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US 4,199,629 AGranted
Forming molecularly oriented containers from reheated preforms
AssigneeMonsanto Company
InventorsPurushottam D. Agrawal, John E. Griesing
Life of this patent
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AssigneeMonsanto Company
InventorsPurushottam D. Agrawal, John E. Griesing
Estimating the term…
In forming containers from injection molded preforms of thermoplastic material such as nitrile-based polymers by a process which includes heating the preforms to orientation temperature followed by distension to container form in a mold, the improvement providing reduced thickness variability in lower portions of the containers which involves controlling preform shrinkage during such heating to between about 4 to 15% of the initial length for nitrile materials by maintaining the ratio of average thickness to inside preform surface area within defined limits and then axially and radially stretching such preforms during distension to predetermined levels. Nitrile preforms convertible to such improved quality containers have values of between about 0.005 to 0.011 inch.sup.-1 for the aforementioned ratio.
A tubular, injection molded preform of thermoplastic material for distending into a container shape said preform comprising a body having a closed end and a finish portion at the opposite end, said preform having a value of between about 0.005 to 0.011 inch.sup.-1 for the ratio of average thickness to inside body surface area wherein average thickness is the arithmetical mean of:
A tubular, injection molded preform for blowing into a circular, molecularly oriented container, said preform comprising a thermoplastic material containing from about 50 to 90 weight percent of a polymerized monomer selected from the group consisting of acrylonitirle, methacrylonitrile and mixtures thereof, said preform satisfying the relation:
An injection molded preform comprising a body having closed and open ends which is free of excessive strains as evidenced by a shrinkage of between about 6 to 15 percent during reheat to molecular orientation temperature, said preform being formed of a polymerized nitrile-group-containing monomer and having a value of between about 0.005 to about 0.011 inch.sup.-1 for the ratio of average thickness to inside body surface area wherein average thickness is the arithmetical mean of the thickness adjacent the open and closed ends.
Dependencies are inferred from the claim text.