Facilities for powder impregnation of at least one yarn-type and / or tape-type substrate to be treated.

Abstract

The invention relates to a facility (100) for powder impregnation of at least one yarn and / or tape type substrate (11a) to be treated, comprising a powder delivery unit, a unit for supplying the substrate to be treated, at least two electrodes (14) and a circulation zone for the powder and the substrate to be treated. The facility comprises a confinement unit (15) having an inlet aperture for the substrate to be treated and the powder (12a), an outlet aperture for the impregnated substrate (11b) and a closed profile section from the inlet aperture to the outlet aperture; the circulation zone is formed by the internal volume of the confinement unit; and the confinement unit is fixed relative to at least one of the electrodes; the substrate to be treated and the powder move in the circulation zone between the inlet aperture and the outlet aperture of the confinement unit.

Description

Technical Field

[0001] This invention relates to the field of impregnating porous substrates with powder materials.

[0002] The present invention particularly relates to an apparatus for impregnating powder onto at least one yarn-type and / or tape-type substrate to be treated.

[0003] Depending on the type of substrate and the powder used, the present invention has a variety of applications in many fields.

[0004] For example, this could refer to the production of bandages impregnated with antibacterial powder in the medical field, or the impregnation of thermoplastic powder into glass fiber yarn for mechanical reinforcement. Background Technology

[0005] Impregnating porous substrates with powder allows for advantageous modification of their properties. Various techniques can be used for this purpose. These techniques typically involve using mechanical, pneumatic, electrostatic, or solvent-based methods to penetrate the powder into the pores of the substrate.

[0006] The applicant's patent EP 2 331 309 describes an apparatus for impregnating a porous substrate, comprising two electrodes positioned opposite each other and capable of generating an alternating electric field in the space between the two electrodes. The substrate and powder are constrained between two conveyor belts capable of transporting the substrate and powder into the space between the two electrodes. Under the influence of the electric field generated by the electrodes, the powder moves almost randomly in various directions. Therefore, the powder penetrates into the pores of the substrate, impregnating its entire thickness, ideally in a uniform manner. This apparatus advantageously allows for the constraint of the moving powder and limits its loss.

[0007] However, this equipment is designed for very wide substrates, typically between 0.5m and 6m in length. Therefore, it is not suitable for smaller substrates, such as yarns or tapes. Furthermore, the equipment is significantly larger than the yarn or tape substrates, making powder penetration into the smaller substrate compared to an electrostatic sprayer less likely, resulting in uneven powder distribution within the substrate. Additionally, small-sized "yarn" or "tape" substrates cannot be pre-deposited with powder using existing powder-spreading techniques.

[0008] Furthermore, miniaturizing such equipment would prove to be complex and not very advantageous. In fact, with narrower conveyor belts, the likelihood of powder escaping from the confined space created by the conveyor belt increases significantly. Therefore, a large amount of powder is wasted compared to the amount of powder to be impregnated in the yarn and / or belt.

[0009] In existing equipment, a portion of the powder that has begun to move does not impregnate the porous material but instead deposits on a conveyor belt positioned above and below the material, allowing for the recovery of this unimpregnated powder at the equipment's exit. Yarn processing is incompatible with this configuration because the conveyor belt is not the width of a yarn. Therefore, processing yarn in conventional equipment results in significant powder loss on the conveyor belt, whose surface area is much larger than the yarn or the belt itself.

[0010] The technical problem to be solved by the present invention is to develop an apparatus that enables the uniform impregnation of substrates, such as tapes or yarns, that are smaller in size than those of prior art substrates, while limiting powder waste and eliminating the need for a preparatory step of depositing powder on the surface of a porous substrate. Summary of the Invention

[0011] To address this problem, the applicant has developed an apparatus for impregnating powder onto at least one yarn-type and / or tape-type substrate to be treated, comprising:

[0012] -Powder conveying unit;

[0013] - A unit for supplying the substrate to be processed;

[0014] - At least two electrodes, connected to an alternating generator and capable of generating an alternating electric field in the space formed between the electrodes; and

[0015] - A circulation zone for powder and substrate to be treated, which extends at least in the region where the alternating electric field is dominant.

[0016] The features of this device are:

[0017] The impregnation apparatus further includes a constraint unit having an inlet orifice for the substrate and powder to be treated, an outlet orifice for the impregnated substrate, and a closed contour portion from the inlet orifice to the outlet orifice; a circulation zone is formed by the internal volume of the constraint unit; and

[0018] - The constraint unit is fixed relative to at least one of the electrodes; the substrate to be treated and the powder move between the inlet and outlet holes of the constraint unit in the circulation zone.

[0019] In other words, the applicant has developed an apparatus for impregnating yarns and / or tapes, in which the substrate and powder circulate within a fixed constrained unit (typically a tube). Advantageously, the impregnation apparatus according to the invention does not require the use of a conveyor belt to move the substrate within the constrained unit. Furthermore, compared to prior art apparatus, the feed unit must move the substrate, thus subjecting it to a certain tension, which may have the effect of reducing the pore size of the substrate to be treated. However, unexpectedly, the impregnated substrate exhibits a similar level of uniform impregnation as achieved by prior art apparatus.

[0020] In practice, a portion of the confinement unit protrudes from the space formed between the electrodes to allow the powder and the substrate to make contact before an electric field is applied to move the powder. Therefore, the powder is deposited as close to the substrate as possible, advantageously on its surface. The distance the powder travels before penetrating into the pores of the substrate is thus reduced. This allows the powder to penetrate deeper into the substrate. Similarly, the electric field strength required to move the powder can be reduced to conserve energy.

[0021] In practice, the electric field applied to the powder must allow the powder to move within the confined cells. Therefore, an alternating field refers to an electric field that is not strictly continuous, but rather has a variable component over time. This variable component can be added to the continuous component, for example, when the field is generated by applying a potential rectified by a sinusoidal potential between the electrodes.

[0022] Typically, the device includes two electrodes placed opposite each other to generate an electric field outside the constraint unit, and the electric field passes through the constraint unit.

[0023] In some cases, particularly when the substrate is made of a conductive material, the substrate forms one of the two electrodes and is connected to the generator. An electric field is then generated between the electrode outside the confinement unit and the substrate inside the confinement unit (which will be killed).

[0024] Without altering the invention, the constraint element can adopt different geometries. In particular, the constraint element is a circular tube.

[0025] As a variant, the constraint unit is an oblong tube. Alternatively, the constraint unit can be a rectangular tube. In the latter two cases, the geometry of the constraint unit has the effect of concentrating the electric field generated by the electrodes. The powder particles thus achieve a higher velocity, allowing them to penetrate deeper into the substrate. Therefore, at the same applied voltage level, this type of device allows for better impregnation than prior art devices. Consequently, higher throughput and greater impregnation depth are achieved due to the constraint unit. Therefore, the constraint unit allows for more compact installations and higher processing speeds.

[0026] According to another embodiment, the constraint unit has at least two parts with different regions.

[0027] The first section has a region, or, in the case of a circular tube, a reduced diameter. This first section typically protrudes upstream of the space formed between the electrodes. This advantageously reduces the free space in which the powder can move, allowing the powder to concentrate closer to the substrate. This configuration is particularly important in the case of vertical mounting, as it allows the powder to be confined along the material to be impregnated into the free space.

[0028] The second section is larger than the first section. This second section is located between the electrodes and is subject to an electric field. Its larger diameter allows the powder to move almost randomly in all directions and penetrate uniformly into the pores of the substrate. In this region, free space around the material is not an issue because the powder is primarily subject to electrostatic forces rather than gravity. This larger area even facilitates the proper release of powder that might become stuck between the confining cells and the porous material to be impregnated.

[0029] Surprisingly, particularly for this configuration, a larger second region was found to facilitate fiber expansion under the influence of an alternating electric field, thereby increasing the porosity of the fiber substrate. The uniformity of powder impregnation within the fiber network was thus improved, as was the impregnation efficiency (i.e., the amount of impregnated powder relative to the amount of deposited powder).

[0030] The arrangement of electrodes facing each other is equivalent to a capacitor with a fixed capacitance. With a constant material thickness, placing constraint cells made of a material with a dielectric constant higher than air allows for an increase in the capacitance of the capacitor formed by the electrodes. However, the greater the increase in capacitance, the higher the electric field present in the circulation zone for the same voltage applied to the electrodes, and the more powder achieves higher speeds without additional energy consumption. Therefore, maximizing the dielectric constant of the material constituting the constraint cells allows for an increase in the capacitance of the capacitor formed by the electrodes and improves the efficiency of the device.

[0031] Specifically, the constraint element is made of a material with a relative permittivity greater than or equal to 2, which allows the constraint element to maximize the effect of the electric field applied to the powder particles.

[0032] According to a preferred embodiment, the constraint element is made of a material with a relative permittivity greater than 5, particularly of materials included in the group consisting of glass, quartz, or ceramic.

[0033] Advantageously, the constraint unit is vertically oriented. In this way, powder that has not penetrated into the pores and remains on the surface of the substrate falls naturally under gravity into a container provided for this purpose below the device.

[0034] In some applications, a substantially continuous electric field can also be applied to certain parts of the device, thereby allowing, for example, a previously treated substrate to be covered by an alternating field, thus ensuring the impregnation of the powder. Attached Figure Description

[0035] Other advantages and features of the invention will become apparent upon reading the following description, which is given by way of illustrative rather than limiting example with reference to the accompanying drawings.

[0036] [ Figure 1 ] Figure 1This is a basic perspective view of a powder transfer impregnation apparatus according to an embodiment of the present invention.

[0037] [ Figure 2 ] Figure 2 yes Figure 1 A vertical sectional view of the device at the constraint unit.

[0038] [ Figure 3a ] Figure 3a This is a mid-length sectional view of the first embodiment of the constraint unit.

[0039] [ Figure 3b ] Figure 3b This is a mid-length sectional view of the second embodiment of the constraint unit.

[0040] [ Figure 3c ] Figure 3c This is a mid-length sectional view of the third embodiment of the constraint unit.

[0041] [ Figure 4 ] Figure 4 This is a diagram of the electric field values ​​along the axis passing through the center of the electrode without any constrained elements.

[0042] [ Figure 5 ] Figure 5 In the case of the existence of elongated elliptical constraint elements, it is similar to Figure 4 The image. Detailed Implementation

[0043] like Figure 1 and 2 As shown, the impregnation apparatus 100 includes a frame 101, a feeding unit for the substrate 11a to be treated, a feeding unit for the powder 12a, and a system that enables actual impregnation to be performed, all fixed to the frame 101.

[0044] The impregnation apparatus 100 is powered by an alternator 22, enabling the delivery of voltages ranging from several thousand to tens of thousands of volts. The alternator 22 specifically powers two electrodes 14 arranged opposite each other. The electrodes 14 are arranged vertically and spaced between 5 mm and 20 mm apart. Each electrode 14 is connected to one of the two terminals of the alternator 22. Other embodiments are possible, in which the electrodes 14 are arranged horizontally. Other electrode geometries are, of course, possible, but must be able to generate a strong alternating electric field on the constraint cell. In some cases, the substrate may be conductive, and in such cases, it must be electrically grounded. In this case, the electrode geometry and electrical connections can be adjusted to again obtain an alternating electric field within the constraint cell environment.

[0045] Electrodes 14 generate an electric field in the space formed between them. Constraint units 15 are placed between the electrodes 14. The constraint units 15 are filled with powder 12a and substrate 11a to be processed.

[0046] The feeding unit for the substrate 11a to be treated includes a mandrel 24 on which the substrate 11a is packaged in the form of a roll 18a. The feeding unit also includes deflecting rollers 19a-19b and a comb 23. The deflecting rollers 19a-19b allow the substrate 11a to be treated to be conveyed from the roll 18a to the impregnation zone, and the comb 23 allows the separation of the various yarns and / or tapes constituting the substrate 11a. In practice, the substrate 11a may consist only of yarns, combined yarns, or individual tapes, or a mixture of several types of substrates 11a.

[0047] The powder 12a supply unit includes a powder reservoir 13. Powder 12a is conveyed from the powder reservoir 13 to the hopper 17 via a feed screw 25. The feed screw 25 enables the generation of a controlled and regular flow of powder 12a without agglomeration. The conveying speed of powder 12a can be varied by adjusting the rotational speed of the feed screw 25.

[0048] The impregnated substrate 11b is removed from the restraint unit 15 via the removal unit 19c, 18b. The removal units 19c, 18b include a return roller 19c and a winding reel 18b that allows storage of the impregnated substrate 11b.

[0049] In practice, the powder flow is optimized to minimize powder loss 12b. Friction between the substrate 11a and the wall of the constraint unit 15 allows any remaining powder 12b that has not yet penetrated the substrate 11a to be conveyed to the lower end of the constraint unit 15. Therefore, the remaining powder 12b is removed from the constraint unit 15 and fed to a second funnel 16, which leads to a recovery tank 20. In the illustrated example, the powder falls into the recovery tank 20 by gravity. Alternatively, in a horizontal configuration of the constraint unit 15, a conveyor belt can be used to move the powder from the outlet of the constraint unit to the recovery tank 20.

[0050] The substrate 11a to be treated can correspond to yarns with diameters ranging from a few micrometers to several hundred micrometers. According to another embodiment, the substrate 11a to be treated can correspond to strips or bands with widths from 0.5 cm to 10 cm. The substrate 11a to be treated can correspond to any porous material, typically multifilament yarns, composite yarns, woven or nonwoven fabrics, braids, rovings, and generally all porous filamentous materials. These materials include all conventional textile materials, whether natural, synthetic, or man-made.

[0051] Powder 12a can correspond to particles with diameters ranging from nanometers to hundreds of micrometers. For example, the powder consists of particles of thermoplastic or thermosetting polymers, designed to melt upon cooling to form a matrix of yarns and / or reinforcing composite materials constituting the substrate. Powder 12a can also correspond to active ingredients, typically antibacterial agents, colorants, flame retardants, etc.

[0052] like Figure 2 As shown, the substrate 11a to be treated and the powder 12a are in contact with each other at the upper portion 152 of the constraint unit 15. This upper portion 152 has a reduced diameter, typically between 1 mm and 10 mm, allowing the powder 12a to be pressed against the substrate 11a to penetrate the constraint unit in a synchronous manner with the substrate. The substrate 11a and the powder 12a are then conveyed to a second portion 153 of the constraint unit 15, which has a larger diameter than the reduced-diameter portion 152. This portion 153 of the constraint unit 15 is located between two electrodes 14 and is subjected to an electric field generated by these electrodes 14. The portion 153 forms a barrier, confining the moving powder 12a within it and preventing its escape. The powder 12a then forms a cloud of moving particles that remains stationary at the level of the portion 153 without the traction exerted by the substrate 11a moving within the constraint unit 15. Within this portion 153, fibers also tend to move, which, depending on their texture and the applied alternating electric field, promotes their expansion. They are then able to occupy the entire space of the area and drag the powder that has penetrated into the porous network.

[0053] The particles of powder 12a are polarized. Therefore, under the influence of the electric field of electrode 14, the particles of powder 12a move randomly within portion 153 of the constraint unit 15. The velocity of the particles of powder 12a is an increasing function of the electric field strength and frequency. The stronger the field, the faster the particles acquire velocity, and the deeper they can penetrate into the pores of the substrate 11a to be treated. The frequency can be adjusted according to the powder particle size. Advantageously, larger particles can be subjected to a lower frequency field, thus giving them time to begin moving by following the oscillations of the electric field. The frequency is typically between tens and hundreds of hertz.

[0054] like Figures 3a to 3c As shown, constraint elements 15a-15c can adopt various geometric shapes.

[0055] Figure 3 illustrates a constraint unit 15a including a portion 353 with a constant diameter from the inlet hole to the outlet hole. This geometry is suitable for porous substrates with low fiber movement and expansion capabilities.

[0056] Adjustments can be made when the effect of powder penetration into the porous substrate is not very significant, and when the desired result corresponds to the powder being more located on the surface of the porous network and less located in the center of the porous network.

[0057] Advantageously, such as Figure 3bAs shown, the restraining unit 15b may include an additional portion 251 located upstream of the portion 253 with a constant diameter. This additional portion 251 has a funnel shape for guiding the powder 12a into contact with the moving yarn and / or belt, and synchronously obtaining the most uniform amount of impregnating powder possible along the yarn or substrate. In practice, in addition to the desired impregnation effect, it is preferable to obtain a constant powder content along the entire length of the impregnating substrate. For this purpose, the flow rate of the powder dispenser can be advantageously adjusted, and the restraining unit should preferably not accumulate powder to avoid drift or variation during impregnation.

[0058] Or, such as Figure 3c As shown, the constraint unit 15c may have a funnel-shaped portion 151, a second portion 152 with a constant diameter, and a third portion 153 with a diameter larger than that of the second portion 152.

[0059] The regions of constraint elements 15a-15c can adopt various geometric shapes. For example, the region can be a circle, an elongated ellipse, a square, a rectangle, or even an ellipse.

[0060] These geometries depend primarily on the appearance and properties of the substrate to be impregnated. Yarns, assemblies, and rovings will require circular cross-sections. Woven fabrics, tapes, and textiles will require elongated elliptical or rectangular sections.

[0061] These slender sections are also ideal for processing multiple yarns or materials in parallel. Placing filamentous or narrow-width materials in parallel advantageously allows for the simultaneous processing of more substrates.

[0062] The shape of the constraint unit 15a-15c affects the electric field strength present in the circulation zone of the powder and the substrate to be treated.

[0063] In fact, Figure 4 In the example shown, when no constraint unit 15 is located between electrodes 14, the electric field between the electrodes is 8 × 10⁻⁶ for a 10 kV sinusoidal voltage applied to the electrodes. 5 V / m. For example... Figure 5 As shown, when the constraint unit 15 is located between the electrodes 14, the electric field reaches 12 × 10⁻⁶. 5 V / m. Therefore, the rectangular or elongated elliptical shape of the constraint unit 15 allows for a 50% increase in electric field relative to the initial value. It has been found that the constraint unit then serves not only as a closed volume in which powder and fibers move to mix, but also as an amplifier of processing effectiveness. Thus, impregnation velocities up to approximately 100 m / min can be achieved for processing.

[0064] Interface 21 allows control of the impregnation equipment 100, such as the speed at which the substrate 11a to be treated moves in the constraint unit 15, the speed at which the powder 12a is conveyed, or even the voltage supplied by the alternator 22.

[0065] In summary, the present invention is an apparatus that enables the impregnation of a substrate, such as a tape or yarn, in a uniform and continuous manner, with high efficiency in terms of production speed and the quality obtained.

Claims

1. An impregnation plant (100) for impregnating a powder (12a) onto at least one yarn and / or tape-like substrate to be treated (11a), comprising: - a powder delivery unit (13, 17, 25); - a unit (18a, 19a, 19b, 23, 24) for supplying the substrate to be treated; - at least two electrodes (14) connected to an alternator (22) and capable of generating an alternating electric field in the space formed between said electrodes (14); and - a circulation zone of said powder and of said substrate to be treated (11a) extending at least in the area where said alternating electric field is predominant, characterized in that: - said impregnation plant (100) further comprises a containment unit (15) having an inlet aperture for said substrate to be treated (11a) and for said powder (12a), an outlet aperture for the impregnated substrate (11b), and a closed profile portion from said inlet aperture to said outlet aperture; said circulation zone is formed by the internal volume of said containment unit (15); and - said containment unit (15) is fixed with respect to at least one of said electrodes (14); said substrate to be treated (11a) and said powder (12a) moving in said circulation zone between said inlet aperture and said outlet aperture of said containment unit (15).

2. The impregnation apparatus according to claim 1, characterized in that Said plant comprises two electrodes (14) placed opposite each other.

3. The impregnation apparatus according to claim 1, characterized in that Said substrate to be treated (11a) forms one of said two electrodes.

4. The impregnation apparatus according to claim 1, characterized in that A portion of said containment unit (15) protrudes from the space formed between said electrodes (14) to allow said powder (12a) and said substrate to be treated (11a) to come into contact so as to be treated.

5. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) is a circular tube.

6. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) is an oblong tube.

7. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) is a rectangular tube.

8. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) has at least two portions (152, 153) of different area.

9. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) is made of a material having a relative dielectric constant greater than or equal to 2.

10. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) is made of a material included in a group comprising glass or quartz or ceramic.

11. The impregnation apparatus according to claim 1, characterized in that Said containment unit (15) is vertically oriented.

Images