Fremgangsmåde og apparat til ekstrudering af genstande, fortrinsvis folier, af ekspanderet polystyren ud fra en blanding af polystyren og kernedannende midler.

摘要

Films of expanded polystyrene are manufactured by feeding polymer of styrene and a nucleating system into an extrusion barrel which comprises a plasticizing section and a mixing section; the mass is conveyed continuously through the plasticizing section where the pressure on the mass is increased as it melts; a volatile (halo) hydrocarbon is injected in the beginning of the mixing section; the mass obtained is intensively homogenized as it is conveyed through the mixing section to the annular orifice of the die where it is extruded with expansion of the polymer, the expanded polymer of styrene is then blown up from the interior to form a tubular film. The pressure may increase as the mass is conveyed through the plasticizing section until it attains a value equal to the pressure of the mass at the entrance to the die. The mixture is homogenized by subjecting it to successive considerable and less considerable tangential forces by passing the mass over a number of grooved mixing elements which divide the annular flow into a number of separate streams. The mass in the last portion of the plasticizing section and the first portion of the mixing section is preferably between 150 DEG and 300 DEG C. The mixture on leaving the die preferably has a temperature between 100 DEG and 160 DEG C. The polymer of styrene may be polystyrene or a polystyrene containing a certain quantity of rubber-like (co)polymers such as a butadiene-styrene copolymer; it may be prepared by mixing the rubber-like polymer with polystyrene or by interpolymerization of a solution of the rubber-like polymer in a styrene monomer.