Chloride Polymerization

Selection of organic peroxides for various commercial appHcations has been reviewed (21,33,48), particularly for vinyl chloride polymerizations (30). 

It seems likely that other polymerizations will be found to depart from Bemoullian statistics as the precision of tacticity measurements improves. One study12 indicated that vinyl chloride polymerizations are also more appropriately described by first order Markov statistics. However, there has been some reassignment of signals since that time. 4 25... 

Acid anhydride-diol reaction, 65 Acid anhydride-epoxy reaction, 85 Acid binders, 155, 157 Acid catalysis, of PET, 548-549 Acid-catalyzed hydrolysis of nylon-6, 567-568 of nylon-6,6, 568 Acid chloride, poly(p-benzamide) synthesis from, 188-189 Acid chloride-alcohol reaction, 75-77 Acid chloride-alkali metal diphenol salt interfacial reactions, 77 Acid chloride polymerization, of polyamides, 155-157 Acid chloride-terminated polyesters, reaction with hydroxy-terminated polyethers, 89 Acid-etch tests, 245 Acid number, 94 Acidolysis, 74 of nylon-6,6, 568... 

Polyamide-6 (PA-6), synthesis of, 174-176. See also PA-6 entries Polyamide endgroups, 161 Poly amide-imide, synthesis of, 291 Polyamides (PAs), 135-193. See also Nylons PA entries acid chloride polymerization of, 155-157... 

Polymerization of vinyl chloride occurs through a radical chain addition mechanism, which can be achieved through bulk, suspension, or emulsion polymerization processes. Radical initiators used in vinyl chloride polymerization fall into two classes water-soluble or monomer-soluble. The water-soluble initiators, such as hydrogen peroxide and alkali metal persulfates, are used in emulsion polymerization processes where polymerization begins in the aqueous phase. Monomer-soluble initiators include peroxides, such as dilauryl and benzoyl peroxide, and azo species, such as 1,1 -azobisisobutyrate, which are shown in Fig. 22.2. These initiators are used in emulsion and bulk polymerization processes. 

Vinyl chloride polymerization occurs via an exothermic radical reaction. In fact, the reaction is approximately 25% more exothermic than polyethylene polymerization. The highly exothermic nature of the reaction and the strong molecular weight dependence on temperature make heat transfer, and its control, critical to the manufacture of polyvinyl chloride. 

Two vinyl chloride polymerization reactors were being operated by the same team of operators. Reactor 3 was in the cool down and dump phase of the process, and reactor 4 was nearly full of monomer and in the polymerization phase. The foreman and three employees set to work... 

The homopolymerization ofl consists of a room-temperature reaction of the monomer dissolved in nitrobenzene in the presence of anhydrous ferric chloride. Polymerizations were carried out under a stream of dry nitrogen. As depicted in Scheme 2, the homopolymerization of 1 to form 6FNE takes place by means of the Scholl reaction. The mechanism of the Scholl reaction was assumed to proceed through a radical-cation intermediate derived from the single-electron oxidation of the monomer and its subsequent electrophilic addition to the nucleophilic monomer. The reaction releases two hydrogens, both as protons, to form the... 

The stability of vinylidene chloride copolymers generated using different polymerization initiators has also been examined. The two common types of initiators for radical polymerization are azo compounds and peroxides. A common azo initiator is azoisobutronitrile or AIBN. The initiation of vinylidene chloride polymerization using AIBN is illustrated in scheme 3. 

Scheme 3. Initiation of Vinylidene Chloride Polymerization Using AIBN as Initiator.

Falk H, Creech JL Jr, Heath CW Jr, et al Hepatic disease among workers at a vinyl chloride polymerization plant. JAMA 230 59-63, 1974... 

That the liquid phase polymerization of isobutylene in the presence of aluminum chloride or boron fluoride occurs even in the absence of a third component may be seen in the results of another worker (Houtman, 88). With solid aluminum chloride polymerization occurred at room temperature when isobutylene vapors were passed over the catalyst and at —80° when the isobutylene was in the liquid state. In both cases the reaction was incomplete probably because the catalyst was covered with a layer of polymer. The reaction at — 80° was not however as explosive in character as when moisture was present. When boron fluoride was added to isobutylene at about —80°, the polymerization started immediately in the gas phase above the liquid (owing to a somewhat higher temperature) and sometimes continued for a considerable time before reaction was noticeable in the liquid phase. There was no difference in behavior between the experiments in which the catalyst was led through or over the liquid. It was pointed out, however, that these results are not necessarily in contradiction with those of Polanyi and Evans and co-workers and that it is possible that the presence of moisture is neces-... 

Fig. 5-3 Temperature dependence of Xn for the aluminum chloride polymerization of isobutylene. After Kennedy and Squires [1965] (by permission of Butterworth, London and Elsevier, Oxford).

Lim and Kolinsky (203) estimated the chain-transfer coefficients of 2,4-dichloropentane and 2,4,6-trichloroheptane (dimer and trimer of vinyl chloride, plus H and CH3 end-groups) as 5 x 10 4 for both compounds at 50° C, though a higher value would be expected for the latter, which has one more —CH2 CHCl-group, than for the former they suggest that this value is appropriate for Ctp for vinyl chloride polymerization. However, the poly-... 

D-glucose in the ratio of 8.3 1 and only a trace of a di-O-methyl-D-glucose, further confirming that it was a (1—>6)-linked polymer. The disaccharide fraction from the zinc chloride polymerization of 1,3,4,6-tetra-O-acetyl-D-glucose gave sophorose and kojibiose in the ratio of 3 1, whereas 1,2,3,6-tetra-O-acetyl-D-glucose gave cellobiose and maltose in the same ratio. 

Acyl organosulfonyl peroxides (19) such as acetyl cyclohexanesulfonyl peroxide are efficient radical initiators for vinyl chloride polymerization. 

A substantially new and critical feature in bottom-entering agitators is the sealing of the shaft double mechanical seals are used here. On modem designs, they are provided with additional standstill seals for emergencies. The standstill seal allows the mechanical seal to be replaced while the reactor is full and under pressure. In a number of polymerizations, particularly in vinyl-chloride polymerization, the rotating elements must be protected by additional water flushing (4) other-... 

Listeria monocytogenes cells partitioned between organic/ aqueous medium Poly(allylamine) used in presence of diacid chloride Polymeric microcapsules (bacteria-mediated lithography) NS Aheme et al., 1996 Whitcombe et al., 1997... 

Figu re 13.4 Two-phase model for vinyl-chloride polymerization in suspension. 

Vinylidene chloride polymerizes by both ionic and free-radical reactions. Processes based on the latter are far more common (23). Vinylidene chloride is of average reactivity when compared with other unsaturated monomers. The chlorine substituents stabilize radicals in the intermediate state of an addition reaction. Because they are also strongly electron-withdrawing, they polarize the double bond, making it susceptible to anionic attack. For the same reason, a carbonium ion intermediate is not favored. 

The increased reactivity of propagating radicals complexed with the metal salt towards uncomplexed monomer has been postulated (87) to account for the increased susceptibility of methyl methacrylate to ultraviolet light or free radicals in the presence of aluminum chloride or aluminum bromide. A similar explanation has been considered to account for the enhanced reactivity in the methyl methacrylate-zinc chloride and acrylonitrile-zinc chloride polymerization systems. However, the complex shown in Reaction 20 must equally be considered. 

If one hydrogen is replaced with chlorine in the ethylene molecule, vinyl chloride is formed. If vinyl chloride polymerizes polyvinyl chloride, known as PVC, is formed. PVC is lightweight, long lasting, and waterproof. In its rigid form, PVC is water-resistant and can be drawn out into pipes, house siding and drainpipes. It is also used in compact discs and computer casings. 

Bengough and Norrish observed this behaviour during vinyl chloride polymerization. They explained it by transfer to polymer chains on which immobile, long-lived and propagating radicals are formed. These centres decay by transfer to monomer or by termination with untrapped radicals from the liquid phase [47], According to these two authors, the acceleration is proportional to the surface area of the solid particles. A similar acceleration of polymerization was observed by Bamford et al. [18] with acrylonitrile... 

For vinyl chloride polymerization in bulk, the rate equation... 

An example of this type of polymerization is demonstrated in Fig. 2. It represents the linear dependence between [M] 1,2 and time in vinyl chloride polymerization [5],... 

EXAMPLE KINETIC ANALYSIS OF VINYL CHLORIDE POLYMERIZATION... 

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