PLASMA CORD COATING DEVICE

Abstract

This invention is directed to a plasma cord coating device comprising a pair of opposite and parallel plate electrodes having a first electrode and a second electrode, a pair of planar and parallel dielectric barriers including a first dielectric barrier, and a second dielectric barrier, wherein the first electrode is covered by the first dielectric barrier on a side facing the second electrode and the second electrode is covered by the second dielectric barrier on a side facing the first electrode to form a gap between the first and the second dielectric barriers. This device includes a first foil which extends through the gap and covers the first dielectric barrier and a second foil which extends through the gap and covers the second dielectric barrier to form a plasma treatment zone between the first foil and the second foil.

Claims

1. A plasma cord coating device comprising: a pair of opposite and parallel plate electrodes having a first electrode and a second electrode; a pair of planar and parallel dielectric barriers including a first dielectric barrier and a second dielectric barrier, wherein the first electrode is covered by the first dielectric barrier on a side facing the second electrode and the second electrode is covered by the second dielectric barrier on a side facing the first electrode so as to form a gap between the first and the second dielectric barriers; a pair of driven conveyor foils comprising a first foil and a second foil, wherein the first foil extends through the gap and covers the first dielectric barrier and the second foil extends through the gap and covers the second dielectric barrier so as to form a plasma treatment zone between the first foil and the second foil; transport means for continuously transporting, in a direction of transport and spaced apart from the first foil and the second foil, at least one cord through the plasma treatment zone; and a gas supply means for directing gas into the plasma treatment zone, wherein said gas supply means is positioned upstream the plasma treatment zone with respect to the direction of transport.

2. The cord coating device of claim 1 wherein the transport means are adapted to transport at least two spaced apart and plane-parallel cords in parallel to the first and the second electrodes and spaced apart from the first foil and the second foil, through the plasma treatment zone.

3. The cord coating device of claim 1 wherein a first roller is arranged upstream of the gap for guiding the first foil into the gap and wherein a second roller is arranged upstream of the gap for guiding the second foil into the gap, and wherein the gas supply means is positioned upstream of the first and the second rollers.

4. The cord coating device of claim 1 wherein at least one of the foils is a closed band guided endlessly over at least two rollers into the gap and out of the gap.

5. The cord coating device of claim 1 wherein at least one of the foils is capable of being unwound from a first storage roll and is capable of being recoiled on a second storage roll.

6. The cord coating device of claim 1 wherein the gas supply means comprises a slot arranged perpendicularly to the direction of transport or a plurality of nozzles arranged perpendicularly to the direction of transport.

7. The cord coating device of claim 1 wherein at least one of the electrodes is cooled by cooling means on a backside of the electrode opposite to the gap, and wherein backside of the electrode is in direct contact with a cooling water reservoir.

8. The cord coating device of claim 1 wherein a distance between the first electrode and the second electrode is adjustable.

9. The cord coating device of claim 1 wherein (i) the first electrode and the first dielectric barrier or (ii) the second electrode and the second dielectric barrier is mounted on a movable support which allows for adjustment of gap width.

10. The cord coating device of claim 1 further comprising exhaust means downstream the gap.

11. The cord coating device of claim 1 wherein the foils are made of a dielectric material.

12. The cord coating device of claim 1 wherein at least one of the foils is comprised of a member selected from the group consisting of a polyimide, a polyester, a polyamide-based polymer, a fluorinated polymer, and a silicone-based polymer.

13. The cord coating device of claim 1 wherein the foils cover the whole width of the electrodes.

14. The cord coating device of claim 1 further comprising at least two cords extending in parallel and coplanar through the gap and being spaced at an equal distance to the first electrode and the second electrode.

15. The cord coating device of claim 1 further comprising cord guiding means arranged upstream and/or downstream of the gap, wherein the cord guiding means comprise a comb-shaped guide having a plurality of teeth for holding cords spaced apart at an essentially equal height between the teeth, wherein the cord guiding means are electrically grounded and in electrically conductive contact with the transported cord.

16. The cord coating device of claim 1 further comprising a power supply connected to at least one of the electrodes.

17. The cord coating device of claim 1 further comprising means for grounding at least one of the electrodes and/or the cords to be coated.

18. A method of plasma treating a cord which comprises passing the cord through the plasma treatment zone of the cord coating device of claim 1.

19. The method of claim 18 wherein multiple cords are transported in a plane-parallel manner and in parallel to the electrodes through the plasma treatment zone and are spaced apart from each other and spaced apart from the conveyor foils.

20. The method of claim 18, wherein the cords are transported through the plasma treatment zone at a speed which is within the range from 1 meter/minute to 100 meters/minute and wherein the cord is a metal tire cord or a polymeric tire cord.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 is a schematic side view of one embodiment of the present invention.

[0049] FIG. 2 shows a schematic top view of elements of the device shown in FIG. 1, viewed from an upper foil onto the cords to be coated and onto the lower foil.

[0050] FIG. 3 shows a schematic perspective view of an inventive example of a guiding means including a comb-shaped guide element for guiding wires.

[0051] FIG. 4 shows a schematic side view of a series of plasma cord coating devices.

DETAILED DESCRIPTION OF THE INVENTION

[0052] FIG. 1 depicts an embodiment of a plasma cord coating device 10 which comprises a first plate electrode 11 and a second plate electrode 12 parallel to the first electrode 11, a first dielectric barrier 21 and a second dielectric barrier 22 which are parallel to each other and to the electrodes 11, 12. A gap 2 is formed between the barriers 21 and 22 which cover the electrodes 11, 12. While the dielectric barriers 21, 22 are shown here in direct contact with the electrodes 11, 12, there could be also a gap or distance between them. Also, it is possible for the electrodes to be coated with the dielectric barriers (barrier layers) or in the alternative to be fully encapsulated in dielectric barriers.

[0053] In the present embodiment illustrated in FIG. 1, the backsides of the electrodes 11, 12 are covered by water casings 31, 32 adapted for cooling the backside of the electrodes in order to ensure a constant operating temperature of the electrodes. Demineralized water could be used in such a case. Moreover, the water reservoirs of the water casings could be in fluid contact with a heat exchanger (not shown). It would also be possible that the electrodes 11, 12 and/or the cooling casings 31, 32 are passively cooled by cooling ribs (not shown). Another option would consist of cooling the electrodes by cooling pipes (not shown).

[0054] In the gap 2 conveyor foils 41, 42 are arranged to transport material plasma deposited in the device 10 (but not on the cords 1) out of the gap 2. In particular, upon running a plasma coating/deposition process it would be difficult to coat only the cords 1 without coating also parts of the coating device (called also fouling). This unintended coating of elements of the device would result in frequent maintenance and cleaning to ensure constant coating conditions. In order to minimize such fouling in the device 10, the inventors have suggested the use of conveyor foils 41, 42 which cover the dielectric barriers 21, 22 in the gap 2 and run essentially in parallel to the dielectric barriers 21, 22 through the gap. The coating foils are comprised, in a preferred example, of a dielectric material with dielectric polymeric materials, such as polyimides, being highly preferred. In fact, polyimides prove to be an excellent choice of material for the plasma conditions. The plasma coating is then carried out between both foils 41, 42 in a plasma treatment zone 3. Preferably, the plasma treatment zone corresponds to the length of the electrodes L (measured in the transport direction t of the cords) and the width w of the electrodes (visible in FIG. 2) and the height d which corresponds to the distance between the two foils 41, 42. For coating the cords 1, the plane-parallel cords 1 run through the gap 2, in particular through the plasma coating zone 3 in parallel to the electrodes 11, 12, in the transport direction t. Transporting and/or guiding of the cords 1 could be carried out by rollers 6. Preferably, the height h of the gap 2 is constant along the transport direction t so that the distance of the cords 1 to the electrodes 11, 12 is kept constant while running through the gap 1.

[0055] In order to inject a plasma gas into the plasma treatment zone 3 a gas supply means 5 is arranged upstream from the plasma treatment zone 3. For instance, such a gas supply means 5 could be formed by a slotted tube arranged in a perpendicular manner to the direction of transport tin front of the plasma treatment zone 3. In an alternative embodiment, a plurality of nozzles could be arranged perpendicular to the direction of transport t and directed towards the plasma treatment zone 3. In particular, the gas supply means 5 could be provided upstream from a roller which guides one of the foils 41, 42 into the gap 2.

[0056] The gas supply means 5 could inject for instance an atomized mixture including a carrier gas, and a monomer or precursor selected from the group consisting of carbon disulfide and acetylene.

[0057] Suitable carrier gas could include for instance any of the noble gases including helium, argon, xenon, and neon. Suitable carrier gases also include nitrogen, carbon dioxide, nitrous oxide, carbon monoxide, and air as well as hydrogen. It is typically preferred for the carrier gas to be a noble gas or nitrogen with noble gases, such as helium, neon, argon, and krypton being preferred. In one embodiment of this invention the carrier gas is argon.

[0058] As a non-limiting example, the carrier gas may include carrier gas atomized with carbon disulfide and the pure carrier gas introduced directly into the plasma chamber. In one embodiment, the at least one of carbon disulfide and acetylene are present in a ratio (total carbon disulfide+acetylene)/carrier gas in a range of from 0.1 to 5 percent by volume. In one embodiment, the at least one of carbon disulfide and acetylene are present in a ratio (total carbon disulfide+acetylene)/carrier gas in a range of from 0.2 to 1 percent by volume.

[0059] In one embodiment, carbon disulfide is used exclusive of acetylene. In one embodiment, acetylene is used exclusive of carbon disulfide. In one embodiment, both carbon disulfide and acetylene are used. In one embodiment, carbon disulfide and acetylene are present in a ratio carbon disulfide/acetylene in a range of 0.1 to 0.5 percent by volume.

[0060] In another example of the invention, a carrier gas is fed from a storage vessel to an atomizer along with carbon disulfide from another storage vessel. Carrier gas and carbon disulfide are atomized in an atomizer to form an atomized mixture. Acetylene from a storage vessel and the atomized mixture are mixed into a stream of carrier gas to form a gas mixture. The gaseous mixture may then be sent to the gas supply means 5, injecting the gaseous mixture into the plasma treatment zone 3, where atmospheric plasma is generated from the gas mixture. In one alternative embodiment, carbon disulfide is not used and no atomized mixture is formed. In another alternative embodiment, acetylene is not used.

[0061] Apart from the above described examples of forming a gaseous mixture for injection into the plasma treatment zone, other methods of mixing and/other materials may be used. The specific materials are not within the main focus of the present invention. Further examples of suitable gaseous materials are for instance known from and listed in United States Patent Application Publications US2018/0294069A1, US2018/0294070 as well as in U.S. Pat. Nos. 9,433,971, 9,133,360, and 9,441,325, which are all incorporated herein by reference for the purpose of disclosing suitable gaseous materials that can be utilized.

[0062] Typically, the foils 41, 42 may be continuously moving through the gap 2, thereby removing continuously material plasma deposited onto the foils 41, 42 out of the gap 2. In an example, each foil could be an endless band (as foil 41 in FIG. 1) which is cleaned at a position outside of the gap 2 by a scraper 7 and/or chemical treatment (not shown) such that the respective foil enters the gap 2 after being cleaned. In another example, a foil may be uncoiled from a first roll or spool and recoiled by a second roll or spool (such as foil 42 in FIG. 1). In both alternatives, a clean foil 41, 42 enters or reenters the gap 2 so as to support constant plasma deposition conditions.

[0063] While the foils 41, 42 ensure a removal of fouling from the device, it is also desirable to remove remainders of the plasma gas which exit the treatment zone 3 downstream from the electrodes. For this purpose, exhaust means 8 are preferably provided downstream from the gap 2. Such means could comprise a pipe having apertures which are arranged perpendicularly to the direction of transport t, and preferably in parallel to the planar electrodes 41, 42. The exhaust 8 may be fluidly connected with a filter device (not shown) which may include one or more filters. In an example, a first filter mechanically filters particles out of the exhaust gas. In addition, or alternatively, a second filter could be an active carbon filter. In addition, or alternatively a third filter could be a high efficiency particulate air (HEPA) filter. The combination of one or more of such filters can efficiently filter the gas received downstream from the plasma treatment zone 3 so that it can be released to the environment in a manner that complies with stringent environmental standards.

[0064] FIG. 1 shows essentially a horizontal arrangement of electrodes 11, 12, dielectric barriers 21, 22 and foils 41, 42. It is emphasized that other orientations of the system would be possible such as vertical or other orientations in between horizontal and vertical.

[0065] FIG. 2 schematically depicts a top view from the upper foil 42 of FIG. 1 onto the cords 1 and the lower foil 41. Also visible are the rollers 6, the (plasma) gas supply means 5 (or in other words the supply means 5 for a gaseous mixture such as described herein above), the lower water casing 31 and the exhaust means 8. FIG. 2 shows also a plane-parallel arrangement of the cords 1. According to the preferred embodiment shown in FIG. 2, the cords 1 are held or guided by circumferential grooves in the rollers 6 such that the cords 1 are transported in parallel to one another in the transport direction t. In the present example, five cords 1 are transportable at the same time through the plasma treatment zone. As visible in FIG. 2, the foil 41 completely covers the first dielectric barrier and the first electrode (having the width w) embedded in the casing 31 such that plasma coating material which is not caught by or deposited on the cords is deposited on the moving foil 41 and transported out of the gap 2.

[0066] In general, the plate electrodes 11, 12 may be connected to a voltage supply. Supply of voltage electricity to the plate electrodes 11, 12 can generate an atmospheric pressure plasma from the gas supplied by the gas supply means 5 into the plasma treatment zone 3, in particular for the example of coating grounded metal cords (e.g. made of steel).

[0067] In general, the cords 1 may be taken from supply spools (not shown) prior to entry into the plasma treatment zone 3 and may be then wound onto storage spools (not shown) after exiting the plasma treatment zone. One or more of such spools could be motor driven, e.g. to pull cords 1 through the plasma treatment zone 3. In other embodiments, the transporting means may include drive rollers or other the like. In particular, one or more of rolls 6 could be driven.

[0068] FIG. 3 shows a further example of a cord guiding means in the form of a plate having a comb-shape 60 with a plurality of teeth, wherein multiple cords 1 are held in parallel between the teeth within a plane. Optionally, guiding means may be electrically grounded. Such guiding means helps to ensure a proper entry of the wires into the plasma treatment zone 3. They could be arranged at multiple positions upstream and/or downstream the plasma treatment zone 3.

[0069] As shown in the embodiment of FIG. 4, multiple plasma cord coating devices 10′ may be arranged in series in a system 100 to extend the exposure of cords 1 to plasma. For instance, rollers and/or guides, such as rollers 6 and/or guiding means 60 shown in FIGS. 1 to 3 could be used. In such an embodiment, the plasma cord coating devices 10′ may operate in identical fashion or apply different coatings in sequence as desired, for example by receiving different gas compositions.

[0070] Cords 1 may be constructed of various metallic or textile materials, in particular those commonly used in reinforcing cords for tires. In one embodiment, the reinforcement cord includes steel, stainless steel, galvanized steel, zinc plated steel and brass plated steel. Textile materials may include polyesters, such as polyethylene terephthalate or polyethylene naphthalate. The textile material can also be a polyamide, such as nylon-6,6, nylon-4,6, nylon-6,9, nylon-6,10, nylon 6,12, nylon-6, nylon-11, or nylon-12. In some embodiments of this invention hybrid materials, such various blends of polyamides and blends of polyesters can be utilized. The textile material can also be an aramid fiber, a glass fiber, cellulosic fiber (such as Rayon) or another known textile cord material.