Polymerization of vinyl chloride

Polymerization reactions. There are two broad types of polymerization reactions, those which involve a termination step and those which do not. An example that involves a termination step is free-radical polymerization of an alkene molecule. The polymerization requires a free radical from an initiator compound such as a peroxide. The initiator breaks down to form a free radical (e.g., CH3 or OH), which attaches to a molecule of alkene and in so doing generates another free radical. Consider the polymerization of vinyl chloride from a free-radical initiator R. An initiation step first occurs ... 

Polylvinyl Chloride) (PVC). Polymerization of vinyl chloride results in the formation of a polymer with the following formula ... 

Wheieas the BPO—DMA ledox system works well for curing of unsaturated polyester blends, it is not a very effective system for initiating vinyl monomer polymerizations, and therefore it generally is not used in such appHcations (34). However, combinations of amines (eg, DMA) and acyl sulfonyl peroxides (eg, ACSP) are very effective initiator systems at 0°C for high conversion suspension polymerizations of vinyl chloride (35). BPO has also been used in combination with ferrous ammonium sulfate to initiate emulsion polymerizations of vinyl monomers via a redox reaction (36). 

C2HBr202, is used as a polymerization catalyst. Tribromo-Z rZ-butyl alcohol [76-08S] C HyBr O, is a modifier in the polymerization of vinyl chloride. 

Miscellaneous Reactions. Epoxy compounds yield chlorosubstituted carbonates (45). The reaction of chloroformates with hydrogen peroxide or metal peroxides results in the formation of peroxydicarbonates that are used as free-radical initiators of polymerization of vinyl chloride, ethylene, and other unsaturated monomers (46,47). 

A VCM (vinyl chloride monomer) production unit uses three vertically mounted agitated reactors for the polymerization of vinyl chloride. Crude material balances infer about 8 to 10% monomer losses. Describe how you would go about assessing whether these losses are due to leaks such as fugitive air emissions. Be specific in recommending procedures and instruments. 

Resin derived from the polymerization of vinyl chloride. 

Group of plastics whose resins are derived from the polymerization of vinyl chloride and other unsaturated compounds. 

Strohmeier and Griibel [21] have reported that some vanadyl carbonyls of CpV(CO)4 (Cp = cyclopentadie-nyl) can photochemically induce the polymerization of vinyl chloride in the presence of CCI4. 

The polymerization of vinyl chloride monomer, in common with other vinyl monomers, proceeds by a free-radical mechanism involving the usual steps of initiation, propagation, and termination. Poly(vinyl chloride) is formed in a regular head-to-tail manner Eq. (1) [3-6]. 

Braun and Schurek [9] assumed that during polymerization a reaction can occur between the polymer and free radicals that leads to the elimination of hydrogen chloride and formation of a double bond. The formation of HCl during the polymerization of vinyl chloride has been observed [10],... 

The effect of the decomposition products of the polymerization initiator incorporated at the beginning of the chain is a controversial one. If the polymerization of vinyl chloride is initiated with organic peroxides, which decompose according to Eqs. (13) and (14) ... 

In the emulsion polymerization of vinyl chloride (VC) initiated with type II MAI composed of PDMS, block efficiency was as high as 95-97%, and solid particles with a narrow range of particle size, 0.1-50 microns, were obtained in high yield [15]. 

Perhaps the only process where such correlations have been published is the bulk polymerization of vinyl chloride as reported by Ray, Jain and Salovey (14). 

Finally, similar autoacceleration in the polymerization rate was reported by Crosato-Arnaldi, Gasparini and Talamini (18) for the bulk polymerization of vinyl chloride. 

The literature on the modeling and design of precipitation polymerization reactors is limited primarily to reactor for the bulk polymerization of vinyl chloride (31-38), although other systems have been discussed, particularly in the patent literature (39,40,41). 

Capek, L Kinetics of the Free-Radical Emulsion Polymerization of Vinyl Chloride. Vol. 120, pp. 135-206. 

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. 

Chain transfer occurs frequently during the polymerization of vinyl chloride. The ratio of propagation events to chain transfer events in a given time period determines the average molecular weight of the final polymer. This finding can be summarized by the empirical formula ... 

As in the case of chromium and tungsten, manganese carbonyl adducts of Me2SO have been used as catalysts for the polymerization of vinyl chloride (248). Preparative studies have allowed the isolation of complexes of the type [MnCCpHjMeXCOlXRaSO)] [RjSO = (CH2)4SO, (CH20)2S0 see ref. 255], and infrared (257) and mass spectral studies (154, 275) have appeared on these and related systems. 

It is clear, however, that a simultaneous increase in polymerization rate and molecular weight could either follow from a reduction in the rate of termination or from an increase in the rate of propagation. This last possibility has seldom been considered, except in some of the very early studies such as in the work of BENGOUGH and NORRISH (2J on the bulk polymerization of vinyl chloride where a "catalytic" action was attributed to the precipitated polymer. 

Vinyl chloride has been associated with cancer in humans in a number of epidemiological studies. In four facilities engaged in the polymerization of vinyl chloride for at least 15 years, workers exposed for at least 5 years had a significant number of excess deaths due to malignant neoplasms (35 deaths observed, 23.5 expected). The excesses were found for four organ systems CNS (3 observed, 0.9 expected), respiratory system (12 observed, 7.7 expected) hepatic system (7 observed, 0.6 expected), and lymphatic and hematopoietic systems (4 observed, 2.5 expected). 

Today, PVC is made from the polymerization of vinyl chloride as shown in the following equation ... 

PVC materials are often defined to contain 50% or more vinyl chloride units by weight. PVC is generally a mixture of a number of additives and often other units, such as ethylene, propylene, vinylidene chloride, and vinyl acetate. Structurally similar products, but with differing properties, are made from the chlorination of PE but almost all PVC is made from the polymerization of vinyl chloride. Typical homopolymers are about 400-1000 units long. 

Fig. 3-20 Typical polymerization vessel for suspension polymerization of vinyl chloride. After Brydson [1999] (by permission of Butterworth-Heinemann and Elsevier, Oxford).

Talamini, G. andE. Peggion, Polymerization of Vinyl Chloride and Vinylidene Chloride, Chap. 5 in Vinyl Polymerization, Vol. 1, Part I, G. E. Ham, ed., Marcel Dekker, New York, 1967. 

Fig. 4-4 Plot of percent conversion versus time for emulsion polymerization of vinyl chloride at 50°C for monomer/water ratio of 26/74 and 0.883% surfactant. The initiator concentrations are 0.0012% (plot 1), 0.0057% (plot 2), and 0.023% (plot 3). After Vidotto et al. [1970] (by permission of Huthig and Wepf Verlag, Basel, and Wiley-VCH, Weinheim).

Fig. 8-9 Dependence of syndiotacticity on temperature for the radical polymerization of vinyl chloride. After Talamini and Vidotto [1967] (by permission of Huthing and Wepf Verlag, Basel and Wiley-VCH, Weinheim).

Addition of a molecule across a triple bond yields a molecule that stiU contains a double bond and is therefore reactive. Polymerization of vinyl chloride yields polyvinyl chloride... 

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