GB1074401A - Improvements in or relating to insulating material - Google Patents

Abstract

Non-electrically conductive fibres, e.g. glass fibres, suitable for forming electrical insulation material are bound together with a resinous material including a copolymer obtained by polymerizing the reaction product of 2 molar proportions of methacrylic acid and 1 molar proportion of the diglycidyl ether of bisphenol-A, which is substantially free from unreacted epoxy groups, with an ethylenically unsaturated comonomer in the presence of benzoyl peroxide and one or more peroxy catalysts which promote a polymerization rate, with respect to said reaction product and comonomer, greater than that achieved with benzoyl peroxide. Suitable comonomers include styrene, diallyl phthalate, triallyl cyanurate, unsaturated polyesters, acetyl triallyl citrate, vinyl toluene, divinylbenzene, polymerizable phosphorus compounds (unspecified), and dialkyl maleates and fumarates. Peroxy compounds suitable as catalyst components include t-butyl perbenzoate, t-butyl hydroperoxide, dicumyl peroxide, cyclohexanone peroxide, cyclohexyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, methyl amyl ketone peroxide, lauroyl peroxide, methylcyclohexyl hydroperoxide, di-t-butyl dipermaleate and di-t-butyl diperphthalate. Inert fillers, e.g. calcium carbonate or mica, mould release agents, e.g. zinc, calcium and aluminium stearates, and colouring materials may be included in the resinous binder. In an example, the bisphenol-A derivative reaction product and styrene are copolymerized in bulk in the presence of filler, pigment and mould release agent.ALSO:Non-electrically conductive fibres, e.g. glass fibres, are bound together to form an electrical insulator with a resinous material including a copolymer obtained by polymerising the reaction product of 2 molar proportions of methacrylic acid and 1 molar proportion of the diglycidyl ether of bisphenol-A (the reaction product being substantially free from unreacted epoxy groups) with an ethylenically unsaturated comonomer in the presence of benzoyl peroxide and at least one peroxy catalyst which promotes a polymerisation rate greater than that achieved with benzoyl peroxide. Suitable comonomers include styrene diallyl phthalate, triallyl cyanurate, unsaturated polyesters, acetyl triallyl citrate, vinyl toluene, compounds (unspecified), and dialkyl maleates and fumarates. The resinous material may include an inert filler, e.g. calcium carbonate or mica, a mould release agent, e.g. zinc, calcium or aluminium stearate, and a colouring material.