WO2004002225A1

WO2004002225A1 - System for encapsulating active principles, method for providing same and uses

Info

Publication number: WO2004002225A1
Application number: PCT/FR2003/001902
Authority: WO
Inventors: Thomas Canova; Sandrine Rochat; Christine Vidil; Dominique Dupuis
Original assignee: Rhodianyl
Priority date: 2002-06-28
Filing date: 2003-06-20
Publication date: 2004-01-08
Also published as: FR2841471B1; AU2003255685A1; FR2841471A1

Abstract

The invention concerns a system for encapsulating at least one active principle comprising at least one composite particle including at least: one core containing the active principle; a mineral coating surrounding said core. Said encapsulating system is characterized in that the mineral coating is obtained in two steps. The first step consists in forming mineral nanoparticles and adsorbing them onto said core in the form of a coating; the second step consists in forming a mineral coat formed on said nanoparticles. The invention also concerns a method for preparing particles forming the encapsulating system, the use of such a system as additive in polymer compositions, said compositions, yarns, fibers, filaments or granules obtained by shaping said compositions and, furthermore articles obtained from said yarns, fibers, filaments or granules.

Description

ACTIVE PRINCIPLE ENCAPSULATION SYSTEM, METHOD FOR PRODUCING SUCH A SYSTEM AND APPLICATIONS

The present invention relates to the field of composite particles into which active substances are introduced.

More specifically, the present invention relates to composite particles comprising a core comprising at least one active principle covered with a mineral shell.

More precisely still, the object of the present invention is a system for encapsulating active substances ensuring the thermal protection in particular of said active substances and their release in a controlled manner.

Active ingredient encapsulation systems are widely used today. In addition to their development in the pharmaceutical sector, these systems have also been widely developed in the textile sector. Indeed, the textile industries seek to market products containing active agents of different natures.

For example, a developed route concerns the introduction into textiles, of agents having bioactive properties, such as antibacterial, fungicidal or even anti-mite properties. Thus, an important objective is to reduce the development of bacteria and fungi on work tools, on building materials, on clothing, in order to reduce the risk of infection by as much, especially in the medical sector.

Another objective is to reduce the harmful effects of dust mites, in particular in terms of development of allergies, by limiting their development in furnishing fabrics such as carpets, rugs, surface coverings, sofas, curtains, the bedding, mattresses or pillows. In the medical sector, it is also of great importance to limit the development of mites.

In order to give textile materials active properties, various means can be used. A first means consists in using primers containing active compounds.

However, such primers have the main disadvantages of having a limited hold and seeing their effects disappear after one or more washes.

Another more interesting means consists in introducing the active agents inside the textile materials. To this end, it is known to introduce an active agent into wires, spun in solution or by coagulation. The active agent is then introduced into the solvent for the polymer.

For polymers formed in the molten phase, it is known to introduce inorganic fillers supporting an element based on active metal. These charges can be introduced during the polymerization process or during the shaping process. Many solutions are proposed for the realization of mineral charges. These fillers must have sufficient dispersibility in the polymer, an acceptable color, a controlled and lasting activity in the polymer and must not alter the properties of the polymers too much.

The active agent responsible for the activity of the filler often leads to a degradation of the properties of the products such as the threads (such as yellowing) in which the filler is dispersed.

In order to control the activity of the fillers while limiting the degradation of the properties of the products induced by these fillers, it is necessary to control the release kinetics of the active agent contained in these fillers.

Another aspect concerns the thermal protection of the active ingredients. In fact, the high temperatures necessary for shaping polymer-based products are often incompatible with the active ingredients which are generally degraded at such temperatures.

Mineral type encapsulation systems capable of releasing active agents such as active cations in a controlled manner are known in the prior art.

US-A-4,775,855 describes for example the use of silver-bearing zeolites.

US Pat. No. 5,180,585 describes mineral fillers with onion structure comprising three layers: a support core (for example silica, titanium dioxide), a layer of bioactive agent in metallic form or not (for example a silver layer), a protective layer (for example silica). The protective layer is described as protecting the polymer from degradations induced by the presence of the bioactive agent, such as yellowing of the polymer for example. As a typical example, mention may be made of the Microfree® fillers sold by the company Du Pont.

Patent application WO-A-99/41298 filed by the applicant describes composite particles comprising an organic polymer core such as a butadiene-styrene copolymer, containing an active material such as an anti-UN agent, and a shell mineral (for example silica).

The major drawback of such a composite particle is that the mineral shell is not sophisticated enough to allow controlled release of the active principle.

It emerges from this review of the prior art, that there is no encapsulation system capable of easily incorporating an active agent within it, said active agent being protected from any degradation, in particular thermal, and being released in a controlled manner. Also, a first objective of the present invention is to provide an encapsulation system comprising a composite particle in which active agents of various origins can be incorporated.

Another objective of the present invention consists in proposing an encapsulation system making it possible to adjust and control the release of the active agent.

Yet another object of the present invention is to provide an encapsulation system comprising a composite particle having improved thermal resistance.

Yet another objective of the present invention is to provide an encapsulation system which can in particular be incorporated into polymers during the stage of preparation of said polymers or during their shaping.

Yet another object of the present invention is to provide an encapsulation system which can be used in polymeric compositions and articles obtained from these compositions. These objectives, among others, are achieved by the present invention which relates to an encapsulation system comprising at least one composite particle comprising at least:

- a heart composed of at least one active principle,

a mineral bark around said heart, said encapsulation system being characterized in that the mineral bark is obtained in two stages: the first stage consisting of the formation of mineral nanoparticles and their adsorption on said heart, in the form of a layer ; the second step consisting in the formation of a mineral coating on said nanoparticles.

According to a remarkable characteristic, the mineral shell is based on a compound chosen from metal oxides and their mixed oxides and / or a precursor of these oxides. It can be chosen from titanium, aluminum, zinc, copper, zirconium, and cerium oxides, zinc sulfide, copper sulfide, zeolites, mica, talc, kaolin, mullite and silica.

It can also be chosen from hydrogen carbonates or halocarbons of aluminum, yttrium, europium, lanthanum, calcium phosphate compounds (calcium hydroxyapathite for example).

Advantageously, the core of the composite particles comprises at least one polymer, which is preferably of an organic nature.

According to this advantageous variant, the nature of the organic polymers constituting the core of the composite particles is preferably of the type of that of the latex particles, that is to say particles of (co) polymers resulting from conventional methods of (co) polymerization of copolymerizable organic monomers.

More generally, this polymer is derived from at least one ethylenically unsaturated monomer which is immiscible with water and which can be polymerized by the radical route. By way of illustration, the monomers are chosen from vinyl aromatic monomers, alkyl esters of α-β ethylenically unsaturated acids, vinyl esters of carboxylic acids, vinyl or vinylidene halides, conjugated aliphatic dienes and α- nitriles β ethylenically unsaturated.

As an illustration of this type of monomer, mention may in particular be made of styrene, butadiene, acrylonitrile, chloropropene, vinyl chloride or vinylidene chloride, isopropene, isobutylene, vinyl acetate, propylene , butylene and vinylpyrrolidone.

The polymer constituting the core of the composite particles according to the invention may also comprise up to 8%, preferably up to 4% of at least one co-monomer carrying ionogenic groups which can be polymerized by the radical route. It may especially be a co-monomer carrying ionogenic groups is chosen from α-β ethylenically unsaturated carboxylic acids, sulfonated ethylenic monomers, hydroxyalkyl esters of α-β ethylenically unsaturated hydroxypropyl acids, amides d 'ethylenically unsaturated α-β acids and the amino esters of ethylenically unsaturated α-β acids.

As examples of these ionogenic groups, it is possible to mention very particularly those chosen from acrylic, methacrylic, itaconic, maleic, crotonic, para-styrenesulfonic, vinylsulfonic, 2-methacryloyloxyethylsulfonic acids,

2-acrylamido-2methylpropylsulfonic, vinylbenzene sulfonate, hydroxyethyl acrylates and methacrylates, acrylamide, methacrylamide and diethylaminoethylmethacrylate.

Preferably, the polymer does not contain monomers with carboxylic or sulphonic functions.

More preferably, this polymer is chosen from polystyrene, acrylates such as PMMA (poly methyl methacrylate), copolymers of styrene and acrylic esters, styrene and butadiene, styrene, butadiene and acrylamide.

Mention may more particularly be made of copolymers of styrene with acrylates or butadiene. They can advantageously be chosen from butadiene-styrene copolymers, acrylic copolymers and butadiene-styrene-acrylamide copolymers. These organic polymers more particularly have a glass transition temperature of between -100 and 150 ° C. According to a particularly advantageous and preferred embodiment of the invention, the glass transition temperature is between -100 and 100 ° C and more preferably between -15 and 100 ° C. In general, the diameter of the particle can vary between 20 nm and 5 μm, preferably 0.5 and 3 μm and more preferably still between 1 and 2 μm.

According to another remarkable characteristic, the thickness of the mineral crust is less than 10% of the diameter of the core of the particle. Thus, if the core of the particle has a diameter of 2 μm, the thickness of the mineral crust is at most 0.2 μm, or a maximum diameter of the particle of 2.4 μm.

According to a remarkable characteristic, the active principle is chosen from the group comprising: bio-active agents, cosmetic active principles, pharmaceutical active principles, agrochemical active principles, anti-UN. Bioactive agents can be of organic origin

By bioactive agent is meant an agent which can prevent the proliferation of certain living species, either by killing them or by limiting their reproduction. In this case, we also speak of a biostatic agent. The bioactive agent can thus be an antibacterial, bacteriostatic, antimicrobial, antifungal, anti-mite agent. These bioactive agents can be of organic origin such as benzyl benzoate or Kertex® (butyl-3-iodo-2-propynyl ester of carbamic acid) sold by TROY), the compounds of the family of pyrethroids , ortho-phenylphenol, isothiazolinones.

These bioactive agents can also be of non-organic origin, such as a metal compound.

The term “metallic compound” for the bioactive agent means both the metal element and the metal ion or any chemical composition containing the metal element, such as complexes or salts.

Advantageously, the bioactive agent is chosen from the following list. - metallic silver, its cation Ag ⁺ , its oxides for example Ag O, its halides, metallic copper, its cations Cu ⁺ and Cu ²⁺ , its oxides CuO and Cu ₂ O, its sulfide CuS, its hydroxides, hydroxycarbonates , oxycations, halides, carbonates, - metallic zinc, its cation Zn, its oxide ZnO, its sulfide ZnS,

ZnSiO ₃ , - the other compounds and ions from groups 3 to 12 of the international classification, such as Ru, Rh, Pd, Os, Ir, Pt, Au, Hg, Cd, Cr, Ni, Pb, Sn. They can be used alone or in combination. According to a preferred embodiment of the invention, the bioactive agent is chosen from the compounds of Ag, Cu, Zn and their combinations. Even more preferably the bioactive agent is a compound of Ag. Generally, the proportion by weight of active principle in the heart relative to the total weight of the particle is less than 50%.

A second object of the invention is a process for preparing the particles forming the encapsulation system according to the invention, as described above. This process mainly comprises the following stages:

(I) the formation of nanoparticles and the adsorption of the nanoparticles thus formed on the cores so that the nanoparticles form a uniform layer around said cores;

(II) the growth of a mineral coating on the layer of nanoparticles, said nanoparticles serving as seeds for the growth of the coating layer, and

(III) optionally drying and recovering the particles thus obtained.

It is advantageous that when the core of the particles consists only of active principle (s), the latter (s) is (are) in solid or liquid form immiscible in the reaction medium.

Preferably, the core of the particles is based on at least one organic polymer. It is obtained conventionally by radical polymerization in emulsion of unsaturated monomers immiscible with water and polymerizable. These techniques are those known to those skilled in the art.

At the end of the radical emulsion polymerization, a dispersion of latex particles is obtained. This polymerization method makes it possible to obtain particles of uniform size.

The incorporation of the active principle can occur at different times of the process and according to different techniques.

According to a first embodiment, the active principle is incorporated into the dispersion at the same time as the monomers before the polymerization or during the polymerization. According to this first embodiment, the active principle is found solidified in the polymer. According to a second embodiment, the active principle is introduced into the heart at the end of the polymerization of the monomers, by bringing said latex particles in dispersion into contact with the said active principle, if necessary, dissolved in a solvent of transfer.

According to one variant, the active principle can be dissolved in a solvent which is neither a solvent nor a swelling agent for the polymer. According to this variant, the active principle in the liquid phase is fixed to the surface of the polymer during the elimination of the solvent, without penetrating inside that. As a transfer solvent, a swelling agent of the polymer is used which does not dissolve the latter, while dissolving the active principle.

If a transfer solvent is used, the polymer cores are isolated from their reaction medium after the polymerization, then are re-dispersed in the transfer solvent.

Of course, the choice of transfer solvent must be made by considering the nature of the active principle to be dissolved and the nature of the polymer to be swollen.

The transfer solvents used are known to those skilled in the art. Such a solvent can for example be acetone. In certain circumstances, the presence of a transfer solvent may not be necessary. Indeed, certain active ingredients can possess by themselves the ability to penetrate latex.

To promote the swelling of said latex particles, the reaction medium can be heated. The choice of temperature is directly linked to the nature of the polymer constituting the cores.

Preferably, the contacting between the active principle, in solution or not in a transfer solvent, and the latex particles in suspension, is carried out with stirring and at a temperature between about 20 and 90 ° C.

At the end of this step, it is possible, if necessary, to remove the transfer solvent before adding the oxide (s) and / or a metal oxide precursor from which the bark is derived.

This solvent can be removed by any conventional method insofar as this is not likely to affect the stability of the polymer cores. One can for example carry out a vacuum distillation of said transfer solvent. However, this elimination step may in some cases not be necessary.

With regard to the stability of the dispersion of polymer cores incorporating the active principle, it may if necessary be advantageous to strengthen it, in particular to prevent any risk of flocculation, during the following steps.

To this end, one or more stabilizing agent (s) can advantageously be added before swelling the polymer, in order to over-stabilize the latter which can be destabilized by the transfer solvent. These stabilizing agents, for example nonionic, are of the polyethoxylated alkylphenol, polyethylene glycol or polyvinylpyrrolidone type.

(PNP).

This stabilizer can be incorporated in an amount of approximately 0.5 to 3% relative to the weight of polymer.

It should be noted that the latex particles already include a stabilizing agent, which is generally PNP. If the polymer is really too sensitive to the transfer solvent, it may be advantageous to protect it by over-stabilizing it with a first mineral layer, before adding transfer solvent.

When the active agent is a cation, it can be envisaged to use a functionalized latex particle (carboxylated in particular) to which this cation is fixed (complexing) this before making the mineral shell. It is also possible to use an organic complex of said cation, incorporated according to the same method of swelling as that described above.

The following steps consist in producing the mineral shell, comprising a first layer constituted by nanoparticles and a second layer constituted by a coating.

According to a preferred embodiment, the production of the mineral bark is done by the alkoxide route, known to a person skilled in the art. In order to produce the layer of nanoparticles, the dispersion of latex particles in organic polymer comprising the active principle and constituting the cores of the composite particles of the encapsulation system according to the invention is brought into contact with a metallic compound, advantageously a compound metal oxygenate, preferably a metal oxide precursor such as a metal alkoxide. In the case of a process for the preparation of nanoparticles based on silica for example, the precursor can be an alkyl silicate.

The precursor is advantageously a metal alkoxide. The alkoxide is generally chosen from the alkoxides of Si, Ti, Zr, Ce, Mg, and Al. Advantageously, this alkoxide is an alkoxide of Si, Ti, Zr or Ce. Quite preferably, the silicon oxide precursor is a silicon alkoxide corresponding to the general formula:

If (OR) ₄

in which R is Cι-C ₆ alkyl, preferably methyl or ethyl.

An example of an alkoxide which can be used for the present invention is methyl silicate SiO (Me) 4.

The precursor can also be a complex.

In an entirely advantageous manner, this alkoxide is previously dissolved in an alcoholic or hydroalcoholic solution.

The reaction is generally carried out in basic medium. Adding a catalyst promoting the hydrolysis of the alkoxide and the precipitation of the metal oxide, product of this hydrolysis. This oxide condenses into nanoparticles which adsorb around the latex particles, forming a uniform layer.

As catalysts, bases of the ammonia, soda or potash type are particularly suitable. These bases are added to the reaction medium in order to obtain a concentration of 0.1 to 3 mol / l of reaction medium.

By nanoparticles is meant amorphous spherical particles, with a size between 10 and 200 nm.

The amount of alkoxide used is directly dependent on the size of the nanoparticles that it is desired to obtain, knowing that these nanoparticles must form a uniform layer on the latex particles.

By way of illustration, this amount can be between 20 and 100% of the weight of polymer.

Other reaction parameters also affect the size of the nanoparticles. The parameters influencing the size of the nanoparticles include the molecular weight and the amount of stabilizing agent used. Thus, the molecular mass is advantageously between 10,000 and 60,000 g / mole. The amount of stabilizing agent is such that a concentration of between 1 and 20 g / l of reaction medium is obtained.

The temperature of precipitation of the silica and of adsorption of the nanoparticles on the latex particles can also be advantageously controlled. Thus, the latter is preferably between 20 and 30 ° C, and more preferably still equal to 25 ° C.

According to a variant of the invention, the layer of nanoparticles is obtained from hydrogen carbonates.

These amorphous compounds decompose, depending on their nature, at low temperature (from 120 ° C, CO ₂ release) or at higher temperature (from 400 ° C) into oxide (or oxohydroxide for aluminum) . They are soluble in acidic medium (pH <4) and are therefore usable for the encapsulation and the release of the active ingredients in acidic medium.

They are obtained by precipitation of salts, for example precipitation of sodium aluminate, sodium carbonate and A1C1 ₃ this at a pH between 5 and 9 for Al (OH) CO ₃ .

They can also and advantageously be obtained by thermal decomposition of urea: in the case of Y (OH) CO ₃ , urea serves as a delay base for precipitating yttrium nitrate.

The composite particles consisting of an organic polymer core, covered with a layer of inorganic nanoparticles, preferably consisting of silica, are then separated from the reaction medium, for example by centrifugation. These particles are resuspended in an alcoholic or hydroalcoholic medium, in order to proceed with the growth of the mineral coating on the nanoparticles.

To this end, these particles are brought into contact with a metallic compound, advantageously a metallic oxygenated compound, preferably a metallic oxide precursor, such as a metallic alkoxide, such as that used in the preceding step and defined above.

The temperature of the reaction medium is increased to a value advantageously between 40 and 65 ° C. Apart from the temperature, the operating conditions are in principle identical to those used for the formation of nanoparticles.

According to a first alternative of the invention and in accordance with the layer of nanoparticles, the mineral coating can be obtained from hydrogen carbonates.

According to a second alternative of the invention, the growth of the mineral coating takes place by the so-called "alkaline silicate" route.

To this end, the dispersion of latex particles is brought into contact in an aqueous medium with alkaline silicates, in the presence of sulfuric acid at a pH between 8 and 9 between 20 and 90 ° C., in order to cause the precipitation of silica , on the layer of nanoparticles.

It is advantageous to add a surfactant such as PNP to the medium, in order to avoid agglomeration of the particles.

The resulting composite particles are then dried.

This can take place directly on the suspension obtained.

It may be advantageous to wash the particles according to conventional methods, such as centrifugation for example, in the case where it is desired to subject the composite particles to a surface treatment prior to drying.

This treatment generally consists in resuspending the aqueous or aqueous-alcoholic particles in composite form, after centrifugation, then in introducing into the suspension, at least one organic compound, such as stearic acid, stearates, polysiloxane oils, among others.

This type of pretreatment makes it possible to avoid, if necessary, the agglomeration of the composite particles during this drying step.

It likewise makes it possible to confer particular properties on the particles, such as for example a hydrophobic character. This treatment also makes it possible to compatibilize the composite particles with the medium into which they will subsequently be introduced.

It will be noted that it is also possible to carry out the spray-drying operation by means of a "flash" reactor, for example of the type described in particular in French patent applications No. 2 257 326, 2 419 754 and 2,431,321. Whatever the synthetic route used for producing the shell, it can be seen that the reaction media are substantially identical. However, it has been demonstrated that the first layer of the bark is a particulate layer, while the second is a continuous layer of coating or cement type.

Thus, it is to the credit of the inventors to have demonstrated, in a completely surprising manner, that experimental modifications, in particular as regards temperature, made it possible to obtain layers of silica of different structure.

Indeed, the temperature of implementation of step (I) of the process, consisting in forming the nanoparticles and in adsorbing them on the latex particles is lower than the temperature implemented in step (II) of the process , consisting in carrying out the coating.

The release profile of the active ingredient contained in the particles depends on the porosity of the mineral coating. Thus, the pores of the coating can have a size of between 0.8 nm and 100 nm.

The inventors were able to demonstrate that the size of the pores was directly correlated to the temperature when the coating was produced. In fact, the higher the temperature, the smaller the pores obtained. Thus, it is therefore easy to obtain particles having different release profiles. Another object of the invention relates to a particle, capable of being used as an encapsulation system for at least one active principle, which comprises: a polymer core,

> a mineral bark around said core,

• a layer of mineral nanoparticles around said core, and • a mineral coating on said layer of mineral nanoparticles.

Another subject of the invention relates to the use of the encapsulation system according to the invention as an additive in the food, cosmetic, pharmaceutical, agrochemical or sanitary field, in compositions based on polymeric matrix.

Any polymeric matrix known to a person skilled in the art can be used in the context of the present invention.

The polymer matrix of the invention is preferably a thermoplastic matrix. The thermoplastic matrix according to the invention is a thermoplastic polymer.

By way of example of polymers which may be suitable for the encapsulation system according to the invention, mention may be made of: polylactones such as poly (pivalolactone), poly (caprolactone) and polymers of the same family; polyurethanes obtained by reaction between diisocyanates such as 1,5-naphthalene diisocyanate; p-phenylene diisocyanate, m-phenylene diisocyanate, 2,4-toluene diisocyanate, 4,4'- diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenyl-methane diisocyanate, 3,3-'dimethyl-4,4'-biphenyl diisocyanate, 4,4'-diphenylisopropylidene diisocyanate, 3,3 '-dimethyl-4,4'-diphenyl diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, dianisidine diisocyanate, toluidine diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanatodiphenylmethane and compounds of the same family and diols with long linear chains such as poly (tetramethylene adipate), poly (ethylene adipate), poly (1,4-butylene adipate ), poly (ethylene succinate), poly (2,3-butylene succinate), polyether diols and compounds of the same family; polycarbonates such as poly [methane bis (4-phenyl) carbonate], poly [l, l-ether bis (4-phenyl) carbonate], poly [diphenylmethane bis (4-phenyl) carbonate], poly [l , l-cyclohexane bis (4-phenyl) carbonate] and polymers of the same family; polysulfones; polyethers; polyketones; polyamides such as poly (4-amino butyric acid), poly (hexamethylene adipamide), poly (6-aminohexanoic acid), poly (m-xylylene adipamide), poly (p-xylylene sebacamide), poly ( 2,2,2-trimethyl hexamethylene terephthalamide), poly (metaphenylene isophthalamide), poly (p-phenylene terephthalamide), and polymers of the same family; polyesters such as poly (ethylene azelate), poly (ethylene-1,5-naphthalate), poly (1,4-cyclohexane dimethylene terephthalate), poly (ethylene oxybenzoate), poly (para-hydroxy benzoate), poly (1,4-cyclohexylidene dimethylene terephthalate), poly (1,4-cyclohexylidene dimethylene terephthalate), polyethylene terephthalate, polybutylene terephthalate and polymers of the same family; poly (arylene oxides) such as poly (2,6-dimethyl-1,4-phenylene oxide), poly (2,6-diphenyl-1,4-phenylene oxide) and polymers of the same family; poly (arylene sulfides) such as poly (phenylene sulfide) and polymers of the same family; polyetherimides; vinyl polymers and their copolymers such as polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride; polyvinyl butyral, polyvinylidene chloride, ethylene-vinyl acetate copolymers, and polymers of the same family; acrylic polymers, polyacrylates and their copolymers such as polyethyl acrylate, poly (n-butyl acrylate), polymethylmethacrylate, polyethyl methacrylate, poly (n-butyl methacrylate), poly (n-propyl methacrylate), polyacrylamide, polyacrylonitrile, poly (acrylic acid), ethylene-acrylic acid copolymers, ethylene-vinyl alcohol copolymers, acrylonitrile copolymers, methyl methacrylate-styrene copolymers, ethylene-ethyl acrylate copolymers , methacrylate-butadiene-styrene copolymers, ABS, and polymers of the same family; polyolefins such as low density poly (ethylene), poly (propylene), low density chlorinated poly (ethylene), poly (4-methyl-1-pentene), poly (ethylene), poly (styrene), and polymers of the same family; ionomers; poly (epichlorohydrins); poly (urethane) as products of polymerization of diols such as glycerin, trimethylol-propane, 1,2,6-hexanetriol, sorbitol, pentaerythritol, polyether polyols, polyester polyols and compounds of the same family with polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicycohexylmethane diisocyanate and compounds of the same family; and polysulfones such as the reaction products between a sodium salt of 2,2-bis (4-hydroxyphenyl) propane and 4,4'-dichlorodiphenyl sulfone; furan resins such as poly (furan); cellulose-ester plastics such as cellulose acetate, cellulose acetate butyrate, cellulose propionate and polymers of the same family; silicones such as poly (dimethyl siloxane), poly (dimethyl siloxane co-phenylmethyl siloxane), and polymers of the same family; mixtures of at least two of the above polymers.

According to a particular variant of the invention, the thermoplastic matrix is a polymer comprising star or H macromolecular chains, and where appropriate linear macromolecular chains. The polymers comprising such star or H macromolecular chains are for example described in the documents FR 2 743 077, FR 2 779 730, US 5 959 069, EP 0 632 703, EP 0 682 057 and EP 0 832 149.

According to another particular variant of the invention, the thermoplastic matrix of the invention is a polymer of statistical tree type, preferably a copolyamide having a statistical tree structure. These copolyamides with a statistical tree structure and their process for obtaining are described in particular in document WO 99/03909.

The thermoplastic matrix of the invention can also be a composition comprising a linear thermoplastic polymer and a star, H and / or tree thermoplastic polymer as described above.

Yet another object of the invention relates to the use of an encapsulation system as defined above, as an additive in the food, cosmetic, pharmaceutical, agrochemical or sanitary field.

Yet another object of the present invention relates to a composition based on a polymer matrix, which comprises as additive at least one encapsulation system according to the invention.

The polymer composition of the invention comprises a polymer matrix. The compositions of the invention can also comprise a hyperbranched copolyamide of the type of those described in document WO 00/68298. The compositions of the invention can also comprise any combination of star, H, tree, hyperbranched copolyamide thermoplastic polymer described above.

As another type of polymer matrix which can be used in the context of the invention, mention may be made of thermostable polymers: these polymers are preferably infusible or have a softening point greater than 180 ° C., preferably 200 ° C. , or higher. These thermostable polymers can, for example, be chosen from aromatic polyamides, imide polyamides such as polytrimellamide -imide, or polyimides such as polyimides obtained according to document EP 0 1 19 185, known commercially under the trade name P84. The aromatic polyamides can be as described in patent EP 0 360 707. They can be obtained according to the process described in patent EP 0 360 707.

As another polymeric matrix, mention may also be made of viscose, cellulose, cellulose acetate, etc. The polymer matrix of the invention can also be of the type of polymers used in adhesives, such as plastisol vinyl acetate copolymers, acrylic latexes, urethane latexes, plastisol PNCs etc.

Among these polymeric matrices, very particularly preferred are the semi-crystalline polyamides, such as polyamide 6, polyamide 6.6, polyamide 11, polyamide 12, polyamide 4, polyamides 4-6, 6-10, 6-12 , 6-36, 12-12, semi-aromatic polyamides obtained from terephthalic and / or isophthalic acid such as the polyamide sold under the trade name AMODEL; polyesters such as PET, PBT, PTT; polyolefins such as polypropylene, polyethylene; aromatic polyamides, polyamide imide or polyimides; latexes such as acrylic and urethane latexes; PVC, viscose, cellulose, cellulose acetate; their copolymers and alloys.

The compositions can contain all the other additives which can be used, for example reinforcing fillers, flame retardants, stabilizers with UN, with heat, matifiers such as titanium dioxide. The proportion by weight of encapsulation system used as an additive in these compositions is preferably less than or equal to 10%.

Yet another object of the invention relates to yarns, fibers, filaments and articles obtained from the compositions described above. In fact, the compositions according to the invention can be shaped into threads, fibers and filaments by spinning. They can also be shaped into molded articles, for example by injection or by extrusion. The yarns, fibers and filaments of the invention can be obtained for example by melt spinning or by wet spinning, from the compositions of the invention.

The compositions are preferably produced by introducing the composite particles into the molten polymer in a mixing device, for example upstream of a spinning device. They can also be produced by introducing the composite particles into a polymer solution, for example upstream of a wet spinning device.

By spinning the compositions of the invention, it is possible, for example, to obtain continuous multifilament yarns, short or long fibers, monofilaments, fiber yarns, plies, ribbons, cables, etc. It can also be continuous swelling yarns (BCF: "Bulk Continuous Filament"), used in particular for the manufacture of textile coverings, such as carpets and rugs.

All the conventional treatments in the textile field can be applied to the yarns, fibers and filaments of the invention, such as drawing, texturing, dyeing, etc. The yarns, fibers and filaments described above then exhibit the properties of the active principle contained in the composite particles, permanently. These can be, for example, anti-mite properties, which are particularly sought after in the textile field.

The invention also relates to articles obtained from the yarns, fibers, filaments described above. Such articles can be obtained in particular from a single type of son, fibers, filaments or on the contrary from a mixture of son, fibers, filaments of different types. The article comprises at least in part yarns, fibers, filaments according to the invention. For a given type of yarns, fibers, filaments - for example yarns, fibers, filaments not containing composite particles -, yarns, fibers or filaments of different natures can be used in the article of the invention.

As articles, mention may be made, for example, of woven, non-woven, knitted articles. The present invention also relates to composite textile articles, that is to say multi-component textile articles. These components can be, for example, short fibers, supports, adhesives or glues, articles obtained from yarns, fibers, filaments such as nonwoven articles, etc.

As composite textile articles, mention may be made, for example, of flocked surfaces, the main components of which are generally short fibers, an adhesive or glue, and a support.

Mention may also be made of tufted surfaces used in particular in carpets, furniture or wall coverings, etc., the main components of which are generally yarns, fibers, filaments or articles obtained from yarns, fibers, filaments, a support. , and possibly an adhesive or glue. In the context of the invention, at least one of the components of the composite textile article comprises composite particles.

In a flocked surface for example, the composite particles may be present in the fibers of the flocked surface and / or in the glue or adhesive used for flocking and / or in the support of the flocked surface.

The fibers of a flocked surface can for example be fibers according to the invention. The adhesive or glue of a flocked or tufted surface can be obtained from a composition according to the invention. The support for a flocked or tufted surface can also be obtained from a composition or an article according to the invention. Thus, if the active principle trapped in the particles is a bioactive agent and in particular an anti-mite, textile articles will have permanent anti-mite properties.

Compositions, threads, fibers, filaments, articles and composite textile articles may for example be used in the manufacture of any product liable to be in contact with mites, such as carpets, rugs, upholstery , surface coverings, sofas, curtains, bedding, mattresses and pillows etc.

The invention will be better understood on reading the nonlimiting examples below, presented by way of illustration.

EXAMPLES

Example 1: Encapsulation of benzyl benzoate within polystyrene / silica particles (double layer) (test 01ADH009)

1 / Preparation of polystyrene particles - Solution 1:

Absolute ethanol: 340g Polyvinylpyrrolidone (PNP) K30 (MM = 40000): 7.2 g

Aerosol OT 75% (Sodium dioctylsulfosuccinate sodium marketed by CYAΝAMID): 2,665 g

Solution 2: Styrene: 60 g

Azotrisisobutyronitrile: 0.65 g Solution 1 and solution 2 are mixed in an IL flask, then the mixture is degassed for 15 minutes with nitrogen. Then, the solution is heated to 71 ° C and maintained for 16 hours at this temperature. The mixture is left to settle in the cold, the mother liquors are removed and redispersed in an equivalent volume of water.

Latex characteristics: Dry extract: 11.15% Particle size: 2 μm

2 / Incorporation of benzyl benzoate in the latex

In an IL flask, 86.5 g of polystyrene latex (size 2 μm) of dry extract 11.15% qs 100 g are mixed with water permuted to have a 10% latex, with a solution containing 1 g of benzyl benzoate dissolved in 180 g of acetone. The whole is heated for 2 hours at 45 ° C.

After these two hours, the acetone is distilled at 45 ° C., with a vacuum of 400 mbar.

3 / Depositing a layer of silica nanoparticles In a 2L reactor fitted with a stirring anchor rotating at 300 rpm, the following are introduced:

- 288.7 g of absolute ethanol

- 20.7 g of 20% ammonia

85 g of the preparation from step 2 / (i.e. 0.85 g of benzyl benzoate)

- a solution containing 0.22 g of PNP K30 (MM = 40,000) in 7.5 ml of absolute ethanol.

The whole is maintained at 25 ° C., then 10 g of tetraethoxysilane (TEOS) diluted in 50 ml of absolute ethanol are added continuously at 0.17 ml / min.

It is left to mature for 2 hours and then the particles are recovered.

4 / Deposit of the silica coating

The procedure is carried out under the same conditions as in step 3 /, with the difference that the reaction temperature is 45 ° C.

At the end of the addition of the 10 g of TEOS, it is left to mature for 2 hours at 45 ° C., then the whole is centrifuged at 4500 rpm for 30 minutes. The pellet obtained is dried at 25 ° C. The level of benzyl benzoate in the particles is 5%.

Characterization of the particles obtained

1 / Benzyl benzoate level in the particles First, the benzyl benzoate present in the mother liquors of encapsulation synthesis is assayed. Mass of mother liquor recovered: 378.7 g

If all of the benzyl benzoate was in the mother liquors, 0.224% of benzyl benzoate should be measured (0.85 / 378.7 = 0.224%).

The result of the determination in the mother liquors is 0.11%. It can therefore be deduced that 51.9% of the benzyl benzoate has been encapsulated. As a result, in the solid, there is 5% benzyl benzoate.

2 / Elution rate in acetone 1 g of finished product (latex particle containing benzyl benzoate + silica shell) is dispersed in 100 ml of acetone for 48 hours. The dosage of benzyl benzoate gives 170 ppm.

Knowing that if all the benzyl benzoate was eluted, the result would have been 220 ppm, we can deduce that 77% of the benzyl benzoate is eluted. The molecule can therefore diffuse through the particle.

Example 2: Encapsulation of Kertex® within polystyrene / silica particles (double layer) (test 01ADH015)

1 / Preparation of polystyrene particles The procedure is as in Example 1.

2 / Incorporation of Kertex® in the latex

- Solution 1:

In an IL flask, 173 g of polystyrene latex (size 2 μm) of dry extract 11.15% qs 200 g are mixed with water permuted to have a 10% latex.

- Solution 2:

3 g of Kertex® dissolved in 300 g of acetone are dissolved. Solutions 1 and 2 are mixed in the IL flask which is then placed on a ROTANAPOR® rotary evaporator. The whole is heated for 2 hours in a water bath at 45 ° C, to achieve swelling. After these two hours, the acetone is distilled at 45 ° C., with a vacuum of 400 mbar.

Mass of acetone recovered: 287 g. Latex + Kertex® mass recovered: 201.5 g.

3 / Depositing a layer of silica particles In a 2L reactor fitted with a stirring anchor rotating at 300 rpm, the following are introduced:

574 g of absolute ethanol

- 41.4 g of 20% ammonia

- 201.5 g of latex + Kertex® obtained in step 2 / - 0.44 g of PNP K30 (MM = 40000)

- 120 g of water.

The whole is maintained at 25 ° C., then 40 g of tetraethoxysilane (TEOS) diluted in 150 ml of absolute ethanol are added continuously for 4.5 h. The mixture is left stirring overnight and the particles are recovered.

4 / Deposition of the silica coating The procedure is carried out under the same conditions as in step 3 /, with the difference that the reaction temperature is 45 ° C.

At the end of the addition of the 40 g of TEOS, the mixture is left stirring for 2 hours at 45 ° C., then the whole is centrifuged at 4500 rpm for 30 minutes.

The centrifugation pellets are resuspended in a volume of water equivalent to the volume of mother liquor and the whole is again centrifuged for 30 minutes at 4000 rpm.

The pellets are then dried in the open air for 1 night, then at 50 ° C. for 7 hours.

We recover a white solid: m = 40g

The silica content relative to the latex is 115%. Example 3: Encapsulation of Kertex® within polystyrene particles (test 01ADH016)

1 / Preparation of polystyrene particles The procedure is as in Example 1.

2 / Incorporation of Kertex® in the latex Solution 1:

In an IL flask, 87 g of polystyrene latex (size 2 μm) of dry extract 11.15% qs 100 g are mixed with water permuted to have a 10% latex. Solution 2: 1 g of Kertex® dissolved in 152 g of acetone is dissolved.

Solutions 1 and 2 are mixed in the IL flask which is then placed on a ROTANAPOR® rotary evaporator. The whole is heated for 2 hours in a water bath at 45 ° C, to achieve swelling.

The latex + Kertex® recovered is centrifuged at 4000 rpm for 15 minutes.

The pellet obtained is then dried in the open air, m = 11 g.

EXAMPLE 4 Encapsulation of 7213 (Agrochemical Active Principle) within Polystyrene / Silica Particles

1 / Preparation of polystyrene particles The procedure is as in Example 1.

2 / Incorporation of 7213 into the latex

In an IL flask, 86.5 g of polystyrene latex (size 2 μm) of dry extract 11.15% qs 100 g are mixed with water permuted to have a 10% latex, with a solution containing 1 g of 7213 dissolved in 180 g of acetone. The whole is heated for 2 hours at 45 ° C.

After these two hours, the acetone is distilled at 45 ° C., with a vacuum of 400 mbar. 3 / Deposit of a layer of silica particles

In a 2L reactor fitted with a stirring anchor rotating at 300 rpm, the following are introduced:

- 288.7 g of absolute ethanol - 20.7 g of 20% ammonia

- 42.5 g of the preparation from step 2 / (i.e. 0.0425 g of 7213)

- a solution containing 0.11 g of PNP K30 (MM = 40,000) in 7.5 ml of absolute ethanol.

The whole is maintained at 25 ° C., then added continuously at 0.17 ml / min,

20 g of tetraethoxysilane (TEOS) diluted in 50 ml of absolute ethanol.

It is left to mature for 2 hours and then the particles are recovered.

4 / Deposition of the silica coating The procedure is carried out under the same conditions as in step 31, with the difference that the reaction temperature is 45 ° C.

At the end of the addition of the 20 g of TEOS, it is left to mature for 2 hours at 45 ° C., then the whole is centrifuged at 4500 rpm for 30 minutes. The supernatant is kept for the assay of 7213.

The pellet obtained is dried at 25 ° C.

Characterization of particles:

Level of 7213 in the particles Initially, the 7213 present in the mother liquors of encapsulation synthesis is assayed.

Mass of mother liquor recovered: 378.7 g

If all 7213 was in mother liquor, we should measure 0.0112% (112 ppm) of 7213

(0.0425 / 378.7 = 0.0112%). The result of the determination in mother liquors is 54 ppm.

We can therefore deduce that 48.2% of the 7213 was encapsulated.

As a result, in the solid, there is 0.13% of 7213.

Determination of 7213 by HPLC 16.9 g of finished product is dispersed (latex particle containing 7213 + silica bark) in IL of water in order to use 22 ppm of 7213 and samples are taken over time, in which 7213 is assayed by HPLC. After 22 hours of contact, it is found that only 0.1 ppm of 7213 has been released.

Example 5: Preparation of samples of polyamide 6.6 powder with or without capsules and characterization.

1 / Preparation of the samples The polyamide 6.6 used is a polyamide 6.6 (PA 6.6) not comprising titanium dioxide, with a relative viscosity of 2.5 (measured at a concentration of 10 g / 1 in sulfuric acid 96%).

The incorporation of the capsules in PA 6.6 is done by mixing. The mixture is dried for 16 hours at 80 ° C. under vacuum of approximately 50 mbar and then introduced into a twin-screw extrusion device which ensures mixing in the molten phase. The incorporation rate of the capsules is 1 to 1.5% by weight relative to the total weight of the composition, depending on the percentage of active ingredient in the capsule. The incorporation rate is adjusted so as to obtain a final incorporation rate of 0.1% w / w of active ingredient in the matrix.

The rod obtained at the outlet of the extrusion device is soaked in water at approximately 20 ° C. then crushed and ground with an ultra-centrifugal Retsch ZM 1000 mill. The particle size of the powder obtained is less than 500 μm.

The operating characteristics of the extruder are specified below p Fade temperature: approximately 282 ° C α Screw speed: 100 revolutions / min α Fade residence time: 4 minutes.

The following samples were produced:

2 / Characterization of the samples by gel permeation chromatography

The powder obtained from the rod exited from the extruder was characterized by a measurement of the molar mass of the matrix. The molar mass measurement is carried out by gel permeation chromatography (GPC) in dichloromethane after derivatization with trifluoroacetic anhydride, compared to standard solutions of polystyrene (PS). The detection technique used is refractometry. The molecular mass of the matrix is estimated as the maximum of the refractometric peak. The results obtained on the powders prepared are specified below.

3 / Characterization of the samples by Yellow Index The powder obtained from the rod exited from the extruder was characterized by a measure of yellow index according to the DLN 6167 standard. The measurements were carried out on a Minolta CR 300 using Illuminant D 65. The results obtained are as follows.

The yellow index is correlated with the degradation of the active ingredient contained in the powder. It can be deduced therefrom that the benzyl benzoate is little degraded during extrusion. Kertex® is more sensitive to the extrusion temperature and therefore more highly degraded, especially when it is incorporated in polystyrene particles without mineral shell (composition D). The mineral bark, consisting of the layer of silica nanoparticles and the silica coating, therefore makes it possible to protect the active ingredient contained in the polystyrene particles.

Example 6 Characterization of the behavior with respect to the mites of the samples of polyamide 6.6 powder / capsules obtained according to example 1 1 / Principle:

This characterization is carried out by a laboratory approved by the Ministry of Agriculture, Fisheries and Food. The objective is to assess the effectiveness of PA powders with or without additives in the control of the evolution of a population of dust mites (Oermatophagoides pteronyssinus). The follow-up is carried out over two mite development cycles, i.e. 6 weeks.

2 / Original mite breeding:

The mites used come from a laboratory strain raised on a substrate composed of a 50/50 mixture (w / w) of wheat germ and brewer's yeast in flakes calibrated by sieving (fragments less than 1 mm). The temperature is between 23 and 25 ° C and the relative humidity maintained at 75% by bringing together a saturated solution of ammonium sulfate. The strain is kept in the dark.

The strain is supplied by the Laboratory of Insects and Mites of Foodstuffs of the National Institute of Agronomic Research of Bordeaux (INRA) according to AFNOR standard NF G 39-011.

3 / Experimental method: The method is directly inspired by the AFNOR NF G 39-011 standard with the following variants: ^α The experimental unit consists of an enclosure of 8 cm in diameter, tight against mites but allowing ventilation and in which is:

"5 g of nutrient medium (food 1 / appendix NF G 39-011)" 5 g of powder to be tested, covering the bottom of the enclosure

^D the research is carried out by depositing 50 mites in these devices ^D 4 repetitions are carried out the same day by experimental factor, including for the control batches made up of the same device but with the powder not additivated.

The control consists of counting the number of living mites after the 6-week period. Since direct counting is made impossible by the structure of the substrate, heat extraction is used according to the recommendations of standard AFNOR NF G 39-011. The efficiency criterion of an additive is then defined as the control coefficient of the mite population (CP), ie: (Population on non-additive powder - population on additive powder)

CP = X 100

Population on non-additive powder

The population counts are all carried out at 6 weeks.

The interpretation of CP is as follows: ^D Plus CP will be close to 0 and the less additivation will be effective since the population on the additivated sample will grow at the same rate as that on the non-additivated sample; ^π The closer CP is to 100, the more effective the additivation will be by eradicating the mite population and halting its expansion process.

4 / Experimental results: The following tables present the synthesis of the data for the different experimental series:

The natural expansion of the mites on the non-additive powders validates the test insofar as it confirms the extremely favorable conditions to which the powders are subjected: the populations of mites not subjected to the additive have in fact an increase factor over 15.

Furthermore, it is found that the results obtained with composition D are equivalent to those obtained with composition C. These results do not call into question the fact that the kertex® contained in composition D was deteriorated during extrusion.

Indeed, it appears that the degradation products of kertex® retain their anti-mite properties.

Claims

1. System for encapsulating at least one active principle comprising at least one composite particle comprising at least: - a core comprising the active principle,

a mineral bark around said heart, said encapsulation system being characterized in that the mineral bark is obtained in two stages: the first stage consisting of the formation of mineral nanoparticles and their adsorption on said heart in the form of a layer ; ^• the second step consisting in the formation of a mineral coating formed on said nanoparticles.

2. Encapsulation system according to the preceding claim, characterized in that the core further comprises at least one polymer, preferably organic.

3. Encapsulation system according to any one of the preceding claims, characterized in that the mineral shell is based on at least one oxide and / or a metal oxide precursor.

4. Encapsulation system according to the preceding claim, characterized in that the mineral shell is based on a compound chosen from the group comprising metal oxides and their mixed oxides, such as oxides of titanium, aluminum, zinc, copper, zirconium, and cerium, calcium sulfate, strontium and barium compounds, zinc sulfide, copper sulfide, zeolites, mica, talc, kaolin, mullite , silica, aluminum hydrogen carbonates or halocarbonates, calcium phosphate compounds such as calcium hydroxyapatite and / or mixtures thereof.

5. Encapsulation system according to one of claims 2 to 4, characterized in that the organic polymer is obtained from one or more unsaturated monomers immiscible with water and polymerizable by the radical route.

6. Encapsulation system according to the preceding claim, characterized in that the monomers are chosen from vinyl aromatic monomers, alkyl esters of ethylenically unsaturated α-β acids, vinyl esters of carboxylic acids, vinyl or vinylidene halides, conjugated aliphatic dienes and ethylenically unsaturated α- β nitriles.

7. Encapsulation system according to any one of claims 5 or 6, characterized in that the monomers are chosen from styrene, butadiene, racryloπitrile, chloropropene, vinyl chloride or vinylidene chloride, isopropene, l isobutylene, vinyl acetate, propylene, butylene and vinylpyrrolidone.

8. Encapsulation system according to any one of claims 2 to 7, characterized in that the organic polymer further comprises at least one co-monomer carrying ionogenic groups polymerizable by the radical route.

9. Encapsulation system according to the preceding claim, characterized in that the co-monomer carrying ionogenic groups is chosen from α-β ethylenically unsaturated carboxylic acids, ethylenic sulfonated monomers, hydroxyalkyl esters of α-β ethylenically unsaturated acids hydroxypropyl, amides of ethylenically unsaturated α-β acids and amino esters of ethylenically unsaturated α-β acids.

10. Encapsulation system according to any one of the preceding claims, characterized in that the active principle is chosen from the group comprising: anti-mites, antifungals, antibacterials, mosquito repellents, cosmetic active principles, pharmaceutical active ingredients, agrochemical active ingredients, anti-UN.

11. Encapsulation system according to any one of the preceding claims, characterized in that the proportion of active principle by weight relative to the total weight of the particle is less than or equal to 50%.

12. Method for preparing the particles forming the encapsulation system according to one of claims 1 to 11, characterized in that it mainly comprises the following steps:

(I) the formation of nanoparticles and the adsorption of the nanoparticles thus formed on the cores comprising the active principle, such that the nanoparticles form a layer around said cores;

(II) the growth of a mineral coating on the layer of nanoparticles, said nanoparticles serving as seeds for the growth of the coating layer, and (III) optionally drying and recovering the particles thus obtained.

13. Method according to claim 12, characterized in that, when the cores are based on at least one polymer, said cores are obtained beforehand during a step of radical polymerization in emulsion of unsaturated monomers immiscible with water and polymerizable as defined in claims 5 to 9.

14. Method according to one of claims 12 or 13, characterized in that the step of preparation of the organic polymer cores is carried out in the presence of at least one emulsifier.

15. The method of claim 14, characterized in that the emulsifier is an anionic emulsifier taken from the group consisting of fatty acid salts, alkylsulfates, alkylsulfonates, alkylarylsulfonates, alkylsulfosuccinates, alkaline alkylphosphates, alkyl sulfosuccinates, sulfonates of alkylphenolpolyglycolic ethers; the condensation products of fatty acids with oxy- and aminoalkanesulfonic acids; sulfated derivatives of polyglycolic ethers, sulfated esters of fatty acids and polyglycols, alkanolamides of sulfated fatty acids.

16. The method of claim 14, characterized in that the emulsifier is a nonionic emulsifier taken from the group consisting of fatty esters of polyalcohols, alkanolamides of fatty acids, polyethylene oxides, alcohols and oxyethylenated alkylphenols, alcohols and oxyethylenated and sulfated alkylphenols.

17. Method according to one of claims 13 to 16, characterized in that the active principle is incorporated in the dispersion at the same time as the monomers prior to the polymerization step.

18. Method according to one of claims 13 to 16, characterized in that the incorporation of the active principle within the core of organic polymer is carried out by bringing said core of organic polymer in dispersion into contact with said active principle, where appropriate if necessary, dissolved in a transfer solvent.

19. Method according to any one of claims 12 to 18, characterized in that the formation of the layer of nanoparticles is obtained by bringing the cores into contact with a metallic compound, advantageously an oxygenated metallic compound, preferably a metal oxide precursor, such as for example a metal alkoxide and by precipitation of said metal compound.

20. Method according to the preceding claim, characterized in that the metallic compound is a silicon alkoxide corresponding to the general formula:

If (OR) ₄

in which R is Cι-C ₆ alkyl, preferably methyl or ethyl.

21. Method according to one of claims 12 to 20, characterized in that the growth of the mineral coating on the layer of nanoparticles is obtained by bringing the hearts covered with the layer of nanoparticles into contact with a metallic compound as defined in claims 19 or 20 and by precipitation of said metallic compound.

22. Method according to any one of claims 12 to 20, characterized in that the growth of the mineral coating on the layer of nanoparticles is obtained by the alkaline silicate route, consisting in bringing the cores covered with the layer of nanoparticles with an alkaline silicate and by precipitation of the corresponding silicon oxide.

23. Method according to any one of claims 12 to 22, characterized in that at least one stabilizing agent is used, of the polyethoxylated alkylphenol, polyethylene glycol or polyvinylpyrrolidone type.

24. Method according to any one of claims 12 to 25, characterized in that the processing temperature of step (II) is higher than the processing temperature of step (I).

25. Method according to any one of claims 12 to 26, characterized in that the implementation temperature of step (I) is between 20 and 30 ° C, preferably equal to 25 ° C.

26. Method according to any one of claims 12 to 27, characterized in that the processing temperature of step (II) is between 40 and 65 ° C.

27. Particle, capable of being used as an encapsulation system for at least one active principle, characterized in that it comprises:

- a polymer core,

- a mineral shell around said heart, ^• a layer of mineral nanoparticles around said heart and

^• a mineral coating on said layer of mineral nanoparticles.

28. Use of an encapsulation system according to any one of claims 1 to 11 or obtained from the process according to any one of claims 12 to 26, as an additive in compositions based on polymeric matrix.

29. Use of an encapsulation system according to any one of claims 1 to 11 or obtained from the process according to one of claims 12 to 26, as an additive in the food, cosmetic, pharmaceutical, agrochemical or health.

30. Composition based on a polymer matrix, characterized in that it comprises as additive at least one encapsulation system according to one of claims 1 to 11 or obtained from the process according to one of claims 12 to 26 .

31. Composition according to the preceding claim, characterized in that the polymer matrix is a polyamide matrix.

32. Composition according to any one of claims 30 or 31, characterized in that the proportion by weight of encapsulation system is less than or equal to 10%.

33. Fibers, threads, filaments and granules obtained by shaping the composition according to one of claims 30 to 32.

34. Articles obtained from fibers, threads, filaments or granules according to the preceding claim.