EP2516521A1

EP2516521A1 - Method for treating the surface of a device for dispensing a fluid product

Info

Publication number: EP2516521A1
Application number: EP10808921A
Authority: EP
Inventors: Pascal Bruna; Serge Herry; Matthieu Laurent; Fabien Nekelson; Sébastien ROUSSEL
Original assignee: Aptar France SAS
Current assignee: Aptar France SAS
Priority date: 2009-12-23
Filing date: 2010-12-22
Publication date: 2012-10-31
Also published as: CN102639618A; JP2013515803A; US20120318677A1; FR2954330B1; WO2011077049A1; FR2954330A1

Abstract

The invention relates to a method for treating the surface of a device for dispensing a fluid product, said method comprising a chemical grafting step in order to form a thin film on at least one supporting surface of at least one component of said device, which is in contact with the fluid product, said thin film preventing interaction between the fluid product and said component.

Description

Surface treatment method of a fluid dispensing device

The present invention relates to a surface treatment method for fluid dispensing devices.

Dispensing devices for fluid products are well known. They may comprise one or more reservoirs, a dispensing member, such as a pump, a valve or a piston displaceable in the reservoir, and a dispensing head provided with a dispensing orifice. These dispensing devices generally comprise component parts made of various materials. Thus, the tank may be of plastic or synthetic material, glass or metal. Various parts, such as pistons or seals may be made of flexible plastic materials, such as elastomers. Other parts are generally metallic, for example crimping capsules, springs or balls forming a valve. In particular in the pharmaceutical field, the risks of interaction between the fluid product to be dispensed and these different materials can be harmful for said fluid product. These interactions may include releasing molecules of these materials into the fluid product. For example, these interactions can degrade certain active ingredients, such as hormones, peptides or enzymes, especially in nasal spray devices.

Existing surface treatment methods all have disadvantages. Thus, some processes can only be used on flat surfaces. Other methods require a limited choice of substrate, for example gold. The plasma-induced polymerization of molecules is complex, expensive, and the resulting coating layer is difficult to control and has aging problems. Similarly, ultraviolet-induced polymerization of molecules is also complex and expensive, and only works with photosensitive molecules. The same is true of atom transfer radical polymerization (ATRP), which is also complex and expensive. Finally, electrografting processes are complex and require conductive support surfaces.

The present invention aims to provide a surface treatment method that avoids the aforementioned drawbacks.

In particular, the present invention aims to provide a surface treatment method that is effective, durable, non-polluting and simple to achieve.

The present invention therefore relates to a surface treatment method of a fluid dispenser device, said method comprising the step of forming by chemical grafting a thin film on at least one support surface of at least a part constituent in contact with said fluid product, said thin film preventing interactions between said fluid product and said constituent part.

In an advantageous embodiment, said grafting step comprises contacting said surface in contact with the fluid product with a solution comprising at least one adhesion primer, said adhesion primer being a cleavable aryl salt and at least one monomer or a polymer selected from the group consisting of vinyl-terminated or acrylic-terminated siloxanes and acrylic or vinyl monomers.

Advantageously, said chemical grafting creates covalent bonds between the molecules of said thin film and said support surface. This creates a strong and lasting connection over time.

Advantageously, said chemical grafting is carried out in an aqueous medium. This allows a non-polluting or green chemistry, which does not present risks for the environment.

In one embodiment, the cleavable aryl salt is selected from the group consisting of aryl diazonium salts, aryl ammonium salts, aryl phosphonium salts, aryl sulfonium salts and aryl salts. iodonium.

The cleavable aryl salts are chosen from compounds of the general formula ArN ₂ ⁺ , X ^" in which Ar represents the aryl group and X ^" represents an anion. The aryl group in an organic compound is a functional group derived from an aromatic ring.

In one embodiment, the anions X ^"are selected from inorganic anions such as halides, such as, ^Cl" or Br ^", the halogenoborates such as tetrafluoroborate and organic anions such as alcoholates, carboxylates, perchlorates and sulfonates.

In one embodiment, the Ar aryl groups are chosen from aromatic or heteroaromatic compounds, optionally mono- or polysubstituted, consisting of one or more aromatic rings of 3 to 8 carbons. The heteroatoms of the heteroaomatic compounds are chosen from N, O, P and S. The substituents may contain alkyl groups and one or more heteroatoms such as N, O, F, Cl, P, Si, Br or S.

In one embodiment, the aryl groups are chosen from aryl groups substituted with attracting groups such as NO 2, COH, CN, CO ₂ H, ketones, esters, amines and halogens.

In one embodiment, the aryl groups are selected from the group consisting of phenyl and nitrophenyl.

In one embodiment, the cleavable aryl salt is selected from the group consisting of phenyldiazonium tetrafluoroborate, 4-nitrophenyldiazonium tetrafluoroborate, 4-bromophenyldiazonium tetrafluoroborate, 4-aminophenyldiazonium chloride, 4- aminomethylphenyldiazonium, 2-methyl-4-chlorophenyldiazonium chloride, 4-benzoylbenzenediazonium tetrafluoroborate, 4-cyanophenyldiazonium tetrafluoroborate, 4-carboxyphenyldiazonium tetrafluoroborate, 4-acetamidophenyldiazonium tetrafluoroborate, 4-phenylacetic acid tetrafluoroborate diazonium, 2-methyl-4 - [(2-methylphenyl) diazenyl] benzenediazonium sulfate, 9,10-dioxo-9,10-dihydro-1-anthracenediazonium chloride, 4-nitronaphthalenediazonium tetrafluoroborate and tetrafluoroborate naphthalenediazonium.

In one embodiment, the cleavable aryl salt is selected from the group consisting of 4-nitrophenyldiazonium tetrafluoroborate, the 4-aminophenyldiazonium chloride, 2-methyl-4-chlorophenyldiazonium chloride, 4-carboxyphenyldiazonium tetrafluoroborate.

In one embodiment, the salt concentration of cleavable aryl is between 5.10 ^"3 M and ^{10" 1} M.

In one embodiment, the concentration of cleavable aryl salt is of the order of 5.10 ^-2 M.

In one embodiment, the cleavable aryl salt is prepared in situ.

Advantageously, said chemical grafting step is initiated by chemical activation of a diazonium salt to form an anchoring layer for said thin film.

Advantageously, said chemical grafting step is initiated by chemical activation.

In one embodiment, said chemical activation is initiated by the presence of a reducing agent in the solution.

In one embodiment, the solution comprises a reducing agent.

By reducing agent is meant a compound which in an oxidation-reduction reaction yields electrons. According to one aspect of the present invention, the reducing agent has a redox potential whose potential difference with respect to the oxidation-reduction potential of the cleavable aryl salt is between 0.3 V and 3 V.

According to one aspect of the invention, the reducing agent is selected from the group consisting of reducing metals which may be in finely divided form such as iron, zinc, or nickel, a metal salt which may be in the form of metallocene and an organic reducing agent such as hypophosphorous acid, ascorbic acid.

In one embodiment, the concentration of reducing agent is between 0.005 M and 2 M.

In one embodiment, the concentration of reducing agent is of the order of 0.6 M.

In one embodiment, said thin film has a thickness of less than 1 micrometer, between 10 and 2000 angstroms, advantageously between 10 and 800 angstroms, preferably between 400 and 1000 angstroms. No conventional coating technique makes it possible to obtain such thin layers chemically grafted.

The term "vinyl or acrylic terminated siloxane" means a saturated hydride of silicon and oxygen formed of straight or branched chains, of alternating silicon and oxygen atoms comprising vinyl units or terminal acrylic units.

In one embodiment, the vinyl-terminated or acrylic-terminated siloxanes are chosen from the group consisting of polyalkylsiloxanes with acrylic or vinyl terminations, such as vinyl-terminated or acrylic-terminated polymethylsiloxane, and vinyl-terminated or acrylic-terminated polydimethylsiloxane, such as polydimethylsiloxane-acrylate (PDMS). acrylate), vinyl-terminated or acrylic-terminated polyarylsiloxanes such as vinyl-terminated or acrylic-terminated polyphenylsiloxane, such as polyvinylphenylsiloxane, vinyl-terminated or acrylic-terminated polyarylalkylsiloxanes such as vinyl-terminated or acrylic-terminated polymethylphenylsiloxane.

In one embodiment, the acrylic or vinyl monomer is selected from the group consisting of vinyl acetate, acrylonitrile, methacrylonitrile, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylate, and the like. propyl, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate and derivatives thereof, acrylamides such as aminoethyl, propyl, butyl, pentyl and hexyl methacrylamides, cyanoacrylates, diacrylates, dimethacrylates, triacrylates, trimethacrylates, tetraacrylates, tetramethacrylates, styrene and its derivatives, parachlorostyrene, pentafluorostyrene, N-vinyl pyrrolidone, 4-vinyl pyridine, 2-vinyl pyridine, vinyl halides, acryloyl and methacryloyl, divinylbenzene.

In one embodiment a potential difference is applied in said solution. By potential difference is meant the difference in redox potential measured between two electrodes.

In one embodiment, the potential difference is applied by a generator connected to two identical or different electrodes immersed in the solution during the soaking step.

In one embodiment, the electrodes are selected from stainless steel, steel, nickel, platinum, gold, silver, zinc, iron, copper, in pure form or in the form of alloy.

In one embodiment, the electrodes are made of stainless steel.

In one embodiment, the potential difference applied by a generator is between 0.1 V and 2 V.

In one embodiment, it is of the order of 0.7 V.

In one embodiment, the potential difference is generated by a chemical battery.

A chemical cell is a cell composed of two electrodes connected by an ion bridge. According to the present invention, the two electrodes are judiciously chosen so that the potential difference is between 0.1 V and 2.5 V.

In one embodiment, the chemical stack is created between two different electrodes dipping into the solution.

In one embodiment, the electrodes are selected from nickel, zinc, iron, copper, silver in pure form or in alloy form.

In one embodiment, the potential difference generated by the chemical battery is between 0.1 V and 1.5 V.

In one embodiment, the potential difference is of the order of 0.7 V.

In one embodiment, the electrodes are chemically isolated to avoid any contact between the substrate immersed in the bath of step b) and the electrodes also immersed in the bath of step b). According to an alternative embodiment, said constituent part is made of metal, in particular a crimping cap, a spring or a ball forming a valve.

According to an alternative embodiment, said constituent part is made of a flexible material, such as an elastomer, in particular a piston or a seal.

According to an alternative embodiment, said constituent part is made of synthetic material, such as polyethylene or polypropylene.

According to an alternative embodiment, said constituent part is made of glass, in particular a reservoir,

Advantageously, the method further comprises the step of forming by chemical grafting at least one additional thin film on said support surface.

Advantageously, the method comprises the step of forming by chemical grafting a first additional thin film on said support surface, said first additional thin film preventing interactions between said support surface and said fluid product.

Advantageously, the method comprises the step of forming by chemical grafting a second additional thin film on said support surface, said second additional thin film limiting the friction between two constituent parts moving relative to each other during the treatment. actuation of the fluid dispensing device.

According to a first variant, said at least one additional thin film is deposited on said support surface during at least one successive chemical grafting step, each carried out in a single-component bath.

According to a second variant, said at least one additional thin film is deposited on said support surface simultaneously during the same chemical grafting step in a multi-component bath.

Advantageously, said fluid product is a pharmaceutical fluid product intended to be sprayed in particular nasally or orally. More particularly, the present invention provides a method similar to that described in WO 2008/078052, which describes a method of preparing an organic film on the surface of a solid support under non-electrochemical conditions. Surprisingly, this type of process has been found suitable for forming a thin film on surfaces intended to come into contact with a pharmaceutical fluid product in dispensing devices, to prevent interactions with said fluid product. Such an application of this grafting method had never been considered.

In a synthetic manner, the process aims to prepare a thin film on the surface of a support which can be made of different materials, such as hard plastics, soft plastics, metal or glass. This method mainly comprises contacting said support surface with a liquid solution. This comprises at least one solvent and at least one adhesion primer allowing the formation of radical entities from the adhesion primer.

The "thin film" can be any polymeric film, in particular of organic nature, for example derived from several units of organic chemical species, and covalently bonded to the surface of the support on which the process is carried out. It is particularly a film covalently bonded to the surface of a support and comprising at least one layer of similar structural units of nature. Depending on the thickness of the film, its cohesion is ensured by the covalent bonds that develop between the different units.

The solvent employed in the process may be protic or aprotic in nature. It is preferable that the primer is soluble in said solvent.

By "protic solvent" is meant a solvent which comprises at least one hydrogen atom capable of being released in the form of a proton. The protic solvent can be chosen from the group consisting of water, deionized water, distilled water, acidified or not, acetic acid, hydroxylated solvents such as methanol and ethanol, low-level liquid glycols. weight such as ethylene glycol, and mixtures thereof. In a first variant, the protic solvent consists only of a protic solvent or a mixture of different protic solvents. In another variant, the protic solvent or the mixture of protic solvents may be used in admixture with at least one aprotic solvent, it being understood that the resulting mixture has the characteristics of a protic solvent. Acidified water is the preferred protic solvent and, more particularly, acidified distilled water or acidified deionized water.

By "aprotic solvent" is meant a solvent which is not considered as protic. Such solvents are not likely to release a proton or accept one under non-extreme conditions. The aprotic solvent is advantageously chosen from dimethylformamide (DMF), acetone and dimethyl sulfoxide (DMSO).

The term "adhesion primer" corresponds to any organic molecule susceptible, under certain conditions, to chemisorber on the surface of the support by radical reaction such as radical chemical grafting. Such molecules comprise at least one functional group capable of reacting with a radical and also a reactive function with respect to another radical after chemisorption. These molecules are thus capable of forming a film of polymeric nature after grafting of a first molecule on the surface of the support and then reaction with other molecules present in its environment.

The term "radical chemical grafting" refers in particular to the use of molecular entities having an unpaired electron to form covalent link bonds with a surface, said molecular entities being generated independently of the support surface on which they are to be grafted. Thus, the radical reaction leads to the formation of covalent bonds between the support surface in question and the grafted adhesion primer derivative and then between a grafted derivative and molecules present in its environment.

By "derivative of the adhesion primer" is meant a chemical unit resulting from the adhesion primer, after the latter has reacted by grafting radical chemical especially with the surface of the support, or with another radical. It is clear to those skilled in the art that the reactive function with respect to another radical after chemisorption of the adhesion primer derivative is different from the function involved in the covalent bond, especially with the surface of the support. The adhesion primer is advantageously a cleavable aryl salt selected from the group consisting of aryl diazonium salts, ammonium aryl salts, aryl phosphonium salts, arylsulphonium salts and aryl iodonium salts.

As an alternative to the direct covalent bonds on the support surface, obtained in an aqueous medium, it is also possible to use a process for impregnating a previously grafted porous layer.

In an advantageous embodiment of the invention, at least one additional thin film is produced by chemical grafting on the same support surface to give at least one other property to this support surface. Thus, the fluid product may be likely to stick to a surface with which it is in contact, which may in particular have a detrimental effect on the reproducibility of the dispensed dose. The invention advantageously provides for forming by chemical grafting a first additional thin film which prevents the fluid product from sticking to the support surface. Advantageously, it could also be envisaged to apply a second additional thin film by chemical grafting to give a third property to the support surface. For example, in fluid product dispensing devices, some parts move relative to others, and blockages due to friction may interfere with the proper operation of the device. The invention advantageously provides to form by chemical grafting a second additional thin film which limits the friction between two component parts which move relative to each other during actuation. These additional thin films can be applied during successive chemical grafting steps. In this case, each chemical grafting step is carried out in a single-component bath. It should be noted that the order of these successive chemical grafting steps can be arbitrary. Alternatively, the thin films additional can also be applied in a single step of chemical grafting, which is then carried out in a multi-component bath. A combination of the two variants is also conceivable.

The present invention is applicable to multidose devices, such as pump or valve devices mounted on a reservoir and operated for the successive delivery of doses. It also applies to multi-dose devices comprising a plurality of individual reservoirs each containing a dose of fluid, such as pre-dosed powder inhalers. It also applies to single-dose or bidose devices, in which a piston moves directly into a reservoir each time it is actuated. The invention is particularly applicable to nasal or oral spray devices, ophthalmic dispensing devices and syringe-type needle devices.

The invention also relates to the use of a grafting method according to the invention for treating at least one surface of at least one constituent part of a fluid dispenser device in contact with said fluid product, to prevent interactions between said fluid product and said constituent part.

The following examples were carried out in a glass vessel. Unless otherwise specified, they were made under normal conditions of temperature and pressure (about 23 ° C. under about 1 atm) in ambient air. Unless otherwise stated, the reagents employed were directly obtained commercially without further purification. The steel samples have under preliminary UV-ozone treatment for 10 minutes at room temperature.

EXAMPLE 1 Grafting of a Poly (Butylmethacrylate) (BUMA) Barrier Film on Metal Parts of a Pump By pump is meant a manually operated fluid dispensing device comprising a pump body in which one or several pistons. The sodium dodecyl sulphate (0.283 g, 0.5 × 10 ^-3 mol) was solubilized in 33 ml of milliQ water and the butyl methacrylate (0.71 g, 10 ^-3 mol) is added and emulsified under strong magnetic agitation.

The 4-aminobenzoic acid (0.686 g, 7.5 × 10 ^-3 mol) was solubilized in a solution of hydrochloric acid (1.9 mL in 30 mL of MQ water) and hypophosphorous acid (3.2 mL). mL, 3.1 10 ^"2 mol). This solution was added to the BUMA emulsion.

To this emulsion, a solution of NaNO ₂ (0.328 g, 4.8 × 10 ^-3 mol) in 30 ml of MQ water was added, followed by samples of 316 L stainless steel balls and springs from the pump.

After 30 minutes of reaction, the samples were removed and then rinsed successively with an aqueous solution of 10% Palmolive dishwashing liquid with magnetic stirring at 40 ° C., jet of this 10% solution, MQ water bath and then drying under nitrogen. .

Analyzes by IRRAS spectrometry (Hyperion) of a marble confirm the grafting. The specific bands of a BUMA film at 1716 cm ^-1 are present.

The grafting efficiency on the samples was verified by a passivation test. For this, 100 g of sample are mineralized in a solution of 0.1 M hydrochloric acid for 15 h at 40 ° C. 2 ml of this solution were taken. The pH was adjusted to 3.5 with a 250 g / L sodium acetate solution. 1 ml of a solution of 1,10-phenanthroline was added to check for the presence of ferrous ions (red color). EXAMPLE 2 Grafting of a Poly (Dimethylsiloxane) Barrier Film

(PDMS) on metal parts of a pump

Sodium dodecyl benzene sulphonate (0.849 g, 1.5 × 10 ^-2 mol) was solubilized in 100 ml of milliQ water and vinyl-terminated poly (dimethylsiloxane) (3 g, 10 g / l) was added and then The mixture was magnetically stirred to form an emulsion. 4-Aminobenzoic acid (2.058 g, 2.25 10 ^-2 mol) was solubilized in a solution of hydrochloric acid (5.8 mL in 90 mL of MQ water) and hypophosphorous acid (9.7 50% mL) This solution was added to the PDMS emulsion.

To this solution was added 90 ml of an aqueous solution of NaNO ₂ (0.984 g, 1.44 × 10 ^-2 mol) followed by 316 L stainless steel balls and springs.

After 30 minutes of reaction, the samples were removed and then rinsed successively with a solution of 10% Palmolive Liquid Dilute with US agitation at 40 ° C., jet of this 10% solution, water bath and then drying under nitrogen.

These treated samples have also successfully passed the passivation test, the results obtained are summarized in the following table:

Passivation test

Coating Uncoated With coating pBUMA Ή- + 000

PDMS Ή- + 000

Positive test (corrosion)

000 Negative test (no corrosion)

Example 3 Chemical grafting of a PDMS-Acrylic Polymer Film on a Stainless Steel Blade in the Presence of a Potential Difference

Cleaning the stainless steel blades with ethanol, ultrasound (power 100 W, temperature 40 ° C) for 5 minutes is performed.

The preparation of the biphasic solution takes place in two stages. In the beaker (1) are added in order and with magnetic stirring (300 rpm), the PDMS-acrylate (1 g / L); Brij® 35 in solution in water at 8.5% wt (4.37 g / L) and 33 mL of water Dl. The emulsification is then sonicated at 40 ° C under a power of 200 W (100%) for 15 minutes. In the beaker (2) are added, with magnetic stirring (300 rpm), nitrobenzene diazonium tetrafluoroborate (0.05 mol / L); 130 mL of Dl water and hydrochloric acid (0.23 mol / L).

The contents of the beaker (2) are poured into the emulsion of the beaker (1). The stainless steel blades (x 2), a galvanized steel wire (wound on 10 turns, a length of about 25 to 30 cm) and a Ni wire (wound on 10 turns, a length of about 25 to 30 cm) are placed in the beaker (1). Both wires are connected to a potentiostat and an ammeter is connected in series. The potentiostat imposes a constant potential difference of 0.5 V and the intensity of the current is measured over time via the ammeter.

Finally, once the assembly is ready, the hypophosphorous acid (0.7 mol / L) is added last which marks the beginning of the reaction. After 30 minutes of reaction at ambient temperature, the stainless steel blades are removed and rinsed successively with water (cascade) and then with ethanol (cascade) and finally with isopropanol in a soxhlet extractor for 16 hours.

The use of a soxhlet extractor makes it possible to confirm the chemical grafting of PDMS-acrylic on the surface of the stainless steel blade.

An IR spectroscopic analysis is performed which makes it possible to confirm the grafting of PDMS-acrylic by the presence of the characteristic band at 1260 cm ^-1 corresponding to the vibration of the Si-CH ₃ bond.

These stainless steel blades have also passed the passivation test.

Various modifications are also possible for a person skilled in the art without departing from the scope of the present invention as defined by the appended claims.

Claims

claims

1. - Surface treatment method of a fluid dispenser device, characterized in that said method comprises the step of forming by chemical grafting a thin film on at least one support surface of at least one constituent part in contact with said fluid product, said thin film preventing interactions between said fluid product and said constituent part.

2. - Method according to claim 1, wherein said step of grafting comprises contacting said surface in contact with the fluid product with a solution comprising at least one adhesion primer, said adhesion primer being a sodium salt. cleavable aryl and at least one monomer or polymer selected from the group consisting of vinyl-terminated or acrylic-terminated siloxanes and acrylic or vinyl monomers.

3. - The method of claim 1 or 2, wherein said chemical grafting creates covalent bonds between the molecules of said thin film and said support surface.

4. A process according to any one of the preceding claims, wherein said chemical grafting is carried out in an aqueous medium.

5. A process according to any one of the preceding claims, wherein the cleavable aryl salt is selected from the group consisting of aryl diazonium salts, aryl ammonium salts, aryl phosphonium salts, aryl sulfonium salts and aryl iodonium salts.

6. - Process according to any one of the preceding claims, wherein the reducing agent is selected from the group consisting of reducing metals which may be in finely divided form such iron, zinc or nickel, a metal salt which may be in the form of metallocene and an organic reducing agent such as hypophosphorous acid, ascorbic acid.

7. A process according to any one of the preceding claims, wherein said chemical grafting step is initiated by chemical activation.

8. - The method of claim 7, wherein said chemical activation is initiated by the presence of a reductant in the solution.

9. The process as claimed in any one of the preceding claims, in which the vinyl-terminated or acrylic-terminated siloxanes are chosen from the group consisting of polyalkylsiloxanes with acrylic or vinyl terminations, such as vinyl-terminated or acrylic-terminated polymethylsiloxane, and terminated polydimethylsiloxane. vinyl or acrylic such as polydimethylsiloxane-acrylate (PDMS-acrylate), vinyl-terminated or acrylic-terminated polyarylsiloxanes such as polyphenylsiloxane with vinyl or acrylic terminations such as polyvinylphenylsiloxane, polyarylalkylsiloxanes with vinyl or acrylic terminations, such as vinyl-terminated or acrylic-terminated polymethylphenylsiloxane .

The process of any one of the preceding claims, wherein the acrylic or vinyl monomer is selected from the group consisting of vinyl acetate, acrylonitrile, methacrylonitrile, methyl methacrylate, ethyl methacrylate. , butyl methacrylate, propyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate and derivatives thereof, acrylamides such as aminoethyl, propyl, butyl, pentyl and hexyl methacrylamides; cyanoacrylates, diacrylates, dimethacrylates, triacrylates, trimethacrylates, tetraacrylates, tetramethacrylates, styrene and its derivatives, parachlorostyrene, pentafluorostyrene, N-vinyl pyrrolidone, 4-vinyl pyridine, 2-vinyl pyridine, vinyl halides, acryloyl and methacryloyl, divinylbenzene.

Method according to any one of the preceding claims, wherein a potential difference is applied in said solution.

12. - Method according to claim 1 1, wherein the potential difference is applied by a generator connected to two electrodes, identical or different, plunging into the solution during the soaking step

13. - The method of claim 1 1, wherein the potential difference is generated by a chemical battery.

14. A process according to any one of the preceding claims, wherein said constituent part is made of metal, in particular a crimping cap, a spring or a ball forming a valve.

15. - Process according to any one of claims 1 to 13, wherein said constituent part is of flexible material, such as an elastomer, in particular a piston or a seal.

16. - Method according to any one of claims 1 to 13, wherein said constituent part is made of synthetic material, such as polyethylene or polypropylene.

17. - Method according to any one of claims 1 to 13, wherein said constituent part is glass, including a reservoir.

18. A process according to any one of the preceding claims, wherein said thin film has a thickness of less than 1 micrometer, preferably between 10 and 2000 angstroms.

19.- Use of a grafting method according to any one of the preceding claims, for treating at least one surface of at least one constituent part of a fluid dispenser device in contact with said fluid product, to prevent the interactions between said fluid product and said constituent part.