PRODUCTO DE ESPUMA EXTRUDIDA CON DEFECTOS SUPERFICIALES REDUCIDOS

Un producto de espuma de polímero extrudida que tiene características superficiales mejoradas, comprendiendo el producto cera de polietileno y una cantidad mayoritaria de celdas cerradas tal como se midió mediante la Norma ASTM D2856-A, estando las celdas libres de agentes de soplado de halocarbono, y teniendo el producto una densidad de 1, 60 a 60, 00 kg/m3 tal como se midió mediante la Norma ASTM D1622-88. The present invention generally relates to processes for preparing extruded foam products and more particularly to a process for producing such products wherein surface defects are minimized. There has been a movement to replace conventional halo-carbon blowing agents in favor of purportedly more environmentally safe halo-carbon free blowing agents such as carbon dioxide, nitrogen, argon, water, air, nitrogen, and helium. However, these halo-carbon free blowing agents, in particular carbon dioxide, have higher foaming rates and higher volatility leading to greater surface defects in the extruded foam. The present invention employs polyethylene wax to reduce or eliminate the occurrence of surface defects where halo-carbon free blowing agents are employed in an extruded foam manufacture process. The polyethylene wax containing extruded foam products of this invention are characterized by a generally smooth substantially defect free surface and contain a majority of closed cells which are free of any trapped halo-carbon blowing agents.