GB1169193A - Improvements in and relating to Electrical Insulation - Google Patents

Abstract

1,169,193. Insulating coating. MICANITE & INSULATORS CO. Ltd. 29 June, 1967 [7 July, 1966], No. 30578/66. Heading B2E. [Also in Division B5] Insulation tape incorporates a heat-shrinkable plastics material giving the tape a heat shrinkable characteristic at least in the lengthwise direction of the tape and a curable synthetic bonding resin in a set but not fully cured condition, the shrinkable material having the property of shrinking at a curing temperature for the bonding resin. After the tape has been wrapped onto say a stator coil, it can be heated to cause shrinking of the tape and bonding together of overlapping turns thereof by the bonding resin. Mica in the form of mica flakes, splittings, or in the form of mica paper may be bonded to the heat-shrinkable material by the bonding resin. Shrinkable material can be in the form of a perforate or imperforate film or in the form of a fabric, e.g. a fabric woven entirely from filamentary heat-shrinkable plastics material, or from such material as warp with glass as wept, a paper with or without reinforcing strands. Suitable heat shrinkable materials mentioned are radiation-modified polyvinyl chloride, vinyl copolymers with vinylidene chloride or vinyl acetate, radiation-modified polyolefines such as polyethylene and polypropylene and radiation-modified neoprene. Heat-shrinkable polyester resin such as polyethylene terephthalate is preferred. The bonding resin may be epoxy resin. To prevent excessive shrinkage the heat-shrinkable material may be initially in a partially heat-set or heat-stabilised condition. Several tape-making procedures are illustrated. In Figure 4 mica splittings 8 are laid in overlapping relation onto a paper web and a web of heatshrinkable fabric 9 is brought into contact with the mica-carrying web at a roller 11. The fabric 9 is impregnated with epoxy rsein applied in fluid form by drip-feed from trough 12. The composite is passed through a heated oven 13 and the paper web 5 is separated. In other procedures a mica paper web and a heat-shrinkable web are fed together round a roller in a bath containing epoxy resin in a fluid form and the composite passed through a heated oven (Figure 5 not shown); a heatshrinkable web is fed over a roller dipping into epoxy resin in fluid form and then passes through a heat oven before feeding through pinch rollers along with a web of mica paper, one of the pinch rolls being heated sufficiently to cause the epoxy resin to flow and permeate the mica paper (Figure 6 not shown).