| abstract |
Reactive thermoplastic welding aid, preferably in the form of film, based on known resin/polyurethane/EVA copolymer mixtures. The system also contains a reactive acrylate, polybutadiene resin, epoxy resin or other reactivatable or still reactive prepolymer, optionally together with heat-stable accelerators. These thermolytically-labile resin systems are unreactive at extrusion temperature, and the resin system and activation temperature are chosen so that crosslinking to the elastomer only occurs at 160 deg C or above for heat-cured compositions, or on exposure to UV light or electron beam radiation. Preferably the reactive acrylate contains an ester-PU system which undergoes thermal decomposition with the formation of reactive, crosslinking NCO groups. The polymer mixture may also contain a photosensitiser and a thermally stable peroxide, providing chemical activation when exposed to light with a wavelength of 200-600 nm or to electron beam radiation. This enables crosslinking with electron beam radiation in the range of 20-200 kKay at a throughput speed of 0.1-2.2 m/min. Further crosslinking may be obtained by a combination of heat and electron beam radiation. |