North Star

The origin of thin-film-composite reverse osmosis membranes began with a newly formed research institute and one of its first employees, Peter S. Francis. North Star Research and Development Institute was formed in Minneapolis during 1963 to fill a need for a nonprofit contract research institute in the Upper Midwest. Francis was given the mission of developing the chemistry division through support, in part, by federal research contracts. At this time the Initial discoveries by Reid and Breton ( ) on the desalination capability of dense cellulose acetate membranes and by Loeb and Sourlrajan (,2) on asymmetric cellulose acetate membranes had recently been published. Francis speculated that improved membrane performance could be achieved, if the ultrathin, dense barrier layer and the porous substructure of the asymmetric... 

In 1977 the North Star membrane research group was spun off by Midwest Research Institute, forming FilmTec Corporation. Two new thin-film-composite reverse osmosis membranes have been under development at FilmTec Corporation since that time, the NS-300 and the FT-30 membranes. 

NS-300 Membrane. The NS-300 membrane evolved from an effort at North Star to form an interfacial poly(piperazine Isophthala-mide) membrane. Credali and coworkers had demonstrated chlorine-resistant poly(piperazineamide) membranes in the asymmetric form (20). The NS-lOO, NS-200, and PA-300 membranes were all readily attacked by low levels of chlorine in reverse osmosis feedwaters. In the pursuit of a chlorine-resistant, nonbiodegra-dable thin-fiim-composite membrane, our efforts to develop interfaclally formed piperazine isophthalamide and terephthalamide membranes were partially successful in that membranes were made with salt rejections as high as 98 percent in seawater tests. 

A final variation involves the direction at which the Earth s axis points. Today, the axis points at the star known as Polaris, the North Star. But very slowly over time, the orientation of the axis changes, pointing in a slightly different direction. After about 12,000 years, the axis will be pointing toward the star known as Vega, which will then become the new "North Star." This 23,000-year variation is known as axial precession, or precession of the equinoxes, and because of it Earth s surface receives different amounts of solar radiation over the 23,000-year period. 

Cadotte, J. E. Kopp, C. V. Cobain, K. E. Rozelle, L. T. Progress Report on In Situ-Formed Condensation Polymers for Reverse Osmosis Membranes North Star Research Institute, Minneapolis, MI. Office of Saline Water Report. U.S. Department of the Interior June 1974, p 92. 

Poly N-amideimide (UOP) Polybenzooxadinon (Bayer) Polyhidantoin (Bayer) Sulfonated polysulfone Sulfonated PPO (GE) NS-100 (North Star) ... 

The production by Loeb and Sourirajan of the first successful anisotropic membranes spawned numerous other techniques in which a microporous membrane is used as a support for a thin, dense separating layer. One of the most important of these was interfacial polymerization, an entirely new method of making anisotropic membranes developed by John Cadotte, then at North Star Research. Reverse osmosis membranes produced by this technique had dramatically improved salt rejections and water fluxes compared to those prepared by the Loeb-Souri-rajan process. Almost all reverse osmosis membranes are now made by the interfacial polymerization process, illustrated in Figure 3.20. In this method, an aqueous solution of a reactive prepolymer, such as a polyamine, is first deposited in the pores of a microporous support membrane, typically a polysul-fone ultrafiltration membrane. The amine-loaded support is then immersed in a water-immiscible solvent solution containing a reactant, such as a diacid chloride in hexane. The amine and acid chloride react at the interface of the two immiscible... 

Another important group of anisotropic composite membranes is formed by solution-coating a thin (0.5-2.0 xm) selective layer on a suitable microporous support. Membranes of this type were first prepared by Ward, Browall, and others at General Electric [52] and by Forester and Francis at North Star Research [17,53] using a type of Langmuir trough system. In this system, a dilute polymer solution in a volatile water-insoluble solvent is spread over the surface of a water-filled trough. 

An interesting group of composite membranes with very good properties is produced by condensation of furfuryl alcohol with sulfuric acid. The first membrane of this type was made by Cadotte at North Star Research and was known as the NS200 membrane [32], These membranes are not made by the interfacial composite process rather a polysulfone microporous support membrane is contacted first with an aqueous solution of furfuryl alcohol and then with sulfuric acid. The coated support is then heated to 140 °C. The furfuryl alcohol forms a polymerized, crosslinked layer on the polysulfone support the membrane is completely black. The chemistry of condensation and reaction is complex, but a possible polymerization scheme is shown in Figure 5.10. 

When 8-bit microprocessor-based computers became available, we decided that such a computer, even though slower than minicomputers, would be adequate to operate the OMA and our interface controller with the ultracentrifuge. We now have in the system an Altair 8800 computer with 28K of memory (MITS, Albuquerque, NM), a hard-wired arithmetic board and two minifloppy disk drives (North Star, Berkeley, CA), a 700 ASR Terminal (Texas Instruments, Dallas, TX), and a 7202A Graphic Plotter (Hewlett-Packard, Palo Alto, CA). Appropriate software, written in Basic, has been developed to collect intensity data from the OMA automatically and also to treat and plot the data at the end of the experiment. Details of the system and software will be published elsewhere. We also have an improved illumination system with a 200 W Hg-Xe arc lamp and a Model H-20 monochromator with a holo-... 

Very true, Miss Muxdroozol. Also note that the art of navigation would have developed more slowly in the Southern Hemisphere since there is no equivalent to Polaris, the North Star, in the southern skies.6 Polaris appears to stand still, while other stars rotate around it, because it is almost exactly aligned along the celestial North Pole. This property is useful to navigators, because the star always lies in the direction of north. ... 

Cellulose acetate and linear aromatic polyamide membranes were the industry standard until 1972, when John Cadotte, then at North Star Research, prepared the first interfacial composite polyamide membrane.8 This new membrane exhibited both higher throughput and rejection of solutes at lower operating pressure than the here-to-date cellulose acetate and linear aromatic polyamide membranes. Later, Cadotte developed a fully aromatic interfacial composite membrane based on the reaction of phenylene diamine and trimesoyl chloride. This membrane became the new industry standard and is known today as FT30, and it is the basis for the majority... 

The second possibility for improving microcomputer floating point performance lies with the North Star Hardware Floating Point Board (3). This device executes floating point, add, subtract, multiply and divide with up to twelve decimal digits of precision. One byte of data is reserved for the exponent and the other six for the mantissa of each floating point number. 

North Star Computers, Product Catalog" North Star Computers Inc. Berkeley (U.S.), 1980. 

Cadotte, J. E., Cotaan, K. E., Forester, R. H., Petersen, R. I. In siV -formed condensation polymers for reverse osmosis memtvanes. Minneapolis, MN North Star Research Division... 

Polyurea (ultrathin wound modules) Ethyleneimine, North Star Res. Inst (UOP) 500 99..6 70 3.5 pH 2-12... 

North Star Gardens 19060 Manning Trail North Marine on St. Croix, MN 55047... 

The first composite reverse osmosis membrane reported in the technical literature was developed by Peter Francis of North Star Research Institute in 1964 (4). This membrane was formed by float-casting an ultrathin film of cellulose acetate (CA) upon a water surface, removing the membrane from the water surface by lamination onto a pre-formed microporous support film and drying to bond the membrane to the support. This float-casting procedure has since been described in the technical literature for both flat sheet and tubular membranes ( 5, 6, T). 

The use of interfacially formed thin films for membrane separations was, therefore, obvious. Reference to such membranes in Morgan s book characterizes them as retentive to dyes but permeable to salts. Early attempts to use interfacially formed membranes at the North Star Research Laboratories in the late 1960 s tended to confirm the low salt retention described by Morgan. In these early attempts to prepare composite membranes polysulfone support films were saturated in solutions of various diamines, acid acceptors and surfactants. After draining, the films were contacted with hexane solutions of various diacyl chlorides. In this initial work, salt rejections of these membranes were generally too low for practical use in seawater or brackish water applications. Similarly poor results were described in a patent by Scala and co-workers, dating to that era, wherein interfacial condensation membranes were produced (34). 

Biotechnology and Biological Sciences Research Council. Polaris House, North Star Avenue, Swindon SN2 lUH,... 

---