Cooling Homopolymerization

Continuous polymerization systems offer the possibiUty of several advantages including better heat transfer and cooling capacity, reduction in downtime, more uniform products, and less raw material handling (59,60). In some continuous emulsion homopolymerization processes, materials are added continuously to a first ketde and partially polymerized, then passed into a second reactor where, with additional initiator, the reaction is concluded. Continuous emulsion copolymerizations of vinyl acetate with ethylene have been described (61—64). Recirculating loop reactors which have high heat-transfer rates have found use for the manufacture of latexes for paint appHcations (59). 

The homopolymerizations were all run in 28 oz. beverage bottles. The bottles were baked for at least 24 hrs. and then capped with crown, three-hole caps and rubber liners. Cooling of the bottles was effected while purging with nitrogen. After cooling, the bottles were charged with the butadiene blend, the heterogeneous initiator-hexane suspension and modifiers. 

Novolen Process (Figure 7) With this technology, which comprises two vertical stirred gas-phase reactors in series, homopolymers as well as impact and random copolymers are produced. The first reactor operates at 80°C and 20-35 bar monomer pressure and is used exclusively for the homopolymerization of propylene. Propylene is injected as a liquid and cools the exothermic polymerization by its... 

This relationship is shown (Figure 3) for the homopolymerization of styrene, where AHp = 300 B.t.u. per pound and Cp = 0.5 B.t.u. per ° F. per pound. The data show that the monomer entering the heat exchanger (Figure 2) will have to be heated or cooled depending on / and T2. With the monomer entering the exchanger at room temperature (taken as 30° C.), endothermic operation is involved when Tj > 30° C., exothermic when < 30° C., and adiabatic when Tj = 30° C. For a typical reactor temperature of 130° C., the monomer must be... 

An homologous series of epoxy resins with various EEWs was synthesized by standard advancement techniques and subsequently esterified with 15 wt% 1300X13. Isothermal aging kinetics were followed at 175C. Aliquots of resin were withdrawn hourly, rapidly cooled to room temperature, and titrated for EEW. No precautions were taken to exclude air during the isothermal aging. Table Xll summarizes the formulations, reactive moiety equivalent weights, and kinetic calculations for the epoxide-alcohol addition reaction and the epoxide homopolymerization reaction. 

FIGURE 7.1 Schematic of a lab-scale 200 mm diameter iCVD reactor system. For a vinyl homopolymerization, a constant flow of monomer and initiator is metered into the pancake -style vacuum reaction chamber. An array of resistively heated wires, suspended a few centimeters above the substrate, heats the vapors. Laser interferometery provides real-time monitoring of the iC VD polymer thickness. The pressure of the chamber is controlled by a throttling value. Unreacted species and volatile reaction by-products are exhausted to a mechanical pump. For copolymerization, an additional monomer feed line would need to be added to the system (top image). Schematic cross-section of the iCVD reactor showing decomposition of the initiator by the heated filaments. Surface modification through polymerization of the monomer occurs on the actively cooled substrate (bottom image). 

Polymerization. The polymerization runs are made in a 5 liter stainless steel reactor in a bulk homopolymerization. Cocatalyst (5.64 mmol), catalyst (0.2 to O.S mmol), hydrogen (0.2 to 2 bar) and liquid propylene (3. 5 liters) are succesively introduced under a nitrogen blanket and the heating to the polymerization temperature is started. Unless otherwise specified, the polymerization conditions are maintained for three hours. The polymerization is then stopped by simultaneously flashing the residual monomer and cooling down the reactor. The polymer is recovered and dried overnight. 500 to 800 gram of polymer are obtained. 

Homopolymerization of the steroid monomers [2] and [5] was carried out in p-dioxane solvent, using AIBN as the initiator. In a typical experiment, monomer [2] or [5] was dissolved in p-dioxane (15% w/w). To this was added the AIBN initiator (1.00m%). The reaction vessel was first evacuated and then purged with dry nitrogen gas. This process was repeated several times. Then the reaction vessel was placed in an oil bath maintained at 60 C for 48 hrs. Afterwards, the solution was cooled and diethyl ether was added a white solid separated out from the solution. This solid material was filtered and was purified by repeated reprecipitation from dimethylformamide and ether. The yield of the polymers were 85-92%. 

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