Process for preparing photopolymer flexographic element with melt extrusion coated elastomeric surface layer

Claim 1

In a process for preparing a flexographic photopolymerizable element which comprises (a) passing into the nip of a calender a mass of a hot photopolymerizable composition comprising an elastomeric binder, an ethylenically unsaturated compound, and a photoinitiator or photoinitiator system, and while hot (b) calendering the photopolymerizable composition between a support and a multilayer cover element to form a photopolymerizable layer therebetween, the multilayer cover element consisting essentially of a flexible cover film and a layer of an elastomeric composition and optionally between the flexible cover film and the layer of elastomeric composition a flexible polymeric film, the layer of elastomeric composition being adjacent to the photopolymerizable layer and being photosensitive or becoming photosensitive during or after calendering by contact with the photopolymerizable layer, the improvement wherein at least the layer of elastomeric composition of the multilayer cover element is prepared by melt extrusion which comprises (i) feeding into an extruder and mixing at 100 to 300°C an elastomeric polymeric binder, a second polymeric binder and a nonmigratory dye or pigment and optionally one or more ethylenically unsaturated compounds and/or photoinitiator or initiator system; (ii) passing the hot melted mixture at 100 to 300°C into an extrusion die to form a layer, (iii) stretching the layer of extrudate as it passes out of the extrusion die to achieve the desired thickness, (iv) applying the layer of extrudate onto a removable cover film, and (v) optionally applying a flexible removable interleaf film over the bare surface of the extrudate layer.