You can freely build on Making Strong, Porous PTFE: The Gore-Tex Process

What this patent covers

The patent describes a process (Claim 1) for making a porous product from a polymer of tetrafluoroethylene, also known as PTFE. First, a shaped article of "highly crystalline poly(tetrafluoroethylene)" is created using a "paste-forming extrusion technique." After removing any lubricant, this unsintered article is stretched at a very fast rate, "exceeding about 10% per second" (Claim 1), while kept at a temperature between about 35°C and the material's crystalline melt point (Claim 1). This rapid stretching creates a material with a unique microstructure of "nodes interconnected by fibrils," as mentioned in the abstract, resulting in high porosity (Claim 13, 40-97%) and strength. For example, a PTFE rod could be stretched rapidly to become a porous tube, which could then be used in a waterproof fabric.

What is now free to use

All 0 claims of US 3953566 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 making porous PTFE by methods other than rapid stretching of a paste-extruded, highly crystalline PTFE article.

• Does not cover stretching PTFE at rates slower than about 10% per second (Claim 1).

• Does not cover stretching PTFE outside the temperature range of about 35°C and its crystalline melt point (Claim 1).

• Does not cover porous PTFE products made from materials that are not "highly crystalline poly(tetrafluoroethylene)" (Claim 1).

• Does not cover the final porous product itself, only the specific process of making it.

Who is building on this today

WL Gore and Associates Inc. continues to be the primary innovator and manufacturer of ePTFE products, building extensively on this foundational patent. Other companies also produce expanded PTFE, often under license or using alternative processes that avoid the specific claims of this patent, for applications in medical devices, filtration, and sealing.

Products built on expired version of this technology

How to cite this patent in your documentation

WL Gore and Associates Inc. US Patent 3953566. Process for producing porous products. Granted 1976, expired 1993. 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.