Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Temperature control
Reexamination Certificate
2000-03-09
2002-07-02
Nguyen, Nam (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Temperature control
C425S144000, C425S378100, C264S041000, C264S184000
Reexamination Certificate
active
06413070
ABSTRACT:
BACKGROUND OF THE INVENTION
The present application, as presently envisioned, relates to systems and methods for the manufacture of continuous, three-zone reinforced, geometrically symmetrical, microporous membranes having three distinct pore zones, each zone being formed from at least one of a plurality of different pore size producing dopes, more particularly to systems and methods for the continuous manufacture of continuous, reinforced, three-zone microporous membrane including a scrim having two sides at least substantially encapsulated within any one of a plurality pore size producing first dopes produced from a single mother dope batch and at least one additional dope presently preferably produced from the same single mother dope batch coated onto each side of the substantially encapsulated scrim prior to the first dope being quenched and, most particularly, to systems and methods for the manufacture of a geometrically symmetric, continuous, reinforced membrane having three distinct pore zones including a scrim at least substantially and preferably, completely encapsulated by a relatively large pore size middle zone produced from any one of a plurality of different pore size dopes, which may be continuously produced from a single mother dope batch and two outer zones, one on each side of the middle zone, at least one of the three zones having a pore size at least about twenty (20%) percent greater than at least one of the other zones.
Microporous phase inversion membranes are well known in the art. Microporous phase inversion membranes are porous solids which contain microporous interconnecting passages that extend from one surface to the other. These passages provide tortuous tunnels or paths through which the liquid which is being filtered must pass. The particles contained in the liquid passing through a microporous phase inversion membrane become trapped on or in the membrane structure effecting filtration. A slight pressure, generally in the range of about one half (0.5) to about fifty (50) psig (pounds per square inch gauge) is used to force fluid through the microporous phase inversion membrane. The particles in the liquid that are larger than the pores are either prevented from entering the membrane or are trapped within the membrane pores and some particles that are smaller than the pores are also trapped or absorbed into the membrane pore structure within the pore tortuous path. The liquid and some particles smaller than the pores of the membrane pass through. Thus, a microporous phase inversion membrane prevents particles of a certain size or larger from passing through it, while at the same time permitting liquid and some particles smaller than that certain size to pass through. Microporous phase inversion membranes have the ability to retain particles in the size range of from about 0.01 or smaller to about 10.0 microns or larger.
Many important micron and submicron size particles can be separated using microporous membranes. For example, red blood cells are about eight (8) microns in diameter, platelets are about two (2) microns in diameter and bacteria and yeast are about 0.5 microns or smaller in diameter. It is possible to remove bacteria from water by passing the water through a microporous membrane having a pore size smaller than the bacteria. Similarly, a microporous membrane can remove invisible suspended particles from water used in the manufacture of integrated circuits in the electronics industry. Microporous membranes are characterized by bubble point tests, which involve measuring the pressure to force either the first air bubble out of a fully wetted phase inversion membrane (the initial Bubble Point, or “IBP”), and the higher pressure which forces air out of the majority of pores all over the phase inversion membrane (foam-all-over-point or “FAOP”). The procedures for conducting initial bubble point and FAOP tests are discussed in U.S. Pat. No. 4,645,602 issued Feb. 24, 1987, the disclosure of which is herein incorporated by reference. The procedure for the initial bubble point test and the more common Mean Flow Pore tests are explained in detail, for example, in ASTM F316-70 and ANS/ASTM F316-70 (Reapproved 1976) which are incorporated herein by reference. The bubble point values for microporous phase inversion membranes are generally in the range of about two (2) to about one hundred (100) psig, depending on the pore size and the wetting fluid.
Methods and Systems for preparing the dope used to produce microporous membrane are known in the art. There are numerous methods of preparing the dope. Prior methods of dope preparation are discussed in background section of U.S. patent application Ser. No. 09/022,295, now U.S. Pat. No. 6,056,529 issued May 2, 2000, mentioned above under related applications.
It is also known that processing relatively large bodies of dope, such as that used in the production of microporous phase inversion membranes, is accompanied by many difficulties such as the need to formulate separate dope batches for each size pore phase inversion membrane produced as well as the problems in controlling the temperature of the dope during the batching process.
As was pointed out in the '295 application, during production runs of microporous phase inversion membrane, it is important to produce microporous phase inversion membrane having the desired pore size and/or pore size distribution.
As summarized in the '295 application, in the prior batch formulation process, the dope formulation (solvent, nonsolvent, polymer ratio) was key to controlling pore size in the microporous phase inversion membrane. Using the batch formulation method as a predictive control of pore size in microporous phase inversion membrane, microporous phase inversion membrane having a specific pore size was produced from a specifically formulated dope batch.
As described in the '295 application, thermal manipulation to change the pore size in a membrane produced from a dope has long been recognized and has been used in reprocessing out of specification dope, as discussed therein. However, this recognized property of the dope was dependent on raising the temperature of the dope to a temperature higher than that to which the dope had previously been processed. While one prior patent mentioned in the '295 application discussed controlling the process temperature as one factor in enabling continuous production of material with fixed or variable pore size from a single batch of nylon 46 solution, that prior patent failed to provide any specific temperatures other than a wide temperature range. Further, in the only example relative to varying pore size, the patent combined process temperature manipulation with the composition of the dope and the composition of the bath to effectuate the pore size change but only in one direction, from smaller to larger. There was no apparent effort to control the temperature of the solution at a specific temperature or any effort to try to lower the temperature of the solution to produce a smaller pore size.
Following the teachings of that particular prior patent, using thermal manipulation to change the pore size and viscosity of the mixture, as the solution is heated to higher temperatures, the viscosity of the dope becomes such that it might not be usable in a solution casting operation, unless controlled. Specifically, as the particular solution is heated to higher temperatures, processing problems will most likely be encountered including those related to viscosity, degassing of volatile components, foam formation and quenching problems, without adequate viscosity control.
The methods taught in that prior patent are not applicable to Marinaccio style Nylon 66 dopes and the membrane products produced therefrom, for the following reasons: 1) the patent is directed toward attempting to produce a skinned membrane, with a radically altered pore structure just below the qualifying skin layer. In this method, the quality and integrity of the skinned membrane is completely dependent on the quality of the first fe
Baddenhop C. Thomas
Kelly William R.
Meyering Mark T.
Vining Jack H.
Wallace Joseph G.
Cummings & Lockwood
Cuno Incorporated
Nguyen Nam
Nguyen Thu Khanh T.
LandOfFree
System for manufacturing reinforced three-zone microporous... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for manufacturing reinforced three-zone microporous..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for manufacturing reinforced three-zone microporous... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2901773