Conductive monofilament and fabric

Abstract

A conductive monofilament and static dissipative fabric having the same wherein the monofilament includes electrically conductive material and binder and has static dissipation properties.

Claims

1. A static dissipative industrial fabric comprising a plurality of polymeric monofilaments, wherein said monofilaments include electrically conductive material containing metallic particles and a binder incorporated as an outer surface coating or film thereon, said monofilaments having static dissipative properties, wherein the monofilaments include one or more longitudinal grooves, and the conductive material and binder line the one or more longitudinal grooves without filling the longitudinal grooves such that the conductive material and binder form a channel within the longitudinal grooves by forming a film that takes on a substantially similar shape as the longitudinal grooves, and the conductive material and binder reside below a wear surface of the monofilaments, and are located as a continuous coating or film, wherein the conductive material and binder are applied by one of dip or bath coating, spraying, jetting or die coating application method and wherein said fabric is an engineered fabric configured to make nonwoven textiles in airlaid, meltblown or spunbonding processes, or as a papermaking fabric.

2. The fabric in accordance with claim 1, wherein the binder is epoxy, acrylic, vinylidene chloride or copolymers thereof.

3. The fabric in accordance with claim 1, wherein the metallic particles are silver, copper, nickel, zinc or combinations thereof.

4. The fabric in accordance with claim 1, wherein the monofilaments are round or non-round shaped.

5. The fabric in accordance with claim 1, wherein the fabric is woven, MD or CD yarn array, knitted, spiral link assembly, extruded mesh or spiral wound strips of the aforesaid constructions.

6. The fabric in accordance with claim 1, wherein the monofilament is made of polyester, polyamide, polyphenylene sulphide (PPS) or polyetherether ketone (PEEK).

7. The fabric in accordance with claim 1, wherein said fabric is single or multilayered, multilayer woven or laminated.

8. A polymeric monofilament in an industrial fabric said monofilament having a continuous coating or film of conductive material comprised of metallic particles and a binder having static dissipative properties, wherein the monofilament includes one or more longitudinal grooves, and the conductive material and binder line the one or more longitudinal grooves without filling the longitudinal grooves such that the conductive material and binder form a channel within the longitudinal grooves by forming a film that takes on a substantially similar shape as the longitudinal grooves and the conductive material and binder reside below a wear surface of the monofilaments, and are located as a continuous coating or film, and wherein the conductive material and binder are applied by one of dip or bath coating, spraying, jetting or die coating application method, and wherein said monofilament is suitable for use in forming an engineered fabric configured to make nonwoven textiles in airlaid, meltblown or spunbonding processes, or as a papermaking fabric.

9. The monofilament in accordance with claim 8, wherein the binder is epoxy, acrylic, vinylidene chloride or copolymers thereof.

10. The monofilament in accordance with claim 8, wherein the metallic particles are silver, copper, nickel, zinc or combinations thereof.

11. The monofilament in accordance with claim 8, wherein said monofilament is round or non-round shaped.

12. The monofilament in accordance with claim 8, wherein the monofilament is made of polyester, polyamide, polyphenylene sulphide (PPS) or polyetherether ketone (PEEK).

13. The monofilament in accordance with claim 8, wherein said fabric is single or multilayered, multilayer woven or laminated.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Thus by the present invention, its objects and advantages will be realized, the description of which should be taken in conjunction with the drawings wherein:

(2) FIG. 1 is a cross-sectional view of a monofilament according to the teachings of the present invention;

(3) FIG. 2 is a plan of a fabric according to one aspect of the invention;

(4) FIG. 3a is a cross-sectional view of a monofilament according to one aspect of the invention;

(5) FIG. 3b is a cross-sectional view of a monofilament according to one aspect of the invention; and

(6) FIG. 4 is a somewhat schematic view of a die coating application method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) A preferred embodiment of the present invention will be described in the context of engineered fabrics, such as fabrics used in making nonwoven textiles in the airlaid, meltblown and/or spunbonding processes wherein the release of the nonwoven product formed on the fabric is improved by the elimination of static buildup. However, it should be noted that the invention is also applicable to other industrial fabrics such as dryer fabrics used in papermaking and other fabrics used in any dry applications where the dissipation of static electricity is required, for instance, through the fabric media. Also since electrically conductive material is also a good thermal conductor, other applications are possible where thermal conductivity is desirable. Some examples where the instant conductive or static dissipative yarns can be used is in the construction of power cables, such as for example oil well cables, high power transmission lines, as a grounding medium to prevent electrical charge build up during cable constructions, which otherwise has the potential to discharge causing equipment damage, serious injuries and/or deaths. Yet another example is for use in construction of braided sleeves, consisting of various thermoplastic monofilaments, to protect, ground and electromagnetic interference (EMI) shield bundles of multipurpose electrical wires, in plenums, in aerospace applications, such as aircraft controls, lighting, and entertainment, and in automotive applications. Fabric constructions may include woven, MD or CD yarn arrays, knitted fabrics, spiral link assemblies, film or film like structures, extruded mesh, and spiral wound strips of materials of the aforesaid construction. It should be noted that these industrial fabrics are relatively large and are often subject to a very harsh environment. These fabrics may comprise monofilament, plied monofilament, multifilament or plied multifilament synthetic yarns, and may be single-layered, multi-layered, multi-layer woven or laminated.

(8) Turning now more particularly to the drawing, the invention provides for fabrics comprising, as shown in FIG. 1 (cross-sectional view), a functional monofilament or yarn 10 containing electrically conductive material 12. Thus, whereas conductive material by itself may lack the strength to be formed into load bearing monofilaments 10, the invention in a preferred embodiment incorporates these materials 12 primarily in grooves 14 located along the longitudinal length of the monofilament 10. Advantageously, fabrics incorporating monofilaments 10 have static dissipation properties previously available only in metal-based fabrics whilst possessing physical properties equivalent to conventional industrial fabrics. Moreover, fabrics with these monofilaments 10 resist the denting and creasing heretofore associated with metal filament fabrics.

(9) In particular, the invention incorporates the conductive material 12 in a binder. The material utilized is preferably a conductive ink or adhesive which is available, for example, from Engineered Conductive Materials, LLC, or Engineered Material Systems, Inc., 132 Johnson Drive, Delaware, Ohio 43015. This company provides many conductive inks and adhesives. A particularly useful one is a conductive ink using silver particles and a binder. The preferred product has designations CI-1020. Other conductive inks with other metals such as copper, nickel, zinc or their combinations may also be suitable for the purpose. The binder may be epoxy, acrylic, vinylidene chloride, copolymers of these or any other type binder suitable for the purpose.

(10) The conductive material 12 lines the grooves 14 and need not fill all thereof. The conductive material 12 needs however be continuous longitudinally in the grooves 14 to be effective. FIG. 3a illustrates a Scanning Electron Microscope (SEM) image of a preferred embodiment wherein the conductive material 12 is applied to the monofilament 10 as a coating or film. Techniques include, for example, dip or bath coating, spraying, jetting or other means suitable for the purpose. For example a die coating application method, as shown in FIG. 4, may be used where a controlled metering of the conductive material 12 and binder occurs to create a film on the surface of the monofilament, particularly in the groove area, with the internal circumference of the coating die being approximately the same as the outer circumference of the monofilament. FIG. 4 particularly shows an example of a conductive coating setup used in this process, wherein uncoated monofilament from a supply creel 18 is passed through a coating die 16, and a layer of coating of the conductive material 12, supplied from the conductive coating chamber 22, is applied simultaneously onto the monofilament. Metering is controlled by the dimension of the coating die 16 and the coating on the monofilament 10 is now dried in a controlled heating blanket 24 using a hot air blower 26, positioned within the drying chamber. The monofilament 10 is subsequently wound onto an output package (not shown in the figure). Note that while essentially round grooved monofilaments are preferred, other shapes are envisioned such as flat (e.g. rectangular), polygonal or other non-round shapes. Of these, however, shaped monofilaments with one or more grooves for the coating to reside in are preferred.

(11) In the case of grooved monofilaments the conductive material with binder uniformly coats the grooves 14, which provides a continuous channel of conductive coating or film in the groove 14. One or more grooves may be utilized with three shown in FIG. 1 being merely illustrative.

(12) Note that with the dye application process, the die is sized to the dimensions of the monofilament. This leads to the benefit of lower coat weight and lower costs due to the lower amount of material required. The groove 14 has the added benefit of protecting the conductive material 12, since the conductive material resides below the wear surface of the filament where abrasion may occur. In other applications, the coating may be on the outer surface.

(13) The result is a monofilament with electrical conductivity equivalent to that of metallic yarns achieved by way of a durable bonded, flex resistant, thin, low cost and protected conductive coating. The monofilament can be used as is or can be plied or twisted to form a plied monofilament structure according to the desired end usage. FIG. 2 shows a fabric 20 with the monofilament 10 in the cross machine direction, according to one embodiment of the invention.

(14) Note that in incorporating these monofilaments in a fabric, they need not comprise all the yarns used but rather may only be a portion of the monofilaments making up the fabric. They may be used in the machine direction and/or the cross machine direction and in any weave pattern necessary for dissipating the static electricity for the application.

(15) The embodiment shown cross-sectionally in a SEM image in FIG. 3b provides for coating a grooved monofilament 10 with the conductive material 12. Advantageously, this increases the monofilament's conductivity, whilst maintaining the monofilament's physical and functional properties. The conductive material 12 bonds to the surface of the monofilament along the circumference as well as within at least the perimeter of the groove(s). This grooved yarn arrangement serves to protect the conductive material 12 even as the monofilament 10 wears whilst also shielding and protecting the conductive material 12. The protective positioning of the conductive material 12 reduces the loss of conductivity over time, should the coating have less abrasion resistance than the monofilament itself.

(16) Note the monofilament may be made of any material suitable for the purpose including polymers such as polyester or polyamide or others known to those skilled in the art. Also it should also be noted that the conductive material contemplated has conductivity approaching or equivalent to a metal yarn, can be flexed repeatedly while maintaining the desired conductivity (static dissipation) and has very good adhesion to polymers such as polyester, nylon, polyphenylene sulphide (PPS), polyetherether ketone (PEEK) etc.

(17) Thus by the present invention its objects and advantages are realized, and although preferred embodiments have been disclosed and described in detail herein, its scope and objects should not be limited thereby; rather its scope should be determined by that of the appended claims.