Pourous fluorocarbon membrane, method for producing thereof and

Details Pourous fluorocarbon membrane, method for producing thereof and Pourous fluorocarbon membrane, method for producing thereof and

1997-06-20

1999-11-23

Kim, John

Liquid purification or separation

Filter

Supported, shaped or superimposed formed mediums

21032177, 21032186, 210484, 210488, 210489, 210490, 2104931, 2104932, 2104935, 210496, 21050036, 21050042, 264 41, 264136, B01D 6300, B01D 7132, B01D 2700

Patent

active

059884002

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a porous fluorocarbon membrane, method for production thereof and design of cartridge filter based on a porous fluorocarbon membrane. These filters are widely used in fine filtration of chemically active media due to their resistance with respect to agressive media and organic solvents commonly in use. Fluorocarbon membranes and cartridge filters based on said membranes can be conveniently sterylized by thermal treatment since they offer the required thermal stability. At the same time, porous fluorocarbon membranes are inherently hydrophobic, which is a disadvantage in the process of filtration of water-containing aqueous media. However, numerous techniques, well-known in the art, can be used to render fluorocarbon membranes hydrophilic. Therefore, said disadvantage can be readily overcome.


PRIOR ART

Porous fluorocarbon membranes produced from the solution of tetrafluoroethylene/vinylidene fluoride copolymer using both "wet" and "dry" processes, are well-known to those skilled in the art. "Wet" process is most common. First step thereof includes preparation of a casting (working) solution, consisting of a fluorocarbon polymer, solvent and non-solvent for said polymer. The working solution is then cast on a dense surface, which is unable to absorb said solution. Normally glass, polyethylene terephthalate film, stainless steel drum, etc. are used as said surface. At this point, either one of two ways can be employed: cast solution can be allowed to evaporate (in air or other controlled environment), within a specified period of time varying from a few seconds to a few minutes, after which the solution (already partly hardened) may be immersed in a quench bath. Alternatively, membrane casting can be performed directly under the surface of the quench bath, thus completely eliminating the stage of partial evaporation and hardening of the solution. Both methods are used on commercial scale providing membranes principally characterized by low strength and performance (service life and the amount of impurities retained). The above disadvantages encountered in "wet" process for producing porous membrane can be eliminated by using porous support in "wet" process and in membrane design, respectively. In this case porous support acts as a surface coated by a casting solution of fluorocarbon polymer. At this point a new problem emerges, i.e. rate of "wet" casting of membrane on porous support is drastically reduced and reaches only 0.52-1.0 m/min.
In another well-known "dry" process for producing porous fluorocarbon membrane, based on casting solution of tetrafluoroethylene (TFE)/vinylidene fluoride (VF) copolymer, said solution is formed into membrane on dense surface followed by complete evaporation of liquid components of the casting solution and peeling the membrane sheet from said surface. Disadvantages of said process are similar to those encountered in "wet" process, wherein porous support is not used, i.e. low mechanical strength of membrane and relatively low performance thereof. "Dry" process for producing porous fluorocarbon membranes on porous support has not yet been disclosed in prior art.
Another common method for producing porous membranes is known as "thermal" method. This method has been developed for the production of porous membranes from fluorocarbon polymers which are hard to dissolve in the available solvents and at temperatures acceptable for commercial-scale production.
Representative of this genre is U.S. Pat. No. 4,990,294 issued to Yen e.a., which discloses the preparation of blend from fluorocarbon polymer and solvent melt followed by coating the casting surface with the resultant blend from the extruder. The solvent is then removed by lowering the temperature. Disadvantages of said method are as follows: high-temperature destruction of polymer in the course of preparing melt thereof, relatively low rate of porous membrane formation and low strength of said membrane.
An example of "wet" process for producing porous fluorocarbon me

REFERENCES:
patent: 4384047 (1983-05-01), Benzinger et al.
patent: 4929354 (1990-05-01), Meyering et al.
patent: 4965291 (1990-10-01), Kitoh et al.
patent: 4990294 (1991-02-01), Yen et al.
patent: 5013339 (1991-05-01), Mahoney et al.
patent: 5158680 (1992-10-01), Kawai et al.
patent: 5445739 (1995-08-01), Fujimoto et al.

Affiliated with

Also associated with

Rating

Pourous fluorocarbon membrane, method for producing thereof and does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pourous fluorocarbon membrane, method for producing thereof and , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pourous fluorocarbon membrane, method for producing thereof and will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1211169