GB635445A - Improvements in or relating to insulated electrical conductors - Google Patents

Abstract

A conductor is insulated with a coating of a cured cross-linked polyester amide resin applied directly thereon and an outer coating of an organo polysiloxane resin. The polyester amide resin may be produced by reacting (a) a mixture of organic di-carboxylic acids or anhydrides thereof having an average of from 2 to 3 1/2 non-carboxyl carbon atoms per molecule, the mixture composed of from 48 to 92 mole per cent of an acid having the group <FORM:0635445/IV (a)/1> where R and R1 each represent OH or R and R1 together represent O and the remainder is saturated aliphatic dicarboxylic acids having from 4 to 12 carbon atoms, and (b) a mixture of primary aliphatic amines and alkyl polyhydric alcohols, the total number of amino and hydroxyl groups in (b) being substantially equal to or more than the total number of carboxyl groups in (a). Examples of suitable resins of this type are given in Specification 626,145. Organo-polysiloxane resins suitable for the outer coating comprise the following typical structures <FORM:0635445/IV (a)/2> where R and R1 may be the same or different organic radicals attached through carbon silicon linkages to at least some of the silicone atoms. The ratio of R+R1 to Si may vary from 2 to 1, and X may have a value of 4 or more. Numerous suitable organic radicals are given. The polysiloxanes may form linear, branched, cross-linked and cyclic structures. After application to the conductor the polysiloxane resin is cured by heating to a temperature between 150 DEG and 250 DEG C. for a few minutes. A catalyst may be employed to expedite the curing. Stabilizers such as high boiling point amines and phenols may be added to the polysiloxanes to enable them to withstand high temperatures without cracking or deteriorating.