High voltage insulating compositions containing phosphorus compounds

Claim 1

A high voltage electrically insulating composition comprising (1) a polymer; (2) an additive effective in reducing tracking; and (3) a phosphorus-containing compound effective in improving the resistance of the composition to erosion by high voltage stress and selected from the group consisting of (a) compounds having a formula selected from ##STR13## wherein n is selected from 0 and 1; t is an integer; p is integer greater than 1; X is independently selected from oxygen and sulphur; L is a t-valent organic group which, when t is 1, is selected from groups of formula --R and --XR; Q is independently selected from (i) monovalent groups of the formulae --R and --XR and (ii) divalent organic groups formed by two --R groups, two --XR groups, or an --XR group and an --R group attached to the same phosphorus atom; and R is independently selected from (i) a hydrogen atom; (ii) an aryl group; (iii) a substituted aryl group; (iv) an alkyl group; and (v) an alkyl group substituted by at least one group, each of said substituted groups consisting of at least one atom selected from carbon, hydrogen, fluorine, chlorine, oxygen, sulphur, nitrogen, phosphorus and silicon; subject to the provisos that (1) when n is 1, and each of the Q groups is an --XR group, and at least two of the Q groups are O-alkyl or O-aralkyl groups, the molecular weight of the compound is at least 382; (2) when n is O and each of the Q groups is an X-alkyl group, at least one of the X's is oxygen and the molecular weight of the compound is at least 442; and (3) no phosphorus atom is directly bonded to more than two hydrogen atoms; (b) salts of a compound as defined in (a) containing a salt-forming acidic group, the cation in said salt being selected from ammonium ions, quaternary ammonium ions and metal ions wherein the metal is a metal having an atomic number less than 56 and belonging to one of Groups 1A, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIIB and VIII of the Periodic Table; (c) reaction products of at least one compound as defined in (a) and (b) with each other; (d) reaction products of at least one compound as defined in (a) and (b) with said polymer (1); and (e) reaction products of at least one compound as defined in (a) and (b) with said anti-tracking additive (2).