Freeze-coagulation

The earhest frothing process developed was the Dunlop process, which made use of chemical gelling agents, eg, sodium fluorosiUcate, to coagulate the mbber particles and deactivate the soaps. The Talalay process, developed later, employs freeze-coagulation of the mbber followed by deactivation of the soaps with carbon dioxide. The basic processes and a multitude of improvements are discussed extensively in Reference 3. A discussion more oriented to current use of these processes is given in Reference 115. 

Chloroprene mbber is usually manufactured by either batch or continuous emulsion polymerization and isolated either by freeze coagulation or dmm drying of a polymer film. Figure 1 is a schematic flow sheet of this process. 

Eventually, the latexes are dewatered and recovered in solid form by freeze-coagulation and centrifugation, or by mechanical isolation. Mechanical isolation consists of shear coagulation of the latex to form a paste. The paste is then heated and sheared to form a crumb. Finally, the crumb is mechanically dewatered and ground to the desired particle size. A key feature of this method is the relatively low energy consumption of this process (17). 

We prepared a 360-A polymer with a low degree of grafting by blending latexes. The 360-A latex blended with the copolymer latex gave a 15% rubber content with no graft. The resultant latex blend was freeze-coagulated and was treated the same as the previous specimens. 

The scale-up of Run 43 was made in the 10-gal kettle. The latex was freeze-coagulated and worked up in the same manner as the other grafts. 

Charactaization of the water-soluble oligomers requires removal of the latex particles from the serum. This has been accomplished by ultrafiltration [163,164,166,174], serum replacement [167,168], or freeze-coagulation [173], followed by standard concentration techniques (e.g. evaporaton of water, or solvent extraction) or direct analysis of the aqueous solutions [163,164,166,174]. 

Pretreatment of Suspensions. Another important aspect of soHd—Hquid separation is conditioning or pretreatment of the feed suspension to alter some important property of the suspension and improve the performance of a separator that follows. A conditioning effect is obtained using several processes such as coagulation and docculation, addition of inert filter aids, crystalliza tion, freezing, temperature or pH adjustment, thermal treatment, and aging. The first two operations are considered in more detail due to their importance and wide use. 

The development of freeze-drying for the production of blood derivatives was pioneered during World War II (96,97). It is used for the stabilization of coagulation factor (98,99) and intravenous immunoglobulin (IgG iv) products, and also for the removal of ethanol from intramuscular immunoglobulin (IgG im) solutions prior to their final formulation (Fig. 2). 

Samples may separate into two or more phases as they cool in the sample line precipitate, coagulate, and freeze. Laboratory sampling may result in nonrepresentative compositions. Heat tracing may be required and may not be installed on the nonroutine sample locations. 

Erst-, first, initial, original, primary, erstarren, v.t. solidify, congeal, freeze (of cement, etc.) set harden coagulate become stiff or torpid. 

Erstarnmgs-kurve, /. freezing-point curve, -punkt, m. freezing point setting point, solidification point coagulation point, -warme, /. heat evolved on solidification, heat of fusion. 

This is a dry sponge of human fibrin prepared by elotting a foam of human fibrinogen solution with human thrombin. It is then freeze-dried, cut into shapes and sterilized by dry heat at 130°C for 3 hours. Before use, it is saturated with thrombin solution. Blood coagulation occurs in contact with the thrombin in the interstices of the foam. 

The storage temperature of a specimen influences the results of coagulation tests. Generally, when plasma is stored in contact with cells and maintained at4°C for up to 7 hours, the PT is not artifactually shortened (103). However, beyond 7 hours factor VII is activated, thereby shortening the PT (104). At room temperature (25°C), provided the specimen container is well stoppered, the PT has been shown to be stable for up to 48 hours (104). Even freezing plasma at — 20°C and at - 70°C did not activate factor VII. Both PT and APTT results were shown to be stable in plasma frozen at —20°C for 10 days and at -70°C for 21 days (104). 

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