GB1368647A - Insulation of conductors - Google Patents

Abstract

1368647 Insulating coatings on electrical conductors WESTERN ELECTRIC CO Inc 23 Nov 1971 [24 Nov 1970] 54300/71 Heading B2E [Also in Division H1] An electrical conductor, e.g. copper wire, has an insulating layer comprising wood pulp mixed with polyethylene or polypropylene fibres, the fibres being present in an amount of 10% to 90% by weight, said fibres being from 1.5 to 6 denier and from 1/16 to 3/4 inch long. A slurry of wood pulp and polyolefin fibres which were previously washed in stilled water is container in a hopper of a Fourdrinier machine which converts the slurry, which may contain a surfactant, into a ribbon and winds the ribbon onto the conductor in the form of a copper wire bundle. The winding is then polished. The polyolefin may be polyethylene in which case a binder may be included which may be a branched polyethylene powder added to the slurry and the ribbon sheets are bonded under heat and pressure to melt the binder but not the fibres. Alternatively the polyolefin is polypropylene in which case the fibres are coated with a dispersing agent which is also present in solution in the slurry. The binder is then sprayed or rolled onto the insulated wire and may comprise a cross-linked latex copolmer, an acrylic latex or a styrene-butadiene coplymer emulsion, or an emulsion or powder of branched polyethylene such as "Microthene" (R.T.M.) or amorphous polypropylene. The binder may alternatively be added to the slurry before formation of the insulating layer on the wire. The binder improves the electrical dielectric constant and dissipation factor for telephone wires and several graphs (not shown) illustrate the variation of these properties with the varying composition of the insulating material.