Polymerization continuous casting process

Three bulk polymerization processes are commercially important for the production of methacrylate polymers batch cell casting, continuous casting, and continuous bulk polymerization. Approximately half the worldwide production of bulk polymerized methacrylates is in the form of molding and extmsion compounds, a quarter is in the form of cell cast sheets, and a quarter is in the form of continuous cast sheets. 

The majority of polymeric membranes can be formed via a phase separation/inversion process by which a polymer solution (in which the solvent is the continuous phase) inverts into a swollen three-dimensional macromolecular network or gel (where the polymer is the continuous phase). Phase separation can be induced by solvent evaporation (the dry-cast process), nonsolvent/solvent exchange (the wet-cast process), cooling (the thermal-cast process), and polymer leaching (the polymer-assisted process). 

The dry-cast process for polymeric membrane formation involves dissolving the polymer in an appropriate volatile solvent containing a small amount of nonsolvent to form a single-phase solution. Subsequent evaporation of the solvent causes a phase separation to occur at a sufficiently low solvent concentration. The resulting nonsolvent-rich dispersed phase forms the pores, whereas the polymer-rich phase forms the matrix structure of the membrane. Thus, in the cellulose acetate/acetone/water system, acetone evaporates, cellulose acetate (CA) becomes the continuous phase, and water forms the pores. 

For processing of polymeric materials and composites, a number of industrial microwave equipment manufacturers offer equipment for the production of continuous cast-resin components, in which the microwave unit (3.6 or 7.2kW) processes high-viscosity resin systems with flow rates up to 5.0 kg min" The control system provides easy integration into other and/or existing systems. Several furnaces can be switched in cascades to achieve an increase in temperature difference between feeding flow and drain flow and/or an increase in the flow quantity of the medium to be treated. The microwave flow heater is available, which can also be applied in other fields, for example, food, plastic, and chemical... 

AcryHc resins are often ceU-cast (11). In this process no solvent is used, but the fluid monomers are passed into a cell or mold where polymerization takes place to form a soHd sheet. Heavy sections can be produced in this fashion. Formation of cast acryHc is moving toward modified continuous-based casting to increase productivity. Dmm casting on a commercial scale has almost disappeared. 

The Hquid monomers are suitable for bulk polymerization processes. The reaction can be conducted in a mold (casting, reaction injection mol ding), continuously on a conveyor (block and panel foam production), or in an extmder (thermoplastic polyurethane elastomers and engineering thermoplastics). Also, spraying of the monomers onto the surface of suitable substrates provides insulation barriers or cross-linked coatings. 

Continuous SO3 single-pass sulfonation processes, 23 543-552, 550 Continuous solution polymerization, reactors used for, 23 394-395 Continuous steel casting, 23 266-270 difficulties of, 23 266-267 universality of, 23 269-270 Continuous sterilization, in fermentation, 11 35-36... 

In bulk polymerization, no solvents are employed and the monomer acts as the solvent and continuous phase in which the process is carried out. Commercial bulk processes for acrylic polymers are used mainly m the production of sheets, rods and tubes. Rulk processes are also used on a much smaller scale in the preparation of dentures and novelty items and in the preservation of biological specimens. Acrylic castings are produced by pouring monomers or partially polymerized sirups into suitably designed molds and completing the polymerization. Acrylic bulk... 

Esters of methacrylic acid are obtained directly from acetone cyanohydrin by reaction of the latter with concentrated sulfuric acid to give methacrylamide sulfate, followed by reaction with an alcohol. The process is continuous and the methacrylamide sulfate is not isolated. Acetone cyanohydrin is derived from acetone and hydrogen cyanide (Pig. 15-39), Polymerization Procedures. Of particular importmice to the acrylics is the cast or bulk method of polymerization. This method is employed to produce cast polymethyl methacrylate sheets which are widely used in industrial applications. Careful control of polymerization is required to obtain a bubble-free product with good optical clarity. A typical flow sheet for the production of cast eet is shown in fig. lfi-40. Solution, suspension, and particularly emulsion polymerizations are also, widely used with the acrylics. Such polymerization reactions involve relatively conventional batch-type processes. i... 

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