GB1166651A - Improvements in or relating to the Manufacture of Plastics Insulated Wire - Google Patents

Abstract

1,166,651. Coated wire; coating apparatus. BRITISH INSULATED CALLENDER'S CABLES Ltd. 18 April, 1967 [19 April, 1966], No. 17100/66. Headings B2K and B2L. Wire e.g. copper wire, is provided with a covering of plastics insulation in cellular form by coating the wire with a hot solution of the plastics material, drying the coated conductor by maintaining it at a temperature lower than the coating solution temperature but not less than 50‹C. for a time sufficing for the removal of nearly all' the solvent from the coating, and thereafter rapidly raising the temperature of the dried coated wire to a temperature substantially above the coating solution temperature to cause flash evaporation of the residual solvent in the coating to form cells within the coating without breaking the surface thereof. The applied solution of the plastics material may be maintained at a temperature near to its boiling point. The plastics material may be an olefinic polymer or copolymer, e.g. polyethylene. The coating solution may be a solution of the polyethylene in toluene or xylene and the solution is maintained at a temperature not more than 15‹C. below its boiling point. The temperature of the flash evaporation is two to five times the temperature in degrees centigrade at which the drying is effected, e.g. when the drying temperature is .between 60 and 65‹C. the flash evaporation temperature is between 140 and 250‹C. Apparatus for coating wire comprises a coating device comprising a thermostatically controlled heated reservoir 4 for coating solutions, a die 9 for controlling the thickness of the coating applied to the wire 1 as it is drawn through the solution, a thermostatically controlled drying oven 6 through which .the coated wire is drawn in one or more passes, a thermostatically controlled flashing oven 16 through which the dried coated wire is drawn, means for enclosing the coated wire during its passage from the dye to the drying oven and during its passage from the drying oven to the flashing oven, and means for maintaining the atmosphere within each of said enclosing means at a temperature not less than 50‹C. The apparatus may also include means 3 for preheating the wire before it enters the reservoir and also an extension 14 of the drying oven from which the wire passes into the flashing oven. The flashing oven may be of a kind in which the required temperature is maintained without circulation of the ambient medium. The drying oven may be a single multi-pass oven.