Process for the production of blow molded articles accompanied with the recovery of a blowing gas
AssigneeAir Products and Chemicals, Inc.
InventorsHatahiko Fukushima, Tadahiko Handa, Kenji Kodama
Life of this patent
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Abstract
In a blow molding process in which a parison is blown with a blowing gas containing a reactive gas component capable of reacting with the inner walls of the parison, the blowing gas is removed from the resulting blown article with a purging gas and stored for reuse. The mixture of blowing and purging gases in a reserve tank or other suitable means is adjusted to a certain level of pressure and reactive gas concentration and then recycled as the blowing gas in a subsequent blow molding step. The resulting blown articles from this process have improved properties, e.g. improved impermeability against non-polar solvents when fluorine is the reactive gas.
Claims14
In a process for the production of a blow molded thermoplastic article comprising the steps of extruding the thermoplastic material into a molten state to form a parison, introducing from a storage means a blowing gas containing a reactive gas component into the parison and expanding said parison to form the resulting blow molded article, the improvement which comprises:
- adjusting within said storage means said blowing gas to a preselected level of pressure and concentration of said reactive gas before introducing the blowing gas into said parison, purging said blowing gas from the interior of said blow molded article with a purging gas, recovering a mixture of said purging gas and said blowing gas containing a high concentration of the reactive gas component, during an initial stage of said purging, in said storage means and disposing of the remaining mixture of blowing gas and purging gas after the pressure and reactive gas component concentration reaches a preselected level in said storage means.
Dependencies are inferred from the claim text.