DEVICE AND METHOD FOR POWDER-IMPREGNATING A FIBROUS SUPPORT

Abstract

The invention relates to a method for impregnating a fibrous support (S) with a powdered material (P), comprising the steps: - bringing the powdered material (P) into contact with the support (S), - passing the support (S) and the powder (P) between electrodes (3, 3', 4, 4') held at different potentials, to allow the powdered material (P) to penetrate the support (S), characterized in that it further comprises an additional pretreatment step, prior to bringing the powdered material (P) into contact with the support (S), during which the support (S), uncoated with powdered material (P), is passed between electrodes (3, 3') held at different potentials. The invention also relates to the device (100) for carrying out said method. Figure for the abstract: [Fig. 1]

Description

Title of the invention: DEVICE AND METHOD POWDER IMPREGNATION OF A FIBROUS SUPPORT technical field

[0001] The present invention relates to the field of impregnation of porous substrates by powdered materials. The substrates are, for example, textiles or fibrous, porous, non-woven and / or agglomerated materials.

[0002] The supports are to be treated by impregnation with powders having specific physicochemical properties, for example thermoplastics, thermosetting, flame retardants, cosmetic, medical, antimicrobial, hemostatic powders etc.

[0003] The invention focuses in particular on increasing the penetration of powder into the supports, which is particularly advantageous for increasing the performance of the products and for improving impregnation yields when the powders are expensive, for example cosmetic or medical products. Previous Art

[0004] Documents WO99 / 22920 and FR2933327 each describe an installation for impregnating powder into a fibrous or porous substrate. The described installation includes means for moving the substrate onto which the powder is deposited.

[0005] 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.

[0006] 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.

[0007] Document FR3031756 further describes using a thermal pretreatment before applying the powder to the support, in order to improve the penetration of the powder into said support.

[0008] However, thermal pretreatment is energy-intensive and can degrade heat-sensitive substrates.

[0009] There is therefore a need for a powder impregnation process that improves yield, ideally without resorting to thermal pretreatment. Description of the invention

[0010] In order to address this technical problem, the invention proposes a method for impregnating a fibrous support with a powdered material, comprising the following steps: - bringing the powdered material into contact with the substrate, - passage of the support and the powder between electrodes held at different potentials, to make the powdery material penetrate the support, characterized in that it further comprises an additional pretreatment step, prior to the contacting of the powdery material and the support, during which the support not coated with powdery material is passed between electrodes held at different potentials.

[0011] Indeed, the Applicant was surprised to find that samples passed between impregnation electrodes without a vacuum of powdered material exhibited a greater impregnation capacity. Up to 70% more powder can then be impregnated into the support.

[0012] The process may, in addition, have one or more of the following characteristics.

[0013] The support may pass between electrodes before the deposition of powdered material in one direction, then be brought into contact with the powdered material, and finally pass back between the electrodes in the opposite direction once in contact with the powdered material.

[0014] In a preliminary step, a plurality of cut supports can be placed in a tray, said tray having locations of shape and size corresponding to those of the cut supports.

[0015] The invention also relates to the device for impregnating a fibrous support with an associated powdered material, characterized in that it comprises: - means of setting the support in motion, - means of bringing the powdered material into contact with the support, - electrodes, connected to the terminals of a voltage generator having at least two terminals at different potentials, generating an alternating electric field applied along the path of the moving support, characterized in that the means for moving the support cause said support to pass between the electrodes before passing through the means for bringing the powdery material into contact with the support.

[0016] The electrodes can in particular be arranged transversely with respect to the direction of progression of the support, connected alternately, with respect to the direction of progression of the support to the opposite terminals of the alternating voltage generator.

[0017] The pretreatment and impregnation electrodes can be made in the form of metallic strips deposited on a dielectric support, and the means for moving the support can be configured to advance the support continuously.

[0018] The alternation of potentials along the path of the support makes it possible to agitate the particles of powdered material more effectively because they encounter greater gradients.

[0019] The device may include pretreatment electrodes, located in parallel with the means of bringing the powder and the support into contact, the means of bringing the powder and the support into contact depositing powdery material on a conveyor belt means of moving the support, the support covering the conveyor belt and the powdery material exiting the means of bringing the powder and the support into contact, then passing between impregnation electrodes.

[0020] Alternatively, the means for moving the support can be configured to advance it in successive steps, and in that the pretreatment and impregnation electrodes are made in the form of continuous flat electrodes on either side of the support, the successive steps bringing the support forward successively: - between the pretreatment electrodes, - regarding the means of bringing the powder and the support into contact, - between the impregnation electrodes.

[0021] The means for bringing the powder and the support into contact may include a sprinkler which terminates with openings forming a mask for the targeted deposition of powdered material according to a predetermined pattern. Brief description of the figures

[0022] The invention will be better understood upon reading the following description, the details of which are given solely by way of example, and developed in relation to the accompanying figures, in which identical references refer to identical elements:

[0023] [Fig. 1] is a schematic side view of a device according to the invention,

[0024] [Fig.2] is a schematic side view of a second embodiment of device according to the invention,

[0025] [Fig.3] is a schematic side view of a device according to a third embodiment of the invention operating from roll to roll,

[0026] [Fig.4] is a schematic side view of a fourth embodiment of the invention operating by successive steps,

[0027] [Fig.5] is a schematic representation of a fifth embodiment, in which the powder is deposited under the support,

[0028] [Fig.6] is a schematic flowchart illustrating the main steps of the process associated with the device of [Fig.1],

[0029] [Fig.7] is a table summarizing experimental results of impregnation according to the process of the invention.

[0030] The particular embodiments shown are given for illustrative purposes only and are not intended to be limiting. Detailed description of the invention

[0031] Fig. 1 is a schematic representation of an impregnation device 100 of a fibrous or porous support S by a powdery material P.

[0032] The support S is set in motion by drive means 1, here a belt conveyor. The drive means 1 advance the support S in a longitudinal direction L.

[0033] 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 non-bioresorbable, and the powdered material P may, in particular, be a functional powder, for example, an antimicrobial or hemostatic powder. This results in an antimicrobial functional dressing, or a hemostatic implant or patch, which is implanted in a patient's body during surgery. Antimicrobial dressings help prevent wound infection, and hemostatic implants impregnated with coagulant hemostatic powder help prevent massive internal bleeding.

[0034] Their bioresorbable nature makes it possible to avoid a subsequent intervention for the extraction of the implants.

[0035] Medical active powders in general, and hemostatic powder 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 special precautions.

[0036] 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.

[0037] 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.

[0038] The fiber pretreatment station 101 includes aperture electrodes 3, 3', which are connected to a voltage generator G, which brings them to alternating electrical potentials.

[0039] Means for bringing the powdered material P and the support S into contact 5 are arranged above the support S, just after the opening electrodes 3, 3', following the direction of progression L of the support S.

[0040] Said contacting means 5 deposit the powdered material P onto the upper side of the support S, in particular with a substantially uniform and continuous distribution along this surface. According to one embodiment, the powdered material P can be applied following a particular geometric pattern on the surface of the support.

[0041] The pre-treatment electrodes 3, 3' are alternately connected to the terminals of a generator G, in particular an alternating electrostatic generator.

[0042] Only the connections between the generator G and the electrodes 3 located above the support S are shown, but the electrodes 3' located below are also connected to the opposite terminals of said generator G with respect to the electrodes 3 located above.

[0043] The generator G is for example an alternating voltage generator, with a frequency of the order of 100 hertz, and a nominal voltage of several thousand volts, typically in the order of 20 to 50kV.

[0044] The electrodes 3, 3' thus generate a variable electric field applied along the path of the moving support S, with different values ​​and directions along the path of the support S.

[0045] During passage between electrodes 3, 3', the fibers of the support S become electrically charged and repel each other, resulting in a significant swelling of the support S due to the separation of its fibers and the transfer of electrical charges along the fibers. The void ratio and the openings in the volume of the support S are increased.

[0046] At the exit of the fiber opening station 101, the supports S arrive at the powder and support contacting station 103.

[0047] This powder and support contact station 103 includes in particular means for contacting the powder and the support 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 next to it.

[0048] The particles of powdery material P are in particular sufficiently fine to be able to fit between fibers or into pores of the support S.

[0049] Once the powdered material P has been deposited, the supports S arrive at the impregnation station 105.

[0050] The impregnation station 105 includes a second set of electrodes 4, 4', connected to a second voltage generator G'. The electrodes 4, 4' of this second set are also connected alternately to the terminals of the second generator G'.

[0051] According to a particular embodiment, a single generator G can supply the two sets of electrodes 3, 3', 4, 4'.

[0052] The electrodes 3, 3', 4, 4' can, for example, be made 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 document FR2933327. Other shapes of electrodes 3, 3', 4, 4' are of course possible (see [Fig.4]).

[0053] 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 a DC voltage generator. The electric field is then uniform over time, but variable in space. The variable field for impregnation is then generated by the progression of the support S.

[0054] The electrodes 3, 3', 4, 4' can be partly connected to a neutral potential (earth) or connected to opposite terminals of the generator G, G', or more generally to out-of-phase terminals.

[0055] When the powdered material P disposed on the support S passes through the space under said electrodes 4, 4' of the second set, the charged particles of said powdered material P are agitated by the generated electrical force and penetrate the support S.

[0056] The electrodes 4, 4' agitate the particles of powdered material P, via the electric field they generate, because said particles are polarized, and furthermore, the particles collide and repel each other. This agitation allows said particles to infiltrate between the fibers of the support S and become fixed there, and thus allows the powdered material P to penetrate permanently into the support S.

[0057] Passing through the pretreatment station 101 then allows the powdery material P to enter in greater quantity into the support S, with a lower concentration gradient, and thus a better distribution of the powdery material in its volume.

[0058] Fig. 2 shows an alternative embodiment of device 100.

[0059] In this embodiment, the means for moving the support S 1 can convey the support S in two opposite directions of forward and return.

[0060] The device 100 comprises only one set of electrodes 3, 3', used both for pretreatment and for the penetration of the powdery material P into the support S.

[0061] The supports S, arranged here in a plate 10, are then passed once between the electrodes 3, 3' the means of movement moving the support S in the forward direction.

[0062] At the output of the electrodes 3, 3', after pretreatment of the fibers, the deposition of powdery material P is carried out with the means of contacting the powder and the support S.

[0063] When all 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 return movement of the supports S brings them back under the electrodes 3, 3', this time with powdery material P deposited on their surface.

[0064] During this second pass 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 parameterized differently during the return movement of the plate 10 of supports S compared to the first forward pass.

[0065] This embodiment is particularly suitable for small laboratories with limited space limited 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 pretreatment and then for impregnation of the support S. However, the back-and-forth movement means that only one tray 10 of supports S can be processed at a time.

[0066] Fig. 3 shows a side view of an alternative embodiment of device 100.

[0067] In this embodiment, the support S is in the form of a continuous strip, coming from a starting roll RI, and ending after processing in a treated roll R2.

[0068] The device of [Fig.3] is essentially identical to that of [Fig.1], the only difference being the shape of the support S and the absence of plates 10. Additional means for setting in motion can be provided specifically for unwinding and winding the support S onto the rollers RI, R2.

[0069] Fig. 4 shows a fourth embodiment of device 100, operating by successive steps.

[0070] The device 100 of [Fig.4] has two sets of electrodes 3, 3', 4, 4', between which the cut supports S pass and are placed in a tray 10. Between the two sets of electrodes 3, 3', 4, 4', are arranged the means for bringing the powder and the support S into contact. Said means for bringing the powder and the support S into contact 5 here comprise a sprinkler, in which the powdered material P is suspended, and which terminates with openings forming a mask for the targeted deposition of powdered material P according to a predetermined pattern, here specifically on the cut supports S and not on the trays 10.

[0071] The mask can also be used to spread the powdered material P onto 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 deposit several different powdered materials P according to a specific pattern (design, gradient of powdered material P, different functional parts on the same support S, etc.).

[0072] The electrodes 3, 3', 4, 4' are here made in the form of continuous metal plates insulated by a dielectric material, which covers the supports S and trays 10 during their processing.

[0073] The means for moving the supports S 1 operate by successive steps, during which the supports S are advanced by a predetermined length, with a pause between each step. The length of movement at each step is greater than the length of the supports S and platforms 10, and the pause between each step is, for example, from a few seconds to tens of seconds, in order to allow for processing of the supports S after each step.

[0074] A plate 10 carrying cut supports S is positioned between the electrodes 3 of the pre processing following a first step of displacement, coming for example from a stock of trays 10. During the stopping time after this first step of displacement, 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.

[0075] The plate 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 powdery material P is sprinkled onto the supports S.

[0076] During the second step of displacement, a second platform 10 with its supports S is brought between the pretreatment electrodes 3, 3'.

[0077] During the third step of the movement, the platform 10 with its supports S, onto which the powdered material P has been deposited, is brought between the electrodes 4, 4' of the second set. During the pause after this third step, the second generator G' brings the electrodes 4, 4' of the second set to an alternating potential in order to force the powdered material P into the support S.

[0078] During the third step of displacement, the second plate 10 is brought from the pretreatment electrodes 3, 3' to the means of contacting powdered material P, and a third plate 10 is brought between the pretreatment electrodes 3, 3'.

[0079] During the fourth travel step, the treated tray 10 is evacuated to an exit, the second and third trays 10 pass to the next station, and a fourth tray 10 is inserted between the pretreatment electrodes 3, 3'.

[0080] 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 related to the alternating nature of the voltage across 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 bands of the electrodes and less intense when the supports are located between 2 bands of electrodes, i.e. a field that is not spatially homogeneous.

[0081] In contrast, in the embodiment of [Fig. 4], only one pair of electrodes 3, 3', 4, 4' is present on each side of the supports S of a plate 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 alternating voltage, a time which can be extended until the pretreatment and / or penetration of powdered material P is sufficient.

[0082] The [Fig.5] is a schematic side view representation of a device 100 implementing the invention.

[0083] The support S is here again a continuous strip, going from a starting roller RI to an ending roller R2.

[0084] In the embodiment of [Fig.5], the powdered material P is applied to a conveyor belt 11, set in motion by the drive means 1, and the support S, having undergone pretreatment, then comes over the powdered material P deposited on the belt 11.

[0085] To achieve 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.

[0086] The support S passes through the pretreatment station 101, between the pretreatment electrodes 3. In parallel below, in the powder contact station 103, the powder P is deposited onto the conveyor belt 11. The conveyor belt 11 may, in particular, have asperities, grooves, and recessed patterns to accommodate the powder P and manage its distribution in the support S after impregnation.

[0087] The support S is then applied over the powder P on the conveyor belt 11, at the exit of the pretreatment station 101 and the powder contacting station 103. The support S is carried by the conveyor belt 11 to the impregnation station 105, still with the powder P taken between the support S and the conveyor belt 11.

[0088] In the impregnation station 105, the conveyor belt 11, the support S, and the powder P trapped between them pass between the impregnation electrodes 4, 4'. Between the impregnation electrodes 4, 4', the alternating electric field sets the powder particles P in motion, causing them to migrate towards the interior of the support S.

[0089] At the exit of the impregnation station 105, the support S impregnated with powder P is directed towards the roller R2 and wound onto it.

[0090] Figure 6 is a flowchart showing the main steps of the process impregnation 200 implemented in the devices 100 previously described.

[0091] The first step 201 is the pretreatment of the support S, before the powdered material P is brought 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 being brought into contact with the powdered material P.

[0092] The second step 203 is the contacting of the powdered 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.

[0093] The third step 205 is then the second pass 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 the support S.

[0094] The impregnation process 200 and the associated impregnation device 100 They allow for increased penetration of the powdered material P into the substrate S, meaning that less powdered material P is lost during impregnation. This is particularly important in the case of expensive or polluting powdered materials P.

[0095] Figure 7 illustrates the advantages provided by the impregnation process 200 according to the invention.

[0096] Fig. 7 is a table illustrating the results obtained experimentally with three different non-woven S supports, corresponding to the three data lines of the table.

[0097] The three supports S are listed in the "Ref." column and are, in descending order: - cotton, of the type used in cosmetics, hydrobonded non-woven, - non-woven needle-punched polyester ("polyester"), and - airlaid cellulose fibre paper, of the type used in tablecloths and hygiene products, non-woven airlaid.

[0098] For the experiment, the supports S 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 supports S before impregnation is given in grams (g) in the first data column of the table in [Fig. 5].

[0099] When applied, the powder P is scraped into the honeycomb grid, onto which the cut supports S are deposited. The powder P used is a green clay from the company Argile du Velay, reference "cosgreen™ superfine" with particle sizes ranging from 0 to 100 µm.

[0100] Electrodes 3, 3', 4, 4' are at a potential of 40 kV alternating current, at a frequency of 100 Hz. Supports S are held between the electrodes for a period of 15 seconds.

[0101] 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 a pass between the electrodes without powder.

[0102] The third column of the table gives the mass M2 of powder P with which supports S were impregnated with pretreatment by passing between electrodes 3, 3' before the deposition of powder P.

[0103] The mass Mi or M2 of powder P is in particular deduced by weighing the impregnated supports S, from which is subtracted the mass Mo of the supports S before impregnation.

[0104] The fourth column of the table gives the difference in mass AM of impregnated powder P between the supports S with and without vacuum treatment between electrodes 3, 3', 4, 4'. The fifth column gives the percentage of additional impregnated powder P in the support S as a result of the pretreatment.

[0105] In the case of cotton, the mass of impregnated powder P is 0.719 grams without pretreatment and 0.955 grams with pretreatment, i.e. an additional quantity of 0.236 grams, and therefore an increase of 33%.

[0106] 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, i.e. an additional quantity of 0.292 grams, and therefore an increase of 44%.

[0107] In the case of the support S with air-deposited cellulosic fibers, the mass of impregnated powder P without pretreatment is 0.123 grams without pretreatment and 0.209 grams with pretreatment, i.e. an additional quantity of 0.086 grams, and therefore an increase of 70%.

[0108] The Applicant further carried out an additional test, in which a polyester support S was impregnated with thermosetting polyester 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 thermoformable composite materials.

[0109] The quantity of powder P impregnated without pretreatment was 0.603 grams and 0.975 grams with pretreatment. Therefore, there is an excess of powder of approximately 62% which impregnates the support S with the pretreatment.

[0110] We therefore observe a marked and quantifiable technical effect, allowing better impregnation of the supports S and reducing the losses of powder P.

Claims

Claims

1. Method for impregnating a fibrous support (S) with a powdery material (P), comprising the steps: - bringing the powdery material (P) into contact with the support (S), - passing the support (S) and the powder (P) between electrodes (3, 3', 4, 4') brought to different potentials, to cause the powdery material (P) to 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.

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 into contact (5) the powdery material (P) 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) cause said support (S) to pass between the electrodes before passing through the means for bringing into contact (5) the powdery material (P).

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 ge- 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 moving (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 for 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.

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