Device and method for impregnating a fibre support with powder

Abstract

The invention relates to a method for impregnating a fibre support (S) with a powder material (P), the method comprising the steps of: - bringing the powder material (P) and the support (S) into contact; - passing the support (S) and the powder (P) between electrodes (3, 3', 4, 4') that are at different potentials in order to cause the powder material (P) to penetrate into the support (S), characterised in that it further comprises an additional pretreatment step, prior to bringing the powder material (P) and the support (S) into contact, during which the support (S) that is not coated with powder material (P) is passed between electrodes (3, 3') that are at different potentials. The invention also relates to the device (100) for implementing the method.

Description

[0001] DEVICE AND METHOD FOR IMPREGNATING A FIBROUS SUPPORT WITH POWDER

[0002] Technical Field

[0003] The present invention relates to the field of impregnation of porous supports with powdery materials. The supports are, for example, textiles or fibrous, porous, non-woven and / or agglomerated materials.

[0004] The substrates are to be treated by impregnation with powders having specific physicochemical properties, for example thermoplastics, thermosetting agents, flame retardants, cosmetic, medical, antimicrobial, hemostatic powders, etc.

[0005] The invention focuses in particular on increasing the penetration of powder into the supports, which is particularly advantageous for increasing product performance and for improving impregnation yields when the powders are expensive, for example cosmetic or medical products.

[0006] Previous Art

[0007] Documents WO99 / 22920 and FR2933327 each describe an installation for impregnating powder into a fibrous or porous, non-conductive support. The installation described comprises means for moving the support, on which the solid material powder is deposited.

[0008] The method of these documents is intended in particular only for non-conductive supports because the use of conductive material, for example carbon fibers, between electrodes supplied with alternating current will prevent the electric field from being distributed in the thickness of the conductive material and potentially cause flashes due to the use of intense electric fields.

[0009] The powder-coated support is then transported between electrodes connected to an alternating voltage generator, the electrodes on each side of the support being connected to one of the terminals of a voltage generator. The polarized powder will be set in motion by the electric field between the two electrodes, particularly towards the center of the support. The powder then impregnates the support.

[0010] Document FR3031756 further describes using a heat pretreatment before applying the powder to the support, in order to improve the penetration of the powder into said support.

[0011] Heat pretreatment is, however, energy-intensive and can degrade heat-sensitive media.

[0012] There is therefore a need for a powder impregnation process that can improve yield, ideally without resorting to heat pretreatment.

[0013] Statement of the invention

[0014] In order to address this technical problem, the invention proposes a method for impregnating a fibrous support with a powdery material, comprising the steps:

[0015] - bringing the powdered material and the support into contact,

[0016] - passage of the support and the powder between electrodes brought to different potentials, to make the powdery material penetrate into the support, characterized in that it further comprises an additional pretreatment step, prior to bringing the powdery material and the support into contact, during which the support not coated with powdery material is passed between electrodes brought to different potentials.

[0017] Indeed, the Applicant was surprised to find that samples of powdered material having been passed empty between impregnation electrodes had a higher impregnation capacity. Up to 70% more powder can then be impregnated into the support.

[0018] The method may further have one or more of the following characteristics.

[0019] The support can pass between electrodes before the deposition of powder material in one direction, then be brought into contact with the powder material, and finally pass back between the electrodes in the opposite direction once brought into contact with the powder material.

[0020] In a prior step, a plurality of cut supports may be placed in a tray, said tray having locations of shape and size corresponding to those of the cut supports.

[0021] The invention also relates to the device for impregnating a fibrous support with an associated powdery material, characterized in that it comprises:

[0022] - means of moving the support,

[0023] - means of bringing the powdered material into contact with the support,

[0024] - electrodes, connected to terminals of a voltage generator comprising at least two terminals at different potentials, generating an alternating electric field applied to the path of the support set in motion, characterized in that the means for setting the support in motion cause said support to pass between the electrodes before passing through the means for bringing the powdered material into contact with the support.

[0025] The electrodes may in particular be arranged transversely relative to the direction of progression of the support, connected alternately, relative to the direction of progression of the support, to the opposite terminals of the alternating voltage generator.

[0026] The pretreatment and impregnation electrodes can be produced in the form of metal strips deposited on a dielectric support, and the means for moving the support can be configured to advance the support continuously.

[0027] The alternation of potentials along the path of the support allows the particles of powdered material to be agitated more effectively because they encounter greater gradients.

[0028] The device may comprise pretreatment electrodes, located in parallel with the means for bringing the powder and the support into contact, the means for bringing the powder and the support into contact depositing powdered material on a belt of the means for moving the support, the support covering the belt and the powdered material at the outlet of the means for bringing the powder and the support into contact, then passing between impregnation electrodes. Alternatively, the means for moving the support may be configured to advance it in successive steps, and in that the pretreatment and impregnation electrodes are produced in the form of continuous flat electrodes on either side of the support, the successive steps bringing the support successively:

[0029] - between the pretreatment electrodes,

[0030] - at the level of the means of bringing the powder and the support into contact,

[0031] - between the impregnation electrodes.

[0032] The means for contacting the powder and the carrier may comprise a sprinkler which terminates in apertures forming a mask for the targeted deposition of powdered material in a predetermined pattern.

[0033] Brief description of the figures

[0034] The invention will be clearly understood on reading the following description, the details of which are given solely by way of example, and developed in relation to the appended figures, in which identical references refer to identical elements:

[0035] [Fig. 1] is a schematic side view of a device according to the invention,

[0036] [Fig. 2] is a schematic side view of a second embodiment of a device according to the invention,

[0037] [Fig. 3] is a schematic side view of a device according to a third embodiment of the invention operating from roll to roll,

[0038] [Fig. 4] is a schematic side view of a fourth embodiment of the invention operating in successive steps,

[0039] [Fig. 5] is a schematic representation of a fifth embodiment, in which the powder is deposited under the support,

[0040] [Fig. 6] is a schematic flowchart illustrating the main steps of the process associated with the device of Figure 1,

[0041] [Fig. 7] is a table showing experimental results of impregnation according to the method of the invention. The particular embodiments shown are given for illustrative purposes and are not limiting.

[0042] Detailed description of the invention

[0043] Figure 1 is a schematic representation of a device 100 for impregnating a fibrous or porous support S with a powdery material P.

[0044] The support S is set in motion by movement means 1, here a belt conveyor. The movement means 1 move the support S forward in a direction considered longitudinal L.

[0045] The support S is for example a strip of woven or non-woven fibrous material, in particular made of natural, artificial or synthetic fibers, bioresorbable or not, and the powdered material P can in particular be a functional powder, for example antimicrobial or hemostatic. This then produces an antimicrobial functional dressing, or a hemostatic implant or "patch", implanted in the body of a patient during a surgical procedure. Antimicrobial dressings prevent infection of patients' wounds and hemostatic implants impregnated with coagulating hemostatic powder prevent massive internal hemorrhages.

[0046] Their bioresorbable nature makes it possible to avoid subsequent intervention for the extraction of implants.

[0047] Active medical powders in general and the haemostatic powder used in particular are expensive, so that the smallest quantities of said powders not penetrating the support S, and therefore lost, represent a significant loss in terms of cost and constitute medical waste which must be treated with particular precautions.

[0048] The device 100 here comprises trays 10 with recesses, in which a plurality of cut-out supports S, here substantially rectangular hemostatic implants, are arranged.

[0049] The support S, progressing along the longitudinal direction L in its direction of progression, passes in particular sequentially through three stations: a fiber pretreatment station 101, a powder contacting station 103 and an impregnation station 105. The fiber pretreatment station 101 comprises opening electrodes 3, 3', which are connected to a voltage generator G, which brings them to alternating electrical potentials.

[0050] Means 5 for bringing the powdery material P and the support S into contact are arranged above the support S, just after the opening electrodes 3, 3', following the direction of progression L of the support S.

[0051] Said contacting means 5 deposit the powdery material P on the upper side of the support S, in particular with a substantially uniform and continuous distribution along this surface. According to a variant, the powdery material P can be applied following a particular geometric pattern on the surface of the support.

[0052] The pre-treatment electrodes 3, 3' are alternately connected to the terminals of a generator G, in particular an alternating electrostatic generator.

[0053] Only the connections between generator G and electrodes 3 located above support S are shown, but electrodes 3' located below are also connected to the opposite terminals of said generator G with respect to electrodes 3 located above.

[0054] Generator G is, for example, an alternating voltage generator, with a frequency of around 100 hertz, and a nominal voltage of several thousand volts, typically of the order of 20 to 50kV.

[0055] The electrodes 3, 3' thus generate a variable electric field applied to the path of the support S set in motion, with different values ​​and directions along the path of the support S.

[0056] When they pass between the electrodes 3, 3' for a predetermined duration, the fibers of the support S are electrically charged throughout the thickness of the support, and repel each other, which results in a significant swelling of the support S by separation of its fibers and in transfers of electrical charges on the fibers. The void rate and the openings in the volume of the support S are increased.

[0057] In particular, the length occupied by the electrodes 3, 3' of the pretreatment station 101 is sufficiently large so that the support S remains, at the expected speed of progression, between said electrodes 3, 3' for at least two seconds, in particular between five and thirty seconds.

[0058] At the exit of the fiber opening station 101, the supports S arrive in the station for bringing the powder and the support into contact 103.

[0059] This station for bringing the powder and the support into contact 103 notably comprises means for bringing the powder and the support into contact 5, specifically for depositing the powdery material P only on the supports S, for example by means of a mask with recovery of the powdery material deposited alongside.

[0060] The particles of powdered material P are in particular sufficiently fine to be able to be inserted between fibers or into pores of the support S.

[0061] Once the powdered material P has been deposited, the supports S arrive in the impregnation station 105.

[0062] The impregnation station 105 comprises a second set of electrodes 4, 4', connected to a second voltage generator G'. The electrodes 4, 4' of this second set are in particular also connected alternately to the terminals of the second generator G'.

[0063] According to a particular embodiment, a single generator G can supply the two sets of electrodes 3, 3', 4, 4'.

[0064] The electrodes 3, 3', 4, 4' can for example be produced in the form of strips of conductive material, arranged transversely with respect to the direction of travel L of the support S, on plates of dielectric material 30, 40. The electrodes are then those described in the document FR2933327. Other forms of electrodes 3, 3', 4, 4' are of course possible (see figure 4).

[0065] The electrodes 3, 3' are in particular configured so as not to induce massive ionization of the support S, avoiding any breakdown. Only a displacement of the electrons of the support S is induced, without supply of electrons from the electrodes 3, 3' to the support S or vice versa.

[0066] In particular, the strips of conductive material can be connected alternately, following the direction of progression of the support S, to different terminals of the generator G, G'. The generator G, G' can then be at direct voltage. The electric field is then uniform in time, but variable in space. The variable field for impregnation is then generated by the progression of the support S.

[0067] The electrodes 3, 3', 4, 4' can be partly connected to a neutral potential (earth) or else connected to opposite terminals of the generator G, G', or more generally to out-of-phase terminals.

[0068] When the powdery material P placed on the support S passes through the space under said electrodes 4, 4' of the second set, the charged particles of said powdery material P are agitated by the generated electric force and penetrate the support S.

[0069] The electrodes 4, 4' in particular agitate the particles of powdery material P, via the electric field that they generate, because said particles are polarized, and in addition the particles collide and repel each other. This agitation allows said particles to infiltrate between the fibers of the support S and to attach there, and therefore the powdery material P to penetrate permanently into the support S.

[0070] Passing through the pretreatment station 101 then allows the powdered material P to enter the support S in greater quantity, with a lower concentration gradient, and thus a better distribution of the powdered material in its volume.

[0071] Figure 2 shows an alternative embodiment of device 100.

[0072] In this embodiment, the means 1 for moving the support S can convey the support S in two opposite directions, forward and backward.

[0073] The device 100 comprises only one set of electrodes 3, 3', used both for pretreatment and for penetration of the powdered material P into the support S.

[0074] The supports S, arranged here in a tray 10, are then passed a first time between the electrodes 3, 3', the movement means moving the support S in the forward direction. The supports S are in particular held between the electrodes 3, 3' for a predetermined duration, greater than two seconds, typically from five to thirty seconds.

[0075] At the outlet of the electrodes 3, 3', after pretreatment of the fibers, the deposition of powdery material P is carried out with the means for bringing the powder and the support S into contact. When all of the supports S are covered with powdery material P, the supports S have reached an extreme position, and the movement means 1 then reverse the movement of the plate 10. The movement in the return direction of the supports S brings them again under the electrodes 3, 3', this time with powdery material P deposited on their surface.

[0076] During this second passage under the electrodes 3, 3', the particles of powdered material P are set in motion and penetrate into the support S. The generator G can in particular be configured differently during the return movement of the plate 10 of supports S compared to the first passage in the forward direction.

[0077] This embodiment is particularly suitable for small laboratories with limited space and producing limited series of products. Indeed, only one set of electrodes 3, 3' is present, with a single generator G of limited capacity. The same electrodes 3, 3' are used for the pretreatment and then the impregnation of the support S.

[0078] However, the back and forth movement means that only one tray of S media can be processed at a time.

[0079] Figure 3 shows in side view an alternative embodiment of device 100.

[0080] In this embodiment, the support S is in the form of a continuous strip, coming from a starting roll R1, and ending after treatment in a treated roll R2.

[0081] The device of Figure 3 is essentially identical to that of Figure 1, the only difference being the shape of the support S and the absence of trays 10. Additional movement means may be provided specifically for unwinding and winding the support S onto the rollers R1, R2.

[0082] Figure 4 shows a fourth embodiment of device 100, operating in successive steps.

[0083] The device 100 of Figure 4 has two sets of electrodes 3, 3', 4, 4', between which pass the supports S cut out and placed in a tray 10. Between the two sets of electrodes 3, 3', 4, 4', the means for bringing the powder and the support S into contact are arranged. Said contacting means 5 here comprise a sprinkler, in which the powdery material P is suspended, and which ends with openings forming a mask for the targeted deposition of powdery material P according to a predetermined pattern, here specifically on the supports S cut out and not on the trays 10.

[0084] The mask can also be used to spread the powder material P on the supports S according to a specific pattern. Several sprinklers with specific masks can be used successively on the supports S between the two sets of electrodes, for example to carry out a deposition of several different powder materials P according to a specific pattern (design, gradient of powder material P, different functional parts on the same support S etc.).

[0085] The electrodes 3, 3', 4, 4' are here produced in the form of continuous metal plates insulated by a dielectric material, which covers the supports S and plates 10 during their treatment.

[0086] The means 1 for moving the supports S operate in successive steps, during which the supports S are advanced by a predetermined length, and with a stopping time between each step. The length of movement at each step is greater than the length of the supports S and plates 10, and the stopping time between each step is for example from a few seconds to tens of seconds, in order to allow processing of the supports S after each step.

[0087] A tray 10 carrying cut supports S comes between the pretreatment electrodes 3 following a first displacement step, coming for example from a stock of trays 10. During the stopping time after this first displacement step, the generator G brings the electrodes 3, 3' to a variable potential, in order to generate a variable electric field in the space between said electrodes 3, 3' where the tray 10 and the supports S are located.

[0088] The tray 10 with the supports S is then brought by the next displacement step under the sprinkler forming contacting means 5. During the stopping time after this second step, the powdered material P is sprinkled onto the supports S.

[0089] During the second displacement step, a second plate 10 with its supports S is brought between the pretreatment electrodes 3, 3'. During the third displacement step, the plate 10 with its supports S on which the powdery material P has been deposited is brought between the electrodes 4, 4' of the second set. During the stopping time after this third step, the second generator G' brings the electrodes 4, 4' of the second set to an alternating potential in order to make the powdery material P penetrate into the support S.

[0090] During the third movement step, the second plate 10 is brought from the pretreatment electrodes 3, 3' to the means for bringing powdery material P into contact, and a third plate 10 is brought between the pretreatment electrodes 3, 3'.

[0091] During the fourth movement step, the treated tray 10 is evacuated to an outlet, the second and third trays 10 pass to the next station, and a fourth tray 10 is inserted between the pretreatment electrodes 3, 3'.

[0092] In the embodiments of figures 1 to 3, the electric field between the electrodes 3, 3', 4, 4' of the same set is variable according to the direction L of progression of the support S in addition to the variability linked to the alternating nature of the voltage at the terminals of the generators G. The supports S advancing between the electrodes 3, 3', 4, 4' thus undergo a double variation of the field: more intense when the supports are located under the strips of electrodes and less intense when the supports are located between 2 strips of electrodes, i.e. a spatially non-homogeneous field.

[0093] On the other hand, in the embodiment of Figure 4, only one pair of electrodes 3, 3', 4, 4' is present on each side of the supports S of a tray 10, and the electric field is consequently less variable in space. However, the supports S remain fixed for a predetermined time interval under the electrodes 3, 3', 4, 4', whose generators G, G' are at alternating voltage, a time which can be extended until the pretreatment and / or the penetration of powdered material P is sufficient.

[0094] Figure 5 is a schematic side view representation of a device 100 implementing the invention.

[0095] The support S is here again a continuous strip, going from a starting roller R1 to an arrival roller R2. In the embodiment of figure 5, the powdery material P is applied to a conveyor belt 11, set in motion by the movement means 1, and the support S having undergone pretreatment then comes over the powdery material P deposited on the belt 11.

[0096] To do this, the pretreatment station 101 is located in parallel with the powder contacting station 103. In particular, in the embodiment shown, the pretreatment station 101 is located above the powder contacting station 103.

[0097] The support S passes into the pretreatment station 101, between the pretreatment electrodes 3. In parallel below, in the powder contacting station 103, the powder P is deposited on the belt 11. The belt 11 may in particular have asperities, grooves and hollow patterns to accommodate the powder P and manage its distribution in the support S after impregnation.

[0098] The support S is then applied over the powder P on the belt 11, at the outlet of the pretreatment stations 101 and the powder contact station 103. The support S is driven by the belt 11 towards the impregnation station 105, still with the powder P caught between the support S and the belt 11.

[0099] In the impregnation station 105, the belt 11, the support S and the powder P taken between the two pass between the impregnation electrodes 4, 4'. Between the impregnation electrodes 4, 4', the alternating electric field sets the powder particles P in motion, which then migrate towards the interior of the support S.

[0100] At the outlet of the impregnation station 105, the support S impregnated with powder P is directed towards the roller R2 and wound onto it.

[0101] Figure 6 is a flowchart showing the main steps of the impregnation process 200 implemented in the devices 100 previously described.

[0102] The first step 201 is the pretreatment of the support S, before bringing the powdery material P into contact with said support S. This step is carried out by means of the electrodes 3, 3' between which the support S passes before coming into contact with the powdery material P. The second step 203 is the bringing into contact of the powdery material P and the support S, previously passed between the pretreatment electrodes 3, 3'. This step 203 is carried out with the contacting means 5.

[0103] The third step 205 is then the second passage between electrodes, either the same 3, 3' as those of the first step 201 in a return direction, or an additional set 4, 4' dedicated, so that the powdery material P penetrates into the support S.

[0104] The associated impregnation method 200 and impregnation device 100 allow increased penetration of powder material P into the support S, which means that less powder material P is lost during impregnation. This aspect is particularly important in the case of expensive or polluting powder materials P.

[0105] Figure 7 illustrates the advantages provided by the impregnation method 200 according to the invention.

[0106] Figure 7 is a table illustrating the results obtained experimentally with three different non-woven S supports, corresponding to the three data lines in the table.

[0107] The three S brackets are listed in the "Ref." column and are, in descending order:

[0108] - cotton, of the type used in cosmetics, hydro-bonded non-woven,

[0109] - non-woven needle-punched polyester (“polyester”), and

[0110] - airlaid cellulose fiber paper, of the type used in tablecloths and hygiene products, non-woven airlaid.

[0111] For the experiment, the S supports are cut into 5 x 10 cm rectangles and inserted into a tray 10 whose surface is covered with a honeycomb grid. The mass Mo of the S supports before impregnation is given in grams (g) in the first data column of the table in Figure 5.

[0112] The P powder, when applied, is scraped into the honeycomb grid, on which the cut S supports are placed. The P powder used is a green clay from the company Argile du Velay, reference “cosgreen™ superfine” with particle sizes ranging from 0 to 100 pm. The electrodes 3, 3', 4, 4' are at a potential of 40 kV alternating current, at a frequency of 100 Hz. The S supports are held between the electrodes for a period of 15 seconds.

[0113] The second column of the table gives the mass Mi of powder with which the supports S were impregnated, directly coated with powder and then passed between the electrodes 4, 4' without pretreatment by passing between the electrodes without powder.

[0114] The third column of the table gives the mass M2 of powder P with which supports S were impregnated with pretreatment by passing between the electrodes 3, 3' before the deposition of powder P.

[0115] The mass M1 or M2 of powder P is in particular deduced by weighing the impregnated supports S, from which the mass Mo of the supports S before impregnation is subtracted.

[0116] The fourth column of the table gives the difference in mass AM of impregnated P powder between the supports S with and without vacuum treatment between the electrodes 3, 3', 4, 4'. The fifth column gives the percentage of additional P powder impregnated in the support S due to the pretreatment.

[0117] In the case of cotton, the mass of impregnated powder P is 0.719 grams without pretreatment and 0.955 grams with pretreatment, an additional quantity of 0.236 grams, and therefore an increase of 33%.

[0118] In the case of polyester, the mass of impregnated powder P without pretreatment is 0.666 grams without pretreatment and 0.958 grams with pretreatment, an additional quantity of 0.292 grams, and therefore an increase of 44%.

[0119] In the case of the air-deposited cellulose fiber support S, the mass of impregnated powder P without pretreatment is 0.123 grams without pretreatment and 0.209 grams with pretreatment, an additional quantity of 0.086 grams, and therefore an increase of 70%.

[0120] The Applicant also carried out an additional test, during which a polyester support S was impregnated with polyester thermosetting resin powder having an average diameter of 41 μm, with and without pretreatment as detailed above. The product thus obtained can then be used in the context of thermoformable composite materials. The quantity of powder P impregnated without pretreatment was 0.603 grams and 0.975 grams with pretreatment. There is therefore an excess of powder of the order of 62% which impregnates the support S with the pretreatment.

[0121] We therefore observe a marked and quantifiable technical effect, allowing better impregnation of the supports S and reducing losses of powder P.

Claims

Claims

1. Method for impregnating a fibrous support (S) with a powdery material (P), comprising the steps: - bringing the powdered material (P) into contact with the support (S), - passage of the support (S) and the powder (P) between electrodes (3, 3', 4, 4') brought to different potentials, to make the powdery material (P) penetrate into the support (S), characterized in that it further comprises an additional pretreatment step, prior to bringing the powdery material (P) into contact with the support (S), during which the support (S) not coated with powdery material (P) is passed between electrodes (3, 3') brought to different potentials for a predetermined duration.

2. Method according to claim 1, characterized in that the support (S) passes between electrodes (3, 3') before the deposition of powdery material (P) in one direction, then is brought into contact with the powdery material (P), and finally passed back between the electrodes (3, 3') in the opposite direction once brought into contact with the powdery material (P).

3. Method according to claim 1 or 2, characterized in that during a prior step, a plurality of cut supports (S) are placed in a tray (10), said tray (10) comprising locations of shape and dimension corresponding to those of the cut supports (S).

4. Device for impregnating a fibrous support (S) with a powdery material (P), characterized in that it comprises: - means for setting in motion (1) the support (S), - means for bringing the powdered material (P) into contact (5) with the support (S), - electrodes (3, 3', 4, 4'), connected to the terminals of a voltage generator (G, G') comprising at least two terminals at different potentials, generating an electric field applied to the path of the support (S) set in motion, characterized in that the means for setting in motion (1) the support (S) make passing said support (S) between the electrodes before passing through the means for bringing the powdered material (P) into contact (5).

5. Impregnation device according to claim 4, characterized in that the electrodes (3, 3', 4, 4') are arranged transversely relative to the direction of progression (L) of the support (S), connected alternately, relative to the direction of progression of the support to the terminals of a voltage generator (G, G').

6. Device according to one of claims 4 or 5, characterized in that the pretreatment and impregnation electrodes (3, 3', 4, 4') are produced in the form of metal strips deposited on a dielectric support (30, 40), and in that the means for setting in motion (1) the support (S) are configured to advance the support (S) continuously.

7. Device according to one of claims 4 to 6, characterized in that it comprises pretreatment electrodes (3, 3'), located in parallel with the means for bringing the powder and the support into contact (5), the means for bringing the powder and the support into contact (5) depositing powdery material (P) on a belt (11) of the means for moving (1) the support (S), the support (S) covering the belt (11) and the powdery material (P) at the outlet of the pretreatment electrodes (3), then passing between the impregnation electrodes (4, 4').

8. Device according to one of claims 4 or 5, characterized in that the means for setting in motion (1) the support (S) are configured to make it advance in successive steps, and in that the pretreatment and impregnation electrodes (3, 3', 4, 4') are produced in the form of continuous flat electrodes, one per face of the support (S), the successive steps bringing the supports (S) successively: - between the pretreatment electrodes (3, 3'), - at the level of the means of bringing the powder and the support into contact (5), - between the impregnation electrodes (4, 4').

9. Device according to the preceding claim, characterized in that the means for bringing the powder and the support (5) into contact comprise a sprinkler which ends with openings forming a mask for the targeted deposition of powdered material (P) according to a predetermined pattern.

Images