Producing of thermal insulating materials on the basis of silica gel by one-stage processing technology

Abstract

The one-stage processing technique for producing of thermal insulation materials based on silica gel has been developed. Silica gel is AlF3, waste products including following main stages: hydrothermal synthesis polysilicate, granulation, classification and foaming. As compared with well-known analogs, it differs significantly in lower power consumption, does not require complex and expensive equipment, provides the possibility of varying boundary-granulometric composition of the foam product (0.5 to 30 mm). The main influence on the stability of the product quality is caused by the processes of depolymerization and condensation occurring on the stage of hydrosilicates synthesis from the silica gel because of NaOH addition. It was found out that a final foamed product with a bulk density less than 200 kg/m3 can be produced only if depolymerization and polycondensation of the silica gel stages are separated at the time. The values of process parameters (silica module, suspension temperature, the intensity of her mixing, foaming temperature, the quantity and type of modifiers) synthesis of heat-insulating materials have been defined. The required concentration of dissolved silica in the suspension is provided by its intensive mixing for 15–30 min. The temperature of the mixture should not exceed 35–40°C. The most effective technique for the speed polycondensation control is to additive a carbon. Its amount should not be more than 0.2–0.3%. Fast transition gel susp ension is achieved when it is heated to 70–80°C for 10–15 min. After aging and foaming of gels at a temperature of 450–500°C the proposed processing technique allows one to produce the thermal insulation materials possessing the characteristics which are not inferior to those of the foreign ones.