Conductive polymer compositions containing fillers

Claim 2

A conductive polymer composition which has a resistivity at 23°C of less than 10 6 ohm. cm and which comprises a polymer having carbon black and/or graphite dispersed therein, characterised by comprising (1) 20 to 91% by volume of a polymer component; (2) 4 to 65% by volume of a conductive filler component which consists essentially of carbon black and/or graphite; and (3) an arc-controlling additive which is distributed in the polymer component.

Claim 3

A composition according to Claim 1 characterised in that the arc-controlling additive is a-particulate material which is present in amount 5 to 65%, preferably 10 to 35%, by volume of the composition.

Claim 4

A composition according to Claim 2 characterised in that the particulate material is a hydrated inorganic material, preferably alumina trihydrate.

Claim 5

A composition according to Claim 2 or 3 characterised in that the conductive filler and the arc-controlling additive have a total surface area of at least 1,800 m 2 per cc. of composition.

Claim 6

A composition according to any one of claims 2 to 4, characterised in that the polymer component has at least 5% crystallinity and the conductive filler component (a) comprises carbon black having a particle size, D, which is from 20 to 50 millimicrons and a surface area, S, in m 2 /g such that S/D is not more than 10, and (b) is present in amount such that the composition has a resistivity at 23°C of less than 20 ohm.cm.

Claim 7

A composition according to Claim 5 characterised in that the quantity is less than 1.

Claim 8

An electrical device which comprises an element composed of a conductive polymer composition and at least two electrodes for passing current through the element, characterised in that the conductive polymer composition is as claimed in any one of claims 1 to 6.

Claim 9

A circuit protection device comprising an element composed of a conductive polymer composition which exhibits PTC behavior and a pair of electrodes for passing current through the element, characterised in that said conductive polymer composition has a resistivity of less than 10 ohm.cm and comprises (a) 20 to 91% by volume of a polymer component having at least 10% crystallinity; (b) 4 to 65 % by volume of carbon black; and (c) 5 to 65% by volume of alumina trihydrate the carbon black and the alumina trihydrate having a total surface area of at least 1,800 m 2 /cc of composition.

Claim 10

A circuit protection device comprising an element composed of a conductive polymer composition which exhibits PTC behavior and a pair of electrodes for passing current through the element, characterised in that said conductive polymer composition has a resistivity of less than 10 ohm.cm and comprises (a) 20 to 91% by volume of a polymer component having at least 10% crystallinity; (b) 4 to 65 % by volume of carbon black; and (c) 5 to 65% by volume of alumina trihydrate the carbon black and the alumina trihydrate having a total surface area of at least 1,800 m 2 /cc of composition.