Electrocoated conductive fabric

Abstract

The present invention generally relates to an insulated electrically conductive textile comprising a textile selected from the group consisting of nonwoven, woven, and knit comprising nonconductive fibers or yarns and at least 1 elongated conductive element and either another elongated conductive element or another conductive body. The conductive bodies cross at a point to form an electrical junction that is covered with an insulating coating. The insulating coating is substantially located only on the conductive bodies and is substantially continuous along the outer perimeter of the elongated conductive elements.

Description

TECHNICAL FIELD

The present invention generally relates to an insulated electrically conductive fabric with insulated electrically conductive bodies in the fabric while maintaining the electrical connection between those elements and the process for making the fabric.

BACKGROUND

Electrically conductive fabrics often need to be insulated, both to protect the circuit from the environment or protect the user from the circuit. Most conductive fabrics with insulation are made by insulating the conductive materials before they are incorporated into a fabric. For example, an insulated wire may be woven into or stitched onto a fabric. This precludes easy or automated electrical connections within the fabric.

Connections can be made more easily if the conductive materials are not insulated when incorporated into the fabric. In this case, insulating the conductive materials has meant the application of a film or thick coating to the entire fabric, which creates a stiff, impermeable product.

There is a need for an electrically conductive fabric that is flexible, breathable (permeable to vapors or gases) that insulates the electrical elements in the fabric while maintaining the electrical connection between those elements.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings.

FIG. 1 is a schematic of a top view of one embodiment of the insulated conductive fabric;

FIG. 2 is a schematic of a cut-away view of one embodiment of the insulated conductive fabric;

FIG. 3 is a schematic of a side view of one embodiment of the insulated conductive fabric;

FIG. 4 is a schematic of an insulated conductive connector;

FIG. 5 is a schematic of a top view of one embodiment of the conductive fabric before being insulated;

FIG. 6 is a schematic of an electrophoretic bath with the conductive fabric;

FIG. 7 is a schematic of the electrophoretic process to form an insulated conductive fabric;

FIG. 8 is a photograph on the top view of an insulated conductive fabric; and,

FIG. 9 is a photograph on the cross-sectional view of an insulated conductive fabric.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a top view of one of the embodiments of the insulated electrically conductive textile 10 comprising nonconductive yarns 100 and at least 2 insulated conductive bodies which may be insulated elongated conductive elements 201 and/or insulated electrically conductive connectors 202. In one embodiment, the textile 10 comprises at least 2 insulated elongated conductive elements 201 and in another embodiment, the textile 10 comprises at least 1 insulated electrically conductive connector 202 and at least 1 elongated conductive element 201. The conductive bodies 201, 202 cross at least one point in the textile 10 forming an electrical junction.

FIG. 2 shows an illustrated cut-away view of the textile 10 and FIG. 3 shows an illustrated cross-section of the textile 10. The insulated elongated conductive elements 201 shown contain an elongated conductive element 210 surrounded by an insulating coating 212. An elongated conductive element 210 means a single independent unit of a continuous slender body having a high ratio of length to cross-sectional distance, such as cords, wires, tapes, threads, yarns, or the like. The elongated conductive element 210 can be a single component, or multiple components combined to form the continuous elongated element. The electrical junction 110 between two insulated elongated conductive elements 201 may be seen in FIG. 3 and as a cross-sectional photograph in FIG. 9.

Referring now to FIG. 4, one of the insulated conductive bodies shown is an insulated conductive connector 202. The insulated conductive connector 202 is formed from an electrically conductive connector 211 with an insulting coating 213. Electrical connectors can be any of a number of devices or materials designed to connect two electrically conductive components in a semi-permanent or permanent manner, including but not limited to crimp connectors, insulation displacement connectors, wire lug terminals, pin/socket terminals, clip connectors such as “alligator” clips, snap connectors, rivets, and zippers such as those used in apparel closures, and the like. Electrical connection is guaranteed between the elongated conductive element and the electrical connector by mechanically crimping, soldering, or otherwise affixing with electrically conductive material such as conductive paint, elastomer/rubber, epoxy, or glue the two components together.

The elongated conductive elements 210 and conductive connectors 211 may be formed from any conductive material. In one embodiment the conductive bodies 210, 211 are formed from any metal including copper, aluminum, nickel, carbonyl nickel, molybdenum, silver, gold, zinc, cadmium, iron, tin, beryllium, lead, steel, bronze, brass, and alloys of one or more of the foregoing metals. In another embodiment, the conductive bodies 210, 211 comprise carbon, such as carbon fiber, carbon filaments, or carbon-doped polymers. In yet another embodiment, the conductive bodies 210, 211 are combinations of metal and polymers or yarns such as silver-coated yarns or metal-doped polymers or certain conductive polymers such as poly(aniline), poly(pyrrole), poly(thiophene), poly(acetylene), poly(fluorene), poly(3-hexylthiophene), poly(naphthalene), poly(p-phenylene sulfide), or poly(para-phenylene vinylene). Additionally, the elongated conductive elements 210 are of a material that is able to be formed into an elongated element such as a wire or yarn.

The insulated elongated conductive elements 201 are preferably flexible. Flexible, as used herein in association with an insulated elongated element 201 or fabric 10, shall mean the ability to bend around an axis perpendicular to the lengthwise direction of the strand with light to moderate force while still maintaining a working electrical connection. In one embodiment, the flexible elongated element or fabric requires no more than about 1000 grams of force to be pressed through a 15 mm wide slot to a depth 6 mm, such as performed by a Handle-O-Meter manufactured by Thwing vAlbert Instrument Co., Philadelphia, Pa.

The insulated electrically conductive fabric 10 may be of any stitch construction suitable to the end use, including by not limited to woven, knitted, non-woven, and tufted textiles, or the like. The conductivity of the insulated electrically conductive fabric 10 will vary according to the end use. In one embodiment where the insulated electrically conductive fabric 10 is used as a heating garment, such as a glove, the surface resistance of the insulated conductive fabric 10 may be approximately 0.01 to 100 ohms.

Woven textiles can include, but are not limited to, satin, twill, basket-weave, poplin, and crepe weave textiles. Jacquard woven structures may be useful for creating more complex electrical patterns. Knit textiles can include, but are not limited to, circular knit, reverse plaited circular knit, double knit, single jersey knit, two-end fleece knit, three-end fleece knit, terry knit or double loop knit, warp knit, and warp knit with or without a microdenier face. The fabric 10 may be flat or may exhibit a pile.

As used herein yarn shall mean a continuous strand of textile fibers, spun or twisted textile fibers, textile filaments, or material in a form suitable for knitting, weaving, or otherwise intertwining to form a textile. The term yarn includes, but is not limited to, yarns of monofilament fiber, multifilament fiber, staple fibers, or a combination thereof. The nonconductive yarns 100 have a low conductivity such that any flow of electric current through it is negligible. In one example, a non-conductive yarn will have a resistivity of at least 1×10¹³ ohms/inch.

The non-conductive fibers or yarns 100 may be any natural or man-made fibers including but not limited to man-made fibers such as polyethylene, polypropylene, polyesters (polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polylactic acid, and the like, including copolymers thereof, nylons (including nylon 6 and nylon 6,6), regenerated cellulosics (such as rayon or Tencel™), elastomeric materials such as Lycra™, high-performance fibers such as the polyaramids, polyimides, PEI, PBO, PBI, PEEK, liquid-crystalline, thermosetting polymers such as melamine-formaldehyde (Basofil™) or phenol-formaldehyde (Kynol™), basalt, glass, ceramic, cotton, coir, bast fibers, proteinaceous materials such as silk, wool, other animal hairs such as angora, alpaca, or vicuna, and blends thereof. Nonconductive yarns that are less porous are more preferred as they absorb less of the electrophoretic bath chemistry and solvent.

The insulating coatings 212, 213 on the insulated conductive bodies 201, 202 are organic or inorganic polymers that are either soluble or dispersible in the process solvent, most commonly water, and possess ionizable moieties such that the polymers or polymer dispersions can be forced to migrate in solution by application of an electrical current. Suitable aqueous polymer dispersions incorporate an ionizable functional group into the structure of the polymer and/or may be stabilized by ionizable surfactants. Preferred polymers undergo a change in solubility at the working electrode, either by a change in the oxidation state of the polymer itself, by reaction with the reduction or oxidation products of the working electrode itself, by disruption of the stabilizing surfactant dispersion, by exceeding the local solubility limit, or by other means know in the art. More preferred polymers are those that may be chemically cross-linked to form an insoluble durable coating.

In one embodiment, the invention utilizes electrocoating to selectively coat the conductive portions of a conductive fabric 1 shown in FIG. 5, while not depositing on the nonconductive fibers or yarns 100. This forms the insulated conductive fabric 10 shown in FIG. 1 with insulated conductive bodies 201, 202 while the fabric 10 remains flexible, air permeable, and vapor permeable. It also allows for further treatments of the nonconductive fibers and yarns 100 for wicking, odor control, flame retardation, etc. Electrocoating creates a very even, continuous coating on the conductive elements, even in crevices and other partially occluded areas that convention coatings traditionally miss or undercoat.

Electrocoating (e-coating) is a method of depositing polymer-based paint or coatings onto conductive surfaces via electrically-induced precipitation. E-coating is commonly used in the automotive industry, for example. It involves using one partially or fully conductive article as one electrode (working electrode) (in our case the conductive fabric) and a second conductive article (typically a graphite electrode) (counter electrode) into an aqueous bath containing ionizable moieties and passing a current between the two electrodes.

The organic or inorganic polymers, or organic or inorganic compounds, collectively referred to as “ionizable moieties”, are deposited onto an electrically conductive substrate, typically carbon or metallic. In the invention, the substrate may be formed of individual fibers, or as a fabric of fibers. In either case, the ionizable moieties deposit at and may or may not chemically bond to the surfaces of the conductive bodies 210 and 211. For example, polymers incorporating ionizable moieties in the structure of the polymer may chemically bond to the electrode or may be electrochemically transformed into a non-soluble species. Latexes that are dispersed using ionic surfactants can be caused to precipitate out at the electrode by disturbing the surfactant-mediated dispersion, not chemical bonding to the conductive body itself. The conditions for electrodeposition are maintained until the desired thickness of deposition is achieved.

The process is performed by immersing a conductive textile 1 in an electrolysis cell 500 containing a solution 501 (preferably aqueous) with an organic compound or polymer, or inorganic compound or polymer having ionizable moieties 400 as described above, detailed in FIG. 6, and shown as step 650 in FIG. 7. The electrophoretic process may be cationic or anionic (the process being specified whether the conductive fabric serves as the cathode or anode). In a cationic electrophoretic process, the working electrode serves as the cathode at which reduction takes place that is the cathode supplies electrons to the solution and attracts cationic species in the solution. In an anionic electrophoretic process, the polarity of the system is reversed, with the working electrode acting as the positively charged anode that attracts anionic species in the solution. With metal working electrodes, a cationic process is preferred because the negative charge on the working electrode effectively prevents electrolytic dissolution of the metal working electrode. In anionic electrophoretic processes, metal working electrodes may undergo oxidation to form soluble metal cations in solution, which contaminate the bath and may cause solution precipitation of the coating material. In one embodiment, the electrodeposition is performed where the conductive textile 1 acts as the cathode, where the other electrode 510 in contact with the solution of ionizable moieties acts as a anode, and where the application of an electric potential causes the negatively ionizable moiety in solution to migrate to the anode.

The insulating coating 212, 213 (formed from the ionizable moieties) is simultaneously deposited on the conductive bodies 210, 211 and the electrical junctions, forming a continuous insulating coating on the insulated conductive bodies 201, 202 and the electrical junctions between them. The insulating coating 212, 213 on the insulated conductive bodies 201, 202 is of the same material and chemical make up as the insulating coating on the electrical junctions. The insulating coating covers greater than 99% of the surface area of the electrical junctions between the conductive bodies (elongated conductive elements 201 and electrically conductive connectors 202). The insulating coating deposits substantially only on the conductive elements in the conductive textile. The portion of the insulating coating on the nonconductive fibers or yarns 100 of the conductive textile comprise less than 10% by weight, more preferably 5% by weight, more preferably 2% by weight, and more preferably 1%, of the insulating coating after the electrophoretic process. In another embodiment, the amount of insulating material added to the nonconductive elements is less than 50%, more preferably less than 25%, more preferably less than 10%, of the amount of insulating material added to the conductive elements. Preferably, the insulating coating is substantially continuous along the outer perimeter of the insulated elongated conductive elements 201 and the insulated electrically conductive connectors 202. In another embodiment, the insulating coating covers at least 95%, more preferably 99%, of the surface area of the insulated elongated conductive elements 201 and the insulated electrically conductive connectors 202.

Once the desired amount of insulating coating is deposited onto the insulated conductive bodies 201 and 202 in the now insulated conductive textile 10, the insulated conductive textile 10 is removed from the solution 660, rinsed 670, and cured 680. How the insulated conductive textile 10 is cured in step 680 shown in FIG. 7 depends on the materials of the conductive bodies 201 and 202, nonconductive yarns 100, and insulating coatings 212 and 213. The curing may be at room temperature or at an elevated temperature.

Additionally, before placing the conductive textile 1 into the solution, there may be additional cleaning 610 and rinsing 620, and/or pretreating with an acid bath 630 and rinsing 640 steps to prepare the conductive bodies 210 and 211 for the electrophoretic process.

The insulated electrically conductive textile 10 preferably has an air permeability of greater than about 25 cfm at 125 Pa using TexTest air permeability test equipment (ASTM D737). In one embodiment, the air permeability of the insulated conductive fabric 10 is at least 90%, more preferably at least 96% of the air permeability of the uncoated conductive fabric 1. This range of air permeability has been shown to create textiles that may be used as garments and other textile applications where the fabric needs to “breathe”. Prior art methods for insulating conductive elements in a textile involving applying an insulting material to the entire textile would not achieve this level of air permeability. In another embodiment, the insulated electrically conductive textile has a vapor permeability of greater than about 1000 g/m²/24 hours, in one embodiment with an upper limit of 15,000 g/m²/24 hours as measured by ASTM E 96-95. Having this range of vapor permeability has also been shown to create textiles that may formed into wearable and comfortable garments.

EXAMPLES

The example fabric was made starting with a coarse plain weave fabric with a weight of heavy 6.25 oz/sq yd formed from polyester filament yarns. The polyester yarns used in the warp direction were 1134 denier at 22 ypi woven with 2 ends per dent.

The polyester yarns used in the weft direction were 1148 denier with 18 ppi. Every 2½ inches the fill yarn was replaced by three consecutive conductive yarns. The first and third conductive yarns were from IntraMicron of Alabama, consisting of 250 solid copper filaments that were each 33 microns in diameter. The middle conductive yarn was a silver-coated nylon 3-ply yarn, with two monofilament yarns wrapped (S- and Z-) around a 24 filament core yarn with a denier of 204.

Every 30 inches one pair of warp yarns was replaced by a pair of the same copper yarns used in the weft. On either side of the warp copper warp yarns were a pair of silver-coated nylon yarns with 2-ply with 34 filaments in each singles yarn and a total denier of 407.5, inserted as a leno weave. The conductive yarns formed a connected electrical network.

Fabric samples (A) were prepared for electrocoating from the aforesaid fabric construction by scouring according to standard textile processing techniques known in the art. Samples were then heat-set at 400° F. for 5 minutes to stabilize the fabric for further processing. A set of control fabric samples (B) was made from greige fabric of the aforesaid construction. Sections of fabric, approximately 16″ by 36″ were cut from the weft direction of the fabric such that each section contained at least one set of conductive yarns in the warp and the fabric edges were within 1″ of the nearest set of weft conductive yarns. The raw edges of the fabric were turned and sewn to create a piece of fabric with finished edges. The female half of uncoated rivet-style metal snaps were inserted 8.5″ apart on center through the set of weft conductive yarns nearest to the edge of the fabric. The metal snaps served to connect the fabric with conductive yarns to a metal frame (C) that would carry the fabric through the electrocoating process. The metal frame had the corresponding male uncoated rivet-style metal snaps affixed to it such that the fabric samples could be snapped to it and held in place during the electrocoating process.

The e-coating process had 12 tanks that samples were passed through prior to the drying/curing ovens:

1. caustic clean

2. caustic clean

3. water rinse

4. conditioning rinse

5. acid/zinc phosphate bath

6. water rinse

7. water rinse

8. deionized water rinse

9. e-coat bath

10. water rinse

11. water rinse

12. water rinse

Experiment I: Fabric sample (A-1) was snapped to a metal frame and loaded into the rack conveyor system of a commercial electrocoating process as shown in FIG. 6. The coating system used was an 800-series black cationic epoxy from PPG Industries of Pittsburgh, Pa., typically used for automotive and other small metal parts. Sample (A-1) was immersed sequentially in Tanks 3, 4, and 6-12. A black coating was observed on the conductive yarns on the fabric, while the non-conductive yarns retained only a slight discoloration from excess electrocoating formula that had not been successfully rinsed out. The fabric sample was then carried by the rack conveyor system into a series of ovens to dry and cure the electrocoating. The entry temperature of the curing ovens was set at 400° F., decreasing to 250° F. at the exit. Total dwell time in the curing ovens was about 20 minutes. The fabric sample shrank a small amount during the curing process. Initial continuity checks were made using a multimeter attached to the snaps at each end of the fabric sample. All fabric samples retained electrical continuity through the part after processing, including continuity from warp to weft yarns. Attempts to measure the conductivity of the coated conductive yarns using the multimeter probes directly on the conductive yarns were unsuccessful, indicating that the deposited coating electrically insulated the conductive yarns.

Experiment II: Fabric sample (A-2) was snapped to a metal frame and loaded into the rack conveyor system of a commercial electrocoating process as shown in FIG. 6. The coating system used was an 800-series black cationic epoxy from PPG, typically used for automotive and other small metal parts. In this case, the fabric sample was sent through the entire electrocoating process, tanks 1-12, identical to metal parts processing. A black coating was observed on the conductive yarns on the fabric, while the non-conductive yarns retained only a slight discoloration from excess electrocoating formula that had not been successfully rinsed out. The fabric sample was then carried by the rack conveyor system into a series of ovens to dry and cure the electrocoating. The entry temperature of the curing ovens was set at 400° F., decreasing to 250° F. at the exit. Total dwell time in the curing ovens was about 20 minutes. The fabric sample shrank a small amount during the curing process. Initial continuity checks were made using a multimeter attached to the snaps at each end of the fabric sample. All fabric samples retained electrical continuity through the part after processing, including continuity from warp to weft yarns. Attempts to measure the conductivity of the coated conductive yarns using the multimeter probes directly on the conductive yarns were unsuccessful, indicating that the deposited coating electrically insulated the conductive yarns.

Experiment III: Fabric sample (B) was snapped to a metal frame and loaded into the rack conveyor system of a commercial electrocoating process. The coating system used was an 800-series black cationic epoxy from PPG, typically used for automotive and other small metal parts. Sample (B) was immersed in Tanks 3, 4, and 6-12. A black coating was observed on the conductive yarns on the fabric, while the non-conductive yarns retained only a slight discoloration from excess electrocoating formula that had not been successfully rinsed out. The fabric sample was then carried by the rack conveyor system into a series of ovens to dry and cure the electrocoating. The entry temperature of the curing ovens was set at 400° F., decreasing to 250° F. at the exit. Total dwell time in the curing ovens was about 20 minutes. The fabric sample (B) shrank a slightly larger amount than samples (A-1) and (A-2) during the curing process. Initial continuity checks were made using a multimeter attached to the snaps at each end of the fabric sample. All fabric samples retained electrical continuity through the part after processing, including continuity from warp to weft yarns. Attempts to measure the conductivity of the coated conductive yarns using the multimeter probes directly on the conductive yarns were unsuccessful, indicating that the deposited coating electrically insulated the conductive yarns.

FIG. 8 is a microscope image of the top of the electrocoated fabric and FIG. 9 is a cross-sectional image of the electrocoated fabric. In FIG. 8, the white-looking yarns are the nonconductive yarns and the dark-looking yarns are insulation coated conductive yarns. Referring now to FIG. 9, the white-looking yarns are the nonconductive yarns and one can see the conductive elements (grayish fibrous material) surrounded by the conductive coating (the dark-looking material). As can be seen from FIG. 9, most of the coating (dark areas) surrounded the conductive elements with little to none on the nonconductive elements. Measurements indicate that less than 10% of the total amount of coating deposited was deposited on the nonconductive elements. The resultant fabric maintained its electrical connections through the fabric and an air permeability of 47.2 cfm at 125 Pa using TexTest air permeability test equipment (ASTM D737). The air permeability was greater than 98% of the air permeability of the untreated fabric.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. An insulated electrically conductive textile comprising a textile selected from the group consisting of nonwoven, woven, and knit comprising nonconductive fibers or yarns and at least 2 conductive bodies having an electrically insulating coating that cross at a point to form an electrical junction, wherein the electrically insulating coating is substantially located only on the conductive bodies, wherein the electrically insulating coating covers at least 50% of the surface area of the conductive bodies and greater than 99% of the surface area of the electrical junction, and wherein the insulating coating on the conductive bodies and the electrical junction are formed of the same materials.

2. The insulated electrically conductive textile of claim 1, wherein the conductive bodies comprise at least 2 elongated conductive elements.

3. The insulated electrically conductive textile of claim 1, wherein the conductive bodies comprise at least 1 elongated conductive element and at least one electrically conductive connector.

4. The insulated electrically conductive textile of claim 1, wherein the insulating coating is formed on the conductive bodies and the electrical junction simultaneously.

5. The insulated electrically conductive textile of claim 1, wherein the conductive bodies comprise a metal selected from the group consisting of stainless steel, nickel, aluminum, copper, tin, silver, gold, and alloys thereof.

6. The insulated electrically conductive textile of claim 1, wherein the conductive bodies comprise carbon.

7. The insulated electrically conductive textile of claim 1, wherein the electrically insulating coating comprises a polymeric material.

8. The insulated electrically conductive textile of claim 1, wherein the conductive textile is flexible.

9. The insulated electrically conductive textile of claim 1, wherein the electrically insulating coating covers at least 95% of the surface area of the conductive bodies.

10. The insulated electrically conductive textile of claim 2, wherein the electrically insulating coating is continuous between the elongated conductive elements.

11. The insulated electrically conductive textile of claim 3, wherein the electrically insulating coating is continuous between the electrically conductive connector and the elongated conductive element.

12. The insulated electrically conductive textile of claim 1, wherein the nonconductive fibers comprise less than 10% by weight insulating coating.

13. A process for producing an insulated electrically conductive textile comprising: providing an solution comprising an ionizable moiety;depositing a conductive textile selected from the group consisting of nonwoven, woven, and knit comprising nonconductive fibers or yarns and at least two conductive bodies forming an electrical junction and a conductive electrode in contact with the solution;applying an electric potential between the conductive textile and the conductive electrode, causing the ionizable moieties to deposit selectively on the elongated conductive bodies of the textile forming an electrically insulating coating substantially only on the conductive bodies, wherein the electrically insulating coating covers at least 50% of the surface area of the conductive bodies and greater than 99% of the surface area of the electrical junction;removing the insulated conductive textile from the solution;rinsing the insulated conductive textile; andcuring the insulated conductive textile.

14. The insulated electrically conductive textile of claim 13, wherein the conductive bodies comprise at least 2 elongated conductive elements.

15. The insulated electrically conductive textile of claim 13, wherein the conductive bodies comprise at least 1 elongated conductive element and at least one electrically conductive connector.

16. The process of claim 13, further comprising cleaning and rinsing the conductive textile before depositing the conductive textile into the aqueous solution.

17. The process of claim 13, further comprising pretreating with an acid bath and rinsing the conductive textile before depositing the conductive textile into the aqueous solution.

18. The process of claim 13, wherein the conductive electrode comprises graphite.

19. The process of claim 13, wherein the conductive textile serves as the anode.

20. The process of claim 14, wherein the electrically insulating coating is substantially continuous along the outer perimeter of the elongated conductive elements.

21. The process of claim 13, wherein the nonconductive fibers comprise less than 10% by weight insulating coating after the textile is cured.

22. The insulated electrically conductive textile of claim 14, wherein the electrically insulating coating is continuous between the elongated conductive elements.