Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B15/00—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00
  • B29B15/08—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00 of reinforcements or fillers
  • B29B15/10—Coating or impregnating independently of the moulding or shaping step
  • B29B15/12—Coating or impregnating independently of the moulding or shaping step of reinforcements of indefinite length

Definitions

• the substrates are to be treated by impregnation with powders having physicochemical properties, for example thermoplastic, thermosetting, retardant or flame retardant powders, disinfectant, hydrophobic powders, etc.
• powders having physicochemical properties for example thermoplastic, thermosetting, retardant or flame retardant powders, disinfectant, hydrophobic powders, etc.
• the electrodes connected to different potentials can be located on the same side of the support, and, on the other side of the support, no electrode is present opposite or a plate electrode with floating potential is present.
• the electrodes may comprise electrodes on each side of the support, with facing electrodes connected to the same potential among the three or facing electrodes connected to potentials out of phase two by two.
• the different potentials can be generated by several separate and synchronized generators, or by a single generator with several output terminals. Combinations of these two options are possible.
• the device may comprise a tubular containment member, through which the support to be treated or impregnated passes and into which powder is also poured, the electrodes being located at the level of said containment member, between an inlet of the support and the powder and an outlet of the impregnated support.
• the electrodes may have phase-shifted potentials with a decreasing phase shift in the direction of support progression to drive the powdered material in the opposite direction of support progression by variation of the electric field.
• the invention also relates to the method of impregnating a fibrous or porous support with a powdery material by applying an electric field, comprising the steps:
• FIG. 1 is a schematic representation in side view of an embodiment of an impregnation device according to the invention
• FIG. 2 is a longitudinal sectional view of the electrodes of the device of Figure 1 and the electric field vectors at different times of an oscillation period
• FIG. 3 is a schematic side view representation of an alternative embodiment of an impregnation device
• FIG. 4 is a partial perspective schematic representation of a third embodiment of an impregnation device for a narrow or wire support
• FIG. 9 are schematic representations of different electrode arrangements for the impregnation devices of Figures 1, 3 and 4.
• FIG. 1 is a schematic representation in side view of a device 100 for impregnating a fibrous or porous support S according to a first embodiment of the invention.
• the impregnation device 100 comprises means 1 for moving the support S, here a longitudinal conveyor, which moves the support along a longitudinal axis with a predetermined direction of progression, denoted by an arrow.
• the impregnation device 100 comprises means 5 for depositing a powdery material or powder P, for example a sprinkler, a doser, a pourer or a grid through which the powder particles P pass.
• a powdery material or powder P for example a sprinkler, a doser, a pourer or a grid through which the powder particles P pass.
• the deposition of powder P is done, in the example of figure 1, by gravity by means of a pourer 5 which pours powder P by gravity, with possibly mechanical agitation of the pourer 5 to set it in motion.
• the deposition is therefore done on the upper surface of the support S.
• the support S coated with powder P then passes in the direction of progression under a containment conveyor 3, which covers the powder P and serves to confine it spatially.
• the support S then passes under transverse electrodes 4, here three in number, and connected to alternating high voltage generators G1, G2, G3, which generate three phase-shifted potentials u, v, w, each supplying one of the electrodes 4.
• Electrodes 4 are for example produced in the form of a thin metal strip deposited on a dielectric support.
• Generators G1, G2, G3 generate potentials of the order of several thousand or even tens of thousands of volts.
• the electrodes 4 are phase-shifted two by two by an angle generally of 10 to 180°.
• the powder is stirred by forces electrostatic, and penetrates into the support S, which then impregnates said support S with a controllable gradient in its thickness, or even with a homogeneous distribution of the powder P in the thickness of the support S.
• phase shift between the electrodes 4 induces a component of the electric field parallel to the support, which longitudinally displaces the powder P. This results in a disruption of the agglomerated powder P packets which could form by electrostatic attraction of the powder P particles when the latter is polarizable or sufficiently conductive. This phenomenon is linked to the generation of a progressive and not a stationary wave in the impregnation zone.
• phase shift for two or three phase-shifted potentials u, v, w is advantageously maintained in the order of 10 to 45°, and in particular 15 to 30°.
• the embodiment of Figure 1 presents, opposite the first set of three electrodes 4, a second set of identical electrodes 4, but connected differently to the potentials u, v, w.
• the electrodes 4 located at the top are in particular connected in order to the first potential u, then to the second v, and finally to the third w.
• the electrodes 4 located at the bottom are, following the same convention, connected in order to the third potential w, then to the first u and finally to the second v.
• the electrodes 4 have, in pairs facing each other, electric fields which are alternately strong and weak, with, in the center of the space between the electrodes 4 facing each other, essentially transverse fields.
• the means for moving the support S comprise an endless conveyor with cyclic movement, for example a hollow roller around which the support S is wound.
• Conveyor 1 passes the support S pressed against its external face coated with powder P at the level of the electrodes 4 during its cycle.
• the means 1 for setting the support S in motion comprise, for example, two coils, forming a source of the untreated support S and conditioning the support S once impregnated.
• the electrodes 4 are located at the level of said tubular confinement member 7, and here comprise in particular on one side of the confinement member 7 three electrodes 4 connected, from bottom to top, respectively to the first u, second v and third w potentials.
• the confinement member 7, the electrodes 4 and their connections to the different potentials u, v, w can be reversed so that the phase shift contributes to advancing the powder P in the direction of progression of the support S.
• phase shift between the potentials u, v, w thus makes it possible to move the powder P backward or forward relative to the support S.
• Electrodes 4 in figure 4 Opposite these electrodes 4 in figure 4 is located a single plate electrode 40 connected to ground.
• electrodes 4 and plate electrode 40 presented in each of the preceding figures are interchangeable.
• a plate electrode 40 connected to no potential, including ground, and is therefore at floating potential.
• the electrodes 4 are then located on the side of said deposit of powder P.
• the floating potential of the plate electrode 40 reduces the electric field as it approaches said plate electrode 40. This results in an electric field gradient across the thickness of the support S which can, in a controlled manner, limit the deep penetration of the powder P into the support S.
• a reverse assembly with the plate electrode 40 on the upper side and the three electrodes 4 on the lower side (or a deposit of powder P under the support S) is also possible.
• Figure 6 is substantially identical to Figure 5, but differs in that the plate electrode 40 is connected to ground. By connecting the plate electrode 40 to ground, the electric fields remain relatively homogeneous and therefore of high standard up to the part close to the plate electrode 40, where they quickly cancel out as they approach said plate electrode 40.
• Figure 7 shows an assembly with two sets of electrodes 4, located on either side of the passage for the support S.
• the 4 opposite electrodes are connected to the same potential, from left to right the first u, the second v and the third w.
• Figure 8 is a variant of the assembly of that of figure 7, in particular, the electrodes 4 opposite each other are not connected to the same potential.
• the electrodes 4 of the set located at the top in figure 8 are connected, from left to right to the first u, to the second v and to the third w respectively.
• the electrodes 4 of the set located at the bottom in figure 8 are connected, from left to right, to the third w, to the first u and to the second v respectively.
• This assembly corresponds to the case of Figure 1 in particular. It makes it possible to obtain the complex electric field detailed in Figure 2, and which makes it possible to disperse the powder agglomerates P.
• An embodiment having a succession of pairs of electrodes 4 on each side of the support S is also possible, the electrodes 4 facing each other being able to be connected to the same potential u, v or to a phase-shifted potential u, v.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Electrostatic Spraying Apparatus (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Preliminary Treatment Of Fibers (AREA)

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Citations (4)

• 2024
  • 2024-03-25 FR FR2402976A patent/FR3160346A1/fr active Pending
• 2025
  • 2025-03-24 WO PCT/FR2025/050231 patent/WO2025202576A1/fr active Pending

Patent Citations (4)

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