WO2014200377A2

WO2014200377A2 - Process for obtaining nanoparticles of silica incorporating hydrophilic products or water miscible and process for their immobilization and encapsulation when applied to textile fibres

Info

Publication number: WO2014200377A2
Application number: PCT/PT2014/000040
Authority: WO
Inventors: Jaime Isidoro NAYOLOR DA ROCHA GOMES
Original assignee: Ecoticket, Lda
Priority date: 2013-06-12
Filing date: 2014-06-12
Publication date: 2014-12-18
Also published as: PT107002A; WO2014200377A3

Abstract

The present invention is about a process of obtaining nanoparticles of silica, that involves the steps that are necessary for the dissolution of sodium silicate or trietheylortosilicate (TEOS) in water; addition of a solvent and the addition of an anionic tensoactive agent and stirring at room temperature to form a w/o emulsion and a sol-gel; addition of a product to encapsulate, hydrophilic or partially miscible in water, followed by stirring; addition of an acid or an acid salt continuing with the mixing; evaporation of the solvent so as to obtain the nanoparticles of silica. The invention is also about a process of immobilization and encapsulation of nanoparticles obtained in any of the claims from 1 to 10, by padding a textile material with the nanoparticles that involves a condensation polymerization reaction, during an alkaline washing of the material, so as to cause the encapsulation of the nanoparticles and the products in the pores of the 'nanoparticles, by forming a polymeric film around them.

Description

DESCRIPTION

"PROCESS FOR OBTAINING NANOPARTICLES OF SILICA INCORPORATING HYDROPHILIC PRODUCTS OR WATER MISCIBLE AND PROCESS FOR THEIR IMMOBILIZATION AND ENCAPSULATION WHEN APPLIED TO TEXTILE FIBRES"

Field of the invention

The present invention concerns the field of application of nanoparticles, containing antimicrobial ou antimosquito products, to textile fibres.

Background of the invention

The excessive use of antimicrobials implied that some have created habituation and resistance of bacteria, such as Triclosan, still used a lot on products of great consumption. In hospitals the situation is. still more serious, being estimated that thousands per year of patients are contaminated by multi-resistance Such a for example MRSA (meticellium resistant staphilococus aureus) .

For this reason it is necessary to develop new antimicrobials that do not cause habituation or resistance and eliminate efficiently all the types of bacteria and fungus, i,e. that have a large spectrum of activity. The antimicrobials are also applied to textile articles, to avoid namely odors, formed by the proliferation f bacteria that form in areas of the body that sweat the most, such as the armpits and the feet.

Furthermore, textile articles have been a very important market for antimicrobial products that can be applied on synthetic fibers during the extrusion of fibers, or in the case - of natural fibers are applied by conventional finishing processes on woven fabric or knitwear. Processes such as coating are also used in the case of silver nanoparticles .

In the case of textiles one important characteristic is the durability of the antimicrobial products. With the wear and the domestic washing of textile articles, the products are gradually removed and the textile article loses the antimicrobial properties. Another consequence of the loss of the antimicrobial products is their effect on the environment.

Silver, for example, one of the antimicrobials most used and most efficient, when in the form of nanoparticles of size below 20 nm, can penetrate the skin of living organisms of rivers and their margins, and can enter the food chain of man. It can also penetrate the skin of human beings and can for that reason caused alarm, even though there isn't any proof of its toxicity. For these reasons, a new generation of antimicrobials is needed, that do not cause habituation, do not present problems of toxicity and that have durability, mainly in what concerns the washfastness . Natural antimicrobials have also been tested, such as chitosan but normally they don't have the efficiency nor are sufficiently durable when compared with synthetic or inorganic antimicrobials. The antimicrobial that we propose is based on hydrophilic such as the peroxy compounds or soluble in water such as hypochlorite.

The peroxides that are best well known and used as antimicrobial are hydrogen peroxide, H202, used a lot as a disinfectant on wounds, and peracetic acid, used a lot as a antimicrobial on applications as food products, in small doses. The problem of the application on textile articles of these two products is their binding to fibers and other surfaces such as for example food packaging, due to the fact of being liquids and not having consistency in this form so as to be able of binding through chemical bonds to these surfaces.

Nanotechnology has an important role in the functionalization of surfaces of textile articles and surfaces of other materials, such as paper, polymers, animal skins and other materials that interact with the human being.

Nanotechnology on these surfaces takes in most cases the form of nanoparticles that due to their small dimension have the particularity of conveying an effect more durable than other forms of functionalizing the surfaces of different surfaces of different substrates, since they are not so exposed to the forces of abrasion that act on those surfaces. On textile materials for example, where the domestic washing specially in the washing machine, is a process in which the abrasion forces caused by the movement of the textile articles on each other and of the movement of the textile article itself are very large, the finishes deposited on the fibers do not normally resist to more than a small number of washes due to being exposed to these forces.

On the contrary, the nanoparticles resist a lot more to these forces because they are less exposed and trapped between the fibers that make up the textile material .

In patent WO 2004060378 particles of alumina and silica are described in which the functional product is adsorbed in the particles already made. Besides the fact that these particles aren't specifically nanoparticles, putting at risk the durability in textile articles, there is also the problem of not having a strong bond between the particles and the functional products, nor having a specific bond between nanoparticles and the textile material .

The document of patent US2007/0079447 describes a preparation of ethyl 3-N-n-butyl-N-acetiloaminopropionate impregnated in textile fibers. The simple impregnation of this product, leads to the greatest part of the product being removed at the first domestic wash, since it is not bound by any fixing agent. So as to even work, it would be necessary for the product remained after some washes. The waste of product is huge and the efficacy very small.

The document of the patent WO2006/117702 describes microcapsules of materials different to silica containing an active product such as antimicrobial and insect repellent for application to textiles.

The document of the patent WO2005/018795 also reveals microcapsules similar to the previous paragraph but that bind differently to the nanoparticles of the invention .

Brief description of the figures

Figure 1 shows a photo by electron microscopy of nanoparticles before washing

Figure 2 shows a photo by electron microscopy of nanoparticles after alkaline washing

Figure 3 shows a photo by electron microscopy of a woven fabric containing the nanoparticles, after alkaline washing where the protecting film can be seen Figure 4 shows a graphic representing the resistance to washing of ethyl 3-N-n-butyl-N-acetiloaminopropionate (IR3535) incorporating the nanoparticies of silica applied in a cotton fabric.

Summary of the invention

In the present invention it is proposed the incorporation of hydrophilic or partially miscible products in water, normally peroxides, in solid products so as o increase their stability and in the second place allow their fixation ^' and binding to the surfaces where it is intended to have antimicrobial or anti-insect properties. It is yet proposed in this invention the immobilization of peroxides and ethyl 3-N-n-butyl-N-acetiloaminopropionate in silica particles, that themselves are bound to the surfaces where they are intended to be bound, such as textile articles. In the present invention it is proposed that the solid product be porous so as to absorb the peroxides and retain them in its pores, insomuch as the proposed product is composed by nanoparticies of a metal oxide, preferably silicon oxide (silica) .

Detailed description of the invention

The nanoparticies of this invention incorporate hydrophilic products or soluble/miscible in water, formed by a modified sol-gel process (Stober et al) in which the precursor of silica is a silicate.

An application of this patent is the antimicrobial functionalization, incorporating hydrophilic products with antimicrobial activity, such as hydrogen peroxide and peracids . These products have the advantage over other antimicrobial products since they not cause habituation nor resistance of bacteria.

In the present invention, the products are incorporated during the process of synthesis of the nanoparticles and afterwards they are bound to the textile material with a fixing agent or a binder. It is not possible to incorporate hydrophobic functional products without any available electrons to establish hydrogen bonds with the silica particles and hope that these products have a good durability or a good resistance to washing. In patent WO 2004060378 it isn't specified if the products are hydrophobic or hydrophilic.

In patent the products are all hydrophilic or contain groups that can establish hydrogen bonds with silica and/or being products that are soluble in water, such as salts, can be deposited in the pores and on the surface of silica during the process of formation of the nanoparticles by the sol-gel process. The nanoparticles stay in aqueous dispersion after the evaporation of the solvent, and may be applied in this form on textile surfaces and other surfaces of other materials, namely paper .

Preferentially dispersants can be applied and thickening agents, to improve the properties of the dispersion. In the case of intending to obtain dried nanoparticles for application in non-aqueous medium, the active solid substance deposits in the drying phase of the particles.

Other products identified as being useful to trap in silica nanoparticles, are products that eliminate or repel insects, the one that has the conditions needed to be incorporated into the nanoparticles is IR3535 from Merck (ethyl 3-N-n-butyl-N-acetiloaminopropionate ) .

It was verified that when adding hydrophylic products during the process, mixing the product right at the beginning with an inorganic precursor of silica such as sodium orthosilicate, that the products stay trapped in the inside of the nanoparticles through hydrogen bonds. In such a way that hydrogen peroxide in a test of controlled release in water at 60°C it only leaves the particles completely after 30 minutes, which however is not sufficient for textile applications since domestic washing is longer than 30 minutes and all the peroxide would eventually be lost.

Even though the nanoparticles in textile materials show a greater durability maybe because they are inside the fibers and fixed by an acrylic binder, even so they do not withstand more than 10 washes in a machine after their impregnation in the textile fabric. (Gomes, Nano and Green conference, NY 2009)

When applying the product to surfaces as textile materials with a silane fixing agent and after the incorporation of the product if the textile material is washed in alkaline conditions, we realized of the increase in durability of the product in the nanoparticles.

As a means of retaining the product in the pores of the nanoparticles for durability purposes, when applied to surfaces, we applied a hydrolysable silane, such as trimethoxysilane, that forms a film by polymerizing that surrounds the nanoparticles, trapping the product in its interior, consisting in a subsequent process of encapsulation of the nanoparticle itself through the formation of a film of silane, surrounding it.

The present invention consists in the nanoparticles of silica, or another porous metal oxide such as alumina, that contains hydrophilic products or that are soluble/miscible in water with repellent properties of insects or are antimicrobial, and that are in the form of sol-gel or in the form of aqueous dispersion, and are applied by padding processes on conventional textile materials that are normally used on these materials. This thermofixation with silanes will occur at temperatures above 120°C in a process of thermofixation, after padding the woven fabric, or knitwear, with a dispersion of nanoparticles , and its passage through squeezing rollers of the machine (stenter) . The nanoparticles are then surrounded by a film of silane through a reaction of condensation polymerization, during an alkaline washing of the material.

The polymerization is accelerated by the release of water during the post-thermofixation in a tumbler or in an oven/stenter . Other products based on silane can be used in which the CH3 radical of the methoxy group is replaced by another radical (ethyl, propyl, butyl).

The hydrophilic substance, or a substance that is soluble/miscible in water, that was incorporated in the nanoparticles stays in this way retained by a silane film that forms itself around the particles and simultaneously binds them to the fibers. The nanoparticles containing the hydrophilic or water soluble/miscible substance, stay in this way retained in the fiber and with very high washfastness . In another embodiment of this patent, products are chosen with functional products that make it possible the reaction with the silane, for a greater durability. In one preferential case we used hydrogen peroxide and observed a washfastness of more than 50 washes after the application of nanoparticles being applied with glycidyltrimethoxysilane in a cellulosic material (cotton) at a temperature between 100°C and 150°C whereas when the nanoparticles are inserted in water the hydrogen peroxide is released in 30 minutes and ' when applied on textile materials with a binder normally used in textile finishing, an acrylic binder, it didn't resist to more than 10 washes.

The trimethoxysilane has the property of hydrolysing in water, polymerization at acid pH and/or heating causing the release of water, and in this way adhere to other surfaces, binding the particles through the formation of a film that surrounds the silica particles, binding them in this way to these surfaces.

In the present patent the nanoparticles of silica are prepared by a sol-gel process. Sol-gel is a metal oxide matrix, zinc oxide or silicon oxide, for example, that forms itself spontaneously in aqueous medium and in the presence of a surfactant (tensoactive agent) , by hydrolysis of a substituent group of a precursor, such as TEOS, tetraorthoethylsilicate, or sodium silicate, and further polymerization for acid catalysis to form the matrix of silicon oxide.

We may add that the process of preparation of the sol-gel is normally made in aqueous medium and for that reason the precursor is hydrophilic such as silicate and the incorporation of the product is by direct dissolution in water, if it is hydrophobic or miscible in water, such as TEOS, it should be previously mixed in ethanol so as to be miscible in water.

Taking as an example the sol-gel of silicon oxide, the first phase of the formation is the hydrolysis, normally the acid hydrolysis, of the precursor of silica for the formation of the silicon hydroxide. With the continued addition of acid or acid salt, such as ammonium chloride, occurs the condensation polymerization of the silicon hydroxide with the formation of the . polymeric matrix of silicon oxide. The polymeric matrix can incorporate other hydrophilic products in its interior through hydrogen bonds. In this way, sol-gel can be used with functional products, as long as they are hydrophilic, such as flame retardants amongst others. We can from sol- gel precipitate silica nanoparticles that have the advantages over other metal oxides insomuch that they are porous and are able to incorporate the functional product that was introduced in the sol-gel. The silica nanoparticles are produced by a sol- gel Stober process, in which the sol-gel is surrounded by an emulsion W/0 in which the solvent is an organic solvent, as for example of ether of petroleum or cyclohexane, and an aqueous contains the active product that is intended to insert in the nanoparticles . That product can be an antimicrobial, an insecticide or insect repellent, vitamins, enzymes, hydrating agents, as long as they are all hydrophilic or soluble in water. Based on this variation of the Stober process, it is possible to contain the products that are incorporates in the sol-gel in "micro-reactors", that are aqueous drops of sol-gel dispersed in the organic solvent, in a way that makes it possible to trap better the product inside the nanoparticles that are formed when more acid is added to the sol-gel. It is also possible to control better the size of the nanoparticles through a control of the size of the drops by altering the surfactant such as is the common practice with emulsions.

Preferentially an aqueous solution with a precursor of silica, sodium orthosilicate is added to the organic solvent and with agitation a sol-gel emulsion is formed. Next to the emulsion of sol-gel an aqueous solution containing the active product is added. After mechanical agitation an acid salt is added for the formation of the nanoparticles. We can apply the sol-gel just as it is or we can evaporate the solvent and apply the resulting aqueous dispersion of particles. Nanoparticles can furthermore be filtered and dried so as to be applied in this form.

The active products that are introduced in these nanoparticles that we claim, are the antimicrobial hydrogen peroxide and peracetic acid, two hydrophilic products miscible with water and with hydroxyl groups that form hydrogen bonds with silica, and the insect repellent ethyl 3-N-n-butyl-N-acetiloaminopropionate exists with the commercial name IR3535 (Merck) .

Although this product is not hydrophilic and is only partially miscible in water, it is enough for it to be inserted in the drops of sol-gel of the emulsion, it is an ester and has the same formula than alanine, an amino acid, which means that it is an example of two families of products that are hydrophilic and miscible in water, that we claim as being appropriate to be incorporated in silica nanoparticles, by having the capacity of bonding to silica through hydrogen bonds formed between the hydroxyl or amino groups and the silica. These nanoparticles are next bound to textile fibres and encapsulated through the formation of a silane film surrounding them.

Objects of the invention

The first object of this invention is a process of obtaining silica nanoparticles, comprising the following steps : dissolution of sodium silicate or triethylorthosilicate (TEOS) in water and addition of an organic solvent; addition of an anionic tensoactive agent and stirring at room temperature; addition of a product to encapsulate, hydrophilic or partia±±y misciDle m water, toxlowed- Py stirring; addition of an acid or an acid salt continuing stirring;

Evaporation of the organic solvent so as to obtain said nanoparticles .

In case of triethylorthosilicate of Ethyl (TEOS) in step a) is used, since it is not miscible with water, it should be previously mixed with ethanol.

In step a) as organic solvent, we can use, for example, petroleum ether or cyclohexane

In one embodiment of the invention, the hydrophilic product of step c) is a peroxide, such as hydrogen peroxide, or a peracid with the general formula R- COOOH, wherein R is an alkyl group, for example peracetic acid, or sodium hypochlorite. In another embodiment of the invention the product partially miscible with water of step c) is ethyl 3 N-n-butyl-N-acetylamino propionate .

Preferentially the acid salt of step c) is ammonium chloride. The nanoparticles obtained in step e) are in the form of sol-gel or in an aqueous dispersion.

The hydrophilic product or the partially miscible product of step c) , is trapped in the pores of the nanoparticles obtained in step e) after evaporation of the solvent;

A second object of this invention is a process of immobilization and encapsulation of the silica nanoparticles obtained in any of the claims 1 to 10, comprising the following steps: a) padding of a textile material with said nanoparticles ; b) passing the material through squeezing rollers of a stenter; c) reaction of condensation polymerization of the hydrolysable silane of the nanoparticle, during an alkaline treatment of the material, so as to allow the encapsulation of the nanoparticles by the formation of a polymeric film surrounding them; d) thermofixation in a tumbler or in an oven/stenter .

Preferentially the textile material of step a) is cotton. Generally the padding process of step a) is done in a pad-mangle. In a specially preferential embodiment of this invention, the hydrolysable silane of step c) is ethyl 3 N- n-butyl-N-acetylamino propionate.

The alkaline treatment of step c) is, normally, alkaline washing.

Experimental part

For obtaining the nanoparticles , 10 to 20 g of sodium orthosilicate, , are dissolved in 100 ml of water and added to 200 ml of solvente. We add to 5 ml of triton and stir at room temperature for 1 hour. 5 ml of the hydrophilic product to be encapsulated (peroxides or ethyl 3 (N-n-butyl-N-acetylamine) propionate) are added and the stirring continues for a further 30 minutes. We add next lOg of ammonium chloride continuing the stirring. After 1 hour the stirring is stopped and the solvent is evaporated at a temperature above 60 °C so as to obtain a dispersion of silica nanoparticles.

By this method the particles come out with a size of approximately 200 nm and a regular dimensional distribution, not deviating too much from this size.

The sol-gel that is formed, can be used in this form in the application to the surface of the materials, namely textile materials, during the process in which the solvent is evaporated in the application, or the solvent is removed and preferentially recycled after the formation of the sol-gel and be applied in this form of a dispersion of nanoparticles .

When the solvent is evaporated, including water, during the process of application to the surface of the textile materials and others, the peroxides that are distributed between the inside of the nanoparticles and the aqueous phase of the sol-gel, stay trapped in the pores of the nanoparticles. The nanoparticle of the present invention is not reactive and the binding to substrates is with bifunctional products (coupling agents) , those particularly suitable being silanes of general formula (CH₃0) 3-Si-R-CH₂CH₂OH) , since it is known the reaction of the hydrolysable groups such as the trimethoxysilane with silica, and also having the glycidyl group CH2CH20H, that after forming the epoxy ring in alkaline conditions it reacts with the cellulose, reaction which is well known, binding in this way 'the nanoparticles to the textile fiber, occurring the reaction between the GLYMO, trimethoxyethylglycidyl (epoxy) with the hydroxyl groups of the fiber, trimethoxyethylglycidyl (epoxy) serving as a linker group, between the two materials, silica and cellulose. There is still the possibility of the reaction of the epoxy with amino groups of wool, silk and polyamide, the nanoparticles being bound in this way to these fibers.

The hydrophilic products to "encapsulate", such as peroxides and partially water miscible products such as ethyl 3 N-n-butyl-N-acetylamino propionate with amino groups and oxygen, stay trapped in the silica nanoparticles through hydrogen bonds which increases their durability in relation to other products, turning them in functional products (antimicrobial and insect repellent) , ideal for inserting into the porous silica particles.

So as to form the polymeric film, and in this way trap the product inside the nanoparticles, we polymerize the silane with one or more washes (see in the annex photos of electron microscope of fibers with nanoparticles before and after alkaline washes, where it is possible to see the film after the hydrolysis caused by the alkaline washing) . Examples

The present invention is next illustrated by the following examples, not exclusive, of the matter in the protection of the present patent proposal

Process of production nanoparticles

Example 1

Sodium orthosilicate, 10 to 20g, are dissolved in 100 ml of water and 200 ml of solvent are added. Triton (5 ml) is added with stirring at room temperature for an hour. We add 5 ml hydrogen peroxide and continue stirring for 30 minutes more. Ammonium chloride, lOg/1, are added next, while continuing stirring.

After 1 hour we end the stirring and evaporate the solvent at a temperature of 60°C so as to obtain a dispersion of silica nanoparticles .

Example 2

Sodium orthosilicate, 10 to 20g, are dissolved in 100 ml of water and 200 ml of solvent are added. Triton (5 ml) is added with stirring at room temperature for an hour. We add 5 ml ethyl 3 N-n-butyl-N-acetylamino propionate (IR3535) and continue stirring for 30 minutes more. Ammonium chloride, lOg/1, are added next, while continuing stirring .

After 1 hour we end the stirring and evaporate the solvent at a temperature of 60°C so as to obtain a dispersion of silica nanoparticles. Example 3

Sodium orthosilicate, 10 to 20g, are dissolved in 100 ml of water and 200 ml of solvent are added. Triton (5 ml) is added with stirring at room temperature for an hour. We add 5 ml peracetic acid and continue stirring for 30 minutes more. Ammonium chloride, lOg/1, are added next, while continuing stirring.

After 1 hour the stirring is ended and the solvent is evaporated at a temperature of 60°C so as to obtain a dispersion of silica nanoparticles.

Processo of application on cellulosic fabrics Example 4

To a cotton white fabric, a process of padding in a pad-mangle is used, an equipment made of a dipping tank, where the formulation of nanoparticles is introduced and where the fabric goes through, and by two squeezing rollers, where the- 100% cotton fabric goes through. The formulation contains 40 g/1 of the dispersion of the nanoparticles of silica with IR3535 (30% solids), 2 g/1 of a dispersing agent and 10 to 20 g/1 of sodium carbonate.

After padding the fabric, it undergoes a thermofixation in a stenter at a temperature between 100°C and 190°C. Process of application on textile articles Example 5

To textile articles (total 5 Kgs) made of different textile fibers, cellulosics (cotton and viscose) , wool, polyester, polyamide and acrylic fibres, placed in a dyeing machine with rotation of the material (in the same fashion of a washing machine) the suspension being app ied at acid pH so as to adhere to the fibers. Then excess water is removed by spinning (centrifuge) and the textile articles are then placed in a tumbler at a set temperature of 130°C .

Example 6

Processo of encapsulation of the nanoparticles

A fabric weighing 10 Kg with nanoparticles, the nanoparticles containing the product with IR3535, produced in the way described in example 3, undergoes an alkaline washing at 40°C in an aqueous solution, at alkaline pH (8 to 12) , adjusted with sodium carbonate, for a period of 30 minutes. The washing is carried out in an industrial washing machine or a domestic one, at a liquor ratio of 1:5. After the washing it is observed (in an electronic scanning microscope SEM) the formation of a film that covers the nanoparticles present in the fibers from the hydrolysis of the silane that was introduced in the process described in example 3.

Washfastness test

According with figure 1 it can be confirmed the durability of the product to washing, by measuring the reflectance curve (440 nm) of the samples of fabric (100% cotton) after successive washes in the washing machine. The initial quantity of product applied was 2.65 g/Kg of fibre

By a colorimetric process with an FBA, fluorescent brightening agent, it can be verified that ethyl 3 N-n- butyl-N-acetylamino propionate (IR3535) withstands the washes, the FBA being activated and emitting a more intense whiteness in the presence of IR3535. The FBA used was Blankophor (BASF) . The product only starts to^' diminish after 30 washes and even after 50 washes there is more than 60% of the product, as it can be seen in table 1, being sufficient to repel mosquitos if we start with a concentration of 50g/l of sol-gel of ethyl 3 N-n-butyl-N- acetylamino propionate. Another proof is the effect on repellency itself that lasted 10 washes as it can be seen on table 1.

Antimosquito test To determine the presence of IR3535 on the textile fibers a colorimetric method was used making it react with a product that reflects in the wavenumber 440 nm. In table 1 the durability of the product to washes can be confirmed, by measuring the reflectance curve (at 440 nm) of the samples of fabric (100% cotton) after successive washes in the washing machine. The initial quantity of product applied was 2,65 g/Kg of fiber.

Repellency test

(WHO, 2006, Guidelines for testing mosquito adultticides for indoor residual spraying and treatment of mosquito nets, World Health Organization, Geneva, 2006) .

The test used was the tunnel test of dimensions 25x25x60 cm. The tunnel is divided into two compartments of the tunnel is on a fabric treated with the antimosquito product and deliberately perforated with 1 cm holes. In this method 100 female mosquitos of the anopheles type are intrododuced in one of the compartments and in the other is introduced a guinea pig. Mosquitos are left for two hours and are then counted those that passed through the holes in the fabric, and counted those that fed and those that were inhibited of doing so. As a comparison we can analyse a test in by the same method on another active product, DEET (microencapsulated) , that had an index of repellency (IRE) before washing of 40% and a BFI of 65% (Pennetier et al, Transactions of the Royal Society of Tropical Medicine and Hygiene (2008) 102, 259-262).

Table 1. Values of the indexes of repellency (IRE) and of the reduction of blood feeding (BFI) (Tests carried out at the IHMT-Institute of Hygiene and Tropical Medicine, Lisbon, Portugal) .

Test Sample IRE % BFI%

0 washes 1 52.9 73.8

10 washes 2 25.9 62.7

Claims

1. A process for obtaining silica nanoparticles comprising the following steps: a) dissolution of sodium silicate or triethylorthosilicate in water and addition of an organic solvent; b) addition of an anionic tensoactive agent and stirring at room temperature; addition of a product to encapsulate, hydrophilic or partially miscible in water, followed by stirring; addition of an acid or an acid salt continuing stirring;

Evaporation of the organic solvent so as to obtain said nanoparticles.

2. The process according to claim 1 wherein the solvent organic of step a) is petroleum ether or cyclohexane .

3. The process according to claim 1 wherein the hydrophilic product of step c) is a peroxide.

4. The process according to claim 3 wherein the peroxide is hydrogen peroxide or a peracid with the general formula R-COOOH, wherein R is an alkyl group.

5. The process according to claim 4 wherein the peracid is peracetic acid.

6. The process according to claim 1 wherein the hydrophilic product of step c) is sodium hypochlorite.

7. The process according to claim 1 wherein the product partially miscible with water of step c) is ethyl 3-N-n-butyl-N-acetylaminopropionate .

8. The process according to claim 1 wherein the acid salt of step c) is ammonium chloride.

9. The process according to claim 1 in which the nanoparticles obtained in step e) are in the form of sol-gel or in an aqueous dispersion.

10. The process according to claim 1 in which the hydrophilic product or the partially miscible product of step c) , is trapped in the pores of the nanoparticles obtained in step e) after evaporation of the organic solvent. process of immobilization and encapsulation of the silica nanoparticles obtained in any of the claims 1 to 10, comprising the following steps: a) padding of a textile material with said nanoparticles; b) passing the material through squeezing rollers of a stenter; c) reaction of condensation polymerization of the hydrolysable silane of the nanoparticle, during an alkaline treatment of the material, so as to allow the encapsulation of the nanoparticles by the formation of a polymeric film surrounding them; d) thermofixation in a tumbler or in an oven/stenter .

12. The process according to claim 11 wherein the textile material of step a) is cotton. 13. The process according to claim 11 wherein the padding process of step a) is done in a pad-mangle.

14. The process according to claim 11 wherein the hydrolysable silane of step c) is ethyl 3-N-n-butyl-N- acetylaminopropionate .

15. The process according to claim 11 wherein the alkaline treatment of step c) is alkaline washing.