Patent ID: 7803299

Claim:
Process for obtaining an extruded profiled element based on a cross-linkable rubber composition, the profiled element being intended to constitute in the cross-linked condition a tread for a tyre and being delimited in width by two lateral faces which connect to one another radially inner and outer faces of the tread, conducting means being provided in the profiled element to connect the inner face electrically to the outer face between the lateral faces and all along the length of the profiled element, the remainder of the profiled element being based on an electrically insulating material, characterized in that the conducting means, viewed in a cross-section of the profiled element, have a layered structure comprising electrically conducting layers which are essentially concentric and have a curvature towards at least one of the inner and outer faces, and at least one of the layers emerges at the surface of the outer face; the conducting means comprising a rubber composition based on at least one diene elastomer comprising an inorganic reinforcing filler as reinforcing filler and a conducting ionic solution comprising: a polyether which is a copolymer of oxyethylene and oxypropylene containing a majority of oxyethylene units, preferably in an amount between 20 and 50 phr (phr: parts by weight per 100 parts of the elastomer(s)), an ionic salt of a monovalent or divalent metal, such as lithium perchlorate or zinc dichloride, preferably in an amount between 5 and 30 phr, and a polar solvent, such as polypropylene glycol carbonate, preferably in an amount between 5 and 15 phr; the process comprising the steps of: A) introducing the electrically insulating material for a tread into an input of a main extruder which opens coaxially into an extrusion head, and introducing the electrically conducting material intended to constitute the conducting means having a layered structure into an input of at least one satellite extruder which opens radially upstream from the extrusion head inside the main extruder, B) propelling the insulating material and the conducting material within the extruders, C) producing, within the main extruder and upstream from the extrusion head, a uniformly distributed mixture of the insulating material and the conducting material, the mass fraction of the insulating material in the mixture being equal to or greater than 80% and that of the conducting material being less than or equal to 20%, and D) passing the mixture of step C into a channel of the extrusion head to obtain, at the outlet of an extrusion orifice of the extrusion head, the extruded and cross-linkable profiled element for a tread.