EP0540322A2 - Fils isolés en polymère expansé et câbles coaxiaux comportants ce fil - Google Patents

Fils isolés en polymère expansé et câbles coaxiaux comportants ce fil Download PDF

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Publication number
EP0540322A2
EP0540322A2 EP92309898A EP92309898A EP0540322A2 EP 0540322 A2 EP0540322 A2 EP 0540322A2 EP 92309898 A EP92309898 A EP 92309898A EP 92309898 A EP92309898 A EP 92309898A EP 0540322 A2 EP0540322 A2 EP 0540322A2
Authority
EP
European Patent Office
Prior art keywords
foamed
insulated wire
insulation layer
plastic insulated
foamed plastic
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Withdrawn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
EP92309898A
Other languages
German (de)
English (en)
Other versions
EP0540322A3 (en
Inventor
Masanori Hattori
Shoji Yamamoto
Yoshiaki Oishi
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.)
Furukawa Electric Co Ltd
Original Assignee
Furukawa Electric Co Ltd
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 Furukawa Electric Co Ltd filed Critical Furukawa Electric Co Ltd
Publication of EP0540322A2 publication Critical patent/EP0540322A2/fr
Publication of EP0540322A3 publication Critical patent/EP0540322A3/en
Withdrawn legal-status Critical Current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
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • H01B11/1834—Construction of the insulation between the conductors
    • H01B11/1839—Construction of the insulation between the conductors of cellular structure
    • 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
    • H01B7/02—Disposition of insulation
    • H01B7/0233—Cables with a predominant gas dielectric
    • 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
    • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
    • H01B7/182—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring comprising synthetic filaments

Definitions

  • the present invention relates to foamed plastic insulated wires for electronic signal transmission, used in electronic apparatuses, and coaxial cables using the same, and more specifically, to foamed plastic insulated wires subject to a shorter time delay, improved in mechanical properties, and adapted for use as high-speed electronic signal transmission lines of computers, and coaxial cables using the same.
  • electric wires used in electronic signal transmission lines of computer systems are manufactured by twisting a plurality of wires of a predetermined diameter together into a stranded conductor, and covering this conductor with a foamed polymer insulation layer in order to ensure electrical insulation and increase the velocity of propagation of the insulated conductor.
  • the conductor may be a solid wire used in place of the stranded conductor.
  • a drain wire formed of e.g. an annealed copper wire plated with tin or silver
  • a laminated tape made of an aluminum foil and a polyethylene terephthalate film, for example, is wound around the resulting structure, and is then shielded by means of an insulation material such as polyvinyl chloride.
  • the foamed polymer insulation layer is formed by wrapping an expanded, amorphous-locked polytetrafluoroethylene tape (hereinafter referred to as E(xpanded)PTFE tape) around the conductor, as is disclosed in Published Examined Japanese Utility Model Application No. 2-34735, for example.
  • E(xpanded)PTFE tape expanded, amorphous-locked polytetrafluoroethylene tape
  • a foaming agent is blended with a tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), tetrafluoroethylenehexafluoropropylene copolymer (FEP), ethylenetetrafluoroethylene copolymer (ETFE) or ethylenechlorotrifluoroethylene copolymer (ECTFE), which is capable of heat fusion, and the resulting material is extrusion-foamed on the peripheral surface of the conductor.
  • PFA tetrafluoroethylene-perfluoroalkyl vinyl ether
  • FEP tetrafluoroethylenehexafluoropropylene copolymer
  • ETFE ethylenetetrafluoroethylene copolymer
  • ECTFE ethylenechlorotrifluoroethylene copolymer
  • the latter method for forming the foamed polymer insulation layer has an advantage over the former method in being lower in cost. If the expansion ratio for the extrusion foaming is made higher in order to increase the propagation velocity, however, the mechanical strength of the resulting insulated layer is greatly lowered. As a result, the foamed polymer insulation layer may be crushed during the manufacture of the coaxial cable, so that the electrical properties of the cable are lowered. Even though the cable is manufactured with great care, moreover, rupture of the insulation layer and remarkable crushing may be caused when a jacket or shield layer is removed from the peripheral surface of the cable as the cable is attached to a connector.
  • the resin outer layer is made of thermoplastic polyimide, polyether sulfone, polyether ether ketone, polyarylate, polycarbonate, or other resin such that the propagation speed and characteristic impedance cannot be influenced thereby, and has a dielectric constant of 4 or less, density normalized tensile strength (DNTS) of 500 kgf/g/cm or more, and thickness of 0.010 to 0.030 mm.
  • DNTS density normalized tensile strength
  • the DNTS is a value obtained by dividing the tensile strength of a sample of 20-cm length by the weight per unit length. The larger the DNTS value of the material, the higher the strength of the outer layer can be, despite its thin structure.
  • the DNTS value of the composite layer, formed of the foamed polymer insulation layer and the resin outer layer is 300 kgf/g/cm or more, which is larger than the DNTS value of about 250 kgf/g/cm for the case of the layer using the EPTFE tape. Therefore, this composite layer is highly resistant to crushing or the like. As mentioned before, moreover, its formation entails lower cost. On the other hand, the resin outer layer mentioned above is lacking in flexibility, and the insulation layer buckles when the foamed plastic insulated wire is bent during its arrangement.
  • the foamed polymer insulation layer and the resin outer are cut by means of a laser beam during cable assembly, moreover, the outer layer inevitably yellows or is carbonized. If a heated cutter is used for the cable assembly, furthermore, the operation requires so much care that its efficiency becomes low.
  • a foamed plastic insulated wire comprising a conductor, a foamed polymer insulation layer formed around the conductor, and a skin layer (resin outer layer) formed around the insulation layer, wherein the skin layer is reinforced by glass fibers which are located inward of the skin layer along the length thereof, or which are embedded in the skin layer. Glass fibers, however, have no extensibility and thus are extremely lacking in flexibility. Accordingly, the above foamed plastic insulated wire including glass fibers at an outer portion thereof has little flexing capability, and the shield layer itself cannot be cut with a laser beam when the wire is subjected to cable assembly operation.
  • An object of the present invention is to provide foamed plastic insulated wires to be used for signal transmission, which enjoy improved mechanical characteristics, e.g., high resistance to crushing or the like, and in which a foamed polymer insulation layer cannot be ruptured or crushed during cable assembly operation, despite the value of the time delay substantially equal to that of the conventional wires, and coaxial cables using the same.
  • Another object of the present invention is to provide foamed plastic insulated wires which are free from yellowing and carbonization even during cable assembly operation using a laser, and coaxial cables using the same.
  • a foamed plastic insulated wire which comprises a conductor, a foamed polymer insulation layer formed on the periphery of the conductor, and at least one multifilament made of a plastic material having no aromatic ring in its molecular structure, the multifilament being longitudinally extended or spirally wound on the periphery of the foamed polymer insulation layer so as to be fixed thereto.
  • a coaxial cable in which a drain wire is extended longitudinally on the periphery of the foamed plastic insulated wire, a common conductor foil is wound around the drain wire and the foamed plastic insulated wire, and a shield layer is formed on the common conductor foil.
  • a foamed polymer insulation layer which covers the peripheral surface of a conductor, is composed of a foam, such as a polyolefin, e.g., a blend of high- and low-density polyethylene, a blend of high- and medium-density polyethylene, a blend of high-, medium-, and low-density polyethylene, a blend of an ethylene-propylene copolymer and high-density or high molecular polyethylene, or a blend of ethylene-methyl methacrylate and an ethylene-propylene copolymer; or a thermoplastic fluoropolymer resin, e.g., polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.
  • a foam such as a polyolefin, e.g., a blend of high- and low-
  • the respective expansion ratios of these foams should be 60% or more, preferably 70% or more.
  • the resin is foamed by extrusion in the method for forming the foamed plastic insulation layer on the periphery of the conductor.
  • a conventional method may be used for this foam extrusion without any restrictions.
  • Plastic multifilaments (mentioned later) are fixed on the periphery of the foamed polymer insulation layer.
  • Preferred plastic multifilaments are those made of a plastic material having no aromatic ring in the molecular structure thereof, e.g., polyethylene multifilaments, polytetrafluoroethylene (PTFE) multifilaments, nylon multifilaments, etc.
  • polyethylene multifilaments e.g., polyethylene multifilaments, polytetrafluoroethylene (PTFE) multifilaments, nylon multifilaments, etc.
  • PTFE polytetrafluoroethylene
  • Multifilaments made of a plastic material having an aromatic ring in its molecular structure e.g., diallyl phthalate, polyarylate, polyether imide, polyether ether ketone, etc. are not desirable because yellowing or carbonization occurs during laser cutting operation.
  • the tensile strength of these multifilaments should be 10 kg/mm2 or more. This is because multifilaments having a tensile strength lower than 10 kg/mm2 cannot produce a satisfactory effect to reinforce the foamed polymer insulation layer.
  • the multifilaments are each obtained by stranding four or more monofilaments of 5 to 20 deniers. If less than four monofilaments which are each thinner than 5 deniers are used for the multifilament, disconnection is liable to occur when the multifilament is laid on the periphery of the foamed polymer insulation layer, thus significantly lowering the working efficiency. If, on the other hand, monofilaments of more than 20 deniers are used, the overall outer diameter of the multifilament becomes 50 ⁇ m or more. Thus, the roundness of the multifilament is almost lost and the pliability lowers.
  • the multifilament thickness should range from 20 to 200 deniers.
  • Multifilaments thinner than 20 deniers have so low a tensile strength that they are liable to snap during wire arrangement, resulting in a substantial reduction in productivity.
  • the outer diameter of the resulting foamed plastic insulated wire is too large to ensure necessary electrical properties.
  • the thickness of the polyethylene multifilaments should range from 20 to 100 deniers, and that of the PTFE multifilaments from 40 to 200 deniers, for example.
  • the foamed plastic insulated wire according to the present invention is manufactured by longitudinally extending or spirally winding the plastic multifilaments around the foamed polymer insulation layer and then fixing the multifilaments to the periphery of the insulation layer.
  • the number of multifilaments used and the pitch of coiling are selected so that the mechanical strength of the composite layer, formed of the foamed polymer insulation layer and the multifilaments, ensures crushing strength and tensile strength high enough to prevent the insulation layer from being crushed or ruptured during the manufacture or assembly of coaxial cables.
  • the above number and pitch are selected so that the DNTS value of the composite layer is 250 kgf/g/cm or more. Normally, it is necessary only that one to six multifilaments be fixed to the periphery of the foamed polymer insulation layer.
  • the multifilaments arranged around the insulation layer are coated with, e.g., an ultraviolet-curing resin to a suitable thickness, and the resin is cured by ultraviolet irradiation.
  • a polyolefin-based adhesive is applied and heated to put the foamed polymer insulation layer and the multifilaments together.
  • a low-dielectric material such as polyethylene or polypropylene, is deposited to a thickness of 10 to 50 ⁇ m on the peripheral surface of the insulation layer by extrusion coating.
  • PFA containing fluorocarbon as a foaming agent and 1% by weight of boron nitride as a nucleating agent and having a melt flow rate of 20 g/10 min.
  • a foamed polymer insulation layer 2 was formed having an expansion ratio of 65% and thickness of 0.3 mm.
  • a drain wire 5 with a diameter of 0.2 mm was paralleled to the periphery of the resulting foamed plastic insulated wire, and at the same time, a laminated tape 6, made of an aluminum tape with a thickness of 9 ⁇ m and a polyethylene terephthalate tape with a thickness of 4 ⁇ m, respectively, was wound around the structure, as shown in Fig. 2. Thereafter, a sheath 7 of polyvinyl chloride with a thickness of 0.5 mm was put on the resulting structure to form a coaxial cable.
  • the time delay (ns/m) of this coaxial cable was measured by means of TDR (Time Domain Reflectometry), using an IE-0120 TDK System manufactured by Iwatsu Denshi K.K.
  • the conductor 1 was drawn out of the foamed plastic insulated wire shown in Fig. 1, and the DNTS value of the composite layer, formed of the foamed PFA layer 2, PTFE multifilaments 3, and polypropylene layer 4, was measured.
  • the foamed plastic insulated wire was wound around a mandrel having a outer diameter twenty times as large as the outer diameter of the wire, and the composite layer was checked for buckling to examine its buckling strength. Further, a laser beam was applied to the wire to cut the composite layer completely, and the wire was then checked for yellowing or carbonization to examine its laser working properties.
  • the polyvinyl chloride sheath and the shield tape were stripped off together from the coaxial cable, at a distance of 50 mm from its end, by means of a stripper produced by Carpenter MFG. Co., Inc., U.S.A., and the foamed PFA layer 2 was then checked for rupture to examine the cable assembly performance.
  • Table 1 collectively shows the results of these examinations.
  • a stranded conductor was formed by twisting seven wires with a diameter of 0.1 mm together, and polyolefin, which was composed mainly of ethylenemethyl methacrylate containing 2 to 10% by weight of polypropylene and which was loaded with a foaming agent, was extrusion-foamed on the periphery of the conductor, whereupon a foamed polymer insulation layer was formed having an expansion ratio of 70%, outer diameter of 0.90 to 0.93 mm, and thickness of 0.3 to 0.32 mm.
  • TEKMILON (R) NA210 from Mitsui Petrochemical Industries, Ltd.; tensile strength: 150 kg/mm2, thickness: 100 deniers) were uniformly arranged around the insulation layer in parallel relation, and were fixed by means of PPET 1303S (trademark; polyolefin-based adhesive from Toa Gosei-Kagaku Kogyo Co., Ltd.).
  • a coaxial cable was manufactured using the resulting foamed plastic insulated wire in the same manner as in Embodiment 1. This coaxial cable was checked for the time delay, DNTS value of the composite layer, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.
  • a foamed plastic insulated wire was manufactured in the same manner as in Embodiment 1, except that two PTFE multifilaments were arranged around the PFA layer. Using this wire, a coaxial cable was manufactured in the same manner as in Embodiment 1.
  • This coaxial cable was checked for the time delay, DNTS value of the composite layer, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.
  • a foamed plastic insulated wire and a coaxial cable were manufactured in the same manner as in Embodiment 2, except that the foamed polymer insulation layer was made of a blend of 50% by weight of high-density polyethylene and 50% by weight of low-density polyethylene (melt flow rate: 0.35 g/10 min.).
  • This coaxial cable was checked for the time delay, DNTS value of the composite layer, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.
  • a foamed plastic insulated wire and a coaxial cable were manufactured in the same manner as in Embodiment 2, except that the foamed polymer insulation layer was made of a blend of 15% by weight of high-density polyethylene and 85% by weight of an ethylene-propylene copolymer containing 7% by weight of ethylene (melt flow rate: 2.7 g/10 min.).
  • This coaxial cable was checked for the time delay, DNTS value of the composite layer, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.
  • a wire having only the foamed PFA layer of Embodiment 1 thereon was manufactured, and a coaxial cable was manufactured using this wire.
  • This coaxial cable was checked for the time delay, DNTS value, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.
  • a resin outer layer with a thickness of 40 to 50 ⁇ m was formed on the periphery of the foamed PFA layer of the wire of Comparative Example 1 by extrusion-coating the layer with PFA (PFA 340J from Mitsui Du-Pont Fluorochemicals Co., Ltd.).
  • the resulting wire was checked for the time delay, DNTS value, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.
  • a wire was manufactured in the same manner as in Comparative Example 2, except that the resin used for the resin outer layer was polyarylate (U-8000 from Unitika Ltd.).
  • the resulting wire was checked for the time delay, DNTS value, buckling strength, laser working properties, and cable assembly performance. Table 1 shows the results.

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  • Organic Insulating Materials (AREA)
  • Communication Cables (AREA)
EP19920309898 1991-10-30 1992-10-29 Foamed plastic insulated wires and coaxial cables using the same Withdrawn EP0540322A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP28445291 1991-10-30
JP284452/91 1991-10-30

Publications (2)

Publication Number Publication Date
EP0540322A2 true EP0540322A2 (fr) 1993-05-05
EP0540322A3 EP0540322A3 (en) 1993-09-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920309898 Withdrawn EP0540322A3 (en) 1991-10-30 1992-10-29 Foamed plastic insulated wires and coaxial cables using the same

Country Status (2)

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EP (1) EP0540322A3 (fr)
TW (1) TW219341B (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1442074A1 (fr) * 2001-11-05 2004-08-04 Radio Frequency Systems, Inc. Dielectrique alveolaire microcellulaire utilise dans des lignes de transmission

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2537873A1 (de) * 1975-08-26 1977-03-03 Felten & Guilleaume Carlswerk Koaxiales hochfrequenzkabel mit laengswassersperre
JPS54169781U (fr) * 1978-05-22 1979-11-30
US4399322A (en) * 1982-02-01 1983-08-16 The United States Of America As Represented By The Secretary Of The Navy Low loss buoyant coaxial cable
DE8633630U1 (de) * 1986-12-16 1987-05-14 Dietz, Volker, 8011 Baldham Flexibles Kabel mit niedrigem spezifischem Gewicht

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1442074A1 (fr) * 2001-11-05 2004-08-04 Radio Frequency Systems, Inc. Dielectrique alveolaire microcellulaire utilise dans des lignes de transmission
EP2208750A3 (fr) * 2001-11-05 2010-07-28 Radio Frequency Systems, Inc. Ligne de transmission comprenant un dielectrique alveolaire microcellulaire

Also Published As

Publication number Publication date
EP0540322A3 (en) 1993-09-15
TW219341B (fr) 1994-01-21

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