WO2012007388A1

WO2012007388A1 - Method for polymer plasma deposition

Info

Publication number: WO2012007388A1
Application number: PCT/EP2011/061654
Authority: WO
Inventors: Julie Hubert; François RENIERS; Hans Miltner
Original assignee: Solvay SA; Universite Libre de Bruxelles ULB
Current assignee: Solvay SA; Universite Libre de Bruxelles ULB
Priority date: 2010-07-12
Filing date: 2011-07-08
Publication date: 2012-01-19
Anticipated expiration: 2013-01-12

Abstract

The present invention is related to a method for the deposition of a polymeric layer comprising inorganic particles onto a substrate, said method comprising the steps of: -generating a plasma in a gaseous medium by means of a of a plasma; -placing the substrate in contact with the plasma,or in a post-plasma area of said plasma; -introducing in said plasma or in the post-plasma area a precursor of the polymer; -introducing in said plasma or in said post-plasma area an aerosol comprising said particles.

Description

METHOD FOR POLYMER PLASMA. DEPOSITION

Field of the Invention

[0001] The present invention is related to a method for the deposition of a polymer layer comprising inorganic particles .

[0002] The present invention is also related to an article comprising a substrate and a polymeric layer comprising inorganic particles.

Technological background

[0003] The conventional methods of polymerisation often require the addition of solvents, catalysts, initiators and inhibitors of reaction. Other ways of synthesis, having smaller environmental impact can be envisaged. For several years, polymers have been obtained by vacuum plasma polymerisation. It is the case for example of polystyrene or polypyrrole.

[0004] In the case of chlorinated polymers, the processing by conventional methods such as extrusion or coextrusion is further complicated by the thermal sensitivity of the C-Cl bond. At extrusion temperature, these bonds tend to break, CI being released. For that reason, large amounts of acid scavengers are used in the polymer composition to neutralise HC1. This phenomenon is particularly true for PVDC . As a consequence, PVDC coating is usually performed by wet coating by either monophasic (solution) or emulsion (latex) liquids. [0005] The plasma polymerisation represents, in certain cases, an interesting alternative to the conventional methods, for both the technical aspects and the properties of the synthesized polymers. Indeed, this low-temperature process, without solvents, has smaller environmental impact and often requires less steps than most of the existing industrial processes (mainly for complex polymers) .

[0006] Furthermore, the properties of plasmas polymers synthesized by plasma polymerisation differ from their conventional analogues in the fact that they are produced by recombination of radical fragments generated by high energy particles resulting from the plasma. As a consequence, they are not constituted, of regularly repeated units but tend to form cross linked and less ordered (amorphous) polymers.

[0007] The cross linked character of these coatings (layers) improves both their thermal stability

(infusible) and their solvent resistance (insoluble) .

[0008] The plasma polymerisation process also allows easy and convenient production of polymer layers having low thicknesses (typically from 50 nm to 1 ym) , which is difficult for conventional processes such as extrusion .

[0009] The plasmas deposition processes also allow the control of polymerisation parameters allowing to make polymeric layers with particular chemical functions, and thicknesses, bringing specific chemical and physical properties .

[0010] More recently, plasma deposited layers were obtained by atmospheric plasma polymerisation processes, allowing to reduce the constraints associated with the vacuum technology (pumping devices, degassing, etc.). In that context, the use of dielectric barrier discharges DBD seems to be particularly simple and effective.

[0011] As a way of example, layers of polyacrylic acid have been produced by plasma polymerisation at atmospheric pressure. Examples of such deposition processes can be found in the following documents:

- M. Tatoulian, F. A. Arefi-Khonsari , J-P. Borra, Plasma Processes and Polymers, 4, 2007, pp 360-369;

- L. J. Ward, W. C. E. Schofield, and J. P. S. Badyal, Chemistry of Materials . , 15, 2003, 1466-1469;

I. Topala, N. Dumitrascu, G. Popa, Nuclear Instruments and Methods in Physics Research B, 267, 2009, pp 442- 445. 14,15,16.

[0012] In the conventional deposition processes, described in the art, inorganic particles can be incorporated into a polymer in the liquid state, either into a melted polymer in an extrusion process, or dispersed in a liquid in a solvent coating process. This dispersion in the liquid state is not possible in case of cross-linked polymeric layers deposited by plasma polymerization process .

[0013] In document "Thin Solid Films", 78, 198 1, pp

309-318 , Kay et Al . describes fluoropolymer layers containing metal particles produced by etching and deposition of a metallic electrode and simultaneous polymerisation of a precursor. It describes in particular a radiofrequency (rf) diode including a metals such as molybdenum, placed on an electrode, and perfluoroalkanes as precursor. This system presents however various severe drawbacks. Firstly, it is difficult to control the size of the deposited metallic particles. Secondly, the plasma controlling simultaneously the polymerisation of the layer and the erosion of the electrode, it is necessary to make compromises with regard to either the optimal polymerisation conditions or the metallic particles deposition .

[0014] Document "Vacuum", 39, 1, 1989, pp 13-15 describes the deposition of a metal along with a polymer layer wherein the metal is evaporated from a hot surface. This document describes more specifically layers of amorphous hydrocarbons produced by a glow discharge, using mixtures such as benzene/argon or butane/argon. Metals

(silver, gold or copper) are simultaneously incorporated into the growing layer by evaporation from a hot tungsten plate. In this case, the deposition rate of the metal can be uncoupled from the plasma conditions, but, the size of the particles remains determined by the nucleation and growth process, hence is hardly controllable. Furthermore, several materials are hardly evaporable, requiring unrealistic temperatures in industrial processes

(particularly refractory materials such as alumina) .

Aims of the Invention

[0015] The present invention aims to provide a process for the deposition of a polymeric layer comprising inorganic particles that does not present the drawbacks of prior art deposition processes.

[0016] More particularly, the present invention aims to provide a polymeric layer deposition process wherein inorganic particles having controlled size distribution are homogeneously dispersed in the polymeric layer.

[0010] Other advantages of the method according to the invention will be apparent from the following description.

Summary of the Invention

[0017] The present invention is related to a method for producing an article comprising a substrate and a hybrid layer deposited on the substrate, said hybrid layer comprising polymer and inorganic particles, said method comprising the step of exposing the substrate to a plasma generated in a gaseous medium comprising at least one precursor of the polymer and inorganic particles by means of a plasma device comprising a discharge area.

[0018] Preferably, the substrate is exposed to the plasma in the discharge area.

[0019] Advantageously, the plasma device further comprises a post-discharge area, said method comprising the exposition of the substrate in the post-discharge area.

[0020] Preferably, the method comprise the step of introducing the precursor of the polymer and the inorganic particles at least partially in the discharge area, more preferably, the precursor of the polymer and the inorganic particles are introduced exclusively in the discharge area.

[0021] As a preferred alternative, the method comprise the step of introducing the precursor of the polymer and the inorganic particles exclusively in the post-discharge area.

[0022] Preferably, the method comprise the step of introducing the inorganic particles exclusively in the post-discharge area.

[0023] Advantageously, the gaseous medium comprises further comprises a plasma generating gas such as Argon or Helium.

[0024] The present invention can also be described as a method for the deposition of a polymeric layer comprising inorganic particles onto a substrate, said method comprising the steps of:

- generating a plasma in a gaseous medium by means of a plasma device;

- placing the substrate in contact with the plasma, or in a post-plasma area of said plasma; - introducing in said plasma or in the post-plasma area a precursor of the polymer;

- introducing in said plasma or in said post-plasma area an aerosol comprising said particles.

[0025] According to particular preferred embodiments, the methods of the present invention comprises one or a suitable combination of at least two of the following features:

- the aerosol consists essentially or consists of said inorganic particles;

- the inorganic particles comprise, consist essentially of or consist of at least one inorganic compound CI comprising at least one metal or amphoteric element El, wherein the compound CI is selected from the group cons i sting of oxides , oxyfluorides , oxyhydroxyf luorides and mixtures thereof, and the element El is selected from the group consisting of Zn, Ti, Zr, Ce and mixtures thereof;

- the inorganic particles comprise, consist essentially of or consist of at least one inorganic compound C2 comprising at least one metal or amphoteric element E2, wherein the compound C2 is selected from the group consisting of oxides, fluorides, oxyfluorides, oxyhydroxyfluorides and mixtures thereof, and the metal or amphoteric element E2 is selected from the group consisting of Si, Mg, Ca, Sr and mixtures thereof;

- the inorganic particles comprise, consist essentially of or consist of inorganic carbon;

- the inorganic particles comprise, are essentially, or are exfoliable nanoparticles having a sheet-like structure, of which the lateral size is advantageously below 900 nm, preferably below 300 nm, more preferably below 70 nm ; this lateral size is preferably above 10 nm, more preferably above 30 nm;

the inorganic particles comprise, consist essentially of or consist of at least one crystalline silicate selected from the group consisting of nesosilicates, s o r o s i 1 i c a t e s , c yc 1 o s i 1 i c a t e s , t e c t o s i 1 i c a t e s , inosilicates and mixtures thereof;

the inorganic particles comprise, consist essentially of or consist of at least one metal bicarbonate or carbonate ;

the inorganic particles comprise, consist essentially of or consist of at least one metal oxide or hydroxide ;

the inorganic particles comprise, consist essentially of or consist of at least one metal salt, including a halogenide or an oxysalt;

the inorganic particles comprise, consist essentially of or consist of zinc borate, in particular anhydrous zinc borate;

the inorganic particles are of such a chemical nature that they can act as pigments;

the inorganic particles comprise, consist essentially of or consist of metallic particles, preferably transition metals, preferably, said metallic particles have diameters smaller than lOnm;

the inorganic particles are dispersed in a liquid medium before the production of the aerosol;

the inorganic particles are stabilised in a colloidal solution;

the liquid is nebulised in the plasma or post-plasma by means of carrier gas;

said precursor comprises , consists essentially of or consists of a halogenated organic compound, preferably a chlorinated organic compound; - the precursor comprises, consists essentially of or consists of a chlorinated organic compound having a Cl/C ratio higher than 0.1, preferably higher than 0.25, preferably higher than or equal to 0.5, more preferably higher than or equal to 1 ;

- said precursor comprises, consists essentially of or consists of a polychlorinated organic compound selected from the group consisting of polychloroalkane, polychloroalkene, polychloroalkyne, polychloroarene, tertiary amine comprising perchloroalkanes groups and mixture thereof, said polychlorinated organic compound being preferably a perchlorinated organic compound;

- the pressure in the plasma reactor is comprised between lOOhPa and 2000 hPa, preferably between 500 and 600;

- the temperature of ionic and neutral species in the plasma is below 400°C, preferably below 150°C;

- the plasma is a dielectric barrier discharge (DBD) plasma , a pulsed DC plasma, or microwave plasma

- the aerosol comprises organometallic precursor able to produce said inorganic particles

- the precursor does not comprise silicium atom

- the gaseous medium further comprises a plasma generating gas, such as argon, helium, neon, xenon, nitrogen or mixture thereof preferably argon;

- chlorinated gas, such as Cl₂, is injected in the gaseous medium;

- the precursor further comprises fluorine atoms.

[0026] As an alternative to the projection of an aerosol, the organometallic precursor may be in a gaseous form, or in solution in liquid droplets.

[0027] Another aspect of the invention is related to an article comprising a substrate and a polymeric layer comprising inorganic particles, said polymeric layer being producible according the method of the invention.

[0028] According to particular preferred embodiments, the article of the present invention comprises one or a suitable combination of at least two of the following features:

- said polymeric layer is cross-linked;

- the polymeric layer is a chlorinated polymer having a Cl/C ratio higher than 0,5, preferably higher than 0,75, more preferably higher than or equal to 1 ;

- said polymeric layer comprises, consists essentially of or consists of a polymer selected from the group consisting of PVC, PVDC, polychloropropene, Poly (chloro-p-xylene) , Poly (chlorotrifluoroethylene) , Poly (vinyl chloroacetate) , Poly (2-chlorostyrene) and mixture thereof;

- said polymeric layer comprises, consists essentially of or consists of a polymer selected from the group consisting of PVC, PVDC and mixture thereof.

Brief Description of the Drawings

[0029] Fig.l represents an example of experimental setup for carrying out the process of the present invention wherein the substrate is in the discharge area.

[0030] Fig. 2 represents an example of experimental setup for carrying out the process of the present invention, wherein the substrate is in a post-plasma (post- discharge) area.

[0031] Fig.3 represents an example of experimental setup for carrying out the process of the present invention, wherein the substrate is in a post-plasma (post- discharge) area, and the precursor and inorganic particles are also injected in the post-discharge (post-plasma) area. [0032] Fig. 4 represents the experimental setup used in the example.

Detailed Description of the Invention

[0033] The present invention discloses a process wherein a polymeric layer is deposited by a plasma process said polymeric layer being deposited along with inorganic particles .

[0034] By polymeric layer or polymer coating, it is meant in the present document a layer comprising a polymer.

[0035] To this aim, an organic compound precursor of the polymer (monomer) is injected in a plasma (or in post plasma zone) in the vicinity of a substrate to be coated. The substrate itself can be either in contact of the plasma, or in the post-plasma zone. Simultaneously, an aerosol comprising the inorganic particles to be deposited is injected in the plasma or in the post-plasma zone, the inorganic particles being deposited along with the polymer

[0036] In the present invention, an aerosol is to be understood as a suspension of fine solid particles or liquid droplets in a gas.

[0037] The aerosol of the present invention may be either obtained by direct projection of the inorganic particles by means of a carrier gas of a fine powder of the inorganic material, or, preferably by nebulisation of a liquid suspension comprising said particles. Preferably, said suspension is a stabilised suspension, such as a colloidal suspension comprising the inorganic particles.

[0038] Contrary to prior art methods, the particles are produced before the deposition process, and no dimensional changes have been observed, thereby having a preliminary control of the size distribution.

[0039] More particularly, the use of stable colloidal solutions avoids the aggregation of small particles and their dispersion in the atmosphere. This is of particular importance in the case of nanometric particles, potentially hazardous in the atmosphere, and stabilised colloidal solutions also permit to obtain homodisperse size particle distribution.

[0040] Depending on the nature of the inorganic particles, they can be introduced either directly in the plasma, or in a post-plasma area, independently of the fact that they are dispersed in a liquid or not. As an example, post-plasma injection may reduce potential degradation of the particles, and direct injection may increase their reactivity .

[0041] The nature and function of the inorganic particles is not particularly limited.

Function of the inorganic particles.

[0042] In certain embodiments, the inorganic particles are not used for the particular purpose of modifying at least one property of the polymeric layer ; for example, in accordance with this embodiment, they can be used just as a "filler" or "extender", merely for decreasing the concentration of polymer in the polymeric layer and, thereby, possibly reducing its cost.

[0043] In certain other embodiments, the inorganic particles are used for modifying at least one property of the polymeric layer. For example, the inorganic particles can be used:

- for increasing its hardness (e.g. AI₂O₃) ;

- for increasing its scratch resistance (e.g. AI₂O₃, S1O₂) ; - for increasing its thermal stability, notably by acting as acid scavenger (e.g. CaCOs) ;

- for increasing its UV resistance, notably by absorbing UV radiation (e.g. ZnO, Ce0₂, Ti0₂ and TiOF₂) ; - for increasing its light resistance, notably by reducing the photocatalytic activity of UV absorbers such as ZnO (e.g. Si0₂, MgO, CaO, SrO) ;

for increasing its thermal conductivity (e.g. metal oxides, inorganic carbon) ;

- for increasing its electrical conductivity (e.g. metal oxides, inorganic carbon) ;

- for providing its dielectric properties (e.g. BaTiOs) ; as antistatic agent (e.g. carbon nanotubes, graphite, carbon black, carbon nanofibers) ;

for modifying (increasing or decreasing) its hydrophilicity or hydrophobicity ;

- for emitting light (e.g. quantum dots) ;

- for reducing the permeability to air, oxygen or organic liquids such as hydrocarbons (e.g. clays, layered aluminum hydroxide, inorganic carbon such as graphite) ;

- for increasing the fire resistance, including increasing the flame resistance and reducing the smoke generation (e.g. ZnB0₃) ;

- for increasing the strength and stiffness (e.g. needle- shaped inorganic fillers such as wollastonite) ;

- as biocide, anti-fouling and/or anti-odour agent (e.g. silver) ;

as pigment, for colouring the coating (e.g. titanium dioxide) ;

- and in any combinations of above uses (e.g. polyhedral oligomeric silsesquioxanes , known as « POSS », as notably commercially available from Hybrid Plastics, can be used to increase at least the scratch resistance, the hardness and the hydrophobicity) .

Nature of the inorganic particles.

[0044] In a first embodiment, the inorganic particles comprise, consist essentially of or consist of at least one inorganic compound CI comprising at least one metal or amphoteric element El, wherein the compound CI is selected from the group of oxides, o x y f 1 u o r i de s , oxyhydroxyfluorides and mixtures thereof, and the element El is selected from the group consisting of Zn, Ti, Zr, Ce and mixtures thereof. For example, in accordance with this first embodiment, the inorganic particles can comprise, consist essentially of or consist of at least one inorganic compound selected from the group of ZnO, Zr02, Ce02, Ti0₂, T1OF₂ and mixtures thereof. The inorganic particles in accordance with this first embodiment are useful, and can thus be used, notably for increasing the UV resistance of the polymeric layer.

[0045] In a second embodiment, the inorganic particles comprise, consist essentially of or consist of at least one inorganic compound C2 comprising at least one metal or amphoteric element E2, wherein the compound C2 is selected from the group consisting of oxides, fluorides, oxyfluorides , oxyhydroxyfluorides and mixtures thereof, and the metal or amphoteric element E2 is selected from the group consisting of Si, Mg, Ca, Sr and mixtures thereof. For example, in accordance with this first embodiment, the inorganic particles can comprise, consist essentially of or consist of at least one inorganic compound selected from the group of Si0₂, MgF₂, CaF2, SrF2 and mixtures thereof. The inorganic particles in accordance with this second embodiment are useful, and can thus be used, notably for increasing the light resistance, of the polymeric layer when inorganic particles according to the first embodiment are used by reducing the photocatalytic activity of UV absorbers such as ZnO. Among silica grades, a certain silica (Si0₂) , which is an altered novaculite found only in the Ouachita Mountains of western Arkansas, can be preferred because of its lower Mohs hardness. [0046] In a third embodiment, the inorganic particles comprise, consist essentially of or consist inorganic carbon. For example, in accordance with this third embodiment, the inorganic particles can comprise, consist essentially of or consist of inorganic carbon selected from the group of carbon black, graphite, carbon nanofillers and mixtures thereof. The inorganic particles in accordance with this embodiment are useful, and can thus be used, notably for increasing the thermal conductivity of the polymeric layer; they can also be used to increase the electrical conductivity or as electro-dissipative agents; they can also be used as pigments.

The carbon nanofiller.

[0047] Any carbon nanofiller is desirable. The skilled person will easily recognize the carbon nanofiller which fits best its composition and encompassed end uses. The carbon nanofiller can be notably chosen from carbon nanotubes, vapor grown carbon fibers, carbon nanohorns and mixtures thereof.

T_}___9a-_rbon__nan_o_tube_s _L

[0048] A carbon nanotube (CNT) is intended to denote any material the structure of which comprises at least one graphene layer wound in the form of a hollow cylinder capped at least one of its ends, and preferably at each of them, by a half molecule of a fullerene. The term "cylinder" must be understood, with a broad geometric meaning, as a surface resulting from the rotation of a straight line parallel to a fixed rectilinear axis, thereby generating a curve around said axis. As examples of possible shapes of this curve, the circle and the ellipse can be notably cited. In the carbon nanotubes useful for the present invention, the carbon atoms are generally linked in a covalent manner between each other, their electronic orbitals 2s, 2p_x and 2p_y being in a hybrid sp² configuration .

[0049] The structure of the certain carbon nanotubes useful for the present invention can comprise no more than one graphene monolayer ; the case being, the carbon nanotubes are generally referred to as "single wall carbon nanotubes" (SWCNT) .

[0050] The structure of certain other carbon nanotubes useful for the present invention can also comprise a coaxial assembly of several SWCNT ; the case being, the carbon nanotubes are generally referred to as "multiwall carbon nanotube" (MWCNT) . The MWCNT comprise generally above 3, preferably above 6, and more preferably above 10 coaxial SWCNT; in addition, the MWCNT comprise generally less than 60, preferably less than 40, and more preferably less than 20 coaxial SWCNT.

[0051] The number average diameter of the carbon nanotubes useful for the present invention may vary to a large extent, depending notably on whether SWCNT or MWCNT are used. Thus, on one hand, the number average diameter of a SWCNT is usually above 0.3 nm, and preferably above 0.6 nm; besides, the diameter of a SWCNT is usually below 3.0 nm, and preferably below 2.0 nm. On the other hand, the number average diameter of a MWCNT is generally of at least 3 nm and preferably above 6 nm; it is generally of less than 60 nm, preferably of less than 40 nm, and more preferably of less than 20 nm. Certain suitable SWCNT have a number average diameter of from about 10 to about 15 nm.

[0052] The carbon nanotubes useful for the present invention have usually a length considerably much higher than their diameter (see for example Kirk-Othmer Encyclopedia of Chemical Technology (^® John Wiley & Sons 2005), volume 17, Nanotechnology, pages 2 to 4) . Concretely, the number average length of the carbon nanotubes useful according to the present invention, measured along their longitudinal axis, can be several hundredths or even several thousand times higher than their number average diameter. This number average length is usually above 100 nm, preferably above 1 micron, and more preferably above 3 microns. It is generally below 100 microns, preferably below 50 microns, more preferably below 30 microns. The number average diameter and the number average length of the carbon nanotubes can be determined by any technique known from the skilled in the art; advantageously, an electronic microscopy technique coupled with a software image analysis technique will be used. The carbon nanotubes useful for the present invention may be fabricated by any known technique.

[0053] Various methods to fabricate and subsequently purify them are described in « Carbon Nanotubes - Preparation and Properties », supra, pages 139 to 160. Non limitative examples of such methods include: arc discharge, pulsed laser vaporization (PLV) , chemical vapor deposition (CVD) and gas-phase process. Arc discharge is a plasma- based process using a solid carbon electrode for MWCNT, or carbon composite for SWCNT. Pulsed-laser vaporization (PLV) method is used essentially for producing SWCNT, using a high power pulsed laser aimed at powdered graphite loaded with a metal catalyst. Chemical vapor deposition (CVD) can be used for making both SWCNT and MWCNT, by flowing heated precursor gas over a metallic catalyst. Also, a gas-phase process is available to produce both SWCNT and MWCNT. The carbon nanotubes have usually a purity of above 65 % of elemental carbon, the remaining consisting possibly of residual catalytic impurities. Preferably, the carbon nanotubes contain at least 90 % of elemental carbon, and more preferably at least 95 % of elemental carbon. [0054] SWCNT are commercially available notably from

Sumitomo Shoji. MWCNT are commercially available notably from Hyperion Catalysis, Mitsui Bussan, Nikkisou, Nanocyl, Applied Sciences, Shenzhen Nanotech, CNI, Sun Nanotech and Iljin Nanotech, Arkema, Bayer Materials Science.

[0055] The structure of vapor grown carbon fibers is generally close to that of carbon nanotubes . Vapor grown carbon fibers have generally a multi-layered shell having a very thin central hollow portion, wherein a plurality of carbon hexagonal network layers are grown around the hollow portion so as to form annular rings. The number average diameter of a vapor grown carbon fiber is usually above 30 nm, and very often at least 60 nm. On the other hand, the number average diameter of a vapor grown carbon fiber is usually below 1000 nm, very often below 500 nm, and often of at most 200 nm. The number average diameter of the vapor grown carbon fibers useful for the present invention may vary to a large extent, depending notably on the type of the vapor grown carbon fibers that are used. Thus, vapor grown carbon fibers are commonly classified in different types, depending on their number average diameter and other properties :

- standard vapor grown carbon fibers having a number average diameter from 120 mm to 200 nm, referred by certain manufacturers as "vapor grown carbon fibers- high" (VGCF-H) ; usually, such standard vapor grown carbon fibers have a specific surface area (BET) of from about 10 to about 17 m²/g ; their bulk density can be notably of about 0.04 g/cm³ ;

- finer vapor grown carbon fibers, referred by certain manufacturers as "vapor grown carbon fibers-small" (VGCF-S) , having a number average diameter between 90 nm and 120 nm ; usually, such finer vapor grown carbon fibers have a specific surface area (BET) of between 17 and 22 m²/g ; their bulk density can be notably of about 0.02 g/cm³ ;

- still finer vapor grown carbon fibers, referred by certain manufacturers as vapor grown nanofibers (VGNF) , having a number average diameter of from 60 to 90 nm ; usually, such still finer vapor grown carbon fibers have a specific surface area (BET) of from 22 to 38 m²/g ; their bulk density can be notably of about 0.02 g/cm³.

[0056] The vapor grown carbon fibers useful for the present invention have usually a length considerably much higher than their diameter. Concretely, the number average length diameter of the vapor grown carbon fibers useful according to the present invention, measured along their longitudinal axis, can be several tens or even several hundredths times higher than their number average diameter. This number average length is usually above 1 micron, and very often above 5 microns. It is generally below 200 microns, and very often of at most 100 microns; it is preferably of at most 50 microns.

[0057] Certain particularly valuable vapor grown carbon fibers useful for the present invention have a number average diameter of from about 10 to about 20 microns. The number average diameter and the number average length of the vapor grown carbon fibers can be determined by any technique known from the skilled in the art; advantageously, an electronic microscopy technique coupled with a software image analysis technique will be used. The vapor grown carbon fibers may be fabricated by any known technique .

[0058] For example, vapor grown carbon fiber (VGCF) can be produced by thermally decomposing a raw material gas, such as hydrocarbon gas, in a vapor phase in the presence of a metallic catalyst, and by growing the decomposition product into a fibrous shape. Vapor grown carbon nanotubes are notably commercially available as VGCF™ from Showa Denko K.K., and as PYROGRAF^® from ASI or its subsidiary Pyrograf Products, Inc.

T_}___9a-_rbon__nanohorn_s _L

[0059] Carbon nanohorns have generally a graphitic carbon atom structure close to, if not similar, to that of normal carbon nanotubes. An important characteristic of the carbon nanohorns is that, when many of the nanohorns group together, an aggregate (a secondary particle) of about 100 nanometers is created. The aggregates of carbon nanohorns have generally a dahlia-like shape with a large number of horn-shaped short single-layered nanotubes that stick out in all directions; the tips of these short nanotubes are generally capped with five-membered rings. The structure of the dahlia-like aggregates is reported to be very complex at the core: the core part seems to consist of a planar graphitic network for the most part; it is so stable that one cannot separate it even after ultrasonication in a solvent or thermal treatment; then, the core part is supposed to be constructed not only with weak interlayer interaction of planar network but also with relatively tight covalent bonding.

[0060] Unlike carbon nanotubes, carbon nanohorns can be made simply without the use of a catalyst. In particular, carbon nanohorn aggregates can be produced with a yield of more than 90 % through laser vaporization of carbon at room temperature. Thus, compared with normal nanotubes, the nanohorns can be easily prepared with high purity. They are expected to become a low-cost raw material .

[0061] Carbon nanohorns are reported to be the best conductor of electricity on a nanoscale level that can ever be possible, and also probably the stiffest, strongest, and toughest fiber that can ever exist. The surface of the carbon nanohorns can be modified chemically or can be partially damaged intentionally to modify their surface properties, e.g. their adsorbability . The carbon nanohorns are notably commercially available from NEC and from Reade Advanced Materials.

[ 0062 ] In a fourth embodiment, the inorganic particles comprise, are essentially, or are exfoliable nanoparticles having a sheet-like structure, of which the lateral size is advantageously below 900 nm, preferably below 300 nm, more preferably below 70 nm ; this lateral size is generally above 10 nm, preferably above 30 nm. The thickness of the sheets ranges generally from 0.5 to 15 nm, and is preferably between 0.8 and 5.0 nm. For example, in accordance with this fourth embodiment, the inorganic particles can comprise, can be essentially or can be exfoliable nanosilicates having a sheet-like structure.

[ 0063] Among such exfoliable nanosilicates having a sheet-like structure, it can be cited clays (including natural clays such as Bali clay, and synthetic clays), kaolins (which typically comprise hydrated aluminum silicate, such as mullite or kaolinite) , talcs (which typically comprise hydrated magnesium silicate) , micas (including natural micas such as muscovite and phlogopite, and synthetic micas, wherein the natural or synthetic micas typically comprise hydrated aluminum and potassium silicates, like KAI2 [AIS13O10 (F, OH) 2] ) , and mixtures thereof .

[ 0064 ] Materials containing nanoparticles possessing a layered structure preferred for the realization of the present invention are layered silicates known in the literature under the naming " phyllosilicates in layers 2:1 " or phyllosilicates "TOT", due to the relationship 2:1 between the tetrahedrons layers (layers " T ") and the octahedrons layers (layers "0")·

[0065] According to the structure of these silicates, spaces between layers can contain some water or other constituents, such as potassium, sodium or calcium cations., There can also be isomorphic substitution within the hydrated aluminum silicate layers, ions Al³⁺ or Fe³⁺ substituting the Si⁴⁺ ions of the tetrahedral network or the ions Mg²⁺ or Fe²⁺ substituting other cations of the octahedral network. Examples of these phyllosilicates in layers 2:1, are hectorite, saponite, montmorillonite, synthetic mica, montronite, beidellite, stevensite, vermiculite, halloysite, kaolinite, smectite and hydrotalcite . Preferred layered Phyllosilicates 2:1 are constituted by the group consisting of montmorillonites of general formula Al₄Si80₂o (OH) ₄. n¾0 (as well as the compounds wherein the spaces between the layers comprise constituents mentioned here above or resulting from isomorphic substitution defined here above) .

[0066] In a fifth embodiment, the inorganic particles comprise, consist essentially of or consist of at least one crystalline silicate selected from the group consisting of nesosilicates, sorosilicates , cyclosilicates , tectosilicates , inosilicates and mixtures thereof.

[0067] Non limitative examples of nesosilicates are olivine [ (Mg, Fe ) ₂Si0₄] , forsterite (Mg₂Si0₄) , fayalite (Fe₂Si0₄) , alite [Ca₃ ( (Si0₄) 0) ] , belite (Ca₂Si0₄) , andalousite, sillimanite and kyanite [all three are of formula Al₂0(Si0₄)], phenakite, topaz and thaumasite.

[0068] Non limitative examples of sorosilicates are prehnite, hemimorphite [Zn₄(Si₂0v) (OH)₂] and the compound of formula CaMg(Si₂0₇).

[0069] Cyclosilicates are silicates with tetrahedrons that usually link to form rings of three (Si₃0₉)^"6, four (S14O12)^"8, six (SieOis)^"12 or nine (S19O27)^"18 units. Beryl is a cyclosilicate .

[0070] Non limitative examples of tectosilicates are quartz, cristobalite, tridymite, orthose [K (AIS13O8) ] , anorthite [Ca (AI2S12O8) ] and celsiane [Ba (AI2S12O8) ] .

[0071] Inosilicates have usually a crystalline structure usually in the form of chains. Inosilicates can be subdivided notably in pyroxenes [with a crystalline structure usually in the form of simple chains (SiOs)^-2] and amphiboles [with a crystalline structure usually in the form of double chains (Si40n)^-6] . An exemplary inosilicate is xonotlite ; typically, its formula is CaeSieOiv (OH) ₂ ·

[0072] Non limitative examples of pyroxenes are diopside [CaMg (S1O3) ₂] , spodumene [LiAl (S1O3) ₂] , wollastonite [Ca(SiC>3) ] , enstatite [Mg(SiC>3) ] , hypersthene, hedenbergi te , augite, pectolite, diallage, fassaite, spodumene, j effersonite, aegirine, omphafacite and hiddenite .

[0073] Non limitative examples of amphiboles are calcium amphiboles such as tremolite

[Ca₂Mg₅ [Si₄Oii, (OH, F) ] ₂] , actinote [ C a₂ (Mg, Fe) ₅ [ Si₄Ou, OH] ₂ ] and hornblende, iron-magnesium amphiboles such as grunerite and c umm i n g t o n i t e , and sodium amphiboles such as glaucophane, arfvedsonite and riebeckite.

[0074] Inosilicates are preferred over other crystalline silicates. Pyroxenes are very preferred.

The crystalline silicate can be further characterized by its elementary formula, e.g. Zn₄Si₂0gH₂ for hemimorphite .

[0075] The elementary formula of the crystalline silicate includes advantageously at least one alkaline earth metal. Preferably, the elementary formula includes one or more alkaline earth metal (s), said alkaline earth metal (s) being the sole metal (s) included in the elementary formula. Examples of crystalline silicates of this type are notably BaSiC^ (barium metasilicate ) , Ba₂Si307 (barium disilicate) , Ba₂Si0₄ (dibarium silicate), CaSi03

(monocalcium silicate or wollastonite) , Ca₂Si0₄ (dicalcium silicate) , Ca3Si0₅ (tricalcium silicate) , MgSi03 (enstatite) , Mg₂Si0₄ (forsterite) .

[ 0076] The alkaline earth metal can be notably magnesium, calcium or barium. It is preferably calcium. Good results are obtained when the crystalline silicate is wollastonite. To the purpose of the present invention, wollastonite is intended to denote any pyroxene of formula Ca(Si03), including β-wollastonite and a-wollastonite (also referred to as pseudo-wollastonite) eniantropes, as well as monoclinic wollastonite and triclinic wollastonite (also referred to as p a r a w o 11 a s t o n i t e ) . Wollastonite is commercially available notably from NYCO as NYAD or NYGLOS^® minerals .

[ 0077 ] Benefits from using crystalline silicates having an aspect ratio in the preferred specified ranges lie usually in a higher tensile strength, tensile modulus and heat deflection temperature (when compared to using crystalline silicates with an aspect ratio lower than desired) , in an improved processability and in a better surface aspect (when compared to using crystalline silicates having an aspect ratio higher than desired) .

[ 0078 ] The inorganic particles in accordance with this fifth embodiment are useful, and can thus be used, notably for increasing the tensile or flexural strength and/or modulus of the polymeric layer.

[ 0079] In a sixth embodiment, the inorganic particles comprise, consist essentially of or consist of at least one metal bicarbonate or carbonate. The metal carbonate is advantageously selected from the group consisting of alkali metal carbonates, such as sodium carbonate and potassium carbonate, alkaline-earth metal carbonates, and mixtures thereof. Good results are obtained with natural or synthetic (precipitated) calcium carbonate or with a closely associated material often used interchangeably with calcium carbonate, namely dolomite [CaMg(C03)2] · The inorganic particles in accordance with this sixth embodiment are useful, and can thus be used, notably for increasing the thermal stability of the polymeric layer ; these ones can further be useful as "fillers" (esp. to decrease the cost of the coating), and/or as pigments.

[0080] In a seventh embodiment, the inorganic particles comprise, consist essentially of or consist of at least one metal oxide or hydroxide. The metal of the at least one metal oxide or hydroxide is not particularly limited, and can be notably selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Al, Fe, Co, Ni, Cu and mixtures thereof ; in a particular embodiment, the metal is at least one of a lanthanide, such as cerium, or an actinide, such as thorium. Non limitative examples of oxides and hydroxides in accordance with this embodiment are magnesium oxide, calcium oxide, magnesium hydroxide, magnesium oxide, copper (II) oxide, nickel (II) oxide, cerium oxide, cerium hydroxide, and thorium oxide.

[0081] In a eighth embodiment, the inorganic particles comprise, consist essentially of or consist of at least one metal salt, including a halogenide or an oxysalt. The metal oxysalt can be selected from the group consisting of carbonates, silicates, nitrates, phosphates, antimonates, bismuthates, sulfates and mixtures thereof. The metal is not particularly limited, and can be notably selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Fe, Co, Ni, Cu and mixtures thereof, with Na and Ca being preferred choices ; in a particular embodiment, the metal is at least one of a lanthanide (in particular cerium) or actinide. Non limitative examples of oxysalts in accordance with this embodiment are magnesium carbonate, cerium carbonate, calcium phosphate, sodium antimonate and barium sulfate.

[0082] In a ninth embodiment, the inorganic particles comprise, consist essentially of or consist of zinc borate, in particular anhydrous zinc borate. Zinc borate inorganic particles are useful, and can thus be used, notably for increasing the fire resistance of the polymeric layer.

[0083] In a tenth embodiment, the inorganic particles are of such a chemical nature that they can act as pigments. Non limitative examples of such inorganic particles suitable for use in the present invention include blue pigments such as Prussian blues, ultramarine blue, azurite (2 CUCO3. Cu (OH) ₂) and mixtures thereof; green pigments such as chromium oxide, dihydrated chromium oxide, β- and γ-malachi tes , pseudo- malachite, jarosite and mixtures thereof ; yellow pigments such as chrome yellow, lead chromate (medium chrome yellow) , cadmium sulfide, massicot, orpiment, natroj arosite and mixtures thereof ;

- orange pigments such as molybdate oranges ;

red pigments such as realgar, vermillion or cinnabar, cerium sulfide and mixtures thereof ; violet pigments such as manganese violet (manganese ammonium phosphate) ; - white pigments such as titanium dioxide (including rutile T1O2 and anatase T1O2) , zinc sulfide, lithopone (e.g. silver seal lithopone) , sachtolith (as notably commercialized by Sachtleben) , barium sulfate, zinc white or zinc oxide, lead silicate, antimony trioxide or valentinite, and mixtures thereof ;

black pigments such as carbon black ;

iron oxides, which can vary in color from light yellow, through red, to a dark brown and black ;

and mixtures thereof.

[ 0084 ] Depending upon the final properties to be achieved by the coating, the skilled person can, when useful, easily combine two or more than two of the above described embodiments, e.g. by selecting certain inorganic particles according one embodiment and certain inorganic particles according the another embodiment.

Average particle diameter of the inorganic particles

[ 0085 ] The term average particle diameter when used herein refers to the D₅o median diameter computed on the basis of the intensity weighed particle size distribution as obtained by the so called Contin data inversion algorithm. Generally said, the D₅o divides the intensity weighed size distribution into two equal parts, one with sizes smaller than D₅o and one with sizes larger than D₅o .

[ 0086 ] In general the average particle diameter as defined above is determined according to the following procedure. First, if needed, the inorganic particles are isolated from a medium in which they may be contained (as there are various processes for their obtention or manufacture, the products may be available in different forms, e.g. as neat dry particles or as a suspension in a suitable dispersion medium) . The inorganic particles are then dispersed in a dispersion medium for the determination of the particle size distribution preferably by the method of dynamic light scattering. In this regard the method as described in ISO Norm Particles size analysis - Dynamic Light Scattering (DLS) , ISO 22412 : 2008 (E) is recommended to be followed. This norm provides i.a. for instructions relating to instrument location (section 8.1.), system qualification (section 10), sample requirements (section 8.2.), measurement procedure (section 9 points 1 to 5 and 7) and repeatability (section 11) . Measurement temperature is usually at 25°C and the refractive indices and the viscosity coefficient of the respective dispersion medium used should be known with an accuracy of at least 0.1 %. After appropriate temperature equilibration the cell position should be adjusted for optimal scattered light signal according to the system software. Before starting the collection of the time autocorrelation function the time averaged intensity scattered by the sample is recorded 5 times. In order to eliminate possible signals of dust particles moving fortuitously through the measuring volume an intensity threshold of 1.10 times the average of the five measurements of the average scattered intensity may be set. The primary laser source attenuator is normally adjusted by the system software and preferably adjusted in the range of about 10, 000 cps . Subsequent measurements of the time autocorrelation functions during which the average intensity threshold set as above is exceeded should be disregarded. Usually a measurement consists of a suitable number of collections of the autocorrelation function (e.g. a set of 200 collections) of a typical duration of a few seconds each and accepted by the system in accordance with the threshold criterion explained above. Data analysis is then carried out on the whole set of recordings of the time autocorrelation function by use of the Contin algorithm available as a software package, which is normally included in the equipment manufacturer's software package.

[0087] The average particle diameter of the inorganic particles is not particularly limited. In general, it is lower than the thickness of the coating so as to improve the surface aspect, although, in particular rare instances, coatings having an irregular surface may be desirable. The average particle diameter of the inorganic particles is preferably two times; more preferably five times, still more preferably ten times lower than the thickness of the coating.

[ 0088 ] The average particle diameter of the inorganic particles can be notably of at most 100 ym, at most 50 ym, at most 20 ym, at most 10 ym, at most 5 ym, at most 2 ym, at most 1 ym (1000 nm) , at most 500 nm, at most 200 nm, at most 100 nm, at most 80 nm, at most 60 nm, at most 40 nm or even of at most 20 nm. On the other hand, the average particle diameter of the inorganic particles can be of at least 1 nm, at least 2 nm, at least 5 nm, at least 10 nm, at least 20 nm, at least 30 nm, at least 100 nm, at least 200 nm or even at least 500 nm. Certain preferred inorganic particles are nanoparticles , of which the average particle diameter is of at most 1 ym ; possible ranges for the average particle diameter of nanoparticles used in accordance with the present invention are : from 1 to 1000 nm, from 3 to 300 nm, from 1 to 200 nm, from 2 to 150 nm, from 1 to 100 nm, from 2 to 50 nm, with other ranges obtainable by combining any above specified lower limits with any above specified upper limits being as if explicitly herein written out.

Inorganic particles content

[ 0089] The inorganic particles content in the coating is not particularly limited. It can vary to a large extent depending notably on the encompassed properties of the coating, and other considerations such as its cost.

[ 0090 ] The inorganic particles can be contained in the coating in an amount of notably at least 0.1 wt . %, at least 0.2 wt . %, at least 0.5 wt . %, at least 1 wt . %, at least 2 wt . %, at least 5 wt . %, at least 10 wt . % or at least 20 wt . %, based on the total weight of the coating. Besides, the inorganic particles can be contained in the coating in an amount of notably at most 50 wt . %, at most 40 wt . %, at most 30 wt . %, at most 20 wt . %, at most 10 wt . %, at most 5 wt . %, at most 2 wt . % or at most 1 wt %, based on the total weight of the coating. Possible suitable ranges for the inorganic particles content of the content are : from 0.1 wt . % to 10 wt . %, from 0.2 wt . % to 20 wt. %, from 0.3 wt . % to 30 wt . %, from 1 wt . % to 30 wt . %, from 1 wt . % to 20 wt . %, from 1 wt . % to 10 wt %, from 2 wt . % to 20 wt. % and from 3 wt . % to 30 wt. %, with other ranges obtainable by combining any above specified lower limits with any above specified upper limits being as if explicitly herein written out.

Melting point and boiling point of material of which the inorganic particles are composed

[0091] The material of which the inorganic particles are composed has generally a melting point (T_m,i) at atmospheric pressure above 25°C. The melting point T_m, i can be of at least 100°C, at least 200°C, at least 400°C, at least 700°C or at least 1000°C. Besides, the material of which the inorganic particles are composed has generally a melting point at the pressure existing into the discharge or post-discharge of the atmospheric plasma (T_m,_P) above 25°C. The melting point a T_m,_P can be of at least 100°C, at least 200°C, at least 400°C, at least 700°C or at least 1000°C.

[0092] In addition, the melting point T_m, i is often above the temperature of the discharge or post-discharge zone of the plasma in which the inorganic particles are introduced. The melting point T_m,_p is also often above the temperature of the discharge or post-discharge zone of the plasma in which the inorganic particles are introduced. However, in a special embodiment in accordance with the present invention, the melting points T_m, i and/or T_m,_P of the material of which the inorganic particles are composed are lower than or equal to the temperature of the discharge or post-discharge zone of the plasma in which the inorganic particles are introduced.

[ 0093 ] The material of which the inorganic particles are composed has generally a boiling point at atmospheric pressure (T_b,i) above 100°C. The boiling point T_b,i can be of at least 400°C, at least 700°C, at least 1000°C or at least 2000°C. Besides, the material of which the inorganic particles are composed has generally a boiling point at the pressure existing into the discharge or post-discharge of the atmospheric plasma (T_b,_P) above 100°C. The boiling point T_b,_P can be of at least 400°C, at least 700°C, at least 1000°C or at least 2000°C. The material of which the inorganic particles are composed can get degraded or decomposed before boiling.

[ 0094 ] In addition, the boiling point T_b,i is usually above the temperature of the discharge or post-discharge zone of the plasma in which the inorganic particles are introduced. Likewise, the boiling point T_b,_P is usually above the temperature of the discharge or post-discharge zone of the plasma in which the inorganic particles are introduced .

[ 0095 ] Within the possible polymeric layers, the chlorinated polymers present a particular interest. Those polymers are particularly difficult to process using conventional method such as extrusion or coextrusion due to the unstability of the C-Cl chemical bond. At conventional extrusion temperature, large amount of chlorine can be emitted in the environment, degrading the properties of the final polymer, and representing a potential hazard for the health. This is particularly true for PVDC, strongly limiting its use. For that reason, PVDC is usually coated using solvent methods (emulsion or monophasic) .

[0096] Nevertheless, PVDC thin coatings are quite useful in numerous industries. More specifically, its unique barrier properties render this polymer highly attractive for the packaging industry. Indeed, it is one of the few polymer having both high gas barrier properties and low water vapour transmission rate.

[0097] Surprisingly, the use of a precursor having a

Cl/C ratio higher than 1 allows to obtain layers having properties close to those of pure PVDC. Preferably, this Cl/C ratio of the precursor is higher than 2. Advantageously, the precursor is a perchlorinated compound, or comprises a perchlorinated functional group such as a perchloroalkyl group.

[0098] In order to avoid the degradation of the chlorinated precursor, and the oxidation of the growing chlorinated polymeric layer, the partial pressure of oxygen in the plasma device is preferably maintained below lOhPa, advantageously below 5, even more preferably below 1 hPa. This may be achieved by using a purging procedure before initiating the deposition of the polymeric layer and/or by maintaining an oxygen-free gas flow as gaseous medium in which the plasma is generated. For example, the plasma reactor containing the gaseous medium in which the plasma is generated may be maintained at a pressure above atmospheric pressure for avoiding oxygen contamination from the atmosphere outside the plasma reactor and maintaining a rare gas flow for compensating gas leaks.

[0099] Preferably, the precursor will be a polychlorinated organic compound selected from the group consisting of polychloroalkane, polychloroalkene, polychloroalkyne, polychlorobenzene and a tertiary amine comprising perchloroalkane functional groups. Said tertiary amine preferably has the following structure:

wherein Ri, R2 et R3 are perchloroalkane groups, having a formula of the type C_nCl2n+i. The advantage of such a tertiary amine is a better control of the scission mechanisms of the precursor, inducing a better control of the aliphatic chains radicals length in the reactive medium. Long chains fragments being preferred, improving the deposited layer properties, perchlorotributylamine is a preferred precursor.

[0100] Advantageously, the precursor is liquid at room temperature and atmospheric pressure. Said precursor is preferably brought to the reactive medium by means of bubbling a carrier gas into the liquid precursor, thereby saturating said carrier gas by the precursor vapour. The precursor partial pressure can then be controlled by controlling the liquid precursor temperature. Said carrier gas would preferably be an inert gas such as a rare gas, preferably helium or argon.

[0101] Preferably, the saturated carrier gas will also be used to produce the aerosol comprising the inorganic particles. Said carrier gas can be for example injected in a nebuliser containing a colloidal solution of the inorganic particles.

[0102] The substrate can be placed either directly into contact to the plasma or in a post-plasma area. By post-plasma area, it is meant in the present invention an area out the plasma, located downstream of a plasma forming gas flow introduced in the plasma wherein reactive species such as radicals are still present. That post-plasma area is particularly useful for delicate substrate surfaces such as polymers. Preferably, the plasma forming gas is the same as the carrier gas, used for both carrying the polymeric precursor and producing the aerosol.

[0103] Direct plasma contact may also be advantageous, as it can induce an activation of the substrate surface and/or a cleaning by etching, thereby improving interfacial properties such as adhesion between the substrate and the polymeric layer.

[0104] The plasma used in the present invention preferably be a cold plasma. The low temperature of the neutral and ionic species in such cold plasma allows to reduce thermal degradation of the precursor, minimizing dechlorination in the case of chlorinated compounds, thereby improving the Cl/C ratio of the deposited layer.

[0105] By cold plasma, or non-thermal plasma, it is meant in the present invention a partially or wholly ionized gas comprising electrons, ions, atoms, molecules and radicals out of thermodynamic equilibrium characterized by an electron temperature significantly higher than the neutral and ionic species temperature. Preferably, in the present invention, the ionic and neutral temperature (i.e. macroscopic temperature) is lower than 400°C. Advantageously, said neutral and ionic species temperature is lower than 150°C, as at higher temperature, dechlorination of chlorinated species becomes noticeable. Ideally, the neutral and ionic species in the plasma is minimized, lower than 100°C and/or close to room temperature .

[0106] The plasma is also preferably an atmospheric plasma. Advantageously having a pressure comprised between about 1 hPa and about 2000 hPa, preferably between 100 and 1200 hPa, ideally between 500 and 600 hPa, with other ranges obtainable by combining any above specified lower limits with any above specified upper limits being as explicitly herein written out.

Example

[0107] The precursor used in this example is hexachlorobuta-1 , 3-diene . It has a vapour pressure at room temperature of 0,3hPa. During the experiment, its temperature is maintained at 37 °C. It was conveyed to the plasma rector by bubbling argon in the liquid precursor and transported through a tube. The argon flow was maintained at 121/min.

[0108] The plasma reactor was a DBD reactor. The working frequency was 15kHz and the voltage was 1600V. The pressure was maintained between 400 and 415 Torr. The deposition time was comprised between 1 and 5 minutes. The air was first evacuated from the reactor down to a pressure of about 5 Torr before introducing the saturated gas carrier .

[0109] The inorganic particles used in the experiments were cerium oxide particles commercialised under the trade name AdNano ceria 50. The particles were first dispersed in the precursor (C₄CI6) and nebulised in the vicinity of the substrate during the polymer layer growth .

[0110] The substrates used were stainless steel,

PVC, silicon wafers and quartz. No difference between the different substrates has been found.

[0111] XPS measurements have shown that the deposited layers have Cl/C atomic ratios up to 0.6. Cerium oxide was also homogeneously deposited, XPS measurement showing up to 3.6 at . % of Ce at the deposited layer surface .

Claims

1. Method for the deposition of a chlorinated polymeric layer comprising inorganic particles onto a substrate, said method comprising the steps of :

- generating a plasma in a gaseous medium by means of a plasma device;

- placing the substrate in contact with the plasma, or in a post-plasma area of said plasma;

- introducing in said plasma or in the post-plasma area a chlorinated precursor of the chlorinated polymer;

2. Method according claim 1 wherein the inorganic particles are dispersed in a liquid medium before the production of the aerosol.

3. Method according to claim 2 wherein the inorganic particles are stabilised in a colloidal solution.

4. Method according to any of claims 2 or 3 wherein the liquid is nebulised in the plasma or post- plasma by means of a carrier gas.

5. Method according to any of the previous claims wherein the chlorinated precursorhas a Cl/C ratio higher than 0,25.

6. Method according to claim 5 wherein said chlorinated precursor is a polychlorinated organic compound selected from the group consisting of polychloroalkane , polychloroalkene, polychloroalkyne, polychloroarene, tertiary amine comprising perchloroalkanes groups and mixture thereof.

7. Method according to claim 6 wherein said polychlorinated organic compound is a perchlorinated organic compound.

8. Method according to any of the previous claims wherein the gaseous medium comprises further comprises a plasma generating gas such as Argon or Helium.

9. Method according to any of the previous claims wherein the plasma is a dielectric barrier discharge

(DBD) plasma, a pulsed DC plasma, or a microwave plasma.

10. Method according to any of the previous claims wherein the pressure in the plasma is comprised between lOOhPa and 2000 hPa, preferably between 500 and 600.

11. Method according to any of the previous claims wherein the temperature of ionic and neutral species in the plasma is below 400°C, preferably below 150°C.

12. Method according to claim any of the previous claims wherein the inorganic particles comprise at least one inorganic compound CI comprising at least one metal or amphoteric element El, wherein the compound CI is selected from the group consisting of oxides, oxyfluorides , oxyhydroxyfluorides and mixtures thereof, and the element El is selected from the group consisting of Zn, Ti, Zr, Ce and mixtures thereof.

13. Method according to any of the previous claims wherein the inorganic particles comprise at least one inorganic compound C2 comprising at least one metal or amphoteric element E2, wherein the compound C2 is selected from the group consisting of oxides, fluorides, oxyfluorides , oxyhydroxyfluorides and mixtures thereof, and the metal or amphoteric element E2 is selected from the group consisting of Si, Mg, Ca, Sr and mixtures thereof.

14. Method according to any of previous claims wherein the inorganic particles comprise inorganic carbon .

15. Method according to any of previous claims wherein the inorganic particles comprise exfoliable nanoparticles having a sheet-like structure, of which the lateral size is advantageously below 900 nm, preferably below 300 nm, more preferably below 70 nm ; this lateral size is preferably above 10 nm, more preferably above 30 nm.

16. Method according to any of previous claims wherein the inorganic particles comprise at least one crystalline silicate selected from the group consisting of n e s o s i 1 i c a t e s , s o r o s i 1 i c a t e s , c y c 1 o s i 1 i c a t e s , tectosilicates , inosilicates and mixtures thereof.

17. Method according to any of previous claims wherein the inorganic particles comprise at least one metal bicarbonate or carbonate.

18. Method according to any of previous claims wherein the inorganic particles comprise at least one metal oxide or hydroxide.

19. Method according to any of previous claims wherein the inorganic particles comprise at least one metal salt, including a halogenide or an oxysalt.

20. Method according to any of previous claims wherein the inorganic particles comprise zinc borate, in particular anhydrous zinc borate.

21. Method according to any of previous claims wherein the inorganic particles are of such a chemical nature that they can act as pigments.

22. Method according to any of previous claims wherein the inorganic particles comprise metallic particles, preferably transition metals.

23. Substrate comprising a polymeric layer comprising inorganic particles, said polymeric layer being produced according to any of previous claims.

24. Substrate according to claim 23 wherein said polymeric layer is cross-linked.

25. Substrate according to any of claims 23 or 24 wherein the polymeric layer is a chlorinated polymer having a Cl/C ratio higher than 0,5, preferably higher than 0,75, more preferably higher than or equal to 1.