You can freely build on How Plastic Soda Bottles Are Made Stronger Using Stretched Molecules
This patent expired in 1990. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
EI Du Pont de Nemours and Co
Patent granted
1973
Expired
1990
Forward citations
170
What this patent covers
The patent describes a process for creating a plastic bottle made of polyethylene terephthalate (PET) that is biaxially oriented. Biaxial orientation means the plastic molecules are stretched in two directions—lengthwise and widthwise—during the manufacturing process. This alignment significantly increases the strength and impact resistance of the plastic. By achieving a specific inherent viscosity and density, the resulting bottle can withstand the high internal pressure of carbonated liquids, such as soda or beer, without deforming or bursting.
What is now free to use
All 0 claims of US 3733309 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover bottles made from materials other than polyethylene terephthalate (PET).
Does not cover non-oriented plastic containers, such as simple blow-molded jugs that lack the specific molecular alignment described.
Does not cover the specific machinery or injection molding equipment used to stretch the plastic, only the resulting physical properties of the finished article.
Who is building on this today
Major global packaging companies like Amcor and Berry Global continue to refine PET bottle manufacturing. The technology is now a commodity standard used by every major beverage manufacturer, including Coca-Cola and PepsiCo.
Products built on expired version of this technology
Standard 2-liter soda bottles
Single-serve plastic water and soda bottles
Carbonated beverage packaging
How to cite this patent in your documentation
EI Du Pont de Nemours and Co. US Patent 3733309. Biaxially oriented poly(ethylene terephthalate)bottle. Granted 1973, expired 1990. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.