News Column

Patent Issued for Gas Permeation Devices

May 28, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventor Chand, Ramesh (Chino Hills, CA), filed on October 18, 2011, was published online on May 13, 2014.

The patent's assignee for patent number 8720794 is Real Sensors, Inc. (Hayward, CA).

News editors obtained the following quote from the background information supplied by the inventors: "(1) Field of the Invention

"The invention generally relates to gas permeating or gas emitting systems. More particularly, the invention relates to a gas permeating system using an amorphous fluorpolymer material.

"(2) Description of the Related Art

"Other permeation devices or tube devices are known in the related art and are widely used to deliver or generate known gas mixtures of various chemicals. Devices in the related art are used for the testing and calibration of air pollution instruments, chemical and petrochemical process analyzers and safety equipment.

"An early device was disclosed by Andrew E. O'Keefe in his U.S. Pat. No. 3,412,935 (the '935 patent). In the '935 patent O'Keefe describes the use of material such as sulfur dioxide kept inside a tube made with polytetrafluoroethylene (PTFE), in the form of liquefied gas under its own pressure. The sulfur dioxide will permeate in the form of gas through the solid wall of the PTFE tubing, and the rate remained fairly constant, as long as the tube was kept at a contestant temperature. The permeation rate was however, low generating concentrations in low ppm (parts per million) range; and the permeation rate was substantially dependent on the temperature of the device, in the range of 10 to 15% increase for every one (1) degree Celsius increase in temperature. Similar results have been obtained with other materials such as fluorinated ethylene-propylene (FEP), perfluoroalkoxy fluorocarbon (PFA) and others.

"Subsequently, Chand in U.S. Pat. Nos. 3,856,204 and 4,399,942 described the use of silicone material to obtain higher permeation rates and low temperature dependency. However, the use of silicone has been limited to mostly non-corrosive materials and was found unsuitable for gases like nitrogen dioxide and sulfur dioxide.

"Paul R. Resnick, Min-Hong Hung and others have developed various types of amorphous fluoropholymer material, more formally known as fluorinated (ethylenic-cyclo oxyaliphatic substituted ethylenic) copolymer, with certain variations commonly known as Teflon AF as a trade name sometimes associated with I.E. Du Pont de Nemours and Company.

"In U.S. Pat. No. 5,310,838 issued on May 10, 1994 Hung and Resnick disclosed a Fluoropolymer comprising repeat units of perfluoro-2,2-dimethly-1,3-dioxole with a repeat unit of another fluoromonomer such as tetrafluoroethylene.

"In U.S. Pat. No. 5,324,889 issued on Jun. 28, 1994 Resnick disclosed various amorphous perfluoropolymers directed toward the use of cladding materials for optical fibers, encapsulating materials for electronic components, laminates other uses were impervious surfaces were needed.

"As the use of silicone in permeation devices has limitations regarding the use of corrosive material there is room in the art for new means and methods of creating gas permeation devices. While the known prior art uses various types of amorphous fluoropholymer materials for impervious surfaces there is room in the art for unobvious or more artful uses for amorphous fluoropholymer materials."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "The embodiments of the present inventions overcomes shortfalls in the related art by presenting an unobvious and unique combination, configuration and use of an amorphous fluoropolymer material [chemical name: fluorinated (ethylenic-cyclo oxyaliphatic substituted ethylenic) copolymer], as the material through which gas permeates within disclosed embodiments of gas permeation devices.

"One embodiment of amorphous fluoropolymer material is made by E.I. DuPont Company and is marketed under their trade name Teflon AF. The disclosed gas permeation devices made with Teflon AF produced unexpected results with superior permeation rates substantially higher as compared to other known materials. Moreover, the disclosed devices have shown much less temperature dependency and are useful for the controlled release of materials which were found too corrosive for the silicone material of the related art.

"The unexpected results of the disclosed devices are supported in the less impressive results reported in the related art. For example, O'Keeffe, in the '935 patent describes the increase in permeation rate of his device made with FEP material to increase almost 100% when the temperature is increased approximately 9 degrees Celsius. Additionally, the usefulness of the O'Keeffe device is limited to the generation of permeation rated less than 1,000 nanograms/minute. While these issues were addressed by Chand in his prior patents, the effective use of the prior art devices was limited to non-corrosive and non-reactive gases to the silicone material. The devices of the prior art were found to be unstable for substances such as sulfur dioxide and nitrogen dioxide.

"The novelty and unobvious nature of the disclosed embodiment is supported by unexpectedly good test results. For example, the results obtained with sulfur dioxide showed astounding improvements as compared to the known related art. Permeation rates from less than 200 to over 10,000 nanograms per minute were achieved using Teflon AF. Additionally, the temperature dependency was found to be cut in less than half, as compared to the prior art devices using FEP and PTFE.

"Additionally, the embodiments of the present inventions overcome shortfalls in the related art by the artful use and unobvious configuration of membranes made with amorphous fluoropolymer material. For example, in one embodiment, an amorphous fluoropolymer membrane is manufactured with a plurality of protrusions, with the protrusions inserted into voids of a top cap. Membrane protrusions within the top cap voids present a significant and unobvious departure from the related art.

"These and other objects and advantages will be made apparent when considering the following detailed specification when taken in conjunction with the drawings."

For additional information on this patent, see: Chand, Ramesh. Gas Permeation Devices. U.S. Patent Number 8720794, filed October 18, 2011, and published online on May 13, 2014. Patent URL:

Keywords for this news article include: Chemicals, Chemistry, Silicones, Siloxanes, Chalcogens, Legal Issues, Sulfur Oxides, Sulfur Dioxide, Nitrogen Dioxide, Real Sensors Inc..

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Source: Journal of Engineering

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