Coagulation by freezing and

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). 

The caseinate micelles of milk, which are quite stable to heat, may also be destabilized by freezing. On frozen storage of milk, the stability of caseinate progressively decreases and this may lead to complete coagulation (deMan, 1999). Enzymes have also been linked to protein denaturation, as it is known that low temperature decreases the activity of enzymes in tissue, but does not inactivate them (Lim et al., 2004 Zaritzky, 2006). 

Polymerization is carried out at 40°C and is allowed to continue until a 90% conversion is reached. The latex is cooled to 20°C and tetraethylthiuram disulphide is added the product is then allowed to stand for about 8 hours until the desired molecular weight is reached. The latex is then acidified with acetic acid just short of coagulation, which is ultimately accomplished by freezing on the surface of a cooled (about — 15°C) rotating drum partially immersed in the latex. The resulting film of polymer is stripped from the roll, washed, dried in air at 120°C and cut into small pieces. This method of isolation is used because polychloroprene is tacky and it is difficult to coagulate the latex directly to crumb. 

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