There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit, and perfluoro(propyl vinyl ether) unit, wherein the content of hexafluoropropylene unit is 7.6 to 10.3% by mass with respect to the whole of the monomer units; the content of perfluoro(propyl vinyl ether) unit is 1.3 to 2.4% by mass with respect to the whole of the monomer units; and the melt flow rate at 372° C. is 4.5 to 9.5 g/10 min.

There is provided a copolymer containing tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 2.8 to 3.9% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 2.8 to 4.0 g/10 min, and the number of functional groups of 20 or less per 10.sup.6 main-chain carbon atoms.

There is provided a copolymer containing tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 4.6 to 5.2% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 22.0 to 28.0 g/10 min, and the number of functional groups of 50 or less per 10.sup.6 main-chain carbon atoms.

An insulated electrically conductive element, including at least one inner electrically conductive element and at least one outer insulating element, and to a method for producing such an insulated electrically conductive element.

An object of the present invention is to provide an insulated wire which includes an insulating layer with a low relative permittivity and has excellent heat resistance and excellent abrasion resistance. The insulated wire of the present invention includes a conductor (A), and an insulating layer (B) formed on the periphery of the conductor (A), the insulating layer (B) is formed from a resin composition that contains a resin (I) with a relative permittivity of 3.0 to 4.0 and a fluororesin (II).

The present invention aims to provide and insulated wire having an insulation layer which is excellent in insulation properties and has a low dielectric constant. The insulated wire of the present invention includes a conductor (A) and an insulation layer (B) formed around the periphery of the conductor (A). The insulation layer (B) is formed from a resin composition containing an aromatic polyether ketone resin (I) and a fluororesin (II). The fluororesin (II) is a copolymer of tetrafluoroethylene and a perfluoroethylenic unsaturated compound represented by the following formula (1):
CF.sub.2═CF—Rf.sup.1  (1)
wherein Rf.sup.1 represents —CF.sub.3 or —ORf.sup.2, and Rf.sup.2 is a C1-C5 perfluoroalkyl group. The aromatic polyether ketone resin (I) and the fluororesin (II) satisfy a melt viscosity ratio (I)/(II) of 0.3 to 5.0.

Provided is a tetrafluoroethylene/hexafluoropropylene copolymer which is less likely to form a lump, or is less likely to form a large lump even if a lump is formed, during the formation of an electric wire. The tetrafluoroethylene/hexafluoropropylene copolymer has a melt flow rate measured at 372° C. of 35.0 to 45.0 g/10 minutes and a swell of −8.0% to 5.0%, the sum of the numbers of —CF.sub.2H groups and unstable end groups being 120 or less per 1×10.sup.6 carbon atoms.

A copolymer having tetrafluoroethylene units and second polymerized monomer units in a range from 0.2 to 1 percent by weight, based on the total weight of the copolymer. Rf is a linear or branched perfluoroalkyl group having from 1 to 8 carbon atoms and optionally interrupted by one or more —O— groups, n is independently from 1 to 6, and z is 0, 1, or 2. The copolymer has a melt flow index in a range from 0.02 grams per 10 minutes to 19.4 grams per 10 minutes. The copolymer can be extruded to make articles, such as insulated cables. A method of making the copolymer is also disclosed.

A communications cable is provided that includes a pair of twisted pair of wires, each coated with a fluoropolymer insulator. The twisted pair of wires is configured to carry a differential signal, such as a differential data signal and/or a differential power signal. The fluoropolymers are highly effective insulators and significantly reduce both the effects of internal and external electromagnetic interference while maintaining low cable attenuation, even when operating within a temperature range of −40° C. to 150° C.

The invention relates to the field of cables for an offshore environment (known as “downhole cables”). More particularly, the invention relates to an electrical cable having an insulating multilayer structure based on fluorinated polymers and polyolefins. This structure is made up of multiple layers that are intercohesive and obtained by coextrusion. The invention also relates to the use of said cable as a drilling material for extracting petroleum or natural gas.