EP1211696A1 - Isolierter elektrischer Leiter - Google Patents

Isolierter elektrischer Leiter Download PDF

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Publication number
EP1211696A1
EP1211696A1 EP00870285A EP00870285A EP1211696A1 EP 1211696 A1 EP1211696 A1 EP 1211696A1 EP 00870285 A EP00870285 A EP 00870285A EP 00870285 A EP00870285 A EP 00870285A EP 1211696 A1 EP1211696 A1 EP 1211696A1
Authority
EP
European Patent Office
Prior art keywords
layer
tape
mica tape
film
polymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00870285A
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English (en)
French (fr)
Inventor
Noel Mortier
Alain Jacques
Eric D. Nyberg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Compagnie Royale Asturienne des Mines
TE Connectivity Corp
Original Assignee
Compagnie Royale Asturienne des Mines
Tyco Electronics Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Compagnie Royale Asturienne des Mines, Tyco Electronics Corp filed Critical Compagnie Royale Asturienne des Mines
Priority to EP00870285A priority Critical patent/EP1211696A1/de
Publication of EP1211696A1 publication Critical patent/EP1211696A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/29—Protection against damage caused by extremes of temperature or by flame
    • H01B7/295—Protection against damage caused by extremes of temperature or by flame using material resistant to flame
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/02—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances
    • H01B3/04—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances mica
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/443—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from vinylhalogenides or other halogenoethylenic compounds
    • H01B3/445—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from vinylhalogenides or other halogenoethylenic compounds from vinylfluorides or other fluoroethylenic compounds

Definitions

  • This invention relates to insulated electrical conductors and the method of producing them.
  • Polyimides e.g. polypyromellitimides, and ethylene-co-tetrafluoroethylene copolymers such as those sold by E.I. du Pont de Nemours and Company, under the trademarks KaptonTM and TefzelTM respectively, are known to have good thermal, mechanical, and flammability properties, as are certain polyetherimide polymers. These polymers, therefore, are used as insulation material for high performance wire and cable.
  • Existing thin-wall, high performance wire and cable constructions utilize several different types of jacket construction. These include single or multi-layer cross-linked poly(ethylene-co-tetrafluoroethylene) (e.g. Specification 55TM wire), polyimide (e.g.
  • Kapton Kapton
  • a composite wire construction consisting of a Kapton tape polyimide inner layer covered with a PTFE (polytetrafluoroethylene) tape outer wrap.
  • PTFE polytetrafluoroethylene
  • Specification 55 wire is rated for a maximum of 200°C but has relatively low cut-through resistance at elevated temperatures.
  • Most polyimides are not thermoplastic, and they therefore cannot readily be applied to a conductor by melt extrusion. Typically, they are formed into a tape, and the conductor is wrapped with that tape in an overlapping fashion. However, the polyimide tapes are not self-sealing.
  • Characteristics that are particularly desired in a high-performance (especially airframe) wire and cable are light weight and small diameter, good cut-through, arc-track and abrasion resistance and thermal stability, low flammability, insensitivity to water and common solvents, and a smooth outer surface contour. None of the currently available polymers including fluoropolymers either alone or in combination with other materials, for example polyimides, provides a wire insulation which meets all of these desired performance characteristics. It would be particularly desirable to produce an insulated conductor exhibiting this desired combination of performance characteristics and also comprising materials which are individually resistant to arc-tracking and hydrolysis. This would eliminate failure modes which may result from damage to an outer protective layer, thereby exposing a sub-layer to degradation (for example, tearing of a polytetrafluoroethylene outer layer protecting a polyimide layer beneath).
  • thermoplastic polymers having melt or glass transition temperatures significantly above the wire's service temperature rating (but below the polymer's softening temperature). These materials, however, are either very expensive (e.g. polyarylether ketones), susceptible to hydrolysis (e.g. certain condensation polymers), prone to arc-tracking (e.g. many aromatic polymers), and/or have insufficient resistance to thermal degradation (e.g. polyolefins and polyesters).
  • Fiber can be incorporated in wire constructions by a number of methods, for example spiral wrapping continuous fibers directly, wrapping tape comprising densely packed fibers imbedded in a suitable polymer, wrapping dense fabric as a tape, with or without a polymer impregnation, or by braiding fiber on the wire.
  • Wires comprising braided fibers underneath an extruded polymer outer layer for the purpose of improving cut-through at elevated temperatures suffer from two serious drawbacks, however. First, they are expensive to process because the fibers must be applied by braiding, an inherently slow process.
  • Mica tapes have long been used for the insulation of wire and cable in conjunction with one or more polymer layers. This is due to this mineral's excellent thermal and dielectric properties which provide good fire resistance and high insulation values. Mica itself is also very stable to a wide range of chemicals, including those which promote hydrolysis.
  • existing mica tapes suffer from one or more of the following disadvantages
  • mica sheet and tape articles and methods for their fabrication which are thinner to reduce weight and size, more flexible to conform to a variety of substrates (especially small diameter wire), provide improved thermal performance. It would also be valuable to provide mica sheets or tapes and methods for their fabrication comprising materials which are self-sealing or otherwise allow bonding of the mica tapes to each other and to a variety of other materials employed in wire insulation, for example to a tape-wrapped or extruded outer polymer layer, in order to meet a variety of important handling and performance requirements.
  • This invention is related to an insulated electrical conductor comprising an elongate electrical conductor; an electrical insulation surrounding the conductor, said insulation comprising: an inner, electrically insulating layer that surrounds and is in direct physical contact with the conductor, the inner layer comprising a wrapped, coated mica tape layer as hereinafter described; and an extruded or tape-wrapped polymeric, outer electrically insulating layer that surrounds and is in direct physical contact with the inner micaceous layer.
  • Multiple layer constructions of the aforementioned type are also contemplated by the present invention.
  • the present invention is related to an insulated electrical conductor comprising:
  • the invention is further more specifically related to an electrical conductor wherein said fluoropolymer layer is obtained by laminating a fluoropolymer film onto said mica tape.
  • the layer thickness of said coated mica tape is lying between 15 ⁇ m and 75 ⁇ m.
  • the conductor further comprises a layer of glass fibers between said coated mica tape and said fluoropolymer layer.
  • the polymer impregnant is a silicone polymer comprising linear segments represented by the formula -Si(R 1 ) (R 2 )-O-, wherein R 1 and R 2 may be methyl or phenyl groups.
  • said fluoropolymer may be selected from the group consisting of polytetrafluoroethylene, poly(hexafluoropropylene-co-tetrafluoroethylene), poly(perfluoropropylvinylether-co-tetrafluoroethylene), and poly(perfluoromethylvinylether-co-tetrafluoroethylene), and mixtures thereof.
  • said outer layer may have a thickness of between about 50 and 300 ⁇ m, preferably between about 75 and 200 ⁇ m.
  • Said outer layer may comprise a perfluoropolymer, preferably poly(ethylene-tetrafluoroethylene).
  • Said outer layer may comprise a tape-wrapped polymer film, preferably a tape-wrapped polymer film which comprises a perfluoropolymer.
  • the insulated electrical conductor of the invention there may be interposed between the conductor and the mica tape layer, a separately applied polymer layer.
  • the present invention is equally related to a method of fabricating a coated mica tape or sheet comprising the steps of :
  • said method comprises the steps of :
  • said method of fabricating a coated mica tape or sheet comprising the steps of :
  • said laminating may be done in an oven, at a temperature of about 300°C. Said laminating may be done by a number of rolls.
  • one of said rolls is preferably at a temperature of about 300°C.
  • the invention further comprises a novel coated mica sheet or tape article comprising a mica paper core containing 2 to 30% by weight of a first polymer impregnant, and a second polymer layer either directly deposited from a liquid dispersion of the second polymer, preferably an aqueous dispersion or being laminated in the form of a coated film of the second polymer, on at least one side of the impregnated mica paper.
  • the invention comprises a novel method of fabricating this mica sheet or tape article.
  • the term "impregnated mica tape or sheet” refers to the impregnated mica paper prior to application of the dispersion applied polymer layer. After application of the second polymer layer, the mica sheet or tape of the present invention will be referred to as "coated" mica sheet or tape.
  • Figure 1 is a cross-section of a first embodiment of the insulated electrical conductor of this invention
  • Figure 2 is a second embodiment of the insulated electrical conductor of this invention having a polymer layer interposed between the coated mica tape layer and the conductor;
  • Figure 3 is a third embodiment of the insulated electrical conductor of this invention comprising a polymer layer interposed between two layers of coated mica tape;
  • Figure 4 is a first embodiment of the coated mica sheet or tape of the invention having a polymer layer coating applied to one side only of the impregnated mica paper;
  • Figure 5 is a second embodiment of the coated mica sheet or tape of the invention comprising a polymer coating on both the top and bottom surfaces of the impregnated mica paper;
  • Figure 6 is a third embodiment of the coated mica sheet or tape of the invention comprising two polymer layers (which may be the same or different) applied to both the top and bottom surfaces of the impregnated mica paper;
  • Figure 7 is a fourth embodiment of the coated mica sheet or tape of the present invention comprising three polymer layers (the same or different polymer) applied to each surface of the impregnated mica paper; and
  • Figure 8 is another embodiment of the coated mica sheet or tape of the invention comprising a yarn layer interposed between two polymer layers.
  • Figure 9 is describing an embodiment of the method of production of an insulated electric conductor according to the present invention.
  • Figure 10 is describing another embodiment of the method of production of an insulated electric conductor according to the present invention.
  • FIG. 1 is a front-view cross-section through the insulated electrical conductor of a first embodiment of this invention.
  • the insulated wire comprises an elongated electrical conductor 10, shown as strands of metal wire 12 each with a metal plating 14.
  • Electrical conductor 10 may alternatively be a solid wire rather than the stranded wire shown, but stranded wire is generally preferred in applications where vibration is a factor, such as in aerospace applications. Both solid and stranded wire of various metals may suitably be insulated using the coated mica tape of the present invention.
  • the electrical conductor 10 is typically of copper, but may be of copper alloy, aluminum, or other conductive metals. If the metal wire is of copper or a copper alloy, it is typically plated with a metal plating 14 to protect the copper from oxidation effects, and to improve the solderability of the conductor, although unplated copper or copper alloy wire is also suitable for use as the electrical conductor of this invention.
  • Typical metal platings 14 are of tin, silver, nickel, or other commonly employed plating metals. Such platings are typically produced by electroplating a uniform thickness of high purity metal to the individual wires comprising the strand.
  • Stranded copper wire is available in several configurations.
  • the wire may have a unilay construction, where a central core is surrounded by one or more layers of helically wound strands in the same lay direction and same lay length; may be constructed with concentric stranding where a central core is surrounded by one or more layers of helically wound strands in alternating lay directions and increasing lay length; or may be constructed with unidirectional concentric stranding where a central core is surrounded by one or more layers of helically wound strands in the same lay direction and increasing lay length.
  • Such stranded copper wires are readily available from numerous commercial sources. For example, Hudson International Conductors, Ossining, New York, supplies a unilay stranded copper wire consisting of nineteen strands of 200 ⁇ m diameter (32 AWG) copper, each individually coated with an electroplated layer of tin.
  • a 19/32 AWG stranded wire has a nominal outside diameter of approximately 950 ⁇ m, and has an equivalent conductor diameter of 813 ⁇ m (20 AWG), i.e. it is regarded as the effective equivalent of an 813 ⁇ m diameter (20 AWG) solid copper wire.
  • the electrical conductor 10 is surrounded by a two-layer electrical insulation 20.
  • the inner electrically insulating layer 22 of this first embodiment immediately surrounds the electrical conductor and comprises a wrapped coated mica tape in accordance with the present invention which will be described in greater detail later in this application.
  • the coated mica tape layer 22 is itself surrounded by an extruded or tape-wrapped polymeric outer electrical insulating layer 24 which will also be hereinafter described in greater detail.
  • the coated mica tape forming the inner electrically insulating layer 22 is wrapped over the electrical conductor 10 by a process known to those of ordinary skill in the art.
  • Standard tape-wrapping machines are commercially available, for example from companies such as United States Machinery Corporation, North Billerica, Massachusetts, or E.J.R. Engineering and Machine Company Incorporated, Lowell, Massachusetts; and the techniques of using these or like machines to wrap an electrical conductor with an insulating tape are well known.
  • the inner layer 22 may consist of one or a plurality of layers of coated mica tape.
  • the tape is wrapped with approximately 0% overlay, i.e. "butt-wrapped".
  • butt-wrapping In butt-wrapping, however, small gaps between adjacent wraps of tape are inevitable in a production manufacturing environment. It is thus preferred to provide at least two coated mica tape layers which can be obtained using an overlap of approximately 50%, or alternatively, by applying two tapes, each of which is butt-wrapped.
  • the second butt-wrapped tape layer should be wrapped such that it largely covers the small gaps which may occur between the adjacent wraps of the innermost first tape layer.
  • the two-layer butt-wrapped construction will provide a smoother finished wire surface contour, particularly in conjunction with an extruded outer layer, but the extent of overlap is not a critical feature of this invention. If desired, further layers of coated mica tape can also be applied to provide improved mechanical strength to the wire, e.g. greater cut-through resistance.
  • the thickness of the inner layer is preferably lying between 15 ⁇ m and 75 ⁇ m.
  • At least one surface of the coated mica tape preferably comprises a thermoplastic polymer coating as thin as 1 ⁇ m; more preferably both surfaces of the tape are coated with a thermoplastic polymer coating with the mica paper layer being sandwiched therebetween.
  • this tape polymer coating layer reaches its melt temperature it will function as an adhesive and the coated tape will bond or self-seal to an adjacent layer, for example another mica tape layer or to the outer extruded or tape-wrapped layer 24.
  • the tapes should have a relatively smooth surface and be in intimate contact. This is readily achieved by employing sufficient tension during the tape-wrapping step.
  • any suitable furnace which will provide the necessary temperature to the bond area will do (e.g. an induction, infrared or forced air oven). It is desirable that the coating polymer on the mica paper be compatible with the outer insulating layer 24, as hereinafter described, and also with the coating layer of a differently coated mica tape if a second such tape having a different polymer as a coating is also applied over the first tape layer.
  • the outer electrically insulating layer 24 may comprise any polymer which may be suitably applied by extrusion and/or tape-wrapping. Suitable materials for the outer electrically insulating layer 24 include for example polyethylenes, polyethylene copolymers, and fluoropolymers (e.g.
  • PVDF poly(vinylidenefluoride)
  • ETFE poly(ethylene-co-tetrafluoro-ethylene)
  • CTFE chlorotrifluoroethylene
  • FEP poly(hexafluoro-propylene-co-tetrafluoroethylene)
  • PFA poly(perfluoropropylvinylether-co-tetrafluoroethylene)
  • MFA poly(perfluoromethylvinylether-co-tetrafluoroethylene)
  • PTFE polytetrafluoroethylene
  • PET poly(ethylene-co-terepthalate)
  • PBT poly(butylene-co-terepthalate)
  • PEN poly(ethylene-co-napthalate)
  • polyimides is not preferred for aerospace wire and cable, but is appropriate for some applications.
  • the most preferred polymers for use in outer layer 24 are PFA, MFA, or ETFE, especially radiation cross-linked ETFE.
  • outer layer 24 has been described by reference to their primary polymeric constituents, and it should be appreciated that they may also contain other constituents such as are conventional in the polymer formulation art; for example, antioxidants, UV stabilizers, pigments or other coloring or opacifying agents (such as titanium dioxide), prorads (radiation enhancing agents) to promote radiation crosslinking, flame retardants, additives to promote marking, and the like.
  • Outer layer 24 may also comprise more than one layer, for example a thin outermost polymer layer which contains additives to promote marking or provide a particular color, while the bulk of the underlying outer layer 24 will not contain some or all of these additives.
  • coated mica tape and outer layers, layers 22 and 24, respectively, which together comprise the wire insulation may be applied in one or in separate operations depending upon the relative line speeds suitable for each. If the outer layer 24 is tape-wrapped, then a one-step operation to apply both layers 22 and 24 is feasible. If the outer layer is applied by extrusion, which typically runs at 10 to 100-fold the line speeds of tape-wrapping, then separate processing steps for applying layers 22 and 24 is generally preferred.
  • FIG. 2 A second embodiment of the invention is shown in FIG. 2 in which an inner polymer layer 16 is located between the conductor 10 and the coated mica tape layer 22.
  • This inner layer 16 may be applied by conventional methods such as powder coating, tape-wrapping or extrusion. Inner layer 16 may provide a greater degree of control over wire handling and installation properties such as insulation strip force and/or shrink-back.
  • Suitable polymers include polyethylenes, polyethylene copolymers, and fluoropolymers (e.g. PVDF, ETFE, CTFE, FEP, PFA, MFA, and PTFE).
  • FIG. 3 A third embodiment of the invention is presented in FIG. 3 in which a polymer layer 18 is located between two coated mica tape layers 22A and 22B.
  • Polymer layer 18 generally provides an improved adhesive bond between layers 22A and 22B, thereby improving desired performance properties such as wrinkling and abrasion resistance.
  • the mica tape layer shown in the various embodiments may include a layer or layers which do not comprise coated mica paper.
  • layer 22 is intended to denote the layer which comprises at least one coated mica paper layer, and it is located nearer to the conductor than outer layer 24. According to the invention, the thickness of said outer layer is lying between 50 ⁇ m and 300 ⁇ m.
  • the coated mica tape per se, and also its method of fabrication, used in layer 22 as shown in the illustrative embodiments of the present invention, are both novel.
  • This coated mica paper sheet is fabricated as follows: mica paper is first impregnated with an oligomer (polymer precursor) or first polymer solution such as a silicon resin in solvant, the solvent is evaporated and the oligomer impregnant is cured to provide sufficient structural integrity to permit further processing. The impregnated paper is then coated with a second polymer layer or with a mixture of polymers as hereinafter described.
  • Commercial mica paper having a thickness of up to 75 ⁇ m, preferably less than 50 ⁇ m, most preferably less than 35 ⁇ m or even preferably less than 20 ⁇ m, is suitable.
  • Suitable paper for example, is sold under the trade name CogemicaTM by Cogebi, of Belgium.
  • the paper may be formed from any of the known naturally occurring or synthetic micas as heretofore described, employing equipment and techniques known to
  • the mica paper is impregnated with a monomer, oligomer or polymer normally in a non-aqueous solvent to provide a paper which is dimensionally stable, can be handled in subsequent processing steps without tearing, and has the required performance characteristics, especially moisture resistance.
  • the polymers currently used for mica paper impregnation are suitable, as are other polymers, provided they can be applied to the paper as a solution which itself does not damage the mica paper.
  • Suitable solvents include relatively non-polar liquids such as higher alcohols, ketones, and aliphatic and aromatic hydrocarbons, and mixtures thereof, for example.
  • Impregnation polymers may be thermosets (or precursors thereof) or thermoplastics.
  • thermoset impregnant a solution of the monomer or oligomer precursor of the thermoset polymer, for example polymer precursor solutions of polyimides, epoxies, or silicones.
  • polymer precursor solutions are well-known for mica paper impregnation, for example the polyimide precursor solutions sold under the tradename KerimidTM (Ciba Geigy), epoxy precursor solutions sold as Epon 828TM (Shell), and silicone precursor solutions sold as Wacker KTM (Wacker GmbH).
  • polymer impregnants such as silicone or hydrocarbon elastomers which form solutions in suitable solvents.
  • polyimides and silicone precursor thermosets are the preferred impregnants.
  • the methyl and phenyl substituted silicone polymers -Si(R 1 ) (R 2 )-O-, where R 1 and R 2 are methyl or phenyl groups, provide excellent thermal stability and arc track resistance.
  • the impregnant polymer solution may be applied by any of a variety of methods, for example by dip, kiss, contact, or spray coating or vacuum impregnation .
  • the solvent is evaporated, normally at a temperature greater than its boiling point, and for thermosetting impregnants, a higher temperature heat treatment may be necessary to complete the crosslinking reaction and obtain optimal mechanical strength.
  • dimethylsilicone polymer impregnant as an example, from 2 to 30% by weight of impregnant may be applied to the mica paper (as percent initial mica paper weight) to provide the required dimensional stability and strength to the impregnated paper to prepare it for the subsequent step of coating.
  • the mica paper is impregnated with from 3 to 15% by weight of dimethylsilicone polymer containing functional groups suitable for catalytic and/or heat initiated cross-linking.
  • Relatively low levels of impregnation polymer are surprisingly effective at providing the mica paper with the solvent resistance necessary for the subsequent step of coating.
  • the use of lower levels of polymer impregnation provides several advantages. First, the resultant impregnated mica tape is less prone to stiffening due to oxidation of the impregnant when exposed to high use temperatures; hence it is less prone to fraying or cracking, which may expose the conductor.
  • the reduced level of impregnant affords a mica tape that, although solvent stable, is still sufficiently porous to provide a remarkably strong bond to the subsequently applied coating and/or adhesive which are applied.
  • the polymer particles of the coating or of the adhesive are able to interpenetrate the surface of the mica paper to form a strongly adherent bond.
  • the optimum range of impregnation loading using polymers other than dimethylsilicone may be different but will normally be within the above-indicated 2 to 30% by weight loading range.
  • One or more polymer layers may be applied sequentially to the impregnated mica paper.
  • FIG. 4 is shown a first embodiment of the coated mica sheet or tape 28 of the present invention consisting of two layers: an impregnated mica paper 30 and a single polymer layer 40 obtained by the application of a first polymer film.
  • Polymer layer 40 may be obtained in a single laminating step, or from multiple steps using several films.
  • FIG. 5 is presented a second embodiment of coated mica sheet or tape 28 consisting of three layers: impregnated mica paper 30, polymer film 40 on one side of the mica paper, and a second polymer film 50 on the other side of the paper.
  • Polymer films 40 and 50 may be of the same polymer or different, and may be applied in one coating step or in multiple steps.
  • a third embodiment of this coated mica sheet or tape is the five-layer construction illustrated in FIG. 6.
  • an additional thin polymer film 44 and 54 is applied to polymer layers 40 and 50, respectively.
  • Polymer layers 44 and 54 are distinguished from layers 40 and 50, respectively, by chemical composition and/or molecular weight.
  • Layers 44 and 54 may be alternatively an adhesive layer which promotes adhesion between two sheets or tapes, or to another material to which the sheet or tape is to be bonded.
  • FIG. 7 A fourth embodiment of the present sheet or tape invention is presented in FIG. 7. This is a seven-layer construction having thin polymer layers 46 and 56 cast directly onto the two faces of the impregnated mica paper. On polymer layer 46 is cast a further thin polymer layer 40, and on polymer layer 56 is cast a layer 50 of greater thickness than polymer layer 40. Finally, additional thin layers 44 and 54 are cast on top of layers 40 and 50. Layers 46 and 56 may, for example, promote adhesion between mica layer 30 and layers 40 and 50. A variety of other embodiments are possible, all of which are included within the scope of the present invention, for example a seven-layer construction with layers 40 and 50 being of equal thickness.
  • Fillers, additives and reinforcements may be included in one or more of the polymer layers.
  • Fillers include infusible polymer particles and/or inorganic particles such as clays, glass spheres, glass fibers, and fumed silica, among others.
  • Additives which may be present in the polymer layers include antioxidants, UV stabilizers, pigments or other coloring or opacifying agents (such as titanium dioxide), prorads (additives to promote radiation crosslinking), and flame retardants.
  • One may also include in one or more of the polymer layers continuous fibers, for example glass fibers or yarns, oriented polymer fibers, or glass fabrics.
  • FIG. 8 shows another embodiment of the invention in which a yarn layer 50' is positioned between two fluoropolymer layers of nonsymmetric thickness 54, 56.
  • the present invention is equally related to the method of producing an insulated electrical conductor, wherein a coated mica tape inner layer is surrounding said conductor, said coated mica tape containing from about 2 to about 30 weight percent of a first polymer impregnant, and being coated on at least one side by laminating a fluoropolymer film onto said tape.
  • the mica tape is sprayed with a fluoropolymer, possibly the same fluoropolymer used for the reinforcing fluoropolymer film.
  • the sprayed layer is then dryed until the solvent has disappeared and the fluoropolymer is in powder form on the tape. After that, it is brought into contact with the film in an oven at +-300°C to allow the bonding of the fluoropolymer to the mica tape.
  • both the mica tape and the fluoropolymer film are sprayed in this way, prior to the bonding.
  • an adhesive polymer layer e.g. a silicon adhesive layer having preferably a similar composition than the impregnant of the mica tape is applied to the mica tape or to the fluoropolymer film ,or to both, prior to the bonding of the two.
  • an adhesive layer is always present in the resulting tape.
  • the bonding of the mica tape and the reinforcing fluoropolymer layer takes place in a furnace at about 300°C. It can also be done by rolling the tape 101 and the film 102 together between a number of rolls, as is shown in figure 9. All of these rolls can be put in a furnace or one of these rolls (100) can be heated to +-300°C, in order to acquire the optimal bonding between the mica tape and the reinforcing film.
  • a curing of said adhesive is necessary before or after the joining of the two parts. Said curing may take place at a temperature of +/- 120 °C.
  • an adhesive e.g. silicone based
  • a fluoropolymer sprayed onto the film, or vice versa after which the film is laminated onto the mica tape, by one of the previous methods, e.g. by use of rolls.
  • mica paper (CogemicaTM, Cogebi), 15 ⁇ m thick, 30 cm width and 100 m length, and having an initial tensile strength of 2.3 N/cm, was impregnated with either a dimethyl or phenylmethyl silicone oligomer solution in toluene (both 50 wt% solutions as purchased; Wacker K).
  • the silicone oligomer solutions were applied by kiss-coating to one side of the mica paper after dilution with toluene to the desired concentration as indicated in Table 1.
  • the toluene was evaporated at 150°C/30 seconds, which also induces polymerization.
  • the weight percent silicone polymer present in the impregnated mica paper was determined by extraction with refluxing KOH solution.
  • Table 1 are summarized the tensile strengths and water absorption characteristics for several samples prepared using two different concentrations of both dimethyl and phenylmethyl silicone oligomer solutions. It is evident that small amounts of silicone resin impregnation, as little as 4% by weight for Sample 3, impart very good water resistance. In contrast, the untreated mica paper disintegrates virtually immediately upon contact with water. A further important and surprising result is the remarkable increase in tensile strength for impregnated mica paper at all loadings using silicone oligomer materials. For example, only 4% dimethyl silicone (Sample 3) provides an 8-fold increase in this property. Increased tensile strength provides a mica tape which can, for example, be wrapped at greater tensions.
  • Sample Silicone Type Silicone solution concentration Measured silicone in impregnated paper Tensile Strength (N/cm) Water Absorption 1 n.a. no treatment n.a. 2.3 Disintegr ation 2 dimethyl 25% 15% 24.0 0.4% 3 dimethyl 10% 4% 19.0 1.2% 4 methylph enyl 15% 20% 18.7 --- 5 methylph enyl 6% 8% 13.8 ---
  • a mica tape according to the invention is impregnated by spraying fluoropolymer on the mica paper in two steps. In a first step, said spraying is done on one side of the mica, using FEP as spray product. In a second step, the other side of the mica paper is sprayed with the same product, FEP.
  • a PTFE film is laminated onto this mica tape to form the reinforcing layer (e.g. a DF1700 film, Chemfab corporation).
  • said film Prior to laminating, said film is sprayed with a fluoropolymer, namely FEP on one side of the film. Then the film passes through a drying oven at 100°C. After that, the FEP is in powder form on the film, in a density of 4gr/m2.
  • a fluoropolymer namely FEP
  • the assembling of the mica tape 101 to the chemfab film 102 is done in an oven at 300°C. Three metal rolls are placed in this oven (figure 10). The product is going under and above these rolls to provide a good contact between the mica and the film. A pressure is exerted on the tape and film by the two top rolls 103 and 100. The speed of the rolls is 1m/minute. An other assembling method is by calendering at 310 °C .
  • the mica papers were impregnated as for Sample 3 in Example 1, then coated on each surface with 2 ⁇ m of a 1:1 mixture of PTFE 30B/FEP 120A.
  • Glass yarn (Owens-Corning; D1800 1/0 1.OZ 620-1 7636) was applied to one surface of mica sheets during the application of a 10 ⁇ m layer of PTFE 30B layer.
  • the glass yarns were continuously fed onto the PTFE aqueous dispersion layer (wet) then immediately dried and sintered as above.
  • the tensile strengths of these four tapes are presented in Table 2.
  • OasisTM tape a Dupont Corporation product, is used to construct commercial composite airframe wire. This tape comprises a 16 ⁇ m polyimide layer coated with PTFE and FEP on both surfaces. The inclusion of 1 yarn/mm width triples the tensile strength; and 2 yarns/mm provides a greater strength than provided by commercial Oasis tape.
  • a mica tape was constructed by lamination of a thin polymer film to a silicone impregnated mica paper. This allowed the determination that such a construction, once slit into tape, can be tape-wrapped onto conductor in long lengths at resonable speeds.
  • One side of the impregnated mica paper prepared as for Sample 2 of Example 1 (20 ⁇ m thick after impregnation) was kiss coated with a 5 ⁇ m thick layer of phenylmethyl silicone resin (25% solution in toluene) which was then dried at 150°C/30 sec to provide a tacky surface.
  • a 19 ⁇ m thick PTFE film (DF1700 film; Chemfab Corporation) using a two-roll calender, followed by an oven heat cure (300°C/ 2 min).
  • the PTFE surface of this DF1700 film in contact with the silicone layer on the impregnated mica paper was coated with 1 ⁇ m FEP which promotes adhesion. This was slit using circular knives to a width of 4 mm, providing a coated mica tape having a thickness of only 49 ⁇ m, well within the target for use in thin-wall insulated conductors.
  • Wire samples (0.35 mm 2 (20 AWG), nickel plated 19-strand copper conductor) were prepared for measurement of robustness during tape-wrapping. This tape was wrapped at 10 ft/min in three continuous lengths of 300 ft without a break. Tensions were sufficient to provide a wrinkle-free wrapped surface.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Insulating Bodies (AREA)
EP00870285A 2000-12-01 2000-12-01 Isolierter elektrischer Leiter Withdrawn EP1211696A1 (de)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006005426A1 (en) * 2004-07-09 2006-01-19 Tyco Electronics Uk Ltd. Fire resistant wire and cable constructions
EP2040267A1 (de) * 2007-09-21 2009-03-25 Nexans Stromkabel, das gegen die Fortpflanzung von Lichtbögen resistent ist

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2629540A1 (de) * 1975-07-07 1977-01-27 Allied Chem Elektrisches kabel fuer kernkraftwerke
US4514466A (en) * 1982-06-04 1985-04-30 General Electric Company Fire-resistant plenum cable and method for making same
WO1986003329A1 (fr) * 1984-11-29 1986-06-05 Habia Cable Sa Revetement isolant souple resistant au feu pour conduites, fils cables electriques et fibres optiques
US5422614A (en) * 1993-02-26 1995-06-06 Andrew Corporation Radiating coaxial cable for plenum applications
WO2000074075A1 (en) * 1999-06-02 2000-12-07 Tyco Electronics Corporation Insulated electrical conductor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2629540A1 (de) * 1975-07-07 1977-01-27 Allied Chem Elektrisches kabel fuer kernkraftwerke
US4514466A (en) * 1982-06-04 1985-04-30 General Electric Company Fire-resistant plenum cable and method for making same
WO1986003329A1 (fr) * 1984-11-29 1986-06-05 Habia Cable Sa Revetement isolant souple resistant au feu pour conduites, fils cables electriques et fibres optiques
US5422614A (en) * 1993-02-26 1995-06-06 Andrew Corporation Radiating coaxial cable for plenum applications
WO2000074075A1 (en) * 1999-06-02 2000-12-07 Tyco Electronics Corporation Insulated electrical conductor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006005426A1 (en) * 2004-07-09 2006-01-19 Tyco Electronics Uk Ltd. Fire resistant wire and cable constructions
EP2040267A1 (de) * 2007-09-21 2009-03-25 Nexans Stromkabel, das gegen die Fortpflanzung von Lichtbögen resistent ist
FR2921511A1 (fr) * 2007-09-21 2009-03-27 Nexans Sa Cable electrique resistant a la propagation d'arc electrique
US7750246B2 (en) 2007-09-21 2010-07-06 Nexans Electric cable that withstands electric arc propagation
CN101393780B (zh) * 2007-09-21 2012-11-07 尼克桑斯公司 电缆
RU2467421C2 (ru) * 2007-09-21 2012-11-20 Нексанс Электрический кабель, устойчивый к распространению электрической дуги

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