Manufacture of extruded products

Abstract

In the manufacture of a cross-linked extruded product, a polymer capable of being cross-linked by the use of hydrolyzable unsaturated silane is metered into a first screw extrusion machine together with compounding ingredients comprising a hydrolyzable unsaturated silane, a free-radical generator and a silanol condensation catalyst. The compounding ingredients are mixed with the polymer in the barrel of the first extruder. The mixture of ingredients is fed directly without exposure to the atmosphere to a second screw extrusion machine in which its temperature is raised sufficiently to effect grafting of silane groups to the polymer (the amount of free-radical generator being sufficiently low to limit direct free-radical cross-linking to a level that will not prevent extrusion of the material). The reaction mixture is extruded from the second extruder through an extrusion die to form an elongate shaped product, and the grafted polymer is cross-linked in the shaped product by the action of moisture.