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
  • H01B3/44—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
  • H01B7/00—Insulated conductors or cables characterised by their form
  • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
  • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
  • H01B7/2806—Protection against damage caused by corrosion

Definitions

• the present invention relates to a fluorine-containing polymer, and an electric wire and cable coated therewith and, more particularly, to a fluorine-containing polymer containing a very small amount of an alkali metal and an alkali earth metal, and an electric wire and cable coated with the polymer.
• TFE tetrafluoroethylene
• a polymer having unstable polymer main chains and polymer terminal groups When a polymer having unstable polymer main chains and polymer terminal groups is used as a coating material for electric wire or cable, they are decomposed by heat or a shear force applied during coating to form cells and voids in the coating material and, therefore, a core wire can not be completely coated and insulating performances are lowered.
• the kind of the unstable polymer terminal group varies depending on the polymerization method and the kind of a polymerization initiator and a chain transfer agent.
• a conventional persulfate salt for example, ammonium persulfate, potassium persulfate, etc.
• carboxylic acid terminal groups are formed. It is known that these carboxylic acid terminal groups are a source of a volatile component produced during melting of the polymer.
• U.S. Patent No. 3,085,083 has proposed a method of stabilizing the unstable terminal groups by bringing a fluorine-containing polymer into contact with water at a temperature within a range from 200°C to 400°C (wet heat treatment) , while Japanese Kokoku (Examined) Patent Publication No. 5 - 10204 (corresponding to U.S. Patent No.
• 4,626,587) has proposed a method of reducing the number of unstable main chains of a TFE/HFP copolymer by applying a high shear force to the copolymer in a twin-screw extruder and subjecting the resulting pellets to the fluorination reaction to improve the color tone of the pellets and to stabilize the unstable terminal groups.
• U.S. Patent No. 3,085,083 also describes that a base, a neutral salt or a basic salt, which contains an alkali metal or an alkali earth metal, is added to increase a reaction rate in a wet heat treatment.
• a base or salt of the alkali metal or alkali earth metal is often added.
• a fluorine-containing polymer prepared by using a compound containing an alkali metal or an alkali earth metal (for example, polymerization initiator) or a fluorine-containing polymer post-treated with a compound containing an alkali metal or an alkali earth metal contains a large amount of the alkali metal or alkali earth metal, electrical characteristics of an electric wire or cable coated with the fluorine-containing polymer are likely to be impaired and a core wire is likely to be corroded.
• an object of the present invention provides a fluorine-containing polymer, which does not impair electrical characteristics of a coated electric wire and does not corrode a core wire, although it contains an alkali metal or an alkali earth metal, and an electric wire or cable coated with the fluorine-containing polymer.
• the object described above can be achieved by a fluorine-containing polymer comprising 70 to 95% by weight of tetrafluoroethylene, 5 to 25% by weight of hexafluoropropylene and 0 to 20% by weight of perfluoroalkyl vinyl ether, wherein a melt flow rate (MFR) (g/10 min., ASTM D2116) at 372°C is within a range from 0.1 to 100, and the total content (ppm) of an alkali metal and an alkali earth metal does not exceed the value obtained by calculating from the melt flow rate (MFR) at 372°C according to the formula (1) : 5.2 ⁇ e 0.125(MFR) + 2 and exceeds the value obtained by calculating according to the formula (2) : 0.35 ⁇ e 0.125(MFR) and by an electric wire or cable coated with the fluorine-containing polymer.
• MFR melt flow rate
• the fluorine-containing polymer used in the present invention is, for example, a copolymer comprising at least two monomers selected from the group consisting of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether.
• the fluorine-containing polymer to be treated is a tetrafluoroethylene/hexafluoropropylene copolymer (FEP)
• the copolymer preferably comprises 72 to 96% by weight of tetrafluoroethylene and 4 to 28% by weight of hexafluoropropylene.
• the fluorine-containing polymer is a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA)
• the copolymer preferably comprises 92 to 99% by weight of tetrafluoroethylene and 1 to 8% by weight of perfluoropropyl vinyl ether.
• the fluorine-containing polymer is a copolymer of tetrafluoroethylene and a plurality of perfluoroalkyl vinyl ethers (MFA)
• the copolymer preferably comprises 84 to 99.45% by weight of tetrafluoroethylene, 0.5 to 13% by weight of perfluoromethylvinyl ether, and 0.05 to 3% by weight of perfluoroalkyl vinyl ether having alkyl other than methyl, such as perfluoropropyl vinyl ether.
• polymers may be prepared by copolymerizing the other monomer in such amount that essential properties of each polymer are not impaired.
• the other monomer include hexafluoropropylene, perfluoroalkyl vinyl ether, ethylene, vinylidene fluoride and chlorotrifluoroethylene.
• the fluorine-containing polymer is preferably prepared by the emulsion polymerization or suspension polymerization, particularly the emulsion polymerization.
• the polymerization conditions are the same as those in the case of the conventional emulsion polymerization or suspension polymerization, except that the amount of the compound containing the alkali metal or alkali earth metal (for example, a polymerization initiator, a chain transfer agent, a dispersant, etc.) is controlled so that the amount of the alkali metal or alkali earth metal does not exceed the total content thereof to be contained in the resulting polymer.
• the alkali metal or alkali earth metal for example, a polymerization initiator, a chain transfer agent, a dispersant, etc.
• the amount In the post-treatment of the resulting fluorine-containing polymer, for example, before or after the step of drying the fluorine-containing polymer or during the extrusion step, even when using the compound containing the alkali metal or alkali earth metal, the amount must be controlled so that the total amount of the alkali metal or alkali earth metal in the fluorine-containing polymer is within the above defined range.
• the total content (ppm) of the alkali metal or alkali earth metal in the fluorine-containing polymer does not exceed the value obtained by calculating from the melt flow rate (MFR) (g/10 min., ASTM D2116) at 372°C according to the formula (5): 1.3 ⁇ e 0.125(MFR) + 2 and exceeds the value obtained by calculating according to the formula (6): 0.7 ⁇ e 0.125(MFR)
• alkali metal or alkali earth metal examples include hydroxides such as potassium hydroxide or sodium hydroxide, carbonate salts such as potassium carbonate or calcium carbonate, sulfate salts such as potassium sulfate, or nitrate salts such as potassium nitrate.
• the fluorine-containing polymer of the present invention does not substantially have unstable terminal groups.
• -CF 2 H accounts for at least half of polymer chain terminals and substantially all polymer chain terminals comprise -CF 2 H, or -CF 2 H and -CH 3 .
• the fluorine-containing polymer is a tetrafluoroethylene/hexafluoropropylene copolymer (FEP), a tetrafluoroethylene/perfluorovinyl ether polymer (PFA), a copolymer of tetrafluoroethylene/hexafluoropropylene/perfluoroalkyl vinyl ether, or a copolymer of tetrafluoroethylene, perfluoromethyl vinyl ether and perfluoroalkyl vinyl ether having alkyl other than methyl, such as perfluoropropyl vinyl ether, it may have a melt viscosity of 0.1 to 100 kPa ⁇ s at 372°C.
• the coated electric wire or cable can be produced in the same method of producing an electric wire and cable by coating with a conventional fluororesin, except that the fluorine-containing polymer described above is used as the coating material.
• the kind of the electric wire or cable is not specifically limited.
• the core wire may be a single core, a strand wire, or a coaxial cable.
• the fluorine-containing polymer used in the present invention can also be used as an internal insulating material.
• a melt flow rate (g/10 min.) was measured at 372°C in accordance with ASTM D2116.
• a dielectric dissipation factor was measured by a standing wave method using a coaxial cable in accordance with ASTM D2520.
• emulsion polymerization method polymerization pressure: 4.2 MPa, polymerization temperature: 95°C, initiator: ammonium persulfate (APS), emulsifier: C 7 F 15 COONH 4
• the dispersion was dried again and extruded into pellets in a twin-screw extruder. During the extension, water and air were fed (extrusion amount: 50 kg/hour, water: 5.5 kg/hour, air: 50 NL/min.) in the extruder to stabilize polymer terminals by the wet heat treatment.
• the structure of the polymer terminals after the treatment was analyzed by a Fourier transform infrared spectroscopy. As a result, those other than -CF 2 H terminal groups were not detected.
• the dielectric dissipation factor was measured at 500 MHz. As a result, it was 6.10 ⁇ 10 -4 .
• the dielectric dissipation factor of a polymer which was treated in the same manner as in Example 1 except that the content of potassium was changed to 70 ppm, was measured. As a result, it was 8.94 ⁇ 10 -4 .
• the dielectric dissipation factor of a polymer which was treated in the same manner as in Example 2 except that the content of potassium was changed to 100 ppm, was measured. As a result, it was 9.95 ⁇ 10 -4 .
• coated electric wires each having a wire size (core material of copper) of 511 ⁇ m (20.1 mil) and a coating thickness of 196 ⁇ m (7.7 mil) were produced. These coated electric wires were produced by molding at a rate of 305 m/min (1000 ft/min) using a single-screw extruder having a diameter of 5.1 cm (2 inch).

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Organic Insulating Materials (AREA)
• Insulated Conductors (AREA)

Applications Claiming Priority (3)

Publications (2)

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Cited By (8)

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Citations (4)

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• 2000
  • 2000-09-06 WO PCT/JP2000/006048 patent/WO2001018076A1/ja active Application Filing
  • 2000-09-06 CN CN 00812587 patent/CN1221578C/zh not_active Expired - Lifetime
  • 2000-09-06 EP EP00956959A patent/EP1260526A4/de not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (1)

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