Installation for impregnating at least one thread- and / or ribbon-type substrate to be treated with powder

Abstract

The present invention relates to an installation (100) for impregnating at least one substrate to be treated (11a) of thread and / or tape type with powder, comprising a powder conveying 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 installation comprises a confinement unit (15) having an inlet orifice for the substrate to be treated and the powder (12a), an outlet orifice for the impregnated substrate (11b), and a closed contour from the inlet orifice to the outlet orifice, the circulation zone being formed by the internal volume of the confinement unit, which is fixed relative to at least one of the electrodes, and the substrate to be treated and the powder are movable in the circulation zone between the inlet and outlet orifices of the confinement unit.

Description

[Technical field]

[0001] The present invention relates to the field of impregnating a porous substrate with a powder material.

[0002] The invention particularly relates to an installation for impregnating with powder at least one substrate of thread and / or tape type to be treated.

[0003] The present invention finds multiple applications in many fields, depending on the type of substrate and powder used.

[0004] As examples, mention may be made of the production of bandages impregnated with antibacterial powders in the medical field, or the impregnation of glass fibre threads with thermoplastic powders for mechanical reinforcement. [Background technology]

[0005] Impregnating a porous substrate with a powder makes it possible to advantageously modify its properties. To do this, different techniques may be used. In general, these techniques consist of infiltrating the powder into the pores of the substrate by mechanical, pneumatic, electrostatic devices or by means of solvents.

[0006] The applicant's patent application WO 2005 / 023363 describes an installation for impregnating a porous substrate comprising two electrodes located opposite each other and capable of generating an alternating electric field in the space located between these two electrodes. The substrate and the powder are confined between two conveyors capable of conveying the substrate and the powder in the space located between the two electrodes. Under the influence of the electric field generated by the electrodes, the powder is made to move in all directions in an almost random manner. The powder thus penetrates into the pores of the substrate and impregnates it ideally uniformly throughout its thickness. Such an installation advantageously makes it possible to confine the moving powder and to limit its losses. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 2331309 Summary of the Invention [Problem to be solved by the invention]

[0008] However, such equipment is provided for very wide substrates, typically 0.5m to 6m. It is therefore not suitable for substrates of smaller dimensions, i.e. threads or tapes. Moreover, the dimensions of the equipment are significantly larger than those of thread- or tape-type substrates, the powder has a low probability of penetrating the substrate, which presents a small volume compared to electrostatic applicators, and the dispersion powder in the substrate is not uniform. Moreover, small-sized "thread" or "tape"-type substrates cannot have powder pre-deposited on their surfaces by conventional dusting techniques.

[0009] Moreover, miniaturization of such installations would prove to be complicated and not very advantageous. Indeed, in the case of narrower conveyors, the probability of powder escaping from the confinement space formed by the conveyor increases significantly. Thus, a large amount of powder would be wasted compared to the amount of powder that would be impregnated into the yarn and / or tape.

[0010] In prior art installations, part of the powder to be transferred does not impregnate the porous material and is deposited on conveyors that are located above and below the material and allow this non-impregnated powder to be recovered at the outlet of the installation. The processing of yarns is not compatible with this configuration, since the conveyor is not the width of the yarn. The processing of yarns in prior art installations therefore leads to significant losses of powder on the conveyor, whose surface is much larger than the yarn or tape.

[0011] The technical problem that the present invention aims to solve is to develop an installation that makes it possible to uniformly impregnate substrates of smaller dimensions than those of the prior art, such as tapes or threads, while limiting the waste of powder and without going through a preliminary step of depositing powder on the surface of the porous substrate. [Means for solving the problem]

[0012] To address this problem, the Applicant has developed an installation for impregnating a powder onto at least one substrate of the yarn and / or tape type to be treated, said installation comprising: A powder conveying unit; a unit for supplying a substrate to be treated; at least two electrodes connected to an alternating current generator and capable of generating an alternating electric field in a space defined between the electrodes; a circulation area of ​​the substrate and powder to be treated, which extends at least within the area in which the alternating electric field extends; Equipped with.

[0013] Such facilities include: the impregnation installation further comprises a containment 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 region is formed by an interior volume of the containment unit; The containment unit is fixed relative to at least one of the electrodes, and the substrate and powder to be treated are movable between an inlet orifice and an outlet orifice of the containment unit in a circulation region. It is characterized by:

[0014] In other words, the applicant has developed an installation for impregnating yarns and / or tapes in which the substrate and powder circulate in a fixed confinement unit, typically a tube. Advantageously, the impregnation installation according to the invention does not require the use of a conveyor to move the substrate in the confinement unit. Moreover, compared to prior art installations, the feed unit must move the substrate and therefore apply a constant tension to the substrate, which may have the effect of reducing the size of the pores in the substrate being treated. However, unexpectedly, the impregnated substrate has a uniform impregnation amount comparable to prior art installations.

[0015] In practice, a part of the confinement unit protrudes from the space formed between the electrodes to allow contact between the powder and the substrate to be treated before the application of the electric field that displaces the powder. The powder is thus as close as possible to the substrate and advantageously deposited on its surface. The distance that the powder travels before penetrating the pores of the substrate is thus reduced. This allows the powder to penetrate deeper into the substrate. Similarly, the strength of the electric field required to displace the powder can be reduced in order to save energy.

[0016] In practice, the electric field applied to the powder must allow it to move within the confinement unit. By alternating electric field we therefore mean an electric field which is not strictly continuous but has a variable component over time. This variable component may potentially be added to the continuous component, for example if the electric field results from the application of a potential between electrodes resulting from the rectification of a sinusoidal potential.

[0017] Typically the arrangement comprises two electrodes arranged opposite each other to generate an electric field outside the containment unit which passes through the containment unit.

[0018] In some cases, especially 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(s) outside the confinement unit and the substrate inside the confinement unit when it is stopped.

[0019] The containment unit may adopt different shapes without modifying the invention, in particular the containment unit is a circular tube.

[0020] As a variant, the confinement unit is an oval tube. Alternatively, the confinement unit is a rectangular tube. In these two scenarios, the shape of the confinement unit has the effect of concentrating the electric field generated by the electrodes. The powder particles therefore gain a higher velocity, allowing them to penetrate deeper into the substrate. For an equally applied voltage level, this type of installation therefore allows a better impregnation than the prior art installations. Thus, thanks to the confinement unit, the yield is higher and the depth of impregnation is greater. This confinement unit therefore allows a more compact installation and a faster processing speed.

[0021] According to another embodiment, the containment unit has at least two portions of different areas.

[0022] The first part has one area or, in the case of a circular tube, a reduced diameter. This first part typically projects upstream of the space formed between the electrodes. Advantageously, it makes it possible to reduce the free space through which the powder may move so as to concentrate it closer to the substrate. This configuration is particularly relevant in the case of vertical installations, since it makes it possible to limit the fall of the powder into the free space along the material to be impregnated.

[0023] The second part has a larger area than the first part. This second part is placed between the electrodes and subjected to an electric field. The diameter is larger than the first part, which allows the powder to move almost randomly in all directions and penetrate the pores of the substrate uniformly. In this region, the powder is mainly subjected to electrostatic forces rather than gravity, so free space around the material is not an issue. This larger area is further advantageous for proper release of powder that may be stuck between the confinement unit and the porous material to be impregnated.

[0024] Unexpectedly, it was found that, especially in this configuration, the larger second area favors the swelling of the fibers under the action of the AC electric field, thus increasing the porosity of the fibrous substrate, thus improving the uniformity of the powder impregnation in the fiber network and also improving the impregnation efficiency, i.e. the amount of powder impregnated relative to the amount of powder deposited.

[0025] The configuration of electrodes arranged oppositely corresponds to a capacitor of determined capacity. At a given material thickness, it is possible to increase the capacitance of the capacitor formed by the electrodes by arranging the confining unit from a material whose dielectric constant is higher than that of air. However, the more the capacitance of the capacitor is increased, the higher the electric field that exists in the circulation area for the same voltage applied to the electrodes, and the faster the powder is obtained without consuming additional energy. Thus, by maximizing the dielectric constant of the material that constitutes the confining unit, it is possible to increase the capacitance of the capacitor formed by the electrodes and thus improve the efficiency of the device.

[0026] In particular, the containment unit is made of a material having a relative dielectric constant of 2 or greater, thereby enabling the influence of the containment unit on the electric field applied to the powder particles to be maximized.

[0027] According to a preferred embodiment, the containment unit is made of a material having a relative dielectric constant greater than 5, in particular from the group comprising glass, quartz or ceramic.

[0028] Advantageously, the confinement unit is oriented vertically, so that the powder that has not penetrated into the pores and remains on the surface of the substrate falls naturally under the influence of gravity into a container provided in the installation for this purpose.

[0029] In some applications, it is also possible to apply an essentially continuous electric field to certain parts of the installation, making it possible, for example, to cover a previously treated substrate with an alternating electric field, thus ensuring impregnation of the powder.

[0030] Other advantages and features of the present invention will become apparent from reading the following description, given by way of illustrative and non-limiting example with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a basic perspective view of a powder transfer and impregnation equipment according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view of the installation of FIG. 1 at the containment unit. [Figure 3a] FIG. 2 is a central longitudinal cross-sectional view of the trapping unit of the first embodiment. [Figure 3b] FIG. 2 is a central longitudinal cross-sectional view of the trapping unit of the first embodiment. [Figure 3c] FIG. 2 is a central longitudinal cross-sectional view of the trapping unit of the first embodiment. [Figure 4] 13 is a graph of the electric field value along an axis passing through the center of the electrode in the absence of a confinement unit. [Diagram 5] 5 is a graph similar to that of FIG. 4 in the presence of an oval confinement unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] As shown in Figures 1 and 2, the impregnation installation 100 comprises a frame 101 on which is fixed a supply unit for the substrate to be treated 11a, a powder conveying unit 12a and a system making it possible to carry out the actual impregnation.

[0033] The impregnation installation 100 is powered by an AC voltage generator 22 that makes it possible to supply voltages of the order of several thousand to several tens of thousands of volts. The AC voltage generator 22 in particular makes it possible to supply two electrodes 14 arranged opposite each other. The electrodes 14 are arranged vertically and spaced apart by a distance of 5 mm to 20 mm. Each electrode 14 is connected to one of the two terminals of the generator 22. Other embodiments are also possible in which the electrodes 14 are arranged horizontally. Other electrode shapes are of course possible, but they must be able to generate a strong AC electric field on the confinement element. In some cases the substrate may be conductive and in this case must be electrically grounded. In this case the shape and the electrical connection of the electrodes may be adapted to obtain an AC electric field again in the environment of the confinement unit.

[0034] The electrodes 14 generate an electric field in the space formed between them. The containment unit 15 is disposed between the electrodes 14. The containment unit 15 is filled with powder 12a and the substrate 11a is treated.

[0035] The supply unit for the substrate 11a to be treated comprises a mandrel 24 on which the substrate 11a to be treated is accommodated in the form of a reel 18a. The supply unit also comprises deflection rollers 19a-19b making it possible to transport the substrate 11a to be treated from the reel 18a to the impregnation area, and a comb 23 making it possible to separate the various threads and / or tapes constituting the substrate 11a to be treated. In practice, the substrate 11a to be treated may consist only of threads, only of aggregated threads, only of tapes or of a mixture of several types of substrates 11a.

[0036] The powder conveying unit 12a comprises a powder reservoir 13. The powder 12a is conveyed from the powder reservoir 13 into the funnel 17 by a feed screw 25. The feed screw 25 makes it possible to generate a regulated and regular flow of the powder 12a without lumps. By adjusting the rotation speed of the feed screw 25, the conveying speed of the powder 12a may be changed.

[0037] The impregnated substrate 11b is extracted from the containment unit 15 by an extraction unit for the impregnated substrate 11b. The extraction unit 19c, 18b comprises a return roller 19c and a take-up reel 18b capable of storing the impregnated substrate 11b.

[0038] In practice, the powder flow is optimized to minimize losses of powder 12b. Friction of the substrate 11a against the walls of the containment unit 15 allows the remainder of the powder 12b that has not penetrated the substrate 11a to be transported to the lower end of the containment unit 15. The remaining powder 12b is thus extracted from the containment unit 15 towards the second funnel 16 opening into the collection tank 20. In the example shown, the powder falls by gravity into the collection tank 20. Alternatively, in a horizontal configuration of the containment unit 15, a conveyor may be used to move the powder from the outlet of the containment unit to the collection tank 20.

[0039] The treated substrate 11a may correspond to threads with a diameter of a few microns to a few hundred microns. According to another embodiment, the treated substrate 11a may correspond to a tape or strip with a width of 0.5 cm to 10 cm. The treated substrate 11a may correspond to any porous material, typically multifilament yarns, aggregated yarns, woven or non-woven fabrics, braided yarns, rovings and generally all porous filamentary materials. The materials include all conventional textile materials, whether natural, synthetic or artificial.

[0040] The powder 12a may correspond to particles with a diameter ranging from the nanometer scale to several hundred microns. For example, the powder consists of particles of thermoplastic or thermosetting polymers intended to melt after cooling so as to form a matrix of a composite material reinforced by threads and / or tapes that constitute the substrate. The powder 12a may also correspond to active ingredients, typically antimicrobial agents, colorants, flame retardants, etc.

[0041] As shown in FIG. 2, the substrate 11a to be treated and the powder 12a come into contact with each other at the top 152 of the confinement unit 15. This top 152 has a reduced diameter, typically between 1 mm and 10 mm, and allows the powder 12a to be pressed against the substrate 11a to be treated in order to move with the substrate and penetrate the confinement unit. The substrate 11a to be treated and the powder 12a are then conveyed to a third part 153 of the confinement unit 15, the diameter of which is greater than the reduced diameter part 152. This part 153 of the confinement unit 15 is positioned between the two electrodes 14 and is subjected to the electric field generated by these electrodes 14. Part 153 forms a barrier in which the moving powder 12a is trapped and cannot escape. The powder 12a then forms a swarm of moving particles, which stagnates at the level of part 153, without the traction effect provided by the substrate 11a to be treated moving in the confinement unit 15. In this section 153, the fibers also tend to move, which promotes the swelling of the fibers according to their texture and the applied AC electric field. They then occupy the entire space of the region, and can then attract the powder that has infiltrated into the porous network.

[0042] The powder particles 12a are polarized. Under the influence of the electric field of the electrode 14, the powder particles 12a are therefore made to move irregularly within the portion 153 of the confinement unit 15. The speed of the powder particles 12a is an increasing function of the strength and frequency of the electric field. The stronger this field is, the faster the particles can be obtained and the deeper they can penetrate into the pores of the substrate 11a to be treated. The frequency may be adjusted depending on the particle size of the powder. Advantageously, larger particles may be subjected to a lower frequency electric field and given time to move by following the oscillations of the electric field. The frequency is generally from tens to hundreds of Hertz.

[0043] As shown in Figures 3a-3c, the containment units 15a-15c may take on a number of shapes.

[0044] Figure 3a shows a containment unit 15a that includes a constant diameter section 353 from the entrance orifice to the exit orifice. This shape is adapted to porous substrates that have a low ability to displace and swell fibers.

[0045] It may also be adapted where the effect of penetration of the powder into the porous substrate is less important and where the desired result corresponds to a position of more powder on the surface of the porous network and less in the center.

[0046] Advantageously, as shown in FIG. 3b, the containment unit 15b may comprise an additional section 251 located upstream of the constant diameter section 253. This additional section 251 has the shape of a funnel and is intended to guide the powder 12a in such a way that it comes into contact with the moving yarn and / or tape and in such a way as to obtain the most uniform amount of impregnated powder possible along the yarn or substrate. In fact, in addition to the desired impregnation effect, it is preferable to obtain a constant powder content over the entire length of the impregnated substrate. To this end, the flow rate of the powder dispenser may be advantageously adjusted and the containment unit preferably does not accumulate powder and avoids drifts or variations in impregnation.

[0047] Alternatively, as shown in FIG. 3c, containment unit 15c may have a funnel-shaped portion 151, a second portion 152 of constant diameter, and a third portion 153 having a larger diameter than second portion 152.

[0048] The regions of the containment units 15a-15c may adopt several shapes. By way of example, the regions may be circular, oval, square, rectangular or elliptical.

[0049] These shapes depend mainly on the appearance and properties of the substrate to be impregnated: yarns, yarn bundles and rovings require circular sections; braids, ribbons and fabrics require oval or rectangular cross sections.

[0050] These elongated sections are also well suited for processing several threads or materials in parallel: the parallel arrangement of threads or narrow strips of material advantageously allows more substrates to be processed simultaneously.

[0051] The cross-sectional shape of the containment units 15a-15c affects the strength of the electric field that exists in the circulation area of ​​the powder and the substrate being treated.

[0052] Indeed, in the example shown in FIG. 4, when the confinement unit 15 is not positioned between the electrodes 14, the electric field between the electrodes is 8×10 5 When the containment unit 15 is positioned between the electrodes 14 as shown in FIG. 5 V / m. The rectangular or oval shape of the confinement unit 15 thus makes it possible to increase the electric field by 50% with respect to the initial value. It turns out that the confinement unit then acts not only as a closed volume in which the powder and the fibres move to mix, but also as an amplifier of the effectiveness of the treatment. It is therefore possible to reach impregnation speeds of up to about 100 m / min to carry out the treatment.

[0053] The interface 21 makes it possible to control the impregnation installation 100, for example the movement speed of the substrate 11a to be treated in the confinement unit 15, the conveying speed of the powder 12a, or even the voltage delivered by the alternating voltage generator 22.

[0054] In conclusion, the present invention is an installation making it possible to uniformly and continuously impregnate substrates such as tapes or threads, with high efficiency in terms of the production rate and quality obtained. [Explanation of symbols]

[0055] 11a substrate, 11b substrate, 12a powder, 12b powder, 13 powder reservoir, 14 electrode, 15 containment unit, 15a containment unit, 15b containment unit, 15c containment unit, 16 funnel, 17 funnel, 18a reel, 18b take-up reel, 19a deflection roller, 19b deflection roller, 19c return roller, 20 collection tank, 21 interface, 22 AC voltage generator, 23 comb, 24 mandrel, 25 supply screw, 100 impregnation device, 101 frame, 151 funnel-shaped portion, 152 second portion, 153 third portion, 251 additional portion, 253 constant diameter portion, 353 constant diameter portion

Claims

1. An installation (100) for impregnating at least one substrate (11a) to be treated in the form of threads and / or tapes with a powder (12a), a powder conveying unit (13, 17, 25), a unit (18a, 19a, 19b, 23, 24) for supplying said substrate to be treated, at least two electrodes (14) connected to an alternating current generator (22) capable of generating an alternating electric field in a space formed between said electrodes (14); a circulation area of ​​said powder and of said substrate to be treated (11a) extending at least within the area prevailing in said alternating electric field; Equipped with said impregnation installation (100) further comprises a containment unit (15), said containment unit having an inlet orifice for said substrate (11a) and said powder (12a) to be treated, an outlet orifice for said impregnated substrate (11b) and a closed contour section from said inlet orifice to said outlet orifice, said circulation area being formed by the internal volume of said containment unit (15), - an impregnation installation (100), characterized in that said containment unit (15) is fixed relative to at least one of said electrodes (14) and that said substrate (11a) and said powder (12a) to be treated are movable, in said circulation zone, between said inlet orifice and said outlet orifice of said containment unit (15).

2. 2. Impregnation installation according to claim 1, characterized in that the installation comprises two electrodes (14) arranged opposite each other.

3. 3. An impregnation installation according to claim 1 or 2, characterized in that the substrate forms one of the two electrodes.

4. 4. An impregnation installation according to any one of claims 1 to 3, characterized in that a part of the containment unit (15) protrudes from the space formed between the electrodes (14) to allow contact between the powder (12a) and the substrate (11a) to be treated.

5. Impregnation installation according to any one of claims 1 to 4, characterized in that the containment unit (15) is a circular tube.

6. Impregnation installation according to any one of claims 1 to 4, characterized in that the containment unit (15) is an oval tube.

7. Impregnation installation according to any one of claims 1 to 4, characterized in that the containment unit (15) is a rectangular tube.

8. 8. Impregnation installation according to any one of the preceding claims, characterized in that the containment unit (15) has at least two portions (152, 153) of different areas.

9. Impregnation installation according to any one of the preceding claims, characterized in that the containment unit (15) is made of a material having a relative dielectric constant of 2 or more.

10. 10. Impregnation installation according to any one of the preceding claims, characterized in that the containment unit (15) is made of a material comprised in the group comprising glass or quartz or ceramic.

11. 11. Impregnation installation according to any one of the preceding claims, characterized in that the containment unit (15) is oriented vertically.

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