Process for the production of blow molded articles

Claim 2

In a process for the production of blow. molded thermoplastic articles comprising the steps of extruding a thermoplastic in a molten state to form a parison, blowing said parison within a closed mold to conform its walls to the contour of said mold, cooling said resulting blow molded article, and recovering the cooled article, the improvement which comprises: (a) introducing a liquefied gas into said parison as it is being blown with a blowing gas, (b) vaporizing said liquefied gas from the heat of the molten parison to cause said parison to conform to the contours of said mold and to cool said blow molded article, (c) recovering a mixture of said blowing gas and vaporized liquefied gas, and (d) using said mixture as at least a portion of the blowing gas during the blowing step.

Claim 3

The process of Claim 1 wherein said liquefied gas is liquefied nitrogen. 1

Claim 4

In an apparatus for blow molding an article comprising in combination a blowing mold having an internal surface corresponding to the contour of the article to be produced and into which an expandable parison is introduced and blow pin means for injection into the interior of the parison enclosed within said blowing mold, the improvement which comprises: (a) liquefied gas feed line means, connected between said blow pin means and a source of a liquefied gas which is injected into the interior of an at least partially expanded parison to simultaneously cool and complete the formation of said article, for introducing the liquefied gas to said blow pin means; (b) valve means in said liquefied gas feed line for controlling the flow of the liquefied gas to said blow pin means; (c) storage means for storing the gas that results from the vaporization of the liquefied gas upon contact with the inner walls of the at least partially expanded parison; (d) exhaust line means connected between said blow pin means and said storage means for passing the vaporized gas from said blow pin means and said storage means; and (e) blowing gas line connected between said storage means and said blow pin means for passing the gas from said storage means into said blow pin which gas at least partially expands the parison upon injection into the parison.

Claim 5

In an apparatus for blow molding an article comprising in combination a blowing mold having an internal surface corresponding to the contour of the article to be produced and into which an expandable parison is introduced and blow pin means for injection into the interior of the parison enclosed within said blowing mold, the improvement which comprises: (a) liquefied gas feed line means, connected between said blow pin means and a source of a liquefied gas which is injected into the interior of an at least partially expanded parison to simultaneously cool and complete the formation of said article, for introducing the liquefied gas to said blow pin means; (b) valve means in said liquefied gas feed line for controlling the flow of the liquefied gas to said blow pin means; (c) storage means for storing the gas that results from the vaporization of the liquefied gas upon contact with the inner walls of the at least partially expanded parison; (d) exhaust line means connected between said blow pin means and said storage means for passing the vaporized gas from said blow pin means and said storage means; and (e) blowing gas line connected between said storage means and said blow pin means for passing the gas from said storage means into said blow pin which gas at least partially expands the parison upon injection into the parison.

Claim 6

The apparatus of Claim 3 wherein said valve means is immediately adjacent said blow pin means.