PU tube in the presence of catalysts and a variety of special additives, interaction, through a complex chemical reaction to prepare a rigid polyurethane foam. The compression strength is large, up to 4~20MPa. Thermal conductivity 0.052. With low thermal conductivity, low moisture permeability, low water absorption, to meet the requirements of cold preservation. It has excellent chemical properties such as hydrolysis resistance, anti-aging, acid and alkali resistance.