GB1106366A - Electrical apparatus incorporating polyaryl sulphone as insulating material - Google Patents

Abstract

1,106,366. Electric insulation; capacitors. IMPERIAL CHEMICAL INDUSTRIES Ltd. 23 April, 1965 [30 April, 1964], No. 18067/64. Headings H1A and H1M. Electrical apparatus incorporates insulation which comprises a polyarylsulphone formed of repeating units of the formula -Ar-SO 2 - where Ar is a divalent aromatic residue which may vary from unit to unit in the polymer chain, and in at least some of the units Ar is derived from a compound of formula (where Z is -O-, -S-, or the residue of a 4,4<SP>1</SP>-bisphenol) and in any other units Ar is similarly derived from benzene, diphenyl, or a polynuclear aromatic hydrocarbon containing not more than two aromatic nuclei, so that in the divalent aromatic residues containing two benzene rings each benzene ring bears one of the valencies, and one or more of the hydrogen atoms bound to aromatic rings may be replaced by halogen atoms or alkyl or alkoxy groups having 1-4 carbon atoms and a minor proportion of the -SO 2 - links may be replaced by -CO- links. The residues Ar may be derived from diphenyl ether or diphenyl sulphide and optionally also in minor proportion from diphenyl. The electrical apparatus may contain the polyarylsulphone in the form of a moulding, casting or film. Such a film may be oriented by drawing. A capacitor may comprise metallic layers separated by a polyarylsulphone film as dielectric, and the manufacture thereof may involve flexure of the polyarylsulphone film. Such capacitors may comprise stocks of metallized laminµ, or may be in the form of helices made by rolling up sheets of metallic foil interleaved with sheets of the dielectric film. Such polyarylsulphones may have a power factor which is essentially unchanged over a wide range of temperature. The polyarylsulphones are also useful for insulation generally, e.g. as slot liners, insulation for commutator segments and V-rings, phase insulation for electric motors, and insulation for chokes, transformers, television scanning coils and cable manufacture. Films may be made by compressionmoulding, melt-extrusion, calendering, or casting from a solution of the polymer in a suitable solvent, e.g. nitrobenzene or dimethylformamide. In moulding or extrusion, temperatures of at least 300‹ C. are required to obtain the material in a sufficiently mobile form, but temperatures above 330‹ C. may cause thermal degradation. Orientation may be effected by stretching, suitably at 240-260‹ C. The stretching method used depends largely on the process used for forming the film. Longitudinal stretching may be effected by the use of feed and draw rolls, and the film may then be transversely stretched by tentering. Alternatively tentering alone may be employed using a tenter in which the pairs of clamps diverge laterally while the distance between adjacent pairs is also increased, thus simultaneously stretching the film both laterally and longitudinally. Alternatively, tubular film may be made by meltextrusion and drawn by passage between two pairs of nip rolls while simultaneously inflated, in known manner.