Blow Molding Cooling
“In a typical blow-molding process employed in the manufacture of plastic containers, such as PET (polyethylene terephthalate) bottles, the plastic starting material is heated to about 95.degree. C., which is 20.degree. C. above its glass transition temperature. The supplied heat softens the plastic starting material so it can be stretched to and shaped to fill the mold. Compressed air at a pressure of about 30 bar and a temperature between about 20.degree. C. and 30.degree. C. is blown in the interior of a preform of the container, urging the container against the walls of the mold. The container hereby takes on the shape of the mold cavity.”
“Before the blow-molded container is removed from the mold, the mold is cooled to below the glass transition temperature of the plastic material, i.e., below about 70.degree. C. for PET. In current molding machines, the mold is cooled by flowing chilled water at about 12.degree. C. through cooling channels arranged in or on the mold. The water is chilled in a closed-loop refrigeration system and pumped through insulated pipes systems to the blow mold, where it flows through the cooling channels. During the molding process, the water temperature rises by about 2.degree. C. The water is then returned from the mold to the refrigeration system to remove heat.”
Recent US Patents
12/28/2010
7,857,613
Mold cooling by recovery of energy from spent compressed air in blow-molding process
Leone of Nestle Waters, Connecticut, cooled by expansion through a votex tube the compressedgas used in a blow-molding. This cold gas is then routed through cooling channels in the mold. (RDC 6/29/2011)