Polymer composition and electrical wire insulation
AssigneeRaychem Corporation
InventorDavid John Durston
Life of this patent
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Abstract
Polymer blend for insulating electrical wires comprises a first polymer (polyester) having an inherent L.O.I. not higher than 21% and up to 40% by weight of a polyimide-siloxane (PIS) copolymer. Preferred polyesters are polybutylene terephthalate or polyester-ester block copolymers. Preferred wire constructions have core insulation layer of polyethylene or polyester overlaid with jacket of the polyester/PIS copolymer blend.
Claims12
An insulated wire or cable which comprises
- (1) a wire;
- (2) a primary core insulation layer;
- and
- (3) overlaying the primary core insulation layer, a melt-extruded insulating jacket layer composed a polymeric composition which has a Limiting Oxygen Index of at least 28% and which comprises
- (a) a first polymeric component which
- (i) in the absence of any other component has a Limiting Oxygen Index of at most 21%,
- (ii) comprises at least one polyester which is free of halogen, phosphorus and sulfur, and
- (iii) is substantially halogen-free, and
- (b) a second polymeric component which is present in amount at most 35% by weight of the composition and which is a polyimide-siloxane polymer.
A method of preparing an insulated wire or cable which comprises melt-coextruding over a wire first and second insulating polymeric compositions so that the second composition forms an inner layer and the first composition forms an outer layer, the first composition being melt-extruded at a temperature of at most 270.degree. C. and comprising
- (a) a first polymeric component which (i) in the absence of any other component, has a Limiting Oxygen Index of at most 21% and (ii) is substantially halogen-free,
- (b) a second polymeric component which (i) is present in amount at most 50% by weight, based on the weight of the composition, and (ii) is a polyimidesiloxane polymer, and
- (c) magnesium hydroxide which is present in amount 15 to 40% based on the weight of the first composition;
- the melt extruded first composition having a Limiting Oxygen Index of at least 27%.
Dependencies are inferred from the claim text.