Thermal phase-separation

T0693 see Environmental, Thermal-Phase Separation Unit... 

T0693 see Environmental, Thermal-Phase Separation Unit T0712 SrVE Services, Steam Injection and Vaennm Extraction (SIVE)... 

The literature describes numerous manufacturing methods for synthetic membranes. A recent review by Pusch and Walch (1) considers membranes from a number of techniques for manufacturing membranes and discusses applications ranging from microfiltration to desalination to gas separation. In this paper, a thermal phase-separation technique of preparing membranes Is presented. The method Is a development of an Invention described In US Patent 4,247,498 by Anthony J. Castro (,2). This technique Is similar In many respects to the classical phase-inversion methods however, the additional consideration of thermal solubility characteristics of the poly-mer/solvent pair offers new possibilities to membrane production. 

The development of solvent resistant commercial mlcroporous membranes via thermal phase separation began with an unexpected laboratory discovery. The early workers were searching for a way to make a concentrate of an antl-statlc agent In polypropylene that t Current address Department of Chemistry, University of Florida, Gainesville, FL 32611. 

Figure 4. Representation of the Thermal Phase-Separation Process Diagram...

The products of the thermal phase-separation membranes form a wide range of styles and configurations. Three pore sizes are currently In commercial production In polypropylene flat stock, rated at 0.45, 0.2, and 0.1 micrometers, having maximum pore sizes of about 1.0, 0.55, and 0.3 micrometers, respectively. The last two are particularly attractive for depyrogenatlon work which has been described by J. R. Robinson, et al W. A similar membrane-manufacturing process Is also used for making hollow fibers and tubes which are especially useful in cross-flow applications (10) and plasmapheresis ( ). 

The exploration of the thermal phase-separation process has added a new dimension to the science of microporous membranes. New and useful products can be made from a large spectrum of polymers ranging from hydrophobic polymers, like polypropylene or PVDF, to hydrophilic ones, like nylon which we have not touched upon in this article. 

Monji N, Hoffman AS. A novel immunoassay system and bioseparation process based on thermal phase separating polymers. Appl Biochem Biotechnol 1987 14 107-120. 

The Accurel system has a microporous polymer sponge (e.g., of PP, LDPE, HDPE, polyamide) used as carrier for incorporating liquid additives into a thermoplastic melt. The earner is produced by a thermal phase separation process. A microcellular structure with cells of microns connected by pores of 0.5 microns and internal surface 90m /g, absorb up to 2.5 times its own weight of liquid. The key to this solution is the miscibility of a polymer with... 

Although there are many types of membranes employed in various gas separation and water purification processes, similar membrane formation processes are often employed. The phase inversion process promoted by nonsolvent addition and the thermal phase separation process based on the fundamentals discussed above are the most prevalent processes to produce membranes. In addition to References 20-22,References 25-31 " also discuss these processes, and therein applications are covered in more detail than will be attempted in this chapter. 

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