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US 6,300,469 B1Granted
Production of reduced gas-permeable polyalkylene terephthalate films by strain induced crystallization
AssigneeSealed Air Corporation (US)
InventorsRichard Freundlich, Rudy Nwana, Glenn Mathus
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Abstract
PET with low gas permeability and good mechanical properties is produced utilizing strain-induced crystallization. This strain-induced crystallization process is utilized to produce PET films and sheets, among other products.
Claims6
A method of increasing the crystallinity of polyethylene terephthalate comprising:
- melting substantially amorphous polyethylene terephthalate in an extruder having an adapter tube with a restricted portion;
- cooling said melted polyethylene terephthalate in the adapter tube to crystallize said polyethylene terephthalate;
- heating said cooled polyethylene terephthalate to a temperature less than the melting point of said cooled and heated polyethylene terephthalate;
- and
- processing said heated polyethylene terephthalate.
2 more elements
A method of producing polyethylene terephthalate films, comprising:
- melting polyethylene terephthalate in an extruder having an adapter tube with a restricted portion;
- cooling said melted polyethylene terephthalate in the adapter tube to crystallize said polyethylene terephthalate
- by decreasing the temperature applied to the melt by at least 10° C. and up to about 38° C. so that the applied temperature is in the range of 229° C. to 285° C.;
- heating said cooled polyethylene terephthalate to a temperature less than the melting point of said cooled polyethylene terephthalate;
- and
- blowing said heated polyethylene terephthalate into a film.
3 more elements
A method of increasing the oxygen barrier properties of polyethylene terephthalate, comprising:
- melting polyethylene terephthalate in an extruder having a restricted portion between upstream and downstream unrestricted portions;
- cooling said melted polyethylene terephthalate in the restricted portion of the extruder
- by decreasing the temperature applied to the melt by at least 10° C. and up to about 38° C. so that the applied temperature is in the range of 229° C. to 285° C.;
- heating said cooled polyethylene terephthalate to a temperature less than the melting point of said cooled polyethylene terephthalate;
- and
- blowing said heated polyethylene terephthalate into a film.
3 more elements
A process for increasing the crystallinity of polyethylene terephthalate which comprises
- subjecting amorphous PET to heating at a temperature which exceeds 254° C.;
- and
- crystallizing the heated PET, by simultaneously cooling the heated PET by decreasing the temperature applied to the melt by at least 10° C. and up to about 38° C. so that the applied temperature is in the range of 229° C. to 285° C.;
- and
- passing the PET, while said PET is being cooled, to an adapter which has an aspect ratio, defined as L/D wherein L is length and D is diameter and wherein the L/D has a numerical ratio of 16 to 21;
- and
- subjecting the PET to a pressure of 1500 to 6200 psi, to form PET with a crystal content of 5 to 40%;
- and
- heating the crystal containing PET to a temperature of over 260° C. to a temperature less than the PET melting point.
6 more elements
Dependencies are inferred from the claim text.