Classifications

• • 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
  • H01B3/42—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 polyesters; polyethers; polyacetals
• • 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
• • 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
  • H01B3/441—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 alkenes

Definitions

• This invention relates to insulation for electrical wire or cable (hereinafter "wire") in which a strong bond is achieved at an interface between a layer of polyolefin-based material and a layer of polyvinylidene fluoride-based material.
• the invention is especially useful in multi-layer insulation of electrical wires, making it possible to achieve high-performance bonding between layers of such materials while retaining an acceptable balance in the complex relationships of other wire performance requirements, which are specialised and different from the criteria for other kinds of article such as mouldings or packaging films.
• Dual wall wire insulation comprising a polyolefm inner layer (core) and polyvinylidene fluoride (PVDF) outer layer (primary jacket or PJ) has been commercially available for over 30 years, and is available from several different manufacturers. These products all have negligible adhesion between the inner (polyolefin) and outer (PVDF) layers, which are consequently easily separable. It has been necessary to accept certain disadvantages arising from this lack of bonding, which limits the robustness of the construction. For example, the outer insulation layer can crack and peel off the inner layer if subjected to mechanical stress, exposure to certain fluids, contact with sharp objects, or impact.
• Abrasion and flexural fatigue resistance of the insulation, as well as resistance to wrinkling on bending (which can cause difficulties in sealing the wire or inserting it into grommets or connectors) are also detrimentally affected by having two readily separable insulation layers. It has not been thought possible to bond layers of two such dissimilar classes of material as polyolefins and PVDFs on a wire at commercially acceptable cost and manufacturing efficiency. Moreover, available bonding techniques could unacceptably affect the wire performance characteristics.
• the conventional approach to the bonding of polyolefins and PVDF is to employ a tie layer material (e.g. US patent 5,589,028), but these tend to be expensive, and when used on wire may compromise other properties, e.g. heat ageing, and add complexity to the manufacturing process in forming the extra layer. They may also be of limited effectiveness in terms of the bond strength developed.
• the dissimilar insulation materials of a polyolefin-based core and a polyvinylidene fluoride-based PJ can be bonded together to a significant level of adhesion on an electrical wire or cable; that this bonding tends to reduce or eliminate the aforementioned robustness problems on a wire; and that this bonding can be achieved, contrary to expectation, without unacceptable effects on crack propagation resistance, cost, or on the general balance of wire performance characteristics.
• the invention accordingly provides an electrical wire having insulation comprising:
• an electrical wire having insulation comprising:
• the respective layers have been brought into contact with each other at a temperature above the melting or softening point of the polymeric material in at least one of the layers, thus tending to maximise the intimacy of their interfacial contact and so possibly encouraging the formation of adhesion-promoting interfacial cross-links in the subsequent cross-linking reaction.
• the polyolefin-based layer (i) in addition to the polymeric portion of the formulation, for which the requirements are stipulated above, may contain whatever else is required in the way of additives such as anti-oxidants, pigments, fillers, flame retardants, etc, as known per se, to give the required mechanical, thermal, electrical etc. properties to the polymer.
• the polyvinylidene fluoride-based layer (ii) also may contain other additives as known per se to give it required properties in addition to bonding.
• the bond strength described in this application can be measured in terms of peel strength between bonded strips of the two materials in question.
• a standard method which can be used for such a test is ASTM 1876-95. By this definition, a significant bond could be one for which the peel force exceeds 5N, and a strong bond one of peel force greater than 10N.
• a convenient method for gauging the bond strength between the said layers, (i) and (ii), when they have been fabricated onto a wire, is to place a sample wire, of total length 60mm, into acetone (e.g. Fisher Scientific UK, AR certified grade acetone), to a depth of acetone equivalent to 70% of the length of sample wire, at 23 (+/- 3)°C, for a period of 1 hour.
• acetone e.g. Fisher Scientific UK, AR certified grade acetone
• Wires with negligible bonding of the insulation layers experience an extension of the PVDF PJ, along the axis of the wire, that is independent of any extension of the polyolefin core, and/or wrinkling of the PJ such that it delaminates from the core in places.
• the above-mentioned extension of the PJ typically results in a PJ "tube" extending for 1mm or more beyond the cut end of the core in the sample wire, following the above test.
• Wires with significantly bonded insulation layers experience an extension of the core and PJ, together, without separation, beyond the cut edge of the conductor, along the axis of the wire and/or wrinkling of the core and PJ layers together, without delamination. Any such wrinkling of the core and PJ together can be distinguished from wrinkling of the PJ only by examining a cross-section of the wrinkles under a microscope.
• Methods of fabricating the wire may include any process which causes intimate contact between the above-mentioned layers. (i) and (ii). Examples include coating of one material onto a pre-formed layer of the other, dual or multi-walled extrusion to form insulation layers respectively containing one or other of the aforementioned two classes of material.
• the olefin-based material (i) is preferably the inner layer and the PVDF-based layer (ii) preferably the outer layer on the wire.
• the layers made from the two different materials could be coextruded, tandem extruded, multipass extruded, or coated by other means.
• Known wire insulation processes such as tube draw-down extrusion may be used, to form one or more of the layers, but pressure extrusion as known per se is preferred for optimum adhesion of the second and any subsequent insulation layers to be applied to a pre-formed underlying layer.
• the insulation on the wire is exposed to a cross-linking reaction, which may involve chemical reagents such as peroxides, but preferably is effected by radiation, especially from a source of ionising radiation capable of causing the formation of free radicals and thus, cross-links, in the polymers, some of which should preferably be formed in the region of the interface between the two materials.
• a cross-linking reaction which may involve chemical reagents such as peroxides, but preferably is effected by radiation, especially from a source of ionising radiation capable of causing the formation of free radicals and thus, cross-links, in the polymers, some of which should preferably be formed in the region of the interface between the two materials.
• Penetration of the radiation into the material at least as far as the interface is therefore desirable, although not necessarily essential if ion or radical mobility, for example, enables molecular reactions to continue at or near the interface after the radiation process.
• the radiation source could, for example, be a radio-isotope, or an X-ray source, or possibly a non-ionising radical-generating source, for example a UV source, but is preferably an electron beam, more preferably one providing a beam dose greater than 2 Mrads, preferably at least 5 Mrads, more preferably at least 10 Mrads, very preferably at least 15Mrads, into the material.
• Additives preferably include a cross-linking promoter ("pro-rad") in the polyolefin-based material and/or in the PVDF-based material.
• cross-linking promoter e.g., pro-rad
• Known cross-linking materials may be used, preferably methacrylate/acrylate based ones, and, very preferably, those of the type trimethylolpropanetrimethacrylate (TMPTM), in the polyolefin material and/or in the PVDF-based material.
• TMPTM trimethylolpropanetrimethacrylate
• Material 1 Material 2 Dose(Mrad) Peel (N) EMA copolymer with 9wt% MA content VDF/HFP copolymer of 10wt% HFP content + 7.5 wt % additives 20 4 EMA copolymer with 28wt% MA content Same as above 20 45
• Material 1 Dose(Mrad) Peel force (N) 100% HDPE VDF/HFP copolymer of 10wt% HFP content +7.5wt% additives 20 0 20% HDPE + 80% EEA copolymer of 15wt% EA content Same as above 20 70
• Material 1 Dose(Mrad) Peel (N) EVA copolymer with 25wt% VA content PVDF homopolymer 15 4 As above VDF/HFP copolymer of 10wt% HFP content 15 17.5
• Material 1 Material 2 Dose(Mrad) Peel (N) 20 % HDPE + 80% EEA copolymer of 15wt% EA content VDF/HFP copolymer of 10wt% HFP content +7.5wt% additives 20 70 19 % HDPE + 77 % EEA copolymer of 15wt% EA content + 4% TMPTM pro-rad Same as above 20 > 130
• a wire was made as above, in which the crosslinking promoter in the inner layer was 4% TMPTM, and the outer layer of insulation was comprised solely of the PVDF/HFP copolymer containing 10wt% HFP.
• This coated wire product was then passed through an electron beam, and received a radiation dose of 20 Mrads.
• This wire was subjected to the acetone immersion test, confirming that the insulation layers were significantly bonded together.
• a wire of the same construction as the second example was made by tandem pressure extrusion of the inner and outer insulation layers. This coated wire product was then passed through an electron beam, and received a radiation dose of 20 Mrads. This wire was subjected to the acetone immersion test, confirming that the insulation layers were significantly bonded together.
• wire A A wire of the above construction and manufacturing process
• wire B a market leading commercially available polyolefin/PVDF dual-walled wire
• Equipment conventional type wire scrape abrader, wire size 0.75mm 2 (conductor cross sectional area), blade type flat, width 3.5mm held perpendicular to wire, with 0.05mm radiused edges each side, applied load 1.8kg, stroke length 10cm, at 55 cycles/minute Wire Type No. of scrape cycles to abrade through PJ at 44°C A > 800 B 272 Wire Type No. of scrape cycles to abrade through PJ at 5°C A > 1350 B 212

Landscapes

• Spectroscopy & Molecular Physics (AREA)
• Physics & Mathematics (AREA)
• Organic Insulating Materials (AREA)
• Insulated Conductors (AREA)
• Laminated Bodies (AREA)
• Processes Specially Adapted For Manufacturing Cables (AREA)
• Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
• Inorganic Insulating Materials (AREA)
• Resistance Heating (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Die Bonding (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Communication Cables (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1998
  • 1998-09-17 GB GBGB9820214.6A patent/GB9820214D0/en not_active Ceased
• 1999
  • 1999-09-17 CZ CZ20010482A patent/CZ299046B6/cs not_active IP Right Cessation
  • 1999-09-17 TR TR2001/00761T patent/TR200100761T2/xx unknown
  • 1999-09-17 AU AU61019/99A patent/AU766430B2/en not_active Expired
  • 1999-09-17 RO ROA200100291A patent/RO121928B1/ro unknown
  • 1999-09-17 IL IL14133899A patent/IL141338A0/xx active IP Right Grant
  • 1999-09-17 PL PL346214A patent/PL192515B1/pl unknown
  • 1999-09-17 ES ES99947633T patent/ES2260937T3/es not_active Expired - Lifetime
  • 1999-09-17 KR KR1020017002898A patent/KR100638181B1/ko active IP Right Grant
  • 1999-09-17 HU HU0103585A patent/HU226699B1/hu unknown
  • 1999-09-17 EP EP99947633A patent/EP1116243B1/en not_active Expired - Lifetime
  • 1999-09-17 DE DE69930532T patent/DE69930532T2/de not_active Expired - Lifetime
  • 1999-09-17 JP JP2000571464A patent/JP2002525819A/ja active Pending
  • 1999-09-17 CN CNB998110302A patent/CN1331160C/zh not_active Expired - Lifetime
  • 1999-09-17 AT AT99947633T patent/ATE321345T1/de not_active IP Right Cessation
  • 1999-09-17 CA CA002340386A patent/CA2340386C/en not_active Expired - Fee Related
  • 1999-09-17 WO PCT/GB1999/003116 patent/WO2000017889A1/en active IP Right Grant
  • 1999-09-17 ID IDW20010554A patent/ID29877A/id unknown
  • 1999-09-17 RU RU2001107973/09A patent/RU2231147C2/ru not_active IP Right Cessation
  • 1999-09-17 BR BR9913843-3A patent/BR9913843A/pt not_active IP Right Cessation
• 2001
  • 2001-02-08 IL IL141338A patent/IL141338A/en not_active IP Right Cessation
  • 2001-02-12 ZA ZA200101181A patent/ZA200101181B/en unknown
  • 2001-03-15 NO NO20011307A patent/NO324458B1/no not_active IP Right Cessation

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