Feed vinyl acetate monomer process

The co-monomers such as vinyl acetate, acrylate esters, or carbon monoxide are fed together with ethylene, or introduced by liquid pumps, into the suction of the secondary compressor. The concentration in the feed of the co-monomer which is required to achieve a certain level of the co-monomer in the resulting polymer depends on the reactivity ratios, ri and r2, which are the ratios of rate constants of chain-propagation reactions [5]. The values for the co-monomers used in the high-pressure process are presented in Table 5.1-3. In the case of vinyl acetate, both reactivity ratios are identical and therefore the composition of the copolymer is the same as that of the feed. The concentration of vinyl acetate, for example, in... 

Process Load the reactor with the initial charge, using a presolution of the poly(vinyl alcohol) in 300 g of the water. Rinse in the sodium bicarbonate and ammonium persulfate with the remaining water. Switch on the agitator and purge with nitrogen. Then pump in the initial vinyl acetate and pressurize with ethylene gas. Raise the temperature to 35 to 40°C and maintain at this temperature. Start to add the reducing initiator feed to go in over about 8 h. After 1 h, start to add the continuous monomer feeds (1) and (2) to go in over about 7h. At all times the unreacted monomer should be kept at 1 to 2% of the reaction mixture to ensure even copolymerization of the A-methylol acrylamide. 

An example of a continuous aqueous dispersion process is shown in Figure 12.5 [92]. A monomer mixture composed of acrylonitrile and up to 10% of a neutral comonomer, such as methyl acrylate or vinyl acetate, is fed continuously. Polymerization is initiated by feeding aqueous solutions of potassium persulfate (oxidizer), sulfur dioxide (reducing agent), ferrous iron (promoter), and sodium bicarbonate (buffering agent). The aqueous and monomer feed... 

The post-polymerisation of vinyl acetate (Vac)-containing latexes with tert-butyl hydroperoxide TBH/ascorbic acid (AsA) as a redox initiation system is investigated. Volatile organic compounds (VOCs) such as acetone and tert-butyl alcohol are produced in this process. The influence of the TBH/AsA ratio, initiator concentration, reaction temperature and feeding time on the reduction of residual VAc and VOC formation during the post-polymerisation is investigated. A total reduction of residual VAc monomer is achieved, with the formation of VOCs kept within acceptable limits. 11 refs. 

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