (A), which is a hydrophilic silica, with an aqueous solution of (B) + (C), and

(β) the dehydration of the resulting gel.

14. The method of claim 13, characterized in that said dehydration is carried out by lyophilization.

15. Process according to claim 13, characterized in that said formation of the gel is carried out with stirring at an angular speed of 1000 to 2500 rpm, preferably with stirring at an angular speed of 1500 to 2000 rpm, for 10 minutes. at 20 minutes.

16. A process according to any one of claims 13 to 15, characterized in that it comprises the steps of: (1) contacting with stirring

A gelling agent (A) which is a pyrogenic hydrophilic silica, with

(Bl) hydrogen peroxide,

(B2) inorganic and organic acids lacking fluorine, and

(B3) mixtures thereof, and • an agent (C) selected from the group consisting of

(Cl) anionic and nonionic surfactants,

(C2) the sequestering agents,

(C3) polyols,

(C4) NaOH or KOH, and (C5) their mixtures; then (2) lyophilize the gel thus obtained.

17. Gel obtained from an aqueous solution of H ₂ O ₂ , characterized in that it is capable of being prepared according to the process of any one of claims 12, 13 (α), 15 and 16 ( 1 °), and in that said starting H ₂ O ₂ solution contains more than 8% by weight of H ₂ O ₂ , preferably more than 12% by weight of H ₂ O ₂ and better still more than 20% by weight of H ₂ O _2. weight of H ₂ O ₂ .

18. Gel according to claim 17, characterized in that said starting H ₂ O ₂ solution contains at most 60% by weight of H ₂ O ₂ , and better still at most 50% by weight of H ₂ O ₂ .

19. Process for the preparation of a gel, characterized in that it comprises the steps of: (1) contacting with stirring

A gelling agent, which is a pyrogenic hydrophilic silica, with an aqueous solution of a mixture of a substance (B) which may be harmful in aqueous solution, which is chosen from the group consisting of

(Bl) hydrogen peroxide,

(B2) inorganic and organic acids lacking fluorine, and (B3) their mixtures, and

An agent (C) chosen from the group consisting of

(Cl) anionic and nonionic surfactants, (C2) sequestering agents, (C3) polyols,

(C4) NaOH or KOH, and (C5) their mixtures;

(3 °) contacting with demineralised water, with stirring, the powder obtained at the end of step (2 °) to obtain, at the time of use, a gel identical or equivalent to that of the outcome of step (1 °).