Stretch Blow Molding
“In the stretch blow molding (SBM) process, the plastic is first molded into a "preform" using the injection molding process. These preforms are produced with the necks of the bottles, including threads (the "finish") on one end. These preforms are packaged, and fed later (after cooling) into a reheat stretch blow molding machine. In the SBM process, the preforms are heated (typically using infrared heaters) above their glass transition temperature, then blown using high pressure air into bottles using metal blow molds. Usually the preform is stretched with a core rod as part of the process. In the single-stage process both preform manufacture and bottle blowing are performed in the same machine. The stretching of some polymers, such as PET (polyethylene terephthalate) results in strain hardening of the resin, allowing the bottles to resist deforming under the pressures formed by carbonated beverages, which typically approach 60 psi.The main applications are bottles, jars and other containers.” (Wikipedia, Stretch Blow Molding, 3/30/2011)
Recent US Patents
2/15/2011
7,887,744
Method of injection stretch blow molding heatproof bottles
Yanagimachi and Nakazawa of A. K. Technical Laboratory, Japan,have developed preform for an injection-molded PET with a body wall thickness of 3.0-4.5 mm. The preform is high-temperature mold-released from an injection cavity mold and an injection core. Pre-blowing of the preform is restricted at 5.+-.0.5 seconds after the mold release, at a temperature of 112-117.C. of the pre-blow mold, and for a pre-blowing time of 0.5-1.0 second. Air blowing is applied to expand only the body of the preform. Stretch blow molding is performed restrictively at 3-4 seconds after the mold release from the pre-blow mold, at a temperature of 103-107 C. of the blow mold, and for an air blowing time of 6-9 seconds, thereby stretch blow molding the preform into a bottle and simultaneously heat setting to impart heat resistance to the bottle. (RDC 8/26/2011)
10/26/2010
7,820,257
Preforms for preparing lightweight stretch blow molded PET copolymer containers and methods for making and using same
Kjorlaug et al of The Coca-Cola Company, Georgia has developed an injection molded preform for making a stretch blow molded container having an overall stretch ratio of from about 12 to about 16. The PET copolymer has a free blow volume of from about 650 to about 800 ml at 100 C. and 90 psi. (RDC 2/15/2011)